Waste Reduction in Metal Casting and Heat Treatment Industry

WASTE AUDIT STUDY

THERMAL METAL WORKING INDUSTRY

PREPARED FOR

ALTERNATIVE TECHNOLOGY DIVISION TOXIC SUBSTANCES CONTROL PROGRP

CALIFORNIA DEPARTMENT OF HEALTH SERVICES

PREPARED BY

JACOBS ENGINEERING GROUP INC.

PASADENA, CALIFORNIA

DECEMBER 1990

ABSTRACT

This report presents the results of Jacobs Engineering Groups waste audit study of the thermal metal working industry. The goal of this study was to identify waste reduction techniques available to the industry.

The report focuses on source reduction, recycling, and treatment methods for businesses performing thermal metal working with specific focus on casting and heat treating. The processes examined include melting, mold and core making, shakeout, and case hardening by means of thermal and/or chemical methods. Support operations which may be found at thermal metal working businesses, but have been explored in previous studies, include machining operations, metal parts cleaning and stripping, metal surface treatment and plating, and paint application.

Three thermal metal working plants were surveyed as part of the project: a ferrous metal foundry, a heat treating plant and a non-ferrous foundry. Waste reduction and treatment techniques were identified and analyzed based on the information collected during these surveys, as well as from detailed literature review and discussions with industry representatives. The results include a waste reduction assessment format for generators to perform their own waste reduction opportunities assessments. Source reduction techniques, recycling and resource recovery techniques appear to offer high promise of minimizing waste generation.

A waste reduction Index was developed for use by foundries to measure waste reduction effectiveness. The index compensates for variation in production activity. Examples are developed here for brass foundry sand waste, iron foundry sand waste, and iron foundry baghouse waste.

. i

ACKNOWLEDGEMENTS

Jacobs Engineering Group Inc. would like to acknowledge the efforts of Mr. Benjamin Fries, Mr. Bal Lee, and Mr. Eric Workman of the Alternative Technology Division and various individuals at the cooperating thermal metal working firms for their assistance in this study.

The Jacobs project manager for this study was Dr. Michael Meltzer. The principal author and investigator was Dr. Maria Zdunkiewicz. Mr. Carl Fromm and Mr. Michael Callahan provided quality assurance and control.

This report was submitted in fulfillment of Contract No. 88-TO326 by Jacobs Engineering Group Inc. pursuant to a contract between Jacobs and the Department of Health Services. Work for this Final Report was completed as of December 1990.

ii

DISCLAIMER

The statements and conclusions of this report are those of the Contractor and not necessarily those of the State of California. The mention of commercial products, their source, or their use in connection with material reported herein is not to be construed as either an actual or implied endorsement of such products.

CONTRACTORS DISCLAIMER

This report was prepared by Jacobs Engineering Group Inc. as an account of work performed for The State of California DeDartment of Health Services (client). Neither Jacobs Engineering Group Inc., nor any persons acting on its behalf; (a) makes any warranty or representation, expressed or implied, with respect to the accuracy, completeness or usefulness of the information contained in this report, or that the use of any information, cost estimate apparatus, method, or process disclosed in this report may not infringe privately owned rights; or (b) assumes any liabilities with respect to the use of, or damage resulting from the use of, any information, cost estimate, apparatus, method, or process disclosed in this report, including consequential or other indirect or contingent liabilities whether due to the negligence of Jacobs Engineering Group Inc. or otherwise. Any person, entity or .third party using this report or its contents or relying thereon does so at Its own risk and does hereby release, defend and indemnify Jacobs Engineering Group Inc. from and against any liability, cost or expense such person, e n t i or third party may incur as a resuit of said use, or reliance.

REGULATORY CAVEAT

All text pertaining to law and regulations contained within this report are provided for general information only. That information is not reliable for use as a legal reference. The generator must contact the appropriate legal sources and regulatory authorities for up-to-date regulatory requirements, and their interpretation and implementation.

CONTRACTS

Contract No. 88-TO326 provided $27,000 to prepare this report. No subcontractors were involved in its preparation.

iii

CONTENTS

ABSTRACT ACKNOWLEDGEMENTS DISCLAIMER CONTRACTORS DISCLAIMER REGULATORY CAVEAT CONTRACTS

1 .O SUMMARY AND CONCLUSIONS

1 .I Regulatory Aspects 12 1.3 Waste Reduction Economics 1.4 Waste Reduction Assessment Format 1.5 Waste Reduction Index

Waste Streams and Reduction Measures

2.0 RECOMMENDATIONS

Page i ii iii iii iii iii

1-1

1-1 1 -2 1-2 1 -2 1-6

2-1

2.1 Metal Casting 2-1 2.2 Heat Treating 2-1 2.3 Waste Reduction Alternatives Assessment A - Non-Ferrous Foundry 2-2 2.4 Waste Reduction Alternatives Assessment B - Heating Treating Plant 2-2 2.5 Waste Reduction Alternatives Assessment C - Ductile and Gray

Iron Foundry 2-3 2.6 Regulations 2-3 2.7 Advancing Technology 2-3

3.0 INTRODUCTION 3-1

3.1 Study Purpose 3.2 Industry Overview 3.3 Project Approach 3.4 Focus 3.5 Forging, Tempering, and Rolling

3-1 3-1 3-1 3-2 3-2

4.0 WASTE REDUCTION PROGRAMS . 4-1

4.1 Environmental Benefits 4.2 Program Requirement 4.3 The Waste Minimization Opportunity Assessment

4-1 4-1 4-2

5.0 REGULATORY ASPECTS 5-1

5.1 Regulatory Caveat 5-1 5.2 Laws, Regulatlons and Ordinances 5-1

5.2.1 Land Disposal Restrictions (Existing and Proposed) 5-1 5.2.1 .I Treatment Standards for Foundry Sand 5-2 5.2.1.2 Treatment Standards for Solid Wastes with Metals 5.2.1.3 Proposed Treatment Standards for Eaghouse Waste

5-3

and Gas Scrubber Waste 5-6 .

iv

CONTENTS (continued)

Page

5.2.2 Waste Storage 5.2.3 Waste Transport 5.2.4 Waste Reduction

WASTE REDUCTION AND TREATMENT ALTERNATIVES FOR THE METAL CASTING INDUSTRY

6.0

5-6 5-7 5-7

6-1

6.1 Description of Hazardous Waste Generation Processes 6-1

6.2.1 Input Material Characterization 6-6

6.2.1.3 Blast Cleaning Materials 6-9

6.2 Input Materials and Hazardous Waste Characterization 6-6

6.2.1.1 Mold and Core Materials 6-6 6.2.1.2 Melting Materlals (Furnace Charge) 6-8

6.2.1.4 Cleaning Solutions and Coating Materials 6-9 6.2.1.5 Oils 6-9

6.2.2 Hazardous Waste Characterization 6-9

6.2.2.2 Cleaning Room Wastes 6-1 3

6.2.2.4 Slag Wastes 6-1 3 6.2.2.5 Miscellaneous Wastes 6-1 4

Waste Reduction and Treatment Options for Baghouse Dust and Scrubber Wastes 6-1 4 6.3.1 Source Reduction 6-1 4

6.3.1 .I Alter Raw Materials 6-1 4 6.3.1.2 Install Induction Furnace 6-1 4

6.3.2 Recycling 6-1 4 6.3.2.1 Recycle to the Original Process 6-1 5 6.3.2.2 Recycle Outside of the Original Production Process 6-1 5

6.3.3 Treatment 6-1 7 6.3.3.1 Cement-Based Chemical Stabilization 6-1 7 6.3.3.2 Lime/Pouolan-Based Chemical Stabilization 6-18 6.3.3.3 Chemical Reduction 6-1 8

6.3.3.5 Polysllicate Treatment at the Cupola Furnace Stack 6-1 8

6.2.2.1 Spent Foundry Sand 6-1 1

6.2.2.3 Dust Collector and Scrubber Wastes 6-1 3

6.3

6.3.2.3 Recycle to Cement Manufacturer 6-1 7

6.3.3.4 Solubility Control 6-1 8

6.3.3.7 Thermoplastic Binding 6-1 9 6.3.3.8 Encapsulation 6-1 9

Waste Reduction and Treatment Options for Hazardous Slags 6-1 9 6.4.1 Source Reduction 6-1 9

6.4.1 .I Alter Feed Stock 6-1 9 6.4.1.2 Alter Desulfuriiation Agent 6-1 9 6.4.1.3 Alter Product Requirements 6-20 6.4.1.4 Improve Process Control 6-20

6.4.2 Recycling 6-20 6.4.2.1 Recycle to Process 6-20 6.4.2.2 Recycle to Other Process Lines 6-20

6.4.3 Treatment 6-21

6.3.3.6 Sulphating Process for Zinc In EAF Dust 6-1 8

6.4

-

V


Page

6.5

6.4.3.1 Mixing of Treated Desulfurization Slag with Furnace Dust 6-21

6.4.3.2 Improved Treatment Methods 6-21 6-22

6.5.1 Source Reduction 6-22 6.5.1.1 Material Substitution 6-22 6.5.1.2 Waste Segregation 6-22

6.5.2 Recycling 6-23 6.5.2.1 Screening and Separation of Metal from Sand 6-23 6.5.2.2 The PMET Process - Metal and Sand Reclamation 6-24 6.5.2.3 Sand Reclamation by Wet WashinglScrubbing 6.5.2.4 Sand Reclamation by Dly Scrubbing/Attrition

Waste Reduction and Treatment Options for Spent Casting Sands

6.5.2.5 Thermal Reclamation of Sand 6.5.2.6 Reuse of Detoxifiedllmmobllird Sand as

6.5.2.7 Use of Sands as a Construction Material

6.5.3.1 Sodium SilicatelLime Immobilization

6.5.3.2 Sodium SilicatelPozzalime or Portland

Ingot Molds

6.5.3 Treatment of Sand

(Furness Process)

Cement Immobilization (Trezek Process)

7.0 WASTE REDUCTION AND TREATMENT ALTERNATIVES FOR HEAT TREATING INDUSTRY

7.1

7.2

7.3

Description of Hazardous Waste Generation Processes 7.1.1 Furnace Operation

7.1.2 Quenching 7.1.3 Descaling 7.1.4 Hazardous Waste Characterization 7.2.1 7.2.2 Quenching Wastes 7.2.3 Parts Cleaning and Coating Waste Reduction and Treatment Options for Case Hardening Baths and Salt Pots 7.3.1 Source Reduction

7.1.1.1 Heat Treating Other Than Case Hardening 7.1.1.2 Case Hardening

Parts Cleaning and Surface Coating

Case Hardening Baths and Salt Pots

7.3.1.1 Alter Raw Materials (Bath Composition) 7.3.1.2 Clean All Work Placed in the Bath 7.3.1.3 Use Graphite Cover on the Surface of a

Cyanide Bath 7.3.1.4 Dry Work Completely Prior to Liquid

Case Hardening (Safety) 7.3.1.5 Remove Impurities (Sludges) 7.3.1.6 Minimize Dragout 7.3.1.7 Replace Pot Lining

6-24 6-26 6-26

6-27 6-28 6-28

6-28

6-29

7-1

7-1 7-1 7-1 7-2 7-3 7-3 7-3 7-4 7-4 7-0 7-9

7-9 7-9 7-9

7-10

7-10

7-10 7-10 7-10 7-11

vi


Page

7-1 1 7-1 1 7-1 2 7-1 3 7-1 3 7-1 3 7-1 3 7-1 3 7-1 4 7-1 4 7-1 4 7-1 5 7-1 5 7-1 5 7-1 5 7-1 5

8-1

8-1 8-1 8-2

9-1

9-1 9-2

10-1

7.3.2 Treatment

Waste Reduction and Treatment Options for Quenchant Wastes 7.4.1 Source Reduction

7.3.2.1 Chemical Treatment 7.3.2.2 Electrochemical Treatment

7.4.1 .I Minimize Dragout of Molten Salts 7.4.1.2 Minimize Dragout of Quenchant 7.4.1.3 Temperature Control of Oil Quenchant System 7.4.1.4 Use Modlfied Systems

7.4.2.1 Desludging 7.4.2.2 Dewatering of Quenching Oil 7.4.2.3 Ultrafiltration of Water-Polymer Quenchants

7.4.3.1 Water and Brine Bath Quenchants 7.4.3.2 Quenching Oil Dragout

7.4

7.4.2 Recycling

7.4.3 Treatment

8.0 WASTE REDUCTION INDEX

8.1 Introduction 8.2 Approach 8.3 WRI for the Thermal Metal Working Industry

9.0 WASTE REDUCTION ECONOMICS

9.1 Low Capital Cost Measures 9.2 Capital Investment

10.0 REFERENCES

vii

TABLES

Waste Reduction and Treatment Alternatives for the Metal Casting Industry

Waste Reduction and Treatment Alternatives for the Heat Treating Industry

Achievable BDAT Concentrations

EPAs Treatment Standards for Some Metal - Containing Federal "Listed" Wastes

Proposed Treatment Standards for Non-RCRA Solid Wastes with Metals

Proposed Treatment Standards for Baghouse Waste

Typical Composition of Refractories

Operating Composition of Liquid Carburizing Baths

Compositions and Properties of Sodium Cyanide Mixtures for Cyaniding Baths

Example Cost Information

Table

Table

-1

2

Table 5-1

Table 5-2

Table 5-3

Table 5-4

Table 6-1

Table 7-1

Table 7-2

Table 9-1

Figure 6-1

Figure 6-2

Figure 6-3

Figure A-I

Figure A-2

Figure B-1

Figure C-I

Figure C-2

FIGURES

Simplified Flow Diagram of the Basic Operations for Producing a Steel Casting

Primary Sources of Waste Sand

Simplified. Process Flow Diagram for the PMET Sand Treatment Process

Foundry Flow Diagram

Air Pollution Control Equipment, Molding and Coremaking Operations

Simplified Flow Diagram for Heat Treating Process at Plant B

Foundry Melt Process Schematic

Plant C Sand System Process Schematic

1-3

1-5

5-2

5-4

5-5

5-6

6-10

7-5

7-7

9-4

6-2

6-12

6-25

A-7

A-0

6-2

c-3

c-7

viii

APPENDICES

A. WASTE REDUCTION ALTERNATIVES ASSESSMENT FOR PLANT A

A.l Process Description A.2 Foundly Waste Streams A.3 A.4 Future Waste Reduction Alternatives:

Present Waste Reduction and Treatment Practices

Sand Reclamation and Detoxification Systems

B. WASTE REDUCTION ALTERNATIVES ASSESSMENT FOR PLANT B

B.1 Austenitizing 8.2 Quenching 8.3 Tempering 8.4 Sandblasting 8.5 Plating and Stripping

FOR PLANT C C. WASTE REDUCTION ALTERNATIVES ASSESSMENT

c.1

c.2

c.3

c.4 c.5

C.6 c.7

Melting C.l.l Process Description and Input Materials c.1.2 Waste Streams' C.1.3 Waste Reduction Coremaking C.2.1 C.2.2 Waste Streams C.2.3 Waste Reduction Mold Making C.3.1 C.3.2 Waste Streams C.3.3 Waste Reduction Pouring

Process Description and Input Materials

Process Description and Input Material

Shakeout C.5.1 Process Description. Input Materials, and Waste Streams . . (2.5.2 Waste Reduction Surface Cleaning Heat Treating

D. WASTE REDUCTION ASSESSMENT FORMAT Table of Contents

E. STATUTES AND REGULATIONS AFFECTING HAZARDOUS WASTE GENERATORS Table of Contents

ORDER FORM FOR HAZARDOUS WASTE CONTROL LAWS AND REGULATIONS

F.

G. TOXIC SUBSTANCES CONTROL DIVISION

Page

A-1

A-1 A- 1 A-2

A-5

B-1

B-1 B-1 8-3 0-4 8-5

c-1 c-1 c-1 c-2 C-4 c-5 c-5 C-6 C-6 C-6 C-6 C-6 C-8 C-8 C-8 C-8 C-8 c-9 c-9

D-1 D-1

E-1 E-1

F-1

G-1

ix

APPENDICES (Continued)

H. CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARDS

I. FEDERAL AND STATE AGENCIES

J. ACRONYMS

K. WASTE REDUCTION INDEX

Page

H-1

1-1 -

J-1

K-1

X

SECTION 1.0

SUMMARY AND CONCLUSIONS

This study identifies and describes waste reduction measures appropriate for California thermal metal working industries. It presents a procedure for assessing a plants processes and improving its waste management system.

The study focuses primarily on source reduction measures, secondarily on recycling techniques, and finally on treatment methods appropriate to thermal metal working plants and processes. This report concentrates on the casting and heat treating industry. These processes are responsible for most of the waste generation from thermal metal operations in California. They require waste reductlon measures different from those described for fabricated metal and metal finishing industries.

Effective waste reduction reduces environmental risk, and includes both technology-based strategies and organizational and management changes within a plant. Creating successful programs involves: 1) careful planning and organization in order to bring management and other groups within the plant together in an effective way; 2) an accurate means of analyzing the companys waste streams, assessing its needs, and selecting appropriate waste reduction measures; 3) selection of realistic, achievable goals; and 4) a means of implementing the program through obtaining the necessary funding and firm support of management, and assembling a waste reduction team that has the technical know-how to make the project a success.

1.1 REGULATORY ASPECTS

The federal, state, and local ordinances and regulations that influence hazardous waste management In the California thermal metal working industry include:

0

0 0

0 0

0 0 0

Resource Conservation and Recovery Act (RCRA) prohibitions on land disposal of untreated waste State of California Hazardous Waste Reduction and Management Review Act Superfund Amendments and Reauthorization Act (SARA) - Title 3, which include emergency planning and community right to know requirements State right-to-know legislation State land disposal restrictions and standards for generators, transporters, and owners or operators of treatment, storage, or disposal (TSD) facilities Discharge requirements set by local Publicly Owned Treatment Works ( P O N S ) Federal regulations governing wastewater discharges and pretreatment standards Clean Water Act control measures for wastewater discharges.

1-1

1.2 WASTE STREAMS AND REDUCTION MEASURES

The major hazardous waste streams from the casting industry include baghouse and/or scrubber wastes associated with the control of air emissions from the furnace, hazardous slags generated during the melting and treatment operation of certain metals, and spent casting sands which can no longer be reused. Waste reduction measures include options such as segregating metal contaminants from the spent casting sands, recycling metal wastes back into the process, and reusing sands for molding purpose. Specific source reduction, recycling, and treatment methods are summarized in Table 1-1 for each hazardous waste category.

The major hazardous waste streams from the heat treating industry include cyanide-containing waste generated in liquid carburizing, cyaniding, and nitriding; spent quenchants and dragout wastes, coating wastes related to selective carburizing or nitriding; and wastes from parts cleaning operations. The source reduction, recycling and treatment options for these wastes are presented in Table 1-2. Effective options include altering process chemicals and minimizing drag-in and dragout losses of chemicals. Waste reduction measures for parts cleaning and coating wastes can be found in the DHS Waste Audit Study on the Fabricated Metal Products Industry (August 1989) and the USEPA report on Waste Reduction in Parts Cleaning Operations

The focus of this study did not include examination of forging, tempering, and rolling processes because the hazardous wastes generated from them and waste reduction alternatives are covered under operations already examined in this report.

1.3 WASTE REDUCTION ECONOMICS

(1 989).

Cost savings associated with many waste reduction measures provide strong arguments for their use. Typical benefits include reduction or avoidance of: 1) treatment, storage, and disposal fees; 2) transportation costs; 3) raw material costs; 4) insurance and liability costs; and 5) excessive operating costs resulting from inefficient processes. For this study, assessments were made of three plants - a ferrous foundry, a heat treating plant and a nonferrous foundry. The assessments revealed the monetary and environmental benefits that can be derived from implementing waste reduction. Reductions in waste volumes and landfill disposal costs were measured for the ferrous foundry. Recycling of hazardous slag and baghouse dust from the heat resistant alloy production line, where induction furnaces are employed, to a cupola furnace producing gray iron reduced disposal costs by approximately $17,000 per year.

Reduction in waste volumes were also measured for the non-ferrous foundry. Reclamation of metals at brass foundry by use of an existing ballmill system allowed the company to save $1 57,000.

1.4 WASTE REDUCTION ASSESSMENT FORMAT

The format provided in Appendix D can help plant staff to identify the waste reduction measures most appropriate for their thermal metal working processes, as well as providing them with procedures for estimating the profitability of such methods, and for implementing them.

-

1 -2

TaDle 1-1


Waste Stream Alternative Method* Reference

Baghouse Dust and Scrubber Wastes Use induction furnace

Alter raw materials

Recycle to original process Recycle outside of original process (pyrometallurgical methods, rotary kiln technology, electrothermic shaft furnace, llll zinc oxide enrichment)

'

Hazardous Slags

Recycle to cement manufacturer Cement-based chemical stabilization Umelpouolan-based chemical stabilization Chemical reduction Precipitation using magnesium hydroxide (solubility control) Polysilicate treatment at the cupola furnace stack Sulphating process for zinc in EAF dust Thermoplastic binding Encapsulation

Alter feed stock Alter desulfurization agent Alter product requirements Improve process control

SR SR R

R

R T T T

T T T T T

SR SR SR SR

Stephens 1988 USEPA 1985. Danielson 1973

Morris 1985, Chaubal 1982, Kellogg 1966, Krishnan 1982 and 1983, Miyashita 1976, Bounds 1983 Kelly 1989, AFS 1989

Stephen 1984

Turpin 1985, Edige 1989 Appendix C Chaubal1982 USEPA, 1988 Chaubal 1982

Stephens 1988 Stephens 1988 Stephens 1988 Stephens 1988

SR = Source Reduction R = Recycling T =Treatment

I I I

Table 1-1 (Continued)


Waste Stream Alternative Method' Reference

Recycle to process R Recycle to other process line Mix treated desulfurization slag with furnace dust

R T

Improve treatment methods (desulfurization slag quench reactor) T

Spent Casting Sands Alter raw sand Recycle to other process lines Use as a construction material Segregate shot blast from sand waste

Detoxify with sodium silicate Screen sand to remove metal Reclaim metals in mineral acid leaching

followed by metal recovery process Reclaim sand by wet washlnglscrubbing Reclaim sand by dry scrubbinglattriiion Reclaim sand thermally Sodium silicatenime (Furness) process Sodium silicatelpouolime (lrezek) process

A

b. Reuse as ingot molds

SR R R R R T R R

R R R T T

Stephens 1988 Appendix C Stephens 1988

Vondracek 1988, Stephens 1988

DHS 1989 Stephens 1988 Smith 1982 DHS 1989 DHS 1989 DHS 1989 DHS 1989 HazTech News 1988

* SR = Source reduction R = Recycling T = Treatment

Table 1-2

WASTE REDUCTION AND TREATMENT ALTERNATIVES FOR THE HEAT TREATING INDUSTRY

Waste Stream Alternative Method* Reference

Spent Baths and Salt Pots From Case Hardening

Use noncyanide bath Avoid bath contamination (clean all work placed in the bath) Use graphite cover made of artificial graphite powders Dry work completely prior to liquid case hardening Increase longevity of molten bath by periodic removal of sludges Minimize dragout Replace pot lining (use modified basic brick instead of

Chemical treatment of cyanide wastewaters with low cyanide

Electrochemical treatment of cyanide wastewater

ceramic material)

content

with high cyanide contents (> 200ppm) -L rh

Quenchant Waste Minimize dragout of molten salt Minimize dragout of oil used as quenchant Control temperature in oil quenching system

Filter oil and recycfe to the original process Dewater oil by draining, evaporation, or centrifuge separation Employ ultrafiltration for water soluble polymer quenchants Chemicaf treatment of cyanides in spent aqueous and brine

Recover oil in oll/water separator for off-site recycling

5 Use modified quenchants

quenchants

SR SR SR SR SR SR SR

T

T

SR SR SR SR R R R

T T

ASM 1981

DHS 1989

DHS 1989

ASM 1981

* SR = Source reduction R = Recycling T = Treatment

1.5 WASTE REDUCTION INDEX

A waste reduction Index (WRI) was developed for use by foundries to measure the effectiveness of implementing a waste reduction program. The index compensates for variation in productive activity. It can be applied to a specific waste stream, or to a combination of waste streams.

The WRI uses a baseline period from which it can be measured over successive intervals Of time. WRls are developed here for the following waste streams:

0

0

0 iron foundry baghouse waste

brass foundry hazardous sand waste

iron foundry hazardous sand waste

1 -6

SECTION 2.0

RECOMMENDATIONS

In order to achieve maximal reduction of environmental risk, industrial efforts should follow the waste reduction hierarchy of strategies. This entails first identifying and implementing all source reduction techniques appropriate to the plant's processes, then implementing recycling methods, and finally, in order to manage the waste streams that remain, using treatment techniques.

The investigation of waste reduction measures should be started by developing a flowchart showing the various waste stream generation points and establishing the relationships between different operations throughout the entire process. As a next step, a thorough analytical study is recommended to quantify the metallic content in each wastestream if It is not known. It is recommended to focus on waste currently being manifested to landfills (see Section 5.0 for regulatory constraints) since these wastes usually represent the most expensive waste management problems.

In order to assess a plant's waste management needs, and to identify the opportunities that exist for waste reduction, It is recommended that plant staff use the procedure detailed in Appendix D of this report. The procedure focuses on the different industrial processes within a plant, and provides a method for identifying promising waste reduction techniques. The Industrial processes examined in this report include metal casting and heat treating.

21 METALCASTING

The main recommendations for reducing metal casting waste in ferrous foundries are to control the quality of scrap metal used for casting, replace electric arc or cupola furnaces by induction furnaces, and recycle slag and/or furnace dust from pollution control equipment back to the original process or to another process line. For example, slag from electric arc furnaces employed in the production of heat resistant alloy can be added to the feed at cupola furnaces producing gray iron.

The main recommendations for reducing metal casting waste in nonferrous brass foundries are to: 1) segregate spent nonhazardous foundry sand from shot blasting and grinding dust, 2) detoxify hazardous sand, 3) reuse stabilized and detoxified sand in production of Ingot molds, and 4) reclaim metals from metallic rich waste streams. Metallic rich streams include wheelabrator baghouse waste and furnace dust with high zinc contents. Reclamation can be by either physical separation such as screening and/or mineral acid leaching. This generates nonhazardous sand and metallics for use as a furnace feed or for off-site sale.

2.2 HEATTREATING

Source reduction methods that are very effective for heat treating operations include input material control, careful examination of parts drainage and dragout removal of chemicals from cyanide bearing baths and quenching media, thorough drying of workpieces to prevent spattering from high temperature baths, and extension of bath lifetimes through impurity

removal. Recycling of spent process bath solutions, rinsing, filtration, evaporation, desludging and other separation techniques are also very effective methods for reducing waste streams from carburizing, cyaniding, nitriding, quenching, and selective case hardening operations. These and other options are elaborated upon in section 7.0.

2.3 WASTE REDUCTION ALTERNATIVES ASSESSMENT A - NON-FERROUS FOUNDRY This foundry manufactures brass plumbing fiures, using scrap car radiators as raw materials. Waste streams include raw slag, spent casting sands, waste casting metal, floor sweepings, furnace fumes and airborne dust from molding operations.

Floor sweepings are returned to the furnace. Crushing and screening operations are employed to remove and reuse the metal contents of solidified slag and spent foundry sand. Slag dust from these operations is sent to smelters for further metal recovery. Waste foundry sand is also sent out for recovery of Its remaining metal content. Metal reclamation strategies have proved to be cost effective, generally paying for themselves within two years.

Aluminum materials are strictly segregated from process streams, because they can "poison" the brass. Zinc oxide fumes from furnaces are collected in baghouses, and used offsite as an additive for fertilizer manufacturing. Airborne dust from sand molds is collected by hydrofilters employing wet scrubbers and cyclone separators. Reclaimed sand is used again in the molding process.

2.4 WASTE REDUCTION ALIERNATlVES ASSESSMENT B - HEAT TREATING PLANT The plant in this study uses three basic quenching media: oil, water, and a mixture of nitritelnitrate molten salts. Implementation of dragout minimization techniques would reduce both the cost of make-up quenching oil or molten salts media and waste handling cost. The extending of quenching oil life by proper temperature conditioning would prevent formation of carbonaceous contaminations and would reduce subsequent VeatmenVhandling cost. The dragout from oil baths is collected in clarifiers and sent for off-site recycling. On-site recycling such as gravity oil/water separation and subsequent mechanicalnhermal conditioning could bring input material savings and reduced haulage expense.

The plant electroplates some metal workpieces to render them impervious to the carburizing atmosphere in the furnace. Segregation of spent cleaning solutions from plating wastes could reduce the quantity of wastewater to be treated and subsequently the quantity of sludge cake generated for off-site disposal at a Class I landfill.

Plant B is currently investigating the possibility for off-site copper recovery from the sludge by providing the sludge to copper recyclers in Utah, Nevada, and Arizona. However, a minimum metal content in the wastestream is specified as an acceptance criterion. Waste segregation could play an important role in increasing the copper contents in the cake by treating concentrated spent plating solutions rather than a dilute stream commingled with low-metal content cleaning solutions.

2-2

2.5 WASTE REDUCTION ALTERNATIVES ASSESSMENT C - DUCTILE AND GRAY IRON FOUNDRY

This foundry employs one cupola furnace in a gray iron production line. Since July 1988, Plant C has been recycling the hazardous slag from electric induction furnaces in the heat resistant alloy production line by charging the slag to the cupola furnace. This operation separates the metal from the slag, rendering the slag nonhazardous.

At present, experiments are being carried out on the detoxification of residuals from the cyclone scrubber, part of the cupola furnace pollution control system. Silicate treatment technology is being employed to immobilize lead, zinc, cadmium and other heavy metals carried over with the gases and particulates from the stack. A sodium nitratehydrated lime solution Immobilizes these elements in the quench zone of the stack at temperatures above 1,300"F. This process has been shown to reduce the nonfixated zinc and cadmium content to desired levels. The plant is presently working on Improving the efficiency of lead fixation.

The hazardous sand from dust collection in heat resistant alloy production line is segregated from other foundry non-hazardous sand and is recycled as a feed component to the cupola furnace.

2.6 REGULATIONS

Hazardous waste, worker health and safety, and other environmental and safety requirements change continually at the state, federal, and local level. The generator must keep up-to-date on these changes, and also must maintain flexibility regarding its waste management options to accommodate such changes.

2.7 ADVANCING TECHNOLOGY

The generator should keep abreast of improved technology in hazardous waste reduction and management. Information sources include trade journals, chemical and equipment suppliers, equipment expositions, conferences, and industry association newsletters. Advancing technology can provide the generator with cost-effective alternatives for Improved operations that can lead to less waste generation and greater competitive advantage.

2-3

SECTION 3.0

INTRODUCTION

3.1 STUDY PURPOSE

The purpose of this study is twofold: to investigate waste reduction methods currently used in thermal metal working industries and to develop a set of worksheets to be used by plant staff to identify opportunities to reduce waste.

3.2 INDUSTRY OVERVIEW

Thermal metal working industries are categorized as follows under the Standard Industrial Classification (SIC) System:

0 332, 336: foundries, casting

0 3398: metal heat treating

0 346: forgings, stampings

0 3493, 3495: springs

0 331, 335: rolling, drawing, extruding, finishing

According to -3 for California, published by the U.S. Department of Commerce, Bureau of the Census, there were 279 nonferrous foundries (SIC 336), 96 iron and steel foundries (SIC 332), 116 establishments under SIC 339 categoty (heat treating, grinding), 114 establishments under SIC 331, 105 under SIC 335, and 493 under SIC 346.

3.3 PROJECT APPROACH

This study analyzes: 1) source reduction techniques that allow thermal metal working industries to minimize or prevent hazardous waste generation within their industrial processes; 2) recycling techniques that convert potential waste streams into usable process materials; and 3) treatment techniques that render remaining wastes less hazardous.

Source reduction methodologies that prevent or minimize generation of hazardous waste at its point of origin receive the primary focus in this report, because it is these techniques that are widely considered to be the most promising for reducing adverse impacts of hazardous wastes on the environment (SA6 1988, EPA 1988). Ffecycllng methods are treated as next in importance. Both source reduction and recycling reduce the quantity of hazardous waste escaping from the industrial process where it is generated. Finally, treatment methods are discussed for reducing the environmental impact of wastes that do escape the process.

This report examines waste reduction applicable to a large segment of the thermal metal working industry. Cross index information has been developed on types of operations and

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relevant hazardous wastes generated by the thermal metal working industry versus waste reduction and treatment techniques that have been already developed in previous DHS and EPA Waste Audit Studies. it was found that the metal casting and heat treating industry generate the most thermal metal Industry-specific wastes that are totally different from those that have already been studied.

3.4 FOCUS

This report focuses on processes associated with thermal metal working. From the business patterns data reported in Section 3.2, and from examination of the waste streams of the different industrial processes listed &I Section 3.2, it appears that the processes that are both common in California, and generate significant hazardous wastes are: . Ferrous foundry processes . Nonferrous foundry processes . Heat treating. The study does not include examination of the primary metal industry, which is practically nonexistent in California. The establishments registered in California under primary metal SIC codes were found during this study to function as interstate product exchange sales offices and do not represent hazardous waste generators under the SIC codes of interest to this study.

The report does not address processes altering the surfaces of metal workpieces to prepare them for assembly into the finished products. These processes are covered in detail in the following Waste Audit Study reports, which are available from the DHS Alternative Technology Division:

1. 2. 3. 4. 5.

6. 7.

3.5

Waste Audit Study: Automotive Paint Shops Waste Audit Study: Metal Finishing Industries Waste Audit Study: Fabricated Metal Products Industry Waste Audit Study: Precious Metal Products and Recycling Guide to Solvent Waste Reduction Alternatives, Final Report and Symposium Proceedings Guide to Oil Waste Management Alternatives, Final Report and Symposium Proceedings Reducing Californias Metal Bearing Waste Streams, Final Report and Symposium Proceedings.

FORGING, TEMPERING AND ROLLING

Forging, tempering, and rolling processes were not included as separate sections in this report because any significant hazardous waste streams generated appear to be covered under operations already examined in the report (for instance, quench oils are covered in Section 7.0).

. 3-2

SECTION 4.0

INDUSTRIAL WASTE REDUCTION PROGRAMS

4.1 ENVIRONMENTAL BENEFITS

The benefits of waste reduction can be understood in terms of environmental risk reduction. Risk reduction is the lessening of potential dangers to human health and the environment. It includes both technology-based strategies, and those that involve organizational and management changes within a company. The latter includes better worker training programs or segregation of waste streams. Whatever methods are used, waste reduction programs can benefit the environment by:

0 preventing the generation of wastes, residues, and contaminants that, If released, could pose a threat;

recycling and reusing wastes by feeding them back as raw materials into 0 industrial processes. ?

4.2 PROGRAM REQUIREMENT

There is a continuum of activities that individual workers, groups of workers within a plant, and the plant as a whole can engage in to reduce health and environmental risks. But in order for these activities to take place, an effective organized risk reduction program is essential.

To create a successful program, attention must be paid to the following steps:

0 Planning and Organization 0 Assessment of Needs 0 Selection of Attainable Goals 0 Implementation

Because a waste reduction program impacts many functional groups within a plant, the planning and organizational phase of the program needs to bring these groups together in an effective way. Although the complexity of the program depends on the size and waste problems of the plant, it is critical to have a strong management commitment to support the program. The potential benefits from a serious waste reduction program that often convince management to lend their support include economic advantages, improved regulatory compliance, reduction in liabiliies associated with generation and disposal of hazardous waste, improved public image, and reduced environmental impact (USEPA 1988).

Assessment of a companys waste reduction needs includes examining the content and volume of hazardous waste streams it generates, and the processes or operations that generate them. The object of this step is to prioritize the needs of the company, based on environmental risk, liability, and economic criteria.

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The assessment phase also includes identification of waste reduction methodologies that appear promising for solving the particular problems of the plant. Once the origins and causes of waste generation are understood, it is possible to identify possible ways to minimize waste in the assessed areas. Many of the ideas and knowledge on how to do this can come from plant staff with hands-on knowledge of the company's operations. This Is supplemented through use of the technical literature and contacts with trade associations, state and local environmental agencies, consultants and equipment vendors.

Selection of the program's goals Is done through analysis of the technical and economic feaslblllty of the waste reduction options Identified. Technical evaluation determines whether a proposed option is possible to Implement (i. e., is the necessary equipment and/or expertise available), and whether it will work in a specific application. Economic analysis is conducted using standard measures of profitability such as payback period, return on investment and net present value.

Successful Implementation of waste reduction methodologies depends on several factors, most notably obtaining the necessary funding. Waste reduction is generally accompanied by process efficiency improvements and cost reductions. Nevertheless, the company's capital resources may be tied up elsewhere. 11 is essential to know the level within an organization that has approval for capital projects, and to have a team that can present the financial, technical and environmental benefits in such a manner as to sell the project to management.

4.3

In order to aid companies and other organizations in creating effective waste reduction programs, the Environmental Protection Agency has developed a recommended procedure for identifying and implementing source reduction and recycling applications that includes the steps discussed In the previous section. The agency has published a detailed EPA Manual for Waste Reduction Omortunity Assessments (1968) that outlines this procedure in depth. The manual employs a series of worksheets that guide plant engineers or other staff personnel through the methods for evaluating promising waste reduction strategies. The manual also includes methodologies for analyzing the feasibility of potential options on economic and technical bases as well. An extensive opportunity assessment is a valuable, effective tool for choosing the best waste reduction strategies for a particular plant.

THE WASTE REDUCTION OPPORTUNITY ASSESSMENT

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SECTION 5.0

REGULATORY ASPECTS

5.1 REGULATORY CAVEAT

All text pertaining to laws and regulations contained within this report are provided for general information only. The information provided here is not reliable for use as a legal reference. The generator must contact the appropriate legal sources and regulatory authorities for up-to- date regulatory requirements, and their Interpretation and implementation.

5.2 LAWS, REGULATIONS AND ORDINANCES

A variety of federal, state, and local laws, regulations and ordinances influence hazardous waste management and waste reduction in the thermal metal working industry. These include: the Federal Resource Conservation and Recovery Act (RCRA) and its amendments, which prohibit land disposal of untreated hazardous wastes; the State of Californias land disposal restrictions and standards set for generators, transporters, and owners or operators of treatment, storage, or disposal (TSD) facilities; the Federal Clean Water Act, which requires water quality control for wastewaters discharged to surface waters or municipal sewers; and the State of California Hazardous Waste Reduction and Management Review Act of 1989 (known as Senate Bill No. 14, signed into law on October 1, 1989). Appendix E identifies major environmental regulatory requirements that affect hazardous waste generators. This section summarizes existing and proposed land disposal restrictions and new waste reduction rquirements that affect the thermal metal working Industty.

5.2.1 Land Disposal Restrictions lExistina and ProDosed)

To facilitate the movement away from land disposal and to spark development of alternative methods for managing hazardous waste, the State of California passed a number of laws and regulations restricting land disposal and emphasizing alternative management methods. These restrictions have caused increases in waste disposal costs, since the restricted wastes now require some form of treatment prior to land disposal. These increased waste disposal costs are viewed as a driving force for the thermal metal working industry to implement waste reduction technologies.

The State of Californias original restrictions prohibited the land disposal of: liquids containing cyanide, certain metals, certain acids, PCBs; and liquids and solids containing halogenated organics (California Code of Regulations (CCR) 566900 et seq). The regulations specify the waste concentrations and schedule of restrictions. The State of Californias most recent Land Disposal Restrictions, described in the Hazardous Waste Management Act of 1986 expand the original restrictions by prohibiting land disposal of all untreated hazardous wastes in California.

The Hazardous Waste Management Act of 1986 required the California Department of Health Services to prohibit the land disposal of all untreated hazardous waste on or before May 8, 1990 and to specify the standards or treatment levels for treating hazardous waste prior to land disposal. The summary of the proposed treatment standards that would affect the thermal

.. 5-1

metal working industry is presented below.

5.2.1.1 Treatment Standards for Foundry Sand

RCRA Waste

If waste foundry sand Is a RCFIA waste (hazardous according to Federal criteria) it is subject only to applicable Federal land disposal restrictions (40 CFR Part 268). The Federal treatment standards were promulgated on May 8, 1990 with a 9O-day extension. The sand may be considered hazardous according to the federal criteria if it contains any of the eight metals identified in 40 CFR I 261.24 above the federal thresholds or exhibits any other hazardous characteristics pursuant to 40 CFR Part 261, Subpart C.

Non-RCRA Waste

Waste foundry sand is hazardous by State standards if it exhibits the characteristics delineated in CCR Title 22, Article 11.

The following treatment standards have been developed for metal levels in non-RCRA hazardous waste foundry sand. The prohibition date for land disposal of untreated non-RCRA hazardous waste foundry sand is January 1, 1991.

Table 5-1

Treatment Standards for Non-RCRA Hazardous Waste Foundry Sand

Waste Extraction Test (WET)

mg/L

Copper 200 Lead 30 Zinc 250 Cadmium 1 .o Nickel 20

The treatment standards for waste foundry sand are based on sand reclamation and metal recovery used in conjunction with chemical stabilization applied to the unrecoverable waste fraction. Generators will be required to meet the treatment standards before disposing of the waste to the land. Wastes managed by methods other than land disposal are not subject to the treatment standard.

A waste that meets its treatment standards may be disposed of in a land disposal facility. If untreated waste meets the standards, then It does not have to be further treated prior to disposal. If a waste does require treatment, any technology may be used-not necessarily the Best Demonstrated Available Technology (BDAT).

-

. 5-2

To determine if a waste meets the treatment standards, representative samples must be tested by a certified hazardous waste testing laboratory using the California Waste Extraction Test (Wq procedure as described in CCR 566700. Representative samples are defined as exhibiting average properties of the whole waste (EPA 1985).

if a sample of waste foundry sand contains hazardous concentrations of contaminants other than the five metals included in these treatment standards, the waste will also be subject to appropriate treatment standards for solids with metals, solids with organics, aqueous wastes with metals, and/or aqueous wastes with organics. Standards tor solid wastes with metals are given below as an example.

5.21.2 Treatment Standards for Solld Wastes with Metals

RCRA Solid Wastes with Metals

RCRA solid wastes with metals include "characteristic" wastes (D wastes) and "iisted" wastes (K and F wastes). The characteristic wastes are those containing any of the eight RCRA metals above the extractable concentrations (EP Toxicity levels) identified in 40 CFR Part 261.24. Although the EP levels are numerically the same as California's STLC levels in Section 66699 Titie 22, CCR, California's extraction procedure is more aggressive than EPA's. Therefore some wastes containing the eight metals are hazardous only in California.

EPA treatment standards for some "listed" metal-bearing wastes are given in Table 5-2; Foil waste is generated from metal heat treating operations. The Federal standards for these wastes are based on the Toxicity Characteristics Leaching Procedure (TCLP).

Non-RCRA Solid Wastes with Metals

Non-RCRA solid wastes with metals are those solid wastes containing metal compounds that are not regulated by EPA as hazardous wastes.

It has been proposed that non-EPA-regulated metal-containing solid wastes other than the waste generated from air pollution control equipment, auto shredder waste, foundry sand, incinerator ash and sulfur sludge be subjected to the treatment standards in Table 5-3.

Wastes containing EPA-regulated metals may become non-RCRA wastes if the concentrations of extractable metals are below the EP toxicity limits but exceed the STLC levels using the WET test or the TTLC levels. Non-RCM standards are based on the California Waste Extraction Test (WET) procedure.

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..

Table 5-2

EPA's Treatment Standards for Some Metal-Containing Federal "Llsted" Wastes

TCLP, max. ppm

FOO6 KO46 KO61 KO62 KO71 KO86 KIOI 8K102 KO48-KO52 KO01 KO22 Foil sludge sludge dust sludge sludges ash ash (low As) ash sludge ash sludge

Sb As 0a Be cd 0.066 Cr" ~ r ' ' Cr. total 5.2 co cu Pb 0.51 Hg Mo

Se NI 0.32

Ag 0.072 Th V Zn CN. total

- - - 0.14

5.2

0.24

0.32

- -

0.094 - 0.37

-

0.025

-

0.066

0.094 5.2

- 0.37 0.51

0.32

0.004

1.7

0.048 0.025

5.2

0.51

- 0.32

- -

0.066

5.2

0.51

0.32

0.072

110 CN; amenaMe 9.1

m: KO62 and KO71 sludges did not need stablllzatbn because of very low TCLP values of raw wastes (metal sulfdes) Data Source: Federal Register, Volume 53, No. 159, August 17. 1988.

I I I

Table 5-3 Proposed Treatment Standards for Non-RCRA Solid Wastes with Metals

Propased Treatment standards

Metals STLC, mal WET, mSn, merage

Arsenic Barium Cadmium Chromium (VI) Lead Mercury Selenium Silver Antimony Beryllium Chromium (Ill) Cobalt Copper Molybdenum Nickel Thallium Vanadium Zinc

5.0 100.0

1 .o 5.0 5.0 0.2 1 .o 5.0

15.0 0.75

560.0 80.0 25.0

350.0 20.0 7.0

24.0 250.0

15.0 100.0

1 .o 5.0

67.0 0.2 1 .o 5.0

15.0 0.75

560.0 80.0

230.0 350.0 20.0 7.0

24.0 250.0

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5.2.1.3 Proposed Treatment Standards for Baghouse Waste and Gas Scrubber Waste.

Treatment standards are proposed for the California Waste Code (CWC) 591 that is designated for baghouse waste. Baghouse waste refers to the dust that is collected in a baghouse or other dry air pollution control devices. Baghouse waste is being divided for the purposes of the proposed treatment standard into baghouse waste from sources other than foundries and baghouse waste from foundries.

The non-RCFM hazardous wastes include fly ash, bottom ash, retort ash, baghouse waste and gas scrubber waste that contain any of the metals or metal compounds listed in Section 66699(b), Tile 22, California Code of Regulations (CCR), if any of the metals exceed the criteria given in Section 66699(a), Tile 22, CCR. The proposed treatment standards for non-RCRA baghouse waste are summarized in Table 5-4.

Table 5 4

PROPOSED TREATMENT STANDARDS FOR BAGHOUSE WASTE

Metals From Foundries Other Sources

WET, mg/l WET, mgll

Arsenic Cadmium Copper Lead Nickel Selenium Vanadium Zinc

15 1

350 70 20

1 24

250

15 1

40 20 20 1

24 250

Hazardous wastes that are RCRA wastes are only subject to the Federal land disposal restrictions (40 CFR Part 268) unless the RCRA waste is mixed with a non-RCRA waste. EPA established treatment standards for RCRA characteristic wastes on May 8, 1990.

5.2.2 Waste Storaae

Many of Californias hazardous waste storage requirements, including permits, training, contingency plans, and record keeping, apply to businesses that store hazardous wastes in tanks or containers (e.g. drums) for longer than 90 days on-site. The time period for calculating the S w a y period begins when the business has accumulated 100 kilograms of hazardous waste or one kilogram of extremely hazardous waste or acutely hazardous waste. The exception to this is if the business generates more than the above-specified quantities during

-

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any calendar month. Then, the time period begins when any amount of hazardous waste first begins to accumulate in that month (25123.3 CHSC).

Waste quantities below the levels mentioned above are not subject to the 90-day accumulation time limit. If sufficient waste reduction measures are implemented, businesses that are small quantity generators might take a long time to reach the 90-day accumulation limit. Therefore, these accumulation time limits may encourage waste reduction for many businesses.

5.2.3 Waste Transoort

Small quantities of wastes are usually accumulated in drums. Waste transport fees are typically based on the number of drums to be picked up. Often shipments of fewer than 10 to 15 55- gallon drums are charged a higher transport rate. Smaller thermal metal working businesses that are not permitted storage facilities and, thereby avoid the 90-day accumulation time limit may be exposed to high waste management costs. It may not appear to be in the interest of these businesses to implement waste reduction measures.

Other statutory requirements that have become a priority are the federal Superfund Amendments and Reauthorization Act (SARA) emergency planning and community right-to- know requirements, as well as State of California citizens right-to-know legislation. The state law requires local governments to implement programs to regulate hazardous materials storage (Chapter 6.95, Div. 20, CHSC). These regulatory programs may affect facilities in two ways: (1) compliance with the local programs will often require capital investments to upgrade the facilities and will require time for the facilities to develop their permit applications and hazardous materials management plans; and (2) since the local programs permit fees are based on the types and quantities of hazardous materials stored at facilities, decisions on source segregation and batch treatment of wastes, and the storage and use of hazardous materials will be influenced by these local programs. The impact of item (1) above may be a reduction in the capital and time that facilities are able to allocate to implementing waste reduction. On the other hand, because of the additional public scrutiny, there is added incentive to implement source reduction and recycling techniques that can reduce the quantities of hazardous materials present at the facilities, and thus, the associated liabilities as well. Source reduction techniques that might be especially encouraged by the right-to-know legislation are material substitutions that replace hazardous chemicals with nonhazardous ones which are able to perform the same functions. Item (2) above could also both discourage and encourage waste reduction. Segregation of materials and batch treatment may require additional storage tanks. This could increase storage permit fees and exposure to liability costs due to spills or other releases. Alternatively, storage permit fees may encourage facilities to reduce their material inventories and waste generation to minimize their permit costs.

5.2.4 Waste Reduction

On October 1,1989, Senate Bill No. 14 sponsored by Senator Roberti was signed into law by Governor Deukmejan. This law emphasizes prevention of generation of hazardous waste through source reduction methods that include changing input materials, process modifications, operational improvements and product reformulation. The bill stresses source reduction approaches over more traditional waste management approaches such as recycling and detoxification by treatment.

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The following is a summary of key SB14 requirements:

1. Every generator in the state responsible for more than 12,000 kg of hazardous waste routinely generated in a calendar year (or 12 kg/year of extremely hazardous waste) will be required to conduct and document a source reduction evaluation review and prepare a souce reduction plan by September 1, 1991 and every four years thereafter.

The reviews will list the types and quantities for all major hazardous waste streams 0.0, those greater than 5% of total volume) which are generated routinely. Feasible source reduction measures for each listed hazardous waste stream will be identified and characterized including the rationale for either adoption or rejection. The plans will set forth the implementation timetable.

Waste management performance reports must be prepared by September 1,1991, and every four years thereafter. The reports will document the assessment of the effects of each hazardous waste management measure implemented on waste generation and will also address contributing external factors, such as changes in business activity, waste classification and natural phenomena.

All reviews, plans and performance reports must be certified by a registered professional engineer or other qualified professional.

All reviews, plans and performance reports can be requested by the administering agency. Failure to comply with such request within 30 days may result in enforcement actions and the fine of $1 ,OOO per day of violation.

Confidential business Information will be protected from public disclosure.

2.

3.

4.

5.

6.

The source reduction evaluation review and plan conducted and completed for each site shall include:

1. Identification of all routinely generated hazardous waste streams which result from ongoing processes or operations that have a yearly volume exceeding 5% of the total yearly volume of hazardous or extremely hazardous waste generated at the site.

2. For each hazardous waste stream: '

a. estimate of the quantii of hazardous waste generated

b. evaluation of potentially viable source reduction approaches available to the generator including:

1) Input material changes

3) Production process changes 4) Product reformulation

2) Operational improvements -

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3. Specification of and rationale for technically feasible and economically practicable source reduction measures which will be implemented by the generator with respect to each hazardous waste stream identified

Full documentation of any statement explaining the generators rationale for rejecting any available source reduction approach

Evaluation and quantification of the effects of the chosen source reduction method on emissions and discharges to air, water or land

Timetable for making reasonable and measurable progress towards implementation of the selected source reduction measures.

Review and certification by a professional engineer or by an environmental assessor who has demonstrated expertise in hazardous waste management.

4.

5.

6.

7.

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SECTION 6.0


6.1 DESCRIPTION OF HAZARDOUS WASTE GENERATION PROCESSES

The majority of hazardous wastes generated by the metal casting industry are from foundry operations. Foundries range in size from small job shops to the large manufacturing plants that turn out thousands of tons of castings each day. Most California foundries fall in the small to medium size range, and many are jobbing foundries (as opposed to captive suppliers).

Generation of hazardous wastes is directly related to the type of material melted (pig iron, steel, brass or aluminum), and depends on the types of molds and cores used as well the as technology employed. Although there may be differences in certain plants, basic foundry operations typically include: patternmaking, molding, core making, melting, pouring and cleaning. In California, the metal casting industry is based on the use of secondary (recycled) metals. In addition to foundries, many plants engaged in metal fabrication do their own casting.

Figure 6-1 presents a simplified flow diagram of the basic operations for producing a sand casting. The process begins with the patternmaking. A pattern is a specially made model of the component to be produced, and is used for generating molds. Generally, sand is placed around the pattern and, in the case of clay-bonded sand, rammed to the desired hardness. In the case of chemical binders, the mold is chemically hardened after light manual or machine compaction. Molds are usually produced in two halves so that the pattern can be easily removed. When these two halves are reassembled, a cavity remains inside the mold in the shape of the pattern.

Internal passageways within a casting are formed by the use of cores. Cores are parts made of sand and binder that are sufficiently hard and strong to be inserted in a mold. Thus, the cores shape the interior of a casting, which cannot be shaped by the pattern itself. The patternmaker supplies core boxes for the production of precisely dimensioned cores. These core boxes are filled with specially bonded core sand and compacted much like the mold itself. Cores are placed in the drag, .or bottom section of the mold, and the mold is then closed by placing the cope, or top section, over the drag. Mold closing completes the production of the mold, into which the molten metal is then poured.

Casting production begins with melting of the metal. Molten metal is then tapped from the melting furnace into a ladie for pouring into the mold cavity, where it is allowed to solidify within the space defined by the sand mold and cores. Cupola furnaces, electric arc furnaces (EAFs), hearth (reverberatory), crucible, and induction furnaces are all typical in the industry, and are described below:

.

6 1

Figure 6-1 S

IMP

LIFIED

FLOW

DIA

GR

AM

OF THE B

AS

IC

OP

ER

ATIO

NS

FOR

PR

OD

UC

ING

A STEEL C

AS

TING

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n e cuoola furnace Is the oldest furnace used in the metal casting industry (patented in 1794). It is still employed for the production of ferrous metals such as gray iron. It Is a fixed bed cylindrical shaft furnace where alternate layers of metal along with replacement coke are charged at the top. The metal is melted by direct contact with the countercurrent flow of hot gases from the coke combustion. The molten metal collects In the well, where It Is discharged for use by intermittent tapping or by continuous flow. Conventional cupolas are lined with refractory to protect the shell against abrasion, heat, and oxidation. The lining thickness ranges from 4.5 to 12 inches. The most commonly used lining is fireclay brick, or block. As the heat progresses, the refractory lining in the melting zone is progressively fluxed away by the high temperature and oxidizing atmosphere. Spent lining is a significant source of wastes generated by foundries. This material is usually disposed of as non-hazardous wastes.

The cupola fumace Is generally equipped with an emission control system. The two most common types of collection are the high-energy wet scrubber and the dry baghouse. High quality foundry grade coke is used as a fuel source. The amount of coke in the charge usually falls in a range of 8 to 16% of the metal charge. In cupola fumaces (see Figure C-1 in Appendix C), coke in the metal feed is used as a source of fuel. The burning of the coke is Intensified by the blowing of oxygen enriched air through nozzles.

Flectric arc fumaces are used by ferrous foundries and steel mills. Heat supplied to the fumace during melting Is provided by an electrical arc established from three carbon or graphite electrodes. The fumace is lined with refractories that deteriorate during the foundry process, thereby generating some of the slag. The slag is a protective nonmetallic residue resulting from the mutual dissolution of flux. Flux is used to remove undesirable substances such as sand, ash, or dirt and nonmetallic impurities. The slag serves to protect the molten metal from the air and to extract certain impurities. Depending upon the type of melting, fireclay, alumina, silica, or other types of refractories are used. The removed slag is a waste.

Along with metal scrap and shop retums (such as heads, gates, and casting scrap), a carbon raiser (carbon rich scrap) and lime or limestone are added to the furnace charge. Fume and dust collection equipment at the electric arc furnace is required to control air emissions.

hduction fumaces have gradually become the most widely used means for melting iron and, increasingly, nonferrous alloys. This furnace has excellent metallurgical control coupled with a relatively pollution-free operation. Induction furnaces are available in a wide range of sizes. Coreless units having a capacity of a few pounds are favored by the precision cast metal producers. Large coreless units range up to 75 tons powered at 21,000 KW. In a coreless furnace, the refractory-lined crucible is completely surrounded by a water-cooled copper coil. Channel type units have with the coil surrounding a small appendage of the unit called an inductor. They have been built with a capacity of over 200 tons powered at 4,000 KW per inductor.

.. 6-3

Induction furnaces are alternating current electric furnaces. The primary conductor is a coil. It generates a secondary current by electromagnetic induction that develops heat within the metal charge. Typically used refractories are oxides of silica (SO,), which is classified as an acid, alumina (A120J, classified as neutral, and magnesia (MgO) classified as a basic material. Silica Is the clear choice in iron melting because it does not readily react with the acid slag typically produced In high-silica iron. Alumina is the usual choice for aluminum melting furnaces.

Reverberatow fhearth) and crucible furnaces are widely used furnaces for batch melting of nonferrous metals such as aluminum, copper, zinc, and magnesium. In a crucible furnace, the molten metal is contained In a pot-shaped shell (crucible). Electric heaters or fuel-fired burners outside the shell generate the heat that passes through the shell to the molten metal. In many metal-melting operations, slag or dross buildup develops at the metal surface line and heavy unmelted slush residue collects on the bottom. Both of these residues shorten crucible life and must be removed and either recycled or managed as wastes.

Regardless of the type of furnace employed, the melting operations are similar. Recycled scrap metal along with fluxing agents are charged to the furnace for melting. Inside the furnace, fluxing agents help to remove nonmetallic impurities such as sulfur from the melt. The mixture of fluxing agent and impurities, known as slag, floats on the surface of the molten metal and protects it from oxidation. In some operations, degassing of the metal is performed either under vacuum or by purging with inert gas such as nitrogen or argon. The object of degassing is to remove oxygen from the metal.

Once the molten metal has been treated to achieve the desired properties, lt is poured into a mold or cast. Casting materials may include silica sands, chromite sands, heat-cured furan, or phenolic resins, or many other heat resistant materials. These materials are often mixed with a clay or organic resin binder and pressed around a pattern of the part. When cured, the pattern is removed, leaving a cavity In the sand mold. In some casting operations, the pattern remains inside the mold and is burned out by the molten metal. Once the poured metal has solidified and cooled, the casting is shaken out of the mold, and the risers and gates are removed. Risers (also called Veeders") are shapes that are attached to the casting to provide a liquid-metal resewoir and control solidification. Metal in the risers is needed to compensate for the shrinkage that occurs during cooling and solidification. Gates are the channels through which liquid metal flows into the mold cavity proper. Heat treatment, cleaning, finishing, and inspection are usually the final steps in producing a sand casting.

After casting, the metal part is very often subjected to blast cleaning so as to remove any casting sand, metal flash, or oxide. Blast cleaning of castings is a process in which abrasive particles, usually steel shot or grit are propelled at high velocity to impact the casting surface and thereby forcefully remove surface contaminants. For aluminum castings, the process is often used to provide a uniform cosmetic finish in addition to merely cleaning the workpiece. This is especially true of engine components such as heads and manifolds. Cast components sometimes require special surface characteristics such as resistance to deterioration or an appealing appearance. This is achieved by coating of castings. The most important - prerequisite of any coating process is cleaning of the surface.

6-4

The choice of cleaning process depends not only on the types of soil to be removed but also on the characteristics of the coating to be applied. The cleaning process must leave the surface in a condition that is compatible with the coating process. For example, If a casting is to be treated with phosphate and then painted, the cleaning process must remove all oils and oxide scale because these Inhibit good phosphating.

If castings are heat treated before they are coated, the choice of heat treatment conditions can influence the properties of the coating, particularly a metallic or conversion coating. In most cases, heat treatment should be done in an atmosphere that is not oxidizing. Oxides and silicates formed during heat treating must be removed before most coating processes.

Molten salt baths are used for cleaning complex interior passages in castings. in one electrolytic, molten salt cleaning process, the electrode potential is changed so that the salt bath is alternately oxidilng and reducing. Scale and graphite are easily removed with reducing and oxidizing baths, respectively. Molten salt baths are fast compared to other nonmechanical methods, but castings may crack if they are still hot when salt residues are rinsed off with water.

Pickling in an acid bath is usually done prior to hot dip coating or electroplating. Overpickling should be avoided because a graphite smudge can be formed on the surface. Cast iron contains silicon; therefore, a film of silica can form on the surface as a result of heavy pickling. This can be avoided by adding hydrofluoric acid to the pickling bath. Special safety and environmental protection regulations must be met when using pickling.

Chemical cleaning is different from pickling because, in chemical cleaning, the cleaners attack only the surface contaminants, not the Iron substrate. Many chemical cleaners are proprietary formulations, but in general they are alkaline solutions, organic solvents, or emulsifiers. Alkaline cleaners must penetrate contaminants and wet the surface in order to be effective.

Organic solvents that were commonly used in the past Include naphtha, benzene, methanol, toluene, and carbon tetrachloride. These have been largely replaced by chlorinated solvents, such as those used for vapor degreasing. Solvents effectively remove lubricants, cutting oils, and coolants, but are ineffective against such inorganic compounds as oxides or salts. Emulsion cleaners are solvents combined with surfactants; they disperse contaminants and solids by emulsification. Emulsion cleaners are most effective against heavy oils, greases, slushes, and solids entrained in hydrocarbon films. They are relatively ineffective against adherent solids such as oxide scale.

After wet cleaning, short-term rust prevention is accomplished by the use of an alkaline rinse. This can be followed by mineral oils, solvents combined with inhibitors and film formers, emulsions of petroleum-base coatings and water, and waxes.

The following coating operations are used:

0 electroplating 0 hot dip coatings 0 hard facing 0 thermal sprayed metals and ceramics

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0 diffusion coatings 0 conversion coatings 0 porcelain enamelling 0 organic coatings 0 fused dry-resin coatings

Waste reduction and treatment options for these processes have already been investigated - the reader is referred to the DHS studies listed in Section 3.4.

6.2

The major wastes generated in the casting process include baghouse and/or scrubber wastes associated with the control of air emissions from the furnace, hazardous slags produced during the melting and treatment operation of certain metals, and spent casting sands which can no longer be reused. Metal for melting and sand for core and mold materials are the major input materials of foundries, while product and waste materials make up the output.

INPUT MATERIALS AND HAZARDOUS WASTE CHARAClERlZATlON

6.2.1 lnmt Material Characterization

The major input materials at foundries consist of the following basic components:

0

0

0

0

Core and mold materials such as sand, binders and additives

Furnace charge (e.g., metal scrap), refractories, fuels, fluxes, electrodes

Other materials such as grinding wheels, shot, abrasives

Oil for forklifts, hydraulics, machines.

6.2.1.1 Mold and Core Materials

The refractory molds used in casting consist of a particulate refractory material (sand) that is bonded together to hold its shape during pouring. The most common type of molding process is green sand molding. The term 'green" means that the mold which is tempered with water is not dried or baked. Green sand is composed of four major materials - sand, clay, carbonaceous material, and water. The sand constitutes 85 to 95 percent of the green sand mixture. Most often the sand is inert silica, but olivine (green colored) and zircon sand are also used. Approximately 4 to 10 percent of the mixture is made up of some sort of clay, such as western or southern bentonite, and fire clay. The clay acts as a binder for the green sand, providing strength and plasticity. Carbonaceous materials make up 2 to 10 percent of the green sand mixture. Carbon is added to the mold to provide a reducing atmosphere and a gas film during pouring that protects against oxidation of the metal. Some of the more common carbonaceous materials include sea coal (a finely ground bituminous coal), cereal (ground corn starch), proprietary petroleum products, and wood flour. The final additives of green sand are water, which activates the clay binder and is usually added in small percentages (2 to 5 percent), and cellulose, which controls sand expansion and water content.

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The second type of sand molding process is based on resin binders that include:

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0

0

0

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0

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Furan acid catalyzed no-bake binders. Furfuryl alcohol is the basic raw material. The binders can be modified with urea, formaldehyde, and phenol. Phosphoric acids are used as catalysts. The amount of furan ranges between 0.0 to 2.0 wt% based on sand weight. Acid catalyst levels vary between 20 to 50% based on the weight of binder.

Phenolic acid catalyzed no-bake binders. These are formed in a phenoilformaldehyde condensation reaction. Strong sulfuric acids are used as catalysts.

Estercured alkaline phenolic no-bake binders. These are formed with a two- part binder system consisting of a water-soluble alkaline phenolic resin and liquid ester co-reactants. Typically 1.5 to 2.0% binder based on sand weight and 20 to 25% co-reactant based on the resin are used to coat washed and dried silica sand in most core and molding operations.

Silicate/ester-catalyzed no-bake binders. Sodium silicate binder and a liquid organic ester (glycerol diacetate and triacetate or ethylene glycol diacetate) that functions as hardening agent are used.

Oil urethane no-bake resins that are three component systems consisting of part A, an alkyd oil type resin; Part 6, a liquid amine/metallic catalyst; and Part C, a polymeric methyl di-Isocyanate.

The phenolic urethane no-bake (PUN) binder.

The polyol-isocyanate system (mainly for aluminum, magnesium, and other iight- alloy foundries). The nonferrous binders are similar to PUN system consisting of Part I (a phenol formaldehyde resin dissolved in a special blend of solvents) Part II (a polymeric MDI-type isocyanate in solvents), and Part 111 (an amine catalyst)

Alumina-phosphate no-baked binder. This consists of an acidic, water soluble alumina-phosphate liquid binder and a free flowing powdered metal oxide hardener.

Novoiac shell-molding binders. Phenol-formaldehyde novolac resins and lubricant (calcium stearate in the quantity of 4 to 6% of resin weight) is used as a cross- linking agent.

Hot box binders. The resins are classified as furan or phenolic types. The furan types contain furfuryl alcohol, the phenolic types are based on phenol, and the furan-modified has both. Both chloride and nitrate catalysts are used. The binders contain urea and formaldehyde.

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o Warm box binders. These consist of furfuryl alcohol type resin that is formulated for a nitrogen content less than 2.5%. Copper salts of aromatic sulfonic acids in an aqueous methanol solution are used as catalyst.

The third type of sand molding process is based on unbonded sand molds using a polystyrene foam pattern imbedded in loose unbonded traditional sand. The foam pattern left in the sand mold is decomposed by molten metal.

Core sands are used to produce internal cavities within a casting. The core sands are composed of mixtures of sand with small percentages of a binder. Cores must posses the characteristics of strength, hardness, and collapsibility. Often the cores must be removed within a casting through a small orifice and therefore the sand must collapse after the casting solidifies.

The sand base material for core sands is typically silica sand. Olivine and zircon sands have also been used when specifications require core sands with higher fusion points or densities. Binder materials used to hold the individual grains of sand together vary considerably in composition and binding properties. Oil binders and synthetic binders are most common. Oil binders are combinations of oils from vegetable andlor animal extractions and petrochemicals. Typical synthetic resin binders include phenolics, phenolformaldehyde, urea-formaldehyde, urea- formaldehydeflurfuryl alcohol, phenolic-isocyanate, and alkyd isocyanate. Their composition is very similar to molding sand binders.

Core sand binders will either partially or completely degrade when exposed to the heat of the molten metal during the pouring operation. Once loose, sand that has had its binder fully degraded is often mixed with molding sand for recycling or can be recycled back into the core sand process. Partially decomposed core sands which are removed during the shakeout process and contain only partially degraded binder are called core butts. The core butts can be crushed and recycled back into the molding sand process, or may be taken directly to the landfill for disposal along with broken or offspec cores and core room sweepings. The molding sand and the core sand wastes might account for 66 to 88 percent of the total waste generated by ferrous foundries.

6.2.1.2 Melting Materials (Furnace Charge)

The metallics charge to the furnace varies depending on the type of cast to be produced. In California, the metal casting industry is based on the use of secondary (recycled) metals. As an example, in a basic steel making operation, a typical metallic charge may consist of 30 to 50% shop retums such as heads, gates, and casting scrap and 50 to 70% purchase scrap.

The metal charge to cupolas in ferrous foundry typically consists of foundry returns such as gates, runners, and internally generated scrap castings that usually constitute 30 to 50% of the pouring weight; pig iron, which is considered a premium charge material; cast iron scrap; and steel scrap. -

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Nonferrous foundries are dlfferent from ferrous foundries in that they generally melt ingots from a scrap metal recycling facility. The ingots are much more consistent in metallurgy than typical ferrous scrap.

Refractories are the materials that can withstand high temperatures. They are used to line furnaces and metal pouring ladles. The three essential types of refractories are acid, basic, and neutral. Table 6-1 presents typical compositions of refractories. The refractories are subject to deterioration during the foundry process and, therefore, must be replaced occasionally.

- Fuels are used in certain types of furnaces. In cupola furnaces, petroleum coke is used. In reverberatory furnaces, fuel oil or fuel gas can be used.

Fluxes and flocculants are used to facilitate removal of Inert materials composed of metal oxides, melted refractories, sand, coke ash, and other materials. Typical fluxes include limestone, fluorspar, and soda ash. Silica is also an example of a typical flocculant. In some cases, desulfurization agents, such as calcium carbide, may also be added to the melting ladle to produce ductile iron.

6.2.1.3 Blast Cleaning Materials

In cleaning castings, steel shot is typically used, sometimes a shot and grit mixture is used. In the past, chilled iron grit and malleable abrasives were used. Today, practically all the shot and grit used is high-carbon cast steel that is heat treated and drawn to give a desired tempered microstructure and hardness. Some parts undergo a sandblasting. A proper abrasion-resistant sand is used.

6.2.1.4 Cleaning Solutions and Coating Materials

Molten salt baths, pickling acids, alkaline solutions, organic solvents, and emulsifiers are the basic materials used in cleaning operations. Plating solutions, molten metal baths, alloys, powdered metals, volatilized metal or metal salt, phosphate coatings, porcelain enamels, and organic coatings are used in the coating Industry. The reader is referred to the DHS studies listed in Section 3.4 for more information.

6.2.1.5 Oils

Hydraulic oils for forklifts, hydraulics, and lube oils for machines are used by the metal casting industry. The reader is referred to the "Guide to Oil Waste Management Alternatives, Final Report and Symposiums Proceedings" (see Section 3.4 of this report).

6.2.2 Hazardous Waste Characterization

Foundries manufacture product castings that are sold. The manufacture generates the following wastes:

o Spent system sand from molding and core making operations and used core - sand not returned to the system sand (sweepings, core butts)

o Cleaning room wastes: particulates, abrasives, shots

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Flreclay

Super duty Medium duty Semi silica

Alumlna type (high)

50% 60%

, 70% ,8096 '90%

Mullite Corundum

Slllca type

Silica super duty Conventional

Bask type

Chrome Magnesite

49-56 57-70 72-80

4147 3137 20-26 11-15 7.5-9 1834

0.2-1.0

95-97 94-97

3.0-6.0 0.7-1.0

Magnesite high periclase 0.55.0 Chrome magnesite 44

4044 25-38 18%

47.5-52.5 57.5-62.5 67.572.5 77.5-82.5

89.91 60-78

98-99.5

0.150.35 0.45-1.20

15-34 0.3-1.5 0.2-1.0 16-27

1.5-2.5 1.3-2.1 1.0-1.5

2.0-2.8 2.03.3 3.04.0 3.04.0 0.40.8 0.53.1 Trace

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- I

-_ - _- - -_ I

-_

2.53.5 1.83.5

1.03.5 0.5-1.5 0.7-1.5

14-19 85-93 92-98 27-53

2.5-4.0 4.0-7.0 1.03.0

- 304 .0 - 3.04.0 - 3.04.0 - 3.04.0 - 1.0-2.0 - 1.03.0 - 0.3-1.0

0.3-2.2 0.02-0.10 03-2.2 0.10-0.30

11-17 1.0-2.0 0.3-7.0 0.5-1.0 0.2-1.0 0.04.6 - I

o o Slag o

o Deteriorated refractories.

Dust collector wastes and scrubber wastes

Miscellaneous wastes such as waste oil from forklifts and hydraulics, empty drums of binder, etc.

6.2.2.1 Spent Foundry Sand

Much foundry waste is spent sand used in coremaking, molding, and shakeout operation. Most foundries reuse some portion of their foundry sand; in many cases most of the sand is reused. However, some new sand and binder are typically added to the used sand to maintain the molding properties and enhance casting quality. Although some sand is lost to spills and shakeout, an additional amount of sand must often be removed so the system can accommodate the new sand that must be added. This amount of removed sand, combined with the sand lost to spills, shakeout, and sand not reused becomes the waste sand. Figure 6-2 illustrates the primary sources of waste sand.

Waste materials generated produced from the molding sand are oflen the dusts or sludges that are collected as part of the air pollution control system located over the molding and shakeout operations. They can also be in the form of large clumps that are screened out of the molding sand recycle system or as sand that has been cleaned from the castings.

Core sand binders either partially or completely degrade when exposed to the heat of the molten metal during the pouring operation. Once loose, sand that has had its binder fully degraded is often mixed with molding sand for recycling or can be recycled back into the core sand process. Partially decomposed core sands which are removed during the shakeout process and contain only partially degraded binder are called core butts. The core butts can be crushed and recycled back into the molding sand process, or may be taken directly to the landfill for disposal along with broken or offspec cores and core room sweepings. The molding sand and the core sand wastes might account for 66 to 88 percent of the total waste generated by ferrous foundries.

Foundries casting copper-based alloys (brass or bronze foundries) in particular, generate hazardous waste sand contaminated with cadmium, lead, copper, nickel, and zinc, oflen in high total and extractable concentrations.

Some core-making processes use strongly acidic or basic substances for scrubbing the off- gases from the core-making process. In the free radical cure (FRC) process In coremaking, acrylic-epoxy binders are cured using an organic hydroperoxide and SO, gas. A wet scrubbing unit is used to absorb SO, gas. A 5 to 10% solution of sodium hydroxide at a pH of 8 to 14 provides efficient neutralization of the SO, and prevents the by-product (sodium sulfite) from precipitating out of solution. Usually, pH controlled sludges are discharged to the sewer system as non-hazardous wastes. If not properly treated, they may be classified as hazardous corrosive waste.

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6.22.2 Cleanlng Room Wastes

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Waste Reduction in Metal Casting and Heat Treatment Industry

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