Coal Char Gasification on a Circulating Fluidized Bed for Hydrogen Generation: Experiments and Simulation

Abstract

Char is the solid product of coal pyrolysis and its utilization is closely related to the scale of coal pyrolysis and tar processing. Char gasification is a promising choice for char utilization as it can provide hydrogen, which is needed for tar hydrogenation and chemical synthesis. However, reliable and mature coal char gasification technology has not yet been developed. The fluidized bed has been adopted as a gasifier in many studies, and its gasification temperature is relatively low. In this work, the feasibility of char gasification using a fluidized bed has been studied. A pyrolyzed bituminous coal char was gasified in a mixture of O2 and steam using a circulating fluidized bed. The height of the fluidized bed is 2360 mm and the inner diameter is 66 mm. The reactor is made of Ni‐Cd alloy steel, and a loopseal was used for solid circulation. In the experiments, the gasification temperature was varied between 870 and 900 °C, and the effects of O2/char and steam/char mass ratios on the gasification results were analyzed. The volume fraction of combustible gas, dry gas yield, carbon conversion, and lower heating value of the best case were 43.92 %, 1.64 Nm3 kg−1, 0.85, and 5.17 MJ N m−3, respectively. In addition, a simple model and a complex model were established by using Aspen Plus software. The two models were used to simulate char gasification, and the simulation results were validated with the experimental results. The results indicated that the complex model is more accurate than the simple model and is more suitable to simulate char gasification in a circulating fluidized bed.

Effects of Pyrolysis Atmosphere and Temperature on Coal Char Characteristics and Gasification Reactivity

“…Thec harw ith poor reactivityi s usuallyc ombusted with air, whereas the char with good reactivity can be gasified with O 2 /steam. [6] If the char is used for gasification, al arge amounto fs yngas will be produced. The H 2 separated from the syngas can be used in the tar hydrogenation process.…”

“…The char, as the residue of coal pyrolysis, is finally combusted or gasified. The char with poor reactivity is usually combusted with air, whereas the char with good reactivity can be gasified with O 2 /steam . If the char is used for gasification, a large amount of syngas will be produced.…”

Techno‐Economic Analysis of a Coal Staged Conversion Polygeneration System for Power and Chemicals Production

“…Process simulation and energy performance analysis have been carried out using the commercial simulation software Aspen Plus . As a steady‐state modeling software, Aspen Plus has been widely applied in modeling and techno‐economic analysis of the coal‐to‐SNG process , , , the coal‐based polygeneration process coupled with CO 2 capture , , coal or char gasification , , the biomass‐to‐synthetic natural gas (SNG) process , , as well as the Claus process for valuable elemental sulfur recovery . Furthermore, the software package of Aspen Plus contains many built‐in blocks, which can be directly used in the appropriate part.…”

Techno‐economic analysis of novel power generation system based on coal partial gasification technology

“…The most common way of char utilization is combustion. Based on the different reactivity of volatiles and char in coal, cascading utilization of coal is proposed . It aims at high‐efficiency utilization of coal by separation conversion of high‐reactivity and low reactivity matters.…”