Improvement For The Concentration Techique Of Waste Acid From Titanium Dioxide Production By Sulfuric Acid Method

This paper mainly makes improvement and optimization to the present three-stage evaporation for titanium waste acid of CHONGQING YU-GANG TIOXIDE CO LTD. In the process of waste acid by traditional technique, sulfate is extremely easy to crystallize because of the increases of acid concentration , Therefore, the heater exchanger and pipes have serious scaling phenomenon , the utilization of equipment is low and operation cycle is short.In view of the above situation , a new method of waste acid concentration has been systematically studied .The new craft bases on the solubility principle method. In the process of first level enrichment, the new craft use vacuum crystallizing method to make the heating process and crystallization independently. Therefore, we can choose the crystallization temperature and time, and the sulfate under appropriate temperature can not crystallize when the solution is heated, Then about 70% of sulfate has separated out from the waste acid by centrifuge, and the remaining sulfate has been removed. Using the external heating type evaporator. Finally , the waste acid concentration rise from 65%. to 80%, by evaporation. The finished product acid can be sent back to the process of titanium dioxide production. Moreover,using the 5% sulfuric acid to clean sulfate separated from the waste acid can get the purity more than 90% of the ferrous sulfate, and this products can be used as a finished product to sell.Meanwhile, carrying on preliminary process design based on the empirical data and the original process equipments forms a set of new waste acid concentration technique. In this paper, new technical process, technical character and the mass balance has been introduced in detail. And from the massive literature material and the various property data, a thermodynamic model of reaction system is established. The material and thermal balance of each reaction stage is calculated, and the consumption of the new technique is determined as well. Then, the new craft's major equipments, including the vacuum crystallizer,the evaporator and the heater exchanger etc. , are selected through calculation. Moreover, all the diagrams of Process Flow Diagram(PFD), Pipe and Instrument Diagram(PID),equipments,and plant layout are drawn with AutoCAD software. Finally the comparison of the new and old technology investment shows that the new technique has apparent technique advantage and can make an increase more than 2.21 million yuan economic benefits for the company annually.The new craft has overcome several serious defects existed in the traditional process, and the technical difficult problem of equipments and piping scaling can be fundamentally solved . The merits of the new craft are simple operation, high utilization ratio and little pollution . Also the economic efficiencies and the development of the new craft are extremely optimistic. So this craft is of strong technical superioritys and worth promoting.