Impact of finite-rate kinetics on carbon conversion in a high-pressure, single-stage entrained flow gasifier with coal–CO2 slurry feed

Abstract

Coal-CO 2 slurry feed has been suggested as an attractive alternative to coal-water slurry feed for single-stage, entrained-flow gasifiers. Previous work demonstrated the system-level advantages of gasification-based plants equipped with CO 2 capture and CO 2 slurry feed, under the assumption that carbon conversion remains unchanged. However, gasification in carbon dioxide has been observed to be slower than that in steam. In view of this, the impact of CO 2 slurry feeding on gasification kinetics and ultimately on carbon conversion and oxygen consumption in a pressurized, single-stage entrained-flow gasifier processing Illinois 6 coal is studied here using a 1-D reduced order model. Results show that the CO 2 gasification reaction plays a dominant role in char conversion when the feeding system is CO 2 slurry, increasing the CO content in the products by up to a factor of two. CO inhibition of the gasification reaction and a higher degree of internal mass transport limitations lead to an up to 60% slower gasification rate, when compared to a system based on coal-water slurry. Accordingly, a gasifier with CO 2 slurry feed has a 7%-point lower carbon conversion for a given outlet temperature. The gasifier exit temperature must be raised by 90K in order to achieve the same conversion as in a water slurry-fed reactor; the peak reactor temperature increases by 220K as a result. Net oxygen savings of 8% are estimated for a system with a CO 2 slurry-fed gasifier relative to one with water slurry and the same level of conversion.

Numerical analysis of gasification and emission characteristics of a two-stage entrained flow gasifier

“…The ROM description via RNM allows for detailed finite-rate chemical kinetics but with simplified flow representation in the gasification process. A number of ROM studies for coal gasification process have been reported [11][12][13][14][15][16][17][18][19][20][21][22]. For example, Monaghan et al have developed ROMs with multiple reactors to study entrained flow gasifiers, in which the reactors are constructed based on the zero axial velocity boundaries from CFD simulations [11,12].…”

“…Thereafter, ROMs have been effectively used to investigate the effects of operation conditions on gasification characteristics [16][17][18][19]. Recently, dynamic ROMs with reactor volumes being adaptively adjusted according to oxygen split have been developed considering the fact that oxygen split may result in the change in flow patterns [22].…”

Degradation mechanism of Cr2O3‐Al2O3‐ZrO2 refractories in a coal‐water slurry gasifier: Role of stress cracks

“…As a current technique, large‐scale coal gasification is an essential approach to using coal resource in a clean and efficient way . It is achieved via the reactions among coal, water, and oxygen in a gasifier vessel operated under a high‐pressure of 2‐8.5 MPa and a high‐temperature within 1300°C‐1600°C . In China, the annual capacity of coal gasification reached 5.1 billion cubic meters in 2018.…”

“…[9][10][11][12][13][14][15][16] It is achieved via the reactions among coal, water, and oxygen in a gasifier vessel operated under a high-pressure of 2-8.5 MPa and a high-temperature within 1300°C-1600°C. [17][18][19][20] In China, the annual capacity of coal gasification reached 5.1 billion cubic meters in 2018. Even so, it is still far below that (17 billion cubic meters per year) targeted by the government by end of 2020.…”

Techno-economic assessment of two novel feeding systems for a dry-feed gasifier in an IGCC plant with Pd-membranes for CO2 capture

“…On the other hand, there are specific cases where CO 2 is the preferred feeding gas. Contrary to nitrogen, CO 2 cannot be considered as inert; it affects the kinetics of many reactions (Botero et al, 2013(Botero et al, , 2012.…”