Patent EA-004437-B1 (EA)
Title: Method of operating a furnace
Inventor: HILTON MICHAEL
IPC: F23D99/00
Filed: 2001-11-15
Abstract: 1. A method of operating a furnace utilising a hydrogen-rich gas as furnace fuel, the furnace having a multiplicity of burners for burning fuel supplied thereto, which method comprises: (a) providing ignition means for lighting a flame at least one predetermined burner selected from the multiplicity of burners; (b) supplying to each of the multiplicity of burners an oxygen-containing gas and a combustible gas comprising a hydrocarbon gas in amounts capable of forming an ignitable mixture; (c) igniting a flame at the at least one predetermined burner; (d) allowing a flame to propagate from the at least one predetermined burner to the other burners of the multiplicity of burners; and (e) altering the composition of the combustible gas over a period of time so as to replace at least a major part of the hydrocarbon gas by a hydrogen-rich gas until an at least predominantly hydrogen flame is established at each of the multiplicity of burners. 2. A method according to claim 1, wherein the multiplicity of burners is arranged in an array in the furnace such that a flame ignited at the at least one predetermined burner can propagate to each of the other burners of the array. 3. A method according to claim 1 or claim 2, wherein the multiplicity of burners is mounted in a top portion of the furnace so that the flames from the multiplicity of burners extend downwards in operation of the furnace. 4. A method according to claim 1 or claim 2, wherein the multiplicity of burners is mounted in a bottom portion of the furnace so that the flames from the multiplicity of burners extend upwards in operation of the furnace. 5. A method according to any one of claims 1 to 3, wherein the furnace is a steam reformer furnace having a plurality of reformer tubes, each containing a charge of a steam reforming catalyst, the reformer tubes being arranged with their axes extending in a substantially vertical direction, wherein the multiplicity of burners is arranged in an array in a top portion of the furnace for heating the reformer tubes to a steam reforming temperature by means of flames extending downwards from the multiplicity of burners, and wherein a reactant mixture comprising a mixture of steam and a hydrocarbon feedstock to be reformed is passed upwardly under steam reforming conditions through the heated reformer tubes. 6. A method according to any one of claims 1 to 5, wherein the hydrocarbon gas comprises methane or natural gas. 7. A method according to any one of claims 1 to 6, wherein the furnace is a steam reformer furnace used to produce synthesis gas for a downstream synthesis plant and wherein the hydrogen-rich gas comprises an unreacted waste gas stream from the downstream synthesis plant. 8. A method according to claim 7, wherein the downstream synthesis plant is selected from a methanol synthesis plant, a Fischer Tropsch plant, and an oxo plant. 9. A method according to any one of claims 1 to 8, wherein the combustible gas supplied to the predetermined burner in step (d) is natural gas, wherein the oxygen-containing gas is air, and wherein the combustible gas and air are supplied to the multiplicity of burners in amounts sufficient to provide a mixture of about 4o by volume of natural gas and about 96% by volume of air at each of the multiplicity -of burners. 10. A method according to claim 9, wherein, after a flame has been established at each of the multiplicity of burners, the amount of natural gas supplied to the multiplicity of burners is increased, incrementally or continuously, to provide a mixture of about 4% by volume of natural gas and about 96% by volume of air. 11. A method according to any one of claims 1 to 10, wherein in step (d) the composition of the combustible gas is altered until the combustible gas substantially consists of the hydrogen-rich gas. 12. A method according to claim 11, wherein step (d) is effected over a period of from about 5 seconds to about 1 minute. 13. A method according to any one of claims 1 to 12, wherein the flow rate of hydrogen-rich gas during step (d) is reduced compared with the flow rate of hydrogen-rich gas during subsequent operation of the furnace. 14. A method according to claim 13, wherein the volume flow rate of the hydrogen-rich gas during step (d) is less than about 25% of the full operating flow rate of hydrogen-rich gas for which the furnace is designed.