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Environmental Assessment During Process Synthesis - Chapters 7 and 8 . David T. Allen Department of Chemical Engineering University of Texas. Software exploration Green Chemistry Expert System. TOPIC AREAS • Green Synthetic Reactions - search a database for alternatives

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environmental assessment during process synthesis chapters 7 and 8

Environmental Assessment During Process Synthesis - Chapters 7 and 8

David T. Allen

Department of Chemical Engineering

University of Texas

software exploration green chemistry expert system
Software explorationGreen Chemistry Expert System

TOPIC

AREAS

• Green Synthetic Reactions - search a database for alternatives

• Designing Safer Chemicals - information on chemical classes

• Green Solvents/Reaction Conditions - alternative solvents / uses

- solvent properties

software demonstration green chemistry expert system
Software demonstration Green Chemistry Expert System

search Green Synthetic Reactions for adipic acid references

adipic acid synthesis traditional vs new
Adipic Acid SynthesisTraditional vs. New

Traditional Route - from cyclohexanol/cyclohexanone

Cu (.1-.5%)

C6H12O+ 2 HNO3 + 2 H2O C6H10O4 + (NO, NO2, N2O, N2)

V (.02-.1%)

92-96% Yield of Adipic Acid

• Carbon - 100%

• Oxygen - 4/9 x 100 = 44.4%

• Hydrogen - 10/18 x 100 = 55.6%

• Nitrogen - 0%

Product Mass = (6 C)(12) + (10 H)(1) + (4 O)(16) = 146 g

Reactant Mass = (6 C)(12) + (18 H)(1) + (9 O)(16) + (2 N)(14) = 262 g

Mass Efficiency = 146/262 x 100 = 55.7%

hazardous

global warming

ozone depletion

Davis and Kemp, 1991, Adipic Acid, in Kirk-Othmer Encyclopedia of Chemical Technology, V. 1, 466 - 493

adipic acid synthesis traditional vs new5
Adipic Acid SynthesisTraditional vs. New

New Route - from cyclohexene

Na2WO4•2H2O (1%)

C6H10 + 4 H2O2 C6H10O4 + 4 H2O

[CH3(n-C8H17) 3N]HSO4 (1%)

90% Yield of Adipic Acid

• Carbon - 100%

• Oxygen - 4/8 x 100 = 50%

• Hydrogen - 10/18 x 100 = 55.6%

Product Mass = (6 C)(12) + (10 H)(1) + (4 O)(16) = 146 g

Reactant Mass = (6 C)(12) + (18 H)(1) + (8 O)(16) = 218 g

Mass Efficiency = 146/218 x 100 = 67%

Sato, et al. 1998, A “green” route to adipic acid:…, Science, V. 281, 11 Sept. 1646 - 1647

maleic anhydride synthesis benzene vs butane mass efficiency
Maleic Anhydride SynthesisBenzene vs Butane - Mass Efficiency

Benzene Route (Hedley et al. 1975, reference in ch. 8)

V2O5

2 C6H6 + 9 O2 2 C4H2O3 + H2O + 4 CO2

(air) MoO3

95% Yield of Maleic Anhydride from Benzene in Fixed Bed Reactor

Butane Route

(VO)2P2O5

C4H10 + 3.5 O2 C4H2O0 + 4 H2O

(air)

60% Yield of Maleic Anhydride from Butane in Fixed Bed Reactor

Felthouse et al., 1991, “Maleic Anhydride, ..”, in Kirk-Othmer Encyclopedia of Chemical Technology, V. 15, 893 - 928

maleic anhydride synthesis benzene vs butane summary table
Maleic Anhydride SynthesisBenzene vs Butane - Summary Table

1 Rudd et al. 1981, “Petroleum Technology Assessment”, Wiley Interscience, New York

2 Chemical Marketing Reporter (Benzene and MA 6/12/00); Texas Liquid (Butane 6/22/00)

3 Threshold Limit Value, ACGIH - Amer. Conf. of Gov. Indust. Hyg., Inc. , www.acgih.org

4 Toxicity Weight, www.epa.gov/opptintr/env_ind/index.html and www.epa.gov/ngispgm3/iris/subst/index.html

5 ChemFate Database - www.esc.syrres.com, EFDB menu item

maleic anhydride synthesis benzene vs butane tier 1 assessment
Maleic Anhydride SynthesisBenzene vs Butane - Tier 1 Assessment

Benzene Route

Butane Route

Where i is the overall stoichiometric coefficient of reactant or product i

maleic anhydride synthesis benzene vs butane tier 1 assessment9
Maleic Anhydride SynthesisBenzene vs Butane - Tier 1 Assessment

Benzene Route

Butane Route

chapter 8
Chapter 8

Identifying and estimating air emissions and other releases from process units

1. Identify waste release sources in process flowsheets

2. Methods for estimating emissions from chemical processes

3. Case study - Benzene to Maleic Anhydride process evaluation

benzene to ma process
Benzene to MA Process

V2O5

2 C6H6 + 9 O2 ----------> 2 C4H2O3 + H2O + 4 CO2

MoO3

AP-42, Chapter 6, section 6.14, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm

typical waste emission sources from chemical processes ch 8
Typical waste emission sources from chemical processes - Ch 8

1. Waste streams from process units

2. Major equipment- vents on reactors, column separators, storage tanks, vacuum systems, ..

3. Fugitive sources - large number of small releases from pumps, valves, fittings, flanges, open pipes, ..

4. Loading/unloading operations

5. Vessel clean out, residuals in drums and tanks

6. Secondary sources - emissions from wastewater treatment, other waste treatment operations, on-site land applications of waste, ..

7. Spend catalyst residues, column residues and tars, sludges from tanks, columns, and wastewater treatment, …

8. Energy consumption - criteria air pollutants, traces of hazardous air pollutants, global warming gases,

process release estimation methods
Process release estimation methods

1. Actual measurements of process waste stream contents and flow rates or indirectly estimated based on mass balance and stoichiometry. (most preferred but not always available at design stage)

2. Release data for surrogate chemical or process or emission factors based on measured data

3. Mathematical models of emissions (emission correlations, mass transfer theory, process design software, etc.)

4. Estimates based on best engineering judgement or rules of thumb

emission estimation methods based on surrogate processes
Emission estimation methods: based on surrogate processes

Waste stream summaries based on past experience

1. Hedley, W.H. et al. 1975, “Potential Pollutants from Petrochemical

Processes”, Technomics, Westport, CT

2. AP-42 Document, Chapters 5 and 6 on petroleum and chemical industries,

Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm

3. Other sources

i. Kirk-Othmer Encyclopedia of Chemical Technology, 1991-

ii. Hydrocarbon Processing, “Petrochemical Processes ‘99”, March 1999.

emission factors major equipment
Emission Factors - major equipment

Average Emission Factors for Chemical Process Units Calculated from the US EPA L&E Database

Process Unit EFav ; (kg emitted/103 kg throughput)

Reactor Vents 1.50

Distillation Columns Vents 0.70

Absorber Units 2.20

Strippers 0.20

Sumps/Decanters 0.02

Dryers 0.70

Cooling Towers 0.10

emission factors criteria pollutants from energy consumption
Emission factors - criteria pollutants from energy consumption

AP-42, Chapter 1, section 1.3, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm

emission factors co 2 from energy consumption
Emission factors - CO2 from energy consumption

AP-42, Chapter 1, section 1.3, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm

emission correlations models storage tanks and waste treatment
Emission correlations/models - storage tanks and waste treatment

Software Tools

Storage tanks

TANKS 4.0 - program from EPA - www.epa.gov/ttn/chief/tanks.html

Wastewater treatment

WATER8 - on Air CHIEF CD - www.epa.gov/ttn/chief/airchief.html

Treatment storage and disposal facility (TSDF) processes

CHEMDAT8 - on Air CHIEF CD

tier 2 environmental assessment indexes
Tier 2 environmental assessment indexes

1. Energy: [total energy (Btu/yr)] / [production rate (MM lb/yr)]

2. Materials: [raw materials (MM lb/yr)] / [production rate (MM lb/yr)]

3. Water: [process water (MM lb/yr)] / [production rate (MM lb/yr)]

4. Emissions: [total emissions and wastes (MM lb/yr)] / [production rate (MM lb/yr)]

5. Targeted emissions: [total targeted emissions and wastes (MM lb/yr)] / [production rate (MM lb/yr)]

benzene to ma process21
Benzene to MA Process

V2O5

2 C6H6 + 9 O2 ----------> 2 C4H2O3 + H2O + 4 CO2

MoO3

AP-42, Chapter 6, section 6.14, Air CHIEF CD, www.epa.gov/ttn/chief/airchief.htm

air emission and releases sources benzene to ma process
Air emission and releases sources:Benzene to MA Process

Source Identification

1. Product recovery absorber vent

2. Vacuum system vent

3. Storage and handling emissions

4. Secondary emissions from water out, spent catalyst, fractionation column residues

5. Fugitive sources (pumps, valves, fittings, ..)

6. Energy consumption

benzene to ma process conclusions from emissions summary
Benzene to MA Process Conclusions from emissions summary

1. Chemical profile:

CO2 > CO > benzene > tars-oxygenates > MA

2. Toxicity profile:

Benzene > MA > CO > tars-oxygenates > CO2

3. Unit operations profile:

Absorber vent > energy consumption > vacuum system vent

- Pollution prevention and control opportunities are centered

on benzene, the absorber unit, and energy consumption -

pollution prevention storage tanks
Pollution prevention - Storage Tanks

Emission Mechanisms; Fixed Roof Tank

LTOTAL = LSTANDING + LWORKING

Vent

Vapor pressure of liquid drives emissions

DT

DP

Liquid

Level

- Weather, paint color/quality

- Weather

- liquid throughput, volume of

tank

Roof Column

storage tank comparison tanks 4 0 program
Storage tank comparison -TANKS 4.0 program

Gaseous waste stream flowsheet

• Toluene emissions only

• 100 kgmole/hr absorber oil rate

• 15,228.5 gallon tank for each comparison

Pollution prevention strategies

• replace fixed-roof with floating-roof tank

• maintain light-colored paint in good condition

• heat tank to reduce temperature fluctuations