Modeling Study of the Slag Behaviors and SiC Refractory Wall Corrosion on the Top Cone of a Membrane Wall Entrained-Flow Gasifier

Abstract

Slag behaviors on the top cone are significant characteristics that relate to the refractory wall corrosion and safe operation in a membrane wall gasifier. The slag flow and heat transfer model was established to predict the slag behaviors on the top cone of a gasifier. The results showed that the closer to the top outlet of the gasification chamber, the thinner the slag thickness, the higher the slag layer heat flux density and refractory wall surface temperature. The mean slag thickness of the top cone was thinner and the mean heat flux density of the top cone was higher than that of the bottom cone, thus the protection of the upper refractory wall was weakened. Especially, the heat transfer rate of the overall top cone significantly decreased when the cone angle increased. Moreover, the refractory wall corrosion model was built based on the active oxidation behavior. The results showed that the refractory wall surface temperature and linear corrosion rate significantly increased, while the gas temperature increased.

Modeling Study of the Slag Behaviors Based on Temperature–Time–Viscosity of Crystalline Slag in an Entrained-Flow Gasifier

“…Subsequently, several modified models about slag behaviors were built and used in different processes. 16 − 21 Yong et al 22 , 23 considered that the temperature profile inside slag was controlled by boundary conditions instead of linear variation. The shear stress from the gasifier chamber gas flow was not negligible, which had different influence on the slag layer thickness and refractory brick corrosion rate while concurrent or countercurrent flowed with the slag.…”

“…The author simplified the physical model of the slag layer on the basis of some assumptions: The slag on the wall was divided into liquid layer and solid layer, and the interface temperature was defined as the temperature of critical viscosity ( T cv ); the liquid slag was considered as Newtonian fluid, and the slag was regarded as solid when the temperature was higher than T cv . Subsequently, several modified models about slag behaviors were built and used in different processes. − Yong et al , considered that the temperature profile inside slag was controlled by boundary conditions instead of linear variation. The shear stress from the gasifier chamber gas flow was not negligible, which had different influence on the slag layer thickness and refractory brick corrosion rate while concurrent or countercurrent flowed with the slag. , There were different opinions on the definition of liquid–solid interface: some authors considering the slag still regarded it as flowing when the temperature was between T cv and the flow temperature; other authors considered that the interface viscosity of the solid slag and liquid slag layer should be absolutely viscosity (about 100 Ps·s) when the slag types were not crystal slag .…”

Numerical Analysis of Fracture Failure Behavior of Refractory Lining in Coal-Water Slurry Gasifier

“…Fatigue crack growth has always been the main failure mechanism for a refractory lining serving at elevated temperature and high pressure conditions, leading to early failure of the refractory lining prior to the design life. 8 − 10 This will not only affect the operation cycle and stability of the gasifier, but also cause production accidents. Therefore, determining the fracture failure of refractory lining under service loads for guiding the safe operation and timely maintenance of a CWS gasifier will be of paramount importance.…”

Numerical Simulations of Solidification Characteristics of Molten Slag Droplets in Radiant Syngas Coolers for Entrained-Flow Coal Gasification

“…11,12 The slag deposition and accumulation will strongly affect the heat-recovery efficiency and the safety operation of the RSC. 13,14 Hence, it is of great importance to gain a clear understanding of the heat transfer and solidification characteristics of molten slag droplets in the industrial RSC.…”

“…A radiant syngas cooler (RSC) is regarded as a crucial heat-recovery device in entrained-flow coal gasification units. − The syngas produced from the gasifier enters the RSC, carrying a great number of fly ash particles and molten slag droplets, and all of them transfer heat to the membrane wall. , However, the molten slag droplets may collide with the membrane wall and the bottom cone of the RSC, and they are more likely to deposit on the wall when they are in the molten state. , The slag deposition and accumulation will strongly affect the heat-recovery efficiency and the safety operation of the RSC. , Hence, it is of great importance to gain a clear understanding of the heat transfer and solidification characteristics of molten slag droplets in the industrial RSC.…”