Patent ID: 12258885

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, it should be noted that the present disclosure is not limited thereto, and may include all modifications, equivalents, or substitutions within the spirit and scope of the present disclosure.

Terms used herein are used to merely describe specific embodiments, and are not intended to limit the present disclosure. As used herein, an element expressed as a singular form includes a plurality of elements, unless the context clearly indicates otherwise. Further, it will be understood that the term “comprising” or “including” specifies the presence of stated features, numbers, steps, operations, elements, parts, or combinations thereof, but does not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, parts, or combinations thereof.

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It is noted that like elements are denoted in the drawings by like reference symbols whenever possible. Further, the detailed description of known functions and configurations that may obscure the gist of the present disclosure will be omitted. For the same reason, some of the elements in the drawings are exaggerated, omitted, or schematically illustrated.

FIG.1is a block diagram illustrating a combined power generation system according to an embodiment of the present disclosure.

The combined power generation system100of the present disclosure includes: a gas turbine110including a compressor111that compresses air, a combustor113that combusts a mixture of the compressed air compressed by the compressor and fuel, and a turbine section that obtains rotational power by the combustion gases generated by the combustor; a heat recovery steam generator (HRSG)130in which steam is generated by heat of exhaust gases from the gas turbine; and a steam turbine120driven by the steam generated by the HRSG.

The compressor111sucks and compresses ambient air. The compressor111is connected to the turbine section115by a rotary shaft so that the compressor can rotate with the rotation of the turbine section115. The compressor111has a plurality of blades and vanes in multiple stages to compress the incoming air.

The combustor113may combust a mixture of fuel and compressed air compressed by the compressor111. The fuel may be a gaseous fuel such as natural gas or petroleum gas.

The rotary shaft of the turbine section115may be rotated by the combustion gases generated by the combustor113. The turbine section115has the plurality of blades and vanes arranged in multiple stages so that the rotary shaft is rotated by the combustion gases.

The HRSG130may also be referred to as a heat recovery boiler. The HRSG130may recover heat from the high-temperature exhaust gases from the gas turbine. This heat is utilized to heat water, ultimately resulting in generation of steam. The generated steam can be piped to drive the steam turbine120.

A central rotary shaft of the steam turbine120may be rotated by the steam generated in the HRSG130. The steam turbine120may include a high-pressure turbine section121, a medium-pressure turbine section123, and a low-pressure turbine section125, with a rotary shaft connected therebetween. The high-pressure turbine section121, the medium-pressure turbine section123, and the low-pressure turbine section125may be supplied with high-pressure steam, medium-pressure steam, and low-pressure steam, respectively, from the steam generated by the HRSG130.

The HRSG130may generate steam using exhaust gases from the steam turbine120. The HRSG130may have a plurality of superheaters, economizers, reheaters, and evaporators sequentially arranged according to steam pressure to heat exchange with the exhaust gases. The HRSG130according to the present disclosure may include a plurality of heat exchangers151,152to cool the compressed air by performing a heat exchange process between a portion of the compressed air from the compressor111and the exhaust gases from the turbine section115. In a normal state operation of the gas turbine110, the temperature of the exhaust gases remains lower than the temperature of the compressed air. This temperature difference allows the exhaust gases to serve as cooling fluid for lowering the temperature of the compressed air. This cooling action may facilitate to maintain the optimal operating temperature of the internal components within the turbine section115.

The HRSG130sequentially includes a high-pressure superheater137, a second medium-pressure superheater138B, a high-pressure evaporator134disposed below a high-pressure drum131, a high-pressure economizer141, a first medium-pressure superheater138A, and a medium-pressure evaporator135disposed below a medium-pressure drum132, a second low-pressure superheater139B, a medium-pressure economizer142, a first low-pressure superheater139A, a low-pressure evaporator136disposed below a low-pressure drum133, and a low-pressure economizer143, according to a flow direction of the exhaust gas.

The superheaters137,138A,138B,139A,139B may heat the saturated steam generated in the drums131,132,133, to generate superheated steam with a higher temperature. The superheated steam generated by the high-pressure superheater137may be supplied to the high-pressure turbine section121. A high-pressure valve122may be installed in a high-pressure superheated steam flow path between the high-pressure superheater137and the high-pressure turbine section121to regulate a flow rate of superheated steam.

The superheated steam generated by the first medium-pressure superheater138A and the second medium-pressure superheater138B may be supplied to the medium-pressure turbine section123. A medium-pressure valve124may be installed in a medium-pressure superheated steam flow path between the first/second medium-pressure superheater138A,138B and the medium-pressure turbine section123to regulate a flow rate of superheated steam.

According to an embodiment, the first medium-pressure superheater138A may be configured as a reheater. The reheater may reheat the steam that has dropped in temperature after working in the high-pressure turbine section121to increase the superheat degree.

The superheated steam generated by the first low-pressure superheater139A and the second low-pressure superheater139B may be supplied to the low-pressure turbine section125. A low-pressure valve126may be installed in a low-pressure superheated steam flow path between the first/second low-pressure super heater139A,139B and the low-pressure turbine section125to regulate a flow rate of superheated steam.

The evaporator evaporates water supplied to the HRSG130to generate steam. The high-pressure evaporator134may be disposed below the high-pressure drum131, the medium-pressure evaporator135may be disposed below the medium-pressure drum132, and the low-pressure evaporator136may be disposed below the low-pressure drum133. The feedwater may flow sequentially through the low-pressure evaporator136, the medium-pressure evaporator135, and the high-pressure evaporator134, in which the feedwater is evaporated by the exhaust gases to generate steam.

The economizers,141,142,143, also known as a feedwater preheater, use heat from the exhaust gases to raise the feedwater temperature to recover lost heat, increase boiler efficiency, and save fuel.

When upstream/downstream directions are defined based on the flow direction of the exhaust gas, the high-pressure economizer141may be disposed downstream of the high-pressure evaporator134to preheat the feedwater. The medium-pressure economizer142may be disposed downstream of the medium-pressure evaporator135to preheat the feedwater. The low-pressure economizer143may be disposed downstream of the low-pressure evaporator136to preheat the feedwater.

The exhaust gases may enter the HRSG130and pass from the high-pressure superheater137to the low-pressure economizer143for heat exchange before being discharged to an exhaust stack145.

The HRSG130may further include a medium-pressure heat exchanger151and a low-pressure heat exchanger152. The medium-pressure heat exchanger151may be disposed upstream of the medium-pressure evaporator135and cools the compressed air by heat exchange between the compressed air and the exhaust gas. The low-pressure heat exchanger may be disposed upstream of the low-pressure evaporator136to re-cool the compressed air that has been cooled by the medium-pressure heat exchanger151.

The medium-pressure heat exchanger151may be disposed nearby the upstream side of the medium-pressure evaporator135to perform heat exchange between the compressed air and the exhaust gases to cool the compressed air. Specifically, the medium-pressure heat exchanger151may be disposed between the first medium-pressure superheater138A and the medium-pressure evaporator135.

The low-pressure heat exchanger152may be disposed nearby the upstream side of the low-pressure evaporator136to perform heat exchange between the compressed air and the exhaust gases to further cool the compressed air. Specifically, the low-pressure heat exchanger152may be disposed between the first low-pressure superheater139A and the low-pressure evaporator136.

The combined power generation system100may further include a compressed air flow path161connecting, and flowing (i.e., delivering) the compressed air, from the compressor111to the plurality of heat exchangers151,152, a cooling air flow path165connecting, and flowing (i.e., delivering) the cooled compressed air, from the plurality of heat exchangers151,152to the turbine section115. The combined power generation system may further include a bypass flow path167connecting, flow (i.e., delivering) the compressed air from the compressed air flow path to the cooling air flow path.

According to an embodiment, the compressed air flow path161may branch off from a flow path from the compressor111to the combustor113(the “compressor-combustor path”) and connect to the medium-pressure heat exchanger151, and connect from the medium-pressure heat exchanger151to the low-pressure heat exchanger152. In other words, an upstream part of the compressed air flow path161may be disposed between and connecting the compressor-combustor path and the medium-pressure heat exchanger151and a downstream part of the compressed air flow path161may be disposed between and connecting the medium-pressure heat changer151and the low-pressure heat exchanger152.

The cooling air flow path165may connect from the low-pressure heat exchanger to a cooling air inlet of the turbine section115.

According to an embodiment, the bypass flow path167may connect from an upstream midpoint of the compressed air flow path161to a downstream midpoint of the cooling air flow path165. The downstream midpoint of the cooling air flow path165where the bypass flow path167joins may be referred to as a bypass flow joint point. Accordingly, the portion of the compressed air introduced into the compressed air flow path161may flow through the bypass flow path167directly into the turbine section115without flowing through the plurality of heat exchangers151and152.

According to an embodiment a main valve170may be installed in the compressed air flow path161to regulate the air flow rate in the compressed air flow path161. In addition, a bypass valve180may be installed in the bypass flow path167to regulate the air flow rate in the bypass flow path167.

The combined power generation system100of the present disclosure may further include a plurality of temperature sensors including temperature sensors190,195installed in the cooling air flow path165to measure the temperature of the cooling air (i.e., “the cooled compressed air” throughout the specification) entering the turbine section115.

The first temperature sensor190may be installed near the cooling air inlet of the turbine section115in the cooling air flow path165between the cooling air inlet of the turbine section115and the bypass flow joint point. The second temperature sensor195may be installed in the cooling air flow path165at a point before the bypass flow joint point (i.e., at a point upstream than the bypass flow joint point based on the flow direction of the cooled compressed air).

The first temperature sensor190may measure the temperature of the cooling air within the cooling air flow path165immediately before the cooling air enters the turbine section115. Thus, the first temperature sensor190may measure the temperature of a mixture of two airs: the cooled compressed air that has been cooled by passing through the plurality of heat exchangers151and152and the compressed air that has flowed through the bypass flow path167.

The second temperature sensor195may be installed in the middle of the cooling air flow path165before the cooling air flow path meets the bypass flow path167. The second temperature sensor195may measure the temperature of the cooling air (i.e., the cooled compressed air) that has been cooled through flowing through the plurality of heat exchangers151and152.

The combined power generation system100of the present disclosure may further include a controller200that regulates the opening degree of the main valve170and the bypass valve180.

As illustrated inFIG.2, the controller200may be configured to increase the opening degree of the bypass valve180when the measured temperature of the cooling air from the temperature sensor190is lower than a target value, and to decrease the opening degree of the bypass valve180when the measured temperature of the cooling air from the temperature sensor190is higher than the target value.

The controller200may receive a temperature measurement signal of the cooling air from the first temperature sensor190to control the main valve170and the bypass valve180depending on the temperature of the cooling air.

First, the controller determines whether the measured temperature of the cooling air is within a target range, i.e., a set temperature range (S10). When the measured temperature of the cooling air is within the target range, the controller200may keep the opening degree of the main valve170and the bypass valve180unchanged.

When the measured temperature of the cooling air is out of the target range, the controller200determines whether the measured temperature is lower than the target range (S20).

When the measured temperature is lower than the target value, the controller may increase the opening degree of the bypass valve180(S30) to allow more of the compressed air to flow through the bypass flow path167without passing through the plurality of heat exchangers151and152, thereby further increasing the temperature of the cooling air.

Conversely, when the measured temperature is higher than the target value, the controller may decrease the opening degree of the bypass valve180(S40) to allow more of the compressed air to pass through the plurality of heat exchangers151and152, thereby further lowering the temperature of the cooling air.

FIG.3is a flowchart illustrating a method of controlling an operation of the combined power generation system according to another embodiment of the present disclosure.

The controller200may be configured to controls the temperature of the cooling air by regulating the opening degree of the main valve170when it is determined that the temperature control by the bypass valve180fails (i.e., being not operable), and controls the temperature of the cooling air by regulating the opening degree of the bypass valve180when it is determined that the temperature control by the bypass valve180is operable.

Specifically, first, the controller200may determine whether the measured temperature of the cooling air from the temperature sensor190is within a target range, i.e., a set temperature range (S110). When the measured temperature of the cooling air by the temperature sensor190is within the target range, the controller200may keep the opening degree of the main valve170and the bypass valve180unchanged.

When the measured temperature of the cooling air measured by the temperature sensor190is out of the target range, the controller determines whether the temperature control by the bypass valve180has failed (S120). When the temperature of the cooling air cannot be regulated by the bypass valve180due to a failure of the bypass valve180or the like, the controller200may attempt to regulate the temperature of the cooling air by adjusting the opening degree of the main valve170only (S130).

Next, when the temperature control by the bypass valve180has not failed, i.e., when the temperature control by the bypass valve180is possible, the controller determines whether the measured temperature of the cooling air is lower than the target range (S140).

When the measured temperature is lower than the target value, the controller may increase the opening degree of the bypass valve180(S150) to allow more of the compressed air to flow through the bypass flow path167without passing through the plurality of heat exchangers151and152, thereby further increasing the temperature of the cooling air.

Conversely, when the measured temperature is higher than the target value, the controller may decrease the opening degree of the bypass valve180(S160) to allow more of the compressed air to pass through the plurality of heat exchangers151and152, thereby further lowering the temperature of the cooling air.

FIG.4is a diagram illustrating a combined power generation system according to another embodiment of the present disclosure.

In this combined power generation system100, the plurality of heat exchangers may further include a high-pressure heat exchanger153disposed downstream of the high-pressure evaporator134.

The high-pressure heat exchanger153may be disposed between the high-pressure evaporator134and the high-pressure economizer141in the HRSG130.

The compressed air flow path161may connect from the compressor110to the high-pressure heat exchanger153, connect from the high-pressure heat exchanger153to the medium-pressure heat exchanger151, and then connect from the medium-pressure heat exchanger151to the low-pressure heat exchanger152. In other words, an upstream portion of the compressed air flow path161may be disposed between and connecting the compressor110and the high-pressure heat exchanger153, a middle portion of the compressed air flow path161may be disposed between and connecting the high-pressure heat exchanger153and the medium-pressure heat exchanger151, and a downstream portion of the compressed air flow path161may be disposed between and connecting the medium-pressure heat changer and the low-pressure heat exchanger152.

The cooling air flow path165may connect from the low-pressure heat exchanger to the compressor110, as in the embodiment described above. In addition, the bypass flow path167may connect from the middle of the compressed air flow path161to the middle of the cooling air flow path165.

According to this embodiment, the combined power generation system130may be further equipped with an additional heat exchanger to perform heat exchange between the compressed air and the exhaust gases to further cool the compressed air using the exhaust gases.

Since the operation control method of the combined power generation system100of the present embodiment is as described in the above embodiment, a redundant description will be omitted.

According to the combined power generation system and the operation control method thereof, the plurality of heat exchangers is provided inside the HRSG so that exhaust gases are additionally utilized as a cooling source to cool the compressed air, thereby shortening startup time. Furthermore, no separate construction site is necessary for the cooling system to cool the compressed air.

While the embodiments of the present disclosure have been described, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure through addition, change, omission, or substitution of components without departing from the spirit of the invention as set forth in the appended claims, and such modifications and changes may also be included within the scope of the present disclosure. Also, it is noted that any one feature of an embodiment of the present disclosure described in the specification may be applied to another embodiment of the present disclosure.