Patent ID: 7931466
Filing Date: 2011-04-26
Classification: F23G

Abstract:
1. In a process wherein a plant gas stream is combusted in a flare assembly, said plant gas stream having a flow rate and an initial actual Btu content, said plant gas stream having a predetermined minimum Btu content target value to be met before it is combusted in said flare assembly, said initial actual Btu content being at least one of an essentially steady state Btu content and a dynamic Btu content that randomly moves above and below said predetermined minimum Btu content target value, the improvement comprising providing a source of fuel that can be added to said plant gas stream at least one addition point, measuring the flow rate of said plant gas stream downstream of said at least one addition point, periodically sampling said plant gas stream downstream of said at least one addition point, analyzing each said sample for its initial actual Btu content, said sampling and analyzing steps being conducted a finite number of times over at least one predetermined time period, selecting a steady state Btu content set point and a dynamic Btu content set point, making a first comparison of the analysis results of the most recent of said initial actual Btu contents with said steady state set point and determining the amount of fuel required to be added, if any, to said plant gas stream to raise the Btu content of that stream at least to said steady state set point, obtaining a historical minimum Btu content for said flare assembly based on the operation of said assembly over a time period, averaging the results of the analyses of a plurality of recent initial actual Btu contents plus said historical minimum Btu content, making a second comparison of said averaging results with said dynamic set point and determining the amount of fuel required to be added, if any, to said plant gas stream to raise the Btu content of that stream at least to said dynamic set point, and adding fuel to said plant gas stream based on the larger fuel requirement of said first and second comparisons.