Research On Corrosion Measurement Of Water Wall Tubes Based On Array Method

The water wall tubes of boiler in our country is seriously affected by high temperature corrosion.Nearly 80%of power station boilers have been unable to operate normally due to the serious corrosion of water wall tubes,which has caused great losses to the national economy,and may even threaten the life safety of workers.Especially with the increase of boiler capacity,the high temperature corrosion caused by sulfur and chlorine in coal-fired boiler and potassium and chlorine in biomass boiler is more serious,which will make the water wall tubes gradually thinner and the material strength continuously reduce.The water wall tubes will burst and leak at any time,endangering the safe operation of the whole boiler.Therefore,it is necessary to monitor the corrosion of water wall tubes,which can effectively prevent the occurrence of tube explosion accident and is of great significance to the normal operation of boiler.This paper designs an array method suitable for corrosion monitoring of water wall tube rows based on the field fingerprint method.Firstly,the principle of the field fingerprint method is briefly introduced,and the formula for calculating the residual thickness of the water wall tubes is derived.Then,the factors that affect the measurement accuracy of the method are analyzed.On this basis,a set of corrosion monitoring device suitable for water wall tubes is designed to monitor the change of water wall tubes thickness all the time.Finally,two parts of simulation and experiment are used to study the change law between the thickness and voltage of the water wall tubes.Based on Maxwell,the paper establishes a three-dimensional model of the water wall tubes.By changing the thickness of the water wall tubes and the number of thinned pipes,various models are designed,and then the boundary conditions of each model are defined separately to solve the voltage distribution of the water wall tubes model.Finally,a calculation formula for the residual thickness of a single pipe with a correction coefficient a of about 3 and a correction formula for the residual thickness of a large-area corroded multi-pipe water wall tubes with a correction coefficient βbetween 0.85 and 0.95 are obtained.On the self--built water wall tubes corrosion depth measurement test bench,a constant current source is applied to the water wall tubes,and then the voltage acquisition module is used to measure the voltage of each part;In the aspect of thickness,hydrochloric acid is used to accelerate the corrosion of the heating surface of the water wall tubes,so that different thickness of the water wall tube row can be obtained,and then the corresponding voltage under different thickness can be measured.Through the analysis of the data results,the law between n the wall thickness and the voltage is obtained,that is,the voltage increases with the decrease of the wall thickness.Finally,the calculation formula of the residual thickness of the water wall tubes bank with the correction coefficient a between 2.8 and 3.2 is obtained,which verifies the simulation results.