LEL Monitoring Systems
Automatic Air Recirculation Control Systems
During the exsiccation process of the inks and the vaporization of the solvent, a lot of energy is required to heat the fresh air up to the desired temperature.
The NIRA LEL Monitoring Systems continuously check the solvent concentration inside the drying stations and in case the solvent concentration exceeds a certain limit (± 50% LEL), the NIRA LEL system, for safety reason, sends out an alarm (PL“d” contact) in order to immediately stop the machine production.
When the solvent concentration inside the drying station is lower than its admissible level, the exhaust air can be recycled and reused as fresh air.
The NIRA Automatic Air Recirculation Systems are logic systems able to control the air recycled on the bases of the solvent concentration inside the drying stations, detected by the NIRA LEL Monitoring Systems.
All drying stations are always equipped with their own supply fan and their own suction fan (or suction systems). Through some mechanical ducts and some modulating dampers, the NIRA automatic air recirculation system controls the hot air recycled but always keeping continuously the solvent concentration under control and in full safety conditions.
These automatic air recirculation systems drastically reduce the energy costs (electricity, natural gas or fuel oil) associated to air heating systems for the drying stations. The energy saving, through these systems, can go from 30 up to 60% of the current energy consumption.
These LEL monitoring systems and automatic air recirculation systems can be integrated on any type of machines, like coating, laminating, flexographic and gravure press machines.
The energy saving is based on the following process information:
– Number of the drying stations;
– Average air flow in evacuation from each drying station (in Nm3/h);
– Average inlet air temperature (in °C);
– Average drying temperature (in °C);
– Average solvent concentration in evacuation from each drying station (in gr/m3 or % LEL);
– Average machine working hours per year (in h/y);
– Average coating, laminating and printing speed (in mt/min.);
– Average coating, laminating and printing coverage (in %);
– Type of heating systems (Natural gas, electricity or fuel oil);
– Energy cost (€/m3 – €/kWh or €/kg);
Together with these process information and after a technical inspection, we will be able to provide detailed proposals, air flow reductions, energy saving estimations and investments payback time.ENERGY TIPS – PROCESS HEATING
Automatic Air Recirculation Systems for water-based and solvent-based application
During normal solvent-based applications, the solvent concentration in evacuation from the drying stations is detected through a LEL monitoring system (Lower Explosion Level).
e recycled and sent back at the inlet air duct. These air recirculation systems allow thermal energy saving and flow rate optimization. Usually, during water-based applications, these air recirculation systems are excluded or they are set to a low air recirculation percentages (± 30%).
To achieve an air recirculation system during water-based applications, it’s possible to use Relative Humidity sensors, but unfortunately these sensors cannot be exposed to any vapors of solvents because it may alter their readings and even lead to their breakup.
In order to avoid this issue, we have developed an external sampling system. The sample gas (vapor) is sucked, by an ejector, inside the sampling system. Inside the sampling system, the sample gas (vapor) is analyzed by a Relative Humidity sensor; if the relative humidity of the gas is lower than a certain level, the exhaust air can be recycled and sent back at the inlet air duct. Considering the high temperature inside the drying stations during water-based applications (±100°C), these innovating air recirculation systems will allow a huge energy saving, up to 50%, of your actual thermal energy consumption.
NOTE: The NIRA automatic air recirculation systems for water-based applications can be combined together with any other type of automatic air recirculation system for solvent-based applications.
For any queries about our systems and services, please get in touch directly with us.