Preparation Of Zeolite By Coal Fly Ash From Coal Gasification

Coal fly ash is solid waste collected from coal chemical and thermal power plant.The emission of coal fly ash caused serious environmental pollution. It is meaningfulto synthesize coal fly ash into artificial zeolite for waste disposal of coal fly ash.Today, for many scientific researches about synthesized coal fly ash into artificialzeolite, the resource of coal fly ash is mainly from thermal power plant fly ash andthe synthesized artificial zeolite is generally used for removal of heavy metal ionsfrom water. Therefore, it is scarce to study on preparation of zeolite by coal fly ashfrom coal gasification and to make use of the synthesized artificial zeolite. Faced withthis fact, in this work, raw material of coal fly ash is produced by shell furnace coalgasification and zeolite is prepared by hydrothermal synthesis with coal fly ash.Experimental conditions of synthesized zeolite are optimized and investigated byorthogonal experiment and single factor experiment, so that optimum conditions forremoval of the ammonia ion is obtained.The components of coal fly ash are determined by national standard method andcharacterized by XRD and SEM. Produced by coal gasification, the characteristic ofcoal fly ash showed simple components, low amounts of carbon, and the structure ofsmooth spherical particles with amorphous state, and high activity Therefore, it canbe used to prepare artificial Zeolite.The optimum experimental condition of synthesized zeolite is investigated byorthogonal design and the cation exchange capacity (CEC) is used to measure theproperty of products. The optimum synthesis conditions by orthogonal experimentalwere determined to be450℃of calcination temperatures,110℃of crystallizationtemperatures,8h of crystallization time,3mol·L-1of NaOH and4:1of ratio inliquid-to-solid. Under these conditions, the CEC of zeolite product is268.6cmol·kg-1.Single factor experimental was used for further study in investigation of experimentalconditions. The factors of calcinations temperature, concentration of NaOH,crystallization time, crystallization temperature and liquid-solid ratio was investigatedand to explore the effect of this factors on cation exchange capacity (CEC) of zeolite products. By method of single factor, the optimum experimental conditions weredetermined to be that500℃of calcination temperature,110℃of crystallizationtemperatures,6h of crystallization time,4mol·L-1of NaOH and4:1of ratio in liquid-to-solid, the CEC of zeolite product is277.1cmol·Kg-1, which is30times higherthan that of coal fly ash. Compared with the optimum experimental conditions oforthogonal, the CEC of zeolite is little higher in optimum experimental conditions ofsingle factor experiments. But it requires higher concentration of NaOH andcalcination temperatures. Therefore, considering the costs of production, the optimumexperimental conditions of orthogonal is more realistic.The products of zeolite were characterized by XRD and SEM. The results ofSEM for zeolite showed that crystal morphology of zeolite was significantly changedand surface structure of zeolite is rough and porous. The results of XRD showed thatthere are two kinds of XRD pattern about amorphous and crystal diffraction. What’smore, all crystal diffraction peaks of zeolite are so similar that these products can bethought as a same type of zeolite. The products of zeolite were characterized by XRDand a match pattern of XRD was found with software of Jade6.5. The result showedthat the type of zeolite synthesized in this experimental is zeolite Na P1.In this research, it is successful to synthesize coal fly ash produced by coalgasification into zeolite. The exchange capacity of zeolite products from ourexperimental is so good that synthesized zeolite can be widely used in treatment ofammonia and nitrogen wastewater. The work can provide theoretical evidence forresource utilization of gasification ash.