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Kinetic behavior and economic evaluation of supercritical fluid extraction of oil from pequi (Caryocar brasiliense) for various grinding times and solvent flow rates
The Journal of Supercritical Fluids 140 (2018) 188–195
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Kinetic behavior and economic evaluation of supercritical fluid extraction of oil from pequi (Caryocar brasiliense) for various grinding times and solvent flow rates
T
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Julio C.F. Johnera, , Tahmasb Hatamia, Giovani L. Zabotb, M. Angela A. Meirelesa a
LASEFI/DEA/FEA (School of Food Engineering)/UNICAMP (University of Campinas), Rua Monteiro Lobato, 80, 13083-862, Campinas, SP, Brazil Laboratory of Agroindustrial Processes Engineering (LAPE), Federal University of Santa Maria, UFSM, Presidente Vargas Av., 1958, Cachoeira do Sul, RS, 96506-302, Brazil b
G R A P H I C A L A B S T R A C T
A R T I C LE I N FO
A B S T R A C T
Keywords: Cold pressed extraction Supercritical fluid extraction SFE Pequi COM Cost of manufacturing
This paper presents the techno-economic influence of grinding time (GT) (10 s–90 s) and CO2 flow rate (FR) (1.08 × 10−4–2.17 × 10−4 kg/s) on the supercritical fluid extraction (SFE) performance of oil from pequi (Caryocar brasiliense) under 60 °C and 40 MPa. Then, in the economic approach, the best extraction curves were described in terms of Cost of Manufacturing (COM) in the laboratory scale for each combination of GT and FR for selecting the suitable mass to feed mass ratio (S/F) that yielded the lowest COM and the highest productivity. Thereafter, with this S/F, eight scenarios were tested in pilot (100 L) and industrial (500 L) scales with CO2 recycle, which included the purchase cost of pequi and acquisition cost of equipment. Within these eight scenarios tested, the most promising one indicated a COM of only US$ 37.03/kg pequi oil, whereas approximately 85% of the COM is dependent on the purchase cost of pequi and other raw materials (e. g., CO2).
⁎
Corresponding author. E-mail address: [email protected] (J.C.F. Johner).
https://doi.org/10.1016/j.supflu.2018.06.016 Received 31 May 2018; Received in revised form 22 June 2018; Accepted 22 June 2018
Available online 28 June 2018 0896-8446/ © 2018 Elsevier B.V. All rights reserved.
The Journal of Supercritical Fluids 140 (2018) 188–195
J.C.F. Johner et al.
1. Introduction
Walita 400 W, RI1364/07, Varginha, Brazil) for 10, 30, 50, 70, and 90 s. A sieve shaker (Bertel, N. 1868, Caieiras, Brazil) with 16–80 mesh sieves was used to determine the particle diameter of the ground material. The average diameter was calculated according to the proposed equation by the American National Standard Institute [12].
Pequi (Caryocar brasiliense) is the most collected fruit of the Brazilian Cerrado that has an orange-yellow pulp and is well known as tiny gold or pequi [1,2]. Regarding the minerals in the pulp, 100 g of pequi pulp contains approximately 72.5 mg of calcium, 1.2 mg of iron, 3.4 mg of zinc, 184.4 mg of phosphorus, 95.2 mg of magnesium, and 631 mg of potassium [3]. Moreover, pequi oil is composed (in mass) of 53% oleic acid, 2.7% linoleic acid, and 39% palmitic acid, and it has been demonstrated to be an anti-inflammatory and antioxidant agent [2,4,5]. The traditional process of oil extraction from pequi consists of intensive cooking in water and subsequent removal of the supernatant. The main disadvantages of this extraction method are its low yield, high-temperature requirement, and the fact that the oil is not filtered [6]. To overcome these limitations, extraction with supercritical CO2 could be employed for the extraction of pequi oil due to its mild temperatures (40–60 °C) and high extraction performance [7,8]. The advantage of supercritical fluid extraction (SFE) is not limited to its high performance at low or moderate temperatures. Easy separation of solute from the solvent, employing a non-toxic solvent, and high purity of extract are other advantages of this technology. To the authors’ knowledge, there is only one paper regarding the extraction of pequi oil by SFE up to now, which has been recently performed by our research group. Johner et al. [9] investigated the extraction of oil from pequi using SFE and SFE assisted by pressing (SFEAP) at 40 °C–60 °C and 20 MPa–40 MPa. The authors reported that 60 °C and pressure of 40 MPa provided the highest yield, 48 g extract/ 100 g raw material, during 48 min of extraction. Despite these new findings, such scientific paper did not present any information on the effect of grinding time (GT) and CO2 flow rate (FR) on the dynamic extraction yield. Furthermore, an economic evaluation is a demand for showing the feasibility of the process applied to pequi. Economic evaluation of processes performed under high-pressure is an important strategy to understand the processes because it provides insights even at earlier stages of research. COM and itemized costs are valuable outcomes within the economic approach because they can contribute to confirming the feasibility and technical potential of a specific process. According to some reports, decisions regarding operational conditions can be pondered and dealt within the research background using the economic assessment, and the results can encourage further advances toward commercial application of natural oils and bioproducts [10,11]. Based on this context, the current study aims at investigating the techno-economic influence of GT and FR on the dynamic extraction yield of oil from pequi and on the economic responses. The following responses are presented and discussed: yield of oil, cost of manufacturing (COM), contribution of itemized costs (cost of raw material, cost of operational labor, cost of utilities, and fixed capital investment) and project indices (return on investment, payback time, gross margin, internal rate of return, and net present value).
2.2. Supercritical fluid extraction The experimental assays were performed using a commercial highpressure apparatus inside a stainless-steel extractor with 2.5 cm of height and 2 cm of internal diameter. In a typical SFE experimental assay, the extractor was filled with 2 g of samples, and glass wool was packed at the bottom and top of the extractor to prevent entrainment of particles. Extractions were performed using CO2 (purity > 99.5%) as the solvent (White Martins, Campinas, Brazil) at pressures of 40 MPa and static time of 10 min. The extractor was heated by an oven and its temperature was fixed at 60 ± 1 °C using a heat controller. The experimental assays were performed for 10 min (static time) and for 20–40 min (dynamic time) by flowing supercritical CO2 through the bed. Extracts were accumulated in glass vials and were periodically weighed on an analytical balance. The CO2 flow rate was adjusted by a gas flow meter with the measurable range of 3.25 × 10−5–4.30 × 10−4 kg CO2/s at the standard condition. Prior to venting CO2 to the ambient, it is also passed through a totalimeter at the end of the line to measure the total CO2 consumed. The average flow rate of CO2 was calculated by dividing the total CO2 consumed per total dynamic time of extraction. The minimum flow rate considered in this study was 1.08 × 10−4 kg CO2/s to prevent the fluctuation of flow rate and control it precisely. 2.3. Economic evaluation of SFE of pequi oil The economic evaluation was done in the SuperPro Designer 9.0® software (Intelligen Inc., Scotch Plains, NJ, USA). Considering the SFE process (Fig. 1), a flowsheet was designed to evaluate the economic feasibility of obtaining bioactive compounds from pequi in two different scales: 100 L and 500 L. In the experimental study, the yield was evaluated for the extraction up to 40 min for S/F of 130 g CO2/g dry pequi pulp. For a representation scope, a Gantt chart for an extraction time of 40 min is presented in Fig. 2. The procedures include mainly pequi pulp loading, CO2 pressurizing, bed heating, static time, oil extraction, bed depressurizing, and bed unloading. The total batch duration of SFE in 2 extraction vessels is 2 h and the SFE was designed to operate for 7920 h per year, which corresponds to 3 daily shifts for 330 days per year. The yearly remaining time was considered for cleaning and equipment maintenance. 2.3.1. Economic input data Commonly, equipment purchase cost for one or two discrete sizes is available. Alternatively, costs for other equipment sizes or capacities must be estimated. Scaling the equipment cost to the required capacity is possible through the power law (Eq. (1)) [13–15], where C1 is the equipment cost with capacity Q1, C2 is the known base cost for equipment with capacity Q2, and M is a constant depending on the equipment type. Values of M were obtained in the scientific literature [13–16] because the cost of a specific item is a function of size, materials of construction, design pressure and design temperature. The base costs acquired in 2018 (local quotation, including import fees for the items not produced in Brazil) are presented in Table 1 for calculating the costs in a larger scale.
2. Material and methods 2.1. Raw material Pequi was acquired in the city of Barra do Garças (Brazil) after being collected from the Xingu region of Mato Grosso (Brazil). The fruits were manually peeled using a knife (Tramontina, 21198315, Carlos Barbosa, Brazil) in a dark environment to avoid any degradation of the carotenoids and other light-sensitive bioactive compounds. The pulp was manually cut using a knife (Tramontina, 22902/007, Carlos Barbosa, Brazil) in a dark environment at 20 °C. The pulp slices were frozen at −18 °C and, thereafter, transported to the laboratory (LASEFI/FEA/ UNICAMP). The pulp was then dried in a circulation oven (Marconi, MA035 / 5, Piracicaba, Brazil) at 45 °C for 24 h and, in the sequence, frozen at −18 °C (Metalfrio, HC -4, São Paulo, Brazil). Afterward, the dried pulp was ground in a mini-processor-coupled mixer (Philips
Q C1 = C2 ⎛ 1 ⎞ Q ⎝ 2⎠ ⎜
M
⎟
(1)
As some studies report [17–19], there is a trend of reducing the COM when the capacity is increased. Therefore, the data provided in Table 1 were used to estimate the total cost of the SFE plant composed 189
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Fig. 1. Flowsheet of SFE for pequi pulp oil extraction.
Fig. 2. Gantt chart for one batch of SFE for obtaining pequi oil; the case study of oil extraction for 40 min. 190
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2.3.2. COM, productivity, and itemized costs The COM of bioactive extracts depends on the sum of three main components: direct manufacturing costs (e.g. seeds, ethanol, and CO2), fixed manufacturing costs (e.g. equipment) and general expenses (e.g. management costs and research & development). Capital costs associated with buildings and equipment, and other costs as storage of raw materials and extracts, electrical facilities, instrumentation, engineering and management fees, was also considered. The protein flour generated after performing SFE can be considered harmless and clean. Firstly, the COM was evaluated for the SFE performed in the laboratory scale with extraction vessels of 5 mL. The goal was to have a response of the economically feasible time (and consequently the S/F ratio) that is suitable for performing the oil extraction on a larger scale. Thereafter, these feasible time and S/F ratio were selected for studying the COM in 100 L and 500 L scales. Secondly, the COM was evaluated for the SFE performed in 100 L and 500 L scales. A total of 8 scenarios were studied, which consisted of testing the feasible extraction time, the plant estimated cost based on direct quotation and the estimated cost extrapolated by 50%, and the cost of acquiring pequi as low price (LP) or high price (HP). The cost of pequi pulp commonly ranges from US$ 7.00/kg to US$ 14.00/kg. Therefore, these values were selected as LP and HP, respectively. The productivity of pequi oil in larger scales was simulated based on the amount of oil obtained experimentally. The behavior of the yields and composition was assumed to have the same performance in larger scales as the findings obtained in the laboratory scale. The percent contribution of the itemized costs (fixed capital investment – FCI, cost of raw materials – CRM, cost of operational labor – COL, and cost of utilities – CUT) was evaluated for the best scenario. It is worthwhile noting that all the values of COM were estimated for scenarios when the investors have all capital resources to start the projects. Indeed, the analyses were developed for scenarios where no bank financing is required. In such a case, the final values of COM presented in the study do not include costs of amortization for the bank credit. If credit is needed, all fees and charges should be taken into account.
Table 1 Base cost for equipment composing the SFE plant. Item
SFE Jacketed extraction vesseld CO2 electrical pump Cooler Heater Separation vesseld Manometer Blocking valve Backpressure valve Safety valve Flowmeter Temperature controller Piping, connectors, mixers, splitters, and crossheadse Structural material for supporting the equipment
Ma
Unit base cost (US$)b,c
Quantity (un.)
Total base cost (US$)b
0.82
4,900.00
2
9,800.00
0.55 0.59 0.59 0.49 0 0.60 0.60 0.60 0.60 0.60 0.40
11,685.00 1,360.00 430.00 1,100.00 70.00 60.00 1,300.00 90.00 280.00 180.00 660.00
1 1 1 2 4 6 2 1 1 4 –
11,685.00 1,360.00 430.00 2,200.00 280.00 360.00 2,600.00 90.00 280.00 720.00 660.00
0.40
300.00
–
300.00
Total cost of SFE plantb (US$)
30,765.00
a M constant depending on equipment type, based on Green and Perry [13], Peters and Timmerhaus [16], Smith [14] and Turton, Bailie, Whiting, Shaeiwitz and Bhattacharyya [15]. b Based on an operating plant with extraction and separation vessels of 1 L. c Direct quotation for reference year of 2018. d Supporting pressures up to 60 Mpa. e Total cost.
of two extraction vessels (100 L or 500 L) and two separation vessels (100 L or 500 L). Other input data, as the cost of raw materials, wage, and utilities are presented in Table 2.
Table 2 Input economic parameters used for simulating the COM of pequi oil obtained from pequi pulp by SFE; scales of 100 L and 500 L for the vessels. Economic parameter
Values for 100 L scale
Values for 500 L scale
Dimension
Fixed capital investment (FCI) Total cost of SFE planta,b Annual depreciation ratec Annual maintenance ratec Project lifetime Annual time worked
693,519.00 10 6 25 7920
2,254,122.00 10 6 25 7920
(US$) (%) (%) (years) (h/year)
Cost of raw material (CRM) Pequi pulp (scenario of low price – LP) Pequi pulp (scenario of high price – HP) Transport and pre-processing of pequi pulpd Industrial CO2e
7.00 14.00 40 3.00
7.00 14.00 40 3.00
(US$/kg) (US$/kg) (US$/ton) (US$/kg)
Cost of operational labor (COL) Wage (with benefits and administration)f Number of workers per shift Total wage per day (3 shifts/day)
16.80 2 806.40
16.80 3 1,209.60
(US$/h.worker) (Worker/shift) (US$/day)
Cost of utilities (CUT) Water (for cooling and cleaning)e Steame Glycol solutione Electricitye
1.00 12.00 10.00 0.50
1.00 12.00 10.00 0.50
(US$/ton) (US$/ton) (US$/ton) (US$/kW.h)
a b c d e f
The design is similar to that one shown in Fig. 1 (2 extraction vessels and 2 separation vessels). Estimated cost using the power law of capacity (Eq. (1)). based on Peters and Timmerhaus [16]. The pre-processing steps include drying (when needed) and storing the samples until further use. direct quotation for the reference year of 2018. Bureau of Labor Statistics, http://www.bls.gov/fls/country/brazil.htm, USA, accessed on January 18th, 2018. 191
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Table 3 Average diameter of pulp of pequi for various grinding times. Grinding time (s)
diameter (mm)
Standard deviation
10 30 50 70 90
> 3.36 2.29 2.34 2.27 2.33
– 0.16 0.04 0.04 0.01
reduced slightly with increasing GT from 30 s to 50 s, and remained approximately constant with further increasing the GT. The reason is that increasing GT from 10 s to 30 s caused a significant reduction in particle diameter from more than 3.36 mm to 2.29 mm (Table 3). It consequently increased the yield due to the enhancing of mass transfer specific area. Noticeably the particle size for GT of 10 s was bigger than the mesh size of the largest sieve shaker in our lab, which is a sieve shaker with 3.36 mm mesh size. However, further increasing GT from 30 s to 90 s did not influenced the particle diameter to a large extent. Besides the independence of diameter with GT after 30 s, another reason for the slight reduction of yield is sticking some oil content of pequi to the wall and blades of the grinder with increasing GT, which means some slight losses. In the best condition, 49.07 g extract/100 g raw material was obtained. Considering the GT of 30 s favored the highest performance in the extraction yield shown in Fig. 3A, the influence of CO2 flow rate on the yield of oil was evaluated at GT of 30 s (Fig. 3B). The yield, at the same S/F ratio, increased with decreasing CO2 flow rate. This behavior is due to the shorter contact time of CO2 with solid particles at higher flow rates. Consequently, a reduction in the overall mass transfer occurred for higher values of S/F. It is interesting to compare the results of the current study with those obtained by Johner et al. [9] even though the SFE equipment employed were not the same. The authors performed dynamic SFE yield from pequi at a GT of 50 s, a temperature of 60 °C, a pressure of 40 MPa, a CO2 flow rate of 2.93 × 10−4 kg/s, and S/F of 352. Their reported SFE yield at S/F of 130 was approximately 49 g oil/100 g pequi pulp, and the corresponding SFE yield in the current study at the same GT, temperature, pressure, S/F, but at a CO2 flow rate of 1.44 × 10−4 kg/s was 47 g oil/100 g pequi pulp. This small difference between the SFE yield in the previous and current study indicates the reliability of the experimental data.
Fig. 3. Influence of grinding time on the kinetic extraction of oil of pequi using SFE at 40 MPa, 60 °C, and CO2 flow rate of 1.44 × 10−4 kg/s (A) and CO2 flow rate on the kinetic extraction of oil of pequi using SFE at 40 MPa, 60 °C, and grinding time of 30 s (B).
3.2. Economic evaluation of SFE of oil from pequi 3.2.1. COM and itemized costs Fig. 4 shows the COM of SFE performed in the 1 L scale for the whole kinetic curves using SuperPro Designer 9.0®. The COM decreased initially, reached its lowest level at a certain S/F, and, thereafter increased at higher S/F values. This behavior is well-known in extraction processes of bioactive compounds [17,20,21]. Commonly, the range of lower COM is closer to the end of the constant extraction rate period. In this work, an economically feasible S/F (35–72 g CO2/g pequi pulp) and a technologically feasible S/F (72–130 g CO2/g pequi pulp) were identified as promising values of S/F within each approach (economic and technical). Therefore, once S/F of 72 g CO2/g pequi pulp matches both approaches, the values of COM of SFE of oil from pequi in the 100 L and 500 L scales were simulated considering this S/F. Furthermore, for the 1 L scale, the FR of 1.7 kg/min and GR of 30 s were the best conditions. In such case, they were also selected for the sequential studies (the FR was scaled proportionally to the size of plant). The values of COM for oil obtained from pequi by SFE in 100 L and 500 L scales are presented in Fig. 5. In this figure, DQ is the calculated cost based on direct quotation, DQ + 50% is the calculated cost extrapolated by 50%, LP is the low price (US$ 7.00/kg), and HP is the high price (US$ 14.00/kg). Among eight scenarios evaluated in this work, the COM ranged from US$ 37.03/kg oil to US$ 60.69/kg oil. The
2.3.3. Sensitivity analysis For sensitivity analysis, some commercial products with similar characteristics to those produced in this work were used as a reference (even though there is not oil obtained by SFE under commercialization). The average market selling prices practiced worldwide for 1 kg of pequi oil (obtained by pressing) typically range from US$ 75.00 to US$ 150.00. Therefore, these values were used as a reference in the simulation of the main general profitability factors, as return on investment (ROI), payback time, gross margin (GM), internal rate of return (IRR) after taxes and net present value (NPV). The 8 scenarios became 16 in this section after the inclusion of these two limits of the selling price. 3. Results and discussion 3.1. Supercritical fluid extraction The influence of GT on the yield of oil from pequi is presented in Fig. 3. The data of this figure are the average of two repeated experimental assays for each condition of GT, where the error bar in each point indicates the corresponding standard deviation. The yield of oil significantly increased with increasing GT from 10 s to 30 s, then, 192
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of 500 L could reduce 7–16% of COM. However, the processing in a 100 L scale plant can be interesting, especially for regional raw materials (no commodities) which are farmed in small or medium quantities, as it is the case of pequi. Therefore, manufacturing plants with too big capacity are not mandatorily required.
3.2.2. Sensitivity analysis The sensitivity analysis is presented in terms of the project indices (ROI, IRR, GM, NPV and payback time) calculated after performing the simulation (Table 4). The revenue was calculated considering the sale of oil from pequi in a year. Among the 16 scenarios, the highest ROI (1103%) was obtained in the scenario 6. According to El-Halwagi [23] and Fernández-Ronco et al. [24], values of ROI over 15% are suitable for recommending a project to operate with profitability. The ROI was larger than 80% in most of the cases in the current study. This finding enables us to indicate the feasibility of the SFE from pequi pulp for such selling prices (> US$ 75.00/kg). As the ROI, the higher the GM the more attractive is the project. In the same scenario of the highest ROI (scenario 6), the GM was 75%, which means the company would retain approximately US$ 0.75 from each dollar generated by selling the oil from pequi. Values of IRR and NPV were also larger for scenario 6. When consulting the scientific literature, IRR of 14.9% and 23.4% for US$ 7.27/ kg turmeric rhizomes and US$ 1.59/kg turmeric rhizomes, respectively, were reported [21]. Values of NPV from US$ 7 mi to US$ 35 mi are reported in a two-step intensified extraction process that operates at 0.1 MPa for recovering phytochemicals from Brazilian ginseng roots [25]. The payback time is also presented (Table 4). Differently from the other parameters, the shorter the payback time the more feasible is the project. It ranged from 0.06 year (scenario 6) to 1.15 year (scenario 11), which could be attractive for investors. Those payback times are quite acceptable because the initial investment can be rapidly recovered. In the same trend, Zabot et al. [20], reported payback times of 0.6–1.5 years for the integrated extraction of tocotrienols-rich oil and bixin-rich extract from annatto seeds using supercritical technology in a 100 L scale. The economic viability can be understood as an optimized trade-off between the concomitant changes of yield and concentration of biocompounds, from the income side, and the investment and operation expenditures, from the fixed and variable costs, respectively [11]. Therefore, balancing the technical and economic approaches, we infer that SFE performed during 40 min (S/F of 72 g CO2/g pequi pulp) with the lowest FR (among those tested) and with pulp particles submitted to GT of 30 s as the most suitable integrated conditions.
Fig. 4. Cost of manufacturing (COM) of pequi oil obtained by SFE in extraction vessels of 1 L: (A) different grinding times (GT) for a flow rate of 1.7 kg/min; (B) different flow rates (FR) for a grinding time of 30 s.
Fig. 5. Cost of manufacturing (COM) of pequi oil obtained by SFE in extraction vessels of 100 L (gray) and 500 L (blue) at 30 min and S/F of 72 g CO2/g pequi (flow rate of 1.7 kg/min) using the pulp grinded for 30 s; DQ: calculated cost based on direct quotation; DQ + 50%: calculated cost extrapolated by 50%; LP: low price (US$ 7.00/kg); HP: high price (US$ 14.00/kg) (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).
4. Conclusion This work provided SFE of oil from pequi pulp, investigated the impacts of GT and FR on its performance, and evaluated the process economically. Based on the experimental evidences, GT of 30 s and FR of 1.08 × 10−4 kg CO2/s (5 mL scale) resulted in the highest yield, 53.65 g oil/100 g pequi pulp. In the economic evaluation, the COM was attractive in the pilot and industrial plants (< US$ 60.69/kg oil). The project indices were also positive. Taking into the payback times, several scenarios indicated they were shorter than 1 year, which is interesting and quite acceptable because the initial investment can be rapidly recovered. Accordingly, the best scenarios indicated a COM of only US$ 37.03/kg pequi oil, whereas approximately 85% of the COM is dependent on the purchase cost of pequi and other raw materials (e. g., CO2). After presenting this techno-economic approach, we expect to encourage novel studies for enabling the transference of the technology to larger scales.
main increase on the COM is related to the price of purchasing pequi. When US$ 7.00/kg (LP) is considered, the values of COM do not exceed US$ 44.09/kg oil because the raw materials represent the main percent influence on the COM (Fig. 6). It is obvious from Fig. 5 that a high capital cost (DQ + 50%) leads to a high COM. However, once the FCI represents no more than 3.3% of the COM, the differences of COM evaluated between DQ and DQ + 50% were small (no more than 3.1%). This acts against the impression that high-pressure technologies are expensive because of the sophisticated equipment. Indeed, the main influence on the COM is generally attributed to the raw materials, as also reported elsewhere [18,22]. Typically, applications of SFE in larger scales enable achieving lower values of COM. In the case of SFE from pulp of pequi, the capacity 193
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Fig. 6. Contribution of each component (CRM, CUT, COL, and FCI) on the COM for pequi oil obtained by SFE in 100 L and 500 L scales considering low price (US$ 7.00/kg) and calculated cost based on direct quotation (100 L plant: US$ 693,519.00; 500 L plant: US$ 2,254,122.00). Table 4 Project indices of applying SFE for obtaining pequi oil in 100 L and 500 L scales. Scenario
Purchasing cost of pequi pulp (US$/kg)
Scale
Cost of SFE plant
Selling price of oil (US$/kg)
Productivity of oil (kg/ year)
Payback time (year)
ROI (%)
GM (%)
IRR (%)
NPV (1 M US$)
1 2 3
7.00 7.00 7.00
100 L 100 L 100 L
by
75.00 150.00 75.00
178,092 178,092 178,092
0.39 0.12 0.49
254 835 203
43 72 42
149 311 121
23.7 80.5 23.5
4
7.00
100 L
by
150.00
178,092
0.15
667
71
254
80.2
5 6 7
7.00 7.00 7.00
500 L 500 L 500 L
by
75.00 150.00 75.00
890,462 890,462 890,462
0.28 0.09 0.34
360 1103 298
48 75 48
203 396 166
133.8 417.6 132.9
8
7.00
500 L
by
150.00
890,462
0.11
913
74
325
416.7
9 10 11
14.00 14.00 14.00
100 L 100 L 100 L
by
75.00 150.00 75.00
178,092 178,092 178,092
0.95 0.17 1.15
105 591 87
21 60 20
81 274 67
11.1 67.8 10.8
12
14.00
100 L
by
150.00
178,092
0.20
489
61
225
67.5
13 14 15
14.00 14.00 14.00
500 L 500 L 500 L
by
75.00 150.00 75.00
890,462 890,462 890,462
0.60 0.13 0.77
167 769 130
27 64 25
126 352 98
74.2 358.0 67.5
16
14.00
500 L
Normal Normal Extrapolated 50% Extrapolated 50% Normal Normal Extrapolated 50% Extrapolated 50% Normal Normal Extrapolated 50% Extrapolated 50% Normal Normal Extrapolated 50% Extrapolated 50%
by
150.00
890,462
0.16
637
62
286
351.3
Normal: calculated cost based on direct quotation (100 L plant: US$ 693,519.00; 500 L plant: US$ 2,254,122.00); Extrapolated by 50%: calculated cost extrapolated by 50% (100 L plant: US$ 1,040,278.00; 500 L plant: US$ 3,381,183.00); ROI: Return On Investment; GM: Gross Margin; IRR: Internal Rate of Return after taxes; NPV: Net Present Value at 7%.
Acknowledgments
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The authors thank the CAPES (2952/2011), CNPq (302423/20150), FAPESP (RT2015/13299-0), and the Research Support Foundation of the State of Rio Grande do Sul (FAPERGS) for the financial support. References [1] A. Giroldo, A. Scariot, Land use and management affects the demography and conservation of an intensively harvested Cerrado fruit tree species, Biol. Conserv. 191 (2015) 150–158. [2] F.D. De Araujo, A review of Caryocar brasiliense (Caryocaraceae)—an economically valuable species of the central Brazilian cerrados, Econ. Bot. 49 (1995) 40–48. [3] A.M. Alves, D.C. Fernandes, A.G. de Oliveira Sousa, R.V. Naves, M.M.V. Naves, Características físicas e nutricionais de pequis oriundos dos estados de Tocantins, Goiás e Minas Gerais/Physical and nutritional characteristics of pequi fruits from Tocantins, Goiás and Minas Gerais States, Braz. J. Food Technol. 17 (2014) 198.
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[19] Á.L. Santana, G.L. Zabot, J.F. Osorio-Tobón, J.C. Johner, A.S. Coelho, M. Schmiele, C.J. Steel, M.A.A. Meireles, Starch recovery from turmeric wastes using supercritical technology, J. Food Eng. 214 (2017) 266–276. [20] G.L. Zabot, M.N. Moraes, M. Meireles, Process integration for producing tocotrienols-rich oil and bixin-rich extract from annatto seeds: a techno-economic approach, Food Bioprod. Process. 109 (2018) 122–138. [21] J.F. Osorio-Tobón, P.I. Carvalho, M.A. Rostagno, M.A.A. Meireles, Process integration for turmeric products extraction using supercritical fluids and pressurized liquids: economic evaluation, Food Bioprod. Process. 98 (2016) 227–235. [22] S.C. Alcázar-Alay, J.F. Osorio-Tobón, T. Forster-Carneiro, M.A.A. Meireles, Obtaining bixin from semi-defatted annatto seeds by a mechanical method and solvent extraction: process integration and economic evaluation, Food Res. Int. 99 (2017) 393–402. [23] M.M. El-Halwagi, Sustainable Design Through Process Integration: Fundamentals and Applications to Industrial Pollution Prevention, Resource Conservation, and Profitability Enhancement, Butterworth-Heinemann, 2017. [24] M.P. Fernández-Ronco, A. de Lucas, J.F. Rodríguez, M. García, I. Gracia, New considerations in the economic evaluation of supercritical processes: separation of bioactive compounds from multicomponent mixtures, J. Supercrit. Fluids 79 (2013) 345–355. [25] R. Vardanega, P.I. Carvalho, J.Q. Albarelli, D.T. Santos, M.A.A. Meireles, Technoeconomic evaluation of obtaining Brazilian ginseng extracts in potential production scenarios, Food Bioprod. Process. 101 (2017) 45–55.
[10] G.L. Zabot, M.N. Moraes, M.A.A. Meireles, Process integration for producing tocotrienols-rich oil and bixin-rich extract from annatto seeds: a techno-economic approach, Food Bioprod. Process. 109 (2018) 122–138. [11] M. De Melo, A. Silvestre, C. Silva, Supercritical fluid extraction of vegetable matrices: applications, trends and future perspectives of a convincing green technology, J. Supercrit. Fluids 92 (2014) 115–176. [12] A. Standard, Method of Determining and Expressing Particle Size of Chopped Forage Material by Screening, ASAE, St. Joseph. MI, 1998. [13] D. Green, R. Perry, Perry’s Chemical Engineers’ Handbook, eighth ed., McGraw-Hill Education, New York, 2007. [14] R. Smith, Chemical Process Design and Integration, Wiley, Chichester, 2005. [15] R. Turton, R.C. Bailie, W.B. Whiting, J.A. Shaeiwitz, D. Bhattacharyya, Analysis, Synthesis and Design of Chemical Processes, Prentice Hall, Upper Saddle River, 2012. [16] M.S. Peters, K.D. Timmerhaus, Plant Design and Economics for Chemical Engineers, fourth ed., McGraw-Hill, Auckland, 1991. [17] G.L. Zabot, M.N. Moraes, P.I. Carvalho, M.A.A. Meireles, New proposal for extracting rosemary compounds: process intensification and economic evaluation, Ind. Crops Prod. 77 (2015) 758–771. [18] J. Viganó, G.L. Zabot, J. Martínez, Supercritical fluid and pressurized liquid extractions of phytonutrients from passion fruit by-products: economic evaluation of sequential multi-stage and single-stage processes, J. Supercrit. Fluids 122 (2017) 88–98.
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Contents lists available at ScienceDirect
The Journal of Supercritical Fluids journal homepage: www.elsevier.com/locate/supflu
Kinetic behavior and economic evaluation of supercritical fluid extraction of oil from pequi (Caryocar brasiliense) for various grinding times and solvent flow rates
T
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Julio C.F. Johnera, , Tahmasb Hatamia, Giovani L. Zabotb, M. Angela A. Meirelesa a
LASEFI/DEA/FEA (School of Food Engineering)/UNICAMP (University of Campinas), Rua Monteiro Lobato, 80, 13083-862, Campinas, SP, Brazil Laboratory of Agroindustrial Processes Engineering (LAPE), Federal University of Santa Maria, UFSM, Presidente Vargas Av., 1958, Cachoeira do Sul, RS, 96506-302, Brazil b
G R A P H I C A L A B S T R A C T
A R T I C LE I N FO
A B S T R A C T
Keywords: Cold pressed extraction Supercritical fluid extraction SFE Pequi COM Cost of manufacturing
This paper presents the techno-economic influence of grinding time (GT) (10 s–90 s) and CO2 flow rate (FR) (1.08 × 10−4–2.17 × 10−4 kg/s) on the supercritical fluid extraction (SFE) performance of oil from pequi (Caryocar brasiliense) under 60 °C and 40 MPa. Then, in the economic approach, the best extraction curves were described in terms of Cost of Manufacturing (COM) in the laboratory scale for each combination of GT and FR for selecting the suitable mass to feed mass ratio (S/F) that yielded the lowest COM and the highest productivity. Thereafter, with this S/F, eight scenarios were tested in pilot (100 L) and industrial (500 L) scales with CO2 recycle, which included the purchase cost of pequi and acquisition cost of equipment. Within these eight scenarios tested, the most promising one indicated a COM of only US$ 37.03/kg pequi oil, whereas approximately 85% of the COM is dependent on the purchase cost of pequi and other raw materials (e. g., CO2).
⁎
Corresponding author. E-mail address: [email protected] (J.C.F. Johner).
https://doi.org/10.1016/j.supflu.2018.06.016 Received 31 May 2018; Received in revised form 22 June 2018; Accepted 22 June 2018
Available online 28 June 2018 0896-8446/ © 2018 Elsevier B.V. All rights reserved.
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1. Introduction
Walita 400 W, RI1364/07, Varginha, Brazil) for 10, 30, 50, 70, and 90 s. A sieve shaker (Bertel, N. 1868, Caieiras, Brazil) with 16–80 mesh sieves was used to determine the particle diameter of the ground material. The average diameter was calculated according to the proposed equation by the American National Standard Institute [12].
Pequi (Caryocar brasiliense) is the most collected fruit of the Brazilian Cerrado that has an orange-yellow pulp and is well known as tiny gold or pequi [1,2]. Regarding the minerals in the pulp, 100 g of pequi pulp contains approximately 72.5 mg of calcium, 1.2 mg of iron, 3.4 mg of zinc, 184.4 mg of phosphorus, 95.2 mg of magnesium, and 631 mg of potassium [3]. Moreover, pequi oil is composed (in mass) of 53% oleic acid, 2.7% linoleic acid, and 39% palmitic acid, and it has been demonstrated to be an anti-inflammatory and antioxidant agent [2,4,5]. The traditional process of oil extraction from pequi consists of intensive cooking in water and subsequent removal of the supernatant. The main disadvantages of this extraction method are its low yield, high-temperature requirement, and the fact that the oil is not filtered [6]. To overcome these limitations, extraction with supercritical CO2 could be employed for the extraction of pequi oil due to its mild temperatures (40–60 °C) and high extraction performance [7,8]. The advantage of supercritical fluid extraction (SFE) is not limited to its high performance at low or moderate temperatures. Easy separation of solute from the solvent, employing a non-toxic solvent, and high purity of extract are other advantages of this technology. To the authors’ knowledge, there is only one paper regarding the extraction of pequi oil by SFE up to now, which has been recently performed by our research group. Johner et al. [9] investigated the extraction of oil from pequi using SFE and SFE assisted by pressing (SFEAP) at 40 °C–60 °C and 20 MPa–40 MPa. The authors reported that 60 °C and pressure of 40 MPa provided the highest yield, 48 g extract/ 100 g raw material, during 48 min of extraction. Despite these new findings, such scientific paper did not present any information on the effect of grinding time (GT) and CO2 flow rate (FR) on the dynamic extraction yield. Furthermore, an economic evaluation is a demand for showing the feasibility of the process applied to pequi. Economic evaluation of processes performed under high-pressure is an important strategy to understand the processes because it provides insights even at earlier stages of research. COM and itemized costs are valuable outcomes within the economic approach because they can contribute to confirming the feasibility and technical potential of a specific process. According to some reports, decisions regarding operational conditions can be pondered and dealt within the research background using the economic assessment, and the results can encourage further advances toward commercial application of natural oils and bioproducts [10,11]. Based on this context, the current study aims at investigating the techno-economic influence of GT and FR on the dynamic extraction yield of oil from pequi and on the economic responses. The following responses are presented and discussed: yield of oil, cost of manufacturing (COM), contribution of itemized costs (cost of raw material, cost of operational labor, cost of utilities, and fixed capital investment) and project indices (return on investment, payback time, gross margin, internal rate of return, and net present value).
2.2. Supercritical fluid extraction The experimental assays were performed using a commercial highpressure apparatus inside a stainless-steel extractor with 2.5 cm of height and 2 cm of internal diameter. In a typical SFE experimental assay, the extractor was filled with 2 g of samples, and glass wool was packed at the bottom and top of the extractor to prevent entrainment of particles. Extractions were performed using CO2 (purity > 99.5%) as the solvent (White Martins, Campinas, Brazil) at pressures of 40 MPa and static time of 10 min. The extractor was heated by an oven and its temperature was fixed at 60 ± 1 °C using a heat controller. The experimental assays were performed for 10 min (static time) and for 20–40 min (dynamic time) by flowing supercritical CO2 through the bed. Extracts were accumulated in glass vials and were periodically weighed on an analytical balance. The CO2 flow rate was adjusted by a gas flow meter with the measurable range of 3.25 × 10−5–4.30 × 10−4 kg CO2/s at the standard condition. Prior to venting CO2 to the ambient, it is also passed through a totalimeter at the end of the line to measure the total CO2 consumed. The average flow rate of CO2 was calculated by dividing the total CO2 consumed per total dynamic time of extraction. The minimum flow rate considered in this study was 1.08 × 10−4 kg CO2/s to prevent the fluctuation of flow rate and control it precisely. 2.3. Economic evaluation of SFE of pequi oil The economic evaluation was done in the SuperPro Designer 9.0® software (Intelligen Inc., Scotch Plains, NJ, USA). Considering the SFE process (Fig. 1), a flowsheet was designed to evaluate the economic feasibility of obtaining bioactive compounds from pequi in two different scales: 100 L and 500 L. In the experimental study, the yield was evaluated for the extraction up to 40 min for S/F of 130 g CO2/g dry pequi pulp. For a representation scope, a Gantt chart for an extraction time of 40 min is presented in Fig. 2. The procedures include mainly pequi pulp loading, CO2 pressurizing, bed heating, static time, oil extraction, bed depressurizing, and bed unloading. The total batch duration of SFE in 2 extraction vessels is 2 h and the SFE was designed to operate for 7920 h per year, which corresponds to 3 daily shifts for 330 days per year. The yearly remaining time was considered for cleaning and equipment maintenance. 2.3.1. Economic input data Commonly, equipment purchase cost for one or two discrete sizes is available. Alternatively, costs for other equipment sizes or capacities must be estimated. Scaling the equipment cost to the required capacity is possible through the power law (Eq. (1)) [13–15], where C1 is the equipment cost with capacity Q1, C2 is the known base cost for equipment with capacity Q2, and M is a constant depending on the equipment type. Values of M were obtained in the scientific literature [13–16] because the cost of a specific item is a function of size, materials of construction, design pressure and design temperature. The base costs acquired in 2018 (local quotation, including import fees for the items not produced in Brazil) are presented in Table 1 for calculating the costs in a larger scale.
2. Material and methods 2.1. Raw material Pequi was acquired in the city of Barra do Garças (Brazil) after being collected from the Xingu region of Mato Grosso (Brazil). The fruits were manually peeled using a knife (Tramontina, 21198315, Carlos Barbosa, Brazil) in a dark environment to avoid any degradation of the carotenoids and other light-sensitive bioactive compounds. The pulp was manually cut using a knife (Tramontina, 22902/007, Carlos Barbosa, Brazil) in a dark environment at 20 °C. The pulp slices were frozen at −18 °C and, thereafter, transported to the laboratory (LASEFI/FEA/ UNICAMP). The pulp was then dried in a circulation oven (Marconi, MA035 / 5, Piracicaba, Brazil) at 45 °C for 24 h and, in the sequence, frozen at −18 °C (Metalfrio, HC -4, São Paulo, Brazil). Afterward, the dried pulp was ground in a mini-processor-coupled mixer (Philips
Q C1 = C2 ⎛ 1 ⎞ Q ⎝ 2⎠ ⎜
M
⎟
(1)
As some studies report [17–19], there is a trend of reducing the COM when the capacity is increased. Therefore, the data provided in Table 1 were used to estimate the total cost of the SFE plant composed 189
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Fig. 1. Flowsheet of SFE for pequi pulp oil extraction.
Fig. 2. Gantt chart for one batch of SFE for obtaining pequi oil; the case study of oil extraction for 40 min. 190
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2.3.2. COM, productivity, and itemized costs The COM of bioactive extracts depends on the sum of three main components: direct manufacturing costs (e.g. seeds, ethanol, and CO2), fixed manufacturing costs (e.g. equipment) and general expenses (e.g. management costs and research & development). Capital costs associated with buildings and equipment, and other costs as storage of raw materials and extracts, electrical facilities, instrumentation, engineering and management fees, was also considered. The protein flour generated after performing SFE can be considered harmless and clean. Firstly, the COM was evaluated for the SFE performed in the laboratory scale with extraction vessels of 5 mL. The goal was to have a response of the economically feasible time (and consequently the S/F ratio) that is suitable for performing the oil extraction on a larger scale. Thereafter, these feasible time and S/F ratio were selected for studying the COM in 100 L and 500 L scales. Secondly, the COM was evaluated for the SFE performed in 100 L and 500 L scales. A total of 8 scenarios were studied, which consisted of testing the feasible extraction time, the plant estimated cost based on direct quotation and the estimated cost extrapolated by 50%, and the cost of acquiring pequi as low price (LP) or high price (HP). The cost of pequi pulp commonly ranges from US$ 7.00/kg to US$ 14.00/kg. Therefore, these values were selected as LP and HP, respectively. The productivity of pequi oil in larger scales was simulated based on the amount of oil obtained experimentally. The behavior of the yields and composition was assumed to have the same performance in larger scales as the findings obtained in the laboratory scale. The percent contribution of the itemized costs (fixed capital investment – FCI, cost of raw materials – CRM, cost of operational labor – COL, and cost of utilities – CUT) was evaluated for the best scenario. It is worthwhile noting that all the values of COM were estimated for scenarios when the investors have all capital resources to start the projects. Indeed, the analyses were developed for scenarios where no bank financing is required. In such a case, the final values of COM presented in the study do not include costs of amortization for the bank credit. If credit is needed, all fees and charges should be taken into account.
Table 1 Base cost for equipment composing the SFE plant. Item
SFE Jacketed extraction vesseld CO2 electrical pump Cooler Heater Separation vesseld Manometer Blocking valve Backpressure valve Safety valve Flowmeter Temperature controller Piping, connectors, mixers, splitters, and crossheadse Structural material for supporting the equipment
Ma
Unit base cost (US$)b,c
Quantity (un.)
Total base cost (US$)b
0.82
4,900.00
2
9,800.00
0.55 0.59 0.59 0.49 0 0.60 0.60 0.60 0.60 0.60 0.40
11,685.00 1,360.00 430.00 1,100.00 70.00 60.00 1,300.00 90.00 280.00 180.00 660.00
1 1 1 2 4 6 2 1 1 4 –
11,685.00 1,360.00 430.00 2,200.00 280.00 360.00 2,600.00 90.00 280.00 720.00 660.00
0.40
300.00
–
300.00
Total cost of SFE plantb (US$)
30,765.00
a M constant depending on equipment type, based on Green and Perry [13], Peters and Timmerhaus [16], Smith [14] and Turton, Bailie, Whiting, Shaeiwitz and Bhattacharyya [15]. b Based on an operating plant with extraction and separation vessels of 1 L. c Direct quotation for reference year of 2018. d Supporting pressures up to 60 Mpa. e Total cost.
of two extraction vessels (100 L or 500 L) and two separation vessels (100 L or 500 L). Other input data, as the cost of raw materials, wage, and utilities are presented in Table 2.
Table 2 Input economic parameters used for simulating the COM of pequi oil obtained from pequi pulp by SFE; scales of 100 L and 500 L for the vessels. Economic parameter
Values for 100 L scale
Values for 500 L scale
Dimension
Fixed capital investment (FCI) Total cost of SFE planta,b Annual depreciation ratec Annual maintenance ratec Project lifetime Annual time worked
693,519.00 10 6 25 7920
2,254,122.00 10 6 25 7920
(US$) (%) (%) (years) (h/year)
Cost of raw material (CRM) Pequi pulp (scenario of low price – LP) Pequi pulp (scenario of high price – HP) Transport and pre-processing of pequi pulpd Industrial CO2e
7.00 14.00 40 3.00
7.00 14.00 40 3.00
(US$/kg) (US$/kg) (US$/ton) (US$/kg)
Cost of operational labor (COL) Wage (with benefits and administration)f Number of workers per shift Total wage per day (3 shifts/day)
16.80 2 806.40
16.80 3 1,209.60
(US$/h.worker) (Worker/shift) (US$/day)
Cost of utilities (CUT) Water (for cooling and cleaning)e Steame Glycol solutione Electricitye
1.00 12.00 10.00 0.50
1.00 12.00 10.00 0.50
(US$/ton) (US$/ton) (US$/ton) (US$/kW.h)
a b c d e f
The design is similar to that one shown in Fig. 1 (2 extraction vessels and 2 separation vessels). Estimated cost using the power law of capacity (Eq. (1)). based on Peters and Timmerhaus [16]. The pre-processing steps include drying (when needed) and storing the samples until further use. direct quotation for the reference year of 2018. Bureau of Labor Statistics, http://www.bls.gov/fls/country/brazil.htm, USA, accessed on January 18th, 2018. 191
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Table 3 Average diameter of pulp of pequi for various grinding times. Grinding time (s)
diameter (mm)
Standard deviation
10 30 50 70 90
> 3.36 2.29 2.34 2.27 2.33
– 0.16 0.04 0.04 0.01
reduced slightly with increasing GT from 30 s to 50 s, and remained approximately constant with further increasing the GT. The reason is that increasing GT from 10 s to 30 s caused a significant reduction in particle diameter from more than 3.36 mm to 2.29 mm (Table 3). It consequently increased the yield due to the enhancing of mass transfer specific area. Noticeably the particle size for GT of 10 s was bigger than the mesh size of the largest sieve shaker in our lab, which is a sieve shaker with 3.36 mm mesh size. However, further increasing GT from 30 s to 90 s did not influenced the particle diameter to a large extent. Besides the independence of diameter with GT after 30 s, another reason for the slight reduction of yield is sticking some oil content of pequi to the wall and blades of the grinder with increasing GT, which means some slight losses. In the best condition, 49.07 g extract/100 g raw material was obtained. Considering the GT of 30 s favored the highest performance in the extraction yield shown in Fig. 3A, the influence of CO2 flow rate on the yield of oil was evaluated at GT of 30 s (Fig. 3B). The yield, at the same S/F ratio, increased with decreasing CO2 flow rate. This behavior is due to the shorter contact time of CO2 with solid particles at higher flow rates. Consequently, a reduction in the overall mass transfer occurred for higher values of S/F. It is interesting to compare the results of the current study with those obtained by Johner et al. [9] even though the SFE equipment employed were not the same. The authors performed dynamic SFE yield from pequi at a GT of 50 s, a temperature of 60 °C, a pressure of 40 MPa, a CO2 flow rate of 2.93 × 10−4 kg/s, and S/F of 352. Their reported SFE yield at S/F of 130 was approximately 49 g oil/100 g pequi pulp, and the corresponding SFE yield in the current study at the same GT, temperature, pressure, S/F, but at a CO2 flow rate of 1.44 × 10−4 kg/s was 47 g oil/100 g pequi pulp. This small difference between the SFE yield in the previous and current study indicates the reliability of the experimental data.
Fig. 3. Influence of grinding time on the kinetic extraction of oil of pequi using SFE at 40 MPa, 60 °C, and CO2 flow rate of 1.44 × 10−4 kg/s (A) and CO2 flow rate on the kinetic extraction of oil of pequi using SFE at 40 MPa, 60 °C, and grinding time of 30 s (B).
3.2. Economic evaluation of SFE of oil from pequi 3.2.1. COM and itemized costs Fig. 4 shows the COM of SFE performed in the 1 L scale for the whole kinetic curves using SuperPro Designer 9.0®. The COM decreased initially, reached its lowest level at a certain S/F, and, thereafter increased at higher S/F values. This behavior is well-known in extraction processes of bioactive compounds [17,20,21]. Commonly, the range of lower COM is closer to the end of the constant extraction rate period. In this work, an economically feasible S/F (35–72 g CO2/g pequi pulp) and a technologically feasible S/F (72–130 g CO2/g pequi pulp) were identified as promising values of S/F within each approach (economic and technical). Therefore, once S/F of 72 g CO2/g pequi pulp matches both approaches, the values of COM of SFE of oil from pequi in the 100 L and 500 L scales were simulated considering this S/F. Furthermore, for the 1 L scale, the FR of 1.7 kg/min and GR of 30 s were the best conditions. In such case, they were also selected for the sequential studies (the FR was scaled proportionally to the size of plant). The values of COM for oil obtained from pequi by SFE in 100 L and 500 L scales are presented in Fig. 5. In this figure, DQ is the calculated cost based on direct quotation, DQ + 50% is the calculated cost extrapolated by 50%, LP is the low price (US$ 7.00/kg), and HP is the high price (US$ 14.00/kg). Among eight scenarios evaluated in this work, the COM ranged from US$ 37.03/kg oil to US$ 60.69/kg oil. The
2.3.3. Sensitivity analysis For sensitivity analysis, some commercial products with similar characteristics to those produced in this work were used as a reference (even though there is not oil obtained by SFE under commercialization). The average market selling prices practiced worldwide for 1 kg of pequi oil (obtained by pressing) typically range from US$ 75.00 to US$ 150.00. Therefore, these values were used as a reference in the simulation of the main general profitability factors, as return on investment (ROI), payback time, gross margin (GM), internal rate of return (IRR) after taxes and net present value (NPV). The 8 scenarios became 16 in this section after the inclusion of these two limits of the selling price. 3. Results and discussion 3.1. Supercritical fluid extraction The influence of GT on the yield of oil from pequi is presented in Fig. 3. The data of this figure are the average of two repeated experimental assays for each condition of GT, where the error bar in each point indicates the corresponding standard deviation. The yield of oil significantly increased with increasing GT from 10 s to 30 s, then, 192
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of 500 L could reduce 7–16% of COM. However, the processing in a 100 L scale plant can be interesting, especially for regional raw materials (no commodities) which are farmed in small or medium quantities, as it is the case of pequi. Therefore, manufacturing plants with too big capacity are not mandatorily required.
3.2.2. Sensitivity analysis The sensitivity analysis is presented in terms of the project indices (ROI, IRR, GM, NPV and payback time) calculated after performing the simulation (Table 4). The revenue was calculated considering the sale of oil from pequi in a year. Among the 16 scenarios, the highest ROI (1103%) was obtained in the scenario 6. According to El-Halwagi [23] and Fernández-Ronco et al. [24], values of ROI over 15% are suitable for recommending a project to operate with profitability. The ROI was larger than 80% in most of the cases in the current study. This finding enables us to indicate the feasibility of the SFE from pequi pulp for such selling prices (> US$ 75.00/kg). As the ROI, the higher the GM the more attractive is the project. In the same scenario of the highest ROI (scenario 6), the GM was 75%, which means the company would retain approximately US$ 0.75 from each dollar generated by selling the oil from pequi. Values of IRR and NPV were also larger for scenario 6. When consulting the scientific literature, IRR of 14.9% and 23.4% for US$ 7.27/ kg turmeric rhizomes and US$ 1.59/kg turmeric rhizomes, respectively, were reported [21]. Values of NPV from US$ 7 mi to US$ 35 mi are reported in a two-step intensified extraction process that operates at 0.1 MPa for recovering phytochemicals from Brazilian ginseng roots [25]. The payback time is also presented (Table 4). Differently from the other parameters, the shorter the payback time the more feasible is the project. It ranged from 0.06 year (scenario 6) to 1.15 year (scenario 11), which could be attractive for investors. Those payback times are quite acceptable because the initial investment can be rapidly recovered. In the same trend, Zabot et al. [20], reported payback times of 0.6–1.5 years for the integrated extraction of tocotrienols-rich oil and bixin-rich extract from annatto seeds using supercritical technology in a 100 L scale. The economic viability can be understood as an optimized trade-off between the concomitant changes of yield and concentration of biocompounds, from the income side, and the investment and operation expenditures, from the fixed and variable costs, respectively [11]. Therefore, balancing the technical and economic approaches, we infer that SFE performed during 40 min (S/F of 72 g CO2/g pequi pulp) with the lowest FR (among those tested) and with pulp particles submitted to GT of 30 s as the most suitable integrated conditions.
Fig. 4. Cost of manufacturing (COM) of pequi oil obtained by SFE in extraction vessels of 1 L: (A) different grinding times (GT) for a flow rate of 1.7 kg/min; (B) different flow rates (FR) for a grinding time of 30 s.
Fig. 5. Cost of manufacturing (COM) of pequi oil obtained by SFE in extraction vessels of 100 L (gray) and 500 L (blue) at 30 min and S/F of 72 g CO2/g pequi (flow rate of 1.7 kg/min) using the pulp grinded for 30 s; DQ: calculated cost based on direct quotation; DQ + 50%: calculated cost extrapolated by 50%; LP: low price (US$ 7.00/kg); HP: high price (US$ 14.00/kg) (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).
4. Conclusion This work provided SFE of oil from pequi pulp, investigated the impacts of GT and FR on its performance, and evaluated the process economically. Based on the experimental evidences, GT of 30 s and FR of 1.08 × 10−4 kg CO2/s (5 mL scale) resulted in the highest yield, 53.65 g oil/100 g pequi pulp. In the economic evaluation, the COM was attractive in the pilot and industrial plants (< US$ 60.69/kg oil). The project indices were also positive. Taking into the payback times, several scenarios indicated they were shorter than 1 year, which is interesting and quite acceptable because the initial investment can be rapidly recovered. Accordingly, the best scenarios indicated a COM of only US$ 37.03/kg pequi oil, whereas approximately 85% of the COM is dependent on the purchase cost of pequi and other raw materials (e. g., CO2). After presenting this techno-economic approach, we expect to encourage novel studies for enabling the transference of the technology to larger scales.
main increase on the COM is related to the price of purchasing pequi. When US$ 7.00/kg (LP) is considered, the values of COM do not exceed US$ 44.09/kg oil because the raw materials represent the main percent influence on the COM (Fig. 6). It is obvious from Fig. 5 that a high capital cost (DQ + 50%) leads to a high COM. However, once the FCI represents no more than 3.3% of the COM, the differences of COM evaluated between DQ and DQ + 50% were small (no more than 3.1%). This acts against the impression that high-pressure technologies are expensive because of the sophisticated equipment. Indeed, the main influence on the COM is generally attributed to the raw materials, as also reported elsewhere [18,22]. Typically, applications of SFE in larger scales enable achieving lower values of COM. In the case of SFE from pulp of pequi, the capacity 193
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Fig. 6. Contribution of each component (CRM, CUT, COL, and FCI) on the COM for pequi oil obtained by SFE in 100 L and 500 L scales considering low price (US$ 7.00/kg) and calculated cost based on direct quotation (100 L plant: US$ 693,519.00; 500 L plant: US$ 2,254,122.00). Table 4 Project indices of applying SFE for obtaining pequi oil in 100 L and 500 L scales. Scenario
Purchasing cost of pequi pulp (US$/kg)
Scale
Cost of SFE plant
Selling price of oil (US$/kg)
Productivity of oil (kg/ year)
Payback time (year)
ROI (%)
GM (%)
IRR (%)
NPV (1 M US$)
1 2 3
7.00 7.00 7.00
100 L 100 L 100 L
by
75.00 150.00 75.00
178,092 178,092 178,092
0.39 0.12 0.49
254 835 203
43 72 42
149 311 121
23.7 80.5 23.5
4
7.00
100 L
by
150.00
178,092
0.15
667
71
254
80.2
5 6 7
7.00 7.00 7.00
500 L 500 L 500 L
by
75.00 150.00 75.00
890,462 890,462 890,462
0.28 0.09 0.34
360 1103 298
48 75 48
203 396 166
133.8 417.6 132.9
8
7.00
500 L
by
150.00
890,462
0.11
913
74
325
416.7
9 10 11
14.00 14.00 14.00
100 L 100 L 100 L
by
75.00 150.00 75.00
178,092 178,092 178,092
0.95 0.17 1.15
105 591 87
21 60 20
81 274 67
11.1 67.8 10.8
12
14.00
100 L
by
150.00
178,092
0.20
489
61
225
67.5
13 14 15
14.00 14.00 14.00
500 L 500 L 500 L
by
75.00 150.00 75.00
890,462 890,462 890,462
0.60 0.13 0.77
167 769 130
27 64 25
126 352 98
74.2 358.0 67.5
16
14.00
500 L
Normal Normal Extrapolated 50% Extrapolated 50% Normal Normal Extrapolated 50% Extrapolated 50% Normal Normal Extrapolated 50% Extrapolated 50% Normal Normal Extrapolated 50% Extrapolated 50%
by
150.00
890,462
0.16
637
62
286
351.3
Normal: calculated cost based on direct quotation (100 L plant: US$ 693,519.00; 500 L plant: US$ 2,254,122.00); Extrapolated by 50%: calculated cost extrapolated by 50% (100 L plant: US$ 1,040,278.00; 500 L plant: US$ 3,381,183.00); ROI: Return On Investment; GM: Gross Margin; IRR: Internal Rate of Return after taxes; NPV: Net Present Value at 7%.
Acknowledgments
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