Article pubs.acs.org/IECR
Cite This: Ind. Eng. Chem. Res. 2018, 57, 5351−5358
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. 2018.57:5351-5358. Downloaded from pubs.acs.org by UNIV OF TEXAS SW MEDICAL CTR on 10/11/18. For personal use only.
Dan F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710, United States
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) (Gas Encyclopedia by Air Liquide, https://encyclopedia.airliquide.com/ethylene). In this paper, an optimized design and operation for MTO based ethylene oxide (EO) production processes has been developed, which has less manufacturing costs compared with the one from the current literature (Ind. Eng. Chem. Res. 2013, 52, 18−29). The developed EO system could produce 200,000 tons of ethylene oxide per year at a 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. is 4−8% at their optimal steady-state 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 environment.2 Furthermore, because of the dangerous operating conditions of the reactor and the exothermic properties of ethylene and EO reactions, the operation of an EO reactor can be very dangerous and easily turned into a runaway reaction. 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 gas-expanded liquid phase using hydrogen peroxide (H2O2) as the oxidant, methyltrioxorhenium (MTO) as the homogeneous catalyst, methanol as the solvent, and pyridine-N-oxide as the catalyst promoter.9 The reaction is carried in a continuous
1. INTRODUCTION In 2011, the global demand for 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 in 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 a toxic flammable gas at ambient pressure and temperature. Its explosion range is 3.6% through 100% of EO in air.6 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 out 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 © 2018 American Chemical Society
Received: Revised: Accepted: Published: 5351
December 6, 2017 March 9, 2018 March 23, 2018 March 23, 2018 DOI: 10.1021/acs.iecr.7b05060 Ind. Eng. Chem. Res. 2018, 57, 5351−5358
Article
Industrial & Engineering Chemistry Research
Figure 1. Ethylene oxide based product family (EPA, 1986).4
phenomena and the kinetic reaction of ethylene epoxidation in the gas-expanded liquid phase.10 The third paper by Ghanta et al., also published in 2013, 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. in their last research found that the MTO based catalyst process is not only economically better than the conversational process but also environmentally 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 concerns. 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 the H2O2 regeneration process to convert the generated O2 to H2O2 and reused by the epoxidation reactor to enhance material use efficiency; (ii)
Figure 2. Conventional gas-phase ethylene epoxidation with silver based catalyst.2
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 the gas-expanded liquid phase process for ethylene epoxidation, there are two different metal-based catalysts 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 be at play in an 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 2010 discussed the thermodynamic modeling of the process and the flammability calculation of the reaction.9 The second paper by Ghanta et al. in 2013 discussed the transport 5352
DOI: 10.1021/acs.iecr.7b05060 Ind. Eng. Chem. Res. 2018, 57, 5351−5358
Article
Industrial & Engineering Chemistry Research
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 and temperature of 104 °F, and the reactor volume is 19.69 ft3. 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 a pressure of 10 bar, and it recovers 99.90 mol % of 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 a total condenser which operates at a pressure of 6.76 bar, and it recovers 99.99 mol % of water in the 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 a pressure of 1 bar. It recovers 99.90 mol % of ethylene oxide in the top stream (EO-PRODUCT). The bottom stream (METHANOL) recovers the methanol solvent and recycles it back to R-101. Finally, the PUMPS subflowsheet 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. The H2O2 REGENERATION subflowsheet 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 the 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.
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 sequences from the literature. The developed EO system could produce 200,000 tons of ethylene oxide per year at a purity of 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 includes hydrogen peroxide, water, methanol, ethylene, ethylene oxide, and oxygen. According to Lee et al.,9 the system can be presented thermodynamically well by using the UNIQUAC model for the liquid phase and the Peng−Robinson equation of state for the 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 models that are used to build the simulation environment in Aspen Plus. Table 1. Binary Interaction Parameters9 Components
Interaction Parameters
a
Ethylene−Methanol Methanol−Ethylenea Ethylene oxide−Methanolb Methanol−Ethylene oxideb a
0.010 0.010 −245.7 629.7
Peng−Robinson equation of state. bUNIQUAC model.
Table 2. Simulation Process Models Simulation Model from Aspen Plus
Equipment
RCSTR Flash2 RadFrac RStoic Compr Pump Heater
R-101 and R-102 F-101 T-101, T-102, and T-103 R-103 C-101 P-101, P-102, P-103, P104, and P-105 E-101, E-102, E103, E-104, E-105, E-106, and E-107
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 is still a challenge to the process, further in-depth research to understand the catalyst activity and stability are still needed. This work has used Ghanta M. et al. results regarding catalyst activity and cost analysis, which have the simulation operation criteria agree with those he published in 20109 and 2013.2 Also,
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 a leaching rate of 0.11 lb MTO/h.7 The residence time of the reactor is set as 0.25 h as suggested.10 In F-101, the process stream 102 flashes out to recover most of the remaining unreacted ethylene to the vapor outlet. The drum operates to a pressure of 5 bar and temperature of 104 °F. The vapor outlet, which is mostly ethylene, is compressed and cooled down to 5353
DOI: 10.1021/acs.iecr.7b05060 Ind. Eng. Chem. Res. 2018, 57, 5351−5358
Article
Industrial & Engineering Chemistry Research
Figure 3. Flowsheet of the newly developed EO production process.
Table 3. Flow Rate Information (lb/h) of the Developed EO Process Streams Stream Index
Hydrogen peroxide
Water
Methanol
Ethylene
Ethylene oxide
Oxygen
101 102 201 303 WATER METHANOL EO-PRODUCT
43,144.0 4,344.5 0.1 0.0 5.0 0.0 0.0
43,144.0 63,693.5 20.7 19.4 65,945.1 6.6 0.0
226,863.0 226,863.0 167.2 225.0 7.0 226,434.0 30.2
38,756.0 6,756.0 4,479.3 2,273.9 0.0 0.0 2.8
1,411.1 51,661.1 140.7 169.1 0.0 1,101.3 50,250
0.0 0.0 0.0 2,041.2 0.0 0.0 0.0
Table 4. Reaction Settings for the Simulation Model Reaction
Reaction Type
Reaction Rate
1
LHHW
−r = kCH2O2CELCcat.
215
Power Law
−r = kCH2O22
10
Rate Constant 6.2 × 10 ft 3
1000 lbmol·s
16
$/lb $/lb $/lb $/lb $/lb $/lb 10−7 10−7 10−6 10−6
s
−1
Reference Temp. 68 °F 284 °F
Activation Energy kJ
57 mol kJ
52.7 mol
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 a 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 a reaction-limiting reactant, and ethylene is fed excessively. Since only the epoxidation reaction is presented at these conditions and it is possible 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/h. Using the chilled water to cool down and control the epoxidation exothermic reaction, the reactor operating cost is $116.52/h based on the cost rates of chilled water in Table 5.
Table 5. Raw Material and Utilities Cost Raw Material Ethylene 0.32 Ethylene Oxide 0.79 Hydrogen Peroxide 0.37 Methanol 0.94 Methyltrioxorhenium (MTO)7 5000 Water Treatment 0.005 Utilities14 Chilled water 9.65 × Cooling water 2.12 × Low pressure steam 1.90 × Medium pressure steam 2.20 × Electricity 0.0775
−6
$/kJ $/kJ $/kJ $/kJ $/kWhr
this work is performed at the same EO production rate reported by Ghanta et al., i.e., 50,250 lb/h of EO. 5354
DOI: 10.1021/acs.iecr.7b05060 Ind. Eng. Chem. Res. 2018, 57, 5351−5358
Article
Industrial & Engineering Chemistry Research
the lower and the upper flammability zone of EO, ethylene, and methanol. The depressurization process in F-101 will require energy of 1.04 × 105 Btu/h which will cost $0.21/h 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 are secured out of EO and ethylene flammability zones. The decomposing process in R-102 releases energy equal to 5.34 × 106 Btu/h, and it costs $1.19/h 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 remaining 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 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%
Table 6. Project Investment for the Developed EO Process Items Equipment Cost: Reactors Towers Compressors Heat Exchangers Pumps Flash Drums Total Fixed Capital Investment Sales Revenue Cost of Manufacturing (COMd) Taxes Discount Rate Land Cost Working Capital Salvage Value Investment Time Depreciation19
Value
Units
2,613 58,116 2,429 1,555 988 539 66,240
$k $k $k $k $k $k $k
333,699 293,939
$k/year $k/year
40 10 25,000 15,000 5,000 12 (2 Building + 10 Operation) MACRS, 5 years recovery period
% % $k $k $k year
The estimated cost for the reactor using an Aspen Process Economic Analyzer (APEA) is shown in Table 6. Next, in the flash drum F-101, the product stream of the 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 flow rate 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
Figure 4. T-101 temperature and composition profiles for ethylene and ethylene oxide. 5355
DOI: 10.1021/acs.iecr.7b05060 Ind. Eng. Chem. Res. 2018, 57, 5351−5358
Article
Industrial & Engineering Chemistry Research
Figure 5. T-102 temperature and composition profiles for water and methanol.
mole, which is the safe composition and not explosive according to Lee et al.9 With the recovery of 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 the utility cost in Table 5 is $55.12/h, and the estimated capital column cost is $616,000. 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/h, and the estimated column cost is $11,339,000. 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. Ethylene oxide and methanol relative volatility in stream 109 is relatively low, and the 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 an upper azeotrope composition as shown in Figure 6. The condenser of T-103
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.
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 low-pressure 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/h, and the estimated column cost is $16,142,000. 5356
DOI: 10.1021/acs.iecr.7b05060 Ind. Eng. Chem. Res. 2018, 57, 5351−5358
Article
Industrial & Engineering Chemistry Research
Figure 7. T-103 temperature and composition profiles for ethylene and ethylene oxide.
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 flow rate 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 the main production stream (101 through 109) and its related equipment, the hydrogen peroxide recycle process is not designed in detail. Assuming a well designed hydrogen peroxide process can achieve a 50−50% H2O2/H2O mixture by a model similar to that of the Ghanta study in his dissertation work,18 the required reactions to regenerate hydrogen peroxide are done with a conversion reactor model with the ability to produce a 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 a small amount of EO due to economic conversion. Block PUMPS is a subsheet that contains pumps and heaters that are connected in 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 the inlet pressure, as well as to compress first and cool a stream later,14 therefore, the PUMPS unit 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 such as land cost and salvage values as 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.
Figure 8. Cumulative discounted cash flow diagram.
It should be noted that the MTO based catalyst process has proven the ability to produce EO more efficiently and safely 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) a 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) a heat integration network study such as pinch technology analysis which improves the model farther in terms of saving utilities; (iii) a preform details study for producing H2O2 onsite which will help in designing the given regeneration H 2 O 2 block on the flowsheet; and (iv) consideration of another catalyst such as Nb-based catalyst which may solve the cost problem of the MTO catalyst and its stability. 5357
DOI: 10.1021/acs.iecr.7b05060 Ind. Eng. Chem. Res. 2018, 57, 5351−5358
Industrial & Engineering Chemistry Research
■
Table 7. Summary of the Economic Performance Items Raw material (CRM) Waste Treatment (CWT) Utilities (CUT) Operating labor (COL) Direct supervisory and clerical labor Maintenance and repairs Operating supplies Laboratory changes Patents and royalties Total Direct Manufacturing Costs Depreciation Local tax and insurance Plant Overhead costs Total Fixed Manufacturing Costs Administration costs Distribution and selling cost Research and development Total General Manufacturing Costs Total Cost Sales Revenue Profit
Formula
19
CRM CWT CUT COL 0.18 COL 0.06 FCI 0.009 FCI 0.15 COL 0.03 COM 0.1 FCI 0.32 FCI 0.708 COL + 0.036 FCI 0.177 COL + 0.009 FCI 0.11 COM 0.05 COM
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 SilverCatalyzed 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/prospects-look-good-for-global-ethyleneoxide-ethylene-glycol-markets/ (publish August 8, 2013). (4) Environmental Protection Agency. Locating and estimating air emissions from sources of ethylene oxide. EPA report: EPA-450/4-84007L, September, 1986. (5) Rebsdat, S.; Mayer, D., Ethylene Oxide. In Ullmann’s Encyclopedia of Industrial Chemistry, 6th ed.; Hawkins, S.; Russey, W. E.; PilkartMuller, 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. (9) Lee, H. J.; Ghanta, M.; Busch, D. H.; Subramaniam, B. Towards a CO2-free ethylene oxide process: Homogenous ethylene oxide in gasexpanded 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. 2013, 59, 180. (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 trioxide-peroxide 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; pp 207−231. (16) ICIS. http://www.icis.com/chemicals/channel-info-chemicalsaz/ (accessed September 8, 2017). (17) Ethylene oxide high purity; Dow. http://msdssearch.dow.com/ PublishedLiteratureDOWCOM/dh_0931/0901b803809315b9. pdf?filepath=rds/RDS_00012116.pdf&fromPage=GetDoc (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; pp 150−225.
Cost ($ k) 217,608 341 2,486 794 143 3,974 596 119 8,755 23,4816 6,624 2,120 2,946 11,690 737 32,103 14,592 47,432 293,939 326,072 32,133
4. CONCLUSION 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 the 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 good control and design for the process to recycle unreacted hydrogen peroxide and ethylene with safe and secure presentation of an exploitable mixture of oxygen and flammable gas.
■
Article
AUTHOR INFORMATION
Corresponding Author
*Phone: 409-880-7818; Fax: 409-880-2197; E-mail: Qiang.xu@ lamar.edu. ORCID
Qiang Xu: 0000-0002-2252-0838 Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This work was supported in part the Lamar University Visionary Initiative Project and an Anita Riddle Faculty Fellowship. 5358
DOI: 10.1021/acs.iecr.7b05060 Ind. Eng. Chem. Res. 2018, 57, 5351−5358
