Vertical Heat Recovery Steam Generator Low-Pressure Flow Stability
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Solution Overview
Problem
Current vertical heat recovery steam generators face challenges in achieving stable flow through evaporators at low pressures due to inadequate heating surface configurations, leading to potential corrosion and inefficiencies.
Innovation Solution
A vertical heat recovery steam generator design featuring a condensate preheater, a separate low-pressure preheater, and a low-pressure evaporator, with a flow medium flowing successively through each without additional pressure compensation, ensuring a sufficient pressure drop and maintaining a minimum temperature to prevent corrosion, using a combination of heating surfaces and a recirculation circuit for temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the preheating of feed water takes place exclusively in the condensate preheater, then the system structure is simplified, but stable flow through the low-pressure evaporator cannot be achieved
Solution Approach 1:
The heating surface is segmented into two separate components: a condensate preheater for high-pressure system preheating and a separate low-pressure preheater for low-pressure system preheating. This segmentation allows each component to be optimized for its specific function, enabling stable flow through the low-pressure evaporator while maintaining overall system efficiency.
Solution Approach 2:
The flow medium serves multiple functions by passing through both the condensate preheater and the low-pressure preheater in sequence. The same flow medium is used for preheating feed water in the low-pressure system and for heat recovery, demonstrating multi-functionality that resolves the contradiction between structural simplicity and flow stability.
2Reliability
If small inside diameters are used in the preheater tubes to produce sufficient pressure drop, then flow stability is achieved, but the tubes are more prone to corrosion
Solution Approach 1:
Different sections of the heating surface are designed with different local qualities: the low-pressure preheater uses small inside diameters to generate sufficient pressure drop for flow stability, while the condensate preheater uses larger diameters to minimize corrosion risks. This local differentiation allows each region to be optimized for its specific operational requirements.
Solution Approach 2:
The flow medium is preheated in the condensate preheater before entering the low-pressure preheater, ensuring that the temperature remains above the corrosion threshold when the medium passes through the small-diameter tubes of the low-pressure preheater, thereby preventing corrosion while maintaining flow stability.
3Productivity
If the flow medium temperature is allowed to drop below design temperature in the low-pressure preheater, then preheating efficiency is improved, but corrosion occurs in the tubes
Solution Approach 1:
The system incorporates temperature monitoring and control mechanisms that provide feedback to maintain the flow medium temperature above the corrosion threshold in the low-pressure preheater. This feedback control allows the system to operate at optimal preheating efficiency while preventing tube corrosion through active temperature management.
Solution Approach 2:
The flow medium undergoes preliminary heating in the condensate preheater before entering the low-pressure preheater, ensuring that sufficient temperature margin is maintained. This preliminary action prevents the temperature from dropping below the corrosion threshold while still allowing effective preheating to occur in the low-pressure system.
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 design achieves stable flow and prevents corrosion in the low-pressure evaporator, enhancing the efficiency and stability of the steam generator operation across the entire load range without additional economic or operational disadvantages.
Implementation Method 1
a condensate preheater with at least one condensate preheater heating surface, through which a flow medium flows and which is disposed in a hot gas channel, through which hot gas flows
Implementation Method 2
a condensate preheater with at least one condensate preheater heating surface, through which a flow medium flows and which is disposed in a hot gas channel, through which hot gas flows
Implementation Method 3
a low-pressure preheater with at least one low-pressure preheater heating surface, through which the flow medium flows and which is disposed in the hot gas channel
Implementation Method 4
a low-pressure preheater with at least one low-pressure preheater heating surface, through which the flow medium flows and which is disposed in the hot gas channel
Implementation Method 5
a low-pressure evaporator with at least one low-pressure evaporator heating surface, through which the flow medium flows and which is disposed in the hot gas channel
Implementation Method 6
a low-pressure evaporator with at least one low-pressure evaporator heating surface, through which the flow medium flows and which is disposed in the hot gas channel
Data Source
AI summary
A vertical heat recovery steam generator, the low-pressure stages of which are designed as a once-through system, having a condensate preheater with at least one condensate preheater heating surface, through which a flow medium flows and which is disposed in a hot gas channel through which hot gas flows, a low-pressure preheater with at least one low-pressure preheater heating surface through which the flow medium flows and which is disposed in the hot gas channel, and a low-pressure evaporator with at least one low-pressure evaporator heating surface through which the flow medium flows and which is disposed in the hot gas channel. The flow medium flows successively through the at least one low-pressure preheater heating surface and the at least one low-pressure evaporator heating surface in one pass and without additional pressure compensation.