Design of heat integrated water networks with multiple contaminants considering non-isothermal mixing

A new stepwise optimization method for the minimization of energy and water in multiple-contaminant systems was proposed in this paper.For water networks(WUN),non-isothermal mixing inside unit operations between freshwater and reuse water was considered to reduce the number of heat transfer units.We can only consider heat recovery between freshwater and refuse water in heat exchanger networks(HEN).The nonlinear programming(NLP) model of WUN and mixed-integer nonlinear programming(MINLP) model of HEN were established.An improved particle swarm optimization was proposed for optimizing such systems.The results of an example showed that the optimized network was simpler and 2.4% of annual cost can be saved,indicating the feasibility and effectiveness of the above method.