METHOD AND INSTALLATION FOR CONCENTRATING CAUSTIC SODA AND CONSTRUCTION OF EVAPORATION APPARATUS Russian patent published in 1999 - IPC

FIELD: inorganic compounds production. SUBSTANCE: three-step heating is employed wherein: in the step I, heating is provided by secondary vapor from step III and, in the steps II and III, by high-temperature heat carrier. Initial 43-45% caustic soda solution is concentrated to 50-55% in the step I, and further to 70-75 and 98% in the steps II and III, respectively, using, as high-temperature heat carrier, superheated steam at 1400 C, obtained from burning hydrogen in oxygen. Step III solution is subjected to evaporation of residual moisture to achieve 99% product concentration. Secondary vapors coming out of steps I and II are additionally purified. Installation contains three in-series connected evaporators, the first one being provided with collector for gases escaping the third evaporator, while the second and third evaporators are provided with combustion chambers; heat exchanger for concentrating secondary vapors; wash water vessel; vacuum evaporator to evaporate residual moisture; separator; heat exchanger to cool secondary vapors until condensed; vacuum pump; Venturi tube connected to secondary vapor-purification cyclone. Evaporation apparatus structure is distinguished by having cone-shaped casing with combustion chamber mounted on its top and being provided with pipeline mixer with separator on its end. Pipe for charging caustic soda and discharging water vapor is disposed in the zone where combustion chamber abut on evaporator cover. EFFECT: simplified process flowsheet, reduced power consumption, and reduced fire danger and corrosive activity of medium. 4 cl, 2 dwg