Thermal Stress Of Slag On Walltube Created By Boiler Load Shift And Theory Reasearch On Fuzzy Online Optimization Of Boiler Sootblow

Slag and ash deposit on coal-fired boiler in thermal power plant not only decrease the boiler efficiency and the plant economy, but also are hidden trouble of many safety accident. And Sootblowing is an effective and common means to account for this problem. Aiming at the status that the use ratio and skill of the sootblowers in plant at home are poor, the research on online monitoring of ash deposit and slag and sootblowing optimization is carried out. The research takes No. 1 boiler of the Beilun power plant in Ningbo as an example, which load is 600 MW electricity.Firstly, the spontaneous drop of slag on walltube at the time of boiler load shift is researched and it is the innovative research on the effect on the slagging of boiler operation. It is gained from presenting mechanism of slag thermal stress that the slag thermal stress is composed of slag shaping thermal stress and temperature grads thermal stress. Model is built to calculate slag thermal stress. And it is calculated and analyzed the distribution and quantity of slag thermal stress created by boiler load shift. Thermal stress quantity can be as big as E/1000 and is enough to destroy slag structure and to make some drop. It is also concluded that the walltube parameters can only affect on thermal stress of the slag that is near to contact surface and contribute little to slag drop. The stress of slag rests with the structure, physical characteristic, and heat transfer status of slag. Taking NO. 1 boiler of Beilun Thermal Power Plant as example, the walltube thermal stress and the destroying impact on slag are researched. And the conclusion is that Downing load can distory the small slag and outer part of thick slag, which is helpful to keep walltube clean and useless for preventing from furnace accident caused by slag.The ash fouling online monitoring models are built for furnace, convection heating surface and tri-sectional regenerative air preheater based on the analysis and summarization the researches on the ash fouling monitoring technic and models of boiler. Clean factor (CF) is chosen to express the effect on heat transfer of ash fouling and is calculated by heat transfer steady-state model. Thus clean factor has good adaptability to boiler load, coal quality, excess air coefficient, working medium flow, and boiler efficiency etc. The calculated result gained by inputting the data of history database of the object boiler validates the correctness and adaptability to boiler load of clean factor model. The CF correlation of some monitored modules and the CF sensitivity to sootblowing are studied and analyzed from the view of the characteristic of heating surface itself and measuring point collocation. The error transfer law is researched from operation data calculation and mathematic theory to find out how the measurement error of main monitored parameters influences the clean factor. And the law gained from differential calculus is coincident well with the calculated result.Grounded upon the research on the sootblower operation, the effect on all kinds of boilerperformance of ash fouling on heating surface is analyzed roundly. And the sootblowing income is divided into five categories. So is the sootblowing cost. It is concluded that the categories of sootblowing income and cost on different heating surface are not all the same. The method to calculate accurately the income and cost is studied. The magnitude of all income and cost categories is calculated and compared by calculating the boiler performance change with the clean factor. The minimum income is the electricity reducing of draft fan and the minimum cost is the electricity cost of sootblower drive. Also it is gathered that sootblowing reasonably can bring about several decuple profit compared with the sootblowing cost.The boundary and content of sootblowing operation optimization are defined afresh. The optimized goal of sootblowing is set a tradeoff between all categories of sootblowing income and cost and the optimized unit is a single monitored surface modul...