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Article
Mathematical Simulation of Unsteady Flow through Hollow Fiber Membrane

Authors: Raghad Samir Mahmood --- Riyadh Zuhair Al Zubaidy
Journal: Journal of Engineering مجلة الهندسة ISSN: 17264073 25203339 Year: 2008 Volume: 14 Issue: 3 Pages: 2912 -2928
Publisher: Baghdad University جامعة بغداد

Abstract

Water flowing through hollow fiber membrane comprises two types of flow each having its own hydraulic characteristics. The first is the flow inside the fiber channel, and the second is the flow through the fiber porous wall. Water flow through hollow fiber membrane, HFM, is unsteady nonuniform flow due to the accumulation of rejected material on the fiber surface causing a change in the hydraulic resistance along the fiber length with time. Under these conditions, a mathematical model was developed to simulate water flow through hollow fiber membrane based upon the equations governing the flow inside the fiber channel and through the fiber wall, equations governing conditions imposed by flow boundaries, and implicit finite difference technique for solving partial differential equations. The model was verified by using published laboratory experimental data. A very good agreement was obtained between the measured and predicted flowrate values under the same conditions. The mathematical model was applied to three types of commercially available fiber modules to investigate variation of flux, the transmembrane pressure, the thickness of the rejected materials along the fiber length, the flowrate, and the effect of the pot length on the fiber hydraulic performance. It was found there is considerable variation in the hydraulic performance of the three types of fiber. Therefore, the mathematical model provides a tool to work on finding the optimal design of the hollow fiber membrane.

ان جريان الماء في الاغشية الليفية المجوفة يتضمن نوعين من الجريان لكل منهما خواصة الهيدروليكية. الاول جريان الماء داخل قناة الليف والثاني جريان الماء خلال جداره النفاذ. ان جريان الماء في الاوعية الليفية هو جريان غير ثابت وغير منتظم لتتغير المقاومة الهيدروليكية على امتداد الليف مع الزمن نتيجة تراكم الترسبات على سطح الليف. تحت هذه الظروف تم اعداد نموذج رياضي لمحاكاة جريان الماء خلال الليف بالاعتماد على المعادلات التي تحكم الجريان داخل قناته وخلال الجدار النفاذ له والمعادلات التي تحكم الجريان عند حدود الجريان. تم التحقق من اداء النموذج الرياضي باستخدام قياسات مختبرية منشورة ووجد بان هنالك توافق جيد بين هذه القيم والقيم المستحصلة من النموذج. استخدم النموذج في تحري تغاير التدفق والضغط عبر غشاء الليف وسمك الترسبات على امتداد الليف والتصريف الكلي واثرالطول المحكم من الليف لثلاثة انواع من الالياف المجوفة التجارية. وجد بان هنالك تفاوت كبير في الاداء الهيدروليكي للانواع الثلاث من الالياف. لذا فان النوذج الرياضي المعد يوفر الاداة للعمل على ايجاد التصميم الامثل لللالياف المجوفة.

Keywords

Article
Membranes Separation Process For Oily Wastewater Treatment
عملية الفصل بالأغشيةِ لمعالجة المياه الملوثة بالزيوت

Authors: Zaid Waadulla Rashad --- Maha H. Al-Hassani --- Ahmed Faiq Al-Alawy --- Hasan Ferhood Makki
Journal: Journal of Engineering مجلة الهندسة ISSN: 17264073 25203339 Year: 2011 Volume: 17 Issue: 2 Pages: 235-251
Publisher: Baghdad University جامعة بغداد

Abstract

Pilot-scale dead end microfiltration membranes were carried out to determine the feasibility of the process for treating the oily wastewater which discharge from some Iraqi factories such as power station of south of Baghdad and the general company of petrochemical industries. Polypropylene membranes (cylindrical shape) with different pore diameters (1 and 5 micron) were used to conduct the study on micromembrane process. The variables studied are oil concentration (100 – 1000 ppm), feed flow rate (20 – 40 l/h), operating temperature (31 – 50°C) and time (0 – 3 h). It was found that the flux increases with increasing feed flow rate, temperature and pore size of membrane, and decreases with increasing oil concentration and operating time. It was found also that the effect of feed oil concentration has the greatest effect on the fouling of membrane among other variables. The percent rejection of oil improved significantly with decreasing oil concentration but decreased with increasing feed temperature, pore size of membrane and operating time. Feed flow rate has slightly effect on oil rejection. The type of oil used in this work is 20W-50 gasoline and diesel engine oil.A general model of dead end filtration mode has been successfully evaluated to explain fundamental mechanisms involved in flux decline during dead end microfiltration of oily water emulsions. Analysis of the fall in flux with time for the polypropylene membrane (5 μm) indicates that intermediate and standard pore models give the best prediction for experimental behavior. Empirical correlations for the prediction of the flux and percent reject of oil were determined in this study. These equations have the correlation coefficient 98.87% and 91.49% respectively.

اغشية المايكرو فلتر ذو النهاية المسدودة بمنظومة ريادية نفذت لتحديد دراسة لعملية معالجة المياه الملوثة بالزيوت التي تطرح من بعض المصانع العراقية مثل محطة كهرباء جنوب بغداد والشركة العامة للصناعات البتروكيمياوية. اغشية البولي بروبلين باقطار مختلفة (1 و 5 مايكرون) تم استخدامها لاجراء الدراسة على عملية غشاء المايكرو. المتغيرات التي تم دراستها هي تركيز الزيت (100 – 1000 جزء بالمليون) , معدل الجريان (20 – 40 لتر/ساعة) , درجة حرارة التشغيل (31 – 50 م°) والزمن (0 – 3 ساعة). لقد وجد بأن معدل التدفق يزداد بزيادة معدل الجريان للقيم (المغذي) , درجة الحرارة وحجم المسام للغشاء , ويقل بزيادة تركيز الزيت وزمن التشغيل. وكذلك وجد بأن تركيز الزيت ذو تأثير اكبر على تلوث الغشاء من بين المتغيرات الاخرى. نسبة الرفض للزيت تتحسن بشكل ملحوظ بنقصان تركيز الزيت الداخل ولكن تقل بزيادة درجة حرارة اللقيم (المغذي) , حجم المسام للغشاء وزمن التشغيل. معدل جريان اللقيم (المغذي) له تأثير قليل على نسبة رفض الزيت. ان نوع الزيت المستخدم في هذا العمل هو20W-50 زيت محرك الديزل والكازولين. نموذج عام من نمط ترشيح النهاية المسدودة قُيم بنجاح لتوضيح اليات اساسية تستخدم في هبوط الجريان خلال المايكرو فلتر ذو النهاية المسدودة لمستحلبات الماء الزيتية. تحليل الهبوط في الجريان مع الزمن لغشاء البولي بروبلين (5 مايكرون) يوضح بأن نماذج المسام المتوسطة والقياسية تعطي افضل تنبؤ للسلوك التجريبي. معادلات الارتباط التجريبية لحساب الجريان ونسبة الرفض للزيت تم تحديدها في هذه الدراسة. هذه المعادلات لها معامل الارتباط 98.87% و 91.49% على التوالي

Keywords

Article
Microfiltration Membranes for Separating Oil / Water Emulsion

Abstract

This research was aimed to study the efficiency of microfiltration membranes for the treatment of oily wastewater and the factors affecting the performance of the microfiltration membranes experimental work were includes operating the microfiltration process using polypropylene membrane (1 micron) and ceramic membrane (0.5 micron) constructed as candle; two methods of operation were examined: dead end and cross flow. The oil emulsion was prepared using two types of oils: vegetable oil and motor oil (classic oil 20W-50). The operating parameters studied are: feed oil concentration 50 – 800 mg/l, feed flow rate 10 – 40 l/h, and temperature 30 – 50 oC, for dead end and cross flow microfiltration. It was found that water flux decreases with increasing operating time and feed oil concentration and increases with increasing operating temperature, feed flow rate and pore size of membrane. Also, it was found that rejection percentage of oil increases with increasing flow rate and rejection percentage decreases with increasing time, feed oil concentration, feed temperature and pore size of membrane for dead end and cross flow microfiltration. In cross flow microfiltration, reject concentration (concentrate) increases with increasing flow rate, feed concentration, time and feed temperature. The dead end filter has more flux compared to cross flow filter, while, in cross flow the oil rejection percentage is best than dead end. Flux for vegetable oil is more than motor oil but rejection percentage for vegetable oil is less than that for motor oil. The highest recovery ratio was found is 44.8% for cross flow process with recirculation of concentrating stream to feed vessel. The highest rejection percentage of oil was found is 98 % and 97.8 % for cross flow and dead ends respectively.

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