Question

Destoner is a form of separator that separates the:

(A) Feed material into two fractions as per the difference in shape factor

(B) Feed material into heavy particles from the lighter particles

(C) Feed material into two fractions only as per the difference in specific gravity

(D) Feed material into multiple fractions as per the difference in specific gravity

Choose the correct answer from the options given below:

• (A) only.
• (B) and (C) only.
• (C) only.
• (B) and (D) only.

Hint:

Recall what property difference a destoner actually uses, and how many output streams it produces.

Answer 1

The Correct Option is B

Step 1: A destoner is a grain cleaning machine used to remove heavy impurities such as stones, clods, and metal pieces from grain. It works purely on the difference in specific gravity (density) between the grain and the impurities, not on shape.

Step 2: The feed is spread on a vibrating, inclined deck through which air is blown upward. This fluidizes the material so it stratifies by density, the lighter grain rises to the top of the bed and moves toward the lower end of the deck, while the heavier stones sink to the bottom and are carried up the vibrating deck to a separate outlet.

Step 3: This gives exactly two output streams, a light (grain) fraction and a heavy (stone) fraction. So statement (C), that it separates feed into two fractions based only on specific gravity, is correct.

Step 4: Statement (B), that it separates heavy particles from lighter particles, describes the same stratification in plain words and is also correct.

Step 5: Statement (A) is wrong because separating by shape factor is the job of a disc separator or indent cylinder separator, not a destoner. Statement (D) is wrong because a destoner gives only two fractions, an accept stream and a reject stream, never multiple density grades.

So both (B) and (C) correctly describe a destoner, giving answer option 2.