(42g) A Parametric Study for Oxygen Plant Based on the Claude Cycle

The air liquefaction system for oxygen plants in gas industries is based on the Claude cycle. The effect of process parameters on the overall system is difficult to analyse via manual calculations and this provides the motivation to use process simulators for understanding the steady state and dynamic behaviour of such systems. In this paper, a mathematical model for an industrial oxygen plant that produces 80 m3/hr of oxygen at Mitt Oxygen Pvt. Ltd. Bhavnagar was developed and analyzed. The effect of cycle pressure ratio, heat exchanger effectiveness, inlet air temperature, flow fraction and turbo-expander efficiency on overall performance were studied and optimal operating parameters were determined. It was found that with increase in pressure ratio the losses associated with the upper turbo-expander stage increase and this eventually reduces the excess refrigeration available in that stage. The excess refrigeration, which is passed to the final throttle stage for liquefaction, decreases the liquid yield. When forward stream pressure is increased, at a certain pressure ratio the gain in refrigeration by increase in enthalpy drop across the expanders is balanced by the loss refrigeration due to increase in expander losses. The study on the effect of heat exchanger performance on the cycle reveals that, compared to the rest of the heat exchangers, the inlet temperature to the expanders have more pronounced effect on the liquid yield of the cycle. For expander it was found that the effect of variation of isentropic efficiency is more sensitive when the flow through expander is at its optimum value, which yields maximum liquefaction.The results of this study are utilized to develop guidelines for improving the plant performance of the oxygen plant.