Investigation of the Coal Gasification Process Under Various Operating Conditions Inside a Two-Stage Entrained Flow Gasifier

Numerical simulations of the coal gasification process inside a generic 2-stage entrained-flow gasifier fed with Indonesian coal at approximately 2000 metric ton/day are carried out. The 3D Navier–Stokes equations and eight species transport equations are solved with three heterogeneous global reactions, three homogeneous reactions, and two-step thermal cracking equation of volatiles. The chemical percolation devolatilization (CPD) model is used for the devolatilization process. This study is conducted to investigate the effects of different operation parameters on the gasification process including coal mixture (dry versus slurry), oxidant (oxygen-blown versus air-blown), and different coal distribution between two stages. In the two-stage coal-slurry feed operation, the dominant reactions are intense char combustion in the first stage and enhanced gasification reactions in the second stage. The gas temperature in the first stage for the dry-fed case is about 800 K higher than the slurry-fed case. This calls for attention of additional refractory maintenance in the dry-fed case. One-stage operation yields higher H2, CO and CH4 combined than if a two-stage operation is used, but with a lower syngas heating value. The higher heating value (HHV) of syngas for the one-stage operation is 7.68 MJ/kg, compared with 8.24 MJ/kg for two-stage operation with 75%–25% fuel distribution and 9.03 MJ/kg for two-stage operation with 50%–50% fuel distribution. Carbon conversion efficiency of the air-blown case is 77.3%, which is much lower than that of the oxygen-blown case (99.4%). The syngas heating value for the air-blown case is 4.40 MJ/kg, which is almost half of the heating value of the oxygen-blown case (8.24 MJ/kg).

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Numerical Simulation of Coal Gasification in a 1 t/h Two-Stage Entrained Flow Gasifier

Volume 6: Energy Systems: Analysis, Thermodynamics and Sustainability ◽

10.1115/imece2007-43303 ◽

2007 ◽

Cited By ~ 2

Author(s):

Min Du ◽

Yingli Hao ◽

Yan Wang

Keyword(s):

Particle Size ◽

Coal Particle ◽

Particle Deposition ◽

Coal Gasification ◽

Volatile Component ◽

Operating Conditions ◽

Two Stage ◽

Entrained Flow ◽

Second Stage ◽

Entrained Flow Gasifier

Coal gasification has received increasing attention in the past two decades due to the growing demand for clean gaseous fuels. Numerical simulations of the coal gasification process inside a two-stage dry feed entrained flow gasifier were carried out using the commercial CFD solver FLUENT. The predicted main product gas components and carbon conversion were in well agreement with the measured data, which verified the validity of the model. A series of calculations were carried out to investigate the effects of operating parameters on the performance of gasifier, including the coal particle size, coal type and coal feeding ratio between the first and the second stages. The flow field, coal particle deposition on the wall, gas temperature and mole fraction inside of the gasifier were analyzed. And the simulation results indicated that the performance of gasifier is improved with decreasing particle size. The low volatile component fraction or high ash content in coal is not propitious to the gasification performance. And the performance of gasifier of the case with coal distribution with 75% (first stage) vs. 25% (second stage) is better than the case with 50% (first stage) vs. 50% (second stage) and the case with 100% for the first stage. The calculation is helpful for designing the operating conditions of the gasifier.

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Experimental Study on Coal Gasification in a Full-Scale Two-Stage Entrained-Flow Gasifier

Energies ◽

10.3390/en13184937 ◽

2020 ◽

Vol 13 (18) ◽

pp. 4937

Author(s):

Guangyu Li ◽

Luping Wang ◽

Chaowei Wang ◽

Chang’an Wang ◽

Ping Wu ◽

...

Keyword(s):

Experimental Study ◽

Coal Gasification ◽

Full Scale ◽

Input Rate ◽

Two Stage ◽

Entrained Flow ◽

Operation Period ◽

Entrained Flow Gasifier ◽

Coal Resource ◽

First Time

In this paper, coal gasification characteristics in the reductor were investigated in a full-scale two-stage pressurized entrained-flow gasifier, which has been seldom conducted previously. The present study aimed at elucidating the effects of gasifying agent concentration, coal input rate, and operation period under full reductor load on the performance of a utility two-stage pressurized entrained-flow gasifier for the first time. When the steam input in the combustor was raised from 3318 kg/h to 5722 kg/h, the total outputs of H2, CO, and CO2 were increased by 1765 Nm3/h and 2063 Nm3/h, respectively, while the CH4 output was decreased by 49 Nm3/h. The coal conversion rate was minimal at low steam input. In addition, more coal gasified in the reductor could increase the output of CH4, while CH4 could reach 1.24% with the coal input in the range of 8000–10,000 kg/h. The present work can offer a further understanding of the gasification performance in the reductor of the full-scale two-stage pressurized entrained-flow gasifier, and motivates the potential for clean utilization of coal resource.

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Co-Gasification Characteristics of Coal and Biomass Using CO2 Reactant under Thermodynamic Equilibrium Modelling

Energies ◽

10.3390/en14217384 ◽

2021 ◽

Vol 14 (21) ◽

pp. 7384

Author(s):

M. Shahabuddin ◽

Sankar Bhattacharya

Keyword(s):

Steady State ◽

Thermodynamic Equilibrium ◽

Operating Conditions ◽

Heating Value ◽

Entrained Flow ◽

Cold Gas Efficiency ◽

Lower Heating Value ◽

Entrained Flow Gasifier ◽

Gas Efficiency ◽

Increasing Temperature

This study assessed the entrained flow co-gasification characteristics of coal and biomass using thermodynamic equilibrium modelling. The model was validated against entrained flow gasifier data published in the literature. The gasification performance was evaluated under different operating conditions, such as equivalence ratio, temperature, pressure and coal to biomass ratio. It is observed that the lower heating value (LHV) and cold gas efficiency (CGE) increase with increasing temperature until the process reaches a steady state. The effect of pressure on syngas composition is dominant only at non-steady state conditions (<1100 °C). The variation in syngas composition is minor up to the blending of 50% biomass (PB50). However, the PB50 shows a higher LHV and CGE than pure coal by 12%and 18%, respectively. Overall, biomass blending of up to 50% favours gasification performance with an LHV of 12 MJ/kg and a CGE of 78%.

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Effect of Radiation Models on Coal Gasification Simulation

Volume 6: Energy, Parts A and B ◽

10.1115/imece2012-86997 ◽

2012 ◽

Cited By ~ 1

Author(s):

Xijia Lu ◽

Ting Wang

Keyword(s):

Wall Temperature ◽

Coal Gasification ◽

Cfd Simulation ◽

Stokes Equations ◽

Heterogeneous Reactions ◽

Coal Slurry ◽

Radiation Model ◽

Entrained Flow ◽

Gasification Process ◽

Coal Particles

Adequate modeling of radiation heat transfer is important in CFD simulation of coal gasification process. In an entrained-flow gasifer, the non-participating effect of coal particles, soot, ashes, and reactive gases could significantly affect the temperature distribution in the gasifier and hence affects the local reaction rate and life expectancy of wall materials. For slagging type gasifiers, radiation further affects the forming process of corrosive slag on the wall which can expedite degradation of the refractory lining in the gasifier. For these reasons, this paper focuses on investigating applications of five different radiation models to coal gasification process, including Discrete Transfer Radiation Model (DTRM), P-1 Radiation Model, Rosseland Radiation Model, Surface-to-Surface (S2S) Radiation Model, and Discrete Ordinates (DO) Radiation Model. The objective is to identify the pros and cons of each model’s applicability to the gasification process and determine which radiation model is most appropriate for simulating the process in entrained-flow gasifiers. The Eulerian-Lagrangian approach is applied to solve the Navier-Stokes equations, nine species transport equations, and seven global reactions consisting of three heterogeneous reactions and four homogeneous reactions. The coal particles are tracked with the Lagrangian method. Six cases are studied—one without the radiation model and the other five with different radiation models. The result reveals that the various radiation models yield uncomfortably large uncertainties in predicting syngas composition, syngas temperature, and wall temperature. The Rosseland model does not yield reasonable and realistic results for gasification process. The DTRM model predicts very high syngas and wall temperatures in the dry coal feed case. In the one-stage coal slurry case, DTRM result is close to the S2S result. The P1 method seems to behave stably and is robust in predicting the syngas temperature and composition; it yields the result most close to the mean, but it seems to underpredict the gasifier’s inner wall temperature.

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