Patent ID: 8529117

Claim:
A mixing apparatus for mixing a first gas and a second gas, which mixing apparatus comprises: i) a linear first tube for supply of the first gas, said first tube comprising an inlet for the first gas at an upstream end and tapering to form a nozzle at a downstream end, said nozzle having an opening of internal area of less than 10 mm 2 at the outlet for the first gas and providing a pressure drop in the supply of the first gas through said first tube, and ii) a linear second tube for supply of the second gas, said second tube comprising an inlet for the second gas at an upstream end, a first portion which forms an annulus around the outer surface of the first tube upstream of the nozzle, which annulus has a length of 5 to 50 mm and a cross-section area of 2 to 10 times the area of the opening of the nozzle and which acts to provide a pressure drop in the supply of the second gas through said second tube, and a second portion which forms a sheath around the nozzle of the first tube and which forms an area of expanded cross-section compared to the annulus, and wherein: a) the dimensions of the nozzle and annulus are such that the pressure drops caused in the supply of the first and second gases are in a ratio of 2:1 to 1:2, b) the angle of the external taper of the nozzle is less than 12° compared to the longitudinal axis of the first tube, and c) any change in diameter of second tube in the second portion takes place by a slope or a taper with an angle of less than 12° compared to the longitudinal axis of the second tube.