scholarly journals Particle Lagrangian CFD Simulation and Experimental Characterization of the Rounding of Polymer Particles in a Downer Reactor with Direct Heating

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 916
Author(s):  
Juan S. Gómez Bonilla ◽  
Laura Unger ◽  
Jochen Schmidt ◽  
Wolfgang Peukert ◽  
Andreas Bück
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Residence Time ◽  
Cfd Simulation ◽  
Numerical Approach ◽  
Particle Dispersion ◽  
Direct Heating ◽  
Residence Time Distributions ◽  
Downer Reactor

Polypropylene (PP) powders are rounded at different conditions in a downer reactor with direct heating. The particles are fed through a single central tube, while the preheated sheath gas is fed coaxially surrounding the central aerosol jet. The influence of the process parameters on the quality of the powder product in terms of particle shape and size is analyzed by correlating the experimental results with the flow pattern, residence time distribution of the particles and temperature distribution predicted by computational fluid dynamics (CFD) simulations. An Eulerian–Lagrangian numerical approach is used to capture the effect of the particle size distribution on the particle dynamics and the degree of rounding. The simulation results reveal that inlet effects lead to inhomogeneous particle radial distributions along the total length of the downer. The configuration of particle/gas injection also leads to fast dispersion of the particles in direction of the wall and to particle segregation by size. Broad particle residence time distributions are obtained due to broad particle size distribution of the powders and the particles dispersion towards the wall. Lower mass flow ratios of aerosol to sheath gas are useful to reduce the particle dispersion and produce more homogenous residence time distributions. The particles’ residence time at temperatures above the polymer’s melting onset is determined from the simulations. This time accounts for the effective treatment (rounding) time of the particles. Clear correlations are observed between the numerically determined effective rounding time distributions and the progress of shape modification on the particles determined experimentally.

Impacts of combustion phasing, load, and speed on soot formation in spark-ignition engines

2019 ◽  
Vol 21 (3) ◽  
pp. 514-539
Author(s):  
Mitchell D Hageman ◽  
David A Rothamer
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Residence Time ◽  
Engine Speed ◽  
Soot Formation ◽  
Direct Injection ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
The Impact

The premixed prevaporized engine operation method was used to study the effects of main combustion thermodynamic properties and residence time on soot formation in a spark-ignition engine. Select cases were repeated under early-injection, nearly homogeneous, spark-ignition direct-injection operation to determine if the impact of the investigated parameters was the same or if the impact of in-cylinder liquid fuel injection and the resulting heterogeneous fuel-air mixture alters the trends. The original premixed prevaporized study hypothesized that soot is more likely to form after main combustion than during the main combustion event under completely homogeneous conditions. This hypothesis was tested in this study by performing premixed prevaporized combustion phasing sweeps at equivalence ratios (Φs) of 1.35 and 1.40. Both sweeps showed low sensitivity of the particle size distribution to significant changes in peak temperature and pressure during combustion, providing supporting evidence for the original hypothesis. This information was then used to design experiments to isolate the impacts of pressure (engine load) and residence time (engine speed). A premixed prevaporized load sweep showed that particulate emissions increase as a function of load/pressure. A spark-ignition direct-injection load variation showed similar pressure dependence for cases with in-homogeneous in-cylinder fuel-air distributions. A premixed prevaporized residence time variation (performed by changing engine speed) demonstrated an increase in soot formation with increased residence time. The results for identical spark-ignition direct-injection residence-time variations suggest a trade-off in soot formation between the effects of increased mixing time and increased residence time for spark-ignition direct-injection operation. The premixed prevaporized load and speed points were each investigated using Φ sweeps to determine the critical enrichment threshold for soot formation (ΦC) and the dependence of soot formation for Φ > ΦC. The spark-ignition direct-injection investigations were performed at Φ = 0.98, such that any soot formation above the non-fuel-related baseline particle size distribution could be attributed either to mixture heterogeneity or in-cylinder fuel films.

scholarly journals CFD simulation of solids suspension in stirred tanks: Review

2010 ◽  
Vol 64 (5) ◽  
pp. 365-374 ◽  
Author(s):  
Aoyi Ochieng ◽  
Mrice Onyango
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Concentration Distribution ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Cfd Modeling ◽  
Small Scale ◽  
Stirred Tanks ◽  
Solids Concentration

Many chemical reactions are carried out using stirred tanks, and the efficiency of such systems depends on the quality of mixing, which has been a subject of research for many years. For solid-liquid mixing, traditionally the research efforts were geared towards determining mixing features such as off-bottom solid suspension using experimental techniques. In a few studies that focused on the determination of solids concentration distribution, some methods that have been used have not been accurate enough to account for some small scale flow mal-distribution such as the existence of dead zones. The present review shows that computational fluid dynamic (CFD) techniques can be used to simulate mixing features such as solids off-bottom suspension, solids concentration and particle size distribution and cloud height. Information on the effects of particle size and particle size distribution on the solids concentration distribution is still scarce. Advancement of the CFD modeling is towards coupling the physical and kinetic data to capture mixing and reaction at meso- and micro-scales. Solids residence time distribution is important for the design; however, the current CFD models do not predict this parameter. Some advances have been made in recent years to apply CFD simulation to systems that involve fermentation and anaerobic processes. In these systems, complex interaction between the biochemical process and the hydrodynamics is still not well understood. This is one of the areas that still need more attention.

CFD Simulation of Spouted Bed Working with a Size Distribution of Sand Particles: Segregation Aspects

2017 ◽  
Vol 899 ◽  
pp. 95-100
Author(s):  
Kássia Graciele dos Santos ◽  
L.V. Ferreira ◽  
Ricardo Correa Santana ◽  
Marcos Antonio de Souza Barrozo
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Cfd Simulation ◽  
Computational Simulation ◽  
Particle Diameter ◽  
Spouted Bed ◽  
Particle Segregation ◽  
Cfd Method ◽  
Mean Particle Diameter

Spouted bed simulations are usually performed using only one granular phase with a mean particle diameter representing the entire particle mixture, instead of a particle size distribution. In this study, the effect of the particle size distribution is accounted through the simulation of a mixture with five granular phases. The results showed that the particle segregation occurs. Larger particles are more concentrated in the upper region, while the smaller particles are preferably positioned in the lower region of the bed. Computational simulation using CFD method reproduced well the segregation experiments with different participle sizes of sand.

Synthesis of Titania Powder by Titanium Tetrachloride Oxidation in an Aerosol Flow Reactor

1991 ◽  
Vol 249 ◽  
Author(s):  
M. Kamal Akhtar ◽  
Yun Xiong ◽  
Sotiris E. Pratsinis
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Residence Time ◽  
Titanium Tetrachloride ◽  
Flow Reactor ◽  
Geometric Standard Deviation ◽  
Process Conditions ◽  
Average Particle ◽  
Powder Size

ABSTRACTVapor phase synthesis of titania particles by oxidation of titanium tetrachloride (TiCI4) was studied in an aerosol reactor between 1200 K and 1723 K. The effect of process variables (reactor residence time, temperature, reactant concentration) on powder size and phase characteristics was investigated using the differential mobility particle sizer, scanning electron microscopy and X-ray diffraction. The morphology of the particles remained unchanged under the process conditions investigated; titania particles were primarily anatase though the rutile weight fraction increased with increase in reactor temperature. The geometric number average diameter of the particles was between 0.13 µm and 0.35 [m and the geometric standard deviation of the particle size distribution was about 1.4. The average particle size increased with increasing temperature, TiCI4 concentration and residence time. The observed changes in the particle size distribution were compared with those predicted by solving the aerosol dynamic equation by a sectional method and accounting for coagulation and first order chemical reaction.

scholarly journals PENINGKATAN RECOVERY EMAS DI CARBON IN LEACH PLANT PT. ANTAM TBK UNIT BISNIS PERTAMBANGAN EMAS PONGKOR, JAWA BARAT (STUDI KASUS KADAR BIJIH 3,5 – 4,5 GPT DI PLANT 1)

2020 ◽  
Vol 1 (1) ◽  
pp. 49-58
Author(s):  
Nurhakim Zafar ◽  
Sudesno. Yudhistira ◽  
Adiputra. Hoppy
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Residence Time ◽  
Fine Fraction ◽  
Gold Recovery ◽  
Business Unit ◽  
Mining Operations ◽  
Recovery Plant ◽  
Cyanide Consumption

ABSTRAK Sejarah pengolahan mineral emas di Unit Bisnis Pertambangan Emas (UBPE) Pongkor PT Antam Tbk menunjukkan adanya tren menurunnya kadar bijih. Meskipun demikian, metallugist di UBPE Pongkor PT Antam Tbk secara berkelanjutan mencari berbagai penyebab dan cara untuk meningkatkan nilai recovery Plant walaupun kadar bijih yang cenderung menurun. Berdasarkan hasil pengolahan data terhadap Plant 1 dan Plant 2 di UBPE Pongkor, menunjukkan adanya potensi perbaikan di area Plant 1 UBPE Pongkor PT Antam Tbk. Makalah ini akan berfokus pada pengurangan kadar emas dalam sand tailing saat kadar bijih antara 3,5 sampai 4,5 gram per ton (gpt) di Plant 1 dalam rentang 2 bulan. Berdasarkan hasil analisa data yang diperoleh dengan menggunakan metode Anova, diperoleh hasil bahwa fraksi halus, kadar sianida, dan waktu tinggal slurry adalah hal – hal yang paling berpengaruh dalam proses pengolahan emas di UBPE Pongkor. Serangkaian perbaikan dan inovasi dilakukan untuk menyelesaikan masalah ini, yaitu dengan cara memodifikasi distribusi ukuran grinding ball, mengatur waktu mixing dan injeksi sianida dalam tangki, serta mengatur waktu dan memonitoring waktu tinggal slurry di dalam tangki leaching dan CIL.Berdasarkan hasil perbaikan dan inovasi yang dilakukan, terlihat bahwa nilai recovery plant meningkat dari sebelumnya 89,4% menjadi 92,7%. Hal ini diperoleh dari nilai perbandingan distribusi ukuran bola 1 : 2 untuk grinding ball 40-60 mm dan 60-80 mm. Sementara itu, penyesuaian terbaik kadar CN adalah 600 - 650 ppm ditambah dengan optimalisasi injeksi sianida menggunakan pompa dosing sehingga dapat mengurangi waktu mixing sianida yang 3x sehari menjadi 1x sehari dan menurunkan kadar CN dari 1,23 menjadi 1,13 kg NaCN/ton bijih. Berdasarkan hasil pengaturan mill feeder dan pompa slurry, waktu tinggal di tangki leaching dari 51 jam menjadi 60 jam. Kata Kunci : Emas, recovery, fraksi halus, sianida, waktu tinggal slurry   ABSTRACT History of mineral processing at Gold Business unit at PT Antam Tbk shows a consistent trend of decreasing grade due to intensive mining operations. Therefore, The Metallurgist  PT Antam Tbk Gold Business Unit is looking for roots caused and solutions to raise up plant recovery although the grade of gold declined. After deep data analyzing process at plant 1 & 2, it’s shown that plant 1 at Gold Business Unit PT Antam Tbk have a room for recovery improvement. This research focus on reducing sand tailing to improved gold recovery at feed grade between 3.5 and 4.5 ppm at plant 1. Deep analysis was applied to processing big data from the plant using ANOVA Methode, it’s shown that fine fraction, Cyanide and slurry residence time were the major factor of gold recovery. Series improvement were applied to solved this problem, such as modifying grinding ball particle size distribution, adjusting cyanide feeding on leaching thank based on feed grade, and monitoring slurry residence time. It was observed that the plant plant 1 recovery was increasing from 89,4% to 92.7%. The best grinding ball particle size distribution was 1 : 2 for 50 & 80 mm grinding ball. While the best applied cyanide concentration was between 600 - 650 ppm with some modification to improve process control of cyanide feeding. It’s shown that cyanide mixing process was decreased from 3 times a day to only one a day and also the cyanide consumption was reduced from 1.23 to 1.13 kg/ton ore.  Some modification also carried out to increase slurry residence time. It’s proved that by applying the improvement it’s shown that the slurry residence time rose from 50 h to 61 h. Keywords : gold, recovery, fine fraction, cyanide, residence time.

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