Ash formation and deposition in coal and biomass fired combustion systems: Progress and challenges in the field of ash particle sticking and rebound behavior

Advances in coal gasification, hydrogenation, and gas treating for the production of chemicals and fuels.

A review of the Residence Time Distribution (RTD) applications in solid unit operations

Relationship between coal ash composition and ash fusion temperatures

In the entrained-flow gasifiers used in integrated gasification combined cycle (IGCC) plants, the majority of mineral matter transforms to liquid slag on the wall of the gasifier and flows out the bottom. However, a small fraction of the mineral matter is entrained (as fly ash) with the raw syngas out of the gasifier to downstream processing. This molten/sticky fly ash could cause fouling of the syngas cooler. To improve gasification availability through better design and operation of the gasification process, a better understanding of slag behavior and the characteristics of the slagging process is needed. Char/ash properties, gas compositions in the gasifier, the gasifier wall structure, fluid dynamics, and plant operating conditions (mainly temperature and oxygen/carbon ratio) all affect slagging behavior. Because coal has varying ash content and composition, different operating conditions are required to maintain the slag flow and limit problems downstream. In Part I, we review the main types and the operating conditions of entrained-flow gasifiers and coal properties used in IGCC plants; we identify and discuss the key coal ash properties and the operating conditions impacting slag behavior; finally, we summarize the coal quality criteria and the operating conditions in entrained-flow gasifiers. In Part II, we discuss the constitutive modeling related to the rheological studies of slag flow.

https://www.mdpi.com/1996-1073/6/2/784/pdf

Slag Behavior in Gasifiers. Part I: Influence of Coal Properties and Gasification Conditions

A slag flow submodel has been developed to simulate the slag flow and phase transformation behaviors in coal gasifiers. The volume of the fluid (VOF) model is used to capture the free surface of the slag flow, and the continuum surface force (CSF) model is employed to calculate the surface tension between the gas phase and the liquid slag phase. The slag is treated as a Newtonian fluid when the slag temperature is above the critical viscosity temperature (Tcv), and plastic fluid is treated when the slag temperature is between the flow temperature (Tf) and the Tcv. The ash particle deposition, viscosity−temperature dependence, and different thermal conductivity for different slag phase are all included in the present simulation. For membrane wall coal gasification, the liquid slag and solid slag layer increases along the flow and total slag thickness increases as the operating temperature decreases. The velocity profiles and viscosity profiles at different operating temperatures are performed. The liquid s...

Molten Slag Flow and Phase Transformation Behaviors in a Slagging Entrained-Flow Coal Gasifier

In a slagging combustion system, some of ash/slag generated through the combustion of solid fuels is molten and adheres to tube surfaces or the refractory wall during operation. A submodel for pred...

Submodel for Predicting Slag Deposition Formation in Slagging Gasification Systems

Numerical and experimental investigations on gas–particle flow behaviors of the Opposed Multi-Burner Gasifier

Modeling and comparison of different syngas cooling types for entrained-flow gasifier

Experimental and numerical studies on the gas-particle flow field and temperature field in the industrial-scale radiant syngas cooler (RSC) have been carried out. The bench-scale cold model experiment was presented for measuring the gas flow field in the RSC. The accuracy and performance of four turbulent flow models were evaluated according to the comparison of predicted results with experimental results. The ash particle trajectories were predicted by the stochastic Lagrangian model and the interaction between the gas and particle phase was also considered by two-way coupling method. A discrete ordinate model (DOM) was used for solving the radiative heat transfer equation when the radiative properties were calculated by weighted-sum-of-gray-gases model (WSGGM). The Ranz−Marshall correlation for the Nusselt number was used to account for convection heat-transfer between the gas phase and the particle phase. The ash particle radiative heat transfer was also considered. The physical properties of gas mixtu...

Jianjun Ni

Papers

Molten Slag Flow and Phase Transformation Behaviors in a Slagging Entrained-Flow Coal Gasifier

Submodel for Predicting Slag Deposition Formation in Slagging Gasification Systems

Numerical and experimental investigations on gas–particle flow behaviors of the Opposed Multi-Burner Gasifier

Modeling and comparison of different syngas cooling types for entrained-flow gasifier

Experimental and Numerical Study of the Flow Field and Temperature Field for a Large-Scale Radiant Syngas Cooler