Research On Integrated Energy Utilization In Multi-Fuel And Multi-Unit Power Plant

Energy is the important material foundation of the national economic and social development. The utilization of Energy has greatly stimulated the world's economy and the development of human society. With the development of economy, the consumption of energy is also increasing, while the global non-renewable energy supply is dwindling. The serious situation forced people to reasonably use conventional energy, vigorously exploit new energy and seek renewable energy. The research on integrated energy utilization in multi-fuel and multi-unit power plant is significant to adjust energy consumption structure, improve energy efficiency, and reduce the pollution of the environment.The unit economic operation and coal/gas optimal allocation is one of the effective methods to save energy and reduce cost, which does not need to modify the major equipment and is convenient to implement. It works reliably under comprehensive conditions of the system security constraints, power quality requirements and non-diffusion of blast furnace gas (BFG). In the paper five units in a power plant have been taken as study object. Among them, Unit 1, Unit 2 and Unit 3 are the largest coal, BFG, COG and light/heavy oil mixing combustion 350MW power sets. Unit 0 is gas-steam combined cycle unit, which burns low calorific value BFG first in the world. Unit 4 is a 350MW unit which mainly burns low calorific value BFG and nature gas first in the world. Moreover, both Unit 0 and Unit 3 have the ability for heat supply. To perform comprehensive economic management and allocation for load and fuel between various units, the load and BFG should be considered. So univariate coal characteristic curve cannot be applied in solving target problem. A lot of unit tests have been taken to gain sufficient data with which dual variable coal cost characteristic surfaces have been established by least-square method. An optimal solution has been found by successive gradient optimization. Theoretical analysis shows that, once units which participate in the load and the fuel distribution are confirmed, the solution from successive gradient optimization is optimal. The successive gradient optimization was analyzed in the application of unit load and fuel distribution, and the 5 units of power plant were calculated. It was showed that the successive gradient optimization method was suitable for coal characteristic curve of convex function within the power generating units'load and fuel dual variable optimization allocation problem.The solving model and algorithm on the unit comprehensive utilization of energy problem are also given in this paper. Some factors influencing optimization result are compared.Comparing with the conventional thermal power units, another difficulty of optimization between BFG units is that, as comprehensive utilization of energy equipments, it should not only meet the needs of grid dispatching to ensure the safety of power grid, but also adapt to special conditions of blast furnace or unit maintenance. Therefore, daily optimization schemes and emergency optimization schemes are also put forward in this paper. Such schemes can make units operation meet the BFG comprehensive utilization goal and meet the conditions of minimizing the coal consumption of the whole power plant.The load and fuel distribution optimization between five units is worked out. Results show that, the coal consumption of the plant can be reduced by dual variable successive gradient optimization methods in the units'load and fuel optimal distribution and impressive economic benefits can be achieved.