Abstract
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.
Highlights
Integrated gasification combined cycle (IGCC) is a promising clean coal technology with an inherent advantage of low emissions, and it has potential for cost-effective carbon dioxide (CO2)capture to generate energy and chemicals [1]
This study briefly introduces coal properties and operating conditions used in major commercial entrained-flow gasifiers in IGCC plants; identifies and discusses the key coal quality and operating conditions impacting slag flow behavior; summarizes the coal quality criteria and operating conditions for use in entrained-flow gasifiers
In the entrained flow gasifiers used in IGCC plants, the low availability in the gasification system is largely due to the slag buildup in the gasifier and the fouling in the syngas cooler downstream of the gasification system in gasification section
Summary
Integrated gasification combined cycle (IGCC) is a promising clean coal technology with an inherent advantage of low emissions, and it has potential for cost-effective carbon dioxide (CO2). Large amounts of unconverted carbon from the gasifier and failure of the refractory lining in the entrained-flow gasifiers are other major concerns [10] These issues are related to slag behavior and influenced by fuel properties and operating conditions. At high temperature the molten slag layer can corrode/penetrate deeply into a gasifier’s wall (i.e., refractory lining) even though the same layer can act as a thermal barrier to protect the wall at lower temperature [11,21] This corrosion/penetration results in rapid refractory wearing/changing in the microstructure and properties of refractory that could cause possible cracking. Understanding the key coal ash properties (i.e., ash fusion temperature, critical viscosity temperature, viscosity) and optimal operation conditions (i.e., temperature), as well as the characteristics of slag flow, are important to improving gasifier availability by improving the design and operation of the gasification process. Part II will discuss the constitutive modeling related to rheological studies of slag flow
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