Abstract: At least during some part-load operation of a gas turbine wherein a fuel gas is combusted with air with the formation of a flame and the combustion products are let down through a turbine, the fuel gas comprises the product of a stage of catalytic autothermal steam reforming of a light hydrocarbon feedstock gas and the amount of air fed to the gas turbine combuster, relative to the amount of hydrocarbon fed to the catalytic autothermal steam reforming stage, is greater than the maximum amount of air that enables a flame to be sustained in said combustor if that amount of hydrocarbon were to be fed directly to the combustor.

Abstract: Apparatus for mixing or otherwise agitating fluid material comprises an elongated vessel (1) to contain the material, means (6, 7, 9, 10) to impose oscillatory motion upon the material in a lengthwise direction, and a plurality of stationary obstacles (19, 35) mounted on the inner wall (2) of the vessel and arranged in sequence lengthwise. The obstacles present sharp ridge-form tips (20, 37) each ridge pointing in a direction (30) at right angles to that of the oscillating motion. Each adjacent pair of obstacles and the length of vessel wall between them define a trough-shaped space (26) in which the oscillating motion repeatedly forms vortices and then ejects those vortices vigorously into the remainder of the fluid outside the trough, so promoting the agitation of that fluid. The invention applies particularly to cylindrical vessels in which the obstacles are ring-shaped (19) or are constituted by the successive turns of a helix (35).