Gasification Tests Research Articles

Stability evaluation method of gasification coal pillar under thermal coupling condition for prevention of environment secondary pollution

The instability of gasification coal pillars can easily induce the further development of water-conducting fractures, which leads to the connection of gasification combustion space and aquifer, and then causes groundwater pollution. Therefore, it is crucial to assess the stability of gasification coal pillar to forestall the potential risk of environmental contamination resulting from underground coal gasification. In this paper, based on the shape of the combustion space area of underground coal gasification, considering the influence of the mechanical properties of the coal pillar and the temperature field under the condition of thermal coupling, the calculation method of the yield zone width of gasification coal pillar is proposed. Considering the destabilizing factors affecting the coal pillar and the relationship between actual and ultimate bearing capacities after stripping and yielding, a stability evaluation method for the ‘hyperbolic’ coal pillar is proposed. Additionally, the effects of various factors on the stripping, yielding, and safety factor of the coal pillar are analyzed. The new method was applied to the Ulanqab underground coal gasification test site, which proved its effectiveness. The research results are of great practical significance for designing underground coal gasification production and preventing environmental pollution.

Three-dimensional computational fluid-dynamic simulation of polypropylene steam gasification

Among the recycling techniques, gasification allows to obtain a hydrogen-rich gas from polypropylene (PP), a widely used thermoplastic material. In this work, devolatilization and steam gasification tests of PP were conducted in fluidized bed reactors. The results show a gas yield of 1.3 and 3.0 Nm3/kgPP, and a tar content of 117.3 and 20.9 g/Nm3 from devolatilization and gasification, respectively. Experimental results provide an overall overview of this process, able to produce a syngas with an H2-content of 50 vol%dry.Experimental data coupled with kinetic analysis were used to develop a computational fluid dynamic model (CFD) capable of describing both thermal degradation and subsequent gasification reactions. Although some discrepancies on water conversion and H2/CO ratio probably related to the influence of steam in radical chain-scission the model allows to describe gas production and hydrocarbons evolution providing important support for modeling and sizing of fluidized bed reactors on an industrial scale.

The Impact of Temperature on the Production of High Calorific Value Syngas using Cogasification Technology

Cogasification represents a thermochemical reaction employed to transform by combining biomass or fossil carbonaceous materials into combustible matters. Widely acknowledged as the most appealing approach among various combustible material to useful energy. This method offers significant potential for environmentally friendly energy production, boasting low carbon emissions. This study conducted gasification tests utilizing an updraft gasifier, incorporating parameters variable at 650°C to 850°C. The materials utilized consisted of a blend of Municipal-Solid-Waste (MSW) and coconut shells, maintaining a steam to biomass at 1.3. Optimum temperature at 750°C, the syngas revealed 41.30% mol CO, 20.90 mol% CO2 37.25 mol% H2, and 0.55 mol% CH4. Notably. The highest H2 gas production was achieved at this temperature. Furthermore, the net caloric value at this temperature, surpassed other variations, reaching 374.67 kJ/mol, accompanied by the generation of 11.38% of tar and 21.1% char.

A Route for Bioenergy in the Sahara Region: Date Palm Waste Valorization through Updraft Gasification

The Adrar region (Algeria) has a total of 397,800 date palm trees (Phoenix dactylifera L.). Due to annual palm cleaning, large quantities of lignocellulosic biomass are produced. Depending on the variety, an average of 65 kg of biowaste is obtained per palm tree. Since the value of this biowaste is underrated, most of the palms are burned outdoors, causing air and visual pollution. This work explores the gasification potential of lignocellulosic waste from date palms (Phoenix dactylifera L. Takarbouche variety) into useful energy. The technology investigated is air updraft fixed-bed gasification, thanks to an originally designed and built reactor, with the capability to process 1 kg of feedstock. Four types of palm waste—namely, palms, petioles, bunch, and bunch peduncles—are first characterized (bulk density, proximate analysis, fixed carbon, elemental composition, and calorific value) and then used as feedstock for two gasification tests each. The syngas produced for the four date palm wastes is combustible, with an outlet temperature between 200 and 400 °C. The operating temperature inside the gasifier varies according to the feature of the biomass cuts (from 174 °C for the peduncles to 557 °C for palms). The experimental setup is also equipped with a cyclone, allowing for the recovery of some of the tar produced during the tests. Finally, the results show that the residence time has a positive effect on the conversion rate of date palm waste, which can significantly increase it to values of around 95%.

Experimental investigation of chestnut shells gasification

Fossil fuels substitution with renewable energy sources is necessary for an effective decarbonization. Biomass can represent a valid alternative to fossil fuels, reducing greenhouse gas emissions. Furthermore, bioenergy generation avoids costs and problems related to biomass disposal. This study presents the energetic valorisation of chestnut shells, a byproduct of the chestnut transformation processes. Through a thermo-conversion system based on gasification, this material was considered not as a waste, but as a resource to be exploited to produce bioenergy and biochar. The fuel gas produced through the gasification process can partially replace the LPG currently used to meet the energy required for the brulage and steam peeling processes. Experimental gasification tests were carried out to evaluate this biomass by means of a laboratory scale micro-gasifier (Imbert downdraft type). Chestnut shells were pelletized with a pelletizer machine to avoid the bridging effect inside the gasifier and increase its energy density. The fuel gas obtained was sampled and analyzed to measure its composition and HHV. In addition, the gasification efficiency was calculated obtaining a value of 70%, a result in line with the ones obtained with higher quality biomasses.

Performance assessment of a demonstration-scale biomass gasification power plant using material and energy flow analyses

In this study, biomass gasification was investigated in a 1.5 MWth bubbling fluidized bed demonstration plant using air or an air/steam mixture as gasifying agent, and olivine as bed material. The gasification tests were performed in autothermal conditions and keeping constant the equivalence ratio at 0.30. The gasification products, such as producer gas, elutriated particles, tar, and contaminant gases were comprehensively characterized. Moreover, the performance of the whole gasification plant and that of its specific process units were quantitatively assessed by employing material and energy flow analyses. The results indicated that steam addition improved the producer gas quality by promoting tar and char conversion into permanent gases, thus increasing the producer gas specific yield, even if the lower heating value of the producer gas and cold gas efficiency slightly decreased. Material flow analysis highlighted that the carbon conversion efficiency was mainly affected by the carbon loss due to the solid particles collected by the cyclone, while energy flow analysis revealed that the cold gas efficiency was significantly influenced by the energy the system used to convert the starting biomass into producer gas. The biomass conversion efficiency into electrical energy was about 24 %.

Experimental investigation and chemometric analysis of gasification and co-gasification of olive pomace and Sida Hermaphrodita blends with sewage sludge to hydrogen-rich gas

In the paper the results of the systematic study on oxygen/steam co-gasification of sewage sludge blends with biomass waste such as olive pomace or energy crops such as Sida Hermaphrodita to hydrogen rich gas were presented. In the first part of the experimental campaign the oxygen/steam gasification of sewage sludge, Sida Hermaphrodita and olive pomace, respectively, at 700, 800 and 900 °C were gasified. Only small amount of the total gas was produced in the oxygen/steam gasification of analyzed sewage sludge in all studied temperatures. The carbon conversion rate varied between 64% at 700 °C to 66% at 900 °C. The hydrogen amount in the total gas produced in the sewage sludge gasification was 28%vol. at all studied temperatures. The main conclusion from this part of experiments was that gasification of sewage sludge is ineffective. Different conclusions were drawn on the basis of Sida Hermaphrodita and olive pomace gasification tests at all studied temperatures. Therefore in the second part of the experimental campaign the co-gasification experiments of Sida Hermaphrodita/olive pomace blends with 10%w/w and 20%w/w of sewage sludge. The co-gasification experimental campaign covered series of tests at temperatures of 700, 800 and 900 °C, respectively. The comprehensive analysis of the experimental results of co-gasification and the physical and chemical parameters important for the co-gasification process performance were also conducted with the application of chemometric methods, such as hierarchical clustering analysis and principal component analysis. Based on the experimental results the optimal fuel blends as well as the optimal conditions of co-gasification were determined. It was proven that steam co-gasification of sewage sludge with selected biomass is beneficial in terms of the total gas produced and its composition.

Techno-Economic Evaluation of Downdraft Fixed Bed Gasification of Almond Shell and Husk as a Process Step in Energy Production for Decentralized Solutions Applied in Biorefinery Systems

The objective of the present study was to carry out a technical study of the gasification of almond shells and husks at different temperatures and, subsequently, an economic analysis for the in situ installation of a decentralized unit to produce electricity, through a syngas generator, that would overcome the use of fossil fuels used in this agroindustry. The gasification tests were carried out at three different temperatures (700, 750 and 800 °C) and the results for the tests carried out were as follows: a 50:50 mixture of almond husks and shells was found to have a lower heating value of value of 6.4 MJ/Nm3, a flow rate of 187.3 Nm3/h, a syngas yield of 1.9 Nm3/kg, cold gas efficiency of 68.9% and carbon conversion efficiency of 70.2%. Based on all the assumptions, a 100 kg/h (100 kWh) installation was proposed, located near the raw material processing industries studied, for an economic analysis. The technical–economic analysis indicated that the project was economically viable, under current market conditions, with a calculated net present value of k€204.3, an internal rate of return of 20.84% and a payback period of 5.7 years. It was concluded that thermal gasification is a perfectly suitable technology for the recovery of raw materials of lignocellulosic origin, presenting very interesting data in terms of economic viability for the fixed bed gasification system.

Enhanced Sewage Sludge Gasification by Bauxite‐Modified Carbide Slag for Hydrogen‐Rich Syngas Production with In Situ CO2 Capture

Calcium‐looping gasification is attractive to dispose massive sewage sludge for hydrogen‐rich syngas with in situ CO2 capture but still challenged by apparent drop of CO2 sorbent reactivity, sorbent attrition, and uncertainty of sorbent performance during multi‐cycle gasification. Herein, bauxite‐modified carbide slag is prepared as a cheap CaO‐based CO2 sorbent by a simple mechanical mixing method. Based on physical and chemical characterization as well as thermogravimetric analyses, it is found that the bauxite‐modified carbide slag (CS) contained the inert component of mayenite, which is beneficial to improve pore characteristic and promote stability and mechanical strength of sorbent during multi‐cycle CO2 capture. Fluidized bed gasification tests verify that adding carbide slag increases H2 yield and efficiency of sewage sludge gasification. Moreover, appropriate increase in reaction temperature and steam flow rate enhances sewage sludge gasification with bauxite‐modified carbide slag. During multi‐cycle fluidized bed gasification, modified carbide slag CS‐5 (with 5 wt% bauxite) presents more stable performance and better anti‐attrition characteristic in comparison to carbide slag without modification. After five cycles of fluidized bed gasification, the yield and concentration of H2 are increased while the fraction of fine particles produced by attrition is largely decreased for CS‐5 in comparison to ordinary carbide slag.

Optimizing performance of iron-rich sludge ash as cost-effective oxygen carrier by calcium-based additive for syngas production from biomass chemical-looping gasification

Chemical-looping gasification tests were conducted on pine sawdust using thermogravimetric analyzer and horizontal sliding resistance furnace to investigate the regulation effects of calcium-based additive on iron-rich sludge ash oxygen carrier. The impacts of temperature, CaO/C in mole, multiple redox cycles, CaO addition modes on gasification performances were analyzed. The TGA results indicated that the CaO addition could effectively capture CO2 from syngas to from CaCO3, which subsequently decomposed at high temperatures. From in-situ CaO addition experiments, the temperature rise resulted in higher syngas yields, while a decrease in syngas LHV. With the CaO/C growing, the H2 yield grew from 0.103 to 0.256Nm3/kg at 800.0℃, and the CO yield boosted from 0.158 to 0.317Nm3/kg. Multiple redox manifested that the SA oxygen carrier and calcium-based additive kept higher reaction stability. The possible reaction mechanisms showed that the syngas variations from BCLG were influenced by the calcium roles and valence change of iron.

Effect of gasification reaction on pore structure, microstructure, and macroscopic properties of blast furnace coke

To address the deterioration of coke properties and subsequent fines caused by coke gasification reaction inside blast furnaces, orthogonal gasification tests were conducted on industrial coke simulating a blast furnace environment, and the effects of reaction temperature, carbon dioxide concentration, and reaction time on the pore structure, microstructure, and macroscopic properties of coke were analyzed. An increase in the reaction temperature led to the reaction of carbon dioxide with the internal coke through the pores and cracks, and a critical value was observed for both the reaction time and CO2 concentration on the pore structure. Temperature had a significant effect on the degree of graphitization and graphitization defects, whereas the effects of CO2 concentration and reaction time on the microstructure were mainly due to changes in the pore structure. The macroscopic properties of coke (compressive strength and reactivity) were influenced by both its pore structure and microstructure. As the reaction temperature and time increased, the compressive strength of the coke increased initially and then decreased.

Strong metal-support interaction induced sintering-resistant Ni nanoparticles supported on highly CO2-activating vanadium hydroxyapatite for dry reforming of methane

Sintering of Ni-based catalysts and the following detrimental carbon depositions are still the major challenges to be overcame in the high-temperature dry reforming of methane (DRM) process. Herein, we for the first time induced classical strong metal-support interaction (SMSI) between Ni nanoparticles and vanadate substituted hydroxyapatite (VAP) under H2 atmosphere at as low as 300 ℃ (Ni/VAP-H300) to hinder the sintering of Ni nanoparticles during DRM process. TEM and element mapping analysis unambiguously exhibit the configuration of Ni nanoparticles encaged within the partially reduced VAP overlayer and subsequent linear-scan EDS investigations on the Ni/VAP-H300 at the reaction time of 25 h, 100 h and 260 h further elucidate the relatively intact VAP overlayer during the reaction, thus the CH4 conversion merely decreasing from 92 % to 79 % after stability test for 260 h. In contrast, Ni nanoparticles supported on conventional hydroxyapatite (Ni/HAP) give inferior stability, CH4 conversion drastically decreasing from 91 % to 42 % only after 25 h due to the absence of SMSI. Moreover, there also occurs electron-transfer between Ni nanoparticles and the adjacent VAP overlayer, thus showing higher CH4 decomposition activity compared with Ni/HAP. Combined with the excellent CO2-activating property of VAP support identified by CO2-TPD and gasification tests of the deposited carbon, the as-obtained Ni/VAP demonstrates outstanding initial activity and decent stability during DRM, which broadens the horizons of improving catalytic stability even under harsh reaction conditions by precisely exploiting the SMSI.

Ce/Pumice and Ni/Pumice as heterogeneous catalysts for syngas production from biomass gasification

This work presents a study of synthesis and characterization of catalysts-based cerium and nickel supported on the pumice stone (Ce/Pumice and Ni/Pumice) to be used in the gasification process of an invasive species present in the Canary Islands, such as Pennisetum setaceum to obtain syngas. Specifically, the effect of the metal impregnated on the pumice, and the effect of catalyst on the gasification process was studied. For this purpose, the composition of the gas was determined and the results obtained were compared with those obtained in non-catalytic thermochemical processes. Gasification tests were performed using a simultaneous thermal analyzer coupled with a mass spectrometer, providing a detailed analysis of the gases released during the process. The results showed that during the catalytic gasification process of the Pennisetum setaceum, the gases produced appear at lower temperatures in the catalytic process that in the non-catalytic process. Specifically, H2 appears at 640.42 °C and 641.84 °C when Ce/pumice and Ni/pumice were used as catalyst, respectively, compared to 697.41 °C for the non-catalytic process. Moreover, the reactivity at 50 % of char conversion for the catalytic process (0.34 and 0.38 min−1 for Ce/pumice and Ni/pumice, respectively) was higher than for the non-catalytic process (0.28 min−1), indicating that the incorporation of Ce and Ni on the pumitic material increases the gasification rate of the char compared to the pumitic support. Catalytic biomass gasification is an innovative technology that can provide new opportunities for research and development of renewable energy technologies, as well as for the creation of green jobs.

The Combined Impact of Ni-Based Catalysts and a Binary Carbonate Salts Mixture on the CO2 Gasification Performance of Olive Kernel Biomass Fuel

In the present work, the individual or synergistic effect of Ni-based catalysts (Ni/CeO2, Ni/Al2O3) and an eutectic carbonate salt mixture (MS) on the CO2 gasification performance of olive kernels was investigated. It was found that the Ni/CeO2 catalyst presented a relatively superior instant gasification reaction rate (Rco) compared to Ni/Al2O3, in line with the significant redox capability of CeO2. On the other hand, the use of the binary eutectic carbonate salt mixture (MS) lowered the onset and maximum CO2 gasification temperatures, resulting in a notably higher carbon conversion efficiency (81%) compared to the individual Ni-based catalysts and non-catalytic gasification tests (60%). Interestingly, a synergetic catalyst-carbonate salt mixture effect was revealed in the low and intermediate CO2 gasification temperature regimes, boosting the instant gasification reaction rate (Rco). In fact, in the temperature range of 300 to 550 °C, the maximum Rco value for both MS-Ni/Al2O3 and MS-Ni/CeO2 systems were four times higher (4 × 10−3 min−1 at 460 °C) compared to the individual counterparts. The present results demonstrated for the first time the combined effect of two different Ni-based catalysts and an eutectic carbonate salt mixture towards enhancing the CO production rate during CO2 gasification of olive kernel biomass fuel, especially in the devolatilization and tar cracking/reforming zones. On the basis of a systematic characterization study and lab-scale gasification experiments, the beneficial role of catalysts and molten carbonate salts on the gasification process was revealed, which can be ascribed to the catalytic activity as well as the improved mass and heat transport properties offered by the molten carbonate salts.

An Experimental Study on the Quantitative and Qualitative Characteristics of Tar Formed during Ex Situ Coal Gasification

Over the three-day gasification test of a large coal block with oxygen in atmospheric pressure conditions, the yield and composition of the tar collected was investigated. The tar was sampled approximately every 7 h into sorption tubes directly from the reactor outlet. Sand, with a moisture content of 11%, was used as an insulating material to simulate the environment of the gasified coal seam. Light aromatic hydrocarbons (BTEX), phenols, and polycyclic aromatic hydrocarbons (PAHs) were determined in the tar. The results that were obtained were recalculated into the concentrations of the individual components of the tar and its mass stream in the process gas. The residence time of the tar in the reactor, its molar mass, and the H/C ratio were also calculated. As the reaction progressed, the water that was contained in the wet sand started to react with the gasified coal, which significantly affected the composition and amount of the obtained process gas and the produced tar. Due to an increase in the amount of generated gases and steam, the residence time of the tar vapours in the reactor decreased as the gasification progressed, ranging from approximately 1 s at the beginning of the process to 0.35 s at the end. The obtained tar was characterised by a high average content of BTEX fractions at approximately 82.6%, PAHs at 14.7%, and phenols at 2.7%. Benzene was the dominant BTEX compound, with a concentration of 83.7%. The high content of the BTEX compounds, especially benzene, was a result of secondary processes taking place in the tar (hydrocracking and steam reforming), and as a result of which, in the presence of hydrogen and steam, the heavier components of the tar were transformed into lighter ones. The total yield of the tar from this UCG (underground coal gasification) process—calculated per 1 ton of gasified coal—was 1.8% (counted on the basis of the analysed tar composition). Comparing this result to the efficiency of the classic coking process, the tar yield was about three times lower.

Pyrolysis and Gasification of a Real Refuse-Derived Fuel (RDF): The Potential Use of the Products under a Circular Economy Vision

Refuse-Derived Fuels (RDFs) are segregated forms of wastes obtained by a combined mechanical-biological processing of municipal solid wastes (MSWs). The narrower characteristics, e.g., high calorific value (18-24 MJ/kg), low moisture content (3-6%) and high volatile (77-84%) and carbon (47-56%) contents, make RDFs more suitable than MSWs for thermochemical valorization purposes. As a matter of fact, EU regulations encourage the use of RDF as a source of energy in the frameworks of sustainability and the circular economy. Pyrolysis and gasification are promising thermochemical processes for RDF treatment, since, compared to incineration, they ensure an increase in energy recovery efficiency, a reduction of pollutant emissions and the production of value-added products as chemical platforms or fuels. Despite the growing interest towards RDFs as feedstock, the literature on the thermochemical treatment of RDFs under pyrolysis and gasification conditions still appears to be limited. In this work, results on pyrolysis and gasification tests on a real RDF are reported and coupled with a detailed characterization of the gaseous, condensable and solid products. Pyrolysis tests have been performed in a tubular reactor up to three different final temperatures (550, 650 and 750 °C) while an air gasification test at 850 °C has been performed in a fluidized bed reactor using sand as the bed material. The results of the two thermochemical processes are analyzed in terms of yield, characteristics and quality of the products to highlight how the two thermochemical conversion processes can be used to accomplish waste-to-materials and waste-to-energy targets. The RDF gasification process leads to the production of a syngas with a H2/CO ratio of 0.51 and a tar concentration of 3.15 g/m3.

Tannery Sludge Gasification in a Fluidized Bed for Its Energetic Valorization

The present article deals with the valorization of the organic content of tannery sludges to produce energy vectors. In this scenario, gasification is a viable option to obtain a flexible gaseous stream (syngas) of interesting energetic value, under operating conditions that do not favor the oxidation of Cr(III) (typically found in tannery sludges) to the more harmful Cr(VI) state. To this end, an industrial tannery sludge was characterized through proximate/ultimate analyses and determination of the heating value, showing its capability to act as a solid fuel in a gasification process, and metal analyses, showing that its Cr(VI) content was below the detection limit (2 ppm). The material was subjected to gasification tests in a lab-scale fluidized bed (FB) reactor. The reactor, with a 41 mm inside diameter and a 1 m height, was electrically kept at an operating temperature of 850 °C. The fluidization velocity was 0.30 m/s at 850 °C, i.e., 7.5 times the value of the minimum fluidization velocity. The gasifying stream was composed by O2 (3% vol.) diluted in N2. The adopted oxidant equivalence ratio (ER) levels were 0.15 and 0.24, to ensure substoichiometric (i.e., reducing) conditions in the FB atmosphere. Under the most reducing operating conditions, it was possible to produce syngas with a lower heating value of 12.0 MJ/N m3 (dry and N2-free basis). It contained, under these conditions, about 42% H2, 36% CO, and 4% CH4, plus 16% CO2 and other components. The tar produced from the process, fully characterized by gas chromatography–mass spectrometry, showed a favorably low concentration of about 25 g/N m3. FB bottom and fly ashes were analyzed for their carbon and metal contents. In bottom ash, the total Cr concentration resulted in the range of 8–12 g/kg, with a Cr(VI) concentration between 8 and 10 ppm. In the elutriated stream, the total Cr concentration was about 55 g/kg, with a Cr(VI) concentration between 4 and 7 ppm. The Cr(VI) concentration was higher when higher values of the ER were used, but it resulted in 3–4 orders of magnitude lower than the total Cr concentration, showing the appropriateness of the process to produce syngas with very limited oxidation of chromium in the solid residues.

Gasification of Solid Recovered Fuels with Variable Fractions of Polymeric Materials

Gasification is a promising thermochemical technology used to convert waste materials into energy with the introduction of low amounts of an oxidant agent, therefore producing an environmental impact that is lower when compared to incineration and landfilling. Moreover, gasification allows a sustainable management of wastes and reduces the use of fossil fuels responsible for the increment of greenhouse gases. This work aimed to perform gasification tests with solid recovered fuels (SRF) containing organic fractions mainly retrieved from construction and demolition wastes to assess the potential for energy conversion. Tests were conducted in a pilot-scale downdraft gasifier (maximum feedstock input of 22 kg/h) at c.a. 800 °C, using SRF samples containing different proportions of polymeric wastes ranging between 0 and 20 wt %. Gas and chars obtained as by-products were analysed to evaluate their properties and to establish valid pathways for their valorisation. The addition of polymeric wastes reduced char production but rose both tar and HCl concentrations in the gas. The SRF with 10 wt % of polymeric wastes generated the best results, producing the highest calorific value for the gas (3.5 MJ/Nm3) and the highest cold-gas efficiency (45%). Possible char applications include their use as catalysts for tar decomposition, or as an additive in construction materials. Gasification can therefore be considered a valid solution for the energetic valorisation of these SRFs.

Gasification as possible technological solution for driftwood management in bodies of waters

This work studies the possibility of the thermochemical conversion, through gasification, of wood waste that accumulates along river bodies. Thanks to the startup SEADS (Sea Defense Solutions), tree branches were collected from the Lamone river (province of Ravenna - IT) in various conservation states. The wood wastes were pre-treated through a chipping process to make them suitable for chemical/physical analyses and subsequent gasification process using the All Power Labs Power Pallet 30 (PP30) commercial micro-gasifier. The elemental analysis show how the wood material undergoes a certain chemical degradation due to weathering, which leads to an HHV of 18.76 MJ/kg, lower than virgin biomass. The gasification process was firstly simulated through a numerical method that gave positive outputs: syngas with a higher heating value of 4.61 MJ/kg and a gasification efficiency of 63.03%. A subsequent gasification test was used to validate the numerical model that was also used to estimate the electrical (18.91%) and thermal (25.21%) efficiency of a cogeneration power plant, powered by the PP30 gasification reactor.

Experimental simulations of methane-oriented underground coal gasification using hydrogen - The effect of coal rank and gasification pressure on the hydrogasification process

This paper presents a series of surface experimental simulations of methane-oriented underground coal gasification using hydrogen as gasification medium. The main aim of the experiments conducted was to evaluate the feasibility of methane-rich gas production through the in situ coal hydrogasification process. Two multi-day trials were carried out using large scale gasification facilities designed for ex situ experimental simulations of the underground coal gasification (UCG) process. Two different coals were investigated: the “Six Feet” semi-anthracite (Wales) and the “Wesoła" hard coal (Poland). The coal samples were extracted directly from the respective coal seams in the form of large blocks. The gasification tests were conducted in the artificial coal seams (0.41 × 0.41 × 3.05 m) under two distinct pressure regimes - 20 and 40 bar. The series of experiments conducted demonstrated that the physicochemical properties of coal (coal rank) considerably affect the hydrogasification process. For both gasification pressures applied, gas from “Six Feet” semi-anthracite was characterized by a higher content of methane. The average CH4 concentration for “Six Feet” experiment during the H2 stage was 24.12% at 20 bar and 27.03% at 40 bar. During the hydrogasification of “Wesoła" coal, CH4 concentration was 19.28% and 21.71% at 20 and 40 bar, respectively. The process was characterized by high stability and reproducibility of conditions favorable for methane formation in the whole sequence of gasification cycles. Although the feasibility of methane-rich gas production by underground hydrogasification was initially demonstrated, further techno-economic studies are necessary to assess the economic feasibility of methane production using this process.