H2-rich Gas Production Research Articles

Catalysis/CO2 sorption enhanced pyrolysis-gasification of biomass for H2-rich gas production: Effects of activated carbon, NiO active component and calcined dolomite

This study aims to reveal the effects of activated carbon (AC), NiO active component and calcined dolomite addition on the H2-rich gas production from pyrolysis-gasification of biomass, the experiments were conducted on a two-staged fixed-bed reactor with sawdust (SD) as biomass feedstock. It was found that the H2-rich gas production was largely enhanced by AC catalyst due to its catalytic effect on volatiles gasification as well as its self-gasification during the process. Lower impregnation ratio of ZnCl2 or H3PO4 to biomass was preferable to the H2 production. H3PO4 activation char (PAC) might keep more active structures with higher AC yields compared with ZnCl2 activation char (ZAC). NiO would mainly enter into the micropores of AC, possibly covered some of the active sites on AC surface, thus caused the decrease in AC self-gasification, although certain catalytic effect of NiO on H2 production was also observed. Additional calcined dolomite introduction together with NiO/AC catalyst could further increase the H2 concentration and yield. A remarkable synergistic strengthening effect was found between NiO/PAC-SD catalyst and calcined dolomite, the maximum H2 concentration and yield of 62.54 vol% and 1343.52 mL/g biomass were achieved with the addition of NiO/PAC-SD-1 and calcined dolomite due to the combination of in situ CO2 sorption enhancing effect and NiO/PAC-SD-1 catalytic effect as well as the enhanced AC self-gasification. It is thus illustrated that the catalysis/sorption enhanced pyrolysis-gasification of biomass using NiO/AC catalyst and calcined dolomite is an effective way to produce a H2-rich gas and shows a good prospect in the carbon-constrained future.

H2-rich gas production from steam gasification of a winery waste and its blends with industrial wastes. Effect of operating parameters on gas quality and efficiency

A winery waste and its blends with industrial wastes were gasified by steam via a two-step process, employing a fixed bed reactor and a thermal analysis-mass spectrometer unit. Solid materials were characterized in terms of elemental analysis, heating value, internal structure and chemical functional groups, whereas bio-oil, pyrolysis gas and syngas were quantitatively analysed. The effect of temperature, steam-to-biomass ratio and fuel composition on carbon conversion, cold gas efficiency, energy recovery, reaction rate, gas composition and quality were determined and kinetic analysis was performed. When industrial wastes waste wood shavings and refused derived fuel were blended with grape husks and curls at ratios 30:70, upgraded fuels were produced. At 850 °C organic matter was almost completely converted to syngas upon steam gasification. A first-order kinetic model fitted the experimental results successfully, with activation energy values ranging between 54.3 kJ/mol and 143.5 kJ/mol. An increase in steam-to-biomass ratio from 0.5 to 3 resulted in a higher concentration of hydrogen in product gas, while excess steam enhanced hydrogen yield up to 74%. Energy recovery from all fuels was high, cold gas efficiency reached a value of 66% and the higher heating value of syngas ranged between 9.6 and 11.4 MJ/m3.

Catalytic pyrolysis of oily sludge with iron-containing waste for production of high-quality oil and H2-rich gas

Oily sludge (OS), as a kind of organic hazardous waste with complex components, is suitable for treatment by pyrolysis. To attain effective removal of petroleum hydrocarbons and explore synergistic disposal for multi-source solid wastes, the catalytic effects of steel slag (SS) and red mud (RM) were investigated in this work. They could reduce the activation energy, accelerate OS degradation and shift the degradation of petroleum hydrocarbons towards lower temperature. What’s more, RM with higher iron content worked better, gained more pyrolytic gas and higher H2 production as well. More pyrolytic gas production was obtained when RM addition was at a low proportion. However, excessive catalyst would play a certain inhibitory role. The addition of RM promoted oil recovery at low temperature (400–500 °C) but brought more gas originating from oil cracking at high temperature (600 °C). At 400 °C, the oil yield elevated continuously with prolonging retention time. Nevertheless, even if the retention time was long enough, the harmless disposal for OS could not be completed with the catalysis of RM. Finally, the pristine minerals in RM were co-pyrolysis with OS individually to explore catalytic contributions. Metal oxides could enhance the gas yield and reduce the oil yield. The order of catalytic capacities was Fe2O3＞CaO＞SiO2＞Al2O3. Fe2O3 promoted H2 production and conversion from heavy oil into light fuels. Besides, Fe2O3 was reduced into Fe3O4 with part of [O] shifting into oil. CaO, SiO2, and Al2O3 could reduce the oxygen content in the pyrolytic oil through their acid-base properties to improve the oil quality. This work summarized the functions of various components in RM, might provide inspiration for getting insight into the application of collaborative treatment of different solid wastes.

Catalytic Steam Reforming of Benzene as a Bio-tar Model Compound over Ni–Fe/TiO2 Catalysts

Bio-tar formed during biomass gasification can cause the blockage or corrosion of pipelines and devices. Catalytic reforming through Ni-based catalysts is a potential method to achieve tar elimination, while carbon deposition is the main obstacle. In this study, the steam reforming of benzene was investigated over modified Ni/TiO2 catalysts, and the effects of metal promoters, reaction temperatures, and steam-to-carbon (S/C) molar ratios were explored. The results indicated that the Fe promoter was promising to simultaneously achieve the H2-rich gas production and suppress the carbon deposition over the catalyst. When the reaction temperature was 800 °C and the S/C molar ratio was 1.00, the benzene conversion ratio and the H2 yield, respectively, reached 96.31% and 102.53 mmol/gbenzene. Ni–Fe alloys were generated after the modification with the Fe promoter, which improved the dispersion of Ni components. Besides, the adsorption of H2O molecules was enhanced which favored the formation of lattice oxygen and accelerated the reforming of benzene. Furthermore, the accumulation of lattice oxygen promoted the oxidation of amorphous carbon and suppressed the formation of graphitic carbon, thereby protecting the active Ni sites from the coverage of the carbon layer. Therefore, the resistance of carbon deposition of the Fe-modified Ni/TiO2 catalyst was improved.

H2 rich gas production from agricultural waste mixture over Ni/kaolin and Ni/bentonite catalyst by gasification

Biomass gasification is an attractive technology in order to utilize agricultural waste which is the mixture of oil extracted sunflower seeds (pulp), tea, and tobacco waste. In this study, natural clay-based catalysts were synthesized using the impregnation method with the different Ni loading amounts (10, 20, 30 wt%), different support materials (kaolin and bentonite). The catalysts were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF), Scanning electron microscopy (SEM), and Brunauer–Emmett–Teller analysis (BET). Gasification of biomass mixture was performed using air as the gasification agent using an updraft tubular gasifier. Studies were carried out at 650–850 °C and the time range of 15–30 min without a catalyst, and the studies with catalyst were carried out at a constant temperature of 650 °C. The highest hydrogen yield was obtained as 6.86 mol/kg biomass at 650 °C, 15 min with 30% Ni/Calcined Kaolin.

Catalytic biomass gasification in decoupled dual loop gasification system over alkali-feldspar for hydrogen rich-gas production

Gasification of biomass with steam and oxygen was carried over alkali-feldspar in a decoupled dual loop gasification (DDLG) system. This system has a moving bed reformer (MBR), a fluidized bed gasifier (FBG), a riser combustor (RC) and a particle grading cyclone (PGC). Through the PGC, two loops, i.e. a gasification loop of FBG-RC-PGC utlizing quartz sand as circulating bed material and a reforming loop of MBR-RC-PGC utilizing alkali-feldspar as circulating bed material, are formed. The effects of process variables such as reformer temperature, steam to biomass ratio (S/B) and air equivalence ratio (ER) on product gas composition, heating value, tar content, yield of product gas, carbon conversion, water conversion and cold gas efficiency were investigated. The maximum water conversion 35.2% and cold gas efficiency 82.3% were observed at reformer temperature 850 °C. The increase of S/B promoted the H2-rich gas production and the maximum concentration of 42.1 vol % was achieved at the S/B of 1.0. In addition, the use of steam and oxygen together as gasification agent enhanced the tar removal and carbon conversion. The lowest tar content 1.1 g/Nm3 and high carbon conversion 97.2% were obtained at S/B of 0.6 and ER of 0.35.

Recent development of biomass gasification for H2 rich gas production

Biomass gasification for hydrogen (H2) production provides outstanding advantages in terms of renewable energy resources, carbon neutral, high efficiency, and environmental benefits. However, the factors influencing H2 production from biomass gasification are complex, which makes determining the optimal operating conditions challenging. Biomass gasification also poses challenges owing to the high associated tar content and low gas yield, which need to be overcome. This review summarizes the influence of the gasification parameters on H2 production. Catalytic gasification technology and some of the latest catalysts, such as composites and special structure catalysts, are also summarized herein based on the requirements of high-purity H2 production. Moreover, novel technologies, such as staged gasification, chemical looping gasification, and adsorption-enhanced reforming for producing H2 rich gas are introduced. Finally, the challenges and prospects associated with biomass gasification for H2 production are presented.

Catalytic Pyrolysis of Oil Sludge with Iron-Containing Waste for Production of High-Quality Oil and H2-Rich Gas

Catalytic Pyrolysis of Oil Sludge with Iron-Containing Waste for Production of High-Quality Oil and H2-Rich Gas

Hydrothermal gasification of Scenedesmus obliquus and its derivatives: a thermodynamic study using Aspen Plus

AbstractThis study presents the simulation of hydrothermal gasification (HTG) of Scenedesmus obliquus microalgae and their derivatives using Aspen Plus V11. The effect of operating parameters such as temperature, pressure, and biomass concentration on the yield and composition of gaseous products using whole algae, lipid, and lipid extracted algae (LEA) as feedstocks was examined. The results showed that reaction pressure exhibited minimal impact whereas temperature, biomass concentration, and feedstock composition had significant effects on the composition of gaseous products. It was also found that a low temperature (400 °C) and biomass concentration of 40 wt% favored the production of methane‐rich gas. In contrast, high temperature (700 °C) and low biomass concentration (10 wt%) favored hydrogen‐rich gas production in all the three feedstocks considered. The highest mole fraction achieved for CH4 was 53.45, 61.70, and 52.20 mol%, which corresponded to a CH4 yield of 31.14, 56.90, and 30.15 mmol g−1 for whole algae, lipid, and LEA respectively. For H2 rich gas production, the highest mole fractions achieved were 55.77, 52.29, and 55.34 mol%, which correspond to H2 yields of 75.44, 105.51, and 73.49 mmol g−1 for whole algae, lipids, and LEA, respectively. The ranking order for the yield and lower heating value of the product gas from the HTG process is lipid > whole algae > LEA. This study has shown that hydrogen‐rich and methane‐rich gas can be produced from the hydrothermal gasification of microalgae as a function of the reaction conditions and feedstock composition. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Supercritical water gasification of waste water produced from hydrothermal liquefaction of microalgae over Ru catalyst for production of H2 rich gas fuel

Ru supported on activated carbon (C), Al2O3, CeO2, MgO, TiO2, and ZrO2 were prepared and employed to boost supercritical water gasification (SCWG) of microalgae hydrothermal liquefaction (HTL) downstream water at 600 °C for 1 h. Effects of catalysts, water density, and Ru/C loading on total organic carbon (TOC) reduction, carbon gasification efficiency (CGE), and gas yield were examined. All the Ru catalysts showed a positive effect on TOC reduction and converted organics in the HTL downstream water to fuel gas, with H2 and CH4 as the two most abundant component. With the addition of Ru/C, almost complete removal of TOC, the highest CGE, and H2 yield were achieved due to its largest metal dispersion. With the addition of Ru/C, increasing water density and catalyst loading favored TOC reduction and CGE increase as well as the total gas yield. The highest H2 content of 50% and yield of 2.62 mmol/g(aq.) were obtained at the highest catalyst loading of 12.0 mg(Ru/C)/mL(aq.). This study suggested that SCWG with the addition of Ru/C was a promising strategy to produce fuel gas rich in H2, from the organics in the microalgae HTL downstream water.

Optimised production of tailored syngas from municipal solid waste (MSW) by sorption-enhanced gasification

Sorption-enhanced gasification (SEG) is a promising indirect gasification route for the production of synthetic fuels since it allows the H2, CO and CO2 content of the resulting syngas to be adjusted. This SEG process has been successfully demonstrated at pilot scale for lignocellulosic biomass and other agricultural and forest waste products, mainly focusing on H2-rich gas production. Within this work, the potential application of the SEG process to a material derived from municipal solid waste (MSW) as feedstock is experimentally demonstrated in a 30 kWth bubbling fluidised-bed (BFB) gasifier. The influence of the sorbent-to-biomass ratio, steam excess and gasification temperature has been carefully analysed in order to understand their effect on SEG performance. Moreover, main conditions able to affect the resulting syngas composition, specifically in terms of H2, CO and CO2 content, have been indicated. Gasification temperature turned out to be the variable that most influenced syngas composition due to the limiting mechanisms associated with the carbonation of the CaO used as bed material. This operating variable also determined biomass conversion, together with solids residence time in the gasifier, resulting in a wide variation of fixed carbon conversion under the studied conditions. Finally, tar yield and composition were evaluated as a function of temperature and the sorbent-to-biomass ratio used, resulting in tar contents as low as 7 g/Nm3 (dry gas), consisting mainly of 1-ring aromatic compounds.

Carbon-coated mesoporous silica-supported Ni nanocomposite catalyst for efficient hydrogen production via steam reforming of toluene

Catalytic steam reforming of biomass tars is a promising technique for H2-rich gas production. However, the undesired deactivation of nickel-based catalysts due to nanoparticle (NP) sintering and carbon deposition remains a challenge for industrial applications. In this study, we prepared a carbon-coated ordered mesoporous silica-supported Ni-based catalyst (Ni-SiO2@C) via an evaporation-induced self-assembly (EISA) and calcination process. Characterizations revealed that the Ni-SiO2@C has a regular mesostructure with graphitic carbon layers protected Ni NPs (average 5.5 nm in diameter) highly dispersed and embedded into the silica wall of mesoporous channels. Compared to the SBA-15 and activated carbon-supported catalysts (NiO/SBA-15 and Ni/AC), the Ni-SiO2@C exhibits a higher toluene (a biomass tar model compound) conversion efficiency of 99.9% at 550 °C with an excellent stability for at least 46 h during steam reforming. The good performance can be attributed to the improved Ni NP dispersion, electron transfer and hydrothermal stability by enhanced metal-support interaction (MSI) as well as carbon coating. This work provides a cost-effective and easy handling approach for the synthesis of anti-sintering and coke-resistant tar reforming catalysts.

Catalytic steam co-gasification of biomass and coal in a dual loop gasification system with olivine catalysts

A dual loop gasification system (DLG) has been previously proposed to facilitate tar destruction and H2-rich gas production in steam gasification of biomass. To sustain the process auto-thermal, however, additional fuel with higher carbon content has to be supplied. Co-gasification of biomass in conjunction with coal is a preferred option. Herein, the heat balance of the steam co-gasification of pine sawdust and Shenmu bituminous coal in the DLG has been analyzed to verify the feasibility of the process with the help of Aspen Plus. Upon which, the co-gasification experiments in the DLG have been investigated with olivine as both solid heat carriers and in-situ tar destruction catalysts. The simulation results show that the self-heating of the DLG in the co-gasification is achieved at the coal blending ratio of 28%, gasification circulation ratio of 19 and reforming circulation ratio of 20 when the gasifier temperature 800 °C, reforming temperature 850 °C, combustor temperature 920 °C and S/C 1.1. The co-gasification experiments indicate that the tar is efficiently destructed in the DLG at the optimized reformer temperature and with olivine catalysts.

H2 production from a plasma-assisted chemical looping system from the partial oxidation of CH4 at mild temperatures

A plasma-assisted chemical looping system for the production of H2 (PCLH) was investigated in this study. This system allows the partial oxidation of CH4 at mild temperatures (573–773 K). Four active oxygen carriers: Fe2O3, NiO-impregnated Fe2O3 (NiO/Fe2O3), SrFeO3−δ and NiO-impregnated SrFeO3−δ (NiO/SrFeO3−δ) were compared, each working both as a packed material for the plasma reactor and an oxygen source for the partial oxidation of CH4. Similar conversions of CH4, and low yields of H2 were obtained in Fe2O3 and SrFeO3−δ. It was concluded that in these cases, H2 was mainly produced from direct cracking of CH4 by plasma. In contrast, when using NiO/Fe2O3 and NiO/SrFeO3−δ, substantial production of H2 was achieved. It is proposed that there is a synergistic effect between the catalyst and the oxygen carrier; the presence of the metallic Ni phase was responsible for catalysing the production of H2, and the oxygen from the support helped prevent the build-up of coke. As a result, the activity of Ni was continuously maintained for H2 production. The chemical loop is closed with the oxygen carriers being regenerated in air with plasma and then used in the next looping cycle. The high H2 production capability in NiO/Fe2O3 was repeatable; whilst, NiO/SrFeO3−δ deactivated in the second and third cycles. Amongst the temperatures studied, NiO/Fe2O3 at 673 K resulted in the best performance for H2-rich gas production. A further increase in the operating temperature led to a total combustion of CH4.

Hydrogen-rich syngas production by chemical looping steam reforming of acetic acid as bio-oil model compound over Fe-doped LaNiO3 oxygen carriers

Ni-based perovskites are promising oxygen carriers for chemical looping steam reforming to produce H2-rich gas from organics. In this study, a series of Fe-doped LaNiO3 perovskites with various Ni/Fe ratios (LaNixFe1-xO3 (0 ≤ x ≤ 1)) were investigated for chemical looping steam reforming of acetic acid as a model compounds of bio-oil. Results illustrated that although LaNiO3 showed higher activity for gas production, the Ni–Fe bimetallic perovskites were more stable during the steam reforming reactions. It was found that Fe doping can promote the content of lattice oxygen in the perovskite which could be released during the steam reforming reaction, thus coking resistant of the perovskite was effectively improved. Among the LaNixFe1-xO3 (0 ≤ x ≤ 1) perovskites, LaNi0.8Fe0.2O3 exhibited the best synergistic effect between Ni and Fe to achieve the highest H2/CO for H2-rich gas production. Operational variables of the steam reforming reactions catalyzed by LaNi0.8Fe0.2O3 for H2 production were further optimized.

Biomass gasification coupled with producer gas cleaning, bottling and HTS catalyst treatment for H2-rich gas production

The aim of the present study is to demonstrate the production of hydrogen-rich fuel gas from J. curcas residue cake. A comprehensive experimental study for the production of hydrogen rich fuel gas from J. curcas residue cake via downdraft gasification followed by high temperature water gas shift catalytic treatment has been carried out. The gasification experiments are performed at different equivalence ratios and performance of the process is reported in terms of producer gas composition & its calorific value, gas production rate and cold gas efficiency. The producer gas is cleaned of tar and particulate matters by passing it through venturi scrubber followed by sand bed filter. The clean producer gas is then compressed at 0.6 MPa and bottled into a gas cylinder. The bottled producer gas and a simulated mixture of producer gas are then subjected to high temperature shift (HTS) catalytic treatment for hydrogen enriched gas production. The effect of three different operating parameters GHSV, steam to CO ratio and reactor temperature on the product gas composition and CO conversion is reported. From the experimental study it is found that, the presence of oxygen in the bottled producer gas has affected the catalyst activity. Moreover, higher concentration of oxygen concentration in the bottled producer gas leads to the instantaneous deactivation of the HTS catalyst.

Integrated process of coal tar upgrading and in-situ reduction of Fe2O3

Producing light fuels or valuable chemicals from coal tar is an important strategy to achieve the high value-added utilization of coal tar. This study proposed an integrated process of coal tar upgrading and in-situ reduction of Fe2O3. The effect of reaction temperature on the product distribution, coal tar component, and crystal phase transition of Fe2O3 were investigated. It is shown that increase of reaction temperature leads to increase production of H2 or CH4 rich gas and decrease of tar. Tar analysis revealed that more polycyclic aromatic hydrocarbons (PAHs) are formed along with the decrease of H/C ratio. The crystal phase transition from oxidation to reduction state can be detected on spent Fe2O3. The reduction degree of Fe2O3 is closely associated with the reaction temperature. Coke deposited on the spent Fe2O3 can be used as reducing agent, producing Fe3C when it was treated under N2 atmosphere. This study provides an integrated method of producing valuable aromatic compounds from coal tar as well as reduction process of Fe2O3 for steelmaking industry.

H2 production from partial oxidation of CH4 by Fe2O3-supported Ni-based catalysts in a plasma-assisted packed bed reactor

H2-rich gas production from CH4 at mild temperature (673 K), was achieved in a single step without introducing a separate oxygen stream. This was conducted in a plasma-assisted packed bed reactor in the presence of Ni-based catalysts doped on an active support, i.e. Fe2O3. Among the tested materials, NiO/Fe2O3 was found to be very promising and its excellent catalytic properties seemed to be induced by the presence of Fe2O3, which suppressed the formation of deposited carbon, and thus maintained the catalytic effect of metallic Ni (formed during NiO reduction by the CH4/Ar plasma). This work demonstrates the potential of plasma-assisted chemical looping partial oxidation for H2 production.

H2–rich gas production from leaves

In order to obtain the most favorable pyrolysis process for producing the highest yield of syngas from a range of leaf plants, the techniques of slow pyrolysis, fast pyrolysis and microwave pyrolysis of apple tree leaves, bamboo leaves, cypress leaves, sycamore tree leaves, and winter green leaves were investigated. The results showed that microwave pyrolysis produced the highest gaseous product yields (hydrogen rich gas) on all the 5 different kinds of leaves The apple tree leaves, sycamore leaves and wintergreen leaves showed higher yields of gas products than bamboo leaves and cypress leaves across all forms of pyrolysis. The experimentally determined higher heating values (HHV) of bio-chars from different leaves ranged from 20 to 28 MJ/Kg, interestingly, which are comparable to some coals. For the same variety of leaves, the HHV of bio-chars via different pyrolysis processes did not change significantly. However, the HHV of bio-chars from different leaves behaved differently, with the bio-char from wintergreen leaves showing the highest HHV, which reached around 27 MJ/Kg; on the contrary, the HHV of bio-chars from bamboo leaves gave the lowest values, some 20–22 MJ/Kg. For the gaseous products, the total amount of H2, CO, CO2 and CH4 reached 95% from all 3 pyrolysis treatments. Importantly, compared with slow and fast pyrolysis, the microwave pyrolysis of different leaves shows the highest content of H2 and CO and the lowest contents of CO2. The HHV of gaseous products of different leaves, using the same pyrolysis treatment, showed similar values but noticeably different when the pyrolysis process is for the same leaves is changed. The HHV of gaseous products via microwave pyrolysis are the highest amongst the different pyrolysis processes with the gaseous products HHV via fast pyrolysis being the lowest. We therefore conclude that microwave pyrolysis is a highly effective and also a highly selective process for H2 rich gas production from natural leaves. Furthermore, the addition of acid, bases and salts as catalysts for the pyrolysis did not noticeably result in any significant activity and products changes during the microwave pyrolysis process.

Gasification of dried sewage sludge using an innovative three-stage gasifier: Clean and H2-rich gas production using condensers as the only secondary tar removal apparatus

Air gasification of dried sewage sludge was performed in a new-type three-stage gasifier consisting of an auger, a fluidized bed, and a tar-cracking reactors. The study aimed to evaluate the possibility of gasification using only condensers for the secondary tar removal method. The effects of Ni- and Fe-impregnated active carbons on the quality of producer gas were also investigated. Finally, to investigate the deactivation behavior of active carbon, a spent active carbon obtained after about 4.3 h of gasification, was used again for approximately 3.7 h of gasification. The active carbons used effectively reduced the contents of condensed and gaseous tars. Ni-impregnated active carbon produced a gas with a high H2 content (26 vol%) and a low NH3 content (198 ppmv), while Fe-impregnated active carbon produced a gas with a low H2S content (96 ppmv). The compositions of the producer gases obtained solely using condensers were similar to those obtained using electrostatic precipitator. During the total ∼8 h of gasification, active carbon could efficiently remove tar; however, its surface area and total pore volume slowly decreased with time.