SIMULATION OF REACTIVE ABSORPTION COLUMN

Abstract

The present investigation pertains to a theoretiCal study on the simulation of reactive absorption column. It basically deals with the development of a mathematical model for these absorbers. It also includes the solution technique for the solution of the model. In the end, studies of the effect of different operating parameters viz. gas pressure, gas and liquid temperatures, gas concentrations and liquid molarity on the model behaviour has been done. Using the basic principles of mass conservation, energy conservation and gas-liquid equilibrium a mathematical model of a reactive absorption column has been developed. These balance equations include component material balance, phase equilibrium, sum equations and enthalpy balance equations. The relation for phase equilibrium for a reactive absorption process has been developed from the principles of chemical thermodynamics to give the "Thermodynamic model." The balance equations, which are non-linear in nature, are linearized using Taylor Series expansions and then transformed into a tri-diagonal matrix system. The resulting system of equations are solved using "Thomas Algorithm" to get the component flow rates and temperatures of 4.3t./ G(4/110. The model developed is tested for the absorption of H2S into aqueous Diethanolamine (DEA). The results of the simulation have been compared with those due to DeLeye and Froment (1986). An examination of the results shows, that the model has been successful in representing the reactive absorption column for the above system, as has been found for the different profiles of temperature, pressure and the molar flow ii rates of gas and liquid. The maximum deviation between the profiles obtained by this simulation with those obtained by DeLeye and Froment (1986) was found to be around 5%. This simulation technique as has been found here requires lesser number of iterations for the solution of the same problem as compared with those by DeLeye and Froment (1986). The effect of operating variables e.g., pressure of the gas, temperature of gas and liquid and the gas and liquid compositions has been made. The results show that the model and its solution technique have been successful in showing the behaviour of the column with a change in the operating variables. A sensitivity analysis of the process shows that for a particular composition of the incoming streams the Pressure of gas plays an important part in deciding the height of the column required for a particular level of separation. Temperatures of the liquid and gaseous streams have been found to be the next in importance in deciding the heigh