Abstract
The ammonia concentration in exhaust gas from composting with vacuum-type aeration is higher than that of positive-pressure aeration thus requiring a new deodorization method. Experiments have been conducted on the deodorization and recovery of high concentrations of ammonia using recovery materials (adsorption materials) made from rice husks and orthophosphoric acid at mass ratios of 1:0.5, 1:1.0, 1:1.5, 1:2.0 and 1:2.5. For 1kg of recovery material, the time and quantity of ammonia adsorption were about 28 hours and 159g (1:2.0), respectively. In this case, the recovery material was filled to a heap height of 50cm in an adsorption reactor about 15cm in diameter and ammonia gas at 4000ppm was flowed through it. This was about 2.6 times and about 23 times the adsorptions of impregnated charcoal and of zeolite, respectively. In terms of pH, it is considered that diammonium phosphate and ammonia dihydrogen phosphate were coated with the rice husks of the recovery materials after adsorption. Re-emission of the ammonia from the recovery materials after absorption was observed when air temperature exceeded 30°C. Thus, further study is needed on the relationship between the re-emission of ammonia and atmospheric temperature.
