In the operation of spray drying towers there are seasonal variations in their operation. In summer, when the moisture content in the air is high, the operating conditions are less advantageous than in winter, when the water content in the air is low. In humid conditions there is a greater tendency for the powder to become sticky and cause more downtime.
Obtaining stability and achieving a consistent quality output is desired in the spray drying process. To do this it is necessary to stabilise all the parameters of the operation. However the one parameter which until now has been difficult to control is the moisture content of the incoming air.
Solution
Dehumidifying the incoming air enables the air to maintain the same low moisture content throughout the year, providing stable inlet conditions, enabling consistent quality and increased performance from the spray drying process. Munters have developed a range of special high performance dehumidifiers which enable this to happen. Munters dehumidifiers control precisely the moisture content of the incoming air giving the following advantages to the spray drying process:
- Consistent production all year - production is no longer affected by outside conditions. This means no more production stops in summer due to weather conditions.
- Stable production conditions assists the operators work by reducing the need for frequent parameter adjustments·
- Stable drying conditions means consistent powder quality.
- Dry inlet air enables increased production from the process.
- Less product sticking to the wall of the spray tower means less water and cleaning time.
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Munters new GTR Desiccant Rotor enables a large dehumidification capacity to be created, ie. to achieve a low process air moisture content using only a single step, so eliminating the need to pre-cool.
In many industries drying is based on conventional heat and vent, this has one common harmful drawback: The drying process affects quality due to outdoor climate and seasonal variations. |
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With Munters new GTR technology, applications such as spray drying benefit in a reduction of absolute moisture content whilst increasing the process air temperature.
The Munters system has many advantages. The moisture in the incoming air is absorbed by a desiccant rotor. The air coming off the dehumidifier system can be controlled to the desired moisture content. As the process is exothermic the temperature difference is dependent on the amount of moisture removed but can be up to 50oC which means the spray dryer heater has less work to do to achieve its temperature of the entering air into the chamber.
Munters GTR means less consumption of expensive power and lower co2 emissions. With Munters GTR typically heating energy savings are 15-20%, with production increases from 15-20%.
With medium summer conditions in Europe, outdoor air introduces a huge quantity of water in the spray tower. For example an air outdoor condition of 25oC @ RH 61% = > 12g/kg and an airflow of 100, 000 kg/h air. Then 1200 l water/h is introduced into the spray tower.
With Munters GTR rotor, we are much more efficient. An air outdoor condition of 25oC and RH 61% (12g/kg) passed through Munters system provides process air 64oC and 2.0g/kg and an air flow 100, 000 kg/h, so only 200 l/h of water is introduced to the spray tower. A saving of 1000 l/h or water!
With 1000 l/h less water introduced into the tower and a 55% slurry, a production increase equal to 29 tonnes of extra powder can be produced in one summer day alone.
Munters systems have been succesfully used in many spray drying situations worldwide. References include:
* Lesaffre
* Sofivo
* Aromes de Bretagne
* Lactalis
* Roche Vitamines
* Bionov
* Nestle