Coretan ttg Inherently safer process design · 2012. 8. 12. · Inherently Safer Design Strategy...

Inherently Safer Process DesignAvailable tools and case studies

Zulfan Adi Putra

Process Enginer

Outline

• What Went Wrong? • Definition of Inherently Safer Process Design

• Inherently Safer Process Design Strategy

• INSET and Index Calculation Tools for Inherently Safer Process Design in:– Process selection

– Flowsheet development

– Process and equipment design

– Planning and scheduling• Case Studies/Examples

– Process selection

– Flowsheet development– Process and equipment design

– Planning and scheduling

– Inherently safer for existing plants

• Conclusion• Future Works

• References

What Went Wrong?case Histories of Process Plant Disasters

What Went Wrong?Case Histories of Process Plant Disasters [5]

Situations What is lacked out of many

Nypro factory, Flixborough UK, 1974.

Failure of temporary installed pipe connecting huge reactors ,

releasing 50 tons of cyclohexane, mixed with air and exploded.

Killing 28 people and destroying the plant

Knowledge to design highly stressed

pipe.

Reduction of hazardous inventories.

Carbaryl production in Bhopal, 1984.

Intermediate chemicals, Methyl Iso Cyanate (MIC), was

leaking, causing more than 2000 people dead and injuring

200,000 people.

Reduction of hazardous intermediates

inventories.

Awareness to select different reaction

routes

Keeping incompatible materials apart

Seveso, Italy, 1976.

A reactor containing an uncompleted batch of 2,4,5-

trichlorophenol (TCP) was left for the weekend. External

steam temperature was so high that a runaway reaction

started. Surrounding area became unfit for habitation

Using unnecessarily hot heating

medium

Many of incidents were the result of leaks of hazardous materials,

and the recommendations described ways of preventing leaks by

providing better equipment or procedures.

However, equipment can fail or neglected, and procedure can lapse [5]

Inherently Safer Process DesignDefinition

Inherently Safer Process Design (1)

• A chemical manufacturing process is said as inherently safer IF:– it reduces or eliminates one or more hazards assoc. with the materials and

operations used in the process when compared to some alternative process,– And this reduction or elimination is accomplished by characteristics which are

permanent and inseparable parts of the process [1]• Hazard � an inherent physical or chemical characteristic that has the potential for

causing harm to people, property or the environment [1]– Example: 10000 lb of propane holds the same amount of energy which could be

released by 28 tons of TNT [2]• Traditional approach � introduce barriers (layers of protection) [1]:

– Operator supervision– Control system– Alarms– Interlocks– Physical protection devices– Emergency response systems

Inherently Safer Process Design (2)

Disadvantages of traditional approach [1]:• Barriers are expensive to build and maintain throughout the life of the process

• Any failure of the barriers could potentially result in an accident

• The hazard still exists, and if something can go wrong, it will go wrong

Inherently safer process design approach [1]:

• Reduce/eliminate hazard � less barriers required � less risk of barrier failures

• Best opportunities are early in the process life cycle including selection of process routes, raw materials, process parameters, and unit operations (flowsheetdevelopment)

• Searching for inherently safer options starts at the earliest stage and never stop

Famous phrase:“What You Don’t Have Can’t Leak”

Inherently Safer Process DesignStrategy

Inherently Safer Design Strategy (1)

• Inherently safer design strategy includes:– Intensification/minimize � reduce the inventories or use small quantities of

hazardous materials

– Substitution � use less hazardous materials or replace with a less hazardous one

– Attenuation/moderate � use less hazardous process conditions (e.g. pressure, temperature), less hazardous form of a material or facilities which minimize the impact of a release of hazardous material or energy

– Simplify � design facilities which eliminate unnecessary complexity and make operating errors less likely

• INSIDE project [3] produced Inherently SHE Evaluation Tool (INSET) toolkit as a guideline for challenging the way things done normally and suggesting alternatives. This toolkit is applicable during the process life-cycle.

Inherently Safer Design Strategy (2)

At earlier stages (route selection until process and equipment design � relevant activities for me):

– Alternatives are identified utilizing inherently safer design strategies within the constraints of process and economics [3, 4, 6, 7]

– Each alternative is ranked based on their safety indices [3, 4, 6, 7]

– Optimum process is then selected based on their rank

INSET and Index Calculation Tools for Inherently Safer Process Design

4 stagesTool A – R which are

overlapped between

stages

INSET Toolkit: Stages

Tool B is used for the entire stagesIt is aimed to challenge route and alternatives in order to obtain a more inherently safer,

healthier, and more environmentally friendly (ISHE) process

INSET Toolkit: Tool B (1)

Identify alternative process options via guideword:


Identify alternative process options via ISHE options:


Identify alternative unit operations viafunctionality prompt list:

INSET Toolkit : Tool B (4)

Identify alternativefor waste to

water, air, etc


Identify alternatives for transportation:


Option evaluations


INSET Toolkit: Example (1)Stage 1: Chemistry Route Selection

INSET Toolkit: Example (2)Stage 2: Chemistry route detail evaluation

INSET Toolkit: Example (3)Stage 3: Process Design Optimization

INSET Toolkit: Example (4)Stage 4: Process Plant Design

Indexing Tools for Process Selection (1)

Available tools for process selection:1. Prototype Index for Inherent Safety (PIIS)

• Developed by Edwards and Lawrence (1993) [6]

• It considers raw materials used and reaction steps (reaction routes)• Chemical score: inventory, flammability, explosiveness, and toxicity

• Process score: temperature, pressure, and yield

• Information is taken from literature and MSDS

2. Inherent Safety Index (ISI)• Developed by Heikkilä (1999) [4]

• It considers reaction routes and separation sections

• Chemical index: chemical reactivity, flammability, explosiveness, toxicity, and corrosiveness

• Process index: inventory, temperature, pressure, equipment, and process structure

• Information is taken from literature and MSDS, and process selection

Indexing Tools for Process Selection (2)

Available tools for process selection:3. i-Safe index

• Developed by Palaniappan (2002) [7]

• Using sub-index values from ISI and PIIS, plus NFPA reactivity rating• Individual (overall) chemical index: flammability, toxicity, explosiveness,

NFPA reactivity

• Individual (overall) reaction index: temperature, pressure, yield, heat of reaction

Indexing Tools for Flowsheet Development

Available tools for flowsheet developments:1. Inherent Safety Index (ISI)

• Developed by Heikkilä (1999) [4]

• It considers reaction routes and separation sections• Chemical index: chemical reactivity, flammability, explosiveness, toxicity,

and corrosiveness

• Process index: inventory, temperature, pressure, equipment, and process structure

• Information is taken from literature and MSDS, and process selection2. i-Safe index

• Developed by Palaniappan (2002) [7]

• Flowsheets are ranked based on scoring scheme proposed in ISI [3]

Indexing Tools for Process and Equipment Design

Available tools for process and equipment design:1. Integrating Dow’s fire and explosion index (F&EI) into process design [2]

• Dow’s F&EI is used as a function of material inventory and operatingpressure

• This function is used as a safety constraint in the process optimization framework

Indexing Tools for Planning and Scheduling

Available tools for planning and scheduling:1. Integrating Dow’s F&EI in inherently safer design and process scheduling [8]

• Alternative designs and expected scheduling options are evaluated based on their technical constraints

• Economical values for each options are evaluated

• Safety indices are calculated for each option

• Pareto curve is developed demonstrating a trade-off between the inherently safer design and various production and operation scheduling

Case Studies of Index Calculation Tools for Inherently Safer Process Design

Case Study for Process Selection (1)

Comparison of Methyl Methacrylate (MMA) process routes [9]: 6 process routes are identified to produce MMA, namely:

1. Acetone cyanohydrin (ACH) route

2. Ethylene route via propionaldehyde (C2/PA)3. Ethylene route via methyl propionate (C2/MP)

4. Propylene route (C3)

5. Isobutylene route (i-C4)

6. Tertiary butyl alcohol (TBA) route


• ISI approach is more in agreement with expert (from industries and universities including professors Kletz, Lees, and Duxbury [9]) evaluations. It is however more laborious.

• PIIS is very reaction-step oriented and does not consider separation sections, lacks of inventory evaluation. Straightforward and fast to use with relatively good results.

• i-Safe is also reaction oriented, easy to use, wider range of subindices than PIIS. Also does not consider separation sections, lacks of inventory, equipment and process subindices.

Case Study for Flowsheet Development (1)

ISI index is used for calculating the safety index while developing the flowsheet [10].

Flowsheet is developed in iCON (a process simulation software, similar to Aspen HYSYS) while the ISI index is calculated in MS Excel.

This allows various design alternatives to be evaluated simultaneously with the safety aspect.


Connecting process simulation software and safety index [10]


Process flow diagram in iCON connected with ISI index in MS Excel [10]Safety can be evaluated simultaneously during flowsheet development

Case Study for Process and Equipment Design (1)

Case study is taken from Suardin et. al., 2007 [2]:Simple Reactor + Distillation units

A � B (gas phase)

Reactant A = hazardous chemicalReactor pressure range = 2 – 8 atm

Feasible conversion = 40% - 70%

Distillation pressure range = 10 -16 atm


Feasible range of conversion without taking into account the inherently safer limit


AIChE (1994) recommends that F&EI < 128This additional safety constraint is included into the optimization

Conversion limit for

ensuring safer design

Case Study for Process Scheduling (1)

A refinery case study for gasoline and diesel productions with NOx emission as the environmental issue.

Variations of demands for gasoline and diesel during the year.Unit operations involved: Fluidized Catalytic Cracker (FCC) for fuels productions and

Selective Catalytic Reduction (SCR) unit for reducing NOx emission.

Different crude properties and different operation mode yield different NOxemissons.

Case Study for Process Scheduling (2)

Pareto curves are constructed to show trade-offs (each dot represents a certain design and production schedule):

As production increases (productions are scheduled more often), profit increases, HOWEVER, the need for NOx removal increases, more chemicals (NH3 and ethanol) used for removing NOx, and hazardous level increases.

These curves show trade-offs of economic, environmental, and safety objectives of the company

Case Study for Inherently Safer Existing Plants (1)

Several examples of inherently safer approaches for existing plants [11]:

Plants and Situations Approaches

Insecticide production from MIC.

At the time of Bhopal incident, DuPont

was purchasing MIC from a supplier and

transporting it by railcar to a plant located

near a major metropolitan area over a

thousand miles away. The facility stored

several million pounds of MIC at site. MIC

was used to make profitable insecticide.

In response to Bhopal incident, DuPont’s

R&D developed:

- an alternative route of a raw material

significantly less hazardous than MIC.

- employed an alternative reactor

technology, converting the new raw

material into MIC in situ and immediately

consume the MIC.

Results: eliminate risk of transporting and

storing MIC


Plants and Situations Approaches

Ethylene Oxide production.

EO is very hazardous (flammability range

from 3% - 100% due to its own oxygent,

decomposes, and polymerizes, through

highly exothermic reactions. Explosions

occurred in the 2nd column where pure EO

is reboiled (BP in Antwerp, 1987 and UC in

TX, 1991)

To eliminate contact between pure EO

and hot surfaces of the reboiler, two

columns are combined. Eliminating the

potential EO decomposition and providing

dilute mixture in the reboiler. (US Patent:

5,529,667).


Hydrochloric Acid Regeneration at Hoogovens Steel Strip mill Products (HSSP) [12]:

Conclusion

Conclusion

1. Inherently safer process design strategy is a pro-active approach to ensure a safer process design

2. Guidelines in the INSET toolkit [3] can be used to generate alternatives. It can be used throughout the process life-cycle. This is relevant for my activities.

3. Quantifying safety aspect of process design options via index calculation tools is useful for benchmarking and for decision making tool. Several index calculation tools are available for use and proven to be reliable (agree with experts’ opinions). Relevant index calculation tools for me could be Inherent Safety Index (ISI) [4] and Integration of Dow F&EI [2] because:

a. ISI is applicable for both route selection and flowsheet development (which are relevant tasks)

b. ISI parameters to be evaluated are already available in the conceptual design phase (phase where relevant tasks are present)

c. Integration of Dow F&EI can be used for equipment design, which is also a relevant task for me

4. Depending on the projects, it could be beneficial to have these tools as toolkits

Future Works

Future Works

Future works on inherently safer process design:1. Develop index calculation toolkits (ISI [4] and Dow F&EI [2]) in MS Excel as toolkits

2. Develop a procedure to link Aspen Plus process simulation with the above index calculation toolkits by utilizing Aspen Worksheet

3. Create a case study to verify the usefulness of the toolkits by:a. developing several options by utilizing INSET toolkit together with process and

technical constraints, b. quantifying their safety indices using index calculation toolkits, and

c. comparing their indices to choose which one is the inherently safer one.

References (1)

[1] Hendershot, D. C., 1997, Inherently safer chemical process design, Journal of Loss Prevention in the Process Industries, Vol. 10, No. 3, pp. 151-157.

[2] Suardin, J., Mannan, M. S. and El-Halwagi, M., 2007, The integration of Dow’s fire and explosion index (F&EI) into process design and optimization to achieve inherently safer design, Journal of Loss Prevention in the Process Industries, pp. 79-90.

[3] INSIDE Project (2001). The INSET toolkit

[4] Heikkila, A, M., 1999, Inherent safety in process plant design: an index based approach, PhD dissertation, Technical Research Center of Finland, VTT, Espoo: Finland.

[5] Kletz, T., 1999, What Went Wrong? Case Histories of Process Plant Disasters 4th Ed., Gulf Publishing Company, Houston, TX, USA.

[6]. Edwards, D. W. & Lawrence, D., 1993, Assessing the inherent safety of chemical process routes: Is there a relation between plant costs and inherent safety?, Chemical Engineering Research & Design, 71 (Part B), pp. 252-258.

References (2)

[7]. Palaniappan, C., 2002, Expert system for design of inherently safer chemical processes, MEng thesis, National University of Singapore.

[8]. Al-Mutairi, E. M., Suardin, J. A., Mannan, M. S. & El-Halwagi, M. M., 2008, An optimization aproach to the integration of inherently safer design and process scheduling, Journal of Loss Prevention in the Process Industries, pp. 543-549.

[9]. Rahman, M., Heikkilä, A. M. and Hurme, M., 2005, Comparison of inherent safety indices in process concept evaluation, Journal of Loss Prevention in the Process Industries, pp. 327 – 334.

[10]. Takriff, M. S. and Bahnuddin, N. N., 2010, Integration of inherent safety assessment into process simulation, 4th International Conference on Safety and Environment in Process Industry, http://www.aidic.it/CISAP4/webpapers/108Takriff.pdf

[11]. Edwards, V. H. and Chosnek, J., 2012, Make Your Existing Plant Inherently Safer, Chemical Engineering Progress, AIChE, January 2012, pp. 48 – 52.

[12]. Zwetsloot, G. I. J. M. and Ashford, N. A., 2003, The Feasibility of Encouraging Inherently Safer Production in Industrial Firms, Safety Science, 41: 219 – 240.

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