Economic optimization of steam plant operation.
详细信息
文摘
The utility system plays an important role in efficient plant operations of chemical processes. In this thesis,economic optimization of steam utility system is investigated in detail. The objective is: 1) to calculate the optimal generation amount of steam and electricity under uncertainty in process and electricity market； 2) to distribute the generated steam in a most efficient way throughout the steam network. In this work,steam distribution system is represented as a network with dynamic process equipment models. Operating constraints and uncertain process disturbances are included to accurately represent plant operations. A cost-benefit analysis reveals that electricity price plays an important role in optimal plant operations. Thus,to maximize the economic profit of a steam plant in the long term,a high quality electricity price prediction model is developed based on a robust switched system identification algorithm. The algorithm is formulated using Expectation-Maximization EM) algorithm to estimate parameters in prediction model,noise distribution and switching dynamics. Dynamic process models and electricity price prediction models are integrated into a linear programming problem that uses plant profit as the performance objective. Random process variables are included to represent process uncertainty. The optimization effect is evaluated by comparing the plant profit from routine operations and from optimized operations. The distribution of optimized plant profit is obtained by solving the distribution problem of stochastic linear programming SLP). A metric based on Earth Movers Distance EMD) is introduced to measure the difference between plant profit distributions. Based on the validation results of developed models and proposed performance evaluation method,the optimized steam plant operations show significant advantage over the routine ones when electricity prices vary considerably.