Modeling And Operation Optimization Of CCPP Gas System

China is a big country of iron and steel.As one of the fundamental pillar industries in China, the iron and steel industry is big energy consumption, whose energy cost accounts for 15% of the total energy cost of China. Recently, with people’s increased awareness of protecting the environment, how to improve the quality of products, reduce resource and energy consumption and reduce pollutant emissions, is a serious problem facing the iron and steel industry. Using the combined cycle power plant to fire the by-product gas to generate electricity is crucial for the efficient recycling of energy and reducing of pollutant emissions of the iron and steel industry. The combination of combined cycle power plant and steel/iron process provides an acceptable new way for the clean production of the iron and steel industry and the circular economy for the future society. The gas system between the combined cycle power plant and the steel/iron process (Referred to as CCPP gas system) plays a connecting role.Its operation status directly affects the security, stability and economy of the subsequent combined cycle power plant. Nevertheless,influenced by the preceding steel/iron process, the flow, pressure and temperature of the CCPP gas system fluctuate obviously, which lead to the surge and low efficiency of gas compressor. And it hinders the further application of the combine cycle power plant in the recovering of by-product gas of the iron and steel industry.Taking the CCPP gas system of the spare power of a steelworks in shanghai as the background and based on the detailed analyzing of the characteristics of gas system, comprehensive and systematic research is made for modeling and operation optimization in CCPP gas system. Furthermore, anti-surge control model system for CCPP gas system is designed in this dissertation. The main work is summarized as follows:1.The CCPP gas system with many components is complex, in which the gas compressor is the core component for the pressure rise of gas.Based on the existing theoretical results and the compressor energy transfer and energy loss mechanism, the first principle model of multi-stage centrifugal compressor was established. The model can be used to predict the designed and off-designed compressor performance.Furthermore, the compressor performance analysis and parameters study can be performed. Based on the compressor model, the CCPP gas system model was developed with cooler model, scrubber model, valve model and gas thermal properties calculation model. It can be used to simulate the operation of the CCPP gas system. And the foundation for research on the operation optimization of gas system and the anti-surge control strategy was established.2. To aim at the difficulty of applying the first principle model to the centrifugal compressor directly, performance prediction model for large centrifugal compressor was established by adopting parallel hybrid model. The model was composed of the first principle model and compensated model in parallel, therefore the advantages of different modeling methods can be exerted. The first principle model was used to describe the basic trends of the main factors affecting the performance of the compressor. The compensated model, which employed the process data, was used to remedy the problem of the error brought about by the theoretical assumptions. However, the process data contains outliers, which lead to the over fitting of the compensated model and the partial or complete failure of the hybrid model. Since it is difficult to remove outliers in multidimensional data by traditional methods, a robust nonlinear data modeling methods based on robust PLS, fuzzy system and improved subtractive clustering algorithm was proposed, which can restrain outliers in the process data, and simplify the architecture of fuzzy system model. By simulation experiment, the efficiency of the hybrid modeling method was verified.3. To aim at the problem of optimal operation of CCPP gas system, the major factors affecting the economy of gas system were analyzed firstly, according to the actual operation situation. Then an optimization program was drafted for CCPP gas system with the cooling water flow was considered as decision variable. Since the CCPP gas system is complex, with many influencing factors, and the variables are highly correlated, operation optimization methods based on historical data were proposed. Operation optimization methods based on process model and process inverse model were proposed respectively, and were applied to the cooler operation optimization of gas system and satisfactory results were obtained. To aim at the problem of sufficient data of a new plant was hard to be obtained for short run time, a new operation optimization idea was proposed. Based on the similarity between the data characteristic of two similar plants, the rich process information and operational experience hidden in the historical data was transferred from the old plant to the new and similar plant for accelerating the operation optimization process of the new plant with a small number of test run. The corresponding operation optimization method based on process model transfer and process inverse model transfer, and the operation optimization method based on prediction model and model transfer were developed. They were applied to the cooler operation optimization of the new and similar gas system, and satisfactory results were obtained.4. Based on the CCPP gas system model and gas compressor model, anti-surge control model system software of CCPP gas system was designed and developed. Hardware structure, data flow, interface design and the main function modules of the system software were described. This system software, which including data processing, mode training, online simulation, results showing, and historical information query and so on, established the foundation for research and applications of anti-surge control strategy. Applying the software to practical gas system of the spare power of a steelworks,better reliability and stability of the gas system was yielded.Finally, future directions for research on modeling and operation optimization of the gas system of the iron and steel industry are discussed after summarizing the whole work in this thesis.