Agglomeration Mechanism Research Articles

CFD-DEM investigation on the agglomeration behavior of micron-sized combusted iron fines

The occurrence of agglomeration due to particle sintering is one of the most significant technical issues hindering the direct reduction process of iron oxide fines (DRI) in a high-temperature fluidized bed. To get a better understanding of the agglomeration mechanism, the (de-)fluidization behavior of micron-sized iron oxide particles in a 3-D fluidized bed is investigated using Computational Fluid Dynamics coupled with a coarse-grained Discrete Element Method (CFD-cgDEM). The inter-particle cohesive force is considered as a temperature-dependent solid bridge force. The coarse-grained method is first verified by comparing results for different scaling factors. Subsequently, the effects of temperature on the bed pressure drop, void fraction distribution, particle velocity distribution, and agglomerate size are investigated. In conclusion, the developed model shows the capacity for reliable prediction of particle agglomeration behavior, which can shed light on the design of the DRI process in high-temperature fluidized beds.

Toward carbon neutrality: The impact of manufacturing agglomeration on total factor energy efficiency

Improving energy efficiency is an effective way to achieve carbon neutrality in the context of growing advocacy for a green economy in both academia and government. In this study, we analyzed the impact mechanism of the manufacturing agglomeration on total factor energy efficiency. Based on this work, we identified 30 provinces (autonomous regions and municipalities) in China using 2002 to 2017 panel data. We used the data envelopment analysis game cross-efficiency model to calculate the interprovincial current state of energy efficiency. We constructed a spatial Durbin model and used an adjacent space weight matrix, geographic distance weight matrix, and economic distance weight matrix to study the impact of manufacturing agglomeration on total factor energy efficiency. The results showed that under different spatial weights, the interprovincial total factor energy efficiency had a significant spatial dependence; under the three spatial weights, we identified a U-shaped relationship between manufacturing agglomeration and total factor energy efficiency. Industrial agglomeration had obvious spatial spillover effects on total factor energy efficiency, and the spillover effects under the weight of geographic distance were higher than other spatial weights. During the sample period, the direct, indirect, and total effects of the manufacturing industry had an impact on energy efficiency. It all had a negative number indicating that there was a crowding effect in manufacturing agglomeration, and it had an inhibitory effect on energy efficiency.

Biologically produced elemental sulfur clogging induced by thiols in gas biodesulfurization systems

The gas bio-desulfurization process involves the biotic oxidation of hydrogen sulfide (H2S) into hydrophilic and usable sulfur, which possesses favorable settleability, facilitating its separation and recovery from the bioreactor. Nonetheless, in thiol-containing gas bio-desulfurization systems, elemental sulfur is prone to aggregating and adhering to packings, pipes, pumps, and valves, leading to sulfur clogging and impeding the operation of the BDS process. This study systematically investigates the underlying mechanisms of sulfur agglomeration and clogging. A suite of analytical techniques, including laser diffraction, scanning electron microscopy (SEM), electrophoretic light scattering (ELS), X-ray diffraction (XRD), and sessile drop method, were employed to analyze the sulfur clogging phenomenon. The results reveal that the presence of thiols is a primary contributor to sulfur agglomeration and clogging. Thiols are commonly found in natural gas, biogas, and landfill gas and have a lowering effect on the surface hydrophilicity of sulfur particles, making them more hydrophobic and exacerbating sulfur aggregation. The accumulation of more agglomerated and less hydrophilic sulfur particles on packings and pipes leads to sulfur clogging. It occurs due to the nucleophilic S8 dissolution that promotes polysulfide formation and removes the hydrophilic biomacromolecules on the particle surface, making the sulfur particles more prone to aggregation. This study represents a pioneering effort to illuminate the mechanism behind sulfur clogging and attribute it to thiols, offering valuable insights for addressing the industrial challenge of sulfur clogging and expanding the application scope of gas bio-desulfurization.

Research on innovative mechanisms of financial agglomeration enabling green coordinated development in the Yangtze River Delta of China

Exploring innovative mechanisms for financial agglomeration affecting the green coordinated development of China's Yangtze River Delta is important for the city to take advantage of financial and innovative resources to promote high-quality green development. Using panel data from 41 cities in the Yangtze River Delta region from 2003 to 2019, the intermediate effects model and spatial Durbin model are conducted to deeply explore the impact of financial agglomeration on coordinated green development and the intermediary role of innovation. Results show that, first, financial agglomeration can drive green technology innovation to significantly improve the coordinated development of “production greening - social optimization - environmental protection deepening”. Second, financial agglomeration significantly improves the green coordinated development in neighboring areas through inter-city innovative spatial connections, and the spatial spillover effect tends to decay with the critical point of the maximum impact range at 240 km. Third, the intermediate mechanism of green technology innovation performs well in the high-level financial agglomeration and financial capital agglomeration areas. The Banking and securities industries are the leading factors in financial capital agglomeration. Low-level financial agglomeration and financial personnel agglomeration cannot play the “driving green” role of the innovation mechanism.

Population Balance Modeling of Diastereomeric Salt Resolution

Diastereomeric salt crystallization is a classical, widely applicable chiral resolution technique, which enables the separation of the enantiomers of both racemate and conglomerate-forming compounds. A resolution method for racemic pregabalin with l-tartaric acid was developed to obtain pure (S)-pregabalin l-tartrate monohydrate crystals with the yield ranging from 43 to 50%. A series of designed resolution experiments were executed at different cooling rates and temperature end points to estimate the crystallization kinetics using population balance modeling. Inline ATR-FTIR measurements of these experiments were used to calculate concentrations in the crystallization phase and to collect solid–liquid equilibrium data by the solubility trace method after product sampling. Since diastereomeric salts are dissociable ionic compounds, solubility product expressions were used in the model to express the relative supersaturation as the driving force of crystallization. As a result, a population balance model with secondary nucleation, growth, and agglomeration mechanisms was identified, and the simulated supersaturation profiles and product size distributions well reproduced the measured data.

Analysis of agglomeration behaviors of aluminized composite propellants

To improve the performance of aluminized propellants, it is important to study the mechanism of agglomeration and approve the methods of inhibiting agglomeration. In this study, organic fluoride was added to the propellants and the dynamic combustion process of the propellants was obtained through visual combustion test system. At the same time, an algorithm which can detect the size of particles out of focus more accurately is also proposed. Then, the agglomeration behaviors, as well as the size distribution of initial condensed products and final condensed products, during the combustion of propellants are discussed. The influence of organic fluoride additive on the evolution of condensed products and the distribution of their sizes were also analyzed. The results show that the condensed products had a coral structure, and underwent the stages of exposure, accumulation, splicing, separation, and combustion to evolve into oxidation cap structures. When organic fluoride is added, special flocculent products were formed instead of coral-like products and the AlF3 was found in the condensed products. Besides, detailed behaviors of condensed products have been found in the gas. The products with an oxidation cap still subsequently interacted with one another in the gas, including through re-fusion and re-separation. The distribution of the initial products was relatively concentrated and stable while that of the final products exhibited a prominent trend of increasing first, then decreasing, and gradually stabilizing. Besides, with the addition of organic fluoride, the main combustion products were converted α - Al2O3 and θ - Al2O3 to γ - Al2O3 and δ - Al2O3, indicating that the addition of organic fluoride significantly improved the performance of the aluminized propellants in terms of suppressing the size of the condensed products.

Design and mechanism of agglomeration of aspirin crystals in pure solvents

Agglomeration with improved flowability for platy crystals is desirable in pharmaceutical downstream processing. The formation of agglomerates in pure solvents without the aid of bridging liquids is a convenient and low-cost method compared with complex spherical crystallization. In this work, the adhesion free energies between aspirin crystals in six solvents were calculated using Lifshitz-van der Waals acid-base theory to screen suitable solvents for agglomeration. The maximum stirring rate for agglomeration was determined by adhesion forces and dispersion forces. Then the agglomerates of plate-shaped aspirin were successfully prepared in acetone, methanol, ethanol, 2-propanol, and ethylene glycol without additives by simple cooling crystallization. The interactions between solvent and crystal surfaces were also used to explain the outcomes. A feasible mechanism for the agglomeration process of platy crystals was elucidated, involving the adhesion of dominant crystal facets at the beginning. The effect of stirring rate, cooling rate, and initial supersaturation on agglomeration degree and particle size of aspirin agglomerates were studied. The obtained aspirin agglomerates under the optimal conditions exhibited a uniform particle size distribution, a high agglomeration degree, and superior flowability.

Study on the ignition combustion and agglomeration mechanism of GAP/CL-20 composite propellants

Study on the ignition combustion and agglomeration mechanism of GAP/CL-20 composite propellants

The impact and transmission mechanisms of financial agglomeration on eco-efficiency: Evidence from the organization for economic co-operation and development economies

Whether financial agglomeration is conducive to eco-efficiency is of great importance for countries to better pursue cleaner production, low carbon emission reduction, and sustainable development paths. This paper focuses on 38 Organization for Economic Co-operation and Development (OECD) members. Based on the scientific accounting of green eco-efficiency by the super-efficiency slack-based measure (SBM) model, the relationship between financial agglomeration and eco-efficiency is thoroughly investigated by combining the spatial Durbin model (SDM), the mediating effects model, and the panel threshold regression (PTR) model, bridging the knowledge gap. Empirical results reveal that (1) Financial agglomeration has strong positive externalities for eco-efficiency in the home country and its neighbors, with the trickle-down effect playing a key role. (2) Financial agglomeration can indirectly promote cleaner production and eco-efficiency by strengthening technological innovation and upgrading industrial structure, with the latter being more strongly mediated. (3) The effect of financial agglomeration in enhancing eco-efficiency has clear stage differences. The low-level financial agglomeration will impede the improvement of green eco-efficiency while the high-level will support it, which is in line with the Environmental Kuznets Curve theory and the law of economic development. The research broadens the theoretical underpinnings of financial agglomeration and eco-efficiency and provides guidance and implications for OECD members and other emerging economies on how to optimize the spatial allocation of financial resources, promote eco-efficiency, and advance green sustainable development.

Regeneration of iron fuel in fluidized beds, Part I: Defluidization experiments and theoretical prediction model

Hydrogen-based direct reduction of iron oxide powder in gas-fluidized beds has become an emerging technology. Agglomeration of fine powder at elevated temperatures is however one key issue hindering the technological development. To obtain better knowledge of the high-temperature agglomeration mechanism, the (de-)fluidization behavior of micron-sized combusted iron particles is experimentally studied in this Part I. Effects of various operating and material variables (temperature, gas flow rate, and particle size) on the fluidization and agglomeration behavior are investigated. Different fluidization regimes (e.g. stable fluidization, agglomerating fluidization, fast defluidization) are categorized based on the experimental results. A theoretical model based on the force balance is developed to predict the regime boundaries of fluidization. The obtained knowledge is applied for experimental design of the hydrogen-based iron direct reduction process in Part II.

Study on the Layout of Ecological Space and the Integrated Management Mechanism of the Yangtze River Delta Urban Agglomeration

The urban agglomeration at the Yangtze River Delta is one of the six most developed and populated urban agglomerations in the world. In recent years, with accelerating urbanization, the land use has changed significantly. Excessive construction aggravates ecological fragility. In this context, this paper first investigates the evolutionary processes and layout of the ecological space in the Yangtze River Delta. The root causes of various problems are then analyzed. Finally, suggestions for further improvement in both detailed tasks and governance aspects are proposed. The applied methods included use of remote sensing (RS), geographic information system (GIS) and statistical analysis. Main results indicate that from 1990 to 2018, the ecological space of the Yangtze River Delta shrank, especially in the city of Shanghai. Ecological space is insufficient in the area, unevenly distributed and fragmented. The major root causes include rapid urbanization without overall planning, regional population surge and improper industrial structure. Suggestions for improvement include overall planning and integrated management, control of population size, active industry structure upgrade, land-use efficiency balanced with ecological indicators, and multiple integrated strategies encouraging application of new energy technologies.

The clustering of knowledge-intensive business services in Greater Mexico City, 2010 through 2020

This article analyzes knowledge-intensive business services (KIBS) clustering and location patterns in Greater Mexico City. Although there is evidence of the importance of KIBS clustering as a factor that precedes innovation, no empirical work has applied point pattern analysis methods to identify intrametropolitan patterns. Little is known about KIBS firms clustering in Mexico and emerging economies in general. This study responds to both challenges, using the M and m functions, point pattern analysis methods that allow capturing concentration intensity and overdensity of same-type KIBS firms, respectively. Firm-level data are taken from Mexico’s National Statistics and Geography Institute’s (INEGI) open-source databases for 2010 and 2020. Results suggest different clustering patterns given our proposed KIBS classification. Overall, the clustering intensity of KIBS firms by class has increased during the analyzed period (2010–2020). Also, although central Greater Mexico City is the main clustering pole of attraction, urban subcenters display KIBS firms clustering depending on proposed KIBS classes. Clustering patterns are explained given existing intrametropolitan infrastructure and value-added differences, but also within- and between-class concentration variations. Despite the lack of firm-level economic data, results allow inferring possible agglomeration mechanisms behind clustering patterns.

Industrial structure optimization, population agglomeration, and carbon emissions—Empirical evidence from 30 provinces in China

The sustainability of the ecological environment has been greatly threatened. Based on carbon emissions and combined with the panel data of 30 provinces in China from 2003 to 2020, this paper studied the various mechanisms of industrial structure optimization and population agglomeration on carbon emissions. The fixed effect model, panel threshold model and spatial spillover model are used to study the direct and indirect effects of industrial structure optimization and population agglomeration on carbon emissions, and the robustness of the results is tested in various ways. In terms of direct effects, the industrial structure optimization has a significant negative effect on carbon emissions, and the significance level is 1%. Population agglomeration has a significant positive effect on carbon emissions, with a significance level of 1%. In terms of indirect effects, 1) by adding the cross term of industrial structure optimization and population agglomeration, it is proved that population agglomeration can promote the carbon emission reduction effect of industrial structure optimization. 2) Population agglomeration was used as the threshold variable to verify the interval effect of industrial structure optimization on carbon emission reduction. The results show that the industrial structure optimization has a double threshold effect of population agglomeration on carbon emissions, and the threshold values are 2.1137 and 5.9263, respectively. And the larger the population agglomeration interval, the weaker the inhibition effect of industrial structure optimization on carbon emissions. 3) The industrial structure optimization, population agglomeration and carbon emissions have significant spatial spillover effects. The industrial structure optimization in neighboring areas has a significant inhibitory effect on carbon emissions, and the population agglomeration in neighboring areas has a significant promoting effect on carbon emissions.

A study of the spillover effects of digital financial agglomeration on economic resilience

IntroductionDigital finance is the combination of digital information technology and traditional finance. And digital financial agglomeration plays a pivotal role in the process of improving economic resilience in the new era.MethodThis paper introduces digital financial agglomeration, measures the economic resilience of each province and conducts spatial correlation tests by using 30 inter-provincial (except Hainan Province) panel data from 2011 to 2020, and constructs a Spatial Durbin Model to empirically analyze the relationship between digital financial agglomeration and economic resilience based on the theory of diffusion effect of digital financial agglomeration and research hypotheses.ResultThe results show that: (1) Digital financial agglomeration can have a positive effect on economic resilience by expanding the scale of consumption. (2) Digital financial agglomeration has a direct effect on the economic resilience of the region and an indirect spillover effect on the economic resilience of neighboring regions. (3) The effects of the main explanatory variables on economic resilience pass the robustness test: the positive effects of digital financial agglomeration, consumption scale and the interaction term of the two on economic resilience are significant.DiscussionThis paper focuses on the phenomenon of digital financial agglomeration, which is a unique perspective, and explores the influence mechanism of digital financial agglomeration on economic resilience from the perspective of spatial spillover effects of digital financial agglomeration, which is somewhat innovative.

A Study of the Spatial Mechanism of Financial Agglomeration Affecting Green Low-Carbon Development: Evidence from China

China has stepped into the assertive stage of transforming the economic development mode and economic growth momentum, while green and low-carbon development is undoubtedly the way to promote high-quality economic development in the new period. As the core of modern economic growth, the spatial scale concentration of finance plays a crucial role in the development of economic transformation. In this paper, the SBM-GML production index method was used to measure the green low-carbon development level of 30 provinces in China from 2003 to 2019. It also empirically examines the impact and effect of financial agglomeration on green low-carbon development from a two-dimensional perspective of time and space using a systematic generalized matrix and a spatial dynamic panel model. At the same time, the spatial spillover effects of financial agglomeration were measured using a partial differential approach combined with the mediating effect model to reveal the path of financial agglomeration on green low-carbon development. It was found that, firstly, financial agglomeration achieves green low-carbon, and high-quality development through economic growth, industrial structure upgrading, and technological innovation improvement. It also achieves the enhancement of green, low-carbon development through the dual improvement of green technological progress and green technological efficiency. Second, financial agglomeration can enhance the green low-carbon development of neighboring regions; the positive effect of financial agglomeration has a significant positive spatial spillover. Third, the relationship between financial agglomeration and green low-carbon development shows a significant inverted U-shaped relationship, i.e., short-term promotion and long-term inhibition; at present, financial agglomeration, as a whole, has not crossed the critical value but still has a promotional effect on green low-carbon development. Finally, this article points out that in order to effectively promote green, low-carbon development, China needs to continuously promote the formation and optimization of financial agglomeration and make concerted efforts in economic growth, industrial structure upgrading, and technological progress.

РОЛЬ «ПЕРВЫХ» И «ВТОРЫХ» ГОРОДОВ В РАЗВИТИИ УРАЛЬСКИХ РЕГИОНОВ (НА ПРИМЕРЕ СВЕРДЛОВСКОЙ И ЧЕЛЯБИНСКОЙ ОБЛАСТЕЙ)

In regional development, a significant role is played by cities that have the status of “first” (the largest city population in the region) and “second” (the second largest population). As a rule, high economic activity (resources, investments, production, etc.) and a rich social life of the population are concentrated there. Indeed, the importance of the “first” and “second” cities in the socio-economic development of the region is high; in their impact on the distribution of labor and material resources throughout the region; in the possibility of influence of these cities on the development of territories through agglomeration mechanisms; in ensuring the quality of life of the population. In this context, the authors show the importance of “first” and “second” cities in the economic and social development of territories that ensure an adequate quality of life for the population of the Ural regions. The main results of the study indicate that there are some problems with population in “first”, and “second” (to a greater extent) cities of the Ural regions: a decrease in the living population; uneven and asymmetric intra-regional migration (gravitating towards regional centers); negative trends in relation to natural population growth (mortality significantly exceeds birth rate). At the same time, these cities have the potential for industrial development and positive trends in ensuring the quality of the urban environ-ment. Based on the analysis, the authors conclude that it is necessary to optimize the settlement and in-dustrial frameworks of the region, the key points of which are connected both with large “first” cities and with “second” cities of the region. At the same time, it is necessary to strengthen the role and dy-namic development of “second” cities. In the hierarchy of urban architecture, cities, performing a func-tional role of the second level, should become the focus of socio-economic development of municipali-ties, a point of attraction for business activity, ensuring the connectivity of territories within the frame-work of agglomeration processes.

Experimental and mechanical analyses of dust agglomeration on photovoltaic surfaces due to condensation

The dust deposited on a photovoltaic (PV) surface decreases the photoelectric efficiency of a module, leading to potential security risks. A few studies have demonstrated that condensation affects dust accumulation on PV surfaces; however, the mechanism remains unclear. Therefore, this study investigated the effects of dust agglomeration dynamic factors on PV surfaces using micro-experiments and mechanical analysis. An experimental platform for dust particle agglomeration due to condensation was designed and developed, and microscopic experiments were conducted to study the dust particle agglomeration process on the PV panel surface. The particles on the hydrophilic PV surface were confirmed to agglomerate owing to condensation. The particle agglomeration process on the hydrophilic PV surface primarily entails three typical processes that occur sequentially: fusion between droplets, fusion between the semi-submerged particles and droplets, and agglomeration between semi-submerged particles. The particles agglomerated on the hydrophilic PV surfaces have a tiled morphology. An analysis of the particle agglomeration mechanism on the hydrophilic PV surface due to condensation was performed. Water surface tension was identified as the main dynamic factor leading to particle agglomeration during condensation. The results provide theoretical guidance for reducing the dust deposited on PV surfaces.

Spatial development and management of strategy for socioeconomic growth of macroregions in Russia

This article deals with issues of spatial development and management of strategy for socioeconomic growth of macroregions with analysis of internal and external directions that impede the spatial development. A system was formulated for management of macroregions’ spatial development. Strategic objectives were determined for priority social and economic development areas. A structure of rural conglomerations was considered where rural areas shall be adjacent to each other or border with hamlet areas, that is, they shall have neighboring borders of municipal settlement with number of permanent populations of not more than 30,000 residents. The conditions for the formation of an agricultural agglomeration mechanism for the development of agricultural patterns in a strategic perspective with the provision of socio-economic effects in the implementation of the set targets are determined. Establishment of agricultural collaborative and corporate clusters was substantiated considering general requirements formulated. The indicators were formulated for productive and economic activities related with structural, dynamic and target block of economic growth.

DEVELOPMENT OF THE SOUTH-BASHKORTOSTAN AGGLOMERATION: PROBLEMS AND PROSPECTS

Introduction. Currently, there is an increase in interregional disproportions and inequalities in regional development effecting increasing gaps between the maximum and minimum values of socio-economic indicators in Russian regions. Regional development requires to determine the territories that, due to the attraction of factors of production and the accumulation of resources, will become points of growth. Thus, according to some authors, agglomerations can become such a point of growth for regional development. This article is devoted to the problems and prospects of regional development of the South Bashkortostan agglomeration. Methodology. The author analyzed the socio-economic development of the agglomeration using the methods of economic, statistical analysis, systematization, synthesis, forecasting and scenarios. Results. Based on the analysis, the author identifi ed modern problems of agglomeration development, such as a decrease in the population of the region, due to natural and migration decline in the population, uneven socio-economic development of the municipalities that are part of the South Bashkortostan agglomeration, a decrease in the investment attractiveness of the territory, an increase in the budget defi cit of individual municipal formations. Conclusions. The results of the study can be applied in the development of strategic documents on the socio-economic development and management mechanism of the South Bashkortostan agglomeration.

Research on the impact of financial agglomeration on the coordinated development of urban ecological green: based on the empirical comparison of four metropolitan areas in the Yangtze River Delta of China.

As key carriers of new urbanization, metropolitan areas should pay more attention to the green and coordinated development of economy, society, and environment. Finance is an important tool to support China's high-quality development. Exploring the key dynamics and mechanisms of financial agglomeration for a green and coordinated development is important to obtain strategic support for the green development of the Yangtze River Delta metropolitan area. Using panel data of 25 prefecture-level cities in the four major metropolitan areas of the Yangtze River Delta region from 2003 to 2019, a Dubin model of three types of spatial weight matrices is constructed to explore the impact of financial agglomeration on coordinated ecological green development. Results show that, first, the positive local and neighborhood effects of financial agglomeration on the coordinated ecological green development are mainly reflected in the Hefei, Hangzhou, and Shanghai metropolitan areas and that the intensity of such effect decreases sequentially. Information transfer and technology correlation are important mechanisms to improve the local effect of financial agglomeration, and the neighborhood effect varies from one metropolitan area to another. Second, in addition to the adverse impact of the concentration of financial personnel on the ecological green integration, the agglomeration of securities, banking, and insurance industries can release "green driving potential energy," and the intensity of contribution gradually weakens. Third, the financial agglomeration of Shanghai exerts the strongest radiation effect, those of Nanjing and Hangzhourespectively demonstrate a "U"-shaped and inverted "U"-shapedimpact, and that of Hefei does not play a role.