Coal Gasification Characteristics Research Articles

Analysis on combustion and gasification characteristics of Datong coal in a CO2 -rich atmosphere by different temperature gradient–Effect of oxygen concentration

Abstract Current technical challenge for state-of-the-art coal power plants covers not only higher thermal efficiency, also lower CO 2 emission or easier CO 2 separation and capturing. One of expected technologies to achieve it, Integrated Gasification Combined Cycle (IGCC) has been developed. In this study, characteristics of combustion and gasification reactions for the Datong coal samples have been investigated using thermo gravimetric-differential thermal analysis (TG-DTA) under different O 2 concentrations (≤ 5%) in a CO 2 -rich atmosphere by giving different heating and gas flow rates in the temperature range of 20 to 1400 °C. The samples of residual ash were subsequently analyzed by an Energy Dispersive Spectrum (EDS) analyzer to investigate Carbon molecular percentage, C%. The TG-DTA results, which were carried out under the coal temperature lower than 1000 °C, show that O 2 concentration (%) has a larger effect on C% in the residual ash. On the other hand, for the case of coal temperature over 1000 °C, C% has no strong dependency on O 2 % after gasification of the coal sample. Furthermore, a CO 2 gas laser beam was used to carry out experiments of rapid heating of coal samples over the targeted temperature in a second under different O 2 concentrations (≤10%) by circulating Air, N 2 , CO 2 or N 2 -CO 2 mixing gases using with the circulating flow system. In the low O 2 concentration range, the coal weight reduction decreases with increasing O 2 concentration with a linear line and the weight reduction of rapid heating using with the laser beam is comparatively lower than that of TG-DTA. The present results might have great significance for the future of coal gasification power generation and coal seam underground coal gasification projects, etc.

Results of Bituminous Coal Gasification upon Exposure to a Pressurized Pilot-Plant Circulating Fluidized-Bed (CFB) Reactor

Pressurized turbulent circulating fluidized-bed (CFB) gasification of bituminous coal is successfully realized in a lab-scale fluidized-bed gasifier, and the effects of the stoichiometric ratio, steam/coal ratio, and preheated temperature of the gasifying agent on coal gasification characteristics are studied in this work. Experimental results prove the feasibility of a high-temperature air/steam-blown gasification process. The lower heater value is increased by 21%, when the preheated temperature of the gasifying agent is increased from 400 to 700 °C. When the stoichiometric ratio and steam/coal ratio increased, the component of syngas has a regular change according to the gasification temperature. With the increase of the stoichiometric ratio, the gasification temperature is increased, the H2 concentration increased first and then decreased, the CH4 concentration decreased, and the CO and CO2 concentrations increased first and vary little in the second stage because of the steady gasification temperatur...

Hydrogen production from coal gasification in supercritical water with a continuous flowing system

The technology of supercritical water gasification can convert coal to hydrogen-rich gaseous product efficiently and cleanly. A novel continuous-flow system for coal gasification in supercritical water was developed successfully in State Key Laboratory of Multiphase Flow in Power Engineering (SKLMF). The experimental device was designed for the temperature up to 800 °C and the pressure up to 30 MPa. The gasification characteristics of coal were investigated within the experimental condition range of temperature at 650–800 °C, pressure at 23–27 MPa and flow rate from 3 kg h −1 to 7 kg h −1. K 2CO 3 and Raney-Ni were used as catalyst and H 2O 2 as oxidant. The effects of main operation parameters (temperature, pressure, flow rate, catalyst, oxidant, concentration of coal slurry) upon gasification were carried out. The slurry of 16 wt% coal + 1.5 wt% CMC was successfully transported into the reactor and continuously gasified in supercritical water in the system. The hydrogen fraction reached up to 72.85%. The experimental results demonstrate the bright future of efficient and clean conversion of coal.

Supercritical water gasification of Victorian brown coal: Experimental characterisation

Supercritical water gasification is an innovative thermochemical conversion method for converting wet feedstocks into hydrogen-rich gaseous products. The non-catalytic gasification characteristics of Victorian brown coal were investigated in supercritical water by using a novel immersion technique with quartz batch reactors. Various operating parameters such as temperature, feed concentration and reaction time were varied to investigate their effect on the gasification behaviour. Gas yields, carbon gasification efficiency and the total gasification efficiency increased with increasing temperature and reaction time, and decreasing feed concentration. The mole fraction of hydrogen in the product gases was lowest at 600 °C, and increased to over 30 % at a temperature of 800 °C. Varying parameters, especially reaction time, did not improve the coal utilisation for gas production significantly and the measured data showed a large deviation from the equilibrium level.

A Review of the Factors Influencing the Physicochemical Characteristics of Underground Coal Gasification

In this article, the physicochemical characteristics of the oxidation zone, the reduction zone, and the destructive distillation and dry zone in the process of underground coal gasification (UCG) were explained. The effect of such major factors as temperature, coal type, water-inrush or -intake rate, the quantity and quality of wind blasting, the thickness of coal seams, operational pressure, the length, and the section of gasification gallery on the quality of the underground gas and their interrelationship were discussed. Research showed that the temperature conditions determined the underground gas compositions; the appropriate water-inrush or -intake rate was conducive to the improvement in gas heat value; the properties of the gasification agent had an obvious effect on the compositions and heat value of the product gas. Under the cyclically changing pressure, heat losses decreased by 60%, with the heat efficiency and gasification efficiency being 1.4 times and 2 times those of constant pressure, respectively. The test research further proved that the underground gasifier with a long channel and a big cross-section, to a large extent, improved the combustion-gasification conditions.

Experimental investigation of role of steam in entrained flow coal gasification

Experimental investigations of the influence of excess oxygen coefficient, H 2O/coal mass ratio using high-temperature steam, mean mass diameter of pulverized coal and coal size fraction on basic characteristics of coal gasification were performed. Experiments were carried out on a laboratory scale (0.09 m i.d. × 1.5 m high) coal gasification apparatus with lignite type of coal. Influence of steam was realized through comparison of results obtained from experiments with (H 2O/coal = 0.287 kg kg −1) and without steam addition (H 2O/coal = 0.024 kg kg −1). High values of carbon conversion, obtained both for finely ground and for coarse pulverized coal points to the easiness of lignite gasification, i.e. to its high suitability for gasification.

04/00724 Steam gasification characteristics of coal with rapid heating: Fushimi, C. et al. Journal of Analytical and Applied Pyrolysis, 2003, 70, (2), 185–197

04/00724 Steam gasification characteristics of coal with rapid heating: Fushimi, C. et al. Journal of Analytical and Applied Pyrolysis, 2003, 70, (2), 185–197

Steam gasification characteristics of coal with rapid heating

Time profiles of weight change of coal samples and the evolution of low molecular weight gases (H 2, CH 4, CO and CO 2) in both steam gasification and pyrolysis of Yallourn brown coal and Taiheiyo subbituminous coal were measured using a thermobalance reactor with a micro GC and a mass spectrometer, in order to examine the reaction mechanism of steam gasification with rapid heating (100 K s −1). It was found that, in the case of slow heating, steam reacted with metaplast and promoted the evolution of tar above 623 K and that a water shift reaction took place above 873 K. Steam gasification of produced char occurred above 1023 K, increasing the evolution of CO, CO 2 and H 2. When the heating rate was high, steam reforming of volatile matter and steam gasification of metaplast took place parallel to metaplast formation and condensation. The char produced by pyrolysis was almost completely gasified and converted into H 2 and CO 2 by steam. The chemical energy of coal was mainly converted into hydrogen energy and the gasification efficiency was slightly increased by rapid heating (i.e. 100 K s −1).

Coal gasification characteristics in a downer reactor

Coal gasification characteristics in a downer reactor

The Effects of Oxygen on Coal Gasification Characteristics.

The effects of oxygen on coal gasification characteristics have been investigated by using Drop Tube Furnace. In the pyrolysis tests the influences of oxygen in the oxidizer have been examined, and results show that the reactions in which oxygen don't take part isn't influenced by pressure. The gasification tests with changing oxygen fraction in oxidizer have been done, and results show that, for the high volatile matter coal gasification efficiency isn't influenced by oxygen fraction, but for the low volatile matter coal, it is improved by increasing the oxygen fraction. Moreover, the reactivity of the low volatile matter coal has been investigated, and the effects of oxygen fraction are clarified by comparing the effects of the temperature and the residence time of coal particle.

Coal gasification characteristics in a downer reactor

Subbituminous coal (Shenwha) was gasified at atmospheric pressure in a downer reactor (0.1 m I.D.×5.0 m high). The effects of reaction temperature (750–850°C), steam/coal mass ratio (0.23–0.86), O 2/H 2O mole ratio (0–1.81) and coal feeding rate (5.3–9.0 kg h −1) on the composition of product gas, carbon conversion, cold gas efficiency, gas yield and calorific value have been determined. In the case of steam injection into the loop-seal, compositions of the product gas (vol. %; N 2 free basis) in the gasification region are H 2 (35.8–39.4%), CH 4 (6.8–15.5%), CO (14.9–15.9%), CO 2 (20.7–29.5%), C 2H 4 (2.8–4.9%), C 2H 6 (2.5–3.5%), C 3H 6 (1.6–3.3%) and C 3H 8 (1.7–2.5%) with a calorific value of 13.0–15.2 MJ/m 3. By changing the reactant gas supplied into the loop-seal for solid circulation from steam to air, product gas yield and carbon conversion increase, whereas calorific value of the product gas decreases from 13.0–15.2 to 6.3–10.6 with reaction temperature.

Numerical study on the coal gasification characteristics in an entrained flow coal gasifier

The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The k– ε turbulence model was used for the gas phase flow while the Random-Trajectory model was applied to describe the behavior of the coal slurry particles. The unreacted-core shrinking model and modified Eddy break-up (EBU) model, were used to simulate the heterogeneous and homogeneous reactions, respectively. The simulation results obtained the detailed information about the flow field, temperature and species concentration distributions inside the gasifier. Meanwhile, the simulation results were compared with the experimental data as a function of O 2/coal ratio. It illustrated that the calculated carbon conversions agreed with the measured ones and that the measured quality of the syngas was better than the calculated one when the O 2/coal ratio increases. This result was related with the total heat loss through the gasifier and uncertain kinetics for the heterogeneous reactions.

Pressurized drop tube furnace test of global coal gasification characteristics

Pressurized drop tube furnace test of global coal gasification characteristics

Pressurized drop tube furnace tests of global coal gasification characteristics

Pressurized drop tube furnace tests of global coal gasification characteristics

Pressurized drop tube furnace tests of global coal gasification characteristics

Pressurized drop tube furnace (PDTF) tests were performed with an Indonesian sub-bituminous coal while temperature, oxygen/coal ratio, steam/coal ratio and pressure were systematically varied. The tests were designed to investigate the effects of these experimental parameters on the pulverized coal gasification characteristics at elevated pressure. The results showed that the gasification at elevated pressure is more productive than that at atmospheric pressure, considering the carbon conversion and cold gas efficiency. The oxygen/coal ratio at the maximum cold gas efficiency ranged between 0.5 and 0.7 g/g. Only when the temperature was sufficiently high, did the increase of steam/coal ratio result in the improvement of cold gas efficiency. As the pressure increased, the contribution of carbon conversion by heterogeneous reactions increased while the conversion by pyrolysis decreased. Copyright © 2000 John Wiley & Sons, Ltd.

98/00272 Coal gasification characteristics in an internally circulating fluidized bed with draught tube

98/00272 Coal gasification characteristics in an internally circulating fluidized bed with draught tube

Coal gasification characteristics in an internally circulating fluidized bed with draught tube

Australian coal was gasified at atmospheric pressure in an internally circulating fluidized bed (0.3 m i.d. × 2.7 m high) with a draught tube (0.1 m i.d. × 0.9 m high) and a gas separator over the draught tube. The effects of reaction temperature (780–900°C), oxygen/coal mass ratio (0.30–0.53), coal feed rate (5.3–12.1 kg h −1) and steam/coal mass ratio (0.30–0.81) on composition of product gas, carbon conversion, cold gas efficiency and gas yield and calorific value were determined. Low-CV gas in the draught tube region and medium-CV gas in the annulus region can be obtained. In the annulus region, the composition of the product gas (vol.%) is H 2 31.8–46.2, CO 18.8–25.6, CO 2 13.2–20.4 and CH 4 5.3–10.4, with a CV of 8.6–13.2 MJ m −3. In the draught tube region, the composition is H 2 8.3–19.7, CO 6.7–13.1, CO 2 18.9–35.3 and CH 4 1.9–4.4, with a CV of 3.3–5.9 MJ m −3.

97/03749 Coal gasification characteristics in a fluidized bed reactor—kinetics of oxygen-char and steam-char reactions in relation to gasification characteristics

97/03749 Coal gasification characteristics in a fluidized bed reactor—kinetics of oxygen-char and steam-char reactions in relation to gasification characteristics

97/03750 Coal gasification characteristics in an internally circulating fluidized bed with draught tube

97/03750 Coal gasification characteristics in an internally circulating fluidized bed with draught tube

Study on flow characteristics in entrained flow gasifier with high speed impinging jet

An entrained flow gasifier simulating the cold mode was tested to estimate its performance for coal gasification and flow characteristics with a developed high speed impinging jet nozzle. The burner was designed for high temperature and high pressure(HTHP) conditions, especially for IGCC(Integrated Coal Gasification Combined Cycle). In order to get proper size of droplets for high viscous liquid such as coal slurry, atomization was achieved by impacting slurry with high speed (over 150m/sec) secondary gas (oxygen/or air)/ Formed water droplets were ranged between 100.mu.m to 20.mu.m in their sizes. The flow characteristics in the gasifier was well understood in mixing between fuel and oxidizer. Both external and internal recirculation zones were closely investigated through experimentation with visualization and numerical solutions from FLUENT CODE.