*5.4. Model Implementation*

The formulated model is in MINLP presentation, containing a large number of continuous variables, binary variables and non-linear terms. The former kind refers to operational aspects, such as designed load, flowrate, temperature, fuel consumption, steam quantity, generated power and device size, while the later kind account for structure aspect, related to the existence of heat exchange matches and the utilization of steam. Non-isothermal mixing, heat exchange area calculation and cost calculation contribute to the non-linear terms. The model is programmed in the general modeling software GAMS and solved by the solver BARON [24], within the Windows 10 computing environment using an Intel(R) Core(TM) i7-8,700k CPU @ 3.70 GHz, 32.0 GB RAM. Here it should be noted that the global optimum cannot be always guaranteed if handling big size problems, but appropriate initial values of the variables will facilitate the search to improve the quality of solutions.
