High Purity Syngas Research Articles

Biomass gasification: Sub-pilot operation of >600 h with extensive tar cracking property and high purity syngas production at H2:CO ratio ∼2 using moving bed redox looping technology

Commercializing biomass-based technologies as an alternative to fossil fuels is necessary for a sustainable future. This study proposes a robust Biomass to Syngas (BTS) chemical looping system to gasify biomass into syngas for a range of downstream applications, with focus on liquid fuel production. The system has been demonstrated on a sub-pilot scale cumulatively for over 600 h, proving the technology's commercial viability. Pelletized corn cob, woody pellets, and unpelletized loose corn cob, were successfully tested, proving the robusticity of the process to handle untreated biomass with batch variation. Tar analysis shows that moving bed reducer can reduce the tar concentration to 0.5 g/m3, owing to uniform residence time, high temperature, and catalytic activity of oxygen carrier, while injection of steam as an enhancer gas increases carbon conversion by char gasification. A variable syngas quality with an H2/CO ratio of ∼2 and a syngas purity greater >70% was achieved, making this syngas suitable for the generation of liquid fuels via Fischer-Tropsch synthesis. The biomass requirement for a chemical looping system decreases by 13.9% over the conventional biomass gasifier for generating the same amount of liquid fuels. Heat integration suggests integrating biomass drying with the combustor exhaust air for process authothermicity.

High-purity syngas production by cascaded catalytic reforming of biomass pyrolysis vapors

A novel pyrolysis followed by in-line cascaded catalytic reforming process without additional steam was developed to produce high-purity syngas from woody biomass. The key to the proposed process is the construction of a cascaded biochar + NiAl2O4 catalytic reforming process in which biochar acts as a pre-reforming catalyst, and NiAl2O4 acts as a primary reforming catalyst. The large oxygenates in the pyro-vapors are deeply cracked in the biochar layer due to the increased residence time in the hot-biochar bed. The remaining small molecules are then reformed with the autogenerated steam from pyrolysis catalyzed by the reduced Ni0 species in the NiAl2O4 catalyst (NiAlO). The results showed that the yield of syngas for the optimized process was 71.28 wt% (including 44.44 mg-H2/g-biomass and 536.48 mg-CO/g-biomass), and the CO2 yield of the process was only 3 kg-CO2/kg-hydrogen. High-purity syngas with 89.47 vol% of (H2 + CO) was obtained, and the gas energy conversion efficiency (GECE) of the process reached 75.65%. The study shows that in the cascaded catalytic reforming process, cracking of the large oxygenates and reforming of the small molecules are promoted sequentially in separated biochar + NiAlO catalyst layers, which maximizes the syngas production and improves the activity and stability of the Ni-based catalyst.

Integrated CO2 capture and utilization with CaO-alone for high purity syngas production

Carbon capture and utilization (CCU) represent a promising strategy to reduce CO2 emissions and promote a sustainable economy. We report an integrated CCU (ICCU) process by integrating CO2 capture with reverse water gas shift reaction by applying simple and low-cost CaO as both sorbent and catalyst. By switching the feeding gas from CO2 source to H2 isothermally, up to 75% of captured CO2 was 100% converted into CO at 600-700 °C and the cycle performance of CaO was significantly improved under ICCU condition. In addition, the simulation confirms the significant economic advantage compared to similar traditional processes. The work could dramatically reduce the cost of materials and simplify CCU processes to advance the development and deployment of carbon neutrality technologies.One-Sentence Summary: A low-cost and widely used material, CaO, was used to not only adsorb CO2 efficiently but also in situ convert CO2 into valuable syngas with > 75% CO2 conversion to realise carbon neutrality, which is a vital target for sustainable future development.

Optimization of synthesis gas production in the biomass chemical looping gasification process operating under auto-thermal conditions

Biomass Chemical Looping Gasification (BCLG) is a promising route to obtain N2 free high purity syngas. In this work, heat and mass balances were solved to determine the auto-thermal operation conditions that maximize the syngas yield in a BCLG system. A Fe-based oxygen carrier and pine wood as fuel were considered for the simulation. Two methods to control the transference of oxygen between the air reactor (AR) and fuel reactor (FR) were analysed. Syngas yield was higher controlling the oxygen fed to the AR by the air flow (OCM-1) than controlling the oxygen supplied to the FR by the oxygen carrier circulation flow (OCM-2).The influence of different operating parameters, such as oxygen carrier transport capacity, preheating of gases fed to the system, steam/biomass ratio, fuel reactor temperature, was also analysed. It is noteworthy that working with OCM-2 it is necessary to optimize the amount of active phase in synthetic oxygen carriers or to dilute the natural oxygen carriers (ores, wastes) with an inert material to maintain realistic temperature difference values between reactors. Therefore, it is recommended to operate with the OCM-1 as it has the advantages of a more flexible operation and the possibility of obtaining pure N2.

Use of bio-glycerol for the production of synthesis gas by chemical looping reforming

Glycerol availabity, a waste generated in the production of biodiesel, has increased during last years. In this work, Chemical Looping Reforming (CLR) of glycerol has been demonstrated in a 1 kWth continuous unit during 35 h using a Ni-based oxygen carrier to obtain a high purity syngas without CO2 emissions. Complete conversion of the glycerol and syngas composition close to thermodynamic equilibrium was obtained in the fuel reactor. Moreover, pure N2 was obtained as product in the air reactor. The influence of the main operating variables on the composition and flow rates of synthesis gas was evaluated. The oxygen-to-glycerol molar ratio was the main parameter since the amount of lattice oxygen transferred by the oxygen carrier in the fuel reactor controlled the syngas composition. The increase of the water-to-glycerol ratio produced an increase in the production of H2 and CO2 with a decrease in the CO content, increasing both the syngas yield and the H2/CO molar ratio in the gas. Fuel reactor temperature affected mainly to the CH4 content, being lower as higher was the temperature. Close to autothermal conditions, it is possible to obtain a syngas composed by H2 ≈ 48–50 vol%; CO ≈ 30–35 vol%; CO2 ≈ 14–18 vol%; and CH4 ≈ 1.6–3 vol%. In addition, different H2/CO ratios can be obtained by modifying the H2O/glycerol ratio and temperature. A H2/CO ratio of 2 could be reached using either a H2O/glycerol ratio of 1.5 at 750 °C or a H2O/glycerol ratio of 2 at 800 °C.

Application of a micro-channel reactor for process intensification in high purity syngas production via H2O/CO2 co-splitting

A stainless steel micro-channel reactor was tailor-made to an in house-design for process intensification propose. The reactor was used for a two-step thermochemical cycles of H2O and CO2 co-splitting reaction, in the presence of La0.3Sr0.7Co0.7Fe0.3O3 (LSCF). LSCF was coated inside the reactor using wash-coat technique. Oxygen storage capacity of LSCF was determined at 4465 μmol/g, using H2-TPR technique. H2O-TPSR and CO2-TPSR results suggested that a formation of surface hydroxyl group was the cause of H2O splitting favorable behavior of LSCF. Optimal operating reduction/oxidation temperature was found at 700 °C, giving 2266 μmol/g of H2, 705 μmol/g of CO, and 67% of solid conversion, when the H2O and CO2 ratio was 1 to 1, and WSHV was 186,000 mL/g.h. Activation energy of H2O spitting and CO2 splitting was estimated at 87.33 kJ/mol, and 102.85 kJ/mol The pre-exponential factor of H2O splitting and CO2 splitting was 595.24 s−1 and 698.79 s−1, respectively.

Design and Operations of a 15 kWth Subpilot Unit for the Methane-to-Syngas Chemical Looping Process with CO2 Utilization

The methane-to-syngas (MTS) chemical looping process is an advanced methane reforming technology for the production of high purity syngas. The developed MTS process utilizes metal oxide oxygen carriers in a cocurrent moving bed reactor to partially oxidize the methane such that the resulting syngas stream is undiluted by nitrogen in air or H2 from overconversion and directly suitable for downstream processing. The oxygen carriers are regenerated with air in a separate fluidized bed reactor producing a spent air stream separate from the product syngas, circumventing the need for cryogenic air separation units. In this work, a 15 kWth subpilot unit is designed and operated in a continuous manner to experimentally confirm the viability of the MTS process. Reactor design considerations and methodology are discussed in detail. An iron–titanium composite oxygen carrier is used as the oxygen carrier for its ability to achieve high methane conversion while regulating the product syngas to the partial oxidation products, CO and H2. Syngas is produced with an H2/CO ratio of ∼2, and a purity of ∼97% is produced with methane conversion exceeding 99%. The coinjection of methane with H2 and/or H2O is explored for the purpose of H2 utilization and flexible H2/CO ratios, allowing the MTS process to produce syngas for a variety of downstream processes without reactor modification. The results indicate that syngas with H2/CO ratios ranging from 1.19 to 2.50 with high methane conversion and syngas purity can be produced with coinjection. No evidence of carbon deposition on the oxygen carrier is revealed, and the oxygen carrier retained structural integrity after subjection to reaction and circulation in the subpilot unit.

Evaluation of Fe substitution in perovskite LaMnO3 for the production of high purity syngas and hydrogen

Chemical looping reforming of methane (CLRM) technology is a new approach for syngas and pure hydrogen generation. During the whole reaction, methane is first partially oxidized to syngas by the lattice oxygen of the oxygen carrier, and then the lattice oxygen of the reduced oxygen carrier is recovered by thermal water splitting, with pure hydrogen produced. LaMnO3 is used as an oxygen carrier for the CLRM. It obtains a high resistance to carbon deposition, while a lower CH4 conversion due to the unstable structure. Fe ion substitution in LaMnO3 can be used to improve its reactivity and thermal stability. La1-xMnFexO3/LaMn1-xFexO3 (x = 0.05, 0.1, 0.15, 0.2) oxygen carriers own higher reactivity and better resistance to carbon deposition, producing high purity syngas and hydrogen. La0.85MnFe0.15O3 sample exhibits the highest CO selectivity (~99%), syngas productivity (3.78 mmol g−1) and H2 productivity (1.76 mmol g−1) due to the higher oxygen vacancy concentration, and its H2/CO molar ratio is maintained at the ideal ratio of 2.0 (1.93–2.07) during the whole process. Notably, no carbon deposition is generated over LaMnO3, La0.85MnFe0.15O3 and LaMn0.9Fe0.1O3 oxygen carriers even after 20 redox cycles, and La0.85MnFe0.15O3 exhibits superior resistance to carbon deposition due to the better structural and thermal stability.

Thermodynamic and mechanism study of syngas production via integration of nitrous oxide decomposition and methane partial oxidation in the presence of 10%NiO–La0.3Sr0.7Co0.7Fe0.3O3−δ

10%NiO–La0.3Sr0.7Co0.7Fe0.3O3−δ (10%NiO-LSCF3773) was synthesized using the EDTAcitrate complexing method. Non-catalytic and catalytic nitrous oxide decomposition and methane partial oxidation using 10%NiO–LSCF3773 was experimentally studied, assuming that the reactions occurred separately in a membrane reactor at feed side and permeate side. The experimental results are in good agreement with the chemical equilibrium composition calculated using Aspen Plus, and the changes of standard Gibbs free energy of each relevant elementary reactions. The mechanism of the reactions was proposed to follow Eley–Rideal surface reaction. The optimal temperature was 800 °C, under atmospheric pressure, where (1) NO2 formation was not detected (2) no production of C2 + and C3 + (3) complete conversion of N2O, CH4 and O2 were achieved (4) high purity syngas was obtained with no significant amount of undesired products and (5) readily utilizable syngas at the ratio of two was achieved.

High purity syngas and hydrogen coproduction using copper-iron oxygen carriers in chemical looping reforming process

Chemical looping reforming presents an attractive alternative to the conventional processes for chemicals and energy production from carbonaceous fuels with significant reduction in carbon emissions and high exergy efficiency. Production of syngas and hydrogen is important because the former is a critical building block for valuable chemicals and latter is a source of clean energy. The use of copper-iron (Cu-Fe) oxygen carriers for coproducing syngas and hydrogen in a chemical looping reforming process is studied via experiments and process simulations. Three different compositions of Cu and Fe oxides are examined for their properties concerning the reactivity towards fuel and the selectivity towards syngas. The feasibility of using a co-current moving bed reactor configuration for syngas production is probed experimentally in a fixed bed reactor by placing the fully oxidized and reduced oxygen carrier in series. The methane conversion and dry syngas purity as high as 99.5% and 97.5%, respectively, are observed for copper oxide (20 wt%) - iron oxide (60 wt%) - aluminium oxide (20 wt%) oxygen carrier in a simulated co-current moving bed reactor. Key performance parameters including effective thermal efficiency for 5 different configurations of the chemical looping reforming process from ASPEN Plus simulation software are compared against the baseline case of the auto-thermal reforming process. Apart from an improvement in the natural gas conversion and syngas purity in the chemical looping reforming process, the net hydrogen production is increased by 28% and effective thermal efficiency is increased by 10% over that of the auto-thermal reforming process.

A novel chemical looping partial oxidation process for thermochemical conversion of biomass to syngas

The Biomass-to-Syngas (BTS) chemical looping process is an advanced thermochemical biomass conversion process for the production of sustainable fuels and chemicals. The BTS process is novel in that it converts biomass feedstock to high purity syngas with adjustable H2:CO molar ratio without needing an air separation unit (ASU), a tar reformer, a steam reformer, or a water-gas-shift (WGS) reactor. In the BTS process, biomass feedstock is partially oxidized to produce syngas by oxygen carriers in a reducer that is operated in a co-current gas-solid moving bed contact mode. The reduced oxygen carriers are regenerated in a fluidized bed combustor via the oxidation reaction with air. The BTS process uses the iron-titanium composite metal oxide (ITCMO) material as the oxygen carrier, which is capable of cracking the volatiles produced in biomass pyrolysis as well as regulating the syngas composition. The co-current moving bed reducer eliminates back-mixing, channeling, or bypassing of solid and gas reactants, resulting in a syngas composition that is close to the thermodynamic equilibrium. In this paper, the rationale of a successful BTS process is discussed along with the thermodynamic characteristics of the ITCMO oxygen carrier, that can effectively react with a woody biomass feedstock, analyzed based on an ASPEN Plus model. Bench scale moving bed reducer experiments are presented, indicating the conversion of wood pellets to syngas with a H2:CO ratio of 2, which is suitable for methanol or liquid fuel synthesis. The gas and solid composition produced in the bench scale reducer matches the prediction from the ASPEN Plus thermodynamic model. This model is further used to analyze the performance of the BTS process under autothermal conditions for methanol production, with a comparison with a baseline indirectly heated gasification process. The results indicate that the BTS process significantly reduces the biomass and steam consumption and appreciably improves the biomass conversion efficiency over that obtained from the baseline process.

Co-gasification of Indonesian coal and microalgae – A thermodynamic study and performance evaluation

A new integrated co-gasification of coal and biomass simulation model was developed using Aspen Plus. It consisted of three main processes: (i) gasification, (ii) reforming and (iii) CO2 absorption. The simulation exhibited a good accuracy when compared to the experimental values under same operating conditions. In co-gasification evaluation, a low-rank Indonesian coal and N. oculata microalgae biomass were considered as feedstocks. The parametric study was carried out using various biomass to coal ratios at different pressures. The performance of the overall process was evaluated in terms of syngas composition, gasification system efficiency (GSE) and cold gas efficiency (CGE). The reforming and CO2 absorption steps enabled the process providing high purity syngas. The increase of biomass/coal ratio enhanced GSE while decreased CGE. High pressure operation was found to be unfavorable for producing high quality syngas as the increase of pressure affected the gasification. Overall, the co-gasification of biomass/coal is a promising approach to utilize low-value coal and biomass feedstocks to produce high value syngas and contributes to minimization of greenhouse gas emissions.

Shale gas-to-syngas chemical looping process for stable shale gas conversion to high purity syngas with a H2 : CO ratio of 2 : 1

The shale gas-to-syngas (STS) chemical looping process was conceived by Fan and associates in 2013 for the production of high-purity syngas from shale gas. The STS process producing syngas does not require the use of molecular oxygen from air separation and steam. This paper describes the rationale for the process concept with experimental data that substantiates the process validity. Specifically, the STS process consists of a co-current gas (shale gas)–solid (metal oxides) moving bed contact mode reducer operation with metal oxides for shale gas conversion to syngas. The reduced metal oxides from the reducer operation are regenerated via an oxidation operation with air. Various active metal oxides or metal oxide composites can be utilized. However, it is through the combination of desired metal oxides and co-current moving bed reducer that high syngas purity and a desirable H2 : CO molar ratio of ∼2 : 1 can be achieved. In this study, active iron–titanium composite metal oxide (ITCMO) materials are used as the oxygen carrier for the demonstration of the STS process. The desirable thermodynamic property of ITCMO is a key factor for the generation of high quality syngas. The co-current moving bed provides a desirable gas–solid contacting pattern that minimizes carbon deposition and maximizes the syngas yield. The syngas produced by the STS process can achieve a H2 : CO molar ratio of ∼2 : 1 with little CO2, CH4 and steam, which is required for downstream processes to produce liquid fuels and chemicals. The experimental results for reaction kinetics including oxygen carrier recyclability and pressure effects are obtained by thermogravimetric analysis (TGA), and syngas generation using a fixed bed, a bench-scale moving bed, and a sub-pilot scale moving bed reactor demonstrations are achieved in this study. The bench and sub-pilot demonstrations confirm that the syngas produced by the STS process is close to thermodynamic equilibrium with the reduced ITCMO. Furthermore, simulation studies are conducted to compare the efficiency of the STS process with a conventional autothermal natural gas reforming process.

Gasification Characteristics of Hydrothermal Carbonized Biomass in an Updraft Pilot-Scale Gasifier

Biocoal pellets were gasified in an updraft high-temperature agent gasification (HTAG) unit with preheated air at 900 °C to study the performance of the air gasification of hydrothermal carbonized biomass. In comparison to raw biomass, hydrothermal carbonization increased the carbon content from 46 to 66% and decreased the oxygen content from 38 to 16%. As a result, the heating value of biomass on a dry basis was increased from 19 to 29 MJ/kg after hydrothermal carbonization. Thermogravimetric analysis (TGA) of biocoal featured early decomposition of hemicellulose and a shoulder attached to the cellulose peak corresponding to lignin decomposition. Char gasification demonstrated a peak near conversion of 0.2. Syngas with 7.9 MJ Nm–3 lower heating value (LHV) was obtained from gasification experiments performed in the pilot-scale gasifier. The maximum cold gas efficiency was 80% at the lowest equivalence ratio (ER) and also resulted in high-purity syngas. The LHV and cold gas efficiency were higher than tha...

Catalytic hydrogenation of olefins and their mixtures using HRh(CO)(TPPMS) 3 complex in an aqueous biphasic medium

The synthesis and characterization of the catalyst precursor HRh(CO)(TPPMS) 3 was carried out by ligand exchange techniques starting from HRh(CO)(PPh 3) 3 with an excess of TPPMS ligand [TPPMS] = (C 6H 5) 2P( m-C 6H 4SO 3Na), or prepared in situ from RhCl 3·3H 2O and TPPMS under high purity syngas. When the hydrosoluble complex was used as a catalyst precursor in the two phase hydrogenation reaction of 1-hexene, cyclohexene, styrene and 2,3-dimethyl-1-butene, the main hydrogenated products were obtained with high conversion rates. Under the following reaction conditions T = 343 K, P = 13.6 atm, 600 rpm and S/C = 600/1, the substrates showed the following reactivity order: styrene > 1-hexene > cyclohexene > 2,3-dimethyl-1-butene. A quaternary equimolar mixture and one quaternary mixture which simulates the olefin quantities present in real naphtha, showed the same hydrogenation order. The catalyst showed recycling properties without significant loss of activity and sulfur tolerance when benzothiophene is present in the olefin mixtures.