Carbon Capture Efficiency Research Articles

Dynamic modelling and simulation of clean coal power generation

Retrofitting coal-fired power plant (PP) with carbon capture technology can be used as an effective transition solution towards clean coal-based energy production. Thus, this study analyses the operational/behavioural performance of retrofitting carbon capture to a coal-fired power plant (PP-PCC plant). A real-time data-driven model representing PP-PCC plant is developed in Matlab/Simulink software facility. The model simulates the dynamic response of integrated plant subjected to operational uncertainty and unprecedented perturbation. A positive variation (increment of flowrate) of air, coal and lean solvent flowrates exhibit significant dynamic responses toward the power plant load, carbon capture efficiency (CC) and energy performance (EP). Where, variation of these variables contribute to the elevation of capture percentage and improvement of energy performance. This study is beneficial for preliminary understanding of the transient variable behaviours of clean coal power generation as one of the mitigation measure to ensure proposed integration is feasible in term of environmental and economic performances.

Insights into the co-combustion of coal and biomass mixtures using a copper-based oxygen carrier in chemical looping combustion

Chemical looping with oxygen uncoupling (CLOU), variant to chemical looping combustion (CLC), is working on strategies to transport gaseous oxygen for fuel combustion. The present work reports the process simulation of CLOU of a coal-biomass mixture with CuO oxygen carrier. Variations in the different parameters are compared by replacing pure coal with an equal fraction of coal-biomass mixture. The presence of alkaline earth metals in biomass is seen to increase the coal char conversion in the fuel reactor. The predicted carbon capture efficiency is found to increase with the fuel reactor temperature range of 900 to 965°C irrespective of fuel used. The carbon capture efficiency was also varied with the solids flow rate varying from 3.48 to 13.64 kg/h. The thermal power output for the coal-biomass mixture is further compared with published literature for pure coal in context of its CLOU mode of operation. [Received: March 2, 2018; Accepted: November 26, 2018]

Coal-fired chemical looping combustion coupled with a high-efficiency annular carbon stripper

Coal-fired chemical looping combustion (CLC) is a promising technology with inherent CO2 separation with a low energy penalty. One of challenges for coal-fired CLC is that char particles with slow gasification kinetics can be easily transferred into the air reactor (AR) by circulated oxygen carrier (OC), thereby decreasing the carbon capture efficiency. An annular carbon stripper (CS) was proposed to efficiently separate the char particles from the mixture of OC and char. A hot system of 10 kWth CLC unit coupled with an annular CS was designed, built, and operated in order to investigate the separation performance of an annular CS at high temperature (850-950 °C). Vietnamese ilmenite was used as OC to burn Shenfu bituminous coal. The system achieved a stable solid circulation at a high temperature with steady coal feeding, and total operation reached 100 h with a thermal input of 3-5 kWth. A 90%-95% char separation efficiency was achieved by the annular CS in various tests, and the carbon capture efficiency reached 95% at 950 °C. A special particle sampling device was designed to collect solid particles from the dense phase of CLC reactor during the continuous operation stage. It was found that the char mass faction in the FR dense phase was 0.45%-5.5% and a fraction of char adhered to the ilmenite surface, which was difficult to separate by the annular CS. Additionally, the sintering and agglomeration of ilmenite was not observed during continuous operation at 850-950 °C. Furthermore, through extrapolating experimental results, it is predicted that 90% carbon capture efficiency can be achieved by using this new annular CS in a scaled-up CLC system.

Carbon capture for blackwater: chemical enhanced high-rate activated sludge process.

Blackwater has more benefits for carbon recovery than conventional domestic wastewater. Carbon capture and up-concentration are crucial prerequisites for carbon recovery from blackwater, the same as domestic wastewater. Both chemical enhanced primary treatment (CEPT) and high-rate activated sludge (HRAS) processes have enormous potential to capture organics. However, single CEPT is subject to the disruption of influent sulfide, and single HRAS has insufficient flocculation capacity. As a result, their carbon capture efficiencies are low. By combining CEPT and HRAS with chemical enhanced high rate activated sludge (CEHRAS) process, the limitations of single CEPT and single HRAS offset each other. The carbon mineralization efficiency was significantly influenced by SRT rather than iron salt dosage. An iron dosage significantly decreased chemical oxygen demand (COD) lost in effluent. Both SRT and iron dosage had a significant influence on the carbon capture efficiency. However, HRT had no great impact on the organic mass balance. CEHRAS allowed up to 78.2% of carbon capture efficiency under the best conditions. The results of techno-economic analysis show that decreasing the iron salt dosage to 10 mg Fe/L could promise profiting for blackwater treatment. In conclusion, CEHRAS is a more appropriate technology to capture carbon in blackwater.

Auto-thermal operation and optimization of coal-fueled separated gasification chemical looping combustion in a pilot-scale unit

As one of the chemical looping combustion (CLC) technologies, separated gasification-CLC (SG-CLC) can realize the carbon separation during coal combustion process with low degradation of oxygen carrier and high performances. In order to realize the auto-thermal operation of the constructed pilot-scale SG-CLC unit, some oxygen was added into the gasification agent to compensate the endothermic gasification of coal using steam. The combustion performances of SG-CLC unit were investigated under different conditions with variables of reaction temperature, coal feed rate, steam mass flow, oxygen flow and type of loosen gas. Ten conditions were designed and conducted to study the effects of variables on the CLC performances. According to the temperature curves, auto-thermal operation was achieved in seven of these tests. Carbon capture efficiencies under auto-thermal operation were almost higher than 97% and the oxygen demands in these test were less than 4.70%. The peak value of solid fuel conversion was 93.91% at 930 °C while the minimum was 87.36% at 830 °C under auto-thermal conditions. The performances demonstrated that the SG-CLC system could offer great possibility for its commercial application under auto-thermal conditions. Furthermore, some measures were put forward to optimize the operation of this SG-CLC system.

DESIGN AND EVALUATION OF A HELICAL-TUBULAR PHOTOBIOREACTOR FOR MICROALGAE PRODUCTION

Photosynthetic microalgae are important bioresource for producing desired and environmentally safe products including biodiesel production as third generation biofuels. Photobioreactor play important role in this process. Designing and manufacture the bioreactor for photocatalysis is still challenging at present time due to the important factors that must be closely considered with regard to light requirements. The aim of the present study was to design and evaluate a helical-tubular photobioreactor for algae production. The design considerations included light intensity controller circuit, surface-to-volume ratio, power required of both air pump and mixing pump to reach up the optimum operating parameters. Experiments were conducted to optimize light intensity and light/dark duration cycle. The photobioreactor performance was evaluated in terms of biomass productivity, lipid productivity, carbon capture efficiency and energy balance of algae production system. The experimental results reveal that the helical-tubular photobioreactor is recommended to be used under light intensity of 8 kLux and light/dark duration cycle of 18:6 h to obtain the highest biomass productivity of 1.80 kg.day-1 and lipid productivity 432 g.day-1 with carbon capture efficiency 87%. The manufactured photobioreactor is capable of produce 4.74 kWday which is equivalent to 4.39 kWday of net energy output.

Bioenergy and full carbon dioxide sinking in sugarcane-biorefinery with post-combustion capture and storage: Techno-economic feasibility

Sugarcane plantations promote impressive drainage of atmospheric carbon dioxide reaching 781 t/h for a 1000 t/h sugarcane-biorefinery. For first-generation bioethanol sugarcane-biorefineries, only 10% of sugarcane carbon dioxide equivalent leaves as hydrous-ethanol, while 90% return to atmosphere through bagasse-fired power cogeneration in steam-Rankine cycles. Thus, a sugarcane-biorefinery exports two bioenergy flows – electricity and hydrous-ethanol – and its impressive Bioenergy Carbon Capture and Storage potential is wasted. Capture of fermentation carbon dioxide merely means 5% of Bioenergy Carbon Capture and Storage efficiency. This work assesses a new sugarcane-biorefinery concept dramatically raising the Bioenergy Carbon Capture and Storage efficiency. With fermentation carbon dioxide already captured, it is advocated to implement 90% post-combustion capture of flue-gas carbon dioxide. Then, captured carbon dioxide is compressed and traded as Enhanced Oil Recovery agent transported to deep-water offshore oil fields via high-pressure pipelines counting on topographic gravitational effects to lower compression power. Aggregating pipeline/compression investment to the biorefinery, it is shown that such new Plantation-Biorefinery-Post-Combustion-Pipeline-Oil-Recovery enterprise is technically feasible for 5.22 MtCO2/y of Bioenergy Carbon Capture and Storage capacity and is economically feasible under certain conditions: (i) idle pipeline capacity rental to fossil carbon emitters at 10–20 USD/tCO2; (ii) recovered oil revenues traded at 1–2 bbl/tCO2 and 50–80 USD/bbl; (iii) carbon-taxation at 40–80 USD/tCO2; and (iv) carbon Cap-and-Trade at 30–70 USD/tCO2. Under such conditions the Plantation-Biorefinery-Post-Combustion-Pipeline-Oil-Recovery can attain 7 MMMUSD net value and 6 years payback-time.

Three-dimensional multiphase full-loop simulation of directional separation of binary particle mixtures in high-flux coal-direct chemical-looping combustion system

Coal-direct chemical-looping combustion (CDCLC) is a promising coal combustion technique that provides CO2 capture with a low energy penalty. In this study, we developed a three-dimensional Eulerian–Eulerian multiphase full-loop model for simulating the circulation and separation of binary particle mixtures in a novel high-flux CDCLC system. This model comprised a high-flux circulating fluidized bed as the fuel reactor (FR), a counter-flow moving bed as the air reactor (AR), a high-flux carbon stripper, two downcomers, and two J-valves. This model predicted the main features of complex gas–solid flow behaviors in the system. The simulation results showed that quasi-stable solid circulation in the whole system could be achieved, and the FR, AR, and J-valves operated in a dense suspension upflow regime, a near-plug-flow regime, and a bubbling fluidization regime, respectively. The multiphase flow model of binary particle mixtures was used to predict the mechanisms of directional separation of binary particle mixtures of an oxygen carrier (OC) and coal throughout the system. A decrease in the baffle aspect ratio of the inertial separator improved the coal selective separation efficiency but resulted in a slight decline in the OC selective separation; this is believed to be the result of weakening of particle collisions with the baffle. A higher FR gas velocity had a slightly negative effect on the OC selective separation efficiency, but improved the coal selective separation efficiency; this can be attributed to an increase in the particle-carrying capacity of the gas stream. A decrease in the coal particle size led to better entrainment of the coal particles by the gas stream and this increased the coal selective separation efficiency. In real CDCLC applications, the operating variables for separation of binary particle mixtures should be comprehensively assessed to determine their positive and negative effects on the carbon capture efficiency, OC regeneration efficiency, gas leakage restraint, energy consumption, and fuel conversion.

Life cycle global warming impact of CO2 capture by in-situ gasification chemical looping combustion using ilmenite oxygen carriers

In-situ gasification chemical looping combustion (iG-CLC), which has been tested on pilot plant level, is regarded as an advanced carbon capture and storage (CCS) technology for reducing CO2 emissions. A life cycle global warming impact (GWI) analysis is performed to consider the lifetime emissions of the low-carbon iG-CLC technology. Herein, the capacity is considered to be 610 MWe using natural ilmenite as oxygen carrier and steam as gasification agent. At the condition of operational pressure of 15 atm and air reactor temperature of 1050 °C, the net power efficiency of 37.7% for achieving 93.5% inherent CO2 capture is obtained in simulations with thermodynamically optimum condition. The life cycle GWI is calculated equal to be 160.3 kg CO2-equivalent/MW h. The effects of several essential parameters, including steam to carbon ratio (S/C), oxygen carrier to fuel ratio (ф), different oxygen carriers and lifetime of oxygen carriers, on the lifecycle GWI have been analyzed and discussed to meet the potential possibility for further reducing greenhouse gas (GHG) emissions. To obtain sufficient carbon capture efficiency, the S/C ratio and ф are suggested to be 1.3 and 1.2 in this study, respectively. The life cycle GWI is heavily dependent on lifetime of ferrum (Fe) when it is less than 2000 h, beyond that range, the GWI is decreasing, but very slowly.

Soluble substrate removal determination through intracellular storage in high-rate activated sludge systems using stoichiometric mass balance approach

In high-rate activated sludge (HRAS) systems, extracellular adsorption and intracellular storage have been referred to as the dominant mechanisms for capturing organic carbon from wastewater. However, the quantification of storage products under short sludge retention time (SRT) of HRAS systems has rarely been studied. Since the measurement of storage products is complex and dependent on several variables, alternative solutions for substrate removal through storage are required to understand the high-rate system’s carbon capture efficiency. To overcome the complexity of storage quantification experimentally, this study proposes a fundamental approach of determining the intracellular storage products from soluble organic carbon removal of domestic wastewater. A substrate partitioning approach was used which represents influent total chemical oxygen demand (COD) removal through storage, extracellular polymeric substance, biomass growth and energy production. The substrate partitioning approach based on stoichiometric analysis showed that storage accounted for 7–11% of influent soluble COD removal in A-stage systems operated at SRT range of 0.3–2 d. The stoichiometric analysis also showed that soluble COD removal through storage is dependent on dissolved oxygen (DO) level and removal through storage increased from 8% to 30% (influent soluble COD) when the DO level decreased from 2 to 0.01 mg/L at SRT of 1.5 d.

A pilot-scale experimental study on CO2 capture using Zeolitic imidazolate framework-8 slurry under normal pressure

Efficient capture of CO2 is of great significance for the reduction of greenhouse gas emissions and the control of global warming. We herein report a pilot experiment demonstrating successful carbon capture under normal pressure using flowable slurry formed with Zeolitic imidazolate framework-8 and 2-methylimidazole-glycol-water solution in continuously cycled setup composed of a sorption bubble column (with height 3.7 m and inner diameter 60 mm) and a desorption tank. A series of factors that affect the carbon capture efficiency were investigated systematically. The experimental results show that the use of finer aperture and installing baffles, lower superficial gas velocity, lower sorption temperature, higher regeneration temperature, and low regeneration pressure are favorable for carbon capture. CO2 concentration in the emission gas could be reduced from 24.9 mol% to 0.5–2.5 mol%, indicating that more than 92% of CO2 could be removed. The working loading of CO2 in the recycled slurry reached 1.53 mol/(L·bar). The slurry could be regenerated under very moderate conditions (333 K and 0.05 MPa), which are far from boiling conditions for the solvent. It was also shown that the performance of the slurry remained stable over more than 100 h of cycling. This work demonstrates that the approach based on the use of the slurry is readily applicable, and could lead to energy savings compared to the traditional amine absorption approach.

Performance analysis and carbon reduction assessment of an integrated syngas purification process for the co-production of hydrogen and power in an integrated gasification combined cycle plant

The integrated gasification combined cycle (IGCC) is prominent in coal-based power plants because of its high efficiency and environmental benefit. Because of global warming, the integration of a carbon capture process (CCP) into the IGCC is exigent. In this study, performance analysis of an integrated syngas purification process was performed for a 500 MW-class IGCC. First, various carbon capture efficiencies were investigated to elucidate the most economical carbon capture efficiency, and a carbon capture efficiency of 90% was recommended. This value includes sour gas (H2S) removal cost, and it is essential for coal-power plants regardless of carbon capture. Thus, the net carbon capture cost was calculated from the difference in the operating costs of the integrated syngas purification process with/without a CCP. The net carbon capture cost per ton of CO2 was determined as approximately 21 USD. In addition, the exergy analysis and H2 co-production from the integrated syngas purification process with pressure swing adsorption (PSA) were presented to suggest the direction of the potential process improvement and carbon reduction assessment. The study can contribute towards decision-making related to investment in near-future candidate technologies for increasing efficiency and carbon emissions.

Demonstration of Chemical Looping Combustion (CLC) with Petcoke Feed for Refining Industry in a 3 MWth Pilot Plant

Chemical Looping Combustion (CLC) is a promising combustion technology with inherent CO2 capture. This process consists in use of metal oxides, called oxygen carriers, to transfer oxygen from Air Reactor into the Fuel Reactor for combustion of Fuels. Accordingly, Air and Fuel are not mixed and the produced flue gas is concentrated in CO2 and not diluted with nitrogen. This inherent CO2 capture results in higher energy and carbon capture efficiencies compared to conventional capture technologies. This paper presents recent achievements of TOTAL in collaboration with IFPEN on CLC development for the refining and chemical industry with petcoke feedstock. A novel concept has been developed with a two-stage combustion reactor, an integrated solid-solid separator (Carbon Stripper), and non-mechanical solid flow control devices. These technologies have been demonstrated at different scales up to a 1 MWth equivalent cold flow prototype and in a 10 kWth continuous pilot plant. These experimental works permitted to carry out a full-scale process simulation with steam and electricity cogeneration. Different sections of CLC are represented in this simulation including reactor system, flue gas treatment, CO2 compression, and steam cycle. In addition, the cost of avoided CO2 has been evaluated for power generation with Chemical Looping technology. Finally, CHEERS project is introduced in which CLC process will be demonstrate in 3 MWth scale via an international collaboration including nine partners from Europe and China.

Performance in Coupled Fluidized Beds for Chemical Looping Combustion of CO and Biomass Using Hematite as an Oxygen Carrier

A system of coupled fluidized beds for chemical looping combustion was successfully conducted using CO and biomass as fuel. A multi-stage fluidized bed was designed as a fuel reactor to improve gas–solid contact. In the experiments, iron ore was used as the oxygen carrier. The effects of operation parameters, such as fuel reactor temperature and feeding rate, were studied. This reactor can convert gas fuel, CO, into CO2 efficiently in the temperature range of 840–900 °C with different inputs, and the conversions of CO are almost above 90%. For biomass experiments, the fuel reactor temperature exhibits positive effects on the fuel conversion and carbon capture efficiency. The carbon conversion and carbon capture efficiency reach 92.5 and 98.5% at 900 °C, respectively. The temperature above 880 °C is optional for the biomass combustion in this reactor. Besides, the feeding rate has small influences on the carbonaceous gas conversion. In comparison to previous work, this reactor shows superiority in terms of...

Carbon capture efficiency, yield, nutrient uptake and trafficability of different grass species on a cultivated peat soil

Loss of organic matter from cultivated peat soils is a threat to farmers, due to the surface subsidence associated with organic matter loss, and to the atmosphere, due to CO2 and N2O emissions from the soil. In a three-year field experiment (2015–2017) on a drained, cultivated fen peat in southern Sweden, we tested whether reed canary grass (Phalaris arundinacea L.) and tall fescue (Festuca arundinacea Schreb.) perform better on peat soils than the commonly grown timothy grass (Phleum pratense L.), without increasing greenhouse gas emissions. In the experiment, we compared yield, nutrient uptake, penetration resistance and loss of organic matter measured as greenhouse gas emissions (CO2, N2O and CH4). Yield of timothy was significantly lower than that of reed canary grass and tall fescue in 2016, and lower than that of reed canary grass in 2017. Yield level increased over time, with total dry matter yield in 2017 of 11.7 Mg ha−1 yr−1 for timothy, 13.5 Mg ha−1 yr−1 for tall fescue and 14.3 Mg ha−1 yr−1 for reed canary grass. Total removal of all macronutrients in 2016 was higher in reed canary grass and tall fescue than in timothy. For nitrogen (N), reed canary grass removed a total of 173 kg N ha−1 yr−1, tall fescue 169 kg ha−1 yr−1 and timothy 121 kg ha−1 yr−1, while the fertilisation rate was only 50 kg N ha−1. There were no differences in trafficability, measured as penetration resistance. Measurements of greenhouse gas emissions in the snow-free season in 2016 and 2017 using manual dark chambers (CO2, N2O and CH4) and in 2016 automatic dark chambers (CO2) revealed only small differences in CO2 emissions between the treatments. The N2O emissions were also low and CH4 emissions were very low and in general negative. The estimated carbon capture efficiency (ratio of C in aboveground biomass plus roots to emitted CO2-C measured by the automatic chambers) for the growing season (May–October) in 2016 was lowest for timothy (0.61) and higher for reed canary grass and tall fescue (0.70 and 0.70, respectively). Reed canary grass and tall fescue are thus promising alternatives to timothy on peat soils regarding yield, nutrient removal and carbon capture efficiency.

Experimental investigation on the coal combustion in a pressurized fluidized bed

Pressurized oxy-coal combustion is considered as one of the most promising carbon capture technologies in terms of high carbon capture efficiency and low cost. However, practical operational experience with pressurized coal combustion in a fluidized bed, especially with continuous coal feeding, is still very limited. In this study, a pressurized fluidized bed combustion system was developed and a series of coal combustion experiments were carried out with continuous coal feeding under the pressures from 0.1 to 0.4 MPa. The effects of the combustion pressure and stoichiometric air coefficient on the fluidized bed combustion performances of a Chinese lignite in terms of the temperature distribution profile, apparent solid holdup, combustion efficiency, conversion ratio of carbon in coal to CO2 and ash composition were investigated. The experimental results show that an increase in pressure is beneficial to the improvement of combustion efficiency, and the positive effect of increasing stoichiometric air coefficient on the conversion ratio of carbon in coal to CO2 is more obvious with a lower combustion pressure. The bottom ash and fly ash have similar chemical compositions under different pressures. Based on the experimental data, a correlation as the functions of pressure and stoichiometric air coefficient is proposed to predict the conversion ratio of carbon in coal to CO2.

Four equation k-omega based turbulence model with algebraic flux for supercritical flows

Hydrocarbon and nuclear fuels will contribute substantially to the growing global energy portfolio for some time to come. At the same time atmospheric carbon levels and economic concerns are increasingly shaping the power generation environment. Supercritical fluid technologies are being investigated to address both concerns. For example, direct fired supercritical CO2 power cycles offer key advantages for carbon capture and thermal efficiency. Additionally, the supercritical water reactor Generation IV nuclear reactor allows higher power densities and more efficient operation than current pressurized or boiling water reactors. As these technologies are developed, a need exists for accurate, yet cost-effective modeling and simulation solutions to assist with design and safety calculations. Supercritical fluid properties are strongly dependent on temperature which results in a number of unique flow features. Among these features are the complex buoyancy and buoyancy-turbulence interaction behaviors exhibited by supercritical flows that are not found in liquid or gas flows. Therefore, standard turbulence models with current model coefficient values are not likely to be applicable to supercritical fluid flows.The subject of this paper is efficient modeling and simulation of supercritical flows to support nascent technologies growing to maturation and operational deployment. We present a framework for developing Reynolds-Averaged Navier-Stokes turbulence models specifically equipped for the challenges of supercritical flows. A novel formulation of the algebraic heat flux model of the buoyancy production of turbulence term is used with a traditional shear stress transport model. To produce a new turbulence model for supercritical channel flows, the empirical coefficients of the resulting four equation model were calculated from data previously published by other authors regarding upward supercritical flow through heated pipes. The presented SST kt-ωt approach was validated against heated tube experiments to show predictive capabilities in moderate flow conditions, where buoyancy effects are important but not dominating of inertial effects.

Chemical looping combustion of biomass in 10- and 100-kW pilots – Analysis of conversion and lifetime using a sintered manganese ore

Chemical looping combustion (CLC) is a type of carbon capture technology that employs metal oxide particles in a redox reaction to transport oxygen to the fuel. As opposed to first-generation carbon capture concepts, CLC does not include a gas separation step and thus offers the advantage of having no thermodynamic energy penalty in the capture process.Manganese-containing oxygen carriers have been shown to offer a good compromise of gas conversion performance, availability, and cost. On the other hand, previously tested manganese materials have often been challenged with high attrition in continuous CLC.By sintering the ore prior to its use as oxygen carrier, the structure of the particles can be reinforced to increase their durability in the process. In this study, a sintered manganese ore was tested for 56 h in two pilot units of different size. The oxygen carrier worked well in the process, was easily fluidized, and did not exhibit any tendency towards agglomeration. Compared to other manganese materials tested in the same units, a higher lifetime based on fines production was reached, while gas conversion performance was similar.Different biomass fuels, mainly biochar of different sizes and black wood pellets, were employed in the study. A clear correlation between gas conversion and the fuel volatile content was detected; this is consistent with results reported in previous studies. The highest gas conversion reached in both units was ∼93.5% using wood char. The highest carbon capture efficiency, 99% and 100% in the 10- and 100-kW unit, respectively, was reached with black pellets.To compare the tested material with the state-of-the-art oxygen carrier ilmenite, some tests were conducted with a bituminous coal that had been used in the same pilot with ilmenite. The results indicate a higher conversion performance for the tested manganese material.

Effects of water condensation on hollow fiber membrane contactor performance for CO2 capture by absorption into a chemical solvent

The present study investigates the impact of water vapor condensation on the performance of hollow fiber membrane contactors for CO2 capture by absorption into a chemical solvent. A one-dimensional adiabatic transfer model for CO2 absorption in Monoethanolamine (MEA) has been implemented in a commercial simulation environment and condensation experiments have been performed in a laboratory scale membrane contactor module. The results from these experiments show that water vapor condensation occurs in the gas phase or at the gas-membrane surface inside the fiber lumen, but not in the membrane pores. This condensation had no effect on the carbon capture efficiency, but did lead to an increase of the gas-side pressure drop and to liquid water at the gas outlet. Using simulations permitted us to better understand why condensation occurs in the fiber lumen. Indeed, it is the combined conditions of rapid heat-transfer within the membrane and relatively slow mass transfer that lead to vapor oversaturation in the gas phase promoting condensation. In industrial conditions for membrane contactor applications where water condensation is most likely to occur, membrane wetting due to condensation may thus not happen, which is an encouraging result for the membrane technology.

CuO supported on manganese ore as an oxygen carrier for chemical looping with oxygen uncoupling (CLOU)

The chemical-looping with oxygen uncoupling (CLOU) is a promising technology that could be used for combustion of solid fuels with inherent separation of carbon dioxide. In this work, manganese ore supported CuO (CMO) oxygen carrier was synthesized. The oxygen transport capacity (Ro) and the reaction reactivity of CMO were investigated in TGA. The CLOU tests with biochar as fuel were performed. The reaction reactivity with biochar was enhanced due to the synergistic effect between manganese ore and CuO, and a value of Ro, 3.31%, was observed in TGA at 950 °C after 15 redox cycles. In fluidized bed tests, CMO shows excellent cycle performance; full conversions of biochar and the values closed to 100% carbon capture efficiency were obtained in the temperature range of 850–950 °C. However, obvious sintering of CMO was observed when the operating temperature reached 1,000 °C, which was further verified by the SEM, BET and PSD results. From XRD patterns, CuMn2O4, CuO, Fe2O3, and SiO2 were detected in the fresh CMO sample. The presence of CuMn2O4 in fresh CMO sample indicated that manganese ore reacted with CuO during calcination. The CuMnO2, Cu2O and Mn3O4 observed in reduced CMO sample indicated that the gaseous oxygen was derived from CuO/Cu2O and CuMn2O4/CuMnO2 systems. The CMO was fully regenerated in air reactor after 10 cycles at 950 °C. In addition, CMO sample showed a higher crushing strength and magnetic property. These results indicated that CMO can be used as a good oxygen carrier candidate for CLOU below 950 °C.