Quality Of Producer Gas Research Articles

Pyrolysis of biomass to produce H-rich gas facilitated by simultaneously occurring magnesite decomposition

This study investigated how biomass pyrolysis varies with the different fractions of magnesite mixing into biomass. The pyrolysis occurred with simultaneous decomposition of magnesite without use of any gasification reagent, and was analyzed in terms of producer gas yield and quality. As magnesite fraction increased from 0 to 30 %, the yield of producer gas and its calorific value increased from 48.6 % to 66.3 % and 8.29 to 8.93 MJ/Nm3, respectively. The carbon and hydrogen conversion increased from 44.1 % to 60.7 % and 43.1 % to 66.2 %, respectively. The characterization results revealed that magnesite particles facilitated the conversion of fixed carbon and the thermal/catalytic cracking of tar to produce H-rich gas. The in-situ generated CO2 from magnesite decomposition could be reduced to CO/CH4 in the reductive atmosphere of the pyrolysis products. This study proposes the concept of converting low-energy–density biomass into gas without oxygen and provides a novel approach for producing H-rich gas from biomass.

Two-stage fluidized bed gasification enhanced with oxidative pyrolysis for low-tar producer gas from biomass

Oxidative pyrolysis of fuel was adopted to configure an advanced two-stage fluidized bed gasification system, aiming to produce low-tar producer gas efficiently. A series of tests were carried out to investigate the effect of oxygen allocation in supply on gasification of pine chips in terms of both efficiency and producer gas quality. Compared with the case without pre-oxidation, coupling oxidative pyrolysis increased gas volume fraction of CO, CH4, and CnHm while decreasing that of CO2 and H2 in the produced gas. Further analysis showed that adopting oxidative pyrolysis reduced fuel gas yield, but the tar in the produced gas was lighter. The generated tar is easily transformed into small-molecule combustible gas by the catalytic action of hot char, thus increasing the calorific value of product gas. The long-term operation of the pilot plant presents a great steady continuous running with a minimum tar content in the producer gas of 1.3 g/Nm3. The above-mentioned results thus well verified the technical advantage and feasibility of the two-stage fluidized bed gasification with oxidative pyrolysis.

Biomass gasification in rotary kiln integrated with a producer gas thermal cleaning unit: An experimental investigation

In this work, gasification of hazelnut shells grains is carried out in a bench-scale rotary kiln by using air as gasifying agent at 800 °C. The producer gas is directly treated in a thermal cleaning unit operating at 800–1100 °C with the aim to reduce the load of contaminants. The producer gas cleaning by thermal methods is usually studied by using model compounds, whilst herewith the behavior of a real producer gas is investigated. Results indicate that at high temperature CO2 reacts with tar and particulate to generate CO, thereby improving the quality of producer gas in terms of heating value, producer gas yield and contaminants content. Benzene is the most abundant organic contaminant of the producer gas, the concentration of which is significantly reduced upon thermal treatment. For the first time, a bench-scale rotary kiln gasifier with lignocellulosic biomass as feedstock is integrated with a thermal cleaning unit, providing experimental evidences about the suitability of rotary kiln for air gasification of lignocellulosic biomass and its integration with a thermal unit. The proposed approach could find application also when other types of gasifier are adopted, although a parametric study should be carried out in order to fully understand the reaction mechanism of contaminant removal and to find optimal operation conditions, also as a function of biomass feedstock features.

Self-adaptive gas flow and phase change behaviors during hydrate exploitation by alternate injection of N2 and CO2

Since hydrate resources play a part of the stratigraphic framework structure in sediments, establishing a safe and economic method for hydrates exploitation remains the primary challenge to this day. Among the proposed methods, the spontaneous displacement of CH4 from hydrate cages by CO2 seems to be a perfect mechanism to address gas production and CO2 storage, especially in today's strong demand for carbon reduction and replacing clean energy. After extensive lab researches, in the past decade, injecting a mixture of CO2 and small molecule gas has become a key means to enhance displacement efficiency and has great potential for application. However, there is a lack of in-depth research on gas flow in the reservoir, while the injected gas always passes through low-saturated hydrate areas with high permeability and then occurs gas channel in a short term, finally resulting in the decreases in gas production efficiency and produced gas quality. Therefore, we explored a new injection-production mode of alternate injection of N2 and CO2 in order to fully coordinate the advantages of N2 in enhanced hydrate decomposition and CO2 in solid storage and heat compensation. These alternate “taking” and “storing” processes perfectly repair the problem of the gas channel, achieving self-regulation effect of CH4 recovery and CO2 storage. The 3-D experimental results show that compared to the mixed gas injection, CH4 recovery is increased by >50% and CO2 storage is increased by >70%. Additionally, this alternate injection mode presented a better performance in CH4 concentration of produced gas and showed outstanding N2 utilization efficiency. Further, we analyzed its self-adaptive gas flow mechanism and proposed an application model of “one injection and multiple production”. We look forward to this study accelerating the application of CO2-CH4 replacement technology.

Experimental analysis of dual-stage ignition biomass downdraft gasifier based on various gasification media for the generation of high-quality producer gas

A dual-stage biomass ignition downdraft gasifier has been set-up with the four experimental approaches such as hot air ignition, hot air plus producer gas ignition, oxygen ignition and oxy-steam ignition approach. The experimental unit has been tested at electrical resistance loads of 15.24 kW, 23.62 kW, 27.43 kW, 32 kW and 38.86 kW. This unit provides a useful energy output of nearly 95.37 % in oxy-steam ignition approach at maximum load. The gasification medium is provided at the combustion zone as well as in pyrolysis zone for the complete and partial combustion in the respective regions through the installed nozzles. In the oxy-steam ignition approach, the enhanced quality of producer gas generates, which contains 94 % combustible gases in the producer gas. The Higher Heating Value (HHV) is 12.317 MJ/Nm3, whereas the biomass consumption rate is attained 21 kg/h at the highest resistive load with 1430–1590 °C grate temperature under the oxy-steam ignition approach. The proportion of tar is obtained 0.2 mg/Nm3 after the syngas cooling and cleaning arrangement with moisture content of 6 %, while a significant improvement of 21.26 % has been noted in efficiency under the oxy-steam ignition approach.

Performance assessment of a demonstration-scale biomass gasification power plant using material and energy flow analyses

In this study, biomass gasification was investigated in a 1.5 MWth bubbling fluidized bed demonstration plant using air or an air/steam mixture as gasifying agent, and olivine as bed material. The gasification tests were performed in autothermal conditions and keeping constant the equivalence ratio at 0.30. The gasification products, such as producer gas, elutriated particles, tar, and contaminant gases were comprehensively characterized. Moreover, the performance of the whole gasification plant and that of its specific process units were quantitatively assessed by employing material and energy flow analyses. The results indicated that steam addition improved the producer gas quality by promoting tar and char conversion into permanent gases, thus increasing the producer gas specific yield, even if the lower heating value of the producer gas and cold gas efficiency slightly decreased. Material flow analysis highlighted that the carbon conversion efficiency was mainly affected by the carbon loss due to the solid particles collected by the cyclone, while energy flow analysis revealed that the cold gas efficiency was significantly influenced by the energy the system used to convert the starting biomass into producer gas. The biomass conversion efficiency into electrical energy was about 24 %.

Role of Experimental, Modeling, and Simulation Studies of Plasma in Sustainable Green Energy

This comprehensive review paper offers a multifaceted examination of non-thermal plasma applications in addressing the complex challenge of tar removal within biomass-oriented technologies. It begins with a concise introduction to the research background, setting the context for our exploration. The research framework is then unveiled, providing a structured foundation for understanding the intricate dynamics of plasma–tar interactions. As we delve deeper into the subject, we elucidate the reactivity of tar compounds and the transformation of alkali metals through plasma-based methodologies, essential factors in enhancing product gas quality. Through an array of empirical studies, we investigated the nuanced interactions between plasma and diverse materials, yielding crucial insights into plasma kinetics, modeling techniques, and the optimization of plasma reactors and processes. Our critical review also underscores the indispensable role of kinetic modeling and simulation in advancing sustainable green energy technologies. By harnessing these analytical tools, researchers can elevate system efficiency, reduce emissions, and diversify the spectrum of available renewable energy sources. Furthermore, we delve into the intricate realm of modeling plasma behavior and its intricate interplay with various constituents, illuminating a path toward innovative plasma-driven solutions. This comprehensive review highlights the significance of holistic research efforts that encompass empirical investigations and intricate theoretical modeling, collectively advancing the frontiers of plasma-based technologies within the dynamic landscape of sustainable energy. The insights gained from this review contribute to the overall understanding of plasma technologies and their role in achieving a greener energy landscape.

Mathematical modeling of tar conversion on downdraft biomass gasification processes

AbstractThe article concerns some problems associated with the use of low‐grade fuels for the production of syngas in fixed‐bed gasifiers. Syngas is typically used to feed internal combustion engines in small power systems. Gas quality can be understood as its various characteristics, such as calorific value, the content of individual components (for example, hydrogen), low tar and soot content, and so forth. Achieving these quality criteria often requires specific conditions for the gasification process, in addition, some of them may be limited by additional requirements that are associated with thermal stability or fuel conversion requirements. When evaluating the technical and economic characteristics of gasification‐based power plants, the optimal efficiency does not always correspond to the higher efficiency of the gasification process and the quality of producer gas. In this regard, the aim is to develop optimization methods for different criteria and to create regime maps that cover physically achievable options. Novel mathematical models of tar conversion are proposed, allowing investigation of the dependencies of tar yield on gasification conditions, including the addition of catalysts or staged air supply. Computational tools based on thermodynamic and kinetic models make it possible to solve some of these problems, first of all, to consider and compare the efficiency of various methods for reducing tar content in producer gas (staged gasification, fuel mixing, thermal, and catalytic methods of tar elimination). The choice of relatively simple mathematical models allows us to conduct numerical calculations in a wide range of conditions and to optimize the parameters of biofuel conversion plants. This approach allows a more flexible choice of gasifier operating conditions, including its work as a part of a power unit. Optimal parameters are calculated for specific conditions: secondary air ratio (1–20%) and fraction of catalytic material (5–10%). The results may be used in the analysis and choice of biofuel gasification conditions at small power plants.

Exploring the synergetic effects of rice husk, cashew shell, and cashew husk biomass blends on fluidized bed gasification for enhanced hydrogen production

The present study, explored the gasification performance of commonly available biomass like rice husk, cashew shell, and cashew husk and their blend for better gasification performance using a 3 kW fluidized bed gasifier in the ER ranging from 0.2 to 0.35 and temperature of 750 °C. The catalytic effect of biomass blends are identified by using FTIR, XRF, proximate and ultimate analysis. The performance of a fluidized bed gasifier is assessed in terms of its producer gas composition, LHV, CCE, CGE and gas yield. The blending of biomass resulted in the enhancement of producer gas quality due to the synergetic effect. At ER of 0.2, maximum hydrogen of 8.1% and LHV of 4.3 MJ/m3 is obtained, and at ER of 0.35, maximum CGE and CCE of 54.9 and 91% respectively are obtained for RH + CS blend. XRF analysis shows that mineral oxide improves the composition of producer gas, and FTIR analysis indicates a decrease in functional groups in the ash of blended biomass compared to individual biomass.

Application of computational fluid dynamics and response surface methodology in downdraft gasification using multiple biomass pellets

Downdraft gasifier is a promising technology converting biomass into synthesis gas (syngas) for decentralized heat and power generation. As biomass is seasonal variation and diversity, the design of the gasifier should consider a variety of biomass feedstock. This study investigated a single-designed downdraft gasifier of different biomass pellets using computational fluid dynamics and optimized for producer gas quality and gasifier efficiencies. Three biomass pellets, i.e., wood, bagasse, and palm-oil empty fruit bunch (PEFB), were considered the primary qualitative variable in addition to the main process variables, i.e., air-inlet temperature and equivalence ratio (ER). Response surface methodology (RSM) and multi-objective genetic algorithm (MOGA) were carried out for process and biomass optimization. Tar yield is considered a response for optimization along with carbon conversion (CCE) and cold gas efficiencies (CGE). The results showed that ER and biomass type are crucial. The range of ER for each biomass should be carefully selected. The maximum efficiencies of the gasifier can be achieved using PEFB pellets, whereas the minimum tar yield was attained using wood pellets. The CCE and CGE of 93.11% and 65.16%, respectively, and the tar yield of 12.36 mg Nm−3, were obtained at an optimum ER of 0.28 and air-inlet temperature of 1272.8 K using PEFB pellets.

Solid recovered fuel gasification in sliding bed reactor

This study examines a solid recovered fuel gasification process in the context of a regional, clean energy supply from an affordable source. The examination of this approach was performed under various equivalence ratios and load regimes. A unique cross/updraft gasification reactor with a fixed (sliding) bed over the circular grate with tangential gasification media intake was utilised. This technology is a perspective in waste-to-energy and waste-to-materials production. The investigated parameters included producer gas quality and purity, overall conversion efficiency and char material yield. It was found that a low material load is very beneficial in terms of gas purity and conversion efficiency, reaching up to 93%. Also, the formation of tar compounds was measured as low as 0.7 g/m3. However, when the equivalence ratio parameter was 0.14, the gas's lower heating value was only 2.4 MJ/m3. Also, a lower heating value equal to 5.0 MJ/m3 was reached in a low-efficiency regime (48%) when the fuel load was more significant (48.5 kg/h), and the equivalence ratio was only 0.04. The low tar content suggests a very clean process. Also, the material valorisation in the form of char is beneficial as this carbon-rich material no longer has a waste character and can be utilised in many fields.

Experimental investigation of a dual stage ignition biomass downdraft gasifier for deriving the engine quality gas

The dual stage ignition biomass downdraft gasifier is the promising technology for huge tar reduction, based on two experimental approaches such as single stage and dual stage ignition. The whole unit has been tested with gradually increasing electric resistive load from 15.24 kW to 38.86 kW with a useful energy output of nearly 86.41 %. In single stage ignition approach, the hot air is only supplied at the combustion zone through a nozzle, while the two-stage ignition approach has supply of the premixed gas (hot air plus producer gas) at the pyrolysis zone for partial combustion. In dual stage ignition, the enhanced quality of producer gas comes from 56 % combustible gas with the HHV of 6.415 MJ/Nm3, while the biomass consumption rate is 59 kg/h at the maximum load with grate temperature of 1310−1360 °C. The tar content after gas cooling and cleaning unit is 8 mg/Nm3 with 15 % improvement in efficiency.

Effect of non-thermal plasma dielectric barrier discharge reactor on the quality of biomass gasification product gas from the gasifier

The primary goal of this research is to determine the effect of key processing parameters of dielectric barrier discharge (DBD) reactor on the components concentration of the fuel gas produced during the biomass gasification. By changing key processing parameters such as plasma input power, flow rate, and temperature, the performance of the DBD reactor is assessed. When the power is increased from 5 to 40 W, the concentrations of CO2 and H2 decrease to 12.9% and 18.5%, respectively, while the concentration of CO increases to 17.2%. At 40 W and 65 ml/min, the amount of tar compound significantly drops from 33 g/Nm3 to less than 1 g/Nm3. However, as input power increases, the concentration of C1–C5 hydrocarbons also tends to rise. The highest concentration of C1–C5 was around 0.60% at 40 W. As the flow rate increases, the concentration of CO2 increases while the concentration of CO tends to decrease at all measured power levels, the maximum concentration of CO2 was at 120 ml/min, whereas the minimum concentration of CO is seen under same conditions. With an increase in flow rate, the concentration of CH4 shows a decreasing tendency. It is seen that at 40 W, the concentration of CO and H2 drops as the temperature rises up to 400 °C. In contrast, there is a rising trend in the concentration of CO2, CH4, and tar compounds while increasing temperature. Hence, the DBD reactor appears to have a profound influence on a gas component produced during biomass gasification.

Influence of Oxygen/Steam Addition on the Quality of Producer Gas during Direct (Air) Gasification of Residual Forest Biomass

Biomass gasification is a relevant option to produce a gaseous fuel, it faces, however, several barriers regarding its quality for energetic applications. Therefore, in this study, air-steam and O2-enriched air mixtures were used as gasification agents during the gasification of residual biomass from eucalyptus to improve the producer gas quality. The steam addition promoted an increase in CO2 and H2 concentrations, whilst decreasing the CO and CH4 concentrations. The steam addition had no evident impact on the lower heating value of the dry producer gas and a positive effect on gas yield and the H2:CO molar ratio, attaining the later values up to 1.6 molH2∙mol−1CO. The increase in O2 concentration in the gasification agent (φ) promoted an increase in all combustible species and CO2 concentrations. The lower heating value of the dry producer gas underwent an increase of 57%, reaching a value of 7.5 MJ∙Nm−3dry gas, when the φ increased from 20 to 40 %vol.O2, dry GA. The gas yield had a significant decrease (33%) with φ increase. This work showed that the addition of steam or O2 during air gasification of residual biomass improved producer gas quality, overcoming some of the barriers found in conventional air gasification technology.

Advancements and challenges in the fluidized bed gasification system: A comprehensive review

A gasifier employs partial ignition of biomass and conversion to gaseous fuels of high calorific value. Bubbling fluidized bed gasifier is a promising one amongst other gasification technologies like fixed bed, entrained flow etc. It has several noteworthy advantages like large- and small-scale applications, efficient heat and mass transfer rates due its fuel flexibility, low capital and operating costs, etc. However, low mixing rate of biomass feedstock and gasifying agent, high tar content in the product gas and low calorific value of producer gas are some of its limitations which need sincere attention to enhance its performance. The present study analyzes the effect of design variables of the proposed gasifier reactor for different feedstock along with the operating variables on the quality of producer gas. This review paper examines the present global status of biofuels, different types of gasification technologies, approaches adopted for the gasification, different parameters affecting gasification performance, enhancement of product gas conditioning, technical and cost-effective viability and the future prospects of gasification.

First and second law thermodynamic analysis of a single and dual-stage ignition biomass downdraft gasifier

The dual-stage ignition biomass downdraft gasifier is an enormous tar reduction technology as against a single-stage ignition biomass gasification. Exergetic analysis of the system guides toward a possible performance enhancement. In dual-stage gasification, around 67.76% of input exergy is destructed in the several components, while 9.16% is obtained as a useful exergy output and 24.34% is found to be as a useful energy output there. The entire unit was assessed with a progressively rising electric load from 15.24 kW to 38.86 kW. The enhanced producer gas quality comes from 57% combustible gas with a higher heating value of 6.524 MJ/Nm3 and tar content of 7 mg/Nm3 after the paper filter, whereas the biomass consumption rate is 58 kg/h at the greatest load with the grate temperature of 1310–1370 °C. The samples of exhaust gas emissions are obtained environmentally favorable. The results even described that the dual-stage ignition biomass downdraft gasifier has significantly greater energetic and exergetic efficiency as compared to the single-stage gasifier.

On-site production of high-purity hydrogen from raw biogas with fixed-bed chemical looping

Chemical Looping Hydrogen processes among others, show an outstanding potential for the decentralized conversion of biogas into high-purity hydrogen. For the first time, a 10 kWth fixed-bed chemical looping system has been coupled directly to a 3 MWth biogas digester in the southern region of Austria in the scope of the Austrian research project Biogas2H2. This experimental lab system resembles a blueprint for a potential future industrial system design. A comprehensive parameter study pointed out the influence of relevant process parameters (temperature, O/R ratio, reduction time, steam quantity in oxidation) on hydrogen purity and process efficiency. At the optimal operating point (850 °C, O/R 1.2), the process efficiency was comparable to the utilization of synthetic biogas in previous investigations within a deviation of 2.9%. Sulfuric compounds were isolated before entering the chemical looping system in order to avoid harmful contamination of the product hydrogen and performance loss, as investigated in preliminary experiments.The generated hydrogen was characterized online by ppm-range gas analysis and exhibited a product gas quality of up to 99.998%, with residual CO and CO2 as only contaminants. The fulfillment of the carbon mass balance within a mean deviation of 9% proved the correct quantification. The results indicate that coupling fixed-bed chemical looping systems to biogas plants enables the production of a fuel cell grade hydrogen and a sufficient process efficiency in upgrading local available biogenic and agricultural residuals to high-purity hydrogen.

Assessing the power generation potential and quality of producer gas from blended of the cotton stalk and pistachio shell in an open core downdraft gasifier

: - The increasing energy demands require a sustainable eco-friendly renewable source of energy. Biomass as a sustainable and pollution-free source of energy is the most promising alternative. In the present study, a mix of the cotton stalk and pistachio shells as a feedstock in a weight ratio of 3:1 are gasified. The air is used as a gasifying agent in a downdraft gasifier. In the experimental work, the equivalence ratio (ø) is varied from 0.186 to 0.267. As a result, the maximum power is calculated as 62.795 kW with a feed rate of 39 kg/hr at an equivalence ratio of 0.267. The experimental analysis shows the maximum cold gas efficiency and calorific value of PG as 87.5% and 6.6332 MJ/m3, respectively at an equivalence ratio of 0.241. The maximum values of CH4 and H2 of PG are measured as 3.94% and 16.78 at an equivalence ratio of 0.227 and 0.247, respectively.

A 3D Transient CFD Simulation of a Multi-Tubular Reactor for Power to Gas Applications

A 3D stationary CFD study was conducted in our previous work, resulting in a novel reactor design methodology oriented to upgrading biogas through CO2 methanation. To enhance our design methodology incorporating relevant power to gas operational conditions, a novel transient 3D CFD modelling methodology is employed to simulate the effect of relevant dynamic disruptions on the behaviour of a tubular fixed bed reactor for biogas upgrading. Unlike 1D/2D models, this contribution implements a full 3D shell cooled methanation reactor considering real-world operational conditions. The reactor’s behaviour was analysed considering the hot-spot temperature and the outlet CH4 mole fraction as the main performance parameters. The reactor start-up and shutdown times were estimated at 330 s and 130 s, respectively. As expected, inlet feed and temperature disruptions prompted “wrong-way” behaviours. A 30 s H2 feed interruption gave rise to a transient low-temperature hot spot, which dissipated after 60 s H2 feed was resumed. A 20 K rise in the inlet temperature (523–543 K) triggered a transient low-temperature hot spot (879 to 850 K). On the contrary, a 20 K inlet temperature drop resulted in a transient high-temperature hot spot (879 to 923 K), which exposed the catalyst to its maximum operational temperature. The maximum idle time, which allowed for a warm start of the reactor, was estimated at three hours in the absence of heat sources. No significant impacts were found on the product gas quality (% CH4) under the considered disruptions. Unlike typical 1D/2D simulation works, a 3D model allowed to identify the relevant design issues like the impact of hot-spot displacement on the reactor cooling efficiency.

Co-gasification of rice husk and woody biomass blends in a CFB system: A modeling approach

In the present study, co-gasification behaviors of rice husk (RH) and blends of two woody biomasses, sawdust (SD) and bamboo dust (BD) in a circulating fluidized bed (CFB) system were studied by using ASPEN plus software. The gasifier performance was evaluated in respect of the gas yield and its higher heating value (HHV), in addition to the char conversion efficiency (CCE) and cold gas efficiency (CGE). The present study effectively showed that the blending of biomasses significantly improves the producer gas quality in terms of H2 production and energy output, as well as the gasifier performance indicators. RH + SD blend showed both the highest higher heating value (4.79 MJ/Nm3) and H2 content (12.51 vol %) at 900 °C and ER of 0.24. The simulation results also showed that the gas yield was the highest for RH + BD blend (1.75 Nm3/kg) followed by RH + SD blend (1.73 Nm3/kg) and then RH (1.41 Nm3/kg) at 900 °C. The highest HHV of RH (4.71 MJ/Nm3), RH + SD (5.17 MJ/Nm3) and RH + BD (5.39 MJ/Nm3) were also obtained at 800 °C and ER of 0.19. Change in the steam/biomass (S/B) also showed a slight variation in gasifier performance parameters.