• Clean Technology
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• v.24 no.1
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• pp.63-69
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• 2018

The reduction reaction characteristics and physicochemical properties were studied for the selection of oxygen carrier, which is the core of the chemical looping combustion (CLC) technology. Fuel conversion and $CO_2$ selectivity of oxygen carrier according to the concentration of reducing gas and the reduction temperature using three kinds of oxygen carrier (SDN70, N018-R2, N016-R4) were measured and compared. In addition, Attrition Index (AI) and BET surface area were measured to analyze the attrition resistance and the surface characteristics of the oxygen carrier. As a result, it was confirmed that all three kinds of oxygen carrier were suitable for use in chemical roofing combustion system, and the best particle was determined to be N016-R4.

• Journal of Hydrogen and New Energy
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• v.29 no.4
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• pp.393-400
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• 2018

To confirm the operating range of two oxygen carriers for chemical looping combustion system, the effects of operating variables on solid circulation rate were measured and discussed using a two-interconnected circulating fluidized bed system at ambient temperature and pressure. Moreover, suitable operating ranges to avoid choking of the fast fluidized bed (air reactor) were confirmed for two oxygen carriers. A continuous long-term operation of steady-state solid circulation more than 24 hours was also demonstrated within the operating windows. Finally we could confirm that those two oxygen carriers are suitable for chemical looping combustion system with high solid circulation rate and smooth solid circulation.

• Journal of Hydrogen and New Energy
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• v.30 no.2
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• pp.170-177
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• 2019

Continuous solid circulation test at high temperature and high pressure conditions and batch type reduction-oxidation tests were performed to check feasibility of a 0.5 MWth chemical looping combustion system. Pressure drop profiles were maintained stable during continuous solid circulation up to 16 hours. Therefore, we could conclude that the solid circulation between an air reactor and a fuel reactor could be smooth and stable. The measured fuel conversion and $CO_2$ selectivity were high enough even at high capacity and even after cyclic tests. Therefore, we could expect high reactivity of oxygen carrier at real operation condition.

• Journal of Hydrogen and New Energy
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• v.29 no.5
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• pp.473-482
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• 2018

To check applicability of recently developed new oxygen carrier for 0.5 MWth chemical looping combustion system, reactivity tests were carried out at high temperature and high pressure conditions. Pressure, temperature, gas velocity, $CH_4$ flow rate, and solid height were considered as operating variables. The new oxygen carrier (N016-R4) showed not only high fuel conversion but also high $CO_2$ selectivity within all the operating conditions in this study. The reactivity of N016-R4 particle was compared with previous oxygen carriers. The N016-R4 particle represented outstanding reactivity among 10 oxygen carriers in terms of fuel conversion and $CO_2$ selectivity.

• Journal of Hydrogen and New Energy
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• v.29 no.6
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• pp.635-641
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• 2018

To select the operating condition of 0.5 MWth chemical looping combustion system, minimum fluidization velocity, transition velocity to fast fluidization and solid circulation rate were measured using mass produced new oxygen carrier (N016-R4) which produced by spray drying method for 0.5 MWth chemical looping combustion system. A minimum fluidization velocity decreased as the pressure increased. The measured transition velocity to fast fluidization was 2.0 m/s at ambient temperature and pressure. The measured solid circulation rate increased as the solid control valve opening increased. We could control the solid circulation rate from 26 to $93kg/m^2s$. Based on the measured minimum fluidization velocity and transition velocity to fast fluidization, we choose appropriate operating conditions and demonstrated continuous solid circulation at high pressure condition (5 bar-abs) up to 24 hours.

• Journal of Hydrogen and New Energy
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• v.32 no.1
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• pp.53-62
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• 2021

Batch type reduction-oxidation tests were performed to check effects of temperature, pressure, gas velocity, and capacity on reduction characteristics of mass produced particle in a 0.5 MWth chemical looping combustion system. The fuel conversion and the CO2 selectivity increased as the temperature increased and as the gas velocity decreased. However the CO2 selectivity showed the maximum and decreased as the capacity increased because the CO emission increased. The results show that high temperature, low gas velocity and low inert gas concentration are preferable to ensure high reactivity of oxygen carrier in the fuel reactor.

• Journal of Hydrogen and New Energy
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• v.28 no.1
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• pp.85-91
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• 2017

To develop a pressurized chemical looping combustor, effect of pressure on minimum fluidization velocity and transition velocity to fast fluidization was investigated in a two-interconnected pressurized fluidized bed system using oxygen carrier particle. The minimum fluidization velocity was measured by bed pressure drop measurement with variation of gas velocity. The measured minimum fluidization velocity decreased as the pressure increased. The transition velocity to fast fluidization was measured by emptying time method and decreased as the pressure increased. Gas velocity in the fuel reactor should be greater than the minimum fluidization velocity and gas velocity in the air reactor should be greater than the transition velocity to fast fluidization to ensure proper operation of two interconnected fluidized bed system.

• Journal of Hydrogen and New Energy
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• v.28 no.4
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• pp.384-391
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• 2017

Effects of operating variables on solid circulation rate were measured and discussed using two-interconnected circulating fluidized bed system at ambient temperature and pressure. OCN 706-1100 particles were used as oxygen carrier. The measured solid circulation rates increased as the lower loop seal gas flow rates and the solid height in the fuel reactor increased. Suitable operating conditions to avoid choking of the air reactor were confirmed. Continuous long-term operations of steady-state solid circulation were also demonstrated at two different conditions based on the operating window.

• Journal of Hydrogen and New Energy
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• v.28 no.5
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• pp.554-560
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• 2017

Reduction reactivity of new oxygen carriers for chemical looping combustion system were investigated using $CH_4$ as a reduction gas in a bubbling fluidized bed reactor and compared with that of former SDN70 oxygen carrier. New oxygen carriers showed good reduction reactivity at different $CH_4$ concentration. N018-R2 particle represented better reactivity than SDN70 at high $CH_4$ concentration. N018-R2 particle showed higher fuel conversion and $CO_2$ selectivity than those of SDN70 particle within the temperature range of $750-900^{\circ}C$. Moreover, attrition loss of N018-R2 particle was almost same with that of SDN70 particle. Consequently, we could select N018-R2 particle as the best oxygen carrier.

• Journal of Hydrogen and New Energy
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• v.27 no.1
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• pp.95-105
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• 2016

Spray-dried NiO-based oxygen carriers developed for chemical looping combustion required high calcination temperatures above $1300^{\circ}C$ to obtain high mechanical strength applicable to circulating fluidized-bed process. In this study, the effect of CBB ($CaO{\cdot}BaO{\cdot}B_2O_3$) addition, as a binder, on the physical properties and oxygen transfer reactivity of spray-dried NiO-based oxygen carriers was investigated. CBB addition resulted in several positive effects such as reduction of calcination temperature and increase in oxygen transfer capacity and porosity. However, oxygen transfer rate was considerably decreased. This was more apparent when a higher amount of CBB was added and MgO was added together. From the experimental results, it is concluded that CBB added NiO-based oxygen carriers are not suitable for chemical looping combustion and a new method to reduce calcination temperature while maintaining high oxygen transfer rate of NiO-based oxygen carriers should be found out.