•Firstly proposed optimizing the synthesis parameter of BaCoO3−δ by MWA-EDTA method.•Orthogonal analysis was applied to optimize the main synthesis process parameter.•Microwave time has the most significant impact on oxygen production performance.•Order of factors: microwave time > pH > calcination temperature > microwave power.Oxyfuel process is a promising technique for carbon capture and storage, and a new application of perovskite-type oxide is as oxygen carrier for CO2 capture in oxy-fuel combustion system. This study proposed a novelty process and an optimization study on the synthesis of the BaCoO3−δ perovskite powders using microwave-assisted EDTA method. OA16 (45) orthogonal experiments were employed to optimize the process parameters such as precursor pH, microwave time, microwave power and calcination temperature. The oxygen production performance of synthesized powders were investigated in a fixed-bed reactor system. It was found that the order of significant factors for oxygen production performance of synthesized perovskite samples is microwave radiation time > pH value of precursor solution > calcination temperature > microwave power. Based on the results of the range analysis, the best oxygen production performance of BaCoO3−δ was found at pH value of precursor solution was 8, microwave radiation time was 30 min, microwave power was 700 W and calcination temperature was 600 °C. Finally, the optimized sample was selected as candidate for multiple oxygen adsorption/desorption cycles tests. Results demonstrate that the prepared perovskites via optimized microwave-assisted EDTA process can be used as a potential oxygen carrier for oxyfuel combustion application.This study proposed a novelty process and an optimization study on the synthesis of the BaCoO3−δ perovskite powders using microwave-assisted EDTA method. OA16 (45) orthogonal experiments were employed to optimize the process parameters such as precursor pH, microwave time, microwave power and calcination temperature. The decreasing order RB > RA > RD > RC indicates that the level of significance of factors are as follows: microwave radiation time (6.68) > pH value of precursor solution (3.50) > calcination temperature (2.00) > microwave power (1.83).

•Carbonation and calcination time should be as short as practically possible to minimize sulfation effect.•If SO2 is present with steam in flue gas, the CaO-based sorbent would lose capacity rapidly within a few cycles.•Synthetic sorbent derived from a sol-gel process had much higher CO2 capture capacity than natural limestone sorbent.•The porous structure of the synthetic sorbent could be retained during cyclic reactions even in the presence of SO2.Calcium looping cycle is considered as one of the most promising post combustion CO2 capture technologies that can curb CO2 emissions from power plants fired with fossil fuel. However the presence of SO2 and steam in the flue gas leads to the sulfation of CaO-based sorbents, and thus reduces the sorbents’ capacity for CO2 capture. In this study, the effect of sorbent sulfation during both carbonation and calcination stage on the cyclic CO2 capture performance was investigated. The results showed that the reaction time, SO2 concentrations and steam greatly influenced the capacity of CaO-based sorbent. The sulfation degree of the sorbent decreased with the reduction of carbonation and calcination time per cycle. High SO2 concentration present with steam led to a rapid loss in capacity of the sorbent within a few cycles. Furthermore, the synthetic sorbent derived from a sol–gel process had much higher cyclic CO2 capture capacities than natural limestone sorbent whether in conditions without SO2 or with SO2 and steam. Microscopic images showed that after multiple cycles in the presence of SO2 and steam, the porous structure of the synthetic sorbent could be retained while limestone experienced serious pore blockage and agglomeration of grains.

Calcium looping cycle for post-combustion CO2 capture has gained increasing attention worldwide. However, CaO-based sorbents derived from natural sources for calcium looping cycle experience rapid loss of capacity during high-temperature cyclic carbonation/calcination reactions. Synthesizing sintering-resistant CaO-based sorbents by adding a support material has been extensively studied as an effective method of combating the problem. The support material in the synthetic sorbents plays an important role in retaining the capacity, and various support materials have been tested in the literature. In practical reactors, sulfur is present and it has been reported that sulfation of sorbents will also reduce the CO2 capture capacity. However, thus far, it is not clear whether/how support material would affect sulfation of sorbents and, thus, CO2 capture. In this paper, four different support materials, such as Ca2MnO4, La2O3, Ca12Al14O33, and MgO, were studied. The cyclic CO2 capture performance of the synthetic sorbents made from CaO and the support materials were investigated in detail, in the presence of SO2 and steam. The results showed that a mass ratio of 20–25% support material would be optimum for synthesizing sorbents with high cyclic CO2 capture capacity, and Ca12Al14O33 and MgO seem to be more effective than Ca2MnO4 and La2O3. The 80:20 wt % CaO/MgO synthetic sorbent achieved the highest CO2 capture capacity under ideal conditions over 100 cycles. However, the CaO/MgO sorbent had a strong affinity to SO2 capture during cyclic reactions, especially in the presence of steam. Under realistic conditions (i.e., both SO2 and steam are present during carbonation), the CaO/MgO sorbent showed the highest cumulative SO2 capture capacity, whereas the CaO/Ca12Al14O33 sorbent obtained the highest CO2 capture capacity after 10 cycles. The smaller average crystallite size of MgO in the sorbent was responsible for the strong SO2 affinity of the CaO/MgO sorbent as well as its stable cyclic CO2 capture abilities under ideal conditions.

Sulfation of calcium-based sorbent is bound to occur during carbonation or calcination of the sorbent in a calcium looping system if SO2 is present in the system, and it will influence the CO2 capture capacity of the sorbent. While the effect of sulfation during the carbonation stage on the CO2 capture capacity has been studied by some researchers, the effect of sulfation during the calcination stage has not been studied extensively. In this study, the effect of sulfation during the calcination stage under oxy-fuel combustion conditions on the CO2 capture capacity of two calcium-based sorbents was investigated. The results showed that the calcination temperature and O2 concentration of 5–20% had little effect on the sulfation of the sorbents, while SO2 concentration and the presence of H2O greatly influenced the cyclic performance of the sorbents. Furthermore, reducing calcination time seems to be an effective way to limit sulfation during calcination, because the sulfation rate is slow in the initial induction stage of the gas–solid reaction.

Multi-cyclic CaO carbonation/calcination is an attractive method for CO2 capture during coal combustion. However, the capture capacity of CaO sharply decreases with increasing carbonation/calcination cycles. In order to improve the stability of CO2 capture capacity of CaO during carbonation/calcination cycles, synthetic CaO/Al2O3 sorbents were synthesized by two methods: wet chemistry and sol–gel-combustion-synthesis (SGCS) to make a further comparison. The results indicate that the SGCS-made CaO/Al2O3 = 80:20 wt% sorbent provides a competitive performance of a capture capacity of 0.43 g-CO2/g-sorbent after 20 cycles.

To improve the stability of CaO adsorption capacity for CO2 capture during multiple carbonation/calcination cycles, modified CaO-based sorbents were synthesized by sol-gel-combustion-synthesis (SGCS) method and wet physical mixing method, respectively, to overcome the problem of loss-in-capacity of CaO-based sorbents. The cyclic CaO adsorption capacity of the sorbents as well as the effect of the addition of La2O3 or Ca12Al14O33 was investigated in a fixed-bed reactor. The transient phase change and microstructure were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FSEM), respectively. The experimental results indicate that La2O3 played an active role in the carbonation/calcination reactions. When the sorbents were made by wet physical mixing method, CaO/Ca12Al14O33 was much better than CaO/La2O3 in cyclic CO2 capture performance. When the sorbents were made by SGCS method, the synthetic CaO/La2O3 sorbent provided the best performance of a carbonation conversion of up to 93% and an adsorption capacity of up to 0.58 g-CO2/g-sorbent after 11 cycles.

The calcium looping cycles method has been identified as an attractive method for CO2 capture during coal combustion and gasification processes. However, it is well-known that the capture capacity of CaO undergoes a rapid decrease after mutiple cycles. In order to improve the stability of CO2 capture capacity in CaO, this paper focuses on the development and performance of the synthetic CaO/La2O3 sorbents for calcium looping cycles.The sorbents were synthesized by three different methods: dry physical mixing, wet chemistry, and sol−gel combustion synthesis (SGCS). Their multicyclic CO2 capture capacity and the effect of the additive La2O3 were investigated in a fixed bed reactor system. The results indicate that the additive of La2O3 plays a positive role in the carbonation/calcination reactions, and the SGCS-made synthetic sorbent is composed of ultrafine well-dispersed hollow structured particles which are beneficial to the gas-phase diffusion on the surface area and can prevent small CaO particles from agglomeration effectively. As a result, the novel synthetic sorbent with the molar ratio of Ca to La of 10:1 made by the SGCS method provides the best performance of a carbonation conversion of 72% under mild calcination conditions and a carbonation conversion of 36% under severe calcination conditions (high temperature and high CO2 concentration) after 20 cycles.

In this study chemical-looping combustion of methane with compound CaSO4 oxygen carrier prepared by impregnation method was investigated in a fixed bed reactor. The effects of reaction temperature, CH4 percent, particle size and sample mass on reduction were discussed and an appropriate condition was determined by contrastive experiments. The results show that Ni-Fe mixed additive greatly improves the reactivity of CaSO4, and the suitable reaction temperature is around 925°C. Carbon deposition is inhibited and higher gas conversion is obtained by lower CH4 percent and more sample mass. However, the sample particle size has a little effect on the reduction. The long-time reduction-oxidation test demonstrates that compound CaSO4 oxygen carrier has a higher conversion. X-ray diffraction analysis reveals that CaSO4 could be fully reduced into CaS which is also almost oxidized into CaSO4.