Hydrogen-rich syngas production of urea blended with biobutanol by a thermodynamic analysis

Both biobutanol and urea are the environment-friendly hydrogen carrier. This study is to compare hydrogen production between steam reforming of biobutanol and autothermal reforming of biobutanol feed using pure steam and vaporization of aqueous urea (VAU) by a thermodynamic analysis. Hydrogen-rich syngas production, carbon formation, thermal neutral temperature (TNT), and hydrogen production cost are analyzed in both steam reforming and autothermal reforming. The results show that hydrogen-rich syngas production with the use of VAU is higher than that with pure steam not only in steam reforming but also in autothermal reforming. When the VAU/butanol molar ratio is 8, and the O₂/butanol molar ratio equals 3, the reforming efficiency reaches up to 81.42%. At the same condition, the hydrogen production cost is lower than that without blending urea. Therefore, using VAU to replace pure steam in biobutanol reforming leads to benefits of increasing the hydrogen-rich syngas yield and lowering cost.     

Hydrogen-rich syngas production and carbon dioxide formation using aqueous urea solution in biogas steam reforming by thermodynamic analysis

Biogas is a renewable biofuel that contains a lot of CH₄ and CO₂. Biogas can be used to produce heat and electric power while reducing CH₄, one of greenhouse gas emissions. As a result, it has been getting increasing academic attention. There are some application ways of biogas; biogas can produce hydrogen to feed a fuel cell by reforming process. Urea is also a hydrogen carrier and could produce hydrogen by steam reforming. This study then employes steam reforming of biogas and compares hydrogen-rich syngas production and carbon dioxide with various methane concentrations using steam and aqueous urea solution (AUS) by Thermodynamic analysis. The results show that the utilization of AUS as a replacement for steam enriches the production of H₂ and CO and has a slight CO₂ rise compared with pure biogas steam reforming at a temperature higher than 800 °C. However, CO₂ formation is less than the initial CO₂ in biogas. At the reaction temperature of 700 °C, carbon formation does not occur in the reforming process for steam/biogas ratios higher than 2. These conditions led to the highest H₂, CO production, and reforming efficiency (about 125%). The results can be used as operation data for systems that combine biogas reforming and applied to solid oxide fuel cell (SOFC), which usually operates between 700 °C to 900 °C to generate electric power in the future.     

Hydrogen-rich syngas production by the three-dimensional structure of LaNiO3 catalyst from a blend of acetic acid and acetone as a bio-oil model compound

Converting biomass bio-oil to hydrogen is valuable strategy. In this study, a blend of acetic acid and acetone has been utilized as a bio-oil model compound, where perovskite in a three-dimensional structure (3D-LaNiO₃) synthesized by a silica template method used as a catalyst. The result shows that the main phase of perovskite at 3D-LaNiO₃ catalyst has lower crystal size, resulting in decrease possibility of agglomeration. The amount of oxygen vacancies and higher ratio of Ni³⁺/Ni²⁺ are produced, enhancing the redox of catalyst. The stronger basic site and lager surface indicated the ability of improving coke deposition resistance. These results explained great activity of 3D-LaNiO₃ catalyst in producing hydrogen-rich syngas. The different steam/carbon mole ratios (S/C) have been discussed at 1 to 4, and the gas yield of H₂ (93.5%) shows highest at 600 °C and S/C = 3. Meanwhile, under this condition, the H₂ gas yield was stable and over 90% throughout 15 h of reaction. By analysis of spent 3D-LaNiO₃ catalyst, the result indicated that it has ability to resist the production of graphite coke deposition which is one of reasons for keeping catalyst activity. On the other hand, the stable of perovskite structure help in produce lattice oxygen for oxidizing coke deposited.     

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.     

Introducing a new salty waste for second-generation bioethanol production

We have introduced the discards of turnip juice as a raw material for bioethanol production for the first time. Pretreatment methods, initial biomass loading, and fermentation time were investigated. Supplementation of different kinds of nitrogen sources, mineral salts and agricultural waste hydrolysates were added in the growth medium. The highest bioethanol concentrations and Q_p values were 7.32, 5.34, 1.55 g/L and 0.61, 0.44, 0.05 g/L.h for S. cerevisiae, K. marxianus and P. stipitis, respectively. Furthermore, Y_p/s values were 0.46 g/g, 0.47 g/g, and 0.37 g/g for the three yeasts. Turnip juice discards are promising raw materials for bioethanol production.     

Hydrogen-rich syngas production by catalytic cracking of tar in wastewater under supercritical condition

This paper presents the results from experimental study of syngas production by catalytic cracking of tar in wastewater under supercritical condition. Ni/Al₂O₃ catalysts were prepared via the ultrasonic assisted incipient wetness impregnation on activated alumina, and calcined at 600 °C for 4 h. All catalysts showed mesoporous structure with specific surface area in a range of 146.6–215.3 m²/g. The effect of Ni loading (5–30 wt%), reaction temperature (400–500 °C), and tar concentration (0.5–7 wt%) were systematically investigated. The overall reaction efficiency and the gas yields, especially for H₂, were significantly enhanced with an addition of Ni/Al₂O₃ catalysts. With 20%Ni/Al₂O₃, the H₂ yield increased by 146% compared to the non-catalytic experiment. It is noteworthy that the reaction at 450 °C with the addition of 20%Ni/Al₂O₃ had a comparable efficiency to the reaction without catalyst at 500 °C. The maximum H₂ yield of 46.8 mol/kg_tar was achieved with 20%Ni/Al₂O₃ at 500 °C and 0.5 wt% tar concentration. The catalytic performance of the catalysts gradually decreased as the reuse cycle increased, and could be recovered to 88% of the fresh catalyst after regeneration. 20%Ni/Al₂O₃ has a potential to improve H₂ production, as well as a good reusability. Thus, it is considered a promising catalyst for energy conversion of tar in wastewater.     

生物质合成气发酵生产乙醇的工艺分析

介绍了生物质合成气发酵制备乙醇的工艺过程。采用Aspen plus软件对工艺过程建立模型,模拟计算乙醇的产量。针对影响乙醇产量的主要参数进行了灵敏度分析,结果表明:气化过程中氧气与干生物质质量比对乙醇产量影响显著,且比值为0.4时,乙醇产量最大;而气化过程中过多蒸汽的加入会降低乙醇产量;发酵过程中CO和H2转化率的提高有利于乙醇产量的增加。     

Refining bioethanol from stalk juice of sweet sorghum by immobilized yeast fermentation

The relationship between total soluble sugar content and Brix in stalk juice of sweet sorghum was determined through one-dimensional linear regression. Meanwhile, bioethanol fermentation experiments were conducted in shaking flasks and 10 l fluidized bed bioreactor with stalk juice of Yuantian No. 1 sweet sorghum cultivar when immobilized yeast was applied. The experimental results in the shaking flasks showed that the order of influence on improving ethanol yield was (NH₄)₂SO₄>MgSO₄>K₂HPO₄, and the optimum inorganic salts supplement dose was determined as follows: K₂HPO₄ 0%, (NH₄)₂SO₄ 0.2%, MgSO₄ 0.05%. When the optimum inorganic salts supplement dose was used in fermentation in 10 l fluidized bed reactor, the fermentation time and ethanol content were 5 h and 6.2% (v/v), respectively, and ethanol yield was 91.61%, which was increased by 9.73% than blank. In addition, the results showed that the fermentation time was about 6–8 times shorter in fluidized bed bioreactor with immobilized yeast than that of conventional fermentation technology. As a result, it can be concluded that the determined optimum inorganic salts supplement dose could be used as a guide for commercial ethanol production. The fluidized bed bioreactor with immobilized yeast technology has a great potential for ethanol fermentation of stalk juice of sweet sorghum.     

Design of experiments and analysis of dual fluidized bed gasifier for syngas production: Cold flow studies

Biomass gasification is a thermo-chemical process widely accepted as a future technology for syngas production. Numerous types of gasification systems have been proposed and studied in the past. Recent developments have shown that Dual Fluidized Bed (DFB) gasifier are commercially more attractive for production of the hydrogen-rich syngas as compared to others. DFB gasification system is very complex in construction and operation. Hence, a detailed understanding of hydrodynamics in such systems is essential for optimum design and scale-up. Hydrodynamics of DFB gasifier mainly depends on the Solid Circulation Rate (SCR). SCR is governed by riser velocity, gasifier velocity, and loop seal velocities. In present work, Central Composite Rotatable Design (CCRD) based Response Surface Method (RSM) was employed to determine the effect of riser velocity, gasifier velocity, recycle chamber velocity, supply chamber velocity, and vertical supply chamber velocity and their interaction on the SCR. Adequacy of regression model developed from RSM was confirmed using ANOVA analysis. The value of coefficient of determination (R²) of the model was 0.9729, which confirms model represents the experimental results satisfactorily. Riser and recycle chamber velocity were found to be most significant parameters, plays an important role in SCR in DFB gasifier.     

Chemical looping gasification of biomass char for hydrogen-rich syngas production via Mn-doped Fe2O3 oxygen carrier

Because of its low cost, an iron-based oxygen carrier is a promising candidate for hydrogen-rich syngas production from the chemical looping gasification of biomass. However, it needs modification from a reactivity point of view. In this study effect of Mn doping on Fe₂O₃ has been investigated for hydrogen-rich syngas production from biomass char at different temperatures (700–900 °C) and steam flow rates (60–100 μL/min). Several techniques (XRD, XPS, BET, and TPR-H₂) have been utilized to characterize fresh and spent oxygen carriers. The result demonstrated Mn-doing boosted the redox activity and the amount of oxygen vacancies, which increased hydrogen gas generation. Hydrogen production displayed different behavior across temperatures due to detecting Fe₂O₃ and MnFeO₃ phases for spent oxygen carriers. For the Fe₂O₃ oxygen carrier hydrogen gas yield is 1.67 Nm³/kg which is due to reduction of Fe₂O₃ phase to Fe₃O₄. However, the MnFe₂O₄ spinel phase detected in the spent MnFeO₃ oxygen carrier is a reason for improving hydrogen gas yield to 1.84 Nm³/kg. Change reaction temperature from 900 °C to 850 °C reduced hydrogen gas yield from 1.84 Nm³/kg to 1.83 Nm³/kg for with MnFeO₃ oxygen carrier. Regarding different steam flows, the proper flow rates that can maintain the formed phases and obtained best hydrogen gas yield are 80 and 90 μL/min, respectively. Meanwhile, the best hydrogen gas yield (2.21Nm³/kg) are obtained with MnFeO₃ oxygen carrier at optimum conditions (850 °C and 90 μL/min).     

Chemical looping steam reforming of bio-oil for hydrogen-rich syngas production: Effect of doping on LaNi0.8Fe0.2O3 perovskite

Chemical looping steam reforming of bio-oil is novel conversion technology utilizing waste energy, which is an advantage to reduce cost and improve environmental. However, complex reaction process between oxygen carrier and bio-oil constrain its development. In this study, perovskite based La_0.8M_0.2Ni_0.8Fe_0.2O₃ (M = Ca, Ce and Zr) were investigated as an oxygen carrier for chemical looping steam reforming of bio-oil model reaction. The perovskites were prepared via sol-gel method and the effect of doping for reforming of acetic acid as bio-oil model compound is also investigated. Among all the perovskite tested, Ce doped La_0.8Ce_0.2Ni_0.8Fe_0.2O₃ oxygen carrier gave superior and stable catalytic performance for 1440 min at 600 °C and steam/carbon mole ratio (S/C = 2). The fresh and spent oxygen carriers were characterized using XRD, H₂-TPR, CO₂-TPD, TG-DTG, Dielectric constant, Raman, XPS and XANES. Doping with base metal generally, improved coke resistance ability of the perovskite. CO₂-TPD and XPS analysis reveal that the highest carbon resistance for La_0.8Ce_0.2Ni_0.8Fe_0.2O₃ perovskite is due to enhanced stronger surface basicity and oxygen adsorption. From DFT simulation and Dielectric constant results, the better activity for La_0.8Ce_0.2Ni_0.8Fe_0.2O₃ is attributed to its adsorption ability of reactants, oxygen and electron transfer from sub-surface to surface of the perovskite.     

Bioethanol production from grape and sugar beet pomaces by solid-state fermentation

A suitable alternative to replace fossil fuels is the production of bioethanol from agroindustrial waste. Grape pomace is the most abundant residue in San Juan and sugar beet pomace could be important in the region. Solid-State Fermentation (SSF) is a technology that allows transforming agroindustrial waste into many valuable bioproducts, like ethanol. This work reports a laboratory scale SSF to obtain alcohol from grape and sugar beet pomace by means of Saccharomyces cerevisiae yeasts. The initial conditions of the culture medium were: sugars 16.5% (p/p); pH 4.5; humidity 68% (p/p). Cultures were inoculated with 10⁸ cells/g of pomace, and incubated in anaerobic environment, at 28 °C, during 96 h. SSF showed ethanol maximum concentrations at 48 h and ethanol yield on sugars consumed was more than 82%. Yield attained creates expectation about the use of SSF to obtain fuel alcohol.     

Hydrogen-rich gas production from a biomass pyrolysis gas by using a plasmatron

Pyrolysis and gasification is an energy conversion technology process that produces industrially useful syngas from various biomasses. However, due to the tars in the product gases generated from the pyrolysis/gasification of biomass, this process damages and causes operation problems with equipment that use product gases such as gas turbines and internal engines.     

Use of bioethanol for biodiesel production

Faced with the energy crisis and environmental degradation, due to the massive use of fossil energy sources, biodiesel is an attractive alternative to diesel fuel. With a view to developing local biodiesel production, using bioethanol as a sustainable reactant for biodiesel production, rather than methanol, is leading to increasing interest, notably in emerging countries. Indeed, bioethanol, which is less toxic than methanol, is produced from local and renewable agricultural resources, being more sustainable and providing access to greater energy independence. However, some issues are limiting the process like purification problems, or the presence of water in bioethanol leading to a drop in yield. Although several studies have already been published on ethyl ester production, most of them primarily focus on homogeneous alkaline catalysis, and report various data. Therefore, this paper aims at presenting a review of previous studies on the subject.     

The effects of syngas impurities on syngas fermentation to liquid fuels

Biomass gasification to generate raw syngas used in anaerobic fermentation processes is one of several emerging technologies for the production of biofuels from biomass. The gasification-fermentation process can utilize a wide variety of lignocellulosic biomass such as prairie grasses, wood chips, and paper wastes, in addition to non-lignocellulosic biomass such as solid municipal wastes. Although the primary components of raw syngas used in the fermentation process are CO, H₂, and CO₂, several impurities can also be present. Some of these impurities may interfere with the fermentation process. Since the impurities will depend upon the feedstock, the gasifier type, and cleanup conditions, an understanding of the positive or adverse effects of the impurities on raw syngas fermentation is critical to understand the need for efficient gas cleaning processes required for commercialization. This work describes the impurities generated during gasification and discusses the potential accumulation of impurities in the fermentation media and the associated potential effects on the microbial fermentation process (e.g. cell toxicity, enzymatic inhibition and end product distribution). A wide distribution of impurity solubilities in the media shows that certain impurities, such as ammonia, are more likely to accumulate in the media. Additionally, entrained tar particulates greater than 0.025 ??m, nitric oxide greater than 0.004 mol%, and ammonia in general have an adverse effect on the fermentation process. Therefore, a cleanup system suitable for raw syngas fermentation processes is evident although the degree of cleanup would likely depend upon the feedstock and the associated gasification process.     

Pretreatment of Japanese cedar wood by white rot fungi and ethanolysis for bioethanol production

Japanese cedar (Cryptomeria japonica) shares around 60% of plantation forests in Japan, and there is a growing demand for thinning of the forest. However, the softwood is one of the most recalcitrant wood species for hydrothermal and thermochemical pretreatments for enzymatic saccharification. In the present paper, we applied combined pretreatments by solvolysis and cultivation with white rot fungi to develop environmentally benign pretreatment system applicable to recalcitrant softwood. Due to the recalcitrance of the softwood, enzymatic saccharification yield from ethanolysis pulp was 10.2%, based on the weight of holocellulose. To increase the sugar yield, the softwood was treated with selective white rot fungi prior to the ethanolysis. Treatment of the softwood with a biopulping fungus, Ceriporiopsis subvermispora FP-90031 and a new fungal isolate Phellinus sp. SKM2102 for 8 weeks increased the sugar yield to 35.7 and 40.8%, respectively. The best pretreatment conditions in terms of overall sugar yield including a soluble fraction were obtained by ethanolysis after the fugal treatment with Phellinus sp. SKM2102, resulting in production of 42.2 g of total reducing sugars per 100 g of the fungus-pretreated biomass. After the combined pretreatment, simultaneous saccharification and fermentation of the water-insoluble pulp fraction were carried out using Saccharomyces cerevisiae. Ethanol production from undecayed Japanese cedar wood was negligible but pretreatments with the two fungi significantly increased the ethanol production, in combination with ethanolysis. The combined pretreatment with solvolysis and Phellinus sp. SKM2102 is attractive for biorefinery of the recalcitrant softwood.     

Process optimization for bioethanol production from cassava starch using novel eco-friendly enzymes

Although cassava (Manihot esculenta Crantz) is a potential bioethanol crop, high operational costs resulted in a negative energy balance in the earlier processes. The present study aimed at optimizing the bioethanol production from cassava starch using new enzymes like Spezyme^® Xtra and Stargen™ 001. The liquefying enzyme Spezyme was optimally active at 90 °C and pH 5.5 on a 10% (w/v) starch slurry at levels of 20.0 mg (280 Amylase Activity Units) for 30 min. Stargen levels of 100 mg (45.6 Granular Starch Hydrolyzing Units) were sufficient to almost completely hydrolyze 10% (w/v) starch at room temperature (30 ± 1 °C). Ethanol yield and fermentation efficiency were very high (533 g/kg and 94.0% respectively) in the Stargen + yeast process with 10% (w/v) starch for 48 h. Raising Spezyme and Stargen levels to 560 AAU and 91.2 GSHU respectively for a two step loading [initial 20% (w/v) followed by 20% starch after Spezyme thinning]/initial higher loading of starch (40% w/v) resulted in poor fermentation efficiency. Upscaling experiments using 1.0 kg starch showed that Stargen to starch ratio of 1:100 (w/w) could yield around 558 g ethanol/kg starch, with a high fermentation efficiency of 98.4%. The study showed that Spezyme level beyond 20.0 mg for a 10% (w/v) starch slurry was not critical for optimizing bioethanol yield from cassava starch, although an initial thinning of starch for 30 min by Spezyme facilitated rapid saccharification-fermentation by Stargen + yeast system. The specific advantage of the new process was that the reaction could be completed within 48.5 h at 30 ± 1 °C.     

Inhibitory effect of Eucalyptus globulus pretreated liquors on bioethanol production from Zymomonas mobilis NRRL B-806

Lignocellulosic wastes from agriculture are potentially useful as a low cost feedstock for production of bioethanol. During pretreatment of lignocellulosic materials, a wide range of inhibitory compounds to microorganisms are formed or released. The present work focused on production of bioethanol by Z. mobilis NRRL B-806 in different culture media. Inhibitory effects of the bio-products yielded in the pretreatment process of Eucalyptus globulus were determined. Results obtained showed that maximum bioethanol production yield Y_E/S for Z. mobilis NRRL B-806 was 87%. Ethanol production and glucose consumption were clearly affected by high inhibitors concentration present in pretreated liquors obtained by auto-hydrolysis.     

Steam reforming of technical bioethanol for hydrogen production

Essentially all work on ethanol steam reforming so far has been carried out using simulated bioethanol feedstocks, which means pure ethanol mixed with water. However, technical bioethanol consists of a lot of different components including sugars, which cannot be easily vaporized and steam reformed. For ethanol steam reforming to be of practical interest, it is important to avoid the energy-intensive purification steps to fuel grade ethanol. Therefore, it is imperative to analyze how technical bioethanol, with the relevant impurities, reacts during the steam reforming process. We show how three different distillation fractions of technical 2nd generation bioethanol, produced in a pilot plant, influence the performance of nickel- and ruthenium-based catalysts during steam reforming, and we discuss what is required to obtain high activity and long catalyst lifetime. We conclude that the use of technical bioethanol will result in a faster catalyst deactivation than what is observed when using pure ethanol–water mixtures because of contaminants remaining in the feed. However, the initial activity of the catalysts are not affected by this, hence it is important to not only focus on catalyst activity but rather on the lifetime of the catalyst.     

Hydrogen-rich syngas production via integrated configuration of pyrolysis and air gasification processes of various algal biomass: Process simulation and evaluation using Aspen Plus software

In the present study, hydrogen-rich syngas production via integrated configuration of pyrolysis and air gasification processes of different algal biomass is investigated at relevant industrial condition. A comprehensive steady state equilibrium simulation model is developed using Aspen Plus software, to investigate and evaluate the performance of pyrolysis and air gasification processes of different algal biomass (Algal waste, Chlorella vulgaris, Rhizoclonium sp and Spirogyra). The model can be used as a predictive tool for optimization of the gasifier performance. The developed process consists of three general stages including biomass drying, pyrolysis and gasification. The model validation using reported experimental results for pyrolysis of algal biomass indicated that the predicted results are in good agreement with experimental data. The effect of various operational parameters, such as gasifier temperature, gasifier pressure and air flow rate on the gas product composition and H₂/CO was investigated by sensitivity analysis of parameters. The achieved optimal operating condition to maximize the hydrogen and carbon monoxide production as the desirable products were as follows: gasifier temperature of 600 °C, gasifier pressure of 1 atm and air flow rate of 0.01 m³/h.