Hydrogen-rich syngas production from municipal solid waste gasification through the application of central composite design: An optimization study

This study aims to investigate the influence and interaction of experimental parameters on the production of optimum H₂ and other gases (CO, CO₂, and CH₄) from gasification of municipal solid waste (MSW). Response surface method in assistance with the central composite design was employed to design the fifteen experiments to find the effect of three independent variables (i.e., temperature, equivalence ratio and residence time) on the yields of gases, char and tar. The optimum H₂ production of 41.36 mol % (15.963 mol kg-MSW⁻¹) was achieved at the conditions of 757.65 °C, 0.241, and 22.26 min for temperature, ER, and residence time respectively. In terms of syngas properties, the lower heating value and molar ratio (H₂/CO) ranged between 9.33 and 12.48 MJ/Nm³ and 0.45–0.93. The predicted model of statistical analysis indicated a good fit with experimental data. The gasification of MSW utilizing air as a gasifying agent was found to be an effective approach to recover the qualitative and quantitate products (H₂ and total gas yield) from the MSW.     

Oxidative dehydrogenation of propane with CO2 - A green process for propylene and hydrogen (syngas)

The CO₂ oxidative dehydrogenation of propane (CO₂-ODHP) reaction provides a platform to utilize carbon dioxide, a greenhouse gas and commonly available propane, in the production of value-added chemicals. A thermodynamic study of the process was achieved by simulation in the Aspen Plus software, using the method of minimization of Gibbs free energy. Sensitivity analysis was performed while varying the feed CO₂/C₃H₈ molar ratio. At higher CO₂/C₃H₈ molar ratios, lower temperatures are required to achieve higher propane conversions. The selectivity towards propylene production increased with lower CO₂/C₃H₈ ratios and higher temperatures. It was found that a feed with CO₂/C₃H₈ molar ratio of 1.0 was the optimum to obtain a syngas ratio (H₂/CO) of unity without compromising propylene product, at 850 °C and 1 bar. At higher CO₂/C₃H₈ molar ratios, selectivity towards CO is enhanced, thus results in lower syngas ratios (H₂/CO), whereas for a specific feed CO₂/C₃H₈ molar ratio higher temperatures favor selectivity to H₂, resulting in relatively higher syngas ratios.     

Hydrogen-rich syngas produced from co-gasification of municipal solid waste and wheat straw in an oxygen-enriched air fluidized bed

The gasification characteristics of solid waste and wheat straw were investigated in an oxygen-rich atmosphere by using a laboratory-scale continuous fluidized bed reactor in the range of oxidation equivalent (ER) of 0.2~0.5 and reaction temperature of 600 °C~900 °C. Gasification of biomass and waste is an economical method for hydrogen production. When air is used as a carrier gas to gasify municipal solid waste, increasing the oxygen concentration can effectively increase the hydrogen concentration of the syngas. The product distribution of gasification reaction under different mixing ratios and reaction parameters was obtained. As is shown in the results, first, when the ER is between 0.2 and 0.5, if ER decreases by 0.1, the hydrogen concentration of gas production will increase by about 30%; second, if the oxygen concentration increases by 5%, the hydrogen concentration of gas production will increase by about 14%, and the calorific value of gas production will increase by about 14–18%; third, after adding wheat straw in a ratio of 1:1, due to the reduction of plastics, the overall yield of syngas decreased, but the yield of hydrogen increased, and the concentration of hydrogen in syngas increased by 6.4%.     

H2-enriched gaseous fuel production via co-gasification of an algae-plastic waste mixture using Aspen PLUS

Thermo-chemical conversion of biomass is a promising technological alternative for producing renewable fuel and reducing waste disposal. This simulation study includes the first attempt to perform co-gasification of algae-plastic waste for H₂-enriched gaseous fuel production. An Aspen Plus-based simulation model was developed to evaluate the influence of gasifier temperature and equivalence ratio on the syngas composition, heating value, and carbon conversion efficiency. Simulation results indicated that the rise in gasifier temperature favoured the H₂ and CO formation, and further, plastic loading enhanced H₂ production to a greater extent. It was observed that the product (H₂ and CO) yield decreased significantly with the rise of the equivalence ratio. At the same time, CO₂ formation increased due to more carbon conversion after enhancing O₂ content in the gasifier. It was also noticed that the synergy of biomass and plastic waste significantly enhanced H₂ content and improved heating value, leading to a produced energy-efficient gaseous product. It is inferred that H₂-enriched feedstock acts as an H₂ donor to the H₂ deficient biomass. Based on the findings, consistency in the simulation results was observed compared with the previous literature. Hence, a mixture of biomass and plastic waste favours obtaining an energy-efficient renewable fuel that could be utilized for different applications.     

Hydrogen-rich syngas production through coal and charcoal gasification using microwave steam and air plasma torch

In the present study, microwave plasma gasification of two kinds of coal and one kind of charcoal was performed with various O₂/fuel ratios of 0–0.544. Plasma-forming gases used under 5 kW microwave plasma power were steam and air. The changes in the syngas composition and gasification efficiency in relation to the location of the coal supply to the reactor were also compared. As the O₂/fuel ratio was increased, the H₂ and CH₄ contents in the syngas decreased, and CO and CO₂ increased. When steam plasma was used to gasify the fuel with the O₂/fuel ratio being zero, it was possible to produce syngas with a high content of hydrogen in excess of 60% with an H₂/CO ratio greater than 3. Depending on the O₂/fuel ratio, the composition of the syngas varied widely, and the H₂/CO ratio necessary for using the syngas to produce synthetic fuel could be adjusted by changing the O₂/fuel ratio alone. Carbon conversion increased as the O₂/fuel ratio was increased, and cold gas efficiency was maximized when the O₂/fuel ratio was 0.272. Charcoal with high carbon and fixed carbon content had a lower carbon conversion and cold gas efficiency than the coals used in this study.     

Electro-stimulated biological production of hydrogen from municipal solid waste

Hydrogen production from municipal solid wastes was investigated by applying a weak current (0.06 A) to a slurry of municipal solid waste in an anaerobic reactor at 55 °C using 4 electrodes (carbon graphite for the cathode and platinum electroplated titanium for the anode). Current application to the organic waste stimulated the hydrogen producing bacteria especially bacteria related to the Thermotogales and Bacillus families. Measured hydrogen production rates were comprised between 16 and 41 mL/h. Comparison of bacterial and archaeal communities in methane-producing (control) and electro-stimulated reactors showed similar species but with different dynamics correlated to hydrogen or methane production. Energy efficiency of the overall bioelectrolysis process using municipal solid waste and an applied voltage of 3V was approximately 12.4%, which is relatively low compared to values reported in the literature for organic wastes and can be explained by the low organic carbon content and availability in the municipal solid waste. Results of this study highlight some important operational constraints with respect to electro-stimulated hydrogen production from organic wastes; related in particular to electrode lifetime expectancies. Results nevertheless illustrate the potential for hydrogen production from municipal solid waste as a possible route for energy recovery.     

Simulation analysis of municipal solid waste pyrolysis and gasification based on Aspen plus

To predict and analyze the municipal solid waste (MSW) pyrolysis and gasification process in an up-draft fixed bed more veritably and appropriately, numerical modeling based on Gibbs energy minimization was executed using the Aspen plus software. The RYield module was combined with the RGibbs module to describe the pyrolysis section, while the RGibbs module was used for the gasification section individually. The proposed model was used to forecast and analyze the target performance parameters including syngas composition, lower heating value (LHV) and carbon conversion rate under different conditions of the gasification temperatures, and ratios and types of gasifying agents. The results indicate that there is a good agreement between the experimental data and the simulated data obtained using this model. The predicted optimum gasification temperature is approximately 750°C, and the best ratio of water vapor as gasifying agent is around 0.4. The mixture of flue gas and water vapor has an economical and recycled prospect among four commonly used gasifying agents.     

Process modelling for the production of hydrogen-rich gas from gasification of coal using oxygen,CO2 and steam reactants

This process modelling studied the effect of different reactants on syngas composition and gasifier heat duty (heat energy required to carry out the operation) and the downstream treatment of CO rich syngas to maximise hydrogen yield. The process modelling was validated against experimental data obtained from a large bench-scale entrained flow gasifier. Results show that considering the H₂/CO ratio, the steam-O₂ reactant favours the most compared to those of the pure oxygen and oxygen-CO₂ reactants. Under comparable operating conditions, the highest H₂/CO ratio of 0.74 was determined using steam-O₂ reactant compared to that of 0.31 and 0.33 using steam-CO₂ and pure oxygen reactant. The catalytic water-gas shift reaction (WGSR) favours the yield of H₂ with complete CO conversion at a temperature of 400 °C using the steam/coal ratio of 1.2. Supplying steam in the gasifier requires more heat energy to be supplied to drive endothermic gasification reaction and maintain the gasifier temperature. Under complete carbon conversion, steam-CO₂ and steam-oxygen reactants require 5–65 kW more energy than pure oxygen.     

Supplying hydrogen vehicles and ferries in Western Norway with locally produced hydrogen from municipal solid waste

Gibbs free energy minimization has been used to estimate the hydrogen production potential of air gasification of the wet organic fractions of municipal solid waste available in the Bergen region in Western Norway. The aim of this work was to obtain an upper limit of the amount of hydrogen that could be produced and to estimate of the number of vehicles: passenger ferries and cars that could be supplied with an alternative fuel. The hydrogen production potential was investigated as function of waste composition, moisture content, heat loss, and carbon conversion factor. The amount of hydrogen annually available for both gasification and gasification combined with water-gas-shift-reaction was calculated for different scenarios. Up to 2700 tonne H₂ per year could be produced in the best case scenario; which would, if only utilised for maritime operations, be enough to supply nine ferries and ten fast passenger boat connections in the Hordaland region in Western Norway with hydrogen.     

Numerical investigation of a multichannel reactor for syngas production by methanol steam reforming at various operating conditions

A novel multichannel reactor with a bifurcation inlet manifold, a rectangular outlet manifold, and sixteen parallel minichannels with commercial CuO/ZnO/Al₂O₃ catalyst for methanol steam reforming was numerically investigated in this paper. A three-dimensional numerical model was established to study the heat and mass transfer characteristics as well as the chemical reaction rates. The numerical model adopted the triple rate kinetic model of methanol steam reforming which can accurately calculate the consumption and generation of each species in the reactor. The effects of steam to carbon molar ratio, weight hourly space velocity, operating temperature and catalyst layer thickness on the methanol steam reforming performance were evaluated and discussed. The distributions of temperature, velocity, species concentration, and reaction rates in the reactor were obtained and analyzed to explain the mechanisms of different effects. It is suggested that the operating temperature of 548 K, steam to carbon ratio of 1.3, and weight hourly space velocity of 0.67 h⁻¹ are recommended operating conditions for methanol steam reforming by the novel multichannel reactor with catalyst fully packed in the parallel minichannels.     

Hydrogen-rich gas production by steam gasification of municipal solid waste (MSW) using NiO supported on modified dolomite

NiO on modified dolomite (NiO/MD) catalysts were developed for hydrogen-rich gas production from steam gasification of municipal solid waste (MSW). The catalysts were prepared through deposition-precipitation method and characterized by various characterization methods. The activity of NiO/MD on the steam gasification of MSW was investigated in a lab-scale fixed bed. The results indicated that the catalysts could significantly eliminate the tar in the gas production and increase the hydrogen yield. In addition, higher temperature contributed to higher hydrogen production and gas yield, meanwhile, the optimal ratio of steam to MSW (S/M) was found to be 1.23. In the experimental conditions, the NiO/MD catalysts showed a good performance over a long lifetime test.     

Experimental study on syngas production by co-gasification of coal and biomass in a fluidized bed

The main results of an experimental work on co-gasification of a Chinese bituminous coal and two types of biomass in a bench-scale fluidized bed are reported in the present study. Experiments were performed at different oxygen equivalence ratio, steam/carbon ratio and biomass/coal ratio. In addition, stabilization of co-gasification process was investigated. It was found that a relatively low oxygen equivalence ratio favors the increase of syngas yield (CO + H₂). There is a maximum value in the curve of syngas yield versus steam/carbon ratio. Moreover, the content of H₂ in gas increases with the increase of biomass ratio while that of CO and syngas yield decrease. A continuous stable operation can be gained.     

Assessing the power generation,pollution control,and overall efficiencies of municipal solid waste incinerators in Taiwan

This paper evaluates the productivity of municipal solid waste incinerators (MSWIs) by addressing the following questions: (1) to what extent should one further increase the production of power generation while maintaining the emission of noxious air at the current level?; (2) To what extent should one further decrease the emission of noxious air while maintaining the production of power generation at the current level?; and (3) To what extent should one increase the production of power generation and decrease the emission of noxious air simultaneously? To effectively address these questions to improve performance, the power generation and pollution control efficiencies are evaluated using TODEA (two-objective data envelopment analysis), as well as the overall efficiency evaluated using Tone’s NS-overall model (slacks-based measure with non-separable desirable and undesirable outputs for evaluating overall efficiency). A MSWI case study in Taiwan with the panel data covering the period of 2004–2008 reveals that the power generation and overall efficiencies of build-operate-transfer are more efficient, on average, than those of public-own-operate and build-own-operate. However, the three building and operation types do not significantly differ in pollution control efficiency.     

Investigation of syngas exergy value and hydrogen concentration in syngas from biomass gasification in a bubbling fluidized bed gasifier by using machine learning

In this study, an artificial neural network (ANN) model as a machine learning method has been employed to investigate the exergy value of syngas, where the hydrogen content in syngas reached maximum in bubbling fluidized bed gasifier which is developed in Aspen Plus® and validated from experimental data in literature. Levenberg-Marquardt algorithm has been used to train ANN model, where oxygen, hydrogen and carbon contents of sixteen different biomass, gasification temperature, steam and fuel flow rates were selected as input parameters of the model. Moreover, four different biomass samples, which hadn't been used in training and testing, have been used to create second validation. The hydrogen mole fraction of syngas was also evaluated at the different steam to fuel ratio and gasification temperature and the exergy value of syngas at the point where the hydrogen content in syngas reached maximum were estimated with low relative error value.     

Characteristics of co-combustion and kinetic study on hydrothermally treated municipal solid waste with different rank coals: A thermogravimetric analysis

This study presents an investigation on the influence of hydrothermally treated municipal solid waste (MSW) on the co-combustion characteristics with different rank coals, i.e. Indian, Indonesian and Australian coals. MSW blends of 10%, 20%, 30% and 50% (wt.%) with different rank coals were tested in a thermogravimetric analyser (TGA) in the temperature range from ambient to 700 °C under the heating rate of 10 °C/min. Combustion characteristics such as volatile release, ignition and burnout were studied for the blend fuel. Different ignition behavior was observed depending on the blends composition and the coal rank. The result of this work indicates that the blending of MSW improves devolatization properties of coal. But it was found that the co-combustion characteristics of MSW and coal blend cannot be predicted only from the pyrolytic and or devolatization phenomena as the other factors such as the coal quality also plays a vital role in deciding the blends co-combustion characteristics. The TGA combustion profiles showed that the combustion characteristics of blends followed those of parent fuels in both an additive and non-additive manners. These experimental results help to understand and predict the behavior of coal and MSW blends in practical applications.     

Syngas production from catalytic gasification of waste polyethylene: Influence of temperature on gas yield and composition

The catalytic steam gasification of waste polyethylene (PE) from municipal solid waste (MSW) to produce syngas (H₂ + CO) with NiO/γ-Al₂O₃ as catalyst in a bench-scale downstream fixed bed reactor was investigated. The influence of the reactor temperature on the gas yield, gas composition, steam decomposition, low heating value (LHV), cold gas efficiency and carbon conversion efficiency was investigated at the temperature range of 700–900 °C, with a steam to waste polyethylene ratio of 1.33. Over the ranges of experimental conditions examined, NiO/γ-Al₂O₃ catalyst revealed better catalytic performance as a view of increasing product gas yield and of decreasing char and liquid yields in the presence of steam. Higher temperature resulted in more H₂ and CO production, higher carbon conversion efficiency and product gas yield. The highest syngas (H₂ + CO) content of 64.35 mol%, the highest H₂ content of 36.98 mol%, and the highest CO content of 27.37 mol%, were achieved at the highest temperature level of 900 °C. Syngas produced with a H₂/CO molar ratio in the range of 0.83–1.35, was highly desirable as feedstock for Fischer–Tropsch synthesis for the production of transportation fuels.     

A linear programming approach for the optimal planning of a future energy system. Potential contribution of energy recovery from municipal solid wastes

In the present paper the mismatch between the energy supply levels and the end use, in a broader sense, was studied for the Hellenic energy system. The ultimate objective was to optimize the way to meet the country's energy needs in every different administrative and geographical region using renewable energy sources (RES) and at the same time to define the remaining available space for energy recovery units from municipal solid waste (MSW) in each region to participate in the energy system. Based on the results of the different scenarios examined for meeting the electricity needs using linear programming and by using the exergoeconomic analysis the penetration grade was found for the proposed energy recovery units from MSWs in each region.     

Hydrogen-rich gas from catalytic steam gasification of municipal solid waste (MSW): Influence of steam to MSW ratios and weight hourly space velocity on gas production and composition

The present work deals with a study coupling experiments and modeling of catalytic steam gasification of municipal solid waste (MSW) for producing hydrogen-rich gas or syngas (H₂ + CO) with calcined dolomite as a catalyst in a bench-scale downstream fixed bed reactor. The influence of steam to MSW ratios (S/M) on gas production and composition was studied at 900 °C over the S/M range of 0.39–1.04, for weight hourly space velocity (WHSV) in the range of 1.22–1.51 h⁻¹. Over the ranges of experimental conditions examined, calcined dolomite revealed better catalytic performance at the presence of steam. H₂ and CO₂ contents increased with S/M increasing, while CO and CH₄ contents decreased sharply, the contents of CH₄, C₂H₄ and C₂H₆ were relatively small, and the influence of S/M was insignificant. The highest H₂ content of 53.22 mol %, the highest H₂ yield of 42.98 mol H₂/kg MSW, and the highest H₂ potential yield of 59.83 mol H₂/kg MSW were achieved at the highest S/M level of 1.04. Furthermore, there was a good agreement between the experimental gas composition and that corresponding to thermodynamic equilibrium data calculated using GasEq model. Consequently, a kinetic model was proposed for describing the variation of H₂ yield and carbon conversion efficiency with S/M during the catalytic steam gasification of MSW. The kinetic model revealed a good performance between experimental results and the kinetic model.     

The effect of IGFC warm gas cleanup system conditions on the gas–solid partitioning and form of trace species in coal syngas and their interactions with SOFC anodes

The U.S. Department of Energy is currently working on coupling coal gasification and high temperature fuel cell to produce electrical power in a highly efficient manner while being emissions free. Many investigations have already investigated the effects of major coal syngas species such as CO and H₂S. However coal contains many trace species and the effect of these species on solid oxide fuel cell anode is not presently known. Warm gas cleanup systems are planned to be used with these advanced power generation systems for the removal of major constituents such as H₂S and HCl but the operational parameters of such systems is not well defined at this point in time. This paper focuses on the effect of anticipated warm gas cleanup conditions has on trace specie partitioning between the vapor and condensed phase and the effects the trace vapor species have on the SOFC anode. Results show that Be, Cr, K, Na, V, and Z trace species will form condensed phases and should not effect SOFC anode performance since it is anticipated that the warm gas cleanup systems will have a high removal efficiency of particulate matter. Also the results show that Sb, As, Cd, Hg, Pb, P, and Se trace species form vapor phases and the Sb, As, and P vapor phase species show the ability to form secondary Ni phases in the SOFC anode.     

Evaluation of hydrogen and methane production from municipal solid wastes with different compositions of fat,protein, cellulosic materials and the other carbohydrates

Municipal solid wastes (MSW) collected in Kyoto city were carefully separated, and the waste-type proportion in MSW was surveyed. A hydrogen/methane fermentation batch experiment was conducted under thermophilic condition using twenty different types of MSW components. Biodegradable wastes in the MSW almost consist of vegetable kitchen waste, and the characteristics of hydrogen and methane fermentation of MSW were similar to that of vegetable kitchen waste. Hydrogen production per g VS added was considerably positively correlated with easily degradable carbohydrates concentration and negatively correlated with cellulosic materials concentration. The various feedstocks could be classified into four groups according to nutrient composition (protein, fat, cellulosic materials and easily degradable carbohydrates), and the feedstocks belonging to carbohydrates rich group showed higher hydrogen yields than the other feedstocks. Rough hydrogen yield could be easily predicted by concentration of easily degradable carbohydrates.