بررسی تاثیر گرانروی بر عملکرد جداکننده دو مرحله‌ای گریز از مرکز با استفاده از دینامیک سیالات محاسباتی

جداکننده‌های دو مرحله‌ای گریز از مرکز، جدیدترین نسل جداکننده‌های ثقلی مورد استفاده در پرعیارسازی و جدایش مواد معدنی هستند. رفتار و الگوی جریان در این جداکننده‌ها بسیار پیچیده است. یکی از پارامترهای کلیدی موثر بر عملکرد و کارایی جداکننده‌های دو مرحله‌ای گریز از مرکز، گرانروی سیال ورودی به جداکننده است. در این مطالعه، به منظور بررسی اثر گرانروی و چگالی سیال بر عملکرد و میدان جریان داخل یک جداکننده دو مرحله‌ای گریز از مرکز، از رویکرد دینامیک سیالات محاسباتی (cfd) و مدل فاز مجزا (dpm) استفاده شد. به همین منظور، مدل‌های حجم سیال و تنش رینولدز به ترتیب برای شناسایی سطح اشتراک بین هسته هوا و سیال ورودی و آشفتگی مورد استفاده قرار گرفت. با افزایش گرانروی و چگالی سیال، سرعت مماسی داخل جداکننده و حجم هسته هوا کاهش می‌یابد که منجر به کاهش کارآیی جدایش می‌شود. همچنین به دلیل افزایش مقاومت سیال، بازیابی واسطه در جریان شناور افزایش می‌یابد. با افزایش گرانروی سیال از 310×1 به 310×3.09 پاسکال ثانیه، مقدار بازیابی واسطه در مراحل اول و دوم جداکننده به ترتیب 56 و 24 درصد افزایش می‌یابد، حجم هسته هوا به ترتیب 39 و 30 درصد کاهش می‌یابد و خطای احتمال (ep) نیز به ترتیب 98 و 131 درصد افزایش می‌یابد. افزایش سهم ذرات راه یافته به محصول میانی و نیز کاهش دقت جدایش در اثر افزایش گرانروی سیال از نتایج برجسته تحقیق حاضر بود که با استفاده از ردیابی ذرات فاز گسسته مشاهده شد.

Numerical Simulation of the Influence of Viscosity on the Performance of a TwoStage Centrifugal Separator

SummaryIn this research, computational fluid dynamics (CFD) and discrete phase model (DPM) were used to investigate the influence of medium viscosity on the flow field and the performance of a twostage centrifugal separator. Volume of fluid (VOF) and Reynolds stress model (RSM) were used to tack the liquidliquid interface and turbulence modeling, respectively. IntroductionTwostage centrifugal separators are the most novel generation of gravity separators that are increasingly used in the beneficiation of coal and minerals. However, the flow behavior and pattern in these separators are very complex and the mechanism of separation in these twostage separators and the effects of different parameters on their performance has rarely been reported. The purpose of this paper is to review the influence of medium viscosity on the fluid flow and the performance of the separator. On this basis, an experimental apparatus was built. In this research, a CFD and discrete phase model (DPM) has been performed. The air core pattern and size, the pressure drop across the separator, the velocity and pressure fields, and the turbulence intensity were studied in response to the changing parameters. Methodology and ApproachesAn experimental setup including a 70 mm Twostage centrifugal separator that was made of transparent Plexiglas and the complementary components such as two tanks, pumps, and instruments were manufactured to perform the physical experiments. The effects of viscosity were changed in three different simulations run. Using the transparent body for the separator, the internal flow pattern including the air core behavior was recorded and the required data were consequently extracted via the image processing technique. The pattern and the size of the air core in each stage of the TriFlo separator and the particle fate were used for the validation of CFD simulation results. The CFD simulation was performed with two Intel(R) Xeon(R) CPU E52630 v3 @ 2.40GHz, 32 GB RAM memory, and 2 TB harddisc memory using Ansys Fluent version 18.0. The duration of each simulation was about 144 hours. Results and ConclusionsWith an increase in the medium viscosity, the performance of the separator was decreased as a consequence of decreasing the tangential velocity, and the air volume fractions inside the separator. Moreover, a high viscosity increases the drag force and consequently the medium recovery into the floating stream. Such an effect consequently increased the separation density of the separator. When the medium viscosity was changed from 1×103 to 3.09×103 Pa.s, the medium recovery of the first and the second stages of the separator were increased by about 56% and 23.7 %, respectively. Ecart probable (Ep) values for the first and second stages were also increased by 98% and 104%, and the air volume fractions were decreased by about 38.73% and 29.35%, respectively.