Physicochemical Properties And Granulation Performance Of Fly Ash Derived From U-GAS Gasifier

U-GAS coal gasification technology has many merits, such as strong adaptability, low operating temperature, high gasification intensity, contains no tar and phenol in the product gas, etc., is one of the more advanced gasification technology. But the process will produce a large amount of fine fly ash with high carbon content, resulting in low carbon conversion rate. Moreover, a large accumulation of fly ash occupation of land, pollute the environment and endanger human health. Therefore, the reasonable use of fly ash becomes the problems of U-GAS gasification process to be solved.Fly ash derived from U-GAS gasifier was investigated in this paper, the physicochemical properties of fly ash were examined, potential application approaches of fly ash were also analyzed. In addition, the granulation process of fly ash was emphatically studied, the feasibility of granular fly ash used in fluidized bed bolier was discussed too. The main results of the paper are as follows:(1) The carbon content of fly ash derived from U-GAS gasifier is as high as 50.49%, and the heating value is 17390KJ/kg; SEM showed that fly ash derived from U-GAS gasifier is irregular shape, almost do not contain rules of spherical particles, is different from ordinary boiler ash; total SiO2 and Al2O3 content in the chemical composition of fly ash is up to 83.11%, with high recycling value; granularity of fly ash particle size is small, the center granularity is only 13μm, the flotation performance of fly ash is poor; fly ash has high ignition temperature and long burning time, the reactivity of fly ash is poor.(2) Fly ash granulated alone is less effective, the incorporation of pulverized coal can significantly improve the granulation and combustion; laboratory optimization selection of sodium silicate as binder of fly ash granulation; pulverized coal and fly ash ratio of 1:1, binder adding quantity of 10% is the optimum parameters for fly ash granulation; the combustion property of granulated product is closed to pulverized coal, it can be used in fluidized-bed boiler alone or blending with pulverized coal.(3) The coal quality of dry granulation products is similar to pulverized coal, the ignition temperature of granulation products and pulverized coal differs 16℃, burnout tempreture differs 4℃, the ignition and burnout temperature appear highly consistency and simultaneous changes in both of the combustion curves, the combustion temperature regions are basically coincident.(4) According to the annual output of 200000 tons of granulation process line, only raw material costs can save 33.4 million yuan/year without considering the interests of the granulation products produced after burning.