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Air-Blown Gasification

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Rafael Kandiyoti – One of the best experts on this subject based on the ideXlab platform.

  • an investigation of the reactivity of chars formed in fluidized bed gasifiers the effect of reaction conditions and particle size on coal char reactivity
    Energy & Fuels, 2006
    Co-Authors: A Cousins, N Paterson, D R Dugwell, Rafael Kandiyoti

    Abstract:

    Coal-derived chars formed during Air-Blown Gasification processes may rapidly lose reactivity, and this can limit the extent of their conversion. To study this effect, a laboratory-scale fluidized bed reactor has been modified to enable char samples to be prepared under strictly controlled conditions of temperature, pressure, particle size, gaseous environment, and residence time. This has been used to gain an insight into the deactivation of the chars as they form and during their subsequent residence time in the bed of the gasifier. The work shows that the char reactivity declines rapidly during its formation as part of the pyrolysis of the coal. This is thought to result from the rapid deposition of secondary, unreactive char within the pores of the material. In this work, it has been shown to occur within the initial 10 s in the reactor, but in reality, this effect probably occurred within 1 s. Temperature, pressure, and particle size have an impact on this process. Subsequently, and over a longer tim…

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  • Gasification Tests With Sewage Sludge and Coal/Sewage Sludge Mixtures in a Pilot Scale, Air Blown, Spouted Bed Gasifier
    Volume 1: Turbo Expo 2002, 2002
    Co-Authors: N Paterson, D R Dugwell, G. P. Reed, Rafael Kandiyoti

    Abstract:

    A series of tests have been done in a pilot scale air blown gasifier, to assess the performance of sewage sludge pellets and sewage sludge pellet/coal mixtures. The aim has been to compare the performances with that achieved with coal alone and to assess the suitability of the sewage containing fuel as a candidate fuel for the Air Blown Gasification Cycle (ABGC). The co-Gasification of sewage sludge with coal raised both the CV of the fuel gas and the fuel conversion compared with values achieved with coal alone. The mixtures were operated under very similar conditions to those needed with coal and no adverse operational problems were encountered. A lower fluidising velocity was needed with the neat pellets to enable a stable bed height to be achieved. However, the conversion of the pellets to gas was very high and the fuel gas CV was higher than that achieved during the co-Gasification tests. Overall, the results suggest that sewage based materials are suitable for use in the ABGC and that their use can improve the process performance.Copyright © 2002 by ASME

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  • factors governing reactivity in low temperature coal Gasification part 1 an attempt to correlate results from a suite of coals with experiments on maceral concentrates
    Fuel, 2000
    Co-Authors: R Messenbock, D R Dugwell, N P Paterson, Rafael Kandiyoti

    Abstract:

    Abstract This paper reports on the first stage of a study attempting to develop laboratory scale tests for the reliable determination and eventual prediction, of the effect of coal properties on the performance of coals in air blown gasifiers. The pyrolysis and Gasification behaviour of a suite of coals have been matched, using a high-pressure wire-mesh reactor (WMR), with those of maceral enriched samples. Reaction conditions were selected to simulate those of the pilot-scale gasifier stage of the Air Blown Gasification Cycle operated by British Coal. Subsequent stages of the study have examined the role of mineral matter and char morphology. The suite of coals previously tested in the pilot scale reactor were originally selected to represent coals of a wide geographical spread, a limited range of properties and were commercially available in the EU. The maceral enriched samples were obtained from different coals, but were of similar rank to those examined in this study. Short hold time experiments (10 s) have been carried out in the laboratory scale reactor. Three distinct types of behaviour have been identified—arising from competing influences of the reactivity of the base char, the impact of secondary char deposition and the effect of melting on the reactivity of the ageing particles. The relative combustion reactivity of the residual chars was measured in an atmospheric pressure TGA test. The reactivities were all low, but differences were apparent between the different samples and were consistent with the observed Gasification behaviour. The use of maceral analysis to predict the behaviour of the whole coals has been examined. Extrapolation from maceral behaviour was found to give reasonable estimates of the behaviour under pyrolysis conditions, but predictions of Gasification behaviour were not reliable.

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D R Dugwell – One of the best experts on this subject based on the ideXlab platform.

  • an investigation of the reactivity of chars formed in fluidized bed gasifiers the effect of reaction conditions and particle size on coal char reactivity
    Energy & Fuels, 2006
    Co-Authors: A Cousins, N Paterson, D R Dugwell, Rafael Kandiyoti

    Abstract:

    Coal-derived chars formed during Air-Blown Gasification processes may rapidly lose reactivity, and this can limit the extent of their conversion. To study this effect, a laboratory-scale fluidized bed reactor has been modified to enable char samples to be prepared under strictly controlled conditions of temperature, pressure, particle size, gaseous environment, and residence time. This has been used to gain an insight into the deactivation of the chars as they form and during their subsequent residence time in the bed of the gasifier. The work shows that the char reactivity declines rapidly during its formation as part of the pyrolysis of the coal. This is thought to result from the rapid deposition of secondary, unreactive char within the pores of the material. In this work, it has been shown to occur within the initial 10 s in the reactor, but in reality, this effect probably occurred within 1 s. Temperature, pressure, and particle size have an impact on this process. Subsequently, and over a longer tim…

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  • Gasification Tests With Sewage Sludge and Coal/Sewage Sludge Mixtures in a Pilot Scale, Air Blown, Spouted Bed Gasifier
    Volume 1: Turbo Expo 2002, 2002
    Co-Authors: N Paterson, D R Dugwell, G. P. Reed, Rafael Kandiyoti

    Abstract:

    A series of tests have been done in a pilot scale air blown gasifier, to assess the performance of sewage sludge pellets and sewage sludge pellet/coal mixtures. The aim has been to compare the performances with that achieved with coal alone and to assess the suitability of the sewage containing fuel as a candidate fuel for the Air Blown Gasification Cycle (ABGC). The co-Gasification of sewage sludge with coal raised both the CV of the fuel gas and the fuel conversion compared with values achieved with coal alone. The mixtures were operated under very similar conditions to those needed with coal and no adverse operational problems were encountered. A lower fluidising velocity was needed with the neat pellets to enable a stable bed height to be achieved. However, the conversion of the pellets to gas was very high and the fuel gas CV was higher than that achieved during the co-Gasification tests. Overall, the results suggest that sewage based materials are suitable for use in the ABGC and that their use can improve the process performance.Copyright © 2002 by ASME

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  • factors governing reactivity in low temperature coal Gasification part 1 an attempt to correlate results from a suite of coals with experiments on maceral concentrates
    Fuel, 2000
    Co-Authors: R Messenbock, D R Dugwell, N P Paterson, Rafael Kandiyoti

    Abstract:

    Abstract This paper reports on the first stage of a study attempting to develop laboratory scale tests for the reliable determination and eventual prediction, of the effect of coal properties on the performance of coals in air blown gasifiers. The pyrolysis and Gasification behaviour of a suite of coals have been matched, using a high-pressure wire-mesh reactor (WMR), with those of maceral enriched samples. Reaction conditions were selected to simulate those of the pilot-scale gasifier stage of the Air Blown Gasification Cycle operated by British Coal. Subsequent stages of the study have examined the role of mineral matter and char morphology. The suite of coals previously tested in the pilot scale reactor were originally selected to represent coals of a wide geographical spread, a limited range of properties and were commercially available in the EU. The maceral enriched samples were obtained from different coals, but were of similar rank to those examined in this study. Short hold time experiments (10 s) have been carried out in the laboratory scale reactor. Three distinct types of behaviour have been identified—arising from competing influences of the reactivity of the base char, the impact of secondary char deposition and the effect of melting on the reactivity of the ageing particles. The relative combustion reactivity of the residual chars was measured in an atmospheric pressure TGA test. The reactivities were all low, but differences were apparent between the different samples and were consistent with the observed Gasification behaviour. The use of maceral analysis to predict the behaviour of the whole coals has been examined. Extrapolation from maceral behaviour was found to give reasonable estimates of the behaviour under pyrolysis conditions, but predictions of Gasification behaviour were not reliable.

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Thomas Kempka – One of the best experts on this subject based on the ideXlab platform.

  • techno economic comparison of onshore and offshore underground coal Gasification end product competitiveness
    Energies, 2017
    Co-Authors: Natalie Nakaten, Thomas Kempka

    Abstract:

    Underground coal Gasification (UCG) enables utilization of coal reserves, currently not economically exploitable due to complex geological boundary conditions. Hereby, UCG produces a high-calorific synthesis gas that can be used for generation of electricity, fuels, and chemical feedstock. The present study aims to identify economically-competitive, site-specific end-use options for onshore- and offshore-produced UCG synthesis gas, taking into account the capture and storage (CCS) and/or utilization (CCU) of produced CO 2 . Modeling results show that boundary conditions favoring electricity, methanol, and ammonia production expose low costs for air separation, low compression power requirements, and appropriate shares of H 2 /N 2 . Hereby, a Gasification agent ratio of more than 30% oxygen by volume is not favorable from the economic and CO 2 mitigation viewpoints. Compared to the costs of an offshore platform with its technical equipment, offshore drilling costs are marginal. Thus, uncertainties related to parameters influenced by drilling costs are negligible. In summary, techno-economic process modeling results reveal that Air-Blown Gasification scenarios are the most cost-effective ones, while offshore UCG-CCS/CCU scenarios are up to 1.7 times more expensive than the related onshore processes. Hereby, all investigated onshore scenarios except from ammonia production under the assumed worst-case conditions are competitive on the European market.

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