Backup Steam Routing for CO2 Recovery During Turbine Trips
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Solution Overview
Problem
In plants combining a gas turbine combined cycle (GTCC) with a CO2 recovery device, there are situations where the supply of steam to the CO2 recovery device is insufficient, such as during plant activation, stoppage, load rejection, or steam turbine trips, leading to a decrease in CO2 recovery rate.
Innovation Solution
A steam supply system and method that includes a low-pressure line, a medium-pressure line, and a control device to manage steam valves, allowing the diversion of medium-pressure steam to the CO2 recovery device through a backup line when low-pressure steam is insufficient, using a control device to adjust valve openings based on plant operation states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-pressure steam supply line is used to supply steam to the CO2 recovery device, then the CO2 recovery rate can be maintained during normal operation, but the steam supply becomes insufficient during plant stoppage, load rejection, or steam turbine trips
Solution Approach 1:
The steam supply system is designed to serve multiple functions through different supply lines. The low-pressure steam supply line serves as the primary supply route during normal operation, while the medium-pressure steam supply line serves as an alternative route during abnormal conditions. This multi-functionality ensures the system can adapt to different operation states and maintain CO2 recovery across various scenarios.
Solution Approach 2:
The system dynamically switches between different steam supply configurations based on the operation state. During normal operation, low-pressure steam is supplied through the dedicated low-pressure line. During plant stoppage, load rejection, or steam turbine trips, the system transitions to supplying medium-pressure steam through the medium-pressure line to the CO2 recovery device, ensuring continuous and reliable steam supply despite changing conditions.
2Reliability
If the low-pressure steam governing valve is closed during plant stoppage or steam turbine trip, then the steam turbine can be protected, but the CO2 recovery device loses its steam supply
Solution Approach 1:
The medium-pressure steam supply line acts as an intermediary solution when the low-pressure steam supply is interrupted. When the low-pressure steam governing valve is closed to protect the steam turbine, the medium-pressure steam supply line provides an alternative steam source to the CO2 recovery device, maintaining productivity without compromising the protection of the steam turbine.
Solution Approach 2:
The system prepares alternative steam supply paths in advance to cushion against potential disruptions. By having the medium-pressure steam supply line ready and available, the system can immediately switch to this alternative route when the low-pressure steam supply is interrupted, preventing CO2 recovery rate decline before it occurs.
3Quantity of substance
If medium-pressure steam is extracted from the medium-pressure line, then the steam supply to the CO2 recovery device can be supplemented, but the medium-pressure steam governing valve must be controlled
Solution Approach 1:
The control device monitors the operation state of the power plant and the steam supply conditions, then adjusts the medium-pressure steam governing valve accordingly. When low-pressure steam supply is insufficient or interrupted, the control device opens the medium-pressure steam governing valve to extract medium-pressure steam and supply it to the CO2 recovery device, ensuring the required steam quantity is maintained through feedback-based control.
Data Source
AI summary
A steam supply method involves a CO2 recovery device, a first line through which low-pressure steam is extracted from a low-pressure line for supply of the low-pressure steam to a steam turbine and to the CO2 recovery device, and a second line through which medium-pressure steam is extracted from a medium-pressure line for supply of the medium-pressure steam to the first line. A low-pressure steam governing valve is provided upstream of a connection position of the low-pressure line with the first line. A medium-pressure steam governing valve of the medium-pressure line, and a steam backup valve of the second line are provided. The method includes closing the low-pressure steam governing valve and the medium-pressure steam governing valve and opening the steam backup valve based on a state of operation of the power plant.