Product Gas Composition Research Articles

Performance Analysis of Gasification Coupled with IC Engine for Emission Control: Enhancing Environmental Sustainability

The gasification of biomass waste, such as Prosopis Juliflora wood( karuvellam wood), holds significant potential for reducing environmental impact and promoting sustainability. This study focused on investigating the gasification process of Prosopis Juliflora wood using an two stage air-preheated, Double throat downdraft gasifier. This gasifier will create reduced emission and tar-free producer gas, which will aid in the operation of the internal combustion engine. Prosopis Juliflora wood's ideal parameter was calculated for different equivalent ratio. Prosopis Juliflora wood's producer gas composition and calorific value (CV) were found to be CO = 18.1%, H2 = 12.7 %, and CV = 1092 kcal/Nm3. After determining the optimal operating point, the focus shifted to using this gas to power internal combustion engine in dual fuel mode. Diesel and producer gas from Prosopis Juliflora wood powered a 10 HP Field Marshall engine, single-cylinder, water-cooled, with a compression ratio of 16.6, coupled with an alternator and load bank. To compare the performance characteristics of diesel engines, combustion and emissions behaviours, were observed and analysed and a thorough analysis of the engine's behaviour during operation with producer gas was conducted. and a thorough analysis of the engine's behavior during operation with producer gas was conducted

Catalytic Pyrolysis of Waste Textiles for Hydrogen-Rich Syngas Production over NiO/Al2O3 Catalyst

Hydrogen production through the catalytic pyrolysis of low-value organic solid waste offers a promising low-carbon and environmentally friendly pathway. However, the design of efficient hydrogen-producing catalysts remains a significant challenge. Herein, NiO/Al2O3 as a catalyst precursor was utilized to investigate the effects of reduction temperature gradients (300–800 °C) on the distribution of three-phase products and the composition of gaseous products during the pyrolysis of waste textiles. Compared to unreduced NiO/Al2O3, increasing the reduction temperature (300–700 °C) led to a gradual decrease in liquid-phase products and a notable increase in gas-phase products, with the latter rising by 10.59% at 700 °C. Most strikingly, hydrogen gas production increased by 6.42% under the same conditions. Multi-characterization analyses, including XRD, TEM, and H2-TPR, revealed significant aggregation of highly dispersed Ni species in NiO/Al2O3 at higher reduction temperatures. The emergence of XRD characteristic peaks and the (111) crystal face of metallic Ni (Ni0) became apparent at 700 °C. More importantly, the XPS test inferred that the increasement of hydrogen-rich gas production was ascribed to the appropriate Ni0/Ni2+ ratio, and the highest hydrogen yield of 41.50% was achieved as the Ni0/Ni2+ ratio reached about 1.57. This work not only provides an effective solution for the consumption of waste textiles, but also converts it into high value-added hydrogen-rich gas.

The Conversion of Ethanol to Syngas by Partial Oxidation in a Non-Premixed Moving Bed Reactor

An experimental investigation into the conversion of ethanol to syngas by partial oxidation in a non-premixed counterflow moving bed filtration combustion reactor was carried out. Regimes of conversion depending on the mass flow rates of fuel and air (separate feeding), as well as a granular solid heat carrier, were studied. Depending on the mass flow rate of the heat carrier, two combustion modes were realized—reaction trailing and intermediate—with different temperature patterns in the gas preheating, combustion, and cooling zones along the reactor. The product gas composition is far from the predictions of the equilibrium model; it contains substation fractions of methane and ethylene. Combustion temperature and conversion are limited by the relatively high level of heat loss from the laboratory-scale reactor. The effect of the heat loss can be reduced by enhancing the absolute flow rate of the reactants.

Co-pyrolysis of waste plastics and tires: Influence of interaction on product oil and gas composition

The co-pyrolysis of different waste plastics and tires was carried out to investigate the effect of their interaction during co-pyrolysis on the yield and composition of the product oils and gases. Different types of waste plastics, consisting of high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET), were co-pyrolysed with the waste tires using a fixed bed batch pyrolysis reactor. The main gases produced from the individual plastics and tires were hydrogen, methane, ethane, ethene, propane, propene, butane, and butene, whereas PET produced mainly carbon dioxide and carbon monoxide. GC/MS analysis of the product oil produced from tire pyrolysis were mostly aromatic compounds produced from the rubber components of the tire. For HDPE, LDPE and PP pyrolysis, the oil produced was of mainly aliphatic composition, PS pyrolysis gave a considerable portion of single ring aromatic and polycyclic aromatic compounds and PET formed mainly oxygenated compounds and aromatic compounds. Co-pyrolysis of the plastics and tires resulted in an increase in gas yield above what would be expected from feedstock addition, suggesting interaction between the feedstocks. Also, oil analysis of the co-pyrolysis oils indicated significant shifts in the oil composition. For the mixed tire with HDPE and LDPE, aliphatic compounds were increased above that expected from addition with lower yields of single ring and polycyclic aromatic hydrocarbons. In contrast, mixing tire with PP produced higher yields of aromatic hydrocarbons and lower yield of aliphatic and alicyclic compounds than expected from additive calculation. Mixing tire with PS produced higher than expected single ring aromatic compounds but lower yields of polycyclic aromatic and alicyclic hydrocarbons. For the tire-PET co-pyrolysis, the production of oxygenated compounds was decreased in comparison to the expected additive data.

Determining Aqueous and Gaseous Product Composition of High-Preforming Titanium for Nitrate Reduction to Ammonia

Reactive nitrogen species are a key commodity and serve as fertilizers that sustain the global agricultural system, however, their use poses two significant challenges. First, most reactive nitrogen compounds are synthesized from ammonia (NH3) generated via the Haber-Bosch process. The Haber-Bosch process is energy-intensive, as it accounts for 2% of the world’s annual energy use (19.3 kWh/kg-N).1 Secondly, fields are often times overfertilized, leading to the release of reactive forms of nitrogen, such as nitrate (NO3 -), to the environment. This reactive nitrogen pollution can lead to harmful algal blooms, hypoxic dead zones in open water and other harmful effects to the environment.2 There is a need for new methods and technologies to separate reactive forms of nitrogen in wastewater and reuse these nutrients as an inexpensive fertilizer supply. To meet this need, our research aims to understand, design, and control a multifunctional electrochemical unit process that enables NH3 manufacturing and water purification in tandem. To this end, we must develop electrocatalysts that have high selectivity towards NH3 and understand the associated reaction mechanisms. Previous research from our group has demonstrated promise to transform NO3 -R to NH3 using titanium (Ti) as the electrocatalyst.3 Ti showed an optimal NH3 Faradaic efficiency of 82% and partial current density of -22 mA/cm2 while using an electrolyte containing 0.4 M NO3 - with a pH of 0.77 and applying a potential of -1 V vs the reversible hydrogen electrode (RHE). Despite this promise with Ti, given the high overpotential of -1 V vs RHE and only NH3 production quantified, this leaves an analytical gap of what other products are being produced and how can we quantify them.Recently, our group has developed an analytical method using ion and gas chromatography (IC and GC), nuclear magnetic resonance (NMR), gas chromatography-mass spectroscopy (GC-MS) and 15N isotope labeling to track all possible NO3 -R products to close the nitrogen mass balance. Thus far we have identified and quantified the aqueous and gaseous products of NO3 -, NO2 -, NOx, NH3, NH4 +, N2, N2O and H2. Furthermore, to understand the NO3 -R mechanism on Ti, we have implemented operando electrochemical mass spectroscopy (EC-MS) to identify and quantify gaseous products at various given potentials. This technique, paired with ex-situ characterization elucidates properties of NO3 -R to NH3 and product production that can inform the experimentation and molecular design of NO3 -R systems.References Erisman, J. W.; Sutton, M. A.; Klimont, Z.; Galloway, J.; Winiwarter, W. How a century of ammonia synthesis changed the world; Nature Publishing Group, 2008.Guest, J. S.; Skerlos, S. J.; Barnard, J. L.; Beck, M. B.; Daigger, G. T.; Hilger, H.; Jackson, S. J.; Karvazy, K.; Kelly, L.; Macpherson, L.; et al. A new planning and design paradigm to achieve sustainable resource recovery from wastewater. Environ Sci Technol 2009, 43 (16), 6126-6130. DOI: 10.1021/es9010515 From NLM Medline.McEnaney, J. M.; Blair, S. J.; Nielander, A. C.; Schwalbe, J. A.; Koshy, D. M.; Cargnello, M.; Jaramillo, T. F. Electrolyte Engineering for Efficient Electrochemical Nitrate Reduction to Ammonia on a Titanium Electrode. Acs Sustain Chem Eng 2020, 8 (7), 2672-2681. DOI: 10.1021/acssuschemeng.9b05983. Blair, S.J., Doucet, M. et al. ACS Energy Lett., 7, 6, 1939-1946 (2022).

Experiment investigation and multiscale modeling of biomass oxidative fast pyrolysis in a fluidized bed reactor

Experiments were conducted in a fluidized bed reactor to study the oxidative fast pyrolysis of biomass. The pressure drops along the bed height were measured, and the yield and composition of gas, liquid, and solid products were analyzed at various O2 concentrations. It was found that with the increase in oxygen concentration, the yield of biogas increased, especially CO2 and CO, while yields of bio-oil and biochar decreased. Under oxidative conditions, the fraction of tar in bio-oil was significantly reduced. A multiscale model was developed in the open-source code MFiX by integrating the reactor model based on the coarse-grained DEM-CFD, the intraparticle model, and the biomass oxidative fast pyrolysis kinetics. The model was verified by comparison with experimental data. As the oxygen concentration increases, the mixing and separation of biomass particles decreases, the residence time increases, the axial distribution moves upward, and the Lacey mixing index decreases. This study established experimental and theoretical foundations for designing and scaling up oxidative fast pyrolysis of biomass in fluidized beds.

Chicken Litter Pyrolysis and Composition of Gaseous Products Formed

Chicken Litter Pyrolysis and Composition of Gaseous Products Formed

Experimental Study on Gasification of Banknote Waste: Effects of Torrefaction Pre-Treatment and Co-Gasification on Producer Gas Composition

There is approximately 500,000 tonnes of potential end-of-life banknote waste worldwide, which is increasing by 2-3% per year. This waste consists of cotton and polymer-based banknotes printed on substrates whose raw materials are cotton and polypropylene, respectively. The vast majority of banknotes in circulation are cotton-based banknotes. End-of-life cotton banknotes, which are lignocellulosic biomass, are generally disposed of by landfill and incineration. Studies to reduce the environmental impact of these wastes to find more effective ways of using them is becoming increasingly important. Syngas, which can be used for the production of electricity, energy and chemicals is obtained by gasification of end-of-life cotton banknotes. In this study, DSC and FTIR analysis were performed as part of the characterization tests of the cotton-based banknote sample. As a result of the analysis, the sample was found to have characteristics similar to those of cotton. Within the scope of the investigation of thermal decomposition kinetics, activation energies were calculated as 134-171 kJ/mol by the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods. Experiments were performed in a fluidized-bed reactor at 800°C with an inlet H2O/O2 ratio of 25. The content of the producer gas formed during gasification was examined according to the maximum mole fraction achieved. In order to facilitate handling, storage and transportation and to improve fuel quality, the effect of torrefaction pre-treatment on the producer gas content was studied by conducting torrefaction to the cotton-based banknote sample at 250°C for 10 min. To overcome the disadvantages of plastic gasification in terms of operational sustainability, the cotton and polymer-based banknote samples were co-gasified. With the torrefaction pre-treatment, the mole fractions of H2, CO and CH4 increased, while the mole fraction of CO2 decreased. This finding revealed the effects of Boudouard, hydrogasification, water-gas and steam reformation reactions. With the co-gasification of cotton and polymer-based banknote samples, H2, CO and CO2 mole fractions decreased while CH4 mole fraction increased. This result showed that as the proportion of polymer-based banknote samples in the feedstock increased, the conversion efficiency decreased and the hydrogasification reaction became dominant.

Performance investigation on a downdraft gasifier using corn waste as a solid biomass and co-feeding with hand gloves and used facemask waste

In India, an abundant source of corn waste is scattered throughout the country, ensure a consistent feedstock supply that can be easily converted into valuable products. Corncob waste, as a solid biomass, has significant potential energy content and can be converted through thermo-chemical processes like gasification. The co-gasification process is a viable solution for managing non-decomposing wastes, such as hand gloves and used face masks, due to their widespread use in domestic and industrial applications. Since hand gloves and used face masks are also difficult to recycle, so that the present investigation aims to utilize the co-gasification process to convert these materials into syngas.A downdraft gasifier, a fixed-bed closed type with a capacity of 5 kW for power generation, was used for the experimental work. The experiment involved using 90% corncob waste co-fed with 5% hand gloves and 5% used face masks. The performance characteristics, including gas composition, product gas composition, char yield, and tar yield, were analyzed. Operating parameters, such as reaction temperature, were varied from 700 to 900 °C, with the equivalence ratio ranging from 0.07 to 0.27.Increasing the reaction temperature led to an increase in the CO and H₂ volume percentages of the producer gas, up to 13.1 vol%, while significantly decreasing the CO₂ amount from 24.6 vol% to 19.3 vol%. CH₄ gas slightly increased from 15.8 vol% at 700 °C to 19.8 vol% at 800 °C but decreased to 19.0 vol% when the reaction temperature was further increased to 900 °C. As a result of the increase in combustible gases, the higher heating value (HHV) of the producer gas also increased with temperature. It was concluded that carbon monoxide (CO) and hydrogen (H₂) yields in the syngas increased at 900 °C, while carbon dioxide (CO₂) and methane (CH₄) decreased. However, further research is needed, especially with pilot-scale autothermal gasifier plants, to investigate the impact of adding hand gloves and used masks on the operations of such gasifiers. The produced green H2 were used an alternate fuel in diesel engine for power production in a localized area such as hospitals, industries, etc., or an effective fuel for fuel cell too.

Thermodynamic and molecular dynamics study of methane dry reforming

The carbon neutrality strategy presents both challenges and opportunities for the metallurgical industry. Hydrogen, recognized as a green energy source, demonstrates significant potential for application in metallurgy. The negative impact of carbon deposition on catalysts is a significant challenge in the large-scale industrial application of methane dry reforming to produce hydrogen-rich reducing gases for ironmaking. This paper investigates the reaction mechanism through thermodynamic calculations and molecular dynamics simulations, systematically examining the effects of temperature, pressure, and feed ratio on the composition of gas products and the amount of carbon precipitation during the preparation process of hydrogen-rich reduction gas. The optimal conditions to produce high-quality reducing gas are identified to be a CO₂/CH₄ ratio of 0.8 at 1100K and 1 atm. At elevated temperatures, increasing the amount of carbon dioxide can reduce the amount of precipitated carbon, while the opposite is true at lower temperatures. The carbon absorbed by the nickel-based catalyst primarily originates from methane, while hydrogen ions activate carbon dioxide to produce carbon monoxide or carboxyl groups. By elucidating the reaction mechanism and quantifying the carbon precipitation, we provide theoretical guidance for industrial application.

Continuous Biological Ex Situ Methanation of CO2 and H2 in a Novel Inverse Membrane Reactor (IMR)

A promising approach for carbon dioxide (CO2) valorization and storing excess electricity is the biological methanation of hydrogen and carbon dioxide to methane. The primary challenge here is to supply sufficient quantities of dissolved hydrogen. The newly developed Inverse Membrane Reactor (IMR) allows for the spatial separation of the required reactant gases, hydrogen (H2) and carbon dioxide (CO2), and the degassing area for methane (CH4) output through commercially available ultrafiltration membranes, enabling a reactor design as a closed circuit for continuous methane production. In addition, the Inverse Membrane Reactor (IMR) facilitates the utilization of hydraulic pressure to enhance hydrogen (H2) input. One of the process’s advantages is the potential to utilize both carbon dioxide (CO2) from conventional biogas and CO2-rich industrial waste gas streams. An outstanding result from investigating the IMR revealed that, employing the membrane gassing concept, methane concentrations of over 90 vol.% could be consistently achieved through flexible gas input over a one-year test series. Following startup, only three supplemental nutrient additions were required in addition to hydrogen (H2) and carbon dioxide (CO2), which served as energy and carbon sources, respectively. The maximum achieved methane formation rate specific to membrane area was 87.7 LN of methane per m2 of membrane area per day at a product gas composition of 94 vol.% methane, 2 vol.% H2, and 4 vol.% CO2.

Performance Study of Eco‐Friendly and Safe Pyrotechnics for Fireworks

AbstractThe combustion of traditional pyrotechnics will pose great risks to the environment and human health. Although sulfur‐free pyrotechnics prepared from metals or expired military gunpowder have been used to solve this problem, the high sensitivity of them has resulted in insufficient safety. Therefore, new eco‐friendly and safe pyrotechnics are urgently needed. In this study, we prepared novel metal‐free pyrotechnic compositions for fireworks based on 5‐amino tetrazole. The optimized formulations are proposed by calculation. Particle size effects on thermal stability and kinetics are tested. Then, the sensitivity tests, moisture absorption, and burst temperature test were analyzed and compared. The combustion heat and specific volume were also measured. The Py‐GCMS and PM2.5 were used to clarify the composition of gas products and confirm their environmental‐friendly performance. The findings revealed that the novel pyrotechnics has a small amount of combustion residue, greater safety performance, and less PM2.5 concentration. The novel pyrotechnics could generate 564.9 mL/g clean and non‐toxic gas composed of 93.2% N2, H2O, and CO2 without any NOx or SO2 vapor. The test results suggest that the new pyrotechnics can effectively increase gas production and reduce the content of CO and PM2.5. So, it has great potential in application.

Two-Stage Global Biomass Pyrolysis Model for Combustion Applications: Predicting Product Composition with a Focus on Kinetics, Energy, and Mass Balances Consistency

This work presents a comprehensive model for lignocellulosic biomass pyrolysis, addressing kinetics, energy balances, and gas product composition with the aim of its application in wood combustion. The model consists of a two-stage global mechanism in which biomass initially reacts into tar, char, and light gases (non-condensable gases), which is followed by tar reacting into light gases and char. Experimental data from the literature are employed for determining Arrhenius kinetic parameters and key energy parameters, like tar and char heating values and the specific enthalpy of primary and secondary reactions. A methodology is introduced to derive correlations, allowing the model’s application to diverse biomass types. This work introduces several novel approaches. Firstly, a pyrolysis model that determines the composition of light gases by solving mass, species, and energy balances is developed, limiting the use of correlations from the literature only for tar and char elemental composition. The mass rate of light gases, tar, and char being produced is also determined. Secondly, kinetic parameters for primary and secondary reactions are determined following a Shafizadeh and Chin scheme but with a modified Arrhenius form dependent on Tn, significantly enhancing the accuracy of product composition prediction. Additionally, correlations for the enthalpies of reactions, both primary and secondary, are determined as a function of pyrolysis temperature. Primary reactions exhibit an overall endothermic behavior, while secondary reactions exhibit an overall exothermic behavior. Finally, the model is validated using cases reported in the literature, and results for light gases composition are presented.

Experimental study on co-gasification of cellulose and high-density polyethylene with CO2

Co-gasification of biomass and waste plastic with CO2 presents an effective strategy for integrating biomass conversion, waste utilization and carbon recycling. In this study, the co-gasification of cellulose and high-density polyethylene with CO2 was investigated experimentally. The effects of mixing ratio and temperature on co-gasification characteristics, including gas yield, product gas composition, lower heating value of syngas and gasification efficiency, were comprehensively evaluated. Additionally, the interaction between cellulose and high-density polyethylene was analyzed. The results suggested that increasing the polyethylene content in feedstock resulted in decreased yields of H2 and CO, increased CH4 yield, increased lower heating value of syngas and reduced gasification efficiency. The interaction between cellulose and high-density polyethylene enhanced the gas yield, with the most significant effect at 40 % polyethylene content. In the range of 900 °C–1000 °C, increasing the temperature resulted in increased gas yield, reduced lower heating value of syngas and increased gasification efficiency. The positive interaction between cellulose and high-density polyethylene on gas yield was more significant at higher temperatures. This work shed light on reaction characteristics for co-gasification of biomass and high-density polyethylene with CO2, laying the foundation for the design and application of this technology.

Synthesis of bentonite-supported Ni, La, and Ca catalysts for hydrogen production through steam reforming of acetic acid

In this study, the production of hydrogen-rich gas through the steam reforming of acetic acid using bentonite-supported catalysts was investigated. Bentonite was treated by washing and calcination. Bentonite-supported Ni, Ca, La, Ni–La, and Ni–Ca catalysts with different active metal loadings of 10 and 30 wt% were synthesized using the wet impregnation method. The catalysts were characterized using XRD, XRF, SEM, EDS, BET, FT-IR, NH3-TPD, and Raman. The activity tests of the catalysts were carried out in a continuous flow tubular reactor at various temperatures (500, 600, 700, and 800 °C). Product gas composition was determined by gas chromatography (μ-GC). The effect of bentonite treatment, active metal type, and bimetallic combinations (Ni/Bent, Ni/Bent*, La/Bent, Ca/Bent, Ni–La/Bent, and Ni–Ca/Bent) were studied. The highest hydrogen yield obtained without a catalyst was 8.61% at 700 °C. This yield increased to 74.5% at 600 °C with 30 wt% Ni–La/Bentonite, and to 42.6% with 30 wt% Ni/Bentonite catalysts, respectively. The experimental results show that bentonite has a suitable catalytic activity on its own and is a promising support material for the steam reforming of acetic acid.

A Comprehensive Approach to Modeling Air Injection-Based Enhanced Oil Recovery Processes

SummaryModeling of air-injection-based processes for enhanced oil recovery (EOR) is a challenging task, mostly due to the complexity of the chemical reactions taking place. Also, the applicability of currently available kinetic models is limited to the reservoir systems they were originally developed for. The objective of this study is to derive a general chemical reaction framework that could be used to develop a kinetic model for a variety of crude oils (i.e., light or heavy oils).The work is based on the modeling of high-pressure ramped temperature oxidation (HPRTO) experiments, and combustion tube (CT) tests, performed on two different oil systems: a volatile oil that is near critical at reservoir conditions (44 °API), and a bitumen sample (10 °API). The HPRTO test is a kinetic experiment that intends to mimic the flow conditions within the reservoir and allows the determination of kinetic parameters of the different reactions. On the other hand, the CT test is meant to provide quantitative information on the combustion performance that can be expected in the field. Therefore, a kinetic model was derived for each of the cases based on the history match of an HPRTO experiment. The resulting model was validated by history matching a CT test for each of the oils. An important feature of these experiments is that they were performed at representative reservoir pressure conditions.The modeling approach chosen is an extension of the methodology originally proposed by Belgrave et al. in 1993, which is arguably the most comprehensive kinetic model available in the air injection literature. However, their model was developed from experiments performed on Athabasca bitumen, and it fails to represent the high-pressure air injection process as it occurs in light oil reservoirs, which are typically encountered at higher pressure conditions. For example, Belgrave’s model is based on the deposition and combustion of semisolid residue commonly known as “coke,” which is rarely present during the combustion of light oils at high pressure.As in Belgrave’s model, this study also describes the original composition of the oil in terms of maltenes and asphaltenes. The main difference lies in the presence and importance of oxygen-induced cracking reactions, as well as the combustion of a liquid-vapor flammable hydrocarbon mixture that is generated by cracking and oxidation reactions, which take place in the gas phase. Also, a unique feature of these simulations is that, apart from history-matching traditional variables such as thermocouple temperatures, fluid recovery, and produced gas composition, they also capture changes in the physical properties of the produced oil, such as viscosity and density, as well as the amount of the residual phases in the post-test core. This enhancement to Belgrave’s reactions allows modeling the air injection process in cases where coke is not the main source of fuel, such as in high-pressure light oil reservoirs.This work changes a paradigm deeply rooted in the original in-situ combustion (ISC) theory, by deriving a general chemical reaction framework that is used to develop a kinetic model for two crude oils, which are at opposite ends of the density spectrum. This allows the consolidation of a new and comprehensive general theory for the description of the ISC process as applied to oil reservoirs. Moreover, as the pseudocomponents representing the fuel are not present in the original oil, the method is not limited to a fluid characterization in terms of maltenes and asphaltenes but could potentially be applied along with any type of characterization of the original oil.

Partial upgrading of bitumen with supercritical water— liquid products characteristics, gas composition and coke morphology

The study aimed to investigate the partial upgrading of bitumen in the absence of water (non-water) and the presence of supercritical water (SCW). Partial upgrading experiments were conducted at the target temperature of 420 °C, with the reaction time varying from zero to 60 min in a batch reactor. The liquid products were analyzed for density, viscosity, composition, total acid number (TAN), olefin content, and elemental analysis. The gas composition and morphology of solid products were also studied. The experimental results revealed that while partial upgrading of bitumen with SCW could accelerate improvement in oil quality, particularly in terms of API and viscosity, it concurrently led to elevated gas and coke formation levels. Moreover, the difference in the distribution of oil fractions between the two environments (absence and presence of SCW) tends to diminish with an extended residence time. Additionally, as the residence time increases, the efficiency of TAN reduction under SCW conditions is less pronounced compared to the non-water conditions. Liquid products obtained in an SCW environment exhibited higher olefin content (between 3 and 4 wt %) compared to non-water conditions (between 1.8 and 2.7 wt %). In both environments, the olefin content was initially increased up to a residence time of 20 min and then decreased. Regarding heteroatoms, the sulphur (S) and nitrogen (N) contents decreased up to 36 % and 72 %, respectively, while a greater reduction was observed in the presence of SCW. More non-hydrocarbon gases (H2S, CO2 and CO) were produced in the presence of SCW. SEM images showed that an extended residence time led to a shift in coke morphology towards a more uniform and compact structure, regardless of the upgrading environment. However, the porous structures of coke samples obtained under SCW are distinguished from those formed without water, which is attributed to the phase inversion of precursors. The findings of this study confirm that SCW plays a beneficial role as a solvent in the partial upgrading of bitumen, expediting the process. However, the increased level of coke formation and olefin contents suggest that it may not function effectively as a hydrogen donor in the process.

Co-gasification of lignite and spent tea waste for the generation of hydrogen-rich syngas in a fluidized bed gasifier

The co-gasification of high moisture and high volatile content low-rank lignite (LG) coal and a common waste generated from the brewed tea leaves was studied in a fluidized bed gasification unit. Multiple experiments were conducted at different temperatures, ranging from 800 °C to 900 °C, at fixed operating parameters to elucidate the catalytic thermo-chemical impact on the gasifier performance parameters. The catalytic effect of alkali and alkaline earth metals (AAEMs), especially CaO, K2O, and Na2O present in the spent tea waste (STW) sample, on the product gas composition and performance parameters during the co-gasification experiments with LG was demonstrated. Mixed blends of LG and STW showed enhancement in the overall reactivity of the steam gasification runs, compared to the LG-only feed, primarily due to the change in the surface morphology, textures, and pore structures of the solid product ash samples, as identified with the electron spectroscopy analysis. Liquid and product samples were analyzed using characterization techniques such as Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) analytical techniques, along with the proximate, ultimate, and X-ray fluorescence (XRF) analysis of the gasification feed samples. An optimized blend ratio of 20 wt % of STW with LG sample enhanced the volumetric gas composition of H2 and CH4 gases from 52.03 % to 61.32 % and 3.98 %–5.45 % (on a dry-N2-free basis) with a relatively constant CO gas composition. It showed a reduced CO2 composition from 28.64 % to 18.25 % (on a dry-N2-free basis) for the gasification temperature of 900 °C. Even at the lower gasification temperatures of 800 °C and 850 °C with LG + STW feed, steam gasification experiments showed relatively comparable or superior performance to gasification experiments at 900 °C with LG-only feed. The present study indicated a holistic way to utilize the spent tea waste generated from millions of homes and commercial establishments in various parts of the world with potential application towards synergistic gasification process with other conventional carbon-source materials.

Effect of long reaction distance on gas composition from organic-rich shale pyrolysis under high-temperature steam environment

When high-temperature steam is used as a medium to pyrolyze organic-rich shale, water steam not only acts as heat transfer but also participates in the chemical reaction of organic matter pyrolysis, thus affecting the generation law and release characteristics of gas products. In this study, based on a long-distance reaction system of organic-rich shale pyrolysis via steam injection, the effects of steam temperature and reaction distance on gas product composition are analyzed in depth and compared with other pyrolysis processes. The advantages of organic-rich shale pyrolysis via steam injection are then evaluated. The volume concentration of hydrogen in the gas product obtained via the steam injection pyrolysis of organic-rich shale is the highest, which is more than 60%. The hydrogen content increases as the reaction distance is extended; however, the rate of increase changes gradually. Increasing the reaction distance from 800 to 4000 mm increases the hydrogen content from 34.91% to 69.68% and from 63.13% to 78.61% when the steam temperature is 500 °C and 555 °C, respectively. However, the higher the heat injection temperature, the smaller the reaction distance required to form a high concentration hydrogen pyrolysis environment (hydrogen concentration > 60%). When the steam pyrolysis temperature is increased from 500 °C to 555 °C, the reaction distance required to form a high concentration of hydrogen is reduced from 3800 to 800 mm. Compared with the direct retorting process, the volume concentration of hydrogen obtained from high-temperature steam pyrolysis of organic-rich shale is 8.82 and 10.72 times that of the commonly used Fushun and Kivite furnaces, respectively. The pyrolysis of organic-rich shale via steam injection is a pyrolysis process in a hydrogen-rich environment.

CFDs Modeling and Simulation of Wheat Straw Pellet Combustion in a 10 kW Fixed-Bed Downdraft Reactor

This research paper presents a comprehensive study on the combustion of wheat straw pellets in a 10 kW fixed-bed reactor through a Computational Fluid Dynamics (CFDs) simulation and experimental validation. The developed 2D CFDs model in ANSYS meshing simulates the combustion process in ANSYS Fluent software 2021 R2. The investigation evaluates key parameters such as equivalence ratio, heating value, and temperature distribution within the reactor to enhance gas production efficiency. The simulated results, including combustion temperature and produced gases (CO2, CO, CH4), demonstrate a significant agreement with experimental combustion data. The impact of the equivalence ratio on the conversion efficiency and lower heating value (LHV) is systematically explored, revealing that an equivalence ratio of 0.35 is optimal for maximum gas production efficiency. The resulting producer gas composition at this optimum condition includes CO (~27.67%), CH4 (~3.29%), CO2 (~11.09%), H2 (~11.09%), and N2 (~51%). The findings contribute valuable insights into improving the efficiency of fixed-bed reactors, offering essential information on performance parameters for sustainable and optimized combustion.