Wood Gasification Research Articles

Chars from wood gasification for removing H2S from biogas

Biomass gasification is a mature thermochemical process used to produce a gaseous fuel to run burners, engines, and gas turbines. One of the byproducts of biomass gasification is char, which is a residue with low value and sometimes this material is even considered waste. Therefore, options for using gasification chars are required. On the other hand, there is a necessity of making biogas production and use more attractive by employing cheap materials for the biogas cleaning process. One of the promising options for using gasification chars is for cleaning biogas produced via anaerobic digestion (AD). The objective of this work was to assess the use of residual gasification chars from fast growing wood species (Eucalyptus Grandis-EG and Pinus Patula-PP) to remove hydrogen sulfide (H2S) from biogas produced via AD. Gasification chars were produced employing a laboratory scale downdraft gasifier. EG char (EG-C30) was produced by gasification of EG using a 30 L min−1 airflow, whereas the PP chars (PP–C20 and PP-C40) were produced from PP using 20 and 40 L min−1 airflow. Results show that these three chars offer potential for biogas cleaning, although PP-derived chars produced at higher airflow rates are more effective. The H2S removal capacity of the chars is ascribed to their large apparent surface area (up to 517 m2 g−1) and the presence of minerals and metals (e.g., Ca, K, and Fe) in the chars’ ash.

Fuel substitution by wood gasification for diesel electricity generator

Gasification is a technology for converting biomass into energy in the form of gas. The gas produced can be used as fuel in a diesel generator with dual fuel system. The purposes of this study were to identify the gasification characteristics of sengon, pine, and caliandra woods, as well as wood pellet to produce burnable gas and to analyze the role of burnable gas produced in reducing diesel input in a dual system generator engine. In this study, a locally designed downdraft gasifier and a commercially available diesel engine generator with 12 kW maximum power output were used. The study investigated wood consumption rate, color of fire, and percentage of diesel savings from each wood type. Gasification process was running well, of which burned woods and wood pellet produced an orange-stable flame. The consumption rate of wood was 18 kg/hour for sengon, 15 kg/hour for calliandra, 8 kg/hour for Pine, while wood pellet was 6 kg/hour. Diesel savings with gas co-firing was 33%, 50% and 95% for sengon, calliandra and pine respectively. The low efficiency of diesel savings may due to heat radiation in the reactor and heat loss in the gas purification process or a decrease in efficiency of the diesel generator engine.

Catalytic pyrolysis of tire waste: Impacts of biochar catalyst on product evolution

Tire scrap is a solid waste that can be potentially used as the feedstock for the production of liquid fuels via the thermochemical process such as catalytic pyrolysis. Nevertheless, it remains challenging to develop the efficient while cost-effective catalyst for the catalytic pyrolysis of tire. In this study, the pyrolysis of tire scrap at 500 °C with the biochar produced from the gasification of poplar wood at 850 °C were conducted. The biochar catalyst significantly affected the evolution of the volatiles and the char properties, while had a slight impact on the yields of the gas, tar and char products. The biochar catalyst catalyzes the cracking of limonene, a major liquid product in tar, to form significantly more propane in gases and alkanes or alkenes in the tar. In addition, the interaction between the biochar with the oxygen-containing organics promoted the re-condensation reaction, which increased the oxygen content in the char, but the biochar catalyst did not influence the evolution of the aromatics. Additionally, the catalytic pyrolysis also makes the biochar catalyst more oxygen-deficient and more resistant towards oxidation. Concluding all the results showed that biochar, which were produced from the gasification of poplar wood can be a potential catalyst for the pyrolysis of tire.

Biomass Chemical Looping Gasification of pine wood using a synthetic Fe2O3/Al2O3 oxygen carrier in a continuous unit

Biomass Chemical Looping Gasification is a novel technology allowing high quality syngas production at autothermal conditions without CO2 emissions to the atmosphere and low tar generation. This work compiles gasification results corresponding to 38 h of continuous operation in a 1.5 kWth unit using pine wood as fuel and a synthetic Fe-based oxygen carrier, Fe20Al. The main operating conditions such as temperature (T = 820–940 °C), steam-to-biomass ratio (S/B = 0.05–0.65), and oxygen-to-biomass ratio (λ = 0.2–0.6) were analyzed at steady state conditions using a novel method for controlling oxygen in the process. A syngas composed by 37% H2, 21% CO, 34% CO2 and 7% CH4, and tars below 2 g/Nm3 could be obtained at autothermal conditions, leading to a syngas yield of 0.8 Nm3/kg dry biomass and a cold gas efficiency of 68%. The material maintained a high reactivity although some Fe lost was observed.

Different reaction behaviours of light or heavy density polyethylene during the pyrolysis with biochar as the catalyst

Polyethylene is a major contributor of plastic waste, which can be converted into liquid fuel via catalytic pyrolysis. In this study, the pyrolysis of light or heavy density polyethylene (LDPE and HDPE) and their mixture with the biochar produced from gasification of poplar wood as catalyst was investigated. The results showed that, during the co-pyrolysis of LDPE and HDPE in absence or presence of biochar catalyst, cross-interaction of reaction intermediates originated from the degradation of LDPE and HDPE substantially promoted the formation of gaseous products and the evolution of heavy organics with π-conjugated structures in the tar. During the pyrolysis of HDPE, more heavy tar while less wax was produced, while it was contrary during the pyrolysis of LDPE. In the catalytic pyrolysis of LDPE, the volatiles could be effectively cracked over the biochar catalyst, forming more gases, while in the catalytic pyrolysis of HDPE, instead of catalyzing the cracking of the heavy components, the biochar catalyzed the polymerisation reactions. The properties of the biochar catalyst in terms of crystallinity, surface functionality, and internal structures also changed remarkably due to the transfer of oxygen-containing species from the polyethylene to biochar and the interaction of biochar with volatiles in the pyrolysis.

Processing technology and experimental analysis of gas-assisted laser cut micro thin wood

Unsupported combustion nitrogen (N2) and flame-retardant helium (He) were used to facilitate laser-cutting of cherry wood, and the effects of process parameters, gas flow, and gas reactivity on the surface quality of thin wood were studied. Using identical processing parameters, the cherry wood was laser-cut with and without the added gases. Through comparing the cutting width, heat affected zone (HAZ), and surface burning conditions under different gas-assistance conditions, the influence of the added gases on the gasification and combustion of cherry wood was analyzed. When N2 gas was used, the cutting width was less than that of laser direct cutting, but the surface of the burning area did not remarkably improve. Under the same conditions, when He gas was added, the burning areas on both sides of the kerf were remarkably reduced and the consistency of kerf was good. This indicated that He gas had good oxygen isolation and flame-retardant effects. The surface of the kerf was observed with a scanning electron microscope, and addition of He gas remarkably improved the burning that occurred when cutting kerf. This study combined gas processing and laser technology, and it provided technical references for reducing post treatment improving the surface quality of laser-processed wood.

Probing Synergies between Lignin-Rich and Cellulose Compounds for Gasification

The fixed-bed gasification of lignin-rich and -deficient mixtures was carried out to probe the synergistic effects between two model compounds, Lignin Pink (LP) rich in Na and Cellulose Microcrystalline (CM). Reaction conditions utilized the most commonly used air ratios in current wood gasifiers at 750 and 850 °C. It was found that by increasing the lignin content in the mixture, there was a selectivity change from solid to gas products, contrary to a similar study previously carried out for pyrolysis. This change in product mix was promoted by the catalytic effect of Na edge recession deposits on the surface of the char. As a result, the water gas shift reaction was enhanced at 850 °C for the LP48CM52 mixture across all air ratios. This was evidenced by a strong correlation between the produced H2 and COx. Meanwhile, by lowering the lignin content in the mixtures, the reactivity of cellulose microcrystalline was found to generate more char at higher temperatures, similar to lignin mixtures when undergoing pyrolysis.

Upgrading Wood Gas Using Bentonite Clay: A Multiscale Modeling and Simulation Study.

Wood gas is the producer gas resulting from gasification of wood biomass and is an important renewable fuel gas in rural areas. This study assessed the capacity of bentonite, a widely used clay mineral, to upgrade wood gas via pressure swing adsorption in order to improve its calorific value (i.e., the amount of energy released per kilogram of gas). Grand canonical Monte Carlo molecular simulations using a self-consistent force field were performed to generate adsorption isotherms for wood gas components—methane, carbon monoxide, carbon dioxide, hydrogen, nitrogen, and oxygen—in montmorillonite (the main crystalline constituent of bentonite) at conditions appropriate to downdraft gasification. The Langmuir adsorption isotherm model was successfully fitted to each component’s adsorption isotherm and was then coupled with a batch equilibrium approach to model a single-stage pressure swing adsorption system with a discharge stream at ambient pressure. A response surface was then computed in terms of the net change in the calorific value as a function of both adsorbent quantity and operating pressure. It was found that the system can improve the calorific value of the gas by over five percent.

Very Sensitive Tar Monitoring in Syngas Streams By Estimation of Oxygen Demand

Motivation: Thermochemical conversion of biomass to syngas by gasification of biological wastes like food or wood residuals wins more and more importance for energy supply because this kind of fuel is sustainable and generally available on demand. The syngas is composed of fuel components like CO, CH4, H2 and light hydrocarbons, but also contains undesired components like particulate matter and particularly tar. The latter constituents represent a complex mixture of aromatic compounds like toluene, phenol or naphthalene, which vary in relative composition and absolute concentration related to the composition of the biomass and the actual quality of the gasification process.Tar content in the raw syngas leads to complications like tar deposition on the walls, coking and clogging of pipes in the equipment of the associated processes in which syngas is used as a fuel. The continuous monitoring of the tar in the syngas even at low concentrations is, therefore, of major importance to enable installation of a feedback operation control of the gasifying process and achieve minimizing of the tar content. In the past, for analysis of tar in syngas well established, but expensive analysis methods like FTIR, NMR and GC/MS were published [1]. Also, tar analysis by LED induced fluorescence spectroscopy was reported in [2], but preliminary tests were conducted in the liquid phase at relatively high concentrations of phenol (8-10%). Recently, online monitoring of the tar concentration in producer syngas by use of a flame ionization detector (FID) was described in [3]. The FID difference signal based on the syngas stream without and with condensation of the tar (cooled filter at 20°C-100°C) represents the tar concentration. This concept of tar analysis seems to be quite accurate for tar concentrations higher than 5g/m3. New concept of more sensitive tar-monitoring in syngas: In this paper, for the first time, a novel concept of continuous tar monitoring in syngas is introduced which has been tested in a lab setup (Fig. 1a). It allows accurate measurements of toluene (used as a model tar) even below 1000ppm. The sensing principle is based on the estimation of the residual oxygen demand for tar combustion.First, a small flow (100ml/min) of the hot syngas stream is extracted from the gasifier and dosed with synthetic air to adjust stoichiometric combustion conditions (λ=1) by use of an electronic mass flow controller (MFC) operated in a feedback loop with the signal of a classical high-temperature Pt/8YSZ/Pt - oxygen concentration cell. In the second step the synthetic air flow is kept constant, but now the syngas is lead over a condensation unit (T=-32°C) and again conducted to the oxygen concentration cell (KS1D, Lamtec GmbH) or to a broadband lambda-probe (LSU 4.9, Bosch GmbH). The latter sensor provides a signal (coulometric current Ip) proportional to the excess oxygen concentration measured after tar condensation (λ>1). The difference signal DIp = Ip(λ>1) – Ip(λ=1) represents the excess oxygen concentration after tar condensation which is directly related to the oxygen demand for tar oxidation. Discussion and outlook: Of course, this method of tar monitoring does not provide an analysis of the tar content because the measured oxygen demand related to the tar concentration depends on the specific mixture of aromatic compounds forming the tar. In addition, even at temperature of approximately -32°C volatile components like toluene, which is one of the major constituents of tar, can only be condensate to a residual saturation concentration of about 800 ppm according to Clausius-Clapeyron equation, which corresponds to a concentration of about 3g/m3 (25°C). This means, at this temperature other components of tar with higher evaporation enthalpies like naphthalene, phenol will be estimated at a much lower sensitivity limit and, therefore, will represent the tar concentration even at considerably lower values than 1000ppm.In the next step this novel procedure of tar monitoring will be automated, tested with naphthalene (model tar) and finally, first experiments will be conducted with syngas of a wood gasifier. These results will be reported as well and limits of detection will be discussed in context with some technical advantages/restrains. Acknowledgement This work is part of the EBIPREP collaboration project (www.ebiprep.eu) financed by the EU International Programme INTERREG V Oberrhein 2017-2020.

Wood gas generator management system for vehicles

This article presents the design and development aspects of a software package and hardware configuration which are allows for the preparation and supply of an air-fuel mixture to a car’s internal combustion engines which using charcoal or firewood as fuel. The software package and hardware should be implemented as a fuel control system. The microcomputer processes the signals from the sensors and allows you to receive data using the semi-automatic control of the fuel system, in addition collects statistical data and provides telemetry output to the dashboard or on the remote display and can be controlled via wireless interface. The following information is recorded in the database: state of sensors, current system settings and actions performed by the user. A remote device running on the Android operating system is connected via the widespread wireless Bluetooth communication channel, real time information about the system and the fuel system control interface are displayed in graphical form.

Techno-economic system comparison of a wood gas and a natural gas CHP plant in flexible district heating with a dynamic simulation model

Biomass combined heat and power plants (CHPPs) can operate target-specifically because of their controllability while supporting decarbonization in district heating. The transition from the German Renewable Energies Act funding, which has promoted biomass CHPPs but is now about to expire, to direct marketing, is a major economic challenge for many biomass-heating grids. To successfully accomplish it, the flexible operation of biomass CHPPs, compared to the previous baseline-operation, is becoming an increasingly important requirement if participation in the electricity markets is to remain profitable.This paper presents a techno-economic assessment of flexible CHPP operation in a modeled district heating system with a CHPP, a peak load boiler and a thermal heat storage. The simulation model compares two cases - a natural gas and a wood-chip gasifier CHPP.The analysis of the results investigates the parameters that need to be adapted to make biomass-fired CHPP heating grids more efficient compared to fossil-fired CHPP heating grids in a flexible operating scenario. It highlights the technical and economic superiority of a fossil-fired CHPP in flexible operation in comparison to the wood gasifier system. The introduction of a CO2-tax on natural gas as a fuel, currently under discussion in Germany, would increase the competitiveness of the wood gasifier.

Waste chars from wood gasification and wastewater sludge pyrolysis compared to commercial activated carbon for the removal of cationic and anionic dyes from aqueous solution

This study compared the properties of waste chars from gasification of wood chips and pyrolysis of wastewater sludge with a commercial activated carbon for the adsorption of dyes. Before the adsorption tests, sludge char was steam-activated at various temperatures between 650 and 900 °C. The activated sample with the largest porosity was chosen for further testing alongside the original sludge char. Results from adsorption tests with methylene blue (cationic dye) and amaranth (anionic dye) were analysed with equilibrium and kinetic models. Wood char showed the highest dye removal efficiency, followed by commercial activated carbon. Monolayer completion was not achieved for these materials in the tested conditions. Sludge char showed maximum adsorption capacities of 13.4 and 8.4 mg/g for the anionic and cationic dye, respectively. Steam activation improved these values to 19.6 and 12.3 mg/g. The cationic dye uptake was in all cases higher compared with the anionic dye.

Experimental study of the co‐gasification of wood and polyethylene in a two‐stage gasifier

AbstractCo‐gasification of wood mixed with 20% (mass fraction) of polyethylene (PE) in a two‐stage NOTAR® fixed‐bed gasifier was studied in the present paper. The ratio of air flow injected in the pyrolyzer and air flow injected in the oxidation zone is called the air ratio (AR). The AR of 0.35, 0.43, and 0.49 were used for test runs. Mass and energy balances were established. The study showed the feasibility of co‐gasification of wood mixed with 20% of PE in the two‐stage gasifier. However, considerable quantity of residues rich in fixed carbon content (17% of the fuel mass and 69% of fixed carbon content) was produced due to a low reactivity of the charcoal obtained after the pyrolysis. AR increasing reduces the gas CO content due to overconsumption of char at the pyrolysis stage. H2 and CH4 highest values are obtained for the intermediate AR = 0.43 which maximized the LHV, energy efficiency, and carbon conversion with respectively 4674 kJ/Nm3, 64.35%, and 74.52%. Low reactivity and carbon content of the pyrolysis char likely lead to lower performance of co‐gasification of PE mixed with wood compared to wood gasification.

How electrical engine power load and feedstock moisture content affect the performance of a fixed bed gasification genset

Performance of wood gasification genset is sensitive to the moisture content in the feedstock and the electrical load (demand of users). This study investigates the influence of these process parameters on the electrical efficiency of the genset (ηglobal), the electrical engine efficiency (ηengine), the cold gas efficiency (CGE), and the syngas composition. Experimental tests were carried out by varying the moisture content from 11% to 23% and the electrical power from 4.7 kW to 12.8 kW on a commercial gasifier equipped with precise measuring tools. The increase of the performance when the electrical load is increased or when the moisture content in the wood chips is decreased is both quantified and discussed. Such behaviour was mainly explained by differences in engine filling rates and reactor temperatures.

Simulation of wood biomass combustion in hot water boiler

Calculation methods based on finite volume methods (CFD method) have proven to be very useful in optimizing (efficiency, emission) heat sources for wood burning. Such heat sources also include gasification hot-water boilers for the combustion of dry wood. One of the important parts of the entire process of converting the primary energy contained in the fuel to the transfer of heat to the heat carrier is the gasification of the fuel in the feed chamber and the subsequent burning of wood gas. The paper presents CFD simulation of wood gasification process in the filling chamber and subsequent burning of wood gas on a model heat source. As a model heat source, was selected a hot-water boiler with lower fuel firing with a flue gas-water heat exchanger tubular heat exchanger. It is a gasification hot water boiler for the combustion of dry wood. The interior of the boiler consists of a filling chamber where the fuel is dried and fused. The wood gas then passes through the nozzle to the combustion chamber, where it burns with the aid of secondary air. The flue gases pass their heat in the heat exchanger through the walls of the pipes into the water.

Gas yield variation in wood biomass co-current air gasification process – continuous operation

The purpose of this work was to study the gas yield variation resulted from the cherry wood gasification with air using a lab-scale rotary kiln gasifier. The feedstock was continuously fed into the preheated reactor at 600°C, in co-current configuration, using atmospheric air as a gasifying agent. The results indicate the importance of oxidation reaction control, through the feeding flow rates of biomass and air and the reactants mixing rate. From the experiment, the hydrogen yields were about 2-4%, while the carbon monoxide varied between 8-21%. Additionally, the paper provides process observations based on the continuous monitoring of gas composition. The specific flow rates of substances and installation operating conditions were linked to process run through syngas composition.

Syngas production using straw pellet gasification in fluidized bed allothermal reactor under different temperature conditions

Straw is one of the most available agriculture waste materials to be utilized as resource. Straw gasification for syngas production is one of the alternatives for resource recovery. Nevertheless, straw gasification might be problematic due to high alkali content, which may cause fouling of the gasifier reactor. In the present study, straw was gasified at different temperatures; in particular 750 °C, 800 °C, 850 °C, 900 °C, and 950 °C furnace temperature, was evaluated and then compared with wood feedstock using allothermal gasifier. The tested temperatures are not the limiting factor for the wood gasification using olivine (Mg2+,Fe2+)2SiO4 bed material and catalysis. Relatively, lower temperature is appropriate for straw gasification where agglomeration with bed material was observed at a higher temperature.

Fabrication and Performance Evaluation of Small Scale Wood Gas Stove for House Hold Purpose Using Water Boiling Test Method

Fabrication and Performance Evaluation of Small Scale Wood Gas Stove for House Hold Purpose Using Water Boiling Test Method

Clean Poultry Energy System Design Based on Biomass Gasification Technology: Thermodynamic and Economic Analysis

Despite growing attention has been paid to waste material gasification for high-efficiency energy conversion, the application of gasification technology in meat waste management is still limited. To fill this gap, this study designed two systems which evaluated the potential of using gasification technology to manage the poultry waste that has been exposed to highly pathogenic avian influenza (HPAI). Two systems are simulated by using Aspen plus combined with a one-dimensional kinetics control gasification model, and wood or dried poultry is selected as the feedstock for the gasifier. The results show that the energy efficiency of the poultry drying system (wood gasification) is 14.5%, which is 12% lower than that of the poultry gasification system when the poultry energy is accounted as energy input. Even though the economic analysis indicates the poultry elimination cost of the poultry gasification system is only 30 $/tonne lower than the poultry drying system, taking the absence of dried poultry burial into consideration, the poultry gasification system has development potentials. The sensitivity analysis shows that labor fee and variable factor has larger effects on the poultry elimination cost, while the uncertainty analysis determines the uncertainty level of the economic analysis results.

Bio-CH4 from palm empty fruit bunch via pyrolysis-direct methanation: Full plant model and experiments with bio-oil surrogate

Abstract A promising, cleaner alternative process of thermochemical conversion of lignocellulosic biomass to biomethane is proposed and rigorously investigated via modelling and experiments for the first time. Using a conventional nickel on calcium aluminate catalyst, operated in bench scale at 1 atm, 400 °C, and with a feed molar steam to carbon ratio of 2, the Low Temperature Steam Reforming of acetic acid, representing a single compound bio-oil surrogate, achieves a promising 81.9% fuel carbon conversion to gases with a methane yield of 15.7 wt% of the feed. This compares to 21 wt% methane yield at equilibrium, thus demonstrating encouraging first time performance and scope for future catalyst optimisation. A comprehensive Aspen Plus model is developed for the first time for an industrial plant producing biomethane from palm empty fruit bunch (50 wt% initial moisture), an under-used agro-industrial waste produced in vast amounts in South-East Asia and Sub-Saharan Africa. Dependency on external heating is completely eliminated by heat recovered from combusting 25% of the gas product. Based on the simulation results of the autothermal plant, a final gas product consisting of 99.2 wt% of CH4 and 0.8 wt% of H2 is predicted with a plant thermal efficiency of 80.6%, i.e., comparable to modelled efficiencies found in the literature for wood gasification to biomethane plants that generate syngas as a necessary intermediate.