||Some synthetic resin production processes use acetone and water to make emulsified resins. During the emulsification process, gas collection and end-of-pipe treatment equipments should be provided to reduce some vaporized acetone which would emit to the atmospheric environment. In this study, a pilot-scale and a field-scale biotrickling filters were set to test their performances on the removal of air-borne acetone. Data from the pilot-scale filter would be helpful to the operations of the field one.|
The pilot filter was constructed of a PP (polypropylene) column (0.30 m inner diameter and 2.1 m high) with the inner space packed with 2.0" crown-type biospheres to a total packing volume of 0.70 m3. The full-scale (field) filter was constructed of stainless steel and has a dimension of 4.5 m(W)×4.5 m(L)×5.5 m(H) packed with 2.0" crown-type biospheres to a total packing volume of around 50 m3.
In the test period of 122 days for the pilot filter, an empty bed residence time (EBRT) of the influent gas through the packed section was controlled at 21, 14, and 8.4 s, respectively. Nutrients were added to the circulation water according to the ratios of COD (influent acetone equivalent):N:P = 150:5:1 (in addition to supplements of fructose and milk), 2500:5:1 (in addition to a supplement of milk), and 2500:5:1 (without any additional supplement), respectively, for nutrition tests. In the test period of 300 days for the field filter, EBRTs were in the range of 5.62-20 s and nutrients were added to the circulation water according to the ratio of COD:N:P = 1250:5:1, 2500:5:1, 3300:5:1, and 12,500:5:1, respectively, for nutrition tests, in addition to fructose and/or milk.
Results indicate that on an average, by the pilot filter, with influent acetone concentrations of 4.4-1143 mg/m3, 84.1% of the influent acetone could be removed; and by the field one, 86.0% of the influent acetone of 1.76-6596 mg/m3 was removed.
Results also display that the acetone removal increased with increasing EBRT for both filters. Maximum removal of 91.7 and 96.9% was observed at EBRT of 21.0 and 19.8 s, respectively, for the pilot and the field filter. With volumetric acetone loadings of L < 260 g/m3.h, 91.2% of the influent acetone could be removed, for the pilot and the field filter. With L = 137 g/m3.h, 94.7% of the influent acetone was removed, for the pilot and the field filter.
An economic analysis indicates that it costs 5.83 NTD for treating 1000 m3 of the acetone-containing air by the pilot filter. It is proposed that the field filter be operated at an EBRT of 14 s and nutrition rate of COD:N:P = 2500:5:1 without additional fructose and milk supplementation.