Focusing on improving the performance of the hydrogen (H2)-based direct reduction shaft furnace (HSF), the current work was undertaken to evaluate the potential benefits of an operation featuring nitrogen (N2) mixing in feed gas using a computational fluid dynamics (CFD) model that describes the in-furnace gas-solid countercurrent reactive flows. A set of simulation cases was carried out under different N2 flow rates and top pressures. Variation in the latter operating parameter was conducted with the intent to mitigate the issue of H2 dilution caused by N2 mixing. The results showed that the in-furnace thermochemical state deteriorates if the N2 flow rate is inadequate. The state is gradually improved by increasing the N2 flow rate as more sensible heat is delivered into the process, thereby resulting in better degrees of solid reduction and H2 utilization. An increase in the top pressure gives rise to higher gas density that enhances the driving force and thus facilitates the reduction reaction. A higher solid reduction degree is consequently achieved by elevating the top pressure. When the top pressure exceeds 5.0 atm, however, the increase in solid reduction degree becomes marginal, while the energy required for compressing the feed gas continues to rise linearly.
{"title":"Operation enhancement of the H2 shaft furnace: a numerical study on the impact of N2 mixing in feed gas","authors":"Shan Yu, Lei Shao, Zongshu Zou","doi":"10.1515/ijcre-2024-0043","DOIUrl":"https://doi.org/10.1515/ijcre-2024-0043","url":null,"abstract":"\u0000 Focusing on improving the performance of the hydrogen (H2)-based direct reduction shaft furnace (HSF), the current work was undertaken to evaluate the potential benefits of an operation featuring nitrogen (N2) mixing in feed gas using a computational fluid dynamics (CFD) model that describes the in-furnace gas-solid countercurrent reactive flows. A set of simulation cases was carried out under different N2 flow rates and top pressures. Variation in the latter operating parameter was conducted with the intent to mitigate the issue of H2 dilution caused by N2 mixing. The results showed that the in-furnace thermochemical state deteriorates if the N2 flow rate is inadequate. The state is gradually improved by increasing the N2 flow rate as more sensible heat is delivered into the process, thereby resulting in better degrees of solid reduction and H2 utilization. An increase in the top pressure gives rise to higher gas density that enhances the driving force and thus facilitates the reduction reaction. A higher solid reduction degree is consequently achieved by elevating the top pressure. When the top pressure exceeds 5.0 atm, however, the increase in solid reduction degree becomes marginal, while the energy required for compressing the feed gas continues to rise linearly.","PeriodicalId":13934,"journal":{"name":"International Journal of Chemical Reactor Engineering","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141646792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wafa Atba, Abdelaziz Smara, M. Chérifi, François Lapicque, S. Hazourli
The degradation of two textile dye molecules was studied using photochemical processes, both in the absence and presence of light. Various methods were employed, including photolysis/UV, combined H2O2/UV photolysis, Fe2+/UV treatment, Photo-Fenton/UV at 350 nm and Photo-Fenton with solar irradiation. The decolorization efficiency of dyes in aqueous solution was evaluated for two specific dyes: Bromothymol Blue (BTB) and Methyl Green (MG). These experiments were carried out in batch mode. The results demonstrated a synergy between light irradiation and the presence of Fenton’s reagents, such as hydrogen peroxide and divalent iron. In addition, it was demonstrated that direct solar irradiation can be used without specific devices to achieve high efficiency at low cost. In the first part, we checked the impact of the various operating parameters. Reaction efficiencies were compared for the same system in the dark and under the assistance of an artificial or solar light source. In the second part, we studied the parameters of the Photo-Fenton process, such as the initial pH of the solution, the initial concentrations of oxidant, iron catalyst, and dye under irradiation from either light source. Whereas the mere photolysis without Fenton’s reagents allowed decolorization yields below 26 %, addition of the oxidant (H2O2) or the catalyst (Fe(II) species amplified the treatment efficiency. However, the presence of both H2O2 and Fe(II) under light irradiation was shown synergetic with yields ranging from 72 to 85 % depending on the dye worked and the light source: because of its broader spectrum in the UV domain, solar irradiation led to the highest decolorization yields. The above results were obtained for well-defined proportions of dye and reagents: for a 20 mg/l dye solution, Fe(II) catalyst concentration equal to 10−3 M, peroxide concentration of 5.10−2 M and a pH of 3. These conditions allowed optimal production of OH· radicals, allowing high efficiency in systems using solar irradiation.
{"title":"Degradation of bromothymol blue and methyl green from aqueous media by Photo-Fenton: comparison between UV-lamp and sun irradiation","authors":"Wafa Atba, Abdelaziz Smara, M. Chérifi, François Lapicque, S. Hazourli","doi":"10.1515/ijcre-2024-0057","DOIUrl":"https://doi.org/10.1515/ijcre-2024-0057","url":null,"abstract":"\u0000 The degradation of two textile dye molecules was studied using photochemical processes, both in the absence and presence of light. Various methods were employed, including photolysis/UV, combined H2O2/UV photolysis, Fe2+/UV treatment, Photo-Fenton/UV at 350 nm and Photo-Fenton with solar irradiation. The decolorization efficiency of dyes in aqueous solution was evaluated for two specific dyes: Bromothymol Blue (BTB) and Methyl Green (MG). These experiments were carried out in batch mode. The results demonstrated a synergy between light irradiation and the presence of Fenton’s reagents, such as hydrogen peroxide and divalent iron. In addition, it was demonstrated that direct solar irradiation can be used without specific devices to achieve high efficiency at low cost. In the first part, we checked the impact of the various operating parameters. Reaction efficiencies were compared for the same system in the dark and under the assistance of an artificial or solar light source. In the second part, we studied the parameters of the Photo-Fenton process, such as the initial pH of the solution, the initial concentrations of oxidant, iron catalyst, and dye under irradiation from either light source. Whereas the mere photolysis without Fenton’s reagents allowed decolorization yields below 26 %, addition of the oxidant (H2O2) or the catalyst (Fe(II) species amplified the treatment efficiency. However, the presence of both H2O2 and Fe(II) under light irradiation was shown synergetic with yields ranging from 72 to 85 % depending on the dye worked and the light source: because of its broader spectrum in the UV domain, solar irradiation led to the highest decolorization yields. The above results were obtained for well-defined proportions of dye and reagents: for a 20 mg/l dye solution, Fe(II) catalyst concentration equal to 10−3 M, peroxide concentration of 5.10−2 M and a pH of 3. These conditions allowed optimal production of OH· radicals, allowing high efficiency in systems using solar irradiation.","PeriodicalId":13934,"journal":{"name":"International Journal of Chemical Reactor Engineering","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141652729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fengxia An, Yiwen Zhang, Lingyan Le, Ying Yu, Fanhui Shen, Kang Yang, Haitao Hu, Fan Ye, Hui Wang
To adapt to the increasing proportion of new energy power generation capacity, coal power must transition from its traditional role as the primary power source to serving as a fundamental backup and system regulation energy source. The circulating fluidized bed technology is known for its wide range of load regulation capabilities; however, emissions of pollutants during load regulation can exhibit significant variability. This study utilized Aspen Plus software to develop a circulating fluidized bed combustion model based on a gas-solid fluid dynamics model, an equivalent coal pyrolysis model, and a multi-phase macroscopic combustion reaction dynamics model of pyrolysis products. This model was used to predict both the temperature distribution within the furnace chamber and the distribution of pollutant concentrations. Predictions of pollutant emissions from 100 % load to 30 % load of the circulating fluidized bed were explored under the original combustion condition and 5 % proportion of recirculated flue gas. Under the primary combustion condition, the emission concentration of NO x showed a decreasing and then increasing trend with decreasing load, while the concentration of nitrous oxide, in contrast to NO x , showed an increasing and then decreasing trend. The effect of recirculated flue gas on pollutant emissions was not significant at reduced loads. This study aims to provide technical support and theoretical guidance for the management of pollutant emissions from the deep peak regulation of actual circulating fluidized beds.
为适应新能源发电能力比例不断增加的趋势，煤电必须从传统的主要电源角色过渡到基本的备用和系统调节能源。循环流化床技术以其广泛的负荷调节能力而闻名，但在负荷调节过程中，污染物的排放会表现出显著的可变性。本研究利用 Aspen Plus 软件开发了循环流化床燃烧模型，该模型基于气固流体动力学模型、等效煤热解模型和热解产物的多相宏观燃烧反应动力学模型。该模型用于预测炉膛内的温度分布和污染物浓度分布。在原始燃烧条件和 5% 的再循环烟气比例下，对循环流化床从 100% 负荷到 30% 负荷的污染物排放进行了预测。在原燃烧条件下，氮氧化物的排放浓度随着负荷的降低呈先降低后升高的趋势，而氧化亚氮的浓度则与氮氧化物相反，呈先升高后降低的趋势。在降低负荷时，再循环烟气对污染物排放的影响并不显著。本研究旨在为实际循环流化床深度调峰污染物排放管理提供技术支持和理论指导。
{"title":"Investigation on NO and N2O emissions characteristics in deep peak regulation circulating fluidized bed boilers","authors":"Fengxia An, Yiwen Zhang, Lingyan Le, Ying Yu, Fanhui Shen, Kang Yang, Haitao Hu, Fan Ye, Hui Wang","doi":"10.1515/ijcre-2024-0103","DOIUrl":"https://doi.org/10.1515/ijcre-2024-0103","url":null,"abstract":"\u0000 To adapt to the increasing proportion of new energy power generation capacity, coal power must transition from its traditional role as the primary power source to serving as a fundamental backup and system regulation energy source. The circulating fluidized bed technology is known for its wide range of load regulation capabilities; however, emissions of pollutants during load regulation can exhibit significant variability. This study utilized Aspen Plus software to develop a circulating fluidized bed combustion model based on a gas-solid fluid dynamics model, an equivalent coal pyrolysis model, and a multi-phase macroscopic combustion reaction dynamics model of pyrolysis products. This model was used to predict both the temperature distribution within the furnace chamber and the distribution of pollutant concentrations. Predictions of pollutant emissions from 100 % load to 30 % load of the circulating fluidized bed were explored under the original combustion condition and 5 % proportion of recirculated flue gas. Under the primary combustion condition, the emission concentration of NO\u0000 x\u0000 showed a decreasing and then increasing trend with decreasing load, while the concentration of nitrous oxide, in contrast to NO\u0000 x\u0000 , showed an increasing and then decreasing trend. The effect of recirculated flue gas on pollutant emissions was not significant at reduced loads. This study aims to provide technical support and theoretical guidance for the management of pollutant emissions from the deep peak regulation of actual circulating fluidized beds.","PeriodicalId":13934,"journal":{"name":"International Journal of Chemical Reactor Engineering","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141653912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In 2015, the participants of the Paris Agreement collectively acknowledged the urgent need for immediate actions to decarbonize their national economies, with the aim of mitigating the adverse impacts of climate change. There is a call for policymakers to step up efforts to significantly reduce greenhouse gas (GHG) emissions in all economic sectors, with a focus on prioritizing options that can deliver substantial emission cuts. Some industry and transport subsectors present significant challenges in terms of technical and economic feasibility. Viable solutions for these sectors, known as “hard-to-abate” sectors, are limited. Green hydrogen has emerged as a promising alternative that is gaining increasing attention. It is poised to play a crucial role in transitioning towards a more sustainable future. There is a growing interest in green hydrogen among researchers, institutions, and nations, all committed to advancing its development, improving efficiency, and reducing costs. This paper explores the concept of green hydrogen, particularly its production processes that rely on renewable energy sources in Uruguay. It demonstrates the significant potential for green hydrogen production, facilitating the transition from fossil fuels to clean energy and promoting environmental sustainability through the widely accepted electrolysis process. Uruguay currently boasts a high percentage of renewable electricity generation (reaching 97 % in 2020). To support this further, there is a need to increase renewable energy capacity, which would impact the energy prices. The cost of energy accounts for more than 40 % of the levelized cost of hydrogen (LCOH) in all studied scenarios. Additionally, optimizing the costs associated with electrolysers, which can exceed 30 % of the LCOH in polymer electrolyte membrane (PEM) electrolysis, is crucial. This optimization is essential for positioning the country as a net exporter of green hydrogen. The range of LCOH values calculated in the different scenarios is between 2.11 USD/kg H2 and 4.12 USD/kg H2. According to updated specialized literature, achieving LCOH values under USD 1.4/kg H2 is essential for this goal.
{"title":"Green hydrogen production in Uruguay: a techno-economic approach","authors":"Betiana Bouzas, E. Téliz, Verónica Díaz","doi":"10.1515/ijcre-2024-0066","DOIUrl":"https://doi.org/10.1515/ijcre-2024-0066","url":null,"abstract":"\u0000 In 2015, the participants of the Paris Agreement collectively acknowledged the urgent need for immediate actions to decarbonize their national economies, with the aim of mitigating the adverse impacts of climate change. There is a call for policymakers to step up efforts to significantly reduce greenhouse gas (GHG) emissions in all economic sectors, with a focus on prioritizing options that can deliver substantial emission cuts. Some industry and transport subsectors present significant challenges in terms of technical and economic feasibility. Viable solutions for these sectors, known as “hard-to-abate” sectors, are limited. Green hydrogen has emerged as a promising alternative that is gaining increasing attention. It is poised to play a crucial role in transitioning towards a more sustainable future. There is a growing interest in green hydrogen among researchers, institutions, and nations, all committed to advancing its development, improving efficiency, and reducing costs. This paper explores the concept of green hydrogen, particularly its production processes that rely on renewable energy sources in Uruguay. It demonstrates the significant potential for green hydrogen production, facilitating the transition from fossil fuels to clean energy and promoting environmental sustainability through the widely accepted electrolysis process. Uruguay currently boasts a high percentage of renewable electricity generation (reaching 97 % in 2020). To support this further, there is a need to increase renewable energy capacity, which would impact the energy prices. The cost of energy accounts for more than 40 % of the levelized cost of hydrogen (LCOH) in all studied scenarios. Additionally, optimizing the costs associated with electrolysers, which can exceed 30 % of the LCOH in polymer electrolyte membrane (PEM) electrolysis, is crucial. This optimization is essential for positioning the country as a net exporter of green hydrogen. The range of LCOH values calculated in the different scenarios is between 2.11 USD/kg H2 and 4.12 USD/kg H2. According to updated specialized literature, achieving LCOH values under USD 1.4/kg H2 is essential for this goal.","PeriodicalId":13934,"journal":{"name":"International Journal of Chemical Reactor Engineering","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141665200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract This study aimed to investigate the performance of the thin layer nanostructures of Co/Al2O3–ZrO2 in the dry reforming of methane (DRM) in a microchannel reactor. The nanostructures were prepared via utilizing the thermal evaporation method. Reactor tests were carried out at various coating times of 2, 3, and 4 min and temperatures of 700, 750, and 800 °C with a feed flow rate of 10 ml/min and a 1:1:8 ratio of helium, carbon dioxide, and methane. Also, grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) were used to identify catalyst features. According to the obtained results, the highest percentage of conversion in all samples was observed at 800 °C. The results of the reactor tests also revealed that the activity of catalyst layers highly depends on coating time. The findings demonstrated that raising deposition time improves the distribution of particle size and catalyst loading. Considering the nanostructure of Co/Al2O3–ZrO2, the sample undergoing 4 min coating time yielded the highest amount of primary methane conversion (89.3 %), primary carbon dioxide conversion (92.4 %), and H2/CO molar ratio (0.91). The stability test of the catalyst layers for 28 h at the optimum condition (P = 1 atm, T = 800 °C, t = 4 min deposition time, CH4/CO2 = 1, and GHSV = 48,000 mL g−1 h−1) showed that the catalysts prepared by this method had a good stability.
{"title":"Exploring the performance of Co/Al2O3–ZrO2 nanocatalysts developed through the thermal evaporation method in dry reforming of methane","authors":"Mohamad jafar Moradi, G. Moradi","doi":"10.1515/ijcre-2024-0061","DOIUrl":"https://doi.org/10.1515/ijcre-2024-0061","url":null,"abstract":"Abstract This study aimed to investigate the performance of the thin layer nanostructures of Co/Al2O3–ZrO2 in the dry reforming of methane (DRM) in a microchannel reactor. The nanostructures were prepared via utilizing the thermal evaporation method. Reactor tests were carried out at various coating times of 2, 3, and 4 min and temperatures of 700, 750, and 800 °C with a feed flow rate of 10 ml/min and a 1:1:8 ratio of helium, carbon dioxide, and methane. Also, grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) were used to identify catalyst features. According to the obtained results, the highest percentage of conversion in all samples was observed at 800 °C. The results of the reactor tests also revealed that the activity of catalyst layers highly depends on coating time. The findings demonstrated that raising deposition time improves the distribution of particle size and catalyst loading. Considering the nanostructure of Co/Al2O3–ZrO2, the sample undergoing 4 min coating time yielded the highest amount of primary methane conversion (89.3 %), primary carbon dioxide conversion (92.4 %), and H2/CO molar ratio (0.91). The stability test of the catalyst layers for 28 h at the optimum condition (P = 1 atm, T = 800 °C, t = 4 min deposition time, CH4/CO2 = 1, and GHSV = 48,000 mL g−1 h−1) showed that the catalysts prepared by this method had a good stability.","PeriodicalId":13934,"journal":{"name":"International Journal of Chemical Reactor Engineering","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141665606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The Laval nozzle is an important component of the supersonic cyclone to achieve the change of gas–liquid two-phase, and the condensation characteristics of the Laval nozzle have an important influence on the separation performance of the supersonic cyclone. In this work, the effect of inlet water vapor mass fraction on the condensation characteristics in the Laval nozzle was investigated using numerical simulation and experimental methods by establishing a three-dimensional numerical model of air-water vapor supersonic condensation flow. The flow field structures in the Laval nozzle under different inlet water vapor mass fractions were investigated, including Mach number, pressure, and temperature and the effects of the inlet water vapor mass fraction on the liquefaction characteristics in the Laval nozzle were investigated. In addition, the droplet distribution in the Laval nozzle were also tested by a particle image velocimetry (PIV) experimental system. The comparison of simulation and experimental results indicates that the numerical model established in this work can effectively describe the real flow situation in the Laval nozzle. The results show that the inlet water vapor mass fraction has a little effect on the flow field structure in the Laval nozzle, and has the significant impact on the water vapor condensation characteristics. With increasing the inlet steam mass fraction from 5 % to 12.5 %, the nucleation rate, droplet number, and separation efficiency in the Laval nozzle increase to 4.05 × 1021 kg−1 s−1, 3.67 × 1014 kg−1, and 79.4 %, respectively, and when further increasing the inlet steam mass fraction to 15 %, these parameters decrease.
{"title":"Effect of inlet water vapor mass fraction on flow characteristics in Laval nozzle","authors":"Lu Wang, Zhenhua Zhai, Jiansheng Chen, Guanghui Chen, Fei Gao, Jipeng Dong","doi":"10.1515/ijcre-2024-0039","DOIUrl":"https://doi.org/10.1515/ijcre-2024-0039","url":null,"abstract":"Abstract The Laval nozzle is an important component of the supersonic cyclone to achieve the change of gas–liquid two-phase, and the condensation characteristics of the Laval nozzle have an important influence on the separation performance of the supersonic cyclone. In this work, the effect of inlet water vapor mass fraction on the condensation characteristics in the Laval nozzle was investigated using numerical simulation and experimental methods by establishing a three-dimensional numerical model of air-water vapor supersonic condensation flow. The flow field structures in the Laval nozzle under different inlet water vapor mass fractions were investigated, including Mach number, pressure, and temperature and the effects of the inlet water vapor mass fraction on the liquefaction characteristics in the Laval nozzle were investigated. In addition, the droplet distribution in the Laval nozzle were also tested by a particle image velocimetry (PIV) experimental system. The comparison of simulation and experimental results indicates that the numerical model established in this work can effectively describe the real flow situation in the Laval nozzle. The results show that the inlet water vapor mass fraction has a little effect on the flow field structure in the Laval nozzle, and has the significant impact on the water vapor condensation characteristics. With increasing the inlet steam mass fraction from 5 % to 12.5 %, the nucleation rate, droplet number, and separation efficiency in the Laval nozzle increase to 4.05 × 1021 kg−1 s−1, 3.67 × 1014 kg−1, and 79.4 %, respectively, and when further increasing the inlet steam mass fraction to 15 %, these parameters decrease.","PeriodicalId":13934,"journal":{"name":"International Journal of Chemical Reactor Engineering","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141687506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract A computational fluid dynamics coupled population balance model (CFD-PBM) was used to numerically simulate the fluid dynamics of bubble swarms in a bubble column containing non-Newtonian fluids. The effects of superficial gas velocity (U g ), the consistency index (K), and the flow index (n) on bubble size distribution (BSD), gas holdup, and fluid dynamic viscosity in a bubble column were analyzed at both local and overall scales. As U g increases, the bubble breakup occurs excessively, the gas holdup increases, and the dynamic viscosity decreases. K and n were used to characterize the rheological properties of power law fluid. As K increases, fluid viscosity increases, bubble breakup rate decreases, gas holdup in the top zone is slightly lower than in the middle zone, and dynamic viscosity increases. Within the range of n from 0.45 to 1.07, when n is smallest, the relative frequency of bubbles smaller than the initial size is relatively large, and the overall and local gas holdup are the highest. When n = 1.07, the fluid exhibits shear-thickening properties, and the dynamic viscosity variations are significant.
摘要 采用计算流体动力学耦合种群平衡模型（CFD-PBM）对含有非牛顿流体的气泡柱中气泡群的流体动力学进行了数值模拟。从局部和整体尺度分析了表层气体速度（U g）、稠度指数（K）和流动指数（n）对气泡柱中气泡大小分布（BSD）、气体滞留和流体动态粘度的影响。随着 U g 的增大，气泡破裂过度，气体滞留增加，动态粘度降低。K 和 n 用于描述幂律流体的流变特性。随着 K 的增大，流体粘度增大，气泡破裂率降低，顶部区域的气体滞留略低于中间区域，动态粘度增大。在 n 从 0.45 到 1.07 的范围内，当 n 最小时，小于初始尺寸的气泡的相对频率相对较大，整体和局部气体截留率最高。当 n = 1.07 时，流体表现出剪切增稠特性，动态粘度变化显著。
{"title":"CFD-PBM simulation of power law fluid in a bubble column reactor","authors":"Mengqiang Duan, Shao-Bai Li, Manju L. Bhusal, Wei Zhang, Yuhuan Ding","doi":"10.1515/ijcre-2024-0010","DOIUrl":"https://doi.org/10.1515/ijcre-2024-0010","url":null,"abstract":"Abstract A computational fluid dynamics coupled population balance model (CFD-PBM) was used to numerically simulate the fluid dynamics of bubble swarms in a bubble column containing non-Newtonian fluids. The effects of superficial gas velocity (U g ), the consistency index (K), and the flow index (n) on bubble size distribution (BSD), gas holdup, and fluid dynamic viscosity in a bubble column were analyzed at both local and overall scales. As U g increases, the bubble breakup occurs excessively, the gas holdup increases, and the dynamic viscosity decreases. K and n were used to characterize the rheological properties of power law fluid. As K increases, fluid viscosity increases, bubble breakup rate decreases, gas holdup in the top zone is slightly lower than in the middle zone, and dynamic viscosity increases. Within the range of n from 0.45 to 1.07, when n is smallest, the relative frequency of bubbles smaller than the initial size is relatively large, and the overall and local gas holdup are the highest. When n = 1.07, the fluid exhibits shear-thickening properties, and the dynamic viscosity variations are significant.","PeriodicalId":13934,"journal":{"name":"International Journal of Chemical Reactor Engineering","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141335349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work reports a CFD-DEM study on the segregation and mixing of binary mixtures of particles in a bubbling fluidized bed. A simplified mixing index was applied to determine the instantaneous mixing state in the bed, with which the effects of superficial gas velocity and initial packing state on the fluidization behavior were further discussed. For the well-mixed initial conditions, the mixing index decreases with fluidization time until a dynamic equilibrium between segregation and mixing is achieved. In contrast, the mixing index first increases and then decreases with fluidization time for completely-segregated initial conditions. However, the final equilibrium between segregation and mixing will not be affected by initial packing states for a given superficial gas velocity. Moreover, the bubbling behavior shows a marked impact on segregation and mixing, i.e., mixing is enhanced during the formation and grow-up of bubbles, while segregation is strengthened during the eruption of bubbles. This makes it possible to improve the fluidization of binary mixtures of particles based on the bubbling behaviors in the fluidized bed.
{"title":"Segregation and mixing of binary mixtures of spherical particles in a bubbling fluidized bed","authors":"Shan Ren, Zhong Zheng, Hongsheng Chen","doi":"10.1515/ijcre-2024-0035","DOIUrl":"https://doi.org/10.1515/ijcre-2024-0035","url":null,"abstract":"\u0000 This work reports a CFD-DEM study on the segregation and mixing of binary mixtures of particles in a bubbling fluidized bed. A simplified mixing index was applied to determine the instantaneous mixing state in the bed, with which the effects of superficial gas velocity and initial packing state on the fluidization behavior were further discussed. For the well-mixed initial conditions, the mixing index decreases with fluidization time until a dynamic equilibrium between segregation and mixing is achieved. In contrast, the mixing index first increases and then decreases with fluidization time for completely-segregated initial conditions. However, the final equilibrium between segregation and mixing will not be affected by initial packing states for a given superficial gas velocity. Moreover, the bubbling behavior shows a marked impact on segregation and mixing, i.e., mixing is enhanced during the formation and grow-up of bubbles, while segregation is strengthened during the eruption of bubbles. This makes it possible to improve the fluidization of binary mixtures of particles based on the bubbling behaviors in the fluidized bed.","PeriodicalId":13934,"journal":{"name":"International Journal of Chemical Reactor Engineering","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140961838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The effect of temperature and silicon concentration on iron precipitation and morphology of hematite particles was discussed. The results showed that increase of initial silicon centration will lead to the decrease of iron removal efficiency, and the Fe content decreases and S content increases in hematite. Increasing temperature is beneficial to increase iron removal rate and Fe content in hematite, but increasing temperature can not decrease silicon content in hematite. The content of Si in precipitate is proportional to the concentration of silicon in solution. Silicon is adsorbed on the surface of hematite in the form of silicic acid. Hematite particle was agglomerated microsphere. Increasing concentration of silicon will increase the disorder degree of hematite crystallization. With the increase of silicon concentration, the agglomeration of hematite particle was more obvious, and the average particle size of hematite particles increased. At 175 °C, the morphology of iron precipitation particles are composed of flake particles and rhomboid massive particles, but when the temperature rises to 195 °C, the agglomeration phenomenon is obvious, small flake particles agglomerate into microspherical aggregates.
{"title":"Hydrothermal precipitation of hematite from the model solution of zinc hydrometallurgical extraction","authors":"Chunlin Li, Zhigan Deng, Fuxian Yang, Chang Wei, Xingbin Li, Minting Li","doi":"10.1515/ijcre-2023-0073","DOIUrl":"https://doi.org/10.1515/ijcre-2023-0073","url":null,"abstract":"Abstract The effect of temperature and silicon concentration on iron precipitation and morphology of hematite particles was discussed. The results showed that increase of initial silicon centration will lead to the decrease of iron removal efficiency, and the Fe content decreases and S content increases in hematite. Increasing temperature is beneficial to increase iron removal rate and Fe content in hematite, but increasing temperature can not decrease silicon content in hematite. The content of Si in precipitate is proportional to the concentration of silicon in solution. Silicon is adsorbed on the surface of hematite in the form of silicic acid. Hematite particle was agglomerated microsphere. Increasing concentration of silicon will increase the disorder degree of hematite crystallization. With the increase of silicon concentration, the agglomeration of hematite particle was more obvious, and the average particle size of hematite particles increased. At 175 °C, the morphology of iron precipitation particles are composed of flake particles and rhomboid massive particles, but when the temperature rises to 195 °C, the agglomeration phenomenon is obvious, small flake particles agglomerate into microspherical aggregates.","PeriodicalId":13934,"journal":{"name":"International Journal of Chemical Reactor Engineering","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139122076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The effect of temperature and silicon concentration on iron precipitation and morphology of hematite particles was discussed. The results showed that increase of initial silicon centration will lead to the decrease of iron removal efficiency, and the Fe content decreases and S content increases in hematite. Increasing temperature is beneficial to increase iron removal rate and Fe content in hematite, but increasing temperature can not decrease silicon content in hematite. The content of Si in precipitate is proportional to the concentration of silicon in solution. Silicon is adsorbed on the surface of hematite in the form of silicic acid. Hematite particle was agglomerated microsphere. Increasing concentration of silicon will increase the disorder degree of hematite crystallization. With the increase of silicon concentration, the agglomeration of hematite particle was more obvious, and the average particle size of hematite particles increased. At 175 °C, the morphology of iron precipitation particles are composed of flake particles and rhomboid massive particles, but when the temperature rises to 195 °C, the agglomeration phenomenon is obvious, small flake particles agglomerate into microspherical aggregates.
{"title":"Hydrothermal precipitation of hematite from the model solution of zinc hydrometallurgical extraction","authors":"Chunlin Li, Zhigan Deng, Fuxian Yang, Chang Wei, Xingbin Li, Minting Li","doi":"10.1515/ijcre-2023-0073","DOIUrl":"https://doi.org/10.1515/ijcre-2023-0073","url":null,"abstract":"Abstract The effect of temperature and silicon concentration on iron precipitation and morphology of hematite particles was discussed. The results showed that increase of initial silicon centration will lead to the decrease of iron removal efficiency, and the Fe content decreases and S content increases in hematite. Increasing temperature is beneficial to increase iron removal rate and Fe content in hematite, but increasing temperature can not decrease silicon content in hematite. The content of Si in precipitate is proportional to the concentration of silicon in solution. Silicon is adsorbed on the surface of hematite in the form of silicic acid. Hematite particle was agglomerated microsphere. Increasing concentration of silicon will increase the disorder degree of hematite crystallization. With the increase of silicon concentration, the agglomeration of hematite particle was more obvious, and the average particle size of hematite particles increased. At 175 °C, the morphology of iron precipitation particles are composed of flake particles and rhomboid massive particles, but when the temperature rises to 195 °C, the agglomeration phenomenon is obvious, small flake particles agglomerate into microspherical aggregates.","PeriodicalId":13934,"journal":{"name":"International Journal of Chemical Reactor Engineering","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139114267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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