Dust Estimation and Venturi Scrubbers

[dogbertcountry2]

I am trying to estimate loading from a new operation of emptying bulk bags into a grinding system and then emptying into a slurry tank. Due to the nature of the moisture involved with the slurry tank, I am prone to think that I should avoid fabric filter dust collectors. We have used venturi scrubbers in other applications at the plan, but I have not personally designed any of these. I have read thread124-186760 of this forum for reference.

I would plan to use the vendor to help size and design the unit (if a good application), but I am not sure what information that he is going to need that I actually have. We have tried to do some potential PSD calculations, but I am confused by this exercise.

From the thread reference, it looks like I am going to have to supply a loading and flow to be scrubbed, but this is where I am not sure how to approach this.

As a side note, it would be absolutely wonderful if I could somehow use the slurry (20% solids) as the scrubbing medium, but I know this seems like a bit of confliction with the whole scrubber functionality. Perhaps a "lighter" strema could be usable???

If anyone could give me some insight on this topic, I would be exceptionally grateful.

Thanks!






thread124-186760

 

[HEC]

Dogbert
Best method of dust control is to not generate the dust. From your post it would appear that you are dry grinding, is this necessary? Also in making the slurry are you dropping the powder into a large tank? Can the powder be added through a venturi or other wet tundish to reduce/eliminate the dust problem?


Mark Hutton

 

[rmw]

There is no reason why you can't use your slurry if you can readily pump it. That's the theory. However, if it is 20% solids and those solids are abrasive, then you are going to have to give serious consideration to venturi throat wear. The efficiency of scrubbing is a function of energy across the throat and if your application calls for high energy your wear could be excessive.

Also, not knowing about the corrosivity of the slurry, if it is high, then you would have to make the venturi of exotic materials which is not unheard of.

You might consider scrubbing with the clean fluid that you are using to make your slurry and then using the scrubber blowdown as slurry make up.

Lime kiln scrubbers in the paper industry scrub with the liquor that the lime is slaked into for example.

rmw

 

[siretb]

I would be cautious about using a slurry in a Venturi.
I have a poor experience where we used dirty water.
What happened is that we had secondary mist generation (the tail of a Rosin ramler distribution); the median drop size was as predicted by theory, and was not escaping, but the very fine tail was much finer than 1 micron, and escaped.
So now I try to use "clean" fluids in Venturis.

 

[ventguy]

You could use a fabric filter to control the dust generated at the grinding and bag-dumping processes before the powder hits the slurry tank, couldn't you?

Peter Ott

http://www.utieng.com

 

[dogbertcountry2]

Thanks for all of the feedback... Wet grinding was not advised due to the "caking" up possibility on the grinding equipment and housings.We looked at dropping it through a venturi type device ("liquid slurry eductor") but management frowned on this due to our lack of experience with this type of use. (We have only used venturis on dust scrubbing.)

The material is not corrosive, but I do appreciate the abrasive to the throat comments.

Fabric filters are trying to be avoided because of some permit exemptions and due to the presence of humidity. Frequent bag changing/cleaning are anticiapted with their use.

I have been trying to learn as much as possible about the venturis dynamics from all sources, but I still have more questions. From what I understand, the divergent section of the venturi is where most of the work is done. The venturi causes droplets for "impact sites". Does the presence of solids suppress dropplet formation? If not, do the particulates not like the impact of solids versus liquid? Do they just "bounce off"?

I have read in the literature that an upper extent of slurry strength is near 30%. Why?

Any help would be appreciated.