Applications of generalized reduced gradient method to the cogeneration problem in a synthetic fiber plant

The present work investigates the effects of fuel cost, purchased electricity cost, condensate recovery, sales price of steam, amount of sale steam as well as the effects of process utility requirements on the optimal cogeneration of steam and power in a synthetic fibre plant in Thailand. The optimization result shows that when purchased electricity is 1.438 Baht/KW and fuel cost increases from 2.62 Baht/litre to 5.00 Baht/litre it is definitely cheaper to buy more and to generate less electricity. Conversely, when fuel cost is 2.62 Baht/litre and purchased electricity increases from 1.438 Baht/KW to be 1.869 Baht/KW, it is better to produce more steam in order to generate more electricity while purchasing as little electricity as possible. With the application of the GRG optimization method, the obtained optimal cogeneration condition help reduce the utility cost by 331 Baht/hr compared to the original operating conditions. Amount of condensate recovery and sales price of steam do not affect the optimal cogeneration conditions. On the other hand the effect of the amount of sale steam is similary to that of increased process steam requirement.