Chemical-Looping with Oxygen Uncoupling of Different Coals Using Copper Ore as an Oxygen Carrier

Abstract

Chemical-looping with oxygen uncoupling (CLOU) has been considered as a revolutionary technology for lowenergy consumption CO 2 capture. In this work, the performance of copper ore in the CLOU processes for diverse ranks of coal was examined in a batch-scale fluidized-bed at various temperatures. Typical Chinese coals (GaoPing anthracite, FuGu bituminous coal, and ShengLi lignite) were used as fuel. The effects of temperature and coal rank on the redox behavior, carbon conversion rate, and instantaneous rates of char conversion and oxygen generation were first investigated. It was found that both increasing the reactor temperature and decreasing the coal rank had beneficial effects on the carbon conversion rate, instantaneous rates of char conversion, and oxygen generation. In the CLOU processes of coal, the rate-limiting step was the burning of coal char with oxygen of low concentration if the oxygen carrier (OC) was excess to coal. And for higher-rank coals like anthracite, the rate-limitation effect was also greater. Then, two additional CLOU tests of anthracite were conducted to examine the accelerative effect of gasification agents. The results demonstrated that introducing the gasification agent (steam or CO 2 ) into the fuel-reactor can increase the instantaneous char conversion rate of high-rank coal. Scanning electron microscopyenergy dispersive X-ray spectroscopy results showed that the porous structure of the used copper ore particles was partly blocked by the adhesion of fly ash. To be noted, all used copper ore particles presented a porous structure, and no serious agglomeration phenomenon was detected within the CLOU process, except for high-volatile lignite at 950 °C.

Assessment of the Redox Characteristics of Iron Ore by Introducing Biomass Ash in the Chemical Looping Combustion Process: Biomass Ash Type, Constituent, and Operating Parameters

“…Furthermore, the PWm–20% sample after 10 redox cycles of testing showed a slightly higher BET surface area than the UOC sample after 10 redox cycles of testing, thereby showing better reactivity. 43 Thus, the BET surface areas indicated that RAm–20%, ULm–20%, and PWm–20% had better cycle stability, which was consistent with previous research conclusions. 44 …”

Using Copper Ore and Hematite Fine Particles as Raw Materials of an Oxygen Carrier for Chemical Looping Combustion of Coal: Spray Drying Granulation and Performance Evaluation

“…All of the parameters present an upward trend with the increase of the temperature. As seen from Table , the temperature is a vital factor affecting the average carbon conversion rate, which was also proven by our previous work . The decrement of combustion efficiency is mainly ascribed to more carbon residues at a relatively low temperature.…”

“…The carbon conversion rate x C and instantaneous carbon conversion rate x inst (on the basis of remaining unreacted carbon) are calculated as The instantaneous oxygen transfer rate during the reduction process, x O 2 ,red ( t ), is determined on the basis of the mass balance of the O atoms in the reactor where F i (including O 2 , CO 2 , CO, H 2 , or CH 4 ) is the molar gas flow in the exhaust gas during the reduction process, which can be calculated as To measure oxygen leaving with H 2 O generating from hydrogen oxidation in the coal, it is assumed that the hydrogen evolution is proportional to the carbon evolution; i.e., the ratio C/H maintains the same value in the gas components as in the coal. Considering the fact that a little methane and hydrogen are detected in the experiment, the H 2 O flow rate is calculated as where f H/C is the hydrogen/carbon molar ratio in the coal.…”

“…Natural ores (such as iron ore, copper ore, etc.) have been considered as the raw materials of OCs as a result of their desirable characteristics of low cost, sufficient reactivity, and superior fluidization. − Iron ore, which is very cheap and environmentally friendly, meanwhile demonstrating acceptable reactivity, has been widely tested in the CLC. − Copper ore, which has high oxygen carrying capacity and good reactivity but is easily sintered and agglomerated, has also been investigated by the CLC community. , In our previous work, Yang et al . physically mixed copper ore and hematite particles as the OC, which showed higher reactivity and desirable synergy compared to hematite or copper ore as the OC alone.…”

Investigation of Chemical-looping Gasification Characteristics of Chinese Western Coals with Hematite-CuO Oxygen Carrier

“…[1] Choosing the right oxygen carrier and better operating conditions are some of the key issues in the chemical-looping gasification process. [2][3][4][5][6] Guo et al suggested that multifunctional oxygen carrier compounds, such as Ca-based oxygen carriers with K or Na pendant groups, coupled with catalytic gasification, could effectively accelerate coal gasification, but the systems suffered alkali metal loss during the recycling process. [7,8] Moreover, Cu-based oxygen carriers usually exhibit greater oxygen donating capacity and much higher reactivity, which can effectively accelerate char gasification.…”