US3471364A - Apparatus for subjecting cellulosic material to counterflow of conditioning fluid - Google Patents

Description

1969 .1. R. STARRETT .v 3.471,3 64

APPARATUS FOR SUBJECTING CELLULOSIC MATERIAL I TO COUNTERFLOW OF CONDITIONING FLUID Filed June 20, 1966 Fis-l INVENTOR. JAMES R. STARRETT ATTORNEY United States Patent US. Cl. 162--237 17 Claims ABSTRACT OF THE DISCLOSURE Apparatus for preconditioning pulp material wherein pulp material is progressively advanced from a tower and through a hollow vessel containing a plurality of successively arranged chambers, all the while being subjected to a counterflow of preconditioning fluid under pressure. In the preferred embodiment the means for producing the counterflow operates on waste steam and has a cleansing function.

This invention relates to a novel system and apparatus for preconditioning and preheating pulp materialsin a refiining process. It will be described in reference to a prefer-red embodiment, as applied to fibrous materials such as sawdust and wood chips. However, it should be understood that neither the form of its embodiment nor the nature of its application is so limited.

Invention embodiments are characterized by simplicity of structure, a high degree of operating efiiciency and a unique compact design. In all these respects they clearly distinguish from the conventional units of the prior art. The latter have been commonly of great bulk, requiring the use of a considerable valuable floor space. Moreover, they usually comprise a large diameter pipe containing a material conveyor means in the form of a large helical screw. The discharge of materials from these prior art pre-conditioning units is quite erratic. Further, it produces many functional problems. For example, in moving material from the pre-conditioner to a device providing a feed opening leading to a digester, there is the problem of a large ratio transition which leads inevitably to plugging and malfunction. This is but a limited example of the many problems solved by the embodiments of the present invention.

A primary object of the invention is to provide improved apparatus for preheating and preconditioning pulp materials for a refining process which is economical to fabricate, more efiicient and satisfactory in use, adaptable to a wide variety of applications and unlikely to malfunction.

Another object of the invention is to provide a pulp preconditioning system having a most unique, compact design.

A further object of the invention is to provide pulp preconditioning apparatus which is economical to operate and functions with an optimal efficiency.

Another object of the invention is to provide pulp preconditioning apparatus having characteristic features which simplify its physical incorporation in a refining system.

An additional object of the invention is to provide a pulp preconditioning system possesing the advantageous structural features, the inherent meritorious characteristics and the means and mode of use herein mentioned.

With the above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring tothe accompanying drawing wherein is shown one but obviously not necessarily the only form of embodiment of the invention,

FIG. 1 is a schematic illustration, in partial section, of an embodiment of the invention, excepting a chip tower;

FIG. 2 is a view taken on line 22 of FIG. 1 including the tower; and

FIG. 3 is a view taken on line 3-3 of FIG. 1.

Like parts are indicated by similar characters of reference throughout the several views.

The embodiment here illustrated will be described as applied to continuously preheat and precondition fibrous material such as wood chips, utilizing live or waste steam, preliminary to a delivery thereof to a continuous digester.

As shown, it includes a large diameter tube 10 forming a chip tower which projects vertically from the top plate 11 of a transition chute 12. The latter forms an integral part of a pressure vessel 13. The plate 11 has a central opening corresponding generally to that defined by the delivery end of the tube 10.

The chute 12 is comprised of parallel side plate 14 and relatively converging front and rear plates 15 and 16. To the underside of plate 16 is fixed a vibrating units 54. Noting FIG. 2 of the drawings, the chute is positioned to discharge to the rear upper quadrant to one end of a cylindrically formed hollow structure 17 forming the main housing of the pressure vessel 13.

Referring more particularly to the details of the chute which is disposed rearwardly of the vessel 13, its front plate 15 is generally vertical but has its lower end displaced forwardly and terminating in a line above and in a spaced relation to a helical metering screw 18. This line occupies a vertical plane commonly occupied by the center line of the screw, Moreover, it is substantially coincident with the center line of the structure 17. The rear plate 16 is angled in the same sense as plate '15 but to a greater degree. Further, the plate 16 depends to have its lower extremity position just inside the rearmost Wall portion of the cylindrical housing 17. From this point the plate 16 is extended inwardly of the housing by an interconnected relatively flat screen 19. The latter is extended by an interconnected transversely arcuate screen 21 which forms a trough in adjacent cupping but spaced relation to the underside of the screw 18 at the one end portion thereof coextensive with the opening from chute 12. The terminal line of the screen 21 approaches the horizontal plane which includes the center line of the screw 18. Connecting with and extending vertically from the terminal line of the screen 21 is an imperforate plate 22. The plate 22 which positions in forwardly sapced relation to and projects upwardly of the lower end of the chute plate 15 defines therewith a flow channel 23. The purpose of this will be further described. It should be noted the screen 21 is located in adjacent but spaced relation to the bottom of the cylinder 17.

Both the fiat screen section 19 and the curved section 21 may be conventionally formed of spaced support bars and spaced transversely oriented screen bars. The details are not described since in and of themselves they are not pertinent to an understanding of the present invention. Sufiice it to say the screen formations produce drain slots.

The pressure vessel 13 includes the hollow cylinder 17 sealed to one end adjacent chute 12 by a head plate 24 and to its other end by a similar plate 25. Each of the plates 24 and 25 has a central opening accommodating the projection therethrough of one end of a shaft 26 which mounts the metering screw 18. Within the screen section 21, substantially the length thereof, the screw 18 has a conically expanded form, its largest diameter occurring adjacent and nesting in an opening 27 in the head plate 24. The opening 27 is sealed by a spider-like closure plate 55. The plate 55 has an outwardly projected arm 28 mounting a bearing 29 for one end of the shaft 26. Plate mounts a similarly projected support arm 28 and fixed thereto a bearing for the opposite end of shaft 26. The side plate of chute 12 remote from the head plate 24 has an integrated extension and together therewith forms a bulkhead 30. The bulkhead 30 which bridges the cylinder 17 is truncated at its upper forward quadrant to define with the cylinder wall a limited passage 31. It is also truncated at its bottom to provide a small passage 20 which communicates with the vessel space beneath the screen section 21. The bulkhead 30 also has an opening 32 in line with and accommodating the projection therethrough of the screw 18.

Bridging the cylinder 17 in parallel spaced relation to bulkhead 30 is a further plate defining a bulkhead 33. The bulkhead 33 has an opening 34 in line with the opening 32. The openings 32 and 34 are defined by the respective ends of a tubular duct 35 which bridges the bulkheads 30 and 33.

The bulkhead 33 and the parallel head plate 25 form, in the cylinder 17, an output chamber 36. Adjacent its top, bulkhead 33 includes a second opening 37 rimmed by the discharge end of a steam tube 38 located in the chamber 36. The tube 38 extends from the bulkhead to a plane adjacent and spaced from the head plate 25. An inspection port is provided in the head plate 25 in a direct line with the adjacent end of tube 38. Mounting 0n the top of the cylinder 17 to project vertically therefrom and in an overlying adjacent relation to the tube 38 is a housing 39. The housing 39 provides the separating chamber 40 of a centrifugal type which is open at its bottom to the output chamber 36. A pipe 41 at the upper end of the housing 39 defines a tangential inlet to the separating chamber 40. It is contemplated that the tangential inlet have in connection therewith a source of live or waste steam, as will be further described. The steam utilized may be salvaged from any on site refining equipment.

It is to be noted that the bottoms of screen 21 and the duct 35 are on the same line. Within the chamber 36 the screw duct 35 is extended by an open trough 42 which includes upwardly divergent sides 43 connecting respectively to opposite side portions of the cylinder wall. The trough 42 terminates at a dependent discharge tube 44 which defines the outlet from the vessel 13. As it projects through the wall of the cylinder 17 the tube 44 has connected to its dependent extremity a conically convergent discharge nozzle 45. Further diverging deflector plates are connected to extend from the trough 42 to define respectively opposite sides of the opening to the tube 44. These latter plates are operative to channel loose materials so as to induce their discharge to and through the tube 44.

Bridging the plates 50 and rotatable therein over the outlet tube 44, relatively adjacent the end of the trough 42, is a rod 51. Fixed to the rod 51 is a dependent plate 52. The plate 52 lies in the path of materials delivered to the outlet by means of the metering screw 18. The rod 51 projects exteriorly of the cylinder 17 where it mounts a projected lug 53 operatively related to a safety switch 54 in a manner and for purposes to be further described.

Referring once more to screw 18, it is coextensive with screen 21, duct 32 and the trough 42, being in relatively nesting relation thereto. Below the transition chute 12 it has one pitch and is conically formed in a manner to provide in operation thereof, a uniform withdrawal and advance of chips from the tubular tower 10. From a point adjacent but preceding bulkhead 30 the screw 18 assumes a generally uniform diameter as it extends through the duct 35 and is continued through the trough 42. Within the trough 42 the pitch of the screw is double that within section 21. The advantages of this will soon become obvious.

Beneath the screen 21 the cylinder 17 has a drain 46 and, in connection with the top of chamber 40, there is a pressure relief valve 47.

In the example illustrated, the top of the tube tower 10 is capped but includes an opening defined by a vertically projected vent stack 48. In this case the stack 48 has connected therewith the delivery end of a screw feeder 49. The feeder 49 provides the means for delivering pulp, such as wood chips, by way of the stack 48 to fill the tubular tower 10 in the preconditioning system and process as contemplated by the present invention.

Let us now consider the use of the described embodiment of the invention for preheating and preconditioning wood chips utilizing waste steam. This use would be preliminary, for example, to the chips entering a continuous digester for chemical treatment.

As is obvious, raw material is fed into the top of the tubular tower 10, at its center. The material will descend in the tube 10 and the transition chute 12 to the screw 18, entering the screw to the rear portion thereof as seen in FIG. 2 of the drawings. In the first instance the raw material will be fed until it fills the major extent of the tube 10 and after that a nearly constant level is maintained by the feed means to provide that sufiicient solids head occurs in the tube to insure a steam pressure within the cylinder 17. In use the length of the time that the raw material is to be exposed to steam or other conditioning fluid is established by the particular height of the tower.

Suitable means is of course provided to energize the shaft 26 and turn the metering screw 18. Due to the conical form of the screw portion at the base of the transition chute 12, the screw functions to draw down material from the tube 10 in a uniform manner. correspondingly, the screw is operative to advance the material uniformly from the base of the chute and transfer it to the chamber 36 by way of the duct 35.

At the same time, waste steam is delivered by way of the tangential inlet to the separating chamber 40 in a manner that centrifugal forces are developed to extract any fines or dirt that may be in the steam, causing the latter to drop into the trough 42 and be carried to the outlet defined by the tube 44. The clean steam moves downwardly around the steam tube 38. With the screw operating, the duct 35 is of course filled and the steam is forced to follow a path the length of the tube 38 to enter its end adjacent the head plate 25. Here the steam is caused to reverse its fiow path and move outwardly between the bulkheads and through the passage 31 defined by the bulkhead 30 to enter the flow passage 23 above the free half of the screw 18 under the transition chute 12. This steam which reaches this point moves freely down and through the screw to move upwardly through the chips in the chute 12 and the tube 10. In the process the steam extracts air and preheats the chips. A portion of steam from the duct 38 also moves through the limited opening 20 in bulkhead 30 under the screen sections 19 to 21 to move therethrough and upwardly of the chute 12 and the chip tower 10 with results again as described with reference to the flow through the passage 23. It is here noted that in some instances it will be deemed unnecessary to have the elements 19 and 21 in an apertured form. In this instance of a preferred embodiment, it is desired that the screens provide means for condensate occurring in the preheating of the wood chips to fall downwardly to and through the screens to exit through the drain 46 and the cylinder 17. Thus, there is both an extensive preheating and a withdrawal of air from the delivered materials within the confines of the chute 12 and tube 10.

As the screw moves material from the chamber defined by the screen 21 to the chamber 36, the doubling of the screw pitch within the chamber 36 reduces the fill or loading of the screw by 50%. This facilitates the ready movement of the conditioned material to the tube 44 and delivery through the limited opening provided by nozzle 45. In process of movement through the chamber 36 the conditioned material is further subjected to clean steam in passage of the steam to the tube 38. This steam functions to additionally heat the material and equalize its moisture content.

The plate dependent from the rod 51 functions as a safety medium. In event the discharge nozzle should build up with material, further delivered conditioned chips will be pushed against the plate 52 to rotate the rod 51 causing its lug to hit the safety switch 54. The effect of this is to shut down the screw. It will be obvious that the safety switch is in the control circuit for the power means selected to drive the screw.

It is noted that the vibrator applied to the chute Plate 16 functions only to insure the smoothness of flow from the chute to the screw 18.

A further point of interest is that the deflector plates 50 at the output tube 44 function to direct any solids that travel beyond the flared sides of the trough 42, or float to the plate 25 prior to dropping from vapor flow forces, down into the down spout provided by the tube 44.

The embodiment of the invention as so provided is exceedingly compact and occupies a minimum of floor space. Moreover it enables a preconditioning unit capable of readily delivering small uniform amounts of material to the feeding device of a continuous digester. Further, the invention embodiments utilize to maximum benefit the condensing surface area of the tubular tower 10. A particular functional advantage of the invention apparatus is that it fully utilizes the natural convection currents of the heat provided by the steam. Embodiments are therefore distinguished by a more uniform heating of the worked materials, which, in process, are subjected to a gradual temperature increase, the removal of entrained air and the equalizing of their moisture content. It is noted that the reduced loading of the screw 18, as achieved by the change in pitch, is a factor in enabling a small and more uniform flow from the invention apparatus to related equipment.

Of further importance in evaluating the invention, only a small amount of pressure is required to move the steam from its entrance point to the area below the tube Excessive pressures can not be maintained in the embodiments and if they occur this will be automatically relieved by an inherent blowing of the contents of the tube lll out through the vent stack.

As described, the invention provides a uniquely effective apparatus having inherent automatic characteristics in its operative function which are highly desirable and lend both economy and utility in the use thereof in any refining system.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

Having thus described my invention, I claim:

1. Preconditioning apparatus for pulp materials including a hollow pressure vessel having means defining an inlet thereto and in connection therewith a vertically projected charge tube, a metering screw within said vessel, one end of said screw being exposed to said tube by way of said inlet, said tube being adapted to receive a charge of material for preconditioning, the charge forming a column and sealing said inlet, bulkhead means forming a chamber in said vessel including therein said one end of said screw, said bulkhead means providing a restricted passage for projection therethrough of said screw, said vessel having an outlet adjacent the opposite end of said screw and means in connection with said vessel for delivery to said chamber of a flow of steam or other conditioning fluid under pressure, said vessel providing means to direct at least a portion of said fluid to move to said inlet and upwardly of said vessel, to and through the charge in said tube, in the process of which to infiltrate and condition the charge, said metering screw being operative to draw down the charged materials as they are conditioned by said upward flow and advance them for discharge from said vessel by way of said outlet.

2. The apparatus as in claim 1 characterized by said vertically projected tube having a generally uniform diameter and a tapered chute means forming a transition channel for directing the materials from said tube to said one end of said screw.

3. The apparatus as in claim 2 wherein said bulkhead means forms in part said transition channel and provides passages for circulation therethrough of portions of said conditioning fluid.

4. Apparatus as in claim 1 characterized by said bulkhead means, in part, forming a containing wall to provide a transition channel limiting the flow of conditioned material from said tube to said one end of said screw.

5. Apparatus as in claim 1 wherein said bulkhead means define a further chamber in communication with said outlet, said further chamber including means in connection therewith for flow therethrough of steam or other conditioning fluid to provide that the material delivered to said tube, first conditioned within said tube, is then further conditioned within said further chamber prior to discharge through said outlet.

6. Apparatus as in claim 1 wherein said bulkhead means includes a plate having an opening defining a limited passage for said screw and a further passage for steam to flow thereby in the area of said screw and to and through the charge of material in said vertical tube.

7. Apparatus as in claim 1 wherein said bulkhead means define a further chamber including said outlet, the said one end of said screw having one pitch in the first mentioned chamber and approximately double the pitch in said further chamber.

Preconditioning apparatus as in claim 7 wherein said one end of said screw has a conically expanded form and said bulkhead means are constituted by a pair of plates interconnected by a limited duct providing for said screw to move materials in a uniform manner from one chamber to the other, the double pitch of the screw in said further chamber reducing the load on said screw in transmittal of materials to and through said outlet to provide thereby for a staged conditioning of materials occupying and moving downwardly of said vertical tube through and from said vessel by way of said outlet.

9. Preconditioning apparatus as in claim 7 wherein said further chamber has in connection therewith a separating chamber and means for transmitting steam therefrom to flow through said chambers and to said vertical tube by way of openings defined in said bulkhead means.

10. Preconditioning apparatus as in claim 7 including means in said further chamber operative to automatically interrupt the operation of said screw in response to a buildup of materials in the vicinity of said outlet.

11. Preconditioning apparatus as set forth in claim 7 wherein a steam channelling means is mounted in said further chamber, the entrance to which is positioned at the end of said vessel adjacent said outlet and there being a passageway through said bulkhead means in communication with said tube and the discharge from said channeling means.

12. Preconditioning apparatus as in claim 1 characterized by a tapered chute forming a transition channel for directing the materials from said tube to said one end of said screw, said chute being connected into said pressure vessel to deliver the materials to an area limited to one end of said screw.

13. Preconditioning apparatus as in claim 12 characterized by means in connection with said chute structure defining a path for inflow of conditioning fluid to the materials in said tube.

14. Preconditioning apparatus as in claim 12 and means forming an apertured trough for said one end of said screw, spaced from the wall of said vessel, to provide thereby for passage of steam and/or escape of fluid condensate from the materials moving down through said tube.

15. Pulp preconditioning apparatus including a pressure vessel having at least two chambers and means defining limited passageways communicating said chambers, one of said chambers having an inlet and the other having an outlet, a feeding device in said one chamber extending through a portion of said limited passages to the other chamber adjacent said outlet, means defining a chip tower rising generally vertically and communicating with the inlet to said one chamber and means defining a separating chamber connected with and opening to said other chamber, said separating chamber being adapted to receive waste steam and deliver clean steam and means for directing clean steam through said other chamber to said one chamber by way of another portion of said limited passageways to move along said feeding means and upwardly through materials forming a column in said tube whereby to extract air from said materials and in the process of movement through said chambers equalize the moisture content of said materials.

16. Preconditioning apparatus for pulp materials including a hollow pressure vessel having a material inlet and in connection therewith a generally vertically projected charge tube, said tube being adapted to receive a charge of material for preconditioning in said vessel, the charge forming a column and eflecting substantially a pressure seal of said inlet, bulkhead means forming a chamber in said vessel exposed to said column by way of said inlet, said vessel having an outlet to the side of said bulkhead means remote from said inlet, means in said chamber operative to draw down the charge of materials in said column and deliver it through said bulkhead means to said outlet and means in connection with said vessel for delivery to said chamber under pressure a flow of steam or other conditioning fluid, there being means for directing the fluid to flow to said material inlet to move upwardly of said vessel and through the charge in said tube, in the process of which to infiltrate and condition the charge.

17. Apparatus as in claim 1 wherein said bulkhead means define a further chamber including said outlet and there being means for directing the materials drawn down to move to said screw to one side thereof and for directing fluid to move in a channelled flow to said tube in a path adjacent the other side of said one end of said screw.

References Cited UNITED STATES PATENTS 2,287,332 6/1942 Steely 162237 2,425,024 8/1947 Beveridge 16Z-236 2,799,579 7/1957 Messing 162-237 2,905,240 9/1959 Sandberg 162-19 X HOWARD R. CAINE, Primary Examiner U.S. Cl. X.R.

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