Convective Dryer System Combustion Gas Segmentation
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Solution Overview
Problem
Existing dryer installations for paper webs face high mechanical energy consumption and thermal energy loss due to inefficient suction and blowing of combustion products, limiting temperature and increasing costs and space requirements.
Innovation Solution
The implementation of an internal casing within the external casing to re-use hot combustion products, mixing them with lower-temperature gases to achieve temperatures above 350°C, and using a venturi-system or turbines to optimize gas flow and distribution, reducing mechanical energy consumption and thermal losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If combustion products are suctioned and blown through long trajectories to distribute over the entire web width, then the combustion products can be distributed across the web, but the mechanical energy consumption increases and thermal energy is lost
Solution Approach 1:
The convective system is divided into multiple independent blowing devices arranged in rows across the web width. Each device handles a specific zone, eliminating the need for long-distance transport and mixing of combustion products across the entire width. This segmentation allows direct local distribution while reducing mechanical energy consumption and thermal losses.
2Area of stationary object
If suction and blowing ducts are sized to cover the entire web width, then complete coverage is achieved, but thermal energy is dissipated through radiation and convection from large duct surfaces
Solution Approach 1:
The duct system is segmented into multiple smaller ducts corresponding to different web width zones. This reduces the total surface area of individual ducts, minimizing thermal energy losses through radiation and convection from duct surfaces while still achieving complete web coverage through the distributed arrangement.
3Object-affected harmful factors
If cold air is aspirated to cool combustion products, then the combustion products become safer to handle, but the temperature of combustion products blown on the web is considerably lower
Solution Approach 1:
The system extracts and removes cold air aspiration from the combustion product flow path. By eliminating the mixing of cold air with hot combustion products, the system maintains high combustion product temperatures for efficient web drying while using alternative methods (direct radiant heating and localized convective blowing) to control temperature distribution.
4Ease of operation
If mixing devices are positioned far from the web to collect combustion products laterally, then the devices can access combustion products, but important mixing energy is consumed
Solution Approach 1:
Instead of positioning mixing devices far from the web to collect combustion products laterally, the system inverts the approach by placing blowing devices directly adjacent to the web. Combustion products are collected and blown directly at the web surface, eliminating the need for lateral collection and extensive mixing operations.
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 heat exchange efficiency, reduces mechanical energy consumption, and allows for a more compact dryer installation capable of operating at higher temperatures, thereby minimizing costs and thermal losses.
Implementation Method 1
using a venturi-system or turbines to optimize gas flow and distribution
Implementation Method 2
convective exchanges between the passing web and the combustion products
Implementation Method 3
The ducts dissipate thermal energy by radiation and convection
Implementation Method 4
using a venturi-system or turbines to optimize gas flow and distribution
Data Source
Figure 1~2
Figure 3a~3b
Figure 4~6
AI summary
The present invention concerns a convective system for a dryer installation for a passing web, more particularly paper. The convective system 7 is an assembly of an exterior casing 13 for suction of combustion products with opening 14 towards the web, with a first 15 and second 16 suction ducts sucking the combustion products into the convective system 7. The combustion products coming from the first suction duct 15 are guided through the exterior casing 13 to a mixing and blowing device 17. Cold air 18 is mixed in this mixing and blowing device 17 with the combustion products 19, resulting in a gas mixture with lower temperature 20. The convective system 7 also has an internal casing 21 inside the external casing 13. This internal casing 21 has at least one opening towards the web 22 and has also openings 34 allowing gas flow from the mixing device 17 to the internal casing 21 of said gas mixture 20. Under the internal casing 21, there is also a blowing duct 23. The second suction duct 16 is also arranged under this internal casing 21 thereby extracting a second flow of combustion products 24 into the internal casing 21. This second flow 24 of combustion products is then mixed with the gas mixture 20 coming from the mixing device 17, resulting in a mixture of gasses 25 with a temperature that is higher than the first gas mixture 20 and higher than e.g. 350 °C or 370 °C, more preferably 390 °C or 410 °C, even more preferably 420 °C, 450 °C or 500 °C. These hot gasses 25 are then blown to the drying web by the blowing duct 23 of the internal casing 21.