Optimal Design of Gas-Expanded Liquid Ethylene Oxide Production

Subscriber access provided by University of Pennsylvania Libraries

Process Systems Engineering

Optimal Design of Gas-Expanded Liquid Ethylene Oxide Production with Zero Carbon Dioxide Byproduct Mhd A. Abou Shama, and Qiang Xu Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b05060 • Publication Date (Web): 23 Mar 2018 Downloaded from http://pubs.acs.org on March 25, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

Optimal Design of Gas-Expanded Liquid Ethylene Oxide Production with Zero Carbon Dioxide Byproduct† Mhd A. Abou Shama and Qiang Xu* Dan F. Smith Department of Chemical Engineering Lamar University, Beaumont, TX 77710, USA Abstract The concept of ethylene epoxidation over methyltrioxorhenium (MTO) catalyst could save the world from global warming since the epoxidation reaction never produces carbon dioxide as byproduct. Unlike the conventional gas epoxidation reaction with oxygen, this reaction takes place in the (ethylene) gas-expanded liquid solvent phase (methanol) while the reaction oxidant is hydrogen peroxide. The reaction takes place at temperatures and pressures close to the ethylene critical point (Pc = 50.42 bar; Tc = 48.56 °F).1 In this paper, an optimized design and operation for MTO based ethylene oxide (EO) production process has been developed, which has less manufacturing costs compared with the one from current literatures.2 The developed EO system could produce 200,000 tons of ethylene oxide per year at purity of 99.9%. It has two reactors for ethylene epoxidation and hydrogen peroxide decomposition, one flash drum, and three distillation columns for product and recycled material purification. The design has secured the safety of the operation by not presenting oxygen and flammable vapor mixtures in any of the process equipment. The EO manufacturing costs $0.52 per pound, and the fixed capital investment of the project is $66,240,000, which is estimated to be paid back after 7.3 years, while the net present value is $56,900,000. Keywords: Ethylene Oxide, Steady state optimization, Modeling and simulation † For publication in Industrial & Engineering Chemistry Research. * All Correspondence should be addressed to Prof. Qiang Xu (Phone: 409-880-7818; Fax: 409880-2197; E-mail: [email protected])

1 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1. Introduction

In 2011, the global demand on ethylene oxide (EO) was estimated to be $29 billion. Compound annual growth between 2013 and 2018 is projected to be 5.7%.3 EO is a widely used intermediate chemical by many important products such as solvents, antifreeze, adhesives, and many other chemicals as shown in Figure 1,4 which highlights the use of EO in our daily lives. EO is a very reactive chemical that involves mostly opening to its ring shape and releasing huge amounts of energy.5 EO is a colorless gas at an ambient temperature, and it smells like ether. It is soluble in organic solvent and is toxic flammable gas at ambient pressure and temperature. Its explosion range is 3.6% through 100% of EO in air.6

Figure 1. Ethylene oxide based product family (EPA, 1986).4

The conventional way to produce EO is through an epoxidation reaction where ethylene is epoxidized to EO using oxygen as oxidant. The reaction is carried over a silver based catalyst at a temperature range of 392-500 °F and a pressure range of 10-30 bar.7 Due to the high temperature and the presence of oxygen in the reactor, ethylene and EO can combust undesirably to form water and carbon dioxide as shown in Figure 2.2 Thus, the selectivity of the epoxidation reaction drops to 85%, and the conversion of ethylene per pass is 4-8% at their optimal steadystate operation.8 The estimated loss of ethylene and EO per year due to the undesired combustion reaction can reach up to $1.2 billon based on $0.32 per bound for ethylene and $0.79 per bound for EO.2 The conventional process also generates about 3.4 million tons of carbon dioxide per year to the atmospheric enviroment.2 Furthermore, because of the dangerous operating


Page 2 of 36

Page 3 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


conditions of the reactor and the exothermic properties of ethylene and EO reactions, the operation of EO reactor can be very dangerous and easily turned into a runaway reaction.

Figure 2. Conventional gas-phase ethylene epoxidation with silver based catalyst.2

In 2009, the Center for Environmental Beneficial Catalysis (CEBC) at Kansas University discovered a new catalyst that could carry out the epoxidation reaction of ethylene to EO in gasexpanded liquid phase using hydrogen peroxide (H2O2) as the oxidant, methyltrioxorhenium (MTO) as the homogenous catalyst, methanol as the solvent, and pyridine-N-oxide as the catalyst promoter.9 The reaction is carried in a continuous stirred reactor at a pressure of 50 bar and at a temperature range of 68-104 °F.10 Under those conditions which are close to the ethylene critical point (Pc = 50.42 bar; Tc = 48.56 °F),1 the ethylene will dissolve better in the solvent and react with H2O2 at the surface sites of the MTO catalyst to produce EO. To complete gas-expanded liquid phase process for ethylene epoxidation, there are two different metal-based catalysts are required to activate the reaction. First, the Nb-based catalyst, which has been studied by Maiti et al., has proved its ability in the EO process.11 Second is the MTO catalyst, which has been studied extensively and many publications have been reported about the rules of the catalyst that can play in olefin epoxidation reaction, such as Abu-Omar and Busch’s studies about the activation of methyltrioxorhenium in olefin epoxidations.12-13 However, the process of ethylene epoxidation to EO using MTO was introduced more clearly by CEBC. CEBC has published three research papers that discussed the main idea of ethylene epoxidation. The first paper by Lee et al. in 2009 discussed the thermodynamic modeling of the process and the flammability calculation of the reaction.9 The second paper by Ghanta et al. in



2012 discussed the transport phenomena and the kinetic reaction of ethylene epoxidation in gasexpanded liquid phase.10 The third paper by Ghanta et al., also published in 2012, compared the economic and environmental differences between rhenium catalyst base (MTO catalyst) and silver catalyst base (conventional ethylene oxide production process).2 In Fact, Ghanta et al. on their last research found that the MTO based catalyst process is not only economical better than the conversational process, but environmentally it is similar to the conventional process based on comparative cradle-to-gate life cycle assessments to the overall environmental impacts on air quality, water quality, and greenhouse gas emissions.2 Generally, the updated MTO based EO production process developed by CEBC contains reaction and separation sections. After the epoxidation reaction is completed, the excess ethylene is recycled back to the main epoxidation reactor by using a flash drum with operating condition that secures the safety of the operation and to optimize the ethylene recovery percentage. Meanwhile, the excess H2O2 is decomposed to H2O and O2 in a separate unit for safety concern. Finally, three steps of distillation columns will be utilized to: (i) purify the EO product under its required specification; (ii) recycle unreacted ethylene and methanol solvent to the main epoxidation reactor; and (iii) purify water and send it to the water treatment process. In this paper, an optimized design and operation for the MTO based EO production process has been developed.

It has two design innovations: (i) the vapor outlet of the

decomposer unit will be recycled to H2O2 regeneration process to convert the generated O2 to H2O2 and reused by the epoxidation reactor to enhance material use efficiency; (ii) the distillation separation sequence has been changed to separate ethylene, water, EO, and methanol sequentially to save more energy than that based on current separation sequence from literatures. The developed EO system could produce 200,000 tons of ethylene oxide per year at purity of


Page 4 of 36

Page 5 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


99.9%. The EO manufacturing costs $0.52 per pound, and the fixed capital investment of the project is $66,240,000, which is estimated to be paid back after 7.3 years. The developed EO system has been virtually demonstrated via plant-wide simulations with Aspen Plus version 8.8 and its economic and energy analyzing associated packages.14

2. Design Methodology Framework

2.1 Simulation Packages This work is performed by using Aspen Plus V8.8. and its economic and energy analyzer packages, where the chemical components list include hydrogen peroxide, water, methanol, ethylene, ethylene oxide, and oxygen. According to Lee et al.,9 the system can be presented thermodynamically well by using UNIQUAC model for liquid phase and Peng Robinson equation of state for gas phase. Also, the interaction parameters used for predicting VLE of ethylene and methanol as wells as ethylene oxide and methanol are changed to values in Table 1.9 Table 2 shows the equipment process model that are used to build the simulation environment in Aspen Plus.

Table 1. Binary Interaction Parameters9

Table 2. Simulation Process Models

2.2 New EO Production Process



As is shown in Figure 3, the developed EO process consists of two reactors (R-101 and R-102), a flash drum (F101), and three distillation columns (T-101, T-102, and T-103). The feed is introduced to R-101 in stream 101 at the pressure of 50 bar, temperature of 104 °F, and mass flow rate shown in Table 3. In R-101, ethylene and hydrogen peroxide react to produce ethylene oxide and water according to reaction 110 in Table 4. The reactor operates at 50 bar and 104 °F with the homogeneous catalyst of MTO at leaching rate of 0.11 lb MTO/hr7. The residence time of the reactor is set as 0.25 hr as suggested.10 In F-101, the process stream 102 flashes out to recover most of remining unreacted ethylene to the vapor outlet. The drum operates to pressure of 5 bar and temperature of 104 °F. The vapor outlet, which is mostly ethylene, is compressed and cooled down to the feed conditions and recycled back to R-101. In the other outlet (stream 103), the stream enters reactor R-102 to decompose the remaining H2O2 to water and oxygen according to reaction 215 in Table 4, before they enter the distillation columns. R-102 operates at the pressure 3.48 bar, temperature of 104 °F, and the reactor volume is 19.69 ft3.

Figure 3. Flowsheet of the new developed EO production process.

Table 3. Flow Rate Information (lb/hr) of the Developed EO Process Streams

Table 4. Reaction Settings for the Simulation Model

The three distillation columns are on series and used to separate and purify the product and recycle underacted reactant and solvent. Thus, the first column (T-101) is a trays column with a partial condenser that operates at pressure of 10 bar, and it recovers 99.90 mole% of


Page 6 of 36

Page 7 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


ethylene oxide in the bottom stream (107) while the top product stream (302) recovers all the remaining ethylene to H2O2 REGENERATION block. The second column (T-102) is a packed column with total condenser which operates at pressure of 6.76 bar, and it recovers 99.99 mole% of water in bottom stream (WATER) while the top stream (108) recovers the remaining ethylene oxide and methanol. The third column (T-103) is a packed column with a partial condenser, which operates at pressure of 1 bar. It recovers 99.90 mole% of ethylene oxide in top stream (EO-PRODUCT). The bottom stream (METHANOL) recovers the methanol solvent and recycles it back to R-101. Finally, PUMPS sub-flowsheet block on the recycle solvent stream is a series of four pumps and four heaters are used to raise the stream pressure and temperature to the required feed condition. H2O2 REGENERATION sub-flowsheet block consists of a conversion reactor (R-103) to convert the generated oxygen from stream 301 and 302 to hydrogen peroxide and recycles that back to reactor R-101. Also, it contains a heater block to raise the pressure and temperature’s stream to operation conditions.

2.3 Equipment Sizing Working on optimizing the model size and operation condition, the column tray and packed sizing is used to define the column size and types. Also, Aspen Process Economic Analyzer is used to define the size of flash drums, heat exchangers, and pumps. To activate this feature in Aspen stream price, process utilities and cost options are needed.

2.4 Capital and Production Costs



Besides the fixed capital investment, the raw material and utility costs are also considered for the production cost. Chemical prices per pound are obtained from Chemical Market Report as shown in Table 5. Different types of utilities are used in the process design as shown in Table 5. Finally, the overall process profitability evaluation is summarized by Table 6.

Table 5. Raw Material and Utilities Cost

Table 6. Project Investment for the Developed EO Process

3. Simulation Results and Discussion

At the pressure of 50 bar and temperature of 104 °F, the ethylene in the feed stream is in its gas phase. Once it mixes with the methanol solvent, it dissolves in the liquid phase where the reaction will take place later in R-101. Meanwhile, the oxidant H2O2 with (50-50) % H2O2/H2O feed compositions is stable and free from decomposing to water and oxygen at the operation conditions, so that the reactor R-101 is secured from existing EO or ethylene and oxygen in its gas or liquid phases. Thus, the operation of R-101 is safer than the operation of the conventional ethylene epoxidation in the gas phase at the high temperature and pressure. Since the MTO catalyst activity still a challenge to the process, further in-depth researches to understand the catalyst activity and stability are still needed. This work has used Ghanta M. et al. results regarding to catalyst activity and cost analysis, which have the simulation operation criterial agree with those he published in 20109 and 20122. Also, this work is performed at the same EO production rate of reported from Ghanta et al., i.e., 50,250 lb/hr of EO.


Page 8 of 36

Page 9 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3.1 Reaction Section In the epoxidation reactor (R-101), the dissolved ethylene and the oxidant H2O2 react on the catalyst site. Reaction 1 shown in Table 4 is based on the pseudo-first order kinetic model.10 Since the MTO catalyst remains active with the high concentration of H2O2, it will form di(peroxo) rhenium complex intermediate, which reacts with ethylene to produce EO Later. But the intermediate activity decreases with the increase of water concentration in the mixture; therefore, H2O2 is selected to be reaction-limiting reactant, and ethylene is fed excessively. Since only the epoxidation reaction is presented in at these condition, and the ability to have H2O2 stable in the reactor where it does not decompose to H2O and O2, the EO reaction selectivity is over 99%.10 Based on the reactor setting, the reactor (R-101) volume is 1,743.14 ft3 and the required cooling duty is 1.14×108 Btu/hr. Using the chilled water to cool down and control the epoxidation exothermic reaction, the reactor operating cost is $116.52/hr based on cost rates of chilled water in Table 5. The estimated cost for the reactor using Aspen Process Economic Analyzer (APEA) is shown in Table 6. Next, in the flash drum F-101, the product stream of reactor R-101 is depressurized to recover most of the unreacted excess ethylene. The depressurization process in F-101 should happen in such a way that it prevents the remaining unreacted hydrogen peroxide from decomposing to water and oxygen to prevent any fire or explosion scenarios. Also, the selected operation temperature and pressure should give back the optimal ethylene recovery flowrate to stream 201. Therefore, the pressure of 5 bar and temperature of 104 °F are identified as the optimal settings for F-101 operations, and ethylene recovery in stream 201 is 66.30%. The mass stream composition of ethylene in steam 201 is 93.16%. Also, the later equipment process will



have balance compositions out of the lower and the upper flammability zone of EO, ethylene, and methanol. The depressurization process in F-101 will requires energy of 1.04×105 Btu/hr which will cost $0.21/hr using low pressure steam at the cost rate which is shown in Table 5. Using APEA, the drum diameter is 7.5 ft, and the drum length is 22.5 ft. Also, the estimated cost of the drum is calculated using APEA as shown in Table 6. Before continuing the separation and purification processes, the unreacted hydrogen peroxide must decompose because it forms serious hazardous scenarios in reboilers of distillation columns if it decomposes in the presence of EO and Ethylene. Thus, another continuous stirred reactor (R-102) with liquid and vapor outlet streams is used to decompose the hydrogen peroxide. R-102 follows reaction 2 in Table 4, and it is set up as discussed in the previous section (process description). At those operation conditions, the vapor compositions of R-102 and stream 301 is secured out of EO and ethylene flammability zones. The decomposing process in R-102 releases energy equal to 5.34×106 Btu/hr, and it costs $1.19/hr to remove it from the reactor using the cooling water at the cost rate shown in Table 5. The estimated cost of R-102 is calculated by APEA, which is shown in Table 6.

3.2 Distillation and Purification Section In the separation and purification steps, three distillation columns are used to separate ethylene, water, methanol, and ethylene oxide. The K-values of components in each stream are calculated by Aspen. In stream 104, the K-value for ethylene is the highest, which is 169.14. Therefore, it is the most beneficial to purify ethylene first for the mixture, so a tray column with 4 stages is used to recover the reminding ethylene and oxygen in the top stream. Since it is very difficult to recover ethylene in the liquid phase, the column condenser is selected to be partial


Page 10 of 36

Page 11 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


vapor to decrease the cost of column operation. Also, the column’s operation pressure at the condenser is increased to 10 bar, such that the chilled water can be used in the condenser as coolant fluid while the reboiler uses the medium pressure steam as the heating fluid source. The EO molar composition in stream 302 (T-101 top stream) is 2% mole, which is the safe composition and not explosive according to Lee et al. 2009.9 With the recovery 99.90% mole of EO in T-101 bottom stream, the column reflux ratio is 31.61 and boil-up ratio is 0.07. Using a sieve tray with tray spacing of 2.5 ft makes the diameter of the column shrink down to 4.69 ft. As shown in Figure 4, the optimal feed tray is selected to be at the bottom of the column since its temperature and ethylene composition are the closest to stream 106. Combining the condenser and reboiler operation cost, the column operation cost regarding to the utility cost in Table 5 is $55.12/hr, and the estimated capital column cost is $616,000.

Figure 4. T-101 temperature and composition profiles for ethylene and ethylene oxide.

For the bottom stream (107) of T-101, the relative volatility of methanol and water is 2.15, and the relative volatility of ethylene oxide and methanol is 1.27. Thus, it is more beneficial to purify water in the next step from the mixture. Based on this consideration, the packed column (T-102) is used to recover 99.99% of the water in the bottom, and then it is sent to the water treatment process. The column has 35 stages, and HETP is 8 ft. Because another separation step is required to get the final product, the condenser of T-102 is set to be the total condenser, which operates with the cooling water with the pressure of 6.76 bar; while the reboiler of the column operates with the help of the medium pressure steam. To operate column T-102 at the optimal cost shown in Figure 5, the feed stage is selected to be stage 28 where the



liquid composition of water and methanol is matched to the feed stream compositions as shown in Figure 5. Therefore, compounding the condenser and reboiler operation cost, the column operation cost regarding to utilities cost in Table 5 is $1,244.57/hr, and the estimated column cost is $11,339,000.

Figure 5. T-102 temperature and composition profiles for water and methanol.

Finally, T-103 is used to separate the ethylene oxide product at the purity of 99.90% mole, which is the industrial purity specification,17 and recover the methanol solvent back to the main epoxidation reactor. Since ethylene oxide and methanol relative volatility in stream 109 is relatively low, and K-values of the components are very close. T-103 is a packed column with 100 stages, and HETP is 3.59 ft. T-103 operates at the atmospheric pressure, and it cannot be pressurized because increasing the pressure in the column will form upper azeotrope composition as shown in Figure 6. The condenser of T-103 is set as a partial vapor condenser, which operates with chilled water, while the reboiler of the column reboiler operates with the help of the lowpressure steam. To have column T-103 running at optimal cost as shown in Figure 7, the feed stage is selected to be stage 7 where the liquid composition of EO and methanol is matched to the feed stream compositions as is shown in Figure 7. Therefore, compounding the condenser and reboiler operation cost, the column operation cost regarding to utilities cost in Table 5 is $1,199.73/hr, and the estimated column cost is $16,142,000.

Figure 6. Vapor and liquid equilibriums for methanol and ethylene oxide at 1 and 6.76 bar, ethylene and ethylene oxide at 10.0 bar, and methanol and water at 10.0 bar.


Page 12 of 36

Page 13 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60



3.3 Recovery Section The developed EO production process contains three recycle loops. The first recycle loop is to recover most of ethylene, and it starts at stream 201 and ends at stream 203. The stream mostly contains ethylene, and its flowrate is shown in Table 3. The stream is compressed back to 50 bar using C-201 and cooled down to 104 °F using E-201 before it is mixed with fresh feed and enters R-101. The second recycle loop is to recover and regenerate hydrogen peroxide. It starts at streams 301 and 302 and ends at stream 304. Since this work focuses only on designing main production stream (101 through 109) and its related equipment, the hydrogen peroxide recycle process is not designed in detail. Assuming a well hydrogen peroxide designed process can achieve 50-50% H2O2/H2O mixture by a model similar to Ghanta study in his dissertation work,18 so the required reactions to regenerate hydrogen peroxide are done with a conversion reactor model with ability to produce 50-50% H2O2/H2O mixture. The third recycle loop is to recover methanol solvent. It starts at stream METHANOL and ends at steam 401. As is shown in Table 3, the stream contains mainly methanol with small amount of EO due to economic conversion. Block PUMPS is sub-sheet that contains pumps and heaters that are connected on series to bring the stream pressure and temperature to 50 bar and 104 °F, respectively. By following design heuristics about liquid compression, which suggest the outlet pressure is three times bigger than inlet pressure, as well as to compress first and cool a stream later,14 therefore, the PUMPS units consists of five pumps and five heaters.



Finally, based on raw material and utility costs in Table 5 and fixed capital investment divided by ten years, the cost of a bound of ethylene oxide is $0.52. Meanwhile, based on calculated economic variables such as manufacturing costs and sales revenues and assumed other variables like land cost and salvage values as are shown in Table 6, the payback period for the project is 7.3 years as shown in Figure 8. Also, the net profit per year is $ 32,133,000, as shown in Table 7. It should be noted that the MTO based catalyst process has proved the ability to produce EO more efficiently and safer than the conventional process. Meanwhile, this work has added valuable bricks to the MTO based catalyst process. However, other important studies are still needed to improve the process for future pilot or even industrial scale applications, such as (i) plant-wide dynamic simulation model study to investigate the controllability and stability of the model which requires lots of supporting information in equipment sizing and control information; (ii) heat integration network study such as pinch technology analysis which improves the model farther in term of saving utilities; (iii) preform details study for producing H2O2 onsite which will help in designing the given regeneration H2O2 block on the flowsheet; (iv) consider another catalyst such as Nb-based catalyst which may solve the cost problem of the MTO catalyst and its stability.

Figure 8. Cumulative discounted cash flow diagram.

Table 7. Summary of the Economic Performance

4. Conclusion


Page 14 of 36

Page 15 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


In this paper, a new MTO based EO production process has been developed, which is safer and more profitable than conventional industrial practice on the gas phase epoxidation. It has optimized design and operation compared with current literature studies in the following two aspects: (i) the vapor outlet of the decomposer unit will be recycled to H2O2 regeneration process to convert the generated O2 to H2O2 and reused by the epoxidation reactor to enhance material use efficiency; (ii) the distillation separation sequence has been changed to separate ethylene, water, EO, and methanol sequentially to save more energy. Based on the conceptual design of a plant with 200,000 tons of EO production per year at purity of 99.9%, the fixed capital investment is about $66,240,000. The resultant plant layout and operating conditions could make EO production cost as low as $0.52. In addition, this work gives a well control and design for the process to recycle unreacted hydrogen peroxide and ethylene with safe and secure of presenting an exploitable mixture of oxygen and flammable gas.

Acknowledgements

This work was supported in part Lamar University Visionary Initiative Project and Anita Riddle Faculty Fellowship.



References:

(1)

Gas Encyclopedia by Air Liquide. https://encyclopedia.airliquide.com/ethylene (accessed September 8, 2017).

(2)

Ghanta, M.; Ruddy, T.; Fahey, D.; Busch, D.; Subramaniam, B. Is the Liquid-Phase H2O2-Based Ethylene Oxide Process More Economical and Greener Than the Gas-Phase O2-Based Silver-Catalyzed Process? Ind. Eng. Chem. Res. 2013, 52, 18-29.

(3)

Prospects Look Good for Global Ethylene Oxide, Ethylene Glycol Markets; Processing Solution for The Process Industries. https://www.processingmagazine.com/prospectslook-good-for-global-ethylene-oxide-ethylene-glycol-markets/ (publish August 8, 2013).

(4)

Environmental Protection Agency. Locating and estimating air emissions from sources of ethylene oxide. EPA report: EPA-450/4-84-007L, September, 1986.

(5)

Rebsdat, S.; Mayer, D., Ethylene Oxide. In Ullmann’s Encyclopedia of Industrial Chemistry, 6th ed.; Hawkins, S.; Russey, W. E.; Pilkart-Muller, M., Eds. Wiley-VCH: New York, 2005; Vol. 13, p 23.

(6)

Lower and Upper Explosive Limits for Flammable Gases and Vapors (LFL/UFL); Matheson Tri Gas. https://www.mathesongas.com/pdfs/products/Lower-(LEL)-&-Upper(UEL)-Explosive-Limits-.pdf (accessed December 5, 2017).

(7)

Weissermel, K.; Arpe, H.-J. Industrial Organic Chemistry, 4th ed.; Wiley-VCH: Washington, DC, 2003.

(8)

Buffum, J. E.; Kowaleski, R. M.; Gerdes, W. H. Ethylene Oxide Catalyst. U.S. Patent 5,145,824, 1992.


Page 16 of 36

Page 17 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(9)

Lee, H. J.; Ghanta, M.; Busch, D. H.; Subramaniam, B. Towards a CO2-free ethylene oxide process: Homogenous ethylene oxide in gas-expanded liquids. Chem. Eng. Sci. 2010, 65 (1), 128-134.

(10)

Ghanta, M.; Lee, H. J.; Busch, D. H.; Subramaniam, B. Highly Selective Homogeneous Ethylene Epoxidation in Gas (Ethylene)-Expanded Liquid: Transport and Kinetic Studies. AIChE J. 2012, DOI: 10.1002/aic.13789.

(11)

Maiti, S.K.; Ramanathan, A.; Thompson, W.H.; Subramaniam, B. Strategies to passivate Bronsted acidity in Nb-TUD-1 enhance hydrogen peroxide utilization and reduce metal leaching during ethylene epoxidation. Ind. Eng. Chem. Res. 2017, 56, 1999-2007.

(12)

Abu-Omar, M.M.; Hansen, P.J.; Espenson, J.H. Deactivation of Methylrhenium trioxideperoxide catalysts by diverse and competing pathways. J. Am. Chem. Soc. 1996, 118 (21), 4966-4974.

(13)

Busch, D.H.; Subramaniam, B.; Lee, H.-J.; Shi, T.-P. Process for selective catalytic epoxidation of olefins into epoxides. U.S. Patent 200,7093,666, 2007.

(14)

Aspen Plus, 8.8; Aspen Technologies: Bedford, MA, U.S., 2015.

(15)

Schumb, W.; Satterfield, R. Hydrogen Peroxide.; Reinhold Pub. Corp.: New York, 1955; 207-231.

(16)

ICIS. http://www.icis.com/chemicals/channel-info-chemicals-az/ (accessed September 8, 2017).

(17)

Ethylene oxide high purity; Dow. http://msdssearch.dow.com/PublishedLiteratureDOW COM/dh_0931/0901b803809315b9.pdf?filepath=rds/RDS_00012116.pdf&fromPage=Ge tDoc. (accessed September 8, 2017).



(18)

Ghanta, M. Development of An Economically Viable H2O2-based, Liquid-Phase Ethylene Oxide Technology: Reactor Engineering and Catalyst Development Studies. Ph.D. Dissertation, University of Kansas, Lawrence, KS, 2012.

(19)

Turton, R.; Bailie, R. C.; Whiting W. B.; Shaeiwitiz, J. A.; Bhattacharyya D. Analysis, Synthesis, and Design of Chemical Processes. 3rd. ed.; Pearson: Boston, 2009; 150-225.


Page 18 of 36

Page 19 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


LIST OF TABLES

Table 1.

Binary Interaction Parameters9

Table 2.

Simulation Process Models

Table 3.

Flow Rate Information (lb/hr) of the Developed EO Process Streams

Table 4.

Reaction Settings for the Simulation Model

Table 5.

Raw Material and Utilities Cost

Table 6.

Project Investment for the Developed EO Process

Table 7.

Summary of the Economic Performance



Table 1. Binary Interaction Parameters9 Components

Interaction Parameters

Ethylene – Methanol a

0.010

Methanol – Ethylene a

0.010

Ethylene oxide – Methanol b

-245.7

Methanol – Ethylene oxide b

629.7

a: Peng Robinson equation of state. b: UNIQUAC model.


Page 20 of 36

Page 21 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 2. Simulation Process Models Simulation Model from Aspen Plus

Equipment

RCSTR

R-101 and R-102

Flash2

F-101

RadFrac

T-101, T-102, and T-103

RStoic

R-103

Compr

C-101

Pump

P-101, P-102, P-103, P104, and P-105

Heater

E-101, E-102, E103, E-104, E-105, E-106, and E-107



Page 22 of 36

Table 3. Flow Rate Information (lb/hr) of the Developed EO Process Streams Stream Index

Hydrogen peroxide

Water

Methanol

Ethylene

Ethylene oxide

Oxygen

101

43,144.0

43,144.0

226,863.0

38,756.0

1,411.1

0.0

102

4,344.5

63,693.5

226,863.0

6,756.0

51,661.1

0.0

201

0.1

20.7

167.2

4,479.3

140.7

0.0

303

0.0

19.4

225.0

2,273.9

169.1

2,041.2

WATER

5.0

65,945.1

7.0

0.0

0.0

0.0

METHANOL

0.0

6.6

226,434.0

0.0

1,101.3

0.0

EO-PRODUCT

0.0

0.0

30.2

2.8

50,250

0.0


Page 23 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 4. Reaction Settings for the Simulation Model Reaction 110 215

Reaction Type LHHW Power Law

Reference

Activation

Temp.

Energy

6.2 × 10

68 °F

57

#$ % 1000 !& ! .

284 °F

52.7

Reaction Rate

Rate Constant

− = . − = "


! !


Page 24 of 36

Table 5. Raw Material and Utilities Cost

Raw Material16 Ethylene

0.32

$/lb

Ethylene Oxide

0.79

$/lb

Hydrogen Peroxide

0.37

$/lb

Methanol

0.94

$/lb

Methyltrioxorhenium (MTO)7

5000

$/lb

Water Treatment

0.005

$/lb

Chilled water

9.65E-7

$/kJ

Cooling water

2.12E-7

$/kJ

Low pressure steam

1.90E-6

$/kJ

Medium pressure steam

2.20E-6

$/kJ

Electricity

0.0775

$/kWhr

Utilities14


Page 25 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 6. Project Investment for the Developed EO Process Items

Value

Equipment Cost: Reactors

Units

2,613

$k

Towers

58,116

$k

Compressors

2,429

$k

Heat Exchangers

1,555

$k

Pumps

988

$k

Flash Drums

539

$k

Total Fixed Capital Investment

66,240

$k

Sales Revenue

333,699

$k/year

Cost of Manufacturing (COMd)

293,939

$k/year

Taxes

40

%

Discount Rate

10

%

Land Cost

25,000

$k

Working Capital

15,000

$k

Salvage Value

5,000

$k

Investment Time

12 (2 Building + 10 Operation)

year

Depreciation19

MACRS, 5 years recovery period



Page 26 of 36

Table 7. Summary of the Economic Performance

Formula19

Cost ($ k)

Raw material (CRM)

CRM

217,608

Waste Treatment (CWT)

CWT

341

Utilities (CUT)

CUT

2,486

Operating labor (COL)

COL

794

Direct supervisory and clerical labor

0.18 COL

143

Maintenance and repairs

0.06 FCI

3,974

Operating supplies

0.009 FCI

596

Laboratory changes

0.15 COL

119

Patents and royalties

0.03 COM

8,755

Items

Total Direct Manufacturing Costs

23,4816

Depreciation

0.1 FCI

6,624

Local tax and insurance

0.32 FCI

2,120

0.708 COL + 0.036 FCI

2,946

Plant Overhead costs Total Fixed Manufacturing Costs

11,690

Administration costs

0.177 COL + 0.009 FCI

737

Distribution and selling cost

0.11 COM

32,103

Research and development

0.05 COM

14,592

Total General Manufacturing Costs

47,432

Total Cost

293,939

Sales Revenue

326,072

Profit

32,133


Page 27 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


LIST OF FIGURES

Figure 1. Ethylene oxide based product family (EPA, 1986).4 Figure 2. Conventional gas-phase ethylene epoxidation with silver based catalyst.2 Figure 3. Flowsheet the new developed EO production process. Figure 4. T-101 temperature and composition profiles for ethylene and ethylene oxide. Figure 5. T-102 temperature and composition profiles for water and methanol. Figure 6. Vapor and liquid equilibriums for methanol and ethylene oxide at 1 and 6.76 bar, ethylene and ethylene oxide at 10.0 bar, and methanol and water at 10.0 bar. Figure 7. T-103 temperature and composition profiles for ethylene and ethylene oxide. Figure 8. Cumulative discounted cash flow diagram.



Figure 1. Ethylene oxide based product family (EPA, 1986).4


Page 28 of 36

Page 29 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. Conventional gas-phase ethylene epoxidation with silver based catalyst.2


Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

H2O2 REGENERATION

304 203

Page 30 of 36

303 EO-PRODUCT

202 E-201

201

C-201

301

302 108

CH3OH C2H4

102

103

F-101

109 E-102

R-102 H2O2/H2O T-101 R-101

103

106

105

104 P-101

T-103

T-102 107

E-101 WATER

401

PUMPS METHANOL

R-101 Epoxidation Reactor

F-101 Flash Drum

R-102 H2O2 Decomposer

P-101 Pump

E-101 Heat Exchanger

T-102 Packed Distillation Column


T-103 Packed Distillation Column

C-201 Gas Compressor


Figure 3. Flowsheet of the new developed EO production process.


T-101 Tray Distillation Column

Page 31 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47





Figure 5. T-102 temperature and composition profiles for water and methanol.


Page 32 of 36

Page 33 of 36

1.0 0.9 Vapor mole fraction for first component

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.8 0.7 0.6 0.5 0.4 0.3 Ethylene - ethylene oxide at 10.0 bar Ethylene oxide - methanol at 1.0 bar Methanol - water at 10.0 bar Ethylene oxide - methanol at 6.76 bar

0.2 0.1 0.0 0.0

0.1

0.2 0.3 0.4 0.5 0.6 0.7 0.8 Liquid mole fraction for first component

0.9

1.0

Figure 6. Vapor and liquid equilibriums for methanol and ethylene oxide at 1 and 6.76 bar, ethylene and ethylene oxide at 10.0 bar, and methanol and water at 10.0 bar.





Page 34 of 36

Page 35 of 36

60 40 Cumulative cash flow ($ Million)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


20 0 -20 -40 -60 -80 -100 0

1

2

3

4

5

6 Year

7

8

9

Figure 8. Cumulative discounted cash flow diagram.


10

11

12


Page 36 of 36

For Table of Contents Only

H2O2 REGENERATION

304 203

303 EO-PRODUCT

202 E-201

C-201

201 301

302 108

CH3OH C2H4

102

103

F-101

109 E-102

R-102 H2O2/H2O T-101 R-101

103 P-101

107

106

105

104

T-103

T-102

E-101 WATER

401

PUMPS METHANOL


Optimal Design of Gas-Expanded Liquid Ethylene Oxide Production

Recommend Documents