Optimum Conditions For Hydrogen Production Research Articles

Energy, techno-economic analysis, and life cycle assessment for co-gasification of polyethylene terephthalate and olive husk by chemical process simulation

Waste-to-energy is emerging as a promising technology that can reduce greenhouse gas emissions and solve waste disposal problems. This study focused on hydrogen production technology through waste gasification. Polyethylene terephthalate (PET), which has a high calorific value was selected as a waste fuel, and biomass of olive husk, which can reduce the problems of gasification for PET, was selected as an additional fuel. In this study, hydrogen production research was conducted through mixed gasification of plastic and biomass, and process simulation was performed using Aspen Plus. Gasifier temperature and steam/fuel ratio were set as major variables to confirm their influences on the co-gasification reaction, and the production of H2, CH4, CO, and CO2, which are the main products of the gasification reaction, was analyzed. In addition, the techno-economic analysis and life cycle assessment were conducted. Based on the analysis results, optimal conditions for hydrogen production were discussed.

Microhydrogen production with water splitting from daily used waste aluminum

a bstract In this study, different types of waste aluminum produced in daily life and their pure equivalents were evaluated and compared in terms of their hydrogen generation performance through the water-splitting reaction. An experimental system was designed for the production process that consisted of electrodes, DC power supply, alkaline solution, and various waste aluminum products. The hydrogen generation rate of the aluminum source was then measured to determine the optimum conditions for hydrogen production with different types of pure and waste aluminum, normality of the aqueous solution, and applied DC voltage. The best results for micro-hydrogen generation were obtained using pure powder Aluminum, which was attributed to the increased active surface area for the reaction. For beverage can waste (and its powder form), the maximum hydrogen generation rate (cm 3 /g.min) was achieved using the powder form of the waste aluminum at 2 N alkaline solution. However, the total amount of hydrogen generation (cm 3 /g) yielded different results compared to the maximum hydrogen generation rate where, when the amount of hydrogen generation volume per mass was considered, the beverage can pieces achieved the best result under constant voltage. This result was attributed to a longer total reaction time. • Hydrogen production from waste Al drink cans are studied. • Parametric study is applied with voltage, concentration and forms of Al. • Micro-production of hydrogen is a good candidates for a sustainable energy system.

Modelling and multi-objective optimization for simulation of hydrogen production using a photosynthetic consortium

AbstractThis study was aimed at finding the optimal conditions for hydrogen production based on statistical experiments and using a simulation approach. A Plackett–Burman design and steepest ascent were used to screen the key factors to obtain the best hydrogen concentration. According to the regression analysis, cysteine, acetate, and aeration had the best effect. The optimal conditions, using the method of steepest ascent, were aeration (0.125 L/min), acetate (200 mg/L), cysteine (498 mg/L). Once this was determined, an experiment with more than two factors was considered. The combinations: acetate + cysteine without aeration and cysteine without aeration increased hydrogen concentration. These last two criteria were used to validate the dynamic model based on unstructured kinetics. Biomass, nitrogen, acetate, and hydrogen concentrations were monitored. The proposed model was used to perform the multi-objective optimization for various desired combinations. The simultaneous optimization for a minimum ratio of cysteine-acetate improved the concentration of hydrogen to 20 mg/L. Biomass optimized the concentration of hydrogen to 11.5 mg/L. The simultaneous optimization of reaction time (RT) and cysteine improved hydrogen concentration to 28.19 mg/L. The experimental hydrogen production was 11.4 mg/L at 24 h under discontinuous operation. Finally, the proposed model and the optimization methodology calculated a higher hydrogen concentration than the experimental data.

Effect of salinity and pH on dark fermentation with thermophilic bacteria pretreated swine wastewater

The utilization of swine wastewater is affected by salinity and pH owing to the extensive use with seawater instead of domestic water as swine farm flushing water in coastal city. Therefore, swine wastewater pretreated with thermophilic bacteria was used as fermentation substrate in this work, the effects of salinity and pH on dark fermentation under mesophilic condition were investigated. The research showed that 1.5% salinity and pH 6.0 were the optimal conditions for hydrogen production with swine wastewater. The activity of hydrogenogen was inhibited at 3.5% salinity and pH 5.0. Soluble organic matter in substrate was accumulated under high salinity and alkaline conditions. The utilization of carbohydrate during dark fermentation was up to 61.1% at 1.5% salinity and 51.5% at pH 9.0. Enhancing of salinity and pH had an advantage in accumulation of total soluble metabolites. Acetate was the main metabolite during dark fermentation, and 1.5% salinity contributed to the formation of butyrate.

Improved photo-fermentative hydrogen production by biofilm reactor with optimizing carriers and acetate concentration

To enhance photo-fermentative hydrogen production (PFHP), biofilm reactor (BR) was employed as an ideal strategy with optimization on key factors of acetate concentration and carriers in this work. Optimal conditions for hydrogen production were acetate concentration of 4 g/L and carriers (silicon sheet) of 10 cm × 1 cm at amount of 1 piece. Biofilm formed on silicon sheet strongly improved hydrogen production compared with control reactor (CR). Cumulative hydrogen volume was enhanced about 20% from 2850 ± 130 mL/L of CR to 3349 ± 153 mL/L of BR and hydrogen yield was increased 20% from 2.61 ± 0.13 mol H2/mol acetate of CR to 3.06 ± 0.15 mol H2/mol acetate of BR at 4 g/L acetate. Protein and deoxyribonucleic acid (DNA) were important components to form the biofilm and they occupied 90% of extracellular polymeric substances (EPS). In particular, DNA, nearly 50% content of EPS, likely indicated a substantial contribution to biofilm formation and bacterial communication. Moreover, it suggested biofilm could regulate free cells to decline EPS secretion for improved hydrogen production. This work indicates BR could be a promising and economic strategy to enhance hydrogen production by photo-fermentation.

Hydrolysis and acidification of activated sludge from a petroleum refinery

The cost-effective treatment of activated sludge that is generated by refining petroleum is a challenging industrial problem. In this study, semi-continuous stirred tank reactors (CSTRs) containing petroleum refinery excess activated sludge (PREAS) were used to comparatively investigate hydrolysis and acidification rates, after the addition of heneicosane (C21H44) (R1) and 1-phenylnaphthalene (C16H12) (R2) to different and individual reactors. Operation of the reactors using a sludge retention time (SRT) of 6 days and a pH of 5.0, resulted in the maintenance of stable biological activity as determined by soluble chemical oxygen demand (SCOD), volatile fatty acids (VFAs) production and oil removal efficiency. The optimum conditions for hydrogen production include a SRT of 8 days, at pH 6.5. Under these conditions, hydrogen production rates in the control containing only PREAS were 1567 mL/L (R0), compared with 1365 mL/L in R1 and 1454 mL/L-PREAS in R2. Coprothermobacter, Fervidobacterium, Caldisericum and Tepidiphilus were the dominant bacterial genera that have the potential to degrade petroleum compounds and generate VFAs. This study has shown that high concentrations of heneicosane and 1-phenylnaphthalene did not inhibit the hydrolytic acidification of PREAS.

Fermentative hydrogen production from indigenous mesophilic strain Bacillus anthracis PUNAJAN 1 newly isolated from palm oil mill effluent

In the present study, a new mesophilic bacterial strain, identified as Bacillus anthracis strain PUNAJAN 1 was isolated from palm oil mill effluent (POME) sludge, and tested for its hydrogen production ability. Effect of physico-chemical factors such as temperature, initial pH, nitrogen source and carbon sources were investigated in order to determine the optimal conditions for hydrogen production. The maximum hydrogen yield of 2.42 mol H2/mol mannose was obtained at 35 °C and initial pH of 6.5. Yeast and mannose were used as the main carbon and nitrogen sources respectively in the course of the hydrogen production. Apart from synthetic substrate, specific hydrogen production potentials of the strain using POME was calculated and found to be 236 ml H2/g chemical oxygen demand (COD). The findings of this study demonstrate that the indigenous strain PUNAJAN 1 could be a potential candidate for hydrogen using POME as substrate.

Continuous Hydrogen Production from Agricultural Wastewaters at Thermophilic and Hyperthermophilic Temperatures.

The objective of this study was to investigate the effects of hydraulic retention time (HRT) (8 to 0.5h) and temperature (55 to 75°C) in two anaerobic fluidized bed reactors (AFBR) using cheese whey (AFBR-CW=10,000mg sugars L-1) and vinasse (AFBR-V=10,000mg COD L-1) as substrates. Decreasing the HRT to 0.5h increased the hydrogen production rates in both reactors, with maximum values of 5.36±0.81L H2 h-1 L-1 in AFBR-CW and 0.71±0.16L H2 h-1 L-1 in AFBR-V. The optimal conditions for hydrogen production were the HRT of 4h and temperature of 65°C in AFBR-CW, observing maximum hydrogen yield (HY) of 5.51±0.37mmol H2 g COD-1. Still, the maximum HY in AFBR-V was 1.64±0.22mmol H2 g COD-1 at 4h and 55°C. However, increasing the temperature to 75°C reduced the hydrogen production in both reactors. Methanol and butyric, acetic, and lactic acids were the main metabolites at temperatures of 55 and 65°C, favoring the butyric and acetic metabolic pathways of hydrogen production. The increased productions of lactate, propionate, and methanol at 75°C indicate that the hydrogen-producing bacteria in the thermophilic inoculum were inhibited under hyperthermophilic conditions.

Optimised hydrogen production by aqueous phase reforming of glycerol on Pt/Al2O3

Aqueous phase reforming of glycerol was studied over a series of γ-Al2O3 supported metal nanoparticle catalysts for hydrogen production in a batch reactor. Of the metals studied, Pt/Al2O3 was found to be the most active catalyst under the conditions tested. A further systematic study on the impact of reaction parameters, including stirring speed, pressure, temperature, and substrate/metal molar ratio, was conducted and the optimum conditions for hydrogen production (and kinetic regime) were determined as 240 °C, 42 bar, 1000 rpm, and substrate/metal molar ratio ≥ 4100 for a 10 wt% glycerol feed. The glycerol conversion and hydrogen yield achieved at these conditions were 18% and 17%, respectively, with negligible CO and CH4 formation. Analysis of the spent catalyst using FTIR provides an indication that the reaction pathway includes glycerol dehydrogenation and dehydration steps in the liquid phase in addition to typical reforming and water gas shift reactions in the gas phase.

Production of hydrogen energy from dilute acid-hydrolyzed palm oil mill effluent in dark fermentation using an empirical model

Hydrogen generation was studied using palm oil mill effluent (POME) as an agro-industrial waste obtained from the palm oil industry. POME was subjected to a dilute acid hydrolysis step by HCl (37% v/v) to release fermentable sugars from cellulosic content. POME hydrolysate obtained was used as a substrate for hydrogen generation. The composition of POME hydrolysate showed glucose and xylose were the main monomeric sugars liberated. Hydrogen production was performed in dark fermentation process, in which the new bacterial strain Clostridium acetobutylicum YM1 was cultivated on POME hydrolysate based on a central composite design (CCD). CCD was constructed by considering three pivotal process variables including incubation temperature, initial pH of culture medium and microbial inoculum size. An empirical model, namely second-order polynomial regression model was generated and adjusted to CCD data. The analysis of empirical model generated showed that the linear and quadratic terms of temperature had a highly significant effect on hydrogen generation (P < 0.01). Furthermore, the quadratic effects of initial pH value of culture medium and inoculum size had a significant effect on hydrogen production at 95% probability level (P < 0.05). The regression model also showed that the interaction effect between temperature and initial pH value of the culture medium on the hydrogen generation was highly significant (P < 0.01). The empirical model suggested that the optimum conditions for hydrogen production were an incubation temperature of 38 °C, initial pH value of 5.85 and inoculum size of 17.61% with predicting the production of a cumulative hydrogen volume of 334.2 ml under optimum conditions. In order to validate the optimum conditions determined, C. acetobutylicum YM1 was cultivated on POME hydrolysate in optimum conditions. Verification test results showed that a cumulative hydrogen volume of 333.5 ml and a hydrogen yield of 108.35 ml H2/g total reducing sugars consumed were produced.

Process Modelling, Thermodynamic Analysis and Optimization of Dry Reforming, Partial Oxidation and Auto-Thermal Methane Reforming for Hydrogen and Syngas production

Abstract In this work, process modelling, thermodynamic analysis and optimization of stand-alone dry and partial oxidation reforming of methane as well as, the auto-thermal reforming processes were investigated. Firstly, flowsheet models were developed for both the stand-alone systems and auto-thermal reforming process using ASPEN HYSYS®. Furthermore, thermodynamic studies were conducted for the stand-alone and auto-thermal reforming processes for temperatures range of 200–1000°C and pressure range of 1–3 bar using Gibbs free energy minimization methods which was also performed using ASPEN HYSYS®. The simulation of the auto-thermal reforming process was also performed at 20 bar to mimic industrial process. Process parameters were optimized in the combined reforming process for hydrogen production using desirability function. The simulation results show that 84.60 kg/h, 62.08 kg/h and 154.7 kg/h of syngas were produced from 144 kg/h, 113 kg/h and 211 kg/h of the gas fed into the Gibbs reactor at CH4/CO2/O2 ratio 1:1:1 for the stand-alone dry reforming, partial oxidation reforming and auto-thermal processes respectively. Equilibrium conversion of CH4, CO2, O2 were thermodynamically favoured between 400 and 800°C with highest conversions of 100%, 95.9% and 86.7% for O2, CO2 and CH4 respectively. Highest yield of 99% for H2 and 40% for CO at 800°C was obtained. The optimum conditions for hydrogen production were obtained at CH4/CO2, CH4/O2 ratios of 0.634, 0.454 and temperature of 800°C respectively. The results obtained in this study corroborate experimental studies conducted on auto-thermal reforming of methane for hydrogen and syngas production.

Biohydrogen production from crude glycerol by two stage of dark and photo fermentation

Hydrogen production from crude glycerol by two-stage processes of dark fermentation using Klebsiella sp. TR17 and photo fermentation using Rhodopseudomonas palustris TN1 (Rps. palustris TN1) was investigated in batch experiments. In dark fermentation, the cumulative hydrogen production and hydrogen yield was 64.24 mmol H2/L and 5.74 mmol H2/g COD consumed, respectively with 80.21% of glycerol conversion rate. The dark fermentation effluent (DFE) was employed for photo fermentation. Effect of DFE concentrations (0–5 times dilution), with and without supplementation of yeast extract (2.3 g/L) + NaHCO3 (0.63 g/L), and glutamate (2–8 mM) were optimized. The optimal conditions for hydrogen production from Rps. palustris TN1 were 5 times dilution of DFE without the supplement of yeast extract + NaHCO3, and 2 mM glutamate. Under the optimum conditions, the cumulative hydrogen production of 3.12 mmol H2/L and hydrogen yield of 0.68 mmol H2/g COD consumed was obtained. The total hydrogen yield of two-stage processes was estimated to be 6.42 mmol H2/g COD consumed which was 10.4% of the theoretical yield.

Effect of inoculum concentration, pH, light intensity and lighting regime on hydrogen production by phototrophic microbial consortium

Photobiological hydrogen production using a bacterial consortium has advantages over pure cultures regarding application to wastewater treatment. Photo-H2 production from organic acids, which were produced by dark fermentation, must be studied in detail to make a hydrogen production process in two stages efficient. In this scenario, our study aimed to determine the optimized culture conditions for hydrogen production by a phototrophic bacterial consortium. The inoculum concentration, pH, light intensity and illumination protocols were the parameters that we evaluated. The optimal conditions for hydrogen production were inoculum concentration of 0.2 g VSS L−1, pH 7.0, light intensity of 5 klux, with a constant illumination regime. The highest hydrogen production potential (P) and substrate conversion efficiency (SCE) were 41.5 mmol H2 L−1 culture and 25.4%, respectively, with a COD removal of 95%.

Isolation, characterization and optimization of photo-hydrogen production conditions by newly isolated Rhodobacter sphaeroides KKU-PS5

Abstract A purple non-sulfur (PNS) photosynthetic bacterium was isolated from an upflow anaerobic sludge blanket (UASB) bioreactor for methane production and was identified as Rhodobacter sphaeroides KKU-PS5 (GenBank Accession no. KC481702) by 16s rRNA gene sequence analysis. Strain KKU-PS5 could utilize glucose, xylose, fructose, arabinose, malate, succinate, acetate, butyrate, lactate and D-mannitol for growth and hydrogen production. Malate was a preferred carbon source while glutamate and Aji-L (waste from the process of crystallizing monosodium glutamate) were the preferred nitrogen sources. The ability to utilize Aji-L as a low-cost nitrogen supplement for photo-biohydrogen production by the strain KKU-PS5 is considered as its desirable characteristic. The threshold substrate concentration of malate was 30 mmol/L. The optimum conditions for hydrogen production from malate were an initial pH of 7.0, FeSO4 concentration of 4 mg/L, temperature of 30 °C and light intensity of 6 klux. Under the optimum conditions, the maximum hydrogen production, the hydrogen yield (HY) and the hydrogen production rate (HPR) of 1330 mL-H2/L, 3.80 mol-H2/mol-malate, and 11.08 mL-H2/L h, respectively, were achieved. Hydrogen production under a dark/light cycle led to a decreased HY and HPR in comparison to continuous illumination.

CaFe2O4 sensitized hierarchical TiO2 photo composite for hydrogen production under solar light irradiation

Abstract Hierarchical spheres of self organized nanosheets of TiO2 are prepared by solvothermal method. The spheres comprising nanosheets are expected to exhibit high conducting properties. The present work is an attempt to explore the conducting properties of these spheres of TiO2 nanosheets that facilitate charge transfer and charge mobility. And at the same time to extend the absorption of TiO2 to visible light, it is combined with a low bandgap semiconductor CaFe2O4. In this perspective, CaFe2O4/TiO2 composite photocatalyst consisting of CaFe2O4 and TiO2 hierarchical spheres of nanosheets is prepared by solid state dispersion (SSD) method. The photocatalysts are characterized by thermo gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption desorption, photoluminescence (PL) and UV–Vis diffuse reflectance spectra (DRS). SEM and TEM images show TiO2 spheres and the mesoporous structure is substantiated by the N2 adsorption desorption studies. UV–Vis DRS of the composites show visible light absorption confirming the sensitization of TiO2 by CaFe2O4. XRD shows the crystallinity of the prepared composites is anatase and SEM confirms that the TiO2 spheres are intact at 400 °C calcination temperature. However, deformation of spheres is seen at higher temperatures. Photocatalytic activity of the composites is studied using methanol water mixtures and optimum conditions for hydrogen production are established. By comparing the activity of CaFe2O4/TiO2 composite under visible and solar light irradiation, the possible charge transfer processes that are responsible for the synergistic activity are visualized. Based on the results, a mechanism highlighting the structure activity correlation has been proposed.

Thermodynamic Analysis of Hydrogen Production from Ethanol-glycerol Mixture Through Dry Reforming

Thermodynamic properties of ethanol-glycerol dry reforming have been studied with the method of Gibbs free energy minimization for hydrogen production from ethanol-glycerol mixture. Equilibrium compositions were determined as a function of CO2/ethanol-glycerol molar ratios (CEG)(1:1-12:1) where ethanol-glycerol is 1:1; reforming temperatures (573-1273 K) at different pressures (1-50 bar). Optimum conditions for hydrogen production are temperatures between 1073 and 1273 K and CEG of 1:1 at 1 bar pressure, whereas temperatures above 1073 K and CEG ratio 1:1 and 1 bar are suitable for the production of synthesis gas. Higher pressure and higher CEG ratio does not encourage hydrogen formation. Under identified optimum conditions, carbon formation can be thermodynamically inhibited

Enhanced thermophilic fermentative hydrogen production from cassava stillage by chemical pretreatments

Acid and alkaline pretreatments for enhanced hydrogen production from cassava stillage were investigated in the present study. The result showed that acid pretreatment was suitable for enhancement of soluble carbohydrate while alkaline pretreatment stimulated more soluble total organic carbon production from cassava stillage. Acid pretreatment thereby has higher capacity to promote hydrogen production compared with alkaline pretreatment. Effects of pretreatment temperature, time and acid concentration on hydrogen production were also revealed by response surface methodology. The results showed that the increase of all factors increased the soluble carbohydrate production, whereas hydrogen production was inhibited when the factors exceeded their optimal values. The optimal conditions for hydrogen production were pretreatment temperature 89.5 °C, concentration 1.4% and time 69 min for the highest hydrogen production of 434 mL, 67% higher than raw cassava stillage.

Biohydrogen production by Thermoanaerobacterium thermosaccharolyticum KKU-ED1: Culture conditions optimization using xylan as the substrate

Thermophilic hydrogen production from xylan by Thermoanaerobacterium thermosaccharolyticum KKU-ED1 isolated from elephant dung was investigated using batch fermentation. The optimum conditions for hydrogen production from xylan by the strain KKU-ED1 were an initial pH of 7.0, temperature of 55 °C and xylan concentration of 15 g/L. Under the optimum conditions, the hydrogen yield (HY), hydrogen production rate (HPR) and xylanase activity were 120.05 ± 15.07 mL H2/g xylan, 11.53 ± 0.19 mL H2/L h and 0.41 units/mL, respectively. The optimum conditions were then used to produce hydrogen from 62.5 g/L sugarcane bagasse (SCB) (equivalent to 15 g/L xylan) in which the HY and HPR of 1.39 ± 0.10 mL H2/g SCB (5.77 ± 0.41 mL H2/g xylan) and 0.66 ± 0.04 mL H2/L h, respectively, were achieved. In comparison to the other strains, the HY of the strain KKU-ED1 (120.05 ± 15.07 mL H2/g xylan) was close to that of Clostridium sp. strain X53 (125.40 mL H2/g xylan) and Clostridium butyricum CGS5 (90.70 mL H2/g xylan hydrolysate).

Biohydrogen production by Thermoanaerobacterium thermosaccharolyticum KKU-ED1: Culture conditions optimization using mixed xylose/arabinose as substrate

Background: Biological hydrogen production by microorganisms can be divided into two main categories i.e. photosynthetic organisms that produce hydrogen using light as energy source and anaerobic bacteria that produce hydrogen via dark fermentation. Dark fermentative hydrogen production by anaerobic bacteria has the advantages of a higher HPR without illumination and of the capability to convert various kinds of substrate. Results: Thermophilic hydrogen producer was isolated from elephant dung and identified as Thermoanaerobacterium thermosaccharolyticum KKU-ED1 by 16S rRNA gene analysis, which was further used to produce hydrogen from mixed pentose sugar i.e., xylose/arabinose. The optimum conditions for hydrogen production from mixed xylose/arabinose by KKU-ED1 were a 1:1 xylose/arabinose mixture at the total concentration of 5 g/L, initial pH of 6.5 and temperature of 55oC. Under the optimum conditions, hydrogen from sugar derived from acid-hydrolyzed sugarcane bagasse at a reducing sugar concentration were achieved. Soluble metabolite product (SMP) was predominantly acetic acid indicating the acetate-type fermentation. Conclusions: The strain KKU-ED1 appeared to be a suitable candidate for thermophilic fermentative hydrogen production from hemicellulosic fraction of lignocellulosic materials due to its ability to use various types of carbon sources.

Optimization of the hydrogen yield from single-stage photofermentation of glucose by Rhodobacter capsulatus JP91 using response surface methodology

Hydrogen production from glucose via single-stage photofermentation was examined with the photosynthetic bacterium Rhodobacter capsulatus JP91 (hup-). Response surface methodology with Box–Behnken design was used to optimize the independent experimental variables of glucose concentration, glutamate concentration and light intensity, as well as examining their interactive effects for maximization of molar hydrogen yield. Under optimal condition with a light intensity of 175W/m2, 35mM glucose, and 4.5mM glutamate, a maximum hydrogen yield of 5.5 (±0.15)molH2/molglucose, and a maximum nitrogenase activity of 246 (±3.5)nmolC2H4/ml/min were obtained. Densitometric analysis of nitrogenase Fe-protein expression under different conditions showed significant variation in Fe-protein expression with a maximum at the optimized central point. Even under optimum conditions for hydrogen production, a significant fraction of the Fe-protein was found in the ADP-ribosylated state, suggesting that further improvement in yields might be possible.