Control of Volatile Organic Compounds Emissions from Manufacturing

subsequent survey in September 1978, showed the incinerator to be
still destroying 99.6 percent of the VOC and with a lower superheat
temperature of 400°C (7506~).
This study pointed out that mixing is a critical factor in efficiency
and that incinerator adjustment after startup is the most feasible and
efficient means of improving mixing and, thus, the destruction efficiency.
0.2.3.2 Monsanto Test ~ata.11 Acryloni trile is produced by
feeding propylene, ammonia, and excess air through a fluidized, catalytic
bed reactor. In the air oxidation process, acrylonitrile, acetonitrile,
hydrogen cyanide, carbon dioxide, carbon monoxide, water, and other
miscellaneous organic compounds are produced in the reactor. The
columns in the recovery section separate water and crude acetoni tril e
as liquids. Propane, unreacted propylene, unreacted air components,
some unabsorbed organic products, and water are emitted as a vapor
from the absorber column overhead. The crude acrylonitrile product is
further refined in the purification section to remove hydrogen cyanide
and the remaining hydrocarbon impurities.
The organic waste streams from this process are incinerated in
the absorber vent thermal oxidizer at a temperature and residence time
sufficient to reduce stack emissions below the required levels. The
incinerated streams include (1) the absorber vent vapor (propane,
propylene, CO, unreacted air components, unabsorbed hydrocarbons), (2)
1 iquid waste acetoni trile (acetoni trile, hydrogen cyanide, acryloni tril e) ,
(3) liquid waste hydrogen cyanide, and (4) product column bottoms
purge (acryloni trile, some organic heavies). The two separate acrylonitrile
p1 ants at Chocolate Bayou, Texas, employ identical thermal oxidizers.
1. Control Device - The Monsanto incinerator burns both liquid
and gaseous wastes from the acryloni trile unit and is termed the
absorber vent thermal oxidizer. Two identical oxidizers are empl oyed.
The primary purpose of the absorber vent thermal oxidizers is hydrocarbon
emission abatement.
Each thermal oxidizer is a horizontal, cylindrical, saddle-supported,
end-fired unit consisting of a primary burner vestibule attached to
the main incinerator shell. Each oxidizer measures 18 feet in diameter
by 36 feet in length.