(h) Quiz on Centrifugation (Test_Refinery_1)

 

Selection one answer for each question.

1.

The separation performance of a batch centrifugal can be improved by:

 

    a) Increasing the amount of massecuite fed into the centrifugal basket.

 

    b) Increasing the size of the crystals (MA) in the massecuite.

 

    c) Reducing the spin speed (RPM) of the centrifugal.

 

    d) Reducing the temperature of the massecuite.

2.

The separation performance of a batch centrifugal can be improved by:

 

    a) Increasing the time taken to remove the sugar from the centrifugal basket.

 

    b) Reducing the temperature of the feed massecuite.

 

    c) Reducing the size of sugar crysrals (MA) in the massecuite.

 

    d) Increasing the time at maximum spin speed (spin time) of the centrifugal.

3.

The separation performance of a centrifugal:

 

    a) Is not altered by changes to the sugar CV.

 

    b) Is improved by boiling sugar with a higher CV.

 

    c) Is improved by boiling sugar with a lower CV.

 

    d) Is best when the CV (Coefficient of Variation) equals 100.

4.

The normal hole size or slot width in a batch centrifugal screen is:

 

    a) Less than 1/5 (0.2) of the average size of the sugar crystals in the massecuite.

 

    b) About the same as the average size of the sugar crystals in the massecuite.

 

    c) More than 5 times bigger than the average size of the sugar crystals in the massecuite.

 

    d) The hole or slot size is not important.

5.

Massecuite that purge too fast during the feeding of a batch centrifugal need:

 

    a) Water to be added to the massecuite during feeding.

 

    b) An increased massecuite temperature.

 

    c) Faster basket speed during feeding and/or a slower massecuite filling rate.

 

    d) Lower basket speed during and/or a faster massecuite filling rate.

6.

When washing the sugar in a batch centrifugal cake it is best to:

 

    a) Apply enough wash water to dissolve at least 10% of the sugar crystals.

 

    b) Wash the cake at least twice during each centrifuge cy.

 

    c)Use a large amount of wash water to ensure the sugar is always well washed.

 

    d) Use the smallest amount of wash water necessary to get the correct sugar quality.

7.

For good washing in a batch centrifugal it its important to:

 

    a) Use wash water that is much cooler than the massecuite temperature.

 

    b) Wash only when the basket is spinning at a constant speed.

 

    c) Adjust the wash jets to spray on to the top half of the basket.

 

    d) Adjust the wash jets to give an even spray over the sugar layer in the centrifugal basket.

8.

Approximately how much sugar can be dissolved in 1 Lb (0.45kkg of water at 140F (60C):

 

    a) 0.2 Lb (0.09 kg).

 

    b) 0.5 Lb (0.23 kg).

 

    c) 1 Lb (0.45 kg).

 

    d) 2.5 Lb (1.1 kg).

9.

A sugar layer left in the basket of a batch centrifugal after discharging plowing) is:

 

    a) Bad, because it wears out the centrifugal screen.

 

    b) Bad, because it reduces the sugar yield from the massecuite and waste energy.

 

    c) Good, because it reduces crystal breakage.

 

    d) Good, because it increases the sugar yield from the massecuite and saves energy.

10.

The benefit of using as an electronic variable speed drive on a batch centrifugal are:

 

    a) A less complex drive system.

 

    b) A lower cost to purchase the centrifugal and smaller control panels.

 

    c) Lower energy consumption and a variable spin speed that can be altered to suit process conditions.

 

    d) More efficient washing of the sugar.

11.

In a battery of 5 batch centrifugals, each taking an average power of 35kw and a peak power of 200 kw, what is the average power taken by the centrifugal battery:

 

    a) 35 kw.

 

    b) 175 kw.

 

    c) 200 kw.

 

    d) 1000 kw.

12

The amount of sugar processed per hour in a batch centrifugal can be increased without reducing the sugar quality by:

 

    a) Increasing the quantity of wash water used.

 

    b) B) Reducing the time required to slow the basket from spin speed to discharge (plow) speed.

 

    c) Reducing the temperature of the massecuite.

 

    d) Reducing the spin time.

13.

Batch centrifugal are used to process refined massecuite. Low grade continuous centrifugals are not used because:

 

    a) Batch centrifugals are more reliable.

 

    b) Batch centrifugals use less electrical power and have a higher thruput per hour.

 

    c) Batch centrifugals give dryer sugar, better washing and do not break the crystals.

 

    d) Batch centrifugals use less wash water and the screens do not wear.

14.

The correct hole size or slot width in a continuous centrifugal screen is:

 

    a) About 5 times the average size of the sugar crystals in the massecuite.

 

    b) About 5 times the average size of the sugar crystals in the massecuite.

 

    c) About equal to the average size of the sugar crystals in the massecuite.

 

    d) Less than 1/5 (0.2) of the average size of the sugar crystals in the massecuite.

 

    e) The hole of slot size is not important.

15.

The screens of a continuous centrifugal should be checked:

 

    a) When the centrifugal basket is replaced.

 

    b) Once per year.

 

    c) Regularly to check for damage, slot wear and deposits at the back of the screen.

 

    d) When the centrifugal motor current increases.

16.

Heating the massecuite going into a continuous centrifugal is important because:

 

    a) It reduces the viscosity of the massecuite and improves the separation performance of the centrifugal.

 

    b) It reduces the power consumption if the continuous centrifugal.

 

    c) It increases the amount of sugar crystals in the massecuite.

 

    d) It increases the life of the centrifugal screens.

17.

A large molasses purity rise across a continuous centrifugal is:

 

    a) Good, because the purity of the sugar is higher and sugar is dryer.

 

    b) Good, because the purity of the molasses is increased.

 

    c) Bad, because less sugar has been dissolved.

 

    d) Bad, because there is more sugar in the molasses and less discharged as crystal.

18.

If the amount of massecuite fed to a continuous centrifugal is reduced then the color line in the basket:

 

    a) Moves towards the top of the basket (ie. Nearer to where the sugar is discharged from the basket).

 

    b) Moves towards the bottom of the basket (ie. Nearer to where the massecuite is fed on to the basket).

 

    c) Cannot be seen as it is covered by the massecuite.

 

    d) Does not change its position.

19.

When comparing the performance of a Batch Centrifugal and a High Grade Continuous Centrifugal (HGCC) on the same massecuite – the sugar discharged from the HGCC is:

 

    a) Wetter with a little more crystal damage.

 

    b) Wetter with a lot less crystal damage.

 

    c) Dryer with a little more crystal breakage.

 

    d) Dryer with a lot more crystal breakage.

20.

Centrifuge baskets should be checked for cracks and corrosion;

 

    a) Every 10 years.

 

    b) Every 5 years.

 

    c) Every year.

 

    d) Only when the vibration level on the centrifugal increases significantly.

21.

The best way to check a centrifugal basket for cracks is to:

 

    a) Undertake a visual inspection.

 

    b) Use crack detection methods such as dye penetrant, magnetic particle or ultrasonic inspection.

 

    c) Weigh the basket; a reduction in weight indicates a problem.

 

    d) Put the basket in a tank of water and look for bubbles.

 

     

 

     

 

     

 

    last updated 10/30/2017