The amount of PCDD/F emissions produced by gasification operations is often within standard limits set by national and international laws (<0.1 ng TEQ/Nm3). However, a recent assessment of the literature indicates that gasification cannot always reduce PCDD/Fs emissions to acceptable levels, and thus a common belief on the replacement of incineration with gasification in order to reduce PCDD/Fs emissions seems overly simplistic. A review that summarizes the evidence on when gasification would likely result in environmentally benign emissions with PCDD/F below legal limits, and when not, would be of scientific and practical interest. Moreover, there are no reviews on dioxin formation in gasification. This review discusses the available data on the levels of dioxins formed by gasifying different waste streams, such as municipal solid wastes, plastics, wood waste, animal manure, and sewage sludge, from the existing experimental work. The PCDD/Fs formation in gasification and the operat... [more]

The growth of the economy in urban centers is invariably accompanied by an increase in human activities and environmental interference, mainly related to waste generation. Due to the nature of these activities, large volumes of varied waste are generated daily without the establishment of compatible and adequate collection, logistics, and final disposal systems, bringing relevant impacts to society on health, the environment, and the economy itself. In Brazil, in 2019 alone, almost 30 million tons of MSW were not collected and the total collected, of approximately 44 million tons, went to landfills, with little or no energy use. There is therefore a great opportunity for energy use using this source, aiming not only to adapt to current legislation, but also to reduce GHG emissions, reduce the population’s exposure to sanitary landfills and open air, and use the energy contained in these wastes. The purpose of this study is to analyze the main conditions and challenges of current techno... [more]

Hydrogen is a versatile vector for heat and power, mobility, and stationary applications. Steam methane reforming and coal gasification have been, until now, the main technologies for H2 production, and in the shorter term may remain due to the current costs of green H2. To minimize the carbon footprint of these technologies, the capture of CO2 emitted is a priority. The in situ capture of CO2 during the reforming and gasification processes, or even during the syngas upgrade by water−gas shift (WGS) reaction, is especially profitable since it contributes to an additional production of H2. This includes biomass gasification processes, where CO2 capture can also contribute to negative emissions. In the sorption-enhanced processes, the WGS reaction and the CO2 capture occur simultaneously, the selection of suitable CO2 sorbents, i.e., with high activity and stability, being a crucial aspect for their success. This review identifies and describes the solid sorbents with more potential for... [more]

Due to its enhancement in the flame speed, ozone added in lean premixed syngas turbulent jet flame was investigated by the three-dimensional direct numerical simulation method in the near field of the flame. In the present study, numerical simulations were conducted in the lean premixed syngas turbulent jet flame configuration to explore the effects of ozone addition on freely-propagating turbulent flames. It was seen that turbulence began to significantly affect the flame surface to produce wrinkles in lean premixed gas flame with ozone added after 4D; ozone started to affect the composition field and temperature field after 8D; it accelerated the generation of intermediate products, OH and O radicals; and it will promote the production of CO2 in the near field range. Ozone will increase the flame surface area of the lean premixed syngas flame during the ignition period and can promote the ignition process and make the combustion occur earlier. The flame surface of the case with ozone... [more]

The efficient use of renewable energy is receiving more and more attention in the context of “carbon neutrality” and “carbon peaking”. For a long time, biomass has been used less efficiently as a renewable energy source, but with the development of fluidized biomass gasification technology, it can play an increasing role in industrial production. A fluidized bed biomass gasifier has a strong nonstationary process due to its complex energy−mass exchange, and analysis of its complex reaction process and products has relied on experiments for a long time. This paper uses a Euler−Euler two-fluid model to establish a three-dimensional CFD model of the fluidized bed biomass gasifier, on which factors affecting syngas generation are analyzed. The simulation shows that increasing the initial bed temperature can effectively improve syngas production, while increasing the air equivalent is not beneficial for syngas production.

Biomass gasification is a versatile thermochemical process that can be used for direct energy applications and the production of advanced liquid and gaseous energy carriers. In the present work, the results are presented concerning the H2 production at a high purity grade from biomass feedstocks via steam/oxygen gasification. The data demonstrating such a process chain were collected at an innovative gasification prototype plant coupled to a portable purification system (PPS). The overall integration was designed for gas conditioning and purification to hydrogen. By using almond shells as the biomass feedstock, from a product gas with an average and stable composition of 40%-v H2, 21%-v CO, 35%-v CO2, 2.5%-v CH4, the PPS unit provided a hydrogen stream, with a final concentration of 99.99%-v and a gas yield of 66.4%.

The NiO-MgO solid solution has been proven to be an efficient catalyst for the carbon dioxide reforming of methane (CRM). However, the challenge is still there for the facilely controlled synthesis of the single-phase solid solution with the uniform composition, and the interactions between NiO and MgO are not consistently correlated with the CRM performance. To address these issues, in this work, the complex-decomposition method was applied to regulate the chemical and structural properties of NiO-MgO catalysts via simply changing the complexing agent, calcination temperature, and Ni/Mg molar ratio. The catalysts were comparatively evaluated for CRM under severe reaction conditions of 750 °C, 0.1 MPa, CH4/CO2 = 1, and a gas hourly space velocity of 60000 mL·g−1·h−1. Irrespective of the complexing agents investigated, NiO-MgO solid solution was exclusively formed. However, the structural and reductive properties of the NiO-MgO catalysts were strongly dependent on the complexing agent,... [more]

This study reports the dry reforming of methane (DRM) using non-thermal plasma in a swirl-induced point-plane electrode discharge reactor to produce syngas. This reactor geometry facilitates better mixing of the reactant gases in the plasma region, thus increasing the residence time and conversion of the reactants. The effect of varying flow rates and compositions of CO2/CH4 (v%/v%) on conversion was studied. A high-voltage AC power input of 50 W and 70 W at a frequency of 19 kHz was provided. The voltage−current characteristics with respect to time were studied. The results show that with an increase in the flow rate of the gas mixture from 0.5 to 2 LPM the conversion of both CO2 and CH4 decreases, while an increase in the concentration of CO2 or CH4 (from 25 to 75%) increases the conversion of the respective reactant. The products, viz. syngas (CO and H2), C2 hydrocarbons, and solid carbon, were characterized and quantified. The maximum total conversion of 44% was obtained for a CO2:... [more]

Biofuels have become a source of renewable energy to offset the use of fossil fuels and meet the demand for electricity, heat, and cooling in the industrial sector. This study aims to (a) develop a simulation of a trigeneration system based on a gas turbine cycle and an absorption chiller unit, using biomass and syngas from spent coffee grounds (SCGs) to replace the conventional system currently supplying the energy requirements of an instant coffee plant located in Guayaquil, Ecuador, and (b) carry out an exergoeconomic analysis of the simulated system to compare the effects of different fuels. The results showed an increase in the exergetic efficiency from 51.9% to 84.5% when using a trigeneration system based on biomass instead of the conventional non-integrated system. Furthermore, the biomass-based system was found to have the lowest operating costs ($154.7/h) and the lowest heating, cooling, and power costs ($10.3/GJ, $20.2/GJ, and $23.4/GJ, respectively). Therefore, the results... [more]

The paper deals with the experimental study of a medium-load spark ignition engine under operation with different fuel mixtures among those deemed as promising for the transition towards carbon-free energy systems. In particular, the performance of a non-conventional ignition system, which permits the variation of the ignition energy, the spark intensity and duration, was studied fuelling the engine with 60−40% hydrogen−methane blends, three real syngas mixtures and one biogas. The paper is aimed to find the optimal ignition timing for minimum specific fuel consumption and the best setup of the ignition system for each of the fuel mixtures considered. To this end, a series of steady-state tests were performed at the dynamometer by varying the parameters of the ignition system and running the engine with surrogate hydrogen−methane−nitrogen mixtures that permit the simulation of hydrogen−methane blends, real syngas, and biogas. The results quantify the increase of spark advance associate... [more]

The performance of a perovskite-based oxygen carrier for the partial oxidation of methane in thermochemical energy storage applications has been investigated. A synthetic perovskite with formula La0.6Sr0.4FeO3 has been scrutinized for Chemical Looping Reforming (CLR) of CH4 under fixed-bed and fluidized-bed conditions. Temperature-programmed reduction and oxidation steps were carried out under fixed-bed conditions, together with isothermal reduction/oxidation cycles, to evaluate long-term perovskite performance. Under fluidized-bed conditions, isothermal reduction/oxidation cycles were carried out as well. Results obtained under fixed-bed and fluidized-bed conditions were compared in terms of oxygen carrier reactivity and stability. The oxygen carrier showed good reactivity and stability in the range 800−1000 °C. An overall yield of 0.6 Nm3 of syngas per kg of perovskite can be reached per cycle. The decomposition of CH4 catalyzed by the reduced oxide can also occur during the reductio... [more]

The consumption of fossil fuels is one of the main drivers of climate change. Lignin derived from biomass is a carbon-neutral raw feedstock, and its conversion into fuels is gaining much attention. The gasification of biomass aims to transform heterogeneous feedstocks into syngas and heat that could be used for various purposes. Lignin is a biomass feedstock of special interest due to its particular properties and its ability to be obtained in abundant quantities as a side product from the paper pulp industry as well as the growing cellulosic ethanol industry. This review explores the existing works regarding lignin gasification from different perspectives and compares the results obtained with other existing thermochemical processes, in addition to providing a perspective on the long-term fate of gasification as a technology compared to other emerging technologies. The analysis indicates that while lignin gasification may grow in importance in the near future due to increased interest... [more]

The perspective of the emerging environmentally friendly and economically efficient detonation gun technology for the high-temperature gasification of organic wastes with ultra-superheated mixture of steam and carbon dioxide is discussed. The technology is readily scalable and allows the establishment of a highly reactive atmospheric-pressure environment in a compact water-cooled gasifier due to very high local temperature (above 2000 °C), intense in situ shock-induced fragmentation of feedstock, and high-speed vortical convective flows enhancing interphase exchange processes. These unique and distinctive features of the technology can potentially provide the complete conversion of solid and liquid wastes into syngas, consisting exclusively of hydrogen and carbon monoxide; microparticles, consisting of environmentally safe simple oxides and salts of mineral residues, as well as aqueous solutions of oxygen-free acids such as HCl, HF, H2S, etc., and ammonia NH3. A small part of the synga... [more]

To become sustainable, the production of electricity has been oriented towards the adoption of local and renewable sources. Distributed electric and thermal energy generation is more suitable to avoid any possible waste, and the Micro Gas Turbine (MGT) can play a key role in this scenario. Due to the intrinsic properties and the high flexibility of operation of this energy conversion system, the exploitation of alternative fuels and the integration of the MGT itself with other energy conversion systems (solar field, ORC, fuel cells) represent one of the most effective strategies to achieve higher conversion efficiencies and to reduce emissions from power systems. The present work aims to review the results obtained by the researchers in the last years. The different technologies are analyzed in detail, both separately and under a more complete view, considering two or more solutions embedded in micro-grid configurations.

Thermochemical processes use heat and series of endothermic chemical reactions that achieve thermal cracking and convert a wide range of solid waste deposits via four thermochemical processes to hydrocarbon gaseous and liquid products such as syngas, gasoline, and diesel. The four thermochemical reactions investigated in this research article are: incineration, pyrolysis, gasification, and integrated gasification combined cycle (IGCC). The mentioned thermochemical processes are evaluated for energy recovery pathways and environmental footprint based on conceptual design and Aspen HYSYS energy simulation. This paper also provides conceptual process design for four thermochemical processes as well as process evaluation and techno-economic analysis (TEA) including energy consumption, process optimization, product yield calculations, electricity generation and expected net revenue per tonne of feedstock. The techno-economic analysis provides results for large scale thermochemical process t... [more]

The tri-reforming process was employed for syngas production from biogas at elevated pressures in this study. In the tri-reforming process, air and water were added simultaneously as reactants in addition to the main biogas components. The effects of various operating parameters such as pressure, temperature and reactant composition on the reaction performance were studied numerically. From the simulated results, it was found that methane and carbon dioxide conversions can be enhanced and a higher hydrogen/carbon monoxide ratio can be obtained by increasing the amount of air. However, a decreased hydrogen yield could result due to the reverse water⁻gas shift reaction. A higher level of methane conversion and hydrogen/carbon monoxide ratio can be obtained with increased water addition. However, negative carbon dioxide conversion could result due to the water⁻gas shift and reverse carbon dioxide methanation reactions. The dry reforming reaction resulting in positive carbon dioxide conver... [more]

The performance of a top-lit updraft gasifier affected by biomass (pine wood) particle size, moisture content and compactness was studied in terms of the biochar yield, biomass burning rate, syngas composition and tar content. The highest biochar yield increase (from 12.2% to 21.8%) was achieved by varying the particle size from 7 to 30 mm, however, larger particles triggered tar generation that reached its maximum of 93.5 g/m³ syngas at 30-mm biomass particles; in contrast, the hydrogen content in syngas was at its minimum of 2.89% at this condition. The increase in moisture content from 10% to 22% reduced biochar yield from 12% to 9.9%. It also reduced the tar content from 12.9 to 6.2 g/m³ which was found to be the lowest range of tar content in this work. Similarly, the carbon monoxide composition in syngas decreased to its minimum of 11.16% at moisture content of 22%. Finally, the biomass compactness increased biochar yield up to 17% when the packing mass was 3 kg. However, the add... [more]

A novel method for quasi-continuous tar monitoring in hot syngas from biomass gasification is reported. A very small syngas stream is extracted from the gasifier output, and the oxygen demand for tar combustion is determined by a well-defined dosage of synthetic air. Assuming the total oxidation of all of the combustible components at the Pt-electrode of a lambda-probe, the difference of the residual oxygen concentrations from successive operations with and without tar condensation represents the oxygen demand. From experiments in the laboratory with H2/N2/naphthalene model syngas, the linear sensitivity and a lower detection limit of about 70 ± 5 mg/m3 was estimated, and a very good long-term stability can be expected. This extremely sensitive and robust monitoring concept was evaluated further by the extraction of a small, constant flow of hot syngas as a sample (9 L/h) using a Laval nozzle combined with a metallic filter (a sintered metal plate (pore diameter 10 µm)) and a gas pump... [more]

A thermal behavior study of lipid-extracted Nannochloropsis gaditana (LEA) was performed in a thermogravimetric analyzer. The study was performed by heating the sample under different heating rates (5, 10, and 15 °C/min) from room temperature to 1000 °C using N2 gas as the medium. This is crucial for thermal stability studies in a kinetic control regime. The following three stages of chemical decompositions were found: (1) moisture removal (2) devolatilization (3) fixed carbon decomposition; maximum decomposition was observed at the second stage. Activation energies of the LEA were studied using the Flynn−Wall−Ozawa model and Kissinger−Akahira−Sunose model. Main sample decomposition was observed from 100−700 °C during volatile matter evaporation. The thermal behavior study findings were used for the gasification of the sample with air to study the effect of varying reaction parameters on the compositions of the synthesis gas yield. Maximum H2 yield was found at 700 °C and 0.7 g, which... [more]

This work focuses on the energy and economic evaluation of a power generation system composed of a downdraft gasifier and gas microturbine. The gasification process was studied using wood pellets as fuel, while the influence of two gasification agents (air and oxygen-enriched air) on parameters, such as low heating value (LHV), composition, and yield of syngas, were analyzed. The syngas produced from oxygen-enriched air gasification in a downdraft gasifier had an LHV higher than 8 MJ/Nm3, being suitable to be supplied in the gas microturbine. Subsequently, syngas use in the gas microturbine was evaluated, and the results demonstrated that microturbine efficiency dropped from 33.00% to 21.35%, while its power decreased from 200 kW to 81.35 kW. The power generation system was modeled using Aspen Plus® v 11.0 software and validated using results obtained from published experimental studies. Accordingly, the integrated generation system presented an overall efficiency of 11.82% for oxygen-... [more]

Gaining energy independence by utilizing new and renewable energy resources has become imperative for Korea. Energy recovery from Korean municipal solid waste (MSW) could be a promising option to resolve the issue, as Korean MSW is highly recyclable due to its systematic separation, collection and volume-based waste disposal system. In this study, gasification experiments were conducted on Korean municipal waste-derived solid fuel (SRF) using a fixed bed reactor by varying the equivalence ratio (ER) to assess the viability of syngas production. Experiments were also conducted on coal and biomass under similar conditions to compare the experimental results, as the gasification applicability of coal and biomass are long-established. Experimental results showed that Korean SRF could be used to recover energy in form of syngas. In particular, 50.94% cold gas efficiency and 54.66% carbon conversion ratio with a lower heating value of 12.57 MJ/Nm3 can be achieved by gasifying the SRF at 0.4... [more]

A two-dimensional (2D) Computational Fluid Dynamics (CFD) scale-up model of the Fischer Tropsch reactor was developed to thermally compare the Microfibrous-Entrapped-Cobalt-Catalyst (MFECC) and the conventional Packed Bed Reactor (PBR). The model implements an advanced predictive detailed kinetic model to study the effect of a thermal runaway on C5+ hydrocarbon product selectivity. Results demonstrate the superior capability of the MFECC bed in mitigating hotspot formation due to its ultra-high thermal conductivity. Furthermore, a process intensification study for radial scale-up of the reactor bed from 15 mm internal diameter (ID) to 102 mm ID demonstrated that large tube diameters in PBR lead to temperature runaway >200 K corresponding to >90% CO conversion at 100% methane selectivity, which is highly undesirable. While the MFECC bed hotspot temperature corresponded to 30% CO conversion, attributing to significantly high thermal conductivity of the MFECC bed. Moreover, a noticeable i... [more]

This is an Aspen Plus v12 model for a Rectisol process used for removing CO2 from a shifted syngas stream arising from steam methane reforming for the purposes of Blue hydrogen production. It is intended for educational use, and is useful as a starting point for those interested in simulating this process. It is not optimized in any way, but it contains a working flowsheet for those interested in modifying it for your own purposes.

The simulation was developed using the simulation strategy given in Adams TA II, Khojestah Salkuyeh Y, Nease J. Processes and Simulations for Solvent-based CO2Capture and Syngas Cleanup. Chapter in: Reactor and process design for in sustainable energy technology. Elsevier (2014). Pages 163-232. ISBN: 978-0-444-59566-9. It is based on the process discussed in Doctor RD, Molburg JC, Thimmapuram PR, Berry GF, Livengood CD. Gasification combined cycle: carbon dioxide recovery, transport, and disposal. US DOE Report, Argonne National Laboratory ANL/ESD-24. 19... [more]

Syngas (CO, CO2, and H2) has attracted special attention due to the double benefit of syngas fermentation for carbon sequestration (pollution reduction), while generating energy. Syngas can be either produced by gasification of biomasses or as a by-product of industrial processes. Only few microorganisms, mainly clostridia, were identified as capable of using syngas as a substrate to produce medium chain acids, or alcohols (such as butyric acid, butanol, hexanoic acid, and hexanol). Since CO plays a critical role in the availability of reducing equivalents and carbon conversion, this work assessed the effects of constant CO partial pressure (PCO), ranging from 0.5 to 2.5 atm, on cell growth, acid production, and solvent production, using Clostridium carboxidivorans. Moreover, this work focused on the effect of the liquid to gas volume ratio (VL/VG) on fermentation performances; in particular, two VL/VG were considered (0.28 and 0.92). The main results included—(a) PCO affected the grow... [more]

The realization of some composite materials that allow the best removal of H2S from syngas was the main objective of this work. Thus, the optimization of the technological parameters for obtaining composites based on Zn-Ti was achieved. The paper studies the influence of calcination temperature on the characteristics of the binary ZnO-TiO2 system used to synthesize a composite material with suitable properties to be used subsequently for syngas treatment. The mineralogical and structural analyzes showed that starting with the calcination temperature of 700 °C the material synthetized is composed mainly of zinc orthotitanate which possess the corresponding characteristics to be finally used in the treatment of the syngas for its desulfurization. At this calcination temperature the material has a compact structure most likely due to sintering of the formed titanates. These composites have a texture that places them rather in the category of non-porous materials, the pore volume and their... [more]