Adaptive Control System for a Sulfur Recovery Process
AssigneeIMB Controls Inc.
InventorIgor Boiko
Life of this patent
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Abstract
Control of a process for producing free sulfur from hydrogen sulfide is accomplished by manipulating the flow rate of a feed stream containing oxygen to a furnace in such a manner that a desired proportion of the hydrogen sulfide fed to the furnace is converted to sulfur dioxide. Combustion of hydrogen sulfide is precisely controlled by the proposed system to maintain the hydrogen sulfide and sulfur dioxide concentrations in the tail gas at acceptable levels to minimize the environmental pollution.
Claims14
For a sulfur recovery plant, comprising a furnace (3), first conduit means (1) for passing a first feed stream (further referred to as acid gas) containing hydrogen sulfide (H2S) into said furnace, second conduit means (5) for passing a second feed stream of air into said furnace to convert part of the H2S contained in the first feed stream to sulfur dioxide (SO2), third conduit means (8) for withdrawing the resulting gaseous reaction mixture, containing free sulfur and unreacted H2S and SO2 gases, from said furnace, a catalytic sulfur converter means (9) to convert a portion of the unreacted H2S and SO2 gases contained in said gaseous reaction mixture to free sulfur;
- a sulfur removal means to remove the free sulfur from the resulting gaseous reaction mixture produced in said catalytic sulfur converter means, thereby producing a tail gas stream containing unreacted H2S and SO2,
- an apparatus comprising
- means for establishing a first signal representative (15) of the actual flow rate of said acid gas flowing through said first conduit means (13), (14) ;
- means for establishing a second signal representative of the actual flow rate of said air flowing through said second conduit means;
- means (22) for analyzing said tail gas stream flowing from said sulfur removal means and establishing a third signal representative (23) of the H2S concentration in said tail gas stream,
- means (24) for analyzing said tail gas stream flowing from said sulfur removal means and establishing a fourth signal representative (25) of the SO2 concentration in said tail gas stream,
- means (59) for establishing a fifth signal representative (26) of the required ratio of H2S concentration in said tail gas stream to SO2 concentration in said tail gas stream through operator entry or programming a default value (should normally be equal to 2),
- means for establishing a sixth signal representative (43) through multiplication of said third signal representative by said fifth signal representative and subtracting from it said forth signal representative;
- means for establishing a principal air flow demand signal (49) ;
- means for establishing a supplemental air flow demand signal (45) (where supplemental air flow demand can be positive, zero or negative quantity);
- means for establishing a total air flow demand signal (51) through summation of said principal air flow demand signal (49) and said supplemental air flow demand signal (45) ;
- and means for manipulating the flow rate of said air in response to said total air flow demand signal (51).
For a sulfur recovery plant, comprising a furnace (3), first conduit means (1) for passing a first feed stream (further referred to as acid gas) containing hydrogen sulfide (H2S) into said furnace, second conduit means (5) for passing a second feed stream of air into said furnace to convert part of the H2S contained in the first feed stream to sulfur dioxide (SO2), third conduit means (8) for withdrawing the resulting gaseous reaction mixture, containing free sulfur and unreacted H2S and SO2 gases, from said furnace, a catalytic sulfur converter means (9) to convert a portion of the unreacted H2S and SO2 gases contained in said gaseous reaction mixture to free sulfur;
- a sulfur removal means to remove the free sulfur from the resulting gaseous reaction mixture produced in said catalytic sulfur converter means, thereby producing a tail gas stream containing unreacted H2S and SO2,
- a method comprising the steps of:
- establishing a first signal representative (15) of the actual flow rate of said acid gas flowing through said first conduit means,
- establishing a second signal representative of the actual flow rate of said air flowing through said second conduit means,
- analyzing said tail gas stream flowing from said sulfur removal means and establishing a third signal representative (22) of the H2S concentration in said tail gas stream,
- analyzing said tail gas stream flowing from said sulfur removal means and establishing a fourth signal representative (24) of the SO2 concentration in said tail gas stream,
- establishing a fifth signal representative (26) of the required ratio of H2S concentration in said tail gas stream to SO2 concentration in said tail gas stream through operator entry or with default value (normally equal to 2),
- producing a sixth signal representative (43) through multiplication of said third signal representative by said fifth signal representative and subtracting from it said forth signal representative;
- producing a principal air flow demand signal (49) ;
- producing a supplemental air flow demand signal (45) (where supplemental air flow demand can be positive, zero or negative quantity);
- producing a total air flow demand signal (51) through summation of said principal air flow demand (49) and said supplemental air flow demand (45) ;
- and manipulating the flow rate of said air in response to said total air flow demand signal (51).
Dependencies are inferred from the claim text.