Browsing by Author "Jeremias, M."
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Item Open Access CO2 as moderator for biomass gasification(Elsevier, 2013-10-03) Pohorely, M.; Jeremias, M.; Svoboda, K.; Kamenikova, P.; Skoblia, S.; Beno, Z.Biomass can be converted into gaseous fuel by high-temperature reactions with a gasifying agent. The gasifying agent consists, in most cases, of oxygen and of a moderator, which is usually water vapour. Here we show that waste CO2 can be used instead of, or together with, water vapour to moderate the process of biomass gasification in a catalytic fluidized bed of dolomitic limestone. Such use of CO2 increased substantially the carbon and energy conversion efficiency and decreased the amount of tars in the produced gas.Item Open Access 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.Item Open Access 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.Item Open Access Transient catalytic activity of calcined dolomitic limestone in a fluidized bed during gasification of woody biomass(American Chemical Society, 2016-04-14) Pohorely, M.; Jeremias, M.; Skoblia, S.; Beno, Z.; Syc, M.; Svoboda, K.Calcined dolomitic limestone mixed with silica sand in a fluidized bed can catalytically enhance the gasification of woody biomass. The lime is prone to attrition and carry over from the reactor and to deactivation caused by pore sintering; therefore, it has to be replenished continuously or periodically to maintain catalytic activity of the fluidized bed. The main aim of this paper was to explore the level of the decrease of the catalytic activity of the fluidized bed if the limestone is not replenished and to estimate a critical period for its top-up. Wood chips were gasified first in a silica sand fluidized bed (1080 g), to obtain background data without the catalytic effect of limestone. After 5 h of operation, dolomitic limestone (1050 g) was added to the fluidized bed and left to calcine. Its catalytic activity was monitored during the following 6 h. During the second part of the experiment, the yield of the main gases (H2, CO, CH4, CO2, and H2O) remained almost unchanged. The yield of minor organic gases and tars rose slightly but still remained far below the value attained with only silica sand. The heavy polyaromatic tar compounds were effectively decomposed during the first 3 h after the addition of dolomitic limestone. It was concluded that the catalytic activity of dolomitic lime remains in an acceptable level during the first 3 h after its addition into the fluidized bed, suggesting that periodic rather than continuous replenishment of limestone should be sufficient.