7 replies to this topic

[mishra.anand72@gmail.com]

Talc is used as additive in polypropylene. This is added in extruder. Talc system comprises of talc unloading system in which talc from big bags is air conveyed in storage silo and talc feeding system in which talc is discharged through loss in weight screw feeder. This both system is designed for low bulk density powder. Talc unloading system is designed for bulk density in the range of 250 -800 kg/m3. Talc feeding system is designed for bulk density in the range of 200 - 300 Kg/M3. Talc is available as either in non compacted or compacted version. Non compacted talc is of lower density. Compacted version talc is of bulk density more than 800 Kg/M3. Quality ppl suggest to go for compacted version because it will be easy to handle, low dusting etc. However I am not able to give green light to procurement because system is designed for low bulk density. What I would like to understand that whether higher bulk density powder can be used in system which is designed for low bulk density. If yes, what is the reference or guiding document. If no , what r the problems higher bulk density can cause in this system designed for low bulk density.

Could u help me please.

[ankur2061]

Mishra,

Solid handling is a very specialized subject and I would recommend you talk to your LIW feeder vendor/manufacturer and provide him the new data for the bulk density and take his concurrence on the issue. LIW feeders are extremely sensitive to changes in physical parameters of the solids handled.

Meanwhile I am providing a web link for an excellent presentation on solid handling and which I would recommend to all who have interest in bulk solid handling systems and their design principles.

http://www.engineeri.....n Lecture.ppt

Regards,
Ankur.

[Qalander (Chem)]

Talc is used as additive in polypropylene. This is added in extruder. Talc system comprises of talc unloading system in which talc from big bags is air conveyed in storage silo and talc feeding system in which talc is discharged through loss in weight screw feeder. This both system is designed for low bulk density powder. Talc unloading system is designed for bulk density in the range of 250 -800 kg/m3. Talc feeding system is designed for bulk density in the range of 200 - 300 Kg/M3. Talc is available as either in non compacted or compacted version. Non compacted talc is of lower density. Compacted version talc is of bulk density more than 800 Kg/M3. Quality ppl suggest to go for compacted version because it will be easy to handle, low dusting etc. However I am not able to give green light to procurement because system is designed for low bulk density. What I would like to understand that whether higher bulk density powder can be used in system which is designed for low bulk density. If yes, what is the reference or guiding document. If no , what r the problems higher bulk density can cause in this system designed for low bulk density.

Could u help me please.

Dear mishra,
Another useful website for powder handling is www.Chemicalprocessing.com if you feel like subscribing to it!

Should prove beneficial
Regards
Qalander

[Andrei]

Ankur, the link you posted was somehow truncated. Can you repost? Thank you.

Mishra,
Here is what I remember about talc, from some 20 years back work.
There is a significant difference in transport behavior of low and high bulk density talc residing in particles electrostatic characteristics. The particle density it is also expected to be higher for high density talc, so settling velocities in a gas-solid mixture are expected to be higher. The shape of the particles and granulometric distribution will also be different, with impact at compounding behavior.
The low bulk density talc has a fluffy aspect, it is easier to transport using air, but more difficult to separate from it. The high density has a more sticky behavior and will require higher air velocities.

Regardless of what are the implications in your unloading/transport/feed system, the main difference will be in the quality of the injected polymer obtained. I think that should be your quality people main concern. The injected products characteristics using light bulk density talc will be significant different from heavy bulk density talc. I remember a significant price difference between light and heavy bulk density talc 20 years back. I would expect to see the same kind of difference now, a more expensive light talc, is this your case? Economists were willing to replace the light talc with the heavy one because it was cheaper. But the quality of the products obtained were not the same, and there were some contracts lost because of their endeavor.

[mishra.anand72@gmail.com]

Ankur, the link you posted was somehow truncated. Can you repost? Thank you.

Mishra,
Here is what I remember about talc, from some 20 years back work.
There is a significant difference in transport behavior of low and high bulk density talc residing in particles electrostatic characteristics. The particle density it is also expected to be higher for high density talc, so settling velocities in a gas-solid mixture are expected to be higher. The shape of the particles and granulometric distribution will also be different, with impact at compounding behavior.
The low bulk density talc has a fluffy aspect, it is easier to transport using air, but more difficult to separate from it. The high density has a more sticky behavior and will require higher air velocities.

Regardless of what are the implications in your unloading/transport/feed system, the main difference will be in the quality of the injected polymer obtained. I think that should be your quality people main concern. The injected products characteristics using light bulk density talc will be significant different from heavy bulk density talc. I remember a significant price difference between light and heavy bulk density talc 20 years back. I would expect to see the same kind of difference now, a more expensive light talc, is this your case? Economists were willing to replace the light talc with the heavy one because it was cheaper. But the quality of the products obtained were not the same, and there were some contracts lost because of their endeavor.

Dear Sir,

I would like to understand implication in my unloading/transport/feed system which is designed for low bulk density talc when I go for high bulk density talc. Just because of quality ppl recommended, I can not go for high bulk density talc without understanding process side implication.

[ankur2061]

Andrei/Mishra,

Just google with the search words "Bin and Hopper Design ". Open the URL with the first hit you come across. It is a powerpoint file.

Regards,
Ankur.

[mishra.anand72@gmail.com]

Andrei/Mishra,

Just google with the search words "Bin and Hopper Design ". Open the URL with the first hit you come across. It is a powerpoint file.

Regards,
Ankur.

but that power point presentation is no way helping me to solve this problem.

[mishra.anand72@gmail.com]

Just talks. No real help??