附录A
Design of orange peel dryer
Author1, Author2, Author3.
Applied Thermal Engineering, 2016, 8 (6): 556-568.
Abstract: Citrus peel is an important food additive for the production. South Africa is the world's third largest citrus export in the world but currently no citrus peel is used for further processing. In contrast, the state had to import these chemicals from overseas despite the quality of raw material sources in the form of citrus waste. Because citrus fruits are seasonal, it is necessary to keep these peels in use in the off-season. The purpose of this study was to investigate the dry dynamics of lemon peel and display design strategies on industrial scale dryers based on laboratory and pilot plant tests. The laboratory tests and dryness of the skin were crushed into three different sizes (3, 6, and 9 mm) to provide drying time (15, 20, and 40 minutes at 150 °C, and 30, 35, 100 and 60 min ° C) To achieve the desired final moisture content (10%) peel. Because the particles are aggregated and the relatively long drying fluidized bed dryer has been selected. After the success of the pilot plant test the initial design of the fluidized bed dryer required capacity has been done.© 2007 Elsevier All rights reserved.
Keywords: dry fluidized bed dryer; food additive
1 Introduction
South Africa is the world's third largest citrus export in the world but currently no food chemicals are produced locally. The new initiative is dealing with local and cit-rus waste to produce valuable food chemicals. This can be seen as an opportunity to generate new jobs and income for local citrus producers. Because citrus fruits are seasonal, it is necessary to save these peels in the off season. This is done by reducing the moisture content of about 85% to 10% of the peel. Citrus fruit candied fruit can be used in baked goods or fast food. The debris of the peel is used for jam. Polysaccharide extract pectin cit-rus skin gelling agent used in jam and some candy. It is also technically possible to produce solid waste from fruit vinegar (fruit waste use, 2007).
Drying is an energy-intensive process that results in the removal of moisture from the body. In general, the effect of the drying process is considerable to exert the external conditions and the internal structure of the material is dry. These factors affect the various drying times in a variety of. The rate of heat transfer during mass drying and the mass transfer mainly depends on the transport mechanism of the boundary layer, but in the descending section the control factor becomes the additional resistance within the dry material (strumillo with kudra, 1986).
Fluidized bed drying technology has an important position of the drying method. This method has been widely used in granular materials; but it also applies to dry solutions where paste and liquid are sprayed into fluidized bed inertia. The fluidized bed dryer is characterized by a particle residence time distribution, near-perfect mixing (true with Baker, 1985). The drying method is supported by hot air through the material layer located in the grid (gas distributor). If the speed of the gas is higher than the initial fluidized bed, the velocity is gradually expanded to reach a similar boiling liquid in a country. This phenomenon is called a fluidized bed. Fluidized bed drying has been extensively studied in the literature (off with Joslin Lin, 1967; reduction, 1978; true with Baker, 1985). Kudra, mujum-dar, lata, and kalwar (1992) studied fluid mechanics, heat transfer and drying characteristics using    a two-dimensional spouted bed. They found that dense particle transfer rates lead to high heat transfer rates, and uniform moisture content and temperature. Bed temperature, so it can be easily controlled. It is particularly important for heat sensitive materials such as in the food industry. However, not only the thermal degra-dation (ie, mass loss, color, shape, texture, nutrient content, etc.) should be considered as a dry product (grain, sugar, fruit, vegetables, etc.) in food but their sensitive mechanical stress and Prolonged drying time as well (Grabowski and mujumdar, 1992lewicky; and Reynette, 1992; talburt and, 1987). In the case of citrus peel dry degradation may occur at temperatures above 150 ° C after 30-40 minutes of short-rate drying period, most of the dryi
ng process at the rate of per-iod, both in terms of gas velocity and dry areas affect the peel drying rate , Mainly because the control mechanism is internal to the vapor transport in the particles (ramsunkar and Ramdio, 2006). As expected the particle-to-fluid heat transfer coefficient depends on the velocity of the gas, it is more in the fluidized bed than in a fixed bed (other et al., 1985; support original, kaguei, and funazkri, 1979). However, in the drying of food products this phenomenon affects the drying rate only before the start of the drying process, and mass transit becomes internal control.
2. research
An ordinary kitchen equipment (Kenwood mincer / de-juicer) is first removed with lemon juice and then passed through the screen of three different sizes, namely small (3 mm), medium (6 mm), large (9 mm) The The laboratory work brought the tray drying experiment from which the data obtained was used to produce the drying rate curve. A laboratory tray dryer (Labcon FSOE-D-8 man-ufactured marketing service, through experiments, RSA) was used to test at two different temperatures (150 and 100 ° C). The skin is evenly dispersed in Petri-months and then placed in a tray dryer. Then remove the sample pre-interval and moisture content for the infrared moisture meter using the infrared-200 (produced by Denver Equipment Inc. USA). Experiments in different water con-tent prov
ide value for the time interval. The same procedure carries out all the particle size.
See the test device experiment (Figure 1), in dry use of liquefied lemon peel in a batch open bed dry. Since continuous drying is impossible to stay for a long time, the required figure is used to test the liquefier bed dryer (as opposed to an industrial
dryer). The hot air dryer provides the combustion LPG (liquefied petro-leum gas) in the combustion chamber (3), the air velocity is measured by the airspeed tube (4). Good fluidized bed particle size achieves all average speeds of 3.5 m / s. All fine particles may escape trapped in strong tropical storms (7). The product collects the shot through the exit. 22 liters up a given size is used for every run. Enter the air temperature at 150 ° C dryer. The final bed temperature reaches 110 ° C; adequate safety to avoid damage to the product. Then take the sample and hold the con-tent in the water regularly to evaluate it. From the production history experiment curve, it is estimated that each device runs for 30 minutes.
Figure 1. Device flow chart
- Very good condition, heat transfer process
-
good mix, that is, the information on the uniformity of the bed
- Better control of drying conditions within the range of dryers
- Stay shorter, so more to strengthen the dry, compared to other industrial dryers - smaller, compared to other industrial dryers
design翻译In addition to the general advantages there is also a good experience and the use of dry-temperature sensitive materials for the use of fluidized bed dryers in the food industry has a specific goal. Allow a longer stay time The continuous dryer should be long enough to have a side of the granular material for the travel product, as described in Figure 4. The results of a comprehensive sizing machine are amplified by the pilot plant dryer according to the performance analysis of the design and pilot plant dryers.
Briefly describe the design process through the following relationship: Fresh citrus peel dry (kg / year) = fresh skin requirements (kg / year) * fraction years (off-season, that is not generated)
Dryer (kg / h) = fresh skin requirements (kg) / dwell time (h)
Air flow (m3 / s) == fluidized bed speed * dryer cross-sectional area
Enlargement ratio = capacity of industrial dryer (kg / h) / capacity of pilot plant Dryer (kg / h)
Cross section area Dryer = liquefied volume of bed / 0.64
0.64 m in the past relationship with the average height of the bed geom-etry according to the dryer. Since the citrus fruit is not in the year of April, this makes the remaining eight months (2/3) a year needed to dry the skin this period. Taking advantage of this opportunity to bind with the required number of annual processing requirements, stripping the drying during this period can be calculated to the required capacity to determine the industrial dryer. The ability to rate the ability to provide a pilot plant dryer --- scale. Use this ratio to determine the size of the industrial dryer required.
3. Decision making
Tray drying was carried out at different temperatures at two different temperatures (150 ° C and 100 ° C) in order to determine the moisture content of the skin at different times in the drying process. Figure 2 shows the dryness of the tray at a dryness of 150 ° C with a particle size of 3 mm. These conditions are shown in Fig. The dry curves were measured under different conditions for the critical moisture content to make different particle sizes and different drying temperatures. The values obtained show that most of the drying process occurs during the deceleration phase (see Table 1). T
he trial also provided a conservative estimate of the time required to achieve the desired water content (about 10%), shown in Table 2. The heat and mass transfer coefficient is usually higher in bed than the tray is dry. The same mass unit dry area particles are not the same for the laboratory tray dryer and the pilot plant bed dryer, but these differences play the role of the rising section of the dry section but most of the drying process occurs during the deceleration period.
A pilot plant was carried out to verify the results of the tray dry. Only large particles (9 mm) method, small particles gathered.
Each plug is completely mixed with the flow element in a sense that all the particles in this element have the same moisture content. The whole particle in this element should have a moisture content of about 64%.
Figure 2 Water content curve vs. time 3 mm at 150 ° C particles (tray dryer)
Figure 3 Drying Rate Curve Particles at 150 ° 3 mm C (Pallet Dryer)

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