Control of Volatile Organic Compounds Emissions from Manufacturing

abrasion on the banks of the water tubes. Energy transfer from the hot
flue gases to form steam can attain greater than 85 percent efficiency.
Additional energy can be recovered from the hot exhaust gases by instal-
lation of a gas-gas heat exchanger to preheat combustion air.
Boilers designed speci fical ly for use as a VOC control device
typical ly use discrete or vortex burners, depending on the heating value 1
of the vent stream. For vent streams with heating values between
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1,100 kJ/scm (300 Btu/scf) and 1,850 kJ/scm (500 ~tu/scf), a discrete
burner would be best suited.31 Streams with lower heating values would I
probably require vortex burners to ensure the desired VOC destruction.
3.1.4.1 Industrial Boiler VOC Destruction Efficiency. VOC destruction
efficiency achievable by boilers depends on the same factors that affect
any combustion technique. Since boiler furnaces typically operate at
hlgher peak temperatures and with longer combustion residence times than
thermal incinerators, the VOC destruction efficiency usual ly would be
expected to match or exceed the 98 percent efficiency demonstrated in
1nc'i nerato rs.
3.1.4.2 Applicability of Industrial Boilers. Use of a boiler for
VOC emission control in the polymers and resins industry is uncommon.
Despite the potential problems, boilers are being used in at least two
polypropylene plants32 and a hi gh-densi ty polyethylene plant. 33 The
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polypropylene plants supplement boiler fuel with waste gas that otherwi se
would be flared. The high density polyethylene plant sends the dehydrator
regeneration gas (a mixture of natural gas and nitrogen) and a degassing
stream from the recycle diluent step (mostly ethylene) to steam-generating
boilers as a fuel .
A boiler would be used as a control devi ce only if the process
generated its own steam or the fuel value of the waste gas was sufficient
to make the process a net exporter of steam. Whenever either condition
exists, installation of a boiler is an excell ent control measure that
provides greater than 98 percent VOC destruction and very efficient
recovery of the heat of combustion of the waste gas,,
3.2 CONTROL BY RECOVERY TECHNIQUES
The three major recovery devi ces are condenser!;, adsorbers , and
absorbers. These devices permit many organic materi a1 s to be recovered