Biomass Gasification Technology Research Articles

Critical factors affecting the integration of biomass gasification and syngas fermentation technology

Gasification-fermentation is a thermochemical-biological platform for the production of fuels and chemicals. Biomass is gasified at high temperatures to make syngas, a gas composed of CO, CO2, H2, N2 and other minor components. Syngas is then fed to anaerobic microorganisms that convert CO, CO2 and H2 to alcohols by fermentation. This platform offers numerous advantages such as flexibility of feedstock and syngas composition and lower operating temperature and pressure compared to other catalytic syngas conversion processes. In comparison to hydrolysis-fermentation, gasification-fermentation has a major advantage of utilizing all organic components of biomass, including lignin, to yield higher fuel production. Furthermore, syngas fermentation microorganisms do not require strict CO:H2:CO2 ratios, hence gas reforming is not required. However, several issues must be addressed for successful deployment of gasification-fermentation, particularly those that involve the integration of gasification and fermentation. Most previous reviews have focused only on either biomass gasification or syngas fermentation. In this review, the critical factors that affect the integration of biomass gasification with syngas fermentation, such as carbon conversion efficiency, effect of trace gaseous species, H2 to CO ratio requirements, and microbial preference of carbon substrate, are thoroughly discussed.

Biomass gasification technology: The state of the art overview

In the last decades the interest in the biomass gasification process has increased due to the growing attention to the use of sustainable energy. Biomass is a renewable energy source and represents a valid alternative to fossil fuels. Gasification is the thermochemical conversion of an organic material into a valuable gaseous product, called syngas, and a solid product, called char. The biomass gasification represents an efficient process for the production of power and heat and the production of hydrogen and second-generation biofuels. This paper deals with the state of the art biomass gasification technologies, evaluating advantages and disadvantages, the potential use of the syngas and the application of the biomass gasification. Syngas cleaning though fundamental to evaluate any gasification technology is not included in this paper since; in the authors’ opinion, a dedicated review is necessary.

Effects of Alkali and Alkaline Earth Metals on N-Containing Species Release during Rice Straw Pyrolysis

To study the effects of inherent and external alkali and alkaline earth metallic species (AAEMs, i.e., K, Ca and Mg) on the behavior of N-containing species release during rice straw (RS) pyrolysis, different pretreatments were applied in numerous experiments. Results indicate that ammonia (NH3) and hydrogen cyanide (HCN) are the major N-containing species and that the yields of isocyanic acid (HNCO) and nitric oxide (NO) are relatively low. The removal of inhert AAEMs shifts N-containing species release to a high-temperature zone according to volatile release behavior because of the increase in activation energy. The formation selectivity of NH3, HNCO, and NO increases by demineralized pretreatment, whereas HCN selectivity decreases. The formation of HNCO is mainly affected by alkaline earth metal. N-containing species release occurs in low temperatures with the addition of external AAEMs. The activation energy of samples impregnated with CaCl2 and MgCl2 sharply decreases compared to the original RS. The total yields of N-containing species are reduced significantly in the presence of KCl, CaCl2, and MgCl2 as additives. The inhibition ability of AAEMs follows the sequence MgCl2 > CaCl2 > KCl. The inhibition effect of MgCl2 can be improved by solution immersion compared with solid powder mixing. The clean biomass pyrolysis and gasification technology with low N-containing species content may be developed according to the results.

Properties and Combustion Characteristics of Molded Solid Fuel Particles Prepared by Pyrolytic Gasification or Sawdust Carbonized Carbon

Pyrolytic gasified charcoal (PGC) and tar are the solid and liquid products, respectively, yielded from biomass gasification technology. In this paper, PGC was molded with adhesives to prepare molded solid fuel (MSF). Tar and PGC were obtained from the pyrolytic gasification of wood chips and sawdust from pine and cedarwood. PGC was molded with phenol resin prepared by wood tar to prepare MSF (MSF-MP). Meanwhile, there were two other methods used to prepare MSF. PGC molded with common phenol resin was one method (MSF-P). PGC was molded with starch adhesive to prepare MSF-S. Wood powder carbonized carbon (WPCC) obtained from the marketplace was employed as a trial sample. The properties and combustion characteristics of MSFs and WPCC were studied. It was found that the shatter strength of these MSFs were more than 95%. MSFs had higher activation energy and comprehensive combustion index compared to WPCC. MSF-MP yielded the following data: shatter strength: 95.86%, lower heating value (LHV): 25.89 MJ∙kg-1, ignition: 325 °C, comprehensive combustion index: 1.73×10-10, and activation energy: 61.38 kJ∙mol-1. The LHV and activation energy of MSF-MP were superior to those of other MSFs. Therefore, MSF-MP has a market potential for use as barbecue charcoal in restaurant or family gatherings. The preparation of MSF-MP is a prospective method for the utilization of PGC and wood tar.

Reforming of lignin-derived tars over char-based catalyst using Py-GC/MS

Tar removal is one of the major challenges in implementation of biomass gasification technology. Syngas tars causes formation of aerosols and soots, which plug filters, reactors and fuel lines. In this study, a char-derived catalyst was tested in removal of tar produced from pyrolysis of kraft lignin in a pyroprobe reactor. The effects of reaction temperature (700, 800 and 900°C), water amount (5–10μl), pressure (0.1–2.2MPa) and atmosphere (inert and hydrogen) on catalytic conditioning of tar components were assessed. The tar components were analyzed by GC/MS. Catechols were the most abundant tar components followed with phenols and guaiacols during non-catalytic kraft lignin pyrolysis. Results indicated that the char-based catalyst effectively decreased the contents of lignin tar. Reaction temperature, water loading and reaction pressure significantly affected the tar removal. An increase in reaction temperature led to an increase in removal efficiency of most tar components except naphthalene. Excessive water loading (10μl) decreased the tar removal efficiency of char-based catalyst. High pressure promoted the catalytic conversion of lignin tar. Tar contents decreased significantly when hydrogen was used as a reaction medium and thus promoted the conversion of lignin into non-condensable gas.

Experimental Investigation of Tar Reduction Properties by Coupling Oxidative Pyrolysis and Partial Oxidation in a Continuous Reactor for Biomass Gasification

AbstractTo develop a deep understanding of multistage biomass gasification technology, the effect of oxygen concentration in the pyrolysis stage on the overall performance of the gasification process was investigated. The results showed that oxygen in the pyrolysis stage promoted the yields of permanent gases and reduced the yield of tar. The GC–MS analysis of pyrolyzed tar compounds indicated that oxidative pyrolysis promoted the conversion of the reactive primary tar compounds to more stable secondary tar compounds. The FTIR analysis of pinewood char showed that oxidative pyrolysis reduced the content of oxygen‐containing functional groups and improved the aromatization of char. The partial oxidation results showed that the CO and CO2 yields both increased with the increase of oxygen concentration in the first stage. The tar yield after the partial oxidation stage was reduced from 0.0809 (0 % O2 in the first stage) to 0.0064 kg kgpinewood−1 (15 % O2 in the first stage).

Development of Tar Removal Technologies for Biomass Gasification using the By-products

Abstract The technical obstacle of biomass gasification technology is the effective removal of tar, which will cause the clogging of pipes and engines. In this research, in order to develop the low-cost and high-efficiency tar removal technologies, the tar removal performances of bio-oil and char, which are the by-products of biomass gasification processes, were investigated. For this research, the scrubber with 100L of bio-oil and the char bed with 10 kg of char and 3 kg of activated carbon were prepared in the pilot-scale gasification plant. The results show that the bio-oil scrubber and the char bed were effective for tar removal and both of them removed about 60% of tar from the producer gas. It is noteworthy that the tar removal performance of the bio-oil scrubber did not decrease with the passage of time. This implies that the bio-oil scrubber had some big advantages, such as no cost for purchase and transportation of absorbent and no need to change the absorbent inside the scrubber.

Experimental investigation on tar produced from palm shells derived syngas using zeolite HZSM-5 catalyst

The efficiency of the gas cleaning step is one of the fundamental steps to the successful operation of biomass gasification technologies for power generation. In the present study, catalytic cracking is selected as the hot gas cleaning technology using zeolite HZSM-5 catalyst in order to reduce tar produced from palm shells gasification in the laboratory scale fixed bed reactor. The experimental conditions for average biomass particle size, nitrogen flow rate and percentage of zeolite HZSM-5 catalyst are in the range of 1.18–7.13 mm, 3–7 L/min, and 2–10 wt% respectively with constant air flow rate of 5 L/min to the inlet of the reactor. From the gas chromatographic analysis of the tar produced from the gasification process, it is found that the phenol in the tar is in the range of 5–8 vol% when the oxygen to nitrogen flow rate ratio is varied from 0.10 to 0.15. A decreasing trend in the phenol concentration is observed when oxygen to nitrogen ratio is increased. The overall oxygenated aromatic compounds in the tar content are comparable when operating with oxygen to nitrogen ratio of 0.12 and 0.15. The lowest concentration of phenol is achieved when 5 wt% of zeolite HZSM-5 catalyst is used with a reduction of 99% and 79% for oxygen to nitrogen ratio of 0.10 or 0.15 respectively when compared to the phenol concentration with the absence of the catalyst. Furthermore, higher percentage of the catalyst results in less chemical compounds found in tar. Tar content increased as lower concentration of oxygen content in gas mixture or larger palm shells particle size is used.

Experiments on biomass gasification using chemical looping with nickel-based oxygen carrier in a 25 kWth reactor

Biomass gasification using chemical looping (BGCL) is an innovative biomass gasification technology, which utilizes lattice oxygen from oxygen carrier instead of molecular oxygen from air. This work attempted to investigate the BGCL performance with nickel-based oxygen carrier in a 25 kWth reactor. The new prototype is composed of a high velocity fluidized bed as an air reactor, a cyclone, a bubbling fluidized bed as a fuel reactor, and a loop-seal. At first, the major reactions in the process were presented and chemical reaction thermodynamics in the fuel reactor was analyzed. The NiO/Al2O3 oxygen carrier was then applied in the reactor. Different variables, such as gasification temperature, steam-to-biomass (S/B) ratio and NiO content, were analyzed. The carbon conversion efficiency increased smoothly within the temperature range of 650–850 °C, while the syngas yield reached the maximum of 0.33 Nm3kg−1 at 750 °C. Additionally, based on the tradeoff between carbon conversion efficiency and syngas yield, it was concluded that 30 wt.% was the optimal NiO content. Besides, in order to get high quality syngas with low CO2 emission, CaO-decorated NiO/Al2O3 oxygen carrier was investigated. Experimental results showed that the addition of CaO enhanced the biomass gasification process and increased the syngas yield.

Economic assessment of solar and conventional biomass gasification technologies: Financial and policy implications under feedstock and product gas price uncertainty

Four configurations of a novel solar-heated biomass gasification facility and one configuration of conventional biomass gasification are analyzed through financial and policy scenarios. The purpose of this study is to determine the potential financial position for varying configurations of a novel technology, as compared to the current state-of-the-art gasification technology. Through the use of project finance and policy scenario development, we assess the baseline breakeven syngas price (normalized against natural gas prices and based upon annual feedstock consumption), the sensitivity of major cost components for the novel facilities, and the implications of policy levers on the economic feasibility of the solar facilities. Findings show that certain solar configurations may compete with conventional facilities on a straightforward economic basis. However, with renewable energy policy levers in place the solar technologies become increasingly attractive options.

The Physical and Chemical Properties of Fine Carbon Particles-Pinewood Resin Blends and Their Possible Utilization

The application of biomass gasification technology is very important in the sense that it helps to relieve the dwindling supply of natural gas from fossil fuels, and the desired product of its gasification process is syngas. This syngas is a mixture of CO and H2; however, by-products such as char, tar, soot, ash, and condensates are also produced. This study, therefore, investigated selected by-products recovered from the gasification process of pinewood chips with specific reference to their potential application in other areas when used as blends. Three samples of the gasification by-products were obtained from a downdraft biomass gasifier system and were characterized in terms of chemical and physical properties. FTIR analysis confirmed similar spectra in all char-resin blends. For fine carbon particles- (soot-) resin blends, almost the same functional groups as observed in char-resin blends appeared. In bomb calorimeter measurements, 70% resin/30% char blends gave highest calorific value, followed by 50% resin/50% soot blends with values of 35.23 MJ/kg and 34.75 MJ/kg consecutively. Provided these by-products meet certain criteria, they could be used in other areas such as varnishes, water purification, and wind turbine blades.

Development оf energy saving technology of two-stage biomass gasification for cogeneration plants

A two-stage fine biomass gasification process for the low - power generation plants based on ICE, providing the tar content in the producer gas of no more than 7.1 mg/m3n that meets the requirements of the ICE producers was developed. Based on the results of experimental studies of the two-stage fine biomass gasification process, the effective process regimes were determined. The optimal range of the specific air flow, which provides a stable process of oxidative biomass pyrolysis in a dense layer at the pyrolysis temperature not exceeding 800oC is 25.0 55.0 m3/(m2 h).Efficiency of the oxidative pyrolysis process reaches 98.0% taking into account the disposal of all heat flows. Efficiency of the coke residue gasification process without the use of sensible heat of the producer gas is on average 78.0%. Using the sensible heat of the producer gas allows to improve gasification process efficiency to an average of 96.4%.Numerical and theoretical studies of gas ICE operation have shown that the gas ICE operation on the producer gas with a calorific value of 7.6 MJ/m3 is optimum. In this case, the fall of ICE effective power is 16.0%, and the cost of electric power generation is 0.39 UAH/(kW∙h). The results of studies have also shown that increasing the natural gas proportion in a mixture of more than 40.0% is not desirable, since it leads to higher cost of electric power generation up to 1.04 UAH/ (kW∙h) that corresponds to the cost of electric power from the external power system.Exergy analysis of a cogeneration plant has shown a high value of total exergy efficiency of 45 %, while exergy efficiency of individual circuit elements, such as a pyrolyzer and gasifier reaches 96 %, and the "ICE-generator" unit - 91 %. Such values of efficiency are caused by deep disposal of all heat flows in the circuit.

Commercialization Development of Crop Straw Gasification Technologies in China

Crop straw gasification technologies are the most promising biomass gasification technologies and have great potential to be further developed in China. However, the commercialization development of gasification technology in China is slow. In this paper, the technical reliability and practicability of crop straw gasification technologies, the economic feasibility of gas supply stations, the economic feasibility of crop straw gasification equipment manufacture enterprises and the social acceptability of crop straw gasification technologies are analyzed. The results show that presently both the atmospheric oxidation gasification technology and the carbonization pyrolysis gasification technology in China are mature and practical, and can provide fuel gas for households. However, there are still a series of problems associated with these technologies that need to be solved for the commercialization development, such as the high tar and CO content of the fuel gas. The economic feasibility of the gas supply stations is different in China. Parts of gas supply stations are unprofitable due to high initial investment, the low fuel gas price and the small numbers of consumers. In addition, the commercialization development of crop straw gasification equipment manufacture enterprises is hindered for the low market demand for gasification equipment which is related to the fund support from the government. The acceptance of the crop straw gasification technologies from both the government and the farmers in China may be a driving force of further commercialization development of the gasification technologies. Then, the crop straw gasification technologies in China have reached at the stage of pre-commercialization. At this stage, the gasification technologies are basically mature and have met many requirements of commercialization, however, some incentives are needed to encourage their further development.

Biomass Energy for Rural Cooking in China: The Semi- Gasification Stove

Biomass energy as a renewable energy increasingly attracts global attention. An in-depth applied research was made on biomass energy for cooking in China's rural areas in this paper. And a novel biomass semi-gasification technology was proposed. This technology does not produce tar which causes serious environmental pollution compared with the biomass gasification technology, and has higher efficiency than the biomass direct combustion technology. This technology has a strong theoretical and practical significance in optimizing the rural energy structure, improving the rural ecological environment, and improving the production and living quality of the farmers in China.

Methanol production via pressurized entrained flow biomass gasification – Techno-economic comparison of integrated vs. stand-alone production

The main objective with this work was to investigate techno-economically the opportunity for integrated gasification-based biomass-to-methanol production in an existing chemical pulp and paper mill. Three different system configurations using the pressurized entrained flow biomass gasification (PEBG) technology were studied, one stand-alone plant, one where the bark boiler in the mill was replaced by a PEBG unit and one with a co-integration of a black liquor gasifier operated in parallel with a PEBG unit. The cases were analysed in terms of overall energy efficiency (calculated as electricity-equivalents) and process economics. The economics was assessed under the current as well as possible future energy market conditions. An economic policy support was found to be necessary to make the methanol production competitive under all market scenarios. In a future energy market, integrating a PEBG unit to replace the bark boiler was the most beneficial case from an economic point of view. In this case the methanol production cost was reduced in the range of 11–18 Euro per MWh compared to the stand-alone case. The overall plant efficiency increased approximately 7%-units compared to the original operation of the mill and the non-integrated stand-alone case. In the case with co-integration of the two parallel gasifiers, an equal increase of the system efficiency was achieved, but the economic benefit was not as apparent. Under similar conditions as the current market and when methanol was sold to replace fossil gasoline, co-integration of the two parallel gasifiers was the best alternative based on received IRR.

Artificial neural network modelling approach for a biomass gasification process in fixed bed gasifiers

The number of the small and middle-scale biomass gasification combined heat and power plants as well as syngas production plants has been significantly increased in the last decade mostly due to extensive incentives. However, existing issues regarding syngas quality, process efficiency, emissions and environmental standards are preventing biomass gasification technology to become more economically viable. To encounter these issues, special attention is given to the development of mathematical models which can be used for a process analysis or plant control purposes. The presented paper analyses possibilities of neural networks to predict process parameters with high speed and accuracy. After a related literature review and measurement data analysis, different modelling approaches for the process parameter prediction that can be used for an on-line process control were developed and their performance were analysed. Neural network models showed good capability to predict biomass gasification process parameters with reasonable accuracy and speed. Measurement data for the model development, verification and performance analysis were derived from biomass gasification plant operated by Technical University Dresden.

Punctuated continuity: The technological trajectory of advanced biomass gasifiers

Recent interest in biofuels and bio-refineries has been building upon the technology of biomass gasification. This technology developed since the 1980s in three periods, but failed to break through. We try to explain this by studying the technological development from a quasi-evolutionary perspective, drawing upon the concepts of technological paradigms and technological trajectories. We show that the socio-economic context was most important, as it both offered windows of opportunity as well as provided direction to developments. Changes in this context resulted in paradigm shifts, characterized by a change in considered end-products and technologies, as well as a change in companies involved. Other influences on the technological trajectory were firm specific differences, like the focus on a specific feedstock, scale and more recently biofuels to be produced. These were strengthened by the national focus of supporting policies, as well as specific attention for multiple technologies in policies of the USA and European Commission. Over each period we see strong variation that likely benefitted the long term development of the technology. Despite policy efforts that included variation and institutionalization, our case shows that the large changes in socio-economic context and the technological challenges were hard to overcome.

Performance analysis of a small-scale combined heat and power system using agricultural biomass residues: The SMARt-CHP demonstration project

A small mobile agricultural residue gasification unit for decentralized CHP (combined heat and power) production is designed and constructed within the framework of the SMARt-CHP LIFE+ project. This unit applies the technology of biomass gasification coupled with an ICE (internal combustion engine) based generator-set for CHP production. The unit is sized for a maximum thermal output of 12 kW in addition to approximately 5 kW electrical output.Four different locations close to biomass feedstock origin in rural areas of Western Macedonia in Greece, two in Ptolemaida and two in Amyntaion, were selected for the demonstrative operation of the unit. Peach, olive and grape residues were utilized as biomass feedstocks while the unit operated continuously on a 24/7 basis.The present paper describes the unit performance in terms of operation stability, application of different agricultural residues as well as the energy output of the process. The results show the effect of different types of biomass feedstock, gasification parameters and engine intake mixture to long-term operation and energy output while the obtained data will aid in the direction of CHP systems scale-up and optimization towards possible commercialization.

Progress of Biomass Gasification Technology in China

Biomass gasification is one of the most promising technologies to exploit energy from renewable biomass. In this paper, brief introduction of the mechanism of biomass gasification technology and the application status of biomass gasification was described in detail. The research progress of biomass gasification technology in China is reviewed. Finally, the features of these technologies are analyzed and the problems that the biomass gasification technology needs to solve and the research direction of this technology are pointed out.

Gasification of High and Low Density Crop Residues

Crop residue constitutes a large fraction of biomass particularly in agricultural based economies like India. The most abundantly generated crop residues are paddy husk, paddy straw, coconut shell, cotton stalk and sugar cane trash. It is estimated that the potential of power generation using crop residue is close to 14 GWe in a country like India. Even though the potential is large, the main drawback with crop residue is that it is sparsely distributed and being of low density causes collection and transportation problem. This drawback could be converted into an advantage by adopting distributed power generation technologies. The distributed power generation would fare well in the power range of few hundred kilowatts and the most appropriate technology would be the biomass gasification technology. Among the biomass gasification technologies, the downdraft technology is ideally suited for power generation. The downdraft technology is proven with solid or woody biomass, whereas there are limitations in terms of acceptance of all types of crop residues. In this paper, performance study of two vastly differing crop residues, namely coconut shell and cotton stalk has been discussed; both the feedstocks have been tested in “post-harvested” condition with minimum amount of pre-processing. The performance with cotton stalk was found to be comparable at part load; however at higher load the gas composition deteriorated due to poor material movement within the reactor. This had implication in terms of maximum power generated. There was loss of power to an extent of 12%. The operational issues with post-harvested cotton stalk has been brought out which are based on detailed measurements.