In-line and in real-time moisture measuring system for hygroscopic resins
All resin dryer parameters are normally controlled and monitored. The actual level of moisture is verified by sending a sample of dry material to the laboratory for analysis. This measurement procedure usually takes an hour to perform and 10-50 grams of resin are needed.
During this hour, in a bottle plant for example, the flow of material could be more than 1000 Kg.
Aquatrim measures the moisture level of all material flow in real-time. The sampling time is 200ms and the resolution is 1 ppM.
In order to optimize the drying process, several parameters need to be precisely controlled:
- Air temperature: The drying air is heated by electrical or gas fired heaters to the necessary process temperature (typically 160-190°C for PET). The dryer controls in real-time the temperature in order to hold a constant level. The upper level of temperature is limited by the material, if the level is too high the material could degrade as will the product quality, while the optimal level is very close to this limit. When the production is stopped, it’s necessary to shift to a stand-by position in order to avoid any possible degradation of the material due to the longer residence time in dryer’s hopper.
- Air flow: The air flow is controlled and regulated to ensure the correct removal of residual moisture from the plastic pellets. Its optimal value depends on the material, and indeed, a higher flow rate corresponds to a higher required power for the drying process.
- Dew point dry air: This parameter is controlled using molecular filters which absorb the residual moisture in the exhaust return air. The molecular filters need to be regenerated when they are full of water; and the regeneration process requires a lot of energy. Additionally, the frequency of regeneration is related to the amount of water extracted from the plastic pellets; which depends on the incoming level of moisture at the input of dryer.
- Residence time inside hopper
- Material quantity
- Material density
The Aquatrim sensor and measurement system performs the following functions:
- Memorize up to 12 recipes
- Trend visualization
- Exporting data & alarms to a USB key
- Three (3) alarm relay contacts (C / NO / NC)
- Analog output 4-20 mA
- Ethernet & serial connection
Aquatrim has the following capabilities and major benefits:
- Aquatrim measures the real-time moisture of plastic pellets before the extruder
- Aquatrim is designed for hygroscopic materials such as PET, PC, ABS, PA…
- The measuring range is from 5 to 1000 ppM (part per million) and material temperatures up to 200°C
- The measurement resolution is 1 ppM
- Aquatrim is completely maintenance-free