Study On New Recovery Technology Of By-products In Process Of Tannin Extract Desulfurization

Tannin extract desulfurization process is a widely applicable liquid-phase desulfurization technology. Although there are many technological advantages in process of tannin extract desulfurization, it has side reactions deficiency which exists in other liquid-phase desulfurization technology. Sodium thiosulfate (Na₂S₂O₃) and sodium thiocyanate(NaSCN) are main by-products in tannin extract desulfurization waste liquid, the content of them are high. It has a good foreground if the two by-products were recoveried. The recovery of the by-products in tannin extract desulphurization waste liquid urgent need to solve because of which has not mature technology.First, tannin extract desulphurization waste liquid was analyzed and the five by-products's solubility was determined which provide a theoretical basisi for reclaiming of by-products in this paper. We can find Na₂S₂O₃ and NaSCN solubility is very large in tannin solution. We also find that the Na2SO4 solubility is relatively small in tannin solution, so we can search the concentrated sulfuric acid was added in tannin extract des-ulphurization waste liquid ,then Na₂S₂O₃ was oxidezed to Na2SO4. But this reaction produces sulfur dioxide which seriously pollutes the environment.Floating TiO₂/EP photocatalyst was prepared by Sol-Gel method using Tetrabutyl tianate (TBT) as precursor and expanded perlite as support in this paper. The catalyst was characterized by XRD, BET, SEM, EDS and IR. Studing on the photoccatalyst oxidation ratio of Na₂S₂O₃ in waste tannin extract solution soat the conditionof 20 W ultraviolet radiation .The influences of the amount of photocatalyst ,the pH , the concentration of tannin extract solution initial, and times of the Catalyst usage were investigated. The results indicated that a volume of 100 mL of Na₂S₂O₃ solution whose concentration was 100 mg/L was oxygenized more than 80% by 0.2 g, charge number 7% of the catalyst. It has development value because of floating on the water surface and large area throwing and recycling.The solubility of Na2SO4 is very small in methanol or ethanol, but NaSCN is easily dissolve in ethanol.So Na2SO4 was recoveried through added the second solvent- anhydrous methanol or ethanol, the recovery rate can reach above 90 percent. Recovery of NaSCN using evaporative crystallization, a series of recovering experiments were designed to examine the influence of temperatue and stirring speed and determined the most appropriate experimental conditions: the speed of rotation is 350r/min, operating temperature is 45℃.