| During the combustion process of the boiler,the acceptance of new energy to the grid enables the unit to operate at low load for a long time,and it is particularly important to ensure stable combustion in the process of continuous load reduction of boiler under deep peak shaving.In addition,changes in the load,coal type and other factors under normal load could cause the actual operation of the boiler to deviate from the optimal state under the combustion adjustment test,so that the NOx emission and thermal efficiency cannot be kept optimal for long periods of time.The multi-objective combustion optimization technology based on the control system has become an effective method to solve the above problems.This paper takes a 660 MW ultra-supercritical thermal power unit as the optimization object and studies a multi-objective combustion optimization control system scheme by analyzing the relationship between the optimization objectives,the control system can dynamically optimize the boiler side parameters in a feed-forward feedback mode under overall load.The overall design scheme is divided into three steps:First,divide the boiler operating loads.Based on the start-stop combination of 6coal mills,according to the operation rules of the four-corner tangential-circle combustion mode and referring to the historical data of the boiler,10 common operating loads are selected from various operating loads;Then,carry out combustion adjustment test establish feedforward interpolation of control system.Under each common working load,combustion adjustment tests are carried out for 45 boiler side adjustable parameters respectively,and the feedforward interpolation module of the control system is used to guide the boiler combustion optimization.Taking the coal quantity and the secondary-air damper as examples,the optimization models are established respectively to obtain the coal feed bias value of six coal mills and the air door opening of each layer of secondary-air;Finally,building the inner and outer loop modules of the control system based on soft sensor technology.On the basis of establishing the soft sensor model of coal quality,flue gas composition and boiler thermal efficiency,etc.,the construction of the inner and outer loops is completed.Real-time calculation of real-time efficiency value of boiler operation process with thermal efficiency model to evaluate the economy of combustion optimization process,and analysis of exhaust smoke components with a flue gas soft measurement model to reflect the environmental protection of the combustion process.After completing the design of the multi-objective combustion optimization control system,it is implanted in the DCS system of the power plant to guide the combustion adjustment of the boiler in the deep peak shaving mode and the comprehensive optimal mode.The researched boiler combustion optimization control system has been put into operation in the power plant.The optimization results show that,with the change of boiler operating loads,the control system can not only ensure stable combustion in the deep peak shaving mode,but also can automatically adjust important parameters such as the opening of the secondary-air dampers of each layer of the boiler and coal quantity in the comprehensive optimal mode.The NOx emission concentration can be reduced by more than 8% under the condition that the boiler combustion process is controlled to maintain high efficiency under normal working loads.Through the above research work,a complete multi-objective combustion optimization control strategy based on DCS system is finally formed. |
PDF Full Text Request