US2878117A - Particle advancing apparatus - Google Patents

Description

March 17, 1959 L. A. CARLSMITH ETAL 2,

PARTICLE ADVANCING APPARATUS Filed June 29. 1956 2 Sheets-Sheet 1 March 1 L. A. CARLSMITH ETAL 2,

PARTICLE ADVANCING APPARATUS Filed June 29, 1956 2 Sheets=-$heet 2.

PARTICLE ADVANCING APPARATUS Lawrence Allan Carlsmith, Amherst, and John P. Rich, Nashua, N. 1-1., assignors to Improved Machinery, Inc., Nashua, N. H., a corporation of Maine Application June 29, 1956, Serial No. 594,791

2 Claims. (Cl. 92-7) This invention relates to the continuous pulping of fibrous material, and is a continuation-in-part of our copending U. S. application for Letters Patent, Serial No. 561,405, filed January 26, 1956. More particularly, the present invention relates to improvements in the novel apparatus and methods for advancing the solid particles of a solid-liquid mixture through said liquid independently of the movement of the liquid as described in said earlier application and dominated by certain of the claims thereof, although not specifically shown and described therein.

Pulping of wood or other fibrous material is carried out, for example, by digesting particles of fibrous materials such as wood chips in a highly heated liquid chemical solution preferably under pressure, as in the well known soda or sulfate processes for the manufacture of paper pulp. As another example, the digestion may also be carried out by steeping the fibrous materials at atmospheric or sub-atmospheric pressure in cold liquid chemical solutions such as nitric acid or caustic. At the present time, such digestion in either case is usually carried out in batches, that is, a digester is filled with the raw material, such as wood chips, after which the chemical digester solution is admitted and suitable reaction conditions maintained for an interval of time sufficient to digest the wood chips. Thereafter, the batch of chips is discharged.

One of the major problems which must be solved in order to provide a continuous pulping process which would consist in continuously feeding the solid raw material, such as wood chips, into one end of the apparatus used for the digestion, and causing such raw material to move through said apparatus while admitting the heated chemical digester solution and finally discharging the material from the other end of the apparatus in the form of pulp, arises from the nature of the reacting mixture itself, that is, the mixture of discrete particles in a liquid. It has proved to be most difficult to control the movement of such particles into a reacting vessel and through the liquid solution of chemicals to an outlet at the other end of the apparatus, since the particles are subject to both sticking and channeling which prevents the uniform movement essential for the production of pulp having uniform characteristics. Further difficulty arises in controlling the movement of the liquid, since it freely drains away from the mass of solid particles, making it impossible to use the liquid as a vehicle for carrying the solid particles through the apparatus.

Still another problem arises from the tendency of the solid particles to plug up strainers and the like used to separate the solid particles from the liquid, particularly when they are mounted in an enclosed continuously operating system.

According to the present invention, we have provided a novel apparatus for advancing the solid particles, such as wood chips, of a solid-liquid mixture through said.

liquid at a rate of movement substantially independent of the rate of movement of the liquid, and without stickice ing or channeling of said particles, as well as novel-means and methods for compacting such solid particles and for causing limited reciprocatory relative movement between the solid particles and the liquid. I

It is a feature of the invention that it is particularly adapted to aid in feeding solid particles suspended in a liquid into a reaction vessel, as well as for thereafter advancing such particles upwardly through such reaction vessel at a uniform rate to discharge at the other end thereof.

It is another feature of the invention that it is selfcleaning in operation, so that plugging difiiculties do not arise even with continuously operating systems.

For the purpose of more fully explaining a preferred embodiment of the invention, reference is now made to the following specification, together with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view of a continuous pulping apparatus employing the particle advancing means of this invention;

Figs. 2 and 3 are enlarged cross-sectional elevations showing at two different stages of operation a portion of the apparatus of Fig. 1 having therein the particle advancing means of ths invention;

Fig. 4 is a cross-sectional elevation of a portion of the means of Fig. l; and

Fig. 5 is an isometric view showing a portion of the means of Figs. 2 and 3.

Referring to the drawings, in Fig. 1 is shown a complete continuous pulping apparatus including a mixing means for suitably mixing and impregnating fibrous material such as wood chips with a liquid chemical solution such as a solution of soda ash to provide a solid particleliquid mixture or slurry. Such mixture is then fed under pressure through an opening in the wall of an upright pressurized reaction vessel of upwardly increasing crosssectional area wherein the chips are treated by heating them under pressure in said solution as they are moved upwardly therethrough until they are discharged as a digested slurry at the top of the reaction vessel. Novel foraminous piston means mounted adjacent the entrance end of the vessel and extending throughout substantially the entire horizontal cross-sectional area thereof adjacent the entrance end of said vessel closely adjacent the inner wall of said vessel are provided for advancing and compacting the chips or other solid particle component of the solid particle-liquid mixture in an'elongate'd mass or zone extending throughout the major portion of the length of the elongated pressurized reaction vessel at a rate substantially independent of the rate of movement of said liquid, the feeding of said mixture through the wall of the vessel preferably taking place in timed relationship to the piston adjacent to the advancing face thereof. 7 Thus, the solid particle-liquid mixture, because of the free movement of liquid through the piston means, may be fed into the reaction vessel, the mass of chips advanced therethrough through said zone at a uniform average rate without sticking or channeling and the digested chips then discharged to so provide uniform digestion as well as to provide control of the degree of digestion by controlling the rate of advance. Since such rate of advance issubstantially independent of the rate of movement of the liquid component of the solid particle-liquid mixture, the liquid may be recirculated for heating it as desired. Additionally, the chip advancing means may also act to cause a limited reciprocatory relative movement between the solid particles and the liquid, or additional means'therefor may be providedif desired.

In more detail, the mixing or impregnating portion of the apparatus includes a tank 12 filled with a suitable liquid chemical solution, and a hopper 14 containing chips or other fibrous materials. A centrifugal pump 16 with the rotor 19 of the valve 18 in one position, the bore 20 of said rotor receives a charge of chips from hopper 14, the chips being kept from passing outwardly from said bore through exhaust pipe 21 by a screen 22 at the opposite end thereof, and in the other position feeds said charge together with a charge of liquid from pump 16 which passes through screen 22 to inject a mixture of chips and liquid into the pressurized reaction vessel 24 through an opening 25 therein. Other types of intermittent feeding means may be used. For example, a centrifugal or other non-positive displacement pump may be used either with a suitable gate valve timed with the piston or with the piston itself used as a valve by positioning the inlet within the piston stroke so as to be closed when the piston is advanced. Under some circumstances, continuous feed, as by a twin intermeshing screw feeder, may be used.

The generally cylindrical upright elongated pressure vessel 24 of generally uniform cross-sectional area at least not decreasing in its upward direction comprises the reaction portion of the apparatus and includes a top discharge mechanism 26 connected to a suitable pulp storage tank (not shown). It is important that vessel 24 although of generally uniform cross-sectional area have a slight taper to provide a gradually increasing cross-sectional area, a taper of about inch of diameter per foot of length, for example, being suitable. A filter section 28 as well as a bottom outlet 29 may be provided in said vessel 24 for recirculation of the liquid component to heat it as desired. Any suitable heating means may be employed, for example, steam may be injected into the liquid, to heat it.

As best shown in Figs. 2 through 4,the novel advancing means includes a foraminous piston means mounted for reciprocatory movement through a limited distance relatively to the length of the vessel 24 within the reaction vessel 24 near the lower end thereof by means of a shaft 30 extending vertically through the bottom of said vessel generally axially thereof. More specifically, said foraminous piston means comprises a circular plate 32 having therein a plurality of perforations 34 preferably extending over its entire surface and sufi'icient in number to allow substantially free passage of the liquid there through but of small enough size to prevent passage of the chips or other fibrous material. Furthermore, the peripheral edge thereof is positioned closely adjacent the inner walls of the reaction vessel 24 so that passage of chips into the bottom portion of said reaction vessel 24 may be prevented.

For feeding the pressurized mixture of chips and liquid to the upper surface of said piston, the opening 25 is provided in the wall of vessel 24 within the extent of the stroke of said piston so that a charge of the solid particleliquid mixture will be fed to the advancing face of said piston prior to the movement of said piston to advance the particles (Fig. 2), the piston passing said opening 25 about midway of its stroke to compact and advance the solid particles in the vessel, the valve 18 then operating to cut off the feed of the solid particle-liquid mixture into the, vessel and recharge said valve with chips, the liquid remaining in the bore 20 of said valve passing through screen 22 to exhaust pipe 21 to be collected for return to tank. 12 if desired (Fig. 3).

The lower end of shaft 30 extends into a hydraulic cylinder 40 mounted beneath the lower end of reaction vessel 24 and forms the piston thereof, said cylinder 46 being provided with an inlet pipe 42 connected to a suitable source of fluid pressure, (not shown) through valve 44 to raise said shaft with the plate 32 to reciprocate said plate, the force of the vessel pressure against the area of the upper end of said shaft being great enough to rapidly lower the plate 32 when the pressure in cylinder 40 is exhausted, the pressure vessel 24 in such circumstances acting as an accumulator to provide the necessary force at a rapid rate. Furthermore, the volume of liquid displaced by shaft 30 varies as the shaft reciprocates, causing the entire volume of liquid in vessel 24 to reciprocate over a limited distance. Means including a double acting solenoid 46 operated by switches 47 and 48 actuated by lugs 36 on piston 30 are provided for alternately connecting pipe 42 to its source of pressure and to exhaust and to reciprocate plate 32 through a predeterminde stroke at any desired rate. A similar solenoid 50 operated by a double throw switch 52 positioned to be operated by lugs 36 at the lower end of the piston stroke is provided for rotating valve 18 to feed a solid particleliquid mixture charge into vessel 24 when said piston is at the lower end of its stroke. If desired, the piston face plate 32 may be provided with short upstanding radially extending fins and the piston may be rotated to aid in distributing the infed chips by, in effect, stirring the liquid at the lower end of vessel 24.

in operation, the solid particle-liquid mixture or slurry of chips and liquid is fed into the reaction vessel 24 by centrifugal pump 16 and valve 18 so that it will be pressurized before entering said vessel, such feeding taking place in timed relation to the piston, i. e., when the piston is in the lower extent of its stroke. The reciprocation of plate 32 for a short distance axially of the vessel 24 at a rate of say 12 strokes per minute serves to provide an axial component of movement of the chips fed through aperture 25 to move them successively upwardly to the bottom of the mass of chips in the reaction vessel and compact them thereon and advance them therethrough by exerting force only against the chips at the bottom end of said mass or zone. Furthermore, since the mass of chips fills the reaction vessel and its bottom extends downwardly toward the plate, such reciprocatory movement acts on the bottom of said mass of chips to advance it upwardly at a desired uniform average rate as Well as to compact it. The taper of the vessel makes it possible for the plate 32 to move the mass of chips upwardly without exerting extraordinarily high pressures on the chips, as too high pressures seriously damage the chips and cause a substantial reduction in the quality of the resulting pulp. The digested chips are discharged as pulp through mechanism 26. During a run, the reaction vessel is kept full of chips to maintain a compacted elongated mass or zone thereof, the individual chips moving slowly upwardly as they are reduced to pulp and discharged through mechanism 26 at the top of the reaction vessel.

Since the liquid component of the mixture passes freely through the perforations 34 in plate 32 during such reciprocation, the reciprocatory movement will not aifect the movement of the liquid so that the chips may be advanced independently thereof, except for the limited reciprocatory movement of the liquid caused by the reciprocation of shaft 30, which limited movement is valuable in that it aids the reaction by continuously washing away from the chips the material dissolved by the liquid chemical solution. Furthermore, the liquid may be continuously recirculated for'heating or the like through filter 28 and outlet 29.

The upward movement of plate 32 due to the pressure in hydraulic cylinder 40 is relatively slow, occupying say of the total cycle, while the downward movement due to the pressure of the vessel acting on the end of shaft 30 is much more rapid, occupying but about 10% of the cycle. This is made possible by using the vessel in effect as a hydraulic accumulator. Such rapid downward movement forces the liquid under plate 32 to move rapidly through the perforations 34, thus flushing away any solid particles that may have become lodged in the perforations 34.

Thus it will be seen that we have provided a novel means for advancing the solid particle component of a practical upflow continuous pulping apparatus for wood chips or other fibrous materials, or a countercurrent washing apparatus for such materials as by introducing washing liquid at the upper filter section 28 and removing it from outlet 29, and in such case pressure operation may not be necessary. Various modifications of the invention within the spirit thereof and the scope of the appended claims will occur to those skilled in this art.

We claim:

1. In apparatus for the continuous treatment of the solid particle component of a solid-particle-liquid mixture in an upwardly arranged elongated reaction vessel having a generally uniform cross-sectional area at least not decreasing in its upward direction by feeding substantially continuously said mixture into said reaction vessel through an opening in the side wall adjacent the lower end thereof to maintain a compacted mass of said solid particles within an elongated zone in the central and opposite upper end portions thereof, advancing the solid particle component thereof upwardly through said zone at a rate substantially independent of the movement of liquid in said vessel to treat said solid particles, meanwhile treating the same, and substantially continuously discharging said treated solid particles from said opposite upper end of said vessel, the improvement comprising foraminous piston means mounted adjacent the lower end of said vessel for generally vertical reciprocatory movement and extending generally in a horizontal plane across substantially the entire cross-sectional area adjacent said lower end of said vessel with its outer periphery closely adjacent the inner walls of said vessel for free passage of said liquid therethrough while preventing passage of said solid particles, means for reciprocating said piston means through a predetermined stroke, and means operated in timed relation to said piston means for feeding said solid particle component into said vessel adjacent to and in advance of said piston means through an opening positioned in the side wall of said vessel within the extent of the stroke of said piston means to advance said solid particles into contact with solid particles at the lower end of said zone and to exert lifting force directly only on particles located at the entrance end of said zone to progressively compact said particles and to advance the mass of said particles progressively upwardly through said zone while permitting free movement of liquid through said piston means.

2. In apparatus for the continuous treatment of the solid particle component of a solid particle liquid mixture in an elongated, generally upright reaction vessel of generally uniform and gradually increasing cross-sectional area throughout the major portion of its length at least not decreasing in cross-sectional area in its upward direction by feeding substantially continuously said mixture into said reaction vessel through an opening in the side wall adjacent the lower end thereof to maintain a compacted mass of said solid particles within an elongated zone in the central and upper portion thereof filling its entire cross-sectional area, advancing the solid particle component thereof upwardly through said zone at a rate substantially independent of the movement of liquid in said vessel to treat said solid particles, meanwhile treating the same, and substantially continuously discharging said treated solid particles from the upper end of said vessel, the improvement comprising foraminous piston means mounted adjacent the lower end of said vessel for generally vertical reciprocatory movement and extending generally in a horizontal plane across substantially the entire cross-sectional area of said vessel with its outer periphery closely adjacent the inner walls of said vessel for free passage of said liquid therethrough while preventing passage of said solid particles, means for reciprocating said piston means through a predetermined stroke, means for feeding solid particle liquid mixture into said vessel adjacent to and in advance of said piston means through an opening in the side wall of said vessel within the extent of the stroke of said piston means including valve means operating in timed relationship to said piston means for receiving in a first position a charge of solid particles and in a second position a charge of liquid for discharging said solid particles and liquid into said vessel prior to movement of said piston means to advance said solid particles into contact with solid particles at the lower end of said zone and to exert lifting force directly only on particles located at the entrance end of said zone to progressively compact said solid particles at the lower end of said zone and to advance the mass of solid particles progressively upwardly throughout the length of said zone while permitting free movement of liquid through said piston means, and discharge means for discharging the treated solid particles from the upper end of said zone at the upper end of said reaction vessel.

References Cited in the file of this patent UNITED STATES PATENTS 1,982,130 Wollenberg Nov. 27, 1934 1,991,244 De La Roza Feb. 12, 1935 2,038,721 Desmond Apr. 28, 1936 2,359,543 Branzell et al Oct. 3, 1944 2,383,684 Richter Aug. 28, 1945 2,709,652 Plunguian May 31, 1952 2,680,683 Obenshain June 8, 1954

Claims (1)

1. IN APPARATUS FOR THE CONTINUOUS TREATMENT OF THE SOLID PARTICLE COMPONENT OF A SOLID-PARTICLE-LIQUID MIXTURE IN AN UPWARDLY ARRANGED ELONGATED REACTION VESSEL HAVING A GENERALLY UNIFORM CROSS-SECTIONAL AREA AT LEAST NOT DECREASING IN ITS UPWARD DIRECTION BY FEEDING SUBSTANTIALLY CONTINUOUSLY SAID MIXTURE INTO SAID REACTION VESSEL THROUGH AN OPENING IN THE SIDE WALL ADJACENT THE LOWER END THEREOF TO MAINTAIN A COMPACTED MASS OF SAID SOLID PARTICLES WITHIN AN ELOGATED ZONE IN THE CENTAL AND OPPOSITE UPPER END PORTIONS THEREOF, ADVANCING THE SOLID PARTICLE COMPONENT THEREOF UPWARDLY THROUGH SAID ZONE AT A RATE SUBSTANTIALLY INDEPENDENT OF THE MOVEMENT OF LIQUID IN SAID VESSEL TO TREAT SAID SOLID PARTICLES, MEANWHILE TREATING THE SAME, AND SUBSTANTIALLY CONTINUOUSLY DISCHARGING SAID TREATED SOLID PARTAICLES FROM SAID OPPOSITE UPPER END OF SAID VESSEL, THE IMPROVEMENT COMPRISING FORAMINOUS PISTON MEANS MOUNTED ADJACENT THE LOWER END OF SAID VESSEL FOR GENERALLY VERTICAL RECIPROCATORY MOVEMENT AND EXTENDING GENERALLY IN A HORIZONTAL PLANE ACROSS SUBSTANTIALLY THE ENTIRE CROSS-SECTIONAL AREA ADJACENT SAID LOWER END OF SAID VESSEL WITH ITS OUTER PERIPHERY CLOSELY ADJACENT THE INNER WALLS OF SAID VESSEL FOR FREE PASSAGE OF SAID LIQUID THERETHROUGH WHILE PREVENTING PASSAGE OF SAID PARTICLES, MEANS FOR RECIPROCATING SAID PISTON MEANS THROUGH A PREDETERMINED STROKE, AND MEANS OPERATED IN TIMED RELATION TO SAID MEANS FOR FEEDING SAID SOLID PARTICLES COMPONENT INTO SAID VESSEL ADJACENT TO AND IN ADVANCE OF SAID PISTON MEANS THROUGH AN OPENING POSITIONED IN THE SIDE WALL OF SAID VESSEL WITHIN THE EXTENT OF THE STROKE OF SAID PISTON MEANS TO ADVANCE SAID SOLID PARTICLES INTO CONTACT WITH SOLID PARTICLES AT THE LOWER END OF SAID ZONE AND TO EXERT LIFTING FORCE DIRECTLY ONLY ON PARTICLES LOCATED AT THE ENTRANCE END OF SAID ZONE TO PROGRESSIVELY COMPACT SAID PARTICLES AND TO ADVANCE THE MASS OF SAID PARTICLES PROGRESSIVLEY UPWARDLY THROUGH SAID ZONE WHILE PERMITTING FREE MOVEMENT OF LIQUID THROUGH SAID PISTON MEANS.

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