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Biomass gasification has yet to obtain industrial acceptance. The high residual tar concentrations in syngas prevent any ambitious utilization. In this paper a novel gas purification technology based on catalytic hydrocracking is introduced, whereby most of the tarry components can be converted and removed. Pilot scale experiments were carried out...
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... source material for our gasification experiments was a mixture of shredded woody biomass like limbs, wood pieces, bark, pine balls and other cut grove ( Figure 1a). It was pre-dried in the open air to reduce wood moisture. The main components are carbon (C), hydrogen (H), oxygen (O), and nitrogen (O) of varying concentration, according to its type and location of collection. The average calorific value is about 16.6 kJ/g. The average moisture content is about 8.9 %. Gasification was carried out in an updraft gasifier of the IUTA Institute. Its thermal output is about 100 kW (Figure 1b). The working flow chart shown in Figure 2 [15] should be self-explanatory. The whole facility was controlled by SPS and WinCC systems. As shown in Figure 2, three Ni/Cr–Ni/Si thermocouples were installed inside the gasifier and nine thermocouples were installed on the wall of gasifier for temperature measurements. Gas concentrations in raw gas (4) and purified gas (5) were analyzed online by non-dispersive infrared sensors (NDIR) and a thermal conductivity detector ...
Context 2
... source material for our gasification experiments was a mixture of shredded woody biomass like limbs, wood pieces, bark, pine balls and other cut grove ( Figure 1a). It was pre-dried in the open air to reduce wood moisture. The main components are carbon (C), hydrogen (H), oxygen (O), and nitrogen (O) of varying concentration, according to its type and location of collection. The average calorific value is about 16.6 kJ/g. The average moisture content is about 8.9 %. Gasification was carried out in an updraft gasifier of the IUTA Institute. Its thermal output is about 100 kW (Figure 1b). The working flow chart shown in Figure 2 [15] should be self-explanatory. The whole facility was controlled by SPS and WinCC systems. As shown in Figure 2, three Ni/Cr–Ni/Si thermocouples were installed inside the gasifier and nine thermocouples were installed on the wall of gasifier for temperature measurements. Gas concentrations in raw gas (4) and purified gas (5) were analyzed online by non-dispersive infrared sensors (NDIR) and a thermal conductivity detector ...
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... Syngas has numerous applications including electricity generation using gas turbines and internal combustion (IC) engines (Zhou et al., 2022;Kumar et al., 2009;Devi et al., 2003). Regardless of its many applications and advantages, commercial scale deployment of gasification technology still faces some challenges due to issues in cleaning the produced syngas (Huang et al., 2011). Impurities, such as tars and particulate matters, are produced during gasification and entrained in the syngas. ...
Biomass gasification is a proven technology for production of biofuels, such as synthesis gas. However, a major obstacle to the safe and durable use of synthesis gas (syngas) for the production of energy and chemicals is the removal of tar from syngas. The goal of this study was to develop a mechanical purification system and evaluate its effectiveness of tar removal by cooling the syngas and using wood shavings as filtration media. The performance of the purification system, comprising cyclone separator, syngas cooler and dry biomass filter, was evaluated using tar-laden syngas generated from a 5-kW downdraft gasifier. Syngas was sampled after the filter using a gas chromatograph, and obtained results revealed that the averaged molar syngas composition was 25.25% CO, 17.6% H2, 9.6% CO2, 2.5% CH4 and 44.5% N2, while the average syngas LHV was 5.54MJ/Nm 3. These results signified that the developed purification system was effective in removing particulate matters, moisture and tars from produced syngas. Thereby yielding syngas of good quality that can safely be utilized not only for cooking but also in internal combustion engines to generate electricity.
... The tar concentration in dry exhaust gas was estimated at 0.078 g/Nm 3 and the tar conversion efficiency stood at 91.8% which was determined by comparing tar content at the inlet of the plasma torch reformer and in the outlet stream. The result complies with the acceptable limit of 0.1 g/Nm 3 while for internal combustion (IC) gas engine and gas turbine applications, tar levels less than 50 and 10 mg/Nm 3 respectively are required [53], and the reported tar yield in most catalytic steam gasification of plastics range 100e200 g/ Nm 3 [54]. Generally, it is known that at around 900 C, oxygenated tarry compounds from low-temperature pyrolysis are converted into aromatic and light PAH compounds. ...
This study describes a novel Hybrid Microwave Plasma Enhanced Gasification (HMPEG) method for converting plastic waste into hydrogen (H2).Thermal processing of plastic waste is a low-cost method of producing H2.Current methods, however, such as pyrolysis and gasification, are limited by inefficient heating and contaminants in syngas, resulting in a low H2 yield. Our approach consists of a novel rotary pyrolysis reactor that employs an external microwave heater and an electrodeless microwave torch reformer, thereby addressing issues with current methods. In this study, pyrolysis of mixed plastic produces pyro-gas which is reformed at a temperature above 1500°C by the steam plasma torch powered by microwave.The result is a 150 g/kg H2 yield with a 67 vol. % higher production rate, an H2/CO ratio of 7, and a conversion efficiency of 97.4%.Tar and dioxin concentrations in the syngas were found to be 0.078 g/Nm3 and 0.024 ng-TEQ/Nm3, respectively, much less than the legal limit. A novel microwave pyrolyzer cuts electrical power consumption by half, and the pure H2 produced is suitable for direct use in hydrogen cars, power generation, and other applications. Once implemented, the energy-efficient HMPEG could aid in expanding H2 commercial plants that use plastic waste as a raw input fuel.
... Synthesis gas has a high potential to complement fossil fuels for decentralized energy generation. Regardless of its many applications and advantages, commercial scale deployment of gasification technology still faces some challenges due to issues in cleaning the produced syngas (Huang et al., 2011). Impurities, such as tars and particulate matters, are produced during gasification and entrained in the syngas. ...
Gasification of biomass and different types of waste is considered one of the potential methods for producing clean biofuels, such as synthesis gas, as well as mitigation of environmental degradation and greenhouse gas emissions. However, it is necessary to clean tars from the synthesis gas before it can safely and durably be used in turbines, microturbines, and internal combustion engines for electricity production, chemical reactors for synthetic fuel, or chemical production. For effective cleaning, the high temperature syngas needs to be cooled. The commonly used direct syngas cooling method is not sustainable as it requires huge amount of water especially for commercial purposes and has problems of disposal of tar-contaminated water. Hence, this study aims to design and fabricate an indirect syngas cooling system using the external free-air convection method. The cooling system was designed using a pipe with a diameter of 2.54cm (1 inch) and 1.27mm thick. The design calculation results indicates that heat transfer rate was about 1.6kW and a pipe length of about 2.73m is required to cool the syngas from 950°C to 250°C. Results obtained from gasification experiments showded that the developed syngas cooling system is capable of condensing tars entrained in syngas during biomass gasification, and hence its development for commercial applications should be encouraged.
... Hydrogen sulfide, carbon dioxide, water, and halogenated chemicals are the most common (but not always the only) impurities that may need to be removed in gas cleaning equipment. Desulfurization protects pipelines and equipment from corrosion and reduces harmful hydrogen sulfide levels in the workplace and the usage units [27,28]. Furthermore, suppose carbonyl sulfide (COS) and other sulfur-containing substances such as thiol derivatives (RSH, also known as mercaptan derivative) and hydrogen sulfide are not eliminated. ...
... it can be seen that values, decreasing from 3.86 to 1.72 g/Nm 3 , are in line with the literature indications when starting from biomass as a parent fuel [27,28]. This highlights the efficacy of both the operating conditions employed and reactor design. ...
Production of syngas from the gasification of a biomass is attracting attention with an eye to the concepts of circularity, sustainability, and recent needs, triggered by socio-political events, to increase the level of self-sufficiency of energy sources for a given community. This manuscript reports on the gasification of spruce wood chips in a demonstration fluidised bed gasifier (1.5 MWth, height of 5.40 m, internal diameter of 1.2 m), with 0.2–0.4 mm olivine inventory (1000 kg). Gasification was carried out in air, at four different values of equivalence ratio (from 27% to 36%). The bed was fluidised at about 0.6 m/s, and the bed temperature resulted in the range of about 960–1030 °C as a function of the different tests. A mass flow rate of biomass in the range of about 360–480 kg/h (as a function of the different tests) was fed to the fluidised bed gasifier. Syngas lower heating value, specific mass and energetic yield, and chemical composition, were reported along with data on the production of elutriated fines. Moreover, tar compounds were collected, quantified and chemically speciated. The effect of the equivalence ratio on the main process parameter was critically discussed, proposing useful analytical relationships for the prediction of syngas lower heating value, tar mass flow rate and chemical composition.
... Tertiary tars are aromatics and polycyclic aromatic hydrocarbons (PAH), like pyrene, benzene, phenanthrene, naphthalene, and benzopyrene (Molino et al., 2016). If the gas is sufficiently chilled, tar compounds can condense in downstream machinery like gas engines and compressors, limiting gasification's technical and financial viability (Huang et al., 2011). Tar accumulation in turbines or gas engines must be less than 30 mg/m 3 . ...
The energy deficiency issues and intense environmental pollution have exacted the production of biofuels which are both renewable and sustainable and can be used to displace fossil fuels. The raw material for manufacturing second-generation biofuels is lignocellulosic biomass (LCB), which is widely available. LCB bioprocessing to produce high-value bio-based products has been the subject of attention. Biomass gasification is a powerful technology to achieve sustainable development goals, reduce reliance on fossil fuels, and reduce environmental concerns. This paper, will provide an overview of the LCB structures and the gasification process. Also, consistent with the concept of “circular bio-economy”, this study focuses on the role of LCB gasification in the environmental impacts, and how gasification can be effective in the pathway of circular bio-economy. The current challenges to gasification and biorefinery and future perspectives are also presented.
... Biomass contributes about 10-14% of the global energy requirement, while in rural and remote areas of developing countries, its contributions are more than 90% [2,14,15]. ...
... Rios et al. [24] and Guan et al. [12] explained tar as a complex mixture consisting of over 100 variety of condensable hydrocarbons including a five-ring aromatic compound as well as polycyclic aromatic hydrocarbons (PAHs). The condensation of these compounds in gasification systems causes plugging of downstream equipment such as compressors and engines and hence limits gasification's technical and economic feasibility [15,25]. Moreover, due to its carcinogenic character, tar compounds are harmful to human health and the environment [12]. ...
Biomass is a promising renewable energy source which is available globally, mostly in developing countries where access to clean and affordable energy is a critical problem. Biomass gasification is an interesting technology that can convert biomasses to a more versatile fuel known as syngas, the energy which can substitute conventional fossil fuels in the future. Syngas can amenably be combusted to produce power and heat as well as a feedstock for synthesis of chemicals and other fuels. The biomass gasification is facing severe operational challenges, one of the problems being tar formation and its removal techniques. Tar condenses at reduced temperature, thus causing blockage in the downstream equipment such as compressors and engines. Many studies have considered syngas cleaning by physical removal and thermal cracking unsuitable as they need downstream processing of scrub liquor and utilizes a part of the produced gas in maintaining the thermal cracking temperature, respectively. The utilization of catalysts has been an interesting focus; however, it has not yet been fruitful as many of the developed catalysts deactivate rapidly, and they are expensive or toxic. The motives of the current study are to review tar formation characteristics and trends on catalytic conversion. In addition, the study elucidates the fascinating behaviour of metallic and oxides of the iron-based catalyst under different syngas composition (oxidizing and reducing environments). The behaviours of the iron-based catalyst indicate its fundamental role in developing a catalyst for tar cracking with respect to less toxic, inexpensive, abundant, and regenerable alternatives.
Graphical abstract
... Tar removal in industrial scale was conducted similar to fractional distillation where heteroatom compounds were feeded to cracking section, while aromatic componds was eliminated through radical-assisted mechanism (Han and Kim, 2008;Huang et al., 2011). The removal of S-, O-and N-compounds proceeded through the hydrotreating process. ...
Biomass valorization via catalytic gasification is a potential technology for commercizalization to industrial scale. However, the generated tar during biomass valorization posing numerous problems to the overall reaction process. Thus, catalytic tar removal via reforming, cracking and allied processes was among the priority areas to researchers in the recent decades. This paper reports new updates on the areas of catalyst development for tar reduction. The catalyst survey include metallic and metal-promoted materials, nano-structured systems, mesoporous supports like zeolites and oxides, group IA and IIA compounds and natural catalysts based on dolomite, palygorskite, olivine, ilmenite, goethite and their modified derivatives. The influence of catalyst properties and parameters such as reaction conditions, catalyst preparation procedures and feedstock nature on the overall activity/selectivity/stability properties were simultaneously discussed. This paper not only cover to model compounds, but also explore to real biomass-derived tar for consistency. The area that require further investigation was identified in the last part of this review.
... According to the available energy potential as garden-waste biomass thermal input (<1000 kW th ), the most suitable conversion technology for producing syngas from FL gasification at the UdeA campus is the fixed-bed downdraft reactor. This technology is chosen due to the low tar content (0.1-6 g/Nm 3 ) in the syngas [11], which is suitable to fuel internal combustion engines, and due to the low self-consumption energy (about 15%) when compared to other gasification technologies [12]. The fluidized bed and updraft fixed bed reactors are not feasible for this power, <1000 kW th , because of the high particle matter (8-100 g/Nm 3 ) and the high tar content in the syngas (10-100 g/Nm 3 ), respectively [11]. ...
... This technology is chosen due to the low tar content (0.1-6 g/Nm 3 ) in the syngas [11], which is suitable to fuel internal combustion engines, and due to the low self-consumption energy (about 15%) when compared to other gasification technologies [12]. The fluidized bed and updraft fixed bed reactors are not feasible for this power, <1000 kW th , because of the high particle matter (8-100 g/Nm 3 ) and the high tar content in the syngas (10-100 g/Nm 3 ), respectively [11]. Nevertheless, the high ash content (~20 wt%) and the low ash melting temperature (~1050 • C) constitute challenges for the FL conversion through downdraft gasification [13,14]. ...
Herein the effect of ash-rich biomass (fallen-leaves, FL) mixed with woody biomass (WB) on the thermodynamic performance of a bioenergy power plant based on a downdraft gasifier coupled to an engine-generator (<20 kW) is analyzed. The WB mass fraction in the mixtures ranged from 0% to 100% which led to the making of five samples (FL100, FL75-WB25, FL50-WB50, FL25-WB75, and WB100). The biopower plant was modelled using the Aspen Plus and Engineering Equation Solver (EES) software under the thermochemical and Ideal Otto cycle approaches. The gasification model validation with experimental data from the literature reached a 6.6% relative error. The implemented model was used to assess garden-waste energy valorization strategies by contrasting their chemical characterization (ash fusibility temperatures) with the power plant performance. The energy recovery of FL with WB showed a positive effect on the specific fuel consumption and the power generated by the biopower plant, which were enhanced by 7% and 6%, respectively, with the FL25-WB75 mixture when compared to FL100. Nevertheless, cold gas and overall plant efficiencies decreased by ~18% on average due to the solid fuel higher heating value as the WB fraction increased. This behavior was found when keeping the reactor temperature below ~1000 • C to avoid ash deposition issues, such as fouling and slagging.
... There are many approaches of primary treatments such as optimization of operating parameters, pyrolysis gas recirculation systems, gasifier structure modification, increment of pyrolysis and reduction zone at the different chamber and changes of air injection with pyrolysis gas recirculation position, etc. [20]; while the secondary method consisting of gas cleaning outside the gasifier, such as catalytic reforming, mechanical treatments and thermal cracking, etc. Currently, gasifier modification in the primary method is the most preferred option for reducing tar concentration [19][20][21][22][23][24]. Gasifier modification involves modifying the new design of nozzle or nozzle inclination system and combustor installation inside the partial oxidation zone [25]. ...
A nozzle inclination angle and swirl combustor inside the low-tar biomass (LTB) gasifier reactor were designed and tested to evaluate these effects on tar reduction to design tar-free producer gas. The tar reduction process is mainly based on the concept of a swirling flow created by the inclined nozzles, with the inclination angle of 55o to the radial line, allowing good mixing between pyrolysis gases and gasifying agents. A separate swirl combustor has created large internal annular and reverses flow zones with the help of swirl flow, resulting in homogenized temperature inside the combustor and providing longer residence time; both have a positive effect on the combustion of mixed gasifying air-pyrolysis gases by the thermal cracking in the partial oxidation zone. Recircling ratio (RR) and combustion degree of volatiles are the two critical parameters for evaluating the performance of inclined nozzles and swirl combustor. The result observed that outstanding tar reduction occurred in this novel system. About 87 and 17% of tar compounds are broken down in the partial oxidation zone and pyrolysis zone using the novel swirl combustor and nozzle inclination angle, respectively; gas outlet has observed producer gas having tar concentration of less than 1%. Finally, this system generated producer gas with the tar concentration at an extremely low level of 7.4 mg/Nm³ for biomass moisture content of 9% and appeared the lower heating value of 4.6-5.1 MJ/Nm³. This lower tar concentration might be directly coupled with an internal combustion engine or a gas turbine for power generation.
