Page 441 - Academic Press Encyclopedia of Physical Science and Technology 3rd Chemical Engineering

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Encyclopedia of Physical Science and Technology EN012I-591 July 26, 2001 15:54

Pollution Prevention from Chemical Processes 607

2. Generate useful technical information about Quick-opening access doors
methodologies and technologies for reducing A dryer which serves as part of the enclosure to
pollution, which could help the U.S. EPA assist other minimize the enclosure size
companies implementing pollution prevention/waste VOC concentration monitors which control air flow to
minimization programs. each dryer stage to maintain the dryers at 25–40% of
3. Evaluate and identify potentially useful refinements the LEL (lower explosive limit)
to the U.S. EPA and DuPont methodologies for Damper controls which maintain a constant exhaust
analyzing and reducing pollution and/or waste rate from the enclosure to ensure a slight vacuum
generating activities. within the enclosure.
The business leadership was initially reluctant to un- If the pressroom had been used as the enclosure, the
dertake the program, and was skeptical of the return to amount of ventilation air requiring treatment would have
be gained when compared against the resources required. been close to 200,000 scfm. Instead, the use of the en-
After completing a few of the projects, however, the busi- closure and the LEL monitors reduced the air flow to
ness leadership realized that the methodology identified the adsorber to 48,000 scfm. This resulted in an invest-
revenue-producing improvements with a minimum use of ment savings for the carbon adsorber of approximately
2
people resources and time, both of which were in short $5,000,000. The installed cost of the 1700-ft enclosure
2
supply. was only $80,000, or $47/ft . Knowing the investment re-
The pollution prevention program assessed 15 manu- quired to treat the entire 200,000 scfm provided a clear
facturing processes and attained the following results: incentive for the business to reduce air flow at the source
through segregation.

A 52% reduction in waste generation.

Total capital investment of $6,335,000.
C. Waste Stream Analysis—Nonaqueous
Savings and earnings amounting to $14,900,000 per
Cleaning
year.
In a sold-out market, a DuPont intermediates process was
Clearly, this is a very attractive return on investment, while operating at 56% of peak capacity. The major cause of
also cutting waste generation in half. No matter which the rate limitation was identified as poor decanter opera-
methodology was used, the EPA’s or DuPont’s, the re- tion. The decanter recovered a valuable catalyst, and the
sults were the same. The key to the site’s success was fol- poor operation was caused by fouling from catalyst solids.
lowing a structured methodology throughout the project Returning the process to high utility required a 20-day
and allowing creative talents to shine in a disciplined shutdown. During the shutdown, the vessel was pumped
way. out and cleaned by water washing. The solids and hy-
drolyzed catalyst were then drummed and incinerated. A
waste stream analysis identified three cost factors: the vol-
B. Incentive for Pollution Prevention—Gas Flow
ume of wastewater that had to be treated, the cost of the
Rate Reduction
lost catalyst, and the incineration cost.
AprintingfacilityinRichmond,Virginia,usesrotogravure An analysis of the process and ingredients indicated
printing presses to produce consumer products packaging that the decanter could instead be bypassed and the pro-
materials. Typical solvents used are toluene, isopropyl ac- cess run at a reduced rate while the decanter was cleaned.
etate, acetone, and methyl ethyl ketone. Driven by the U.S. A process ingredient was used to clean the decanter, en-
EPA’s new source performance standards for the surface abling recovery of the catalyst ($200,000 value). The use
coating industry, the site installed a permanent total en- of the process ingredient in place of water cut the clean-
closure (PTE) around a new press so as to attain a 100% ing time in half, and that, along with continued running of
VOC capture efficiency. Leaks from the hot air convec- the process, eliminated the need to buy the intermediate
tion dryers and other fugitive emissions from the coating on the open market. The results were a 100% elimination
operation are captured in the press enclosure and routed, of a hazardous waste (125,000 gallons per year) and an
along with the dryer exhaust, to a carbon adsorber for re- improved cash flow of $3,800,000 per year.
covery. Overall VOC removal efficiency for the enclosure
and recovery system is greater than 95%. While many
D. Process Analysis—Replace Solvent with
rotogravure press installations use the total pressroom as
a Process Intermediate, Product, or Feed
the enclosure, this facility was one of the first to install a
separate, smaller enclosure around the new press. Notable At a DuPont site, organic solvents used in the manufac-
features of the enclosure include the following: ture of an intermediate monomer were incinerated as a