Kinetic studies of steam gasification of char in the presence of H2, CO2 and CO

Mühlen, H.-J.; Heek, K.H. van; Jüntgen, H.

doi:10.1016/0016-2361(85)90149-8

Cited by 180 publications

(96 citation statements)

References 6 publications

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“…C(O) are the adsorbed oxygen surface complexes and are determined by the forward adsorption reactions which influence the reaction rate. By increasing the pressure, the number of C(O) oxygen surface complexes formed will increase resulting in an increase in the reaction rate which is proportional to the number of these oxygen surface complexes [19,23,24]. At higher pressures as at 2.2 and 3.0 MPa, the formation of CO 2 and CH 4 has been observed from reactions R3 and R4 respectively, which can be explained by other mechanisms proposed by different authors [17,19,23,24].…”

Section: Effect Of Pressurementioning

confidence: 79%

“…By increasing the pressure, the number of C(O) oxygen surface complexes formed will increase resulting in an increase in the reaction rate which is proportional to the number of these oxygen surface complexes [19,23,24]. At higher pressures as at 2.2 and 3.0 MPa, the formation of CO 2 and CH 4 has been observed from reactions R3 and R4 respectively, which can be explained by other mechanisms proposed by different authors [17,19,23,24]. With increasing the pressure further, the surface will be saturated with oxygen surface complexes which means that increases in pressure will not lead to the formation of further C(O) and the reaction rate will not increase so the impact of pressure becomes less significant to independent [19,25].…”

Section: Effect Of Pressurementioning

confidence: 99%

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Experimental study on the impact of reactant gas pressure in the conversion of coal char to combustible gas products in the context of Underground Coal Gasification

Konstantinou

Marsh

2015

Fuel

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Underground Coal Gasification (UCG) is the process by which unmineable coal resources are converted in situ into a combustible gas. Pressurised oxidants such as steam and air or oxygen are injected into the coal seam in order to react with coal and form a product gas. The main gases produced are H 2 , CO, CH 4 and CO 2 , in proportions depending on temperature, pressure and the composition of the reactant gases injected [1][2][3]. Although it can be challenging to accurately measure or reproduce these conditions in a reliable fashion, it is generally believed that at high enough temperatures, free oxygen reacts completely with the solid carbon within a relatively short distance from the injection point. The heat evolved acts to pyrolyse the adjacent coal and the char formed then reacts with carbon dioxide, steam or other gases formed by combustion and pyrolysis [4][5][6]. The key substance, and hence driver of the net gasification process under these conditions is therefore CO 2 which is produced during the oxidation zone [5,7,8]. At the reduction zone CO 2 and steam, which is either introduced deliberately into the cavity or is flowing into the cavity from the oxidation of the surrounding strata, reacts with char and produces around 60% of the total gas product (by volume) during the UCG process. The remaining 40% is produced during the devolatilisation phase, although this is highly dependent on reactor condition, the type of coal and the gaseous reactants [4]. Fig. 1 illustrates the three reaction zones of a reacting channel during a UCG process, which are the oxidation, reduction and pyrolysis zones. During the oxidation zone, as the coal is consumed more coal falls into the growing void, which creates a high coal surface area available for reaction and permits contact between the hot gases and the coal [5,7]. This area is the final reduction zone which converts excess CO 2 to CO and is responsible for the uniform quality of the product gas. Measurement of the upstream gas composition in the oxidation zone has shown comparatively low heating values which demonstrate that the reactions in the oxidation zone do not have such a significant effect on the product gas composition [8,9]. Finally the pyrolysis zone is where the devolatilisation of the coal takes place, forming char that contains active sites for subsequent gas-solid reactions.Experimental study on the impact of reactant gas pressure in the conversion of coal char to combustible gas products in the context of Underground Coal Gasification AbstractThis paper describes an experimental investigation to determine the impact of pressurised reactor conditions within the reduction zone of a gasification process employing a semi-batch reactor with a bituminous coal. The conditions examined with this bespoke pressurised rig were designed to be representative of an Underground Coal Gasification (UCG) process, at pressures up to 3.0 MPa and temperatures up to 900 °C; coal samples were approximately 36 g per test. Current published literature suggests that one ...

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Section: Effect Of Pressurementioning

confidence: 79%

Section: Effect Of Pressurementioning

confidence: 99%

Experimental study on the impact of reactant gas pressure in the conversion of coal char to combustible gas products in the context of Underground Coal Gasification

Konstantinou

Marsh

2015

Fuel

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“…This condition had to be compensated with an increase in the steam-oxygen volumetric flow ratio, which started at 1.19 and ended at 1.23, because steam increases the reactivity of the gasifying mixture. 31,38 With this, more gasifying agent was introduced to insure proper destruction of the feedstock, gasification of carbon, and limit to the production of particulate matter. A consequence of having more PCBs in the feedstock was the decrease of H 2 and CH 4 being produced and an increment of CO and CO 2 .…”

Section: Discussionmentioning

confidence: 99%

Performance of a Semi-Industrial Scale Gasification Process for the Destruction of Polychlorinated Biphenyls

Mendoza

Caballero

Villarreal³

et al. 2006

Journal of the Air & Waste Management Association

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A semi-industrial scale test was conducted to thermally treat mixtures of spent oil and askarels at a concentration of 50,000 ppm and 100,000 ppm of polychlorinated biphenyls (PCBs) under a reductive atmosphere. In average, the dry-basis composition of the synthesis gas (syngas) obtained from the gasification process was: hydrogen 46%, CO 34%, CO 2 18%, and CH 4 0.8%. PCBs, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans (PCDDs/PCDFs) in the gas stream were analyzed by high-resolution gas chromatography (GC)-mass spectrometry. The coplanar PCBs congeners 77, 105, 118, 156/ 157, and 167 were detected in the syngas at concentrations Ͻ2 ϫ 10 Ϫ7 mg/m 3 (at 298 K, 1 atm, dry basis, 7% O 2 ). The chlorine released in the destruction of the PCBs was transformed to hydrogen chloride and separated from the gas by an alkaline wet scrubber. The concentration of PCBs in the water leaving the scrubber was below the detection limit of 0.002 mg/L, whereas the destruction and removal efficiency was Ͼ99.9999% for both tests conducted. The concentration of PCDDs/PCDFs in the syngas were 8.1 ϫ 10 Ϫ6 ng-toxic equivalent (TEQ)/m 3 and 7

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“…The steam gasification of char, as a gas-solid thermochemical conversion, is the rate-determining step (Mühlen et al, 1985) for the entire coal gasification process. The process has been studied by many researchers to understand the kinetics and mechanisms of both non-catalytic and catalytic reactions using fixed- (Haga and Nishiyama, 1988) and fluidized-bed reactors.…”

Section: In Situ Steam Gasification Of Char Gasificationmentioning

confidence: 99%

Toward Low-Temperature Coal Gasification: Experimental and Numerical Studies of Thermochemical Coal Conversion Considering the Interactions between Volatiles and Char Particles

Zhang

Kudo

et al. 2017

KONA

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A novel triple-bed combined circulating fluidized-bed (TB-CFB) coal gasifier, consisting of a downer (pyrolyzer), a bubbling fluidized bed (gasifier), and a riser (combustor) was proposed for realizing low-temperature coal gasification. Several key thermochemical reactions were extracted from those expected in the downer unit: the reforming of refractory tar in both the gas phase and over the char surface, and the steam gasification of the nascent char. This review highlights our recent progress, both experimental and numerical, in studies of thermochemical coal conversion including the various reaction processes, by employing a drop-tube reactor that well approximates the reaction environment in a downer reactor. This discussion can be utilized in designing TBCFBs and optimizing their operation.

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Kinetic studies of steam gasification of char in the presence of H2, CO2 and CO

Cited by 180 publications

References 6 publications

Experimental study on the impact of reactant gas pressure in the conversion of coal char to combustible gas products in the context of Underground Coal Gasification

Experimental study on the impact of reactant gas pressure in the conversion of coal char to combustible gas products in the context of Underground Coal Gasification

Performance of a Semi-Industrial Scale Gasification Process for the Destruction of Polychlorinated Biphenyls

Toward Low-Temperature Coal Gasification: Experimental and Numerical Studies of Thermochemical Coal Conversion Considering the Interactions between Volatiles and Char Particles

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