Proceedings of the 2nd Annual Gas Processing Symposium. Qatar, January 10-14, 2010 PDF
Preview Proceedings of the 2nd Annual Gas Processing Symposium. Qatar, January 10-14, 2010
nd Proceedings of the 2 Annual Gas Processing Symposium 11–1 4 January, 2010, Doha, Qatar Advances in Gas Processing Volume 2: Proceedings of the 2nd Annual Gas Processing Symposium (Farid B enyahia, Fadwa T .Eljack, Editors) nd Proceedings of the 2 Annual Gas Processing Symposium 11–1 4 January, 2010, Doha, Qatar Edited by Farid B enyahia Department of Chemical Engineering, Qatar University, Doha, Qatar Fadwa T . Eljack Department of Chemical Engineering, Qatar University, Doha, Qatar Amsterdam • Boston • Heidelberg • London • New York • Oxford Paris • San Diego • San Francisco • Singapore • Sydney • Tokyo Elsevier Radarweg 29, PO Box 211, 1000 AE Amsterdam, The Netherlands The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK First edition 2010 Copyright © 2010 Elsevier B.V. All rights reserved No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (+44) (0) 1865 843830; fax (+44) (0) 1865 853333; email: [email protected]. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 978-0-444-53588-7 ISSN: 1876-0147 For information on all Elsevier publications visit our web site at books.elsevier.com Printed and bound in Hungary 10 11 12 10 9 8 7 6 5 4 3 1 Preface Natural gas is becoming the fuel of choice for power generation and a multitude of thermo-mechanical applications in the oil and gas industries. It is also becoming a key feedstock in a wide range of petrochemical processes. This trend is driven by environmental, economic and supply considerations with a balance clearly tilting in favor of natural gas. Despite the recent global economic hitch affecting mainly the finance sector, the oil and gas industry is expected to continue its growth globally. The expansion in LNG capacity beyond 2009 and 2010 coupled with planned and on-stream GTL plants poses real technological and environmental challenges. These important developments coupled with a global concern on green house gas emissions that were linked to global warming provided a fresh impetus to engage in new and more focused research activities aimed at mitigating or resolving challenges that ensue. For these very reasons, the second annual gas processing symposium covered themes closely related to sustainability in gas processing. The main themes covered at the symposium constitute the parallel sessions and chapters of this book: 1. Natural Gas Processing Technologies 2. Environmental Sustainability 3. Energy Efficiency in Operations 4. Design & Safety 5. Operational Excellence Given the importance of environmental sustainability in the gas processing sector and beyond, two tracks were scheduled in the technical program, making this chapter a particularly significant one in this book. The rest of the chapters provide an excellent insight into the state of the art in the areas listed above. The organizing committee of the second annual gas processing symposium wishes to express its deepest gratitude to a number of people who made this event possible and enjoyable. Grateful acknowledgement is given to His Highness Sheikh Tamim bin Hamad Al-Thani, the Heir Apparent of the State of Qatar under whose patronage this symposium was held. The support of her Excellency, Professor Sheikha Al-Misnad, President of Qatar University, is gratefully acknowledged. The strong support from the College of Engineering and the Gas processing Center staff at Qatar University is also gratefully acknowledged. The organizing committee also wishes to extend their gratitude to the symposium sponsors and co- sponsors: Qatar Petroleum, Dolphin Energy, Shell, ExxonMobil, and co-sponsors: Qatari Ministry of Environment, American Institute of Chemical Engineers (AIChE), Gas Processing Association (GPA) – GCC Chapter, and the European Federation of Chemical Engineers (EFCE). The organizing committee would like to thank members of the international technical committee for their expert review and advice. Finally, the editors would like to thank the authors who shared their knowledge and expertise in the various papers constituting the core content of this book. Farid Benyahia, Qatar University, Qatar Fadwa T. Eljack, Qatar University, Qatar Second Annual Gas Processing Symposium book editors International Technical Committee Members (Reviewers) Name Affiliation Abdelmajeed Hamouda Qatar University Ber Gerhard Grini Statoil Hydro Dinesh Seth Qatar University Elsadiq Mahdi Qatar University Farayi Musharafati Qatar University Hassan Al-Hammadi University of Bahrain Hazim Qiblawi Qatar University Ioannis Economou National Center for Scientific Research "Demokritos" James Rigby ExxonMobil, Qatar Jong Woon Qatar University Kenneth Hall Texas A&M University Mahmoud El-Halwagi Texas A&M University Mert Atilhan Qatar University Nimir El-Bashir Texas A&M University, Qatar Prof. Faisal Khan Qatar University Prof.Farid Benyahia Qatar University Ramazan Kahraman Qatar University Rex Reklaitis Purdue University Saud Ghani Qatar University Tarek Elmekkawy Qatar University Vladimir Mahalec McMaster University Proceedings of the 2nd Annual Gas Processing Symposium Farid Benyahia and Fadwa T. Eljack (Editors) © 2010 Elsevier B.V. All rights reserved. 1 Biogasification of Waste Monoethanolamine Generated in Post Combustion CO Capture 2 Deshai Bothejua, Yuan Lia, Jon Hovlandb, Trond Risbergb, Hans Aksel Haugenb, Carlos Dinamarcaa and Rune Bakkea aTelemark University College, Faculty of Technology, Porsgrunn, Norway bTelemark Technological Research and Development Centre (Tel-Tek), Porsgrunn, Norway Abstract Monoethanolamine (MEA) contaminated liquid waste generated in post combustion CO capture 2 poses a disposal issue. Anaerobic biogasification potential of waste MEA is evaluated in a series of laboratory experiments conducted under different operating conditions. Provision of a limited amount of oxygen may enhance the methane potential of waste MEA. Co-digestion of MEA together with a readily biodegradable substrate is found to be a solution to overcome ammonia and pH inhibition caused by low C/N ratio and high alkalinity. Substrate inhibition caused by waste MEA can be overcome by acclimatization. MEA degradation pathways via acetic and ammonium, with and without oxygen, are included in an anaerobic digestion model (ADM 1-Ox). Model simulations predicted the experimentally observed digestion characteristics with a fair accuracy. Keywords: ADM 1, amine wastes, biogasification, biodegradation, monoethanolamine 1. Introduction Aerobic and anoxic biodegradability of monoethanolamine has previously been demonstrated while anaerobic biodegradation has only been suggested before, but not demonstrated. The scope of this study is to investigate the suitable operating conditions for converting waste MEA into a CH rich biogas through anaerobic biogasification. A 4 batch test assay was used to study the effects of using different amounts of oxygen on the biogas generation potential of waste MEA. Effects of supplying a limited amount of oxygen in anaerobic digestion of organic wastes has been discussed elsewhere (Botheju et al., 2009). A continuous bioreactor was operated to study the feasibility of adopting a co-substrate feed approach for waste amine treatment. A series of aerobic biodegradation tests was also carried out initially in order to recognize an operable range of feed MEA concentration with minimal biomass inhibition. Another aim of this article is to simulate and validate a model developed to predict the biogasification potential of waste MEA under strict anaerobic and micro-aerobic conditions. 2. Experimental Methodology 2.1. Feed substrates The amine waste used for the batch tests was collected while emptying the Aker Kvaerner pilot facility at Kårstø, Norway. This plant has been used to capture CO (0.2 2 ton CO/h) from natural gas combustion. The short listed waste composition is shown in 2 2 Deshai Botheju et al. Table 1. MEA constitutes a major portion of the waste and the ammonia level indicates the extent of amine degradation. Table 1: Characteristics of the amine wastes used in the batch tests Component Concentration Component Concentration Monoethanolamine 210 g/l COD 232 g/l N-Kjeldahl 40 g/l pH 10.9 Nitrate (NO-) 186 mg/l Phosphorus 1280 µg/l 3 Ammonium (NH+) 14.3 g/l Sulphur 3.5 mg/l 4 Sulfate (SO--) < 144 mg/l 4 The feed used for the continuous bioreactor was a mixture of pure MEA (~30 % COD) and apple juice (drinking grade, 100 %) constituting a total COD load of about 13.7 g/L. 2.2. Aerobic degradation Tests Two series of aerobic biodegradation batch tests were carried out at 35 oC temperature, in order to explore the biodegradation potential of waste MEA at different initial concentrations, while assessing the possibility of microbial inhibition at these concentrations. 2.3. Micro-aerobic batch tests This experimental series was conducted to test the anaerobic biodegradability of the amine waste under different initial oxygen loading conditions. Miniature anaerobic reactors of 60 ml total volume were used, operated for 522 hrs at 35 oC. Reactor liquid volume of 20 ml was used and the rest was a variable head space volume. Different initial air head spaces were used to introduce different initial oxygen loads. Two amine waste concentrations were tested; 125 mg /L and 500 mg/L (as MEA equivalent). 2.4. Continuous flow experiment A continuously fed bioreactor of 0.5 L effective volume was operated for 240 days at 35 oC. During the first 100 days, the reactor was fed a diluted pure MEA solution (analytical grade). Unstable reactor performance was observed due to extreme pH conditions together with NH + and VFA accumulation. A co-substrate was then 4 introduced to stabilise the process; pure MEA mixed with apple juice (drinking grade) at an approximate COD ratio of 1:4 (MEA:apple juice). A vitamin and a mineral solution was also fed together with a pH buffer. The reactor hydraulic retention time was reduced by steps from 40 days on day 101 to 20 days on day 217. 2.5. Analytical methods Gas generation, gas composition, soluble and total COD (chemical oxygen demand), pH, VFA (volatile fatty acids - acetic, propionic, butyric, iso-butyric, valeric and iso- valeric acids), ethanol, NH+-N, MEA, TSS/VSS (total/volatile suspended solids), 4 TS/VS (total/volatile solids) and alkalinity were determined by standard methods [3]. 3. Model simulation As described in a separate paper (Botheju et al., 2010b), simplified MEA biodegradation mechanisms are incorporated into a previously developed oxygen Biogasification of waste monoethanolamine generated in post combustion CO capture 2 3 included ADM 1-Ox model (Botheju et al., 2009), which is based on the generally accepted Anaerobic Digestion Model no. 1 structure (ADM1- Batstone et al., 2002). The model simulations are carried out in AQUASIM 2.1 (Reichert, 1998). ADM1 kinetic and stoichiometric constants are used as suggested in Batstone et al. (2002). No parameter optimization is attempted as the simulations are done to compare the dynamics of the experimental conditions. 3.1. Simulation of Micro-aerobic Batch tests Micro-aerobic condition is simulated by introducing initial air head spaces above the liquid reactor zone. A gas transfer diffusive link controls the exchange of gaseous species between the liquid and the gas phase. The same gas exchange coefficient (K a) L is used for all five gaseous species (CH, CO , O , N , H), while their corresponding 4 2 2 2 2 non dimensional Henry’s Law coefficients (K ) (Sander, 1999) are used as the H conversion factors (Eq. 1). ρ =k a(S −K p ) (1) g1 L liq,g1 H,g1 g1 Three sets of simulations, for air head spaces ranging 0 – 37 ml (equivalent to 0 – 0.39 ml O/ml liquid volume), were carried out, i.e: gas generation of inoculum alone (gas 2 generation due to the degradation of composite particulate matter (Xc) present in the inoculum), and for the 125 and 500 mg/L initial MEA concentrations. 3.2. Continuous Bioreactor The bioreactor is approximated by a CSTR configuration with a mixture of MEA and sugar as feed. The apple juice COD is (quite accurately) simulated as sugar. Simulated hydraulic and mass loadings were as in the experiments (Table 2). Table 2: Different phases of reactor operation, imitated in simulations Duration HRT Flow rate Feed load (days) (d) (ml/d) (kg COD/m3) MEA sugar 100-127 (28) 40 12.5 3.43 10.28 128-144 (17) 30 16.7 3.48 8.12 145-151 (7) 25 20 3.48 8.12 152-184 (33) 20 25 3.48 8.12 185-217 (32) 20 25 4 9.32 4. Results and Discussion 4.1. Aerobic Batch Tests MEA containing reactors consume more oxygen than the control, demonstrating MEA degradation (Fig 1). 500 mg/L MEA initial concentration show less ultimate BOD and slower reaction compared to 125 mg/L MEA (Fig. 1(a)), explained by MEA induced inhibition. Such inhibition was avoided in the second test by using the culture from the first test after longer adaptation and pH adjusted to neutral (Fig. 1 (b)). MEA toxicity and inhibition has also been noticed by others (Lai and Shieh, 1996). 4 Deshai Botheju et al. 0 mg/L amine 125 mg/L amine 500 mg/L amine 0 mg/L amine 500 mg/L amine 600 2000 mg/L amine 1200 mg/L)400 g/L) 900 OD (200 D (m 600 B O 300 B 0 0 0 2 4 6 8 10 0 2 4 6 8 (a) Time (days) (b) Time (days) Figure 1: BOD profiles for the aerobic degradation test series; (a) series 1-non- adopted, non diluted inoculum (b) series 2- adopted and diluted (4x) inoculum First order rate constants for aerobic MEA biodegradation are calculated according to Botheju et al. (2010b) using the experimental BOD data (Table 3). Table 3: Degradation rate constant (K ) values (d-1) for different MEA concentrations 1 and test series MEA con. Rate constant(d-1) (mg/L) 125 1.08 (by series 1) 500 0.66 (average from series 1 and 2) 2000 0.47 (by series 2) 4.2. Micro-aerobic Batch Tests 4.2.1. Cumulative biogas generation Biogasification of waste MEA under strict anaerobic and micro-aerobic conditions is observed (Fig. 2). Measured and simulated biogas generation are similar for both waste MEA input levels tested (125 and 500 mg /L of equivalent MEA concentrations). The observed over prediction by the simulations can be due to the un-optimized kinetic constants and dissimilar initial conditions used, and partial inhibition caused by some toxic components in the feed (e.g. some MEA degradation compounds or additives, including metallic elements). Biogas Vol. (ml)1200 Biogas Vol. (ml)123000 0 0 0 5 10 15 20 0 5 10 15 20 Time (days) Time (days) (a) : 125 mg/L MEA input and 0.03 ml (b): 500 mg/L MEA input and 0.12 ml O2/ml liq. micro-aeration O2/ml liq. micro-aeration Figure 2: Measured (with marker) and simulated (line only) cumulative biogas generation in micro-aerobic batch tests for anaerobic (square; dash line) and micro- aerobic (triangle; continuous line) conditions.
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