Fouling reasons of black water system in gasification plant and optimization

The main influencing factors of fouling in coal gasification black water systems were revealed by analyzing coal samples, scale samples, and black water gray water samples. In terms of coal quality, the ash in coal is the main source of scale, and the use of high-ash coal increases the tendency of fouling. The black water gray water is featured by low water quality, high calcium and magnesium ion contents, turbidity, and dissolved solids, which easily precipitate and crystallize when the temperature and pressure of the system change drastically, leading to fouling. On this basis, a magnetic flocculant combined with ferric oxide and polyacrylamide was prepared. Experiments showed the turbidity of black water was effectively reduced under a certain dosage, and the removal rate of turbidity in black water reached 79.89%, but the turbidity was increased by adding excessive magnetic flocculant.