NOVELTY - The refractory lining (35) defines a throat (56) communicating with bottom of a cylindrical chamber (25). The throat has a tapered portion (56a) tapering at 50 degrees angle to horizontal to a cylindrical portion (56b) of diameter less than that of cylindrical chamber, and a lower portion (56c) increasing in diameter below cylindrical portion. The lining defines a multiplicity of air inlet ducts communicating with cylindrical chamber above throat. A grate (44) with movable elements is below refractory lining. An outlet duct (54) extracts gas from gasifier below refractory lining.    USE - Updraft/downdraft gasifier used in gasification plant (claimed) such as waste wood gasification plant for processing biomass such as straw, bagasse, or other agricultural wastes, waste paper, or wood, by gasification process.    ADVANTAGE - Due to the pressure drop produced by the fan, air enters each heat transfer jacket through the inlet ports, and flows circumferentially around the heat transfer jacket, through the pipe and the inlet port, and through the tubes into the gasification chamber. Thus the air is preheated before it reaches the gasification chamber can be ensured, the greater efficiency of the gasifier can be achieved so that the ability to treat damp material is improved, and tar formation is reduced. The safety for operators of the gasifier can be enhanced, so that ventilation in the immediate vicinity of the gasifier can be ensured. Thus the temperature of some of the exposed surfaces of the gasifier can be reduced. The blowback protection is provided in the unlikely event of a deflagration within the gasifier.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for gasification plant.    DESCRIPTION OF DRAWING(S) - The drawing shows a side sectional view of the gasifier in the plant.    Cylindrical chamber (25)    Refractory lining (35)    Grate (44)    Outlet duct (54)    Throat (56)    Tapered portion (56a)    Cylindrical portion (56b)    Lower portion (56c)