PREVENTION AND RECYCLING METHODS
Input, Storage and Handling
Obsolete, or Contaminated Materials
Polymerized or Off-spec Chemicals
- Test materials first to determine whether they can be used
in current manufacturing processes.
- Return obsolete materials to suppliers.
- Segregate waste streams.
- Store packages to protect from weather.
- Provide secondary containment (and possibility for recovery)
for hazardous materials.
- Improve quality of feed by working with suppliers or
installing purification equipment.
- Re-examine need for each raw material (e.g., reduce or
eliminate by modifying process and improving control).
- Use off-spec material.
- Use inhibitors to prevent unwanted side reactions or polymer
- Reformulate products from powder to pellet.
- Reuse inert ingredients when flushing solids handling
- Switch to reusable containers, tote-bins or bulk shipments.
- Recover product from tank cars and tank pumps and piping
systems to transfer liquids.
- Use dry disconnects.
- Improve physical mixing in reactor by installing baffles,
high rpm motor for agitator, different mixing blade design, multiple impellers, pump
recirculation or an in-line static mixer.
- Distribute feeds better for better yield conversion, both
inlet and outlet.
- Improve ways reactants are introduced into reactor (perfect
ideal reactant concentrations before feeds enter reactor).
- Improve catalyst and continuously upgrade.
- Provide separate reactor for recycled streams.
- Improve heating and cooling techniques for reactor.
- Consider different reactor design (e.g., plug flow instead
of stirred-tank back mix).
- Improve control to maintain optimal conditions in reactor
(e.g., stabilize conditions in operation frequently, use advanced computer controls).
- Ensure that rubber gaskets are not cracked or worn.
- Recover seal flushes and purchase and recycle to process
- Turn off flush when not in use.
- Use seal-less pumps (can-type or magnetically driven).
(e.g., temperature sensitive)
- Reduce tube-wall temperature:
- Use lower pressure steam;
- De-superheat steam;
- Install thermocompressor.
- Use staged heating (waste heat, then low pressure steam,
then de-superheated high pressure steam).
- Use on-line cleaning techniques (recirculating sponge balls
and reversing brushes).
- Use scraped-wall exchanger for viscous streams.
- Monitor exchanger fouling.
- Use non-corroding tube.
Vented or Flared Products
- Increase reflux ratio if column capacity is adequate.
- Add section to column (e.g., with different diameter, trays,
high efficiency packing).
- Retray or repack column.
- Change feed tray for better separation.
- Improve feed distribution, especially for packed column.
- Preheat column feed (e.g., by cross exchange with another
- Remove overhead products from tray near top of column.
- Increase size of vapor line.
- Modify reboiler design (falling film or pumped recirculation
reboilers, high-flux tubes).
- Reduce reboiler temperature (e.g., using lower pressure
steam, de-superheated steam, installing thermocompressor, using intermediate transfer
- Ensure that tubes are not blocked.
- Lower column pressure.
- Improve overhead condensers (retubing, condenser
replacement, supplemental vent condenser addition).
- Forward vapor overhead to next column (use partial condenser
and introduce vapor stream to downstream column).
||Leaks and Volatile
- Establish a leak detection and repair system for all valves,
pumps and seals.
- Monitor major vents (storage tanks, tankers) and flare
system and recover vented products (install condenser or vent compressor).
- Avoid sending hot materials to storage.
- Change metallurgy or use lining.
- Avoid overheated lines, vessel tracing and jacketing.
- Eliminate "dead" zones
- Segregate wastes and recover.
- Replace coil, investigate alternative designs.
- Replace furnace with intermediate exchanger, use high
temperature transfer fluid.
- Use existing steam superheat.
Samples from Quality Control Testing
- Produce only the amount requested or needed.
- Substitute less toxic or non-toxic raw materials.
- Improve on-line control (e.g., with computer control
- Optimize daily operation.
- Automate start-ups, shutdowns and product changeover.
- Program plant to handle unexpected upsets and trips.
- Relocate process equipment and change piping configuration
to avoid contamination from other sources.
- Find a market for waste product.
- Install reusable insulation.
- Redesign or modify processes and technologies to recover
product and unconverted raw materials.
- Reformulate products (e.g. prepare chemicals in pellet form
instead of powder to reduce dust emissions).
- Segregate and reuse dust emissions in the production
- Shift from batch manufacturing to continuous manufacturing.
- Regenerate catalysts.
- Review sampling frequency and procedure to reduce number and
- Recycle samples.
- Consider diversion into neutralization tanks if disks
rupture on the reactor.
- Reduce sample size.
- Review sampling procedures.
- Return unused sample to process (or client).
- Perform in-line monitoring.
- Use electronic or non-mercury thermometers.
||High Chemical Use
High Water Usage
- Continuously monitor water quality and adjust chemical
- Use less toxic biocides instead of chlorine.
- Use blowdown water for non-critical cleaning applications or
as fire pond water.
- Use plastic lumber to replace wooden slats.
Cleaning and Changeover
- Maximize equipment dedication.
- Improve scheduling of production of chemicals that use the
same production line.
- Recover more product (e.g., through scraping down tanks,
pigging or blowing lines).
- Reuse inert ingredients when flushing solids handling
- Avoid unnecessary equipment cleaning; explore feasibility of
eliminating cleaning step between batches.
- Consider in line mixers instead of bulk tanks for mixing.
- Consider alternative cleaning methods (mechanical cleaning
such as plastic media or dry ice blasting).
- Consider less hazardous cleaners (e.g., ultrasonic cleaning
with more biodegradable cleaner).
- Standardize cleaning products used.
- Use less cleaner (by using high pressure sprays, pressurized
air, steam and heated cleaning bath, etc.)
- Reclaim and reuse cleaner if feasible.
- Use multiple stage rinsing.
- Reuse rinse water.
- Clean process equipment with process fluids if possible.
- Use clearable reusable filter media
Chemical Manufacturing: Pollution
Prevention Opportunities Checklist, Industrial Waste Section, County Sanitation Districts
of L.A. County, Whittier, CA, 12/90.
"Use These Ideas to Cut
Wastes," Hydrocarbon Processing, Ken Nelson, Dow Chemical USA, March 1990.
Fact Sheet: Pollution Prevention:
Strategies for Chemical Production, Center for Hazardous Materials Research, Pittsburgh,
"A Pollution Prevention Guide
for Small Chemical Manufacturing Operations" Delaware Department of Natural Resources
and Environmental Control: http:/wwwdnrec.state.de.us/tdelchem.htm
Connecticut Department of
Environmental Protection Industry Specific Fact Sheets: Chemical Processing (6/93)