Knowledge of the core temperature of feed pellets saves resources. It saves both energy for heating and cooling the feed, but also additives like enzymes and vitamins.
In the pelletizing process of feed pellets a lot of frictional heat is generated, that is a well-known fact. Most often, the temperature difference (Delta T) is +10 ºC (see trend curve) in relation to the 81º C, which is prescribed in Danish feed legislation, to reduce salmonella. The knowledge of the core temperature of the pellets makes it possible to utilize the generated frictional heat, without compromising the heat treatment of the feed. At the same time, the inlet temperature can be lowered when the core temperature is known, i.e. the steam supply in the conditioner and thus energy / CO2 is reduced.
Trees do not grow into the clouds. Similarly, there are limits to how much the temperature can be lowered. It is the steam that softens the flour and helps to reduce friction and thus creates a more durable pill. If the steam supply is reduced too much, it will result in an increased power consumption on the pellet press’s main motor, which in turn will increase the CO2 emission of the production. Therefore, it is crucial to find the balance between the pellet press’s power consumption and the steam supply. The exact temperature reduction will depend on the individual conditions in the production, such as the composition of the recipe, the die thickness and the wear of the die.
Above is a trend curve where the conditioner’s temperature has been lowered to 74 ºC and where the temperature after the pellet press is 91 ºC.
Below is a simple calculation of what cost savings could look like:
- In this calculation 10 kg steam / hr – per. ° C are used, with which the temperature must be raised in the conditioner.
- The capacity of the pellet press will be 15 tons per hour.
- The cost of steam can vary as the energy sources differ from production to production. In addition, the efficiency of the steam boiler fluctuates due to age and make. In this calculation, the “rule of thumb” is used, which is DKK 1 per kg steam / hour.
- The calculation uses an average amount of working days of 216 days per year.
Another significant aspect of the start-up process is the lower amount of steam to be used before the flour reaches the right temperature. Partly because a lower temperature must be achieved, but also because the increased energy that is supplied to the matrix means that the feed pellets heat up to the right temperature faster than in the conditioner.
All this means that the product can be approved more quickly and less material is generated for repelletation, which also saves energy / CO2. In addition, it will be possible to run shorter series, as there is a shorter waiting time for the repelletation system to be empty and ready for the next batch. In connection with the reduction of the temperature of the feed pellets, less air will be needed to cool the pellets (m3 / hr). This in turn means a further reduction of energy / CO2.
It is generally crucial to know how the material is processed in the pelletizing process in order to know the production process. There may be e.g. changes in the raw material which help to increase the friction but which are not usually visible in the process. Or also a bad adjustment of the roll, which gives a longer pelletizing time, which increases the frictional heat.
All the heat that is added also helps to destroy the naturally occurring vitamins and enzymes in the raw material. However, a lot of artificial vitamins and enzymes are added to compensate, and also to increase nutrient uptake. However, in this case it is also possible to reduce the supply, as not everyone is equally thermostable. All this will of course require a more in-depth review of one’s production, but if there is a large temperature difference, it is advisable to investigate.
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