Krishna Nimesh|

Design of Dimethyl Ether Synthesis Plant based on Thermodynamic and Kinetic Simulation Study

M.Tech -Advanced petroleum

science and Technology

Evaluation of various options for the synthesis of dimethyl ether using simulations

Evaluation of Various Options for the Synthesis of Dimethyl Ether Using Simulations

By

Krishna Nimesh

A Thesis submitted in partial fulfilment of the requirements for the degree of

Master of Technology

At

CSIR-Indian Institute of Petroleum, Dehradun

DECLARATION

This is to certify that the project entitled “Evaluation of Various Options for the Synthesis of Dimethyl Ether Using Simulations” submitted by KRISHNA NIMESH, a student of CSIR-IIP, Dehradun is the bonafide record of the student’s own work and has been carried out under the supervision and guidance of Dr. S. M. Nanoti (HOD-Refinery Technological Division, CSIR-IIP, Dehradun). It is being submitted for the Degree of Master of Technology in Engineering in the Advanced Petroleum Science and Technology. It has not been submitted before for any degree or examination in any other University.

Abstract

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(Dr. Sunil Kumar)

Scientist ‘C’ (Modelling and Simulation Lab)

CSIR-Indian Institute of Petroleum

Dehradun-248007

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(Dr. S. M. Nanoti)

Scientist ‘G’ (Modelling and Simulation Lab)

HOD-Refinery Technological Division

CSIR-Indian Institute of Petroleum

Dehradun-248007

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(Krishna Nimesh)

Trainee Scientist (PGRPE-2012)

Master of Technology (APST)

CSIR-Indian Institute of Petroleum

Dehradun-248007

Dimethyl Ether is a clean and synthetic fuel. Because of its properties similar to that of liquid fuels such as LPG, Diesel etc. it can be thought as a substitute or alternative fuel to these in the near future. The objective of this project is to evaluate various synthesis routes for the production of Dimethyl Ether and/or Methanol from natural gas with the aim of improving energy efficiency and reduction in polluting emissions such as CO2 footprints, NOx, SOx etc.

Depending upon the route, there are 2 types of DME production processes available in the literature viz. 1-Step and 2-Step processes. In both the processes, production of syngas from carbonaceous feed stocks (Natural Gas, Coal, Biomass etc.) is the common step. When DME is synthesized from the produced syngas through Methanol Dehydration route, it is called 2-step process and if DME is directly produced from syngas it will be a single step process. Both the processes require catalyst for Methanol or DME production.

In this project firstly pre-eliminary steady state thermodynamic or equilibrium simulation has been done for several proposed flowsheets for DME production in ASPEN-HYSYS V8.4. Based on several performance parameters, one best possible flowsheet is chosen for which detailed steady state kinetic simulation is done to find out its industrial feasibility in ASPEN PLUS V8.4. Before these simulation studies, validation of each and every parameter of simulation model for each step was done to maintain its precision and accuracy to be used for the simulation of DME/Methanol synthesis.

Maximum yield of DME/Methanol is directly related to the composition of syngas generated in the respective processes. The important parameters such as H2/CO ratio, (H2-CO2)/(CO+CO2) or R-Value ratio, CO2 % in feed etc. along with temperature and pressure will not only have greater impact on the yield, selectivity of DME/Methanol but also on the economics of the whole plant. Proper syngas composition is the vital parameter for which the suitable reforming processes are identified which are followed by the methanol synthesis and/or methanol dehydration processes. Eight different reforming processes viz. SMR, ATR, SMR+ATR, Bi-Reforming, Tri-Reforming, POX+CO2 recycle and Dry Reforming has been simulated using RGibbs reactor in Aspen Hysys V8.4 in thermodynamic study. These reforming processes were chosen depending upon their suitability to produce specific composition of syngas for the specified DME production Process. Combined reforming i.e. SMR+ATR has been chosen for the final Kinetic study.

The steps such as Methanol synthesis and/or Methanol Dehydration are same in 1-step as well as in 2-step processes. These have been simulated thermodynamically as well kinetically. The 2-step DME synthesis process has been chosen along with SMR+ATR reforming step as the final DME/Methanol Synthesis process. The specific DME production rate for the given process is found out to be around 0.52 per kmol of methane. The specific CO2 footprint is around 0.63 while specific oxygen and water requirements are 0.8 and 0 respectively. The per pass conversion in the Combined Reformer, Methanol Reactor and

DME Reactor for the final flowsheet are found out to be 96.62, 63.32 and 84.59 % respectively.

Pinch Analysis of whole process shows that the given process is a heat surplus process which contains approx 1214 KW of extra heat. The process doesn’t require any external hot utility while the extra heat in the process can be used to produce HP steam of around 700 KW.

Acknowledgement

I would like to thank and express my sincere gratitude to my guide Dr. S. M Nanoti, HOD – Refinery Technological Division, CSIR – IIP, Dehradun for his support, advice and positive attitude.

I am also very grateful to my co-guide Mr. Sunil Kumar, Scientist – Modeling and Simulation Lab for his participation in stimulating discussion and the time he spent helping me. Without his support this project would have not been possible.

I would also like to thank our Director, Dr. M.O. Garg for his kind support and motivation he provided to me throughout the course of this project.

I will always be grateful to Dr. Sudip K. Ganguly, Dean – PGRPE CSIR-IIP, Dehradun for his invaluable guidance and advice.

Also I must express my gratitude to all scientists in the Modelling and Simulation Lab for creating a supportive and friendly working environment.

I also feel a great pleasure to thank all the staff members of the Institute for their cooperation and support which led to the successful completion of the project work.

I also offer my regards and blessings to all of those who supported me in many different ways during the period I spent working on this project.

Most importantly, I would like to thank my family: my parents, brothers and sister for their support, encouragement and love throughout my life.

Table of Contents

Declaration

Abstract

Acknowledgement

List of Figures

List of Tables

Notations

List of Acronyms

Chapters

1. Introduction1.1. D1.2. F1.3. F1.4. F

2. Vdgf2.1. G2.2. G2.3. G

3. Ff3.1. H3.2. H3.3. H

4. Sd4.1. F4.2. F4.3. F

5. Dgf5.1. H5.2. H5.3. H

List of Figures

List of Tables

Notations

Abbreviations

Symbols Definitions Units

List of Acronyms

Chapter – 1: Introduction and Objective

This thesis focuses on the Evaluation, validation and generation of flowsheet for the DME/Methanol synthesis process to be used at industrial scale. In this chapter, an introduction to Dimethyl Ether is given. The objective of the work is presented, and an outline of the thesis is provided.

1. Introduction

With the increase in the modern technologies, life standard of people is also increasing day by day. This advancement has dramatically increased the energy consumption all over the world in the recent year. Fast growing developing countries such as India, China, and South Africa etc. has shown rapid increase in terms of energy consumption. This rising energy demand has shown a very steep decline in the present energy resources such as Petroleum, Coal etc. Petroleum has been used for many purposes, either for energy or chemicals to support modern society. However, we have consumed about half of the global reserves and the remaining half is becoming increasingly expensive to exploit.

Figure-1: Energy Resource Consumption in India and World [1]

Figure-2: Liquids (including biofuel, etc) consumption for India, based on data of US EIA, together with Brent oil price in 2012 dollars, based on BP Statistical Review of World Energy updated with EIA data [2]

The sharp rise of the crude oil price Figure-2 comes from the close link between supply and demand as well as the rapid increase in the oil consumption of several Asian countries. Also, the energy situation is severe both in terms of the remaining resources and their impact on the environment, as exemplified by the “Kyoto protocol” for global warming. In order to lessen the environmental burden, it is strongly required to promote the more effective utilization or the suppressed consumption of petroleum or coal. Hence there is a need of in-depth research to develop sustainable clean technologies or processes which uses either renewable energy resources or some other raw materials like Biomass, Natural Gas etc. instead of present fossil fuels. These potential energy sources can be converted to different fuels having very high calorific energy content. Such fuel will also contain fewer pollutants than that obtained from petroleum or Coal. This is an advantage, because the ‘cleaner’ the fuel is, the less damage it can do to the environment. Well-known examples of technologies that convert carbonaceous feed stocks to liquid fuel are the Fisher-Tropsch and Methanol synthesis processes in which these feed stocks are first converted to Synthesis Gas (Syngas) which can be easily converted into different liquid fuels such as Gasoline, Diesel, Methanol, DME etc.

Fig-4: Various Products from Synthesis Gas (Syngas) [3]

Current fuels are more prone to emissions such as SOx, NOx, CO, CO2 etc. which are responsible for the environmental pollution so there is a need of research for such fuels which can replace or can be used along with them with lesser polluting emissions. One such fuel which is gaining large attention of all researchers all around the world is Dimethyl Ether (DME). It is a clean colourless gaseous fuel that is easy to liquefy and can be transported anywhere. It has a very great scope to be used as an alternative fuel, for electric power generation and in domestic applications such as heating and cooling. It has never been used as an energy material but it is now becoming a second promising synthetic fuel.

1.1 Why DME

As already mentioned DME is a clean gaseous fuel. It can be derived from many sources, including renewable materials (biomass, waste and agricultural products) and fossil fuels (natural gas and coal). It can be efficiently reformed to hydrogen at low temperatures, and does not have large issues with toxicity, production, infrastructure, and transportation as do various other fuels. [4] It is being used as a safe aerosol propellant which has replaced Current Aerosols such as CFC gases which is also environmentally friendly.[5] It also has lower possibility of producing carbonaceous particulate emissions as it contains oxygen and no carbon-carbon bonds as Methanol. However, unlike methanol, DME has a high enough cetane number hence it can be used as a clean high-efficiency compression ignition fuel with reduced NOx, SOx, and particulate matter. Also unlike methanol, DME is a gas at ambient temperature and pressure, so it must be stored under pressure as a liquid similar to LPG (liquefied petroleum gas). DME provides reduced Particulate Matters and NOx emissions, but increased CO and HC, when used as a diesel fuel.[5] It’s vastly superior cold starting, literally smokeless, quieter combustion, no fuel waxing in cold climates to clog fuel lines,

low NOx emissions, lower well-to-wheel greenhouse gas emissions than diesel fuel[6], high oxygen content, lack of sulfur or other noxious compounds, and ultra clean combustion and potentially a CO2 absorber in its production5 makes it a versatile and promising solution in the mixture of clean renewable and low-carbon fuels under consideration worldwide.

1.2 Background of DME production process

DME is produced by converting any carbonaceous feed stocks such as Natural gas, Coal or Biomass into synthesis gas (syngas). The produces syngas is then converted into DME via 2 processes viz. 1-Step/Single Step DME Synthesis Process or Two-Step DME Synthesis Process. In two step process, syngas is first converted to methanol in the presence of copper based catalyst, and then by subsequent methanol dehydration in the presence of a different catalyst such as γ-Alumina into DME. The following reactions occur:

CO + 2 H2 CH3OH -181.6 kJ/DME-mol (1)

2 CH3OH CH3OCH3 + H2O -23.4 kJ/DME-mol (2)

CO + H2O CO2+H2 -41.0 kJ/DME-mol (3)

Alternatively, in 1-step DME synthesis process syngas is directly converted to DME using a dual-catalyst system which permits both methanol synthesis and dehydration in the same process unit, with no intermediate methanol separation[7]. In this process, the intermediate methanol synthesis stage is eliminated. Both the one-step and two- step processes are commercially available. The reactions which are assumed to occur in single step process are as follows:

3 CO + 3 H2 CH3OCH3 + CO2 -246.0 kJ/DME-mol (4)

2 CO + 4 H2 CH3OCH3 + H2O -205.0 kJ/DME-mol (5)

In 1-step process also, reaction from 1 to 3 occurs, but the dual catalyst allows the synergy between the reactions that allows higher syngas conversion per pass or greater productivity as compared to the 2-step process[8] by consuming the intermediate Methanol as soon as it produced. The synergy works in the following way: Methanol which is produced by reaction (1) is consumed by Reaction (2). The water formed by Reaction (2) which would limit the rate of Reaction (2) is consumed by Reaction (3). Reaction (3) generates hydrogen which increases the rate of Reaction (1) [8].

Though it has many advantages over 2-step process, but this process is not proven industrially because of difficulties in the preparation of dual-functionalized catalyst which has very complex mechanism. But this process has very great scope in the near future.

Several companies such as JFE [9], Air Products and Chemical [10], KOGAS [11] etc. have run their plants on bench as well as on pilot scale and have shown very good performance.

On the other hand, 2-step DME process is well proven at commercial scale and several plants has been running in various countries such as Japan, China etc. for several years. Various Industries such as TOYO Engineering Corp.[12], Mitsubishi Gas Chemical[13], Lurgi[14], Uhde[15], Haldor Topsoe[16] etc has their DME plants running successfully at industrial scale.

1.3 Objective

Although 2-step process is well proven, but still it has vast scope of advancement in many areas such as catalysis, operating variables, heat integration, process intensification, reactor designing, separation process etc. In the present work all these parameters are taken care of to evaluate various 1-step and 2-step DME synthesis processes to find out the best suitable process. Detailed kinetics study has been done for the selected process along with pinch analysis to find out the external hot and/or cold utilities if any. Minimization of reforming agents such as Water, Oxygen, CO2 etc., Minimization of Refrigerants for cooling, Miniaturization of process equipments, Minimization of external utilities, Maximization of process to process heat transfer etc. are the main focus of the present work so that the proposed flowsheet can be used in stranded areas at industrial scale.

1.4 Outline of Thesis

First general description and literature review regarding synthesis gas production from Methane reforming processes along with Methanol synthesis and Dimethyl Ether synthesis processes is discussed. The important areas such as Reaction mechanism, Kinetic Models, Reaction parameters, Catalyst etc have been discussed in detail for every process. Steady State thermodynamic simulation has been done for the various processes and the parameters depending upon which the best process is selected is discussed in brief. Steady state Kinetic simulation has been done for the selected process along with pinch analysis to get the better insight of heat integration.

Chapter – 2: Literature Review

Methane Reforming Process Methanol Synthesis Processes Dimethyl Ether Synthesis Process

2. Introduction

The relationships between various parameters in any process and effect of process conditions (i.e. reaction temperatures, pressures and compositions etc.) on the possible product distributions can be easily determined by doing thermodynamic and kinetic studies prior to any scale up. To get the better insight of the overall process reactor designing is done based on kinetic studies so that it can be modified for optimum operating conditions and better yields. It is necessary to have a detailed knowledge of the reaction mechanism which can lead to the generation of very efficient process which results in appreciable profits. One such industrially important process is the Dimethyl Ether synthesis process. As a whole this process itself consists of 2 or 3 sub processes Viz. Syngas Production, Methanol Synthesis and Methanol Dehydration or Dimethyl Ether synthesis depending upon the route through which it is synthesized. An extensive research has already been done on all these processes by many researchers in terms of operating conditions, reaction mechanisms, reactor designing, catalysts etc. for many years.

2.1 Synthesis Gas Production

Synthesis gas or syngas, is an important intermediate step in many existing and emerging energy conversion technologies such as XTL (X=Coal, Biomass, Natural Gas), Methanol, Dimethyl Ether etc. Several processes are available in the literature which can be used to produce syngas [17-26]. Among all these processes Natural gas reforming is gaining more attraction worldwide. It is also known as Methane reforming as it contains more than 80 % of methane [27, 28]. Methane reforming can be performed by different techniques, each of which has their own advantages and disadvantages. The product of natural gas reforming is a mixture of gases known as syngas (Mainly CO and H2) [29].

The composition of Natural gas varies region to region. It mainly composed of saturated hydrocarbons such as methane in high percentage and higher hydrocarbons such as propane and butane in lower quantities. In raw state, it also contains varied levels of impurities such as

nitrogen, carbon dioxide, water and sulphur compounds etc. [29]. Today natural gas is the preferred source for production of syngas, a mixture of hydrogen and carbon monoxide, from which purified hydrogen can be obtained. There are several different catalytic and/or thermal processes for producing syngas from natural gas [30]. The classification is as follows:

1. Catalytic Natural gas Reforming:a. Steam Methane Reforming (SMR)b. Dry Methane Reforming (DMR)c. Catalytic Partial Oxidation of Methane (CPOX)

2. Thermal Natural Gas Reforminga. Partial Oxidation of Methane (POXM)

Other reforming technologies are the combination of above reforming processes which are as follows:

1. Bi-Reforming of Methane: SMR+DMR2. Tri-Reforming of Methane: SMR+DME+POX3. Autothermal Reforming of Methane: POX+SMR

All these types of processes have the same objective and lead to same final product i.e. synthesis gas.

2.1.1 Steam Methane Reforming (SMR)

Steam reforming is a well proven efficient process used mainly for the production of hydrogen and has been in practice since 1930 [31]. Standard Oil Co., USA began the first steam reforming plant in 1930 with light alkanes as feed [32]

Chapter –3: Flow sheet Development

References:

1. https://www.dnb.co.in/IndiasEnergySector2012/Overview_oil.asp ; 30th May, 2014.2. http://oilprice.com/Energy/Oil-Prices/Oil-Demand-in-China-and-India-Falling-Proof-

Prices-are-Too-High.html ; 30th May, 2014.3. Technocal and Economic assessment of synthesis gas to fuels and chemicals with

emphasis on the potential for biomass derived syngas; P.L. Spath, D.C. Dayton; National Renewable Energy Laboratory, NREL/TP-510-34929, December 2003. (http://bioweb.sungrant.org/Technical/Bioproducts/Bioproducts+from+Syngas/Methanol/Default.htm ; 30th May, 2014).

4. Dimethyl ether (DME) as an alternative fuel; Troy A. Semelsberger, Rodney L. Borup, Howard L. Greene; Journal of Power Sources, Volume 156, Issue 2, 1 June 2006, Pages 497–511

5. http://www.dieselnet.com/tech/fuel_dme.php ; 30th May, 2014.6. http://www.me.umn.edu/centers/cdr/cdr_dme.html ; 30th May, 2014.7. http://www.biofuelstp.eu/factsheets/dme-fact-sheet.pdf ; 2nd June, 2014.8. Kinetic understanding of the chemical synergy under LPDMETM conditions-once-

through applications; X.D. Peng, B.A. Toseland, P.J.A. Tijm; Chemical Engineering Science 54 (1999) 2787}2792

9. Method For Producing Dimethyl Ether; Tsutomu Shikada, Yotaro Ohno, Takashi OgaWa, Masatsugu Mizuguchi, Masami Ono, Kaoru Fujimoto; US 6800665 B1, Oct. 5, 2004

10. Liquid Phase process for Dimethyl Ether synthesis; John J. Lewnard; Thomas H. Hsiung, James F. White, Bharat L. Bhatt; US-5218003, Jun. 8, 1993.

11. Method Of Producinga Catalyst Used For Synthesizing Dimethylether From A Synthesis Gas Containing Carbon Dioxide; Young Soon Baek, Won Jun Cho, Yun Bin Yan, Yong Gi Mo, Kyung Hae Lee, Eun Mee Jang; US 8450234 B2, May 28, 2013

12. Process For Producing Dimethyl Ether; Kazuo Shoji, Satoshi Terai; US 7202387 B2, Apr. 10, 2007

13. Process For The Production Of Dimethyl Ether Useful As A Propellant; Nobuyuki Murai, Yokkaichi; Kazuya Nakamichi, Matsuzaka; Masayuki Otake, Yokohama; Takashi Ushikubo, Sagamihara; US 4560807, Dec. 24, 1985

14. Manufacture Of Dimethyl Ether From Crude Methanol; Peter Mitschke, Eckhard Seidel, Thomas Renner, Martin Rothaemela;US 2012/0220804 A1, Aug. 30, 2012

15. http://www.uhde-ftp.de/cgi-bin/byteserver.pl/pdf/technologies/TP_DME_2005.pdf ; 2nd June, 2014.

16. Process for The Synthesis Of A Methanol/Dimethyl Ether Mixture From Synthesis Gas; Jesper Haugaard, Bodil Voss; US 6191175 B1, Feb. 20, 2001.

17. Gasification process combined with steam methane performing to produce syngas suitable for methanol production; Fong, Wing-Chiu Francis; EP 0723930B1, 16.10.2002

18. Gasification reactor and process; Kossak-Glowczewski, Thomas Paul Von, Joachim Papendick, Hans Christian Thul; EP2619290 A2, 31 Jul 2013

19.Method of operation of process to produce syngas from carbonaceous material; Ching-Whan Ko, Michael Sean Slape, Peter S BELL, Kim OCFEMIA; WO2013032537 A1, 7 Mar 2013

20. A biomass gasification system for synthesis gas from the new method; Li-Qun Wang, Yu-Huan Dun, Heng Tang, Tong-Zhang Wang; Natural Sciences, Vol.1, No.3

21. Biomass Gasification Processes in Downdraft Fixed Bed Reactors: A Review; Anjireddy Bhavanam, R. C. Sastry; International Journal of Chemical Engineering and Applications, Vol. 2, No. 6, December 2011

22. Tubular reforming and autothermal reforming of natural gas - an overview of available processes; Ib Dybkjax; Fuel Processing Technology 42 (1995) 85-107

23. http://www.petrochemconclave.com/presentation/2013/Mr.DTse.pdf ; 4th June, 2014.24. Gasification of Petcoke and Coal/Biomass Blend: A Review; Morteza Khosravi, Anil

Khadse; International Journal of Emerging Technology and Advanced Engineering, Volume 3, Issue 12, December 2013

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autothermal reactor design; C.N. Ávila-Neto,  S.C. Dantas,  F.A. Silva,  T.V. Franco, L.L. Romanielo, C.E. Hori, A.J. Assis; Journal of Natural Gas Science and Engineering, Volume 1, Issue 6, December 2009, Pages 205–215

27. http://pubs.usgs.gov/of/2003/of03-409/of03-409.pdf; 4th June, 2014.28. http://www.naesb.org/pdf2/wgq_bps100605w2.pdf; 4th June, 2014.29. A Study On The Characteristics Of The Reforming Of Methane: A Review; Neiva, L.

S.1; a Gama, L; Brazilian Journal Of Petroleum And Gas, v. 4 n. 3, p. 119-127, 2010.30. Catalysis and the hydrogen economy; Armor, J.N.; Catalysis Letter .Vol. 101, n 3-4,

p. 131-135, 2005.31. Catalytic Steam Reforming; Jens R. Rostrup-Nielsen; Catalysis Volume 5, 1984, pp

1-11732. Hydrogen production reactions from carbon feedstocks: fossil fuels and biomass;

Navarro R, Pena M, Fierro J.; Chem Rev. 2007, 107:3952-91.