Chemical Looping Reforming Research Articles

Evaluation of Different Oxygen Carriers for Chemical Looping Reforming of Toluene as Tar Model Compound in Biomass Gasification Gas: A Thermodynamic Analysis

A thermodynamic study on a toluene chemical looping reforming process with six metal oxides was conducted to evaluate the product distribution for selecting an appropriate oxygen carrier with thermodynamic favorability towards high syngas yield. The results show that a suitable operation temperature for most oxygen carriers is 900 °C considering syngas selectivity and solid C formation whether the toluene is fed alone or together with fuel gas. The syngas selectivity of all oxygen carriers decreases with the increasing equivalence ratio, but the decrease degrees are quite different due to their different thermodynamic natures. With the increasing amounts of H2 and CO, the syngas selectivity for various oxygen carriers correspondingly decreases. The addition of CO2 and H2O(g) benefits reducing the solid C formation, whereas the addition of CH4 leads to more solid C being produced. Under the simulated gasification gas atmosphere, a synergetic elimination of solid C and water–gas shift reactions are observed. In terms of syngas selectivity, Mn2O3 possesses the best performance, followed by CaFe2O4 and Fe2O3, but NiO and CuO exhibit the lowest performance. BaFe2O4 presents a high H2 selectivity but a very poor CO selectivity due to the formation of BaCO3, which has a high thermodynamic stability below 1200 °C. Nevertheless, Mn2O3 is more likely to form solid C than feeding toluene alone and has a lower melting point. Considering syngas selectivity, carbon deposit and melting point, CaFe2O4 exhibits the highest performance concerning the tar chemical looping.

Controlling the reaction microenvironments through an embedding strategy to strengthen the chemical looping reforming of methane based on decoupling process

Aiming at the complexity of traditional biomass gasification technology with low conversion efficiency and high tar content and realizing the directional conversion of biomass into syngas, this paper proposed a new decoupling process of biomass pyrolysis and chemical looping reforming of volatile components. Designing a high activity and selective oxygen carrier is the key to the chemical looping reforming process. This study used an embedding strategy to develop the oxygen carrier. NiFe2O4 was embedded in SBA-15 to control the reaction microenvironment. The reaction performance of NiFe2O4@SBA-15 under different conditions was investigated via a combination of fixed-bed reactor and on-line mass spectrometry. The results showed that the CO selectivity was close to 100%. The CH4 conversion and CO selectivity of NiFe2O4@SBA-15 were increased by 121.29% and 114.40% than NiFe2O4, respectively. The optimal embedding ratio (20%) and reaction temperature (900 °C) were determined during the experiment, which was consistent with the thermodynamic simulation results. The gas–solid reaction model was used to solve the reaction kinetics of the oxygen carrier, and the activation energy was 118.23 kJ·mol−1. This study gives a research basis for screening oxygen carrier and the design of reactor in the directional conversion of biomass pyrolysis full volatiles into syngas via chemical looping reforming.

Production of hydrogen by chemical looping reforming of methane and biogas using a reactive and durable Cu-based oxygen carrier

The objective of this work was to assess the suitability of a synthetic Cu-based oxygen carrier in a continuous pilot plant for the production of blue and green hydrogen through the autothermal Chemical Looping Reforming (CLRa). In CLRa, methane is converted to a H2 + CO mixture through partial oxidation and reforming reactions in the fuel reactor. The degree of the partial oxidation of methane was defined by controlling the oxygen flow in the air reactor. Steam was used as reforming gas in natural gas to produce blue H2, but the existing CO2 in biogas was the reforming gas to produce green H2. Operating at 950 °C in the fuel and air reactors, CH4 conversion and H2 yield parameters were 96 % and 2.60 mol of H2 per mole of CH4, respectively. These experimental results were close to the theoretical values that could be achieved in the CLRa process. Furthermore, the physicochemical characterization of the samples extracted from the pilot plant throughout the experimental campaign revealed that the Cu-based oxygen carrier maintained its mechanical integrity and chemical stability under harsh operating conditions. Therefore, it can be concluded that Cu-based oxygen carriers can be considered a promising alternative to Ni-based materials for the production of blue and green hydrogen through the CLRa process.

Accelerated syngas generation from chemical looping CH4 reforming by using reduced ilmenite ore as catalyst

Chemical looping reforming of CH4 (CH4-CLR) is an advanced technology for syngas generation, and ilmenite ore has been considered a promising oxygen carrier material due to its extremely low cost. However, the weak reactivity of ilmenite ore over CH4 prevents its practical application in CH4-CLR. This study has established a facile strategy to enhance the reactivity of CH4 toward ilmenite ore by simply introducing the same but reduced ilmenite ore as the catalyst for a pre-activation of CH4, so as to accelerate the reaction between the CH4 and ilmenite. Results show that the addition of reduced ilmenite ore as catalyst significantly accelerates the reaction between CH4 and ilmenite ore, which successfully reduces the induction period from 150 min to almost 0 min. A higher catalyst to oxygen carrier ratio, higher temperature and deeper reduction stage of the catalyst are all beneficial in accelerating the reaction between CH4 and ilmenite ore.

A strategy of mid-temperature natural gas based chemical looping reforming for hydrogen production

Steam methane reforming (SMR) needs the reaction heat at a temperature above 800 °C provided by the combustion of natural gas and suffers from adverse environmental impact and the hydrogen separated from other chemicals needs extra energy penalty. In order to avoid the expensive cost and high power consumption caused by capturing CO 2 after combustion in SMR, natural gas Chemical Looping Reforming (CLR) is proposed, where the chemical looping combustion of metal oxides replaced the direct combustion of NG to convert natural gas to hydrogen and carbon dioxide. Although CO 2 can be separated with less energy penalty when combustion, CLR still require higher temperature heat for the hydrogen production and cause the poor sintering of oxygen carriers (OC). Here, we report a high-rate hydrogen production and low-energy penalty of strategy by natural gas chemical-looping process with both metallic oxide reduction and metal oxidation coupled with steam. Fe 3 O 4 is employed as an oxygen carrier. Different from the common chemical looping reforming, the double side reactions of both the reduction and oxidization enable to provide the hydrogen in the range of 500–600 °C under the atmospheric pressure. Furthermore, the CO 2 is absorbed and captured with reduction reaction simultaneously. Through the thermodynamic analysis and irreversibility analysis of hydrogen production by natural gas via chemical looping reforming at atmospheric pressure, we provide a possibility of hydrogen production from methane at moderate temperature. The reported results in this paper should be viewed as optimistic due to several idealized assumptions: Considering that the chemical looping reaction is carried out at the equilibrium temperature of 500 °C, and complete CO 2 capture can be achieved. It is assumed that the unreacted methane and hydrogen are completely separated by physical adsorption. This paper may have the potential of saving the natural gas consumption required to produce 1 m 3 H 2 and reducing the cost of hydrogen production. • A mid-temperature chemical looping reforming hydrogen production method via natural gas was proposed. • We provide a possibility of methane hydrogen production from more than 800 °C to about 500 °C under atmospheric pressure. • This paper may have the potential of saving the natural gas consumption and reducing the cost of hydrogen production. • It would be combined with medium-temperature industrial waste heat or parabolic trough concentrating solar energy.

Techno-economic analysis of e-waste based chemical looping reformer as hydrogen generator with co-generation of metals, electricity and syngas

Chemical looping reforming (CLR) is an efficient technology to convert hydrocarbon fuels into CO 2 and H 2 using metal oxide based oxygen carriers. The novelty of the present study is to utilize electronic waste such as printed circuit board (PCB) to generate high quality syngas and metallic components for the CLR process. A portion of the syngas generated during e-waste pyrolysis is used with coal and polypropylene for effective combustion. A techno-economic analysis is performed for the production of hydrogen and electricity in the CLR method. The levelized costs for electricity (LCOE), hydrogen (LCOH), syngas (LCOS), and metal (LCOM) production using e-wastes are estimated as 92.28 $/MWh, 3.67 $/kg, 0.0034 $/kWh, and 24.32 $/ton, respectively. The LCOH is found to be the least of 2.90 $/kg under the co-feed conditions of PCB syngas-PP. The integration of the e-waste based CLR with a steam turbine system achieved a net efficiency of 50%. • E-waste based chemical looping reformer (CLR) is proposed for hydrogen generation. • Mixture of PCB based syngas, coal, and polypropylene (PP) is used as feedstock. • Techno-economic analysis is conducted for CLR integrated steam turbine system. • Levelized costs for hydrogen, electricity, syngas and metal oxides are assessed. • PCB syngas with coal and PP produced a net efficiency of 48.8% with LCOH of 3 $/kg.

Synthesis gas and H2 production by chemical looping reforming using bio-oil from fast pyrolysis of wood as raw material

• CLR of pine wood bio-oil has been demonstrated in a 1 kW th continuous unit. • Complete conversion of bio-oil was found during 60 h of operation. • Carbon deposition can be minimized and controlled in the continuous CLR unit. • Maximum H 2 production and H 2 /CO ratio were found at 650 °C with very low C deposition. • Auto-thermal H 2 production at 650 °C was 13.6 g/100 g of bio-oil with H 2 O/bio-oil = 6. The interest of using bio-oil produced by biomass fast pyrolysis to generate H 2 and high value chemicals is growing up in order to reduce CO 2 emissions by the use of biomass. In the present work, bio-oil Chemical Looping Reforming was demonstrated in a 1 kW th continuous unit during 60 h of operation using a Ni-based oxygen carrier to produce syngas/H 2 . No agglomeration of the oxygen carrier was detected. Complete conversion of the bio-oil was obtained in all cases, obtaining as main products H 2 , CO, CO 2 and in much lower concentration CH 4 . Carbon deposition in the bed appeared in almost all the experiments carried out during the bio-oil reforming, and CO 2 was found in the air reactor outlet, although did not affect to the process performance when oxygen carriers were used. This fact only let to a reduction of the CO 2 capture efficiency. Fuel reactor temperature was a key factor for the H 2 production, the H 2 /CO ratio and the carbon accumulated in the CLR unit. The maximum H 2 production together with the maximum H 2 /CO ratio of 6 were found at the lowest temperature used, 650 °C. In addition, the carbon formed in the fuel reactor was reactive enough so that it could be burnt in the air reactor with minimum accumulation in the continuous unit. The autothermal H 2 production was 13.6 g/100 g of bio-oil without water at 650 °C with a H 2 O/bio-oil = 6, which corresponds to 68 mol H 2 /kg of bio-oil without water. Therefore, the CLR process of bio-oil allows obtaining high H 2 production with low carbon deposition at 650 °C using less amount of water than in conventional bio-oil reforming.

Chemical Looping Combustion: A Brief Overview

The current development of chemical looping combustion (CLC) technology is presented in this paper. This technique of energy conversion enables burning of hydrocarbon fuels with dramatically reduced CO2 emission into the atmosphere, since the inherent separation of carbon dioxide takes place directly in a combustion unit. In the beginning, the general idea of the CLC process is described, which takes advantage of solids (so-called oxygen carriers) being able to transport oxygen between combustion air and burning fuel. The main groups of oxygen carriers (OC) are characterized and compared, which are Fe-, Mn-, Cu-, Ni-, and Co-based materials. Moreover, different constructions of reactors tailored to perform the CLC process are described, including fluidized-bed reactors, swing reactors, and rotary reactors. The whole systems are based on the chemical looping concept, such as syngas CLC (SG-CLC), in situ Gasification CLC (iG-CLC), chemical looping with oxygen uncoupling (CLOU), and chemical looping reforming (CLR), are discussed as well. Finally, a comparison with other pro-CCS (carbon capture and storage) technologies is provided.

Chemical looping reforming for syngas generation at real process conditions in packed bed reactors: An experimental demonstration

Chemical looping reforming (CLR) is a promising technology for syngas production combining autothermal operation with integrated CO2 capture. At large scale, reformer outlet pressure during syngas production is an important factor for the overall plant’s process efficiency and defines the energy requirements for downstream processing. Packed bed reactors are widely used and established in industry for high pressure operating conditions due to their robust and, compared to other reactor types, simpler engineering. In this paper, CLR in packed bed reactors (CLR-PB) is demonstrated under a pressure range of 1 – 5 bar in a lab scale reactor, using NiO/CaAl2O4 as the oxygen carrier (OC). Oxidation, reduction and dry reforming processes were examined in a wide range of temperature (400 – 900 °C), pressure (1 – 5 bar), flowrate (10 – 40 NLPM) and different inlet gas compositions, providing an important foreground for the optimal operating conditions for each process.Furthermore, a full CLR-PB pseudo-continuous cycle has been successfully demonstrated for the first time in a lab reactor setup. During the full cycle operation, CH4 conversion > 99% has been achieved, while the temperature and concentration profiles provided identical results for consecutive cycles verifying the continuity and the feasibility of the process. These results constitute the basis for the scale-up of the process, where heat losses would be minimized and the energy efficiency of the process would be significantly higher.

A natural gas-based eco-friendly polygeneration system including gas turbine, sorption-enhanced steam methane reforming, absorption chiller and flue gas CO2 capture unit

Poly-generation systems have attracted a lot of attention due to the increment of efficiency as well as reducing energy penalties, costs and pollutants. Extensive research has been done on these systems in recent years. The current work is done with the aim of simulating an environmentally friendly poly-generation system in the power plant of Shahrood city in Iran. In this way, a poly-generation system is simulated in Aspen Plus software which consists of: I) a gas turbine (GT) for power generation with natural gas fuel of Shahroud power plant, that its flue gas is utilized to supply heat for other cycles and streams, II) a sorption-enhanced chemical looping reforming (SECLR) which simultaneously generates H2 by steam methane reforming (SMR) and uptakes produced CO2 by calcium adsorbent during the carbonation/calcination reactions. In this section, there is also a chemical looping combustion (CLC) based on redox reactions of Ni/NiO to provide heat of the reactors, III) a NH3/H2O absorption refrigeration system to yield the cooling demand, IV) a high-pressure steam generation unit and V) a MEA-based post-combustion CO2 capture unit (PCC) for flue gas. In this system, an attempt has been made to prevent heat loss by internal streams, especially gas turbine exhaust gas, so that energy loss is minimized. Moreover, environmental issues are also prioritized to reduce the CO2 emissions as much as possible. The proposed process is capable of producing 133.3 MW power, 9.875 MW cooling, 50 kg/s high-pressure steam and 0.384 kg/s hydrogen. The mass flow rates of CO2 captured in the SECLR and PCC sections are 2.6 kg/s and 15.35 kg/s, respectively. Moreover, the total energy efficiency of the integrated system is 68.74%. Ultimately, a sensitivity analysis was performed to identify the key parameters and their influence on the process performance.

Optimisation of syngas production from a novel two-step chemical looping reforming process using Fe-dolomite as oxygen carriers

The production of syngas from hydrogen carbon feedstocks such as natural gas and biomass is of high importance to the chemical industry. In conventional chemical looping steam reforming(CLSR), the composition of the syngas produced is limited by the chemical equilibrium of the water-gas-shift reaction. In this study, we demonstrate that a two-step chemical looping reforming (TS-CLR) process is capable of alleviating the equilibrium limit to produce syngas of higher CO and H2 contents. For example, the total mole fraction of H2 and CO in the syngas produced from the conventional CLSR of toluene at 900 °C is limited to below 89.4 vol% (dry basis), whereas TS-CLR could produce syngas with >94 vol% of CO and H2 under the same condintions. The TS-CLR process is best carried out in a bed of Fe-dolomite oxygen carriers with a Ca:Fe ratio of 1:1 (denoted as C1F1). Compared to the pure Ca2Fe2O5 and Fe2O3/Al2O3 oxygen carriers, the C1F1 affords improvements in syngas yield, carbon conversion and syngas purity. The superior performance of C1F1 is attributed to the promotion of the lattice oxygen activities of Ca2Fe2O5 by MgO, as well as its excellent phase reversibility over redox cycles.

Assessment of a novel coupling integrated process for coproducing syngas and hydrogen from natural gas and biomass feedstocks with in-situ CO2 utilization

Over the past decade, extraordinary sets of chemical looping process concepts have been introduced based on the need to develop clean and efficient energy systems. Herein, a new integrated coupled process based on chemical looping technology for the coproduction of hydrogen and synthesis gas for multi-purpose goals has been proposed and investigated deeply. The proposed novel process is a dual-purpose integrated zero-emission reforming (DPIZER) process with multifunctionality and zero greenhouse gas emission. Also, energy and exergy analysis were performed on the newly designed unit. In addition, the obtained simulation data were validated with experimental tests. The synthesized 10-30wt.%NiO/Al2O3 oxygen carrier was investigated using the X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques and evaluated in chemical looping reforming (CLR) and sorption enhanced chemical looping reforming (SECLR) processes. The obtained results revealed that the efficiency of the novel process proposed in this study showed a great improvement than industrial conventional reforming process. The obtained experimental results revealed the highest methane conversion of about 100% and 90% at 750 °C in CLR and SECLR reactors, respectively. The simulation results revealed the production of highly pure hydrogen (H2/CO = 292), syngas (H2/CO ≈ 1), and ultra-pure hydrogen (H2/CO = 34,833) in three distinct reactors. In general, the process includes the production of ultrapure hydrogen without producing any pollutants such as CO2 and harmful gases from methane feed and biomass.

Mono-dimensional and two-dimensional models for chemical looping reforming with packed bed reactors and validation under real process conditions

Chemical looping reforming (CLR) is an emerging hydrogen/syngas production technology, integrated with CO2 capture.

Flame Spray Pyrolysis Synthesized Ni-Doped Fe/Ce Oxygen Carriers for Chemical Looping Dry Reforming of Methane

Flame Spray Pyrolysis Synthesized Ni-Doped Fe/Ce Oxygen Carriers for Chemical Looping Dry Reforming of Methane

Research Progress on Chemical Looping Reforming of Macromolecular Components of Volatiles from Biomass Pyrolysis Based on Decoupling Strategy

Research Progress on Chemical Looping Reforming of Macromolecular Components of Volatiles from Biomass Pyrolysis Based on Decoupling Strategy

Production of Blue and Green Hydrogen by Chemical Looping Reforming of Methane and Biogas Using a Highly Reactive Cu-Based Oxygen Carrier

Production of Blue and Green Hydrogen by Chemical Looping Reforming of Methane and Biogas Using a Highly Reactive Cu-Based Oxygen Carrier

Controlling the Reaction Microenvironments Through an Embedding Strategy to Strengthen the Chemical Looping Reforming of Biomass Volatile Based on Decoupling Process

Controlling the Reaction Microenvironments Through an Embedding Strategy to Strengthen the Chemical Looping Reforming of Biomass Volatile Based on Decoupling Process

Intensified chemical looping reforming processes with in-situ CO2 capture for high purity H2 production from non-fuel grade bioethanol

This work presents the design and optimization of two intensified and eco-friendly schemes for high purity H2 production from non-fuel grade/undistiled bioethanol through detailed thermodynamic investigation using Aspen plus models. Both of them are chemical looping combustion (CLC) integrated processes; namely, sorption enhanced steam reforming (CLC-SESR) and sorption enhanced chemical looping reforming (CLC-SECLR). Further, the heat and power demand of these processes are met by integrating with heat recovery and steam generation, and power generation sections, thus making them energy-wise self-sustainable. Steady-state Aspen Plus models have been developed for both the schemes, and the processes are investigated thermodynamically to determine the optimal operating parameters through sequential parametric sensitivity analysis. The results demonstrated the efficacy of the proposed CLC-SESR and CLC-SECLR schemes in facilitating low temperature reforming of partially distilled bioethanol of 14 mole % (34.5% by vol.) concentration at 550 °C and 500 °C, respectively resulting in optimal H2 yield (H2Yield) of 97.38% and 82.45%, H2 purity (yH2) of 99.15% and 99.71 %, energy efficiency (η) of 39.47% and 37.30% along with CO2 capture efficiency (CO2Capture) of 99.13% and 99.58%, respectively. Further, reforming of undistilled bioethanol 5 mol% (14.6% by vol.) obtained directly from fermentation step, resulted in improved H2Yield, yH2 and CO2Capture of 99.92%, 99.63%, and 99.48% respectively for CLC-SESR and 83.31%, 99.91% and 99.71% respectively for CLC-SECLR, at the expense of slight decrease in η by ≈ 3% in both schemes. These results on comparison with the results of conventional steam reforming and chemical looping reforming with carbon capture demonstrate the outperformance of proposed schemes in terms of achieving more than 99% H2Yield, yH2 and CO2Capture at almost the same efficiency as of the conventional reforming schemes.

Effect of H2S presence on chemical looping reforming (CLR) of biogas with a firebrick supported NiO oxygen carrier

Biogas containing CH4 and CO2 can be used in CLR for H2 generation, while the H2S presence may affect oxygen carrier activity and reforming property. In this study, a 2000 ppm H2S was mixed with modelled biogas (CH4/CO2 = 3/2) to explore its effects on the CLR process. Experiments were conducted in a batch fluidized bed using a firebrick supported NiO oxygen carrier. The presence of 2000 ppm H2S decreased the oxygen carrier activity, thus resulting in a significant lower gas yield from the biogas as compared to the cases without H2S. Increase of temperature slightly alleviated the interaction between H2S and the oxygen carrier, hence a slightly higher gas (H2 and CO) yield was achieved at 950 °C than 750 and 850 °C. In reforming, H2S was mainly converted to CS2, while COS and SO2 were minors. After several cycles without H2S, the material restored its original activity. Sulfur element and NiS2 crystalline were found in the reduced oxygen carrier according to XRD, XPS, SEM-EDX, HRTEM-EDX and ICP-OES analyses.

Pressurized chemical looping methane reforming to syngas for efficient methanol production: Experimental and process simulation study

This study investigates the potential of applying pressurized chemical looping reforming (CLR) mechanism for syngas to methanol production process combining of experimental demonstration of methane reforming to syngas and simulation for integration in methanol production. The experimental study was conducted using the internally circulating reactor (ICR) that was specially designed to enable pressurized CLR operation where several experimental cases were completed using a NiO-based oxygen carrier. Up to 4 kW of methane feed was reformed to syngas, achieving high conversion efficiencies and high syngas recovery and purity at pressurized conditions up to 4 bar. Co-feeding H2O or CO2 was found to affect mainly the H2/CO ratio. The simulation study evaluated the potential of integrating the CLR process for large scale methanol production through comprehensive thermodynamic analysis using Aspen plus. The results revealed that CLR-based methanol plant is a highly attractive pathway achieving higher methanol production efficiency outperforming the conventional autothermal reforming (ATR) -based plant by ∼5% efficiency. The main benefits of the CLR-based system is the avoidance of the air separation unit required for ATR plants, and the extra power generation through the gas turbine utilizing the hot exhaust gas of the air reactor. A detailed sensitivity study was also conducted to study the effects of the CLR operating pressure, and the reduced syngas purity caused by possible gas leakage in the ICR, on the overall methanol plant performance.