Produccion de etanol, Apuntes de Química

¡Descarga Produccion de etanol y más Apuntes en PDF de Química solo en Docsity! Integrated Project 2019 - 2020 Ethanol Production by catalytic hydration of ethylene AYAOU Basil BODSON Aude DEHOTTAY Loïc FARAI Rihab FARCY Antoine HENDRICKX Daryl LIEGEOIS Thibaut PASTUSZENKO Justine PAULISSEN Sacha RAPPAZZO Julien Abstract This paper discusses all the aspects of the process of ethylene hydration to produce ethanol. A short summary gives all the information known and found about the studied process. Aerwards, the necessary cost to implement this process is presented and analyzed. A literature review shows a glimpse of the other kinds of processes used in the industry to produce ethanol, detailing the catalysts used as well as the dierent raw materials. An overview of the ethanol properties is also displayed in this paper. Finally, the Life Cycle Analysis (LCA) gives the environmental aspect of the ethylene hydration process, underlying sections of the process to improve such as the heat integration. Keywords Ethanol - Process - Ethylene - Hydration - LCA - Market - Feedstock Contents 1 Introduction 2 2 Summary of our process : catalytic hydration of ethylene 2 2.1 Our process . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Thermodynamics •Kinetics and catalysts •Reactor • Separation process • Heat integration • Costs 3 Cost analysis 5 3.1 CAPEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2 OPEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.3 Cash flows . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4 Literature Review 7 4.1 Catalytic Hydration of Ethylene: Other Processes 7 Catalysts 4.2 Comparison with previously obtained results . . 8 4.3 Other process: Fermentation . . . . . . . . . . . . . . 9 First generation: Corn ethanol industry • Second generation : Lignocellulosic ethanol industry • Third generation: Algae, Bacteria • Feedstock origin 4.4 Comparison of all processes . . . . . . . . . . . . . . 10 4.5 Ethanol overview . . . . . . . . . . . . . . . . . . . . . . 11 Market • Raw materials uses • Toxicity and Environment • Recycling • Ethanol alternatives • In the case of Bioethanol 5 Life-cycle assessment (LCA) 14 5.1 Raw material supply . . . . . . . . . . . . . . . . . . . 14 Ethylene • Water 5.2 Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.3 Energy used in the process . . . . . . . . . . . . . . . 15 5.4 Environmental impacts . . . . . . . . . . . . . . . . . 16 Conclusion 6 Conclusion 18 References 19 7 Appendix 21 7.1 CAPEX costs . . . . . . . . . . . . . . . . . . . . . . . . . 21 Ethanol Production by catalytic hydration of ethylene — 2/21 1. Introduction This project was devoted to the study of ethanol pro- duction by catalytic hydration of ethylene. A process for the ethanol synthesis has been developed and the operating conditions optimized in order to reduce pro- duction costs. Before the extended literature review, a summary of the work done will be presented. The purpose of this extended literature review is to compare our process with those found in the literature. Firstly, the cost of our process will be analyzed. Sec- ondly, our process is compared to similar production processes of synthetic ethanol using oil-based products as raw materials. Afterwards, dierent ways of producing ethanol will be discussed and compared to our process. To end this literature review, a broader society overview including market, toxicity,... will be made. Lastly, the LCA of the process will be discussed to ac- knowledge the impacts of the considered process. 2. Summary of our process : catalytic hydration of ethylene This process is mainly used to produce ethanol as a solvent. Considering the entire ethanol production, this type of process represents only 7% of the production (Roozbehani, Mirdrikvand, Moqadam, & Roshan, 2013; Mohsenzadeh, Zamani, & Taherzadeh, 2017). Indeed, producing ethanol via this process is more ex- pensive than using techniques such as fermentation. This is due to the price of ethylene, which uctuates enormously according to the geographical area. Three large companies produce synthetic ethanol: Sasol in South Africa, SADAF in Saudi Arabia and Equistar in the USA. (Roozbehani et al., 2013). 2.1 Our process The process displayed in the Figure 8 was the subject of an in-depth study this year. The following equilibrium describes the main reaction: C2H4 +H2O C2H5OH Because of the equilibrium, the operating conditions play an important role in conversion. Part of the work done this year was useful to determine the optimal con- ditions for a maximized conversion, taking into account the imposed constraints. However, ones must be careful about the fact that other components are present in the process due to impurities in the ethylene feed. Figure 1 – Our process owsheet 2.1.1 Thermodynamics The thermodynamics part was devoted to determine the properties of all the components of our process. To reach this goal, the properties for the pure compo- nents at dierent temperatures and pressures have to be determined. Then, the properties of ideal and real mixtures can be found. The real mixture properties will depend on the choice of the thermodynamic model. These data will be used in the other sections for the design of all unit operations. In this way, concerning the pure components, the Peng-Robinson model was chosen to describe them. For the mixtures, the model that ts the better the experimental data of binary mix- tures was chosen. For this case, the NRTL-RK is the most accurate model. 2.1.2 Kinetics and catalysts Three main reactions are occurring within the studied process: • Ethylene hydration: C2H4 +H2O r1  r2 C2H5OH with r = r1− r2 = k1 · pE · pW − k2 ·KA · pA {1+KE · pE +KW · pW +KA · pA +KDEE · pDEE}2 Ethanol Production by catalytic hydration of ethylene — 5/21 Figure 2 – Final owsheet 3. Cost analysis 3.1 CAPEX The CAPEX is the cost for all the xed structures such as buildings, laboratories, process units or lands. To calculate the CAPEX, the bare module cost is rstly calculated. This is the raw cost of each specic unit. of each specic unit, where the installation Then, the total module cost is calculated. It corresponds to the costand transport are taken into account. There is no corrosive compounds in the process, so the plant can be built in carbon steel. The detail of the bare module cost and the total module cost of each unit is present in the Appendix 7.1. Finally, the grassroots plant cost is computed. This cost takes into account, in addition of the total module cost, others costs like auxiliary facilities (administration buildings, cafeteria and more), land or unexpected costs and fees. Its formula is present in the Appendix 7.1. For this process the total grassroots plant cost is about 12 781 k$. 3.2 OPEX The OPEX is a day-to-day cost that depends on the needs of the process such as electricity, water treat- ment, raw materials, maintenance and cost of workers. The OPEX (operation expenditure) part consists in cal- culating the annual total manufacturing costs (COM) which are based on: the direct manufacturing costs, the xed manufacturing costs and the general expenses. The direct manufacturing costs (DMC) takes into ac- count costs such as raw materials, waste water treat- ment, utilities (electricity, cooling and heating water), operating labour and other direct costs. The xed manufacturing costs (FMC) are the costs that cover the depreciation cost, the local taxes and insur- ance and the plant overhead costs. The general manufacturing costs (GE) take into account the administration costs, the distribution and selling costs and the research and development costs. The dierent costs are calculated by following the for- mulas explained in the referenced book (Whiting, Shaei- witz, Bhattacharyya, Turton, & Bailie, 2013). A sum- mary of the OPEX result costs is displayed in the follow- ing Table 3. The operating labor cost was calculated depending on the number of units operating in the pro- cess. The number of operators required per shift (NWP) is 3. Which leads to a total number of operators required Ethanol Production by catalytic hydration of ethylene — 6/21 (NOL) about 14. Dierent costs Cost (k$/yr) Operating labor 817 Raw materials 11660 Water treatment 13 Utilities 9309 Fixed capital investment 12780 Depreciation 1278 Cost of manufacturing COM 31617 Table 3 – OPEX costs 3.3 Cash flows In order to analyse the protability of the project in- volving both capital expenditures and yearly operating costs, cash ow diagram has to be drawn by using the discounted and the non-discounted approach. As reminder, the discounted approach takes into ac- count the time value of money by including the ination rate into the calculations. One of the hypothesis that were made is that the work- ing capital was assumed to be 0 as a rst approximation. Usually the typical values of the working capital ranges between 15% and 20 % of the xed capital investment. But even without these additional expenses, it can be seen in the Figure 3 that this project is far from being protable because all the other expenses cannot be cov- ered over time. This is because the annual net benet is negative (-8 M$). For an usual protable business, the slope of the cash ow is positive when the plant is ready to operate i.e. after its construction. However, in our case, it can be observed that after the rst year, the cash ow (discounted and non-discounted one) continues to decrease instead of increasing. According to this reference (New capacities, weaker down- stream markets to weigh on ethylene in 2020, n.d.), the price of ethylene bought is around 0.35 $/kg. And know- ing that with the actual price of ethanol 0.72$/kg (accord- ing to (Ethanol T2 FOB Rotterdam Including Duty Swap Platts Future, n.d.)), a negative benet is obtained, if we wanted to balance our costs with our prots, it would be necessary to raise the price of ethanol to 0.98$/kg. But this solution cannot be achieved in reality. An alternative solution is to do a scale-up which means increasing the size of the company, leading to an in- crease in the production size. Therefore, the cost of production per unit product will decrease. It might be interesting to study the economical eect if the plant would produce more than 30 000 tonnes of ethanol per year. Figure 3 – Cash ow diagram Ethanol Production by catalytic hydration of ethylene — 7/21 4. Literature Review 4.1 Catalytic Hydration of Ethylene: Other Pro- cesses In order to determine whether the results obtained make sense or not, a comparison between the latter and the results found in the literature will be made. Dierent catalysts will be mentioned and compared with the one chosen for this project, i.e. zirconium tungstate. 4.1.1 Catalysts Phosphoric Acid Phosphoric acid supported by inert materials1 has been used as catalyst in the hydration of ethylene for years and is still the most widely used catalyst in the industry thanks to its high selectivity (98.5%) The phosphorus content of the latter catalyst is between 50 and 80 % in weight of the total mass of the catalyst. The reaction is an electrophilic addition reaction where a π bond is broken, involving the formation of two covalent bonds. The reaction mechanisms involved in this catalytic re- action are the following. • Transfer of a proton from phosphoric acid to ethy- lene and formation of a CH3CH+ 2 carbocation Figure 4 • Reaction of the latter CH3CH+ 2 carbocation with a water molecule Figure 5 • Catalyst regeneration 1Materials such as porous silica or alumina-silica. Figure 6 As described by (Hidzir, Som, & Abdullah, 2014) and (Matar & Hatch, 2001), the hydration of ethylene is done in a xed bed reactor with phosphoric (V) acid coated onto a solid silicon dioxide as a catalyst. The following operating conditions were described: P (atm) T (°C) Steam to ethylene ratio (S/E) 70 - 80 250 - 300 0.6 Table 4 – Operating conditions These operating conditions lead to a conversion of 4% to 5% of the ethylene into ethanol. Therefore, the remain- ing ethylene is recycled into the process. Nevertheless, the high concentration of phosphoric acid has conse- quence such as corrosion of the reactor (Isobe, Yabuuchi, Iwasa, & Takezawa, 2000). For this reason, Isobe et al. (Isobe et al., 2000) have studied the inuence of phospho- ric impregnated metal phosphate on the conversion of ethylene to ethanol. The reaction takes place in a pack bed reactor at a temperature of 473K and at a pressure of 1 atm. The following results have been obtained: Catalysts Rate of EtOH formation (µmol/min/g · cat) Ge 0.47 Zr 0.064 Ti 0.26 Sn 0.94 H3PO4/SiO2 0.13 It can be seen that the Sn-based catalyst is the most ecient compared to the classical H3PO4/SiO2 cata- lyst. However, and this is one of the reasons why an other catalyst was chosen in our process (Zirconium Tungstate), phosphorous compounds are responsible for environmental pollution (Katada et al., 2008). Ethanol Production by catalytic hydration of ethylene — 10/21 4.3.2 Second generation : Lignocellulosic ethanol in- dustry This type of fermentation uses lignocellulose as a raw material. It is hydrolysed in order to release the sug- ars necessary for fermentation and therefore, for the production of ethanol. The advent of this type of raw material is mainly due to two factors. First, corn ethanol production is limited to 56,78 bil- lion L/year, this limit ensures that sucient corn starch remains for human and animal consumption (of En- ergy, 2019). Second, using cellulose as a feedstock would reduce greenhouse gas emissions by more than 85% compared to reformulated gasoline due to the en- ergy balance (Wang et al., 2011). Since 2014, POET has launched a lignocellulosic ethanol production line. Figure 9 shows how ethanol is produced from lignocel- lulosic feedstock: Figure 9 – Diagram of ethanol production from lignocellulosic feedstock Nevertheless, cellulosic fermentation has disadvantages : 1. Cellulose reduces the eective yield of the biomass. 2. Lignocellulosic fermentation has a higher cost because a pretreatment is needed to extract the holocellulose2 from the lignin(Martel, 2011). 3. Obtaining glucose from biomass is followed by energy3 losses from (Frenzel, Hillerbrand, & Pfen- nig, 2014): (a) The general agricultural process that includes crops cultivation and transport as well as the production of fertilizers; 2Cellulose and hemicellulose combined. 3Value allowing to measure the quality of an energy. (b) The methods, from the literature, used to isolate the carbohydrates. 4.3.3 Third generation: Algae, Bacteria The fermentation is done from algae, bacteria. This type of fuel is still being developed. It would further reduce greenhouse gas emissions because a part of the CO2 is recycled to feed the algae via photosynthesis. On the other hand, cultivating these algae is highly energy consuming and is thus expensive (et environnement par sia partners, 2015). 4.3.4 Feedstock origin On a global scale, in 2014, the majority of biofuel was made from corn ethanol (41%), 19% of the biofuel was made with sugarcane ethanol, 18% of the biofuel pro- duced was biodiesel made from vegetable oils, 15% of the global biofuel production came from unspecied feedstock (ethylene,...), and nally, 2% of the biofuel produced was made from wastes. Figure 10 shows these data in a more graphical way (Richter, 2018). Figure 10 – Shares of bioethanol and biodiesel types from dierent feedstock in global biofuel production in 2014 4.4 Comparison of all processes From a cost perspective, corn ethanol is the cheapest with a production cost of $0.15/L (Koehler & Wilson, 2019) (Olsson, 2007). The two milling ways have a dierent cost distribution: for wet-milling, 39% of the cost price is feedstock and 61% production costs. On Ethanol Production by catalytic hydration of ethylene — 11/21 the other hand, the costs distribution for dry-milling is 50/50. Second-generation fuels are more expensive with a production cost of $0.5/L (Mark, Detre, Darby, & Salassi, 2014). Pre-processing accounts for 30-40% of the cost, which is why the costs are higher. The price of raw materials has an impact on the pro- duction costs. Indeed, the price of corn or cotton does not vary in the same way as the ethylene price, which is linked to the oil court and therefore varies more strongly. Moreover, the geographical location impacts a lot the ethylene price as can be seen in Table 7 below (Lewandowski, 2019): USA Europe Ethylene Price per ton ($) 350 1000 Table 7 – Ethylene price In addition, access to raw materials such as corn, cotton, wood is easier than for ethylene, produced either from oil or from shale gas. It should be noted that some reaction by-products can be valued. Indeed, concerning the corn fermentation, in addition to ethanol production, oil can be recovered and used as food. The ethanol production by direct catalytic hydration of ethylene allows the production of diethylether (DEE) in small quantities but still valuable. The above mentioned processes also have dierent yields. Concerning the rst generation fuel, from 2.28kg of corn 1L of ethanol is obtained. For second generation fuels, the yield depends on the type of hydrolysis. For instance, if hydrolysis is made by a diluted acid, 1L of ethanol if obtained per 5.29kg of raw material, which is quite big compared to the rst generation fuel. (Hoover & Abraham, 2009) Table 8 summarizes the various points discussed above. 4.5 Ethanol overview 4.5.1 Market The ethanol market is broken down as follows (Source: Mordor Intelligence) : Figure 11 – Distribution of ethanol market The biofuels market is the largest, followed by the bever- ages, chemical, pharmaceutical and cosmetics markets. The two largest producers of bioethanol are the USA and Brazil with, respectively, 60.780 and 29.980 billion litres produced in 2018. ADM and POET are two major bioethanol manufacturing companies in the USA. In Brazil, the Cosan company dominates the bioethanol market (Figure 12). Concerning synthetic ethanol, there are companies such as Sasol in South Africa or SADAF in Saudi Arabia. Figure 12 – Distribution of ethanol production. Source: Statista The biofuel market is buoyant. Indeed, it is part of an ecological reasoning, allowing to reduce greenhouse Ethanol Production by catalytic hydration of ethylene — 12/21 Production Costs Yield Access to raw material By-products Corn Fermentation $0.15/L 2.28kg→ 1L Easy Valuable Cellulosic Fermentation $0.5/L 5.29kg→ 1L Easy No Catalytic Hydration of Ethylene $0.86/L 6.44L H2O,570L C2H4:1L EtOH More dicult Less valuable Table 8 – Comparison of all processes gas emissions. This market development is supported by the following Figure 13, which shows the evolution of this market. Figure 13 – Biofuel market 4.5.2 Raw materials uses Ethanol can be used as a reagent in various reactions. Figure 14 – Ethanol molecule Indeed, it is a weak acid with a pKa of 16. In addi- tion, the oxygen of the hydroxyl group gives it a nucle- ophilic character which involves it in several reactions (Wymann, 1990), for example: • Dehydration reaction with alkene formation, which corresponds to the reverse of the studied reaction CH3CH2OH −→C2H4 +H2O • Acid base reactions: CH3CH2OH +MH −→CH3CH2M+H2 More specically and concerning our project, ethanol may be involved in reactions leading to the formation of undesired products such as: • Acetaldehyde CH3CH2OH −→CH3CHO+H2 • Diethyl ether (DEE): This is a 2nd order nucle- ophilic substitution (SN2). 2C2H5OH −→ (C2H5)2O+H2O Other uses of the ethanol as a nal product can be : alcohol drinks, fuels such as bioethanol, solvent and medicinal use. 4.5.3 Toxicity and Environment Toxicity Ethanol can be absorbed by the body via inhalation of the gases or absorption of the liquid. Regardless of whether it is gaseous or liquid, the toxicity of ethanol is related to its concentration. When absorbed, at low blood concentration (0.2 to 0.5 g/L) symptoms such as decreased reex and attention are observed. At medium concentration (0.5 to 1g/L), nausea, vomiting, impaired motor functions and slow- ing of cognition may appear. At high concentration (1 to 3 g/L), there are risks of loss of consciousness and coma and, nally, beyond 3 g/L, there are risks of death. The possible symptoms of ethanol inhalation can be (for Biotechnology Information, n.d.) : cough, headaches, drowsiness, nasal irritation and narcosis. According to the HSDB4 , ethanol has carcinogen5 prop- erties (for Biotechnology Information, n.d.). 4A toxicology database whose information are assessed by a scientic review panel. 5It can cause cancer. Ethanol Production by catalytic hydration of ethylene — 15/21 tion in order to comply with the standards. All of theses steps will have an environmental impact and can be estimated with the simulation software. 5.2 Transport First, an important hypothesis that has been made is to assume that the ethanol production unit is right next to the ethylene production unit. More and more plants which are related try to set up this system in order to reduce the cost and the environmental impacts related to transportation. Moreover, as said previously, the ethanol production unit is near a water source so there is no need for water transport either. A second assumption was to locate the production plant in the USA precisely in Texas. Indeed, rstly, the US are the biggest consumers of ethanol in the world. Then, ac- cording to the table 9, Texas is the biggest oil producing state in the United States. That implies a lower environ- mental impact to transport the oil from the source to the renery. Ranking Oil production [million of barrels] Texas 1850.1 North Dakota 512.3 New Mexico 339.8 Oklahoma 211.8 Table 9 – Crude oil production in the United States in 2019, by state, reference (Statista, 2020) Concerning the way to transport the oil, it is presumed that this raw material is transferred by pipeline. Indeed, according to the reference (Conca, 2018), pipelines requiring signicantly less energy, is cheaper to oper- ate than trucks or rail (about 5$/barrel versus 10$ to 15$/barrel) and have a lower carbon footprint. An ap- proximate distance for oil transportation by pipeline in the state of Texas is assumed to be 500 km. This oil will be transported in liquid phase by pipeline. And, in order to improve the uidity of crude oil before it enters into the device, the crude oil is always heated to a certain temperature (a little higher than the ambient). 5.3 Energy used in the process Every process needs energy to function in order to power the equipment. In the ethanol production unit, the main sources of energy are electricity, vapour and cooling water. In the following, the way these energies are produced will be described. The electricity used in this process is produced by on- shore wind turbines with a power installed above 3 MW . To get an idea, a wind turbine of 2 MW generates annu- ally 4500 MWh. Surprisingly wind energy in the United States is growing. In 2018, the United States ranked 2nd in the world for wind power production with more than 20% of the world total. Moreover, Texas is by far the largest producer of wind energy in the country with a quarter of the installed wind power of the coun- try (Wikipedia, 2020). Therefore, producing electricity with wind turbines is a good assumption as the ethanol production unit is located in Texas. The electricity con- sumption in this process is at high voltage and allows to power the three compressors and represents an overall power of 5155 kW . This large value is due to the fact that the compressor (COMP1) requires a huge net work because it compresses the recycle stream, which has a big volume, from 5 to 61,68 bar. Note that this recycle stream is in vapor phase. Therefore, the ethanol produc- tion unit has an high consumption of electricity with an annual consumption of 41,2 GWh. Moreover, a large amount of heat is required in order to warm up the uxes at the desired temperatures. Thanks to the heat integration, it was found that an annual heat duty of 116 GWh is required for the overall process. This heat will be provided by vapour produced with a boiler. The boiler burns oil as fuel and the heat given o will transform water into steam. This vapour is then routed to the dierent heaters of the unit production. Concerning the cooling system of the process, water taken from a river or a lake is considered as cooling uid. A volume of 1050 m3 of water per year is used to cool ows and the equipment. Cooling helps manage and maintain the temperature of the production process and components. Furthermore, prevention of overheating of the equipment helps increase the productivity and reduces maintenance cost of the machine. A last source of energy that can be considered in the process is the purge recovery. Indeed, the purge is used as fuel gas and its combustion allows to recover thermal energy. Burning the purge allows to spare a lot of energy in this process because the purge is a very important ux and represents an energy economy of 108 GWh per year, which is not negligible. Ethanol Production by catalytic hydration of ethylene — 16/21 5.4 Environmental impacts The environmental impacts associated with all the stages of the ethanol production are evaluated thanks to the simulation software Simapro and will be expressed for the production of 1kg of ethanol. Nowadays, the world is in an energy transition phase towards renewable en- ergies. Therefore, it can be interesting to compare the environmental impacts of two dierent factories, one producing electricity with fossil fuels and another with wind turbines. It was decided to focus this analyse on ve impact categories : 1. Abiotic depletion (fossil fuels) refers to the depletion of nonliving resources and more par- ticularly fossil fuels. It is expressed in terms of MJ which is related to the equivalent energy ex- tracted. 2. Global warming (GWP100a) results of green- house gases concentration in the atmosphere such as carbon monoxide, methane, nitrogen oxide which let in sunlight but capture reected heat by earth. Each greenhouse gas has a dierent warming eect that can be calculated on the basis of a reference value : the warming potential of CO2 and is expressed in terms of the equivalent amount of carbon dioxide (kg CO2 eq). 3. Human toxicity reects the potential harm of chemicals released into the human environment and covers a number of dierent eects such as irritation eects, carcinogenic eects,... Health risks of exposure in the working environment are not included. It is expressed in terms of equiva- lent amount of dichlorobenzene (kg 1,4-DB eq). 4. Fresh water aquatic ecotoxicity refers to the impact on fresh water ecosystems, as a result of emissions of toxic substances to air, water and soil. It is expressed in terms of equivalent amount of dichlorobenzene (kg 1,4-DB eq). 5. Acidication refers to emission which increases acidity of water and soils and has a wide range of impacts ecosystems and materials (buildings). It is expressed in terms of equivalent amount of sulfur dioxide (kg SO2 eq). The impact of the process on the main pollution factors is shown in the Table 10. This makes the comparison between the use of wind turbines or fossil fuels to pro- duce electricity. All data have been calculated for the equivalent of 1 kg of ethanol produced. Label Unit Wind turbines Fossil fuel Abiotic depletion (fossil fuels) MJ 56.58 68.29 Global warming (GWP100a) kg CO2 eq 1.45 2.54 Human toxi- city kg 1,4-DB eq 0.056 0.55 Fresh water aquatic eco- toxicity kg 1,4-DB eq 0.032 0.67 Acidication kg SO2 eq 0.004 0.0071 Table 10 – Comparison of the environmental impacts between two same process using wind turbine or fossil fuel to produce electricity. A rst observation is that producing electricity by wind turbines has a much less impact on the environment. Furthermore, regarding the Figures 15 and 16, the rela- tive % of energy recovered from the waste stream of the process (purge) is much more important when wind tur- bines are used as the environmental impacts decrease. It should be noted that the environmental impacts linked to the construction of the wind turbines are not taken into account for the life cycle analysis of the process. Ethanol Production by catalytic hydration of ethylene — 17/21 Figure 15 – Electricity produced from fossil fuels Figure 16 – Electricity produced from wind turbines Now, regarding the environment, it makes more sense to work by producing electricity from wind turbines. This model is thus chosen for the process. Then, to get an idea of the real impact of the process on the environment, a comparison between our process and a typical one of ethanol production from the soft- ware Simapro has been done in the Table 11. The data of the table have all been computed for a production of 1 kg ethanol with a purity equal to 82% . Label Unit Process with Wind turbines Typical process from Simapro Abiotic depletion (fossil fuels) MJ 56.58 32.9 Global warming (GWP100a) kg CO2 eq 1.45 0.96 Human toxi- city kg 1,4-DB eq 0.056 0.08 Fresh water aquatic eco- toxicity kg 1,4-DB eq 0.032 0.053 Acidication kg SO2 eq 0.004 0.003 Table 11 – Comparison of the environmental between the process and a typical one from the software Simapro. From the Table 11, one notices several relevant infor- mation about our process : • The "abiotic depletion" and "global warming" pa- rameters are 1.5 times higher than the average for our process. That means that it is more energy consuming than a typical process. It is explained by the fact that the recycling stream in our pro- cess is big and undergoes several increases/de- creases of its temperature. • In terms of toxicity, the process is within the stan- dards. One notices that the value of the "fresh wa- ter aquatic ecotoxicity" of our process is smaller than the one from the software. It means that the waste water is discharged in the sea and is correctly cleaned. • Concerning the acidication, the process is a little higher than the standards. 5.4.1 Conclusion To conclude this LCA, based on the comparison between the environmental impacts between our process and a typical one from the software Simapro, it can be consid- ered that the ethanol unit production developed in this Ethanol Production by catalytic hydration of ethylene — 20/21 18) OCDE. (2000). Le développement durable. Sciences Technologie Industrie, 1999(2), 99. of Energy, U. D. (2019). Ethanol feedstocks. (Link) Olsson, L. (2007). Biofuels (Vol. 108). Springer. Perrin, S. (2020). Ethylène-l’elémentarium. (Link) rethink ethanol. (n.d.). http:// rethinkethanol.com/. (Accessed 7th April 2020) Richter, E. (2018). 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Appendix 7.1 CAPEX costs Bare and total module cost Specicity of each unit in order to calculate the bare and total module cost is presented in the Table 12. Unity Working Heat surface pressure (atm) exchange (m2 ) HTX1 61 123 HTX2 61 74.6 HTX3 61 20* Unity Working Net work pressure (atm) required (kW) COMP1 / 5118 COMP2 / 450* COMP3 / 450* Unity Working Volume (m3 ) pressure (atm) REACTEUR 61 619 FLASH 5 4.75 Table 12 – Specicity required for the cost of each unity The values with * means that the value in the owsheet is under the minimal value required to the construction of the unity. So the minimal value for the construction was taken in our calculation and is present in the Table 12. The working pressure of compressors was not searched because there is no need to know it in order to calculate their total module costs. The bare module costs of the compressors takes already the pressure into account. Details about column cost was made by the separation group in the previous reports. The bare module and total module cost of each unit are presented in the Table 13. Unity Bare module Total module cost (k$) cost (k$) HTX1 3.8 53 HTX2 4.2 59 HTX3 6.5 91 COMP1 1309 5237 COMP2 204 818 COMP3 204 818 REACTEUR 183 2562 FLASH 6.3 25.1 COL 80 320 TOTAL 2002 9983 Table 13 – Bare and total module costs of each unit Formulas used to calculate the bare module cost and the total module cost come from the general assignment. Grassroots plant cost The grassroots plant CGR is expressed with the following formula (Whiting et al., 2013): CGR = 1.18CT M +0.5CBM (1) where CT M is the total module cost and CBM is the bare module cost.