False Air Suppression in Printing Drying Tunnels
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Solution Overview
Problem
In printing machines, especially rotogravure presses, the fixed recirculation ratio of air leads to unnecessary fresh air intake and heat usage, causing inefficiencies and safety concerns due to solvent vapor concentration fluctuations, and results in larger exhaust air ducts and treatment installations.
Innovation Solution
The implementation of false air suppression devices that maintain a negative pressure within the drying tunnel, allowing for the recirculation of false air and optimizing air intake based on real-time solvent evaporation needs, reducing fresh air usage and enhancing solvent concentration management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed recirculation ratio is used to maintain solvent concentration below 50% of L.E.L., then safety is improved, but heat energy is wasted and drying efficiency deteriorates
Solution Approach 1:
The recirculation ratio is made dynamically adjustable for each printing unit based on its actual solvent evaporation rate. Sensors detect solvent concentration and control systems adjust the recirculation ratio in real-time, allowing the system to transition from a fixed static configuration to a dynamic adaptive one, optimizing both safety and energy efficiency
Solution Approach 2:
Each printing unit is equipped with independent control of its recirculation ratio based on local solvent evaporation characteristics. Printing units with low ink covering can operate with higher recirculation ratios (e.g., 70-80% or higher) while those with high ink covering maintain lower ratios (e.g., 30-50%), allowing each local zone to operate optimally rather than being constrained by a global fixed ratio
2Reliability
If a fixed recirculation ratio is used to prevent explosions, then safety is improved, but the size of exhaust air ducts and treatment installations increases
Solution Approach 1:
The system dynamically adjusts recirculation ratios based on actual solvent evaporation rates, reducing the total volume of exhaust air that needs to be handled. This dynamic adaptation allows for smaller exhaust air ducts and treatment installations compared to systems designed for worst-case scenarios with fixed high recirculation ratios
Solution Approach 2:
By changing the recirculation ratio parameter based on actual operating conditions rather than maintaining a fixed conservative value, the system reduces the total air flow through the drying tunnel, thereby reducing the size requirements for exhaust air handling components
3Reliability
If more fresh air is introduced to maintain low solvent concentration, then safety is improved, but drying efficiency and energy utilization worsen
Solution Approach 1:
Sensors continuously monitor solvent concentration in the drying air, and this feedback is used by control systems to adjust recirculation ratios in real-time. This closed-loop control ensures safety by maintaining appropriate solvent concentrations while optimizing drying efficiency by using the minimum necessary fresh air rather than excessive amounts
Solution Approach 2:
The system changes the recirculation ratio parameter dynamically based on actual solvent evaporation rates, allowing fresh air intake to be optimized for each printing unit's actual needs rather than using a fixed conservative approach that introduces excessive fresh air and reduces 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 approach minimizes false air intake, reduces air flow, and allows higher solvent concentrations, leading to more efficient drying processes and smaller, less costly exhaust air treatment installations, while maintaining safety by adjusting air recirculation ratios dynamically.
Implementation Method 1
a first false air suppression device (9) arranged at the inlet (8a) of the drying chamber (19) of the drying oven (8), so that the web (2) has to travel through said device (9) before entering the drying chamber (19)
Implementation Method 2
Once the ink is printed on the support, the solvent must be removed, e.g. by evaporation, and to this aim the printed support is dried using a hot air flow, generated inside a tunnel or oven
Implementation Method 3
The warm air used to dry the solvent on the support
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
A ventilation and drying equipment for printing machines, which comprises ovens suitable to dry solvent on a printed support travelling therethrough comprising passages where false air can enter the oven from the outside. Each printing unit comprises at least one false air suppression device which covers at least one of said passages and which is maintained at a pressure lower than the air pressure inside said oven, so as to prevent said false air from entering said oven through said at least one passage. Each false air suppression device is connected with a common recirculation duct in order to share the false air coming from each printing unit on the whole press.