CITRUS OIL RECOVERY - USING MODERN "STATE-OF-THE-ART" CENTRIFUGE TECHNOLOGY AS PART OF ECONOMICAL CITRUS PROCESSING

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1 ASME 2006 Citrus Engineering Conference CEC2006 March 23, 2006, Lake Alfred, Florida, USA CEC CITRUS OIL RECOVERY - USING MODERN "STATE-OF-THE-ART" CENTRIFUGE TECHNOLOGY AS PART OF ECONOMICAL CITRUS PROCESSING Stefan Pecoroni Head of Business Unit Beverage Technology Westfalia Separator Food Tec GmbH Werner-Habig-Str Oelde IGermany Pecoroni.Stefan@GEA-Westfalia.de INTRODUCTION The present citrus oil business is dominated by two trends: The price for orange oil as a bulk product is under serious market pressure. This has been ongoing for a number of years. In many regions of the world, for example, Southern Italy, this has led to a situation where oil is no longer recovered. However, due to insufficient deoiling, this results in giving away a valuable product (even at a low price) and increased waste water treatment costs or losses in revenue when selling the peels for animal feed. Based on 30,000 Ilh emulsion of orange oil coming from the extractors, a return on investment between one and two years can be achieved at present prices as shown in Table 1. Therefore, large processors must focus on increasing production efficiency. In contrast to the economical situation for orange oil, we see a very strong dynamism in the market for other citrus oils. The price for more rare oils like grapefruit, pink grapefruit, lemon, and mandarin is increasing, partly influenced by climatic factors like hurricanes. This makes the recovered oil very valuable and brings an even stronger focus onto production efficiency. In addition, the tendency towards constructing bigger production lines is still very dominant in the market, especially in Brazil and the US. This increases the pressure for the equipment suppliers to provide the industry with units having higher capacity and efficiency. Westfalia Separator has reacted to this trend by introducing new models, such as the new ESE 500 for first stage oil emulsions and the new OSD 60 for second stage emulsions. These machines are tailor-made for these applications. In intense test work, these machines have been optimized for Brazilian as well as American processing conditions on various fruits. Mainly, the capacities have been brought up to a maximum level of 130 GPM depending on fruits and conditions. Published with permission.

2 Furthermore, recovery rates could be optimized by approx. 1O0/0 from 3 Ibslton to a level of 3.3 Ibslton. Citrus Oil Processing As shown in Figure 1, the typical system for the recovery of citrus oil consists of a two-stage separator process. The emulsion coming directly from the combined juiceloil extractor (in the case of FMC or similar models) or coming from the separate oil extraction unit (in the case of Brown or similar models) usually contains oil in an amount of 0.8 to 1.5% by volume (or higher). This emulsion is cleaned from the coarse solids by use of oil finishers or vibrating screens. The light emulsion is then fed into a first stage separator. This is a three phase separation centrifuge, which separates the heavy phase (water) from a light phase (rich emulsion with approx. 75% oil content) and solids. The water is usually recycled to a buffer tank and reused after further cleaning in a make-up system, such as florentine tanks or membrane filters. The rich oil emulsion contains a high content of oil. It is of utmost importance that this emulsion has the least amount of homogenization as possible (i.e., a high amount of free oil is desired). This criterion puts a focus on the design of the first stage separator to be as gentle as possible. This emulsion is then fed to the second separator stage. This is ideally done by gravity to avoid any damage to the oil emulsion due to shear forces of pumps. In the second separator stage, the remaining water is completely removed. This water usually goes to the drain. Also, small amounts of solids, which still might be contained in the oil, are removed. The final product at this stage is brilliant, clear citrus oil. This raw oil can be further processed in various ways depending on the end customer use. This includes processes like winterization (removal of waxes), distillation (for terpene-free oils) and alcoholic extraction in order to produce water soluble flavor components. A typical mass balance is shown in Figure 2. Most important factors for an economical feasible yield are the two separators. In both stages the most important parameter is the residual oil content in the water effluent. Furthermore, the residual oil content in the ejected solids contributes to the overall yield loss. In this respect, it is very important to realize that the solids content and the pectin content of the emulsion coming from the extractors is of very high importance. If the light emulsion feed to the first stage separator contains too much solids, in combination with an excess of pectin, this will hinder significantly the efficiency of the separators. The

3 oil droplets will be attached to the solid particles, making it very difficult to remove them. The pectin acts by increasing the viscosity of the heavy phase, decreasing the efficiency of separation based on Stokes law. The pectin also acts as an emulsifying agent, making it difficult to remove the oil from the emulsion. In the following sections, we will focus on the two stage centrifuge separations of the oil from light (dilute) oillwater emulsions. First Separator Stage In this process stage, separators have been used almost since the beginning of industrial citrus processing. In the past, often second hand dairy machines were more or less successfully converted for this application. Over the last 20 years, Westfalia Separator has developed a range of separators especially dedicated to this market. The current range of machines available can be seen in Figure 3. For high capacities, the separator type ESE 500 (Figure 4) has successfully been developed. This machine was initially developed to serve as an orange juice deoiling separator, to serve the booming NFC juice market. However, it has been modified and successfully applied to concentrate first stage emulsions. The main benefits of theses machines compared to older separators are an increased recovery rate (up to 10%) and many details reducing the total costs of ownership. The machine is equipped with modern features aimed at reducing the maintenance and operation costs, therefore leading to minimized costs of total ownership. The most important features for cost savings in this respect are the short spindle flat belt drive, a special vibration dampening system, and new high speedllow maintenance valves in the ejection mechanism. Figure 5 shows the main features of the short spindle flat belt drive. The benefits of these modifications are: Low bowl position for stability Simple transfer of drive energy No clutch required No complex gear arrangement Motor drive is VSD (variable speed drive with frequency converter) compatible Figure 6 shows the main features of the special vibration dampening systems. The benefits of these modifications are:

4 Smoother operation of machine Reduced mechanical wear Three bearings vs. six on the gear drive machine for less maintenance costs Higher vibration tolerance Figure 7 shows the main features of the new ejection system. The benefits of these modifications are: Low discharge volume to effluent 5000 to 6000 hours between bowl gasket changes Increased machine use In general, the ESE separator offers up-to-date centrifuge technology in combination with high capacity and efficiency especially suitable for big citrus processing plants. Second Separator Stage Since the first centrifuge stage aims mainly at removing the majority of the water from the system with minimum oil losses, the second stage aims primarily at removing all of the water and remaining solids from the clear oil. In this respect, the machines are not only typically much smaller, but also set up differently. This includes different set up of rising channels (inner vs. outer), different thickness of discs and spacers, etc. In the past, most of the separators used for citrus oil duty were of open design. The reason for this was based on the concern that the use of centripetal pumps might create minimum flows along the shaft of the pumps from the heavy phase to the light phase. Based on even low water contamination, a haze would form immediately in the oil. However, the big disadvantage of such open discharge machines lies in the amount of oil and oil components being lost due to evaporation to atmosphere. This can be up to I0/o of the oil recovered and even a higher amount of the "light boilers". In the last few years these problems have been overcome, and now various machines are available with oil discharge via a centripetal pump, avoiding the above mentioned losses. Figure 8 gives an overview of the currently used machines for second stage citrus emulsions. In order to combine the well-known advantages of the OSC 20 with a concept of closed discharge of oil and cost reduction features as described above for the ESE 500, we developed the OSD 60. This is a

5 second stage emulsion machine aiming at the high capacity market and therefore a perfect match for the ESE 500. On top of the increased oil recovery rate of the ESE 500, process losses are further reduced. Compared to older machines like the SB 14 or SA 18, the recovery rate can be improved by approximately 1-2% and the capacity almost tripled. Figure 9 shows an OSD 60. In detail, this separator offers various features to the users. The most important benefits of this machine include: Belt drive design Hydro hermetic feed system Continuous gravity discharge of the heavy phase, minimizing the discharge frequency Discharge only required based on solids holding space being full Large sediment holding space, with capacity up to 10 liters Pump discharge of the oil phase High speed discharging mechanism i.e., no free oil in discharges This separator has been used successfully as polisher, as well as clarifier based on a self-thinker design in citrus oil emulsion second stage separations. SUMMARY Using these two types of separators enables the processor with a high capacity production to renovate his basic oil room setup in the most economical way. At the same time, performance is increased with a significant reduction in overall maintenance costs. Table 1. Total investment oil recovery system: 900,000 USD 30,000 Ilhlemulsion. - Flow 30,000 Ilh with I % oil content = oillh x 22 hours x 150 days x 88% recovery x 0.8 USDII oil = 6,600 1 oillday = 990,000 1 oillseason = 871,200 1 oillseason = 696,960 USDIseason

6 Citrus Oil Recoverv F = Frutt J = Julce W =Water U = Sol~ds 1 Extractor Screen 3 Pump 4 Buffer-Tank 5 Pump 6 Hydrocyclon 7 Is' Stage Ernuls~on 8 Buffer-Tank 9 Pump 10 2nd Stage Emulslon Tank 12 Make up System 13 Buffer-Tank u 15 w 11 14Pump Figure 1 raw fruits [tolh] wash water [Ilh] emulsion [%I Efficiency Extractor Mass Balance Citrus Juice I Oil first stage feed hnf stage 5000 Ilh with 1.2 % Vol I discharge 71 IA Emulsion mth 85 %Vol dlschaw watw 4929 llh Complete 011 lasses 1st stage 4.16% 2nd stage 0.01 "/Q solids 0.02 % Total Losses 4,19 % Figure 2

7 1" stage Capacity Ilh OSD ESB ESD All values based on emulsion with an oil conccntration of approx. I Oio Vol. in the feed to the first stage ESE Figure 3 ESE 500 Figure 4

8 f'" " t i w - 20 &, Vibralrnrr i.hvrp?rt$rrg Mounts. - 4 x Figure 5 Figure 6 Figure 7

9 2nd stage Capacity OSC Figure 8 Second Staqe Citrus Oil Machine Figure 9