Estimation of manufacturing cost of clove (Eugenia caryolhyllus) extracts obtained by supercritical fluid extraction using a commercial simulator

Juliana M. Prado, M. Angela A. Meireles

LASEFI/DEA/FEA (School of Food Eng.)/UNICAMP (University of Campinas) – R. Monteiro Lobato, 80; 13083-862,

Campinas, SP, Brazil (meireles@fea.unicamp.br) ABSTRACT

Supercritical fluid extraction (SFE) has proven to be technically and economically feasible; however, there is no industrial unit operating with it in Latin America. Considering the rich biodiversity of Brazilian flora, and the possibility of adding value to it without degrading the environment, the economic analysis inserted in Brazilian reality is important to provide information for the installation of an industrial SFE unit in this country. Brazil is a major producer of clove (Eugenia caryophyllus); its extract presents antioxidant and antimicrobial properties, with many applications in food and pharmaceutical industries. The objective of the present work was to carry out an economical evaluation of clove SFE inserted in Brazilian reality. The commercial simulator SuperPro Designer v6.0 was used for estimating the cost of manufacturing (COM) of clove oil obtained by SFE. Three scales were evaluated: extractor volumes of 5 L, 50 L and 500 L. Previously published experimental data on clove SFE were used for the COM estimations. COM was reduced with plant scale increase: it varied between US$ 78 and 126 per kg of extract for 5 L extractor, between US$ 39 and 62 per kg of extract for 50 L extractor and between US$ 31 and 48 per kg of extract for 500 L extractor, depending on S/F (solvent to feed ratio) and solvent flow rate. Clove SFE extract is sold in market for around US$ 110/kg. Therefore, SFE in Brazil is economically feasible, after the process is appropriately optimized. Gathering experimental yield data and the chemical composition of clove oil previously published with the economical evaluation of the present work, it is possible to optimize the process: for clove SFE at 313 K/15 MPa, 52 min of cycle time and S/F of 3.65 present the best relation between yield, quality and cost of the process. Keywords: Clove; Cost of manufacturing; Supercritical fluid extraction INTRODUCTION Supercritical fluid extraction (SFE) has proven to be technically and economically feasible. However, there is no industrial unit operating with such technology in Latin America. Considering the rich biodiversity of Brazilian flora, and the possibility of adding value to it without degrading the environment, the economic analysis inserted in Brazilian reality is important to provide information for the installation of an industrial SFE unit in this country. The high cost of investment when compared to classical low-pressure equipments, of steam distillation and organic solvent extraction, were pointed as the main drawback for the installation of a SFE industrial unit [1]. However, some new researches on cost of manufacturing (COM) products by SFE process have shown that despite the high investment cost, the COM of SFE extracts is extremely competitive with the COM of extracts obtained by traditional extraction techniques when all costs involved in the process are taken into account [2-11]. SFE process optimization depends on the yield, time, amount of solvent used, and chemical composition of the product, among others. Interrupting the extraction before the bed is exhausted may be economically advantageous due to lower processing time and consequent higher amount of annual batches [2]. On the other hand, the extracts obtained along the process may present large differences on their chemical composition with extraction time. Economical evaluation allows finding the balance between yield and cost, and the product’s quality may be taken into account. Clove (Eugenia caryophyllus) is a plant adapted to Brazilian cultivation. Its flower buds are rich in volatile oil, which has eugenol as its main compound. Eugenol is a phenolic compound used in pharmaceutical industry for its antiseptic, anti-inflammatory, bactericidal and anaesthetic effects [12]. The oil also has fungicidal, antiviral, antitumor and insecticide properties, and in food industry, it is used as flavouring,

antimicrobial, and antioxidant agent [13-17]. Brazil is a major producer of clove, which has been used as a model raw material in many SFE studies [18-26]. The objective of the present work was to carry out an economical evaluation of SFE of clove inserted in Brazilian reality. MATERIALS & METHODS

The commercial simulator SuperPro Designer v6.0 was used for estimating the cost of manufacturing (COM) of clove oil obtained by SFE. The methodology developed by Prado et al [7] was adapted. A SFE unit including extraction, separation and solvent recycling steps, equipped with two extractors working semi-continuously and three separators in series was built with tools available from the simulator databanks (Figure 1). Plant design was based on the pilot equipment used for determining experimental data [26]. Three scales were evaluated: extractor volumes of 5 L, 50 L and 500 L (Table 1). Prado et al [26] determined experimental data of clove SFE at 313 K/15 MPa using a 5 L extractor. Scale-up criterion to 50 and 500 L consisted in keeping S/F (solvent to feed ratio) constant, as recommended by Prado et al [26].

Streams Equipments

F-1/F-2/F-3/F-4/F-5/F-9 – CO2 feeding B-1 – CO2 pump

F-6/F-6-1/F-10/F-10-1 – raw material feeding C-1 – compressor

F-7/F-11/F-13 – CO2 + extract exit E-1/E-2 – extractors

F-8/F-12 – solid residue exit + CO2 loss H-1 – heat exchanger for CO2 heating

F-14/F-16/F-18 – products exit M-1/S-1 – stream mixer and separator, respectively

F-15/F-17 – extract and CO2 fractionation R-1 – heat exchanger for CO2 cooling

F-19/F-20 – CO2 recycling SE-1/SE-2/SE-3 – separators

F-21 – replacement of CO2 lost T-1 – CO2 tank

TR-1/TR-2 – raw material pre-processing

Figure 1. Scheme of SFE process built in SuperPro Designer simulator, used for economical evaluation. It was considered the industrial unit will run 24-h with three daily shifts, for 330 days, which represents a total of 7920 h of operation per year; 30 days will be destined for plant maintenance [2]. The number of operators needed by shift varies according to the capacity of the plant (Table 1). Labour charges and labour not directly associated with production were estimated by the simulator. Raw material cost is related to plant material and CO2 lost during the process. CO2 loss is mainly due to depressurization of the extractor at the end of each batch [27]. Clove cost varied between US$ 2.54/kg and US$ 3.51/kg within a one year period [28]; the COM was estimated using the highest raw material cost, that is, the worst scenario. Pre-processing costs involve drying and comminution of raw material. Utility costs comprise producing heat exchange agents and the electricity used in the process. Utilities needed for the operation of each equipment were estimated by the simulator energy balance. Cost of waste treatment may be neglected, since the residue of SFE process is the dry exhausted clove, which may be incorporated to the soil as fertilizer. The CO2 lost during system depressurization needs no treatment since in small quantities it is not toxic [29].

To the COM estimated, transportation costs still have to be added. Table 1. Economical parameters used for COM estimation

Industrial units a

2 extractors of 5 L 2 extractors of 50 L 2 extractors of 500 L Depreciation rate

US$ 100,000.00US$ 300,000.00US$ 10 %/year

Labor a

2 extractors of 5 L 2 extractors of 50 L 2 extractors of 500 L

US$ 4.00/h1 operator2 operators3 operators

Raw materials Clove Pre-processing CO2 (2 % loss)

US$ 3.51/kg US$ 40.00/tonUS$ 0.15/kg

Utilities a

Electricity Cooling water Steam

US$ 0.092/kWhUS$ 0.19/tonUS$ 4.20/ton

a – Prado et al [7]; b – SEAGRI [28] RESULTS & DISCUSSION

Figure 2 presents the COM of clove oil obtained by SFE according to experimental data temperature of 313 K, pressure of 15 MPa, (Figure 2b); S/F values were of 1.122a and 28 min for Figure 2b), 2.80 Figure 2a and 52 min for Figure 2b)in international market. The price of clove volatile oil (obtained by steam distillation) varies between US$ 26.00/kg and US$ 86.00/kg [30], depending on raw material origin and chemicalthe product.

Figure 2. Manufacturing cost (COM) of clove oil market. Experimental conditions: temperature of 313 K, pressure of 15 MPa, CO

0

20

40

60

80

100

120

140

5 L 50 L

CO

M (

US

$/k

g e

xtra

ct)

Extractors capacity

40 min 70 min 100 min

(a)

COM estimated, transportation costs still have to be added.

Economical parameters used for COM estimation

US$ 100,000.00 US$ 300,000.00 US$ 1,150,000.00 10 %/year US$ 4.00/h 1 operator 2 operators 3 operators

US$ 3.51/kg b

US$ 40.00/ton US$ 0.15/kg

US$ 0.092/kWh

US$ 0.19/ton US$ 4.20/ton

the COM of clove oil obtained by SFE according to experimental data temperature of 313 K, pressure of 15 MPa, CO2 flow rate of 1.45 × 10-3 kg/s (Figure 2a) and 3.00 × 10

1.12 (40 min for Figure 2a and 16 min for Figure 2b), 1.96, 2.80 (100 min for Figure 2a and 40 min for Figure 2b) and 3.65

Figure 2a and 52 min for Figure 2b). The dotted line represents the selling price of clove oil obtained by SFE The price of clove volatile oil (obtained by steam distillation) varies between US$

, depending on raw material origin and chemical-physical characteristics of

Manufacturing cost (COM) of clove oil obtained by SFE; dotted line represents its selling price in international market. Experimental conditions: temperature of 313 K, pressure of 15 MPa, CO2 flow rate of 1.45 × 10

3.00 × 10-3 kg/s (b).

50 L 500 L

Extractors capacity

100 min 130 min

0

20

40

60

80

100

120

140

5 L 50 L

CO

M (

US

$/k

g e

xtra

ct)

Extractors capacity

16 min 28 min

(b)

the COM of clove oil obtained by SFE according to experimental data of Prado et al [26]: a) and 3.00 × 10-3 kg/s

, 1.96 (70 min for Figure and 3.65 (130 min for

of clove oil obtained by SFE The price of clove volatile oil (obtained by steam distillation) varies between US$

physical characteristics of

obtained by SFE; dotted line represents its selling price in international

flow rate of 1.45 × 10-3 kg/s (a) and

50 L 500 L

Extractors capacity

40 min 52 min

COM was reduced with plant scale increase. Considering the SFE plant would be processing only clove, a 5 L plant is economically unfeasible, but 50 L and 500 L plants would operate with COM far below the product’s selling price. Moreover, comparing Figure 2a and Figure 2b, as solvent flow rate increases with consequent cycle time decrease for the same S/F, the process economic viability improves. Therefore, SFE in Brazil is economically feasible, after the process is appropriately optimized. It is still worthy to remember that the raw material cost used for COM estimations was the highest found in market, that is, the COM can be further reduced with raw material cost decrease. Rosa and Meireles [2] estimated clove oil COM as US$ 9.15/kg for a plant operating with two extractors of 400 L. However, they used lower clove cost (US$ 0.50/kg) since they considered the raw material would be purchased directly from the farm. In our study, it was considered the distributer market price. Moreover, according to the Association for the Advancement of Cost Engineering International, cost estimations can be divided in five classes (1 to 5). Class 5 estimation is based on the lowest definition level of the project, while Class 1 estimation is closer to the full definition of the project, i.e., high maturity. The methodology proposed by Rosa and Meireles [2] can be classified as Class 4-5, while SuperPro Designer can be classified as a Class 2-3 simulator. Other economical parameters evaluated are presented on Table 2 and Table 3. With scale increase the raw material cost share increases, diluting the other costs. The fixed cost of investment is not the main on; for the largest plant, it is below US$ 2.00/kg of extract, in agreement with literature data [27,29]. It is also interesting to notice that for both 50 L and 500 L scales the COM and return time are viable. Prado et al [7] noticed a similar trend, with substantial decrease of COM for scale increase up to 100 L, and posterior lower COM reduction with scale-up. Therefore, due to the lowest investment cost needed for the 50 L plant (US$ 300,000.00) than for the 500 L plant (US$ 1,150,000.00), a 50 L plant may be a good alternative for a first investment on SFE in Brazil. Table 2. Economical evaluation of clove oil production by SFE. Experimental conditions: temperature of 313 K, pressure of 15 MPa, CO2 flow rate of 1.45 × 10-3 kg/s.

Time (min)

Productivity (kg/year)

Operation cost (US$/year)

CRM (%)

COL (%)

FCI (%)

CQC (%)

CUT (%)

Return time (years)

5 L 40 1523 186000.00 35.86 39.16 18.86 5.87 0.25 - 70 1492 169000.00 29.25 43.18 20.80 6.48 0.29 18.45 100 1356 159000.00 24.70 45.95 22.14 6.89 0.32 35.89 130 1206 152000.00 21.38 47.97 23.12 7.20 0.34 -

50 L 40 15228 945000.00 70.62 15.42 11.14 2.31 0.50 1.18 70 14914 771000.00 63.98 18.89 13.65 2.83 0.64 0.98 100 13563 669000.00 58.49 21.76 15.73 3.26 0.76 1.01 130 12065 603000.00 53.86 24.17 17.47 3.63 0.86 1.12

500 L

40 152281 7374000.00 90.49 2.96 5.47 0.44 0.64 0.43 70 149134 5639000.00 87.51 3.88 7.16 0.58 0.88 0.36 100 135628 4621000.00 84.72 4.73 8.73 0.71 1.10 0.36 130 120649 3952000.00 82.12 5.53 10.21 0.83 1.32 0.38

COM: cost of manufacturing; CRM: cost of raw material; COL: cost of labor; FCI; fixed cost of investment; CQC; cost of quality control; CUT: cost of utilities. Other information that can be obtained from cost analysis is the best batch time. To evaluate the optimized cycle time, yield, chemical composition and cost data should be considered. The extract quality has been confirmed up to S/F = 5.11 [26]. By the economical evaluation, S/F of 3.65 (130 min for CO2 flow rate of 1.45 × 10-3 kg/s and 52 min for CO2 flow rate of 3.00 × 10-3 kg/s) is the batch time presenting lower COM. Therefore, it can be concluded that for clove SFE at 313 K/15 MPa, 52 min and S/F of 3.65 present the best relation between cost, yield and product quality. It is still worthy to remember that due to the different colours of the extracts obtained in each separator [26], the selling price of the products may vary.

Table 3. Economic evaluation of clove oil production by SFE. Experimental conditions: temperature of 313 K, pressure of 15 MPa, CO2 flow rate of 3.00 × 10-3 kg/s.

Time (min)

Productivity (kg/year)

Operation cost (US$/year)

CRM (%)

COL (%)

FCI (%)

CQC (%)

CUT (%)

Return time (years)

5 L 16 1951 223000.00 46.32 32.69 15.75 4.90 0.34 30.22 28 2440 206000.00 41.86 35.32 17.02 5.30 0.50 3.47 40 2495 194000.00 38.22 37.53 18.08 5.63 0.56 2.85 52 2375 185000.00 35.14 39.35 18.96 5.90 0.64 2.95

50 L 16 19515 1313000.00 78.64 11.10 8.02 1.67 0.57 1.10 28 24396 1146000.00 75.30 12.71 9.18 1.91 0.90 0.61 40 24949 1026000.00 72.34 14.21 10.27 2.13 1.05 0.53 52 23750 935000.00 69.57 15.58 11.26 2.34 1.26 0.54

500 L 16 195137 11054000.00 93.40 1.98 3.65 0.30 0.68 0.44 28 243969 9391000.00 91.93 2.33 4.30 0.35 1.10 0.25 40 249481 8182000.00 90.67 2.67 4.93 0.40 1.32 0.22 52 237502 7279000.00 89.38 3.00 5.54 0.45 1.62 0.22

COM: cost of manufacturing; CRM: cost of raw material; COL: cost of labor; FCI; fixed cost of investment; CQC; cost of quality control; CUT: cost of utilities. CONCLUSION

Gathering experimental yield data and the chemical composition of clove oil previously published with the economical evaluation of the present work, it is possible to optimize the process: for clove SFE at 313 K and 15 MPa, 52 min of cycle time and S/F of 3.65 present the best relation between yield, quality and cost of the process. Moreover, it was demonstrated that SFE in Brazil is economically feasible, after the process is appropriately optimized. ACKNOWLEDGEMENTS

J.M. Prado thanks FAPESP for the postdoctoral fellowship (2010/08684-8). REFERENCES

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