Search Results (10)

The growing demand for sustainable energy solutions has led to significant interest in biomass gasification and methane reforming. To address this demand, a novel calcium looping process (CaLP) is proposed, which integrates biomass sorption-enhanced gasification (BSEG) with in situ calcium CaCO₃-based methane reforming (CaMR). This process eliminates the need for CaCO₃ calcination and facilitates the in situ utilization of CO₂. The effects of gasification temperature, steam flowrate into the gasifier α_G(H2O/C), reforming temperature, and steam flowrate into the reformer α_R(H2O/C) were systematically evaluated. Increasing the gasification temperature from 600 °C to 700 °C enhances CO and H₂ yields from 0.653 to 11.699 kmol/h and from 43.999 to 48.536 kmol/h, respectively. However, CaO carbonation weakens, reducing CaO conversion from 79.15% to 48.38% and increasing CO₂ release. A higher α_G(H2O/C) promotes H₂ yield while suppressing CO and CH₄ formation. In the CaMR process, raising the temperature from 700 °C to 900 °C improves CH₄ conversion from 64.78% to 81.29%, with a significant increase in CO and H₂ production. Furthermore, introducing steam into the reformer enhances H₂ production and CH₄ conversion, which reaches up to 97.30% at α_R(H2O/C) = 0.5. These findings provide valuable insights for optimizing integrated biomass gasification and methane reforming systems. Full article

Considering the worsening of global warming, development of efficient strategies in carbon capture process is essential. The chemical looping process (CLP) is considered a promising method applicable in various carbon capture strategies. In pre-, post-, or oxy-fuel combustion strategies, the efficiency of CLP has been explored and tested. This review discusses the applied CLP in each type of carbon capture strategy. Chemical looping gasification and reforming are categorized in the pre-combustion system. On the other hand, the popularity of calcium looping and amine looping are recognized as post-combustion strategies. Additionally, numerous oxygen carrier materials have been determined to reach high efficiency in oxy-fuel combustion. The review of the characters and the principle of the method was complemented by justification for real-scale application. Nonetheless, the popularity of CLP’s real implementation as a carbon capture strategy was still limited by several factors, including required cost for the facilities and energy demand. Thus, analysis on the prospect of CLP utilization was also included in this study. Full article

Using traditional Chinese medicine residue biomass as the raw material and industrial limestone as a carbon absorbent, this paper investigates the production of hydrogen-rich synthesis gas in a pilot-scale calcium looping dual fluidized bed (DFB) system. The study focuses on analyzing the distribution characteristics of temperature and pressure, as well as the operation and control methods of the DFB system. The effects of reaction temperature, material layer height (residence time), water vapor/biomass ratio (S/B), and calcium/carbon molar ratio (Ca/C) on gasification products are examined. The experimental results demonstrate that as the temperature (600–700 °C), S/B ratio (0.5–1.5), Ca/C ratio (0–0.6), and other parameters increase, the gas composition shows a gradual increase in the volume content of H₂, a gradual decrease in the volume content of CO, and an initial increase and subsequent decrease in the volume content of CH₄. Within the range of operating conditions in this study, the optimal conditions for producing hydrogen-rich gas are 700 °C, an S/B ratio of 1.5, and a Ca/C ratio of 0.6. Furthermore, increasing the height of the material layer in the gasification furnace (residence time) enhances the absorption of CO₂ by the calcium absorbents, thus promoting an increase in the volume content of H₂ and the carbon conversion rate in the gas. Full article

Biomass gasification is an attractive technology and one of the pathways for producing hydrogen. Due to the variable seasons and low calorific value of biomass, the addition of coal in the gasifier is suggested because coal has a high calorific value and carbon-to-hydrogen ratio. In general, the gaseous product obtained in gasification always contains a high amount of carbon dioxide, therefore, the co-gasification of biomass and coal should integrate with the calcium looping carbon dioxide capture process to provide purified hydrogen. In this work, the model of the co-gasification of biomass and coal integrated with the calcium looping carbon dioxide capture process was developed through an Aspen Plus simulator. The developed model was used to analyze the performance of this process. The sensitivity analysis demonstrated that increasing the gasification temperature, steam-to-feed (S/F) ratio, calcium oxide-to-feed (CaO/F) ratio, and regenerator temperature could improve hydrogen production. Next, further optimization was performed to identify the optimal operating condition that maximizes hydrogen production. The results showed that the optimal operating temperature of the gasifier is 700 °C with an S/F mass ratio of 2 and coal to biomass (C/B) mass ratio of 0.75:0.25. However, the carbonator and regenerator temperatures should be 450 °C and 950 °C, respectively, with a CaO/F mass ratio of 3. Under these operating conditions, the maximum H₂ content and H₂ yield can be provided as 99.59%vol. (dry basis) and 92.38 g hydrogen/kg biomass feeding. The other results revealed that the energy efficiency and carbon capture efficiency of this process are 42.86% and 99.99%, respectively, and that the specific emission of released CO₂ is 80.77 g CO₂/MJ. Full article

Steel converter slag, also called Linz-Donawitz (LD) slag, has been considered as an oxygen carrier for biofuel chemical looping applications due to its high availability. In addition to its content of iron which contributes to its oxygen-carrying capacity, LD slag also contains a significant amount of calcium. Calcium, however, is known to interact with sulfur, which may affect the usability of LD slag. To get a better understanding of the interaction between sulfur and LD slag, batch scale experiments have been performed using solid and gaseous fuel with or without sulfur dioxide, together with LD slag as an oxygen carrier. The reactivity and sulfur interaction were compared to the benchmark oxygen carrier ilmenite. Sulfur increases the gasification rate of biofuel char and the conversion of CO for both LD slag and ilmenite. However, no effect of sulfur could be seen on the conversion of the model tar species benzene. The increased gasification rate of char was suspected to originate from both surface-active sulfur and gaseous sulfur, increasing the reactivity and oxygen transfer of the oxygen carrier. Sulfur was partly absorbed into the LD slag particles with calcium, forming CaS and/or CaSO₄. This, in turn, blocks the catalytic effect of CaO towards the water gas shift reaction. When the SO₂ vapor pressure was decreased, the absorbed sulfur was released as SO₂. This indicates that sulfur may be released in loop-seals or in the air reactor in a continuous process. Full article

Plastic products are widely used due to their superior performance, but there are still limitations in the current methods and technologies for recycling and processing of waste plastics, resulting in a huge wasting of resources and environmental pollution. The element composition of waste plastics determines its great gasification potential. In this paper, three different waste plastic gasification processes are designed in a process simulator based on the conventional Integrated Gasification Combined Cycle (IGCC) system to achieve waste conversion and utilization as well as carbon capture. Design 1 is based on the cryogenic air separation (CAS) process to obtain oxygen, which is sent to the gasifier together with steam and pretreated waste plastics. The synthesis gas is purified and synthesized into methanol, and the residual gas is passed to the gas turbine and steam turbine to achieve multiple production of heat, electricity, and methanol. Design 2 uses a Vacuum Pressure Swing Adsorption (VPSA) process to produce oxygen, which reduces the energy consumption by 56.3% compared to Design 1. Design 3 adds a calcium-looping (CaL) reaction coupled with a steam conversion reaction to produce high-purity hydrogen as a product, while capturing the generated CO₂ to improve the conversion rate of the reaction. Full article

Combined cycle, biomass calcium looping gasification is proposed for a hydrogen and electricity production (CLGCC–H) system. The process simulation Aspen Plus is used to conduct techno-economic analysis of the CLGCC–H system. The appropriate detailed models are set up for the proposed system. Furthermore, a dual fluidized bed is optimized for hydrogen production at 700 °C and 12 bar. For comparison, calcium looping gasification with the combined cycle for electricity (CLGCC) is selected with the same parameters. The system exergy and energy efficiency of CLGCC–H reached as high as 60.79% and 64.75%, while the CLGCC system had 51.22% and 54.19%. The IRR and payback period of the CLGCC–H system, based on economic data, are calculated as 17.43% and 7.35 years, respectively. However, the CLGCC system has an IRR of 11.45% and a payback period of 9.99 years, respectively. The results show that the calcium looping gasification-based hydrogen and electricity coproduction system has a promising market prospect in the near future. Full article

This study investigated the effect of HCl in biomass gasification producer gas on the CO₂ capture efficiency and contaminants removal efficiency by CaO-Fe₂O₃ based sorbent material in the calcium looping process. Experiments were conducted in a fixed bed reactor to capture CO₂ from the producer gas with the combined contaminants of HCl at 200 ppmv, H₂S at 230 ppmv, and NH₃ at 2300 ppmv. The results show that with presence of HCl in the feeding gas, sorbent reactivity for CO₂ capture and contaminants removal was enhanced. The maximum CO₂ capture was achieved at carbonation temperatures of 680 °C, with efficiencies of 93%, 92%, and 87%, respectively, for three carbonation-calcination cycles. At this carbonation temperature, the average contaminant removal efficiencies were 92.7% for HCl, 99% for NH₃, and 94.7% for H₂S. The outlet contaminant concentrations during the calcination process were also examined which is useful for CO₂ reuse. The pore structure change of the used sorbent material suggests that the HCl in the feeding gas contributes to high CO₂ capture efficiency and contaminants removal simultaneously. Full article

Two bimetallic Fe-Cu and Fe-Ca oxygen carriers were studied for chemical looping gasification (CLG) of biomass. The SEM results indicated that there was no obvious agglomeration on the bimetallic Fe-Cu oxygen carrier supported on Al₂O₃ and Fe-Ca oxygen carrier after five redox cycles while agglomeration occurred on CuO supported on Al₂O₃ due to the low melting point of CuO. The XRD results indicated the presence of copper-ferrite and calcium-ferrite phases in the bimetallic materials. The two bimetallic oxygen carriers can be re-oxidized with air to form a crystalline that is similar to the fresh materials. The Fe-Ca oxide became active at 360 °C which was lower than 380 °C for the Fe-Cu oxygen carrier. The high thermal stability and redox reactivity of bimetallic Fe-Cu and Fe-Ca oxygen carriers make the bimetallic oxygen carriers more suitable for recycling during CLG. The method for preparing Fe-Cu oxygen carriers had no significant impact on biomass conversion efficiency but had significant effect on the quality of syngas. Proper control of the biomass/oxygen carrier mass ratio is critical to achieve high selectivity towards gasification instead of combustion. The Fe-Ca oxygen carrier could achieve higher selectivity towards gasification than the Fe-Cu oxygen carrier. Full article

Calcium looping is a promising technology to capture CO₂ from the process of coal-fired power generation and gasification of coal/biomass for hydrogen production. The decay of CO₂ capture activities of calcium-based sorbents is one of the main problems holding back the development of the technology. Taking carbide slag as a main raw material and Ca₁₂Al₁₄O₃₃ as a support, highly active CO₂ sorbents were prepared using the hydrothermal template method in this work. The effects of support ratio, cycle number, and reaction conditions were evaluated. The results show that Ca₁₂Al₁₄O₃₃ generated effectively improves the cyclic stability of CO₂ capture by synthetic sorbents. When the Al₂O₃ addition is 5%, or the Ca₁₂Al₁₄O₃₃ content is 10%, the synthetic sorbent possesses the highest cyclic CO₂ capture performance. Under harsh calcination conditions, the CO₂ capture capacity of the synthetic sorbent after 30 cycles is 0.29 g/g, which is 80% higher than that of carbide slag. The superiority of the synthetic sorbent on the CO₂ capture kinetics mainly reflects at the diffusion-controlled stage. The cumulative pore volume of the synthetic sorbent within the range of 10–100 nm is 2.4 times as high as that of calcined carbide slag. The structure of the synthetic sorbent reduces the CO₂ diffusion resistance, and thus leads to better CO₂ capture performance and reaction rate. Full article