| With stricter policies on environmental protection and strengthening method dealing with water conservation and pollution control, low-SO2 disposal is becoming an urgent task around the country, and enterprises operating beyond the boundary of environmental protection policies are facing shutdown. By request of Laibin smelting plant of Guangxi Huaxi Group Corporation L.T.d, taking tin(Sn) system in Laibin smelting plant as research target, the author conducted an experimental research on low-SO2 disposal with zinc oxide(Sno) basing on the reviewing work of clean production and combining the research project of "Investigation and strategy research on the current disposal situation of low-SO2 gas of Guangxi non-ferrous smelting", proposed by Scientific Standard Office of Guangxi Environmental Protection Department and the "the Eleventh Five-year Plan"of "Key project of low-SO2 gas disposal in non-electric industry" by Laibin municipality.Result of current investigation on low-SO2 gas disposal in Guangxi non-ferrous smelting showed that the concentration ratio of SO2 discharged by zinc and Tin is generally low, only 0.2% on average. Therefore, it can not be used to make acid directly, and indirect acid making method and desulfurization approach by hydrome smelting gas conversion is widely adopted at present. Meanwhile, investigation and research conducted on these enterprises revealed a series of problems:(1) backward smelting technology, and narrow scope of low-SO2 disposal;(2) though acid making disposal approach achieved desirable result, mis- installation and malfunction exists in end gas absorption desulfurization devices; (3) the cost of gas desulfurization approach is very high, and its byproducts are difficult to be comprehensively utilized;(4) inadequate attention was attached to environmental protection management and clean production of the enterprise. Compare with other desulfurization approaches, zinc oxide approach boasts the following advantages:high absorbility, sufficient source of absorbent, high rate of recycling use, cost-saving and operating expenses- saving. All these advantages make it widely applied into the practice of disposing low-S02 in lead zinc smelting enterprises. Research findings of predecessors showed that the parameters of SO2 inlet which affects gas and liquid contacting condition, the solid content of slurry, liquid to gas ratio, superficial gas velocity, and the degree of acidity are the main elements which affect the ZnO desulfurization efficiency.Therefore, this experiment aims at exploring how technological conditions affect the desulfurization efficiency and seeking for reasonable and practical desulfurization disposal parameters by changing the concentration of inlet SO2, the PH value of slurry, solid content in slurry, liquid to gas ratio, surface gas velocity. Taking the zno dusts produced from Zn system of Laibin smelter as the absorbent, the experiment started from November 2009 and completed half year later by accomplishing mono factorial experiment and comprehensive experiment by using ZnO to dispose the low-SO2 gas produced by the Sn system. Low-SO2 in Zn system mainly came from the furnace in fluid bed, the reverberatory furnace and the fuming furnace in the crude smelting workshop.Result of monofactorial experiment showed:(1) when the concentration of inlet SO2 is smaller than 13650mg/m3, the desulfurization efficiency rose with the increasing of concentration of inlet SO2, when the concentration of inlet SO2 arrived at13650mg/m3,the desulfurization efficiency reached its maximum value, then the desulfurization efficiency began to decline with the continuing increasing of concentration of inlet SO2;(2)Under the acidic condition, the desulfurization efficiency increased with the increasing value of the concentration of inlet SO2, they approached the linear relation, however, when the desulfurization efficiency arrived at a certain level (PH=5), the increasing rate was not obvious any more; (3) when the slurry solid content rate was bigger than 12%, the desulfurization efficiency increased correspondingly with the increasing in slurry solid content rate; (4) the desulfurization efficiency increased with the increasing of liquid to gas ratio, but when the liquid to gas ratio arrived at 4.5%, there was no obvious increasing in desulfurization efficiency; (5) when surface gas velocity was smaller than 5.43m/s, the desulfurization efficiency declined with the increasing of the surface gas velocity, when surface gas velocity was bigger than 5.43m/s,they appeared to be direct ratio relationship.Comprehensive experiment result showed that desulfurization efficiency achieved the best result of up to 95.1% under the conditions of concentration of inlet SO2 arriving at 13000mg/m3,the PH value of Zno slurry of 5,the slurry solid content of 14.3%, liquid to gas ratio of 4%, and surface gas velocity of4.8m/s.These research findings provide scientific evidence for IOW-SO2 disposal engineering design and operation in znsn smelting enterprises and were of great significance for enterprises to achieve sustainable mitigation goal. Due to the limitation of time, research cost and the current conditions of the enterprises, weaknesses still exist:the experiment could not yield definite explanations for curvilinearity between surface gas velocity and the desulfurization efficiency, further study is needed in this aspect in the future. |
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