| From the early 1970 s, Shell pulverized coal pressurized technology had appeared.Then this technology had been constantly developed and improved, and gradually put into production. A large amount of shell coal gasification fly ash had appeared with the development and application of the technology. But the application study of this kind of coal ash is not common. Thus, we prepared different types of zeolite on the base of the analysis of the physical and chemical properties of shell coal gasification fly ash. The denitrification capacity of the synthetic zeolite was studied, and the results provided the instructions and data supports for the resource utilization of shell furnace coal fly ash and the application of synthetic zeolite in the treating ammoniated waste water.The components of shell furnace coal fly ash are determined by national standard method and analyzed by XRD and SEM. Results show that the coal fly ash particles are spherical particles with smooth surface, its mineral composition is mostly amorphous glass phase and less crystalline phase in rich Si O2 and Al2O3, and it can be used in the synthesis of zeolite with high reactivity. Denitrification ability of this coal fly ash is limited, and the removal rate of ammonia nitrogen is only 8.22%.The zeolite was synthesized by the hydrothermal method using shell furnace coal fly ash, and the Si/Al of raw material is 4.8.The Si/Al in the reaction system is changed by adding sodium aluminate and the type of synthetic zeolite crystal was analyzed and identified. The synthetic products are mainly Na A zeolite crystalswhen the Si/Al is 1.7 and 2.0 in the reaction system.The products are mixed crystal mainly consisted of Na P1 zeolite and Na A zeolite when the Si/Al is 2.5. The main components of synthetic product are Na P1 zeolites when the Si/Al is 3.0, 4.0 and 4.8. The denitrification ability of Na A zeolite with 1.7 of Si/Al and Na P1 zeolite with 3.0 of Si/Al are both better.Na A zeolite was prepared with 1.7 of Si/Al and synthetic conditions are optimized by single factor experiment and orthogonal experiment.The optimum conditions are determined to be 1 mol·L-1 of Na OH, 100 ℃ of crystallization temperatures, 7 h of crystallization time and 5:1 m L·g-1 of ratio in liquid-to-solid. The denitrification ability of synthesized Na A zeolite under these conditions is best and the removal rate of ammonia nitrogen reached 74.62%. The orthogonal experiment results show that the influence of different factors on denitrification performance of Na A zeolite is alkali concentration > crystallization temperature > ratio in liquid-to-solid > crystallization time. The best products are analysized by XRD, SEM, BET and BJH. Results show that its crystallinity is large and its purity is high. Crystal morphology is completed and inerratic, and the particle size is about 3μm. The pore arrangement of zeolite is in order and closely, and the hole size distribution is average. The specific surface area of zeolite is 51.48 m2·g-1, and pore size is 11.00 nm.Na P1 zeolite was prepared adjusting Si/Al to 3.0. The optimum experimental conditions of synthesized Na P1 zeolite were determined to be 2 mol·L-1 of Na OH, 100 ℃ of crystallization temperatures, 10 h of crystallization time and 4:1 m L·g-1 of ratio in liquid-to-solid by optimizing the synthesis conditions. Under these conditions,the removal rate of ammonia nitrogen of Na P1 zeolite is 72.12%.Orthogonal experiment results show that the influence of various factors on denitrification capability is in the order of alkali concentration > crystallization temperature > crystallization time > ratio in liquid-to-solid.The analysis result of best Na P1 zeolite product shows that its purity is high and crystal particles are out-of-shape and irregular arranged.The size of crystal particles are different and crystal grain size is about 1.5~2 μm.Na P1 zeolite cavities arrange regularly and closely and the hole size distribution is very homogeneous.The specific surface area of zeolite is 36.36 m2·g-1 and pore size is 18.92 nm.Two kinds of zeolites with better denitrification performance were successfully synthesized using shell furnace coal fly ash in this issue, namely Na P1 zeolite and Na A zeolite. They both can be used in the treatment of ammonia nitrogen wastewater. |
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