Abstract: A downdraft gasifier has a gas producer. The gas producer includes an introducing portion provided in an upper portion for introducing solid biomass fuel 4, an air inlet 17 provided in a central portion, a fire grate 14 provided in a lower portion, and a product gas delivery portion provided below the fire grate. In this gasifier, there are provided fire-proofball laid layers in which a plurality of metal balls 15 are disposed in layers on the fire grate substantially uniform, and a preheating unit (such as a burner) for preheating the fire-proof balls. The metal balls 15 are preheated in advance to a predetermined temperature ranging from 500° C. to 800° C. before the solid biomass fuel is introduced into the producer. After that, the solid biomass fuel 4 is introduced into the producer, and gas produced in the producer is delivered from a portion below the fire grate.

Abstract: A method of controlling the rolling efficiency in a continuous hot rolling process. A rolling schedule and a conveying schedule are determined on a mill line for the slabs arranged in succession based on an aimed extraction temperature of the slabs from a heating furnace and a predetermined temperature at the exit of a finish mill. A minimum extraction pitch is calculated for the slabs from the heating furnace under restriction of the side of the mill line, and a different minimum extraction pitch is calculated for slabs from the heating furnace under restriction of the side of the heating furnace based on slab temperature charged to the heating furnace and the aimed extraction temperature. An optimum extraction pitch is determined for slabs from the heating furnace by comparing both of the minimum extraction pitches. With such a method, the continuous hot rolling operation is carried out under an optimum condition.