Insulation for Industrial Dryers

I have never seen a rotary dryer with external insulation, whether partial or full. If the heat loss is too high, internal refractory lining is generally recommended. This keeps the internal temperature at that required for drying your product, and keeps the steel shell cooler to limit expansion and heat loss. Applying external insulation will not affect the shell expansion as the shell is already exposed, in its entirety, to the internal temperature of the system. If the dryer was designed for high temperature operation without refractory lining (end seals designed for full shell expansion), then you may need to deal with the heat loss. Because of the rotating shell, externally applied insulation will be subjected to centrifugal forces that will tend to tear it away from the shell, limiting its usefullness.

Partial insulation in feed end.

Friend, What U have said is right only. From process point of view, we should not loos energy.

And the rotary dryer is designed for medium temperature range. What we are using the dryer is hammer type in shell, as you said refractory lining provided inside the shell means, it wont withstand.

We are having these kind of arrangements for to avoid material sticking in the dryer.

So this option is eliminated. As you said, the end seal is to accommodate the thermal expansion of dryer. But in our case thermal expansion is not equal. material feed end is shell is getting heated up. The shell temperature is around 205 Deg C. You know that, dryer must have its tyre, we are having some standards like this tyre should not deviate more than 5 mm. this is also one limitation.

If suppose am fixing insulation means, thermal localisation will exist so thermal expansion is possible.

Ur comments please

Okay, I understand you are using this rotary dryer as an attrition mill as well, that is, with steel balls (or similar) inside to keep material from lumping, sticking to the shell, and to keep particle size small. Therefore, as you say, using internal refractory is not realistic. As for the insulation, I believe you are applying insulation around the end plate at the feed end, not around the cylinder? This is okay.

You indicated this is counter-current flow, so the hottest end should be the fired end where the product is driest and absorbs less heat. The cooler end should be the feed end, where the product absorbs heat and the hot gas has travelled furthest. You have not said how long this dryer is, or the flame length at the burner end. If the feed end is getting too hot, perhaps you can adjust the burner flame so that heat does not penetrate so deeply into the dryer?

If you wish to wrap the cylinder with insulation and strap it into position so that it does not come loose, I believe that would be okay. Obviously the insulation cannot be in the tire area. Expansion of the shell will not change much because the insulation will only keep some of the heat from escaping by radiant means. The shell still sees the full internal temperature for expansion. Only if there was significant cooling of the shell during heat loss would there be much change and I do not believe that will be the case (such as the dryer located outdoors in very cold climate where outside temperature cools the shell significantly, or there is water mist applied to the shell for some reason).