405
phase transition. Huo et al. [11] applied TGA to study CO 2 gasification reactivity of
biomass, petcoke, and coal chars. Physical structures and chemical components of
various chars were examined. The reactivity of char largely depends on crystallinity.
Diffusion effects were different for different chars. This was due to difference in
intrinsic reactivity and physical properties of chars. Sudiro et al. [12] simulated a
process which may be an alternative to conventional coal gasification. They wanted
to minimize the use of pure oxygen and also to minimize carbon dioxide emission.
They considered simulating an integrated gasification combined cycle (IGCC)plant
for power generation. They also considered synfuel production via Fischer-Tropsch
(FT) synthesis. They suggested to thermally couple a gasifier fed with coal and
steam, and a combustor where coal is burnt with air, which might overcome the
need to use pure oxygen, an expensive feedstock. Hence, amount of nitrogen in
syngas would be minimal. Besides, the required heat in the gasifier would be supplied from the combustor by means of inert solids. A thermodynamic study of the
dual-bed gasification was carried out first; then it was simulated by Aspen Plus.
Finally the dual-bed system was coupled with an IGCC process. The simulation
results were compared with that of an IGCC system fed with pure oxygen. The
global plant efficiency increased by 27.9% and CO 2 emission decreased by 21.8%.
In the next part of the study, this dual-bed was integrated with a liquid-to-coal (LTC)
process to transform syngas to synthetic fuels by an FT reactor. When compared to
a conventional LTC plant, the yield of synthetic fuel increased by 39.4% and energy
efficiency improved by about 70%. Sudiro et al. [3] have addressed some of the
problems related to modeling the dual-bed system, in their previous study [12].
They have considered both mass transfer and chemical kinetics between char particles and gas phase, to model the coal gasification reactor. The model was validated
for both fluid-bed and entrained-flow gasifiers. Sensitivity analysis was performed
with regard to a conventional gasifier fed by petcoke. The effect of residence time
and oxygen/carbon mass ratio in the feed was studied on process variables like char
conversion at gasifier exit, temperature at gasifier exit, and amount of useful syngas
produced. Malekshahian and Hill [5] pyrolysis and CO 2 gasification of petcoke.
4 Reactor Configurations
Based on the geometrical configurations and flow geometry, the gasifiers can be
mainly divided into three categories as fluidized bed, fixed bed, and entrained flow.
However, the fluidized and fixed bed is not suitable for the gasification of petcoke
due to the following reasons:
• Both types of gasifiers operate at a relatively lower temperature as compared to
entrained flow gasifier which results in a lesser carbon conversion for a low reactive petcoke [13].
• Fixed bed and fluidized bed gasifiers have less efficiency, less syngas production,
and lesser carbon conversion as compared to entrained flow gasifier operating on
petcoke as a feed.
Petcoke Gasification: Challenges and Future Prospects
phase transition. Huo et al. [11] applied TGA to study CO 2 gasification reactivity of
biomass, petcoke, and coal chars. Physical structures and chemical components of
various chars were examined. The reactivity of char largely depends on crystallinity.
Diffusion effects were different for different chars. This was due to difference in
intrinsic reactivity and physical properties of chars. Sudiro et al. [12] simulated a
process which may be an alternative to conventional coal gasification. They wanted
to minimize the use of pure oxygen and also to minimize carbon dioxide emission.
They considered simulating an integrated gasification combined cycle (IGCC)plant
for power generation. They also considered synfuel production via Fischer-Tropsch
(FT) synthesis. They suggested to thermally couple a gasifier fed with coal and
steam, and a combustor where coal is burnt with air, which might overcome the
need to use pure oxygen, an expensive feedstock. Hence, amount of nitrogen in
syngas would be minimal. Besides, the required heat in the gasifier would be supplied from the combustor by means of inert solids. A thermodynamic study of the
dual-bed gasification was carried out first; then it was simulated by Aspen Plus.
Finally the dual-bed system was coupled with an IGCC process. The simulation
results were compared with that of an IGCC system fed with pure oxygen. The
global plant efficiency increased by 27.9% and CO 2 emission decreased by 21.8%.
In the next part of the study, this dual-bed was integrated with a liquid-to-coal (LTC)
process to transform syngas to synthetic fuels by an FT reactor. When compared to
a conventional LTC plant, the yield of synthetic fuel increased by 39.4% and energy
efficiency improved by about 70%. Sudiro et al. [3] have addressed some of the
problems related to modeling the dual-bed system, in their previous study [12].
They have considered both mass transfer and chemical kinetics between char particles and gas phase, to model the coal gasification reactor. The model was validated
for both fluid-bed and entrained-flow gasifiers. Sensitivity analysis was performed
with regard to a conventional gasifier fed by petcoke. The effect of residence time
and oxygen/carbon mass ratio in the feed was studied on process variables like char
conversion at gasifier exit, temperature at gasifier exit, and amount of useful syngas
produced. Malekshahian and Hill [5] pyrolysis and CO 2 gasification of petcoke.
4 Reactor Configurations
Based on the geometrical configurations and flow geometry, the gasifiers can be
mainly divided into three categories as fluidized bed, fixed bed, and entrained flow.
However, the fluidized and fixed bed is not suitable for the gasification of petcoke
due to the following reasons:
• Both types of gasifiers operate at a relatively lower temperature as compared to
entrained flow gasifier which results in a lesser carbon conversion for a low reactive petcoke [13].
• Fixed bed and fluidized bed gasifiers have less efficiency, less syngas production,
and lesser carbon conversion as compared to entrained flow gasifier operating on
petcoke as a feed.
Petcoke Gasification: Challenges and Future Prospects