Devnja WTP

RЕCYCLING OF MINING AND METALLURGICALL WASTES AT DEVNJA WASTE TREATMENT PLANT

INTRODUCING IONTECH ENGINEERING Bulgarian based, EPCM company Founded in 1999 by a team of leading

engineers in the field of hydrometallurgy Specialises in:

o Mining and metallurgical projectso Chemical and process plantso Industrial water treatment and reclamationo Waste management

INTRODUCTION The mining and metallurgical industries produce many types of waste streams.

Increasing costs and stricter regulations require more effective methods for treatment of these wastes. One of the most important tasks is the removal or recovery of heavy metals. The effective recovery of these metals is possible only if the separation process is selective enough .

Developed by Iontech Engineering hydrometallurgical technique, which involves leaching, ionexchange and electrolytic processes, can be used for reducing the amount of metal wastes.They can be used also for purification of process liquids for re-use and for the treatment of final wastes

According to the Regulation on the requirements for treatment and transportation of industrial and hazardous waste (adopted with Decree of the Council of Ministers No 53 from 1999; State Gazette No 29/1999)[2], wastes will be disposed via operations, which lead to resource recovery, recycling or reuse, namely R3 - Recycling/reclamation of metals and metal compounds

The metals of interest are copper (Cu), zinc (Zn) and lead (Pb).

DEVNJA WASTE TREATMENT PLANT (DWTP) CAPACITY AND PRODUCTS

№ Product EC#(EINECS)Capacity

t/mCapacity

t/a

1Copper Cathodes

231-159-6 120 1440

2Zinc Cathodes

231-175-3 200 2400

3Lead

231-100-4 200 2400

TYPE AND QUANTITY OF WASTES PROVIDED FOR TREATMENT AND THE VALUABLE METAL CONTENT

DEVNJA WASTE TREATMENT PLANT

Background

Flowsheet development of the Devnja WTPo performed under laboratory and pilot plant scaleo includes:• Evaluation of processing options• Determination of optimal operational parameters• Development of new processing technologies when

warranted• Evaluation of processing options that are

environmentally sustainable and meet legislated requirements

Background

The Environmental Impact Assessment (EIA) of Devnja WTP includes the following main sections:

• definition of the legal and institutional framework• description of the project and the environment• impacts assessment• identification of mitigation measures• presentation of an environmental management plan


Process flowsheet

The process flowsheet contains 7 technological departments, namely:

Acid leaching Caustic leaching Solution purification and concentration Cathode copper production/Cathode zinc production Water and reagents recycling Lead pyrometallurgy Electrolytic lead production


Project operations

Acid leaching - for treatment of wastes with low lead content, like slags from metal casting, baghouse filter dusts, filter cakes and galvanic sludge.Involves :o Grinding and wetting the raw materials in

vibration mill to obtain a pasty product.o Treatment of the pasty product with sulfuric

acid in agitators to dissolve the oxides of zinc and copper.

o Autoclave treatment of the cake with sulfuric acid

o Filtering the pulp from the autoclave treatment in filter press solution, rich in copper and zinc are sent to the “Solution purification and concentration” department and the cake, which has a high lead content is subjected to “Caustic leaching” department


Project operations

Caustic leaching – for treatment of wastes with high lead content, like electrofilter dust and lead dust. Involves:o Treatment of the raw materials with

sulfuric acid in agitators to dissolve the oxides of zinc and copper.

o Autoclave treatment with sodium hydroxide solution

o Thickening. Clarified solution is fed into the “Solution purification and concentration” department and the precipitated at the bottom of the thickener solid phase is filtered through the filter press. Solution is sent to the “Solution purification and concentration” department and the filter cake, which is rich in lead and also contains gold and silver is subjected to the “Lead pyrometallurgy” department.


Project operations Solution purification and concentration-Ion exhange removal of copper

and zinc from solutions obtained in “Acid and Caustic leachin” departments to obtain concentrated copper and zinc solutions,, which are the feed solutions for the Technological departments “Cathode copper production/Cathode zinc production”


Project operations Cathode copper production/Cathode zinc production:o Solvent Extraction process an organic extractant that binds

copper/zinc but not impurity metals is dissolved in an organic solvent (diluent) and is mixed with the copper/zinc containing aqueous solution, obtained in the “Solution purification and concentration”. Sulfuric acid solution, namely spent electrolyte returned from the EW tankhouse is then added to the loaded organic mixture, which strips the copper/zinc into an electrolytic solution ready for electrowinning.

o Electrowinning process - electrolysis of a pregnant electrolyte solution, produced in copper and zinc SX processes, such that copper/zinc ions within it are plated onto the cathode to obtain highly purified cathode copper and cathode zinc


INVESTMENT INTENT FACILITY FOR WASTES TREATMENT

Project operations

Water and reagents recycling :

o Arsenic removal –takes place in two successive stages: 1) Two-stage precipitation of arsenic to obtain the insoluble solid waste, scorodite and 2) final removal of arsenic using ion exchange resin.

o Water treatment - involving the following operations (1) Neutralization with lime milk in stirred reactors; (2) Three-stage counter-current decantation of the suspension from previous operation; (3) Filtration using filter press - the liquid phase, is sent for sulfate removal stage and the cake is a non-hazardous waste (19 08 14).

o Sulfate removal via ion exchange resin.

Project operations

Lead pyrometallurgy-the spent lead acid batteries and lead containing cake, derived from the Caustic leaching department are processed in special Facility, which includes rotating furnace, as well as the cyclone and bag filter for exhaust gases. The resulting melting black lead then is refined to obtain refined lead.


Project operations Electrolytic lead productiono Filtration - The resulted from the caustic leaching department

pulp, containing solution of sodium-lead salt and leach residue - lead dioxide and eventually noble metals is filtered through a filter press. Sodium - lead salt solution then is sent to the process of electrolysis to obtain metallic lead.

o Dissolved lead is sent to the electrowining cells to obtain pure electrolytic lead and regenerate the sodium hydroxide solution, closing the circuit. The liquor feeds electrolysis cell, which operates at 60oC. Lead electrolysis is carried out in cell with cationic membranes, operated with a rich catholyte of a lead concentration around 30 g/l and spent catholyte of 15-18 g/l. The cathodes are of stainless steel.


Location

located in the industrial area of town of Devnya, adjacent to the Varna – Sofia railway line.

Direct access to Port Varna West

20 km. from Varna Airport

the site area - 8686 m2


Production site-Facility Map location


Potential adverse environmental impacts

Emissions to the air Contamination of water resources Contamination of receiving land by inappropriate waste

management Occupational and public health hazards Adverse aesthetic impacts in the neighborhood of treatment

works

The analysis of these impacts showed that they can be easily mitigated for.


Mitigation measures


CONCLUSION The purpose of the Facility for waste treatment - to alleviate the

severe impacts of uncontrolled solid waste disposal into the environment. Proper design/selection, construction, and management of the waste treatment Facility would mitigate such negative impacts.

The assessment of impacts indicated that negative impacts should not be significant as long as process performance is continuously controlled.

The design and management of the Facility will take necessary procedures to ensure the elimination of these impacts.

On the other hand, positive impacts with respect to public nuisance and human health are a direct consequence and key goals of the project implementation.

For more information, please visit:

www. ionteching.com

Devnja WTP

Documents

Transcript of Devnja WTP