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Numerical simulation of fluidized dense-phase pneumatic conveying of powders to develop improved model for solids friction factor

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Particuology 2017年第6期15卷 42-50页

作者： Baldeep Kaur Anu Mittal S.S. Mallick Renhu Pan Soumendu Jana School of Physics and Materials Science Thapar University Patiala Punjab 147004 India Department of Mechanical Engineering Thapar University Patiala Punjab 147004 India Fujian Longking Co. Ltd. Longyan Fujian 364000 China

Accurate prediction of the solids friction factor through horizontal straight pipes is important for the reliable design of a pneumatic conveying system, but it is a challenging assignment to date because of the highly concentrated, turbulent, and complex nature of the gas-solids mixture. Power-station fly ash was transported through different pipeline configurations. Numerical simulation of the dense-phase pneumatic conveying systems for three different solids and two different air flow rates have shown that particle and actual gas velocities and the ratio of the two velocities increases in the flow direction, whereas the reverse trend was found to occur for the solids volumetric concentration. To develop a solids friction-factor model suitable for dense-phase flow, we modified an existing pure dilute-phase model by incorporating sub-models for particle and actual gas velocities and impact and solids friction factor. The solids friction-factor model was validated by using it for scale-up predictions for total pipeline pressure drops in longer and larger pipes and by comparing experimental and predicted pneumatic conveying characteristics for different solids flow rates. The accuracy of the prediction was compared with a recently developed two-layer-based model. We discussed the effect of incorporating the particle and actual gas velocity terms in the solids friction-factor model instead of superficial air velocity.

关键词： pneumatic conveying Dense-phase Numerical analysis Pressure drop Scale-up validation

Experimental and numerical study of installing a dune model in a 90° bend in the horizontal-vertical pneumatic conveying system

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Particuology 2023年第8期79卷 95-108页

作者： Zhenyu Yang Fei Yan Panpan Tu Rui Zhu School of Mechanical Engineering Jiangsu University of Science and TechnologyZhenjiang212000China School of Environmental and Chemical Engineering Jiangsu University of Science and TechnologyZhenjiang212000China

In the pneumatic conveying process,particles move to the bend under the influence of inertia to form a particle rope,which will cause serious wear between the particles and the pipe wall,and then the dune model is designed and installed in the 90° bend to reduce energy consumption and wear in this ***,the minimum pressure drop velocity of particles transported by different size dune models was obtained through experimental *** the energy saving mechanism of the dune model is studied by CFD-DEM *** experimental results show that the installation of the dune model reduces the minimum pressure drop *** numerical simulation results show that the number of collisions between the particles and the tube wall in the vertical tube decreases after the installation of the dune model,which reduces the energy ***,the increasing of tail size of the dune model is beneficial to the diffusion and acceleration of the particles in the vertical tube.

关键词： pneumatic conveying Dune model CFD-DEM Minimum pressure drop velocity Recursiveanalysis

Characterization of the gas pulse frequency,amplitude and velocity in non-steady dense phase pneumatic conveying of powders

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Particuology 2008年第5期6卷 301-306页

作者： Kenneth C.Williams Mark G.Jones Ahmed A.Cenna Centre for Bulk Solids and Particulate Technologies School of EngineeringUniversity of Newcastle

Current modelling techniques for the prediction of conveying line pressure drop in low velocity dense phase pneumatic conveying are largely based on steady state analyses. Work in this area has been on-going for many years with only marginal improvements in the accuracy of prediction being achieved. Experimental and theoretical investigations undertaken by the authors suggest that the flow mechanisms involved in dense phase conveying are dominated by transient effects rather than those of steady state and are possibly the principal reasons for the limited improvement in accuracy. This paper reports on investigations on the pressure fluctuation behaviour in dense phase pneumatic conveying of powders. The pressure behaviour of the gas flow in the top section of the pipeline was found to exhibit pulsatile oscillations. In particular, the pulse velocity showed variation in magnitude while the frequency of the oscillations rarely exceeded 5 Hz. A wavelet analysis using the Daubechie 4 wavelet found that the amplitude of the oscillations increased along the pipeline. Furthermore, there was significant variation in gas pulse amplitude for different types of particulate material.

关键词： pneumatic conveying Powders Dense phase Pulsatile flow Transient flow

Energy loss at bends in the pneumatic conveying of fly ash

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Particuology 2015年第4期13卷 65-73页

作者： Naveen Tripathi Atul Sharma S.S.Mallick P.W.Wypych Department of Mechanical Engineering Thapar University Faculty of Engineering and Information Sciences University of Wollongong

An accurate estimation of the total pressure drop of a pipeline is important to the reliable design of a pneumatic conveying system. The present paper presents results from an investigation into the modelling of the pressure drop at a bend in the pneumatic conveying of fly ash. Seven existing bend models were used （in conjunction with solids friction models for horizontal and vertical straight pipes, and initial acceleration losses） to predict the total pipeline pressure drop in conveying fly ash （median particle diameter： 30 }zm; particle density： 2300 kg/m^3; loose-poured bulk density： 700 kg/m3） in three test rigs （pipelines with dimensions of 69 mm inner diameter （I.D.） × 168 m length; 105 mm I.D. × 168 m length; 69 mm I.D. × 554 m length）. A comparison of the pneumatic conveying characteristics （PCC） predicted using the seven bend models and experimental results shows that the predicted total pipeline PCC and trends depend on the choice of bend model. While some models predict trends that agree with the experimental results, other models predicted greater bend pressure drops for the dense phase of fly ash than for the dilute phase. Models of Pan, R. （1992）. Improving scale-up procedures for the design of pneumatic conveying systems. Doctoral dissertation, University of Wollongong, Australia, Pan, R., ＆ Wypych, P.W. （1998）. Dilute and dense phase pneumatic conveying of fly ash. In Proceedings of the sixth International Conference on Bulk Materials Storage and Transportation （pp. 183-189）, Wollongong, NSW, Australia and Chambers, A.J., ＆ Marcus, R.D. （1986）. pneumatic conveying calculations. In Proceedings of the second International Conference on Bulk Materials Storage and Transportation （pp. 49-52）, Wollongong, Australia reliably predicted the bend losses for systems conveying fly ash over a large range of air flows.

关键词： pneumatic conveying Fluidised dense phase Bend Pressure drop Bend model

An assessment of steady-state conditions in single slug horizontal pneumatic conveying

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Particuology 2021年第5期19卷 187-195页

作者： A.Lavrinec O.Orozovic H.Rajabnia K.Williams M.G.Jones G.E.Klinzing Centre for Bulk Solids and Particulate Technologies The University of NewcastleNSW 2308Australia Department of Chemical and Petroleum Engineering The University of PittsburghPA 15261USA

This study used a 3D coupled CFD–DEM model to assess how slugs tend towards steady state in single slug horizontal pneumatic *** slug length,inlet velocity and initial stationary layer fractions were systematically varied for a total of 72 *** made observation that slugs tend towards a steady state was confirmed via a theoretical *** derivation shows that slugs move towards their steady state lengths *** allowed for a calculation of a characteristic time scale which is a measure of how quickly a slug tends towards the steady *** theoretical estimate which is a function of slug porosity,steady length,velocity and stationary layer fraction has good agreement with simulated results.A link between steady slug length and solids loading ratio was also shown.

关键词： pneumatic conveying Dense phase Slug flow Steady state

Experimental study of the blockage boundary for dense-phase pneumatic conveying of powders through a horizontal slit

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Particuology 2015年第4期13卷 128-134页

作者： Shengyong Hu Fubao Zhou Yingke Liu Jianhong Kang Yifan Zhang Tongqiang Xia Faculty of Safety Engineering China University of Mining and Technology College of Mining Technology Taiyuan University of Technology Key Laboratory of Gas and Fire Control for Coal Mines China University of Mining and Technology

The estimation of the blockage boundary for pneumatic conveying through a slit is of significant importance. In this paper, we investigate the characteristics for blockage of powder （48 gLm average diameter） through a horizontal slit （1.6 m × 0.05 m × 0.002 m）. The results show that the required critical solid mass flow rate increases as the superficial air velocity increases superficial air velocity. The solid loading ratio and superficial air velocity displayed a decreasing power law relationship. This finding agrees with existing theory and experimental results. However, a minimum inlet solid loading ratio exists. When the air velocity is greater than the corresponding air velocity of the minimum solid loading ratio, the solid loading ratio exhibits an increasing trend in power law. We also found that when the inlet conveying pressure increased, the critical solid mass flow rate required for blockage, the inlet solid loading ratio, and the minimum inlet solid loading ratio increased.

关键词： Dense phase pneumatic conveying Blockage boundaw Horizontal slit

Predicting the mode of flow in pneumatic conveying systems—A review

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Particuology 2008年第5期6卷 289-300页

作者： Mark G.Jones Kenneth C.Williams Centre for Bulk Solids and Particulate Technologies School of EngineeringUniversity of NewcastleNewcastle 2308Australia

An initial prediction of the particulate mode of flow in pneumatic conveying systems is beneficial as this knowledge can provide clearer direction to the pneumatic conveying design process. There are three general categories of modes of flow, two dense flows： fluidised dense phase and plug flow, and dilute phase oniy. Detailed in this paper is a review of the commonly used and available techniques for predicting mode of flow. Two types of predictive charts were defined： basic particle parameter based （e.g. particle size and density） and air-particle parameter based （e.g. permeability and de-aeration）. The basic particle techniques were found to have strong and weak areas of predictive ability, on the basis of a comparison with data from materials with known mode of flow capability. It was found that there was only slight improvement in predictive ability when the particle density was replaced by loose-poured bulk density in the basic parameter techniques. The air-particle-parameter-based techniques also showed well-defined regions for mode of flow prediction though the data set used was smaller than that for the basic techniques. Also, it was found to be difficult to utilise de-aeration values from different researchers and subsequently, an air-particle-based technique was developed which does not require any de-aeration parameter in its assessment.

关键词： pneumatic conveying Mode of flow Dense phase Permeability De-aeration

pneumatic conveying OF BIOMASS PARTICLES:A REVIEW

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China Particuology 2006年第3期4卷 183-188页

作者： John R. Grace Department of Chemical and Biological Engineering University of British Columbia 2360 East Mall Vancouver V6T 1Z3 Canada

Processes involving biomass are of growing interest, but handling and conveying biomass particles are challenging due to the unusual physical properties of biomass particles. This paper reviews recent work on pneumatic conveying of biomass particles, especially agricultural particles and pulp fibres. Experimental work has been mainly carried out to determine a range of parameters, such as pressure drop, particle velocity, flow regime and electrostatic charging for both horizontal and vertical conveying. Models ranging from empirical to CFD models are also being developed. Difficulties in representing turbulence and interactions among biomass particles and between the particles and fluid have so far limited the success of advanced modeling. Further work is needed to improve understanding of multiphase biomass pneumatic conveying and to assist in the development of biomass energy and conversion processes.

关键词： biomass multiphase flow pneumatic conveying agricultural modeling particles

Flow characteristics and Shannon entropy analysis of dense-phase pneumatic conveying under high pressure

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Journal of Southeast University(English Edition) 2007年第4期23卷 609-614页

作者：赵长遂梁财陈晓平蒲文灏鹿鹏范春雷东南大学洁净煤发电及燃烧技术教育部重点试验室南京210096

Experiments of dense-phase pneumatic conveying of pulverized coal using nitrogen are carded out in an experimental test facility with the conveying pressure up to 4. 0 MPa and the gas-solid ratio up to 450 kg/m^3. The influences of different conveying differential pressures, coal moisture contents, gas volume flow rates and superficial velocities on the solid-gas ratios are investigated. Shannon entropy analysis of pressure fluctuation time series is developed to reveal the flow characteristics. Through investigation of the distribution of the Shannon entropy under different conditions, the flow stability and the evolutional tendency of the Shannon entropy in different regimes and regime transition processes are discovered, and the relationship between the Shannon entropy and the flow regimes is also established. The results indicate that the solid-gas ratio and the Shannon entropy rise with the increase in conveying differential pressure. The solid-gas ratio and the Shannon entropy reveal preferable regularity with gas volume flow rates. The Shannon entropy is different for different flow regimes, and can be used to identify the flow regimes. Both mass flow rate and the Shannon entropy decrease with the increase in moisture contents. The Shannon entropy analysis is a feasible approach for researching the characteristics of flow regimes, flow stability and flow regime transitions in dense-phase pneumatic conveying under high pressure.

关键词： pneumatic conveying high pressure dense-phase solid-gas ratio Shannon entropy