Temperature control method and apparatus for the air supply in PFBC plants

• US 5,435,122 A
• Filed: 03/11/1994
• Issued: 07/25/1995
• Est. Priority Date: 09/13/1991
• Status: Expired due to Term

• Current Assignee: ABB Carbon AB
• Original Assignee: ABB Carbon AB
• Inventors: Kyrklund, Ben, Novin, Saideh, Ahlin, Roger
• Primary Examiner(s): Casaregola, Louis J.
• Application Number:
  US08/204,348
• Time in Patent Office: 501 Days
• Field of Search: 60/39.02, 60/39.464, 60/728, 415/179
• US Class Current: 60/779
• CPC Class Codes: F01K 23/062 the combustion bed being pressurised pressurised fluid bed combustion per se F23C10/16
• CPC Class Codes: F02C 7/143 before or between the compressor stages

Abstract

A method for temperature control of an air supply in PFBC plants which comprise a low-pressure unit including a low-pressure compressor and a low-pressure turbine, a high-pressure unit including a high-pressure compressor and a high-pressure turbine, wherein air is sucked into the low-pressure compressor whereupon the air is passed via an intermediate cooler, which is traversed by water, into the high-pressure compressor and then into a boiler of the plant. The method includes measuring in a temperature control system a temperature of the air both upstream and downstream of the high-pressure compressor, comparing the two measured temperature values and corresponding set values for the respective upstream and downstream temperature, and activating, based only on one of the comparisons, a shunt valve of an intermediate cooler. The control signal of the shunt valve consists of the output signal from the temperature control system.

Claims

1. A method for temperature control of an air supply in PFBC plants which comprise a low-pressure unit including a low-pressure compressor and a low-pressure turbine, a high-pressure unit including a high-pressure compressor and a high-pressure turbine, wherein air is sucked into the low-pressure compressor whereupon the air is passed via an intermediate cooler, which is traversed by water, into the high-pressure compressor and then into a boiler of the plant, said method comprising the steps of:

measuring in a temperature control system a temperature of the air both upstream and downstream of the high-pressure compressor;

comparing the two measured temperature values and corresponding set values for the respective upstream and downstream temperature; and

activating, based only on one of the comparisons, a shunt valve of an intermediate cooler, the control signal of which consists of the output signal from the temperature control system.

2. A method for temperature control according to claim 1, wherein the set and actual values are compared in individual controllers and wherein the outputs of the controllers are inputted to a maximum selector, the output signal of which corresponds to the signal from the temperature control system.

3. A method for temperature control according to claim 2, wherein with the aid of a reduced value of the output signal from the temperature control system, a follow-up set value is formed, the follow-up set value is transmitted to the controllers which are connected such that the output signal from that controller whose output is not active is reduced toward a signal corresponding to the output signal from a controller which is active.

4. A method for temperature control according to claim 2, wherein the set and actual values for a downstream controller are compared in a first summator and the set and actual values for an upstream controller are compared in a second summator, wherein the output signals of the two summators are supplied to a third summator, and wherein a controller which is to be activated is determined by a polarity of the output signal transmitted by the third summator, the output signal is fed from the third summator to a limiter and then to polarity controlled selectors, the set and actual values for the controller which is to be activated together with a proportional value and an integral value determined for the respective control are supplied to a common controller, an output signal of the common controller corresponds to the output signal from the temperature control system.

5. A method for temperature control according to claim 1, wherein the control signal from the temperature control system for control of the shunt valve is replaced by a set value for manual control of the shunt valve.

6. A method for temperature control according to claim 1, wherein the control signal from the temperature control system for control of the shunt valve is replaced by a set value for control of the shunt valve when a pressure drop across the water side of the intermediate cooler is below a certain minimum value.

7. A device for temperature control of an air supply in PFBC plants which comprise a low-pressure unit including a low-pressure compressor and a low-pressure turbine, a high-pressure unit including a high-pressure compressor and a high-pressure turbine and an intermediate cooler located in the air passage between the low-pressure and high-pressure compressors, said device comprising:

measuring means for measuring a temperature of air upstream and downstream of the high-pressure compressor; and

controlling means for comparing the measured temperatures and corresponding set values for the upstream and downstream temperatures and for forming and supplying a control signal to the intermediate cooler, the control signal determining the cooling effect of the intermediate cooler via a shunt valve.