Coating drying method and device therefor
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Solution Overview
Problem
In drying ovens, the evaporation of moisture and volatile organic compounds (VOCs) from coating films increases vapor pressure, slowing the drying process, and requires energy to process VOCs through catalytic oxidizers, while air leaks lead to tar component condensation and adhesion issues.
Innovation Solution
A method using a heat pump to cool and condense moisture and VOCs from air inside the drying oven, then reheat the air for recirculation, reducing vapor pressure and eliminating the need for VOC processing equipment, and preventing tar component adhesion by controlling air temperature and humidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If air is heated and circulated in the drying oven to dry the coating film, then drying temperature is maintained, but vapor pressure increases due to evaporation of moisture and VOC which decreases evaporation rate and extends drying time
Solution Approach 1:
The patent extracts and removes moisture and VOC from the drying oven air by condensing them in a condenser. The condensed water and VOC are separated and discharged, while the dried air is recirculated back to the drying oven. This extraction of harmful vapors prevents vapor pressure buildup and maintains high evaporation rates throughout the drying process.
Solution Approach 2:
The patent changes the temperature parameter of the air by cooling it below the dew point in the condenser to condense moisture and VOC, then reheating the cooled air before recirculation. This parameter change enables continuous removal of vapors while maintaining the drying temperature in the oven, resolving the contradiction between maintaining drying temperature and controlling vapor pressure.
2Object-generated harmful factors
If catalytic oxidizer is installed to process and combust VOC from the drying oven, then VOC is decomposed and deodorized, but energy is required for processing and high temperature exhaust gas causes energy loss when discharged
Solution Approach 1:
The patent uses phase transition (condensation) to remove VOC from the air stream instead of combustion. By cooling the air below the dew point, VOC condenses into liquid form and is separated in the water-VOC separator. This phase transition approach eliminates the need for energy-intensive catalytic oxidation while effectively removing harmful VOC emissions.
Solution Approach 2:
The patent converts the harmful high-temperature exhaust gas from the catalytic oxidizer into a useful resource by using it to preheat the incoming air through a heat exchanger. This converts the energy waste of hot exhaust discharge into beneficial preheating of fresh air, reducing the energy required for heating the drying air.
3Loss of energy
If preheating oven and cooling zone are added to the drying system for heat pump operation, then energy recovery is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the heat pump system: the heat pump's condenser serves as both the cooling device for condensing moisture and VOC, and the heat pump's evaporator serves as the preheating heat exchanger for incoming air. This integration achieves energy recovery and vapor removal without adding separate preheating and cooling equipment, reducing overall system complexity.
4Productivity
If air is circulated in the drying oven to maintain temperature, then drying efficiency is improved, but air leaks from drying oven to cooling zone cause tar components to condense and adhere to work piece
Solution Approach 1:
The patent implements a feedback control system where air is continuously monitored for vapor content, and the condenser operates to maintain air conditions below the dew point. This feedback mechanism ensures that tar components remain in vapor form and are carried away with the recirculated air rather than condensing on the work piece, preventing adhesion while maintaining drying efficiency.
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 method enhances drying efficiency, saves energy, and prevents tar component adhesion, allowing for quicker and higher-quality coating film drying without the need for VOC processing equipment.
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
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.