Search Results (8)

Chemical looping gasification (CLG) based on interconnected fluidized beds is a viable technology to produce a syngas stream for chemical and fuel production. In this work, microalgae are studied for use in the CLG process; more specifically, the intrinsic kinetics of char gasification have been analyzed, as it is important for the fuel conversion and design of reactor systems. Char produced from fast pyrolysis was used in a thermogravimetric analyzer (TGA) for intrinsic kinetics analysis, and measures were made to eliminate the interparticle and external particle gas diffusion. The effect of typical operational variables, such as temperature, concentration of gasification agents (H₂O and CO₂), and concentration of gasification products (H₂ and CO), were investigated. The TGA data is used to derive a suitable gasification model that can best fit the experimental data. The fitting with experiments then generates values of the model’s kinetics parameters. Based on the model and the kinetics values, the activation energies in the gasification with steam and CO₂ were calculated to be 43.3 and 91.6 kJ/mol, respectively. The model has a good capability in the prediction of the gasification profile with H₂O and CO₂ under a complex reacting atmosphere. Full article

The inefficient disposal of corn stover (CS) and the accumulation of magnesite tailings (MMTs) pose dual environmental threats. Although biomass gasification can utilize CS, its inherent drawbacks result in syngas with low heating value and high tar content. Torrefaction pretreatment can effectively improve biomass properties, and the use of steam as a reaction medium can further optimize the product’s pore structure. This study proposes a steam-assisted torrefaction pretreatment to address the inefficient utilization of CS and the disposal challenges of MMTs. The experimental results demonstrated that torrefaction at 300 °C with 30% water content for 60 min significantly improved the raw material’s properties. The optimized CSBC exhibited a well-developed pore structure and achieved a phenol removal rate of 63.4%. The addition of MMTs further enhanced the pretreatment effect, increasing the removal rate to 75.5% and confirming the superiority of the CSBC–magnesite composite system. The steam atmosphere improved phenol adsorption by regulating pore structures and surface functional groups, offering a feasible approach for utilizing solid waste resources and developing a new in situ tar control strategy. Full article

The thermodynamic modeling of waste oil (WO) gasification by a high-temperature gasification agent (GA) composed of an ultra-superheated H₂O/CO₂ mixture is carried out. The GA is assumed to be obtained by the gaseous detonation of fuel–oxidizer–diluent mixture in a pulsed detonation gun (PDG). N-hexadecane is used as a WO surrogate. Methane or the produced syngas (generally a mixture of H₂, CO, CH₄, CO₂, etc.) is used as fuel for the PDG. Oxygen, air, or oxygen-enriched air are used as oxidizers for the PDG. Low-temperature steam is used as a diluent gas. The gasification process is assumed to proceed in a flow-through gasifier at atmospheric pressure. It is shown that the use of the detonation products of the stoichiometric methane–oxygen and methane–air mixtures theoretically leads to the complete conversion of WO into a syngas consisting exclusively of H₂ and CO, or into energy gas with high contents of CH₄ and C₂-C₃ hydrocarbons and an LHV of 36.7 (fuel–oxygen mixture) and 13.6 MJ/kg (fuel–air mixture). The use of the detonation products of the stoichiometric mixture of the produced syngas with oxygen or with oxygen-enriched air also allows theoretically achieving the complete conversion of WO into syngas consisting exclusively of H₂ and CO. About 33% of the produced syngas mixed with oxygen can be theoretically used for PDG self-feeding, thus making the gasification technology very attractive and cost-effective. To self-feed the PDG with the mixture of the produced syngas with air, it is necessary to increase the backpressure in the gasifier and/or enrich the air with oxygen. The addition of low-temperature steam to the fuel–oxygen mixture in the PDG allows controlling the H₂/CO ratio in the produced syngas from 1.3 to 3.4. Full article

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 syngas product (ideally approximately 10%) can be used for replacing a starting fuel (e.g., natural gas) for the production of a detonation-born gasifying agent, while the rest can be utilized for the production of electricity, heat, and/or chemicals. Full article

An external thermal high-temperature continuous feed moving bed tubular reactor was used for the gasification of high moisture content lignite (30.41 wt.%) under CO₂ and an auto-generated steam atmosphere. The objectives of this study are to illustrate the synergistic gasification characteristics of high moisture content lignite and CO₂ in the tubular reactor; CO₂ and auto-generated steam (steam released from the lignite) were used as gasification agents for lignite gasification. The effects of temperature and CO₂ flow rate were also investigated. Experimental results showed that when the gasification temperature increased from 800 °C to 1000 °C, the H₂ yield also increased from 8.45 mol kg⁻¹ to 17.86 mol kg⁻¹. This may indicate that the H₂O-CO₂ gasification of semi-coke was enhanced with the rise in temperature. At 900 °C, the gas yield increased with the increase in CO₂ flow rate, while the yield of char and liquid product showed an opposite trend. The lower heating value of the H₂-rich syngas varied from 11.73 MJ m⁻³ to 12.77 MJ Nm⁻³. The experimental results proved that the high moisture content lignite in-situ CO₂ gasification process is an effective methodology for the clean and efficient utilization of lignite. Full article

A functionally structured catalyst was explored for ethanol steam reforming (ESR) to generate H₂. Aluminum lathe waste strips were employed as the structured catalytic framework. The mixed metal oxide (Li-Al-O) was formed on the surface of Al lathe waste strips through calcination of the Li-Al-CO₃ layered double hydroxide (LDH), working as the support for the formation of Ni catalyst nanoparticles. NaOH and NaHCO₃ titration solutions were, respectively, used for adjusting the pH of the NiCl₂ aqueous solutions at 50 °C when developing the precursors of the Ni-based catalysts forming in-situ on the Li-Al-O oxide support. The Ni precursor on the Al structured framework was reduced in a H₂ atmosphere at 500 °C for 3 h, changing the hydroxide precursor into Ni nanoparticles. The titration agent (NaOH or NaHCO₃) effectively affected the physical and chemical characterizations of the catalyst obtained by the different titrations. The ESR reaction catalyzed by the structured catalysts at a relatively low temperature of 500 °C was studied. The catalyst using NaHCO₃ titration presented good stability for generating H₂ during ESR, achieving a high rate of H₂ volume of about 122.9 L/(g_cat·h). It also had a relatively low acidity on the surface of the Li-Al-O oxide support, leading to low activity for the dehydration of ethanol and high activity to H₂ yield. The interactions of catalysts between the Ni precursors and the Li-Al-O oxide supports were discussed in the processes of the H₂ reduction and the ESR reaction. Mechanisms of carbon formation during the ESR were proposed by the catalysts using NaOH and NaHCO₃ titration agents. Full article

This research aimed to assess the process conditions, temperature and pressure, on the gasification of alternative refuse-derived fuel (RDF) in the atmosphere of steam and carbon dioxide on a laboratory scale using a fixed bed reactor. For this reason, the selected RDF were analysed, including proximate and ultimate analysis, mercury content and ash composition. After that, isothermal gasification measurements using the thermovolumetric method were performed under various temperatures (700, 750, 800, 900 °C) and pressures (0.5, 1, 1.5 MPa), using steam and carbon dioxide as gasifying agents. The obtained results showed that in the entire analysed range, the increase in temperature positively affect both the steam and CO₂ gasification of RDF. The formation rates of main components (H₂ and/or CO) of the resulting gas, as well as yields of gas components and maximum carbon conversion degrees increase. However, this positive effect was the greater, the lower the process pressure was. In turn, the effect of pressure was more complex. In the case of RDF steam gasification, an increase in pressure had a negative effect on the process, while when using carbon dioxide as a gasifying agent, an improvement of most analysed parameters was observed; however, only at low temperatures, 700–750 °C. Full article

The article presents an experimental laboratory setup used for the empirical determination of the gasification of coal samples in the form of solid rock, cut out in the form of a cylinder. An experimental laboratory set enabled a series of experiments carried out at 700 °C with steam as the gasification agent. The samples were prepared from the coal seam, the use of which can be planned in future underground and ground gasification experiments. The result of the conducted coal gasification process, using steam as the gasification agent, was the syngas, including hydrogen (H₂) with a concentration between 46% and 58%, carbon dioxide (CO₂) with a concentration between 13% and 17%, carbon monoxide (CO) with a concentration between 7% and 11.5%, and methane(CH₄) with a concentration between 9.6% and 20.1%.The results from the ex-situ experiments were compared with the results of numerical simulations using computational fluid dynamics (CFD) methods. A three-dimensional numerical model for the coal gasification process was developed using Ansys-Fluent software to simulate an ex-situ allothermal coal gasification experiment using low-moisture content hard coal under atmospheric conditions. In the numerical model, the mass exchange (flow of the gasification agent), the turbulence description model, heat exchange, the method of simulating the chemical reactions, and the method of mapping the porosity medium were included. Using the construction data of an experimental laboratory set, a numerical model was developed and its discretization (development of a numerical grid, based on which calculations are made) was carried out. Tip on the reactor, supply method, and parameters maintained during the gasification process were used to define the numerical model in the Ansys-Fluent code. A part of the data were supplemented on the basis of literature sources. Where necessary, the literature parameters were converted to the conditions corresponding to the experiment, which were carried out. After performing the calculations, the obtained results were compared with the available experimental data. The experimental and the simulated results were in good agreement, showing a similar tendency. Full article