Fossil-Fired Steam Generator Overflow Line for Power Reserve
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Solution Overview
Problem
Modern steam power plants require flexible and efficient operation to rapidly adjust output in response to frequency disturbances and load changes, but existing fossil-fired steam generators face efficiency losses due to permanent throttling and limited storage capacity, which complicates short-term output increases without invasive structural modifications.
Innovation Solution
The implementation of two supply lines for the overflow line, one branching off before and one after high-pressure preheaters, allows for adjustable injection water enthalpy by mixing water from both points, ensuring sufficient subcooling and maximizing steam production, thereby enhancing power delivery without compromising efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent throttling of turbine valves is used to maintain power reserve, then power availability for frequency disturbances is improved, but efficiency of the steam process deteriorates
Solution Approach 1:
The system prepares for power disturbances by pre-positioning feedwater in the overflow line at different enthalpy levels, so that when a disturbance occurs, the control system can immediately inject the appropriate amount of subcooled water to create power reserve without needing to permanently throttle turbine valves, thus maintaining both power availability and efficiency
2Temperature
If injection water is taken before high-pressure preheaters, then sufficient subcooling is achieved, but the amount of steam produced is reduced
Solution Approach 1:
The overflow line is divided into two separate supply lines: one branching off before the high-pressure preheaters to provide subcooled water, and another branching off after the preheaters to provide water with higher enthalpy. This segmentation allows the control system to select or combine water from different sources to achieve the optimal balance between subcooling and steam production based on operational requirements
Solution Approach 2:
The system changes the enthalpy parameter of the injection water by providing multiple supply options at different stages of the preheating process. By adjusting which supply line is used or combining them, the enthalpy of the injection water can be optimized to achieve both sufficient subcooling and maximum steam production simultaneously
3Productivity
If injection water is taken after high-pressure preheaters, then steam production is increased, but sufficient subcooling cannot be guaranteed
Solution Approach 1:
The overflow line is divided into two separate supply lines: one branching off before the high-pressure preheaters to provide subcooled water, and another branching off after the preheaters to provide water with higher enthalpy. This segmentation allows the control system to select or combine water from different sources to achieve the optimal balance between subcooling and steam production based on operational requirements
Solution Approach 2:
The system creates a composite injection water supply by allowing mixing of water from both supply lines (before and after preheaters) to achieve the desired enthalpy and subcooling characteristics, combining the benefits of both cold subcooled water and warm high-enthalpy water in the appropriate proportions
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 approach enables immediate and safe power reserve creation with reduced throttling of turbine valves, maintaining high efficiency and reducing operational costs by ensuring sufficient supercooling and increased steam production, independent of other measures.
Implementation Method 1
an overflow line is connected to the flow path on the inlet side and leads to an injection valve arranged in a medium-pressure stage
Implementation Method 2
injections are triggered by reducing the temperature setpoint at the outlet of the respective pressure stage. The higher the enthalpy level of the injection water, the more injection mass flow is required to reach the newly required temperature setpoint
Implementation Method 3
the first of which branches off on the flow medium side before a high-pressure preheater and the second on the flow medium side branches off behind the high-pressure preheater
Data Source
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AI summary
The invention relates to a fossil-fired steam generator (1) for a steam power station, having, in a plurality of pressure stages (2, 4), a number of economiser, evaporator and overheating surfaces (12, 14, 16) forming a flow path (2) and which are cross-flown by a flow medium M. In a high pressure stage (2), an overflow line (24) is connected on the inlet side to the flow path (2) and leads to an injection valve (18) arranged in a medium pressure stage (4) of the flow path (2), on the flow medium side, upstream of a overheating surface (16). The aim of the invention is to provide a fossil-fired steam generator of said type in which the efficiency of the steam process is not effected too much. Also, an increase in the power in the short term can be possible, independently from the structure of the fossil-fired steam generator, without having to implement invasive structural modifications of the entire system. Also, the overflow line (24) comprises two supply lines (26, 30), the first of which is connected upstream, on the flow medium side, of a high pressure preheater (10) and the second is connected downstream, on the flow medium side, of the high pressure preheater (10).