Producing high-purity chlorine dioxide gas

Abstract

A high-purity chlorine dioxide gas may use hydrogen peroxide as a reducing agent and may use horizontal generator, evaporation crystallizer, dryer and other devices to produce chlorine dioxide gas (product) and sodium sulfate (by-product). Compared to the conventional chlorine dioxide preparation system, the chlorine dioxide reaction and the sodium sulfate crystallization are performed in two processes. These processes are relatively separate and independent, and continuously produce chlorine dioxide gas with high purity and low moisture content while the by-product salt cake is evaporated, crystallized, filtered and dried, thereby producing sodium sulfate, without generating solid and liquid waste.

1 . The method for producing high-purity chlorine dioxide gas, comprising:
 using hydrogen peroxide as a reducing agent; and   using a horizontal generator, an evaporation crystallizer, a dryer and other devices to produce a product comprising chlorine dioxide gas and a by-product comprising sodium sulfate, wherein   chlorine dioxide reaction is produced by using the horizontal generator to produce chlorine dioxide, adding air into the horizontal generator, and stirring a reaction liquid and diluting the chlorine dioxide gas continuously to produce the chlorine dioxide gas with high purity and low moisture content, and   sodium sulfate crystallization is produced by evaporating, crystallizing, filtering, and drying a salt cake in the evaporation crystallizer and dryer to produce sodium sulfate powder.   
     
     
         2 . A method for producing high-purity chlorine dioxide gas in that hydrogen peroxide, sulfuric acid and sodium chlorate are used as raw materials to produce high-purity and low-moisture chlorine dioxide gas while salt cake is dried to produce sodium sulfate, the method comprising:
 entering sulfuric acid in a horizontal generator via a pipe;   delivering a reducing agent through another pipe such that the reducing agent enters the horizontal generator after being mixed with sodium chlorate in a tertiary pipe;   generating a chlorine dioxide gas when a REDOX reaction occurs;   entering heat source into the horizontal generator by way of a pipe to step heat the reaction liquid, to force the temperature of the reaction liquid to increase from 20-30° C. to 80-85°;   compressing the air by an air compressor such that the compressed air enters into the horizontal generator and stirring the reaction liquid to make the reaction uniform while releasing and diluting the chlorine dioxide gas;   blowing air, by a blower, into the horizontal generator for further diluting the chlorine dioxide gas concentration to 4-9% (V/V);   sending the diluted chlorine dioxide gas to use areas by an induced draft fan;   while the raw material enters the horizontal generator from one end, discharging the reacted reaction liquid from another end of the horizontal generator and into the mother liquid discharge tank for storage;   sending the discharged reaction liquid into the mother liquid lower circulating pipe by a crystallizer feed pump, and circulation, heating, evaporation and concentration between evaporation crystallizer and heater under a pumping action of a circulating pump, wherein the temperature in the evaporation crystallizer is controlled at 70-73° C., the vacuum pressure is controlled at −79 to −81 KPa(g);   concentrating and crystalizing sodium sulfate in the mother liquid and depositing the sodium sulfate at the bottom of the evaporation crystallizer, wherein the sodium sulfate is sent to a filtration device through a feed pump for filtration, washing and decrease water percent;   introducing salt cake solid into a dryer to produce sodium sulfate with dryness up to 99.5%;   returning a filtrate liquid to the mother liquid circulating pipe via the filtrate pipe for recycling, wherein neither solid nor liquid wastes are produced throughout the production process;   sending the clarified mother liquid from the upper part of the evaporation crystallizer to the mother liquid tank by a mother liquid extraction pump for buffering; and   sending clarified mother liquid to the horizontal generator by the mother liquid return pump.