Auxiliary Heat Source Preheats Fossil Power Boiler Startup
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Solution Overview
Problem
Large coal-fired power plants take 12 to 20 hours to reach 80% of their full-load rating, and frequent load cycling reduces the lifespan of boiler and turbine components due to thermal stresses, making them less responsive to fast-changing grid demands.
Innovation Solution
A system that preheats a steam-driven power generation system using an auxiliary heat source and flow control valves to maintain steam and turbine components at optimal temperatures and pressures, reducing startup times and thermal stresses, and includes a smaller auxiliary boiler to efficiently warm the system without the need for continuous operation of the main boiler.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the boiler and turbine components are designed with thick cross sections to withstand high pressure, then the strength and reliability are improved, but the startup time increases due to slow heating rates required to minimize thermal stresses
Solution Approach 1:
The system performs preliminary heating action by circulating hot water through the boiler components and steam piping before steam generation begins. This preheats the thick-walled components to reduce thermal shock and allow faster subsequent startup while still respecting thermal stress limits.
Solution Approach 2:
The patent introduces an intermediary substance (hot water or steam) that transfers heat to the boiler components and piping. This intermediary allows controlled heat transfer through the thick walls, warming them gradually without exceeding thermal stress thresholds, thereby enabling faster startup than direct fire heating alone.
2Productivity
If the boiler operates at high temperatures to reduce warm-up time, then the productivity is improved, but the thermal stresses on components increase reducing their lifespan
Solution Approach 1:
The system performs preliminary heating action by circulating hot water through the boiler components and steam piping before steam generation begins. This preheats the thick-walled components to reduce thermal shock and allow faster subsequent startup while still respecting thermal stress limits.
Solution Approach 2:
The patent changes the heating parameters by using controlled circulation of hot water/steam at regulated temperatures and flow rates. This allows the system to achieve high operating temperatures for fast startup while controlling the rate of temperature change to prevent excessive thermal stresses on components.
3Reliability
If the main boiler is continuously operated to maintain grid stability, then the reliability is improved, but the energy efficiency decreases due to unnecessary fuel consumption during low demand periods
Solution Approach 1:
The system performs preliminary heating action by circulating hot water through the boiler components and steam piping before steam generation begins. This preheats the thick-walled components to reduce thermal shock and allow faster subsequent startup while still respecting thermal stress limits.
Solution Approach 2:
The patent implements periodic action by allowing the boiler to shut down during low demand periods and then rapidly restarting when needed. The preheating system enables this periodic operation by reducing the warm-up time, making it feasible to stop and start the boiler based on actual grid demand rather than continuous operation.
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 coal-fired power plants to quickly respond to sudden grid demands by reducing startup times and minimizing thermal stresses on components, thereby extending their lifespan and improving grid stability.
Implementation Method 1
A system for preheating a steam driven power generation system... using an auxiliary heat source to maintain steam and turbine components at optimal temperatures
Implementation Method 2
flow control valves to maintain steam and turbine components at optimal temperatures and pressures
Implementation Method 3
at least one electric heater operably configured to heat steam directed to the first steam pipe and the third steam pipe
Implementation Method 4
a turbine having at least a high pressure section and an intermediate pressure section, the turbine operable to receive steam and convert the steam to rotational power
Data Source
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AI summary
A system for reheating a power generation system (10) including a boiler (12) having a waterwall (23) and a steam drum (25) with an input fluidly coupled to the waterwall (23) and an auxiliary heat source(70) to provide heated fluid. The system also includes a first flow control valve (94) connected to the auxiliary heat source and the boiler to control a flow of heated fluid from the auxiliary heat source (70) to the waterwall (23); a first isolation valve (390) disposed at a waterwall, to isolate circulation of heated fluid from the steam drum (25) to the waterwall; and a sensor to monitor at least one operating characteristic in the boiler. The system also includes a controller (100) to control at least one of the flow control valve (94), the isolation valve (390), and the auxiliary heat source (70) to control the amount of heated fluid supplied to the waterwall (23) when the boiler (12) is not generating steam.