Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Vacuum treatment
Patent
1995-03-15
1998-04-07
Beisner, William H.
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Vacuum treatment
162 56, 162 60, 210770, 210771, 100 37, 100 90, 100 92, 34305, 34398, 34403, 34405, D21C 918
Patent
active
057360073
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to a new method of liquor removal and/or washing from suspensions of particulate solids. It has particular application to the dewatering of wood pulp fibres in the pulp and paper industries. Measurements are provided on the dewatering of bleached kraft fibre pads.
BACKGROUND OF THE INVENTION
A slurry is a suspension of solid particles in a liquid. There are many cases where the liquid is drained from the suspension to obtain the solids and in some cases some form of de-watering has to be carried out in order to remove the liquor trapped between the particulate solids. The two most commonly used methods are pressing and drying, both of which are expensive. Pressing requires robust machinery and drying requires some heating medium which is often expensive, for example, steam.
This invention applies to the improvement of such operations on two counts; (i) it provides a method of de-watering a solid porous medium structure without the application of high mechanical force, (ii) a method of removing the liquor trapped between the particles as well as a means of washing the liquor out of the porous medium. The method also has potential of particulate elutriation, namely the removing of some small particles from the interstices of the porous medium.
The most common methods of removing the liquor from a bed of solids is to provide a strong physical pressure by some form of mechanical compression, such as a ram, a rolling mechanical press for continuous operation, or forcing the solids through two rotating rolls and into the nip of those rolls to remove the liquor. Although some of the liquor is removed it does not provide a method of removing all the liquor and, generally speaking, further de-watering by drying action is needed.
There are other methods of course, such as centrifugation where large radial forces are used to remove the liquor from the solid as well as concentrating methods (such as a hydrocyclone) which increases the outlet concentration of the particulate suspension. However, in most cases where there is a soluble or contaminant component in the liquor which has to be removed, the particulate suspension or precipitate of solids has to be washed. The washing process can either be carried out by compression or by displacement. In displacement a liquor is either drawn through the suspending solids or forced through those solids to displace the contaminated liquor trapped in between the particulate solids.
In the pulp and paper industry the particulate solids are wood pulp fibres. In the chemical process the black liquor that is formed has to be removed by washing. In some cases simple compression or centrifugation is used but in most cases the wash water is added by forcing it through the pad of fibre suspension. This is usually carried out either on a continuous belt or on a rotating drum and the washed liquor is added to the pad and drawn through the pad, either by suction or by a mild positive force.
In mechanical pulping the conventional technique is to apply large hydraulic and physical pressures using rotating rolls or a screw type press. In some cases the pulp is mixed with water following one stage of the operation and then the liquor is squeezed out in a second stage. In this case it is impossible to arrive at a contaminate free liquor in the solids, although the quantity of liquor can be dramatically reduced as well as a lowering of the contaminant concentration.
OBJECT OF THE INVENTION
It is an object of this invention to provide an improved method of liquor removal and/or washing from suspensions of particulate solids, or one which will at least provide the industry with a useful choice.
SUMMARY OF THE INVENTION
This invention goes a long way to solving some of these problems because it does not necessarily require the addition of a clean wash liquor or wash water to the solids, although in some cases this may be advantageous. The principle is to apply either a pneumatic or vapour pressure force through suspension of solids i
REFERENCES:
patent: 643891 (1900-01-01), Bussells
patent: 675179 (1901-05-01), Wacher
patent: 847676 (1907-03-01), Mackethan
patent: 1151186 (1915-08-01), Johnson
patent: 2534324 (1950-12-01), Von Hildebrandt
patent: 2696148 (1954-12-01), Hornbostel
patent: 2999785 (1961-09-01), Richter et al.
patent: 3127367 (1964-03-01), Endres et al.
patent: 3447451 (1969-06-01), Meskanen
patent: 3938434 (1976-02-01), Cox
patent: 3939763 (1976-02-01), Sato
patent: 3943033 (1976-03-01), Wallen
patent: 4324613 (1982-04-01), Wahren
patent: 4975204 (1990-12-01), Henricson et al.
patent: 4976820 (1990-12-01), Laapotti
patent: 5071513 (1991-12-01), Bluhm et al.
patent: 5186791 (1993-02-01), Seifert et al.
Auckland UniServices Limited
Beisner William H.
LandOfFree
Method of liquor removal from particulate solids does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of liquor removal from particulate solids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of liquor removal from particulate solids will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-9470