Techno-economic analysis of a bio-refinery process for producing Hydro-processed Renewable Jet fuel from Jatropha

Renewable Energy 95 (2016) 63e73

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Techno-economic analysis of a bio-refinery process for producing Hydro-processed Renewable Jet fuel from Jatropha Wei-Cheng Wang Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, 70101, Taiwan

a r t i c l e i n f o

a b s t r a c t

Article history: Received 22 May 2015 Received in revised form 29 February 2016 Accepted 29 March 2016

HRJ (Hydro-processed Renewable Jet) conversion technology has been recently used to produce renewable jet fuel for commercial or military flights. In this study, a techno-economic analysis is carried out for evaluating the production of jatropha-derived HRJ fuel through a bio-refinery process. Each component of the chosen feedstock jatropha can be converted into valuable products. The bio-refinery process is split into 6 parts: (1) Fruit Dehulling; (2) Shell Combustion; (3) Oil Extraction; (4) Press Cake Pyrolysis; (5) Oil Upgrading; (6) Product Separation. The minimum jet fuel selling price (MJSP) from this fruit scenario is calculated to be $5.42/gal based on the plant capacity of 2400 metric tonne of feedstock per day. The co-products obtained from the process not only significantly deduct the production cost but make the entire process energy self-sustainable. We also discuss the oil scenario, which oil is the starting material and the process begins from Oil Upgrading section. The oil scenario offers the MJSP of $5.74/gal with lower capital but higher operating costs. The differences of MJSPs for fruit and oil scenarios are due to feedstock cost, refinery capital cost, co-product credits and energy cost. Based on the sensitivity analysis, the feedstock price, oil content, plant capacity, reactor construction and catalyst usage are important parameters that control the price of the produced fuel. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Renewable energy Techno-economics analysis Biofuel Jet fuel Hydroprocessed Renewable Jet Bio-refinery

1. Introduction The worldwide aviation industry consumes approximately 1.5e1.7 billion barrels (47.25e53.55 billion gallons) of conventional jet fuel per year [1,2]. The challenges of crude oil prices, national security, environmental impact, and sustainability make it difficult to have a long term plan and budget for operating expenses. Biomass-derived jet fuels (bio-jet fuels) are a potential alternative to petroleum jet fuel. With proper certification, bio-jet fuel can currently be blended up to 50% and potentially up to 100% with conventional jet fuel [1]. In US, the Air Force has goals to obtain 50 wt% of the Air Force's domestic aviation fuel as an alternative fuel blend by 2016 [3]. The European Union has set a target of two million tonnes per year of aviation biofuels in Europe in 2020, which is approximately 3e4% of total jet fuel use in Europe [4]. It is estimated that by 2050 25%e40% of biofuel will be used in global aviation, and 15%e40% of carbon emissions can be reduced [5]. Many process technologies that convert biomass-based materials into jet fuel substitutes are available. Some are available at

E-mail address: [email protected]. http://dx.doi.org/10.1016/j.renene.2016.03.107 0960-1481/© 2016 Elsevier Ltd. All rights reserved.

commercial or pre-commercial scale, and others are still in the research and development stage. These technologies are varied and depend strongly on the type of feedstock. Oil-based feedstocks are converted into bio-jet fuels through hydro-processing technologies, including hydro-treating, deoxygenation, and isomerization/ hydrocracking. A patented process developed by Honeywell UOP named Green Jet Fuel™ converts non-edible, second-generation natural oils and wastes into renewable jet fuel [6]. Solid-based feedstocks are converted into biomass derived intermediate through gasification, into alcohols through biochemical or thermochemical processes, into sugars through biochemical processes, and into bio-oils through pyrolysis processes. Syngas, alcohols, sugars, and bio-oils can be further upgraded to bio-jet fuel via a variety of synthesis, fermentative, or catalytic processes. So far, biojet fuels from Fischer-Tropsch (F-T) synthesis and oil hydroprocessing technologies have been approved by ASTM International (ASTM) Method D7566 [7] for blending into jet at levels up to 50%. Among these processes, hydro-processing technologies using vegetable and waste oils represent the only conversion pathways ready for large-scale deployment [8]. HRJ (Hydro-processed Renewable Jet) conversion technology is at a relatively high maturity level, is commercially available, and

64

W.-C. Wang / Renewable Energy 95 (2016) 63e73

was recently used to produce jet fuel for military flights [9]. HRJ fuel is equivalent to conventional petroleum in properties, but has the advantages of higher cetane number, lower aromatic content, lower sulfur content, and potentially lower GHG emissions [10]. The process flow diagram is shown in Fig. 1. Catalytic hydrogenation could be used to convert liquid-phase unsaturated fatty acids or glycerides derived from renewable fats and oils into saturated ones [11] with the addition of hydrogen. The next step is to cleave the propane and produce three moles of free fatty acids (FFAs) [10]. The glycerol portion of the triglyceride molecule is converted into propane by adding H2. The fatty acid products are sent to deoxygenation step, either through decarboxylation route or hydrodeoxygenation route, to remove oxygen content in the form of CO2, CO or H2O. The normal alkanes associated with the fatty acid carbon chain length are therefore produced. To meet the jet fuel specification, the produced bio-jet fuel has to have not only a high flash point, but also good cold flow properties. Therefore, it is required to hydrocrack and hydro-isomerize the normal paraffins produced from deoxygenation to a synthetic paraffinic kerosene (SPK) product with carbon chains ranging from C9 to C15 [10]. The isomerization process takes the straight-chain hydrocarbons and converts them into the branched structures to reduce the freeze point to meet the jet fuel standard [12]. It is accompanied by a hydrocracking reaction, which results in more or less yield from the isomerized species. The hydrocracking reactions primarily involve cracking and saturation of paraffins. The choice of catalyst will result in variation of cracking at the end of the paraffin molecule and therefore adjust the yield of jet fuel range product [11]. The hydro-isomerization and hydrocracking processes are followed by a fractionation process to separate the mixtures to paraffinic kerosene (HRJ SPK), paraffinic diesel, naphtha, and light gases. Jatropha curcas has higher oil yields (gallon per acre) than many other oil-yielding crops. In humid regions or under irrigated conditions, the Jatropha plant can be grown year round [13]. Generally 15e20 kg of jatropha fruit can be harvested from one plant and there are approximately 2500 plants per hectare. The land growing jatropha can be harvested four times a year [14]. The jatropha fruits

By Products Residue

Residue Post Treatment

H2 Biomass

Oil Extraction

Crude Oils

• Fertilizer • Medicine • Animal feeds

H2

Catalyst

Hydrogenation

have two or three seeds and each seed contains more than 33% of oil. The seed yield is 7 tonnes per hectare per year and the oil yield is around 2.2e2.7 tonnes per hectare [15]. The future oil yield is expected to be up to 2640 kg oil/ha in the year of 2020 [15]. The utility of jatropha oil as replacement for petroleum fuel has been well demonstrated [16e19]. In 2008, Air New Zealand, Continental Airlines and Japan Airlines used Jatropha derived green jet fuel as part of the aviation fuel which powers their commercial aircrafts. The residue after oil extraction, named seed cake, can be another energy source due to the considerable amount of oil content (9e12 wt%, contributes to 18.2 MJ/kg of energy) or fertilizer after post-treatment [20]. Pyrolysis and anaerobic digestion are the most promising processes to further convert the seed cake into valuable products [20e23]. Additionally, the husk and seed shells can be converted into value-added co-products through the posttreatments [24]. Many techno-economic studies have been done on determining the biofuel production cost based on jatropha feedstock [17e19,25]. Tewfik et al. [18] pointed out that the price of biodiesel from jatropha is in the range of $1.14e2.66 per gallon for various assumed scenarios. Labib et al. [19] suggested the price of $2.53 per gallon of jatropha-derived biodiesel with a gross profit of $37,403,643 per year. Additionally, Chauhan et al. [17] concluded that biodiesel production from jatropha is economically feasible with 13.5% internal rate of return. An economic analysis of HRJ fuel is described in the literature [26]. The HEFA (Hydro-processed Esters and Fatty Acid) fuel price was found to be $3.85/gal for the plant capacity of 98.28 MM gal/yr and $4.46/gal for the plant capacity of 30.16 MM gal/yr. Additional $0.27/gal e$0.31/gal is required to produce maximum jet fuel because of the increased hydrogen use and decreased yields of jet and diesel fuels. The economic analyses of bio-jet fuels from microalgae and pongamia oils are also studied [27]. The minimum selling prices for jet fuels derived from microalgae and pongamia oils were estimated to be $31.98/gallon and $8.9/gallon, respectively. Based on the sensitivity analysis, the development of technology and market will decrease the prices to be $9.2/gallon and $6.07/gallon, respectively. The techno-economic analysis of

Saturated Triglycerides

Catalyst

H2

C3H8

Propane Cleavage

FFA

Catalyst

CO2 & CO

H2

Catalyst

H2O

Decarboxylation Or Hydrodeoxygenation

C17H36 H2 Catalyst

C18H38

Hydroisomerization & Hydrocracking Paraffins, Iso-paraffins, Cracking Products Hydroisomerization & Hydrocracking

Light Gases Naphtha Jet fuel Fig. 1. Hydro-processed renewable jet (HRJ) process.

Diesel

W.-C. Wang / Renewable Energy 95 (2016) 63e73

fruit scenario, the process is fed with jatropha fruits and starts from Fruit Dehulling section. For the oil scenario, the process starts from jatropha oil and begins from Oil Upgrading section. The minimum bio-jet fuel selling prices based on these two scenarios were obtained and compared in this study. Process models were developed using Aspen Plus™ process simulator. The methods for simulating the process in Aspen Plus™ is listed in Table 1.

jatropha derived biodiesel has been studied recently, based on the transesterification process [28,29]. However, the by-products from HRJdnaphtha, liquefied petroleum gas, propane, and dieseldhave more credits (by-product value) than glycerol from the transesterification process [30]. In addition, HRJ biofuel production requires hydrogen to hydro-treat the bio-oil. It is suggested that the capital cost for HRJ is 20% higher than that of biodiesel production due to the hydro-treating process. In this study, the techno-economic analysis of jatropha derived HRJ fuel through a bio-refinery process is conducted. Two scenarios for the fuel production are simulated according to the difference of the starting materials (feedstocks): jatropha fruit and jatropha oil. Based on the assumption of nth plant design, the minimum jet fuel selling prices (MJSPs) for the two scenarios are determined and compared.

2.1.1. Fruit dehulling In Fruit Dehulling section, jatropha fruits were assumed to be stored in the storage tank when they were delivered from the farm and 100,000 kg/hr (2400 metric tonne per day) of them are sent to dehuller via a belt feeder. The composition of jatropha feedstock is defined as shown in Table 2. Out of the total fruits, the proportions of shells and seeds are 37.5 wt% and 62.5 wt%, respectively [31]. The component of seed is defined based on the compositions of jatropha oil and press cake. The shells are removed from the jatropha fruits within the dehuller. The power requirements for the belt feeder and dehuller are 14.7 kW each and 5.88 kW each with capacity of 47,348 kg/hr and 1000 kg/hr, respectively [20,32]. Shells and seeds are sent to the biomass dryer (modeled using the belt dryer principal), and around 8% of moisture is evaporated [20], condensed and stored in the water container as the process water. Dry shells and seeds are then separated within a separator, which requires the power of 9.62 kW each with capacity of 5000 kg/hr [33]. The shells are sent

2. Methods 2.1. Process description

AIR

The process flow diagram for the jatropha bio-refinery platform is demonstrated in Fig. 2. The entire process is divided into eight distinct sections: (1) Area 100: Fruit Dehulling; (2) Area 200: Shell Combustion; (3) Area 300: Oil Extraction; (4) Area 400: Press Cake Pyrolysis; (5) Area 500: Oil Upgrading; (6) Area 600: Product Separation; (7) Area 700: Storage; (8) Area 800: Utilities. For the

STEAM

65

9329 kg/hr

200000 kg/hr 227317 kg/hr

COMBUSTION GASES 32942 kg/hr

100000 kg/hr

SEEDS

90673 kg/hr (dry feed)

N2

JATROPHA FRUITS

A200 SHELL COMBUSITON

SHELLS

A100 FRUIT DEHULLING

5625 kg/hr

SHELL ASH

27 kg/hr

57730 kg/hr 2564 kg/hr

BIO-CHAR 34936 kg/hr

PRESS CAKES A300 OIL EXTRACTION

A400 PRESS CAKE PYROLYSIS

0.48 kg/hr

BIO-GAS 32400 kg/hr

BIO-OIL

ImpuriƟes 3419 kg/hr

Starting from Oil OIL

169 kg/hr

H2

PROPANE 10797 kg/hr

JET

2893 kg/hr

579 kg/hr

CO2 ALKANES, ISOMERS AND CRACKING PRODUCTS 16130 kg/hr

1988 kg/hr

A700 STORAGE

19375 kg/hr

A600 PRODUCT SEPARATION

PROPANE

A500 FUEL UPGRADING

H2 CATALYSTS Hydro-treaƟng catalyst: kg IsomerizaƟon/ Cracking catalyst: kg

918 kg/hr

2019 kg/hr

DIESEL Fig. 2. Process flow diagram of the bio-refinery process for producing jatropha-derived bio-jet fuel.

A800 UTILITIES WP=12118 KW QH= -30 MMkcal/hr QC= 24 MMkcal/hr Process water = 9329 kg/hr

66

W.-C. Wang / Renewable Energy 95 (2016) 63e73 Table 1 Types of methods for Aspen Plus™ simulation. Aspen parameters

Type

Property method Reference method Component Process type Selected databank Binary Interaction parameter

NRTL NRTL-HOC; SYSOP12 Conventional and Solid Common APV72PURE24; APV72PURE93; APV72SOLIDS; APV72ASPENPCD; NISTV72NIST-TRC Henry; HOCETA

Table 2 Feedstock component. Jatropha fruit Triglyceride (C14:0) Triglyceride (C16:0) Triglyceride (C16:1) Triglyceride (C17:0) Triglyceride (C18:0) Triglyceride (C18:1) Triglyceride (C18:2) Triglyceride (C18:3) Triglyceride (C20:0) Cellulose Hemicellulose Lignin Ether Ash H2O Protein Fixed carbon (Dextrose)

Shell (37.5 wt%) 0.03% 4.18% 0.21% 0.03% 2.11% 17.21% 9.74% 0.06% 0.06% 12.75% 3.75% 7.82% 2.00% 5.63% 7.49% 22.69% 4.25%

Cellulose Hemicellulose Lignin Ether Ash H2O Fixed carbon (Dextrose)

to the Shell Combustion section and the seeds are sent to the Oil Extraction section. It is assumed that the fruit dehulling process is the same based on locations. 2.1.2. Shell combustion In the Shell Combustion section, the shells removed from jatropha fruits are delivered to a combustor, operating at 750
C and 1 atm. The products after combustion are shell ash and product gases. The shell ash contains Na, K, Ca, Si, S and P [31]. The products are first cooled down to 645
C and then split into 97.5 wt% of product gas and 2.5 wt% of shell ash. This cooling duty is utilized to provide the heat to preheat the shells before feeding into combustor. The specifications of the heat exchanger are shown in Table 3. Based on the design, three heat exchangers are required [34]. The high temperature combustible gases can be recycled and provide the heat source to the entire system. The shell ash is rich in sodium and potassium and could be sold as soil fertilizer [31]. It is stored in an ash container at the Storage section. 2.1.3. Oil extraction The seeds from the Fruit Dehulling section are sent to the Oil Extraction unit. Based on the simulation results, after dehulling the

Table 3 Heat exchanger design specifications. Heat exchanger specifications Total heat flux (Gcal/hr) Thermal conductivity (W/m2 K) Inlet temperature (
C) Outlet temperature (
C) Heat transfer area (m2) Shell diameter (mm) Tube diameter (mm) Number of the tubes

Seed (62.5 wt%)

45 55 645 45 1586 1524 261 9

34.00% 10.00% 12.00% 5.32% 15.00% 12.35% 11.33%

Glyceride Glyceride Glyceride Glyceride Glyceride Glyceride Glyceride Glyceride Glyceride Lignin H2O Protein

(C14:0) (C16:0) (C16:1) (C17:0) (C18:0) (C18:1) (C18:2) (C18:3) (C20:0)

0.05% 6.73% 0.35% 0.05% 3.32% 27.53% 15.58% 0.10% 0.10% 5.32% 4.57% 36.30%

stream of jatropha seeds has the temperature of 139
C, which is the inlet temperature of the oil extraction process. It is noted that the extracted oil with temperature above 70
C contains large amount of phosphorus [35]. However, high temperature in the oil extraction process increases oil yield. Therefore, a cooling process after seed pressing is needed. A industrial seed pressing machine is chosen from De Smet Rosedown (Average length of seed is between 16 mme19 mm and the width of seed is between 10 mme12 mm) [35]. The type Mini 500 has expected processing capacity of 210 kg/hr with power requirement of 22 kW. The oil yield in the jatropha seed is around 30e40% [20]. Based on the literatures, 33% of oil yield is assumed in this study. The press cake, the residue after oil extraction, is delivered to Pyrolysis section. The crude jatropha oil leaving the expeller contains 5e15% impurities by weight [20]. Based on the literatures, there are three ways to purify the crude jatropha oil that comes from the seed pressing: (1) sedimentation; (2) filtration; (3) washing with water [36]. For the sedimentation, 15% of the product is expected to be lost. The filtration method requires less process time than sedimentation. The oil flow rate dealt with is 24776 L/hr (the density of jatropha oil is 0.92 g/cm3). The filter type chosen in this study is GL-I-300 [36], with the flow rate of 18000 L/hr and power requirement of 5.5 kW. The amount of power consumed for oil filtration is calculated as 7.59 kW. The resulting clean oil is pumped to Oil Upgrading section and the impurities is stored at Storage section for disposing. The cost of impurity disposal is considered. 2.1.4. Pyrolysis In the Pyrolysis section, the press cake from the oil extraction process is sent to the pyrolysis reactor (modeled using RStoic unit), running at 450
C and 1 atm [37]. Pure N2 was used to flush out the pyrolysis reactor. The amount of N2 is calculated as a function of feed-rate of press cakes. The gas, liquid and solid yields in the

W.-C. Wang / Renewable Energy 95 (2016) 63e73

pyrolyzed products are 38.81 wt%, 53.30 wt% and 7.89 wt%, respectively [37]. The compositions of gas phase products are H2, Methane, N2, O2, CO and CO2 [37]. The liquid phase product, bio-oil, is composed of C, H, O and N, and the mole fractions of those can be obtained from the literatures [38]. The solid phase product, biochar, is composed of C, H, O, N and S. We assume that the press cake contains lignin, protein, H2O and triolein, therefore the mole fraction of each component of the bio-char can be determined via the element balance and the stoichiometric equation, written as Lignin þ Protein þ H2O þ Triolein–> 0.000213847 CH4 þ 0.012168333 N2 þ 0.000118633 O2 þ 0.000522978 CO2 þ 0.000165239 CO þ 0.577657014 Bio-oil þ Biochar þ 0.015004365 H2

(1)

The products after pyrolysis are first separated through a cyclone, in which bio-char is split. The bio-char can be viewed as the valuable products [20]. The vapor-liquid products are cooled down to 25
C and separated via a vapor-liquid separator. The heat removed from the vapor-liquid products is utilized to provide the energy required for the pyrolysis process. The bio-oil is stored at the Storage section and can be upgraded by lowering the oxygen content and removing the impurities [37]. Further deoxygenation or hydro-treating process can be considered to upgrade the bio-oil to valuable fuels. Hydrogen can be directly produced from pyrolysis of press cakes [22]. However, separating the hydrogen from other gas products is costly and is a big challenge. 2.1.5. Oil Upgrading Clean jatropha oil obtained from Oil Extraction section is sent to a hydro-treating reactor (simulated using RStoic unit). The power requirement for pumping the oil depends on the feed-rates of the oil. From engineering manual [39], the fluid horse power for a centrifugal pump is calculated as,

P ¼ Q *P

(2)

where Q is the flow rate (m3/s) and P is the differential pressure (pa). The power consumptions of all the pumps in this section can be determined based on this. In this hydro-treating reactor, there are three sequential reactions taking place: hydrogenation, propane cleavage and deoxygenation [40]. The fatty acid profile of jatropha oil is listed in Table 4, ranging from 14 to 20 carbon numbers. Approximately 78.4 wt% of the oil is unsaturated. When defining the feed, it was assumed that only triglycerides exist in the bio-oils (Other components from the seed such as lignin and protein are assumed to stay in the press cake). The fatty acid compositions are presenting in the form of triglycerides. The first reaction in the hydro-treating reactor, hydrogenation, is used to saturate the unsaturated bonds in the triglycerides (TGs) [41]. In this study, the hydrogenation reaction is running at 360
C and 3 MPa over Pt/Al2O3 catalyst and hydrogen Table 4 Fatty acid profile of jatropha oil. Fatty acid profile

Concentration (%)

Myristic acid C14:0 Palmitic C16:0 Palmitoliec C16:1 Margaric C17:0 Stearic C18:0 Oleic C18:1 Linoleic C18:2 Linolenic C18:3 Arachidic C20:0

0.1 14.2 0.7 0.1 7.0 44.7 32.8 0.2 0.2

67

gas [42]. Per mole of the unsaturated TGs in the jatropha oil are converted into saturate TGs with 3 and 6 mol of hydrogen, respectively. Second, the propane cleave is applied to remove the propane backbone from the TG molecules, turning glycerides into three moles of fatty acids [40]. Trimyristin, tripalmitin, trimargarin, tristearin and triarachidin are converted into propane and myristic acid, palmitic acid, margaric acid, stearic acid and arachidic acid, respectively. The third reaction, deoxygenation, is utilized to remove the oxygen and turn the fatty acids into straight chain alkanes as well as CO2/CO/H2O. It is concluded that all the TGs in the jatropha oil are converted into hydrocarbons [42]. Saturated FFAs are turned into C13H28, C15H32, C16H34, C17H36 and C19H40, respectively, via deoxygenation. There are three pathways occurring at this stage: decarboxylation, decarbonylation and hydrodeoxygenation, which remove oxygen in the form of CO2, CO and H2O. To minimize the hydrogen usage, decarboxylation is chosen as the main reaction at this stage. The hydrogen gas is fed into the hydro-treating reactor only for the hydrogenation and propane cleavage. The hydrogen usage is calculated based on the hydrogen required for saturating the double bonds of the unsaturated triglycerides and cleaving the propane from the glycerol backbone [10,41]. Unreacted FFAs are separated in a reboiler (simulated using RadFrac unit block) and recycled back into the hydro-treating reactor. Alkanes coming out from the reboiler are pumped into the selective hydro-isomerization/hydro-cracking reactor (simulated using RStoic unit). The hydro-isomerization reaction is to rearrange the straight chain alkanes into branched structures. This rearrangement helps reduce the freeze point relative to the normal paraffins. Sometimes the hydro-isomerization is accompanied with cracking, which reduces the chain length and produces more molecules. Based on the literatures, the hydro-isomerization/ cracking reaction is operated at the temperature of 355
C, the pressure of 600 psig, liquid hourly space velocity (LHSV) of 1 and H2-to-feed ratio of 2100 scf/bbl (standard cubic feet/barrel) [43,44]. The catalyst is selected as Pt/HZSM-22/g-Al2O3 [41]. The product distribution and mass yield are listed in Table 5. In this case, large molecules are assumed to crack into small ones and then partially isomerized. The gaseous products in this section are propane, excess H2 and CO2. Propane is dissolved in hexane and separated from the gas products.

2.1.6. Product separation The hydrocarbon products from hydro-isomerization/cracking reactor are sent to the distillation column at Product Separation Section. In this section, four distillation columns (modeled using RadFrac unit; named A, B, C, D) are used to separate all the species,

Table 5 Carbon number distribution of hydro-isomerization/cracking products [43]. Carbon#

Mass %

Isomer Mass %

Normal Mass %

6 7 8 9 10 11 12 13 14 15 16 17 18

0.8 3.9 6.6 9.3 11.5 12.5 12.1 10.4 8.5 9.5 8.5 5.3 1.1

0 2.6 4.9 7.4 9.7 11 10.9 9.5 7.6 8.4 7.7 5 1.1

0.8 1.3 1.7 1.9 1.7 1.5 1.3 0.9 0.9 1.1 0.7 0.3 0

68

W.-C. Wang / Renewable Energy 95 (2016) 63e73

Fig. 3. Product separation diagram.

as shown in Fig. 3. In column A, around 8% of gas phase products such as CO2, H2 and C3H8 are released and C3H8 is further separated from the gas products. The rest of the vapor species is vented to the atmosphere. The liquid products are sent to column B. The C6~C8 hydrocarbons are distillated to the top and the C9~C18 products are left at the bottom [43e45]. The lighter species are sent to column C and C6~C7 hydrocarbons are released as naphtha products, which can be sold as the gasoline blendstock. The heavier products are sent to column D. The hydrocarbon species ranging at C17~C18 are considered as diesel fuel alternatives. The overhead stream of column D and bottom stream of column C can be considered as jet fuel range blendstocks, based on the chemical components and fuel properties (see Table 6). The fuel specifications, including distillation temperature, flash point, density and cloud point were estimated via Aspen Plus™. For calculating the fuel properties, the property method chosen in Aspen Plus™ is NRTL (Non-Random Two-Liquid) thermodynamic method, which correlates the activity coefficients of one compound with its mole fractions, and the reference methods are NRTL-HOC (Hayden-O'Connell) and SYSOP12. 2.1.7. Storage and utilities The products, including jet fuel range, diesel range and light products, as well as the residues from Shell Combustion and Oil Extraction stages, are collected at Storage section (the storage

capacity is 4 weeks). The amount of each item is listed in Table 7. The power consumption, cooling and heating duties for each section are also listed in Table 8. The total cooling and heating duties are 24 Gcal/h and 32 Gcal/h, respectively. The heat generated from shell combustion can be used to offset the total heating duty. The condensed water, with the rate of 9329 kg/hr, is used as the cooling water to offset the cooling duty. Approximately 2,093,053 kg/hr of makeup water is added to the cooling tower. 2.2. Techno-economic analysis Based on the process design and simulation, the capital and operating costs were estimated to determine the overall production cost and MJSP. The annual operating cost calculation for the designed facility, including variable and fixed operating costs (Tables 9 and 10), is based on mass and energy balance calculations using Aspen Plus™ process simulations [46]. The variable operating cost is composed of raw materials, impurity disposal and by-products deduction (Table 9). Raw materials include jatropha feedstocks, nitrogen and hydrogen carrier gases, hydro-treating catalysts, natural gas and makeup water. The unit costs of raw material come from literature studies or vender quotations [32,47e50]. The costs of feedstock are varied based on two different scenarios: (1) jatropha fruit as starting material (fruit scenario); (2) jatropha oil as starting

Table 6 Fuel properties of jatropha-derived jet fuel and compared with standard jet fuel specifications.

Distillation temperature: 10% Recovery (
C) 20% Recovery (
C) 50% Recovery (
C) 90% Recovery (
C) Final BP (
C) Flash Point (
C) Density @ 15
C (kg/m3) Freezing Point (
C), max Cloud Point (
C), max Net Heat of Comb. (MJ/kg)

ASTM jet fuel specification

Properties for SPK blendstock

Jatropha-derived jet fuel

205, max e e e 300, max 38, min 775e840 47

205, max e e e 300, max 38, min 730e770 40

163

42.8, min

e

199.3 256.6 283.4 51.4 783 48.7 e

W.-C. Wang / Renewable Energy 95 (2016) 63e73 Table 7 Production in the Storage section.

Table 10 Lists of fixed operating costs.

Item

Flow rate

Labor

# Required

Salary ($)

Shell ash (kg/hr) Impurities from oil extraction (kg/hr) Bio-char (kg/hr) Bio-oil (gal/hr) Propane (gal/hr) Jet fuel range product (gal/hr) Diesel fuel range product (gal/hr) Light products (kg/hr) FFA impurities (kg/hr) Condensed water (kg/hr)

5394 3419 559 5897 1014 3348 607 2011 22 9329

Plant Manager Plant Engineer Maintenance Supr Maintenance Tech Shift Supervisor Shift Operators Yard Employees Clerks & Secretaries

1 2 1 12 4 28 4 3

$ $ $ $ $ $ $ $

Maintenance Property Insur. & Tax

3% of Inside battery limits (ISBL) 0.7% of Fixed capital investment (FCI)

Table 8 Utilities of the entire process. Power consumption (kW)

Cooling duty (Gcal/hr)

Heating duty (Gcal/hr)

Fruit dehulling Shell combustion Oil extraction Press cake pyrolysis Fuel upgrading Product separation Storage

794 3102 6056 0.09 2160 e e

5 e e 2 8 7 2

9 6 e 2 9 6 e

Total

12112

24

32

material (oil scenario). The transportation costs for both jatropha fruit and oil are included in the feedstock prices. The fee for disposing oil and fatty acid impurities is considered. The byproducts, such as bio-oil, bio-char, propane, diesel, naphtha and shell ash are assumed to be sold based on the current price and deducted from the production cost. For the fixed operating cost, the labor salary, maintenance and property insurance/tax are included, as shown in Table 8. All costs are inflated to 2011 U.S. dollars using the Plant Cost Index from Chemical Engineering Magazine [51], the Industrial Inorganic Chemical Index from SRI Consulting [52], and the labor indices provided by the U.S. Department of Labor Bureau of Labor Statistics [53]. Aspen IPE™ was used to estimate the baseline capital costs, and an exponent term of 0.6 for the purpose of scaling equipment costs

Table 9 Lists of variable operating costs. Raw materials Feedstock price Jatropha fruit ($/kg) Jatropha oil ($/kg) Carrier gas N2 ($/kg) H2 ($/kg) Catalyst Hydro-treating catalyst ($/kg) Hydro-isomerization catalyst ($/kg) Natural gas ($/TCF) Cooling water ($/kg) Disposal fee Oil impurities ($/kg) FFA impurities ($/kg) By-products Naphtha ($/kg) Diesel ($/kg) Propane ($/kg) Bio-Oil ($/kg) Bio-Char ($/kg) Shell Ash ($/kg) a

69

Unit price

Ref

0.14 0.5

a

0.61 2.79

[54] [51,54,55]

a

307 398 4.42 0.00022

[56] [56] [57] [58]

0.02 0.02

[32] [32]

0.81 1.27 0.32 0.373 0.077 0.08

[59] [59] [60] [61] [62] [63]

Vendor quotation; volume size is tonne bases; commercial volume.

147,000 70,000 57,000 40,000 48,000 40,000 28,000 36,000

is assumed. Material and energy balance and flow rate information are used to size equipment and to calculate capital expenses. In addition, the capital costs are estimated based on vendor quotes, previous literatures and standard engineering manuals [28,29,32,64e67]. The plant is assumed to be the nth plant of its kind. The plant assumptions are listed in Table 11. The fixed capital investment (FCI) is the summary of total direct and indirect costs. The total direct cost (TDC) includes the total installation costs, warehouse (4% of ISBL), site development (9% of ISBL) and additional piping (4.5% of ISBL). The total indirect cost is composed of pro-rateable expenses (10% of TDC), field expenses (10% of TDC), home office and construction fee (20% of TDC), project contingency (10% of TDC) and start-up/permits costs (10% of TDC). The total capital investment is the summary of FCI, land and working capital. To calculate MJSP, after the variable and fixed operating costs and total capital investment are determined, a discounted cash flow rate-of-return analysis is applied based on the financial assumptions listed in Table 11. It is noted that uncertainties exist around conceptual cost estimates, and these values are in relative comparison against

Table 11 Lists of plant assumptions based on US case. Parameters

Assumptions

Basis year for analysis Debt/equity for plant financing Interest rate and term for debt financing

2012 60%/40% 8% annually/10 years

Internal rate of return for equity financing Total income tax rate Plant life Plant depreciation schedule Plant salvage value Construction period Fixed capital expenditure schedule

10% 35% 30 years 7 years 0 3 years 8% in year 1 60% in year 2 32% in year 3 0.25 year 50% 75% 100% 8400 h 9% of ISBL 4% of ISBL 4.5% of ISBL 132 acres at $14,000 per acre 5% of fixed capital investment

Start-up time Revenues during start-up Variable costs during start-up Fixed costs during start-up Operating hours after start-up Site development costs Warehouse Additional piping Land purchase Working capital Indirect costs

% of TDC

Prorated expenses Home office and construction fees Field expenses Project contingency Other costs (start-up and permitting)

10 20 10 10 10

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W.-C. Wang / Renewable Energy 95 (2016) 63e73

Site development 7% Warehouse 3%

Additional piping Fruit Dehulling 4% 9% Shell Combustion 3%

Utilities 2%

Oil Extraction 0.4%

Storage 4% Product Separation 7%

Press cake Pyrolysis 8%

Total Direct Capital Cost for the fruit scenario: $229 million

Oil Upgrading 53%

Fig. 4. The distributions of total direct capital cost.

3. Results and discussion Table 12 Comparison of fruit and oil scenarios.

Capital cost (million $) Operating cost (million $ per year) Fuel yield (million gal per year) MJSP ($/gal) Co-product credit (million $ per year)

3.1. Cost analysis Fruit scenario

Oil scenario

387 116 29.8 5.42 91

284 134 29.8 5.74 27

technological variations or process improvements. To address these issues, the sensitivity analysis is carried out to capture the effects of yields on MJSP.

Fig. 4 indicates the proportion of capital cost of each section on the total direct capital costs. The Oil Upgrading part has more than half of the total due to the high costs of hydro-treating and hydroreforming reactors. Second to this section is the Fruit Dehulling part, resulting in 9% total capital costs. The large size of belt feeder and biomass dryer contributed most of the capital in this section. The Pyrolysis section for press cake has 8% of the total. Although this thermo-chemical process produces many valuable co-products such as bio-oil and bio-char, using bio-chemical process such as anaerobic digestion to deal with the press cake [22] or directly selling it are the two alternative options. The Product Separation

Fig. 5. Operating costs for the fruit scenario and the oil scenario.

W.-C. Wang / Renewable Energy 95 (2016) 63e73

71

Fig. 6. Cost sensitivity analysis-Spider Chart.

section accounts for 7% of the total capital cost and is mostly contributed by the distillation columns. The Shell Combustion section needs 3% of the total capital, but the produced combustible gases make the entire process energy self-sustainable. The Oil Extraction section requires less capital compared to other facilities because the cheapest method, mechanical press, was chosen. For a plant with capacity of 2400 metric tonne per day, a total direct capital of $229 million was required. Fruit and oil scenarios, for the production of jatropha-derived jet fuel were compared in this study. The fruit scenario is fed with jatropha fruits and starts from Fruit Dehulling section and the oil scenario is fed with jatropha oil and begins from Oil Upgrading section. The major differences between the fruit and oil scenarios are (1) feedstock cost; (2) refinery capital cost; (3) co-product credit; (4) energy cost. Table 12 lists the main results of these two scenarios. With the same jet fuel yield, the MJSP of the fruit scenario was calculated to be $5.42/gal, $0.32/gal less than the oil scenario. It is noted that the feedstock unit price of the fruit scenario is lower than the oil scenario ($0.14/kg vs $0.5/kg). Transportation costs of jatropha fruit and oil and feedstock processing costs before they reach on-site are included in the feedstock price. As expected, the capital cost of oil scenario was less than the fruit scenario by $103 million due to the absence of Fruit Dehulling, Shell Combustion, Oil Extraction and Pyrolysis sections. However, extra valuable co-products such as bio-oil, bio-char and shell ash can be obtained from the fruit scenario. The credits from the co-products of the fruit scenario are higher than those of the oil scenario by $64 million per year (the prices of co-products are listed in Table 9). Moreover, the operating costs of the fruit scenario are lower than the oil scenario by $18 million per year. Fig. 5 demonstrates

the contribution of each category to the operating costs for these two scenarios. To have the same production rate of jet fuel as the oil scenario, the fruit scenario has to consume more feedstocks because only 33% of each jatropha seed contains oil. Therefore, the total cost of feedstocks of fruit scenario was higher than the oil scenario by $1.22/gal to the cost of jet fuel. The cost of electricity for the fruit scenario was estimated to contribute $0.2/gal jet fuel, 85% higher than the oil scenario. Unlike oil scenario, the combustion gases from burning the shell provided the heating source to the entire process. No natural gas purchase was required for the fruit scenario. As seen in Fig. 5, for the fruit scenario, the credits obtained from the co-products deduct the production cost by $3.06/gal jet fuel and significantly lower the MJSP value.

3.2. Sensitivity analysis In Fig. 6, a spider chart is presenting the sensitivity analysis results for the bio-refinery production of jatropha-derived jet fuel. The parameter changes in y-dir are corresponding to the MJSP changes in x-dir. The steeper the parameters demonstrate, the more effect they have on MJSP. Obviously, the feedstock cost is the most significant parameter that controls production expenses. Twenty-one percent increase on feedstock price leads to 13% more on MJSP. On the contrary, if the price of the jatropha fruit reduces from $0.14/kg to $0.11/kg, the MJSP value drops by 20%. In addition, the oil content in jatropha seeds is also an important factor. Approximately 18% reduction of MJSP was found if 48% of a jatropha seed is oil. However, reduce the oil content down to 22% has less impact on the production cost. As expected, increasing the plant capacity significantly decreases the production cost. Five times of

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W.-C. Wang / Renewable Energy 95 (2016) 63e73

current plant capacity results in 34% drop on MJSP. For the changes of reactor cost (pyrolysis, hydro-treating and hydro-reforming reactors), not much fluctuations of MJSP are shown. For the catalysts (hydro-treating and hydro-reforming catalysts), the prices and loadings of catalyst are the two main concerns which vary the fuel selling price. Double the price of hydro-treating catalyst results in 26% increase on MJSP. Varying the weight hourly space velocities (WHSVs) of hydro-treating reaction from 2 to 1 leads to 16% reduction of MJSP. Double the WHSVs of hydro-reforming reaction has only 5% decrease on MJSP. Moreover, higher by-product selling prices deduct more production cost and reduce MJSP. For example, if the selling price of bio-oil increases to $1.6/kg, the MJSP value decreases by 16%. Various pyrolysis temperatures influence the yields of solid, liquid and gas products and cause various production costs. For the financial part, return on investment plays an important role on the change of MJSP. Double the profit needs 21% higher of fuel selling price. Equity and interest rate have less effect compared to this. 4. Conclusions In this study, the process simulation and techno-economic analysis were performed for the bio-refinery production of jatropha-derived HRJ fuel. The bio-refinery process is split into six steps; (1) Fruit Dehulling; (2) Shell Combustion; (3) Oil Extraction; (4) Press Cake Pyrolysis; (5) Oil Upgrading; (6) Product Separation. The MJSP value are estimated as $5.42 per gallon of jet fuel with $387 million and $116 million capital and operating costs, respectively, based on the plant capacity of 2400 metric tonne per day. The results from fruit scenario are compared with the oil scenario, which gives $5.74 per gallon of jet fuel with $284 million and $134 million capital and operating costs, respectively. The major differences come from the cost of feedstock, refinery capital, the coproduct credit and energy cost. The benefits obtained from feedstock price and co-product credits lower the production cost of the fruit scenario. In addition, recycling the combustible gases from the Shell Combustion section makes the entire process of fruit scenario energy self-sustainable. The feedstock cost raises a great level of uncertainty for the production cost, resulting in a wide range of MJSP found in the sensitivity analysis. Increasing the oil content from 33% to 48% drops MJSP by 22%. Other than those, the plant capacity, reactor construction and catalyst price/loading are significant parameters which cause high degree of uncertainties. The improvement of utilizing or selling the co-products provides a high potential to reduce the bio-jet fuel production cost. Acknowledgements This project was supported by the Ministry of Science and Technology, Taiwan, through grant 104-2628-E-006-007-MY3. References [1] Air Transportation Action Group, Beginner's Guide to Aviation Biofuels, 2009. [2] R.W. Stratton, H.M. Wong, J.I. Hileman, Life Cycle Greenhouse Gas Emissions from Alternative Jet Fuels, 2010. PARTNER (Partnership for Air Transportation Noise and Emissions Reduction) PARTNER-COE-2010-001. [3] K. Blakeley, DOD Alternative Fuels: Policy, Initiatives and Legislative Activity, December 2012. Congressional Research Service 7-5700. [4] International Air Transport Association, Fact Sheet: Alternative Fuels [Accessed 08.01.14], https://www.iata.org/pressroom/facts_figures/fact_ sheets/pages/alt-fuels.aspx. [5] Airportwatchcom, “Sustainable Aviation” Produce its “road-map” for Unduly Ambitious Levels of Jet Biofuels in Future [Accessed 01.04.16], http://www. airportwatch.org.uk/2015/01/sustainable-aviation-produce-its-road-map-forunduly-ambitious-levels-of-jet-biofuels-in-future/. [6] U.O.P. Honeywell, Green Jet Fuel [Accessed 11.06.14], http://www.uop.com/

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