Search Results (41)

This study investigates a hybrid renewable energy system combining the municipal solid waste (MSW) gasification and solar photovoltaic (PV) for electricity generation in Lobito, Angola. A fixed-bed downdraft gasifier was selected for MSW gasification, where the thermal decomposition of waste under controlled air flow produces syngas rich in CO and H₂. The syngas is treated to remove contaminants before powering a combined cycle. The PV system was designed for optimal energy generation, considering local solar radiation and shading effects. Simulation tools, including Aspen Plus v11.0, PVsyst v8, and HOMER Pro software 3.16.2, were used for modeling and optimization. The hybrid system generates 62 GWh/year of electricity, with the gasifier contributing 42 GWh/year, and the PV system contributing 20 GWh/year. This total energy output, sufficient to power 1186 households, demonstrates an integration mechanism that mitigates the intermittency of solar energy through continuous MSW gasification. However, the system lacks surplus electricity for green hydrogen production, given the region’s energy deficit. Economically, the system achieves a Levelized Cost of Energy of 0.1792 USD/kWh and a payback period of 16 years. This extended payback period is mainly due to the hydrogen production system, which has a low production rate and is not economically viable. When excluding H₂ production, the payback period is reduced to 11 years, making the hybrid system more attractive. Environmental benefits include a reduction in CO₂ emissions of 42,000 t/year from MSW gasification and 395 t/year from PV production, while also addressing waste management challenges. This study highlights the mechanisms behind hybrid system operation, emphasizing its role in reducing energy poverty, improving public health, and promoting sustainable development in Angola. Full article

This research study explores the technology of biomass syngas production by using an experimental downdraft fixed-bed gasifier coupled to a two-cylinder engine, designed and implemented at the Polytechnic University of Valencia, Spain. Furthermore, it deals with the study of the experimental and analytical relations between the driving thermodynamic parameters that control the gasification process, in order to contribute to the development of a theoretical model for the design of a small-scale gasification facility. Different experiments have been performed to investigate the variations in parameters such as low heating values, the air–syngas ratio, the reduction and combustion temperature, efficiency, and electrical power generation during the continuous functioning of the gasification power production facility. The results obtained show that the low heating value is directly related to the inlet air flow rate, so that it increases when the air flow increases, while the increase in the inlet air flow of the gasifier makes both the reduction and the combustion temperature increase. Moreover, the efficiency of the motor–generator reaches a maximum value of 0.204 at the maximum power (around 5 kW), being characterized by an excellent operating range for the air–fuel ratio of a gasification facility. Full article

Mixed plastic/biomass co-gasification stands out as a promising and environmentally friendly technology, since it reduces wide solid wastes and produces green hydrogen. High-quality syngas can be obtained by virtue of the process design and optimization of a downdraft fixed-bed co-gasifier. The design is based on the actual reaction zones within a real gasifier to ensure accurate results. The methodology shows that (i) the co-gasifier modeling is validated using the adiabatic RGibbs model in Aspen Plus, (ii) the performance of the co-gasifier is evaluated using cold-gas efficiency (CGE) and carbon conversion efficiency (CCE) as indicators, and (iii) the multi-objective optimization (MOO) is employed to optimize these indicators simultaneously, utilizing a standard genetic algorithm (GA) combined with response surface methodology (RSM) to identify the Pareto frontier. The optimal conditions, resulting in a CGE of 91.78% and a CCE of 83.77% at a gasifier temperature of 967.89 °C, a steam-to-feed ratio of 1.40, and a plastic-to-biomass ratio of 74.23%, were identified using the technique for order of preference by similarity to ideal solution (TOPSIS). The inclusion of plastics enhances gasifier performance and syngas quality, leading to significant improvements in CGE and CCE values. Full article

Awareness of the consequences of waste mismanagement has resulted in urban planners looking for effective disposal techniques with the added benefit of energy generation. The decision regarding an energy conversion technique to adopt on a community level is based on different technology assessment factors with maximum weightage on environmental effects. Gasification techniques in general and thermal gasification strategies in particular are appropriate methods when environmental impacts are to be minimized. Thermal gasification techniques have evolved with different configurations, syngas generation rates, and other advantages and disadvantages; hence, the selection of the right technique is essential, and establishing guidelines for decision-makers is necessary. The six different gasifiers considered in the present study were updraft gasifiers, downdraft gasifiers, cross-draft gasifiers, bubbling fluidized bed gasifiers, circulating fluidized bed gasifiers, and dual-bed fluidized bed gasifiers. The assessments performed in the present study are based on the attributes of the different techniques using the multi-criteria decision method. Multi-criteria decision analysis is an appropriate method proven to be an ideal procedure in these situations. Attribute values for gasifier performance, environmental effects, economic performance indices, and fuel requirements were determined from collected waste assessment data and published information. Analysis was performed for both recycling and non-recycling scenarios of waste utilization by applying different weight scenarios for the attributes. Results of the study indicate that downdraft gasifiers showed the best performance in terms of environmental effects under the recycling scenario, with 0.1% and 0.0125% by volume of carbon dioxide and methane emissions, and under the non-recycling scenario, with 0.125% and 0.02% by volume of carbon dioxide and methane emissions. Downdraft gasifiers had high overall rankings in performance when evaluated against different entropy weights for both scenarios. The results of the study can be applied to urban communities in different climatic regions as well as for different scales of operation. Full article

This study presents the experimental results obtained from hybrid filtration combustion using biomass pellets. The experiments were carried out using a porous media gasifier filled with pellets and inert material. The gasifying agent used was an air–steam mixture, with 40% being steam. The dependence of the temperature in the gasifier’s reaction zone from the volume percentage of inert porous material in the gasifier, the specific heat capacity of this material, as well as the air–steam blowing rate, was investigated. The multifactor experiment method was used. A maximum temperature of 1245 °C was achieved using 28 vol% of porous material with a heat capacity of 1000 J/(kg·°C) and at a blowing rate of 42 m³/h. The maximum hydrogen content in the syngas was 28 vol%. This was achieved at an air–steam blowing rate of 42 m³/h and 40 vol% porous material, with a heat capacity of 1000 J/(kg·°C). The calorific value of the syngas was 12.6 MJ/m³. The highest CO content in the gas was 28 vol% and was obtained at 20 vol% porous material with a heat capacity of 1000 J/(kg·°C) and a blowing rate of 42 m³/h. The obtained information is applicable in the design, management, and control of gas production by way of a hybrid filtration combustion process in a downdraft gasifier. Full article

In this study, a technical analysis of synthesis gas (syngas) and biodiesel blend utilized in an internal combustion engine is presented. The experimental setup is composed of an engine workbench coupled with a downdraft gasifier which was fed with forest biomass and municipal solid waste at a blending ratio of 85:15, respectively. This research paper aims to contribute to the understanding of using fuel blends composed of synthesis gas and biodiesel, both obtained from residues produced in a municipality, since the waste-to-energy approach has been trending globally due to increasing waste generation allied with rising energy demand. The experiments’ controlling parameters regarding the engine are rotation and torque, exhaust gas temperature, and fuel consumption. The gasification parameters such as the oxidation and reduction temperatures, pressures at the filter, hood, and reactor, and the volume of tars and chars produced during the thermochemical process are also presented. Ultimate and proximate analyses of raw materials and fuels were performed, as well as the chromatography of produced syngas. The syngas produced from forest biomass and MSW co-gasification at a blending ratio in mass of 85:15 presented an LHV of around 6 MJ/m³ and 15% of H₂ in volume. From the experiment using syngas and biodiesel blend in the engine, it is concluded that the specific consumption at lower loads was reduced by 20% when compared to the consumption of the same engine operating with regular diesel. The development of co-gasification of forest and municipal waste may then be an interesting technology for electrical energy decentralized generation. Full article

The depletion of fossil-based fuels, fluctuating fuel market, and environmental deterioration demand an aggressive approach towards the advancement of renewable energy technologies. By the time reliable technology for a clean and abundant energy supply is established, existing sources must be economized. Biomass gasification is the way forward in that direction. CFD modeling shows promise in the development of advanced gasification systems. A simplified 3D CFD model of a downdraft gasifier is developed to investigate the effect of gasifying agent composition on the quality of syngas. Simulation results are compared with published experimental data and found to be in reasonably good agreement. Mixing CO₂ with a gasification agent is also investigated as a possible carbon capture and utilization (CCU) strategy. An air-steam mixture is used as a base-case gasification agent. Firstly, the effect of air-to-steam ratio on syngas composition is investigated. Secondly, the effect of oxygen and mixing CO₂ with a gasification agent is investigated in two separate cases. A 50%-50% air-steam mixture is found to produce the best quality syngas. Oxygen is found to have a negligible impact on the quality of syngas. The air-steam-CO₂ = 23%-50%-15% mixture is found to be optimum regarding syngas quality. Full article

A substantial number of off-grid olive oil mills in Morocco are powered by diesel-fired generators, which hugely contribute to air pollution and greenhouse gas emissions. In this research work, a biomass gasification combined heat and power (CHP) plant fueled with local by-products was explored as a renewable alternative to electrify off-grid olive oil mills in this country. The case study considered a gasification CHP plant with a rated power of 80 kW_e, in order to enable adaptation of the producer gas flow rate to abrupt changes in the power generation unit under dynamic operation. A downdraft gasifier and a producer gas conditioning unit were modeled under steady state operation using Cycle-Tempo, while the power generation unit was modeled in the Thermoflex simulation environment under partial and full load operation. Olive cake pellets and olive pruning chips were evaluated as biomass feedstock, with moisture contents ranging from 5% to 20% (wet basis). The results from the simulation of the gasification CHP plant showed net electrical efficiencies and CHP efficiencies around 18% and 35%, respectively. Finally, a profitability assessment of the gasification CHP plant was developed for 2 months of continuous operation, together with a sensitivity analysis. The results for the baseline scenario reveal a payback period of 7–8 years and a 68.5% accumulated profit based on the capital investment, which suggest that biomass gasification CHP plants can represent an economically feasible and sustainable solution for the electrification of off-grid areas in Morocco. Full article

In this study, biomass–specific gasification data is experimentally collected for numerical simulations of fixed–bed reactors. Since biomass properties vary, it is crucial to have characteristic biomass data. Extensive data is collected to determine an appropriate description of specific biomass behavior, including basic data (e.g., heating value, size, densities, ultimate and total analysis etc.), biomass pyrolysis and heterogeneous gasification reaction data. Heterogeneous reactions were comparatively investigated in the forms of powder, particles, and a fixed–bed. The powder was investigated in depth with CO₂, O₂, and H₂O (gas fraction 5–20 vol.%; temperature CO₂, O₂ and H₂O, respectively, at 730–790 °C, 360–405 °C, 720–780 °C), while particle reactions and fixed–bed reaction were only studied with CO₂. A model description for a fixed–bed batch reactor was applied, modified, and compared to experimental fixed–bed batch reactor results. This study concludes that determining the appropriate characteristic particle size and parameters for the porous structure of specific biomass char is essential for simulation based on preliminary biomass characterization. Therefore, in future investigations, the description for biomass-specific differences between powder, single particles, and bulk of biomass char may be of greater focus, also taking into consideration O₂ and H₂O. Full article

In order to exchange the wood biomass energy for electric power with small capacity and high efficiency, it is most effective to use a reciprocating engine operated with a wood gasifier. On the other hand, such a small-capacity system is often installed in urban areas. Therefore, strict emission regulation should be observed. Normally, as the low heating value (LHV) of bio-syngas is small, the engine should be operated with a stoichiometric mixture to achieve a maximum power density. However, the emission with a stoichiometric mixture contains much unburned CO. This means that a stoichiometric mixture operation shows low efficiency and can’t observe the regulations. In this report, a mechanism of the unburned CO is considered, and a method to reduce the unburned CO ratio is shown with experimental results. In the experiment, a commercial reciprocating engine (4-stroke, modified single cylinder) is used. The bio-syngas, a producer gas from a fixed bed gasifier, is produced by a self-made wood pellet gasifier (fixed bed, auto thermal down-draft). The bio-syngas flow rate is calculated with the nitrogen ratio between input air and bio-syngas. The LHV is adjusted with the city gas (as an alternative to methane) and hydrogen. The CO volume ratio of the exhaust from the engine is more than 3 v% when the excess air ratio of bio-syngas/air mixture is 1.3, as the LHV of bio-syngas is less than 5.0 MJ/m³-LHV. On the other hand, the CO volume ratio of the exhaust under operation of the mixture, the bio-syngas, and methane with more than 7.0 MJ/m³-LHV was less than 0.2 v%. The CO in the exhaust with low LHV fuel means that the combustion is not finished in the chamber. The unburned ratio could be predicted in consideration of the gap/clearance as crevice, the temperature boundary layer, and the quenching distance. Full article

In this work, a study was performed on the influence of the ratio of height to the diameter of the reduction zone of a small-size downdraft gasifier as well as of the fuel fraction sizes on the gas quality (the quality was evaluated for CO content). The ratio of a full side area to the volume of a fuel fraction (SVR) was used as a fuel parameter. The maximum CO concentration was observed when using a small fuel fraction with SVR—0.7–0.72 mm⁻¹ and when adhering to the ratio of height to the diameter of the reduction zone H/D—0.5–0.6. The maximum electric power for gasoline generators (nominal power equaled 4 kW) when using the gas received from the fast-growing hybrid willow biomass equaled 2.4 kW. This power is 37.5% lower than when using gasoline and 7.0% lower than when using the gas received from the hardwood biomass. The emissions of harmful gases into the atmosphere by the gasoline generator engine equaled 0.12–0.14% CO and 24–27 mln⁻¹ C_xH_y. The emissions were 64.8 times less for CO and 8.5 times less for C_xH_y when compared with using gasoline. Full article

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-enriched air gasification cases. On the other hand, an economic assessment through risk analysis using Monte Carlo simulations was performed using Crystal Ball^® v11.1.2.4.850 software. The economic results indicated that the implementation of a generation system was economically unfeasible, however, if the electricity rate price was increased by 63%, the proposed configuration could be feasible. Full article

Gasification is a promising thermochemical technology used to convert waste materials into energy with the introduction of low amounts of an oxidant agent, therefore producing an environmental impact that is lower when compared to incineration and landfilling. Moreover, gasification allows a sustainable management of wastes and reduces the use of fossil fuels responsible for the increment of greenhouse gases. This work aimed to perform gasification tests with solid recovered fuels (SRF) containing organic fractions mainly retrieved from construction and demolition wastes to assess the potential for energy conversion. Tests were conducted in a pilot-scale downdraft gasifier (maximum feedstock input of 22 kg/h) at c.a. 800 °C, using SRF samples containing different proportions of polymeric wastes ranging between 0 and 20 wt %. Gas and chars obtained as by-products were analysed to evaluate their properties and to establish valid pathways for their valorisation. The addition of polymeric wastes reduced char production but rose both tar and HCl concentrations in the gas. The SRF with 10 wt % of polymeric wastes generated the best results, producing the highest calorific value for the gas (3.5 MJ/Nm³) and the highest cold-gas efficiency (45%). Possible char applications include their use as catalysts for tar decomposition, or as an additive in construction materials. Gasification can therefore be considered a valid solution for the energetic valorisation of these SRFs. Full article

A theoretical evaluation of the biochar production process using a biomass gasifier has been carried out herein. Being distinguished from the previous research trend examining the use of a biomass gasifier, which has been focused on energy efficiency, the present study tries to figure out the effect of biochar production rate on the overall process performance because biochar itself has now been given a spotlight as the main product. Biochar can be utilized for agricultural and industrial purposes, along with the benefit of climate change mitigation. A thermodynamic model based on chemical equilibrium analysis is utilized to demonstrate the effect of biochar production rate on the producer gas characteristics such as gas composition, LHV (lower heating value) and cold gas efficiency. Three gasifier models using chemical equilibrium model are reconstructed to simulate biochar-producing gasifiers, and seven kinds of biomass are considered as feed material. Depending on the assumptions applied to the models as well as the biomass types, the results of the simulation show a large variance, whereas the biochar yield rate increases. Through regression analysis with a generalized reduced gradient optimization method, simplified equations to estimate the cold gas efficiency (CGE) and LHV of producer gas of the biochar production process were derived as having six parameters of biomass LHV, fractions of ash, carbon and water, reduction zone temperature, and biochar yield rate. The correlation factors between the thermodynamic model and the regression model are 96.54% and 98.73% for the LHV of producer gas and CGE, respectively. These equations can supply the pre-estimation of the theoretical maximum performance of a planning biochar plant. Full article

The conversion of biomass to olefin by employing gasification has recently gained the attention of the petrochemical sector, and syngas composition is a keystone during the evaluation of process design. Process simulation software is a preferred evaluation tool that employs stoichiometric and kinetic approaches. Despite the available literature, the estimation errors of these simulation methods have scarcely been contrasted. This study compares the errors of stoichiometric and kinetic models by simulating a downdraft steam gasifier in PRO/II. The quantitative examination identifies the model that best predicts the composition of products for the gasification of Japanese wood waste. The simulation adopts reaction mechanisms, flowsheet topology, reactions parameters, and component properties reported in the literature. The results of previous studies are used to validate the models in a comparison of the syngas composition and yield of products. The models are used to reproduce gasification at temperatures of 600∼900 °C and steam-to-biomass mass ratios of 0∼4. Both models reproduce experimental results more accurately for changes in the steam-to-biomass mass ratio than for temperature variations. The kinetic model is more accurate for predicting composition and yields, having global errors of 3.91%-mol/mol and 8.16%-g/g_BM, respectively, whereas the simple stoichiometric model has an error of 7.96%-mol/mol and 16.21%-g/g_BM. Full article