Catalytic Gasification Of Biomass Research Articles

Optimization and Techno-Economic analysis of catalytic gasification of wheat straw biomass using ASPEN PLUS model

Biomass gasification efficiently produces heat, electricity, and power. However, removing harmful contaminants from raw syngas is crucial. Tar production is a challenge due to blockage, plugging, and corrosion. Tar steam reforming (TSR) is the most promising technique, converting high molecular weight hydrocarbons into CO, CO2, H2, and CH4. In this study, a model of biomass gasification using wheat straw as biomass feedstock has been developed using Aspen Plus. The gasification flow sheet encompasses gasification, catalytic filter candle, gas cleaning, impurity removal reactor, separator, and subsequent sorbent reactors. Ni-based catalysts with Ni ratios (5%, 10%, and 15%) are used to simulate TSR reactions. Results show that the 15% Ni-Co-Al2O3 catalyst outperforms the 10% and 5% Ni-Co-Al2O3 catalysts. This study explores the impact of temperature, catalyst loadings, and steam-to-carbon (S/C) ratios on toluene conversion and hydrogen yield in catalytic steam reforming, along with temperature, steam-to-biomass ratios, and equivalence ratio on syngas fraction in gasification. It includes a techno-economic analysis of wheat straw gasification to improve syngas energy through efficient tar conversion.

Developing a hybridized thermodynamic and data-driven model for catalytic supercritical water gasification of biomass for hydrogen production

Supercritical water gasification (SCWG) of biomass offers a promising pathway for sustainable energy production. This study presents a novel approach that combines an artificial intelligence (AI) technique with the Gibbs minimization (GM) method to enhance the GM approach by involving the catalyst effect on the gasified yield. The proposed strategy incorporates a modified Gibbs energy calculation, incorporating a delta term that quantifies the influence of the catalyst’s properties on the Gibbs free energy. The delta term is determined using experimental data, including characteristics of biomass and the employed catalysts. An artificial neural network (ANN) model is developed to predict the delta value and is integrated with the GM method to improve the estimation of gasified product yields in the presence of a catalyst. The ANN model establishes correlations between the catalyst specifications such as pore volume, specific surface area, and pore diameter, and delta value. The trained model can predict the delta term, allowing the catalyst’s role to be considered within the GM technique. This integration addresses a limitation of the conventional thermodynamic model, which typically ignores the catalyst’s influence. The developed ANN model exhibits high accuracy, with an R2 value of 0.92 and a mean squared error (MSE) of 0.042. The hybridized GM approach substantially improves the hydrogen yield prediction compared to the basic model, enhancing (reducing) the MSE and mean absolute error by 98% and 93%, respectively. Furthermore, sensitivity analysis reveals that increasing temperature and reducing pressure contribute to improved hydrogen production. Additionally, lower biomass concentrations are shown to be beneficial for enhancing the hydrogen yield.

Heterogeneous Catalytic Gasification of Biomass to Biofuels and Bioproducts: A Review

Heterogeneous Catalytic Gasification of Biomass to Biofuels and Bioproducts: A Review

Effects of inherent AAEMs on catalytic gasification of biomass with large particle size under oxygen-steam atmosphere

Oxygen-steam gasification of biomass is a promising technology because of its ability to improve syngas quality and reduce energy consumption. In this study, a fixed-bed reactor is employed to assess the effects of inherent alkali and alkaline earth metals (AAEMs) on the catalytic gasification of candlenut wood with large particle size under the oxygen-steam atmosphere. Two grain directions, radial and axial, are considered for candlenut wood. Various characterization techniques, SEM, X-ray CT, BET, and FTIR, are employed to analyze biochar samples. GC-MS and GC are determined to tar and syngas respectively. The results show that char yield from biomass with axial grain is higher. Acid-washing removes alkali metals (K and Na) better from biomass with axial grain than radial grain, and vice versa for alkaline earth metals (Ca and Mg). In terms of the gasified chars derived from acid-washed biomass, AAEMs content gradually decreases along the end surface and radial direction, which could also be observed from the 3D reconstruction of X-ray CT images. In all samples, micropores (0–10 µm) dominate and are distributed along the grain direction. In general, pores of 20–30 µm and above 30 µm comprise a minor proportion. Inherent AAEMs facilitate an augmentation in char yield as well as BET and total pore volume of gasified char. AAEMs and grain direction have a slight effect on functional groups of gasified chars. Certain organic matter species and content in tar are remarkably affected by the grain direction, since the discrepancies of pore structure and specific surface area. Acid-washing pretreatment augments the content and organic species of M2-M4 compounds (containing 2–4 benzene rings) in the tar. K and Na significantly boost the char steam gasification, water-gas shift, and steam-tars reforming reactions. A decrement in concentrations of H2 (14.49% and 13.35%), CH4 (0.51% and 0.89%), and CO2 (2.32% and 1.37%) in syngas derived from acid-washed samples are acquired, respectively, compared to that of biomass samples with radial and axial grains. However, a reduction of 4.09% and 1.53% in syngas calorific value could be obtained. The CnHx volume fraction is significantly affected by grain direction and AAEMs, with axial grain yielding a higher volume fraction of C2H4 (49.07%), C2H2 (71.29%), and C3H8 (127.36%) from acid-washed sample than that of radial grain.

Catalytic Gasification and Reforming of Residual Biomass in a Bench Scale System with Low Cost Catalysts.

This paper demonstrates the effectiveness of using of different catalysts for reforming tars contained in the syngas of biomass gasifiers. The conversion of the tar content allows to obtain high quality syngas and to maximize the gas fraction. A bench scale equipment consisting of an autothermal fluidized bed gasifier and a downstream packed bed reformer was used. Pine sawdust was selected as the feedstock for gasification. TGA analysis showed that the temperature must be above 350 °C to ensure the ignition of the biomass and maintain the process in an autothermal steady-state. Dolomite and pyrolysis char were used to test of the fluidized bed catalysts. In the reformer, dolomite, pyrolysis char, iron doped activated carbon and spent HDS catalyst were used. All catalysts decreased the CO2 concentration in the product gas and increased H2 , CH4 and CO. When iron doped activated carbon is used, tar contents below 60 g/Nm3 in the product gas could be obtained, reaching less than 1 g/Nm3 . The best value of LHV (lower heating value) was obtained with pyrolysis char as a catalyst (4.8 MJ/Nm3 ). The results demonstrate that catalytic biomass gasification with downstream tar reforming with low-cost catalysts is a promising solution for energy applications.

High quality syngas production from catalytic steam gasification of biomass with calcium-rich construction waste

High quality syngas was produced by steam gasification of biomass waste with catalyst derived from disposable calcium-rich construction waste after calcination (C-CCW) at high temperature. The effects of biomass gasification parameters including operating temperature, catalyst loading amount and biomass varieties on characteristics of biomass steam gasification were studied. Experiment results indicate that the total gas yield of produced gas derived from steam gasification of corn stalk increased markedly with elevated reaction temperature and catalyst loading amount. Addition of C-CCW on biomass significantly promoted the decomposition of tar in syngas during steam gasification resulting in higher gas yield and better gas quality. The considerable H2 yield (29.70 mmol/g-biomass), CO yield (4.14 mmol/g-biomass), CH4 yield (3.40 mmol/g-biomass), and H2/CO mole ratio (7.17) were achieved after steam gasification of corn stalk with 10.0 wt% C-CCW at 750 °C. There were significant differences in steam gasification performance of different biomass samples owed to the properties of biomass feedstock. Distinct saturation capacities of C-CCW loading amount were observed for enhancing gasification and eliminating tar during steam gasification of diverse biomass feedstocks. C-CCW appeared to have comparable catalytic effect to that of pure CaO and therefore could be an alternative of calcium-containing catalyst.

Catalytic gasification of large particle-size biomass with loaded AAEMs under oxygen-steam atmosphere

To evaluate the effect of alkali and alkaline earth metals (AAEMs) species on the catalytic gasification of large particle-size biomass, a vertical fixed-bed reactor is conducted for candlenut wood gasification under the oxygen-stream atmosphere. The biochar samples derived from gasification are characterized by SEM, X-ray CT, BET, and FTIR. Tar and syngas are analyzed via GC–MS and GC respectively. Advanced X-ray CT technology provides beneficial visualization to assist in the interpretation of the catalytic gasification of large particle-size biomass loaded with AAEMs. The results indicate that a progressive augmentation of AAEMs content along the radial direction and end surface for all loaded samples and biochar samples, which could also be visualized from the 3D reconstruction of X-ray CT. Many large pores (40–60 μm) aligned along the grain direction collapse after the gasification and generate numerous micropores in biochar samples. 10–20 μm pores are more prominent in biochar as the biomass samples are loaded with KCl and CaCl2. The biochar from gasification of biomass loaded with CaCl2 has more well-developed pores, a larger specific surface area, and –OH compounds, aldehydes, ketones and carboxylic acids. The addition of AAEMs facilitates the high generation of M1 compounds (contains 1 benzene ring) in the tar and suppresses the enhancement of M4 compounds, long-chain alkanes, and other compounds. The lowest carbon conversion (57.12 %) is acquired from acid-washed sample. H2 concentration augments but CO concentration declines by loading AAEMs. The highest H2 concentration of 62.1 % is detected by the addition of CaCl2. When loaded with KCl, the syngas calorific value reduces by 1.37 %, whereas loaded with NaCl, CaCl2, and MgCl2 show an augmentation of 11.48 %, 10.56 %, and 2.55 %, respectively. A decrement of CnHx concentration in the syngas derived from gasification of biomass samples loaded with KCl and MgCl2 and an increment one loaded with NaCl and CaCl2 are acquired.

Effects of various carbon-supported iron catalysts on tar removal efficiency and syngas yield during catalytic biomass gasification

Raw biomass, biochar, and activated carbon (AC) were used to produce carbon supported iron catalysts for catalytic biomass gasification. K2CO3 was used to activate the biochar and provide the K promoter of the catalysts. The results showed that the catalyst prepared by co-impregnating and calcining Fe and K on the raw biomass (B-Fe-K) could remove 80.23 % tar, which was much higher than 73.73 % for the catalyst of B-Fe without the K promoter, and 76.25 % for the catalyst by co-impregnating and calcining Fe and K on the biochar (C-Fe-K). The supports of AC and biochar themselves could also remove 63.16 % and 37.23 % tar, respectively. The use of B-Fe-K almost doubled the syngas yield to 473.79 ml/g (including 243.56 ml/g CO, 198.25 ml/g H2, and 31.98 ml/g CO2), compared to 241.37 ml/g syngas (including 108.98 ml/g CO, 66.41 ml/g H2, and 65.987 ml/g CO2) produced by the pyrolysis of biomass without a catalyst. The addition of biochar during the pyrolysis slightly increased the syngas yield to 248.96 ml/g (117.36 ml/g CO, 74.22 ml/g H2, and 57.38 ml/g CO2) while the use of AC could significantly increase the syngas yield to 347.60 ml/g (179.39 ml/g CO, 124.22 ml/g H2, and 43.99 ml/g CO2). It was found that the porosity, dispersion of active sites and the oxidation state of iron oxide are substantial factors determining the performance of catalysts in tar removal efficiency. The addition of potassium and enhancing the porosity of the catalysts enhanced the reducibility of iron resulted in increasing the tar removal efficiency and gas yield.

Characterization and mechanism of red-mud-catalyzed steam gasification of corn stover

Catalytic biomass gasification has received extensive attention from scholars worldwide. This study proposes steam gasification of corn stover using red mud (RM), an industrial solid waste, as a catalyst to produce high-quality reducing gas. Experiments were conducted at different reaction temperatures and gasification times. Characterization of RM and its three main components, Fe2O3, CaCO3, and Al2O3, in the catalytic steam gasification process of corn stover, was performed and its catalytic mechanism was explored by characterizing magnetic separation products. Results show that an increase in reaction temperature significantly promotes the production of CO, CO2, and H2. The promotion of steam to H2 production is caused by the gas-phase reaction and gasification of fixed carbon (FC). Fe2O3 promotes gas-phase reactions, such as the water–gas shift reaction, and effectively catalyzes the steam gasification of FC as an intermediate reactant. The addition of Al2O3 is beneficial for the production of CH4 and H2. The CO2 produced by the decomposition of CaCO3 inhibits the water–gas shift and methane-steam reforming reactions, thus reducing H2 output. The addition of RM is beneficial for the production of H2 and CO2 and inhibits the production of CO. Compared with pure Fe2O3, the superior pore structure and unique solid solution structure of RM provide Fe2O3 with more active surface lattice oxygen, higher redox performance, larger gas–solid contact area, superior ability to prevent carbon deposition, and better catalytic ability.

Improving hydrogen-rich gas production from biomass catalytic steam gasification over metal-doping porous biochar

Biomass to green H2 is a new route to produce sustainable energy. This study aimed to boost H2-enriched gas production via gasification-catalytic steam reforming (GCSR) process of wheat straw (WS) over Ni, Fe, or Zn-doped carbon materials (MDCMs). Initially, steam injection rate (1 g/min) and residence time (15 min) was optimized based on the tradeoff between energy consumption and H2-rich gas generation. The largest gas yield (90.77 mmol/g) and the lowest H2 production efficiency (ƞ: 7.89 g CO2/g H2) were observed for WS-derived biochar. Clearly, it was found MDCMs were favorable for reducing CO2 production due to the strengthened CO2 reforming reactions catalyzed by metal active sites. A higher ƞ (6.72 g CO2/g H2) was achieved for Ni-doping biochar (Ni/C). Importantly, Ni/C showed the ultrahigh carbon conversion efficiency (99.47%) and great tar elimination performance. Overall, GCSR process over MDCMs is a newly promising way to valorize biomass into H2-rich gas.

Recent progress of the transition metal-based catalysts in the catalytic biomass gasification: A mini-review

Biomass is regarded as an important renewable resource, which plays a critical role in the development of sustainable energy systems. Biomass can be converted into energy or valuable chemicals by combustion, liquefaction, pyrolysis, and gasification. Among these processes, thermal gasification cracks biomass into light species at high temperatures, which can be applied to biomass with the greatest variety. As the target product of biomass gasification, syngas or H2-rich gas are very important intermediates in the petrochemical industry. However, the troublesome tar produced during gasification could bring a series of problems. Catalytic biomass gasification is a promising strategy to greatly alleviate these issues. The transition metal-based catalysts for catalytic biomass gasification have been studied in the last decades. Various transition metal catalysts for biomass gasification are reviewed in this article, including monometallic and bimetallic Ni-based catalysts, and other Fe-, Co-, and Pt-based catalysts. The performance of these catalysts is evaluated based on applied reaction parameters, the quality of produced syngas, and the performance of tar reduction. The applications of DFT calculation and AI for mechanism studies of biomass gasification have been summarized, and the cause of catalyst deactivation and regeneration of spent catalysts are also discussed. Therefore, the target of this article is to elucidate conventional biomass conversion pathways and review the recent progress on catalyst development in the biomass gasification process.

Catalytic Biomass Gasification in Supercritical Water and Product Gas Upgrading

AbstractThe gasification of biomass with supercritical water, also known as SCWG, is a sustainable method of hydrogen production. The process produces a mixture of hydrogen, carbon oxides, and hydrocarbons. Upgrading this mixture through steam or dry reforming of hydrocarbons to create synthesis gas and then extra hydrogen is a viable way to increase hydrogen production from biomass. This literature review discusses combining these two processes and recent experimental work on catalytic SCWG of biomass and its model compounds and steam/dry reforming of produced hydrocarbons. It focuses on catalysts used in these processes and their key criteria, such as activity, selectivity towards hydrogen and methane, and ability to inhibit carbon formation and deposition. A new criterion is proposed to evaluate catalyst performance in biomass SCWG and the need for further upgrading via reforming, based on the ratio of hydrogen bound in hydrocarbons to total hydrogen produced during SCWG. The review concludes that most catalysts used in biomass SCWG trap a large proportion of hydrogen in hydrocarbons, necessitating further processing of the product stream.

A Review of the Design and Performance of Catalysts for Hydrothermal Gasification of Biomass to Produce Hydrogen-Rich Gas Fuel.

Supercritical water gasification has emerged as a promising technology to sustainably convert waste residues into clean gaseous fuels rich in combustible gases such as hydrogen and methane. The composition and yield of gases from hydrothermal gasification depend on process conditions such as temperature, pressure, reaction time, feedstock concentration, and reactor geometry. However, catalysts also play a vital role in enhancing the gasification reactions and selectively altering the composition of gas products. Catalysts can also enhance hydrothermal reforming and cracking of biomass to achieve desired gas yields at moderate temperatures, thereby reducing the energy input of the hydrothermal gasification process. However, due to the complex hydrodynamics of supercritical water, the literature is limited regarding the synthesis, application, and performance of catalysts used in hydrothermal gasification. Hence, this review provides a detailed discussion of different heterogeneous catalysts (e.g., metal oxides and transition metals), homogeneous catalysts (e.g., hydroxides and carbonates), and novel carbonaceous catalysts deployed in hydrothermal gasification. The article also summarizes the advantages, disadvantages, and performance of these catalysts in accelerating specific reactions during hydrothermal gasification of biomass, such as water-gas shift, methanation, hydrogenation, reforming, hydrolysis, cracking, bond cleavage, and depolymerization. Different reaction mechanisms involving a variety of catalysts during the hydrothermal gasification of biomass are outlined. The article also highlights recent advancements with recommendations for catalytic supercritical water gasification of biomass and its model compounds, and it evaluates process viability and feasibility for commercialization.

Metal oxide nanoparticles embedded in porous carbon for sulfur absorption under hydrothermal conditions

MOx (M = Zn, Cu, Mn, Fe, Ce) nanoparticles (NPs) embedded in porous C with uniform diameter and dispersion were synthesized, with potential application as S-absorbents to protect catalysts from S-poisoning in catalytic hydrothermal gasification (cHTG) of biomass. S-absorption performance of MOx/C was evaluated by reacting the materials with diethyl disulfide at HTG conditions (450 °C, 30 MPa, 15 min). Their S-absorption capacity followed the order CuOx/C > CeOx/C ≈ ZnO/C > MnOx/C > FeOx/C. S was absorbed in the first four through the formation of Cu1.8S, Ce2S3, ZnS, and MnS, respectively, with a capacity of 0.17, 0.12, 0.11, and 0.09 molS molM−1. The structure of MOx/C (M = Zn, Cu, Mn) evolved significantly during S-absorption reaction, with the formation of larger agglomerates and separation of MOx particles from porous C. The formation of ZnS NPs and their aggregation in place of hexagonal ZnO crystals indicate a dissolution/precipitation mechanism. Note that aggregated ZnS NPs barely sinter under these conditions. Cu(0) showed a preferential sulfidation over Cu2O, the sulfidation of the latter seemingly following the same mechanism as for ZnO. In contrast, FeOx/C and CeOx/C showed remarkable structural stability with their NPs well-dispersed within the C matrix after reaction. MOx dissolution in water (from liquid to supercritical state) was modeled and a correlation between solubility and particle growth was found, comforting the hypothesis of the importance of an Ostwald ripening mechanism. CeOx/C with high structural stability and promising S-absorption capacity was suggested as a promising bulk absorbent for sulfides in cHTG of biomass.

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.

Hydrogen-rich syngas production from biomass gasification using biochar-based nanocatalysts

Nanocatalysts are beneficial for tar elimination and syngas production during biomass gasification. In this study, novel biochar-based nanocatalysts loaded with Ni/Ca/Fe nanoparticles was prepared by one-step impregnation method for catalytic steam gasification of biomass. Results showed that the metal particles were evenly distributed with the particle size of less than 20 nm. With the introduction of nanoparticles, H2 yield and tar conversion were obviously increased. Ni and Fe particles help to maintain the stability of the carrier microporous structure. Fe loaded biochar showed the best catalytic gasification performance, with 87% tar conversion and 42.46 mmol/g H2 production. The catalytic effect of Fe was also higher than that of Ni and Ca if deducting the influence of carrier consumption. It demonstrated that Fe-loaded biochar was a promising catalyst candidate for hydrogen-rich syngas production from biomass gasification.

Low temperature catalytic co-solvent gasification of biomass for hydrogen rich gas

In this study, 6 different solvents were used as co-solvent in hydrothermal gasification of biomass under subcritical water conditions, and their effects on gasification and hydrogen yields were investigated. At 350 °C, synergistic effects were observed on hydrogen production with NMP and THF co-solvents. The hydrogen yields were 3.5 (±0.1) mol H2/kg feed for NMP, and 3.1 mol H2/kg feed for THF. For both NMP and THF, synergistic increases in total gas volumes and hydrogen yields were higher at increasing concentrations up to 25%. At 25% solvent concentration, 4.1 (±0.2) mol H2/kg feed hydrogen yield was obtained with NMP and 3.5 (±0.2) mol H2/kg feed hydrogen yield was obtained with THF. The hydrogen yield increased up to 25.5 (±0.7) mol H2/kg feed, and 24.0 (±0.1) mol H2/kg feed with NiCl2/CaO and KOH/CaO catalyst combinations with co-solvent NMP. Catalyst combinations were more effective than the single catalysts in hydrogen production.

Review on Catalytic Biomass Gasification for Hydrogen Production as a Sustainable Energy Form and Social, Technological, Economic, Environmental, and Political Analysis of Catalysts.

Sustainable energy production is a worldwide concern due to the adverse effects and limited availability of fossil fuels, requiring the development of suitable environmentally friendly alternatives. Hydrogen is considered a sustainable future energy source owing to its unique properties as a clean and nontoxic fuel with high energy yield and abundance. Hydrogen can be produced through renewable and nonrenewable sources where the production method and feedstock used are indicators of whether they are carbon-neutral or not. Biomass is one of the renewable hydrogen sources that is also available in large quantities and can be used in different conversion methods to produce fuel, heat, chemicals, etc. Biomass gasification is a promising technology to generate carbon-neutral hydrogen. However, tar production during this process is the biggest obstacle limiting hydrogen production and commercialization of biomass gasification technology. This review focuses on hydrogen production through catalytic biomass gasification. The effect of different catalysts to enhance hydrogen production is reviewed, and social, technological, economic, environmental, and political (STEEP) analysis of catalysts is carried out to demonstrate challenges in the field and the development of catalysts.

Catalytic O2-steam gasification of biomass over Fe2-xMnxO3 oxides supported on ceramic foam filters

In the present study, catalytic gasification of biomass was investigated by incorporation of a supported Fe2-xMnxO3 catalyst into the freeboard zone of a bubbling fluidized bed gasifier. The material was processed by combining incipient wetness impregnation with microwave-assisted firing methods. These catalysts were characterized by elemental, structural and microstructural analyses, and redox testing by thermogravimetry. Catalytic performance was assessed by comparison with blank tests and used to study the influence of the catalyst temperature, equivalence ratio and gas hourly space velocity on tar decomposition. The catalyst revealed higher activity in converting tar compounds with increasing temperature and equivalence ratio, while increasing the gas hourly space velocity showed a negative impact on catalyst performance. Under optimal operating conditions, the catalyst exhibited a significant impact on tar conversion (83 %) and gasification parameters, such as the gas yield (0.81 to 0.93 Nmdry,gas3∙kgdry,fuel-1), carbon conversion efficiency (55.3 to 65.1 %) and cold gas efficiency (50.7 to 61.6 %). Post-mortem analysis of the tested catalyst provided further information on redox changes and their dependence on temperature, which were co-related with catalytic performance. Elemental mapping showed traces of sulphur, which increased with temperature and did not correlate with the catalytic performance; this was interpreted by thermodynamic modelling, based on the wide redox stability range of divalent manganese oxide and its enhanced tolerance to hydrogen sulphide.

Catalytic biomass gasification in decoupled dual loop gasification system over alkali-feldspar for hydrogen rich-gas production

Gasification of biomass with steam and oxygen was carried over alkali-feldspar in a decoupled dual loop gasification (DDLG) system. This system has a moving bed reformer (MBR), a fluidized bed gasifier (FBG), a riser combustor (RC) and a particle grading cyclone (PGC). Through the PGC, two loops, i.e. a gasification loop of FBG-RC-PGC utlizing quartz sand as circulating bed material and a reforming loop of MBR-RC-PGC utilizing alkali-feldspar as circulating bed material, are formed. The effects of process variables such as reformer temperature, steam to biomass ratio (S/B) and air equivalence ratio (ER) on product gas composition, heating value, tar content, yield of product gas, carbon conversion, water conversion and cold gas efficiency were investigated. The maximum water conversion 35.2% and cold gas efficiency 82.3% were observed at reformer temperature 850 °C. The increase of S/B promoted the H2-rich gas production and the maximum concentration of 42.1 vol % was achieved at the S/B of 1.0. In addition, the use of steam and oxygen together as gasification agent enhanced the tar removal and carbon conversion. The lowest tar content 1.1 g/Nm3 and high carbon conversion 97.2% were obtained at S/B of 0.6 and ER of 0.35.