Browsing by Author "Anthony, Edward J."
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Item Open Access Applying machine learning algorithms in estimating the performance of heterogeneous, multi-component materials as oxygen carriers for chemical-looping processes(Elsevier, 2020-01-09) Yan, Yongliang; Mattisson, Tobias; Moldenhauer, Patrick; Anthony, Edward J.; Clough, Peter T.Heterogeneous, multi-component materials such as industrial tailings or by-products, along with naturally occurring materials, such as ores, have been intensively investigated as candidate oxygen carriers for chemical-looping processes. However, these materials have highly variable compositions, and this strongly influences their chemical-looping performance. Here, using machine learning techniques, we estimate the performance of heterogeneous, multi-component materials as oxygen carriers for chemical-looping. Experimental data for 19 manganese ores chosen as potential chemical-looping oxygen carriers were used to create a so-called training database. This database has been used to train several supervised artificial neural network models (ANN), which were used to predict the reactivity of the oxygen carriers with different fuels and the oxygen transfer capacity with only the knowledge of reactor bed temperature, elemental composition, and mechanical properties of the manganese ores. This novel approach explores ways of dealing with the training dataset, learning algorithms and topology of ANN models to achieve enhanced prediction precision. Stacked neural networks with a bootstrap resampling technique have been applied to achieve high precision and robustness on new input data, and the confidence intervals were used to assess the precision of these predictions. The current results indicate that the best trained ANNs can produce highly accurate predictions for both the training database and the unseen data with the high coefficient of determination (R2 = 0.94) and low mean absolute error (MAE = 0.057). We envision that the application of these ANNs and other machine learning algorithms will accelerate the development of oxygen carrying materials for a range of chemical-looping applications and offer a rapid screening tool for new potential oxygen carriers.Item Open Access Attrition study of cement-supported biomass-activated calcium sorbents for CO2 capture(American Chemical Society, 2016-08-19) Duan, Lunbo; Yu, Zhijian; Erans Moreno, Maria; Li, Yingjie; Manovic, Vasilije; Anthony, Edward J.Enhanced CO2 capacity of biomass modified Ca-based sorbent has been reported recently, but undesired attrition resistance has also been observed. Cement was used as a support for biomass-activated calcium sorbent during the granulation process in this study, in order to improve the poor mechanical resistance. Attrition tests were carried out in an apparatus focused on impact breakage to evaluate how the biomass addition and cement support influence the particle strength during Ca-looping. Results showed biomass addition impaired the mechanical strength and cement support could improve it, which is reflected by the breakage probability and size change after impact of pellets experienced calcination and multiple calcination/carbonation cycles. Larger-sized particles suffered more intense attrition. The mechanical strength of sorbents declined significantly after higher temperature calcination but increased after carbonation. After multiple cycles, the mechanical strength of particles was greatly enhanced, but more cracks emerged. A semi-empirical formula for calculating average diameter after attrition based on Rittinger’s surface theory was developed. Observation on the morphology of particles indicated that particles with more porosity and cracks were more prone to breakage.Item Open Access A calcium looping process for simultaneous CO2 capture and peak shaving in a coal-fired power plant(Elsevier, 2018-11-09) Zhou, Linfei; Duan, Lunbo; Anthony, Edward J.CO2 capture and peak shaving are two of the main challenges for coal-fired power plants in China. This paper proposed a calcium looping (CaL) combustion system with cryogenic O2 storage for simultaneous flue gas decarbonization and peak shaving for a 1000 MWe coal-fired power plant. The philosophy of this concept is that: (1) the boiler always operates at maximum continuous rating (MCR) to ensure the highest boiler efficiency; (2) during off-peak times, the excess energy output from coal combustion is used to provide heat for the calciner and produce pure oxygen for energy storage; (3) at peak times, the O2 produced is used to capture CO2 in the flue gas via the CaL process and reduce the CO2 abatement penalty; and (4) any excess O2 is treated as a by-product for commercial utilization. The whole system was simulated in Aspen Plus® which shows that the net electric efficiency of the proposed system without cryogenic O2 storage system is 35.52%LHV (LHV, low heating value), while that of the conventional CaL system is 34.54%LHV. The proposed system can reduce the methane consumption rate by 38.5 t/h when methane is used as fuel in the calciner. Including the cryogenic O2 storage system, the peaking capability of the proposed system can range from 534.6 MWe to 1041 MWe. Correspondingly, the net electric efficiency is improved from 18.98%LHV to 36.97%LHV. Increasing the rate of oxygen production can reduce the minimum net power output to lower than 534.6 MWe. The peaking capability can be regulated by the rate of oxygen production where excess oxygen serves as a byproduct.Item Open Access Calcium looping sorbents for CO2 capture(Elsevier, 2016-08-12) Erans Moreno, Maria; Manovic, Vasilije; Anthony, Edward J.Calcium looping (CaL) is a promising technology for the decarbonation of power generation and carbon-intensive (cement, lime and steel) industries. Although CaL has been extensively researched, some issues need to be addressed before deployment of this technology at commercial scale. One of the important challenges for CaL is decay of sorbent reactivity during capture/regeneration cycles. Numerous techniques have been explored to enhance natural sorbent performance, to create new synthetic sorbents, and to re-activate and re-use deactivated material. This review provides a critical analysis of natural and synthetic sorbents developed for use in CaL. Special attention is given to the suitability of modified materials for utilisation in fluidised-bed systems. Namely, besides requirements for a practical adsorption capacity, a mechanically strong material, resistant to attrition, is required for the fluidised bed CaL operating conditions. However, the main advantage of CaL is that it employs a widely available and inexpensive sorbent. Hence, a compromise must be made between improving the sorbent performance and increasing its cost, which means a relatively practical, scalable, and inexpensive method to enhance sorbent performance, should be found. This is often neglected when developing new materials focusing only on very high adsorption capacity.Item Open Access Characterization of tar generated from the mixture of municipal solid waste and coal pyrolysis at 800 oC(Elsevier, 2020-03-02) Tursunov, O.; Suleimenova, B.; Kuspangaliyeva, Botagoz; Inglezakis, Vassilis J.; Anthony, Edward J.; Sarbassov, YerbolNowadays, comprehensive perception of the tar characteristics generated from municipal solid waste (MSW) and coal to guide pyrolysis or gasification gas yield upgrading and cleaning has attracted massive research attention. In this study, MSW and coal samples were chosen as principal components. The mixture of these products was pyrolyzed in a horizontal tube furnace at 800 °C with a heating rate of 20 °C/min. The tar derived from the pyrolysis of this mixture was further studied. Gas chromatography–mass spectrometry (GC–MS)coupled with a trace GC and a nuclear magnetic resonance (NMR) spectrometer was applied to investigate the tar composition and characterization along with their molecular chemical structures. 1H and 13C NMR spectra indicated that the functional groups of the tar derived from the mixture of MSW and coal were dominant at the resonances of 0.9–1.8 ppm, 1.5–2.6 ppm and 3.8–4.1 ppm for 1H, 10–40 ppm and 60–80 ppm for 13C. The results from GC–MS showed that the tar derived from the mixture of MSW and coal contained about 20 major chemical compounds such as benzene, methyl isobutyl, toluene, xylene, phenol, cresol, naphthalene and others.Item Open Access CO2 capture and attrition performance of competitive eco-friendly calcium-based pellets in fluidized bed(Wiley, 2018-11-15) Su, Chenglin; Duan, Lunbo; Anthony, Edward J.A system incorporating spent bleaching clay (SBC) into the calcium looping (CaL) process has been proposed. In this paper, prepared sorbents doped with regenerated SBC and cement were tested in a bubbling fluidized bed (BFB) to examine in detail their cyclic CO2 capture capacity and attrition properties. The results revealed that the cyclic CO2 capture capacity of pellets modified by pyrolyzed SBC and/or cement showed significantly better performance than limestone, which is consistent with the thermogravimetric analyzer (TGA) results. This is due to the improvement of pore structure and enhanced sintering resistance created by adding support materials to the sorbent. The elutriation rates of the composites prepared with pyrolyzed SBC and/or cement were consistently lower than for crushed limestone. Scanning electron microscopy (SEM) images indicated that the pellets possessed higher sphericity than limestone particles, thus reducing surface abrasion. Limestone exhibited a high attrition rate (diameter reduction rate) of 10.7 μm/cycle, which could be eliminated effectively by adding regenerated SBC and/or cement. ‘L‐5PC‐10CA’ (85% lime/5% pyrolyzed SBC/10% cement) exhibited an attrition rate of only 7.9 μm/cycle. Based on the analysis of breakage and probability density function (PDF) for particle size distribution, it appeared that pellets without cement experienced breakage (mostly chipping and disintegration) and surface abrasion, whereas ‘L‐10CA’ (90% lime/10% cement) and ‘L‐5PC‐10CA’ mainly suffered surface abrasion, combined with some chipping.Item Open Access CO2 capture performance of gluconic acid-modified limestone-dolomite mixtures under realistic conditions(ACS, 2019-07-10) Wang, Ke; Gu, Feng; Clough, Peter T.; Zhao, Pengfei; Anthony, Edward J.Calcium Looping (CaL) technology has become one of the most attractive ways to capture CO2 from fossil fuel power plants. However, with increasing numbers of cyclic reactions, the CO2 capture capacity rapidly decreases. To address this shortcoming, limestone-dolomite mixtures modified by gluconic acid were explored to prepare highly effective, MgO-stabilized, CaO sorbents that exhibited a high and stable CO2 capture capacity over multiple cycles. The sorbents were all tested over 10 carbonation-calcination cycles and were performed under realistic CaL conditions (calcination in a high CO2 concentration). The results of this research have demonstrated that the inhomogeneous composition that occurs between CaO and MgO - caused by the small CaO crystallite size, porous texture, nanosheet (~100 nm thick) morphology - provides sufficient void space for the volume expansion during carbonation to mitigate the effects of repeated cycle sintering and retain structural stability. A MgO content as low as 10 mol% was able to ensure a superior CO2 capture performance with a fast carbonation rate, high CO2 carrying capacities and remarkable stability. Furthermore, these sorbents retained a conversion (above 90%) over multiple cycles following a recarbonation stepItem Open Access CO2 capture performance using biomass-templated cement-supported limestone pellets(American Chemical Society, 2016-09-09) Duan, Lunbo; Su, Chenglin; Erans Moreno, Maria; Li, Yingjie; Anthony, Edward J.; Chen, HuichaoSynthetic biomass-templated cement-supported CaO-based sorbents were produced by granulation process for high-temperature post-combustion CO2 capture. Commercial flour was used as the biomass and served as a templating agent. The investigation of porosity showed that the pellets with biomass or cement resulted in enhancement of porosity. Four types of sorbents containing varying proportions of biomass and cement were subject to 20 cycles in a TGA under different calcination conditions. After first series of tests calcined at 850 °C in 100% N2, all composite sorbents clearly exhibited higher CO2 capture activity compared to untreated limestone with exception of sorbents doped by seawater. The biomass-templated cement-supported pellets exhibited the highest CO2 capture level of 46.5% relative to 20.8% for raw limestone after 20 cycles. However, the observed enhancement in performance was substantially reduced under 950 °C calcination condition. Considering the fact that both sorbents supported by cement exhibited relatively high conversion with a maximum value of 19.5%, cement promoted sorbents appear to be better at resisting of harsh calcination conditions. Although flour as biomass-templated material generated significantly enhancement in CO2 capture capacity, further exploration must be carried out to find the way of maintaining outstanding performance for CaO-based sorbents under severe reaction conditions.Item Open Access CO2/SO2 emission reduction in CO2 shipping infrastructure(Elsevier, 2019-06-04) Awoyomi, Adeola; Patchigolla, Kumar; Anthony, Edward J.There is an increased focus on the reduction of anthropogenic emissions of CO2 by means of CO2 capture processes and storage in geological formations or for enhanced oil recovery. The necessary link between the capture and storage processes is the transport system. Ship-based transport of CO2 is a better option when distances exceed 350 km compared to an offshore pipeline and offers more flexibility for transportation, unlike pipelines which require a continuous flow of compressed gas. Several feasibility studies have been undertaken to ascertain the viability of large-scale transportation of CO2 by shipping in terms of the liquefaction process, and gas conditioning, but limited work has been done on reducing emissions from the ship’s engine combustion. From 2020, ships operating worldwide will be required to use fuels with 0.5% or lower sulphur content (versus 3.5% now) or adopt adequate measures to reduce these emissions. This study explores the use of the solvent-based post-combustion carbon capture and storage (CCS) process for CO2 and SO2 capture from a typical CO2 carrier. A rate-based aqueous ammonia process model was developed, validated, then scaled up and modified to process flue gas from a Wartsila 9L46 F marine diesel engine. Different modes of operation of the carrier were analysed and the most efficient mode to operate the CCS system is during sailing. The heat recovered from the flue gas was used for solvent regeneration. A sensitivity study revealed that the 4 MWth supplied by the “waste heat recovery” system was enough to achieve a CO2 capture level of 70% at a solvent recirculation flowrate of 90–100 kg/s. The removal of SO2 by the ammonia water solution was above 95% and this led to the possibility of producing a value-added product, ammonium sulphate. The boil-off gas and captured emitted CO2 were recovered using a two-stage re-liquefaction cycle and re-injected into the cargo tanks, thereby reducing extra space requirements on the ship.Item Open Access A comprehensive review of pre-and post-treatment approaches to achieve sustainable desalination for different water streams(Elsevier, 2023-09-09) Poirier, Kristofer; Lotfi, Mohsen; Garg, Kapil; Patchigolla, Kumar; Anthony, Edward J.; Faisal, Nadimul Haque; Mulgundmath, Vinay; Sahith, Jai Krishna; Jadhawar, Prashant; Koh, Liam; Morosuk, Tatiana; Al Mhanna, NajahDesalination is an energy intensive process requiring adequate pre- and post- treatment. The novelty of this paper is that it jointly reviews the technologies for pre-treatment, desalination and post-treatment and bridges the gap between them while comparing the treatment methods needed depending on the type of feed water including seawater, brackish water, municipal and industrial wastewater. Those different streams show wide variability, sometimes containing organics, oil or scaling precursors which require adequate treatment. Nowadays, membrane pre-treatment methods have become promising alternatives to conventional pre-treatment techniques thanks to their flexibility. Hybrid desalination technologies have shown great potential in reducing energy consumption. Moreover, desalination plants produce large quantities of brines which require post-treatment to reduce environmental impacts. Current research on post-treatment is looking into recovering salts, metals and potable water from brines to achieve zero liquid discharge (ZLD). Thermal-based ZLD technologies are capable of extracting those resources while membrane-based ZLD methods are mostly limited to pre-concentration and water recovery due to fouling issues. Several studies have shown that ZLD systems can lower the cost of water and increase profitability if crystals and water are recovered and sold for additional revenue.Item Open Access Copper-based oxygen carriers supported with alumina/lime for the chemical looping conversion of gaseous fuels(Elsevier, 2017-07-29) Haider, Syed K.; Erans Moreno, Maria; Donat, Felix; Duan, Lunbo; Scott, Stuart A.; Manovic, Vasilije; Anthony, Edward J.Copper (II) oxide in varying ratios was combined with either an alumina-based cement (Al300), or CaO derived from limestone as support material in a mechanical pelletiser. This production method was used to investigate its influence on possible mechanical and chemical improvements for oxygen carriers in chemical looping processes. These materials were tested in a lab-scale fluidised bed with CO or CH4 as a reducing gas at 950 °C. As expected, the oxygen carriers containing a greater ratio of support material exhibited an enhanced crushing strength. Oxygen carriers comprised of a 1:3 ratio of support material to active CuO exhibited increased crushing strength by a minimum of 280% compared to pure CuO pellets. All oxygen carriers exhibited a high CO conversion yield and were fully reducible from CuO to Cu. For the initial redox cycle, Al300-supported oxygen carriers showed the highest fuel and oxygen carrier conversion. The general trend observed was a decline in conversion with an increasing number of redox cycles. In the case of CaO-supported oxygen carriers, all but one of the oxygen carriers suffered agglomeration. The agglomeration was more severe in carriers with higher ratios of CuO. Oxygen carrier Cu25Al75 (75% wt. aluminate cement and 25% wt. CuO), which did not suffer from agglomeration, showed the highest attrition with a loss of approximately 8% of its initial mass over 25 redox cycles. The reducibility of the oxygen carriers was limited with CH4 in comparison to CO. CH4 conversion yielded 15-25% and 50% for Cu25Ca75 (25% wt. CuO and 75% wt. CaO) and Cu25Al75, respectively. Cu25Ca75 demonstrated improved conversion, whereas Cu25Al75 exhibited a trending decrease in conversion with increasing redox cycles.Item Open Access Cyclic oxygen release characteristics of bifunctional copper oxide/calcium oxide composites(Wiley, 2016-10-12) Duan, Lunbo; Godino, D.; Manovic, Vasilije; Montagnaro, F.; Anthony, Edward J.Integrated calcium–copper (Ca–Cu) looping is a novel carbon capture technology that uses copper oxide to transport oxygen and calcium oxide to capture CO2 in the same process. Investigations into the oxygen release behavior of the bifunctional CuO/CaO composite are critical to assess the potential for applying this technology to solid fuels such as coal. In this study, three different CuO/CaO composites having different relative percentages (CuO75CaO25, CuO50CaO50, and CuO25CaO75) were manufactured in a commercial granulator and then tested in a bubbling fluidized bed reactor to examine their oxygen release characteristics at temperatures in the 880–940 °C range. All the composites exhibited clear oxygen release properties during the testing, indicating that the solid fuel can be directly oxidized rather than being gasified first in the Ca–Cu looping process. At the same temperature, the oxygen release rate of CuO25CaO75 is the fastest and its final oxygen yield is the largest, followed by CuO75CuO25 and CuO50CaO50. XRD results reveal that Ca2CuO3 is formed in the used samples of CuO75CuO25 and CuO50CaO50, but not in the case of CuO25CaO75, which may explain the performance difference observed. Further examination of the attrition and agglomeration behavior shows that all the composites are stable and strong, and it appears that CuO25CaO75 is the most stable and strongest of the materials examined.Item Open Access Design, process simulation and construction of a 100 kW pilot-scale CO2 membrane rig: Improving in situ CO2 capture using selective exhaust gas recirculation (S-EGR)(Elsevier, 2017-12-01) Darabkhani, Hamidreza Gohari; Jurado Pontes, Nelia; Prpich, George; Oakey, John E.; Wagland, Stuart T.; Anthony, Edward J.Carbon capture and storage (CCS) from natural gas-fired systems is an emerging field and many of the concepts and underlying scientific principles are still being developed. Preliminary studies suggest this approach can boost the CO2 content in the feed gas up to 3 times compared to the ‘no recycle’ case (CO2 concentration increased to 18% vs. 6%), with a consequent reduction in flow to the post-combustion capture unit by a factor of three compared to conventional, non-S-EGR. For this project, Cranfield University developed a pilot-scale 100 kW CO2 membrane rig facility in order to investigate simultaneously EGR and S-EGR technologies, the latter being achieved by using a CO2 sweep air polymeric membrane. A bench-scale membrane rig has also been developed to investigate the permeability and selectivity of different polymeric membranes to CO2. Currently a small-scale polydimethylsiloxane (PDMS) membrane module is also being investigated to study its selectivity/permeability. The tests include exploring the performance improvement of the PDMS membrane using different operating conditions with a view to developing scale-up procedures for the membrane unit for the actual 100 kW pilot-scale rig. Process simulations were performed using Aspen Plus software to predict the behaviour of the pilot-scale rig using a model developed based on empirical parameters (i.e., mass transfer coefficient of CO2 through the membrane and permeance), measured in the bench-scale membrane test unit. The results show that CO2 concentrations of up to 14.9% (comparable to CO2 level in coal combustion) can be achieved with 60% EGR, with a 90% CO2 removal efficiency of the membrane units. However, the results generated with the membrane model in which specific permeance values to PDMS were applied, predicted concentrations of CO2 in flue gases up to 9.8% (v/v) for a selective recycle of 60%. The study shows that the S-EGR technique is an effective method that can provide similar conditions to that of a coal-fired power plant for the post-combustion capture system operating on natural gas-fired units, but also highlights the fact that more research is required to find more suitable materials for membranes that optimise the CO2 removal efficiencies from the flue gas.Item Open Access Developments in calcium/chemical looping and metal oxide redox cycles for high-temperature thermochemical energy storage: A review(Elsevier, 2019-11-27) Yan, Yongliang; Wang, Ke; Clough, Peter T.; Anthony, Edward J.Energy storage is one of the most critical factors for maximising the availability of renewable energy systems while delivering firm capacity on an as- and when-required basis, thus improving the balance of grid energy. Chemical and calcium looping are two technologies, which are promising from both the point of view of minimising greenhouse gas emissions and because of their suitability for integrating with energy storage. A particularly promising route is to combine these technologies with solar heating, thus minimising the use of fossil fuels during the materials regeneration steps. For chemical looping, the development of mixed oxide carrier systems remains the highest impact research and development goal, and for calcium looping, minimising the decay in CO2 carrying capacity with natural sorbents appears to be the most economical option. In particular, sorbent stabilisers such as those based on Mg are particularly promising. In both cases, energy can be stored thermally as hot solids or chemically as unreacted materials, but there is a need to build suitable pilot plant demonstration units if the technology is to advance.Item Open Access Direct capture of carbon dioxide from air via lime-based sorbents(Springer Verlag, 2019-02-21) Samari, Mohammad; Ridha, Firas; Manovic, Vasilije; Macchi, Arturo; Anthony, Edward J.Direct air capture (DAC) is a developing technology for removing carbon dioxide (CO2) from the atmosphere or from low-CO2-containing sources. In principle, it could be used to remove sufficient CO2 from the atmosphere to compensate for hard-to-decarbonize sectors, such as aviation, or even for polishing gas streams containing relatively low CO2 concentrations. In this paper, the performance of lime-based sorbents for CO2 capture from air in a fixed bed was investigated. The effects of sorbent type, particle diameter, air flow rate, and relative humidity on the breakthrough time, breakthrough shape, and global reaction rate over a series of capture and regeneration cycles were examined. The greatest reaction rates and conversions were obtained when the sorbents were pre-hydrated and inlet air was humidified to 55% relative humidity. Humidifying the air alone leads to axial carbonation gradients since there is competition between CO2 and water with the available CaO. Negligible conversion, over the duration of the experiment, is obtained in a dry system without pre-hydration and humid air. A shrinking-core gas–solid reaction model was fitted to the breakthrough curves in order to estimate the surface reaction and effective diffusion constants. Although the surface reaction constants of the two sorbents were similar, the pelletized limestone had a greater effective diffusivity due to its greater porosity. At mild calcination conditions with air at 850 °C, the pelletized particles maintained their activity over nine carbonation–calcination cycles with a conversion drop of only 9% points.Item Open Access The effect of CO on the transformation of arsenic species: A quantum chemistry study(Elsevier, 2020-08-27) Anthony, Edward J.; Zou, ChanTo explore the effect of CO on the transformation of arsenic species, the reaction mechanism of homogeneous and heterogeneous reactions for arsenic oxides (AsO2 and As2O3) with CO were investigated via density functional theory (DFT). The geometries of reactants, intermediates, transition states and products for each reaction were optimized by using the B3LYP method in conjunction with the 6-31G(d) basis set, and the single-point energy of each structure was calculated at the B2PLYP/Def2-TZVP level. Also, thermodynamic and kinetic analyses were conducted to determine the reaction process. The results showed that the homogeneous reaction of AsO2 and CO has two channels and a transition state is found in each case. The homogeneous reaction process of As2O3 and CO undergoes two transition states and, finally, As2O3 is reduced to sub-oxides by CO. Char has a strong adsorption affinity for AsO2 and As2O3 in the presence of CO, and the adsorption mode of the AsO2 molecule on the char surface has a great influence on its reduction. The activation energy of the homogeneous reduction of As2O3 (75.9 kJ·mol-1) is lower than the heterogeneous reduction (94.2 kJ·mol-1), which suggests that As2O3 is more likely to react with CO in the flue gas. The calculation results revealed the mechanism for the influence of CO on arsenic behavior by density functional theory. These results are helpful for a molecular-level understanding of the transformation of arsenic species, which in turn provides a theoretical foundation for the emission and control of arsenic.Item Open Access The effect of H2O on formation mechanism of arsenic oxide during arsenopyrite oxidation: Experimental and theoretical analysis(Elsevier, 2019-12-07) Zou, Chan; Wang, Chunbo; Chen, Liang; Zhang, Yue; Xing, Jiaying; Anthony, Edward J.The effect of H2O on arsenic release behavior was investigated via experiment and first-principles density functional theory (DFT). The experimental results show that sulfide-bound arsenic is the main form present in coal, and that H2O has a positive influence on the release of arsenic during coal combustion. Furthermore, DFT calculations were performed to investigate the mechanism for H2O influence on arsenic oxidation. Thermodynamic and kinetic analyses were also conducted to study the influence of temperature on the reaction process. From thermodynamic analysis, arsenic oxide formation on the FeS2 (1 0 0) surface with and without H2O weakens with increasing temperature. In addition, the equilibrium constant for the reaction with H2O addition is slightly higher than that for the reaction without H2O, which suggests that the degree of the chemical reaction in the presence of H2O should increase. From kinetic analysis, the reaction rate constants increase with temperature, and the activation energy of the arsenic oxide formation reaction with and without H2O is 100.72 kJ/mol and 124.08 kJ/mol, respectively. This indicates that H2O adsorption on the surface can decrease the energy barrier and accelerate the reaction forming arsenic oxide. Based on the thermodynamic and kinetic analyses, it can be concluded that temperature has an inhibitory influence on reaction equilibrium and positive influence on the reaction rate. The experiment and calculation results explain the influence of H2O on the formation mechanism of arsenic oxide and provide a theoretical foundation for the emission and control of arsenic.Item Open Access The effect of HCl and steam on cyclic CO2 capture performance in calcium looping systems(Elsevier, 2017-08-14) Symonds, Robert T.; Lu, Dennis Y.; Macchi, Arturo; Hughes, Robin W.; Anthony, Edward J.Calcium looping is CO2 capture technology that is considered to be technically feasible at an industrial scale using a variety of fuels such as natural gas, coals, biomass, refuse derived fuels, and biofuels. Unfortunately, many of these fuels contain significant quantities of chlorine which principally converts to gaseous HCl during combustion or gasification. To date, very few studies have examined the effect of HCl on sorbent CO2 capture performance using calcium-based sorbents under realistic carbonation and calcination conditions. In this work, experiments were conducted using thermogravimetric analysis and fixed bed reactor testing to determine the effect of HCl addition during carbonation and calcination over repeated cycles using a Canadian limestone. The presence of HCl was found to increase sorbent reactivity towards CO2 capture when steam was injected during calcination. The resulting decomposition of CaCl2 to CaO during calcination caused changes in the particle morphology, which in turn decreased the CO2 diffusional resistance during carbonation. Fixed bed test results provided confirmation of full sorbent dechlorination under typical oxy-fuel calcination conditions. It was shown that both particle surface area and pore volume were higher during tests where HCl was present during carbonation and that greater than 99% HCl capture could be achieved without adversely affecting sorbent CO2 capture performance when steam was present during both carbonation and calcination.Item Open Access Effect of steam hydration on reactivity and strength of cement-supported calcium sorbents for CO2 capture(Wiley, 2017-05-23) Yu, Zhijian; Duan, Lunbo; Su, Chenglin; Li, Yingjie; Anthony, Edward J.Steam hydration was used to reactivate spent cement-supported CO2 sorbent pellets for recycle and the effect of steam hydration on the reactivity of sorbents was investigated in a bubbling fluidised reactor. A specially designed impact apparatus was developed to evaluate the strength of the reactivated pellets as well as determine the effect of “superheating”. It was found that the reactivity of synthetic pellets was significantly elevated over that of raw limestone after steam hydration. The CaO conversion of spent pellets increased from 0.113 to 0.419 after hydration, whereas that of spent limestone ranged from 0.089 to 0.278. The CaO conversions of hydrated samples calcined under different conditions achieved the identical level, proportional to the degree of hydration. As expected, the mechanical strength of synthetic pellets declined severely after reactivation. Large cracks emerged on hydrated limestone as seen in scanning electron microscope images. By contrast, similar cracks were not observed for synthetic pellets after hydration, although hydration did produce higher porosity than seen with limestone and an increased surface area, which enhanced CO2 capacity and was associated with an increase in strength loss. The breakage rate of superheated steam-reactivated limestone derived pellets was about half that of hydrated samples. This demonstrates that superheating treatment (which allows the annealing of stacking faults and mechanical strain produced by hydration) enhances the strength of hydrated pellets. This work demonstrated that combining steam hydration with superheating can both reactivate the spent synthetic pellets and reduce strength decay associated with the hydration process.Item Open Access Emissions from co-firing lignite and biomass in an oxy-fired CFBC(Elsevier, 2018-02-03) Varol, Murat; Symonds, Robert; Anthony, Edward J.; Lu, Dennis; Jia, Lufei; Tan, YewenThe co-combustion of a high-sulfur lignite and biomass blend (up to 50% by weight) has been studied in a small oxy-fired circulating fluidized bed combustion (CFBC) pilot plant. Here the goal is to examine the effect of biomass share on NOx, SO2 and CO emissions. In these tests, a series of runs has looked at the effect of increasing biomass share under air firing, followed by tests in oxy-firing mode. The results show that the emissions are remarkably insensitive to the biomass share, and are comparable to other results for coal combustion, and likely to be well below any current emission guidelines. Overall, there appear to be no direct challenges to oxy-fuel co-firing in terms of gaseous emissions, although the simple lack of studies means that significantly more data are required on CFBC oxy-firing using a much wider range of biomass and coal types. K doping was also examined and did not result in significant formation of K phases on deposit probes.