HRSG Impurity Control via Multi-Stage Drum Evaporation
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Solution Overview
Problem
Combined cycle power plants face challenges with impurity accumulation and corrosion due to high-temperature and high-pressure conditions, where conventional condensate polishers are costly and require skilled personnel, and existing impurity removal methods are ineffective at these conditions.
Innovation Solution
A combined cycle power plant design that includes a heat recovery steam generator with a drum evaporator, a pressure-increasing pump, and a high-pressure assembly to operate condensate at a subcritical to supercritical pressure range, along with optimized impurity control measures such as chemical reagents and a leak-tight condenser to minimize impurity ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional drum type HRSG impurity removal method is used, then impurities are removed at moderate pressures and temperatures, but the method becomes ineffective at high temperature and pressure conditions
Solution Approach 1:
The HRSG system is divided into multiple pressure stages (low-pressure, intermediate-pressure, and high-pressure drum evaporators) with separate impurity removal mechanisms for each stage. This segmentation allows the system to handle impurities effectively across different temperature and pressure conditions, with each drum operating at optimized parameters for its specific range.
Solution Approach 2:
The system changes operating parameters by maintaining different pressure and temperature levels in different drums. The low-pressure drum operates at lower temperatures for effective impurity removal, while the high-pressure drum operates at higher temperatures for steam generation, thus adapting the impurity removal process to varying thermal conditions.
2Reliability
If condensate polisher is installed to remove impurities, then impurity removal is achieved, but highly skilled personnel are required and operation becomes demanding and costly
Solution Approach 1:
The multi-drum HRSG system performs impurity removal automatically through its own operational cycles. Each drum evaporator continuously removes impurities from condensate through evaporation and separation processes that occur naturally during normal operation, eliminating the need for external condensate polishers and reducing operational complexity.
Solution Approach 2:
The impurity removal function is merged with the primary steam generation function in the HRSG system. The same heat recovery process that generates steam also simultaneously removes impurities through evaporation in the drums, combining multiple functions into a single integrated system rather than requiring separate dedicated equipment.
3Object-affected harmful factors
If high purity feed water is maintained to prevent corrosion, then corrosion risk is reduced, but the system requires complex impurity control measures
Solution Approach 1:
The system converts the potential harm of high-temperature operation (which could accelerate corrosion) into a benefit by using the high temperature to completely evaporate and remove impurities in the high-pressure drum. The same thermal energy that could cause corrosion instead serves to purify the water by driving off all contaminants through complete evaporation.
Solution Approach 2:
Impurities are removed progressively through preliminary evaporation stages in the low-pressure and intermediate-pressure drums before the water enters the high-pressure steam generation system. This preliminary action of staged impurity removal prevents corrosion-prone contaminants from reaching the high-temperature high-pressure components.
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 reduces impurity accumulation and corrosion risks, achieving efficient steam generation and power plant operation without the need for costly condensate polishers, by effectively controlling impurities across varying pressure stages.
Implementation Method 1
a heat recovery steam generator arranged to receive exhaust gas from the gas turbine for reheating condensate from the steam turbine
Implementation Method 2
at least one drum evaporator configured to receive a first part of the condensate
Implementation Method 3
generating steam for the steam turbine
Implementation Method 4
a pump configured to receive a second part of the condensate and increase the second part of the condensate to an elevated pressure
Implementation Method 5
a high-pressure assembly configured to receive at least part of the condensate from the pump and operate the condensate at a subcritical up to a supercritical pressure range
Data Source
AI summary
A combined cycle power plant includes a gas turbine, a steam turbine and a heat recovery steam generator. The heat recovery steam generator is arranged to receive exhaust gas from the gas turbine for reheating condensate from the steam turbine and generating steam for the steam turbine. And the heat recovery steam generator includes at least one drum evaporator configured to receive a first part of the condensate; a pump configured to receive a second part of the condensate and increase the second part of the condensate to an elevated pressure; and a high-pressure assembly configured to receive the condensate from the pump and operate the condensate from the pump at a subcritical up to a supercritical pressure range.