Toshimasa Hirama

Fluidized bed pyrolysis of oily sludge for fuel oil recovery.

To recover fuel oil from oily sludge, experimental studies were performed using a fluidized sand bed pyrolyzer. The heat energy for the pyrolysis of sludge was supplied from the heat of a partial combustion of sludge. It was revealed that the yield of recovered oil decreased with increasing bed temperature within the range of from 500 to 600°C. The viscosity of recovered oil decreased with the increase of the oxygen concentration in fluidized gas. The properties of the recovered oil ranked with those of the fuel oil. Moreover, the sulfur content in recovered oil was reduced to 70%, as compared with that in sludge. When lime-Stone or natural zeolite were used as the fluidized particles, relatively low viscous oil could be produced, but its yield value was small compared with the use of silica sand. The estimated value of heat con-sumption for pyrolysis was ranged from 390 to 530 kcal/kg.

Fluidized bed combustion technology of oily sludge.

To develop a new process for heat recovery from oily sludge without any environmental pollution, the combustion experiments of low grade oily sludge having a 3, 500kcal/kg of calorific value were performed using a fluidized bed combustor with a 0.3m square area and a 3.25m height. The combustor was equipped with an air distributor of the pipe-slit type for the continuous discharge of combustion residues such as iron rust and pebbles from the bottom.The use of the above-mentioned air distributor and the continuous feeding of fluidizing particles enabled a continuous and stable operation without the piling of the combustion resides in the bed. Then, the sludge could be completely burned at a bed temperature of above 750°C and a residual oxygen concentration of over 5%. The simultaneous removal tests sulfur-dioxide (SO2) and hydrogen chloride (HCl) were also carried out by means of limestone and/or coral reef rock feeding in the bed. The HCl removal efficiency increased apparently with the value of a Ca/ (S+Cl2) mole ratio, whereas SO2 removal efficiency was slightly affected by a mole ratio that ranged from 2 to 6. The removal efficiencies of SO 2 and HCl were 85% and 55%, respec-tively, at a mole ratio of 3 for coral reef rock.