Part 2. Essential equipment for fruit juice manufacture

Exercise 1. Read and translate the following word-combinations.

The fruit-juice industry, an L-profile roller, high-pressure jets, steam-pipes systems, feed box distribution, wastewater volume, wash water recycling.

Reading. Read the text and say what types of presses and centrifuges are used in fruit-juice industry.

There are belt presses (Figure 33) specifically designed for the fruit-juice industry. They feature efficient design and easy access for cleaning and operation with minimum personnel requirements.

The feed box distributes the processed mash uniformly over the lower belt. The wedge zone curves downwards and gently releases large amounts of juice to form a mash cake ready for pressing. An L-profile roller extracts the juice in the pressing zone and ensures that the juice flows away quickly on both

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sides. A series of press rollers with decreasing diameters results in increase of compressive and shear forces exerted and raise the juice yield to 84%.

While the juice flows quickly to the central collecting pan, the pomace is scraped from the belts by adjustable plastic scrapers and can be conveyed away easily. The belts are cleaned by high-pressure jets and the wash water is recycled to cut down wastewater volume.

After a production cycle, the belt press can be cleaned simply and easily. The drain to the central collecting pan is closed and the pan is filled with cleaning solution. The belts and L-profile rollers are completely immersed in the cleaning solution. Cleaning solution is also sprayed onto the belts by high-pressure jets. After about half an hour of circulation, and rinsing with fresh water, the belt press is ready for another day.

Figure 33. Belt press.

Decanter centrifuges (Figure 34) are used for liquids and solids separation and clarification. The slurry is fed through a fixed central pipe into the distributor located in the scroll. The product is then accelerated smoothly and passes through feed ports in the scroll to the bowl.

Separation takes place in the conical cylindrical bowl which rotates at a preset speed specific to the separation task. The slurry rotates in the bowl at the design speed and forms a concentric layer around the inside of the bowl. The solids contained in the slurry are

deposited against the bowl wall under the influence of centrifugal force.

The scroll rotates at a differential speed to that of the bowl and conveys the separated solids in the direction of the conical end of the scroll. The length of time the solids remain in the bowl is an important factor in determining the dry solids contents of the discharge. Scrolls may be concurrent or countercurrent, single flight or multiple flights depending on the application and process requirements.

Figure 34. Decanter centrifuge.

The separated solids are discharged through openings at the conical end of the bowl. They enter the stationary solids housing and are discharged down the outlet chute.

While the liquid is being clarified, it flows to the cylindrical end of the bowl and overflows the adjustable weir plates which determine the depth of the pond. The clarified liquid is decanted into a fixed central chamber and discharged by gravity.

The two liquids are separated in the liquid zone and decanted through separate discharge systems to prevent cross-contamination.

The clarified liquid can also be decanted with a paring disc and discharged from the bowl under pressure in a closed system. This eliminates the need for a discharge pump.

Exercise 2. Answer the following questions.

1. What are the purposes of presses in fruit-juice industry? 2. What types of presses are used in juice manufacture?

3. What is the juice output in its manufacture with the belt presses? 4. Are the belt presses difficult in operation? Why?

5. What are the purposes of centrifuges in fruit industry?

6. What types of centrifuges are the most widely used ones?

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Exercise 3. Translate the following word-combinations.

A mash cake ready for pressing, to discharge from the bowl, the adjustable weir plates, to form a concentric layer around the inside of the bowl, to be decanted with a paring disc, under the influence of centrifugal force, the central collecting pan, the adjustable plastic scrapers, at a preset speed.

Exercise 4. Complete each sentence with a word or phrase from the box.

scrolls conical cylindrical bowl roller high-pressure jets discharge pump

1. After finishing the production cycle the belt presses are washed by ___.

2. In decanter centrifuges ___ be concurrent or countercurrent depending on the application and process requirements.

3. Juice separation takes place in the ___which rotates at a preset speed. 4. A ___extracts the juice in the pressing zone.

5. Discharging the clarified liquid from the bowl under pressure in a closed system eliminates the need for a ___.

Exercise 5. Match the verbs on the left with their definitions on the right.

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