Spray coating of polymer latex onto fertilizer particles in a fiuidized bed for producing controlled-release urea is an environment friendly technology as it does not need any toxic organic solvent. Since the spray co...Spray coating of polymer latex onto fertilizer particles in a fiuidized bed for producing controlled-release urea is an environment friendly technology as it does not need any toxic organic solvent. Since the spray coating process in a fluidized bed occurs in the presence of particle collisions, the coating of the particles is random, intermittent and multiple, thus making it difficult to investigate the film formation process. In this paper, an experimental model apparatus was designed and used to investigate the effects of the key factors in the spray coating process. This apparatus reasonably simplified the complex process to avoid particle collisions and randomness in the coating. The intermittent coating in the fluidized bed was modeled by periodic coating and dewatering in the experimental apparatus. A large area film was obtained, and the film permeability was measured. The effects of atomizing gas flow rate, spray rate of latex, solid content of latex and gas temperature on film structure and film permeability were investigated. It was found that water transfer played a dominant role in the spray coating process.展开更多
Previous research on wet scrubbers has only studied highly acidic scrubbing solutions because of their high ammonia capture efficiencies; however, the high acidity created practical problems. Lower acidity solutions w...Previous research on wet scrubbers has only studied highly acidic scrubbing solutions because of their high ammonia capture efficiencies; however, the high acidity created practical problems. Lower acidity solutions would reduce corrosion, maintenance, and cost; however, designers may need to use strategies for increasing scrubber effectiveness, such as using lower air velocities. The objective of this studywas to determine if a spray scrubber with slightly acidic and higher p H scrubbing solution （pH from 2 to 8） could effectively remove NH3 from NH3 laden air （such as animal building exhaust air）, and also collect this valuable resource for rater use as a fertilizer. A bench-scale spray wet scrubber treated 20 ppmv NH3/air mixture in a countercurrent contact chamber. First, the solution pH was varied from 2 to 8while maintaining constant air velocity at 1.3 m. s-1. Next, air velocity was increased （2and 3 m.s-1） while solution pH remained constant at pH6. At 1.3 m.s -1, NH3 removal efficiencies ranged between 49.0% （pH8） and 84.3% （pH2）. This study has shown that slightly acidic scrubbing solutions are a practical means of removing ammonia from air especially if the scrubber is designed to increase collisions between solution droplets and NH3 molecules. The NH3 removed from the air was held in solution as NH4＋ and accumulates over time so the solution should be an excellent fertilizer.展开更多
基金financial support of this study by the National Natural Science Foundation of China (NSFC No. 20876085)
文摘Spray coating of polymer latex onto fertilizer particles in a fiuidized bed for producing controlled-release urea is an environment friendly technology as it does not need any toxic organic solvent. Since the spray coating process in a fluidized bed occurs in the presence of particle collisions, the coating of the particles is random, intermittent and multiple, thus making it difficult to investigate the film formation process. In this paper, an experimental model apparatus was designed and used to investigate the effects of the key factors in the spray coating process. This apparatus reasonably simplified the complex process to avoid particle collisions and randomness in the coating. The intermittent coating in the fluidized bed was modeled by periodic coating and dewatering in the experimental apparatus. A large area film was obtained, and the film permeability was measured. The effects of atomizing gas flow rate, spray rate of latex, solid content of latex and gas temperature on film structure and film permeability were investigated. It was found that water transfer played a dominant role in the spray coating process.
文摘Previous research on wet scrubbers has only studied highly acidic scrubbing solutions because of their high ammonia capture efficiencies; however, the high acidity created practical problems. Lower acidity solutions would reduce corrosion, maintenance, and cost; however, designers may need to use strategies for increasing scrubber effectiveness, such as using lower air velocities. The objective of this studywas to determine if a spray scrubber with slightly acidic and higher p H scrubbing solution （pH from 2 to 8） could effectively remove NH3 from NH3 laden air （such as animal building exhaust air）, and also collect this valuable resource for rater use as a fertilizer. A bench-scale spray wet scrubber treated 20 ppmv NH3/air mixture in a countercurrent contact chamber. First, the solution pH was varied from 2 to 8while maintaining constant air velocity at 1.3 m. s-1. Next, air velocity was increased （2and 3 m.s-1） while solution pH remained constant at pH6. At 1.3 m.s -1, NH3 removal efficiencies ranged between 49.0% （pH8） and 84.3% （pH2）. This study has shown that slightly acidic scrubbing solutions are a practical means of removing ammonia from air especially if the scrubber is designed to increase collisions between solution droplets and NH3 molecules. The NH3 removed from the air was held in solution as NH4＋ and accumulates over time so the solution should be an excellent fertilizer.
