Manueldelatorre
Chemical
- Aug 22, 2007
- 1
Corn Feed and corn oil cake are dryed in a serie of 3 flash dryers. The material is transported through dry air which evaporates the water.
The hot air in the system is provided by an arragement which works like:
- air goes to heat exchanger and is heated up to 300 °C
- air goes to the last flash dryer
- after the dryer, part of the air goes to combustor, part is recirculated
- air is heated up again in the combustors and goes to the primary 2 dryers
- system works under vaccum since a fan is placed after the dryer (and respective cyclones)
If the vaccum at the entrance of the last dryer (dryer 3) is less than -9 mbar, big particles of the oilcake could not be transported and fall to a rotative valve at the bottom of the dryer. Since the air is 300°C, agglomeration of too much material has the risk of fire.
When the vaccum falls below -9 mbar, a practice that for years has been done is to cool down hot air that goes to the primary dryers. The control arrangement of the system uses more gas to keep the temperature stable. A consequence of this action is that the vaccum at the dryer 3 increases up to - 11 mbar. We wonder what does that means, since it is enough to transport the materials.
Does a higher vaccum means more air (higher volumetric flow)? Does it just means that more air goes throug the heat exchangers that provide the original energy to the dryer 3? Why does a higher vaccum means that material can be transported?
The hot air in the system is provided by an arragement which works like:
- air goes to heat exchanger and is heated up to 300 °C
- air goes to the last flash dryer
- after the dryer, part of the air goes to combustor, part is recirculated
- air is heated up again in the combustors and goes to the primary 2 dryers
- system works under vaccum since a fan is placed after the dryer (and respective cyclones)
If the vaccum at the entrance of the last dryer (dryer 3) is less than -9 mbar, big particles of the oilcake could not be transported and fall to a rotative valve at the bottom of the dryer. Since the air is 300°C, agglomeration of too much material has the risk of fire.
When the vaccum falls below -9 mbar, a practice that for years has been done is to cool down hot air that goes to the primary dryers. The control arrangement of the system uses more gas to keep the temperature stable. A consequence of this action is that the vaccum at the dryer 3 increases up to - 11 mbar. We wonder what does that means, since it is enough to transport the materials.
Does a higher vaccum means more air (higher volumetric flow)? Does it just means that more air goes throug the heat exchangers that provide the original energy to the dryer 3? Why does a higher vaccum means that material can be transported?