Thermal efficiency of blast furnace stoves used for heating blast (air) may be about __________ percent.

Overfire burning in a furnace is a phenomenon characterised by

A. Supply of excess fuel

B. Supply of excess air

C. Burning carbon monoxide and other incombustible in upper zone of furnace by supplying more air

D. None of these

Which of the following variables does not affect the furnace capacity?

A. Size of the furnace

B. Gas velocity in furnace

C. Ratio of wall surface to surface of stock

D. None of these

__________ is an indirectly heated furnace.

A. Open hearth furnace

B. Muffle furnace

C. Soaking pit

D. Reheating furnace

Reducing atmosphere is maintained in a

A. Calcination kiln

B. Blast furnace

C. Soaking pit

D. L.D. converter