Numerical Simulation Of Thermal Stress Distribution And Corrosion Characteristic Of Refractory Lining At The Nozzle Part In Coal Water Slurry Gasifier

The nozzle is a key component of OMB coal-water slurry gasifier,and there is a large temperature gradient inside the nozzle and in the refractory lining at the nozzle,which causes large thermal stresses in the refractory lining at the nozzle,resulting in damage to the refractory lining.Therefore,it is important to analyze the temperature field and stress field distribution of the refractory lining and steel shell at the nozzle,and to optimize the structure of the established model to ensure production safety,improve the life of the refractory lining,and prevent the damage of the nozzle and the gasifier.The dissertation focuses on the following aspects:The first part takes the refractory lining and steel shell at the nozzle area of an actual coal-water slurry gasifier as the research object,and uses heat transfer and finite element method to establish a three-dimensional finite element model of the refractory lining and steel shell at the nozzle area,and discusses and analyzes the temperature and stress fields of the refractory lining and steel shell in detail.The results show that the temperature at the hot face brick shows a trend of gradually decreasing from the hot end to the inside.And at the heat insulation brick and steel shell,it shows the change trend of gradually decreasing temperature from inside to outside,and the temperature decreases the most at the hot face brick.When the temperature at the hot end of the hot face brick is 1350℃,the temperature at the outermost end of the steel shell is 154℃.The distribution of the stress field generally shows a trend of gradually decreasing from the hot face brick to the steel shell,but the maximum value of stress does not appear at the highest temperature position,but at the contact position between the hot face brick and the steel shell,the stress is as high as 12177 MPa.So in industrial production should pay particular attention to the safety of the refractory lining here.The maximum deformation of the refractory lining was 8.8 mm,in the middle of the upper face at the nozzle exit.And in order to better fit the actual industrial production situation,two representative slag layers were selected and attached to the hot end face of the hot face brick,and different thicknesses of slag layers were set up for finite element simulation.The analysis from different perspectives concluded that the slag layer in most industrial gasifiers has a small effect on the distribution of the temperature field in the refractory lining.For the same slag layer of different thicknesses,even if the slag layer thickness is set to 190 mm,the effect on the temperature transfer in both the refractory lining and the steel shell is relatively small,so it can be inferred that the effect of the attached slag layer on the thermal stress,equivalent effect variation and total deformation will also be small if other conditions are kept constant.In the second part,the refractory lining material distribution of the model was structurally optimized by replacing the two parts of the hot face bricks with heat insulation bricks and backing bricks.The optimized temperature and stress fields were compared with those before the optimization,and the temperature and stress fields of the model were improved to different degrees.The temperature at the steel shell was reduced by about 30℃,and the stress at the connection between the hot face brick and the steel shell was reduced by about one-third,effectively reducing the risk of fracture and failure at the connection between the hot face brick and the steel shell under stress,and largely improving the damage to the refractory lining and the steel shell at the nozzle by thermal stress.The slag layer not only affects the temperature field of the refractory lining,but the erosion behavior of the refractory lining is more likely to lead to damage and failure of the refractory lining.Therefore,the third part erodes high-chromium bricks by co-gasification of coal and rice straw at Sheep Farm Bay and performs a series of analytical characterization of the eroded high-chromium bricks.The results show that a series of oxides in the liquid slag diffuse through the pores to the interior of the high-chromium bricks,react with Cr2O3,etc.,destroying the otherwise dense structure of the high-chromium bricks and reducing their performance.20%RS blended ash has the lowest slag ash melting temperature,resulting in reduced viscosity and increased fluidity,and exhibits the strongest tendency to corrode.