Chemical-Looping Combustion (CLC) technology is a novel combustion technology and has many advantages such as no thermal NOX emissions and inherent CO2 separation without any additional process and energy penalties. This system consists of two separated reactors, an oxidizer and a reducer. The fuel ...
Chemical-Looping Combustion (CLC) technology is a novel combustion technology and has many advantages such as no thermal NOX emissions and inherent CO2 separation without any additional process and energy penalties. This system consists of two separated reactors, an oxidizer and a reducer. The fuel such as CH4, H2, CO or CnH2n+2 reacts with metal oxide in the reduction reactor and releases water vapor and carbon dioxide from the top and metal particles from the bottom. The solid products, metal particles, are transported to the oxidation reactor and react with oxygen in air in the oxidation reactor and produce high-temperature flue gas and metal oxide particles. Metal oxide particles at high temperature are again introduced to reduction reactor and supply the heat required for the reduction reaction. Between the two reactors, metal (or metal oxide) particles play an important role in the transfer of oxygen and heat therefore the looping material between the two reactors is named as a oxygen carrier particle. It is considered that application of syngas from cheap hydrocarbons such as coal, vacuum residue, cokes and biomass, as a fuel for chemical-looping combustor due to the high-rising LNG price. But the syngas fired chemical-looping combustor will show different process performance and require different operating conditions (solid inventory, reaction rate, solid circulation rate, fuel and air flow rate) with those of LNG fired chemical-looping combustor because syngas and LNG have different gas composition and oxygen requirement for complete combustion. Therefore, confirmation of reactivities of oxygen carrier particles for syngas is prerequisite to develop syngas fueled chemical-looping combustor. However, most of previous works are concentrated on the methane or LNG fired chemical-looping combustor and reactivity tests for reduction of methane and LNG. To check the reactivities of oxygen carrier particles, we can use various experimental facilities. But the simplest way to check reaction rate, oxygen transfer capacity, oxygen transfer rate is measurement of solid conversion by using a thermogravimetric analyzer. Another key parameters to confirm inherent CO2 separation and no thermal-NOX emission are gas concentrations from the reducer and oxidizer. To check the gas concentration profiles, we need fluidized bed to ensure sufficient gas flow rate for on-line gas analyzer. In this study, thermo-gravimetric analyzer(TGA) and a batch type fluidized bed reactor were used as experimental facilities to select the best oxygen carrier particle for syngas fueled chemical-looping combustion by measuring of 1) oxygen transfer capacity, 2) reduction and oxidation rate, 3) oxygen transfer rate, 4) carbon deposition characteristics, 5) regeneration ability, 6) fuel conversion, 7) CO2 selectivity, 8) CO, H2 and CH4 emissions and, 9) NO emission. For all tests in the TGA and batch type fluidized bed reactor, air was used as oxidation gas and hydrogen and simulated syngas were used as reduction gas. Especially, hydrogen was used to check the maximum conversion and oxygen transfer capacity of each oxygen carrier particles without carbon deposition. Nitrogen was used during purge and heating. In this study, we tested six kinds of oxygen carrier particls. Four particles (NiO/bentonite, NiO/LaAl11018, CoxOy/CoAl2O4, NiO/NiAl2O4) were developed for LNG fueled chemical-looping combustor in the previous works and two particles (OCN-650 and OCN-800) were mass produced by spray drying method for LNG and syngas fueled chemical-looping combustor. In the reduction tests with hydrogen, CoxOy/CoAl2O4 particle showed very low oxygen transfer capacity than other five particles. After that, reduction tests with syngas were performed for previous four particles (NiO/bentonite, NiO/LaAl11O18, CoxOy/CoAl2O4, NiO/NiAl2O4). Among those particles, NiO-based particles showed better reactivity than Co-based particle and NiO/bentonite showed the best reactivity. Next, two mass produced oxygen carrier particles (OCN-650 and OCN-800) were compared from the viewpoints of maximum conversion, reduction rate, oxygen transfer capacity and attrition resistance. The results from TGA indicated that OCN-650 particle is similar or superior to OCN-800 particle. However, OCN-650 particle has much higher attrition resistance than OCN-800 particle, and therefore, OCN-650 particle was selected as the better particle than OCN-800 particle. Finally, fuel conversion, CO2 selectivity, CO, H2 and CH4 emissions, NO emission, and regeneration ability up to 10th cycle of each particles were tested in the batch type fluidized bed reactor. Most of particles showed sufficiently high fuel conversion, CO2 selectivity and low NO emission. These results indicate that inherent CO2 separation and no NO-free is feasible for those four particles. Based on the results from TGA, batch type fluidized bed reactor, and attrition tester, OCN-650 particle was selected as the best particle from the viewpoints of reactivity and attrition resistance.
Chemical-Looping Combustion (CLC) technology is a novel combustion technology and has many advantages such as no thermal NOX emissions and inherent CO2 separation without any additional process and energy penalties. This system consists of two separated reactors, an oxidizer and a reducer. The fuel such as CH4, H2, CO or CnH2n+2 reacts with metal oxide in the reduction reactor and releases water vapor and carbon dioxide from the top and metal particles from the bottom. The solid products, metal particles, are transported to the oxidation reactor and react with oxygen in air in the oxidation reactor and produce high-temperature flue gas and metal oxide particles. Metal oxide particles at high temperature are again introduced to reduction reactor and supply the heat required for the reduction reaction. Between the two reactors, metal (or metal oxide) particles play an important role in the transfer of oxygen and heat therefore the looping material between the two reactors is named as a oxygen carrier particle. It is considered that application of syngas from cheap hydrocarbons such as coal, vacuum residue, cokes and biomass, as a fuel for chemical-looping combustor due to the high-rising LNG price. But the syngas fired chemical-looping combustor will show different process performance and require different operating conditions (solid inventory, reaction rate, solid circulation rate, fuel and air flow rate) with those of LNG fired chemical-looping combustor because syngas and LNG have different gas composition and oxygen requirement for complete combustion. Therefore, confirmation of reactivities of oxygen carrier particles for syngas is prerequisite to develop syngas fueled chemical-looping combustor. However, most of previous works are concentrated on the methane or LNG fired chemical-looping combustor and reactivity tests for reduction of methane and LNG. To check the reactivities of oxygen carrier particles, we can use various experimental facilities. But the simplest way to check reaction rate, oxygen transfer capacity, oxygen transfer rate is measurement of solid conversion by using a thermogravimetric analyzer. Another key parameters to confirm inherent CO2 separation and no thermal-NOX emission are gas concentrations from the reducer and oxidizer. To check the gas concentration profiles, we need fluidized bed to ensure sufficient gas flow rate for on-line gas analyzer. In this study, thermo-gravimetric analyzer(TGA) and a batch type fluidized bed reactor were used as experimental facilities to select the best oxygen carrier particle for syngas fueled chemical-looping combustion by measuring of 1) oxygen transfer capacity, 2) reduction and oxidation rate, 3) oxygen transfer rate, 4) carbon deposition characteristics, 5) regeneration ability, 6) fuel conversion, 7) CO2 selectivity, 8) CO, H2 and CH4 emissions and, 9) NO emission. For all tests in the TGA and batch type fluidized bed reactor, air was used as oxidation gas and hydrogen and simulated syngas were used as reduction gas. Especially, hydrogen was used to check the maximum conversion and oxygen transfer capacity of each oxygen carrier particles without carbon deposition. Nitrogen was used during purge and heating. In this study, we tested six kinds of oxygen carrier particls. Four particles (NiO/bentonite, NiO/LaAl11018, CoxOy/CoAl2O4, NiO/NiAl2O4) were developed for LNG fueled chemical-looping combustor in the previous works and two particles (OCN-650 and OCN-800) were mass produced by spray drying method for LNG and syngas fueled chemical-looping combustor. In the reduction tests with hydrogen, CoxOy/CoAl2O4 particle showed very low oxygen transfer capacity than other five particles. After that, reduction tests with syngas were performed for previous four particles (NiO/bentonite, NiO/LaAl11O18, CoxOy/CoAl2O4, NiO/NiAl2O4). Among those particles, NiO-based particles showed better reactivity than Co-based particle and NiO/bentonite showed the best reactivity. Next, two mass produced oxygen carrier particles (OCN-650 and OCN-800) were compared from the viewpoints of maximum conversion, reduction rate, oxygen transfer capacity and attrition resistance. The results from TGA indicated that OCN-650 particle is similar or superior to OCN-800 particle. However, OCN-650 particle has much higher attrition resistance than OCN-800 particle, and therefore, OCN-650 particle was selected as the better particle than OCN-800 particle. Finally, fuel conversion, CO2 selectivity, CO, H2 and CH4 emissions, NO emission, and regeneration ability up to 10th cycle of each particles were tested in the batch type fluidized bed reactor. Most of particles showed sufficiently high fuel conversion, CO2 selectivity and low NO emission. These results indicate that inherent CO2 separation and no NO-free is feasible for those four particles. Based on the results from TGA, batch type fluidized bed reactor, and attrition tester, OCN-650 particle was selected as the best particle from the viewpoints of reactivity and attrition resistance.
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