Method and a system for maintaining constant power output in low pressure stages of steam turbine under variable extraction of working fluid

Abstract

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 large variations of extraction or bleed. The method comprises of keeping the flow of working fluid to the low pressure stages constant for a wide range of variations in extraction. The embodiments herein utilizes a pressure reducing and de-superheating stations (PRDS) and an Auxiliary Quick Start™ turbine to maintain the constant flow of working fluid or alternatively two pressure reducing and de-superheating stations (PRDS) for the same. The Auxiliary Quick Start™ turbine or PRDS is used to maintain the constant power output from the low pressure stages of the extraction-condensing type steam turbine.

What is claimed is: 
     
         1 . A method for maintaining a constant power output in low pressure stages of a steam turbine, the method comprises:
 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 maintain a constant supply of working fluid to the low pressure stages of a turbine.   
     
     
         2 . The method according to  claim 1 , wherein a variation in the requirement of the working fluid is sensed based on a variation in a pressure in a low pressure header. 
     
     
         3 . The method according to  claim 1 , wherein the pressure in a low pressure header is detected by a pressure transmitter. 
     
     
         4 . The method according to  claim 1 , wherein 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 turbine. 
     
     
         5 . The method according to  claim 1 , wherein the variation in the requirement of the working fluid includes a decrease in the requirement of the working fluid to an auxiliary process or an increase in the requirement of the working fluid to the auxiliary process. 
     
     
         6 . The method according to  claim 1 , wherein the decrease in requirement of the working fluid to the auxiliary process is sensed by an increase in pressure level in the low pressure header, and wherein the increase in requirement of the working fluid to the auxiliary process is sensed by a decrease in pressure level in the low pressure header. 
     
     
         7 . The method according to  claim 1 , wherein 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. 
     
     
         8 . The method according to  claim 1 , wherein 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, and wherein an excess working fluid is expanded through a condenser. 
     
     
         9 . The method according to  claim 1 , 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. 
     
     
         10 . The method according to  claim 1 , wherein the working fluid is steam. 
     
     
         11 . A system for maintaining a constant power output in low pressure stages of a steam turbine, the system comprising:
 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);   an Auxiliary Quick Start turbine;   a power generator; and   a programmable logic controller;   wherein 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.   
     
     
         12 . The system according to  claim 11 , wherein 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. 
     
     
         13 . The system according to  claim 11 , wherein the PRDS and the Auxiliary Quick Start Turbine are connected to either side of the extraction header. 
     
     
         14 . The system according to  claim 11 , wherein the pressure transmitter detects a pressure in the extraction header to sense a variation in the requirement of the working fluid, and wherein 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. 
     
     
         15 . The system according to  claim 11 , wherein the pressure transmitter detects an increase in a pressure level in the extraction header, when the requirement of the working fluid is decreased, and wherein the pressure transmitter detects a decrease in a pressure level in the extraction header when the requirement of the working fluid is increased. 
     
     
         16 . The system according to  claim 11 , wherein the pressure transmitter sends a command signal based on the detected pressure in the low pressure header to a Programmable Logic Controller (PLC) to regulate an operation of the inlet control valve to regulate a supply of the working fluid to the Auxiliary Quick Start turbine. 
     
     
         17 . The system according to  claim 11 , wherein 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. 
     
     
         18 . The system according to  claim 11 , wherein the working fluid is steam.