Analysis of thermal system network of an ammonia plant using genetic algorithms - part II: network modification

This part of the paper examines two options of modification of the HEN of the ammonia plant based on two methods of pinch analyses, viz., network pinch method (NPM) and retrofitting analysis (RA) using genetic algorithms for both ∆Tmin and Qmin approaches. Using NPM with ∆Tmin and Qmin approaches, it is seen that there is a scope for reduction in hot and cold utilities by 1,758 kW and subsequently reduction in area of HEN by 368 m2and 136 m2which results in decrease of total annual cost by 1.71% and 1.30% respectively. Amongst the combination of modification, it is also found that using NPM with ∆Tmin approach, the hot and cold utility requirements for existing area efficiency and ideal area efficiency can be reduced with a payback period of 1.69 years and 0.80 years respectively.