Paper Stock apparent viscosities

[Jkaen]

Hi all, I was hoping you could help me with a problem we have, we have recieved an enquiry for processing paper stock, and while we have empirical data up to 6% consistency this customer has 12% consistancy stock and I am struggling to find any data that will allow me to calculate pressure drops for this.

Can anybody please point me in the right direction, a way to calculate apparent viscosities and densities would be great, but if that is not possible a way to calculate headloss in a straight pipe would be usefull and I could derive an answer from there

Thanks in advance

 

[hacksaw]

pulp and paper industry has quite a bit of information on that.

 

[JKEngineer]

One source is TAPPI, the Technical Association of the Pulp and Paper Industry. (tappi.org) I know I have seen books with head loss vs. consistancy in the (distant) past and I believe that at least some of them were published by TAPPI.
Jack

Jack M. Kleinfeld, P.E. Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering

http://www.KleinfeldTechnical.com

 

[Diborane]

JKaen,

The paper you want is "Channeling in Bleach Towers and Friction losses in Pulp Stock Lines" by Vernon B. Bodenheimer

Southern Pulp and Paper Manufacturer, September 10, 1969. Good luck finding it anywhere, I'd suggest University Miami, SUNY ESF, or NC state.

The formula is:

delta H = (5.4 F*C^2.5*V^0.15)/D

where
C = % Cons BD (2%-18%)
D = diameter inches (use the ID it makes a difference in pulp lines)
V = velocity in ft/s (make sure when determining velocity to use the pipe ID, also account for the density difference between fiber and water)
F = F1*F2*F3

F1 = temperature correction factor (F = 1.6 -0.006*T) where T is in deg F
F2 = stock type correction factor (kraft pine = 1 kraft hardwood = 0.8)
F3 = pH correction factor (<8.5 F =0.7, >8.5 F=1)

There is a very large list of different F1 factors for other types of pulp in the paper.

 

[Artisi]

Jkaen (Chemical)

The majority of information on head loss for paper stock which is older than about 6 /8 years is out of date and in most cases completely wrong.
One of the authorities on stock pumping and head loss is Prof. Geoff Duffy - who was located at Auckland University New Zealand. It is many years since I was involved with him so he might have moved on. Another source of information worth chasing is in the Australian paper industry journal APPITA - references to Duffy and his work would be in journals of about 6 -8 years ago.

I was involved in pumping paper stock ( as a pump supplier) for over 10 years - and for upto 6% I always used water curves for the head loss, this results in a conservative result as Duffy found that depending the stock type in combination with many other factors the head loss could be less than water. Over 6% you have other problems when trying to pump stock which are not particularly related to the head losses.

I suggest you do a search on the net - I'm sure you will find info there -



Naresuan University
Phitsanulok
Thailand

 

[Diborane]

Just replying to Artis comments.

A normal process pump will have problems with stock consistencies over 4-5%. A specialty pump is needed for medium consistency stock. The impeller shape of one of these pumps is specially designed to fluidize the stock before pumping it. Sulzer is one pump company that supplies these specialty pumps.

One of the difficulties that Artisi may be reffering to is slipstick. This occurs if the velocity of the pulp through the pipes is lower than a critical value (0.8-1 fps). At this condition the stocks mean velocity is <.8 fps but actually pulsates through the lines. This will cause a lot of shaking in lines and potentially the supports will not be able to handle the load.

 

[Artisi]

Just to extend what Diborane has referred to, pumping paper stock is a difficult application for those without any prior experience.

A normal end suction process pump can usually pump paper stock upto around 3-4%, although this is dependent on the stock type and a number of other factors such as the amount of entrained air in the stock etc etc.
For stock of 3-6 % you need to use paper stock pumps for trouble-free pumping.
One factor that needs careful consideration is the approach pipe work to the pump inlet and the pipe/pump connection, for 3-6% stocks the greatest problem is bought about by using good hydraulic principles - the fitting of tapered pipe reducers is usually the greatest cause of inlet pumping problems as the stock tends to "jam" in reducer and can be very quickly become dewatered completely blocking the reducer. For stock pumping the best way to reduce from the suction pipe (usually a much larger diameter than the pump flange size) is against all good hydraulic principles, this is an eccentric square entry - that is a flat plate welded to the approach pipe with short piece of pipe(pump inlet size) welded to the top side of the flat plate, the stock cannot "jam" in this type of reducer because of the highly tubelent flow at this point and therefore cannot dewater.

The standard "paper stock" pumps manufactured by Allis Chalmers, Alhstrom, Sulzer, Worthington etc etc, are capable,under ideal suction conditions of pumping stock upto and including 6% consistency - it is possible to exceed this in the field but I would caution against ever designing for anything above 6%. To exceed 6% you need to look at fitting suction agitators or feeders or using thick-stock pumps.

To put in perspective what 6% paper stock is like - wearing snow shoes, you can walk on it.

Naresuan University
Phitsanulok
Thailand

 

[Latexman]

Jkaen,

Have you tried Section 19E in the Goulds Pump Manual? It goes up to 18%. I do not have experience with this method, I just remembered it was there.

Good luck,
Latexman