Test Operation of a Separated-Gasification Chemical Looping Combustion System for Coal

Abstract

Chemical looping combustion (CLC) has been one of the most attractive topics for the clean utilization of coal. Based on the staged-gasification of the solid fuel, a separated-gasification CLC apparatus for coal was established, which mainly consisted of a gasifier (GR), a reduction reactor (RR), and an air reactor (AR). This design separated the gasification of the coal avoiding the direct solid–solid contact between oxygen carriers and coal which was beneficial to lengthen the life cycle of the oxygen carriers. The established system was tested under both cold and hot conditions. The variable conditions of different amounts of fluidized gas and the air into AR were carried out to verify the feasibility and the stability of this system. Results indicated that the system could be operated stably under the variable conditions, showing acceptable pressure distributions in the reactor system. In the hot operation, the concentration of CO2 at the outlet of RR reached a relatively high level (92.7%–93.2%) while the CO2 concentration at the outlet of AR was 0.93%–1.12% during the stable durations. However, there was still a problematic condition, unstable operation of coal screw feeder, which needed further improvement.

Energy and Exergy Investigations of a Separated-Gasification Chemical Looping Combustion-Combined Cycle System for Power Production

“…On the basis of the design concept of this SG-CLC system, we have successfully built and operated a pilot-scale 20 kW th unit. , After a series of tests, the continuous and stable operation with favorable fuel conversion, high CO 2 capture concentration, and lower mass loss of the OC has been realized, preliminarily verifying the feasibility of this concept. In this study, we have developed a numerical model of a scale-up MW-level SG-CLC-combined cycle system to further predict the feasibility and thermal economy of this novel system for power production.…”

“…Moreover, the RR was designed with a large reactor height to provide sufficient residence time for the syngas to react with the OC. Thus, with the favorable gas–solid contact efficiency and sufficient residence time, the high conversion of syngas has been achieved in our previous pilot-scale tests, in which the CO 2 yield could reach around 97%. , The type of the AR was selected as a counter-flow moving bed, which has the advantages of low pressure drop, stable solid flow, and compact structure, to achieve the reoxidization of the OC by air. In addition, a two-stage separation system, including a first-stage inertial separator and a second-stage cyclone separator, was adopted to separate the reduced OC from the RR to the AR for reoxidation and circulate the unconverted char back to the GR for further conversion.…”

“…19,26,27 In allusion to the above issues, our previous studies proposed a novel separated-gasification chemical looping combustion (SG-CLC) system of coal, aiming to lengthening the gasification time for a more sufficient fuel conversion and reducing the loss of OC for a longer lifetime. 28,29 As shown in Figure 1, the SG-CLC system involves three reactors: a gasification reactor (GR), a reduction reactor (RR), and an AR. Specifically, the type of the GR was designed as a BFB for the gasification of coal, which can provide intense mixing and internal circulation environment for the particles of coal and bed material.…”

Computational Fluid Dynamics–Discrete Element Model Simulation of Flow Characteristics and Solids’ Residence Time Distribution in a Moving Bed Air Reactor for Chemical Looping Combustion

“…Moving bed technology has been widely used in industrial process such as chemical looping, pyrolysis, fluid catalytic cracking, and heat exchange of granular materials. − The granular flow characteristics in moving beds have attracted extensive attention because of its importance for optimization of design and operation . By far, a lot of research has been conducted to investigate solid movements in the widely used silo moving beds, among which the correct evaluation of the mass discharge rate (MDR) is an important topic .…”