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

Abstract

The high-temperature syngas and molten slag droplets discharged from entrained-flow coal gasifiers contain a large amount of heat energy, which can be efficiently recovered by radiant syngas coolers (RSCs). However, it is hard to know the solidification degree of molten slag droplets at the outlet of an RSC during industrial operations. In this work, the industrial-scale RSC and molten slag droplet models are established to predict the solidification degree of slag droplets at the outlet of the RSC. Then, the effects of slag diameter, syngas flow field, slag initial temperature, slag porosity, and slag pore structure are investigated by numerical simulations, and residence time as well as complete solidification time are calculated by coupling of a discrete-phase model and a solidification model. The results indicate that as the slag droplet diameter increases, the residence time of the slag droplet shortens, but the complete solidification time increases. When the slag droplet diameter is greater than or equal to 3.0 mm, the complete solidification time is larger than the residence time, and the slag droplet cannot solidify completely at the outlet of the RSC. The solidification degree in the windward zone is greater than that in the leeward zone. Although the slag initial temperature has little effect on the solidification, a lower slag initial temperature is still conducive to a greater solidification degree. Additionally, the pore structure facilitates solidification, and the promoting effect of penetrated pores is more remarkable than that of closed pores. A larger porosity is also beneficial to accelerate the solidification of molten slag droplets and increase the solidification degree.

Numerical Simulation of the Integral Thermal Deformation Behavior of a Radiant Syngas Cooler for an Entrained-Flow Gasifier

“…The hightemperature syngas from the gasification chamber flows into the RSC as a confined jet. 30 Ni et al 31 verified through experiments that the Realizable k−ε model can accurately predict the gas-phase flow field. Hence, the Realizable k−ε model is used to simulate the gas-phase turbulent flow process in the RSC, and the continuity and momentum equations of the gas-phase flow through time averaging are as follows:…”

“…The high-temperature syngas from the gasification chamber flows into the RSC as a confined jet . Ni et al verified through experiments that the Realizable k – ε model can accurately predict the gas-phase flow field.…”

Optimization of a Sootblowing System for Effective Deposit Removal in Radiant Syngas Cooler Using Numerical Simulation

“…Consequently, some syngas-carrying particles are gradually solidified below the critical melting temperature during the process of descent in RSC. 8 Partially unsolidified fly ash particles adhere to the membrane walls and form a deposit. With the initial formation of a slag layer, the thickness of deposited slag continuously increases.…”

Simulation Study on the Interaction between Chemically Reacting Double Coal Char Particles

“…Coal gasification technology can convert low-quality coal, petroleum char, and other materials into syngas, as one of the important technologies of clean coal utilization technology. , The coal gasification technology can not only be used in the production of coal-based chemicals, coal-based fuel oil, fuel cells, and hydrogen but also be applied to integrated gasification combined cycle (IGCC) power generation, which is the common and leading technology in these industries. − Entrained-flow gasification is characterized by high carbon conversion rate, strong production capacity, and wide adaptability of coal types. It is a flexible and reliable industrial technology and has become mainstream in the gasification process . The gasifier occupies an important position in the process of coal gasification technology.…”

“…It is a flexible and reliable industrial technology and has become mainstream in the gasification process. 9 The gasifier occupies an important position in the process of coal gasification technology. At present, the stable operation of the gasifier has been widely considered.…”