Table of Content

28 December 2023, Volume 23 Issue 12

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Contents

Cover and Content

The Chinese Journal of Process Engineering. 2023, 23(12):  0. 

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Research Paper

Flow characteristics of gas-liquid two-phase flow in microchannel with obstacles

Yuanhao HUO Gang YANG Huichen ZHANG

The Chinese Journal of Process Engineering. 2023, 23(12):  1617-1626.  DOI: 10.12034/j.issn.1009-606X.222454

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The obstacles in the microchannel have a significant impact on the pressure drop and bubble shape of gas-liquid two-phase flow. In this work, experimental and numerical simulation methods are used to explore the effect of obstacles in the channel on the movement characteristics of nitrogen/water gas-liquid two-phase flow in the microchannel. The variations of pressure drop and bubble length under different gas and liquid flow rates in microchannel with obstacles are analyzed. The results show that the pressure drop in the obstacle microchannel is higher than that in the barrier free microchannel, and the maximum pressure drop occurs with the obstacle in the center. Through numerical simulation analysis, this is due to the vortex generated after the obstacle, and the pressure drop is positively related to the vortex length. The bubble length of the obstacle microchannel changes within 25% compared to the barrier free channel, and the bubble length becomes shorter as the obstacle approaches the center. Under different flowing conditions, there are three phenomena when bubbles pass through obstacles, including retraction without rupture, retraction with rupture, and direct rupture without retraction. The retraction lengths increase with capillary number increasing in retraction without rupture. The retraction lengths reduce with capillary number increasing in retraction with rupture. When the retraction length decreases to 0, it become a direct fracture without retraction. The variation range of retraction length gradually increases as the obstacle approaches the center. When passing through all obstacles, different breaking and merging laws are displayed under different working conditions. By numerical simulation, different vortex lengths after the obstacle result in different pressure drops, and there exists sever change at the moment of bubble rupture. When passing through the obstacle, the change of bubble shape is affected by the change of liquid phase velocity around it, different velocities in the sub channels on both sides of the obstacle determine the different rules of the two sub bubbles after passing through the obstacle.

Effect of fluid-structure interaction on liquid water flow in gas diffusion layer at microscale

Jiemin WANG Sai ZHANG Qingtai WANG Xianjun WANG

The Chinese Journal of Process Engineering. 2023, 23(12):  1627-1636.  DOI: 10.12034/j.issn.1009-606X.223096

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This work presents a new method to reconstruct the microstructure of carbon fiber gas diffusion layer (GDL), which is used to study the effect of velocity field in rough channels on GDL seepage. The random distribution model of pore channels in the diffusion layer is obtained by using the rough element and fractal theory. By distinguishing the hydrophilicity/hydrophobicity of the channel wall, four parameters, namely, the dispersion velocity ratio, the slip enhancement coefficient, the viscosity enhancement coefficient, and the microscale effect enhancement coefficient, are obtained. With accurate internal velocity distribution reconstructed as a control factor, and the effective seepage coefficient model is obtained by combining Darcy's law. The flow process of liquid water in GDL duct is simulated, and the influence of different roughness and contact angle on liquid water transmission performance is analyzed. The results show that the distributions of dispersion velocity, viscosity and slip velocity in the diffusion layer are affected by the random distribution of channel roughness elements and the non-uniform fluid solid interaction, and the four control factors act together on the flow process of liquid water and promote the discharge of liquid water. Under the same roughness, when the contact angle is 0o~180o, the promotion of hydrophilic wall slip effect conteracting the inhibition of dispersion effect and viscosity increases, and the promotion of hydrophobic wall slip effect conteracting the inhibition of dispersion effect and viscosity decreases, and the slope of flow change curve increases significantly at first and then decreases gradually. The newly established effective seepage coefficient model of liquid water in the diffusion layer can accurately describe the flow law in GDL, which has certain guiding significance for the internal water management of GDL.

Finite element simulation of the effect of retaining ring on the slurry effective utilization in chemical mechanical polishing

Pengyang QU Pan HUANG Cheng LIAN Shaoliang LIN Honglai LIU

The Chinese Journal of Process Engineering. 2023, 23(12):  1637-1645.  DOI: 10.12034/j.issn.1009-606X.222460

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Chemical mechanical polishing (CMP) enables global and local flatness polishing of a wide range of materials and is now widely used in the field of integrated circuit manufacturing. As one of the main consumables in the CMP process, slurry accounts for 50% of the total cost of the CMP process. However, most of the slurry is discharged into the waste stream by centrifugal force before it reaches the polishing pad-wafer interface, resulting in a very low slurry effective utilization rate. Therefore, optimizing the CMP process parameters to improve the slurry effective utilization can not only reduce the polishing cost but also solve some environmental problems. For the CMP process, the retaining ring not only fixes the wafer to prevent it from slipping out but also helps the slurry to transfer between the pad-wafer interfaces through its multiple grooves to improve the slurry effective utilization. Consequently, in this work, construct a dynamic coupling model of slurry flow and retaining ring rotation, and the finite element method (FEM) was employed to investigate the effect of retaining ring structure (including the number of grooves, groove width, groove area, and the presence of rounded corners at the grooves) on the slurry effective utilization rate during the CMP process. The results showed that the slurry effective utilization rate improved with the increase of retaining ring groove number with the same groove width (3.0 mm). For the same groove area (1785.4±0.3 mm2), the increase of retaining ring groove number led to a decrease in the slurry effective utilization rate. And the same number of grooves, the larger the groove width, the greater the slurry effective utilization rate. Fillet grooves had a higher slurry effective utilization rate than sharp-edged grooves. When the groove width of the retaining ring was enlarged and the groove of the retaining ring was designed as fillet, the slurry effective utilization rate could be improved significantly. This work optimizes the CMP process parameters by FEM simulation and provides theoretical guidance to reduce the CMP cost.

Study on preparation of sustained release microspheres with octreotide based on hydrophobic ion-pairing method

Yu ZHU Yi WEI Donglin SUI Jingxuan LIU Fangling GONG Guanghui MA

The Chinese Journal of Process Engineering. 2023, 23(12):  1646-1656.  DOI: 10.12034/j.issn.1009-606X.223064

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Octreotide (OCT) is widely used for the treatment of acromegaly, neuroendocrine tumors such as gastrinoma, and ruptured esophagogastric variceal bleeding in clinical. However, due to the short half-life of octreotide, the patients need frequent dosing in the treatment of diseases requiring long-term medication such as acromegaly, which leads to poor compliance. Therefore, it is urgent to develop a long-acting sustained-release formulation that can improve patient compliance. And since octreotide is a small molecule peptide drug that is extremely soluble in water, it tends to escape to the external aqueous phase during the preparation of microspheres, resulting in low drug loading and encapsulation efficiency. In this study, HIP-OCT complexes were prepared by hydrophobic ion-pairing (HIP) method. The effects of charge ratio, pH value, and temperature on the binding efficiency of the complexes were investigated, and the water solubility and dissociation of the complexes were observed. The sodium dodecyl sulfate-octreotide (SDS-OCT) with 93.77% binding efficiency, 9.31% water solubility, and 92.10% dissociation was screened as the optimal complex from the four HIP-OCT complexes. Due to the formation of HIP complexes, the hydrophilicity of OCT was changed and the difficulty of OCT encapsulation in double emulsion method was overcome. The SDS-OCT complex microspheres were prepared by the O1/O2/W double emulsion method combined with the premix membrane emulsification technique. Finally, the uniform SDS-OCT microspheres with particle size of 28.02 μm, Span value of 0.776, drug loading efficiency of 6.51%, and encapsulation efficiency of 72.00% were prepared under the negative pressure solidification, drug concentration of 80 mg/mL and poly(D,L-lactic-co-glycolic acid) (PLGA) concentration of 200 mg/mL. The in vitro accelerated release of the prepared SDS-OCT complex microspheres was basically in line with the trend of zero-level release, and the cumulative release was close to 100%. In vivo pharmacodynamic experiments showed that the microspheres had stable and long-term sustained release within one month.

Effect of N-(β-ethyl sulfonate) aminoethyl sulfonate on crystal morphology of taurine

Zhirong CHEN Gaojie DING Shenfeng YUAN Hong YIN

The Chinese Journal of Process Engineering. 2023, 23(12):  1657-1666.  DOI: 10.12034/j.issn.1009-606X.223119

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The objective of this study was to investigate the effect of N-(β-ethyl sulfonate) aminoethyl sulfonate (SA), an inevitable impurity during the taurine production using the ethylene oxide synthetic route, on the morphology of taurine crystals (TCs). Crystal morphology was investigated under different SA concentrations and cooling rates, and the length-diameter ratio of TCs were statistically analyzed. The molecular dynamics simulation method was used to investigate the attachment of the SA molecules on TC faces and the reason for SA changing crystal morphology. The results showed that the average length-diameter ratio of TCs increased as the SA concentration and cooling rate increased. The dosage of 0.04 mol SA per kg H2O could bring in an more than 100% increase of the TCs average length-diameter ratio when the cooling rate was 30 K/h. An increase of approximately 3.8 times in the average length-diameter ratio was observed when the cooling rate increased from 6 K/h to 36 K/h with 0.02 mol SA per kg H2O added. The cooling rate in the crystallization process should be controlled to less than 12 K/h to obtain taurine products with an average length-diameter ratio less than 3. The simulation results showed that the presence of SA increased the attachment energy barrier of taurine molecules on all stable crystal faces and the crystal habit simulated by the modified attachment energy model was consistent with the experimental morphology. The reduction of (111 ?) face area ratio and the expansion of (102) and (102 ?) face area ratios were the fundamental reasons for high length-diameter ratio needle-like morphology of TCs in the presence of SA. In conclusion, this study provides insights into the role of SA in shaping the morphology of TCs and offers recommendations for optimizing the taurine production process.

Oxidative refolding and purification of rhIFN-κ from the inclusion bodies

Jiaqi WU Yuxiang ZHANG Luyao ZHANG Lingying YAN Rong YU Yongdong LIU Yao ZHANG Chun ZHANG

The Chinese Journal of Process Engineering. 2023, 23(12):  1667-1675.  DOI: 10.12034/j.issn.1009-606X.223020

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Interferon-kappa (IFN-κ) has important biofunctions such as antivirus, antitumor, and immunomodulation. The unique secretion and physiological characteristics make it a promising medicine in clinical treatments. The recombinant human interferon-kappa (rhIFN-κ) expressed as inclusion bodies in E. coli require in vitro refolding to restore its biological functions, yet it tends to form precipitates in the process. Moreover, IFN-κ contains two disulfide bonds, but they are difficult to be correctly oxidized during the normal refolding procedure. In this work, a strong anionic surfactant, sodium dodecyl sulfate (SDS), was used to solubilize the inclusion bodies, and polyol 2-methyl-2,4-pentanediol (MPD) was added to the refolding buffer to gradually strip the SDS from the protein during the renaturation process to complete the refolding of rhIFN-κ. Experimentation showed that identified by the oxidative degree of its two disulfide bonds, there were mainly three species of rhIFN-κ after refolding: the completely oxidated rhIFN-κ, partially oxidated intermediate, and unoxidized species. For the SDS/MPD refolding system, the refolding yield for the correctly oxidated rhIFN-κ was closely related to the concentration and ratio of SDS and MPD in the renaturation system. Insufficient SDS or excessive MPD might result in forming aggregates or precipitates, while the correct oxidization of the disulfide bond would be suppressed at high SDS/MPD concentration ratios. Upon further optimization of the redox system and the solution pH, the optimal buffer was found by adding 0.05wt% SDS, 1 mol/L MPD, 0.2 mmol/L GSSG, and 0.1 mmol/L GSH to 20 mmol/L Tris at pH=9.5. Moreover, increasing protein concentration to 2.0 mg/mL would not significantly decrease the refolding yield. Under the optimized condition, the refolding yield could reach 66% after incubation for 24 hours at room temperature. Further purification with reversed-phase liquid chromatography could effectively remove the misfolded species as well as other impurities, achieving purity of 90% rhIFN-κ with only one band in non-reducing SDS-PAGE. The results showed that the SDS/MPD system could effectively suppress aggregation while increasing the rate of correct oxidization of the disulfide bonds. Our study lay a solid foundation for the production and clinical applications for rhIFN-κ in the future.

Study on performance and mechanism of replaced stripping of light rare earth by Ce(Ⅳ) in nitrate solution

Yi WANG Jian LI Mengling HUANG Xuxia ZHANG Hui ZHANG Tao QI

The Chinese Journal of Process Engineering. 2023, 23(12):  1676-1684.  DOI: 10.12034/j.issn.1009-606X.223056

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The traditional solvent extraction leads to a large amount of acid-alkali consumption and saline wastewater discharge. Herein, a new strategy was proposed according to the different extraction ability of Ce(IV) and RE(III) with P507, driven by the oxidation and reduction of Ce. As one of the key procedure, the performance and mechanism of replaced stripping of light rare earth elements (LREEs) by Ce(IV) in nitrate solution was investigated in this study. Pr(III) was selected as the representative element of LREEs for the follow-up experiments. Several operational parameters such as phase ratio, temperature, reaction time, concentration of nitrate and Ce(IV) in aqueous feed, and acidity were investigated. Results indicated that the stripping efficiency of Pr(III) increased significantly with increasing temperature, reaction time and Ce(IV) concentration, while it decreased with the increase of phase ratio. The stripping efficiency of Pr(III) was 98% by 0.56 mol/L Ce(IV) under the optimal conditions, which was higher than that by 1 mol/L HCl solution. This method was generally applicable on the stripping of the other LREEs. The mechanism was explored by slope method and FT-IR spectrometric analysis. The solvation mechanism was carried out, and the key complexes in the organic phase before and after stripping were determined to be Pr(NO3)(HA2)2·(HA) and Ce(NO3)2A2, respectively. From the FT-IR spectrometric analysis, it can be concluded that the H in P-O-H was replaced by the rare earth, which was bonded with P=O. Nitrate was also involved in the reaction because of the presence of the characteristic peaks of nitrate.

Preparation of low phosphorus content silicon from crystalline silicon sawing waste by slag refining method

Lei JIN Xuefeng ZHANG Dong WANG Yong LIN Zhi WANG Guoyu QIAN Wenhui MA Kuixian WEI

The Chinese Journal of Process Engineering. 2023, 23(12):  1685-1693.  DOI: 10.12034/j.issn.1009-606X.223042

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Crystalline silicon sawing waste is an important new energy solid waste. However, during the slicing and storage process, the surface of the silicon sawing waste tends to form a high melting point oxide layer, which makes the internal liquid silicon wrapped by the high melting point oxide layer during the high-temperature melting process, further resulting in longer melting time, high energy consumption, low silicon powder yield, and other challenges. Besides, low-quality silicon is recycled by the existing ordinary lime melting method due to phosphorus contamination of the silicon sawing waste from the electroplated diamond wire during the slicing process. Therefore, the silicon recycled from the melting of silicon sawing waste is a potential raw material for silicone production. In this work, silicon for organic use was successfully prepared by removing the surface oxide layer and non-metallic impurities of elemental phosphorus from crystalline silicon cutting scrap in one step using slag refining. Firstly, the high-temperature melting behavior of the oxide layer was simulated using silicon oxide. The effect of two slag systems, CaO-Al2O3-SiO2 and CaO-SiO2-CaF2, on the dissolution ratio of silicon oxide was compared. The influences of refining time (2~6 min) and refining temperature (1400, 1450, and 1500℃) on the dissolution ratio of silicon oxide were also investigated. Then, the effect of two refining slag systems on phosphorus removal was compared by using silicon sawing waste as raw material. The dissolution mechanism of the oxidation layer and phosphorus removal results were analyzed. The results showed that the dissolution of silicon oxide was mainly influenced by the viscosity of the refining slag system. The dissolution rate of silicon oxide can be improved by reducing the viscosity of refining slag. Compared with the CaO-Al2O3-SiO2 slag system, the dissolution rate of silicon oxide was faster in the CaO-SiO2-CaF2 slag system at the same conditions. The refining experiments showed that increasing the basicity of CaO-Al2O3-SiO2 and CaO-SiO2-CaF2 refining slag systems was beneficial to the phosphorus removal of silicon sawing waste. The maximum removal ratio of phosphorus was 53.81% and 62.04% for the two refining slags, respectively.

Preparation of calcium-iron composite desulfurizer and its synergistic desulfurization effect

Yang LIU Xinyu ZHANG Yang LI Changming LI Lina GAN Jian YU

The Chinese Journal of Process Engineering. 2023, 23(12):  1694-1705.  DOI: 10.12034/j.issn.1009-606X.223068

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In this study, the calcium-iron composite desulfurized with high activity, large pore size, and high sulfur capacity was successfully developed by adopting hydroxyl-rich iron sludge as the structure and reaction additives, investigating the effects of different contents of iron sludge and anions on the desulfurization activity, aiming to address the key technical problems such as poor reactivity and low sulfur capacity of the fixed bed calcium-based particle desulfurized for flue gas with low exhaust emissions, while completing the utilization of red mud. The desulfurization performance test results showed that the calcium-iron dual component desulfurization agent exhibited a strong cooperating desulfurization effect, and the desulfurization performance was significantly higher than that of Ca(OH)2 or FeOOH individually, in which the 30wt% hydroxy iron oxide (FeOOH) desulfurization agent had the optimal sulfur capacity and better than the reported desulfurization agents of the same type, up to 106 mg SO2/g. N2 physisorption desorption, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, and thermogravimetric analysis characterization studied reveal that the structural basis of CaO desulfurizer synergistic desulfurization is the introduction of high specific surface area iron sludge during the hydroxylation process of CaO, which generated a highly reactive CaFeO3Cl·5H2O interfacial phase and inhibited the growth of Ca(OH)2 grains. In addition, the rapid evaporation and expansion of internal water during lime hydroxylation results in the formation of a porous, high specific surface area (67.36 m2/g) fluffy particle structure, exposing more abundant SO2 adsorption and reaction active sites, and the pore channels. Water film and active Fe3+ formed by the decomposition of FeOOH component of calcium-iron desulfurized during the desulfurization process effectively promoted the diffusion, adsorption, and oxidation of SO2, further enhancing the reaction and removal of SO2. This study is expected to be able to provide a cheap and convenient purification material and process for the desulfurization and purification of small and medium-sized boilers or bulk exhaust flue gas.

Preparation of di-[EtPy][CoCl3] ionic liquid catalyst and coupling with oxone for desulfurization

Xiaolong SONG, Shaokang WANG, Hang XU

The Chinese Journal of Process Engineering. 2023, 23(12):  1706-1713.  DOI: 10.12034/j.issn.1009-606X.223008

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By leveraging its catalytic oxidation effect to remove dibenzothiophene (DBT) from model oil, a novel di-[EtPy]/[CoCl3] ionic liquid catalyzer was created using 1,4-dichlorobutane, pyridine, and cobalt chloride. The product was characterized by nuclear magnetic resonance (HNMR), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG), and scanning electron microscopy (SEM-Mapping-EDS). This study constructed an extraction catalytic oxidation system (ECODS) using di-[EtPy]/[CoCl3] catalyst, ketone oxide (PMS) as oxidant, and acetonitrile as extractant to explore the catalytic activity and the removal effect of DBT in octane. The double-end structure of the double ionic liquid gave the catalyst a twofold chance of making contact with the oxidant once it was added, enhancing the release of the sulfate radical from the catalytic oxidant. Under the optimal desulfurization conditions: m(oil)=6 g, m(di-[EtPy]/[CoCl3])=0.10 g, m(acetonitrile)=1.00 g, m[PMS (20wt%)]=0.50 g, t=70 min, T=45.0℃, the removal rate of DBT in fuel oil could be as high as 96.86%. The analysis showed that the dipyridine ring of the catalyst strengthens the π bond and electrostatic interaction with DBT, and the double catalytic sites were the main reasons for the high catalytic efficiency. The desulfurization rate of di-[EtPy]/[CoCl3] catalyst after five cycles was more than 86.00%, which was mainly due to the interaction of ionic liquid and metal ions reducing the loss of catalyst. Finally, the oxidation product was identified as dibenzothiophene sulfone (DBTO2) by GC-MS, and the mechanism of the oxidation process was preliminarily discussed. The research showed that the di-[EtPy]/[CoCl3] ionic liquid as a catalyst had high catalytic activity and desulfurization performance, providing a new catalyst and process system for the industrial removal of DBT.

Study on curing arsenic-containing compounds and solid wastes by iron-based silicate gel

Boyu DU Chao LIU Xing ZHU

The Chinese Journal of Process Engineering. 2023, 23(12):  1714-1724.  DOI: 10.12034/j.issn.1009-606X.223085

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During the mining and metallurgy of non-ferrous heavy metals, a large number of arsenic-containing compounds are exposed to the environment, posing great environmental risks to the surrounding water and soil. Due to their good arsenate affinity, iron ions and their compounds are the main components of commonly used chemical arsenic fixation agents. Whether in arsenic pollutant solidification or arsenic-contaminated site remediation, silicate and hydration processes are important physical barriers to arsenic. Based on this, we synthesized an iron-based silicate gel and evaluated its performance for the solidification/stabilization of typical arsenic compounds [Na3AsO4, Ca3(AsO4)2, AlAsO4, and FeAsO4·2H2O] and arsenic-containing sludge from non-ferrous metallurgy, and explored the arsenic fixation mechanism. The results showed that the iron-based silicate gel with a Fe/Si molar ratio of 1:4 could effectively immobilize the arsenic-containing compounds (Na3AsO4 and FeAsO4·2H2O). However, in the process of curing Ca3(AsO4)2 and AlAsO4, due to the competitive reaction between arsenate and silicate, the toxic leaching of arsenic was higher than that in the process of uncaring. The introduction of CaO could inhibit the competitive reaction, improve the arsenic fixation rate of Ca3(AsO4)2 and AlAsO4, and reach more than 98% of the arsenic fixation efficiency. The synergistic effect of Fe and Ca co-precipitation and physical immobilization is responsible for the immobilization/stabilization of arsenic-containing compounds. The core-shell structure with arsenic-containing compounds as the core and iron-based silicate gel/C-S-H gel as the shell separated arsenic species and reduced toxic leaching when in contact with the surrounding environment. The long-term stability showed that the iron-based silicate gel-cured arsenic-containing waste remained highly stable at pH=8 for 30 days. The CaO-assisted iron-based silicate gel proposed in this work showed great potential for the immobilization of arsenic-containing wastes and arsenic-contaminated land and provided a new way to solidify arsenic-containing pollutants.

Forced oxidation of calcium sulfite and the influence of impurities in wet desulfurization by calcium carbide slag

Yuewu ZHENG Ziheng MENG Lingxian LIAN Jiliang HAN Liwen ZHAO Xingguo WANG Gang XING Ganyu ZHU Huiquan LI

The Chinese Journal of Process Engineering. 2023, 23(12):  1725-1738.  DOI: 10.12034/j.issn.1009-606X.223048

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The main component of calcium carbide slag (CCS) is calcium hydroxide [Ca(OH)2], which can replace limestone ore for wet flue gas desulfurization, but the desulfurization byproducts of calcium sulfite particles are small because of the strong alkalinity of CCS, which may affect the oxidation of calcium sulfite and the crystallization of calcium sulfate (CaSO4). The effects of different process conditions on particle size, oxidation rate, water content, and microcosmic appearance in the process of calcium sulfate oxidation and gypsum crystallization were systematically investigated, and the optimal process condition (calcium sulfate content of 5 g/L, aeration rate of 400 mL/min, initial pH value of 5.5, reaction temperature of 40℃, and reaction time of 4 h) was obtained. The byproduct of desulfurization gypsum (mainly calcium sulfate dihydrate) with large particle size, low water content, high purity, and uniform appearance was obtained under the optimal condition, which is conducive to the subsequent resource utilization of desulfurization gypsum. The leaching sequence of each element in the CCS under the actual operating pH conditions of the CCS slurry (acidic conditions) is Na>Ca>Mg>Si>Fe>Al. The effects of impurities of Na, Mg, Si, Fe, and Al in the CCS on the oxidation process of calcium sulfate and the crystallization of calcium sulfate were investigated under the above optimal reaction condition. The results indicated that Mg, Si, and Fe in the CCS had a significant promotion effect on the oxidation rate of calcium sulfate, while Al and Na in the CCS inhibited the oxidation of calcium sulfate. At the same time, the addition of Si impurity had almost no effect on the crystallization of calcium sulfate, the addition of the impurities of Mg, Fe, and Na had less effect on the crystallization of calcium sulfate, and the addition of Al impurity had a significant adverse effect on the crystallization of calcium sulfate. In this study, the CCS-based calcium sulfate was used as the raw material, and the study of calcium sulfate oxidation and gypsum crystallization was carried out, providing theoretical guidance for the forced oxidation process in the actual industrial desulfurization.