Gasification Chamber Research Articles

Experimental investigation of alterations in coal fracture network induced by thermal treatment: Implications for CO2 geo-sequestration

Hydrogen-rich syngas, produced by underground coal gasification (UCG) process, is a valuable feedstock for chemical industry. However, it can contain large quantities of carbon dioxide (CO2), which requires separation and sequestration to reduce the carbon footprint of the process. This study explores mechanisms influencing coal permeability when CO2 is injected back into the coal through existing gasification chambers. Two main mechanisms affecting permeability are thermal effects associated with underground coal gasification and CO2-related coal matrix swelling.The effects of thermal processes and CO2 flooding on the fracture network of the coal are investigated through a series of comprehensive experiments. Thermal treatment of the studied sample at a temperature of 210 °C shows a notable effect on fracture morphology, increasing width and permeability by up to a factor of 2 and 5, respectively. CO2 flooding, on the other hand, impairs fracture network due to chemisorption driven processes, leading to irreversible changes. Following CO2 flooding experiment, fracture porosity decreases by a factor of three and subsequently permeability declines by 70–80 % within the studied effective stresses range. Our characterization study indicates that thermal treatment significantly increases permeability, compensating for impairments to the fracture network associated with CO2 injection.

CFD Analysis of Gas-Dynamic and Heat Transfer Processes in a Propulsion System Using Polymer Fuel

In the presented work, a computer model of thermodynamic and gas-dynamic processes in a rocket engine of a new type, which uses solid polymers as fuel is considered. The design feature is the presence of a central body - a gasification chamber, where solid polymer fuel is decomposed into volatiles. To conduct the research, a preliminary thermodynamic analysis of the combustion of gasification products was carried out. Based on the results of the thermodynamic analysis using the mathematical model of the turbulent flow of viscous compressible gas, the processes of gas dynamics and heat transfer in the chamber and nozzle of the rocket engine were simulated. Analyses are made for the geometry of a real experimental sample of a polymer-fueled rocket engine developed at Oles Honchar Dnipro National University (Ukraine), which has passed the first successful tests. As a result of CFD simulation, dynamic and thermal fields in the combustion chamber and engine nozzle were obtained, and ways of further improvement of the design were determined.

Reactive particle-laden flow in industrial-scale supercritical water gasification reactor: Modeling and study on flow patterns

Coal gasification in supercritical water (SCW) is a highly complicated reactive particle-laden flow process, which couples multiphase flow hydrodynamics, conjugate heat transfers, and complex chemical reactions. A quantitative understanding is the key issue for reactor design and optimization. In this study, the Eulerian-Eulerian model is used to describe the particles-SCW flow in a novel industrial-scale thermally integrated supercritical water gasification (TISCWG) reactor with conjugate heat transfer boundary conditions and porous media model. The sophisticated chemical reactions are using a species transport model with a seven-step lumped kinetics. Four zones of the TISCWG reactor and four typical flow patterns in the gasification chamber are firstly revealed as 1) the bottom accumulation region with the nonhomogeneous solids distribution and back-mixing of particles, 2) the upper developed fluidization region with the SCW and coal particles moving in a plug-flow regime in the center and a downward annular gravity-driven flow near the wall, 3) the jet-affected region strongly affected by the vortexes near the nozzle and presented as a trans-critical jet regime and 4) the dilute region where dilute solids slow down and fall back into the gasification zone. Flow in the gasification chamber is strongly affected by the heat transfer with the preheat zone, as reflected by an annular gravity-driven flow film flowing downwards near the gasification wall. A funnel-shaped structure promotes a more uniform distribution of solids in the accumulation region rather than a cylindrical structure. The effect of flow patterns on coal gasification processes is also studied. Volatile pyrohydrolysis reactions depend on the time-varying solids distribution and the gaseous products at the system outlet with a typical H2 mole fraction of 61.42% and CO2 of 34.98%.

Research on Temperature Simulation of Underground Coal Gasification Wellbore

This study aims to integrate the theoretical distribution calculation of temperature and pressure during the gasification process through the derivation of heat conduction, thermal radiation and pressure control theory in the underground coal gasification process, and analyze the temperature of the underground coal gasification process through finite element modeling. Field influencing factors and pressure changes over time. It is of great significance to obtain the relevant parameters of the gasification chamber in the underground coal gasification process.

Thermodynamic evaluation of a state-of-art poly-generation system fueled by natural gas and biomass for cooling, power, and hot water generation

The principal objective of this study was to conduct a thorough examination of the thermodynamic aspects of an innovative combined poly-generation facility, encompassing cooling load, hot water, and power generation cycles, powered by a combination of natural gas and biomass. A distinctive feature was the incorporation of syngas into natural gas to enhance overall plant performance. The plant design comprised three key subsystems: a gasification and combustion chamber, a double-effect absorption chiller, and a supercritical carbon dioxide cycle. Energy and exergy analyses were employed to systematically evaluate the thermodynamic behavior of the plant. The outcomes revealed that the exergy and energy efficiencies, along with the net power output, were determined to be approximately 35 %, 78 %, and 7422 kW, respectively. Additionally, the produced hot water and the coefficient of performance (COP) of the absorption chiller were estimated at around 14.71 kg/s and 1.209. Notably, the gasifier and combustion chamber emerged as the least efficient components of the system, primarily due to their elevated rates of exergy destruction. Furthermore, comprehensive parametric investigations were conducted to elucidate the influence of key variables on plant performance. The analysis indicated that variations in gasification temperature positively impacted the thermodynamic performance of the plant. Moreover, an increase in combustion pressure led to a notable enhancement in the net power output of the facility.

IMPLEMENTATION OF THE K-EPSILON (K–Ε) MODEL FOR THE SIMULATION OF COAL GASIFIER /REACTOR

The objective of the present research is to use the standard turbulent kinetic energy and turbulent dissipation (k-e) model to do a numerical modelling and simulation of the gasification chamber or reactor which was used to gasifier Lafia-Obi bituminous coal. The numerical modelling and simulation were implemented with the aid of AutoCAD and Ansys softwares. The gasifier/reactor geometry was modelled using AutoCAD and then imported to Ansys workbench for simulation. Results show the modelled reactor geometry comprising a height of 0.9m, diameter of 0.5m and volume of 0.177m 3. Simulation results show mass fraction of producer gas components comprising of 16% carbon monoxide, 14% hydrogen, 2.7% methane and 18% carbon dioxide. The producer gas yield is in conformity with standard producer gas yield. Temperature profile around the modelled gasifier/reactor was displayed with a maximum of 960K.

Thermo-Mechanical Numerical Analysis of Stress and Damage Distribution within the Surrounding Rock of Underground Coal Gasification Panels

Underground coal gasification (UCG) is a promising technology for extracting synthesis gas from coal seams through in situ gasification. This study aims to investigate the thermo-mechanical behavior and integrity of the surrounding rock in the gasification vicinity to facilitate safe and efficient UCG operations. Rock property testing experiments are conducted under varying temperature conditions, revealing significant temperature dependencies for the thermal and mechanical parameters. A thermo-mechanical coupling model is developed to analyze the stress and damage distribution near the gasification chamber. The influence of the temperature dependency of stress states and failure risks during the gasification process is evaluated. In addition, the effects of panel orientation, chamber width, maintaining duration, operating temperature and operating pressure on the failure behavior of the gasification surrounding rocks are illustrated through parametric analysis. The findings have practical implications for the design and assessment of UCG processes, enhancing the safety and efficiency of coal gasification operations.

Thermal gasification of biomass in fluidized bed

Chemicals, heat, and electricity can all be made with biomass, a renewable energy source. Biomass gasification is more environment friendly than biomass combustion because it produces less carbon dioxide (CO2) and other polluting gases (NOx and SO2). Present paper is focused on biomass gasification using fluidized bed. CFD analysis are performed in a cylindrical fluidized bed gasification chamber with a diameter of 6.6 cm and static bed height of 100 cm. The biomass inlet is located at a height of 0.73 cm with diameter of 0.75 cm; unstructured grid is chosen for the analysis. In this study 39,250 cells and 40,086 nodes are used to perform the simulations. CFD simulations are carried out to investigate the devolatization behavior of biomass. Fluent model of volatile material is modified according to the ultimate and proximate analysis of biomass. To know the effect on conversion efficiency of biomass a different equivalence ratio is considered as a process parameter in the range of 0.2 to 0.3. The stoichiometric ratio considered as 0.4 for biomass gasification. Mass fraction of species generated from partial combustion i.e. gasification.

ВИЗНАЧЕННЯ ТИСКУ У КАМЕРІ ГАЗИФІКАЦІЇ ГАЗОГЕНЕРАТОРА

The purpose of the work: determination of patterns of pressure changes in the gasification chamber of the gas generator. Methodology of the work: a comprehensive approach, which includes theoretical studies of the processes of changing the thermodynamic parameters of the gas phase in the working chamber of the gas generator, a calculation and analytical method for determining the pressure of the working medium, depending on the temperature and its composition in the gas generator. Results: patterns of pressure changes in the working chamber of the gas generator at different operating modes were obtained. Scientific innovation: modeling and calculation of pressure indicators of the working medium in the working chamber of the gas generator, depending on the environmental factors: temperature and composition of the working medium, humidity of solid fuel, were carried out. It is taken into account that the gaseous phase is a real gas, according to the Van der Waals equation. An algorithm for calculating pressure based on data on quantitative indicators of gases in the mixture is proposed. The regularities of the behavior of the gas medium in the range of operating temperatures of the gas generator have been established. Practical significance: the obtained results made it possible to determine the pressure in the working chamber of the gas generator under different modes of its operation and to develop appropriate design solutions for the corresponding nodes (housing, sealing devices, etc.) of gas generators of narrow standard sizes. Key words: gas generator, combustion chamber, pressure, ideal gas, non-ideal gas, gas-air mixture, temperature.

Determining the effect of the structural and technological parameters of a gas blower unit on the air flow distribution in a gas generator

The object of this study is the structural and technological parameters of the gas blower unit in the gasification chamber of a gas generator. The task to enable uniform distribution of air masses in the gas generator has been solved using the ANSYS Fluent software. The study is based on a simulation of the movement of air flows in the characteristic cross-sections of the gas generator, in particular the cross-section of the gasification chamber at the border of the oxidation and reduction zones. Seven structures of the gas blower unit were analyzed, the effectiveness of which was determined by the coefficient of variation. The most effective was the design whose value of the coefficient of variation is the smallest and equal to 93 %. At the same time, the total area of zones with no movement of air masses, that is, the absence of a gasification process, does not exceed 12 % of the total cross-sectional area of the gas generator. The speed of air masses at the boundary of the oxidation and reduction zones is aligned in the entire cross-section of the chamber and is V»4.5 m/s. The average value of the vertical component of the speed of air masses in the cross-section at the inlet to the recovery zone of the gasification chamber is V»0.6 m/s. Under such conditions, the production of synthesis gas of high calorific value with the absence of resins, acids, heavy hydrocarbons, and mechanical impurities is ensured. The correspondence of the simulation results with experimental data is confirmed by the coefficient of determination, which amounted to 0.87. The results reported here could be the basis of a modernized methodology for the study of aerodynamic, heat and mass exchange processes that occur during biomass gasification. This would make it possible to define the rational structural and technological parameters of gas generators and improve the efficiency of the gasification process as a whole.

Energy recovery evaluation and temperature field research of underground coal gasification under different oxygen concentrations

In this paper, UCG simulation experiments were carried out on selected coal samples to study the effects of the gasification agent ratio on the product gas composition and calorific value under different oxygen concentrations. Moreover, an energy recovery evaluation method based on stoichiometric theory was established based on the carbon (C) balance in the generated gas content, and the energy recovery rate and coal consumption of the underground gasification process were evaluated. Based on the composition of the produced gas and the thermodynamic law of conservation, an evaluation model of the underground coal gasification temperature field was established. The gasification chamber temperature in each stage was evaluated by calculating the reaction heat and sensible heat. The experimental and research results showed that when the volume fraction of oxygen in a gasification agent was in the range 40–70 % and the calorific value of the produced gas increased from 10.48 MJ/m3 to 12.48 MJ/m3. The calorific value of the produced gas increased with an increasing oxygen concentration. Furthermore, the energy recovery rate increased from 69.63 % to 83.88 %, indicating that the gasification efficiency of the UCG experiment can be significantly improved with an increasing oxygen concentration. The error between the theoretical value of the coal consumption and the actual monitoring value was within 10 %, which effectively evaluates the coal consumption in the gasification process. The theoretical calculation temperature was consistent with the experimental monitoring temperature results, and the reaction heat was found to also be linearly correlated with the gasification temperature. Therefore, this method can effectively determine the gasification chamber temperature. These monitoring and evaluation methods are expected to guide the analysis of subsurface field experiments.

Preliminary Results of Biomass Gasification Obtained at Pilot Scale with an Innovative 100 kWth Dual Bubbling Fluidized Bed Gasifier

Biomass gasification is a favourable process to produce a H2-rich fuel gas from biogenic waste materials. In particular, the dual bubbling fluidized bed (DBFB) technology consists of the separation of the combustion chamber, fed with air, from the gasification chamber, fed with steam, allowing to obtain a concentrated syngas stream without N2 dilution. In a previous work, an innovative design of a DBFB reactor was developed and its hydrodynamics tested in a cold model; in this work, the novel gasifier was realized at pilot scale (100 kWth) and operated for preliminary biomass gasification tests. The results showed a high-quality syngas, composed of H2 = 35%, CO = 23%, CO2 = 20%, and CH4 = 11%, as a confirmation of the design efficacy in the separation of the reaction chambers. The dry gas yield obtained was 1.33 Nm3/kg of biomass feedstock and the carbon conversion was 73%. Tars were sampled and measured both in the raw syngas, giving a content of 12 g/Nm3, and downstream from a traditional conditioning system composed of a cyclone and a water scrubber, showing a residual tar content of 3 g/Nm3, mainly toluene. The preliminary tests showed promising results; further gasification tests are foreseen to optimize the main process parameters.

Optimization of Air Flow in the Gasification Chamber of the Gasification Boiler Using the PIV Method

The article deals with the optimization of biomass combustion in a small heat source using the optimal distribution of combustion air. Uneven distribution of combustion air was observed during certification tests and in real operation of the used heat source and has an impact on uneven combustion of biomass in the gasification chamber, on increasing emissions and combustion losses. In the first phase of the research, optimization was carried out using CFD simulations, then a transparent model of a real heat source was created, on which the real distribution of combustion air in the gasification chamber was observed using the Particle Image Velocimetry (PIV) method. The results of CFD simulations and the PIV method led to the optimization of the cross-sectional profiles of the four supply channels for gasification air supply. CFD simulations and subsequent PIV measurements on the experimental device were carried out without real combustion, only the air flow in the empty gasification chamber was investigated. This approach was chosen in order to simplify calculations and experiments and on the assumption that with optimal distribution of combustion air in the empty chamber, there will be an optimal even during real combustion. The flow of primary air in the gasification chamber in real operation is influenced by the size and shape of the inserted biomass and its location in the chamber, and this influence is random and difficult to verify. After optimization, the distribution of the primary combustion air in the gasification chamber is uniform and the same amount of air flows into the chamber through the four combustion air inlets.

Experimental Studies of Structural and Technological Parameters of a Downdraft Gasifier Based on Plant Biomass

The relevance of the study is conditioned upon the need to develop and implement structural and technological solutions to improve the efficiency of the chemical and thermal conversion of biomass into combustible gas. Within the framework of the above, the authors of this paper have designed a downdraft gasifier running on plant biomass. The presented research links the heat quantity received from the utilisation of syngas produced during the gasifier operation cycle with the parameters of the gas blow regime and the physico-chemical properties of biomass. For an in-depth study of the influence of the gas blow regime on the yield and calorific value of syngas produced from biomass, the authors introduce the concept of the blow coverage quality coefficient. This coefficient describes the quality of the cross-section coverage of the gasification chamber neck with gas currents of the tuyere zone. The purpose of this study is to establish the influence of the blow coverage quality coefficient, the volume of blow gases and the void ratio of the bulk biomass layer on the heat quantity received from syngas produced during the gasifier operation cycle. A multi-factor experiment was planned and performed, which relates the dependent factor to variables, and the corresponding response surfaces were constructed. The research findings are that the maximum value of the heat quantity received from the utilisation of syngas produced during the one-hour gasifier operation cycle was 519 MJ. This value is achieved with 0.8 blow coverage quality coefficient and a blow gas volume of 47.4 m3/h and 46.75% void ratio of the bulk biomass layer. The measurement results are highly consistent with the calculated data. The coefficient of determination was R2=0.983. The practical value of this study is to substantiate the rational design and technological parameters of the downdraft biomass gasifier operation, which will increase the efficiency of biomass energy production. The findings presented in this study can be used both to design new gasifiers and to improve the efficiency of the available ones

Creep Rupture and Permeability Evolution in High Temperature Heat-Treated Sandstone Containing Pre-Existing Twin Flaws

Utilizing underground coal gasification cavities for carbon capture and sequestration provides a potentially economic and sustainable solution to a vexing environmental and energy problem. The thermal influence on creep properties and long-term permeability evolution around the underground gasification chamber is a key issue in UCG-CCS operation in containing fugitive emissions. We complete multi-step loading and unloading creep tests with permeability measurement at confining stresses of 30 MPa on pre-cracked sandstone specimens thermally heat-treated to 250, 500, 750 and 1000 °C. Observations indicate a critical threshold temperature of 500 °C required to initiate thermally-induced cracks with subsequent strength reduction occurring at 750 °C. Comparison of histories of creep, visco-elastic and visco-plastic strains highlight the existence of a strain jump at a certain deviatoric stress level—where the intervening rock bridge between the twin starter-cracks is eliminated. As the deviatoric stress level increases, the visco-plastic strains make up an important composition of total creep strain, especially for specimens pre-treated at higher temperatures, and the development of the visco-plastic strain leads to the time-dependent failure of the rock. The thermal pre-treatment produces thermal cracks with their closure resulting in increased instantaneous elastic strains and instantaneous plastic strains. With increasing stress ratio, the steady-state creep rates increase slowly before the failure stress ratio but rise suddenly over the final stress ratio to failure. However, the pre-treatment temperature has no clear and apparent influence on steady creep strain rates. Rock specimens subject to higher pre-treatment temperatures exhibit higher permeabilities. The pre-existing cracks close under compression with a coplanar shear crack propagating from the starter-cracks and ultimately linking these formerly separate cracks. In addition, it is clear that the specimens pre-treated at higher temperatures accommodate greater damage.

Application of poultry manure as an energy resource by its gasification in a prototype rotary counterflow gasifier

The paper presents the study focused on the application of poultry manure as an energy resource. Such solution is expected to bring limitation of fossil fuels exploitation, reduction of poultry farming costs, as well as sustainable waste to energy conversion.The study was performed by the use of a prototype gasification installation. The study involved analysis of the outlet gas composition, calorific value and flue gas emission. Measured heat of combustion of dry poultry manure is comparable to wood or straw. It contains relatively large amount of ash (9.11%), volatile components (78.4%) and low amount of sulphur.The chemical composition of obtained ash, shows low contribution of components elevating the melting temperature and high contribution of components decreasing the melting temperature, which indicates slagging tendency. The calorific value of the process gas, ranges from 6.47 MJ/m3 to 9.47 MJ/m3. Measured emission values match the applicable standards, except dust content.Performed studies indicated that poultry manure is a valuable energy resource, which allows to reduce the use of fossil fuels for the needs of poultry farming. Obtained results are essential for the design and operation of gasification installation in order to avoid operation problems associated with slagging of the gasification chamber.

A deep insight on the coal ash-to-slag transformation behavior during the entrained flow gasification process

Recent research provided deep insight on the coal ash-to-slag transformation characterization during the entrained flow gasification process, with experimentation on a 40 kg/hr (dry basis) coal-fed opposed multi-burner (OMB) entrained flow gasifier and simulation via FactSage™ software. A general mechanism is presented to relate the gasifier design temperature, ash fluid temperature, and operating temperature with the degree of the slag polymerization. The change of the high temperature zone, the corresponding particle residence time in the high temperature zone, and syngas composition have obvious effects on the slag mineral transformation behavior. Mineral types formed on the wall of the gasifier chamber were mainly anorthite (CaAl2Si2O8), aluminum oxide (Al2O3), and calcium sulfide (CaS). These minerals transformed to anorthite and diopside (CaMgSi2O6) at the slag hole zone, while the minerals at the lock hopper were anorthite, orthoclase (KAlSi3O8), quartz (SiO2), gypsum (CaSO4), calcite (CaCO3), and halite (NaCl). FactSage™ predicted minerals as anorthite, diopside, orthoclase, and albite (NaAlSi3O8), etc., where the slag temperature was below the ash fluid temperature and when the ratios of CO/CO2 and (CO + H2)/CO2 were lower than 1.0 and 2.0, respectively. By simulation, residual carbon was found to be the dominant factor over syngas composition to cause mineral transformation, and this was verified experimentally. The Ca-based crystals, typically anorthite, was shifted to diopside, near the slag hole zone, and a linear relationship was found between the content ratios of diopside/(anorthite + diopside), CaO/SiO2, and (CaO + MgO)/SiO2. A dimensionless number, θ, was defined to characterize the changing chemical composition and the degree of slag polymerization, with temperature deviation from the design condition. Three zones of θ were identified and related to the deviation between the actual gasification condition from the design condition. A low slag polymerization degree corresponded with a higher temperature deviation between the actual condition and design condition, and this proved that increased residual carbon content and changing iron valence state increased the mineral types when the slag temperature was below the ash fluid temperature.

Особливості сушіння мулових відкладень стічних вод за допомоги енергії довкілля

Analysis of sludge deposits formed during wastewater treatment gives grounds to evaluate them as a valuable raw material for obtaining biomineral fertilizers. Researcher’s efforts are focused on finding new innovative technical solutions and environmentally friendly approaches in order to make these technologies economically viable. The purpose of this study is to obtain reliable experimental data that will form the basis for a multi-stage technology for the disposal of sludge deposits. A method of combined drying is proposed, in which both the energy of the environment (solar energy) and the energy of secondary energy resources: the heat removed by the cooler from the gasification chambers and the enthalpy of the exhaust gases of gas piston engines - are simultaneously used. The real installation is equipped with a "warm floor" of pipes, in the inner space of which heated circulating water circulates from the cooling system of gas generators. In the experimental setup, the "warm floor" is modeled using a special flat, controlled electric heater. Experiments carried out with a round-the-clock supply of heat from circulating water at a temperature of 40 °C indicate that the use of a "warm floor" can increase the specific amount of moisture removed from the material during the day, almost twice. When constructing a pilot industrial dryer, it is advisable to equip it with a "warm floor" with an additional source of thermal energy, which can be used as the heat of the ground, as well as the heat of high-temperature exhaust gases of an internal combustion engine.

In situ experimental study of CO2 gasification of petcoke particles on molten slag surface at high temperature

The gasification reaction of petcoke on wall slag layer was an important issue that should be studied during the co-gasification process of coal and petcoke. In present work, the gasification characteristics of petcoke particles on molten slag surface was investigated using a high temperature stage microscope. The catalytic effect of slag on petcoke gasification on slag surface was demonstrated. The experimental results demonstrated that the catalytic effect of slag only worked when the particle was on the surface of slag. The catalyst vapor had no influence on the reactivity of petcoke. What’s more, the SEM analysis result showed that the reaction surface area of petcoke was decreased as a result of the deposition process. The effect of molten slag on particle temperature could be neglected as a result of the weak endothermic effect. Therefore, the change of petcoke reactivity rely on the synergy between catalytic effect of slag and the decreased reaction surface area. Besides, the increased residence time of petcoke also could increase the carbon conversion compared with that in gasifier chamber.

Design of an updraft gasification stove and its performance test with cassava peel as fuel

In this study, an insulated updraft gasification stove for biomass has been designed and tested for cassava peel. The main components of the stove were forced airflow inlet, biomass bed and gasification chamber and ceramic wool-insulated stainless steel wall. Top lit method was used in the ignition and testing was performed by using water boiling test method. Cassava peel was fed at four levels of bulk densities and moisture content. The result showed that combustion rates were quite high. The bulk density of fuel tend to reduce the rate of combustion and ignition front speed. The cassava peel with moisture content of 8-10% showed reddish-purple flame and small amount of smoke produced while with moisture content above 15%, the fuel could not be ignited in a reasonable time. The thermal system efficiencies of this gasification stove were still quite low, which were between 5.88 to 8.79%.