THERMAL OXIDATION
This illustrates a typical industrial VOC instances. Very common trades include printing industry, commercial bakeries, and odor control.
PLASTIC PIPE MANUFACTURING
Q: Machine is able to make pipes from 300 to 2400 mm in a continuous way and the pipes cut off, according the pre-set length, using a saw synchronized with the continuous longitudinal movement of the laminate. All the emissions data were measured on this machine chimney during the production of those 3 diameters, one at the time; there is only one process/one machine. It is not easy to say which diameter pipe would be "normal"; during this last month, as an example, we produced DN 350, 400, 500, 600, 900, 1000 and 1200 mm pipes…. All different styrene and VOC emissions, but off course, if the pipe is bigger the emissions are higher.
A: I have assumed that the styrene and other VOC emissions go up the same chimney as the emissions from the pipe fabricating machinery. In this case, the test data measure the total combined VOC from both operations. If so, while the total VOC emissions for both the 600 and 800 mm pipe fabricating tests were above the emission standard, the only extreme case was for the 800 mm pipe run. However, the "high" VOC emission concentration of 1810 mg/dscm for this test converts to only 390 ppmv. All of the other VOC concentration levels are much less. In which case:
Thermal or catalytic oxidation makes absolutely no economic sense for a peak of 390 ppmv VOC and a normally 100 ppmv VOC concentration. The catalytic oxidation system that was propsed recognizes that you have to try to run an oxidizer in accordance with the varying VOC load. However, the catalytic oxidizer is sized for 12,500 m3/h, as against a present chimney flow of 9000 to 10,000 m3/h. Also, the preheat and fuel consumption are always ongoing, because you can't just switch the equipment on or off.
With the normally low level of VOC emission and the intermittent fabrication of the 800 mm pipe, the obvious recommendation is pre-concentration, followed by catalytic oxidation. With pre-concentration, the stripping gas volume that needs to be oxidized can be as low as 10% of the 2.6 dscm/second, so the oxidizer and heat exchanger are correspondingly smaller and less costly. The higher concentrations of VOC in the regenerator gas also give lower light-off temperatures in the oxidizer, and this lowers pre-heat requirements even further. There are standard pre-concentrator systems available on the commercial market.
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