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Development of calcium coke for CaC2 production using calcium carbide slag and coking coal

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  • Corresponding authors:

    Xu-zhong Gong    E-mail: xzgong@ipe.ac.cn

    Chuan Wang    E-mail: Chuan.Wang@swerim.se

  • Received: 13 January 2020Revised: 21 March 2020Accepted: 24 March 2020Available online: 26 March 2020
  • A type of calcium coke was developed for use in the oxy-thermal process of calcium carbide production. The calcium coke was prepared by the co-pyrolysis of coking coal and calcium carbide slag, which is a solid waste generated from the chlor-alkali industry. The characteristics of the calcium cokes under different conditions were analyzed experimentally and theoretically. The results show that the thermal strength of calcium coke increased with the increase in the coking coal proportion, and the waterproof property of calcium coke also increased with increased carbonation time. The calcium coke can increase the contact area of calcium and carbon in the calcium carbide production process. Furthermore, the pore structure of the calcium coke can enhance the diffusion of gas inside the furnace, thus improving the efficiency of the oxy-thermal technology.
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Development of calcium coke for CaC2 production using calcium carbide slag and coking coal

  • Corresponding authors:

    Xu-zhong Gong    E-mail: xzgong@ipe.ac.cn

    Chuan Wang    E-mail: Chuan.Wang@swerim.se

  • 1. Key Laboratory of Green Process and Engineering, National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
  • 2. Chemical Engineering School, University of Chinese Academy of Sciences, Beijing 100049, China
  • 3. Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing 100190, China
  • 4. Department of Process Metallurgy, Swerim AB, Lulea 97125, Sweden

Abstract: A type of calcium coke was developed for use in the oxy-thermal process of calcium carbide production. The calcium coke was prepared by the co-pyrolysis of coking coal and calcium carbide slag, which is a solid waste generated from the chlor-alkali industry. The characteristics of the calcium cokes under different conditions were analyzed experimentally and theoretically. The results show that the thermal strength of calcium coke increased with the increase in the coking coal proportion, and the waterproof property of calcium coke also increased with increased carbonation time. The calcium coke can increase the contact area of calcium and carbon in the calcium carbide production process. Furthermore, the pore structure of the calcium coke can enhance the diffusion of gas inside the furnace, thus improving the efficiency of the oxy-thermal technology.

    • Electro-thermal CaC2 production is characterized by poor kinetic conditions because of the limited contact area between the bulk char and CaO, leading to a higher reaction temperature (~2200°C) [12]. As a result, the total energy consumption in electro-thermal CaC2 production is high. The oxy-thermal method involves directly using the heat generated from the coal combustion [3], and, at the same time, coal gas with a high calorific value is also generated [4]. Moreover, the energy consumption in the oxy-thermal method is about 50% less than that in the electro-thermal method [56]. Liu et al. [7] proposed an oxy-thermal method that involves the use of CaO powder. In their study, the reaction temperature was reduced to about 1700°C when CaO and char powders were used to form CaC2 [8]. Furthermore, to improve the reactivity, the use of bio-char as the carbon source for CaC2 production has been recommended [910].

      Studies have shown that the CaO diffusion controls the formation of CaC2 [1114]. Thus, the contact of reactant particles is crucial for the process. An increased contact area will improve the mass transfer rate of CaO, leading to a reduced reaction temperature (improving the reaction rate). Therefore, in both the oxy-thermal and the electro-thermal methods, the full contact of the two materials is needed. Moreover, researchers have reported that using small-particle-size char and CaO will increase the contact area and improve the CaC2 formation efficiency [14]. However, the fluidized bed—enhanced heat transfer—is not suitable for solid–solid reaction, and the contact force of the two particles cannot satisfy the CaO diffusion. The block reaction of the moving bed is an effective way to produce CaC2. Both lumps CaO and char need to have strong thermal and cold strengths to avoid disintegration, thus maintaining the required permeability inside the furnace. In the field of metallurgy, to improve the kinetic conditions of metal oxides reduction by carbon and lower the reduction temperature, carbon-containing metal oxides pellets are generally used [1516]. Moreover, the high reaction temperature in the oxygen-enriched blast furnace [1718] limits the deployment of the oxygen-enriched blast furnace technology due to the demanding requirements of ultra-high-temperature equipment. Therefore, controlling the furnace temperature at a reasonable level in the oxy-thermal process has become a tremendous challenge.

      To improve the production efficiency of CaC2 and realize the recycling of solid waste, researchers have prepared CaO containing carbon pellets (CCCPs) using calcium carbide slag and pulverized char [1920]. In the chlor-alkali industry, massive amounts of calcium carbide slag and pulverized char are generated as byproducts. They not only occupy farmlands and severely pollute the environment but also represent an extreme waste of resources [2124]. Moreover, researchers have tried to improve the thermal strength of CCCP by compacting the CaO and char particles using pressure and a binder. However, a too-dense structure will inhibit the CO overflow during the CaC2 formation, thus limiting the CCCP production [14,25].

      This current work proposes CaC2 production using a solid product, calcium coke, prepared from the co-pyrolysis of coal and calcium carbide slag. The binding property of coking coal will strengthen the bonding strength of CaO and coke, thus forming a type of biomimetic metallurgical coke with thermal strength as high as that of metallurgical coke [2627]. Thus, the calcium coke does not only improve the contact area of CaO and carbon but also facilitates the permeability for gas diffusion inside the furnace. Meanwhile, the CaO in the calcium coke is prone to hydration, and the strength of the calcium coke will reduce in air due to the hydration of CaO. The water resistance of CaO could be improved by controlling the grain size, controlling the specific surface area of CaO, and using some additives [2829]; however, increasing the water resistance might reduce the activity and increase the impurities.

      In the study, the calcium coke was prepared by the co-pyrolysis of coking coal and calcium carbide slag. The co-pyrolysis interval of the green pellets was first determined, and then the characteristics of the calcium coke under different conditions were examined and compared. Furthermore, the hydration resistance of the calcium coke was improved by applying the carbonation coating method.

    2.   Experimental
    • The calcium carbide slag used in the experiment was obtained from Shandong province, China, and the coking coal was obtained from Shanxi province, China. The chemical composition of the calcium carbide slag is presented in Table 1, and the proximate analysis and the ultimate analysis data of coking coal are presented in Table 2. The slag composition was measured using X-ray fluorescence (XRF). Proximate analysis was performed following the Chinese standard methodology GB/T 212–2008, and ultimate analysis data was obtained from an elemental analyzer.

      CaOSiO2Al2O3MgOSO3Fe2O3Cl
      89.885.232.780.380.570.330.43

      Table 1.  Chemical composition of calcium carbide slag wt%

      Proximate analysisUltimate analysis
      AadVdafFCdafCadHadOadNadSad
      10.9912.4687.5476.474.254.521.362.41
      Note: ad—air dry basis; daf—dry ash-free basis; FC—fixed carbon; A—ash; V—volatile matter.

      Table 2.  Proximate analysis and ultimate analysis of coking coal wt%

    • The calcium carbide slag and coking coal were mixed in a certain proportion in a mortar and grinded. A 4-g mixture was placed into a stainless-steel mold (diameter: 13 mm) and pressed vertically with a pelletizing machine (XQ-5, Xiangtan Xiangke Instrument Co., Ltd., China) under 75 MPa for 3 min to make green pellets with a size of ϕ13 mm × 20 mm. The green pellets were dried at 80°C for 24 h, and then they were calcined at various temperatures in the range of 700–900°C in a muffle furnace for 30 min to convert to the different types of calcium coke (Ar atmosphere). Fig. 1 shows the green pellets and the formed calcium cokes after the calcination.

      Figure 1.  Pictures of green pellets and calcium cokes.

      The thermal weight-loss characteristics of the green pellets were determined using an SDTQ600 thermogravimetric analyzer. The thermogravimetric conditions were as follows: a sample mass of 5–10 mg, an atmosphere of pure Ar, a pyrolysis temperature interval of room temperature to 1360°C, a temperature increase rate of 20°C/min, and a gas flow rate of 200 mL/min.

    • The thermal strength of the calcium coke samples formed from various precursors were measured using an automatic high-temperature strength testing device, GKY-II (Xiangtan Xiangke Instrument Co., Ltd., China). The testing device needed to be heated up from room temperature to 1000°C at a heating rate of 10°C/min and held for 5 min before the strength test was started.

      To study the influence of the pyrolysis temperature and the coking coal content on the thermal strength of calcium coke, the green pellets were pyrolyzed for 30 min in Ar atmosphere at 700 and 900°C, respectively. The obtained calcium coke was placed in a high-temperature compressive tester at constant temperature for 5 min to test its thermal strength. Each sample was tested three times, and the average value was taken as the thermal strength of calcium coke.

    • The calcium coke was prepared from green pellets via pyrolysis at 700°C (30 min), and it was then cooled to 300°C (industrial exhaust temperature) under N2 atmosphere. Afterward, N2 was shifted to CO2 (500 mL/min) for different holding times of 0, 5,10, 15, and 30 min, respectively. The calcium coke after carbonation was obtained for the hydration resistance test.

    • The sample composition was detected by X-ray diffraction fluorescence (XRF, AXIOS-MAX, Japan). The phase composition of the specimen was detected using X-ray diffraction (XRD, X'Pert PRO MPD, Holland) with Cu-Kα radiation in the 2θ range of 10° to 90°. The microstructure of the sample was examined using field-emission scanning electron microscopy (SEM, JSM-7001F, Japan) and energy-dispersive spectrometry (EDS, INCA X-MAX, Oxford Instrument, UK). The particle size of CaO with calcination was measured by Nano Measurer 1.2 coupled with a SEM. The pore structure parameters of the sample were determined using an automatic mercury porosimeter (Autopore IV 9500, Micromeritics, USA).

    3.   Results and discussion
    • The reactions involved in the co-pyrolysis of calcium carbide slag and coking coal are expressed as reactions (1)–(10). Fig. 2 shows the thermodynamic calculation of the reaction equations using HSC chemistry software. The standard Gibbs free energy ($\Delta {G^{\ominus}} $) of the reactions (5) and (9) is negative at the range of 100–1200°C, indicating that both reactions occur easily within this temperature range. In the reaction of CaO with SO2 and O2, the $\Delta {G^{\ominus}} $ is less than −400 kJ before 800°C, indicating that CaO can react with SO2 to easily form CaSO4, limiting the sulfur removal [30]. When the temperature is higher than 800°C, CaSO4 will first be reduced to CaS by H2 and CO and then further reduced to H2S [31]. When the pyrolysis temperature is more than 700°C, the $\Delta {G^{\ominus}} $ values of reactions (1) and (10) start to turn negative, implying that the minimum temperature for the co-pyrolysis of the calcium carbide slag and coking coal is 700°C.

      Figure 2.  HSC thermodynamics of related reactions for calcium coke preparation by the co-pyrolysis of calcium carbide slag and coking coal: (a) reactions (1)–(5); (b) reactions (6)–(10).

      To further determine the pyrolysis range of the green pellets (mixture), thermogravimetric analysis of calcium carbide slag and coking coal was carried out in Ar atmosphere, and the results are shown in Fig. 3. Calcium carbide slag has two weightlessness peaks at 450 and 700°C, which corresponds to the weightlessness peaks of Ca(OH)2 and CaCO3 decomposition, respectively [3233]. The coking coal starts to lose weight from 300°C, with the maximum weight loss occurring at 500°C, and the weight loss stops at 900°C. This is because when the pyrolysis temperature is lower than 500°C, the coking coal begin to form semi-coke, which is accompanied by the formation of primary gases (H2 and CH4) with relatively small molecular weight and tar. When the pyrolysis temperature is between 550 and 750°C, the semi-coke decomposition produces a large amount of secondary gases, and at the same time, volume contraction and cracks occur. However, when the pyrolysis temperature is higher than 900°C, the semi-coke condenses and the aromatic structure continues to increase; thus, the structural units are better ordered. Finally, the semi-coke is converted to coke. To completely decompose the CaCO3 contained in calcium carbide slag, the pyrolysis temperature must be higher than 700°C. However, the temperature should not be too high to prevent the generation of water steam from the reaction between the calcium carbide slag and coke. Therefore, the maximum temperature of the co-pyrolysis of green pellets is 900°C.

      Figure 3.  Thermogravimetric (TG) and derivative thermogravimetry (DTG) analyses of (a) coking coal and carbide slag and (b) green pellets with different mass ratio of carbide slag (CS) and coking coal (C).

      Fig. 3(b) shows the weight-loss curve of the green pellets. The weightlessness peak (~400°C) and the weightlessness interval (700–900°C) respectively correspond to the minimum and maximum temperatures required in the pyrolysis of the green pellets. The decomposition peak at about 400°C is associated with the accelerated pyrolysis of coal under the action of calcium compounds and the decomposition of Ca(OH)2. The weight loss at 700 to 900°C is associated with the decomposition of CaCO3 and the CaO-catalyzed reaction of coke with CO2. Obviously, with the increase in the calcium carbide slag content, the weight loss rate at 400°C increases. For the samples with 40wt% calcium carbide slag content (Ca : C = 2:3), the weight loss rate slowed down between 700 and 900°C, indicating that the pyrolysis of coal is not catalyzed by calcium-containing compounds. This weight loss rate may be mainly attributed to the decomposition of CaCO3 in the calcium carbide slag.

    • As shown in the Fig. 4, the thermal strength of calcium coke increased with an increase in the coking coal content at 700°C. When pyrolysis temperature was 900°C, the thermal strength of the calcium coke decreased. Thus, the pyrolysis temperature and the coking coal content has significant impacts on the thermal strength of the calcium coke. A plastic mass is formed in the coking coal pyrolysis as the calcium coke binder will reinforce the solid bridge bond between CaO and coke; this plastic mass refines the calcium coke particles, and thus, the thermal strength of the calcium coke is improved. Additionally, the plastic mass could wet CaO particles, strengthening the solid bridge bond formed between CaO and coke, thus improving the thermal strength of calcium coke. At an increased pyrolysis temperature, uneven distribution of the calcium coke particles and defects in the pore structure will occur, and this will reduce the calcium coke thermal strength.

      Figure 4.  Effect of pyrolysis temperature and coking coal content on thermal strength of calcium coke.

      The coking coal content and pyrolysis temperature may have a significant impact on the calcium coke structure. Furthermore, the pore diameter distribution of calcium coke was determined by the mercury injection method [3435]. Figs. 5(a)5(e) show the pore size distribution of calcium coke containing 10wt%–50wt% coking coal at 700°C. With the increase of coking coal content, the average pore size of calcium coke fluctuation decreases, indicating that too much coking coal will lead to an uneven distribution of the pore size. The particle stress concentration points were distributed in some sintering parts, meaning that a too-high coking coal content is not conducive to the uniform pore size distribution of calcium coke. Fig. 5(f) presents the average pore diameter of calcium coke prepared with different amounts of coking coal. Figs. 4 and 5(f) show that no significant correlation exists between the average pore size and the thermal strength of the calcium coke.

      Figure 5.  Pore size distribution (a)–(e) and pore structure diameter (f) of calcium coke with different coking coal contents at 700°C: (a) 10wt%; (b) 20wt%; (c) 30wt%; (d) 40wt%; (e) 50wt%. D is pore diameter; V is pore volume.

      Fig. 6 shows the XRD pattern of the calcium coke. Because the coke is amorphous carbon, a carbon peak cannot be detected, but a CaO phase can be detected in the calcium coke. Fig. 6 shows that at 700°C, a large amount of CaCO3 is present in the calcium coke. However, no CaS can be detected, indicating that at this temperature, the sulfur in the calcium coke could be removed and released into the gas phase. Moreover, at 800°C, CaCO3 in the calcium coke is decomposed into CaO, and the calcium coke contains trace amounts of CaS and Na2SiO4; thus, sulfur remained in calcium coke in the form of CaS at 800°C. At the pyrolysis temperature of 900°C, a significant CaS peak exists, which proves that high temperature is not conducive to the gaseous removal of sulfur. Therefore, the pyrolysis temperature should not be too high to allow for the gaseous removal of the sulfur in the calcium coke.

      Figure 6.  XRD patterns of calcium cokes with coking coal contents (10wt%–50wt%) prepared at different pyrolysis temperatures: (a) 700°C; (b) 800°C; (c) 900°C.

      Fig. 7 shows the microstructure of calcium coke produced from the green pellet at a pyrolysis temperature of 700°C. With the increase in the coking coal content, the calcium coke particles are refined, and the distributions of calcium and carbon become uniform, which can not only improve the thermal strength of calcium coke but also facilitate the migration of gaseous sulfur. However, a layer structure appears in the calcium coke when the coking coal content exceeded 30wt%, thus destroying the uniform structure of the calcium coke. This can also be noticed in Fig. 5, which shows an increase in the average pore size of the calcium coke (with coking coal content of 50wt% at 700°C) to 39.97 nm and a hump-shaped pore diameter distribution curve.

      Figure 7.  SEM and EDS results of calcium coke with different coking coal contents at 700°C: (a) 10wt%; (b) 20wt%; (c) 30wt%; (d) 40wt%; (e) 50wt%.

    • The fresh calcium coke has high thermal strength. However, it contains rich CaO, and thus, it can easily absorb moisture in the air; hence, it cannot be stored for a long time. To overcome this shortcoming, the surface coating method of CO2 carbonation is proposed to improve the hydration resistance of the calcium coke.

      A HSC thermodynamic calculation software package was used to calculate the standard Gibbs free energy ($\Delta {G^{\ominus}} $) of the Ca(OH)2 decomposition and the CaO carbonation reactions. As shown in Fig. 8, the $\Delta {G^{\ominus}} $ of the CaO carbonation reaction remains negative from room temperature to 1200°C, indicating that the carbonation reaction of CaO can be carried out spontaneously without any external conditions. However, the $\Delta {G^{\ominus}} $ of the Ca(OH)2 decomposition gradually decreases from a positive value at room temperature to a negative value at 500°C, indicating that the Ca(OH)2 decomposition reaction requires the support of additional energy. In this work, the carbonation experiment was carried out at 300°C, which was in line with the exhaust gas temperature from the industrial furnace.

      Figure 8.  Thermodynamic calculation of Ca(OH)2 decomposition and CaO carbonation reactions.

      Fig. 9 shows the hydration resistance test of calcium coke with different carbonation times. Before the calcium coke was subjected to carbonation treatment, its hydration resistance was poor; it started to break into pieces after three days. After the carbonation treatment, the hydration resistance of calcium coke was significantly improved. The hydration resistance time reached 9, 12, and 15 d after carbonation times of 5, 10, and 15 min, respectively. As expected, a longer carbonation time of 30 min showed a good hydration resistance time of more than 15 d. The dense CaCO3 protective layer is believed to inhibit the hydrolysis reaction of the CaO inside the calcium coke.

      Figure 9.  Hydration resistance test results of calcium coke with different coking coal contents (10wt%–50wt%) under different carbonation times.

      The XRD test results of the calcium cokes after carbonation are shown in Fig. 10. Crystal phases of CaO and CaCO3 were detected, and CaO was the main crystal phase, indicating that a CaCO3 protective layer was formed on the calcium coke surface.

      Figure 10.  XRD patterns of calcium coke with different carbonation times (700°C, with 30wt% coking coal).

      During the test, the ambient temperature was maintained at 17 ± 3°C, and the humidity was 16.5% ± 2.5%. The water absorption rate is measured every day, and the water absorption rate in day n ($\Delta {m_n}$) were calculated by Eq. (1).

      where ${m_n}$ and ${m_{n{\rm{ - }}1}}$ is the mass of calcium coke in the day n and day $n\!-\!1$, respectively; ${m_0}$ is the mass of calcium coke at initial stage.

      Figs. 11 and 12 shows changes in the quality and the water absorption rate curve of the calcium coke. It can be seen from the Figs. 11 and 12 that the water absorption rate of all samples is relatively high only on the first day, and then the rate is low. All samples without carbonation had a water absorption rate of 4.5%–5.4% (coking coal content of 10wt%–50wt%) on the first day, while after the second day, the rate was maintained at 2.5%–4.5%. After 5 min of carbonation, the water absorption rate of the samples was between 1%–2% on the first day, and 0.25%–0.75% after the second day. For samples carbonated for 10 min, the water absorption rate was 0.5%–0.6% on the first day and 0%–0.3% after the second day. The water absorption rate of the sample carbonized for 15 min was 0.3%–0.5% on the first day, and maintained below 0.1% after the second day. After 30 min of carbonation, the water absorption rate of all samples was 0.5%–0.9%, and remained below 0.3% after the second day.

      Figure 11.  Curves of the mass change vs. hydration time for the calcium cokes with different carbonation time.

      Figure 12.  Curves of water absorption rate vs. hydration time for the calcium cokes with different carbonation time.

      The results above indicated that the surface carbonation coating can significantly reduce the water absorption rate, and the longer the carbonation time, the smaller the water absorption rate. The improvement in the hydration resistance of calcium coke can solve the storage problem faced in the industry. Furthermore, carbonation treatment at 300°C can be realized by utilizing the waste heat streams of exhaust gases (rich in CO2 content), which are generated in various combustion furnaces located inside the chlor-alkali plant.

      The carbonation treatment not only can improve the hydration resistance of calcium coke but also will affect the thermal strength. Fig. 13 shows the thermal strength diagram of calcium coke with different coking coal contents after carbonation for 30 min. The thermal strength of the calcium coke with 10wt% coking coal was the same as that of the calcium coke before carbonation, while the thermal strengths of the rest calcium coke samples were less than that of the calcium coke before carbonation. The carbonation treatment destroyed the Ca–C structure of the calcium coke samples, and CaO was stripped from the Ca–C structure; thus, the thermal strengths of the calcium coke samples decreased slightly; however, they were still above 30 MPa.

      Figure 13.  Effect of carbonation on the thermal strength of calcium coke pyrolyzed at 700°C for 30 min.

    • Both calcium coke and CCCPs are made of calcium–carbon mixtures and both can be used in the calcium carbide and steel metallurgy processes. The production of CCCP with 30wt% of coke powder involves three steps [20]: the preparation of pulverized char from coal pyrolysis, the co-molding of calcium carbide slag and pulverized char, and the calcination of calcium carbide slag in the presence of char. By comparison, the calcium coke production route is a one-step process, i.e., the co-pyrolysis of coking coal and calcium carbide slag to form a calcium carbon composite material.

      Large differences in structure and performance exist between the CCCP and calcium coke. Fig. 14 shows the thermal strength of CCCPs and calcium cokes (from pyrolysis at 700–900°C). The thermal strength of calcium coke prepared by calcium carbide slag and coking coal was higher than that of CCCP prepared by calcium carbide residue and char powder. Moreover, the thermal strength of calcium coke was two times higher than that of CCCP. The plastic mass formed in the coking coal pyrolysis could refine the calcium coke particles, resulting in uniform carbon distribution, which can be seen in Fig. 7.

      Figure 14.  Change in the thermal compressive strength of CCCP and calcium coke with the calcination temperature (30 min, Ar).

      Calcium coke is obtained from co-pyrolysis of calcium carbide slag and coke coal in which the coking coal pyrolysis process is dominant, thus, a large number of plastic mass are produced, resulting in high thermal strength. However, CCCP is obtained from the co-pyrolysis of calcium carbide slag and coke powder, where the thermal decomposition of calcium carbide slag is dominant. Therefore, no binder with strong cohesive force is produced, leading to low strength.

    4.   Conclusions
    • A new type of calcium coke was developed by the co-pyrolysis of calcium carbide slag and coking coal. The newly developed calcium coke can reduce the reaction temperature of CaC2 production, leading to energy saving in the chlor-alkali industry. The main conclusions drawn from this study are as follows.

      (1) As the coking coal content increased, the thermal strength of the calcium coke increased. The occurrence of a lamellar structure in the calcium coke caused stress concentration and a slight decrease in the thermal strength of the calcium coke. Therefore, the thermal strength of the calcium coke increased with the increase in the coking coal content.

      (2) The carbonation coating method can effectively improve the hydration resistance of calcium coke as a CaCO3 layer is generated. The hydration resistance of calcium coke could reach 12 d with the carbonation time of 10 min, and 30 d with the carbonation time of 30 min, which allows for the storage of calcium coke. Although the carbonation coating method destroys the Ca–C structure in the calcium coke, only a slight decrease of the thermal strength will occur.

      (3) A small particle size can improve the thermal strength. Therefore, the calcium coke has a higher thermal strength than CCCP.

    Acknowledgements
    • This work was financially supported by the Natural Science Foundation of China (Nos. U1610101 and 21776288) and the Green Process Manufacturing Innovation Research Institute, Chinese Academy of Sciences (No. IAGM-2019-A09). Chuan Wang would like to acknowledge the funding support from Vinnova (Dn: 2018-05293).

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