Hello Friends, I am late again due to shifting to some very interesting industry this time making very useful product Furfural from Bagasse.
The incident of yesterday's interaction forced me to come back to the blog for sharing.
Yesterday I met vice president of a growing mid size company in Gujarat. He told me that spray driers can not be counter current and I should learn this fact. The reason he explained is that dried powder shall be carried away by hot incoming air and therefore you need a cyclone separator at the top for separation of solids & air.
Quite interesting ......This forcefully made me to think about fundamentals of drying......but later on. Before that I thought about creativity of Human mind. its brilliant......it's unlimited......it's really really much much bigger than what we can think of.
Yes dear, all of you should take this as a challenge on this blog itself that how to prove this wrong & how to prove it right.
In the beginning I thought I should re-think on the basics of spray driers and then searched on net also. So I found so many picture / images here.
He may not be fully wrong also, but the word 'Spray driers can not be countercurrent' was not right I am sure.
Really its very difficult for me to write any thing on this topic now. The basic reason he mentioned was that if flow is counter current solid particles will go up with the air & you need a cyclone separator for recovery. Is it really so??
I think it is always so whether it is counter current or co-current. Isn't it?? Most of the pictures on the above link are having cyclone separator. So this argument was also not so good for making spray dries co-current.
In fact, If I see the principle of drying and nature of most of the solids where spray drying is essential or most suitable, it is always better / preferable (Few Exceptions depending on nature of solids) to go for counter current as driving force is always higher and moisture content in dried product from the same size is less.
In fact, those applications where spray drier is generally used, I will not prefer to go for it as it is highly energy intensive & capital intensive compared to thin film drying which I have already done for a very highly hygroscopic material. I will try to put the data for that installation in one of the next articles.
I will prefer spray driers mostly for hygroscopic material with sticky nature in wet condition otherwise its better to go for other options.