Steam Turbine Extraction Control for Reheater Temperature
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Solution Overview
Problem
Existing methods for controlling the hot reheater temperature in steam power plants, particularly at low turbine loads, are inefficient and face challenges such as construction and maintenance issues, limited effectiveness in increasing temperature, and negative impacts on cycle and boiler efficiency.
Innovation Solution
A system that includes an extraction line to extract steam from an intermediate stage of the steam turbine, using the extracted steam to heat process fluids, with a control valve and temperature measurement device to modulate the flow and maintain optimal hot reheater temperature, and optional connections to preheaters in the boiler feed water line to preheat boiler feed water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If flue gas flow is increased to control reheater temperature, then reheater outlet temperature increases, but convective heat transfer coefficient decreases and construction/maintenance challenges arise
Solution Approach 1:
The invention extracts steam from an intermediate stage of the steam turbine and redirects it through a extraction line to the reheater inlet. This removes the need to modify flue gas flow paths or damper systems, avoiding construction and maintenance challenges while achieving temperature control through steam extraction and injection rather than flue gas manipulation
Solution Approach 2:
The invention introduces extracted steam as an intermediary substance to transfer thermal energy to the reheater inlet steam. Instead of directly manipulating flue gas flow to control temperature, the extracted steam acts as a mediator that carries thermal energy from the turbine intermediate stage to the reheater, enabling temperature control without modifying the flue gas path
2Temperature
If burner flame is shifted to increase radiant heat to reheater, then reheater outlet temperature increases, but mechanism may seize and effectiveness is limited at low load
Solution Approach 1:
The invention extracts steam from an intermediate turbine stage and redirects it to the reheater inlet, eliminating the need for mechanical burner tilting mechanisms. This extraction-based approach removes the reliability issue of mechanical seizure while providing a more effective temperature control method that works independently of load conditions
Solution Approach 2:
The invention replaces the mechanical burner tilting system with a steam extraction and injection system. Instead of using mechanical actuators to tilt burners and control flame position, the system uses steam extraction lines and control valves to regulate reheater temperature, eliminating mechanical wear and seizure problems
3Temperature
If steam is extracted from intermediate turbine stage, then reheater outlet temperature increases, but turbine power output decreases
Solution Approach 1:
The invention implements a feedback control system where the control valve in the extraction line is modulated based on measured reheater outlet temperature. The control system continuously monitors temperature and adjusts the extraction steam flow to maintain optimal temperature, automatically balancing temperature control needs with power output requirements
Solution Approach 2:
The invention changes the operational parameters of the steam turbine by extracting steam at an intermediate stage and redirecting it to the reheater inlet. This parameter change allows the system to maintain higher reheater outlet temperatures without permanently reducing turbine power, as the extracted steam is returned to the cycle and continues to contribute to power generation in the IP steam turbine
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for efficient control of reheater temperature at low loads, maintaining optimal operating conditions for the IP steam turbine and enhancing overall power plant efficiency by using extracted steam to increase reheater outlet temperature and preheat boiler feed water.
Implementation Method 1
extract steam from an intermediate stage of the steam turbine and use this steam to heat at least one of the process fluids
Implementation Method 2
The extraction line includes a control valve configured and arranged to modulate a flow rate through the extraction line
Implementation Method 3
The control system includes a temperature measurement device configured and arranged to measure a temperature of process fluid in the outlet line
Implementation Method 4
a first preheater in the boiler feed water line upstream of the boiler... so as to enable pre-heating of boiler feed water
Data Source
Figure 1
Figure 2
AI summary
Provided is a power plant and a method of operating thereof. The power plant comprises a boiler (10) for heating process fluids; and a multistage first steam turbine (14) with an outlet line (15) that passes through the boiler (10). The outlet line (15) includes an extraction line (141) that is configured and arranged to extract steam from an intermediate stage of the first steam turbine (14) and heat at least one of the process fluids.