Study on the desulfurization performance of calcium-based desulfurizer and NaHCO3 desulfurizer

The commonly used calcium desulfurizers have low desulfurization efficiency. NaHCO3 desulfurizers can meet the requirements of desulfurization efficiency, but the high price and the difficulty in handling desulfurization products make dry flue desulfurization technology quite difficult to realize the large-scale application. Preliminary research found a new calcium desulfurizer, to understand its performance, comparing investigation into the desulfurization performance of different calcium desulfurizer and NaHCO3 desulfurizer. The results showed that with the high-performance calcium desulfurizer, conventional NaHCO3 desulfurizer, and ultrafine NaHCO3 desulfurizer, the operating time with 100% desulfurization efficiency is 25,200, 21,600, and 6000 s, when the flue temperature of 373.15–573.15 K, the “break-through” temperature is 533.15, 473.15, and 373.15 K, expand the use range of desulfurizer flue gas temperature. Regarding the desulfurizer per unit mass, the production costs of ultrafine NaHCO3 desulfurizer are 5.36 times higher than calcium desulfurizer. Compared with NaHCO3 desulfurizer, high-performance calcium desulfurizer is characterized by several advantages, including high desulfurization efficiency, wider applicable temperatures, and low preparation cost, allowing for significant development potential in flue gas desulfurization.


Introduction
As a large country that uses coal as its main energy source and high-sulfur coal account for more than half of its coal resources (Chen et al. 2021), the development of advanced desulfurization technology is of great significance to the progression of the national economy (Bhasarkar et al. 2015;Chakrabarty et al. 2021;Wang et al. 2020;Zhao et al. 2021). Flue gas desulfurization technology (FGD) is commonly applied for controlling SO 2 emissions worldwide. Dry flue gas desulfurization technology (DFGD) has attracted much attention at home and abroad for several strengths, including reliable operation, low project investments, small areas, basically no corrosion problems in the system, and no wastewater discharge. Among them, the cost of desulfurizer accounts for a large part of the total operating cost of flue gas desulfurization equipment. The development of lowcost, high-efficiency, and widely sourced desulfurizers has become one of the hot topics in the field of flue gas desulfurization research (Sahoo and Sahoo 2014 Currently, for dry desulfurization projects, with NaHCO 3 as the desulfurization agent, in-furnace injection and pipeline injection are applied, and the flue gas temperature can provide good conditions for desulfurization (Subramanyan and Diwekar 2005;Wang et al. 2020). According to a previous study, Michael et al. (Michael et al. 2007) have discovered that at 400 K, the SO 2 concentration ranges between 350 and 500 ppm, and the desulfurization efficiency of NaHCO 3 dry powder reaches 40 to 80% when the sodium-to-sulfur ratio is between 0.5 and 3.0. Based on research by Wu et al. (Wu et al. 2004) for NaHCO 3 powder, when the calciumsulfur ratio is 0.5-2.5 and the particle size is less than 30 µm, the reaction temperature for the best desulfurization effect is between 400.15 and 423.15 K. NaHCO 3 has been employed by the Energy Environmental Engineering and Consulting Firm for higher removal efficiency of acid gases such as SO 2 , HCl, and HF in the flue gas (Nie et al. 2019). NaHCO 3 as compared to slaked lime has higher desulfurization efficiency and utilization rate but requires more raw material cost, and sodium-based desulfurization product Wu et al. 2019), more soluble in water, is more difficult to be treated relative to calcium-based desulfurization product, thus contributing to severe water pollution in the ash yard (Yu et al. 2019). Besides, low-temperature selective catalytic reduction (SCR) denitration catalysts could be activated under 473.15 K or even higher temperatures (Guo et al. 2015), while it has been suggested in numerous experiments the suitable temperature for NaHCO 3 powder is lower than 473.15 K (Liu et al. 2021;Kobayashi et al. 2019). In other words, the arrangement of desulfurization operation is arranged before the denitration catalyst would result in significantly low flue gas temperature and marked humidity, and accordingly, it is of great necessity to reheat the flue gas to meet the temperature requirements for activating the low-temperature SCR denitration catalyst (Yang et al. 2020). Contrarily, the arrangement of desulfurization operation after denitration catalyst would make it easier to provide suitable temperature conditions to activate low-temperature SCR denitrification catalyst, but SO 2 in the flue gas will cause physical poisoning of the low-temperature SCR denitrification catalyst (covering with liquid ammonium bisulfate) (Zhou et al. 2009). Therefore, it is of significant necessity to develop a novel technology with relatively high desulfurization efficiency under dry conditions for industrial flue gas requiring low temperature for denitration (Zhou et al. 2011;Song et al. 2021).
Calcium desulfurizer is most widely used due to its low price and wide distribution of resources. The desulfurization efficiency and calcium utilization rate achieved by traditionally digested calcium-based desulfurizers are generally low, which prompts investigation into more methods to enhance the desulfurization efficiency and utilization rate of calcium. It has been indicated in a preliminary analysis that a steam jet mill could be applied to prepare high-performance calcium-based desulfurizers after pulverization and digestion (Lǖ et al. 2020a, b), whether it can meet the current requirements of dry flue gas desulfurization is not revealed clearly. In this paper, we have compared the desulfurization performance among high-performance calcium-based desulfurizers, traditional desulfurizers, and sodium-based desulfurizers to develop a novel desulfurizer that could meet the requirements of industrial flue gas regarding denitration under low temperature and complete desulfurization operation under dry conditions.

Preparation of desulfurizer
The steam jet mill (shown in Fig. 1) was employed for the digestion and preparation of high-efficiency calcium-based desulfurizer, from Lǖ et al. previous research (Lǖ et al. 2020). Calcium desulfurizer was prepared under experimental conditions of 0.5 MPa steam pressure. The classifier speed and temperature were 2700 rpm and 533.15 K, which was termed as 0 # desulfurizer, whose particle size was D 10 = 0.574 μm, D 50 = 1.331 μm, D 90 = 6.775 μm, a bulk density of 213.4 kg•m −3 , a specific surface area of 24.253 m 2 •g −1 and digestion rate could reach 100%. As depicted in Search Engine Marketing (SEM), X-ray diffraction (XRD), and size report (detail in Fig. 2), 0 # desulfurizer was characterized by the uniform distribution of particles, a honeycomb surface, and an obvious loose porous structure.
The ordinary calcium-based desulfurizer prepared by the traditional digestion best method was termed as 1 # desulfurizer under specific conditions (at 368.15 K for digestion, water-cement ratio (mass ratio) of 0.84:1, the stirring speed of 100 rpm, and 600 s digestion), whose bulk density and specific surface area were 496 kg•m −3 and 19.02 m 2 •g −1 . The digestibility of CaO in quicklime is 87.1%. Based on the analysis of particle size, XRD, and  Fig. 3, the particle size of the desulfurizer was D 10 = 0.742 μm, D 50 = 4.901 μm, D 90 = 39.260 μm, and additionally, it was observed with less uniform particle distribution, and more specifically, with some relatively large particles. Moreover, the particles displayed a dense and layered surface and an irregular shape, and additionally, the particles were disorderly and gathered together to form irregular aggregates.
The NaHCO 3 provided by a coal chemical plant in Sichuan was used as the sodium-based desulfurizer, defined as 2 # desulfurizer. The specific surface area of the desulfurizer was tested to be 1.021 m 2 •g −1 , with a bulk density of 842.9 kg•m −3 , and according to the investigation into particle size, SEM, and other apparent characteristics of the desulfurizer, as depicted in Fig. 4, it could be understood that the particle size of 2 # desulfurizer particles was D 10 = 3.216 μm, D 50 = 13.178 μm, D 90 = 33.465 μm, and additionally, the cylindrical particles were overall less uniformly distributed with the existence of some relatively large ones and were disorderly aggregated.
Compared with 1 # and 2 # desulfurizers, 0 # desulfurizer was discovered with smaller particle sizes. To ensure the accuracy and consistency of the experiment, the LNJ-240A air jet mill (Mianyang Liuneng Powder Equipment Co., Ltd., shown in Fig. 5) was utilized for pulverization of 1 # and 2 # desulfurizers to obtain a desulfurizer with same particle size with 0 # desulfurizer.
Under the pressure of 0.8 MPa and with the rotating speed of the particle classifiers at 3600 rpm, 1 # desulfurizer was pulverized by the jet mill into 3 # desulfurizer, and additionally, the particle size and SEM of 3 # desulfurizer were analyzed, as shown in Fig. 6 (the existence of large particles in 1 # desulfurizer sample required the utilization of ethylene diamine tetraacetic acid (EDTA) titration method for calculation of the content of calcium oxide and CaO digestibility to avoid the error of XRD results). The particle size of 3 # desulfurizer was D 10 = 0.644 μm, D 50 = 1.357 μm, D 90 = 7.973 μm, and 85% digestibility and relatively uniform particle distribution were also observed. However, the surface structure was still relatively dense, and meanwhile, Fig. 2 The apparent characteristics of SEM and XRD of high-performance desulfurizer calcium oxide substances with a dense hexagonal structure were wrapped in the interior, resulting from exposure of incompletely decomposed calcium oxide on the outer surface under the action of the high-speed airflow. The specific surface area of the desulfurizer was tested to be 21.39 m 2 •g −1 , with a bulk density of 178 kg•m −3 , and the overall apparent performance of the particles was significantly improved after pulverization. 4 # desulfurizer, prepared by pulverization of 2 # desulfurizer under the same parameters, size, and SEM of 4 # desulfurizer were analyzed, as shown in Fig. 7. Its particle size was D 10 = 0.612 μm, D 50 = 1.578 μm, D 90 = 7.920 μm, and notably high purity of NaHCO 3 and relatively uniform distribution of particles were discovered. However, the cylindrical powder was split in response to high-speed airflow, and the clearance among particles was smoothed into a flocculent structure. The specific surface area and bulk density of the desulfurizer were 3.594 m 2 •g −1 and 181.1 kg•m −3 , and different improvements would be determined relative to that before pulverization.

Experiment apparatus
The desulfurization performances were compared in the DFGD testbed. The experimental device for DFGD is shown in Fig. 8, which is mainly composed of five parts: (1) simulated gas source, which mainly includes the O 2 , SO 2 N 2 , and cylinders. (2) Flue gas measuring system, a flue gas analyzer, is used to test the concentration of SO 2 (mainly inlet and outlet concentration of SO 2 ). (3) Flue gas pretreatment system, including the experimental gas mixer, piping, insulation, water pump, and steam generator. (4) The reaction assembly, including the experimental flue gas reactor (a quartz tube, a length of 1.2 m, and internal diameter of 0.025 m) and fixed-bed combustion. (5) The title tail gas treating unit (TGTU), with NaOH aqueous solution to remove SO 2 from the exhausted flue gas.

Experimental parameters and methods
A 5*10 −3 kg desulfurizer was placed in the flue gas reactor of each group. The reaction assembly temperature was 423.15 K,  and the flue gas flow was 1.17*10 −5 m 3 •s −1 . The flow rate of the pump was adjusted to ensure the relative humidity in the fixed bed combustion. And the relative humidity was adjusted to 10%.
The SO 2 data were calendared at the outlet of the flue gas reactor (C t ) every 1200 s to acquire the relationship curve between the working time and SO 2 outlet concentration under different humidity conditions. During these experiments, the initial SO 2 concentration was maintained at 0.85 g•m −3 . The desulfurization breakthrough of the flue gas reactor is detected to be more than 70% of the initial SO 2 concentration (C 0 ) when passing through the reactor. Therefore, when an SO 2 concentration higher than 0.2 g•m −3 was measured, the reactor will be deemed to be in a "breakthrough" status. Similarly, the working time required for the reactor to reach the "breakthrough" state is regarded as the breakthrough time of the reactor.
The desulfurization performance is evaluated by calculating the desulfurization efficiency of the desulfurizer. The formula for calculating the desulfurization efficiency F of the desulfurizer is as follows: where F indicates the desulfurization efficiency, C 0 represents the inlet concentration, and C t shows the outlet concentration of SO 2 at working time t.

Experimental instrument
The particle distribution and microscopic morphology of the prepared desulfurizer were analyzed and tested by SEM (Zeiss Instruments in Germany) on EVO18 tungsten wire at 30 kV and Ultra-55 field emission at 10 and 15 kV. The composition of the desulfurizer was tested by XRD (PANalytical Corporation in the Netherlands) under the conditions of the voltage of 40 kV, current of 50 mA, λ = 0.15406 nm, scan rate of 0.5 to 1°/min, the scan range of 0.5 to 10°, and Cu-K radiation.
The particle size composition of the desulfurizer was tested and analyzed under the all-dry condition by using the LS13320 laser particle size analyzer (Beckman Coulter, Inc., USA).
The specific surface area of the desulfurizer was tested at 77 K using a Gemini VII 2390 nitrogen adsorption and desorption instrument.
TH-990F ( III ) intelligent flue gas tester (Wuhan Tianhong) was used to test the SO 2 concentration. To control the influence of moisture, dust, and other impurities in the flue gas on the instrument and the experimental accuracy, the flue gas was tested with dust before entering the flue gas analyzer. After the moisture filter is processed, it is connected to the flue gas analyzer for testing.

Desulfurization performance
It could be seen from Fig. 9 that with the increase of the desulfurization time, the SO 2 outlet concentration remained stable and then displayed a rapid augment, while the desulfurization efficiency kept stable first and then rapidly declined, indicating that desulfurizers could quickly fail after a period of operation. It may be that the desulfurizer has a well-developed pore structure in the initial stage, and the pores promote the diffusion of SO 2 into the desulfurizer and provide a large number of active surfaces for the desulfurization reaction. The desulfurizer reacts directly with SO 2 to form desulfurization products on its surface so that a good desulfurization effect is obtained. With the progress of the reaction, the desulfurization products gradually increase to cover the surface of the desulfurizer. SO 2 must diffuse through the product layer to react. A further reaction occurs; that is, the later stage desulfurizer quickly fails.
It can also be seen from Fig. 9 that the breakthrough times of 0 # , 1 # , 3 # , 2 # , and 4 # desulfurizers were 27,600, 4800, 10,800, 7200, and 24,000 s, respectively. This shows that an ultra-fine desulfurization agent can increase the breakthrough time. 1 # desulfurizer cannot maintain 100% desulfurization efficiency, while 3 # desulfurizer does not reach 100% desulfurization efficiency at the initial stage (0-2400 s), as desulfurization continues when the working time is 2400-7200 s, the desulfurization efficiency can reach 100%. This shows that the 3 # desulfurizer undergoes secondary digestion due to the action of water vapor during the desulfurization process, the activity of the desulfurizer is enhanced, and the desulfurization efficiency is rapidly improved. Compared with 0 # , 2 # , and 4 # desulfurizers, the time to maintain 100% desulfurization efficiency is 25,200, 0, and 21,600 s, respectively. By comparing the desulfurization performance of the three desulfurizers, it can be found that under the same desulfurization conditions, the desulfurization performance of the 0 # desulfurizer is better than that of the NaHCO 3 desulfurizer. From the comparison of 1 # and 3 # , 2 # , and 4 # desulfurizer, it is found that the ultra-fineness of desulfurizer can increase the breakthrough time and the time to maintain 100% desulfurization efficiency. In other words, ultra-refinement can increase the desulfurization efficiency of the desulfurizer.
It has been generally recognized through experimental analysis that the desulfurization performance of traditional calcium-based desulfurizers is lower than that of sodiumbased desulfurizers, and from previous literature (Ahmed et al. 2021;Min et al. 2010), as a result, to meet industrial SO 2 emission standards, the calcium-sulfur ratio of calcium-based desulfurizers were 5:1-10:1, while that of sodium-based desulfurizers was only 1.3:1 to 1.6:1. Low desulfurization efficiency resulted in less frequent utilization of such desulfurizers, and calcium-based desulfurizer were not considered an option in dry desulfurization. However, the intensive processing of traditional calcium-based desulfurizers in this project contributed to its higher desulfurizer efficiency relative to sodium-based desulfurizers under the same desulfurization conditions, which broke through the conventional cognition and would significantly contribute to augmented efficiency of calcium-based desulfurizers in dry flue gas desulfurization.
Instead of the traditional digestion process of calciumbased desulfurizers, a steam jet mill with superheated steam as the pulverizing medium was employed in the present study for pulverization and quicklime digestion to prepare high-efficiency calcium-based desulfurizer which displayed overtly advantageous apparent properties, including specific surface area and desulfurization performance in comparison to sodium-based desulfurizers. Additionally, effective advancements in apparent characteristics of particles and desulfurization performance could be achieved after pulverization of desulfurizers with the help of the jet mill with compressed air at normal temperature as the medium. Therefore, a steam jet mill or jet mill could contribute to the creation of novel processes to promote desulfurization performance, which is of significant importance in the promotion and application of DFGD.

Heating characteristics
At an initial desulfurization temperature of 373.15 K and an up-regulation of 293.15 K every 600 s, the correlation between desulfurization efficiency and temperatures of the different types of desulfurizers was investigated, as shown in Fig. 10.
As depicted in Fig. 10, the continuous increment in temperature resulted in a gradual increase in SO 2 outlet concentration and a decline in desulfurization efficiency, suggesting that temperature negatively modulated the efficiency of desulfurizers. The main reason is that at the same gas flow rate, the higher the reaction temperature, the higher the linear velocity of the desulfurizer penetrated by the gas, which makes it more difficult for the gas flow to transfer mass and react inside the desulfurizer. Moreover, the increase in reaction temperature is not conducive to the adsorption of gas. For the NaHCO 3 desulfurizer, in addition to the above reasons, the higher reaction temperature may lead to the sintering and porosity loss of the desulfurizer.
The desulfurization efficiency of 1 # desulfurizer could reach over 70% at 373.15 to 433.15 K and drop to only 56.47% at 453.15 K (the SO 2 concentration is greater than 0.2 g•m −3 , and the desulfurization efficiency is less than 70%, indicating that the desulfurizer breakthrough at this temperature), reflecting that the critical temperature of 1 # desulfurizer was 433.15 K. As for 3 # desulfurizer, 100% efficiency could be maintained when the temperature was increased from 373.15 to 413.15 K, and the desulfurization efficiency dropped to 81.65% at 473.15 K and rapidly decreased to 46.82% at 453.15 K, from which the  Fig. 10 that the critical temperature for 2 # desulfurizer and 4 # desulfurizer was 453.15 and 473.15 K, respectively. Based on desulfurization characteristics with temperature augment among 1 # , 2 # , 3 # , and 4 # desulfurizers, we could conclude that the critical temperature at which desulfurization efficiency rapidly declined did not exceed 473.15 K. In other words, ordinary calcium-based desulfurizers and sodium-based desulfurizers cannot realize high-efficiency desulfurization under conditions higher than 473.15 K. For 0 # desulfurizer, it was testified in Fig. 10 that 100% desulfurization could be maintained with the desulfurizer temperature increased from 373.15 to 513.15 K. And with the temperature rising to 533.15 and then 553.15 K, the desulfurization efficiency dropped slightly to 96.23% and obviously to 61.76% separately. It was indicated that the critical temperature inducing the rapid decrease of desulfurization efficiency of 0 # desulfurizer was 533.15 K, and more importantly, the applicable high-efficiency desulfurization temperature of 0 # desulfurizer was higher than that of the above four desulfurizers.
According to the results of desulfurization characteristics with temperature increases, the applicable high-efficiency desulfurization temperature of the desulfurizer after jet mill pulverization was higher than that before pulverization, but the difference was not obvious. Additionally, high-efficiency calcium-based desulfurizer, as compared with ordinary calcium-based desulfurizers and sodium-based desulfurizers, could desulfurize at wider applicable temperatures and achieve more desulfurization efficiency at the same temperature. Currently, in the industrial flue gas desulfurization and denitration process, the denitration temperature generally should be maintained up to 473.15 K for higher activity of the denitration catalysts. The use temperature of 1 # and 2 # desulfurizers cannot be higher than 473.15 K, although desulfurizers 3 # and 4 # can be used at 473.15 K, the desulfurization efficiency is not high. After using these four desulfurizers for desulfurization, the flue gas needs to be properly heated and denitrified. For 0 # desulfurizer, the flue gas temperature controlled higher than 473.15 K, which can not only meet the high desulfurization efficiency but also provide suitable reaction conditions for the catalysts in the denitration process.

Energy consumption analysis of desulfurizer preparation capacity
1 # desulfurizer was prepared after full digestion of quicklime via a digester in a simple process. The production cost mainly included the cost of quicklime raw material and that of digestion. The quicklime was about 0.3 ￥•kg −1 and high-temperature water was utilized for digestion (Ding et al. 2019), in which the water-cement ratio was 0.84:1, cost roughly 0.05 to 0.1 ￥•kg −1 , and taken together, the production cost of 1 # desulfurizer was about 0.342 to 0.384 ￥•kg −1 . 2 # desulfurizer could be purchased directly at the price of roughly 2 ￥•kg −1 .
3 # desulfurizer and 4 # desulfurizer require pulverization utilizing a jet mill. The LNJ-240A air jet mill was applied for the pulverization of the two desulfurizers to facilitate the calculation of industrial production. The main parameters of the LNJ-240A air jet mill are shown in Table 1. The rated power was 2.72*10 5 W, and the actual energy consumption was 231.7 Kw·h. The processing capacity of 3 # desulfurizer was 5.33 kg•s −1 ; that is, the total power consumption for the production of 1000 kg of 3 # desulfurizer material was 0.724 Kwh•kg −1 , and the total cost was 1024.06 ￥. Similarly, the output of 4 # desulfurizer was 4.67 kg•s −1 . In other words, the total power consumption of manufacturing 0 # desulfurizer was prepared by pulverizing and digesting quicklime through a steam jet mill, whose parameters were shown in Table 1. The rated power was 7500 W, and the actual energy consumption was 6 Kw·h. The output was 1 kg•s −1 ; that is, production of 1000 kg of 0 # desulfurization consumed 0.099 Kwh•kg −1 of power. Also, superheated steam was utilized as the pulverizing medium for the LNGS-80 steam jet mill. 1.2 kg•s −1 of system steam consumption needed to be taken into consideration, and the production of 1000 kg of material required 667 kg of steam. The cost of superheated steam was 0.2 ￥•kg −1 , so 133.4 ￥ was spent on the steam. Therefore, considering the cost of raw materials, power consumption, and steam, the cost of producing 1000 kg of 0 # desulfurizer was about 532.57 ￥.
According to current market circulation prices, the processing and preparation costs of different desulfurizers were analyzed. In the production of desulfurizer per unit mass, the cost of 1 # desulfurizer was the lowest, followed by 0 # , 3 # , 2 # , and 4 # (the highest). Based on a comparative analysis of desulfurizers with higher efficiency, namely 0 # and 4 # desulfurizers, the production cost of the sodium-based desulfurizer after pulverization was about 5.36 times higher than that of the high-efficiency calcium-based desulfurizer. After 1000 kg of the flue, gas SO 2 was removed through theoretical calculations, 1.156*10 −3 kg of high-efficiency calcium-based desulfurizer were required at the price of 615.65 ￥, while 1.312*10 −3 kg of pulverized sodium-based desulfurizer were needed at the price of 3709.68 ￥, which was 6.02 times higher than that of high-efficiency calciumbased desulfurizer.
Ecological environment pollution has become the focus worldwide, and under such circumstances (Yi et al. 2008;Pan et al. 2020), in response to national policies on energy conservation and emission reduction, energy structure adjustment, carbon neutrality, and peaking carbon dioxide emissions, the industrial application of waste heat from industrial emissions, which could be fully utilized to provide pulverization energy for steam jet mills, to a certain extent, is expected to further reduce the cost of desulfurization. As for the high-performance characteristics of highperformance calcium-based desulfurizers, the authors will further analyze and study them. Therefore, this technology, in which a steam jet mill is applied for quicklime digestion to prepare high-performance calcium-based desulfurizers, could realize relatively high desulfurization efficiency and, accordingly, has great development potential in the field of flue gas desulfurization.

Conclusions
(1) When the SO 2 concentration is 850 mg•m −3 and the desulfurization temperature is 433.15 K, the highperformance calcium-based desulfurizers, ordinary calcium-based desulfurizers, ultra-fine ordinary calcium-based desulfurizers, Na-based desulfurizers, and ultra-fine Na-based desulfurizers the "break-through" time is 27,600, 480, 10,800, 7200, and 24,000 s. The SJM desulfurizer with 100% desulfurization efficiency for the longest time, up to 25,200 s. (2) Pulverization could result in an overt increment in effective desulfurization time of sodium-based and calcium-based desulfurizers. Conventional sodium-based and calcium-based desulfurizers could not desulfurize effectively at 473.15 K before or after pulverization, while high-performance calcium-based desulfurizers could display highly effective desulfurization under temperatures as high as 533.15 K. Under such circumstances, not only a relatively high effectiveness of desulfurization could be achieved, but also a suitable temperature could be provided for the integrated denitration process.
(3) Compared with conventional sodium-based desulfurizer, high-performance calcium-based desulfurizer prepared after quicklime digestion with the help of a steam jet mill is characterized by several advantages, including high desulfurization efficiency, wider applicable desulfurization temperatures, and lower energy consumption, allowing for significant development potential in the field of flue gas desulfurization.
Funding This work is supported by the National Natural Science Foundation of China (no. 51508481) and the Sichuan Science and Technology Program (2020YFG0186). The authors are grateful to the reviewers who help them improve the paper with many pertinent comments and suggestions.

Data availability
The datasets used and analyzed during the current study are available from the corresponding author upon reasonable request.

Materials availability
The datasets used and analyzed during the current study are available from the corresponding author upon reasonable request.

Declarations
Ethics approval and consent to participate Not applicable.

Competing interests
The authors declare no competing interests.