Coating Drying Oven Heat Pump Recirculation to Reduce VOC Energy Loss
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Solution Overview
Problem
In drying ovens, increased vapor pressure due to moisture and VOC evaporation slows down the drying process, and the energy required to process VOCs through catalytic oxidizers results in energy loss, while air leaks cause tar components to condense and adhere to work pieces.
Innovation Solution
The method involves cooling and condensing air taken out of the drying oven to remove moisture and VOCs, then reheating it for recirculation, using a heat pump with multiple stages for efficient cooling and heating, and employing CO2 and chlorofluorocarbon refrigerants for optimal temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If air is continuously supplied to the drying oven for drying the coating film, then the drying process can be maintained, but the vapor pressure inside the drying oven increases which decreases the evaporation rate and slows down drying
Solution Approach 1:
The patent extracts and removes moisture and VOCs from the drying oven air through a condenser that cools the air to condense these components, which are then separated and removed from the air stream, allowing the dried air to be recirculated back to the drying oven
Solution Approach 2:
The patent recovers useful heat from the exhaust air and waste heat from the condenser to preheat the air entering the drying oven, while discarding only the condensed moisture and VOCs, thereby maintaining high evaporation rates while reducing energy consumption
2Object-generated harmful factors
If a catalytic oxidizer is used to process VOCs from the drying oven, then VOCs can be decomposed, but energy is required for processing and the high temperature exhaust gas causes energy loss when discharged
Solution Approach 1:
The patent converts the harmful high-temperature exhaust gas from the catalytic oxidizer into a beneficial resource by using it to preheat the air entering the drying oven through heat exchange, thereby recovering energy that would otherwise be lost and reducing overall energy consumption
Solution Approach 2:
The patent recovers heat from both the catalytic oxidizer exhaust gas and the condenser waste heat, utilizing these thermal resources to preheat fresh air before it enters the drying oven, thereby converting waste heat into useful thermal energy
3Ease of operation
If air is leaked from the drying oven to the cooling zone, then air circulation can occur, but tar components condense and adhere to the work piece causing quality issues
Solution Approach 1:
The patent extracts tar components from the air stream by condensing them in the cooling zone before the air is recirculated back to the drying oven, preventing these harmful components from contacting and adhering to the work piece
Solution Approach 2:
The patent introduces a condenser as an intermediary device between the drying oven and the cooling zone that removes harmful tar components and moisture from the air stream, allowing clean air to be recirculated without causing contamination to the work piece
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 enhances drying efficiency, reduces the need for VOC processing equipment, decreases energy consumption, and prevents tar component adhesion on work pieces, leading to improved coating film quality and energy savings.
Implementation Method 1
cooling the air such that each of at least part of moisture and at least part of a VOC which are contained in the air is condensed to be removed from the air
Implementation Method 2
heating the air after the cooling, and returning the heated air into the drying oven
Data Source
Figure 1
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Figure 3
AI summary
Air is taken out from a drying oven 1 for drying a coating film of a work piece 2, and the air is cooled such that each of at least part of moisture and at least part of a VOC which are contained in the air is condensed to be removed from the air. The air after the cooling is heated, and is returned into the drying oven 1. A heat pump 3 whose heat absorption source is the air taken out from the drying oven 1 and whose heat radiation source is the air after the cooling is provided. By using the heat pump 3, cooling and heating of the air are performed.