Biomass Chemical Looping Gasification Research Articles

Numerical investigation and thermodynamic analysis of syngas production through chemical looping gasification using biomass as fuel

Chemical looping gasification (CLG) is an innovative technology for the thermochemical conversion of biomass to produce high quality synthesis gas. In this study, a one-dimensional transient model considering partial oxidation of fuels and iron-steam reaction for biomass CLG fuel reactor was developed and validated against the experimental study utilizing Fe2O3 as oxygen carrier (OC) and microalgae as fuel. The simulation results and the experimental data are in good agreement in terms of the detailed time-varying outlet gas species concentrations, gas yield, carbon conversion efficiency, and gasification efficiency. The effects of different operating temperature and steam flow on the gasification performance are also well predicted by the adopted reaction mechanisms. Energy and exergy analyses are applied to evaluate the energy sources based on the validated model, which demonstrates that the presence of OC can enhance both the quantity and quality of the valuable syngas.

Identifying the roles of MFe2O4 (M=Cu, Ba, Ni, and Co) in the chemical looping reforming of char, pyrolysis gas and tar resulting from biomass pyrolysis

Biomass chemical looping gasification (BCLG), which employs oxygen carriers (OCs) as the gasification agent, is drawing more attention for its low cost and environmental friendliness. However, the complex products of biomass pyrolysis and the reactions between OCs and the pyrolysis products constrain its development. In this study, MFe2O4 (M = Cu, Ba, Ni and Co) ferrites synthesized via the sol-gel method were investigated as OCs in BCLG for hydrogen-rich syngas production. The properties of the as-prepared and spent OCs were characterized by X-ray diffraction (XRD), H2-temperature programmed reduction (TPR), scanning electron microscopy (SEM), and automatic surface area porosimetry (BET). The three-phase products (char, pyrolysis gas and toluene) derived from biomass pyrolysis were employed as the reactants to investigate the reactivity of the ferrites. Then, BCLG experiments using biomass were conducted on the four ferrites to further determine their performance. The characterization results suggested that the four ferrites are all attractive for the chemical looping process, exhibiting good oxygen transferability and wide distributions of metal cations because of their metal synergistic effects in the spine structure. Reactions with pyrolysis gas and biomass char indicated that BaFe2O4 has a higher reactivity via a solid-solid reaction but a lower reactivity with pyrolysis gas, which make it very favorable for the production of hydrogen-rich syngas. Furthermore, BaFe2O4 showed excellent performance for toluene catalytic cracking with small amounts of carbon deposition. The synergetic effects between Ba and Fe metals considerably enhanced selective oxidation to produce 26.72% more H2 than CoFe2O4 and 13.79% more H2 than NiFe2O4 and CuFe2O4 for biomass gasification. The hydrogen yield produced by BaFe2O4 with the assistance of steam for biomass gasification can reach 41.8 mol/kg of biomass.

Syngas production by chemical looping gasification of biomass with steam and CaO additive

In the present work chemical looping gasification (CLG) of biomass, with introduction of steam and CaO, was conducted in a fixed bed to produce syngas. The addition of steam facilitated both the reforming reaction and water gas shift reaction to produce more gaseous products, especially H2. Depending on gas yield and gasification efficiency, the requirement of steam was sufficient for CLG at steam flow n = 0.6 r/min. It was also confirmed that CaO had a positive effect in gasification and the addition in the ratio of CaO/C = 1 was adequate for syngas production. Moreover, CaO mainly played a role as CO2 absorbent at low temperature but as catalyst above 700 °C. However, the catalysis of CaO received the major attention because of its availability for high syngas yield (1.367 m3/kg) and efficiency (carbon conversion efficiency was 89.28% and gasification efficiency was 88.81%) at 800 °C. CaO was found to retard the sintering and porosity reduction of Fe2O3, the oxygen carrier, by covering Fe2O3 and forming calcium ferrites during multiple redox cycles.

Identifying iron-based oxygen carrier reduction during biomass chemical looping gasification on a thermogravimetric fixed-bed reactor

Establishing a direct relationship between the mass change of iron-based oxygen carrier and gas production is crucial for the efficient operation and the control of the lattice oxygen release in biomass chemical looping gasification. In this study, a thermogravimetric fixed-bed reactor was designed to achieve the simultaneous measurement of the mass change and gas composition in the reduction of the oxygen carrier. Three oxygen carriers of pure iron (III) oxide, natural hematite, and red mud were used as candidates. The phase transfer of the oxygen carrier along with the biomass pyrolysis/gasification was studied. The mass loss rates and the gas composition were matched by three significant phase transition stages. The phase transitions from Fe2O3 to Fe3O4, Fe3O4 to FeO, and FeO to Fe occurred when CO appeared, CO/CO2 = 0.97, and CO/CO2 = 2.61, respectively. The extent of oxygen carrier reduction was 28.61% of pure iron (III) oxide, whereas the oxygen carrier reduction molar ratio was 74.50% of red mud. X-ray diffraction (XRD) spectrums showed the oxygen carrier was reduced to the metallic iron phase. Sintering and agglomeration were found in the reacted oxygen carriers of the scanning electron microscope (SEM) images.

Characterization of combined Fe-Cu oxides as oxygen carrier in chemical looping gasification of biomass

Chemical looping gasification (CLG) of biomass is an innovative biomass gasification technology, where oxygen carrier (OC) has the effects of oxygen supply, heat transfer and catalyst for syngas production. In order to integrate the synergistic effect between Fe and Cu oxides, a novel combined OC containing Fe2O3 and CuO was produced for biomass gasification and investigated in a batch fluidized bed reactor in this work. At first, an OC with 50 wt.% Fe2O3 and 10 wt.% CuO (Fe50Cu10) was selected as the representative OC to evaluate the superiority of combined OC. The mono-metallic OC of CuO is unsuitable as oxygen carrier in the CLG of biomass due to its too low syngas yield, although CuO can greatly accelerate biomass gasification process. In addition, combined Fe-Cu oxides OC is also superior to mono-metallic OC of Fe2O3 at enhancing carbon conversion efficiency on the premise that syngas yield tended to be close. Then the blending ratio of Fe/Cu was optimized and Fe50Cu10 had been proven to be the optimal combined Fe-Cu oxides OC in CLG. Next, the influences of the factors including gasification temperature, steam mole fraction and O/C ratio on the performance of Fe50Cu10 were investigated. 900 °C is the best temperature for gasification and higher team mole fraction gave rise to higher carbon conversion efficiency and syngas yield, while O/C ratio was somewhat different. The optimal O/C ratio was deemed to be 0.78. Besides, 10 redox cycles were conducted to investigate the stability of combined OC reactivity. The combined OC after 3 cycles performed worst reactivity, while better performance was demonstrated after 7–10 cycles. Based on the analysis of SEM-EDX, it was found that sintering caused by Cu atomic was the main cause of the reactivity decline. In addition, it was inferred that the distribution of Cu atomic in the combined OC was more uniform with the cycle number.

锰基载氧体生物质化学链气化反应热力学研究

锰基载氧体生物质化学链气化反应热力学研究

Solar chemical looping gasification of biomass with the ZnO/Zn redox system for syngas and zinc production in a continuously-fed solar reactor

The high-temperature solar-driven chemical looping gasification of lignocellulosic biomass with ZnO/Zn redox pair was investigated as a novel process producing both syngas and metallic zinc. A lab-scale solar reactor (1.5 kW) was operated for continuous combined biomass gasification and ZnO carbo-thermal reduction using solar energy as the source of high-temperature process heat. Experiments were performed at temperatures ranging from 1050 °C to 1300 °C with biomass/ZnO molar ratios from 0.5 to 1, using beech wood as a biomass feedstock. The objective of this study was to unveil the advantages and reliability of the combined process involving biomass pyro-gasification with solid ZnO as an oxidizing agent under continuous process operation for co-production of syngas and metallic Zn. The influence of temperature and reactant molar ratio on syngas production was highlighted and compared to the case of a pyrolysis process without any oxidant. Moreover, the chemical conversion of ZnO to Zn obtained by this endothermic step was also addressed, confirming pure Zn production with low recombination in the collected solid products. The evolved H2 increased significantly, CO production also tended to increase slightly, while CO2 and CH4 decreased when increasing the temperature. The syngas yield of the combined gasification/carbo-thermal reduction (up to ∼8 molsyngas/molbiomass for a biomass/ZnO molar ratio of 0.75 at 1250 °C) was much higher in comparison with pyrolysis. The calorific value of the feedstock was solar up-graded through syngas and Zn production in the case of the biomass gasification using ZnO, whereas pyrolysis was not energetically efficient because of the energy content still remaining in the produced char. The optimal biomass/ZnO molar ratio was evidenced at 0.75 yielding maximum syngas production. The energy upgrade factor of the feedstock by the solar power input and the solar-to-fuel energy conversion efficiency were 1.17 and 19.8% respectively for a molar ratio of 0.75 at 1250 °C.

Chemical-looping gasification of biomass: Part II. Tar yields and distributions

Tar, as a kind of by-product in biomass gasification processes, can adversely affect the efficiency of biomass utilization. Chemical-looping technology has been proposed as a novel way to reduce the tar yield in biomass treatment. As the second part of a two-part series work, the tar evolution characteristic during the biomass-derived chemical-looping gasification (CLG) process using bimetallic Cu-Fe oxides as oxygen carrier (OC) was investigated. The tar collected from batch fluidized bed experiment with Cu5Fe5 (50 mol.% CuO + 50 mol.% Fe2O3) as OC was first analyzed by Gas Chromatography-Mass Spectrometer (GC-MS) to qualitatively determine the organic compounds contained. It was found that the relative molecular weight of the compounds was mostly concentrated at about 200. Subsequently, the effects of steam to biomass ratio (S/B, in weight), temperature, and oxygen carrier to biomass ratio (O/B, in weight) on tar reforming were investigated. The results indicated that the increase of temperature, S/B and O/B were all favorable for the decomposition and conversion of large molecular compounds in tar into small ones. In addition, quantitative analyses of the tar collected under the optimal conditions with different Cu-Fe mixed metal oxides as OCs were also conducted. It was found that the Cu composition in OC could promote the decomposition of small molecular compounds in tar, while the Fe composition was beneficial to decrease the yield of large molecular compounds in tar. Furthermore, synergistic reactivity of the bimetallic Cu-Fe OC was achieved for tar decomposition during the biomass-derived CLG process.

Chemical looping gasification of biomass: Part I. screening Cu-Fe metal oxides as oxygen carrier and optimizing experimental conditions

Fe2O3 and CuO are commonly used as oxygen carrier (OC) for chemical looping gasification (CLG) of biomass. However, Fe2O3 shows relatively low reactivity even though it is cheap, whilst CuO presents too high reactivity to react with the produced syngas and suffers from sintering problem at high temperatures. This paper is the first part of a two-part series work, where synthetic OCs of bimetallic Cu-Fe oxides prepared by the sol-gel combustion synthesis (SGCS) method were proposed for the biomass-derived CLG process. The reforming reactivity of Cu-Fe OCs with sawdust was first investigated in a thermogravimetric analyzer (TGA). The result indicated that Cu-Fe OCs with higher Cu loading ratio demonstrated better reactivity towards sawdust. Subsequently, the performances of five kinds of Cu-Fe OCs in biomass-derived CLG process were evaluated in a batch fluidized-bed reactor. By comparing the product gas components, gas yield, tar yield and carbon conversion, Cu5Fe5 OC (50 mol.% CuO + 50 mol.% Fe2O3) was found to demonstrate the best comprehensive CLG performance. The effects of steam to biomass ratio (S/B), temperature and oxygen carrier to biomass ratio (O/B) on the performance of Cu5Fe5 were further investigated. The optimum operation state can be attained when the S/B was 0.75, the temperature was 800 °C and the O/B was 0.2. The results of XRD and ESEM characterization showed that the addition of Fe2O3 into CuO-based OC significantly improved the sintering resistance, and the existence of CuO component in Fe2O3 was conductive to improving the porous structure of OC.

Syngas production via biomass self-moisture chemical looping gasification

Fresh biomass self-moisture gasification (BSMG) is a promising route for biomass utilization. Unlike conventional biomass steam gasification (BSG), BSMG used the moisture content in biomass as the gasifying agent. In this work, the performance of biomass self-moisture chemical looping gasification (BSM-CLG) was compared with dry biomass chemical looping gasification (DB-CLG) and biomass steam chemical looping (BS-CLG) gasification. The data analyzed was the gas cumulative compositions, the hydrogen-to-carbon monoxide ratio (H2/CO), the lower heating value (LHV) and the gas yield. Results showed that the moisture content increased the gas yield from 0.9927 Nm3 kg−1 to 1.1646 Nm3 kg−1, while the steam increased the H2/CO ratio from 0.6398 mol mol−1 to 0.7436 mol mol−1 in the process. The interaction between OC and biomass moisture increased the biomass reactivity. The differing gasification reactivity was due to different water diffusion between the methods of biomass gasification. The diffusion of moisture content and steam had opposite directions, and the different diffusion led to the moisture content impacted the initial gasification stage, but the steam influenced the biomass molecular structure rearrangement.

Experimental Investigation of Fe–Ni–Al Oxygen Carrier Derived from Hydrotalcite-like Precursors for the Chemical Looping Gasification of Biomass Char

Chemical looping gasification (CLG) of biomass uses the lattice oxygen of oxygen carriers to convert biomass into syngas with a low tar content, high heating value, and low price. It is of key importance to exploit well-dispersed and thermally stable oxygen carriers for the CLG process. In the current work, a series of oxygen carriers with varied Fe and Ni molar ratios were synthesized from hydrotalcite compound precursors (HTlcs), which made the metallic elements mix at the molecular level. Consequently, highly dispersed complex metal oxygen carriers can be achieved after precursor calcinations. CLG of biomass char was carried out in TGA and a fixed bed reactor accompanied by various physical and chemical analyses for the fresh and used oxygen carriers. The result manifested the HTlcs crystalline form, which was formed in the precursors and produced the Fe0.99Ni0.6Al1.1O4 compound after calcination, suggesting that a high degree dispersion of the multimetal oxygen carrier was synthesized. The main H2 upt...

Evaluation of CuO/MgAl2O4 in Biomass Chemical Looping Gasification with Oxygen Uncoupling

Chemical looping gasification (CLG) is a promising method for the utilization of biomass to produce syngas. However, its realization is largely dependent on the use of an oxygen carrier with a high and stable reactivity in cyclic reduction and oxidation. This work focused on the improvement of reactivity and stability of CuO in chemical looping gasification via the addition of MgAl2O4 as an inert material. First, the stability and reactivity of synthesized Cu-based oxygen carriers were studied in a thermogravimetric analyzer (TGA). Then, the characteristics of CLG of biomass and the oxygen carrier in syngas production were investigated by testing gas components, syngas production, and oxygen carrier sintering performance. The results show that CuO supported on MgAl2O4 has a better capacity for oxygen release than pure CuO and a superior stability and gasification activity in the cyclic chemical looping gasification with biomass. A higher operating temperature led to the production of more syngas from biomass gasification with CuO/MgAl2O4 as the oxygen carrier, particularly for CO and H2. CuO/MgAl2O4 also demonstrated a much better effect on methane reforming in CLG. It is believed that CuO/MgAl2O4 is a suitable oxygen carrier for the chemical looping with oxygen uncoupling (CLOU) and CLG of biomass.

Thermodynamic analysis of syngas generation from biomass using chemical looping gasification method

Chemical looping gasification (CLG) is a novel technology to convert carbon-containing feedstock into syngas. In the technology, lattice oxygen of oxygen carrier is used as oxygen source for char gasification, and then the reduced oxygen carrier is regenerated in air atmosphere. In this paper, the mechanism of CLG of biomass using Mn2O3 as oxygen carrier was discussed firstly and then thermodynamic analysis of syngas generation from biomass was performed by Gibbs free energy minimization method. Chemical equilibrium calculations were carried out to study the effects of Mn2O3/biomass, operation temperature, pressure, and steam/Mn2O3 on the gasification characteristics. The optimal thermodynamic conditions were determined to improve H2 and CO concentrations as high as possible. The optimal Mn2O3/corn cob is 0.18 to obtain the highest CO and H2 yields. The results suggest that the preferential conditions are achieved at 1000 °C and atmospheric pressure, under these conditions, the total dry concentration of CO and H2 is 98.8% in the syngas. Steam can be used in the CLG to modify the H2/CO in the syngas. The carbon conversion also increases under oxidizing atmosphere of steam.

Performance of Fe–Ni bimetallic oxygen carriers for chemical looping gasification of biomass in a 10 kWth interconnected circulating fluidized bed reactor

Chemical-looping gasification (CLG) of biomass was investigated in a 10 kWth interconnected fluidized-bed reactor with Fe–Ni bimetallic oxides as oxygen carriers (OC). The thermodynamic analysis of the CLG indicated that the temperature range of 700 °C–950 °C can be suitable for the CLG reactions. The fluidized bed experimental results indicated that biomass was partially oxidized to synthesis gas by the lattice oxygen of the oxygen carrier in the fuel reactor and the synthesis gas composition of CO, H2 and CH4 as well as carbon conversion rate and gasification efficiency increased with the rising reaction temperature, while the CO2 fractions decreased due to the exothermic process. Carbon conversion decreased with the rising ratio of biomass to oxygen carrier. However, there was an optimal value of the gasification efficiency at 70.48% corresponding to the feeding rate of 1.6 kg/h. Compared to the Fe2O3/Al2O3 oxygen carrier, the Fe–Ni bimetallic oxygen carriers displayed a higher the gasification efficiency of biomass, which was correlated with the increasing composition of CO, H2 caused by the synergistic effect between Fe2O3 and NiO. The fresh and used oxygen carriers were characterized by means of XRD, SEM/EDX and BET. The XRD results indicated the mainly reduction products of the oxygen carrier were Fe3O4 in the CLG of biomass and new phase of Ni–Fe kamacite was formed during redox cycles, which could improve the reactivity of the oxygen carrier. Also, the oxygen carriers can be well regenerated and kept good crystalline state. The surface area of the oxygen carrier decreased from 2.486 m2/g to 2.085 m2/g after 120min CLG reactions. The average pore diameter and total pore volume shifted from 39.8 nm, 0.0248 cc/g to 39.4 nm, 0.0205 cc/g, respectively, suggesting that a part of micorpores in the particles of the oxygen carrier were blocked or collapsed. However, reactivity deterioration of the Fe–Ni bimetallic oxygen carrier was not observed during the experiment operation. SEM-EDX results showed that the metal elements were distributed uniformly in the fresh and used oxygen carriers and irregularly blocky particles with smaller average size and porous structure were still present in regenerated oxygen carrier samples. Overall, these results suggested that the Fe–Ni bimetallic oxygen carrier was a good candidate for the CLG of biomass.

Techno‐Economic Comparison of a 7‐MWth Biomass Chemical Looping Gasification Unit with Conventional Systems

AbstractThe chemical looping process is an alternative method to provide conventional gasification (CG) systems with the required oxygen. The syngas produced via chemical looping has a higher calorific value than that generated by a conventional process with air. For comparison, a conventional gasification unit with pure oxygen (CGPO) and a chemical looping gasification (CLG) system were simulated with Aspen Plus. The CGPO reactor consisted of a bubbling fluidized bed and sand as bed material with oxygen supplied via a pressure swing adsorption unit. The CLG comprised a bubbling fluidized‐bed gasifier working in parallel with a fast fluidized‐bed oxidizer. The total capital investment (TCI) of the CLG unit was higher than that of the CGPO unit but the annual operating cost of the former was less which repays the difference in TCI in less than six years.

Chemical-looping gasification of biomass in a 10 kWth interconnected fluidized bed reactor using Fe2O3/Al2O3 oxygen carrier

The aim of this research is to design and operate a 10 kW hot chemical-looping gasification (CLG) unit using Fe2O3/Al2O3 as an oxygen carrier and saw dust as a fuel. The effect of the operation temperature on gas composition in the air reactor and the fuel reactor, and the carbon conversion of biomass to CO2 and CO in the fuel reactor have been experimentally studied. A total 60 h run has been obtained with the same batch of oxygen carrier of iron oxide supported with alumina. The results show that CO and H2 concentrations are increased with increasing temperature in the fuel reactor. It is also found that with increasing fuel reactor temperature, both the amount of residual char in the fuel reactor and CO2 concentration of the exit gas from the air reactor are degreased. Carbon conversion rate and gasification efficiency are increased by increasing temperature and H2 production at 870°C reaches the highest rate. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and BET-surface area tests have been used to characterize fresh and reacted oxygen carrier particles. The results display that the oxygen carrier activity is not declined and the specific surface area of the oxygen carrier particles is not decreased significantly.

CaO-based chemical looping gasification of biomass for hydrogen-enriched gas production with in situ CO2 capture and tar reduction

Steam gasification of biomass undergoes the problem of undesirable CO2 and tar formation. Calcium oxide (CaO), when added to the gasification, could play the dual role of tar reforming catalyst and CO2 sorbent, and thereby produce more hydrogen. However, the deactivation of CaO after carbonation reaction is challenging for continuous hydrogen production and economical perspective. The concept of CaO-based chemical looping gasification (CaO-CLG) plays a key role in overcoming such a challenge. This work primarily aims at studying steam gasification of biomass with the presence of CaO in a uniquely designed chemical looping gasification (CLG) system for hydrogen production with in situ CO2 capture and tar reduction. The effect of solid circulation rates on gas and tar production is studied. A comparison of CaO-CLG, sand-based chemical looping gasification (Sand-CLG) and CaO-based bubbling fluidized bed gasification (CaO-BFBG) is presented mainly focusing on gas and tar production. The maximum H2 and minimum CO2 concentrations as well as maximum H2 yields of 78%, 4.98% and 451.11ml (STP)/g of biomass, respectively, are obtained at the solid circulation rate of 1.04kg/m2s. At the same point, the maximum total gas yield was 578.38ml (STP)/g of biomass and the tar content of 2.48g/Nm3 was the lowest. 30% higher concentration of H2 and triple yield of H2 were found in CaO-CLG compared to Sand-CLG. Compared to CaO-BFBG, CaO-CLG resulted in 15% higher concentration of H2 and almost double yield of H2. Moreover, the lowest tar content of 2.48g/Nm3 was obtained for CaO-CLG while the tar content was 68.5g/Nm3 for Sand-CLG and 26.71g/Nm3 for CaO-BFBG. CO2 concentration obtained for CaO-CLG also significantly reduced by 13–17% as compared to both Sand-CLG and CaO-BFBG.

Natural iron ore as an oxygen carrier for biomass chemical looping gasification in a fluidized bed reactor

Chemical looping gasification (CLG) of biomass was performed in a thermogravimetric analyzer (TG) reactor together with a fluidized reactor with natural iron ore oxygen carrier under inert atmosphere. TG experiments indicated that iron ore can provide oxygen source for biomass conversion in the form of lattice oxygen. In the fluidized bed experiments, the influences of reduction temperature on CLG of biomass were emphatically investigated in terms of gas distribution and solid characters. The gas yield and carbon conversion increased, but the tar content decreased in the temperature range of 1,013–1,213 K. In this temperature range, the conversion of oxygen carrier increased from 24.11 to 53.59 %. X-ray diffraction analysis shows that more FeO was generated with temperature increasing. Scanning electron microscope analysis indicates that sintering was observed at elevated temperature. An optimum mass ratio of biomass/oxygen carrier (B/O) of 0.67 was obtained with aim of achieving maximum gasification efficiency of 76.93 %.

Thermodynamic Analysis and Synthesis Gas Generation by Chemical-Looping Gasification of Biomass with Nature Hematite as Oxygen Carriers

Thermodynamic parameters of chemical reactions in the system were carried out through thermodynamic analysis. According to the Gibbs free energy minimization principle of the system, equilibrium composition of the reactions of chemical-looping gasification (CLG) of biomass with natural hematite (Fe2O3) as oxygen carrier were analyzed using commercial software of HSC Chemistry 5.1. The feasibility of the CLG of biomass with hematite was experimental verified in a lab-scale bubbling fluidized bed reactor using argon as fluidizing gas. It was indicated the experimental results were consistent with the theoretical analysis. The presence of oxygen carrier gave a significant effect on the biomass conversion and improved the synthesis gas yield obviously. It was observed that the gas content of CO and H2 was over 70% in CLG of biomass. The reduced hematite particles mainly existed in form of FeO. It was showed that the reduction of natural hematite with biomass proceeds in a stepwise manner from Fe2O3 →Fe3O4→ FeO. Reduction product of natural hematite can be restored the lattice oxygen by oxidation with air.

Application of Concrete and Demolition Waste as CO2 Sorbent in Chemical Looping Gasification of Biomass

This paper summarizes the results of an experimental investigation into sorbent chemical looping gasification (SCLG) of biomass for the production of high-purity hydrogen and in situ capture of the resulting CO2. The key innovation was the use of concrete and demolition waste (CDW) as the source of CO2 sorbent. A comprehensive series of thermogravimetric analysis (TGA) experiments was carried out over a range of temperatures between 650 and 900 °C and pressures up to 20 atm to benchmark the CO2 capture efficiency of CDW against conventional lime-based sorbents [e.g., calcined limestone (CL) and hydrated Portland cement (HPC)]. Effects of controlling parameters, such as the Ca/C ratio, steam/carbon (S/C) ratio, steam partial pressure, and total pressure, on the gas yield, gas composition, and CO2 capture efficiency were thoroughly examined. Experimental results confirmed that CO2 capture efficiencies as high as 56.4% and high-grade hydrogen production can be achieved when CDW is used as a sorbent. These re...