تحسين اداء مفاعل الطبقة الوشله المشغل بالحالة الغير مستقرة لمعالجة المياه من ملوثات الفينول == Performance Enhancement In Unsteady State Operated Trickle Bed Reactor of Phenolic Wastewater Treatment
Author name:
غيداء ضياء الدين نجيب
Supervisor name:
صفاء الدين عبد الله النعيمي | فرح طالب السوادني
General topic:
Chemical Engineering
Specific topic:
Chemical Processes
Degree:
Master
University:
University of Technology - Department Of Chemical Engineering - Chemical Process Engineering Branch
Language:
English
University location:
Baghdad
First pages:
38T315 - p.pdf
Abstract:
تضمن البحث دراسة عملية ونظرية لاكسدة محلول الفينول بطريقتي (CWAO & PP - CWAO) باستخدام عمود الطبقة الوشله Trickle Bed Reactor لكل من التشغيل المستقروالتشغيل الدوري (Unsteady Periodic Operation) والمتضمن التقطيع الدوري لمعدل جريان السائل (Liquid Flow Mod | Catalyst Wet Air Oxidation (CWAO) and Hydrogen Peroxide Promoted Catalytic Wet Air Oxidation (PP - CWAO) of phenol in aqueous phase are studied experimentally and theoretically in this work using a trickle bed reactor operating in both steady state and periodic operation; liquid flow and hybrid modulation. A laboratory unit was constructed for this purpose, where a versatile reactor setup required "high pressure stainless steel reactor of 0.018 m i.d.×0.76 m height", in which experiments could be carried out under different modes of operation. The effect of key parameters that influence on the performance of trickle bed reactor (TBR) for CWAO and PP - CWAO is studied in a steady - state operation to provide a basis for comparison with periodic experiments and kinetic measurements in TBR under constant operating pressure (0.1 MPa) throughout Initial phenol concentration (0.84 - 1.5 g/L), liquid hourly space velocity (1.16 - 19.87 h - 1), superficial gas velocity (0.163 - 0.655 m/s), and bed temperature (30 - 80oC) for CWAO. Hydrogen peroxide concentration (5 - 40%) and feed rate (0.0499 - 0.1465 L/h) for PP - CWAO at constant liquid hourly space velocity (1.16 h - 1), initial phenol concentration (1.35 g/L), superficial gas velocity (0.163 m/s), and bed temperature (80oC).In periodic operation, the effect of cyclic parameters is investigated in a broader range of cycle period (5 - 180 sec) and split (0.2, 0.5 and 0.7) for both liquid flow and hybrid modulation under some of the conditions chosen on the basis of the steady state results for PP - CWAO.The results showed that the CWAO and PP - CWAO of phenol are kinetically controlled. In CWAO, LHSV and air flow rate have a slight effect on the phenol conversion, whilst they have a positive effect on the rate of reaction. The conversion and reaction rate of phenol increase with increasing initial phenol concentration and bed temperature, but they have a little pronounced effect in the range of temperature. The highest phenol conversion (75.26%) was obtained over Pt/? - Al2O3 at LHSV=1.16 h - 1, bed temperature=80°C, air flow rate=10 L/min and initial phenol concentration=1500 ppm.For PP - CWAO, the promoting effect of hydrogen peroxide was less marked in the range (5 to 25) %H2O2 concentration while at (35 - 40) %H2O2 concentration, the removal efficiency became more pronounced where the phenol conversion enhanced from 73.26% conversion at 25% H2O2 to 88.88% conversion at 40% H2O2. Hydrogen peroxide flow rate has a negligible effect on the removal of phenol. According to the kinetic results, the reaction kinetic was pseudo first order with respect to phenol concentration, (0.3) order with respect to oxygen, and the apparent activation energy equals to (19.8247) kJ/mol. The rate expression for CWO is - r_ph= C_ph^ For periodic operation, the time average conversion enhancement is indeed quite considerable in liquid flow modulation as split is lowered from steady state (? =1) to a value of (? =0.5) and reached as much as 6.66 % over the steady state at cycle period (?_p)= 15 sec; which is close to the hybrid modulation, where enhancement reached to 6.91% at ? =0.2 and (?_p)=5 sec.Intermediate compounds were analyzed for CWAO and PP - CWAO in steady state operation. Four intermediate compounds were indicated, namely oxalic acid, acetic acid, formic acid and maleic acid (carboxylic acid). Acetic acid being the main refractory intermediate in the catalytic oxidation of phenol at the operating conditions employed for CWAO process in steady state operation. The PP - CWAO of phenol in steady state and periodic operation has a positive impact on the intermediate compound mineralization as compared with the CWAO in steady state operation. In the modeling part, a suitable reactor scale model is evaluated and extended to predict the performance of TBR under the employed conditions. The model was solved numerically by finite difference approach with a semi implicit solution of the differential equations. The simulated results for steady - state and periodic operation (liquid flow modulation) performance showed that the expected trends in performance enhancements as experimental results. The experimental data results showed the relative error for the conversion (1.22 - 8.9%) in the broad range of experimental.
