عنوان مقاله
مطالعه شبیه سازی پیرامون اثر پارامترهای عملیاتی و طراحی بر عملکرد راکتور غشایی جابجایی گاز آب
فهرست مطالب
چکیده
مقدمه
مدل راکتور
نتایج و بحث
نتیجه گیری
بخشی از مقاله
مدل راکتور
راکتور غشایی مدلسازی شده دارای شکل هندسی لوله و پوسته می باشد. لوله داخلی متخلخل (غشاء) و لوله خارجی نفوذناپذیر می باشد. واکنش دهنده ها به سمت لوله راکتور و گاز روبشی به سمت پوسته تزریق شدند. کاتالیزور به شکل یک لایه نازک در سمت داخلی غشا ته نشین شده و در نتیجه فقط گازهای سمت لوله در تماس مستقیم با آن بوده و در واکنش رسوب کردند.
کلمات کلیدی:
A simulation study of the effect of operating and design parameters on the performance of a water gas shift membrane reactor Panagiotis Boutikos a, Vladimiros Nikolakis b,∗ a Department of Chemical Engineering, University of Patras, Greece b Institute of Chemical Engineering & High Temperature Chemical Processes, Foundation for Research and Technology Hellas (FORTH/ICE-HT), Stadiou Str, PO Box 1414, 26504 Patras, Greece article info Article history: Received 28 September 2009 Received in revised form 28 December 2009 Accepted 7 January 2010 Available online 14 January 2010 Keywords: Water gas shift Membrane reactor Reactor design abstract The goal of this work is to understand the effect of the relative values of membrane permselectivity, permeation flux and reaction rate on the performance of a water gas shift membrane reactor. This was achieved by simulating the operation of an isothermal tube–shell reactor. Its performance was evaluated based on the CO conversion and H2 recovery, as well as the permeate and retentate H2 molar fractions. The maximum enhancement of CO conversion has been observed when the Damkhöler number (Da) is almost equal to the permeation number (Pe). Improvements in CO conversion can be achieved even when membranes with relatively low permselectivity values (∼10) are used. Further increase of permselectivity primarily increased the purity of the H2 rich stream. The utilization of CO2 selective instead of H2 selective membranes could improve CO conversion only if the CO2 content of the feed is higher than that of H2. Finally, simulations using rate expressions that correspond to different detailed reaction mechanisms resulted only in slight differences in reactor performance. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Fuel cells are devices that can efficiently convert chemical energy to electricity. They can operate using different fuels (i.e. methanol, H2), with hydrogen being the one most commonly used. The use of hydrogen as fuel is considered to be environmentally friendly because, in such a case, the only emission is water. Unfortunately, H2 does not exist as a pure compound on earth. As a result, it must be produced either from electrolysis of water or conversion of hydrocarbons (i.e. biofuels, natural gas, diesel, etc.). Issues related to H2 storage and distribution have rendered on-site H2 production an attractive alternative solution, especially for automotive applications. Steam reforming, autothermal reforming and partial oxidation are three important processes for the conversion of hydrocarbons to H2. The H2 streams produced from the above reactions contain significant amounts of CO, which is undesirable because it poisons the fuel cell catalyst. One way to reduce the CO concentration is the water gas shift (WGS) reaction: CO + H2O ↔ CO2 + H2, HRXN = −41.4 kJ/mol WGS is a reversible exothermic reaction, thus high temperatures which favor fast kinetics are not suitable for achieving high conver- ∗ Corresponding author. Tel.: +30 2610965242; fax: +30 2610965223. E-mail address: vnikolak@iceht.forth.gr (V. Nikolakis). sions. One novel approach for improving the performance ofWGS is the implementation of catalytic membrane reactors. Such reactors combine reaction and separation into one unit. A catalytic membrane reactor that allows the selective removal of one of the WGSR products (H2 or CO2) is expected to increase the CO conversion at high reaction temperatures.
