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Nathalie Monnerie Ju¨rgen Ortner e-mail: [email protected] Deutsches Zentrum fu¨r Luft- und Raumfahrt e.V., Solare Energietechnik; D-51170 Ko¨ln, Germany

Economic Evaluation of the Industrial Photosynthesis of Rose Oxide via Lamp or Solar Operated Photooxidation of Citronellol An economic evaluation regarding the industrial photosynthesis of fine chemical rose oxide using solar light is given and compared to conventional lamps as light source. A plant reaching a capacity of 100 t/a was designed containing app. 1,900 m2 of parabolic troughs, 1,500 m2 of flatbed reactors or 32 high-pressure mercury lamps doped with Thallium iodide (TlI) as a photounit. The investment and production costs were compared and graded. We reached the conclusion that solar application is more profitable than the lamp driven one. 关DOI: 10.1115/1.1354996兴

Introduction During the last decade several solar photochemical methods, producing bulk or fine chemicals, were developed and examined worldwide. The practicability of the approaches was in the central scope of the investigations. Among the reduction of CO2 emissions using the sun as radiation source, the examined reactions were selected because they met the following important requirements: • The required radiation lies in the range of the solar radiation. • The reactions have a quantum yield near unity. The high investment costs of artificial light sources are a major limitation and alternative solar technology claimed to reduce the specific cost. Recently Sattler et al. 关1兴 and Funken et al. 关2兴 published cost estimates regarding solar photooximation of cyclohexane to produce ␧-caprolactam. Hereby the competitiveness of the solar method was proven versus a lamp driven one producing a bulk chemical. The object of this paper is to present a cost estimate regarding solar photochemical production of rose oxide. Rose oxide is a fine chemical with a yearly production rate ranging between 60 and 100 t. Considering the value of this chemical the substitution of artificial light sources by solar equipment will be taken to impose.

Industrial Process Description of Rose Oxide Manufacture The ‘‘photooxidation chemistry’’ is used widely in manufacturing a large variation of chemicals 关3兴. In this context, the synthesis of rose oxide is carried out following this method on an industrial scale. Dragoco, Holzminden 共Germany兲, Fig. 1, produces via photooxidation app. 60–100 t/a of this fragrance 关4,5兴. As artificial light sources high-pressure mercury and sodium vapor lamps were installed. The synthesis scheme of rose oxide is summarized in the following scheme. Contributed by the Solar Energy Division of The American Society of Mechanical Engineers for publication in the ASME JOURNAL OF SOLAR ENERGY ENGINEERING. Manuscript received by the ASME Solar Energy Division, Aug. 2000; final revision, Jan. 2001. Associate Technical Editor: D. M. Blake.

Journal of Solar Energy Engineering

Starting with the photooxidation of citronellol 共1兲 hydroperoxides 共2⫹3兲 were generated, which were subsequently cyclized to rose oxide 共6兲 after their reduction to the corresponding alcohol 共4⫹5兲. In analogy to the published procedure of this photooxidation process 关6兴 we propose the general flow sheet of the corresponding photooxidation plant shown in Fig. 2. In the photooxidation unit 共A兲 a methanol solution of citronellol 共1兲 is illuminated in the presence of the sensitizer Rose Bengal and oxygen. The intermediately generated singlet oxygen reacts with citronellol 共1兲 afford to a mixture of hydroperoxides 共2⫹3兲, which are reduced by sodium sulfite solution in the second step 共B兲. After the reduction water will be separated and the methanol is evaporated from the organic phase and recycled 共B兲. The resulting organic phase containing diols 共4⫹5兲 will be redissolved in toluene and the cyclization to rose oxide is catalytically interact by sulfuric acid 共C兲. After washing the organic phase with sodium carbonate 共D兲 the toluene solvent will be separated by distillation. The pure fragrance is obtained after a final distillation step 共E兲. In the following cost estimate the process flow sheet will be simplified by combining units C, D with the first column of the distillations. Therefore the simplified plant contains a photooxidation, a reduction, a combined cyclization/ distillation and a final distillation facility. Solar variants were successfully tested 关7兴.

Technical Planing Points for the Cost Calculations To determine the size of the solar unit, Cologne was selected as a location due to the production place Holzminden 共Germany兲 and the availability of the needed weather data. The amount of photons in the range between 500 and 600 nm as typically applied for this reaction was calculated for the year 1996 with 1523 sunshine

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MAY 2001, Vol. 123 Õ 171

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Fig. 2 Flow sheet of the photooxidation plant of rose oxide

Fig. 1 Photosynthesis units of the manufacture of rose oxide at Dragoco, Germany

hour. Parabolic trough collectors 共20–50 suns兲 equipped with standard glass reaction tubes and flatbed reactors are proved to be successful for the solar photooxidation reactions 关8兴. Considering the track of a parabolic trough along one axis 共alignment: northsouth兲 a reflecting area of 1,843 m2 is necessary, if the calculation is based on a quantum yield of 68% 关9兴 and a photon density of 1.06 kmol/m2-aperture. For flatbed reactors with a slope of 30° an area of 1,476 m2 is calculated, if the loss of reflection over the year is assumed with 10% and the transmission is 90%. Figure 3 172 Õ Vol. 123, MAY 2001

Fig. 3 Parabolic trough and Plexiglas double skin-sheet reactors †10‡ for solar applications at DLR, Cologne „Germany… Table 1 Basic prices parabolic trough collector electricity heating citronellol sodium sulfite sulfuric acid rose oxide

235 $/m2 6.0 cent/kWh 1.5 cent/kWh 5.5 $/kg 75.0 cent/kg 40.0 cent/kg 60.0 $/kg

flatbed reactor cooling methanol Rose Bengal toluene sodium carbonate

200 $/m2 9.0 cent/kWh 10.0 cent/kg 75.0 $/kg 23.5 cent/kg 22.5 cent/kg

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Table 2 Share capital comparison of photochemical production of rose oxide share capital 100 t/a

solar 共parabolic trough兲 1,000 $

solar 共flatbed reactor兲 1,000 $

1,000 $

solar field 共incl. pipes, pumps etc.兲 photoreactor 共incl. lamps, vessel, etc.兲 reduction cyclization, neutralization and distillation 1 distillation 2 sum 共plant cost兲 extra charge for new processes, fees etc. extra charge for additional facilities share capital

839 0 694 1,468 449 3,450 966 950 5,366

657 0 694 1,468 449 3,268 915 900 5,083

0 866 694 1,468 449 3,477 974 957 5,408

shows an example of a one axis tracking parabolic trough at DLR, Germany. The reader is reminded that the lamp-operated plant utilizes 32 high-pressure mercury lamps, which are doped with thallium iodide 共10 kW兲. These lamps are immersed into a vessel 共6.5 m3兲 made out of steel covered with enamel. The vessels of the combined units B, C and D 共capacity: 15 m3兲 and of the final distillation E are made out of enamel and equipped with glassy columns 共5 respectively 4 theoretical number of trays兲.

Cost of Photochemical Production of Rose Oxide The calculations should be divided in two sections. The first section compares the share capital of the lamp driven plant with the solar one. While the second segment compares the production costs of the two plants. The calculation is based on the listed prices and assumed amortization time of 10 years and interest rate of 6% 共Table 1兲.

Investment Cost of a 100 tÕa Photooxidation Plant The price for the photochemical parabolic trough collectors was estimated by the price 共235 $/m2兲 for a completely installed parabolic trough collectors used for thermal solar energy conversion in collector fields 关11兴. The price for the selected flatbed reactor is calculated with 200 $/m2 关12兴. From an economical point of view some facilities will not be bought and installed exclusively for this application. It merely makes sense that a company will first invest in the photochemical and reduction parts alone and than rent the other equipment from an industrial park being nearby. Therefore, only parts of the investment costs 共23% for unit A, 35% for B and C and 40% for D兲 of these facilities will be taken into our considerations. Table 2 shows the share capitals of the photochemical production of rose oxide. The investment costs of the solar plants are 1 respectively 7% more lower than the conventional lamp driven one. The price

lamp

of the lamp driven photoreactor contains the equipment with lamps 共562,000 $兲. These lamps typically live for about one year, whereas the expected lifetime for the solar parabolic trough collectors exceeds 20 years. The replacement costs of the lamps will be taken into consideration in calculating of the production costs.

Production Cost of a 100 tÕa Photooxidation Plant The survey of production costs presented in Table 3 shows the advantages of the solar forced process. The use of the sun as radiation source reduces the production cost from 21.6 to 20.0 $/kg rose oxide. Related to the sale price of rose oxide this is 2.7%, which corresponds to a yearly effective profit rise of 160,000 $.

Evaluation of the Investment Based on the above mentioned data the investment in a photochemical plant can be evaluated by, i.e., the net present value npv 共discounted difference between the sum of all deposits and the sum of all disbursements兲 n

npv⫽

兺

i⫽0

ei

(1)

共 1⫹r兲 i

or the regular annual payment 共annuity兲. Prerequisite in the considered investment is a normal investment with a single outpayment e0 followed by yearly profits ei and the interest rate r are graded. Both values were calculated for the three variations of the solar sources 共Table 4兲. The npv’s of all investments are positive and therefore, all variants are in the economical sense lucrative. The npv’s of the solar operated plants top about 7%, respectively, 11% the corresponding npv of the lamp-operated one. The possible excess profits are accumulated about 10 years to day 1.2 or 1.9 Mio. $.

Table 3 Annual production cost comparison production costs 100 t/a fixed cost labor, insurance etc. variable cost electricity cooling energy heating energy chemicals lamp replacement sum production cost sale rose oxide

solar 1,000 $

lamp 1,000 $

513 3.9 33.3 83.7 1,371 — 2,004.8 6,498

516 59.9 84.1 83.7 1,371 40.9 2,155.3 6,498

Journal of Solar Energy Engineering

Table 4 Net present value and annuity of lamp and solar operated rose oxide production „100 tÕa… based on a lifetime of 10 years and an interest rate of 6% plant

net present value 关1,000 $兴

annuity 关1,000 $兴

solar parabolic trough flatbed reactor lamp

17,885 18,631 16,690

2,430 2,531 2,268

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present value. This corresponds to an abatement of 1.6 $ per kg production costs of rose oxide. A solar production plant in southern regions is more economical and it is time for the use of such technologies in the industry.

Acknowledgment The authors thank the Arbeitsgemeinschaft Solar des Landes Nordrhein-Westfalen for supporting the projects 共contracts: 255 002 91, 255 135 96 and 263 203 99兲.

References

Fig. 4 Net present values of solar and lamp-operated manufacture of rose oxide depending on global insulation and different costs of electricity, heating and cooling

Evaluation of the Solar Production In Fig. 4 the net present values of a solar manufacture of rose oxide with parabolic troughs is shown depending on the global insolation 共X, black line兲. As pessimistic scenario an increase of the costs for electricity, heating and cooling of 50% is assumed 共upper stroke-dot line兲. For the optimistic scenario the prices will be halved 共stroke-dot line兲. With this graph it is easy to calculate the net present value of any location, if the global insolation is known. All solar variants are more attractive than the conventional lamp-operated one 共line between •兲 calculated with the optimistic prices for cooling, heating and electricity.

Conclusions The authors conclude a solar operated production of rose oxide is economical wise and to be preferred to the lamp-operated process. In the case of manufacturing the fragrance in Germany the solar variation is up to 11% more lucrative regarding the net

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关1兴 Sattler, C., Mu¨ller, F.-J., Riffelmann, K.-J., Ortner, J., Funken, K.-H., 1999, ‘‘Economic Evaluation and Comparison of the Industrial Photosynthesis of ␧-Caprolactam via Solar or Lamp Operated Photooximation of Cyclohexane,’’ Proc. of Renewable and Advanced Energy Systems for 21st Century, April, Maui, HI, US RAES99-7692. 关2兴 Funken, K.-H., Mu¨ller, F.-J., Ortner, J., Riffelmann, K.-J., and Sattler, C., 1999, ‘‘Solar Collectors versus Lamps—A Comparison of the Energy Demand of Industrial Photochemical Process as Exemplified by the Production of ␧-Caprolactam,’’ Energy 共Oxford兲, 24, pp. 681–687. 关3兴 Esser, P., Pohlmann, B., and Scharf, H.-D., 1994, ‘‘The PhotochemicalSynthesis of Fine Chemicals with Sunlight,’’ Angew. Chem. Int. Ed. Engl., 33, pp. 2009–2023. 关4兴 Gollnik, K., 1982, ‘‘Photooxygenation and its Application in Industry,’’ Chim. Industr., 64, pp. 156–166. 关5兴 Ihr Nachbar, N. N., 2000, Zeitung fu¨r die Nachbarn von Dragoco und Haarmann & Reimer, 1. 关6兴 Pickenhagen, W., and Schatkoski, D., 1998, Process for the Preparation of Rose Oxide, Patent EP970118891. 关7兴 Ortner, J., Faust, D., Funken, K.-H., Lindner, T., Schulat, J., Stojanoff, C. G., and Fro¨ning, P., 1999, ‘‘New Developments Using Holographic Concentration in Solar Photochemical Reactors,’’ J. Phys. IV France, 9, Pr3-379-383. 关8兴 Funken, K.-H., and Ortner, J., 1999, ‘‘Technologies for the Solar Photochemical and Photocatalytic Manufacture of Specialities and Commodities: A Review,’’ Zeitschrift fu¨r Physikalische Chemie, 213, pp. 99–105. 关9兴 Schenck, G., and Gollnick., K., 1963, Forschungsberichte des Landes Nordrhein-Westfalen Nr. 1256, Westdeutscher Verlag, Ko¨ln und Opladen. 关10兴 van Well, M., Dillert, R. H. G., Bahnemann, D. W., Benz, V. W., and Mueller, M. A., 1997, ‘‘A Novel Nonconcentrating Reactor for Solar Water Detoxification,’’ ASME J. Sol. Energy Eng., 119, pp. 114–119. 关11兴 Brown, H., Hewett, A. W., Gee, R., and May, K., 1997, ‘‘Performance Contracting for Parabolic Trough Solar Thermal Systems,’’ Energ. Eng., 94, pp. 33–44. 关12兴 Cost estimation of SolAcryl in Elsenfeld, Germany: cost of DSSR in the range of 200–250 $.

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