Addition of ash to prevent agglomeration during catalytic coal gasification in a pressurized fluidized bed

Abstract

The agglomeration of potassium-loaded Wangjiata coal during catalytic coal gasification (CCG) was investigated in a bench-scale pressurized fluidized bed. The pressurized pressure-drop sintering technique was employed to understand sintering characteristic in a CO/H2/H2O mixture atmosphere at 3.5MPa. The ash, which was removed the water-soluble potassium compounds from gasification residue, was added to prevent fluidized bed agglomeration. The effects of the addition of ash on the catalytic activity and recovery of K2CO3 catalyst were also evaluated. The results showed that K2CO3 catalyst lowered the sintering temperature of coal ash, and the agglomeration tendencies increased with increasing amount of K2CO3. The presence of K–Ca–Fe phases was responsible for the agglomeration in CCG pressurized fluidized bed gasifier. The sintering temperature of coal ash increased, and no agglomeration occurred after the addition of water-washed ash. A good correlation was established between the sintering temperature and acid/basic (A/B) ratio in CCG atmosphere at 3.5MPa, and the sintering temperature increased with increasing A/B ratio in ash. The addition of water-washed ash did not decrease the gasification activity or water-soluble potassium recovery. This technique effectively prevented agglomeration in the pressurized fluidized bed gasifier.