Research And Application On Optimization For Steam Power System In Petrochemical Plants

Steam power system, which is considered as a significant component of energy system in petrochemical industry, provides essential utilities including steam, electricity and power for production. On one hand, steam power system forms the foundation for smooth operation; on the other hand, it is also one of the main sources of pollution. Under the new energy-saving and emission reduction conditions, it is beneficial to study the optimal operation of steam power system to accomplish such goals as enhanced economic benefits, reduced pollutant emission and improved comprehensive competitiveness of enterprises. In the past decades, numerous modelling and optimization methods have been proposed to minimize the economic cost of steam power system solely. However, environmental factors have been inadequately taken into account and few academic researches have been adopted in practice. As a result, it is of great value to give a comprehensive research into this problem. To this end, optimization problem for steam power system that considers both economic and environmental factors simultaneously has been discussed and corresponding optimization software is developed. The main contributions of this dissertation are listed as follows:(1) The application background and development situation of steam power system are reviewed. The state of art modelling approaches and solution algorithms are then summarized, which is followed by analysis of problems and shortage concerning modelling approaches. At last, the necessity of multi-objective optimization of steam power system considering economic and environmental aspects is described.(2) Modelling framework for operation optimization of steam power system is described firstly. A multi-period MILP model for steam power system is analysed based on mathematical model of key devices, which is the base of follow-up study.(3) In view of the influence of environmental cost on scheduling of steam power system, main emission including CO2、SO2、NOx are explicitly considered to construct the MOMILP. To solve the optimization problem effectively, the AUGMECON2 algorithm is adopted. Case study in refinery shows that the method can provide multiple sets of viable scenarios for operator to choose, which enhance the flexibility of optimal scheduling.(4) Compared with that in refinery, steam power system in ethylene unit possesses more scheduling method. The differences in internal structure and the connection with the outside are concluded at first. Then, the multi-objective optimization model of steam power system under various environmental standards are solved, by which the scheduling adjustments for adapting to a more rigorous standard are reflected. Meanwhile, the comprehensiveness of the modelling framework is further verified in this case study.(5) Based on the research results proposed above, optimization scheduling software platform that takes economic and environmental factors into account is designed and developed. The primary functional framework, design and development process of back-end and front-end are described in detail. Finally, it is proved that with the assistance of the optimization software, it is more convenient to provide guidance, which verifies the validity and application advantage of the software.In the end, a summary of the research referred above is concluded and the prospect of future study is indicated.