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 the co-pyrolysis of municipal solid waste and wheat straw

The co-thermochemical conversion of Municipal Solid Waste (MSW) and biomass is a new environmental technology and can produce hydrogen-rich syngas. This study investigated the co-pyrolysis of MSW and wheat straw, using a drop-tube furnace experiment. Using a temperature range of 500 °C–1000 °C, the study assessed pyrolysis gas yield, product distribution, gas low heating value, and carbon conversion of co-pyrolysis MSW with different amounts of wheat straw. Adding wheat straw only slightly increases the gas yield and carbon conversion, but improved the carbon monoxide and carbon dioxide in the syngas. At an experimental temperature below 700 °C, adding wheat straw promoted the cracking reaction of hydrocarbon gas, generated by the pyrolysis of MSW. At a temperature of 600 °C, adding 25% wheat straw improved carbon conversion in the blended sample. This study provides a basis for the application of MSW and WS thermo-chemical conversion.     

Hydrogen production from biogas: Process optimization using ASPEN Plus®

This work is part of the VABHYOGAZ (valorization of biogas into hydrogen) program, which targeted the industrial deployment of hydrogen production from biogas in France. To-date, different processes of methane reforming, such as steam reforming of methane (SRM), dry reforming of methane (DRM) and tri-reforming of methane (TRM), have been studied in the literature, but only SRM is applied at industrial scale. Since SRM is an energy-intensive process, a critical analysis of these routes for hydrogen production from biogas is indispensable for process optimization. This has been addressed in this work, by using ASPEN Plus® simulation. Different global processes of hydrogen production from biogas, via DRM, SRM, or TRM, with or without tail gas recycling, have been studied. Among them, hydrogen production using TRM technique (H₂-TRM0.3C process) with a partial recycling of tail gas (30%) was found to be the best option, leading to the highest hydrogen production rate and the best energy yield. H₂-TRM0.3C process was also found to be more efficient than the actual industrial process (H₂-REF), which is based on SRM technique. Under the same conditions, H₂-TRM0.3C process led to a higher H₂ production (8.7% more), a lower total energy consumption (18.6% less), and a lower waste heat generation (15.4% less), in comparison with the actual industrial process (H₂-REF).     

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.     

城市垃圾焚烧与热能利用

结合城市垃圾特点，应用成熟可靠的垃圾焚烧技术，实现了能源有效回收与利用，达到了资源化的目的。     

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.     

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.     

Coal dust gasification in the filtration combustion mode with syngas production

A new method for the gasification of fine solid fuel was proposed and worked out, by partial oxidation in a flow of gaseous oxidant with filtration of the suspended fuel through an inert porous matrix. In this case, the solid fuel gasification was carrying out similar to the filtration combustion of gases. The gasification of fine solid coal allows one to produce a combustible gas rich in H₂ and CO was studied. A possibility of pulverized coal gasification in a fixed bed reactor with production of gaseous products containing up to 13% by volume of hydrogen and carbon monoxide was shown experimentally.     

垃圾在流化床中燃烧特性的实验研究

在一台特别设计的小型流化床燃烧实验台上对垃圾可燃物代表组分进行实验研究。实验结果表明,干燥的垃圾一般在床温仅为500℃就能在很短的时间内迅速燃烧,产生明亮的火焰,并使炉膛温度急剧上升．对于个别物料,例如橡胶在短时间内可能出现炉膛中部温度高于床温的情况、物料的形状变化对于它们在流化床内的燃烧影响较大。一般来说,当物料剪碎后,燃烧产生CO量将有所降低,同时炉膛中部温度升高很多。     

Hydrothermal co-gasification of sorghum biomass and çan lignite in mild conditions: An optimization study for high yield hydrogen production

In this study, response surface methodology (RSM) combined with a 3–factor and 3–level Box–Behnken design (BBD) was performed to obtain high yield hydrogen production from hydrothermal co–gasification of sorghum biomass and low rank Çan lignite in a batch type reactor at 500 °C. The individual and the combined effects of the process parameters of coal amount (%) of the coal/biomass mixtures, initial water volume (mL) of the reactor and amount of the coal/biomass mixtures (kg) on system pressure, total gas yield, hydrogen production and product distribution were determined. Water volume directly affected the system pressure and the reaction medium was supercritical water medium above 48.2 mL with a pressure of 22.06 MPa. The highest values of both total gas volume and hydrogen gas volume were reached by gasification of 5.0 g of feedstock. It has been observed that total gas volume and hydrogen volume were directly affected by the water volume in the reactor and the coal ratio of the coal-biomass mixtures. The highest total gas and hydrogen volumes can be achieved under the conditions where the higher levels of water volume of the reactor and lower levels of coal percentage of the coal/biomass mixture were combined. Optimum conditions for maximum hydrogen production with 5.0 g of coal/biomass mixture were determined with numerical optimization as coal percentage of 25.6% and initial water volume of 68.5 mL. By combining the impregnated K₂CO₃ (3%, (w/w)) and CaO catalysts an excellent hydrogen selectivity was achieved. The hydrogen selectivity was drastically increased from 32.0% to 70.8% by capturing more than 99% of CO₂ with a H₂/CO₂ mol ratio of 88.5.     

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.     

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.     

A review on plasma gasification for solid waste disposal

In this paper a brief review on plasma gasification as a new technology for solid waste disposal is presented. Plasma gasification systems can handle not only biomass but also harmful wastes which can be completely converted into outputs having considerable amounts of useful energy content. There are a variety of plasma gasification systems which have different design and operation characteristics with the utilization of a great range of fuels. The operation and performance evaluation of a plasma gasification system in turn is specified by the required outputs. There is a need for a common approach as a function of fuel, system and process characteristics. Furthermore thermodynamic analysis of plasma gasification process is still one of the current research topics due to the missing general theoretical treatment and terminology compatible for all of the systems. A critical analysis on the available literature in this respect provides a solid contribution to the state of art. An experimental research on the design and performance of a plasma gasification system “MCw gasifier” is on site to fill the determined major gaps of the literature which are outlined in this paper.