Design And Investigation On Evaporation Equipment For 72% (wt) Flake Caustic Soda Production

Evaporation process is an important link in the chlor-alkali production system. It plays an important role in concentrating the electrolyte alkali liquor into commercial caustic soda. And it is also a link with much more energy consuming in the production of caustic soda. Natural circulation evaporator with external calandria is used in the evaporation process for the production of 72% (wt) flake caustic soda. This kind of device has many advantages, such as simple structure, great throughput, high heat transfer efficiency, lower energy cost and easy operation & maintain. It becomes more and more popular in the chlor-alkali industry production.At present, the study and application of natural circulation evaporator with external calandria for 72% (wt) flake caustic soda production have been made some new developments. The evaporation process is very complex owing to many kinds of factors. Lacking of basic data, the design of 72% (wt) flake caustic soda production evaporator depends on much experience. Also, there lacks a completely design and calculate method for this equipment at home and abroad.In this paper, the fluid flow and heat transfer characters in the evaporator with different operation and structure parameters were studied using the theories analysis and CFD numerical simulation method. Therefore, the theory basis to the structure improvement and operation parameters optimization was provided. Major research work and conclusions in the thesis are as follows:(1) The evaporation mechanism of natural circulation evaporator with external calandria used in 72% (wt) flake caustic soda production was studied based on theory analysis from the point of fluid-dynamics and heat transfer. A formula used to estimate the height of vaporization section was given according to Clausius-Clapeyron equation. And the mathematical model of evaporation process was proposed. The program with Visual Basic language was compiled and it was solved with Newton iterative method. The effect of operation and structure parameters of evaporators on the propelling force, heat transfer coefficient, circulation rate and evaporation rate was studied. A comparison between the...