Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Abstract This paper provides an overview of foreign banks and foreign banking regulation in Canada. To study the relationship between regulation and competition, we empirically test foreign banking presence against banking regulations.... more
Abstract This paper provides an overview of foreign banks and foreign banking regulation in Canada. To study the relationship between regulation and competition, we empirically test foreign banking presence against banking regulations. Using international data, our ...
Research Interests:
Research Interests:
Calcium-looping is an emerging technology that can be applied to both flue and fuel gas streams for CO2 capture. A typical proposed process is described as follows: CaO-based sorbent is repeatedly cycled between two fluidised beds; in the... more
Calcium-looping is an emerging technology that can be applied to both flue and fuel gas streams for CO2 capture. A typical proposed process is described as follows: CaO-based sorbent is repeatedly cycled between two fluidised beds; in the lower temperature carbonator CaO-based sorbent strips CO2 from a flue or fuel gas via the exothermic formation of CaCO3; in the calciner, operating at a higher temperature, CaCO3 decomposes to provide a pure stream of CO2 suitable for storage and regenerate CaO. There are several advantages to this system including the ability to reclaim high-grade heat from the carbonation reaction and the use of cheap non-toxic sorbents, which have the potential to be used in the cement industry after use. A disadvantage to the system is that the sorbent reduces in reactivity towards CO2 upon cycling. This can occur for a number of reasons including loss of reactive porosity through sintering, competing reactions with sulphurous molecules and mass loss through a...
ABSTRACT The primary objective of this study was to investigate the integration of combined calcium looping (CaL) and chemical looping combustion (CLC) with steam gasification of biomass through the utilization of composite pellets... more
ABSTRACT The primary objective of this study was to investigate the integration of combined calcium looping (CaL) and chemical looping combustion (CLC) with steam gasification of biomass through the utilization of composite pellets consisting of limestone, CuO and a calcium aluminate cement binder. In this process, the heat released from the exothermic reduction of CuO is used to calcine CaCO3. The technologies can be integrated by combining an oxygen carrier such as CuO with limestone within a composite pellet, or by cycling CuO and limestone within distinct particles. Using a thermogravimetric analyzer (TGA), it was demonstrated that the use of composite CaO/CuO/calcium-aluminate-cement pellets for gasification purposes required oxidation of Cu to be preceded by carbonation as opposed to the post-combustion case where the pellets are oxidized prior to carbonation. Composite pellets were thus tested under this CO2 capture sequence using varying carbonation conditions over multiple cycles. While the pellets exhibited relatively high carbonation conversion, the oxidation conversion declined for all tested conditions likely due to the CaCO3 product impeding passage of O2 molecules to the more remote Cu sites. The reduction in oxygen uptake was particularly important when the pellets were pre-carbonated in the presence of steam. Limestone-based pellets and Cu-based pellets were subsequently tested in separate CaL and CLC loops respectively to assess their performance in a dual-loop process. A maximum Cu content of 50% could be accommodated in a pellet with calcium aluminate cement as support with no loss in oxidation conversion and no observable agglomeration.
Research Interests:
Research Interests:
ABSTRACT The feasibility of using integrated CaO/CuO-based pellets in combined calcium and chemical looping cycles in a fixed bed was investigated with emphasis on CO2 capture performance. Three types of pellets were tested, namely;... more
ABSTRACT The feasibility of using integrated CaO/CuO-based pellets in combined calcium and chemical looping cycles in a fixed bed was investigated with emphasis on CO2 capture performance. Three types of pellets were tested, namely; integrated core-in-shell CaO/CuO-based pellets; integrated homogeneous CaO/CuO-based pellets; and mixed CaO-based pellets and CuO-based pellets. Redox cycles consisted of oxidation/carbonation at 650 °C in 15% CO2; 4% O2, and N2 balance, and reduction/calcination at 850 °C in a CO/H2 mixture. The results showed that mixed pellets exhibited the highest CO2 uptakes of 0.11 g CO2/g bed in the first cycle and 0.07 g/g after 11 cycles (corresponding to CaO conversions of 32.1% and 19%, respectively). This enhanced performance was attributed to the significantly higher pore volume and surface area in the calcined CaO-based pellets, which were superior to those of integrated CaO/CuO-based pellets. The reduction of CuO to Cu2O was found to be partially irreversible, with ∼45% of copper oxide in the pellets in the form of Cu2O despite the excess O2 in the oxidizing environment. It was also noted that cycled core-in-shell pellets were the most susceptible to fragmentation, indicating the low mechanical strength of these pellets. It was concluded that combined calcium and chemical looping cycles in a fixed bed system is a feasible process providing suitable pellets are used. Incorporating CuO in CaO-based pellets reduces the porosity of the pellets, thus compromises CO2 uptake. Among the three groups of pellets, mixed pellets are the most promising for CaL–CLC processes due to their better performance, easier manufacturing, and better quality control than integrated pellets.
Research Interests:
... Dennis Y. Lu, Robin W. Hughes, Tiffany Reid and Edward J.Anthony CanmetENERGY, Natural Resources Canada, Ottawa, Canada ... The pulverized limestone follows a typical reduction in CO2 capture capacity, as seen previously (Abanades and... more
... Dennis Y. Lu, Robin W. Hughes, Tiffany Reid and Edward J.Anthony CanmetENERGY, Natural Resources Canada, Ottawa, Canada ... The pulverized limestone follows a typical reduction in CO2 capture capacity, as seen previously (Abanades and Alvarez, 2003). ...
Research Interests:
ABSTRACT The progressive deactivation of CaO based sorbents is one of the major limitations of the Ca Looping cycle for postcombustion CO2 capture. Techniques using the hydration of the spent CaO sorbent have been identified as a... more
ABSTRACT The progressive deactivation of CaO based sorbents is one of the major limitations of the Ca Looping cycle for postcombustion CO2 capture. Techniques using the hydration of the spent CaO sorbent have been identified as a promising route for the reactivation of CaO sorbents but have so far not been tested at pilot scale using realistic calcination and carbonation conditions. In this work, the performance of sorbents reactivated by two different reactivation techniques (hydration-dehydration and superheating) was assessed in an oxy-fired, pilot-scale dual fluid bed unit. Compared to a spent sorbent, reactivated materials exhibited a approximate to 60% increase in CO2 carrying capacity over 3 h of circulation as well as an increase in the sorbent attrition rate of 25% (superheating) and 50% (hydration-dehydration). In both cases, however, increased attrition did not lead to serious disruptions of system operation. A comparison of sorbent performance at laboratory and pilot scale suggested that high velocity impacts in the transfer lines were the main cause of attrition.
Research Interests:
Calcium oxide particles can absorb CO2 at high temperatures (>600ºC) to form CaCO3, which can be regenerated back to CaO and pure CO2 in a calciner. We are investigating this chemical loop to develop more energy-efficient... more
Calcium oxide particles can absorb CO2 at high temperatures (>600ºC) to form CaCO3, which can be regenerated back to CaO and pure CO2 in a calciner. We are investigating this chemical loop to develop more energy-efficient post-combustion systems. In this work we present ...
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT Increasing atmospheric concentration of CO2 and concern over its effect on climate is a powerful driving force for the development of new advanced energy cycles incorporating CO2 capture. This paper investigates the feasibility... more
ABSTRACT Increasing atmospheric concentration of CO2 and concern over its effect on climate is a powerful driving force for the development of new advanced energy cycles incorporating CO2 capture. This paper investigates the feasibility of CO2 capture using the carbonation reaction of CaO “in situ” in a fluidised bed combustor, where natural gas or petroleum coke (or any other fuel with low ash content) is being burned. The sorbent can be partially regenerated for CO2 capture by combustion of part of the fuel with O2 /CO2 in a separate FBC. The thermodynamic limits in the proposed cycles, in terms of CO2 capture efficiencies, are examined along with the limits imposed by the rapid decay in the sorbent activity during repeated carbonation/calcination cycles, which will be exacerbated by the presence of S. Despite these limitations, it is shown that operating windows exist where it is possible to integrate fuel combustion, CO2 and SO2 capture in a single dual reactor facility. The decay in activity in the sorbent appears to be the major practical limitation to this concept, but this can be compensated for by using a relatively large supply of fresh sorbent, which appears to be acceptable considering the low cost of limestone. Also, a novel concept to reactivate the spent sorbent using sonic energy is outlined here as an alternative to reduce the use of fresh limestone.
Research Interests:
ABSTRACT
Research Interests:
Research Interests: Environmental Engineering, Chemical Engineering, Civil Engineering, Carbon Dioxide, Combustion, and 13 moreCarbon Cycle, Fluidized Bed, Thermogravimetry, Particle Size, Fluidized Beds, Calcium Carbonate, Carbonation, Environmental, Water Vapor, Fluidized Bed Combustion, Sulfur Dioxide, Thermal gravimetric analysis, and Gas
Liquid fuels such as bitumen, tars, and pitches are byproducts of heavy oil upgrading processes, and are usually contaminated with high sulphur and sometimes heavy metals contents as well. Fluidized bed combustion (FBC) appears to be a... more
Liquid fuels such as bitumen, tars, and pitches are byproducts of heavy oil upgrading processes, and are usually contaminated with high sulphur and sometimes heavy metals contents as well. Fluidized bed combustion (FBC) appears to be a promising technology for the combustion of such fuels due to its inherent fuel flexibility and low emissions characteristics. The combustion of three liquid fuels, i.e., no. 6 oil, bitumen and pitch was investigated in a pilot-scale bubbling FBC unit. An efficient liquid fuel feeding system was developed and a bubbling FBC was successfully used to combust all three liquid fuels. The proportion of fuel escaping in the form of unburnt hydrocarbons in the flue gas was less than 0.4 percent and combustion efficiencies higher than 98.5 percent were achieved. However, combustion of liquid fuels tended to occur in the freeboard and, therefore, good mixing of the fuels in the bed was critical in achieving satisfactory combustion performance.
Research Interests:
Research Interests:
ABSTRACT Calcium looping is an emerging technology for CO2 capture that uses a regenerable CaO-based sorbent. Here, a novel hydration-based reactivation strategy for spent sorbent, proposed by Industrial Research Limited of New Zealand,... more
ABSTRACT Calcium looping is an emerging technology for CO2 capture that uses a regenerable CaO-based sorbent. Here, a novel hydration-based reactivation strategy for spent sorbent, proposed by Industrial Research Limited of New Zealand, is investigated. They have called the process Ca(OH)2 “superheating” and suggested that Ca(OH)2 becomes more chemically stable under CO2, allowing release of steam at an elevated temperature (“superheated dehydration”). To investigate this, Ca(OH)2 powder and pellets and hydrated calcined limestone and dolomite have been heated in various different atmospheres in a thermogravimetric analyzer with a mass spectrometer performing online gas analysis of the off-gas. The “superheated dehydration” effect was observed for Ca(OH)2 pellets and hydrated calcined limestone, but not for Ca(OH)2 powder or hydrated calcined dolomite. These findings are consistent with a mechanism involving formation of an impermeable carbonate layer, which prevents H2O diffusion until rupture. The carbonate layer has a critical thickness that is not reached in the case of the Ca(OH)2 powder, but is in the case of the Ca(OH)2 pellets and hydrated calcined limestone. The network of MgO in the dolomitic particles results in CaO grains that are not large enough to accommodate the impermeable carbonate layer.
Research Interests:
ABSTRACT Calcium looping cycles require an oxy-fired calciner burning coal for sorbent regeneration. Thus, in addition to O2 and CO2, the flue gases will include both steam and SO2, and similarly, carbonation of real flue gases will occur... more
ABSTRACT Calcium looping cycles require an oxy-fired calciner burning coal for sorbent regeneration. Thus, in addition to O2 and CO2, the flue gases will include both steam and SO2, and similarly, carbonation of real flue gases will occur in the presence of steam. However, to date, most research has been done without either of these two gaseous components present. Here, batch combustion experiments were performed in a pilot-scale fluidized-bed reactor to study the effects of steam and SO2 addition on CO2 capture by limestone-based sorbents calcined under oxygen-enriched air and oxy-fuel conditions. The initial fast kinetically controlled CO2 capture stage was dramatically reduced when the sorbent was calcined at realistic temperatures in the presence of SO2. This is attributed to both greater sintering due to higher local calcination temperatures required by high CO2 concentrations and CaSO4 formation. By contrast, steam in the synthetic flue gas during carbonation extended the initial, high-efficiency CO2 capture period compared with that observed during carbonation with dry synthetic flue gases. A comparison between pilot-scale fluidized-bed combustion (FBC) and thermogravimetric analysis (TGA) results showed that sorbent reactivity was considerably lower during pilot-scale FBC testing, as anticipated given the higher calcination temperatures employed in the FBC reactor and the presence of the other feed gases. The enhanced CO2 capture efficiency in FBC reactors with steam present was also confirmed by TGA tests. These results are important because they demonstrate how sorbent deactivation effects seen in realistic FBC calcium-looping operation can be successfully reduced by the presence of steam in the carbonator.
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT Limestone attrition in circulating fluidized-bed combustors (CFBCs) has received limited attention. Although there are a number of early studies on attrition in bubbling-bed systems, most current studies focus on simultaneous... more
ABSTRACT Limestone attrition in circulating fluidized-bed combustors (CFBCs) has received limited attention. Although there are a number of early studies on attrition in bubbling-bed systems, most current studies focus on simultaneous calcination and sulfation. However, this subject is increasing in importance as CO2 looping cycles are proposed. CO2 looping cycles involve repeatedly calcining the CaCO3 component of the limestone to drive off a pure stream of CO2 for storage or sequestration. Here, we have looked at five limestones from across Canada, the United States, and Mexico to determine the extent of their attrition under calcining conditions in fluidized-bed systems. This work shows that attrition varies very significantly from limestone to limestone, and even among different batches. It is clear, therefore, that each limestone will have to be carefully categorized to determine its potential for use in such cycles. Also, since limestones crush differently, even those limestones that are double-sieved may have very different initial size distributions. This will affect the results seen in tests carried out under realistic conditions. This work shows that most of the material loss in multiple calcination/carbonation cycles is in the first few cycles, and that even a very low level of sulfation can be a very effective means of reducing that material loss.
Research Interests:
Experiments were performed using a dual fluidized bed reactor system, operated in a batch mode, in order to investigate the effects of steam and simulated syngas on CO capture and sorbent conversion efficiency for a naturally occurring... more
Experiments were performed using a dual fluidized bed reactor system, operated in a batch mode, in order to investigate the effects of steam and simulated syngas on CO capture and sorbent conversion efficiency for a naturally occurring Polish calcitic limestone. In addition, the effect of high partial pressures of CO on the calcination process was examined using either oxygen-enriched air
Research Interests:
Research Interests:
Abstract Petroleum coke may be used as a fuel for entrained-flow slagging gasification. It may be blended with coal to provide a more attractive feedstock. The coal provides the benefits of enhancing reactivity and increasing the amount... more
Abstract Petroleum coke may be used as a fuel for entrained-flow slagging gasification. It may be blended with coal to provide a more attractive feedstock. The coal provides the benefits of enhancing reactivity and increasing the amount of slag coating the gasifier ...
Research Interests:
This study examines the loss of sorbent activity caused by sintering under realistic CO 2 capture cycle conditions. The samples tested here included two limestones: Havelock limestone from Canada (New Brunswick) and a Polish (Upper... more
This study examines the loss of sorbent activity caused by sintering under realistic CO 2 capture cycle conditions. The samples tested here included two limestones: Havelock limestone from Canada (New Brunswick) and a Polish (Upper Silesia) limestone (Katowice). Samples ...
Research Interests:
... In addition, different operating times, ie., number of cycles (25 min455 min/125 cycles) were examined, with the carbonator operating at temperatures of 600700 °C and the calciner at 850900 °C. The samples collected came from the... more
... In addition, different operating times, ie., number of cycles (25 min455 min/125 cycles) were examined, with the carbonator operating at temperatures of 600700 °C and the calciner at 850900 °C. The samples collected came from the calciner, carbonator and cyclone. ...
Research Interests: Mechanical Engineering, Chemical Engineering, Carbon, Biomass, Scanning Electron Microscopy, and 13 moreAdsorption, Fuel, Atmospheric Pressure, Nitrogen, Fluidized Bed, Desorption, Thermogravimetry, Surface Area, Carbonation, Pilot Plant, Fluidized Bed Combustion, gas pycnometry, and Difference Operator
Research Interests: Mechanical Engineering, Chemical Engineering, Scanning Electron Microscopy, Comparative Study, Quantitative analysis, and 11 morePorosity, Fuel, Atmospheric Pressure, Fluidized Bed, Thermogravimetry, X ray diffraction, Quantitative Analysis, Fluidized Bed Reactor, Carbonation, Pilot Plant, and Fluidized Bed Combustion
ABSTRACT