Spray drying is the process of converting a mixture in its liquid form to a powder. This is done by removing the moisture component from the liquid solution. The solution, sometimes called an emulsion, is sprayed through a nozzle into a chamber that simultaneously has hot air being blown into it. This is the preferred method of drying of many thermally-sensitive materials such as foods and pharmaceuticals.
The hot air is a key point of focus for the spray drying process to be as efficient and cost effective as possible. The question is how can the integrity of BTU’s required to properly preform the drying process be maximized?
Removable insulation blankets are the answer to this dilemma. Custom insulation blankets can be manufactured to fit every part no matter how complicated. The insulation jackets can be removed and replaced for repairs.
What type of insulation is used in the insulation blanket? That depends on the temperature of the air, the ambient temperature, the location and any weight factors that may come into play.
The hotter the air, the thicker the insulation layer required to drastically reduce the amount of BTU’s lost to the ambient air. If there are weight concerns for the equipment, an aerogel insulation should be used. Aerogel weighs about 0.42lbs./Ft², needled fiberglass weighs around 1.5lbs./Ft². Another important factor is the location. Is the dryer in an area that is subject to moisture, rain, snow any adverse weather conditions? Is the dryer subject to a washdown process? If the dryer is in a dry location, there is no chance of adverse weather, and will not see a washdown then type E needled fiberglass can be used.
Type E needled fiberglass comes in different density’s ranging from 4 to 6lbs./Ft.³ up to 9 to 11lb.s/Ft.³. The higher the density, the less susceptible the insulation is to become “packed” or the volume reduced. When the volume is reduced the thermal efficiency is reduced. Aerogel insulation should be used in areas that are subject to adverse weather or washdown cycles. Aerogel insulation is the most thermally efficient solid insulation available and is far thinner than type E needled fiberglass. 10mm of aerogel insulation is equal to 1” thickness of type E needled fiberglass insulation. A huge advantage of aerogel insulation is it is Hydrophobic, meaning it will not absorb liquid water, yet it still breathes to help prevent CUI (corrosion under insulation).
In conclusion, spray dryers should have all components insulated that see the hot air. Removable insulation jackets are the answer to any insulation dilemma that may occur. For large “tank” type areas, fixed insulation can be used if it meets the criteria for thermal efficiency, weight and reactivity to water.