US2312706A

US2312706A - Method and apparatus for separating heavy particles from paper pulp suspensions

Info

Publication number: US2312706A
Application number: US241360A
Authority: US
Inventors: Freeman Horace
Original assignee: Nichols Engineering and Research Corp
Current assignee: Nichols Engineering and Research Corp
Priority date: 1938-11-19
Filing date: 1938-11-19
Publication date: 1943-03-02
Anticipated expiration: 1960-03-02
Also published as: CH237791A; GB533235A; NL60422C; FR861506A; DE746910C

Description

March 2, 1943.

H. FREEMAN METHOD AND APPARATUS FOR SEPARATING HEAVY PARTICLES FROM PAPER PULP SUSPENSIONS Filed Nov. -19, 1958 2 Sheets-Sheet l INVENTOR [Yo/"ace Freeman ATTORN EYS March 2, 1943. H. FREEMAN METHOD AND APPARATUS FOR SEPARATING HEAVY PARTICLES FROM PAPER PULP SUSPENSIONS Filed Nov. 19, 1958 2 Sheets-Sheet 2 ACCEPTED STOCK 70 MPER MAOY/IVE VII/77751444722 7111K INVENTOR HORACE FREEMAN BY M,%

SUPPLY OF PULP $706K ATTO R N EYS [UNITED STATE s PAT-surf oma I Horace Freeman, Three Rivers, Quebec, Canada, 7 assignor to-Nichols Engineering & Research Corporation, New York Delaware N. Y., a corporation of A Application- November is, 1938, Serial No. 241,360

2 Claims.

This invention relates to improved systems and methods for separating relatively heavy or compact undesired particles from fluids, .such for example as fibrous pulp suspensions.

In ca y ng out the invention in its preferred forms, separating devices may be used of the general type disclosed in my United States Patent No. 2,102,525; reference to which is hereby made.

With the apparatus of the above mentioned patent, materials such as paper pulp suspensions for example, may be so treated that substantially all undesired particles, even particles of almost microscopic fineness, are removed providing they have a specific gravity substantially greater than the desired suspended matter. However, some paper stock such as the inexpensive grades used for newsprint paper, embodies numerous dark colored undesired particles of dirt, bark or other material, which are made evident in the usual newsprint paper as small blemishes or specks. Many of these specks aredue to particles which are only slightly heavier and/or more compact than the desired suspended matter and prior to this invention no satisfactory, dependable and inexpensive method of removing same has been found. One of the objects of the present invention therefore is to remove undesired particles of the last mentioned character from liquid suspensions such as paper stock, so that particles of this character will no longer be present to an extent suflicient materially to disfigure the paper when printed or otherwise used.

Further objects of this invention include the provision of improved systems and methods for treating fluid or liquid suspensions so as to more expeditiously and thoroughly remove therefrom the undesired particles. The invention also invoives improved methods for carrying out with a greater degree of thoroughness the general methods disclosed in my above mentioned patent.

Various further and more specific objects, features and advantages will more clearly appear from the detailed description given below taken in connection with the accompanying drawings which form a part of this specification and illustrate merely by way of example a preferred form of the apparatus of the invention.

Theinvention consists in such novel features,

arrangements and combinations of parts as may be shown and described in connection with the apparatus herein disclosed and also such novel methods as are disclosed and described herein after.

In the drawings,

Fig. 1 comprises a vertical sectional view of one of the separating units of the apparatus embodying the invention; r

Fig. 2 somewhat schematically illustrates a system in which several'of said separating units or similar units may be interconnected for the purposes of the present invention; and

Fig. 3 schematically illustrates a portion of the system of Fig. 2 and certain modifications and alternative embodiments of such system.

The separating unit shown in Fig. 1 is similar to those shown and described in my above mentioned patent, but with certain improvements as to its construction and method of. operation, hereinafter referred to. This device may comprise an elongated upstanding chamber I0 provided with a head portion II including an inlet l2 for conducting a stream of the material to be treated into the device. The head portion as shown and as further disclosed in the above mentioned patent is preferably so shaped that the incoming stream will be tangentially introduced and directed downwardly into the chamber l0 and thereby forming a helically flowing annular body of the material in the manner indicated by the helical lines l3 in Fig.1. This downwardly flowing annular body is preferably so confined within the cylinder that its crosssectional area will not be materially greater than that of the introduced stream, with the result that a high velocity vortex is formed under pressure. This vortex continues downwardly through the upper section II of the cylinder Ill, thence through the middle of an annular obstruction as indicated at l5 into a lower portion IQ of the cylinder l0. That is, the obstruction l5 may for example comprise a partition preferably of flexible material such as rubber and having an aperture at its mid portionwhich forms a constriction for the helically moving body of fluid, and

below this point of constriction the helically flowing body preferably expands again as shown vortex being enclosed and confined merely by the outer vortex. At the disc or partition I5 the inner vortex as shown will also be constricted by reason of the constriction of the outer vortex,

and above this constriction the inner vortex will expand again as indicated at II' on its way to -of the outer vortex. 1

Below the lower ends of the vortices another partition or disc-like member may be provided as at 20 which may have a plurality of apertures, for example, a central aperture as at 2! and one or more smaller apertures as at 22 near the periphery. Below this partition a small conical chamber as at 23 may be provided with a somewhat restricted conduit or connection 24 opening into a settling chamber 25. In the operation of the, above described con struction the heavier particles are thrown to the periphery of the outer vortex and carried down by the latter along the inside walls of the chamber l0, thence inwardly along partition I5, through its aperture, anddown along the peripheral portions ofchamber portion l5 tothe partition 20. Any heavier particles remaining in the inner vortex are forcefully thrown to the pected to be carried down into the settling chamber and thus become wasted as well as clogging the connections. However, I have found that such difllculties may in fact be avoided or overcome while still maintaining a downward current sirable material pass out through the connection 26. This connection is preferably providedqwith an orifice or restriction 21 of predetermined size.

' which limits the outward flow, but is so designed peripheral zones of the latter-and thence into the outer vortex and are thus also carried down to the partition 20. Meanwhile the vortex seppatent. However. in operating these units in the manner described in said patent, the settling chamber as at 25 was initially filled with liquid and thereafter during normal operation of the device and until the settling chamber needed to be emptied of dirt, it was kept closed with the liquid therein in a quiescent condition except that the undesired particles were allowed to fall by the action of gravity through the connection 24, with a consequent gradual displacement of liquid upwardly through the'conn'ection 24. While this method of operating the device is urprisingly effective in removing-even, the finest particles which have a substantially greater specific gravity than the desired suspension, yet in some cases this action did not serve to remove certain of the undesired particles which were but slightly heavier or more compact than the desired suspended matter, i. e., some of the bark dirt, sawdust and the like. It is believed that this difllthat it is not clogged or blocked by the dirt and desirable material, such as fiber, passing through it. With the separating unit treating paper stock,

and having a 4" cylinder and other dimensions in the same proportions as disclosed in my above mentioned patent, I have found that the size of the orifice should be approximately /4" (onequarter inch) in diameter, the connection 25 being of so-called standard ,41" pipe, whose internal diameter is 0.364" An adjustable valve in lieu of the orifice 21 may be used, but

should be of specialdesign for use with paper stock, as valves or petcocks of conventional type have been found to plug or clog. It has been culty was due either to the presence of the slight forcefully draw downwardly the undesired particles, several dimculties arise which would at first seem prohibitive of such a procedure. That is, such a downward current would be expected to interfere with the reversing action at the bottom of the vortices or cause turbulent conditions disturbing the desired quiescent settling action in the lower portions of the device, also substantial proportions of the desired pulp could also be exfound that satisfactory operation may be obtained when the flow from the chamber 25 is equivalent to from 1% to 3% of the main flow of stock through the apparatus, 1. e., entering at l2 and leaving at l8. By making the connection 24 to chamber 25 relatively short, and by in-- turn the disturbance in chamber 25, and aiding the settling of the heavy material, which otherwise may be carried out through connection 26.

The above described arrangement in addition to removing the more troublesome particles, has the further important advantage that the capacity of the vortex device may be substantially increased. That is, due to the downwardly flowing stream through the connection 24 at the bottom of the device, the time required for particles to settle or pass into the chamber 25 is materially reduced and as a consequence it is possible to pump the suspension to be treated into the device at a substantially greater rate and still insure that the main exit stream through outlet l8 will be substantiallyfree of the undesired particles. I

In Fig. 2 I have shown an arrangement whereby this may be economically accomplished. As here shown, a plurality of the separating units as at 40 are arranged in parallel, a suflicient number being provided forv continuously treating all of the pulp stock necessary for a single paper machine or a group of machines as desired. The stock may be introduced under pressure as by a pump 4|, through a manifold 42 intothe several inlets of the units 4|). The principal supplies of treated stock are conducted from the outlets of the several units while still under pressure into a manifold 43 which is in turn connected to the paper machine or other equipment for receiving the treated stock. Each of the units 40 may be provided with a settling chamber 25 and connections thereto and therefrom, the same asfor the device of Fig. 1. All of the waste pipes from the settling chambers 25 may be connected to a waste manifold as at 44 and all of the connections 26 from the various settling chambers may be connected to a manifold 45 running to a CilCll-I latory system which includes the apparatus which will now be described, for recovering that portion of the suspended matter which is carried out of the settling chambers through pipes 26.

This circulatory system may include a pump 46, a tank 41 and a separating unit 48, this unit being preferably like or similar to the units 40 as well as that of Fig. 1, like parts thereof being identified by the same reference characters.

The tank 41 is preferably provided witha water inlet as at 49 equipped with a suitable float operated valve as at 50, 50' whereby the liquid level in the tank is kept just slightly above the level of an overflow 5|. The liquid overflowing at 5| will comprise the recovered suspension which may be conducted by a pipe 52, either to the intake of pump 4| with the main supply of stock, or to the white water system of a paper machine, or if desired, to the main intake of a paper machine. In cases where this recovered suspension is conducted into the whitewater system, the white water with the recovered suspension may be conducted into the main supply of stock entering the intakes of the units 40.

These various alternative connections are schematically illustrated in Fig. 3 wherein the conduit 52 is shown connected by a by-pass running into the conduit 43 containing the main iupply of accepted stock being conducted to the paper machine. Alternatively, the suspension within conduit 52 may be conducted by conduit 1| into a white water tank 12 as shown. This tank may be supplied with white water through conduit 13 from the paper machine and the mixture of white water and suspension may be conducted from this tank through

conduits

14 and 15 as shown, into the main supply of pulp stock entering pump 4|. Also, if desired, as shown the stock may be conducted from conduit 52 through a by-pass 15 directly to the conduit 15 without going into the white water" tank. The various conduits 10, 1|, 14 and 16 may as shown be provided with valves, making possible the alternative methods of operation above referred to.

The bottom of the tank 41 and'intake of pump 46 may be interconnected by a conduit 53. The inlet to conduit 53 is preferably protected by a bafiie as at 54 to prevent air entrainment. As shown, the manifold 45 may be connected into the conduit 53. The outlet of the pump 46 may be connected as by pipe 55, having a pressure adjusting valve 56, to the inlet l2 of the separating unit 48. The outlet l8 of the separating unit may be connected into the side of tank 41 as by a pipe 51, also having an adjustable valve 58.

With the above described arrangement, the various units of the apparatus may be made of such proportions and so operated that the liquid within tank 41 before finally passing out the overflow, will largely be recirculated through the separating unit 48 a plurality of times, for example about 8 times. Thus while the liquid admitted to this circulatory systemthrough manifold 45 will contain a large amount of the undesired particles, as well .as desired suspended matter, the final recovered product passing out of the overflow will be substantially confined to a diluted suspension of the desired material. And most of the undesired particles separated therefrom will be lodged in the settling tank 25 of the unit 48. As will be noted on the drawings, if desired this settling tank may also be provided with one of the bleed-off conduits as at 26 for the same purpose as in Fig. 1, but in this case the amount of desired suspended matter drawn off will be insignificant and may pass to waste.

It will be apparent that with the arrangement in Fig. 2 a single separating unit as at 48 may be used to recover thesmall amount of desired suspension withdrawn from thelower portions of a large group of the primary separating units as at 40. Also if desired the circulating system of Fig. 2 may be used for directly cleaning or separating with a .higher degree of efflciency, suspensions which have not passed through primary separating units.

It will be observed that the tank 41 fulfills several functions in the system. That is, it supplies a volume of the liquid to be treated by the separating unit 48 so that sufficient liquid will always be available for continuously operating the unit 48' with the most advantageous inlet and outlet pressures therefor, which may be shown by pressure indicators 68 and GI. Also the tank 41 provides in effect a settling chamber so that that portion of the liquid therein which embodies most of the undesirable particles may be drawn oil from the bottom, whereas the desired suspended material may be withdrawn from the overflow at the top. Furthermore, the tank provides a large volume of the liquid into which variable quantities of water may be introduced from time to time at a point remote from the overflow without greatly varyingthe consistency of the recovered suspension at the overflow. Suflicient water may be thus introduced to considerably dilute the dirty suspension for easier cleaning and so as to maintain an overflow stream of substantial size even though the amount of liquid introducedthr'ough the manifold 45 may be quite small. It will be noted that directly out at the overflow.

the pipe 51 from the outlet of the separating .unit is connected into a side wall of the tank 41 at a point below the overflow, so that the cleaner stock will be at the side of the tank nearest the overflow. However, the pipe 51 is spaced considerably below the overflow so that a substantial part of the stock coming in through pipe 51 will be recirculated in the system instead of going Also the pipe 51 is preferably introduced into the tank at a point as shown, spaced substantially from the bottom of the tank so that the inrushing liquid will not cause turbulence in the zones at the bottom of.

the tank where the undesired particles have settled.

Where the separating devices are used for satisfactory results may be obtained if the pressure within the inlet to each separating device 40 is in the neighborhood of from to 30 lbs. per square inch, and in this event the pressure within the outlets to these units may be in the neighborhood of from 3 to 8 lbs. per square inch. Under these conditions there will be at least some substantial positive pressure within the chambers at the bottom of the units 40, that is, a pressuregreater than the mere static head of liquid above these chambers. The amount of such pressure will determine to a considerable extent the amount of liquid withdrawn through the pipes 26 and hence in order to be able to regulate this amount, inlet, and outlet pressure gauges as at 60 and 6| should preferably be providedat one or more of the units III and also a pressure gaugeas at 62 on one or more of the chambers 25. With inlet and outlet pressures as above indicated for the units 40, each of these units will be able to treat in the neighborhood of 18Cv to 240 gallons of paper pulp suspension per minute, and the pressure within the chambers 25 will be in the neighborhood of from 3 to 10 lbs. per square inch. It may be noted that if the liquid is allowed to flow out through the outlet manifold 43 without being subjected to any substantial pressure, the action oi. the reversing vortices in the units 40 may be such as to produce a vacuum effect at the inlets to the chambers 25 which in turn would prevent any positive downward flow of liquid into these cham bers and hence prevent operation of the units in the preferred manner above described. That is, as disclosed in my above mentioned patent, the action of the vortices is so intense as to cause a small substantially evacuated space to be established along the entire vertical axis of the vortices; hence care must be taken with the present invention to so adjust the main inlet and outlet pressures that such evacuated space does not extend down into the region of the inlet connection to the settling tank.

The inlet and outlet valves fortheunit 48 are preferably so adjusted that the inlet pressure as indicated at 60 will be in the neighborhood of from 18 to 20 lbs. per square inch and the outlet pressure as indicated at 6| will be at from 1 to.

be at least about 3" in diameter to minimize frictional resistance.

Tests of the system of Fig. 2 with inexpensive newsprint paper pulp stock have shown that nearly all of the specks of bark dirt, sawdust'and the units 40, in some cases it may be found de-' sirable to use a device at 48 of the same general proportions but considerably smaller than the devices 0, for example a device with a cylinder 2" in diameter instead of 4". With such devices the separating forces on the particles in the vortices are in general adversely proportional to the diameter of the vortices, other conditions being substantially the same. Hence with such smaller vortex devices the eifectiveness of the separating action is greatly'increased. Since only a small percentage of the total pulp supply need be passed through a device such as at 48, the fact that such a device if made smaller has a lower capacity, is not prohibitive. Also with such a smaller vortex device in some cases it may be unnecessary to add additional liquid to the circulating supply as described above in connection with the tank 41.

While the invention has been described with respect to certain particular preferred examples which give satisfactory results, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and

itis intended, therefore, in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent is:

1'. The method of separating from paper pulp suspension, undesired particles which are heavier or more compact than the desired suspended matter, which comprises establishing a downwardly and helically flowing annular body of the suspension, providing an annular obstruction in the path of such flow for directing the same as a more restricted flow through the center of such obstruction,.then causing such helical flow to expand andfcontinue downwardly beneath the obstruction, then returning the suspension upwardly as a helically flowing core of the suspension confined within and by said downwardly flowing annular body of the suspension, whereby said particles, are thrown by centrifugal force to, and carried down in the peripheral zones in the downwardly flowing suspension, withdrawing the desired suspension from the upper portion of such core, maintaining a sufficient difference in pressure in the suspension as introduced into and withdrawn from said helical flows whereby at least some positive pressure is applied to the suspension in the region beneath said flows, and

causing said particles to be further drawn by a downwardly and slowly moving stream including a small portion of the suspension from said region, said stream being conducted through a constricted path to'a settling chamber, and maintaining said stream by withdrawing a small por tion of the suspension from a point above the settlings in such settling chamber, independently of said upwardly returned suspension.

'2. Apparatus for continuously separating from the supply of pulp suspensions as used in the manufacture of paper or the like, the undesired particles which are heavier or more compact than the desired suspended matter, comprising a device or devices for maintaining vortices of the suspension for centrifugally expelling said particontinuously receiving such diluted portion and maintaining a vortex thereof to separate further undesired particles therefrom, a settling tank for receiving the suspension recovered by the latter device, means for conveying the recovered suspension from said tank together with white water resulting from the manufacture of the paper or the like, into the original supply of suspension to be treated, and means for introducing the resulting mixture into said first named device or devices.

HORACE FREEMAN.