Drying Oven Air Circulation and Heat Recovery
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Solution Overview
Problem
Existing drying methods for material webs are inefficient due to high energy consumption and slow drying speeds, as they involve heating fresh air and releasing moist exhaust air into the environment, and existing heat recovery systems are complex and costly.
Innovation Solution
The method involves regulating air transport and circulation in each drying chamber independently based on exhaust air humidity and temperature, allowing for operation at lower chamber pressures than ambient pressure, and utilizing moist air from downstream chambers to preheat the material web, potentially omitting heating in the first chamber to enhance energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fresh air is heated in each drying chamber and moist exhaust air is released into the environment, then the material web can be dried in stages from chamber to chamber, but the energy consumption is very large and the drying speed is low
Solution Approach 1:
The patent recovers thermal energy from the moist exhaust air by passing it through a heat exchanger that preheats the fresh air entering the first drying chamber. This recovers the thermal energy that would otherwise be wasted when exhaust air is released into the environment, thereby reducing the energy required to heat fresh air in each chamber while maintaining the staged drying process.
Solution Approach 2:
The patent establishes continuous air circulation where exhaust air from the last chamber is continuously recirculated through the heat exchanger to preheat incoming fresh air. This creates a continuous thermal energy transfer process that maintains efficient drying operation without interruption, ensuring that thermal energy is constantly recovered and reused throughout the drying process.
2Loss of energy
If separate heat recovery systems are installed to use warm exhaust air for heating the wet material web, then heat recovery can be achieved, but the systems are complex and expensive and require additional energy for transport and circulation
Solution Approach 1:
The patent merges the heat recovery function directly into the existing air circulation system by integrating a heat exchanger that simultaneously handles both the exhaust air and fresh air flows. This eliminates the need for separate heat recovery systems with independent circulation loops, reducing system complexity while achieving effective heat recovery from exhaust air to preheat incoming air.
Solution Approach 2:
The heat exchanger serves multiple functions: it recovers thermal energy from exhaust air, preheats fresh air entering the drying chambers, and maintains continuous air circulation. This multi-functional component replaces what would otherwise require separate systems for heat recovery and air circulation, thereby reducing overall system complexity and cost.
3Ease of operation
If the ratio of air transported to air circulated is fixed by the blower system, then the system is simpler to operate, but the amount of air transported and pressure difference cannot be independently adjusted
Solution Approach 1:
The patent segments the air handling function into two independent control systems: a blower that controls the overall air transport and pressure difference between chambers, and a recirculation fan that independently controls the amount of exhaust air recirculated through the heat exchanger. This segmentation allows independent adjustment of air transport ratio and circulation amount, providing operational flexibility while maintaining system simplicity through dedicated control functions.
Solution Approach 2:
The patent introduces dynamic adjustability by allowing the recirculation fan speed to be varied independently of the blower speed. This enables the system to dynamically adapt the ratio of transported air to circulated air based on drying requirements, while the blower maintains the necessary pressure differential. The dynamic control of separate fan speeds provides versatility without compromising operational simplicity.
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 reduces energy consumption and enhances drying speed by optimizing air flow and heat recovery, minimizing energy losses and eliminating the need for separate heat recovery systems.
Implementation Method 1
the air in each of the drying chambers is circulated by an air circulation fan assigned to the chamber in question
Implementation Method 2
a suitable heater, if necessary to mix it with circulating air, heat it up
Implementation Method 3
the web can be dried in stages, i.e. from chamber to chamber
Data Source
Figure 1
AI summary
The invention relates to a method for drying a material web (5) in a drying oven (1) having a plurality of drying chambers or regions (3) which are connected in series behind one another. In the drying chambers, air which is sucked in from the surroundings is heated and circulated, in order to remove moisture from the material web (5) and to discharge used moist air to the surroundings. The material web (5) passes through the drying chambers or regions (3) one after another, carried by a transport means, wherein dry air is blown or sucked into the final drying chamber (3a), from which the material web (5) leaves the drying oven (1), is heated and circulated and is subsequently guided from the final drying chamber (3a) to the adjoining drying chambers (3b to 3f) one after another and is circulated in each case in the latter, before the air which is blown or sucked in at the final drying chamber (3a) is blown or sucked out at the first drying chamber (3f), into which the moist material web (5) enters into the drying oven (1). The air is circulated in each of the drying chambers (3) by in each case one air circulation fan (G) which is assigned to the relevant chamber, and dry air is blown or sucked into the final drying chamber (3a) or the air is blown or sucked out of the final drying chamber (3f) by at least one further fan.