Process Sensors (Europe) Limited
Process Sensors

 Applications - Bio Fuels & By-Products

  Why Measure?
The renewable energy market encapsulates a diverse range of calorie-rich by-products from production processes such as lumber, sugar and bioethanol production. The biofuel ,whether it be sawdust, straw, distillers grains (DDGS) , paper, etc is frequently pelletised in order to create fuel that is easy to handle and transport and is consistent in terms of its performance. Moisture needs to be carefully controlled so that material entering the hammer mill contains the optimum level for processing and good pellet formation. Using sawdust as an example, a moisture content of 8-10% is required for mechanical durability. If moisture levels are lower, there will be an excess of fines and dust which in itself is inefficient, but worse still, could potentially result in an explosion. If moisture content is too high, calorific value decreases according to the equation: GJ/tonne= 19.2-(0.2164 x Moisture Content %). If the wet sawdust actually manages to pass through to the hammer mill, which it rarely does owing to the fact it clogs up the screens and causes stoppages, it will fetch a low price and may only be fit for use as mulch! Even in instances where pelletisation doesn’t occur , it is important to measure the moisture content of the biofuel as practically all fuels are sold based on MC%. Other forms of renewable energy harness wind or solar power through the use of wind turbines and solar panels. NIR non contact coat weight and moisture measurement is frequently applicable to these manufacturing processes, e.g. measurement of epoxy coatweight on paper used in the fabrication of the turbine blades.
 

 

Biofuel Applications

Wood pellets Wood Pellets grasses, e.g.miscanthus Wheat-bioethanol
Straw Rapeseed  -biodiesel  
Bagasse - bioethanol Corn – bioethanol, briquettes(stalks)  

Sensor
The MCT 360 moisture in biofuels gauge, enclosed in a cast aluminium enclosure, is designed to operate under adverse environmental conditions; dust, high humidity and extreme temperatures. An air purge attachment which attaches to the window is sold as an integral part of the gauge, as is the cooling panel. The air purge keeps the window and optical path free of dust and steam. In the event temperatures exceed 50°C routinely a vortex cooler and clean air supply can be attached to cool the gauge. A 4-20mA , 0-10V or digital signal comes directly from the sensor head. An operator interface is practical for display and calibration purposes but isn’t essential. An Atex 22 MCT 360 is available for use in potentially explosive dust environments and the MCT 330-HD will operate up to temperatures of 65°C without any need for cooling. For coating applications the guardian cross web profile system will enable tight control of the coat weight.

Accessories
Commonly sold accessories sold to this industry include: a sapphire viewing window mounted in a stainless steel flange for viewing into a hopper, a probe to measure moisture in vertically falling product and a powder sampler to measure moisture in falling product when the flow is insufficient, or density is too low to obtain good product presentation across the probe window. A product loss sensor is useful to ensure measurements don’t update when there is a break in production, and a product hi/lo alarm board will alert the operator when moisture exceeds the limits set.

Gauge outputs, Operator Interface & Display


 

Up to 3 x 4-20MA or 0-10V
RS232 or RS485
Optional bus
Optional Operator Interface and display unit

 

 

The measurement
Measurement accuracy is very dependent on particle size, homogeneity and state of equilibration of the product. Accuracy will be higher on sawdust than woodchips of variable size, this is owing to the fact that smaller wood chips will be dryer than larger woodchips due to the larger surface area to mass ratio. Hog fuel will have a lower accuracy due to the fact that it is a mixture of various components of the tree and any product measured in close proximity to a dryer exit will be in a state of variable equilibration, and will not give a reliable moisture measurement..


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