Sensors in fluid bed dryers play an important role during the drying process of wet products. Different sensors are installed in the FBD or fluid bed dryer, and their role is to monitor and regulate different critical parameters to ensure good product quality and efficient drying.
Whenever you want to buy a fluid bed dryer, you must ask about the sensors installed in the fluid bed dryer, and you can also mention your requirements to the manufacturer to add any specific type of sensor.
Why Sensors Are Required
To understand why we need sensors in fluid bed dryers, let’s have a brief look at the working of fluid bed dryers.
The fluid bed dryers are used in the pharmaceutical industries for drying the wet mass, and the process of drying is started after loading the wet mass in the product trolley of the FBD. The hot processed air comes inside the fluid bed dryer through the perforated bottom of the FBD and results in fluidisation of the product. For uniform drying, each particle must have constant contact with the hot air, and then the hot air leaves the drying chamber through filters and is exhausted.
Sensors are required in FBd to monitor and regulate all the parameters during the drying process, and without these sensors, the product will be over-dried or under-dried and different other roles of sensors are also discussed here.
Types Of Sensors
The most commonly installed sensors in a fluid bed dryer are as follows,
- Temperature Sensors
- Air Pressure/Air Flow sensors
- Product Level Sensor
- Solid Flow Monitor
- Moisture Sensor
- Product Trolley Level Sensor
- Particle size sensors
- Vibration Sensor
- Current/Voltage Sensor
- Oxygen Sensor
Temperature Sensors
Temperature sensors monitor the temperature of the air and the product, andthe following temperature sensors are installed in the fluid bed dryer
- Inlet air temperature sensor
- Outlet air temperature sensor
- Product temperature Sensor
Inlet air temperature sensor
The inlet air temperature sensor is installed in the inlet air duct and monitors/regulates the temperature of incoming air. If the temperature of incoming air is low, it will result in under-drying, and if the temperature of incoming air is high, it will result in over-drying. So this temperature sensor is very important for monitoring the air temperature that directly impacts product drying.
Outlet air temperature sensor
This sensor is installed in the return air duct and monitors the temperature of air that leaves the drying chamber after the drying process.
Product Temperature Sensor
The product temperature sensor has direct contact with the product and provides us with real-time data regarding the temperature of the product under drying in the product trolley.
Air Pressure Sensors
Two types of sensors related to air are installed in the fluid bed dryer, which are
- Air Flow Sensor
- Pressure Sensors
Air Flow Sensor
Air flow sensors measure the volume of air coming inside the product trolley through a plenum from the AHU. Air flow sensors are of great importance because low air flow volume will result in improper fluidization and higher air volume may damage filters or result in the production of finer particles during the drying process.
Pressure Sensors
Pressure Sensors sense a pressure drop between the product and the filter, which may be due to filter choking.
Product Level Sensor
A product-level sensor is installed to monitor the level of product loaded in the fluid bed dryer product trolley. It helps to identify overloading or underloading of the product trolley.
Solid Flow Monitor
A solid flow monitor is also known as a broken bag detector and is one of the most important sensors installed in the outlet duct of FBD. It senses the powder in the outlet duct, which occurs due to filter damage and shuts down the fluid bed dryer.
Moisture Sensor
Moisture sensor in the fluid bed dryer directly senae the moisture level in the product to be dried and helps to find out the end point of drying when the required level of moisture in the product is achieved.Examples are NIR sensors to provide real-time data of product moisture content.
Product Trolley Level Sensor
This sensor ensures that the product trolley alignment is fine and it is positioned correctly in its place.
Particle size sensors
Some fluid bed dryers are equipped with sensors which measure the particle size distribution during the drying process.
Vibration Sensor
A vibratory sensor in the fluid bed dryer helps to protect the FBD by shutting down the fluid bed dryer in case of abnormal vibrations of the fluid bed dryer.
Current/Voltage Sensor
These sensors monitor electric systems installed in FBD, which are involved in the operations of motors and other electrical components.
Oxygen Sensor
In specific conditions, oxygen sensors are installed in fluid bed dryers to monitor the level of oxygen in the drying chamber of FBD. It is required in cases where oxygen-sensitive materials are dried in fluid bed dryers.
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