Question

What is the maximum permissible amount of ash on carbonization after coal is washed?

(a) 2%

(b) 6%

(c) 14%

(d) 21%

The question was asked by my college director while I was bunking the class.

This interesting question is from Cements, Metallurgical Coke and Synthetic Resins in chapter Miscellaneous Materials of Engineering Material & Metallurgy

Answer 1

Right option is (b) 6%

The explanation is: As coal contains foreign substances, they need to be washed to rid them of this impurity. This is done either in gravity or floatation type machine. This coal, after washing and draining, must not exhibit ash content of more than 6% on carbonization.