| Energy is the important pillar of economic development and motivation in China.And as the global resources dwindling and environmental problems becoming increasingly serious,how to realize the energy conservation and emission reduction is a main problem for the social sustainable development.Thermal power generation still play an important role in Chinese energy structure,and the supercritical unit,because of its energy saving and high efficiency,has gradually become a mainstay of thermal power units in our country.Therefore making an energy efficiency analysis on the supercritical unit has important practical significance.In actual operation of thermal power units,the parameters of thermal system can't remain unchanged all the time.When the parameters of the thermal system change,they will inevitably affect the thermal economy of the unit.In order to study the influence of the thermal system disturbance on the energy efficiency of the unit,in view of the structural characteristics of the thermal system of the supercritical unit,the analysis model and the calculation of the thermal economy of the unit were carried out.The main research contents and achievements are as follow:(1)According to the energy conservation equation and mass conservation equation,the thermal economic analysis model of coal-fire power unit and the energy efficiency analysis model of thermodynamic system under multivariate disturbance were improved,by adding the influence of auxiliary steam water which directly flow into or out from the steam turbine on the energy efficiency into the model,which made the model more perfect.(2)Based on the calculus of the matrix,the integral model of the energy efficiency analysis model of the thermodynamic system under multivariate disturbance was derived.And according to the different types of disturbances,the energy efficiency analysis models were established,which were suitable for the partial disturbances and overall disturbances.The correctness of the model was verified by making calculation on a 660 MW supercritical unit,and the accuracy of the integral model and the original model in a certain range of disturbance were compared.(3)The sensitivity coefficients of the overall disturbances of the unit were calculated.The calculation results showed that,under the 100%THA load,the absolute sensitivity coefficient of the main steam pressure disturbance was equal to 0.00158/MPa,the absolute sensitivity coefficient of the main steam temperature disturbance was equal to 0.000162/?,and the absolute sensitivity coefficient of the reheat steam temperature disturbance was equal to 0.000121/?.With the unit load decreasing,the influence of the main steam pressure disturbance and the reheat temperature disturbance on the energy efficiency were gradually increasing,but the influence of the main steam temperature disturbance is gradually decreasing.(4)The sensitivity coefficients of the partial disturbances of the unit were calculated.The calculation results showed that,with the unit load decreasing,the influence of the auxiliary steam flow disturbances on unit energy efficiency were gradually increasing,the influence of the steam extraction pressure loss disturbances were decreasing,but the influence of the upper difference disturbances of the heaters remained unchanged.Besides,the upper temperature difference and the extraction steam pressure lose sensitivity coefficients of No.1 and No.6 heaters were significantly higher than other heaters`,which indicated that No.1 and No.6 heaters` operating conditions should be monitored.(5)The influence of the overall multiple combination disturbances on the energy efficiency of the unit was calculated,which was compared with the original model and the conventional heat balance method.The calculation results showed that under the calculation of overall multiple disturbance,the relative error between integral model and conventional heat balance method was less than 3.5%,and the accuracy of the integral model was slightly higher than the original model in general.(6)The relative sensitivity coefficients of different types of disturbances were compared.The results showed that the influence of the overall disturbance on the energy efficiency of the unit was much greater than the partial disturbance,the influence of working fluid temperature disturbance on the energy efficiency of the unit was greater than the working pressure disturbance.And the relative sensitivity coefficient of the main steam pressure was not changed with the change of the load. |
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