Study On Technology Of Yunnan Lignite S Wax Production By Indirect Electro-oxidation

The lignite wax is a scarce mineral-a kind of hard wax of high melting point that is extracted by organic solvents from the lignite, whose primary product is dark brown, referred to as course wax. Because of its deep color, it can only be used for making carbon paper, shoes oil, which do not have requirement on color, severely limiting its use. Decolorization on lignite wax and further deep processing of lighter lignite wax, and expansion of its scope of application, have been a research focus at home and abroad. Germany began to produce light color S wax in the1930s, but the technology has been kept secret. Our country produces1000tons of crude wax products ever year and there is no S wax product at present. The products totally dependent on imports from abroad. Xundian, Zhao tong and Ashan found waxy lignite resources and reserves are large recent years, therefore the condition that our country begin to develop the industry of S wax is pipe. In order to promote development of China’s lignite wax especially S wax, The research contents could be summarized as follows.First, with hot toluene as extracting solvent, lignite wax was extracted. The effects of extraction temperature, lignite moisture, crushing particle size were inspected on the influence of the extraction rate.Second, cold toluene as an extraction agent, lignite wax’s deresination process was researched.Third, chromic acid and sulfuric acid as the oxidant, with deresinated wax as raw material, oxidation decolorization was researched whiel chromate dosage amount of sulfuric acid, the reaction time on product yield and the impact of color were also examined.Fourth, analyzing that pure chromium sulfate and sulfuric acid as raw materials, the influences of initial concentration of sulfuric acid, chromium sulfate concentration, temperature current density, cathodic sulfuric acid were examined, Therfore, the optimum process conditions was determined. Under the optimum processing conditions, with the oxidation waste as raw materials, electro-oxidation was done and the cycle continues.Fifth, the diffusion dialysis was applied to process the acid lotion produced in the refining process, and the use of reduction and precipitation method also applied for the waste water containing of Cr3+Experimental results obtained were as follows.First, with hot toluene as extracting solvent, lignite wax was extracted. The optimal conditions for the extraction of lignite wax from Eshan lignite were that:the best combination is A3B2C2D2, the extraction temperature is95℃, the extraction time is90min, the moisture of is14.64%, the ratio of coal and solvent is1:3. The optimal conditions for the extraction of Montan wax from Xundian lignite were that:the best combination was A4B2C2D2, the extraction temperature is100℃, the extraction time is150min, the moisture of was12.63%, and the ratio of coal and solvent was1:3.Second, cold toluene as an extraction agent could take off20%resin from lignite wax. The production contained about2%resin.Third, the oxidation refinement technology of resin removed lignite wax was studied. The optimum reaction conditions were determined as follows:T1is4h, T2is3h, with wax: Na2Cr2O7·2H2O:H2SO4at ratio of1:2:5(weight). Under the condition, the color of wax was lighter and the yield can be up to83.5%.Fourth, the optimum conditions of electro-oxidation of Cr2(SO4)3were that:the current density was1100A/m2, concentration of Cr2(SO4)3was0.6mol/L to0.7mol/L, concentration of sulfuric acid of anode chamber was1.5mol/L to2.5mol/L, concentration of sulfuric acid of cathode chamber was0.5mol/L to1.0mol/L, normal atmospheric temperature, under these conditions, when the conversion of Cr3+was70%, the current efficiency was60%to70%.Fifth, waste acid was treatment by diffusion dialysis, the recovery ratio of sulphuric acid was more than80%. The retention rate of Cr3+was more than80%.The results showed that the recovery of sulphuric acid from waste acid could be achieved by diffusion dialysis. Washing water after treatment could meet the national discharge standard.