DeNOx Boiler Bypass Valve for Catalyst Activation
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Solution Overview
Problem
Existing gas temperature control systems for DeNOx boilers in engine cogeneration plants fail to quickly raise the temperature of water to the activation temperature of denitrification catalysts, leading to incomplete nitrogen oxide decomposition and subsequent air pollution.
Innovation Solution
A gas temperature control apparatus with bypass gas flow channels and flow control valves that adjust the flow rate of combustion gas to ensure high-temperature combustion gas reaches the denitrification catalyst layer, utilizing water-cooled plugs and control motors to maintain optimal temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If water is heated in a conventional boiler without bypass gas flow control, then the boiler structure is simple, but it takes about two hours to raise water temperature to catalyst activation temperature, causing nitrogen oxide to be discharged without decomposition
Solution Approach 1:
The boiler is divided into a combustion tank and a heat exchange tank, with separate fire tubes for each function. The combustion tank receives high-temperature combustion gas directly, while the heat exchange tank receives preheated gas through fire tubes, allowing independent temperature control zones that accelerate water heating without complicating the overall system
Solution Approach 2:
High-temperature combustion gas is directed through bypass flow channels to preheat water in the heat exchange tank before the main combustion process completes. This preliminary heating action reduces the time to reach catalyst activation temperature by preparing the thermal environment in advance
2Productivity
If high-temperature combustion gas is introduced directly to the denitrification catalyst layer, then catalyst activation is achieved quickly, but the temperature becomes non-uniform causing incomplete nitrogen oxide decomposition
Solution Approach 1:
Fire tubes serve as intermediaries between the combustion tank and heat exchange tank. These tubes transfer thermal energy from high-temperature combustion gas to water in a controlled manner, mediating the temperature transfer to achieve both rapid heating and uniform temperature distribution throughout the heat exchange medium
Solution Approach 2:
Different regions of the boiler are assigned different temperature characteristics: the combustion tank maintains high temperature for rapid heating, while the heat exchange tank receives moderated temperature through fire tube conduction, creating local quality zones that simultaneously achieve fast activation and uniform decomposition conditions
3Measurement precision
If bypass flow control valves are used to control combustion gas flow rate, then temperature control precision is improved, but the valve structure becomes more complex
Solution Approach 1:
The bypass flow control valve incorporates a water-cooled plug that uses the process water itself as a cooling medium. The valve plug is cooled by circulating water from the heat exchange tank, allowing the valve to withstand high temperatures without requiring external cooling systems or complex temperature control mechanisms, achieving precise flow control through simple thermal self-regulation
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 solution reduces the time required to reach activation temperature, minimizes nitrogen oxide discharge, and extends the lifespan of the denitrification catalyst by maintaining uniform combustion gas temperature.
Implementation Method 1
a cooling water inlet and a cooling water outlet formed at the other side end of the water cooled plug to cool heat of a high-temperature combustion gas
Implementation Method 2
a denitrification catalyst layer formed between the first fire tube and the second fire tube to remove nitrogen oxide
Implementation Method 3
combustion gas of a low temperature state is introduced into a denitrification catalyst layer during the above time period
Data Source
AI summary
A gas temperature control apparatus for a DeNOx boiler in an engine cogeneration plant is installed to maintain a reaction temperature of denitrification catalyst used to remove nitrogen oxide generated from an internal combustion engine in the engine cogeneration plant. The apparatus includes a connection passageway between a high-temperature gas part of a combustion tank of the boiler and an intermediate-temperature gas part formed after a first heat exchange, and a flow control valve mounted in the passageway to thereby control a volume of bypass combustion gas. The apparatus can easily raise temperature of combustion gas even though temperature of the inside water of the boiler does not reach a normal operation state since the flow control valve mounted in the connection passageway between the high-temperature gas part and the intermediate-temperature gas part. thereby greatly reducing a time period to reach an activation temperature of the denitrification catalyst.