Modelling identification and control of production of glycerine from tallow fat by hydrolysis

Abstract

This research is proposed to develop a comprehensive mathematical framework for the design of multivariable control for the aqueous hydrolysis of tallow fat into oleo chemicals such as glycerine and fatty acids due to its emerging demand in the form of personal-care, health-care, animal feed, pharmaceutical products etc. Though chemistry and know-how behind the process are known, dynamics and operational safety behind combined system needs to be understood from the view point of minimal energy utilization. Establishment of inherent safety aided with intense process controls is the aim behind this investigation. Tallow is one of the resources for glycerine and other oleo chemicals which are obtained by subsequent hydrolysis, saponification or trans-esterification. Steam hydrolysis is being practiced by many industries where continuous high pressure hydrolysis process is considered. Generally the process occurs in a spray column/tower. The above process involves reaction of fat with excess of water under conditions of high temperature (220-320 qC) and pressure of 40-60 bars. High pressure pumps are used to feed melted fat mixed with water from the bottom of the tower and pressurized water from the top. Between these, the fat and water form a continuous phase in the heat-exchange section where complete hydrolysis takes place in approximately three hours. Continuous countercurrent flow is maintained due to the density difference between the two phases in the heat exchange section. The fatty acids, black in color, float on the top where-from they are drawn off and distilled. The unreacted water containing glycerine is removed from the bottom of the tower and also distilled to produce pure glycerine. As the temperature and pressure play important roles in the degree of hydrolysis through equilibrium production, it is necessary to understand the mechanism and kinetics in order to find out the safer dynamics of the processunder wide range of temperature and pressure. A state of art review on hydrolysis process shows less r