The Temporal-spacial Distribution Of Energy Consumption And Energy Saving Of Large Coal-fired Power Units

Energy, the civilization basis of society development, is undoubtedly one lifeline of China’s economy. Coal consumption for power generation has long been more or less half of its total consumption amount. Additionally, large-scale coal-fired power generation units with a capacity of300MW or above have already played a decisive role in the overall energy structure. Thus, further improving these systems can contribute significantly to the reduction of fuel consumption of power generation or even the whole industry area.In general, fuel consumption rate of a real coal-fired power generation unit depends highly on many factors, such as environment-and-resource situation, operation condition and external load change, which make it vary largely with time. Corresponding to these features and on the basis of the first and second laws of thermodynamics and the off-design prediction of steam turbine performance, detailed distribution characteristic from the perspective of all operating conditions, the coupling mechanism of thermodynamic performances among components and system at the process, component and system levels, dynamic response principles of fuel consumption rate with main decision variables were comprehensively and thoroughly investigated. Energy-saving diagnosis of unit states considering complicated external factors was also studied in a penetrating manner and further improved to guide deep reduction of their fuel consumption. From these viewpoints, this research is expected to be of significant practical value.According to the deep and detailed data investigation of the fuel consumption conditions of existing coal-fired power plants in China and comparisons with the situation in developed countries, current fuel consumption levels of different units were clarified. It is, thus, pointed out that the contribution differences of various coal-fired power plants are the key reasons, leading to the high-level fuel consumption rate of the whole coal power generation industry. In this context, the overall fuel consumption levels in2015and2020are reasonably predicted based on the data of2010, which is necessary for the development of energy-saving policy and solution of thermal power plants.Considering the environment and load conditions, off-design performance predictions of turbine and condenser were effectively combined to reveal the spatial distribution of fuel consumption in one specified unit for all load conditions, from the1st and2nd laws of thermodynamics. Thus, the spatial-temporal distribution principle of fuel consumption within turbine thermal system at different environmental temperatures and loads is concluded. New calculation method of turbine exhausted steam in accordance with the relationship between pressure ratio and efficiency of the final stage group was proposed, which provided a reliable analysis approach to accurately evaluate the energy consumption distribution of one unit at its reference state. Then, the sensitivities of fuel consumptions of1000MW ultra-supercritical coal-fired power plants with wet and dry cooling systems on main decision variables were obtained separately at different load factors. These form solid basis for the accurate energy-saving diagnosis of existing units.The specific fuel consumption analysis, a variant of2nd law of thermodynamics, was successfully introduced to the energy-saving diagnosis of power plants. Focusing on the existing power generation units, the comparisons of fuel consumption distribution between reference state and the real operating state at the same boundary conditions can reveal the sites and magnitudes of additional fuel consumption rates and corresponding energy-saving potential, provide certain specific energy-saving measure and solution, and further improve the method and approach for the energy-saving diagnosis of large-scale coal-fired power generation units.