Furnace control

Apparatus comprising:

• a first furnace having at least first and second coils;
• a second furnace having at least first and second coils;
• means for splitting a first fluid stream into at least second, third, fourth and fifth fluid streams, for passing said second fluid stream through the first coil of said first furnace, for passing said third fluid stream through the second coil of said first furnace, for passing said fourth fluid stream through the first coil of said second furnace, and for passing said fifth fluid stream through the second coil of said second furnace;
• means for establishing a first signal representative of the actual pressure of said first fluid stream;
• means for establishing a second signal representative of the desired pressure of said first fluid stream;
• means for comparing said first signal and said second signal and for establishing a third signal which is responsive to the difference between said first signal and said second signal, wherein said third signal is scaled so as to be representative of any change in the flow rate of said second, third, fourth and fifth fluid streams required to maintain said first signal substantially equal to said second signal;
• means for establishing a fourth signal representative of the actual flow rate of said first fluid stream;
• means for multiplying said fourth signal by a splitting factor representative of the percentage of said first fluid stream which should pass through said first furnace to thereby establish a fifth signal representative of the desired total flow rate of fluid through said first furnace;
• means for establishing a sixth signal representative of the actual total flow rate of fluid through said first furnace;
• means for combining said fifth signal and said sixth signal to establish a seventh signal which is representative of any change in the flow rate of said second fluid stream and said third fluid stream required to maintain the actual total flow rate of fluid through said first furnace substantially equal to the desired total flow rate represented by said fifth signal;
• means for establishing an eighth signal representative of the actual temperature of said second fluid stream after said second fluid stream has passed through said first furnace;
• means for establishing a ninth signal representative of the desired temperature of both said second fluid stream after said second fluid stream has passed through said first furnace and said third fluid stream after said third fluid stream has passed through said first furnace;
• means for comparing said eighth signal and said ninth signal and for establishing a tenth signal which is responsive to the difference between said eighth signal and said ninth signal, wherein said tenth signal is scaled so as to be representative of the flow rate of said second fluid stream required to maintain said eighth signal substantially equal to said ninth signal;
• means for combining said third, seventh and tenth signals to establish an eleventh signal;
• means for manipulating the flow rate of said second fluid stream in response to said eleventh signal;
• means for establishing a twelfth signal representative of the actual temperature of said third fluid stream after said third fluid stream has passed through said first furnace;
• means for comparing said twelfth signal and said ninth signal and for establishing a thirteenth signal which is responsive to the difference between said twelfth signal and said ninth signal, wherein said thirteenth signal is scaled so as to be representative of the flow rate of said third fluid stream required to maintain said twelfth signal substantially equal to said ninth signal;
• means for combining said third, seventh and thirteenth signals to establish a fourteenth signal;
• means for manipulating the flow rate of said third fluid stream in response to said fourteenth signal;
• means for establishing a fifteenth signal representative of the actual temperature of said fourth fluid stream after said fourth fluid stream has passed through said second furnace;
• means for establishing a sixteenth signal representative of the desired temperature of both said fourth fluid stream after said fourth fluid stream has passed through said second furnace and said fifth fluid stream after said fifth fluid stream has passed through said second furnace;
• means for comparing said fifteenth signal and said sixteenth signal and for establishing a seventeenth signal which is responsive to the difference between said fifteenth signal and said sixteenth signal, wherein said seventeenth signal is scaled so as to be representative of the flow rate of said fourth fluid stream required to maintain said fifteenth signal substantially equal to said sixteenth signal;
• means for combining said third signal and said seventeenth signal to establish an eighteenth signal;
• means for manipulating the flow rate of said fourth fluid stream in response to said eighteenth signal;
• means for establishing a nineteenth signal representative of the actual temperature of said fifth fluid stream after said fifth fluid stream has passed through said second furnace;
• means for comparing said nineteenth signal and said sixteenth signal and for establishing a twentieth signal which is responsive to the difference between said nineteenth signal and said sixteenth signal, wherein said twentieth signal is scaled so as to be representative of the flow rate of said fifth fluid stream required to maintain said nineteenth signal substantially equal to said sixteenth signal;
• means for combining said third signal and said twentieth signal to establish a twenty-first signal;
• and
• means for manipulating the flow rate of said fifth fluid stream in response to said twenty-first signal.

Apparatus comprising:

• a first furnace having at least first and second coils;
• a second furnace having at least first and second coils;
• means for splitting a first fluid stream into at least second, third, fourth and fifth fluid streams, for passing said second fluid stream through the first coil of said first furnace, for passing said third fluid stream through the second coil of said first furnace, for passing said fourth fluid stream through the first coil of said second furnace, and for passing said fifth fluid stream through the second coil of said second furnace;
• means for establishing a first signal representative of the flow rate of said first fluid stream;
• means for multiplying said first signal by a splitting factor representative of the percentage of said first fluid stream which it is desired to pass through said first furnace to thereby establish a second signal representative of the desired total flow rate of fluid through said first furnace;
• means for establishing a third signal representative of the actual total flow rate of fluid through said first furnace;
• means for combining said second signal and said third signal to establish a fourth signal which is representative of any change in the flow rate of said second fluid stream and said third fluid stream required to maintain the actual total flow rate of fluid through said first furnace substantially equal to the desired total flow rate represented by said second signal;
• means for establishing a fifth signal representative of the actual temperature of said second fluid stream after said second fluid stream has passed through said first furnace;
• means for establishing a sixth signal representative of the desired temperature of both said second fluid stream after said second fluid stream has passed through said first furnace and said third fluid stream after said third fluid stream has passed through said first furnace;
• means for comparing said fifth signal and said sixth signal and for establishing a seventh signal which is responsive to the difference between said fifth signal and said sixth signal, wherein said seventh signal is scaled so as to be representative of the flow rate of said second fluid stream required to maintain said fifth signal substantially equal to said sixth signal;
• means for combining said third signal and said seventh signal establish an eighth signal;
• means for manipulating the flow rate of said second fluid stream in response to said eighth signal;
• means for establishing a ninth signal representative of the actual temperature of said third fluid stream after said third fluid stream has passed through said first furnace;
• means for comparing said ninth signal and said sixth signal and for establishing a tenth signal which is responsive to the difference between said ninth signal and said sixth signal, wherein said tenth signal is scaled so as to be representative of the flow rate of said third fluid stream required to maintain said ninth signal substantially equal to said sixth signal;
• means for combining said third signal and said tenth signal to establish an eleventh signal;
• means for manipulating the flow rate of said third fluid stream in response to said eleventh signal;
• means for establishing a twelfth signal representative of the actual temperature of said fourth fluid stream after said fourth fluid stream has passed through said second furnace;
• means for establishing a thirteenth signal representative of the desired temperature of both said fourth fluid stream after said fourth fluid stream has passed through said second furnace and said fifth fluid stream after said fifth fluid stream has passed through said second furnace;
• means for comparing said twelfth signal and said thirteenth signal and for establishing a fourteenth signal which is responsive to the difference between said twelfth signal and said thirteenth signal, wherein said fourteenth signal is scaled so as to be representative of the flow rate of said fourth fluid stream required to maintain said twelfth signal substantially equal to said thirteenth signal;
• means for manipulating the flow rate of said fourth fluid stream in response to said fourteenth signal;
• means for establishing a fifteenth signal representative of the actual temperature of said fifth fluid stream after said fifth fluid stream has passed through said second furnace;
• means for comparing said fifteenth signal and said thirteenth signal and for establishing a sixteenth signal which is responsive to the difference between said fifteenth signal and said thirteenth signal, wherein said sixteenth signal is scaled so as to be representative of the flow rate of said fifth fluid stream required to maintain said fifteenth signal substantially equal to said thirteenth signal;
• and
• means for manipulating the flow rate of said fifth fluid stream in response to said sixteenth signal.

A method for controlling the pressure of a first fluid stream which is split into second and third fluid streams with the second fluid stream being passed through the first coil of a furnace and the third fluid stream being passed through the second coil of said furnace and for controlling the temperature of said second fluid stream after said second fluid stream has passed through said furnace and the temperature of said third fluid stream after said third fluid stream has passed through said furnace, said method comprising the steps of:

• establishing a first signal repesentative of the actual pressure of said first fluid stream;
• establishing a second signal representative of the desired pressure of said first fluid stream;
• comparing said first signal and said second signal and establishing a third signal which is responsive to the difference between said first signal and said second signal, wherein said third signal is scaled so as to be representative of any change in the flow rate of said second and third fluid streams required to maintain said first signal substantially equal to said second signal;
• establishing a fourth signal representative of the actual temperature of said second fluid stream after said second fluid stream has passed through said furnace;
• establishing a fifth signal representative of the desired temperature of both said second fluid stream after said second fluid stream has passed through said furnace and said third fluid stream after said third fluid stream has passed through said furnace;
• comparing said fourth signal and said fifth signal and establishing a sixth signal which is responsive to the difference between said fourth signal and said fifth signal, wherein said sixth signal is scaled so as to be representative of the flow rate of said second fluid stream required to maintain said fourth signal substantially equal to said fifth signal;
• combining said third signal and said sixth signal to establish a seventh signal;
• manipulating the flow rate of said second fluid stream in response to said seventh signal;
• establishing an eighth signal representative of the actual temperature of said third fluid stream after said third fluid stream has passed through said furnace;
• comparing said eighth signal and said fifth signal and establishing a ninth signal which is responsive to the difference between said eighth signal and said fifth signal, wherein said ninth signal is scaled so as to be representative of the flow rate of said third fluid stream required to maintain said eighth signal substantially equal to said fifth signal;
• combining said third signal and said ninth signal to establish a tenth signal;
• and
• manipulating the flow rate of said third fluid stream in response to said tenth signal.

A method for controlling the pressure of a first fluid stream which is split into second, third, fourth and fifth fluid streams with the second fluid stream being passed through the first coil of a first furnace, the third fluid stream being passed through the second coil of said first furnace, the fourth fluid stream being passed through the first coil of a second furnace, and the fifth fluid stream being passed through the second coil of said second furnace, for controlling the temperature of said second, third, fourth and fifth fluid streams after said second, third, fourth and fifth fluid streams have passed through said first and second furnaces respectively, and for controlling the percentage of said first fluid stream which is passed through said first furnace, said method comprising the steps of:

• establishing a first signal representative of the actual pressure of said first fluid stream;
• establishing a second signal representative of the desired pressure of said first fluid stream;
• comparing said first signal and said second signal and establishing a third signal which is responsive to the difference between said first signal and said second signal, wherein said third signal is scaled so as to be representative of any change in the flow rate of said second, third, fourth and fifth fluid streams required to maintain said first signal substantially equal to said second signal;
• establishing a fourth signal representative of the actual flow rate of said first fluid stream;
• multiplying said fourth signal by a splitting factor representative of the percentage of said first fluid stream which should pass through said first furnace to thereby establish a fifth signal representative of the desired total flow rate of fluid through said first furnace;
• establishing a sixth signal representative of the actual total flow rate of fluid through said first furnace;
• combining said fifth signal and said sixth signal to establish a seventh signal which is representative of any change in the flow rate of said second fluid stream and said third fluid stream required to maintain the actual total flow rate of fluid through said first furnace substantially equal to the desired total flow rate represented by said fifth signal;
• establishing an eighth signal representative of the actual temperature of said second fluid stream after said second fluid stream has passed through said first furnace;
• establishing a ninth signal representative of the desired temperature of both said second fluide stream after said second fluid stream has passed through said first furnace and said third fluid stream after said third fluid stream has passed through said first furnace;
• comparing said eighth signal and said ninth signal and establishing a tenth signal which is responsive to the difference between said eighth signal and said ninth signal, wherein said tenth signal is scaled so as to be representative of the flow rate of said second fluid stream required to maintain said eighth signal substantially equal to said ninth signal;
• combining said third, seventh and tenth signals to establish an eleventh signal;
• manipulating the flow rate of said second fluid stream in response to said eleventh signal;
• establishing a twelfth signal representative of the actual temperature of said third fluid stream after said third fluid stream has passed through said first furnace;
• comparing said twelfth signal and said ninth signal and establishing a thirteenth signal which is responsive to the difference between said twelfth signal and said ninth signal, wherein said thirteenth signal is scaled so as to be representative of the flow rate of said third fluid stream required to maintain said twelfth signal substantially equal to said ninth signal;
• combining said third, seventh and thirteenth signals to establish a fourteenth signal;
• manipulating the flow rate of said third fluid stream in response to said fourteenth signal;
• establishing a fifteenth signal representative of the actual temperature of said fourth fluid stream after said fourth fluid stream has passed through said second furnace;
• establishing a sixteenth signal representative of the desired temperature of both said fourth fluid stream after said fourth fluid stream has passed through said second furnace and said fifth fluid stream after said fifth fluid stream has passed through said second furnace;
• comparing said fifteenth signal and said sixteenth signal and establishing a seventeenth signal which is responsive to the difference between said fifteenth signal and said sixteenth signal, wherein said seventeenth signal is scaled so as to be representative of the flow rate of said fourth fluid stream required to maintain said fifteenth signal substantially equal to said sixteenth signal;
• combining said third signal and said seventeenth signal to establish an eighteenth signal;
• manipulating the flow rate of said fourth fluid stream in response to said eighteenth signal;
• establishing a nineteenth signal representative of the actual temperature of said fifth fluid stream after said fifth fluid stream has passed through said second furnace;
• comparing said nineteenth signal and said sixteenth signal and establishing a twentieth signal which is responsive to the difference between said nineteenth signal and said sixteenth signal, wherein said twentieth signal is scaled so as to be representative of the flow rate of said fifth fluid stream required to maintain said nineteenth signal substantially equal to said sixteenth signal;
• combining said third signal and said twentieth signal to establish a twenty-first signal;
• and
• manipulating the flow rate of said fifth fluid stream in response to said twenty-first signal.

In a process in which a first fluid stream is split into second, third, fourth and fifth fluid streams, with the second fluid stream being passed through the first coil of a first furnace, the third fluid stream being passed through the second coil of said first furnace, the fourth fluid stream being passed through the first coil of a second furnace and the fifth fluid stream being passed through the second coil of said second furnace, a method for controlling the temperature of said second, third, fourth and fifth fluid streams after said second, third, fourth and fifth fluid streams have passed through said first and second furnaces respectively and for controlling the percentage of said first fluid stream which is passed through said first furnace, said method comprising the steps of:

• establishing a first signal representative of the flow rate of said first fluid stream;
• multiplying said first signal by a splitting factor representative of the percentage of said first fluid stream which it is desired to pass through said first furnace to thereby establish a second signal representative of the desired total flow rate of fluid through said first furnace;
• establishing a third signal representative of the actual total flow rate of fluid through said first furnace;
• combining said second signal and said third signal to establish a fourth signal which is representative of any change in the flow rate of said second fluid stream and said third fluid stream required to maintain the actual total flow rate of fluid through said first furnace substantially equal to the desired total flow rate represented by said second signal;
• establishing a fifth signal representative of the actual temperature of said second fluid stream after said second fluid stream has passed through said first furnace;
• establishing a sixth signal representative of the desired temperature of both said second fluid stream after said second fluid stream has passed through said first furnace and said third fluid stream after said third fluid stream has passed through said first furnace;
• comparing said fifth signal and said sixth signal and establishing a seventh signal which is responsive to the difference between said fifth signal and said sixth signal, wherein said seventh signal is scaled so as to be representative of the flow rate of said second fluid stream required to maintain said fifth signal substantially equal to said sixth signal;
• combining said third signal and said seventh signal establish an eighth signal;
• manipulating the flow rate of said second fluid stream in response to said eighth signal;
• establishing a ninth signal representative of the actual temperature of said third fluid stream after said third fluid stream has passed through said first furnace;
• comparing said ninth signal and said sixth signal and establishing a tenth signal which is responsive to the difference between said ninth signal and said sixth signal, wherein said tenth signal is scaled so as to be representative of the flow rate of said third fluid stream required to maintain said ninth signal substantially equal to said sixth signal;
• combining said third signal and said tenth signal to establish an eleventh signal;
• manipulating the flow rate of said third fluid stream in response to said eleventh signal;
• establishing a twelfth signal representative of the actual temperature of said fourth fluid stream after said fourth fluid stream has passed through said second furnace;
• establishing a thirteenth signal representative of the desired temperature of both said fourth fluid stream after said fourth fluid stream has passed through said second furnace and said fifth fluid stream after said fifth fluid stream has passed through said second furnace;
• comparing said twelfth signal and said thirteenth signal and establishing a fourteenth signal which is responsive to the difference between said twelfth signal and said thirteenth signal, wherein said fourteenth signal is scaled so as to be representative of the flow rate of said fourth fluid stream required to maintain said twelfth signal substantially equal to said thirteenth signal;
• manipulating the flow rate of said fourth fluid stream in response to said fourteenth signal;
• establishing a fifteenth signal representative of the actual temperature of said fifth fluid stream after said fifth fluid stream has passed through said second furnace;
• comparing said fifteenth signal and said thirteenth signal and establishing a sixteenth signal which is responsive to the difference between said fifteenth signal and said thirteenth signal, wherein said sixteenth signal is scaled so as to be representative of the flow rate of said fifth fluid stream required to maintain said fifteenth signal substantially equal to said thirteenth signal;
• and
• manipulating the flow rate of said fifth fluid stream in response to said sixteenth signal.