Excess Oxygen Coefficient Research Articles

Thermodynamic analysis of the air separation unit and CO2 purification unit in the semi-closed supercritical CO2 cycle with nearly zero emission

The natural gas-fired semi-closed supercritical CO2 cycle is an efficient oxyfuel combustion power generation technology featuring nearly zero emissions. This study investigated the interaction of the semi-closed supercritical CO2 power unit with the air separation unit (ASU), which supplies O2 for combustion and adiabatic compression heat for the heat recovery process in the power unit, and the CO2 purification unit (CPU), which refines the CO2 in the exhaust gas to 99.97% for enhanced oil recovery (EOR) applications. The detailed thermodynamic models of the power unit, ASU, and CPU have been constructed to explore the impact of variations in oxygen purity and excess oxygen coefficient on the overall thermodynamic performance of the system. The results demonstrate that the net electric efficiency peaks at an oxygen purity of 98%, and a one percent decrease in oxygen purity reduces the net electrical efficiency by approximately 0.36% to 0.97% points. Moreover, the net electric efficiency decreased by 0.10% points when the excess oxygen coefficient increased from 3.00% to 13.67%. These findings may offer valuable guidance for developing oxyfuel combustion power generation technologies.

Overall scheme design of a closed solid oxide fuel cell hybrid engine for ships

A scheme of compact closed solid oxide fuel cell hybrid engines for ship power and propulsion on ships is proposed. A zero-emission closed engine at the effective equivalence ratio of 1 is achieved by recirculating water and fuelling by liquid hydrocarbon fuel and oxygen. The adiabatic pure oxygen reforming temperature of the reformer is higher than the specified anode inlet temperature. A turbine is placed in front of the solid oxide fuel cell anode. Detailed potential distributions are considered using a two-dimensional solid oxide fuel cell model, and thermodynamic models of the hybrid engine are built. The performance of the reformer is more sensitive to the oxygen-carbon ratio rather than the steam-carbon ratio, which leads to a huge change of the pressure ratio of the turbine. Therefore, the power ratios of turbines and SOFC are also affected by the oxygen and steam carbon ratio and excess oxygen coefficient. The optimized power ratio is 1.02–1.13, which results in a significant change in the efficiency of the engine. Under the specified operating conditions, the engine can achieve a high efficiency of 67 %. Under the off-design conditions, with the increase of the mass flow of fuel or the current density, the power of the engine can be changed from 20 % to 160 % of the designed power.

Simulation of DME-O2 Combustion in a Hollow Cone Impinging Jet Combustor for Direct-Fired Supercritical CO2 Power Cycle

ABSTRACT Combustion is critical in the direct-fired supercritical CO2 power cycle. A hollow cone impinging jet combustor is designed. Instead of methane, dimethyl ether is used as the fuel for the direct-fired supercritical CO2 cycle, with a higher hydrocarbon ratio and oxygen. The dimethyl ether combustion process is simulated by Fluent, based on the k-ε turbulence model and Eddy-Dissipation Concept combustion model, combined with the dimethyl ether combustion mechanism. The effects of the CO2 recycling ratio, the excess oxygen coefficient, and in-combustor pressure are investigated to support improving combustion performance. The results indicate that the recycled CO2 intensifies the movement of the mixture in the combustor, reduces the peak temperature, and makes temperature distribution more uniform. As the excess oxygen coefficient increases, the peak temperature is enhanced, and the combustion is more sufficient. The effect of in-combustor pressure is complex. On the one hand, increasing in-combustor pressure reduces the jet penetration and inhibits the contact between dimethyl ether and O2, leading to a lower peak temperature. On the other hand, it prolongs the residence time of the high-temperature exhaust, making the reaction between dimethyl ether and O2 more sufficient. The optimal operating condition of the combustor is a CO2 recycling ratio of 0.95, an excess oxygen coefficient of 1.20, and an in-combustor pressure of 30 MPa. Moreover, the obtained combustion products parameters, such as temperature, component concentration, and mass flow rate, can guide the performance analysis for the direct-fired supercritical CO2 power cycle.

Industrial-scaled Cu-Fe composite oxygen carrier for chemical looping combustion through extrusion-spheronization

It is crucial for the preparation of the high-performance and low-cost oxygen carrier (OC) in an industrial-scaled application to lay the foundation for the commercialization of chemical looping combustion (CLC) technology. In this work, a bimetallic OC (RCu-10 M) is prepared in an industrial-scaled extruder coupling with roller, composited by the red mud (aluminum industrial waste), copper ore and montmorillonite as raw materials. First, a thermogravimetric analyzer (TGA) is used to carry out 100 redox cycles using H2 as the reducing agent. RCu-10 M OC demonstrate remarkable redox stability and sintering-resistance across multiple cycles, and the oxygen donating capacity do not diminish as the number of cycles increases. The effects of temperatures and excess oxygen coefficients on the reactivities of RCu-10 M OC with Shenhua bituminous coal are then investigated by using a batch fluidized bed reactor. RCu-10 M OC maintains high combustion efficiency, exceeding 94.7 % at 950 °C, with an excess oxygen coefficient of 2.0. Finally, a lab-scaled interconnected fluidized bed reactor is applied to examine the realistic performance of RCu-10 M OC using CH4 fuel. The results demonstrate that the RCu-10 M OC successfully operates for ca. 100 min of continuous time, and there is no de-fluidization occurrence, and the bed pressure decrease is stable during operation, indicating that the RCu-10 M OC exhibits good fluidization properties and had the potential to be used in large-scale fluidized bed reactors. Further characterization data reveal that the chemical composition of RCu-10 M OC is stable throughout multiple cycles, as indicated by the almost uniform distribution of elements.

Co-firing of coal and biomass under pressurized oxy-fuel combustion mode: Experimental test in a 10 kWth fluidized bed

• Pressurized oxy-fuel combustion of coal/biomass in a fluidized bed is successful. • Stable, pressurized, oxy-fuel combustion mode using coal/biomass can be realized. • Increased pressure leads to higher combustion efficiency and CO 2 enrichment. • Increased pressure has the advantages of reducing CO, NO x , and SO 2 emissions. • Increased pressure makes the fly ash particles finer with surface more cracked. Pressurized oxy-fuel combustion (POFC) of solid fuels in fluidized beds possess the potential for CO 2 capture at low cost. However, the practical experience of oxy-coal combustion in pressurized fluidized beds (PFB) is still very limited, and there is a lack of attempts on the co-firing of coal and other fuels. In this study, the co-firing of coal and biomass in a POFC mode at a 10 kW th PFB was tested. The dynamic behaviors of the start-up process and combustion mode switching were investigated. The effects of key operating parameters, including combustion pressure ( P ), biomass blending ratio ( M b ), and excess oxygen coefficient ( α ), on the temperature distributions, CO 2 enrichment and conversion, pollutant emissions (CO, NO X , SO 2 ), and solid residues were methodically studied. The results show that the stable, pressurized, and oxy-fuel combustion mode with coal and biomass mixtures as fuels can be successfully realized in a fluidized bed. Increasing P and M b not only conduces to better temperature distribution, more CO 2 enrichment in flue gas, and higher combustion efficiency but also has the advantage of reducing NO x and SO 2 emissions by over 30%. In the oxy-fuel PFB, the positive effect of α on the combustion performance is more significant than that under atmospheric conditions. As P increases, the fly ash surface is more cracked, and the particle size distribution of fly ash decreases, while the bottom slag surface is smoother. Besides, the increase in P results in a decreased specific surface area and cumulative pore volume but an increased average pore diameter in fly ash.

Oxidizer effects on ammonia combustion using a generated non-premixed burner

In the present study, the pure ammonia combustion in a model combustor is performed to seek ammonia-fueled applications. To this aim, effects of the oxygen enrichment with an oxygen concentration of 100% in the oxidizer on flame characteristics, temperature profiles and NO profiles during the ammonia combustion were evaluated in terms of excess air/oxygen coefficients. Furthermore, in order to better understand the effect of an oxygen of 100% usage under the oxy-ammonia combustion conditions, the air-ammonia combustion has been studied as well and their results are compared and discussed each other. According to the results predicted, the oxidizer with an oxygen content of %100 provides better flame stability in the case of pure ammonia combustion. The most stable flame for oxy-ammonia combustion can be achieved when the excess oxygen coefficient is 1.0 or 1.2. Furthermore, the minimum NO levels emerge under the fuel-rich condition. Temperature and NO emissions decrease considerably under the air-ammonia combustion. However, except the fuel-rich conditions, flame stabilities are not satisfactory due to ammonia's flame speed under the air-ammonia combustion. Moreover, the air-ammonia combustion under the fuel-rich condition seems as a good option for obtaining the lowest NO levels. On the other hand, the oxy-enrichment condition is thought as a promising method for pure ammonia combustion provided that NO emissions should be optimized by using NO reduction methods. • Oxy- and air-ammonia combustion have been taken place. • Temperature and NO X values have been demonstrated. • Equivalence ratio effect on the flame has been studied. • It is revealed that oxy-ammonia combustion performance is favorable. • NO X values are more favorable for air-ammonia than oxy-.

Effect of oxygen-staging on fluidized preheating combustion of pulverized coal under O2/CO2 atmosphere

Oxy-fuel combustion with low NOx emission has been received more attention in recent years. In this work, a series of oxygen-staged experimental investigations of Shenmu bituminous coal with the preheated combustion technology was carried out under O2/CO2 atmosphere to obtain the effect of oxygen-staged on combustion and NOx emission. The results showed that the increase of excess oxygen coefficient of the primary air(λPr) decreased the temperature difference at each measuring point in the circulating fluidized bed, promoted the production of coal gas, facilitated the release of elements, and improved the mass conversion ratio of volatile matter up to 92.3%. Besides, the increase of λPr inhibited the conversion process of N-5 to N-6. At the same time, the release of nitrogen-containing volatile matter during the partial gasification process was also reduced. As the λPr increases, reducing the excess oxygen coefficient of the secondary air(λSe) or increasing the oxygen partial pressure of primary air were beneficial to reduce the emissions of NOx to a certain extent.

Optimization of the flame characteristics of H2–O2 coaxial injection applied to hydrogen-fueled argon cycle engines

The argon power cycle is one of the most promising technologies for high efficiency and low emission hydrogen-fueled internal combustion engines. The application of coaxial injection technology in the hydrogen-fueled argon engine can improve the mixing process and the combustion performance of the H2/O2 mixture. In this study, an innovative H2–O2 coaxial injection combustion system was designed to investigate the jet flame characteristics of oxygen coaxially wrapped by hydrogen in a controllable argon thermal atmosphere. The findings of this study could provide a new perspective for designing hydrogen-fueled argon engines in the future. The influences of co-flow temperature, jet injection pressure, and excess oxygen coefficient were all determined. Observations of the flame showed a bright blue flame with a reddish glow in the far-burner region. Experimental results show that the flame length, cross-sectional area, and area/perimeter ratio first decrease with increasing jet injection pressure and subsequently increase, reaching maximum values at 0.4–0.6 MPa. When increasing the co-flow temperature from 1023 K to 1223 K, the cross-sectional area of the flame increases significantly by 61.1% at an excess oxygen coefficient of 0.4. Furthermore, the liftoff flame height shrinks when the co-flow temperature and the excess oxygen coefficient increase, while it rises along with an increasing jet injection pressure.

Effects of oxygen concentration and inlet velocity on pulverized coal MILD combustion

The inlet velocity is an important parameter in the Moderate or Intense Low-Oxygen Dilution (MILD) combustion. Different inlet velocities not only change the flow of the flue gas, but also affect the dilution effect of the circulating flue gas and the temperature distribution of the furnace. In coal MILD-oxy combustion, different oxygen concentrations change the amount of flue gas and inlet velocity when the excess oxygen coefficient is fixed. Therefore, the change of inlet velocity is worthy of attention in MILD-oxy combustion. In this work, the MILD combustion characteristics with different inlet velocities at different oxygen concentrations are discussed by changing the burner diameter. The results show that increasing the inlet velocity suppresses the temperature peaks in both MILD-air and MILD-oxy combustion. When the inlet velocity is fixed, the flame temperature is increased with the O2 concentration. The facilitation of char gasification reaction with increasing oxygen concentration is also partly due to the increase of temperature and char gasification is also partially affected by the O2 concentration. In terms of heat transfer, the inlet velocity has a large effect on convective heat transfer.

Sensitivity Analysis and Optimization of Operating Parameters of an Oxyfuel Combustion Power Generation System Based on Single-Factor and Orthogonal Design Methods

The main purpose of this paper is to quantitatively analyze the sensitivity of operating parameters of the system to the thermodynamic performance of an oxyfuel combustion (OC) power generation system. Therefore, the thermodynamic model of a 600 MW subcritical OC power generation system with semi-dry flue gas recirculation was established. Two energy consumption indexes of the system were selected, process simulation was adopted, and orthogonal design, range analysis, and variance analysis were used for the first time on the basis of single-factor analysis to conduct a comprehensive sensitivity analysis and optimization research on the changes of four operating parameters. The results show that with increasing oxygen purity, the net standard coal consumption rate first decreases and then increases. With decreasing oxygen concentration, the recirculation rate of dry flue gas in boiler flue gas ( χ 1 ) and an increasing excess oxygen coefficient, the net standard coal consumption rate increases. The net electrical efficiency was just the opposite. The sensitivity order of two factors for four indexes is obtained: the excess oxygen coefficient was the main factor that affects the net standard coal consumption rate and the net electrical efficiency. The influence of oxygen concentration and oxygen purity was lower than that of excess oxygen coefficient, and χ 1 has almost no effect.

Experimental study of SO2 emissions and desulfurization of oxy-coal combustion in a 30 kWth pressurized fluidized bed combustor

Pressurized oxy-fuel combustion (POFC) has attracted wide attention due to its potentials of high efficiency and low cost in CO2 capture. Compared with numerical simulation and system analysis, there are few experimental studies about POFC. In order to investigate the SO2 emissions and desulfurization behaviors of limestone under continuous fuel-feeding POFC conditions, a series of oxy-coal combustion experiments were conducted with a 30 kWth pressurized fluidized bed combustor. The results showed that the SO2 emission was almost independent of combustion pressure and excess oxygen coefficient, while it was higher in air than in O2/CO2 atmosphere because less sulfur was retained by the coal ash. Although the higher CO2 partial pressure caused by an increase in combustion pressure from 0.1 MPa to 0.4 MPa had negative effects on the calcination of limestone and inhibited the indirect desulfurization, the higher combustion pressure was beneficial to improve the direct desulfurization efficiency. An increase in combustion temperature from 850 °C to 950 °C significantly improved the desulfurization efficiency of limestone with both atmospheric and pressurized oxy-coal combustion. SEM images were obtained and used to show the surface morphology of limestone products under different combustion conditions, which was helpful to the understanding of the desulfurization behaviors of limestone.

Experimental investigation and simulation optimization of a pilot-scale supercritical water oxidation system

Supercritical water oxidation (SCWO) technology has an excellent performance in treating high concentration and refractory organic wastes. While the high treatment cost is one of the key drawbacks currently restricting its large-scale application. In this study, a SCWO pilot system with a novel jet reactor (treatment capacity of 200 kg/h) was experimentally investigated, and the process model was developed to optimize the system by Aspen Plus. The energy and exergy efficiency of the system was evaluated, and the wastewater treatment cost in different operating conditions was estimated. The results show that chemical oxygen demand (COD) removal efficiency could be increased with the increase of the temperature, pressure, and the excess oxygen coefficient. By locating the electric heater 1 (H1) before the heat exchanger 2 (H2), and improving the outlet temperature of the oxygen compressor (MP1), the wastewater treatment cost could be reduced to 53.5 $/t, and the energy and exergy efficiency of the SCWO system could be improved to 81.61% and 8.91%, which is 26.28% and 6.23% higher than that of the current system, respectively. Both the reaction temperature and COD concentration of the wastewater have positive effects on the wastewater treatment cost, e.g. the wastewater treatment cost could decrease from 80.88 $/t to 59.27 $/t when the reaction temperature increases from 380 °C to 420 °C, and the SCWO system could achieve the energy self-sufficient operation when the COD concentration is over 60,000 mg/L.

Effect of oxy-fuel combustion on flame characteristics of low calorific value coal gases in a small burner and combustor

Currently, using oxygen instead of air in a combustion process is being widely discussed as an option to reduce fuel consumption and utilization of oxygen is expected to improve the thermal efficiency and combustion performances. The main goal of this study is to determine the combustion behaviors of low calorific value coal gases under oxy-fuel combustion conditions and to compare with the results of air-fuel combustion conditions in the existing burner and the combustor. The coal-derived low calorific value coal gases (syngases) have been properly oxy-combusted using the existing burner within the present study. Temperature and emission values have been experimentally measured and investigated on different axial and radial positions by using thermocouples and a flue gas analyzer throughout the combustion chamber. All experiments have been performed under a thermal power of 10 kW and an excess oxygen coefficient of λ = 1.2 combustion conditions for both turbulator distances of 7 cm and 2 cm. The burner walls were overheated due to using of pure oxygen instead of air during combustion when the turbulator position of the burner was further to the burner exit (7 cm). Because of that, the turbulator position of the burner has also been changed as a small modification to alleviate overheating of the burner walls and hence, it was drawn near to the burner exit (2 cm). Therefore, it can be said that the burner either can be used with modification or the burner material should be changed to be withstood higher temperature levels. It is consequently concluded that the flame that has emerged under combustion condition with 2 cm of the turbulator distance is wider and smoother than that of the flame showing up under combustion condition with 7 cm of the turbulator distance. CO, CO2 and NOX emissions have also been determined on different axial and radial positions. According to the measurements, it has been demonstrated that CO2 and NOX decrease while CO increase on the axial measurements as the turbulator distance is draw near to the burner exit. When the oxy-fuel combustion results are compared with the air-fuel combustion results, it can be concluded that the oxy-fuel combustion performances of the coal-derived syngases are better than that of the air-fuel combustion, which corresponds to an increment of about 22% in their flame temperatures. However, it has been obtained that oxy-fuel NOX values are not lower than that of the air-fuel values due to the higher flame temperatures. It has been revealed that oxy-fuel CO emission values are lower and oxy-fuel CO2 emission values are higher (approximately 30%) than values of the air-fuel combustion due to the absence of nitrogen in the oxidizer.

Oxy-fuel combustion study of biomass fuels in a 20 kWth fluidized bed combustor

Oxy-fuel combustion is one of the promising carbon capture technologies considered to be suitable for future commercial applications with stationary combustion plants. Although more and more biomass and waste are now being burned in stationary combustion plants, research on oxy-fuel combustion of biomass has received much less attention in comparison to oxy-fuel combustion of coal. In this work, a series of tests was carried out in a 20 kWth fluidized bed combustor under oxy-fuel conditions firing two non-woody fuels (miscanthus and straw pellets) and one woody fuel (domestic wood pellet). The effects of the combustion atmosphere (air and oxy-fuel) and oxygen concentration in the oxidant of the oxy-fuel combustion on gas emissions and temperature profiles were systematically studied with the overall excess oxygen coefficient in the combustor being maintained roughly constant throughout the tests. The experimental results showed that replacing the air with an oxy-fuel oxidant of 21 vol% O2 and 79 vol% CO2 resulted in a significant decrease in combustion temperature and ultimately led to the extinction of the biomass flame due to the larger specific heat of CO2 compared to N2. To keep a similar temperature profile to that achieved under the air combustion conditions, the oxygen concentration in the oxidant of O2/CO2 mixture had to be increased to 30 vol%. A drastic decrease in CO emissions was observed for all three biomass fuels (up to 80% reduction when firing straw) under oxy-fuel combustion conditions providing that the oxygen concentration in the oxidant of O2/CO2 mixture was above 25 vol%. NOx emissions were found to decrease with the oxygen concentration in the oxy-fuel oxidant, due to i) the increase of bed temperature, which implies more volatile-N released and converted in the dense bed zone and ii) the less dilution of the gases inside the dense bed zone, which leads to a higher CO concentration in this region enhancing the reduction of NOx. Similar NOx emissions to those obtained with air combustion were found when the oxygen concentration in the oxy-fuel oxidant was kept at 30 vol%. Further analysis of the experimental results showed that the gas emissions when firing the non-woody fuels were controlled mainly by the freeboard temperature instead of the dense bed region temperature due to the characteristically high volatile matter content and fines of this kind of biomass fuels.

Experimental Study on Mercury Oxidation in a Fluidized Bed under O2/CO2 and O2/N2 Atmospheres

The effects of the temperature, oxygen concentration, and excess oxygen coefficient on mercury oxidation under O2/CO2 and O2/N2 coal combustion were experimentally analyzed in a fluidized bed. The results suggested that both the concentration and proportion of Hg0 increased as the temperature increased under oxy-coal combustion. Mercury was also primarily in elemental form at high temperatures under oxy-coal combustion. Mercury oxidation was much less effective in the presence of CO2. The percentages of Hg0 and Hg2+ increased as the excess oxygen coefficient increased under oxy-coal combustion.

Comprehensive investigation of process characteristics for oxy-steam combustion power plants

Oxy-steam combustion, as an alternative option of oxy-fuel combustion technology, is considered as a promising CO2 capture technology for restraining CO2 emissions from power plants. To attain its comprehensive process characteristics, process simulation, thermodynamic assessment, and sensitivity analysis for oxy-steam combustion pulverized-coal-fired power plants are investigated whilst its corresponding CO2/O2 recycled combustion (oxy-CO2 combustion) power plant is served as the base case for comparison. Techno-economic evaluation and integration with solar parabolic trough collectors are also discussed to justify its economic feasibility and improve its thermodynamic performance further, respectively. It is found that oxy-steam combustion exhibits better performance than oxy-CO2 combustion on both thermodynamic and economic aspects, in which the cost of electricity decreases about 6.62% whilst the net efficiency and exergy efficiency increase about 0.90 and 1.01 percentage points, respectively. The increment of oxygen concentration in oxidant (20–45mol.%) and decrease of excess oxygen coefficient (1.01–1.09) in a certain range are favorable for improving oxy-steam combustion system performance. Moreover, its thermodynamic performance can be improved when considering solar parabolic trough collectors for heating recycled water, even though its cost of electricity increases about 2$/(MWh).

Experimental and chemical kinetic study of CO and NO formation in oxy-methane premixed laminar flames doped with NH3

The present work focuses on the oxy-fuel combustion of methane doped with ammonia in a premixed laminar burner operating at atmospheric pressure, and includes both experiments and a chemical kinetic study. CO and NO formation/emission were examined as a function of the stoichiometry and oxidizer composition. The experimental results showed that, for all oxidizer compositions studied, an increase in the excess oxygen coefficient generally decreases both the CO and NO emissions. Moreover, for the O2/CO2 environments, decreasing the oxygen concentration in the oxidizer, for a given excess oxygen coefficient, leads to higher CO emissions, but lower NO emissions. In air firing, the CO emissions were found to be significantly lower than those measured under oxy-fuel conditions, while the NO emissions were higher than those from the oxy-fuel cases. The chemical kinetic study allowed to identify the main reactions that directly (with the aid of a rate-of-production analysis) and indirectly (through a sensitivity analysis) influence both the CO and NO emissions. Under oxy-fuel conditions, CO2+H↔CO+OH and 1CH2+CO2↔CH2O+CO significantly contribute to CO formation additionally to those reactions found in air-fired combustion, while CO oxidation takes place through CO+OH↔CO2+H for all studied conditions. Formation of NO occurs for all conditions mainly with HNO as intermediate, particularly through HNO+H↔H2+NO. Once NO is formed, interconversion to NO2 occurs.

Comparison of combustion characteristics of petroleum coke and coal in one-dimensional furnace

The effect of primary air fraction ƒ1, outer secondary air swirl strength and excess oxygen coefficient on the combustion characteristics of petroleum coke, Hejin lean coal and Shenmu soft coal are researched on a one-dimensional furnace using a dual channel swirl burner. The results show that with the increase in primary air fraction ƒ1, the NOx emission concentrations of both Hejin lean coal and petroleum coke increase, and the combustion worsens in the earlier stage, but the burn-out rate of Shenmu soft coal is improved. The NOx emission concentration obtains a minimum value with an increase in ƒ1. The ignition and burn-out rate of petroleum coke and Shenmu soft coal are optimal when Ωdl is minimum and Ωdl= 0.87, respectively. However, both the NOx emission concentration of petroleum coke and Shenmu soft coal are minimum when Ωdl= 1.08. The increase in excess oxygen coefficient delays the ignition of petroleum coke, worsens the combustion condition and increases the NOx emission concentration, but it greatly decreases the NOx emission concentration of Shenmu soft coal.

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.