Hydrogen-enriched Syngas Production Research Articles

Torrefaction/carbonization-enhanced gasification-steam reforming of biomass for promoting hydrogen-enriched syngas production and tar elimination over gasification biochars

Biomass to H2-enriched syngas is a very promising route to produce clean energy. This work proposed a new concept of promoting H2-enriched syngas production and tar elimination through torrefaction/carbonization-enhanced gasification-steam reforming (T/CEGSR) of wheat straw (WS) over its gasification biochar materials (GCMs). WS torrefied at 280 °C (WS-280) subjected to gasification-steam reforming (GSR) over C-control presented the maximum gas yields and H2/CO molar ratio (1.72). By introducing C[10 %O2] for GSR of WS-280, the maximum cumulative gas yield (112.10 mmol/greactants), H2 yield (59.91 mmol/greactants), and syngas yield (94.10 mmol/greactants) were achieved. Furthermore, C[10 %O2] were superior to C-control, C[Ar] and C[CO2] in light of carbon conversion efficiency, cold gas efficiency, and tar yield, reaching 97.45C%, 118.40 %, and 3.36 g/Nm3, respectively. Simply put, this study provides a newly sustainable and promising route by combining biomass torrefaction/carbonization with GSR using gasification biochar for enhancing H2-enriched syngas production while reducing tar formation.

Process simulation and optimization of groundnut shell biomass air gasification for hydrogen-enriched syngas production

In this study, a detailed steady-state equilibrium simulation model was designed using ASPEN Plus software to analyze and assess the efficiency of the groundnut shell biomass air gasification process. The developed model includes three general stages: biomass drying, pyrolysis, and gasification. The predicted results are quite similar to those found in the literature, which is consistent with simulation results being validated against experimental data. The effect of different operating parameters, like the gasification temperature, gasification pressure, and the equivalence ratio (ER), on the syngas composition and H 2 /CO ratio is investigated using sensitivity analysis. The findings of the sensitivity analysis revealed that raising the temperature preferred H 2 and CO production, whereas increasing the pressure has favored CO 2 and CH 4 production. Increasing the ER value also boosted CO and CO 2 yield. Moreover, in an effort to optimize the amount of H 2 generated within the process, the sensitivity analysis was used to evaluate the simultaneous effect of operational parameters on the molar fraction of H 2 . To maximize H 2 as a desired product, the following operating parameters were achieved: gasification temperature of 894 °C, gasification pressure of 1 bar, and ER of 0.05, resulting in an H 2 molar fraction of 0.64. • A new approach of pyrolysis/gasification process is developed for H 2 production. • Groundnut shell biomass gasification process is studied under relevant condition. • Gasification model is developed using Aspen Plus software. • Sensitivity analysis of operating condition on the process performance is studied. • Optimum operating condition to maximize syngas production have been determined.

Hydrogen-enriched syngas production by lignite chemical looping gasification with composite oxygen carriers of phosphogypsum and steel slag

Chemical looping gasification (CLG) is a clean and efficient carbon energy conversion pathway using oxygen carriers (OCs). Industrial solid wastes, such as phosphogypsum (PG) and steel slag (SS), used as practical resources to prepare OCs, have been proven to be a promising strategy. Single industrial waste has been used for OCs preparation; however, two or more types of waste have not been used for OCs preparation. In this work, PG and SS were used to prepare OCs for hydrogen-enriched syngas production through CLG technology. The prepared OCs by PG and SS increase the solid waste utilization rate and significantly reduce preparation costs. Further, the reaction process and the effects of reaction conditions were studied based on the FactSage calculation and verified in fixed bed experiments. The results show that SS effectively improved PG-OCs performance. Moreover, the most economic optimal conditions for producing hydrogen-enriched syngas (found to be 72.51%) were determined as a reaction temperature of around 1023 K, lignite/OCs mass ratio of 1, 50 wt% - 67 wt% of SS/OCs mass ratio, and water vapor/OCs mass ratio of 0.6. In conclusion, SS-PG OCs are the new era for hydrogen-enriched syngas production in CLG.

Cellulose gasification with Ca–Fe oxygen carrier in chemical-looping process

Biomass-derived chemical looping gasification (BCLG) is a novel technology for lignocellulose energy applications. Ca–Fe oxygen carriers have been proven to be a potential material for efficient lignocellulose conversion and hydrogen-enriched syngas production in process studies. In this study, Thermogravimetry-mass spectrometry (TG-MS), pyrolysis chromatography-mass spectrometry (Py-GC-MS) and fixed-bed experiments were conducted, and the cellulose BCLG product was analyzed to explore the mechanism of reaction between Ca–Fe OCs and biomass char or volatiles. The mechanism of the synergistic effect of Ca–Fe was analyzed to explain the characteristics of the OCs. The results suggest the Ca-based materials act as catalysts to promote the decomposition of cellulose monomers at primary reaction and char at secondary reaction, and also promote the reforming and oxidation of volatiles by chemisorption. Ca participates in the construction of inert substances, such as Ca2Fe2O5, to avoid the deep oxidation of CO and H2. Fe-based material supplies oxygen and promotes the reforming of volatile. Compared with Fe2O3 and CaO/Fe2O3, CaFe2O4 shows a better performance on carbon conversion and H2 production below 850 °C.

Cellulose Gasification with Ca-Fe Oxygen Carrier in Chemical-Looping Process

Biomass-derived chemical looping gasification (BCLG) is a novel technology for lignocellulose energy applications. Ca-Fe oxygen carriers have been proven to be a potential material for efficient lignocellulose conversion and hydrogen-enriched syngas production in process studies. In this study, Thermogravimetry-mass spectrometry (TG-MS), pyrolysis chromatography-mass spectrometry (Py-GC-MS) and fixed-bed experiments were conducted, and the cellulose BCLG product was analyzed to explore the mechanism of reaction between Ca-Fe OCs and biomass char or volatiles. The mechanism of the synergistic effect of Ca-Fe was analyzed to explain the characteristics of the OCs. The results showed the Ca-based materials act as catalysts to promote the decomposition of cellulose monomers at primary reaction and char at secondary reaction. And also promote the reforming and oxidation of volatiles by chemisorption. Ca participates in the construction of inert substances, such as Ca 2 Fe 2 O 5 , to avoid the deep oxidation of CO and H 2 . Fe-based material supplies oxygen and promotes the reforming of volatile. Compared with Fe 2 O 3 and CaO/Fe 2 O 3 , CaFe 2 O 4 showed a better performance on carbon conversion and H 2 production below 850 °C.

Air-steam gasification of biomass based on a multi-composition multi-step kinetic model: A clean strategy for hydrogen-enriched syngas production

Biomass, as a renewable energy source, has high potential for supplying the energy needs of modern societies. Gasification is a thermochemical route for converting biomass into combustible gas at high temperatures. The main purpose of the present study was to develop an Aspen Plus model of air-steam gasification of biomass (sawdust) to predict the gasification characteristics and performances. The prediction capability of the model was evaluated by comparison with experimental data obtained in a fluidized bed biomass gasifier. First, the influence of gasification temperature on gas composition, product yields and gasifier performances was investigated. The biomass feeding rate and air flow rate were set at~0.445 kg/h and 0.5 Nm3/h, respectively, while the gasifier temperature was varied between 700 °C to 800 °C. With the increase of temperature, the gas yield (DGY) increased steadily from 1.72 to 2.0 Nm3/kg, while the HHV of the produced syngas (HHVgas) increased initially from 5.38 to 5.73 MJ/Nm3 and then decreased to 5.69 MJ/Nm3. After determining optimal temperature (800 °C), the influence of equivalence ratio (ER) and steam/biomass ratio (S/B) on gasification characteristics, dry gas yield (DGY) and tar yield (TRY) was studied. As ER increased from 0.19 to 0.23, TRY decreased from 9.13 g/Nm3 to 8.45 g/Nm3. In contrast, DGY initially increased from 2.02 Nm3/kg to 2.43 Nm3/kg as ER increased from 0.19 to 0.21 and then dropped to 2.24 Nm3/kg at ER of 0.23. An increase in S/B from 0.61 to 2.7 also resulted in a slight increase in HHVgas; however, TRY showed a decreasing trend (from 9.65 g/Nm3 to 8.95 g/Nm3). The results showed that the model developed in this paper is a promising tool for simulating the biomass gasification at various operating conditions.

Thermodynamic evaluation of sorption-enhanced chemical looping gasification with coal as fuel

Chemical looping gasification (CLG) is regarded as an efficient way for the utilization of solid fuel and hydrogen-enriched syngas production. In this work, a thermodynamic analysis is carried out to evaluate the CLG performance of coal on the basis of Gibbs free energy minimization. In order to enhance the gasification process, CO2 sorption is employed and sorbents are circulated in the whole system. The influence of operating parameters on the CLG performance as well as heat requirement of the system is further examined. The results reveal that the addition of sorbent can promote the hydrogen production and provide the heat for the reaction in the fuel reactor (FR), whereas additional energy input is still required for the whole system. A proper increase of oxygen carrier circulation rate can achieve the auto-thermal condition of the system.

Direct production of hydrogen-enriched syngas by calcium-catalyzed steam gasification of Shengli lignite/chars: Structural evolution

Calcium has been proved to be efficient for the catalytic steam gasification of lignite. In this study, we studied the steam gasification of lignite with Ca(OH)2 added by wet impregnation for to produce hydrogen. The effect of calcium on the microstructural evolution and char gasification behavior in the presence of steam were studied. The distribution of the gaseous products was examined by using fixed-bed micro reactor equipment for steam gasification. Partially gasified chars obtained at different temperatures (400, 500, 600, and 700 °C) in the gasification process were characterized by scanning electron microscopy coupled with energy dispersive spectroscopy, 13C nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and Raman spectroscopy. The results suggested that a “Ca-carboxylate-like structure” was formed due to the addition of calcium to lignite. This Ca-carboxylate-like structure increased the thermal stability of the original carboxylic structure in lignite. As a result, the calcium-added coal retained more oxygen-containing structures, formed more defects, and possessed significantly lower aromatic structures due to the formed Ca-complexes during steam gasification. Therefore, it can be inferred that the Ca-complexes in the lignite char increased the gasification reactivity of char.

Chemical looping gasification of biomass with Fe2O3/CaO as the oxygen carrier for hydrogen-enriched syngas production

Biomass-derived chemical looping gasification is a novel technology to convert biomass into renewable hydrogen-enriched syngas. In this study, bimetallic Fe-Ca oxides were synthesized to be used as oxygen carriers to promote the hydrogen production from the chemical looping gasification of rice straw. The effects of Fe/Ca ratio, temperature together with the cyclic performance of oxygen carrier were studies in terms of produced syngas distribution, solid structure evolution and the durability of oxygen carrier. Results found that two types of calcium ferrites (Ca2Fe2O5 and CaFe2O4) were formed with different Fe/Ca ratios, and Fe and Ca were uniformly distributed within oxygen carriers by wet impregnation method. Compared with pyrolysis or steam gasification, the hydrogen production was largely promoted during the steam chemical looping gasification process due to the iron re-oxidation by steam. When the ratio of Fe:Ca was1:1, the formed oxygen carrier (Ca2Fe2O5) produced the highest hydrogen yield (23.07 mmol/g biomass) at 800 °C, which benefited from one step reduction and oxidation properties of Ca2Fe2O5. A temperature of no less than 800 °C was needed for the completed redox of Ca2Fe2O5 during chemical looping gasification with steam. The cyclic stability test for Ca2Fe2O5 showed that the continuously accumulated Si from biomass ash would destroy the bimetallic Fe-Ca structure to generate CaSiO3 and Fe2O3 after 3 times of cycle, and this led to the decreased hydrogen production during chemical looping gasification cycle. The great hydrogen selectivity of Fe:Ca = 1:1 (Ca2Fe2O5) makes it a suitable candidate of oxygen carrier, but the cyclic durability should be enhanced to enable a better application for chemical looping gasification conversion of biomass.

Production of hydrogen enriched syngas from municipal solid waste gasification with waste marble powder as a catalyst

Marble processing leads to the production of high amount of waste marble powder (WMP) as a byproduct, which can be a potential health risk and has hazardous impacts on the surrounding environment. However, marble is composed of calcite making it suitable for the calcium-based catalyst. Moreover, no study has been carried out to utilize this WMP in municipal solid waste (MSW) gasification process. Therefore, there is a need to address its utilization as a potential catalyst/sorbent in the gasification of municipal solid waste (MSW). A laboratory scale batch-type fixed bed reactor was used to study the effect of WMP addition on the CO2 adsorption, steam reforming capability and char gasification in the presence of steam. Produced gas composition, gas yield, carbon conversion efficiency and tar yield were examined at different WMP to MSW ratios. Effect of temperature and steam rate varying from 700 to 900 °C and 2.5–10 ml/min respectively were also considered in this study. WMP showed a good capacity towards hydrogen enriched syngas production as well as CO2 adsorption and tar reforming. The H2 concentration increased significantly with an increase in the WMP to MSW mass ratio, while CO2 decreased. A significant effect of temperature and steam rate was also observed on the produced gas composition, gas yield, and tar content. This study helps us to understand the effect of WMP addition in MSW gasification process and thus assists in the industrial application.

Hydrogen enriched syngas production via gasification of biofuels pellets/powders blended from olive mill solid wastes and pine sawdust under different water steam/nitrogen atmospheres

In this work, we study the gasification of pellets produced, after densification, by blending olive mill solid wastes, impregnated or not by olive mill waste water, and pine sawdust under different steam/nitrogen atmospheres. The charcoals necessary for the gasification tests were prepared by pyrolysis using a fixed bed reactor. The gasification technique using steam was chosen in order to produce a hydrogen-enriched syngas. Gasification tests were performed using macro-thermogravimetric equipment. Tests were carried out at different temperatures (750 °C, 800 °C, 820 °C, 850 °C and 900 °C), and at different atmospheres composed by nitrogen and steam at different percentages (10%, 20% and 30%). Results show that the mass variation profiles is similar to the usual lingo-cellulosic gasification process. Moreover, the increase of temperatures or water steam partial pressures affects positively the rate of conversion and the char reactivity by accelerating the gasification process. The increase of the gasification yields demonstrates the promise of using olive mill by-products as alternative biofuels (H2 enriched syngas).

Thermodynamic analysis of hydrogen-enriched syngas generation coupled with in situ CO2 capture using chemical looping gasification method

The CaO-based chemical looping gasification (CaO-based CLG) of biomass was considered as a potential technology to improve hydrogen-enriched syngas production and capture in situ CO2 effectively. Thermodynamic analysis with Gibbs free energy minimization through Lagrange multiplier method was performed for CaO-based CLG to produce hydrogen-enriched syngas. The analysis was conducted to investigate the effects of different operation parameters [including CaO/C ratio (0–3.0), pressure (0.1–5.0 MPa), gasification temperature (600–700 °C) and S/C ratio (0.5–3.0)] on hydrogen fraction, syngas yield, gas LHV and in situ CO2 capture efficiency. The results suggested that the preferential conditions for producing hydrogen-enriched syngas in CaO-based CLG were achieved at 600 °C, atmospheric pressure, S/C ratio of 2.0 and CaO/C ratio of 2.0. CaO-based could capture in situ CO2 effectively and the capture efficiency reached 92.6%. Under these optimal operation parameters, the hydrogen fraction, gas yield and gas LHV reached 98.5%, 1.87 mol mol C −1 and 10.7 MJ Nm−3, respectively. Ultimately, the heat and mass balance of gasification was obtained at the optimal operation conditions, and gasifier did not need any external heating except from the heat carried by CaO.

Development of Fe-Promoted Ni–Al Catalysts for Hydrogen Production from Gasification of Wood Sawdust

The production of renewable hydrogen-enriched gas from biomass waste is a promising technology for the development of a sustainable economy and society. Until now, there are still challenges of the technology in terms of the efficiency of hydrogen production. A catalyst is known and has been tested to enhance hydrogen production from biomass gasification, in particular, using Ni-based catalysts, which have high reactivity for hydrogen production and are cost-effective. However, developing a Ni-based catalyst with high thermal stability and resistance of coke deposition on the surface of the catalyst is still a challenging topic. In this work, Ni–Al catalysts doped with low-cost Fe metal were investigated for hydrogen-enriched syngas production from gasification of biomass using a two-stage fixed bed reactor. NiO–Fe2O3–Al2O3 catalysts with various Ni/Fe molar ratios (9:1, 8:2, 6:4, 5:5, 4:6, 2:8, and 1:9) were studied, aiming to understand the influence of Fe addition on the production of hydrogen and the ...

Catalytic pyrolysis of petroleum sludge for production of hydrogen-enriched syngas

Petroleum sludge has attracted wide attention owing to its large quantity, hazardous character, and difficulty in processing. Furthermore, petroleum sludge contains a high proportion of hydrocarbons which are valuable for recovery. In this paper, the possibility of producing hydrogen-enriched syngas from different petroleum sludge by a two-stage catalytic pyrolysis under different temperature has been examined. X-ray photoelectron spectroscopy and C13 nuclear magnetic resonance were employed to characterize the pyrolysis residues. The pyrolysis of three different petroleum sludge samples was discussed along with possible reaction mechanisms. It was found that heavy oil components vaporized in the first stage of pyrolysis. Thereafter, the gaseous compounds were cracked in the second catalytic stage forming H2, CH4, CO, and other small molecules. Higher catalytic temperatures can enhance the yield of H2 while lower temperatures would favor the generation of CH4 and CO. The pyrolysis of samples collected from a sludge storage tank gave the highest H2 yield (0.13 Nm3 per kg sludge) among the three sludge samples examined. Additionally, after solid particles were removed by extraction (dissolution and centrifugation), catalytic pyrolysis produced 30% more H2 at 1000 °C. Finding of this paper indicates staged-catalytic pyrolysis is a promising method to convert hazardous petroleum sludge into high valuable syngas.

Characteristics and catalytic properties of Ni/CaAlOx catalyst for hydrogen-enriched syngas production from pyrolysis-steam reforming of biomass sawdust

The production of hydrogen-enriched syngas from the thermo-chemical conversion of biomass was studied using Ni/CaAlOx catalysts prepared by co-precipitation method. The effect of Ca addition with different molar ratios of Ca:Al (1:3, 1:2, 1:1, 2:1, 3:1) on the properties and catalytic behavior in relation to syngas production and the coke formation on the surface of the catalysts were investigated. Catalysts were characterized by BET, XRD, TPR, SEM, and TEM. The SEM and TEM results showed that rod-shaped nano-particles were highly dispersed on the surface of the catalyst. The particle size of NiO was slightly affected with the increase of Ca content in the catalyst. It appeared that the selectivity of CO was increased and the selectivity of CO2 was reduced with the increase of Ca addition to the catalyst. For example, CO2 concentration was reduced from 20 to 12vol.%, when the molar ratio of Ca/Al was increased from 1:3 to 3:1 for the Ni/CaAlOx catalyst; it is suggested that the water gas shift reaction was inhibited and CO2 reforming reactions were promoted in the presence of the catalyst with higher Ca content. The CO/H2 molar ratio could be manipulated by changing the Ca content in the catalyst, while the H2 concentration remained almost constant (around 45vol.%). Thus, using the Ni/CaAlOx catalyst developed in this work could provide a promising route to control the syngas composition, which is an important factor for syngas applications.

Microwave-induced low temperature pyrolysis of macroalgae for unprecedented hydrogen-enriched syngas production

An efficient methodology based on low temperature microwave-induced pyrolysis has been developed for syngas production from macroalgae.