US2427495A

US2427495A - Apparatus for producing fiber from vegetable growth materials

Info

Publication number: US2427495A
Application number: US420062A
Authority: US
Inventors: Philip G Deuchler
Original assignee: Certain Teed Products Corp
Current assignee: Certainteed LLC
Priority date: 1941-11-22
Filing date: 1941-11-22
Publication date: 1947-09-16
Anticipated expiration: 1964-09-16

Description

Sept. 16, 1947. P. G. DEUCHLER API ARATUS FOR PRODUCING FIBER FROM VEGETABLE GROWTH MATERIALS Filed Nov. 22,1941

2 Sheets-Sheet 1 L INV ENTOR 16, 1947. P. s. DEUCHLER APPARATUS FOR PRODUCING FIBER FROM VEGETABLE GROWTH MATERIALS 2 Shets-Sheet 2 Filed Nov. 22, 1941 X! W M R Y wp m mu. m M. P

Patented Sept. 16, 1947 APPARATUS FOR PRODUCING FIBER FROM VEGETABLE GROWTH MATERIALS Philip G. Deuchler, Snyder, N. Y., assignor to Certain-Teed Products Corporation, New York, N. Y., a corporation of Maryland Application November 22, 1941, Serial No. 420,062

1 Claim.

This invention relates to an apparatus for producing from vegetable growth material fibers having particular qualities for matting and felting purposes. The invention especially relates to an improvement in an apparatus for mechanical defibration in which individualized fibers are produced which retain all or the greater part of the encrusting and bonding substances of the original growth. The invention particularly relates to an apparatus for producing fiber capable of felting to form a web of high absorptive capacity but at the same time strong and flexible.

In my co-pending application Serial No. 371,- 585, filed December 24, 1940, I have described an improvement in a process of mechanical defibration by virtue of which the qualities of the fibers, particularly affecting strength and flexibility of the felt, are improved. The process of said application and the apparatus of my present invention have particular reference to the process of mechanical defibration described in the patent to Asplund, No. 2,008,892, of July 23, 1935. In the process of said patent defibration is effected of vegetable material in the form of bundles of fibers, such as chips of wood, which prior to and during the defibrating action itself is subjected to an atmosphere or gaseous medium at a temperature sufiicient to soften the encrusting substances of the vegetable growth. In practice steam at a pressure sufiicient to provide the softening temperature, preferably not less than 212 F. and normally substantially higher, is used to provide the treating atmosphere or medium. Following this defibration step, as disclosed in said patent, the fibers are discharged to atmospheric pressure and a suspension thereof in water, including that used for condensing the steam and the condensed steam itself, is made for delivery of the fiber to the paper-making machine.

In the inventive process of my application Serial No. 371,585, after such mechanical defibration but while still subjected to the atmosphere of steam at a temperature preferably not reduced to a great degree below that of defibration, I apply a treating material, such as a chemical, to act upon the encrusting substances of the fibers to modify them so that, if desired,

these encrusting substances may be removed. Removal is not in all cases effected but the character of the fiber is modified by such treatment. he r su t fiber is improved for certain purposes such as roofing and flooring felts because, while retaining high absorptiveness, the flexibility and the strength of the felt made therefrom are increased. This makes it possible to use the felts made of this wood or vegetable fiber in the ordinary roofing and floor covering manufacturing processes and apparatus.

It is an object of my present invention further to improve the fiber as produced in the Asplund process or as produced in the process of my earlier application. This improvement may be carried out so as to increase the flexibility of the fiber and strength of the felt made therefrom over that possible with these earlier processes. Within the scope of the invention the-treatment may be carried on so that substantially greater amounts of the encrusting substances carried by the fiber as produced by my earlier process may become modified. They may become so modified that they may be removed asextractable material in accordance with the extraction or removal procedure disclosed in my said application Serial No. 371,585 or by other known procedure. Also within the scope of the invention the process may be carried on so that fibers are secured in which hydration has occurred. The amount of hydration may be slight or may be of substantial degree.

In one phase of the invention, following the discharge of the fiber and the gas or steam from the defibrating machine, particularly of the type described in said Asplund Patent No. 2,008,892, I deliver the gas or steam and the fiber carried thereby to a dwell chamber in which the gas or steam is maintained at a high temperature. When steam is used it may be maintained at a substantial pressure or may be heated to provide the atmosphere of high temperature. Preferably, in order to have the greatest practical effect upon the fiber, the temperature of the atmosphere is maintained without great reduction below that at which the defibration takes place.

To secure such a dwell chamber according to the invention a simple modification of the Asplund apparatus may be made in which the discharge valves, which are mechanically or otherwise operated in connection with the operation of the defibrating machine, are moved to a distance and a chamber of substantial volume or providing a long length of travel of the fiber is interposed between the discharge of the defibrator and these valves. Within the scope of the invention, however, such a dwell chamber or space may be provided on the discharge side of the valves of the Asplund machine, Such a space may operate at a pressure somewhat reduced below that obtaining within the casing of the defibrator to allow for the pressure drop necessary to deliver-the steam and the fiber carried thereby through the discharge valves. In either case the temperature of the steam may be well above atmospheric temperature and preferably such as would be provided, for example, by steam at 100 to 150 lbs. gauge pressure. The invention, however, is not limited to the particular pressures indicated but comprises within its scope the subjection of the fiber after defibration to an atmosphere Of a gas or of a vapor at the temperature, usually not substantially below 212 F.,which is necessary to soften the encrusting substances which in the original growth bind the fibers together.

For the purpose of carrying out according to the invention the treatment proposed of the mechanically defibrated fiber, the chamber to which the fiber and gas or vapor are delivered is so constructed and arranged as to provide a substantial time of dwell therein for the fiber before it is discharged therefrom. Instead, therefore, of utilizing merely a discharge pip'e connected between the discharge valve of the Asplund defibrating apparatus and the so-called cyclone" into which in practice the fiber and the exhaust steam at atmospheric pressure are delivered for condensation of the steam and suspension of the fiber in water, I may utilize an enlarged chamber or pressure vessel constructed so as to be capable of confining the gas or vapor, particularly at a pressure substantially above atmosphere. be such as itself to afford the requisite dwell. Devices may be constructed within the chamber, however, to direct movement of the fiber while it is subjected to the gas or vapor atmosphere and to avoid accumulation thereof in piles or bunches which would interfere with all portions of the fiber receiving the proper treatment. Bafiles or a spiral chute or other means may be installed for causing and controlling movement from the inlet of the fiber into the chamber toward the outlet thereof or toward the bottomof the chamber. Within the scope of the invention the chamber, whether on one side or the other of the discharge valves of the Asplund machine, may be provided merely by a pipe of sufiicient size and length to afford the required time of travel therethrough from the defibrator to the point where the gas or vapor and the fiber shall be discharged from the apparatus for further handling.

When the enlarged chamber is to be provided between the defibrating machine and the discharge valves thereof, this may be accomplished in a simple embodiment of the invention by removing the valves from the position illustrated in the Asplund patent to a place at a substantial distance therefrom and connecting them to the machine by a long discharge pipe. Such a position, for example, may be adjacent to the cyclone" which collects the steam and fiber discharged from the machine as mentioned above. For practical purposes, however, in most cases an enlarged pressure vessel will be inserted in the discharge pipe between the valves and the defibrati'ng machine. Such an enlarged chamber may provide for continuous movement, as above suggested, of the fiber and the steam therethrough toward the valves while securing' the requisite dwell by virtue of the length of travel secured within the chamber. In accordance with the invention the gas or vapor delivered into this chamber from the defibrating machine or otherwise maintained in this chamber surrounding the fibrous material is at a temperature, preferably The volume of the chamber may not substantially less than 212 F., to secure the softening of the encrusting substances on the fiber and the modification thereof.

Owing to the close proximity of the deflbrator disc casing and the discharge valves in the normal Asplund machine no opportunity is afforded for subjecting the fiber after defibration to the action of an atmosphere of a gas or vapor, such as steam, at elevated temperature for any substantial period of time. In the process of the invention utilizing a chamber of substantial volume or a travel of the steam and fiber through a long distance before discharge, the time during which the defibrated material is subjected to the high temperature atmosphere may be increased so as to be measured in minutes. Dwell to the extent of /2 minute up to 5 minutes or more may be accomplished with benefit. In my application Serial No. 371,585 I have pointed out that the treatment of the defibrated material as with chemicals may be effective within a few seconds of time. While this treatment affords improvement and enables a certain amount of the encrusting substances carried by the fibers to be converted to a condition where they may be extracted, if desired, by suitable subsequent processes, the present invention affords a process which makes possible such modification of the encrusting substances that removal of the substances may be effected even to the extent of substantially complete removal of these substances. This removal may be accompanied in some cases by hydration of the fiber.

The process of the invention may be carried out in such .a way that the fiber is subjected to an atmosphere of gas or vapor at elevated tem-' peratures merely with a substantial dwell and without treatment with active agents. It may, however, be accompanied by treatment of the fiber with chemicals or other modifying agents, utilizing the dwell of the fiber in the chamber to make effective and to increase the, action of the chemicals or agents upon the encrusting substances carried on the fibers. Thus the chemical or other agent may be introduced in the same manner as described in my prior application Serial No. 371,585 and the fiber may be discharged to the chamber of the invention and subjected therein to the gas or vapor for a substantial period of time. The chemicals or agents so applied may continue their action with the resulting modification of the encrusting substances beyond that possible with the process disclosed in said application. To secure improvement by the process of the invention in some cases it may be desirable or necessary to increase the amount of chemicals or agents which are distributed upon the fibers over that utilized in the process of said application. Within the scope of the invention, however, in substitution for the injection of chemicals in the manner described in said application or in addition to such injection, or in addition to or in substitution for other prior art methods of treatment of the fibers or of the material from which they are produced, I may inject chemicals into the dwell chamber hereinabove proposed. These chemicals or other agents, however applied, are thus afforded a substantial time to act upon the encrusting substances carried by the separated fibers or upon the remaining portions of such encrusting substances after treatment as proposed in the prior art further to modify these substances to a condition which makes their more complete removal possible.

In another phase of the invention I provide means for maintaining the gas or vapor at the elevated temperature, particularly when a vapor is used, at a pressure substantially different from and usually greater than that of the atmosphere. As the Asplund apparatus operates continuously to discharge therefrom the steam and the fiber carried thereby it is necessar or desirable to effect generally continuous removal from the dwell chamber of the fiber after its modification in said chamber. When a gas or a vapor, such as steam, is delivered to the chamber together with the fiber carried thereby at a pres-, sure which is without marked reduction below the pressure at which defibration is efiected the dwell chamber must be made pressure tight. To accomplish this the connection between the defibrator and the dwell chamber may be made by means of a pipe in the ordinary manner. To effect removal of the fiber from the dwell chamdiscussion I feed into the chamber water in amounts necessary to effect within the pressure chamber the desired suspension of the fiber. Under the pressure of the gas or vapor within the chamber discharge of this water and the suspended material then may be effected through a valve or other restriction for controlling this discharge. This discharge may be continuous and the rate thereof may be controlled while maintaining the pressure within the dwell chamber requisite for securing softening or treating temperature.

It is necessary, however, to continually replace this water withdrawn from the dwell chamber in order to provide water to continue effecting the suspension of the material which is delivered into the chamber. This I may do by forcing water into the chamber under pressure in amounts approximately equal to the amount withdrawn. In practice the white water from the paper-making machine may be delivered by means of a pump to the dwell chamber to eifect the suspension. The

water carrying the fibers discharged from the dwell chamber may be then delivered, if necessary with the aid of another pump, to the chest or to the head box of the paper-making machine or to other points in the paper-making process.

In some cases the amount of water delivered may be suflicient to effect complete condensation of steam, or other condensable medium when such is used as the atmosphere and'conveying medium in the Asplund process. In other cases any excess of the medium may be exhausted through a suitable vent in the dwell chamber designed and adjusted to retain the pressure therein.

When a non-condensable gas or vapor is used as the atmosphere medium in the dwell chamber it may require to be vented while retaining a given pressure in the chamber. In some cases the medium may be withdrawn from the chamber for reheating or replenishment to be delivered again to the apparatus at a suitable place for its reuse. In the case of a gas or vapor which is active upon the fiber or its encrusting substances the redelivery may be effected by return directly to the dwell chamber, after the gas or vapor has been suitably reinforced or regenerated to its active condition, to carry out the modification of the fiber in the dwell chamber according to the invention. In some cases, however, especially in conjunction with the Asplund process, the gas or vapor may be returned to the Asplund apparatus to serve the function disclosed in the patent of heating the chips or pieces of material vapor may be delivered at the proper tempera-' ture for deflbration of the fiber or for treating the fiber in the dwell chamber.

In some applications of the invention a condensable vapor heated to the requisite temperature may be bled into the dwell chamber to maintain the heated atmosphere therein, the vapor condensing and being withdrawn as liquid. In other cases the medium or atmosphere of the dwell chamber may be maintained at the requisite temperature by heating the medium within the chamber by means of suitable heating devices installed therein.

The invention will be further understood from the description of the drawings to follow, in which Fig. 1 shows the arrangement of the dwell chamber in connection with the defibrating machine,

Fig. 2 is a vertical cross-section of the dwell chamber,

Fig. 3 is a cross-section of Fig. 2 on line 33.

In Fig. 1 the defibrating apparatus of the type illustrated in the Asplund Patent No. 2,008,892

is shown in elevation with portions thereof broken away to reveal the essential parts which have a bearing on the invention. As described in the Asplund Patent No. 2,008,892, through the opening 3 in the preheater chamber 5 the chips of wood or pieces of vegetable growth material are delivered by means not illustrated in Fig. 1 but shown and described in said patent, Through pipe 1 controlled by valve 8 steam is introduced into the preheater chamber 5 to maintain therein an atmosphere of steam at a pressure such as will afford -a temperature not substantially less than 212 F. and preferably in practice that of steam at about to 1'70 lbs. pressure. The Chips received into the preheater chamber 5 fall to the bottom portion thereof into engagement with the screw feed member ll arranged in the conduit portion l3 and,rotated upon shaft l5 passing through stufling box I! by a suitable drive such as a chain drive 19. The shaft l5 and the screw mounted thereon are rotated in such a direction that the chips are fed into the casing 2| of the defibrator which carries the stationary segments 22. Mounted upon a shaft 25, in bearings 21, extending through stuffing box 29 into casing 23 is the rotating disc 3| carrying segments 33.

Under the action of the screw feed member H the heated chips are delivered to the defibrating discs and upon passing between the segments thereof the fiber together with the steam from the preheater chamber is discharged through pipe 35, in which are mounted discharge valves 31 and 39, into-the chamber 4|. As described in the Asplund patent steam for conveying the fiber through the casing 23 of the defibrator and through the pipe 35 may pass through the equalizer 36 between the preheater chamber and the casing M of the defibrator. The chamber 4| is so constructed, as will be hereafter described, as to provide for a substantial time of dwell of the defibrated fiber therein while subjected to the steam atmosphere. The-travel of the steam and the fiber carried thereby is downwardly in chamber 4| and provision is made at the bottom portion thereof for withdrawal of theflber while maintaining the atmosphere of steam within the chamber, preferably at a pressure suflicient to provide the requisite temperature for.maintaina 41 of the chamber 4|.

7 ing in soft condition the bonding and encrusting substances on the fiber and to secure substantial modification thereof.

In Fig. 2 is illustrated one construction of the chamber 4| for carrying out the process of the invention. The pipe 35 is connected by a flanged connection to the top of the chamber 4| to cause the steam and the fiber carried thereby to enter the chamber and move over the topmost baifle of a series of baffles 43 arranged in said chamber 4| These baiiies are connected to the wall of the chamber 4| at one side thereof but do not reach the opposite side of the chamber. Between said baffles 43 are positioned bafiles 45 which extend from said opposite wall toward the side to which the baffles 43 are connected. The vertical spacing of the baffles and the distance between the end thereof and the wall are such in consideration of the volume of steam and fiber delivered into the chamber that the fiber is carried by the steam through the tortuous passage as shown in Fig. 2 between the bafiies 43 and 45 until the lowermost baille 45 is reached. Over the edge of this lowermost baffle the fiber falls into a mass of water maintained in the lowermost compartment Because of the tortuous passage a long travel of the fiber while subjected to the heat of the steam is provided which secures the necessary time of dwell which is a feature of the invention for effecting modification of the fiber after defibration in the defibrating apparatus. As the fiber is delivered by the defibrating apparatus in a generally continuous although somewhat pulsating flow, it is desirable to provide for continuous withdrawal of the modified fiber from the dwell chamber 4|. To accomplish this in a suitable cylindrical portion 49 of the compartment 41 is mounted an agitator upon shaft 52, extending through stufllng box 53 in the end wall of the cylindrical portion 49. The shaft 52 may be rotated by suitable means, not shown in the drawing, to cause the vanes 54 of the agitator 5| to stir up and mix the fiber with the water sufficiently to be withdrawn therewith upon discharge from the compartment 41. Discharge of this suspension of fiber in the water is accomplished by control of the valve 55 in pipe 51 connected to the compartment 41. As pressure of the steam is maintained in the dwell chamber 4| this pressure may be utilized to force the suspension of fiber in the water through the pipe 51 and valve 55 into a suitable stock discharge box 59 or other receptacle or conveyor for receiving the fiber to be delivered to the next operation in the paper-making process or for other use.

In order to maintain a suitable volume of water in the compartment 41 water to replace that withdrawn through the pipe 51 is introduced through pipe 6| controlled by valve 63 so that the infiow of water approximates that withdrawn through the pipe 51. A gauge glass 64 may be provided upon the wall of the compartment 41 to indicate the level of water in said compartment.

At the upper portion of the compartment 41 or, if desired, at some other suitable place a vent pipe 65 is connected, controlled by a valve 61 set to maintain within the chamber pressure of steam requisite for modifying the fiber but so as to relieve to atmosphere or to the stock discharge box 59 any excess of steam or undue increase of pressure thereof. If desired, at the top of the chamber 4| a pipe connection 69 controlled by valve may be made from a supply of steam at suitable pressure to maintain within the chamber 4| the requisite amount and pressure of the steam in those cases where the steam received from the defibrating machine is insufficient or at a temperature too low to be effective for modification of the fiber in the dwell chamber. The valves, 55, 63, 61 and.19 in Fig. 2 are shown diagrammatically as hand.control valves. In place of such valves, however, automatic devices may be used, for example, the valve 63 may be arranged as a water level control for actuation by variations of the water level in the compartment 41. The valve 61 may be a pressure relief valve opening only when the pressure within the chamber 4| exceeds a predetermined amount. Similarly the valve 10 may be of the type which will open upon a reduction of pressure in the chamber 4| and will close upon restoration of this pressure to a predetermined amount,

Through the pipe 13 controlled by valve 15 from a suitable supply under pressure a treating agent, such as a solution of a chemical or a solvent or other treating material capable of acting upon the encrusting substances or the fiber or both, is introduced so as to impinge upon or act upon the fiber as it is received into the dwell chamber. It will be apparent from the above description that if, for example, a solution of caustic soda were introduced through the pipe 13 in suitable amounts of, for example, between 2% and 8% of dry caustic soda based on the weight of the fiber, the fiber as it falls over the first baffle 43 will receive an application of the solution of caustic soda. This fiber carrying the treating material then will move between the

baffles

43 and 45 in their tortuous passage and a time adequate for action thereof upon the ligneous and other encrusting substances carried by the fiber to efiect substantial modification thereof is proyided. In consideration of the maintaining of the relatively high temperature in the dwell chamber, in the preferable practice of the invention this method of application of the treating material or of the chemical becomes particularly effective. If necessary to produce a full action of the chemicals upon the fiber sufiicient water carrying suflicient amount of chemicals may be introduced through the pipe 13 to cause continuance of the action throughout the length of the tortuous passage. In some cases, therefore, not only may the ligneous or other encrusting substances upon the fibers be modified but the cellulosic portion of the fiber itself may become changed to afford a modified character in the fiber. Within the scope of the invention the chemicals or other treating agent which may be leached in the Water contained within the compartment 41 may be recovered from the water discharged from said compartment or said wa ter or a portion thereof may be utilized as the vehicle for introducing chemicals or other agents through the pipe 13.

.As indicated above, in some cases it may be desirable to return to the defibrating apparatus some or all of the steam or other atmospheric medium which has been used in the dwell chamber for reuse in the defibrating apparatus. In Fig. 1 is shown a pipe 89 controlled by valves 8| connected from the bottom portion of the chamber 4| to the steam inlet pipe 1 at the top of the preheater chamber 5. It will be understood that by shutting the valve 8 and opening the valves 8| a circuit of the gas or vapor medium is established through the defibrating apparatus,

' the pipe 35, the dwell chamber 4| and the pipe 80, which enables the medium to be reused for 9' heating the material to be defibrated prior to and during defibration and for maintaining the fiber in heated condition in the dwell chamber.

-If necessary to effect recirculation of the medium a. fluid circulating device 83 may be placed in the pipe 80 or at some other convenient point in the circuit.

In Fig. 1 also is shown a pipe 90 connected between the upper and lower portions of the dwell chamber 4| to provide a circulating circuit within said dwell chamber. In the pipe 90 may be connected a' suitable heater, indicated by the rectangle 9| in Fig. 1, which may be of any suitable common type for heating gases or vapors. Valves 92 and,93 are provided'in the pipe 90 for shutting off Or controlling circulation through the circuit provided with the pipe 90 and the heater 9|.

It will be clear from the above description of the drawings that the gas or vapor introduced through the pipe I may be used not only in the defibrating apparatus but also in the dwell chamber 4| to continue or to effect in the latter the modification, softening or removal of the encrusting substances of the vegetable growth material or in some cases in addition the modification of the cellulosic material itself. Within the scope of the invention the gas or vapor medium introduced may be inert or may be active upon the fiber and it constituent materials. Recirculation of such a medium may be practiced when desired or when convenient or economical to do so. Especiall when an inert or inactive gas or vapor is used or when a non-condensable vapor is used the medium may be recirculated through both portions of the combined apparatus of the invention and of the Asnlund patent or may be recirculated only through the dwell chamber itself. In the case of an active medium in place of the heater 9| a regenerative apparatus may be inserted in the pipe 90 to restore the active properties of the medium. It will be obvious that instead of substituting a regenerative apparatus for the heater 9| such a regenerative apparatus may be installed in the pipe 90 in series with and in addition to the heater 9|.

From a consideration of the drawings it will also be understood that re-heating of the medium, particularly of steam, may be accomplished in two different ways in the apparatus shown in Fig. 1. Steam may be withdrawn from the chamber 4|, for example, through the valve 93, heated in the heater 9| and returned again to the chamber 4| through valve 92. This circuit thu may be constituted merely of the chamber 4 I, the heater 9| and the pipe connections therebetween. If necessary, an impelling device similar to fluid circulating device 83 may be included in pipe 90.

Steam, however, may be withdrawn from the chamber 4| through the pipe 80 under the impelling action of the fluid circulating device 83 and may be delivered to the pipe 1. By suitable adjustment of the valves 8 and 8| this withdrawn steam may be mixed with fresh steam injected through pipe 1. This mixing will re-heat the withdrawn steam. This re-heating may take place to the required extent to accomplish in the preheater chamber the softening of the chips or pieces of vegetable material for defibration in the defibrator between the segments 22 and 33 of the defibrator. Such a method of heating may be practiced so as to maintain in the dwell chamber 4| 2. temperature suflicient to secure the softened condition of the encrusting substances upon the fibers so that modification thereof in said.

chamber may be accomplished in accordance with the invention.

Although in the Asplund patent steam is indicated as an inert gaseous medium, within the scope of the present invention this medium constitutes an active medium to the extent of its capacity to effect modification of the encrusting substances when subjected thereto for a substantial period of time. Thus the gaseous medium used in the dwell chamber of the invention may be said to be in a condition active or activated to effect modification of the encrusting substances or capable of efiecting such modification whether by virtue of the inherent active properties of such gas or vapor or by virtue of a substance or material injected into said atmosphere or applied to the fibers contained therein.

Having thus described my inventionv I new claim:

Apparatus for producing fiber from vegetable growth material comprising means providing a preheater chamber for confining a gaseous or vapor medium, means for delivering pieces of said vegetable material into said chamber, means for delivering a gas or vapor medium into said chamber to maintain therein an atmosphere of said gas or vapor at a temperature sufficient to soften the encrusting substances of the vegetable growth which bind the fibers together in the pieces, means within said chamber for mechanically defibratlng said pieces while subjected to said atmosphere of gas or vapor substantially at said temperature into more or less individualized fibers which carry substantially all of said encrusting and bonding substances of the original growth material, conduit means for conveying said gas or vapor medium from said chamber together with said individualized fibers, a dwell chamber connected at its upper end with said conduit, bailies in said dwell chamber providing a tortuous passageway of relatively reduced cross section but of substantial length leading downwardly through the chamber, means for feeding into said dwell chamber on the fibers therein steam under pressure anda chemical adapted to react with the encrusting substances on the fibers for forming reaction compounds thereon, means for maintaining a mass of water in the lower end portion of said dwell chamber, means for stirring up the fibers in the water for enabling the water to carry the fibers out of the chamber, means for taking steam fro-m the lower end portion of said dwell chamber and heating the steam and then returning it in heated condition to the dwell chamber near its upper end, and means for forcing steam and vapor from the lower end portion of the dwell chamber into the upper end portion of the preheater chamber.

PHILIP G. DEUCHLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENT Number Name Date 1,052,675 Loomis Feb. 11, 1913 1,122,404 Loomis Dec'. 29, 1914 1,728,258 Sheperd Sept. 17, 1929 1,913,607 McMillan June 13, 1933 1,982,130 Wollenberg Nov. 27, 1934 2,007,348 Scharmann July 9, 1935 (Other references on following page) Number UNITED STATES PATENTS Name Date Howard May 11, 1937 Kreissler Nov. 29, 1938 Ofiermanns June 27, 1939 Basler Dec. 9, 1941 Taylor Sept. 2, 1879 Mason Aug. 23, 1932 Asplund July 23, 1935 Robinson Jan. 3, 1939 Mason Apr. 27, 1943 Woodbridge Sept. 15, 1863 Herron June 2, 1874 Blackman Sept. 13, 1887 Sammet Jan. 30, 1912 Hussey Mar. 10, 1931 Ellis Mar. 22, 1932 Mason Aug. 15, 1933 Hawlander 'Dec. 26, 1933 Heritage Sept. 22, 1942 Number Number 15 Der Papler Fabrikant.

Name Date Beveridge June 29, 1943 Heritage Aug. 6, 1946 FOREIGN PATENTS Country Date Australia Apr. 10, 1933 Sweden Nov. 30, 1939 Sweden Apr. 11, 1940 Germany Sept. 17, 1935 Great Britain Oct. 19, 1937 OTHER REFERENCES Techniech-Wessenschaftlicher Tiel. J. G. 36-1936, pages 519 to 531, Heft. 49.

Der Papler Fabrikant. Verein Der Zellstoff und Papier Chemiker U. Ingenieure. o Heft 34, pages 313 to 319.