8 replies to this topic

[theoneajit]

Dear all,

I am working on improving the bulk density of various phosphate products during spray drying. All most all products Bulk density is close to 1 except dipotassium phospahte. I tried to do all the possibilties like increasing the inlet air temp, maintaining higher outlet temp, incresing the atomiser speed and reducing the feed. But none of the above have given me a break through. At present Bulk density of DKP(dipotassium phospahte) is 0.3 to 0.4. I could obsserve one thing that out of all the products DKP has very high solubility hence inlet feed % solids are always maintained high as it doest crystalise so easilty. Is there any relation that for some solutions feed % solids should be less to get high Bulk density? generally bulk density increases with increase in % solids. is there any relation or thumb rule to maintain feed conditions depending on specific feed ? or relation between molecular weight and feed solids or Bulk density?
If you have come across such problem then kindly share your ideas. This topic is very less discessed.
I need your inputs
Bye
Ajit

[anshulagr]

You may try changing feed conc and temp in addition to parameters you have already tried.
for increasing bulk density, the particle size distribution shall be wide such that fines
fits in the void volume between coarser particles.

Thanks
Anshul

Dear all,

I am working on improving the bulk density of various phosphate products during spray drying. All most all products Bulk density is close to 1 except dipotassium phospahte. I tried to do all the possibilties like increasing the inlet air temp, maintaining higher outlet temp, incresing the atomiser speed and reducing the feed. But none of the above have given me a break through. At present Bulk density of DKP(dipotassium phospahte) is 0.3 to 0.4. I could obsserve one thing that out of all the products DKP has very high solubility hence inlet feed % solids are always maintained high as it doest crystalise so easilty. Is there any relation that for some solutions feed % solids should be less to get high Bulk density? generally bulk density increases with increase in % solids. is there any relation or thumb rule to maintain feed conditions depending on specific feed ? or relation between molecular weight and feed solids or Bulk density?
If you have come across such problem then kindly share your ideas. This topic is very less discessed.
I need your inputs
Bye
Ajit

[katmar]

In spray drying it is possible to evaporate water at the surface so fast that the outer surface solidifies faster than water can diffuse from the centre. This results in a hollow particle, like a ping pong ball and the bulk density can be very low. The solution is to dry more slowly to allow the water to diffuse from the centre to the surface before the surface solidifies. As you already have an existing dryer you cannot change its size and the only way to slow down the drying is to cool the inlet air. This may result in a product that is not totally dried. If you were designing a new dryer you could make it larger with a longer residence time, but that isn't an option now.

[theoneajit]

I tried to reduce the inlet feed temp from 110 to 85 and atomiser speed from 38 to 36 Hz but there is not much improve in the BD, Whare as i am getting more coarser product now -100 mesh is 60-65 % compared to earlier 70-75 %. The inlet & outlet temp have not been changed.
At present i am getting 0.4 Bulk density I need to increase it to atleast 0.6. Can I calculate the residence time, & what shall I do more to increase the residence time?

Thanks,
AJIT

[theoneajit]

I didnt mention in the above post that inlet temp of feed was reduced to 85 deg C.
I am getting the BD 0.8 for all other products where as not getting for dipotassium phosphate(DKP). Is there any reason for not getting BD this product? I can only see the difference between DKP & other products is that DKP has very high solibility. Any inputs on this ?

[theoneajit]

Hi all,
I reduced the feed solution inlet temp up to 75deg C from 110 deg C & atomiser speed to 34 Hz from 40Hz. The product -100 is 50 % now compared to earlier 80% earlier. But there is not much increase or no effect on Bulk density.

Really waiting for your comments.............

Bye,
AJIT

[theoneajit]

I am Really waiting for your comments.............

Bye,
AJIT
[/quote]

[theoneajit]

Dear all,
I am happy to inform you that I got 100% increase in the BD.
Steps Involved:
1. Increase the temp of S/D feed to get high SG
2. Reduce Temp of S/D feed to increase Voscosity.

[JMW]

Interesting.
Is the feed gas free?

I ask because the coffee extract spray drying operation (for granulated instant coffee) relies on entrained gas for the granule texture.
In that case it is the gas (CO2 I seem to recall) content that is critical and it is measured using an Entrained Gas Density meter and a pressure sensor.

But if not and if viscosity is a key factor then if the viscosity varies due to quality variations (which can be significant with some fluids) rather than just temperature, temperature regulation alone may be insufficient. Perhaps an inline viscometer can help you automatically maintain the target viscosity.
This won't work for an entrained gas fluid.
Well, not easily or directly.
There is a way to determine the viscosity of the gas entrained liquid from the viscosity of the gas free liquid but it ain't pretty.