Temperature Calculation - Starch and Water

[Mohanad990]

Hello,

I work in a paper manufacturing facility where we use starch in our process to be applied on the surface of the paper.

Recently we added a heat exchanger to cool the water used for dilution of starch.

The incoming starch is at 122C (29% solids) and we dilute with 20C water (coming out from HE) to 19% solids and store it in a storage tank. The temperature of starch in the storage tank is 85C.

The problem is that the temperature of water did not have an effect on the temperature of starch in the storage tank.

We tried to add a HE to make it colder, but still almost same Temperature was achieved.

Why is that?

 

[Latexman]

What was dilution water T before HE?

And the initial and final concentrations of starch are exactly the same, before and after HE was added?

Good Luck,
Latexman

 

[EdStainless]

So your dilution water flow is about 1/3 of the total.
How much higher is the HC of the starch solution than straight water?
I would expect the mixture to be about 30C cooler.
Which would be roughly 90C.
So what is the problem?

Are you saying that it was 85C in the tank before you added the HX?
IF so then you just moved the heat loss from your piping and tank to a HX.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Compositepro]

Starch solutions are non-Newtonian. You are probably not getting good mixing in your storage tank.

 

[georgeverghese]

Simple calc tell me tank temp would be 87degC,with 0.52 kg of 20degC water for every 1kg of hot starch soln.; nearly the same as you've got in the tank - 85degC. So you want the 19% starch tank to be cooler than 85degC? What temp do you want it to be?
Tell us more about this additional HX you've installed to make the tank colder.

 

[pierreick]

Hi,
You could find pointers in the link attached:

https://library.e.abb.com/public/78...lier_StarchContinuousPrep_V072019EN_print.pdf

You may want to drop them an email.
Good luck
Pierre