Method for operating a waste heat steam generator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Load-dependent, transient temperature fluctuations in the flow medium exiting the evaporator of a heat recovery steam generator designed according to the once-through principle are not optimally managed, leading to inefficiencies and reduced system flexibility.
Innovation Solution
The method involves an expanded regulation and control device that adjusts the flow rate of the bypass line based on a heat energy characteristic parameter, subcooling setpoint at the evaporator inlet, and superheat setpoint at the evaporator outlet, using a flow control valve and feed water control device to minimize temperature fluctuations by manipulating the evaporator inlet temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the flow rate of the bypass line is reduced when heat energy supplied increases, then the outlet temperature of the economizer is increased and subcooling at the evaporator inlet is reduced, but the formation of water-steam mixture at the evaporator inlet must be reliably avoided
Solution Approach 1:
The control device reduces the bypass line flow rate in advance when heat energy supplied increases, before the actual temperature change or subcooling measurement at the evaporator inlet occurs. This preliminary action prevents water-steam mixture formation by proactively adjusting the economizer outlet temperature.
Solution Approach 2:
A control device monitors heat energy supplied to the heat recovery steam generator and uses this feedback to dynamically adjust the bypass line flow rate. This closed-loop control ensures the outlet temperature of the economizer is regulated to maintain proper subcooling and prevent water-steam mixture formation.
2Adaptability or versatility
If load-dependent regulation is applied to manage transient temperature fluctuations, then system flexibility and component load are improved, but the complexity of the regulation and control device increases
Solution Approach 1:
The control device performs multiple functions: it regulates the bypass line flow rate based on heat energy supplied, manages transient temperature fluctuations, maintains proper subcooling, and prevents water-steam mixture formation. By consolidating these functions into a single control system, the patent achieves high adaptability without proportionally increasing complexity.
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 effectively reduces fluctuations in the evaporator outlet temperature, enhancing system flexibility and reducing component load, with simulations showing a decrease in overheating fluctuations from approximately 90K to 50K.
Implementation Method 1
a parameter characteristic of this heat energy supplied to the heat recovery steam generator is used to control or regulate the flow rate of the bypass line in order to reduce the flow rate of the bypass line when the parameter increases. As a result, the flow rate of the bypass line can be adjusted accordingly even if the heat energy supplied to the heat recovery steam generator increases, and thus even before the measurement of an actual change in temperature or supercooling at the inlet of the evaporator.
Implementation Method 2
heat recovery steam generator with an evaporator, an economizer with a number of economizer heating surfaces
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a method for operating a waste heat steam generator, in particular one designed according to the forced flow principle, comprising an evaporator (16), through which a flow medium flows; an economizer having a number of economizer heating surfaces (10, 14), and having a bypass line (4), which on the flow medium side is connected in parallel to a number of economizer heating surfaces (10, 14). In the method, a variable (30) that is characteristic of the heat energy supplied to the waste heat steam generator (1) for controlling or regulating the flow rate of the bypass line (4) is used, wherein the regulating or controlling of the flow rate of the flow medium through the bypass line (4) takes place at the inlet of the evaporator (16) subject to a supercooling target value (26). The regulating or controlling of the flow rate of the flow medium through the bypass line (4) also takes place at the outlet of the evaporator (16) subject to an overheating target value (110).