Heat Recovery Steam Generator Control for Low Load Adaptability
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Solution Overview
Problem
Combined cycle power plants face challenges in generating sufficient high-quality steam and maintaining catalyst efficiency at low gas turbine loads, leading to potential thermal stresses and inadequate steam supply for steam turbines and cogeneration processes.
Innovation Solution
A control method for the heat recovery steam generator that optimizes thermal exchange between gas turbine exhaust fumes and the steam circuit using a control device with detecting, error calculating, set point calculating, and actuating modules to adjust steam flow and temperature, ensuring adequate steam generation and catalyst efficiency even at low loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the gas turbine operates at reduced load, then the plant can meet reduced energy demand, but the exhaust fumes flow rate and temperature decrease, causing insufficient steam generation
Solution Approach 1:
The patent implements dynamic control of the steam generator by adjusting the opening degree of the steam control valve based on real-time detection of exhaust fumes parameters and steam generation status. This dynamic adjustment allows the system to adapt to varying load conditions, maintaining adequate steam generation even when exhaust fumes flow rate and temperature decrease at reduced gas turbine loads.
Solution Approach 2:
The control system continuously detects parameters such as exhaust fumes temperature, steam pressure, and steam flow rate, then feeds this information back to adjust the steam control valve opening degree. This feedback mechanism ensures that steam generation remains sufficient across different operating conditions, resolving the contradiction between load adaptability and steam quantity maintenance.
2Adaptability or versatility
If the gas turbine operates at low load, then energy demand is reduced, but the exhaust fumes temperature is insufficient to heat the catalytic converter, leading to increased CO emissions
Solution Approach 1:
The control system detects exhaust fumes temperature and catalytic converter status in real-time, then adjusts the steam control valve to maintain adequate thermal energy in the exhaust stream. This feedback control ensures the catalytic converter receives sufficient heat even at low loads, preventing CO emission increases while enabling flexible low-load operation.
3Use of energy by moving object
If the steam generator is designed for maximum thermal efficiency at nominal conditions, then steam generation efficiency is optimized, but the system cannot provide sufficient steam at reduced loads
Solution Approach 1:
Rather than designing for fixed nominal conditions, the patent implements a dynamic control system that continuously adjusts the steam control valve based on actual operating parameters. This allows the steam generator to maintain effective steam generation across the full range of loads, from minimum to maximum, resolving the contradiction between efficiency optimization and load adaptability.
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
The method ensures stable steam generation and reduced CO emissions, maintains efficiency, and increases plant flexibility by reducing fuel consumption and start-up times, allowing for efficient operation at minimum technical load and enhanced cogeneration services.
Implementation Method 1
The steam circuit extends inside the exhaust fumes flow chamber, in such a way as to use the heat of the hot fumes coming from the gas turbine unit to generate steam
Implementation Method 2
A catalyst is also often installed along the exhaust fumes flow chamber, configured to reduce the carbon monoxide content in the fumes generated by the gas turbine unit
Data Source
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AI summary
Method for controlling the thermal exchange in a heat recovery steam generator (4) of a combined cycle power plant (1) comprising the steps of: - detecting at least one working parameter (QMPcur; Tcur) indicative of the current thermodynamic conditions in at least one first element (25, 40) of the steam generator (4) ; - calculating a thermal exchange error (et) as the difference between the detected working parameter (QMPcur; Tcur) and a respective predefined reference value (Qref; Tref); - assigning a pressure set point value (SPHP; SPMP) to a regulating member (19; 27) of the heat recovery steam generator (4) on the basis of the thermal exchange error (et) calculated; - regulating the regulating member (19; 27) on the basis of the pressure set point value (SPHP; SPMP) assigned.