US3157565A - Apparatus for impregnation of cellulosic material - Google Patents

Description

E. GREMLER Nov. 17, 1964v APPARATUS FOR INPREGNATION OF' CELLULOSIC MATERIAL Filed July 17, 1961 2 Sheets-Sheet 1 FIG-2 ATTORNEYS FIG-5 20% Nov. 17, 1964 E. GREMLER 3,157,565

APPARATUS FOR INPREGNATIO OF CELLULSIC MATERIAL Filed July 17, 1961 2 Sheelzs-Sheel'I 2 FIG-4 l se 3% 5 l 7s 6' ,7l :1T-3x77 f 72 INVENTOR.

ENRIQUE GREMLER ATTORNEYS United States Patent O 33157555 APPARATUS FR Bt/EREGNATHGN OF CELLULQSEC MATERAL Enrique Gremler, Hamilton, hio, assignor to The Black Clawson Company, Hamilton, hio, a corporation of llio Filed duly i7, i961, Ser. No. 34,470 3 Claims. (Cl. 162-236) This invention relates to apparatus and methods for continuously treating cellulosic materials for use in the manufacture of pulp and paper products.

The invention has special relation to apparatus and ethods for effecting treatment of raw cellulosic material without requiring steam in the reaction chamber and which are capable of effecting adequate impregnation of the cellulosic material by the treating liquor under room temperature conditions and atmospheric pressure. lt is a primary object of this invention to provide such apparatus which is capable of continuous operation with the raw cellulosic material being continuously introduced into the chamber wherein treatment is eected without requiring either heat or super atmospheric pressure, without requiring high power or developing undesirably high temperature in the material, and with the impregnated material being continuously discharged from the chamber.

An additional object of the invention is to provide such continuous treating apparatus wherein the raw cellulosic material is fed into the reaction chamber by a feeding mechanism which is constructed to'compress and split the material to a degree substantially eliminating liquid and voids therefrom, while effecting a high degree of frictional working of the particles of material on each other, wherein the inlet of the reaction chamber is maintained submerged in treating liquor so that this compressed material is received in the chamber below the level of the liquor and therefore is caused to absorb this liquor as it expands `while submerged ytherein to effect the desired impregnation, and wherein the impregnated material is discharged `from the chamber through an additional feeder mechanism which compresses the material to express the absorbed liquor therefrom While also effecting substantial debering thereof.

It is also anobject of this invention to provide a method of treating cellulosic material wherein the raw material is rst compressed to a degree susbtantially eliminating liquid and voids therefrom and is then twisted and split apart while it is further compressed in the absence of air and liquor to effect separation of the individual fibers and bundles of fibers, wherein the material is then directly submerged in treating liquor While shielded from exposure to air in order to cause expansion of the compressed material while submerged in liquor and thereby to effect yimpregnation of the material by absorption of liquor as it expands while submerged therein, and wherein the impregnated material is then subjected to a further compression step for the purpose of expressing absorbed liquor therefrom Mld also effecting substantial defiberimr thereof.

A further object of the invention is to provide methods and apparatus as outlined above wherein the raw cellulosic material is iirst compressed into ribbon form with accon panying elimination of air and the natural juices of the material therefrom, wherein the compressed material is then forced to change its configuration from ribbon form into a substantially solid plug of log-like section with accompanying splitting and twistig of the component bundles of fibers therein, and wherein the compressed plug of split iibers is then directly submerged 'm treating liquor without exposure to air to cause the fibrous material to expand and simultaneously to absorb liquor into all the interstices thereof.

A still further object of the invention is to provide meth- 3,157,565' Patented Nev.. 17., 19.64

ods and apparatus as outlined above wherein some of the liquor expressed from the cellulosic material after absorption thereof is added to the raw material before its initial compression to lubricate the material during compression and to assist in the elimination of the natural -juices therefrom prior to impregnation with fresh digesting liquor.

Other objects and advantages will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings- Fl'G. l is a somewhat schematic ilow diagram illustrating a typical treatment system in accordance with the invention;

FIG. 2 is a side elevational view of the reaction chamber and associated equipment in the system of FIG. l;

FG. 3 is a plan view of a portion of FIG. 2;

FlG. 4 is an enlarged fragmentary section on the line 4 4 of FIG. 3 showing details of the feeder unit of FIGS. 1 3;

FG. 5 is a section on the line 5 5 of FIG. 4;

FIG. 6 is a plan view of a fragment of FlG. 4; and

FIG. 7 is a diagram illustrating the action of the feeder on the cellulosic material.

Referring -to the drawings, which illustrate a preferred embodiment Vof the invention, the complete system as shown in FIG. 1 includes a hopper 10 or similar device for containing Va supply of chips or other raw cellulosic material to be treated, and for convenience the term chips will be used hereinafter as including any suitable raw starting material. The hopper lt) delivers the chips to the inlet end of a metering conveyor 11 which includes a feed Worm l2 by which the chips are fed to the inlet of the mixing conveyor 13. The mixinor conveyor includes a casing 15 enclosing a mixing conveyor worm le, and the casing 1S is provided near its inlet end with an inlet 17 for liquid. A screened outlet f8 is provided ahead of the main outlet 19 of the conveyor 13 for discharging excess liquid which has not been absorbed b the chips as described hereinafter.

The mixing conveyor 13 delivers Wet chips to the inlet of the feeder 2l) which is described in detail hereinafter in connection with FIGS. 4,-7. The function of the feeder Ztl is to compress the chips to a degree effecting maximum practical elimination of fluids therefrom, to split the chips longitudinally in order to increase the exposed areas thereof without damaging the fibers, and then to discharge the compressed chips into the inlet 21 lof an inclined tube 22. Which forms the reaction chamber. The tube 22 is filled with digesting liquor to a level submerging its inlet 21, and a screw 23 therein advances the chips upward through the liquor, past one or more screened outlets Z4, to a main outlet 2S lwhich drops the chips into the inlet of a discharge unit 26 similar to the feeder 20. The discharge unit 26 compresses the chips again to eliminate the majority of the liquor therefrom and then delivers the compressed chips to a conveyor 27 by means of which the chips are delivered to the desired next station of treatment thereon such as suitable detlbering apparatus, not shown.

FG. l also illustrates the liquor oW throughout the system, with the fresh or refortiiication liquor being initially supplied from a tank 3@ by a pump 31 and lline 32 to the recycled treating liquor tank 33 which is also provided with a supply line 34 for Water. A lpump 35 is connected to supply treating liquor from the tank 33 by a line 36 directly to the feeder 20 for admission to the reaction chamber 22 as described hereinafter. A line et) leads from the screened outlets 24 back to the tank 33 to return excess liquor from the digesting chamber for recycling. A line 41 is connected to receive the liquor extracted from Athe chips in the discharge unit 26 and to conduct this Waste liquor to a third tank 42.

Vor other gas.

Part of the waste liquor from the tank 42 is used to wet the raw chips in the mixing conveyor 13 and for this purpose a pump 44 and line 45 supply the waste liquor from tank 42 to the inlet connection 17 of the mixing conveyor casing 15. Liquor draining from the screened outlet 18 of the mixing conveyor is conducted by line 46 back to the tank 42 and close to the suction of pump 44, as indicated at 47, and surplus Waste liquor from line 41 is-overowed by line 43 from the tank 42 to the tank 33. The liquid expressed from the raw chips in the feeder 20 is discharged through a line 49 directly to the sewer.

In accordance with the invention, the feeder 2i) is of such construction and mode of operation as to be capable of compressing the raw chips to a degree substantially eliminating liquid and voids therefrom while at the same time effecting a high ydegree of rubbing of the chips on each other in such manner as to cause substantial twisting and splitting of the individual bundles of fibers therein. YIt is important in the practice of the invention, however, to minimize frictional engagement of the chips on metal, in Vorder torprevent the development of temperatures capable of charring the chips. It is further of great importance in the Vpractice of the invention that the operation of the feeder and its associated equipment result in eliminating as much as possible of the natural juices Vof the raw material before actual digesting treatment thereon begins.

The compressed material treated as described in the feeder 20 is supplied continuously to the reaction chamber 22'under such conditions that it is received directly below the level of treating liquor within the chamber 22, and liquor is directly applied thereto immediately upon entry to chamber 22 as described hereinafter. Therefore as the chips start to expand after release from the feeder 20, they can absorb only the liquor rather than air, steam Conditions are controlled within the reaction chamber to assure that substantially all expansion of which the compressed chips are capable will take place while they are submerged in the liquor, and they are then conveyed to the discharge outlet end of the chamber 22 under conditions Vdraining the unabsorbed Y liquor therefrom. The discharge unit subjects the imabove this level, and the tube 22 is accordingly shown as inclined at asuitable angle such that the lower screened outlet 24 is above the level of the inlet 21 and thus may act asV an overiiow control for the desired levelrof liquor. The screw conveyor 23 within the tube 22 serves to convey the chips upwardly from the inlet 21 to the outlet 25 Ywhile mixing them thoroughly with the liquor, and the rate of rotation of this screw controls the time of treatment of the chips in the liquor.

A feeder 20 meeting the requirements of the invention as outlined above is illustrated in detail in FIGS. 4-7. 'It includes a main frame 55 which includes an inlet 56 Vfor receiving the wet chips from the mixing conveyor 15,

and which supports a driven compaction screw 60 having a central shaft portion 61 and continuous screw flights 62.

'Ihe discharge end of the screw 60 is tapered and coopriphery for the escape of the fluids from the compressed chip mass as it progresses through the throat.

T he discharge end of the throat casing 65 is directly connected with a plug pipe 7% of predetermined contiguration and proportions to produce the desired effects in accordance with the invention. More specifically, the plug pipe includes a frustoconical section 71 at its inlet end which is of a diameter providing a free iiow area which is substantially greater than the annular ilow area between the ends of the screw shaft 61 and casing 65. The section 71 tapers at a relatively iiat angle, for example about 15", to a minimum diameter which is not greater than and ,preferably somewhat less than the minimum ow area lat the outlet end of the casing 65, and the remainder 72 of the interior of the pipe 70 is preferably cylindrical. Preferred results in the practice of the invention have been obtained with the diameter of the pipe section 72 in the range of 80-l00% of the discharge flow area from theV casing 65.

The connection between the feeder 20 and the reaction chamber 22 is provided by a generally bell-shaped housing 75 which surrounds the pipe 7() and llares from a nn'nimum diameter matching the outer diameter of the pipe 70 to a maximum diameter substantially greater than that of the pipe 70. The housing 75 thus defines a space into which the pipe 7i) projects and which serves as a connection through which the material discharged from the pipe 70 reaches the lower end of the reaction chamber 22. As best seen in FIG. 6, the housing 75 is provided on opposite sides with a pair of inlet connections 77 for admitting liquor, and these inlets are located on opposite sides of the pipe 70 so that the fresh liquor admitted therethrough will flow continuously past the pipe '76 towards the inletend of the reaction chamber 22;r

In the operation of the system with the feeder 20 constructed as described, the waste liquor mixed with the raw chips in the mixing conveyor 15 has the dual func tion of lubricating the chips and also diluting the natural juices, and the chips may absorb as much as of the'orde of an additional 25% of liquid in the form of waste liquor at the mixing conveyor 15. Then as the chips are pro gressively compressed within the throat casing 65, the uids which are present in the chips are squeezed out through the weep holes 67, and it has beenY found readily possible to eliminate in this manner as much as 50% ofV the original volume of natural juices. This is a very desirable result, since it correspondingly reduces the necessity for washing out or bleaching whatever natural juices remain in the pulp. It should be understood that the'invention is not limited to the use of waste liquor to pre- Wet the chips, such other chemicals or water could be used,Vv

butrthe practice as described has proved to be very advantageous. y,

The chips reach an initial maximum degree of compression just before they are discharged from the throat casing 65, and then as they reach the larger endV of the tapered section 71 of the plug pipe 70, they are able to expand to an appreciable extent, for example Y10% or more. This resultris particularly contributed to by the abrupt ending of they screw shaft 61, since this provides a more 0r less dead space immediately beyond the screw into which the compressed chips can collapse temporarily. Then as the pressure of the following material forcesthe chips further Valong through the plug pipe 70, a recompression occurs by reason of the decreasing Ytaper of the section 71 until maximum compression is reached as the chips pass through the cylindrical section 72.

During the temporary expansion at the inlet end of th plug pipe 79, the chips are still shielded from -an exposure both to air and to liquor by the compressed plug within the outlet end of the plug pipe 70, so that what occurs is more in the naturev of a temporary relaxation of pressure accompanied by substantial rearrangement of the original chips and movement of the chips relative to each other. The result of this compound action appears to be a definite rubbing and twisting of chip on chip which produces a substantial degree of desirable splitting of the individual chips along the length of the component fibers thereof. At the same time, there is a minimum amount of movement of the chips on metal, thus correspondingly minimizing friction of a type tending to cause an undesirable temperature rise when the system is operated with the liquor at room temperature.

The action of the feeder is illustrated diagrammatically in FIG. 7, which represents an axial section through the chip mass as it progresses through the casing 65 and plug pipe 70 and with the stippling which is employed as hatching being varied to represent changes in compression. Thus the stippling increases in intensity from left to right in FlG. 7 through the sections A-E to represent the increasing compaction Iof the ribbons of chips which reaches a maximum at E in the space surrounding the end portion `of the screw shaft. The lighter stippling in the space F immediately beyond the screw shaft represents the temporary collapse and expansion of the chips which is followed by the rapidly increasing compression through the section G to the maximum represented by the most dense stippling in the plug H within the cylindrical portion of the plug pipe.

The net result of the structural and operational factors just described is to produce in the cylindrical portion 72 of the plug pipe a mass of chips forming a dense plug of log-like section, and this plug continuously advances to the outlet end of the plug pipe within the housing 75. The compression on the plug relaxes immediately as soon as the material thereof emerges into the housing 75, and at the same time a continuous supply of fresh liquorflows past the end of the plug from the inlets 77. This liquor flow facilitates the tendency of the material of the plug to expand and break up, and this action is accompanied by expansion of the individual bundles of the chips. Since the expanding bundles are submerged in fresh liquor from the instant when they begin to expand, their expanding action is accompanied by absorption of the liquor in a manner comparable with that of a sponge which is compressed and then released under water.

The remainder of the treatment in the system of the invention involves only control of the rate of rotation of the screw 23 and control of the maintained concentration of the liquor in the chamber 22 to eect the desired degree `of impregnation of the chips before they reach the discharge end of the chamber 22, and typical examples will be given hereinafter. When the chips reach the outlet 25, they drop into the inlet of the discharge unit 26, and the latter may be of essentially the same construction as the feeder 2t) except that the plug pipe Sil thereof discharges to atmosphere at the inlet to the conveyor 27.

The relative proportions `of the screw 6l?, casing 65 and plug pipe 7 il are of importance in accomplishing the purpose of the invention `as outlined above, and an illustrative set of dimensions will accordingly be given .with which preferred results have been obtained. In Ithis example, the discharge end of the screw shaft 6l is 6.44 inches in diameter and the discharge end of the casing 65 is 12.64 inches in inner diameter providing an exit flow area from the casing 65 of approximately 98.8 square inches. The plug |pipe 7@ in this example has a maximum inner diameter of approximatelyV 13.315 inches, and the tapered section 7l is 4.25 Iinches in axial length and has a minimum diameter `of 10.50 inches. Thus the flow area of the plug pipe varies from a maximum of approximately 136 square inches to a minimum of approximately 86.6 square inches which is `'approximately 87.6% of the exit ow area from the casing 65. The axial length of the plug pipe section 72 is also important to maintain the proper back pressure on the chips and thereby to assu-re formation of the desired densely packed plug, and satisfactory results are obtained in this example when the section 72 is 10.75 inches in length.

The system cf the invention lis applicable to a variety of treatments, including treatments involving cooking at elevated temperatures, but it has been proved to 'be especially satisfactory for treatment with caustic solution which is initially a-t room temperature. It is also of substantial interest to note that lthe operation of the system of the invention produces a relatively slight temperature rise, for example from a starting temperature of 70 F. to only -l00 =F., thus demonstrating that there is no possibility of accidental charring or blackening of fiber. The time of treatment is subject to variation in accordance with the desired results, but in general there is a definite relation between time of treatment :and the concentration of the treating liquor, as now discussed.

ln general, the strength of the .pulp is Iincreased if the concentration of the strength of the caustic solution is increased, and satisfactory results have been obtained utilizing up to as much as 35 grams per liter of NaOH. At the lower concentrations of caustic, .the pulp is not as strong but is more Vopaque and substantially easier to bleach. For example, highly satisfactory results from these standpoints have 4been obtained using l0 grams per liter of NaOH at a starting temperature of 70 F. anda retention time in the tube 22 of approximately 2() minutes. It should also not be overlooked that lthe system and method of the invention can be employed 'satisfactorily in the production of ground wood utilizing water without chemicals as the treating liquor in ythe reaction chamber.

While the methods and forms yof 'apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is: i

l. Apparatus for continuously treat-ing cellulosic material comprising means defining a chamber having an inlet adjacent the lower end thereof and Ian outlet located at a level above that of said inlet, means for maintaining treating liquor in said chamber at a level between said inlet and outlet to submerge said inlet therewith, feeder means for supplying cellulosic material to said chamber including a screw :and a perforate casing cooperating to compress said material to a degree substantially eliminating liquids therefrom, means directly connecting said feeder means with said inlet to cause discharge of said compressed material into said chamber below the level of said liquor therein and thereby -to ffect impregnation of said material by said liquor through absorption as said material expands while 'submerged in said liquor, said connecting means including a pipe directly connected with the discharge end of said casing, the inlet end of said pipe being of frustoconical shape converging from an entering diameter larger than said discharge end of said casing to a uniform diameter providing a cross-sectional area less than that defined by the discharge ends of said screw and said casing and thereby acting to rearrange and compress said material from said casing into a substantially solid plug and to discharge ysaid plug into said chamber, discharge means connected with said outlet, and means Ifor conveying said impregnated material upwardly Iin .said chamber to said discharge means 4while draining unabsorbed liquor therefrom.

2. Apparatus for continuously treating cellulosic material comprising means defining a chamber having an inlet adjacent the lower end thereof and an outlet located at a level above that of said inlet, means for maintaining treating liquor in said chamber at a level between said inlet and outlet to submerge said inlet therewith, feeder means for supplying cellulosic material to said chamber including a screw and a perforate casing cooperating to compress said material to a degree substantially eliminating liquids therefrom, said casing and said screw having the ends thereof in substantially coplanar relation to provide a low pressure space immediately adjacent said screw end, means 7 directly connecting said feeder means with said inlet to cause discharge of said compressed material into said chamber below the level of said liquor therein and thereby to effect impregnation of said material by said liquor through absorption as said material expands while submerged in said liquor, said connecting means including a pipe directly connected with the discharge end of said casing, the inlet end of said pipe being of frustoconical shape converging from an entering diameter providing a oW area larger than the ow area defined by said discharge ends Vof said casing and said screw to a uniform diameter providing a cross-sectional area less than that defined by the discharge ends of said screw and said casing and thereby acting to rearrange and compress said material from said casing into a substantially solid plug and to discharge said plug into said chamber, discharge means connected with said outlet, and means for conveying said impregnated material upwardly in said chamber to said discharge means While draining unabsorbed liquor therefrom.

3. Apparatus for continuously treating cellulosic ma erial comprising feeder means including a screw and a perforated casing cooperating to compress raw cellulosic material into at least one continuous ribbon of generally rectangular section While substantially eliminating fluids therefrom, a pipe connected to the outlet end of said casing to receive the output theretrom, said pipe having a frustol conical section at the inlet end thereof providing an entering ow area larger than the exit flow area dened by said casing and said screw to provide for temporary expansion of the ribbon material discharged from said casing, said casing and said screw having the ends thereof in substantially coplauar relation to provide a low pressureY space immediately adjacent said screw end, the remainder of said pipe being of a flow area which is not greater than the ow area past said screw through the discharge end of said Casing to effect continuous conversion of said ribbon material into a substantially solid'plug, and means for continuously delivering said plug directly into a bath of impregnating liquor While shielding said plug Yfrom air.

References Cited in the file of this patent UNITED STATES PATENTS 20 2,862,813 Birdseye Dec. 2, 1958 2,975,096 Ginaven V Mar. 14, 1961 FOREIGN PATENTS 580,129 Canada Q July 28, 1959

Claims (1)

1. 3. APPARATUS FOR CONTINUOUSLY TREATING CELLULOSIC MATERIAL COMPRISING FEEDER MEANS INCLUDING A SCRES AND A PERFORATED CASING COOPERATING TO COMPRESS RAW CELLULOSIC MATERIAL INTO AT LEAST ONE CONTINUOUS RIBBON O GENERALLY RECTANGULAR SECTION WHILE SUBSTANTIALLY ELIMINATING FLUIDS THEREFROM A PIPE CONNECTED TO THE OUTLET END OF SAID CASING TO RECEIVE THE OUTPUT THEREFROM, SAID PIPE HAVING A FRUSTOCONICAL SECION AT THE INLET END THEREOF PROVIDING AN ENTERING FLOW AREA LARGER THAN THE EXIT THEREOF PROVIDING AN ENTERING FLOW AREA LARGER THAN THE EXIT FLOW AREA DEFINED BY SAID CASING AND SAID SCREW TO PROVIDE FOR TEMPORARY EXPANSION OF THE RIBBON MATERIAL DISCHARGES FROM SAID CASING, SAID CASING AND SAID SCREW HAVING THE ENDS THEREOF IN SUBSTANTIALLY COPLANAR RELATION TO PROVIDE A LOW PRESSURE SPACE IMMEDIATELY ADJACENT SAID SCREW END, THE REMAINDER OF SAID PIPE BEING OF A FLOW AREA WHICH IS NOT GREATER THAN THE FLOW AREA PAST SAID SCREW THROUGH THE DISCHARGE END OF SAID CASING TO EFFECT CONTINUOUS CONVERSION OF SAID RIBBON MATERIAL INTO A SUBSTANTIALLY SOLID PLUG, AND MEANS FOR CONTINUOUSLY DELIVERING SAID PLUG DIRECTLY INTO A BATH OF IMPREGNATING LIQUOR WHILE SHIELDING SAID PLUG FROM AIR.

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