Research On Process For NaOH Desulphurization-biomass Reduction Smelt Of Spent Lead Paste

Lead paste in spent lead acid battery can be called spent lead paste,which contains PbSO4(50～65%),PbO2(25～45%),PbO(10～15%),Pb(0.5～3%)and a small amount of impurities.The process for NaOH desulphurization-biomass reduction smelt of spent lead paste was investigated in order to develop a method of lead smelt at low temperature.The method means a process of lead smelt less or without producing environmental pollution caused by Sulfur oxide and lead.To realize the objective without pollution,this study used NaOH as desulphurization agent and biomass as reductant in the treatment process of spent lead paste,and five kinds of biomass reductant(poplar,willow,cornstalk,reed and bagasse)were chosen.The main study contents included three parts:(1)study of specific characteristics of biomass reductants,(2)study of process for simultaneous NaOH desulphurization and biomass reduction smelt of spent lead paste,(3)study of process for NaOH desulphurization in advance and than biomass reduction smelt of spent lead paste.Experimental results indicated that:(1)The results of TG-DTA analysis showed that the poplar was thermal decomposedinto volatile within 200℃ to 500℃,accounting for 86%of the weight.And then the poplar formed solid residues within 500℃ to 800℃.accounting for 8%of the weight.The results of ash content analysis show that apart from bagasse,ash contents of poplar,willow,corn straw and reed were lower(1.75%～3.09%).These two typical characteristics of biomass are the key factors to realize low temperature reduction smelting of spent lead paste.(2)The optimum conditions for the reduction and smelting spent lead paste with poplar are as follows:spent lead paste of 100 g,poplar of 7 g,NaOH of 13.19 g,smelting temperature of 925℃,mixed abrasive time of 10 min and smelting time of 30 min.Under these conditions,the lead content of crude lead is 98.23%,the direct yield of lead is 98.30%,the slag rate is 1.45%,and the desulphurization degree is 95.27%.The comparative experimental results of different kinds of biomass reduction smelting waste lead paste show that:The reduction effect of these five biomass reductants is poplar>willow>reed>cornstalk>bagasse.(3)The optimum conditions for leaching spent lead paste are as follows:spent lead paste of 50 g,NaOH of 7.26 g,leaching temperature of 50℃,leaching time of 30 min,liquid-solid ratio of 2:1,Under these conditions,the desufurization rate is 98.46%and the mass of leaching residue is 43.6 g.The optimum conditions for reduction smelting of leaching residue are as follows:poplar of 7.0 g,smelting temperature of 825℃ and smelting time of 20 min.Under these conditions,the lead content of the crude lead is 97.39%,the vertical yield is 92.76%,and the slag rate is 5.10%.(4)The percentage of Pb and S in total Pb and S in smelting products in the experiment of simultaneous NaOH desulphurization and reduction smelt were 99.7%and 98.48%,respectively.The desulfurization rate in the experiment of NaOH desulphurization in advance and than reduction smelt experiment was 97.35%.The experimental data indirectly show that the amount of Pb and S entering the flue gas is very small,which indicates that the technology for NaOH desulfurization-biomass reduction smelting of spent lead paste can produce less lead dust and sulfur dioxide pollution.