9 For a coal containing  and  ash, the coke produced per ton of coal would be

a) 750 kg with  ash

b) 800 kg with  ash

c) 650kg with  ash

d) 600 kg with  ash

10 The refractory lining for soaking pits must not have

a) Resistance to iron oxide attack

b) Low abrasion resistance

c) Good load bearing capacity

d) High abrasion resistance

11 The refractory materials for Hall-Heroult cell should be resistant to

a) Abrasion

b) thermal spalling

c) Molten aluminum attack

d) Mechanical shock

12 The sensible heat in flue gases is  fuel. If the efficiency limit and the relative efficiency of the regenerator is  and  respectively, then heat recovered in preheated air is

a) 11200kj

b) 9744kj

c) 12180kj

d) 11690kj