Browsing by Author "Erans Moreno, Maria"

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    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.
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    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.
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    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, Huichao
    Synthetic 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.
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    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.
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    Effect of SO2 and steam on CO2 capture performance of biomass-templated calcium aluminate pellets
    (Royal Society of Chemistry, 2016-03-29) Erans Moreno, Maria; Beisheim, T.; Manovic, Vasilije; Jeremias, M.; Patchigolla, Kumar; Dieter, H.; Duan, Lunbo; Anthony, Edward J.
    Four types of synthetic sorbents were developed for high-temperature post-combustion calcium looping CO2 capture using Longcal limestone. Pellets were prepared with: lime and cement (LC); lime and flour (LF); lime, cement and flour (LCF); and lime, cement and flour, doped with seawater (LCFSW). Flour was used as a templating material. All samples underwent 20 cycles in a TGA under two different calcination conditions. Moreover, the prepared sorbents were tested for 10 carbonation/calcination cycles in a 68-mm-internal-diameter bubbling fluidized bed (BFB) under three environments: with no sulphur and no steam; in the presence of sulfur; and with steam. When compared to limestone, all the synthetic sorbents exhibited enhanced CO2 capture performance in both a TGA and BFB, with the exception of the sample doped with seawater. In the BFB tests, the addition of cement binder during the pelletisation process resulted in the increase of CO2 capture capacity from 0.08 gCO2/gsorbent (LF) to 0.15 gCO2/gsorbent (LCF) by the 10th cycle. The CO2 uptake in the presence of SO2 dramatically declined by the 10th cycle; for example, from 0.22 gCO2/gsorbent to 0.05 gCO2/gsorbent in the case of the untemplated material (LC). However, as expected all samples showed improved performance in the presence of steam and the decay of reactivity during the cycles was less pronounced. Nevertheless, in the BFB environment, the templated pellets showed poorer CO2 capture performance. This is presumably because of material loss due to attrition under the FB conditions. Namely, by contrast, the templated materials performed better than untemplated materials under TGA conditions. This indicates that reduction in attrition is critical in the case of employment of templated materials in realistic systems with FB reactors.
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    Enhanced sorbents for the calcium looping cycle and effects of high oxygen concentrations in the calciner
    (2017-05) Erans Moreno, Maria; Anthony, Edward J.; Manovic, Vasilije
    Increasing CO2 emissions from the energy and industrial sectors are a worldwide concern due to the effects that these emissions have on the global climate. Carbon capture and storage has been identified as one of a portfolio of technologies that would mitigate the effects of global warming in the upcoming decades. Calcium looping is a second generation carbon capture technology aimed at reducing the CO2 emissions from the power and industrial sectors. This thesis assesses the improvement of the calcium looping cycle for CO2 capture through enhanced sorbent production and testing at lab-, bench- and pilot-scale, and a new operational mode with high oxygen concentrations in the calciner through experimental campaigns in Cranfield’s 25 kWth pilot unit. Novel biomass-templated sorbents were produced using the pelletisation technique and tested at different conditions in a thermogravimetric analyser (TGA) and a bench-scale plant comprising a bubbling fluidised bed (BFB) reactor. Moreover, the effects of sorbent poisoning by SO2, and the influence of steam were studied in order to explore the effects of real flue gas on this type of material. In addition to the chemical performance, the mechanical strength, i.e. resistance to fragmentation of these materials was tested. In additon, two different kinds of enhanced materials were produced and tested at pilot-scale. Namely, calcium aluminate pellets and HBr-doped limestone were used in experimental campaigns in Cranfield’s 25 kWth pilot plant comprising a CFB carbonator and a BFB calciner. The suitability of these materials for Ca looping was assessed and operation challenges were identified in order to provide a basis for synthetic sorbent testing at a larger scale. Lastly, a new operational mode was tested, which is aimed at reducing the heat provided to the calciner through high oxygen concentration combustion of a hydrocarbon (in this case natural gas) in the calciner. This approach reduces or even eliminates the recirculated CO2 stream in the calciner. In consequence, this results in a lower capital (reduced size of the calciner) and operational cost (less oxygen and less fuel use). Several pilot plant campaigns were performed using limestone as solid sorbent in order to prove this concept, which was successfully verified for concentrations of up to 100% vol oxygen in the inlet to the calciner.
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    Fragmentation of biomass-templated CaO-based pellets
    (2016-10-18) Erans Moreno, Maria; Cerciello, Francesca; Copolla, Antonio; Senneca, Osvalda; Scala, Fabrizio; Manovic, Vasilije; Anthony, Edward J.
    The use of biomass templating materials with a cheap production method as an enhanced sorbent for CO2 uptake has been proposed recently. However, the attrition and fragmentation behaviour of this type of material, which is a vital parameter for calcium looping sorbents, has not yet been investigated in detail. In this work the fragmentation behaviour of biomass-templated sorbents is investigated. Three types of materials were prepared using a mechanical pelletiser: 1. lime and cement (LC); 2. lime and flour (LF); and 3. lime, cement and flour (LCF). These samples were heat treated in a pressurised heated strip reactor (PHSR) and in a bubbling fluidised bed (BFB) and changes in particle size distribution were measured to assess fragmentation. Results indicated that the addition of biomass enhances the propensity to undergo fragmentation. Upon heat treatment in the PHSR the particle size of LC was not modified significantly; on the contrary the mean particle diameter of LF decreased from 520 μm to 116 μm and that of LCF from 524 μm to 290 μm. Fragmentation tests in the BFB confirmed the trend: 67% of the particles of LF fragmented, against 53% of LCF and 18% of LC samples. The addition of cement to the LF samples partially counteracts this performance degradation with respect to attrition. However, calcium aluminate pellets (LC) showed the lowest rate of fragmentation amongst all of the samples tested.
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    Operation of a 25 kWth calcium looping pilot-plant with high oxygen concentrations in the calciner
    (JoVE, 2017-10-25) Erans Moreno, Maria; Jeremias, M.; Manovic, Vasilije; Anthony, Edward J.
    Calcium looping (CaL) is a post-combustion CO2 capture technology that is suitable for retrofitting existing power plants. The CaL process uses limestone as a cheap and readily available CO2 sorbent. While the technology has been widely studied, there are a few available options that could be applied to make it more economically viable. One of these is to increase the oxygen concentration in the calciner to reduce or eliminate the amount of recycled gas (CO2, H2O and impurities); therefore, decreasing or removing the energy necessary to heat the recycled gas stream. Moreover, there is a resulting increase in the energy input due to the change in the combustion intensity; this energy is used to enable the endothermic calcination reaction to occur in the absence of recycled flue gases. This paper presents the operation and first results of a CaL pilot plant with 100% oxygen combustion of natural gas in the calciner. The gas coming into the carbonator was a simulated flue gas from a coal-fired power plant or cement industry. Several limestone particle size distributions are also tested to further explore the effect of this parameter on the overall performance of this operating mode. The configuration of the reactor system, the operating procedures, and the results are described in detail in this paper. The reactor showed good hydrodynamic stability and stable CO2 capture, with capture efficiencies of up to 70% with a gas mixture simulating the flue gas of a coal-fired power plant.
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    Process modelling and techno-economic analysis of natural gas combined cycle integrated with calcium looping
    (VINČA Institute of Nuclear Sciences, 2016-07-04) Erans Moreno, Maria; Hanak, Dawid P.; Jordi, Mir; Edward, Anthony; Manovic, Vasilije
    Calcium looping (CaL) is promising for large-scale CO2 capture in the power generation and industrial sectors due to the cheap sorbent used and the relatively low energy penalties achieved with this process. Because of the high operating temperatures the heat utilisation is a major advantage of the process, since a significant amount of power can be generated from it. However, this increases its complexity and capital costs. Therefore, not only the energy efficiency performance is important for these cycles, but also the capital costs must be taken into account, i.e. techno-economic analyses are required in order to determine which parameters and configurations are optimal to enhance technology viability in different integration scenarios. In this study the integration scenarios of CaL cycles and natural gas combined cycles (NGCC) are explored. The process models of the NGCC and CaL capture plant are developed to explore the most promising scenarios for NGCC-CaL integration with regards to efficiency penalties. Two scenarios are analysed in detail, and show that the system with heat recovery steam generator (HRSG) before and after the capture plant exhibited better performance of 49.1% efficiency compared with that of 45.7% when only one HRSG is located after the capture plant. However, the techno-economic analyses showed that the more energy efficient case, with two HRSGs, implies relatively higher cost of electricity (COE), 44.1€/MWh, when compared to that of the reference plant system (33.1€/MWh). The predicted cost of CO2 avoided for the case with two HRSGS is 29.3 €/ton CO2.