Control schemes for thermal management of power production systems and methods

A power production plant comprising:

• a turbine;
• a power generator;
• a heat exchange unit (HEU);
• one or more compressors or pumps;
• and
• a control unit;
• wherein the HEU is configured for heat exchange between a plurality of streams passing between a first HEU end having a first operational temperature and a second HEU end having a second, lower operational temperature, the plurality of streams comprising at least a first stream passing from the first HEU end toward the second HEU end and at least a second stream passing from the second HEU end toward the first HEU end;
• wherein the HEU includes a recirculation line and a recirculation valve that are interposed between a turbine exhaust stream and a recycle stream or are interposed between a turbine exhaust stream and an oxidant stream;
• and
• wherein the control unit is configured to receive a signal defining an operating condition of the power production plant and, based thereon, output one or more signals effective to one or both of:
• divert a portion of one or more of the plurality of streams around a section of the HEU;
• and
• cause the recirculation line and the recirculation valve to implement flow of fluid between one of the at least a first stream and one of the at least a second stream.

A method for control of a power production plant, the method comprising:

• passing a plurality of streams through a heat exchange unit (HEU) defining a first HEU end having a first operational temperature and a second HEU end having a second, lower operational temperature, the plurality of streams comprising at least a first stream passing from the first HEU end toward the second HEU end and at least a second stream passing from the second HEU end toward the first HEU end so that the at least a first stream is cooled and the at least a second stream is heated;
• and
• implementing a control function that alters a mass flow of one or more of the plurality of streams passing through the HEU, the control function being effective to:
• cause a portion of the at least a first stream to be passed to the at least a second stream so that a mass flow of the at least a second stream is increased while passing through a section of the HEU;
• or
• cause a portion of the at least a second stream to be passed to the at least a first stream so that a mass flow of the at least a first stream is increased while passing through a section of the HEU.

A method for control of a power production plant, the method comprising:

• passing a plurality of streams through a heat exchange unit (HEU) defining a first HEU end having a first operational temperature and a second HEU end having a second, lower operational temperature, the plurality of streams comprising at least a first, higher temperature stream passing from the first HEU end toward the second HEU end and at least a second, lower temperature stream passing from the second HEU end toward the first HEU end so that the at least a first, higher temperature stream is cooled and the at least a second, lower temperature stream is heated;
• and
• implementing a control function that causes a portion of the at least a first, higher temperature stream to bypass a section of the HEU so that a mass flow of the at least a first, higher temperature stream through the section that is bypassed is reduced, wherein the control function is implemented in response to a signal defining an operating condition of the power production plant;
• wherein the at least a second, lower temperature stream is a recycle stream that is being heated in the HEU, wherein the at least a first, higher temperature stream is an exhaust stream being cooled in the HEU, and wherein a portion of the recycle stream is passed to the exhaust stream such that a mass flow of the exhaust stream passing through a section of the HEU is increased.

A method for control of a power production plant, the method comprising:

• passing a plurality of streams through a heat exchange unit (HEU) defining a first HEU end having a first operational temperature and a second HEU end having a second, lower operational temperature, the plurality of streams comprising at least a first, higher temperature stream passing from the first HEU end toward the second HEU end and at least a second, lower temperature stream passing from the second HEU end toward the first HEU end so that the at least a first, higher temperature stream is cooled and the at least a second, lower temperature stream is heated;
• and
• implementing a control function that causes a portion of the at least a first, higher temperature stream to bypass a section of the HEU so that a mass flow of the at least a first, higher temperature stream through the section that is bypassed is reduced, wherein the control function is implemented in response to a signal defining an operating condition of the power production plant;
• wherein the at least a second, lower temperature stream is an oxidant stream that is being heated in the HEU, wherein the at least a first, higher temperature stream is an exhaust stream being cooled in the HEU, and wherein a portion of the oxidant stream is passed to the exhaust stream such that a mass flow of the exhaust stream passing through a section of the HEU is increased.

A method for control of a power production plant, the method comprising:

• passing a plurality of streams through a heat exchange unit (HEU) defining a first HEU end having a first operational temperature and a second HEU end having a second, lower operational temperature, the plurality of streams comprising at least a first, higher temperature stream passing from the first HEU end toward the second HEU end and at least a second, lower temperature stream passing from the second HEU end toward the first HEU end so that the at least a first, higher temperature stream is cooled and the at least a second, lower temperature stream is heated;
• implementing a control function that causes a portion of the at least a first, higher temperature stream to bypass a section of the HEU so that a mass flow of the at least a first, higher temperature stream through the section that is bypassed is reduced, wherein the control function is implemented in response to a signal defining an operating condition of the power production plant;
• and
• adding heat to one or more of the plurality of streams passing through the HEU, wherein the heat is added at an intermediate temperature range within the HEU at a point that is positioned between the first HEU end and the second HEU end, and wherein the heat is added using a heater that is operated independent of the HEU.