Control of bed height in a fluidized bed gasification system

Claim 1

A method of controlling the bed height in a fluidized bed apparatus comprising a vessel in which a particulate material is fluidized by fluidizing gas flowing upwardly through said vessel, and wherein the flow of at least one of said particulate material and said gas are controlled by a control signal deduced from pressure detectors associated with said vessel so as to generate a predetermined bed height, characterized in that the interior of the vessel is divided into a plurality of adjacent zones and the gas pressure differential across each zone is periodically measured, a predetermined number of the latest pressure differential is averaged for each of said zones to compute an average differential pressure, the average differential pressure is divided by the vertical length of the respective zone to calculate a fluidized bed density corresponding to each zone, a predetermined number of the most recent fluidized bed densities calculated for each of said zones is averaged to obtain an average fluidized bed density for each zone, wherein, however, values for any zones for which the most recently calculated average fluidized bed density is non-positive are disregarded and the lowermost zone which is also adjacent to a zone for which the most recently calculated average bed density is non-positive is reserved while, for all remaining zones a weighting factor for each zone is calculated by the formula: where zone A is adjacent to and above zone B, the height of the bed within the reserved zone is then calculated by dividing the fluidized bed density of the reserved zone by the fluidized bed density of the zone adjacent to and below the reserved zone, and the vertical height of the reserved zone and the last weighting factor calculated for the reserved zone, and said signal control is generated to be representative of said height of said bed within said reserved zone.

Claim 2

A method of controlling the bed height in a fluidized bed apparatus comprising a vessel in which a particulate material is fluidized by fluidizing gas flowing upwardly through said vessel, and wherein the flow of at least one of said particulate material and said gas are controlled by a control signal deduced from pressure detectors associated with said vessel so as to generate a predetermined bed height, characterized in that the interior of the vessel is divided into a plurality of adjacent zones and the gas pressure differential across each zone is periodically measured, a predetermined number of the latest pressure differential is averaged for each of said zones to compute an average differential pressure, the average differential pressure is divided by the vertical length of the respective zone to calculate a fluidized bed density corresponding to each zone, a predetermined number of the most recent fluidized bed densities calculated for each of said zones is averaged to obtain an average fluidized bed density for each zone, wherein, however, values for any zones for which the most recently calculated average fluidized bed density is non-positive are disregarded and the lowermost zone which is also adjacent to a zone for which the most recently calculated average bed density is non-positive is reserved while, for all remaining zones a weighting factor for each zone is calculated by the formula: where zone A is adjacent to and above zone B, the height of the bed within the reserved zone is then calculated by dividing the fluidized bed density of the reserved zone by the fluidized bed density of the zone adjacent to and below the reserved zone, and the vertical height of the reserved zone and the last weighting factor calculated for the reserved zone, and said signal control is generated to be representative of said height of said bed within said reserved zone.