Research on synchronous optimization of steam power system for processing units and thermal power plant operation

The steam power system of the units in the refinery is usually designed and operated independently, which ignores the connection with the steam power system of the thermal power plant. Steam power system in thermal power plant is often optimized under fixed steam and power demand, ignoring the connection to the steam power system of the units. To achieve the overall optimization of the steam power system of the refinery, this paper proposed a method for synchronous optimization of steam power system for processing units and the thermal power plant operation. Firstly, the equipment model coefficients were obtained by using the design and operation data of the turbines and boilers of the thermal power plant, and steam power system constraints for the thermal power plant were established according to the existing structure. Then, based on design and operational flexibility of steam power system for units, the units were divided into three categories. The first category of units cannot adjust the steam and power demand, the second category of devices can adjust the steam demand by temperature and pressure reduction, and the third category of units cannot only adjust the steam demand by temperature and pressure reduction, but also adjust the steam and power demand through drive selections. The model parameters for turbines in units used the literature values, then established the steam power system constraints of the units by collecting data of steam and power demand of units. Finally, a coupling model is established through connection of steam and power between the thermal power plant and the units. The coupling model takes the annual cost as the objective function, which includes the operating cost of the thermal power plant and the annual investment cost of turbines and motors for units. Equipment load distribution plan of the thermal power plant and steam power system design plan of units is obtained through optimization. The feasibility of the synchronous optimization method is demonstrated through a calculation example. Compared with the independent optimization, the synchronous optimization reduces annual expenses by USD 4.51 million. © 2022 Chemical Industry Press. All rights reserved.