Clarification machines.

Mixed juice from the extraction mills or diffuser is purified by addition of heat, lime, and flocculation aids.

Heated to 990-1040 C, the neutralized juice is inoculated, if necessary, with flocculants such as polyacrylamides and pumped to a continuous clarification vessel, a large, enclosed, heated tank in which clear juice flows off the upper part while muds settle below. This settling and separation process is known as defecation. Muds are pumped to rotary vacuum filters, where residual sucrose is washed out with a water spray on a rotating filter. Clarified juice, meanwhile, is pumped to a series of three to five multiple-effect evaporators.

Exercise 2. Answer the following questions.

1. What are two types of juice extraction?

2. What extraction method is the most effective? Why? 3. What are the disadvantages of extraction by diffusion? 4. What is the purpose of juice clarification?

5. What devices are used in juice clarification?

87

Exercise 3. Rewrite the following sentences replacing the words underlined with the expressions from the text which have similar meanings.

1. The crushed cane goes forward through a series of roll mills. 2. Cane can be cut by whirling knives.

3. The sliced cane goes through the crusher.

4. A bagasse diffuser is used for increasing extraction. 5. Sugarcane is loaded manually onto a moving table.

Exercise 4. Translate the following word-combinations.

a) For finer cane preparation, a current of maceration water, a multicell countercurrent diffuser, to be loaded by crane, extraction by milling, a costly environmental problem, partially milled cane, a continuous clarification vessel, to be washed out with a water spray;

b) cane sugar – a sugar cane, a roll mill – a mill roll, a vacuum filter – a filter vessel, a juice evaporator – an evaporator part, maceration water – water treatment system, residual sucrose – sugar residuals.

Exercise 5. Checking facts and ideas.

Decide if the following statements are true or false.

1. A "bagasse diffuser" is used in order to increase extraction from partially milled cane after two or three mills.

2. Cane is cut by hand.

3. Juice clarification is carried out with chemicals in a clarification vessel. 4. Extraction of sugar by milling is about 95 percent.

5. Sugar extraction by diffusion is the most widely used in Australia and south Africa because cane quality is the highest there.

Exercise 6. Match the terms on the left with their definitions on the right.

1) maceration a) a porous device for removing impurities from a liquid passed through it water b)adeviceforgrindingany solid into powder

Дата добавления: 2015-11-16