The Chinese Journal of Process Engineering

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Chin. J. Process Eng.. 2020, 20(6): 0.

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Research progress on supercooling degree suppression of inorganic hydrated salt phase change materials

Wen TAO Yi ZHANG Xiangfa KONG Wanchun ZHANG Chuangang FAN

Chin. J. Process Eng.. 2020, 20(6): 619-627. DOI: 10.12034/j.issn.1009-606X.219273

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Inorganic hydrated salt, as a kind of important phase change materials (PCMs), possess the characteristic of high latent heat of phase change, easy availability and high safety, has a great potential in the application of middle-low temperature thermal energy storage in the future. However, the inherent supercooling and phase separation of the inorganic hydrated salt decreased the thermal stability of these materials, and these problems always resolved by adding nucleating agents and thickening agents. The leakage problems of hydrate salt in liquid state always resolved by the absorption and the microencapsulation method, to limit them in a certain area. So far, by means of porous matrix adsorption, such as expanded graphite, bentonite, foam metal, inorganic hydrated salt PCMs can be absorbed in these matrix and well packaged to prevent them from leakage. Through the microencapsulation method, inorganic hydrate salt can be encapsulated in the organic or inorganic polymer shells such as polymethyl methacrylate, melamine-formaldehyde resin or the polyurethane, inorganic SiO2 shell is another choice for the encapsulation of the materials. Through the absorption or micro-encapsulation method, the dispersibility of the inorganic hydrate salt can be further improved, the supercooling degree of the inorganic hydrate salt can be reduced and the phase separation can be modified, the thermal stability of the materials can be further enhanced, which is an effective way to conquer the leakage problems of the inorganic hydrate salt in the phase change process. In this work, the study on the supercooling and phase separation of inorganic hydrated salt were summarized, for the inhibition of the supercooling and phase separation of inorganic hydrated salt, some methods including absorption of porous materials or microencapsulation method were proposed. Finally, suggestions for future research on energy storage using inorganic hydrated salts were provided.

Application of melt crystallization in the purification of heavy aromatics

Ting LI Jingwei HOU Xiao LI Shugang MA Hao WANG Jing CHEN Yuan WANG Yuan ZHOU Zian WAN

Chin. J. Process Eng.. 2020, 20(6): 628-637. DOI: 10.12034/j.issn.1009-606X.219286

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Melt crystallization is of great importance in the purification of homologues, azeotropes and heat-sensitive substances. It has been widely utilized in numerous chemical industries because of its high selectivity for pure products, low energy consumption, no gaseous phase, no recovery of solvents and the convenience to industrialization. This work reviewed the development and application status of melt crystallization technology in the purification of high value-added products, based on the different crystallization processes in recent years. Examples were compared to emphasize the advantages as well as disadvantages. There were a large number of high value-added products in poor quality heavy aromatics such as ethylene tar, reforming aromatics and coal tar, which contained great number of naphthalene, xylene, durene, anthracene, phenanthrene, carbazole, acenaphthylene and so on. The separation and purification of these products were extremely meaningful both economically and technologically. Melt crystallization played a promising role in the purification of these high value-added products. Considering the advantages of engineering application, the hybrid of distillation and melt crystallization, the ultrasound-assisted crystallization and other coupling processes had been designed to meet the requirements in various industrial areas, which explored quite promising application areas of melt crystallization. Batch process played a really important role in the industrial scale process, which facing the problems of large labor cost and unstable product quality. Although many efforts had been made to improve the continuous crystallization, it was still not as universal as batch crystallization due to the existence of the drawbacks, such as blockage and encrustation. Novel research with suitable interpretation into the mechanism were potential solutions for the shortcomings of the current process. Finally, studies on mass and heat transfer, enhanced controller of crystals and crystallization systems for multicomponent promised a bright future for the design of novel crystallizers, models and some assistive technologies.

Simulation of negative wake of particle settling in surfactant wormlike micellar fluid

Zhiguo WANG Heng ZHANG Jingjie LIN Xiaohui SU Yihua DOU

Chin. J. Process Eng.. 2020, 20(6): 638-645. DOI: 10.12034/j.issn.1009-606X.219283

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As a novel smart fluid, wormlike micellar fluids (WLMFs) have been used in the oil and gas enhancement and other process industry engineering. However, this fluid has an entangled wormlike micellar network and demonstrates complex viscoelastic rheology such as shear banding, extensional hardening and shear induced structure in flowing. It is urgent to investigate the particles settling and transport behavior in the complex flow of WLMFs. Amazingly, the negative wake may occur as the particle settling in this complex fluid, which means the fluid can flow at the opposite of particle settling direction. The negative wake of sphere particle settling in the WMFs plays an important role in the interaction between the fluid and particle. In this work, sphere particle settling behavior in viscoelastic surfactant (VES) wormlike micellar fluid was investigated by POLYFLOW based on the Giesekus constitutive equation. The effects of relaxation time and migration factor on the flow velocity and stress distribution around particles were analyzed. Furthermore, the mechanism of the negative wake in the rear of the particle and the effects on particle drag were investigated. The results showed that the Giesekus model could correctly interpret the behavior of non-linear shear thinning and extensional stress in the process of particle settlement in WLMFs. More extensional strain at the rear of particle was caused by the fluid elasticity. Furthermore, the negative wake occurred at the rear of particle for the interaction of fluid elasticity and shearing thinning. It can extend the downstream of particle settling with increasing the fluid elasticity (De number) and decreasing the ratio of extensional viscosity to zero shear viscosity (Tr, Trouton number). The negative wake promoted drag reduction and resulted in the increasing of particle setting velocity. The results can develop the theory of the multiphase flow of complex fluid and promote the application of viscoelastic surfactant wormlike micellar fluid.

Effect of pH on the chelating mechanism and stability constant of chitosan-Cu(II) chelate complex

Ying FENG Qingjin ZHANG Juecheng WANG Jianwei ZHANG

Chin. J. Process Eng.. 2020, 20(6): 646-654. DOI: 10.12034/j.issn.1009-606X.219299

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Heavy metal ions in water or soil are serious pollution, and human health is seriously endangered by pollution. The removal of heavy metal ions quickly and efficiently has become an important research field. Chitosan is a natural high molecular polymer with excellent flocculation and metal chelation. The effect of pH values on the stability constant and chelation properties of chitosan chelated Cu2+ was studied by ultraviolet spectrophotometry in this work. The chelation performances of chitosan to copper ions were investigated with the pH value increasing from 1 to 9. The experimental results showed that the chelating ability of active groups on chitosan carbon chain with copper ion was enhanced with the increase of the pH value. When the pH values of the solution system ranged from 5 to 6, the stability constant of the chelate was the maximum value of 1.1×108, when the pH was close to 7, some chelate products precipitated and the stability constant decreased. The change of pH value had no obvious effect on the coordination ratio (n) of the chelate under acidic conditions and the ratio (n) was 2. The chitosan-Cu(II) chelate could be separated out by adjusting the pH value of the solution. With the increase of pH value, some floccules precipitated from the solution and the concentration of Cu2+ decreased. When the pH value was about 9, the Cu2+ concentration reached a minimum value of 1.5 mg/L. The precipitate of chitosan reacted with copper ions was analyzed by microscopic image, X-ray diffraction pattern and Fourier transform infrared spectroscopy (FT-IR), the results showed that the main component of the precipitate was chitosan-Cu(II) formed by chelation of –NH2 with Cu2+. This study could provide a theoretical basis for the removal of metal ions by chitosan.

Performance and modelling of bromide dynamic adsorption onto D301 anion exchange resin

Chunyi YUAN Yuzhu SUN Ying YANG Xingfu SONG Jianguo YU

Chin. J. Process Eng.. 2020, 20(6): 655-666. DOI: 10.12034/j.issn.1009-606X.219342

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The adsorption of bromide ions from the mother liquor produced during the process of mining potassium from rock-salt mines onto D301 anion exchange resin in a Perspex column was investigated. Relevant breakthrough curves were obtained, which would provide valuable information for the process design at a real scale. Experiments were carried out to study the effects of the initial adsorbate concentration, bed length, and flow rate. The bed capacities were found to increase with increasing initial adsorbate concentration and decreasing flow rate. When the initial Br? concentration increased from 1000 mg/L to 4000 mg/L, the adsorption capacity increased from 1.8 mg/mL to 6.4 mg/mL. The breakthrough time and the exhaust time increased with increasing bed length and decreasing flow rate, whereas they remained almost the same when changing the initial adsorbate concentration. Five adsorption models, including Bed Depth Service Time (BDST), Thomas, Yoon-Nelson, Wolborska and Modified dose response (MDR) were applied to predict the breakthrough curves and to determine the characteristic parameters of fixed-bed column. The MDR model was found to be the best fit to the experimental data. This study indicates that the D301 anion exchange resin can be used to extract bromide ions from mother liquors effectively in the competition with high concentrations of chloride ions.

Industrialized application of high efficient extraction of vanadium and chromium by sub-molten salt method

Xindong WANG Lanjie LI Hao DU Beibei ZHAO

Chin. J. Process Eng.. 2020, 20(6): 667-677. DOI: 10.12034/j.issn.1009-606X.219274

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In order to ensure the sub-molten salt project to achieve production and efficiency, the processes of liquid phase oxidation of vanadium slag, liquid?solid separation, crystallization of sodium vanadate and three-effect evaporation were systematically studied. The experimental results showed that under the combined action of nano-micro aeration oxidation and scale-up effect, the sub-molten salt demonstration project can achieve the simultaneous extraction of vanadium and chromium at low temperature (140~180℃) and low pressure (0.6~1.0 MPa), the leaching rates of vanadium and chromium were 93% and 85% respectively. Nano-micro-aerated sub-molten salt technology showed excellent leaching performance for vanadium slag from different raw materials. The automatic vertical filter press adopted three-stage counter-current washing mode, which ensured that the water content of tailings was less than 30wt%, the vanadium content was less than 0.15wt%, and the chromium content was less than 0.05wt%. The crystallization rate of sodium vanadate reached 61.5% by using OSLO cooling crystallizer, and the concentration of circulating alkali solution was increased from 45wt% to 50wt% by adding a temperature and pressure reducer at the steam interface of the three-effect evaporation system. In addition, the leaching of vanadium and chromium from vanadium?chromium mud produced during the treatment of wastewater from traditional sodium roasting process was studied by using submerged salt production line. The efficient leaching of vanadium and chromium from vanadium?chromium mud was achieved under the conditions of reaction temperature of 175℃, reaction pressure of 0.65 MPa and feed-in and feed-out speed of 0.25 t/h. The leaching rates of vanadium and chromium were 93.68% and 96.76%. When the concentration of chromium in solution reaches 25~30 g/L, the crystallization process of sodium chromate can ensure that all the chromium dissolved in each liquid phase oxidation reaction was precipitated, and the crystallization rate of sodium chromate was 17.65%.

Research on the effect of bottom blowing on bath stirring in a 250 t converter

Duogang WANG Nailiang CHENG Xiaobin ZHOU

Chin. J. Process Eng.. 2020, 20(6): 678-686. DOI: 10.12034/j.issn.1009-606X.219281

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This work focus on the effects of bottom blowing operations on the bath mixing, plume velocities, “dead zone” volumes, shear stresses on bottom refractory and gas efficiency of the bottom blowing. It was found that the mixing time increased when bottom blowing flow rate decreased or the tuyere number decreased. The mixing time decreased 54.8% when the bottom blowing flow rate increased from 15 L/min to 50 L/min by applying 12 tuyeres. If the total bottom blowing flow rate was constant (50 L/min), the mixing time increased 52.9%, when 3 tuyeres were applied compared to that of 12 tuyeres. When the tuyere number used in the bottom blowing decreased, the volume of “dead zone” and “low-velocity zone” increased 4.89% and 28.9%, respectively. Moreover, blowing flow rate increased when the tuyere number decreased to 3 when the total flow rate was not changed. The maximum value of velocity in the liquid–gas region increased from 0.34 m/s to 0.64 m/s. As a result, strong shear stress, which was not favorable for bottom refractory, was formed in the vicinity of the bottom blowing tuyeres. The intensity of the shear stress increased 52% on the bottom refractory. Furthermore, based on the numerical analysis results, it was found that the transfer index of bottom blowing gas were affected by the blowing operations. The utilization rate of gas energy of the bottom blowing decreased although the kinetic energy increased with increasing of bottom blowing flow rate. The utilization rate of gas energy was slightly changed if the total flow rate was small. It was also found that higher utilization rate of gas energy of the bottom blowing can be obtained when more tuyeres were applied in the process based on the current model. If the bottom blowing flow rate was 50 L/min, the utilization rate of gas energy decreased 18.4% and 23.3% when the tuyere number decreased from 12 to 6 and 3, respectively.

A new 3D printing molding-degreasing-sintering process

Yaohua CHENG Huiguang BIAN Chuansheng WANG Ning CAI

Chin. J. Process Eng.. 2020, 20(6): 687-694. DOI: 10.12034/j.issn.1009-606X.219304

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In recent years, 3D printing is widely used in various industries due to its advantages. The traditional metal material 3D printing processes are mainly based on selective laser sintering technology. The equipments and raw materials are very expensive. Additionally, because of various limitations of the raw materials and the intensity of the laser beam, there are various problems in the processed parts and their post-treatment process. In China, the equipments for 3D printing and raw materials in the form of metal powder are mostly imported and expensive. Aiming at this situation, a new 3D printing molding?degreasing?sintering process which was based on 316L stainless steel powder and polymer material formulation was proposed in this work. Firstly, the formula material was fully mixed by the open mill, crushed and dried. The particle size of mixed material was relatively uniform. Then, the metal blank was 3D printed by using the self-developed powder feeding 3D printer, and the metal body was degreased by solvent degreasing method. Finally, the sintering experiments were carried out to study the samples obtained under different sintering conditions. The optimum sintering process was obtained through the analysis about physical and mechanical properties of the samples. The results showed that with the increase of sintering temperature, the densification degree of sintered products gradually increased, and the physical and mechanical properties were gradually improved. When the sintering temperature was 1370℃, the physical and mechanical properties of the obtained metal products were the best. The properties of metallurgical products produced by this technology are similar to those produced by traditional powder metallurgy, the sintered density reached 7.43 g/cm3, the tensile strength reached 501.2 MPa, the impact displacement reached 4.54 mm, the elongation reached 27.1%, the bending resistance reached 16.54 KN, and the hardness reached 80.74 HRB. At the same time, through micro-contrast, mechanism analysis and experimental verification, it was proved that 1370℃ was the best sintering condition, and the sintered products had the advantages of uniform composition, fine structure and stable performance. The research of this molding method was beneficial to reduce the cost of metal 3D printing and the difficulty of molding complex metal products, and the method had broad prospects.

Formation and characteristics of used activated coke from flue gas purification process by activated coke in moving bed

Fengqin YU Yunjia LI Zhouen LIU Wensong LI Weidong ZHANG Shiqiu GAO Guangwen XU Jian YU

Chin. J. Process Eng.. 2020, 20(6): 695-702. DOI: 10.12034/j.issn.1009-606X.219268

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The multi-pollutant removal using activated coke (AC) in moving bed under low temperature and dry state showed great prospect in desulfurization and denitrification process of flue gas from steel sintering process. The abrasion of AC in this process was the crucial factors which restricted the wide application of this technology. Being aimed at the used AC which was produced in the process of SOx and NOx removal from Baogang sintering flue gas, the texture properties, including the specific surface area, pore volume structure, the content of heavy metals and alkali metals in ash, surface functional group characteristics and desulfurization and denitration performance of AC were investigated to obtain the formation and variation behavior of used AC. Compared to fresh AC, an obvious increase in the content of N, S and O elements and transition metal oxides were observed in the used AC powder in particle size at 0.2?5 mm, and its specific surface area also increased from 191.0 m2/g to 499.0 m2/g. As a result, the NO conversion rate increased greatly from 20% to 70% at 150℃, and the penetrating sulfur capacity was enhanced from 0.27 mg SO2/g to 11.08 mg SO2/g at 120℃. The used AC exhibited a good potentiality for reutilization.

Analysis of condensation characteristics of moist air in low temperature drying system using circulating hot air

Jinai DOU Shizhong ZHANG Chen YUE

Chin. J. Process Eng.. 2020, 20(6): 703-710. DOI: 10.12034/j.issn.1009-606X.219279

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Air drying is one of the widely used farm products process technologies. Due to the thermal-sensitivity performances of the farm products, the low operation temperature makes waste heat recovery from the drying chamber exhaust wet air become difficult, and the conventional open air-drying process is energy consumption. A novel closed air drying system is proposed through integrating the top air drying cycle and a bottom organic Rankine cycle (ORC). After verified the mathematical model of the wet air waste heat recovery through the wet air condenser, condensed water mass flow rate and the energy saving characteristics of the proposed system were investigated through analyzing the key parameter influences on the overall performance indices. The results showed that under the operation condition in this study, compared to the wet air inlet temperature and mass flow rate, increasing the relative moisture content in the wet air improved the condensed water mass flow rate and heat exchanged substantially. Also the maximal value of mass flow rate of condensed water was obtained with the optimal wet air mass flow rate at 0.10~0.15 kg/s. The overall net power output of the system increased prominently as both the dew point temperature of the drying cabin outlet wet air and the evaporation temperature of the bottom ORC increased. Therefore, for the conventional heat-sensitive farm products drying process, the low drying temperature and high dew point temperature for the wet air at drying chamber outlet, and the evaporation temperature at 313~323 K of the ORC were recommended.

Optimization of reaction conditions for preparation of penicillin G sulfoxide by direct oxidation of penicillin fermentation broth

Feng YAN Weige ZHANG

Chin. J. Process Eng.. 2020, 20(6): 711-717. DOI: 10.12034/j.issn.1009-606X.219233

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The process of direct oxidation of penicillin G sulfoxide with penicillin fermentation broth was studied with peroxyacetic acid as oxidant, and a series of experiments were conducted to investigate the effects of different influencing factors on the conversion rate of penicillin G sulfoxide. The residual penicillin in the mycelium after oxidation was analyzed. The direct oxidation process of penicillin fermentation broth was established and optimized. The results showed that the stirring speed, reaction temperature, peroxyacetic acid feeding dosage and peroxyacetic acid concentration were the key factors affecting the conversion rate of penicillin G sulfoxide, other factors had little effect on the process. Peroxyacetic acid directly oxidized the penicillin fermentation broth and released penicillin remaining in the mycelium. So its conversion rate was higher than the conversion of penicillin G potassium salt. The optimum oxidation process conditions were reaction temperature of 5~10℃, stirring speed of 100 r/min, adding a high concentration of peroxyacetic acid in a molar ratio of 1.3 times of penicillin at 30 minutes, stirring reaction for 10 minutes after adding peroxyacetic acid. The conversion rate of penicillin G sulfoxide reached 98.6%, and the conversion rate increased by 1.2% than that of penicillin G potassium salt.

Performance of selective catalytic reduction of NOx over Ce-Fe/ZSM-5 catalysts for denitrification of gas turbines

Dianer WANG Ling WANG Guolong GAO Xin XU Peng WU Yaping ZHANG

Chin. J. Process Eng.. 2020, 20(6): 718-727. DOI: 10.12034/j.issn.1009-606X.219285

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An effective high temperature denitration catalyst hasn’t been proposed for gas turbine flue gas condition. Therefore, Ce?Fe/ZSM-5 catalyst was prepared to be used in denitration for gas turbine flue gas by impregnation method with ZSM-5 sieved as the carrier, Fe as the active component and Ce as the active additive. Based on the gas turbine flue gas condition, the physical and chemical properties such as denitrification performance, surface acidity and redox ability of the catalyst were systematically studied to research structure-activity relationship between catalyst structure and denitration effect. The results showed that when the Fe load was 4wt%, the NOx conversion rate of Fe/ZSM-5 catalyst was 77.11% at 550℃. The high temperature denitrification effect of Ce?Fe/ZSM-5 catalyst was significantly improved after Ce doping. When the Ce load was 1wt%, the NOx conversion rate remained at 95.92% at 550℃, the catalyst had excellent medium-high temperature catalytic activity, which was 18.81% higher than that of Fe4/ZSM-5. Moreover, the increase of oxygen content and NO2 concentration can improve the selective catalytic reduction (SCR) performance of the catalyst. The hydrothermal aging test showed that the catalyst had good hydrothermal stability. After aging at 10vol% H2O, 600℃ and 10vol% H2O, 800℃, the NOx conversion rate of catalyst was maintained about 90% in the range of 450?550℃. Characterization results indicated that proper cerium doping can promote the dispersion of iron oxides, enhance the content and strength of Lewis acid site, and increase the proportion of absorbed oxygen, the synergistic effect between Ce and Fe also improved the redox ability of catalyst at high temperature, these might be the reason for the better high temperature catalytic activity.

Experimental study on the combustion of typical coal fuels in domestic decoupling stoves

Jian HAN Xinhua LIU Jingdong HE

Chin. J. Process Eng.. 2020, 20(6): 728-736. DOI: 10.12034/j.issn.1009-606X.219258

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Burning bituminous coal, anthracite or semicoke in traditional domestic coal-fired stoves generally suffers from low thermal efficiency and large pollutant emissions, thus causing serious environmental problems. Decoupling combustion technology invented by the Institute of Process Engineering, Chinese Academy of Sciences combines the advantages of both traditional updraft and downdraft combustion modes, which can be used to suppress the emissions of multiple pollutants simultaneously and realize high-efficiency heating and cooking. In this work, in order to clarify the adaptability of domestic decoupling stoves to various civil coal fuels, the pollutant emissions and cooking power of a tested domestic decoupling stove were experimentally investigated by burning several kinds of civil coal fuels such as bituminous lump coal, anthracite lump coal, lump semicoke and bituminous briquettes. Further, the characteristic size of bituminous briquettes was optimized according to the pollutant emissions and cooking power of the tested domestic decoupling stove. The experimental results indicated that the decoupling combustion could facilitate the simultaneous suppression of nitrogen oxides (NOx) and carbon monoxide (CO) emissions because of the unique stove structure and draft type, as well as the reduction of sulfur oxide (SO2) and particulate matter (PM) by using clean briquettes from bituminous coal as the fuels. Briquette size had significant effects on the pollutant emissions of domestic decoupling stoves. If burning bituminous briquettes with optimized sizes in domestic decoupling stoves, the average NO, SO2, CO and PM emission concentrations at the baseline oxygen content of 9vol% were lower than 190, 300, 380 and 30 mg/m3 respectively, and the cooking power was high up to 1.65 kW.

Numerical simulation of combustion process of petroleum coke partially substituting heavy oil in combustion space of float glass furnace

Zhimin WANG Junlin XIE Shuxia MEI Feng HE Mingfang JIN

Chin. J. Process Eng.. 2020, 20(6): 737-744. DOI: 10.12034/j.issn.1009-606X.219278

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The numerical simulation in the combustion space of a float glass furnace was carried out. Under the premise of ensuring the same fuel calorific value, the flow field distribution characteristic of heavy oil combustion and co-combustion of petroleum coke and heavy oil was studied. The results showed that the two fuels can co-fire well, and the temperature system in the furnace was basically unaffected. In contrast, the petroleum coke's ignition time was longer than that of the heavy oil, so the average ignition point of the fuel during co-combustion lags behind when only heavy oil was used and the flame was longer. When the fuel was co-firing, more O2 was needed, the combustion was not enough, and a large amount of CO was generated. Finally, the total NOx emission at the flue gas outlet was reduced by 30.02% compared with the case using heavy oil only, and the NOx emission reduction effect was obvious.

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