METHOD OF AUTOMATICALLY CONTROLLING PROCESS OF EVAPORATION OF ELECTROLYTIC ALKALI IN MULTIPLE-EFFECT EVAPORATOR Russian patent published in 2003 - IPC

FIELD: chemical engineering. SUBSTANCE: invention, in particular, relates to production of commercial sodium hydrate via evaporation of electrolytic alkali after diaphragm electrolysis. Subject of invention consists in creating automatic control of process ensuring specified productivity regarding commercial caustic and its quality (purity) involving automatically according evaporating solution loadings between evaporation steps as follows. Temperature of saturated water steam accepted for computation of temperature depression value indicative of current NaOH concentration is continuously measured from current value of absolute pressure (vacuum) in separator of the evaporator. Thus computed temperature depression value is used as controlled variable in regulators of middle alkaline solution and final caustic concentrations. Level control in intermediate tank for middle alkaline solutions is achieved by automatically adjusting task of heating steam pressure regulator in boiler of second-step evaporator so providing accord between productivities of the first and second step. EFFECT: increased productivity of process and improved purity of product. 3 dwg, 3 ex