METHOD AND A SYSTEM FOR MAINTAINING CONSTANT POWER OUTPUT IN LOW PRESSURE STAGES OF STEAM TURBINE UNDER VARIABLE EXTRACTION OF WORKING FLUID

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of the Indian Provisional Patent application with serial number 4243/CHE/2012 filed on Oct. 11, 2012 with title, “A Method and a System for Maintaining Constant Power Output in Low Pressure Stages of Steam Turbine under Variable Extraction of Working Fluid” and the contents of which is incorporated in entirety.

BACKGROUND

1. Technical Field

The embodiments herein generally relate to steam turbines and particularly relates to an extraction-condensing type steam turbine used in a cogeneration system. The embodiments herein more particularly relates to a method and a system for maintaining a constant power output in the low pressure stages of an extraction-condensing type steam turbine during a large variation in the extraction or bleeding of a working fluid.

2. Description of the Related Art

The turbines are rotating machines which convert the energy contained in a working fluid into a useful work. In general, a turbine comprises a shaft and a circular disk or a ring. The outer circumference of the circular disk comprises a series of blades. The series of blades are aligned based on the specific speed and an application of the turbines. There are numerous types of turbines depending on the type of input, such as steam, water, wind, gas, etc.

A steam turbine especially used in a cogeneration system, caters to the industries using the steam as a process fluid for the heating and cooling purposes. In the process industries, such as distilleries, paper mills etc, a demand for the steam depends on a production capacity of a particular product. The variations in the flow of steam to the steam turbines are due to the various reasons like a quantity of steam available, the load variations and the process requirements. The different volumes/loads of steam are required for different processes. The performance of a turbine is also a function of an inlet flow of the working fluid. A reduction in the inlet flow of the working fluid results in a drastic reduction in a performance of the turbine. In the process industries, the working fluid is extracted from the intermediate stages to run an auxiliary process. When the flow of the working fluid is drastically affected, it gives rise to the off-design conditions. The off-design conditions generate difficulties in operating a turbine stage at the optimal conditions.

The off-design conditions correspond to a change in a pressure, a temperature, a flow of working fluid etc. The steam turbines are very sensitive to a change in the design condition and operated under rated parameters such as a temperature, a pressure, a quantity of steam, etc. The performance of a steam turbine deteriorates under the off-design conditions. The biggest challenge in a cogeneration system is to deal with the off-design conditions. The steam turbines used in the cogeneration systems are often of an ‘extraction-condensing’ type. These turbines exhaust a steam both to a process and to the condenser. These steam turbines however experience the variations in a flow at the high pressure bleed or at an extraction point due to the variations in the auxiliary process. This variation in the flow of working fluid causes the steam turbine to operate under the ‘off-design’ conditions thereby deteriorating a performance significantly.

Hence there is need for a method and system for maintaining a constant power output from the low pressure stages of a steam turbine, despite the variations in an extraction of a flow of a working fluid. Also there is a need to run a plurality of steam turbines stages at optimal conditions.

The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

OBJECTS OF THE EMBODIMENTS

The primary object of the embodiments herein is to provide a method for regulating a flow of working fluid during an extraction of the working fluid between the two stages in the steam turbine.

Another object of the embodiments herein is to provide a method for regulating a flow of working fluid during an extraction of the working fluid between the two stages in the steam turbine.

Yet another object of the embodiments herein is to provide a method and a system for maintaining the optimal operating conditions in the steam turbine by maintaining a constant flow of a working fluid to a plurality of low pressure stages.

Yet another object of the embodiments herein is to provide a method and a system for producing additional power using an Auxiliary Quick Start™ turbine in a co-generation system.

These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY

The various embodiments herein provide a method and a system for maintaining a constant power output from the low pressure stages of an extraction-condensing type steam turbine under the variations of bleeding. The bleeding refers to a process of extracting a required quantity of a working fluid from the passage between any two intermediate turbine stages during a flow. The present invention specifically addresses a method of controlling the effects caused by extracting a large quantity of the working fluid between the turbine stages. The method results in maintaining a constant flow of a working fluid through the remaining stages of the steam turbine. The present invention provides a solution for maintaining a flow of a working fluid in the low pressure stages of the steam turbine. The present invention utilizes a pressure reducing and de-superheating stations (PRDS) or a PRDS and an Auxiliary Quick Start™ turbine to maintain a constant flow of a working fluid to a plurality of low pressure stages of the steam turbine which in turn results in a constant power output.

According to an embodiment herein, a system of the present invention comprises an extraction-condensing type steam turbine, a control valve, an extraction header with a pressure transmitter, a generator, a Pressure Reducing and De-superheating stations (PRDS), an Auxiliary Quick Start™ turbine, a Programmable Logic Controller (PLC) based control system, a bypass pipeline, and a condenser. The extraction-condensing type steam turbine supplies a required quantity of a working fluid (preferably steam) to an auxiliary process and to the condenser simultaneously. The control valve regulates an intake of the working fluid to the high pressure stage of the steam turbine. The extraction header extracts and supplies the working fluid, which is drawn out from a passage between the successive stages of the steam turbine to an auxiliary process. The PRDS adjusts and controls the characteristics of the working fluid i.e. the PRDS reduces the pressure and temperature to a suitable level required by the auxiliary process. The present invention uses a PRDS for controlling the characteristics of the working fluid. The PRDS and the Auxiliary Quick Start™ turbine are connected to either side of the extraction header which is provided with a pressure transmitter. The PRDS supplies the extracted working fluid to the auxiliary process and the Auxiliary Quick Start™ turbine uses any excess working fluid to produce power. The bypass pipeline is connected to the Auxiliary Quick Start™ turbine for discharging the excess working fluid to the condenser. The condenser converts a working fluid (steam) from a gaseous state to a liquid state.

According to an embodiment herein, a method for maintaining a constant power generation output in an extraction-condensing type steam turbine is provided. The method comprises running the extraction-condensing type steam turbine at a normal operating condition wherein the extraction-condensing type steam turbine consists of at-least one high pressure stage and at-least one low pressure stage. Then the working fluid from the outlet of the high pressure stage is extracted through an extraction header and processed at a PRDS before being forwarded to the auxiliary process. The PRDS adjusts and changes the pressure and temperature of the extracted working fluid to a predetermined state required for the auxiliary process. In the event of an availability of an excess working fluid, an Auxiliary Quick Start™ turbine is used to expand the steam to a condenser and produce additional power. The Auxiliary Quick Start™ turbine is activated only when there is an excess of the working fluid left behind after utilization in the auxiliary process. The excess working fluid is then exhausted to a condenser through a bypass pipeline.

The various embodiments herein provide a system and method for maintaining a constant power output in low pressure stages of a steam turbine. According to an embodiment herein, a method is provided for maintaining a constant power output in low pressure stages of a steam turbine. According to an embodiment herein, the method comprises the steps of sensing a variation in a requirement for a working fluid in a process and sending a command signal based on the sensed variation in the requirement to regulate a control valve to a turbine to adjust a supply of working fluid to the turbine.

According to an embodiment herein, a variation in the requirement of the working fluid is sensed based on a variation in a pressure in a low pressure header.

According to an embodiment herein, the pressure in a low pressure header is detected by a pressure transmitter.

According to an embodiment herein, the command signal is sent by the pressure transmitter based on the detected pressure in the low pressure header to a Programmable Logic Controller (PLC) to regulate an operation of the control valve to regulate the supply of working fluid to the auxiliary Quick start turbine.

According to an embodiment herein, the variation in the requirement of the working fluid for an auxiliary process includes a decrease in the requirement of the working fluid or an increase in the requirement of the working fluid.

According to an embodiment herein, the decrease in requirement of the working fluid for the auxiliary process is sensed by an increase in pressure level in the low pressure header. The increase in requirement of the working fluid for the process is sensed by a decrease in pressure level in the low pressure header.

According to an embodiment herein, the pressure transmitter sends a command signal to the PLC to open the control vale to increase a supply of working fluid to the turbine, when an increase in the requirement of the working fluid is sensed.

According to an embodiment herein, the pressure transmitter sends a command signal to the PLC to close the control vale to reduce a supply of working fluid to the turbine, when a decrease in the requirement of the working fluid is sensed. An excess working fluid is expanded through a condenser.

According to an embodiment herein, the method further comprises operating an auxiliary Quick Start turbine, when an excess working fluid is available after a utilization of the working fluid in an auxiliary process.

According to an embodiment herein, the working fluid is steam.

The various embodiments herein provide a system for maintaining a constant power output in low pressure stages of a steam turbine. According to an embodiment herein, the system comprises an extraction-condensing type steam turbine, an inlet control vale, an extraction header with a pressure transmitter, a pressure reducing and de-superheating stations (PRDS), a power generator and a programmable logic controller (PLC). The PRDS adjusts and controls a characteristic of a working fluid based on a requirement of an auxiliary process, to maintain a constant flow of a working fluid to a plurality of low pressure stages of a steam turbine to produce a constant power output.

According to an embodiment herein, the PRDS adjusts and controls a pressure and temperature of the working fluid based on a requirement of an auxiliary process to maintain a constant flow of a working fluid to a plurality of low pressure stages of a steam turbine to produce a constant power output.

According to an embodiment herein, the PRDS and the Auxiliary Quick Start Turbine are connected to either side of the extraction header.

According to an embodiment herein, the pressure transmitter detects a pressure in the extraction header to sense a variation in the requirement of the working fluid to the auxiliary process. The variation in the requirement of the working fluid includes a decrease in the requirement of the working fluid or an increase in the requirement of the working fluid.

According to an embodiment herein, the pressure transmitter detects an increase in a pressure level in the extraction header, when the requirement of the working fluid to the auxiliary process is decreased. The pressure transmitter detects a decrease in a pressure level in the extraction header when the requirement of the working fluid is increased.

According to an embodiment herein, the pressure transmitter sends a command signal based on the detected pressure in the low pressure header to the Programmable Logic Controller (PLC) to regulate an operation of the control valve to regulate a supply of the excess working fluid to the Auxiliary Quick start turbine.

According to an embodiment herein, the pressure transmitter sends a command signal to the PLC to open the control vale to increase the supply of the working fluid to the turbine, when an increase in the requirement of the working fluid is sensed.

According to an embodiment herein, the pressure transmitter sends a command signal to the PLC to close the control valve to reduce a supply of working fluid to the auxiliary Quick start turbine, when a decrease in the requirement of the working fluid to the auxiliary process is sensed.

According to an embodiment herein, the PRDS supplies the excess working fluid to the auxiliary Quick Start turbine to produce an additional power, when an excess working fluid is available after a utilization of the working fluid in an auxiliary process.

According to an embodiment herein, the working fluid is steam.

According to an embodiment herein, the Auxiliary Quick start Turbine is replaced with a second PRDS in case the variations in requirement of working fluid are for short durations. The second PRDS is connected to the condenser through a bypass line.

The various embodiments herein provide a method and a system for maintaining a constant power output from an extraction-condensing type steam turbine under the variations of bleeding. The bleeding refers to a process of extracting a required quantity of a working fluid from the passage between any two intermediate turbine stages during a flow. The present invention specifically addresses a method of controlling the effects caused by extracting a large quantity of the working fluid between the turbine stages. The method results in maintaining a constant flow of a working fluid through the remaining stages of the steam turbine. The present invention provides a solution for maintaining a flow of a working fluid in the low pressure stages of the steam turbine. The present invention utilizes two pressure reducing and de-superheating stations (PRDS) or a PRDS and an Auxiliary Quick Start™ turbine to maintain a constant flow of a working fluid to a plurality of low pressure stages of the steam turbine which in turn results in a constant power output.

According an embodiment herein, a system of the present invention comprises an extraction-condensing type steam turbine, an inlet control valve, an extraction header with a pressure transmitter, a generator, a Pressure Reducing and De-superheating stations (PRDS), an Auxiliary Quick Start™ turbine, a Programmable Logic Controller (PLC) based control system, a bypass pipeline, and a condenser. The extraction-condensing type steam turbine supplies a required quantity of a working fluid (preferably steam) to an auxiliary process and to the condenser simultaneously. The inlet control valve controls an intake of the working fluid to the high pressure stage of the steam turbine. The extraction header extracts and supplies the working fluid, which is drawn out from a passage between the successive stages of the steam turbine to an auxiliary process. The PRDS adjusts and controls the characteristics of the working fluid i.e. the PRDS reduces the pressure and temperature to a suitable level required by the auxiliary process. The present invention uses a PRDS for controlling the characteristics of the working fluid. The PRDS and the Auxiliary Quick Start™ Turbine are connected to either side of the extraction header which is provided with a pressure transmitter. The PRDS supplies the extracted working fluid to the auxiliary process and the Auxiliary Quick Start™ Turbine uses any excess working fluid to produce power. The bypass pipeline is connected to the Auxiliary Quick Start™ Turbine for discharging the excess working fluid to the condenser. The condenser converts a working fluid (steam) from a gaseous state to a liquid state.

According to an embodiment herein, a method for maintaining a constant power generation output in an extraction-condensing type steam turbine is provided. The method comprises running the extraction-condensing type steam turbine at a normal operating condition wherein the extraction-condensing type steam turbine consists of at-least one high pressure stage and at-least one low pressure stage. Then the working fluid form the outlet of the high pressure stage is extracted through an extraction header and processed at a PRDS before being forwarded to the auxiliary process. The PRDS adjusts and changes the pressure and temperature of the extracted working fluid to a predetermined state required for the auxiliary process. In the event of an availability of an excess working fluid, an Auxiliary Quick Start™ Turbine is used to expand the steam to a condenser and produce additional power. The Auxiliary Quick Start™ Turbine is activated only when there is an excess of the working fluid left behind after utilization in the auxiliary process. The excess working fluid is exhausted to a condenser through a bypass pipeline.

These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

FIG. 1 illustrates a block diagram of a system for maintaining a constant power output from an extraction-condensing type steam turbine with a PRDS system and an Auxiliary Quick Start™ turbine, according to an embodiment herein.

FIG. 2 illustrates a block circuit diagram of a system for maintaining a constant power output from an extraction-condensing type steam turbine with two PRDS systems, according to an embodiment herein.

FIG. 3 illustrates a block circuit diagram of a system comprising a PRDS system and an Auxiliary Quick Start™ turbine with an inlet flow to the turbine is 24 Tons per Hour (TPH) and an extraction flow is 15 TPH, according to an embodiment herein.

FIG. 4 illustrates a block circuit diagram of a system comprising a PRDS system and an Auxiliary Quick Start™ turbine with an inlet flow to the turbine of 24 Tons per Hour (TPH) and an extraction flow of 12 TPH and the excess working fluid is redirected to the Auxiliary Quick Start™ turbine, according to an embodiment herein.

FIG. 5 illustrates a block circuit diagram of a system comprising two PRDS systems with an inlet flow to the turbine is 24 Tons Per Hour (TPH) and an extraction flow is 15 TPH, according to an embodiment herein.

FIG. 6 illustrates a block circuit diagram of a system comprising two PRDS systems with an inlet flow to the turbine of 24 Tons per Hour (TPH) and an extraction flow of 12 TPH, and the excess working fluid is sent to the second PRDS system, according to an embodiment herein.

FIG. 7 illustrates a block circuit diagram of a system comprising two PRDS systems with an inlet flow to the turbine of 21 Tons per Hour (TPH) and an extraction flow of 12 TPH, according to an embodiment herein.

Although the specific features of the embodiments herein are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the embodiments herein.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, a reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.

According to an embodiment herein, a system of the present invention comprises an extraction-condensing type steam turbine, a control valve, an extraction header with a pressure transmitter, a generator, a Pressure Reducing and De-superheating stations (PRDS), an Auxiliary Quick Start™ turbine, a Programmable Logic Controller (PLC) based control system, a bypass pipeline, and a condenser. The extraction-condensing type steam turbine supplies a required quantity of a working fluid (preferably steam) to an auxiliary process and to the condenser simultaneously. The control valve regulates an intake of the working fluid to the high pressure stage of the steam turbine. The extraction header extracts and supplies the working fluid, which is drawn out from a passage between the successive stages of the steam turbine to an auxiliary process. The PRDS adjusts and controls the characteristics of the working fluid i.e. the PRDS reduces the pressure and temperature to a suitable level required by the auxiliary process. The present invention uses a PRDS for controlling the characteristics of the working fluid. The PRDS and the Auxiliary Quick Start™ Turbine are connected to either side of the extraction header which is provided with a pressure transmitter. The PRDS supplies the extracted working fluid to the auxiliary process and the Auxiliary Quick Start™ Turbine uses any excess working fluid to produce power. The bypass pipeline is connected to the Auxiliary Quick Start™ Turbine for discharging the excess working fluid to the condenser. The condenser converts a working fluid (steam) from a gaseous state to a liquid state.

According to an embodiment herein, a method for maintaining a constant power generation output in an extraction-condensing type steam turbine is provided. The method comprises running the extraction-condensing type steam turbine at a normal operating condition wherein the extraction-condensing type steam turbine consists of at-least one high pressure stage and at-least one low pressure stage. Then the working fluid from the outlet of the high pressure stage is extracted through an extraction header and processed at a PRDS before being forwarded to the auxiliary process. The PRDS adjusts and changes the pressure and temperature of the extracted working fluid to a predetermined state required for the auxiliary process. In the event of an availability of an excess working fluid, an Auxiliary Quick Start™ Turbine is used to expand the steam to a condenser and produce additional power. The Auxiliary Quick Start™ Turbine is activated only when there is an excess of the working fluid left behind after utilization in the auxiliary process. The excess working fluid is then exhausted to a condenser through a bypass pipeline.

According to an embodiment herein, a variation in the requirement of the working fluid is sensed based on a variation in a pressure in a low pressure header.

According to an embodiment herein, the pressure in a low pressure header is detected by a pressure transmitter.

According to an embodiment herein, the method further comprises operating an Auxiliary Quick Start™ turbine, when an excess working fluid is available after a utilization of the working fluid in an auxiliary process.

According to an embodiment herein, the working fluid is steam.

According to an embodiment herein, the PRDS and the Auxiliary Quick Start™ Turbine are connected to either side of the extraction header.

According to an embodiment herein, the pressure transmitter sends a command signal to the PLC to close the control valve to reduce a supply of working fluid to the Auxiliary Quick Start™ turbine, when a decrease in the requirement of the working fluid to the auxiliary process is sensed.

According to an embodiment herein, the PRDS supplies the excess working fluid to the Auxiliary Quick Start™ turbine to produce an additional power, when an excess working fluid is available after a utilization of the working fluid in an auxiliary process.

According to an embodiment herein, the working fluid is steam.

According to an embodiment herein, the Auxiliary Quick Start™ Turbine is replaced with a second PRDS in case the variations in requirement of working fluid are for short durations. The second PRDS is connected to the condenser through a bypass line.

According to an embodiment herein, a method for maintaining a constant power generation output in an extraction-condensing type steam turbine is provided. The method comprises running the extraction-condensing type steam turbine at a normal operating condition wherein the extraction-condensing type steam turbine consists of at-least one high pressure stage and at-least one low pressure stage. Then the working fluid form the outlet of the high pressure stage is extracted through an extraction header and processed at a PRDS before being forwarded to the auxiliary process. The PRDS adjusts and changes the pressure and temperature of the extracted working fluid to a predetermined state required for the auxiliary process. In the event of an availability of an excess working fluid, an Auxiliary Quick Start™ Turbine is used to expand the steam to a condenser and produce additional power. The Auxiliary Quick Start™ Turbine is activated only when there is an excess of the working fluid left behind after utilization in the auxiliary process. The excess working fluid is exhausted to a condenser through a bypass pipeline.

FIG. 1 illustrates a block diagram of a system for maintaining a constant power output from an extraction-condensing type steam turbine with a PRDS system and an Auxiliary turbine, according to an embodiment herein. The extraction-condensing type steam turbine of the present invention comprises a high pressure stage 103 and a low pressure stage 105 as shown in the FIG. 1. The extraction-condensing type steam turbine comprises a plurality of low and high pressure stages and is not limited to only one low pressure stage and high pressure stage. The high pressure stage 103 intakes a working fluid from a boiler 101. The boiler 101 converts the working fluid from liquid phase to a vapor phase of preferred temperature and pressure. The boiler 101 then supplies the working fluid (in vapor phase) to the high pressure stage 103. The working fluid fed to the high pressure stage 103 is controlled by an inlet control valve 102. The working fluid rotates the rotor wheel of the high pressure stage 103 and advances to the low pressure stage 105 of the extraction-condensing type steam turbine. The rotor wheels of the high and low pressure stages are mounted on a shaft 104. Also, a generator 106 is coupled to the shaft 104 for generating electrical power. The necessary working fluid required to run an auxiliary process is extracted from the flow of working fluid during a passage between the high pressure stage 103 and low pressure stage 105. A required working fluid is extracted through an LP header 107 which is provided with a pressure transmitter. The extraction is controlled by a valve of a pressure reducing and de-superheating station (PRDS) 108. The LP header 107 is further connected to an Auxiliary Quick Start™ Turbine 109a. The Auxiliary Quick Start™ turbine 109a is coupled to a generator to produce power. The flow of working fluid to the Auxiliary Quick Start™ turbine 109a is controlled by a second control valve 112. The PRDS 108 supplies the required flow of the working fluid to the auxiliary process at a predetermined temperature and pressure.

With respect to FIG. 1, the Auxiliary Quick Start™ Turbine 109a is activated only when there is a sudden or large variation in the bleeding process. This variation is sensed at the extraction header 113 by the pressure transmitter through any consequent rise or fall in pressure in the header. The large variation in the bleeding occurs when the flow required by the Auxiliary process reduces or drops below the normal requirement. The excess working fluid available in this case is prevented from going towards the low pressure stage 105, which is running at its full capacity, and is instead passed through the Auxiliary Quick Start™ Turbine 109a. The excess steam from the auxiliary turbine 109a is passed to a condenser 111 through a bypass line 110.

FIG. 2 illustrates a block circuit diagram of a system for maintaining a constant power output from an extraction-condensing type steam turbine with two PRDS systems 108,109b, according to an embodiment herein. The extraction-condensing type steam turbine comprises a plurality of low and high pressure stages and is not limited to only one low pressure stage and high pressure stage. The high pressure stage 103 receives a working fluid from a boiler 101. The boiler 101 converts the working fluid from liquid phase to a vapour phase of preferred temperature and pressure. The boiler 101 then supplies the working fluid (in vapour phase) to the high pressure stage 103. The working fluid fed to the high pressure stage 103 is controlled by an inlet control valve 102. The working fluid rotates the rotor wheel of the high pressure stage 103 and advances to the low pressure stage 105 of the extraction-condensing type steam turbine. The rotor wheels of the high and low pressure stages are mounted on a shaft 104. Also, a generator 106 is coupled to the shaft 104 for generating electrical power. The necessary working fluid required to run an auxiliary process is extracted from the flow of working fluid during a passage between the high pressure stage 103 and low pressure stage 105. A required working fluid is extracted through an LP header 107 which is provided with a pressure transmitter. The extraction is controlled by a valve of a pressure reducing and de-superheating station (PRDS) 108. The LP header 107 is further connected to secondary PRDS system 109b instead of an Auxiliary Quick Start™ Turbine 109a (as shown in FIG. 1).

The Auxiliary Quick Start™ Turbine is replaced with a secondary PRDS system 109b, in case of a drop in the requirement of a steam for the process persists only for a short duration. In this case, the PRDS-2 109b initially starts dumping the excess working fluid to a condenser 111 through a bypass pipeline 110. The flow to the inlet control valve 102 is also simultaneously reduced from the boiler 101. As the flow gradually reduces at the inlet of the high pressure stage 103, the second PRDS 109b continuously exhausts any excess steam till there is no more excess steam and this is sensed by the extraction header 113 by the pressure transmitter. The flow of the working fluid towards the low pressure stage 105 is maintained at the original level without any deviation. When the second PRDS-2 109b is operated, the boiler 101's output is simultaneously reduced and the inlet control valve 102 is used to control the working fluid intake to the high pressure stage 103.

When the inlet flow of working fluid to the high pressure stage 103 is reduced, the quantity of the working fluid through the second PRDS-2 109b is also reduced. The flow of working fluid through the second PRDS-2 109b is adjusted in a controlled manner in order to maintain a constant flow of the working fluid to the low pressure stage 105 by a second inlet control valve 112. Thus the low pressure stage 105 is isolated from all the variations in the flow of the working fluid and the resulting off-design operation. The above method focus on maintaining a constant flow of the working fluid in a plurality of low pressure stages of a steam turbine 105 thereby offsetting the losses that are caused by running them at off-design conditions. In case of a subsequent increase in the demand of the working fluid due to the auxiliary Process, the boiler 101 output is increased without affecting the low pressure stage 105 of the extraction-condensing type steam turbine.

FIG. 3 illustrates a block diagram of a system comprising a PRDS system and an Auxiliary turbine with an inlet flow to the turbine is 24 Tons per Hour (TPH) and an extraction flow is 15 TPH, according to one embodiment herein. FIG. 3 illustrates a scenario where the inlet flow from the boiler 101 to the turbine 103 is 24 Tons per Hour (TPH) and the extraction flow before PRDS for an auxiliary process (301) is 15 TPH. The extraction-condensing type steam turbine comprises a plurality of low and high pressure stages and is not limited to only one low pressure stage and high pressure stage. The high pressure stage 103 intakes a working fluid from a boiler 101 with the inlet flow of 24 Tons per Hour (TPH). The working fluid fed to the high pressure stage 103 is controlled by an inlet control valve 102. The working fluid rotates the rotor wheel of the high pressure stage 103 and is advanced to the low pressure stage 105 of the extraction-condensing type steam turbine. The rotor wheels of the high and low pressure stages are mounted on a shaft 104. Also, a generator 106 is coupled to the shaft 104 for generating electrical power. The exhaust steam from the turbines 105 is passed to the condenser 1111. The necessary working fluid required to run an auxiliary process 301 is extracted from the flow of working fluid during a passage between the high pressure stage 103 and low pressure stage 105. A required working fluid is extracted through an LP header 107 which is provided with a pressure transmitter 113. The extraction is controlled by a valve of a pressure reducing and de-superheating station (PRDS) 108. The LP header 107 is further connected to an Auxiliary Quick Start™ Turbine 109a. The Auxiliary Quick Start™ turbine 109a is coupled to a generator to produce power. The flow of working fluid to the Auxiliary Quick Start™ turbine 109a is controlled by a second control valve 112. The PRDS 108 supplies the required flow of the working fluid to the auxiliary process at a predetermined temperature and pressure. The Auxiliary turbine remains idle when there is no excess working fluid at the extraction header. When the inlet flow of steam from the boiler 101 to the High Pressure (HP) turbine 103 is 24 TPH, a steam flow of 15 TPH (301) is extracted through the LP header 107 for an auxiliary process and a steam flow of remaining 9 TPH (304) is fed to the Low Pressure (HP) turbine stages 105. As a result the steam flow (302) sent to the Auxiliary Quick Start™ 109a is 0(zero) TPH and the exhaust steam flow (303) passed from the Auxiliary Quick Start™ turbine 109a to the condenser 11 through a by-pass line 110 is 0 TPH.

FIG. 4 illustrates a block diagram of a system comprising a PRDS system and an Auxiliary turbine with an inlet flow of 24 TPH from the boiler 101 to the turbine 103. The extraction flow (301) is dropped to 12 Tons per Hour (TPH) and the excess 3 TPH flow (302) is redirected to the Auxiliary turbine, according to one embodiment herein. The Auxiliary Quick Start™ turbine 109a is activated only when there is a sudden or large variation in the bleeding process. This variation is sensed at the extraction header 107 by the pressure transmitter 113 through any consequent rise in pressure in the header. The excess working fluid is prevented from going towards the low pressure stage 105, which is running at its full capacity, and is instead passed through the Auxiliary Quick Start™ turbine 109a which in turn produces 500 kW of additional power.

According to the embodiments herein, a method and a system is provided for maintaining a constant power output from the low pressure stages of an extraction-condensing type steam turbine under the variations of bleeding. The bleeding refers to a process of extracting a required quantity of a working fluid from the passage between any two intermediate turbine stages (103, 105) during a flow. The present invention specifically addresses a method of controlling the effects caused by extracting a large quantity of the working fluid between the turbine stages (103, 105). The method results in maintaining a constant flow of a working fluid (304) through the remaining stages of the steam turbine. The present invention provides a solution for maintaining a constant flow of a working fluid (304) in the low pressure stages of the steam turbine. The present invention utilizes a pressure reducing and de-superheating stations (PRDS) 108 or a PRDS 108 and an Auxiliary Quick Start™ turbine 109a to maintain a constant flow (304) of a working fluid to a plurality of low pressure stages of the steam turbine 105 which in turn results in a constant power output.

According to one embodiment herein, a system comprises an extraction-condensing type steam turbine, a control valve 102, an LP extraction header 107 with a pressure transmitter 113, a generator 106, a Pressure Reducing and De-superheating stations (PRDS) 108, an Auxiliary Quick Start™ turbine 109a, a Programmable Logic Controller (PLC) based control system, a bypass pipeline 110, and a condenser 111. The extraction-condensing type steam turbine supplies a required quantity (301) of a working fluid (preferably steam) to an auxiliary process and to the condenser 11 simultaneously. The control valve 102 regulates an intake of the working fluid to the high pressure stage of the steam turbine. The working fluid rotates the rotor wheel of the high pressure stage 103 and is advanced to the low pressure stage 105 of the extraction-condensing type steam turbine. The rotor wheels of the high and low pressure stages are mounted on a shaft 104. Also, a generator 106 is coupled to the shaft 104 for generating electrical power. The extraction header 107 extracts and supplies the working fluid, which is drawn out from a passage between the successive stages of the steam turbine 103,105 to an auxiliary process. The PRDS 108 adjusts and controls the characteristics of the working fluid i.e. the PRDS 108 reduces the pressure and temperature to a suitable level required by the auxiliary process. The present invention uses a PRDS 108 for controlling the characteristics of the working fluid. The PRDS 108 and the Auxiliary Quick Start™ Turbine 109a are connected to either side of the extraction header 107 which is provided with a pressure transmitter 113. The PRDS 108 supplies the extracted working fluid to the auxiliary process and the Auxiliary Quick Start™ Turbine 109a uses any excess working fluid (302) to produce power. The bypass pipeline 110 is connected to the Auxiliary Quick Start™ Turbine 109a for discharging the excess working fluid (303) to the condenser. The condenser converts a working fluid (steam) from a gaseous state to a liquid state. The excess flow of working fluid (302) from the LP header 107 to the Auxiliary Quick Start™ Turbine 109a is controlled by a control valve 112.

When the inlet flow of steam from the boiler 101 to the High Pressure (HP) turbine 103 is 24 TPH, a steam flow of 12 TPH (301) is extracted through the LP header 107 for an auxiliary process and a steam flow of remaining 9 TPH (304) is fed to the low Pressure (HP) turbine stages 105. As a result the steam flow (302) sent to the Auxiliary Quick Start™ turbine 109a is 3 TPH and the exhaust steam flow (303) passed from the Auxiliary Quick Start™ turbine 109a to the condenser 111 through a by-pass line 110 is 3 TPH. The excess working fluid is prevented from going towards the low pressure stage 105, which is running at its full capacity, and is instead passed through the Auxiliary Quick Start™ turbine 109a which in turn produces 500 kW of additional power.

FIG. 5 illustrates a block diagram of a system comprising two PRDS systems 108,109b with an inlet flow from the boiler 101 to the turbine 103 is 24 Tons Per Hour (TPH) and an extraction flow of steam (301) for an auxiliary process is 15 TPH, according to one embodiment herein. As shown in FIG. 5, the Auxiliary Quick Start™ Turbine is replaced with a secondary PRDS-2 system 109b and the system comprises two PRDS systems 108,109b with an inlet flow to the turbine of 24 Tons per Hour (TPH) and an extraction flow (301) is 15 TPH which is the normal operating condition. In this case, the PRDS-2 109b remains inactive as there is no excess working fluid to be sent to the condenser.

When the inlet flow of steam from the boiler 101 to the High Pressure (HP) turbine 103 through the inlet control valve 102 is 24 TPH, a steam flow of 15 TPH (301) is extracted through the LP header 107 for an auxiliary process and a steam flow of remaining 9 TPH (304) is fed to the Low Pressure (HP) turbine stages 105. As a result the steam flow (302) sent to the second PRDS 109b is 0(zero) TPH and the exhaust steam flow (303) passed from the second PRDS 109b to the condenser 111 through a by-pass line 110 is 0 TPH. The excess flow of working fluid (302) from the LP header 107 to the second PRDS 109b is controlled by a control valve 112. A variation in the extraction of the steam flow from the LP header 107 for an auxiliary process is detected by a pressure transmitter 113.

With respect to FIG. 5, the extraction-condensing type steam turbine comprises a plurality of low and high pressure stages and is not limited to only one low pressure stage and high pressure stage. The high pressure stage 103 intakes a working fluid from a boiler 101 with the inlet flow of 24 Tons per Hour (TPH). The working fluid fed to the high pressure stage 103 is controlled by an inlet control valve 102. The working fluid rotates the rotor wheel of the high pressure stage 103 and is advanced to the low pressure stage 105 of the extraction-condensing type steam turbine. The rotor wheels of the high and low pressure stages are mounted on a shaft 104. Also, a generator 106 is coupled to the shaft 104 for generating electrical power. The exhaust steam from the turbines 105 is passed to the condenser 111.

FIG. 6 illustrates a block diagram of a system comprising two PRDS systems 108,109b when an inlet flow of steam from the boiler 101 to the turbine 103 is 24 Tons per Hour (TPH) and an extraction flow (301) of steam to the auxiliary process from the LP header 107 is 12 TPH. The excess flow of steam (302) is redirected to the second PRDS system 109b, according to one embodiment herein. The flow of working fluid through the second PRDS-2 109b ensures that there is a constant flow of the working fluid to the low pressure stage 105. Thus the low pressure stage 105 is isolated from all the variations in the flow of the working fluid and the resulting off-design operation The Second PRDS dumps the excess working fluid of 3 TPH (302) to a condenser 111 through a bypass line 110.

When the inlet flow of steam from the boiler 101 to the High Pressure (HP) turbine 103 through the inlet control valve 102 is 24 TPH, a steam flow of 12 TPH (301) is extracted through the LP header 107 for an auxiliary process and a constant steam flow of 9 TPH (304) is fed to the Low Pressure (HP) turbine stages 105. As a result the steam flow (302) sent to the second PRDS 109b is 3 TPH and the exhaust steam flow (303) passed from the second PRDS 109b to the condenser 111 through a by-pass line 110 is 3 TPH. The excess flow of working fluid (302) from the LP header 107 to the second PRDS 109b is controlled by a control valve 112. A variation in the extraction of the steam flow from the LP header 107 for an auxiliary process is detected by a pressure transmitter 113.

With respect to FIG. 6, the extraction-condensing type steam turbine comprises a plurality of low and high pressure stages and is not limited to only one low pressure stage and high pressure stage. The high pressure stage 103 intakes a working fluid from a boiler 101 with the inlet flow of 24 Tons per Hour (TPH). The working fluid fed to the high pressure stage 103 is controlled by an inlet control valve 102. The working fluid rotates the rotor wheel of the high pressure stage 103 and is advanced to the low pressure stage 105 of the extraction-condensing type steam turbine. The rotor wheels of the high and low pressure stages are mounted on a shaft 104. Also, a generator 106 is coupled to the shaft 104 for generating electrical power. The exhaust steam from the turbines 105 is passed to the condenser 111.

FIG. 7 illustrates a block diagram of a system comprising two PRDS systems 108, 109b when an inlet flow of steam from the boiler 101 to the turbine 103 is 21 Tons per Hour (TPH) and an extraction flow (301) of steam to the auxiliary process from the LP header 107 is 12 TPH. There is no excess working fluid and hence no flow is redirected to a second PRDS 109b. The flow of working fluid through the second PRDS-2 109b ensures that there is a constant flow of the working fluid (304) to the low pressure stage 105. Thus the low pressure stage 105 is isolated from all the variations in the flow of the working fluid and the resulting off-design operation The exhaust steam (303) dumped from the second PRDS 109b to a condenser 11 through a bypass line 110 is 0(zero) TPH.

When the inlet flow of steam from the boiler 101 to the High Pressure (HP) turbine 103 through the inlet control valve 102 is 21 TPH, a steam flow of 12 TPH (301) is extracted through the LP header 107 for an auxiliary process and a constant steam flow of 9 TPH (304) is fed to the Low Pressure (HP) turbine stages 105. As a result, the steam flow (302) sent to the second PRDS 109b is 0 (zero) TPH and the exhaust steam flow (303) passed from the second PRDS 109b to the condenser 111 through a by-pass line 110 is 0 (zero) TPH. The excess flow of working fluid (302) from the LP header 107 to the second PRDS 109b is controlled by a control valve 112. A variation in the extraction of the steam flow from the LP header 107 for an auxiliary process is detected by a pressure transmitter 113.

With respect to FIG. 7, the extraction-condensing type steam turbine comprises a plurality of low and high pressure stages and is not limited to only one low pressure stage and high pressure stage. The high pressure stage 103 intakes a working fluid from a boiler 101 with the inlet flow of 21 Tons per Hour (TPH). The working fluid fed to the high pressure stage 103 is controlled by an inlet control valve 102. The working fluid rotates the rotor wheel of the high pressure stage 103 and is advanced to the low pressure stage 105 of the extraction-condensing type steam turbine. The rotor wheels of the high and low pressure stages are mounted on a shaft 104. Also, a generator 106 is coupled to the shaft 104 for generating electrical power. The exhaust steam from the turbines 105 is passed to the condenser 111.

The embodiments herein provide a method and a system for maintaining a constant power output (power generation) in the low pressure stages of an extraction-condensing type steam turbine, under a large variation of an extraction of working fluid. The embodiments herein prevent any variations in the flow of the working fluid towards the low pressure stage which could deteriorate its performance. The embodiments herein provide the solutions for tackling the large variations in the flow of working fluid which is applicable to the existing steam turbines. The embodiments herein also provide a method of producing additional power by using an Auxiliary Quick Start™ Turbine thereby minimizing the off-design losses in the turbines used in the combined heat and power (CHP) applications.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.

Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

METHOD AND A SYSTEM FOR MAINTAINING CONSTANT POWER OUTPUT IN LOW PRESSURE STAGES OF STEAM TURBINE UNDER VARIABLE EXTRACTION OF WORKING FLUID

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