Failure Mode And Mechanism Analysis Of Water-Cooled Wall Tube Bursting In Coal-Fired Boiler

With the rapid development of modern industry,the application of high-temperature furnace tubes for coal-fired boilers is becoming more and more widespread,its structure is also continuously complicated,and the working environment is becoming more and more harsh,resulting in high-temperature furnace tubes that are prone to burst failure,which not only brings huge economic loss,but also causes inconvenience to users,and more seriously,it may endanger the lives and property of people.Therefore,the key to solving the coal-fired boiler water-cooled wall tube burst failure is to further explore the form and mechanism of coal-fired boiler water-cooled wall tube burst failure and propose countermeasures,Existing research is mainly to study the failure form and mechanism of a typical tube sample collected,a variety of typical failure tube samples are collected to study the failure form and mechanism in depth is less.This study conducts research on four typical failure tube samples,the form and mechanism of burst failure of coal-fired boiler water-cooled wall tubes are further clarified through experimental comparison,metallographic research,metal element research,corrosion product research,environmental media research,etc.The main research contents are as follows:Experimental schemes and prepare samples of burst pipe fittings are designed.There are four typical forms of water-wall pipe burst failure: long-term overheating,short-term overheating,hydrogen corrosion,and sulfur corrosion.Generally,only one type of burst failure tube sample that is frequently contacted to research and analysis mechanism,the study also collects the above four typical tube samples,especially the superheated tube sample has both short-term overheating characteristics and long-term characteristics,such tube-like burst characteristics are very rare.Through the analysis of the chemical composition of the above four typical tube samples,metallographic transformation,the change of metal elements,hardness transformation,and the environmental medium transformation,the study further explores the root cause and mechanism of high-temperature corrosion cracking,and proposes solutions.During the operation of the boiler,the water wall tube is overheated and overheated,and the tube wall expansion and deformation exceeds 30%.The metallographic structure will be globalized,and the metal properties of the water wall tube will be reduced,causing the water wall tube to burst and fail.The amount of ions in the boiler incoming water exceeds the standard,and it is easy to cause scaling on the inner wall of the water-cooled wall tube to the fire side and corrosion under the scale.The generated hydrogen cannot be taken away by water vapor in time,so that hydrogen has the opportunity to penetrate into the metal of the water-wall tube wall,which cause hydrogen corrosion damage.The corrosion of the outer wall of the water wall tube to the fire side is mainly sulfur corrosion,and the sulfur content in coal is high.Under the condition of partial oxygen deficiency,high temperature flue gas corrosion is prone to occur outside the water wall tube.Due to the reducing atmosphere,sulfur unable to burn to form sulfur trioxide,the metallic iron on the wall of the water-cooled wall begins to react with elemental sulfur and sulfide,and corrodes the wall of the water-cooled wall.Through in-depth research and comparison of the above four typical failure tube samples,the root cause and mechanism of high-temperature corrosion burst are further clarified,production and maintenance can be better guided,and a more comprehensive and reasonable prevention of high-temperature corrosion burst failure of water-cooled wall pipes is given to enterprises.Huge economic losses are reduced and the safety of people’s lives and property are ensured.