Re: Mannose Processing - Sticking To Everything
Originally Posted by Gary Blenkhorn
What is the moisture content throughout the mill process? I have worked in the salt industry for over 30 years and found that anything over a 2% moisture content would create a cohesiveness problem.
Thanks for the input. The dew point is typically -8 to -4°C (frost point). It is really dry. Moisture of the NaCl is typically 0.2 - 0.4%. We process NaCl in other formulations and have never had any issues. The issue is with the mannose. ■
Re: Mannose Processing - Sticking To Everything
Originally Posted by johngateleyWas the sister plant originally optimised?
I still recommend asking your material suppliers for advice since no properties are realistically available from outside.
The sister plant was not optimized for processing mannose but they do control temperature and humidity in the conveying/milling process with nitrogen so the temperature is held to 4°C +/-.
Contacting the supplier is good idea as there is so little information that applies in the community. ■
Re: Mannose Processing - Sticking To Everything
Originally Posted by Roland Heilmann- there`s a local pressure drop / speed change of the airflow?
- areas of turbulence / direction change?
- there`s something like "pockets" in the design of the chute / mill body, where material can come to rest, remain stopped and build / layer up?
A forum member, very knowledgeable on pneumatic conveying is Mr. Teus Tuinenburg, you might want to approach him.
BTW, there's a specific forum "pneumatic conveying".
Regards
R.
Thanks for the input. The flow design has not been checked but it is apparent that there is not enough airflow to scrub the surfaces and prevent build up. Installation of pressurized air jets to wash those areas has been discussed that the additional air volume may affect the pneumatic conveying and cyclone efficiency. The cyclones were not designed for material this light and the loss will be great let alone that the rotary valves at the base of the cyclones will fill and become useless in delivering material from one side to the other. ■
Re: Mannose Processing - Sticking To Everything
Have you considered the use of a grinding aid such as stearic acid? We used this in the intensive grinding of mixtures of salt with various materials such as metal hydroxides and it had a dramatic effect on the flow of the material in the mill. It was pretty much standard practice to use it for Spex milling in the lab.
I suspect that your problem is based on the presence of surface hydroxyl groups which can contribute to adhesive forces through the formation of hydrogen bonds. The stearic acid, or other grinding aid (oleic acid is another) react with these groups, blocking the formation of hydrogen bonds and acting as an inter-particle lubricant.
The trick might be finding something that will not interfere with the functionality of your formulation. ■
Celestial Issues
Hi,
What causes the temperature to change from 16oC to 50oC?
Is the airflow fast enough for this material?
Is the equipment big enough? (Same thing really.)
Is the carrier gas dry?
Have you tried roughening the surfaces in contact?
A 50/50 mix with sodium chloride doesn't seem like the overall formulation is all that limited.
My guess is that there is an imbalance betwen the cohesiveness and the equipment dimensions or selection.
What does your raw material supplier know about his other customers? ■
John Gateley johngateley@hotmail.com www.the-credible-bulk.com
Mannose
Originally Posted by johngateleyWhat causes the temperature to change from 16oC to 50oC?
Is the airflow fast enough for this material?
Is the equipment big enough? (Same thing really.)
Is the carrier gas dry?
Have you tried roughening the surfaces in contact?
A 50/50 mix with sodium chloride doesn't seem like the overall formulation is all that limited.
My guess is that there is an imbalance betwen the cohesiveness and the equipment dimensions or selection.
What does your raw material supplier know about his other customers?
Temperature rise is attributed to the milling process. 35°C max is more realistic.
Airflow is optimal for the equipment determined by the efficiency of the cyclones.
Carrier gas (atmosphere) is humidity controlled - dew point is typically -8° to -4°C.
Roughening the surface is out of the question. It's 0.25 RA.
Within the formulation, there is enough sodium chloride to allow the 50/50 mix. Our sister plant has a different product and they process 1:10 mixture (10% mannose, 90% NaCl) with the same problems that I've seen.
Thanks for your input,
Kaos1 ■
Re: Mannose Processing - Sticking To Everything
NaCl is very hygroscopic - what is the moisture level in your atmosphere? You say humidity controlled but what level is it controlling to?
What is the moisture content throughout the mill process? I have worked in the salt industry for over 30 years and found that anything over a 2% moisture content would create a cohesiveness problem. ■
Gary Blenkhorn
President - Bulk Handlng Technology Inc.
Email: garyblenkhorn@gmail.com
Linkedin Profile: http://www.linkedin.com/in/gary-blenkhorn-6286954b
Offering Conveyor Design Services, Conveyor Transfer Design Services and SolidWorks Design Services for equipment layouts.
Flow
Did you have somebody check the flow design characteristics at those specific locations you mention? Could it be that
- there`s a local pressure drop / speed change of the airflow?
- areas of turbulence / direction change?
- there`s something like "pockets" in the design of the chute / mill body, where material can come to rest, remain stopped and build / layer up?
A forum member, very knowledgeable on pneumatic conveying is Mr. Teus Tuinenburg, you might want to approach him.
BTW, there's a specific forum "pneumatic conveying".
Regards
R. ■
Similitude Lost.
Originally Posted by kaos1Kaos1
Thanks for your feedback.
Was the sister plant originally optimised?
I still recommend asking your material suppliers for advice since no properties are realistically available from outside. ■
John Gateley johngateley@hotmail.com www.the-credible-bulk.com
Mannose processing - sticking to everything
Hello,
Has anyone processed mannose through a milling and blending equipment train including pneumatic conveying, cyclones, and/or rotary valves? In our Pilot mill, I find that it sticks to the infeed chute prior to the mill and in the body of the mill post size reduction. The mill is of fan and screen design (Retsch SR300) constructed of 316 stainless steel. It does not seem to be an issue of heat/melting as this characteristic is observed at 16°C in the infeed chute of the mill. The melting point of mannose is 133 - 140°C. I doubt that it is exceeding 50°C in the process. I've also tried a 50/50 mix with NaCl with no difference in its sticking. I am limited to what I can add to it defined by the overall formulation.
Mannose is light and fluffy with a density of around 0.35 g/cc. I suspect that the culprit is either electrostatic charge or cohesion/adhesion. This process once optimized will have to be scaled up to much larger equipment.
Thanks for any input. ■