US2905240A

US2905240A - Apparatus for impregnating wood chips

Info

Publication number: US2905240A
Application number: US474422A
Authority: US
Inventors: Nels H Sandberg
Original assignee: Waldorf Paper Products Co
Current assignee: Waldorf Paper Products Co
Priority date: 1954-12-10
Filing date: 1954-12-10
Publication date: 1959-09-22
Anticipated expiration: 1976-09-22

Description

3 Sheets-Sheet 1 INVENTOR IVH II R. I

r N. H. SANDBERG APPARATUS FOR IMPREGNATING WOOD CHIPS Sept. 22, 1959 Filed Dec. 10, 1954 /Ve/s H Sana bar H MNN v.0 On

ll I 1 &% mm SN sh IIIN'W;

QN Q Q ATTORNEY Filed D90. 10, 1954 pt- 22,1959? N. H. SAND'BERG 2,905,240

, APPARATUS FOR IMPREGNA'I'ING WOOD CHIPS 3 Sheets-Sheet 2 2 INVENTOR /V/S fl. Sana berg BY EN /9 ATTORNEY Sept. 22, 1959 N. H. SANDBERG 2,905,240

' APPARATUS FOR IMPREGNATING woon CHIPS Filed Dec. 10, 1954 3 Sheets-Sheet 3 IINVENTOR 2] 20 27 /Ve/s H Sandbar-g 57: 3 BQY (nan/n ATTORNEY APPARATUS FOR HVIPREGNATIN G WOOD CHIPS Nels H. Sandberg, St. Paul, Minn., assignor to Waldorf Paper Products Company, Ramsey County, M1nn., a corporation of Minnesota Application December 10, 1954, Serial No. 474,422 6 Claims. (Cl. 162-437) This invention relates to an improvement in method of preparing paper pulp and deals particularly with a process of preparing wood chips and producing pulp from these chips. V

In an application for patent recently filed, Serial No. 442,873, filed July 1-2, 1954, I disclosed a method of preparing wood chips which included the step of soaking the chips in liquor under hydrostatic pressure. By immersing the chips in a liquor and subjecting the chips to pressure, the liquor acts to heat the chips and the pressure tends to impregnate the liquor into the chips. At the same time however, the temperature of the chips in the liquor is lower than would be experienced if the chips were submitted to steam pressure and temperature.

I have found that there are certain advantages in providing a different type of feed than was shown in my previous application. In the previous arrangement I disclosed the use of a rotary pocketed feed member which delivered the chips from atmospheric pressure to a zone of elevated pressure. The chips dropped by gravity from this rotary feed member into an inclined feed screw which fed the chips downwardly into the impregnat-e chamber. Here a horizontal feed screw conveyed the. chips through the length of the impregnate impregnating chamber. An inclined outlet screw conveyed the chips upwardly to a point above the level of liquid in the impregnating chamber, allowing the chips to drop into a preheating chamber where the chips were heated at 'an elevated temperature.

It has been found that a somewhat more constant supply of chips may be provided through the use of a plug forming screw which forces the chips through a tapering passage and into the impregnating chamber. A feed of this type is somewhat more constant than that provided by a rotary valve which operates between chambers subjected to substantial variations in pressure. As a result the chips are more thoroughly and uniformly impregnated than would otherwise be possible.

In thechip impregnating process the chips are usually soaked or impregnated with a liquor such as sodium sulphite, sodium hydroxide and water, the amount of liquor being supplied being in certain proportion to the chips supplied. Where the amount of chips fed to the impregnation chamber varies, and where the liquor supply re mains constant, it is virtually impossible to evenly impregnate the chips to produce a uniform pulp. Thus the particular-type of feed arrangement employed is of importance to the results obtained.

An added feature of the present invention resides in the provision, of a chip impregnating apparatus which includes a rotary feed valve which feeds the relatively dry chips'into a small heating chamber which is nor mally subjected to relatively low steam pressure and temperature. With this arrangement, the rotary feed valve is not subjected to high pressure differential-s, thus making the rotary feed easier to operate and to maintain,

Patented Sept. 22, 1959 and rendering it more efi'ective. Furthermore, this rotary feed valve may be oversize if necessary so that the small heating chamber is at all times virtually filled. The heating chamber cannot readily be overfilled, as the rotary feed valve would then not dump its contents, but would merely rotate without emptying its pockets. A constant supply of chips for the plug forming screw is thus at all times maintained.

A further feature of the present invention lies in the provision of a pressure seal at the inlet end of a chip impregnating chamber which includes the combination of a plug forming screw and an auxiliary feed outwardly thereof. One of the major difliculties experienced in a plug forming screw type of seal lies in the fact that if the feed is not constant and if the stock is not of proper density the steam pressure inwardly of the plug forming screw will force the stock past the screw thus blowing the stock at high pressure through the chamber inlet. This not only creates a temporary delay in operation but also may have serious consequences due to the pressure with which the pulp is blown from the apparatus. With the present arrangement the danger of serious consequences due to the blowing out of the plug of chips is obviated by the rotary valve, as in the event the plug blows out, the chips are merely forced into the heating chamber adjoining the impregnating chamber.

A further feature of the present invention lies in the fact that the chips entering the impregnating chamber may be subjected for a short time to elevated temperature and pressure, which, however, is substantially less than the pressure encountered in the impregnating chamber. As a result the dry chips are given a relatively dry heating prior to immersion. This process has been found extremely beneficial to the results obtained.

These and other objects and novel features of my invention will be more clearly and fully set forth in the following specification and claims.

In the drawings forming a part of the specification:

Figure 1 is a side elevational view of a pulp forming apparatus partly broken away to show the interior construction.

Figure 2 is an end elevational view of the construction shown in Figure 1.

Figure 3 is a side elevational view, partly showing the feed portion of the apparatus.

Figure 4 is a vertical sectional view through the outlet end of the impregnating chamber, the position of the section being indicated by the lines 4-4 of Figure 1.

The apparatus disclosed is quite similar in general to that disclosed in my previously filed application with the exception of the arrangement at feed end of the impregnating chamber. However, the entire system is shown somewhat diagrammatically so that the invention can be more readily understood.

The relatively dry chips which are to be made into pulp are fed in any suitable way to a hopper 10 which forms the inlet of the apparatus. At this point the chips are at atmospheric pressure and are usually at room temperature. By the term relatively dry, I mean to imply that the chips contain their natural moisture content of about 10% to 40% moisture.

From the hopper 10 the chips are fed into a rotary valve 11 which includes a rotating element 12 having angularly spaced pockets 13 therein. The number of pockets 13 is not of importance, it being necessary that the pockets not overlap the inlet and outlet simultaneously.

From the valve 11, the chips fall by gravity or are blown from the pockets by steam entering the heating chamber. 15 through a steam line 14. This heating chamber 15 is of sufiicient diameter to hold the necessary in section,

quantity of chips to compensate for variations in feed and so that the chamber may always supply the necessary amount to the lateral feed conveyor chamber 16 to maintain a feed plug.

As is shown in Figure l of the drawings the rotor i2 of the rotary valve 11 is operated by a shaft 17 driven by a suitable motor 19, which rotates at the proper speed to effect the desired speed of rotation 'of the rotor 12. The chamber 16 is equipped with a screw conveyor 20 driven by a shaft 121 extending through an end of the chamber and through a suitable seal 22. A sprocket 123 is mounted on the shaft 21 and is connected by a chain 124 to the sprocket of a suitable drive motor 125. The screw conveyor 20 directs the chips toward a tapered plug forming chamber 26, and the end 27 of the conveyor 20 extending into the tapered chamber 26 is tapered.

The tapering conveyor screw thus forces the chips through the tapered chamber 26 compacting the chips into a solid plug and forcing them into the relatively small diameter orifice 29 leading to one end 30 of the impregnating chamber 31. With this arrangement substantially greater steam pressure can be maintained within the impregnating chamber 3-1 than is experienced in the feed conveyor chamber '16.

The impregnating chamber 31 is provided with a feed screw 32 extending therethrough. The outlet end of the conveyor is best illustrated in Figure 4. An inclined tubular member 37 supports a feed screw 39 and is upwardly inclined from the impregnating chamber 31 so that the impregnating chamber may be filled with liquor to a liquor line 40 (Figure 4) which is above the level of the chamber. The chips are conveyed upwardly by the conveyor 39 and dropped into a tubular passage 41 leading to a cooking chamber 43. The shaft 44 of the conveyor 39 extends from the upper end 45 of the passage 37 and is driven by a suitable motor 46 connected by sprockets and by the chain 47 to the shaft 44. An outboard bearing 48 near the upper end of the shaft assists in overcoming the end thrust of the conveyor.

The chips are conveyed through the cooking chamber 43 by a conveyor 49 mounted upon a shaft 50 which extends through an end of the cooking chamber. This shaft 50 supports a sprocket 51 which is connected by a chain 52 to a suitable sprocket 53 on a drive motor 54.

In the cooking of the chips, the length of the cooking operation is dependent upon a number of features such as the liquor used, the chips used, and the type of pulp being made. In some systems a single elongated cooking chamber is sufiioient to properly cook the chips. However, in other systems a longer cooking period is required. As the length of the cooking chambers are usually limited due to the necessity of continuously feeding the pulp through the chambers and due to space restrictions, in the present process I have disclosed

additional cooking chambers

55, 56 and 57 which are connected in series. Furthermore, as it is sometimes desirable to increase the temperature of the chips as they are cooked, one or more rotary transfer valves such as 59' may be provided between the various cooking chambe'rS.

In the arrangement illustrated the cooking chamber 43 delivers chips through the transfer valve 59, driven by the motor 60 into the cooking chamber 55. A conveyor 61 on a conveyor shaft 62 conveys the chips from the inlet end to the outlet end of the chamber 55 delivering the chips to the passage 63 leading to the cooking chamber 56. The chamber 56 is likewise provided with a conveyor 64 mounted upon a shaft 65 which forces the chips from the passage 63 to the passage 66. The passage 66 delivers the chips to the cooking chamber 57 and the chips are conveyed by the conveyor 67 mounted upon the'shaft 69 to a vertical passage 70 leading to the chamber 71. The

shafts

62 and 69 are driven by a chain 72 by a motor shaft 73 and the shafts 65 and 50 are driven by the chain 52 and motor 53.

The passage 71 includes a driven screw conveyor 74 leading to the defibrator 75 which is of the Asplund type. This defibrator passes the pulp while still under elevated temperature and pressure between a pair of relatively rotating attrition discs before the pulp is exhausted through a relatively small orifice to atmospheric pressure.

A steam manifold 76 extends into the impregnating chamber '31 and communicates with the outlet passage 37 at a point above the liquid level so as to maintain pressure within the soaking chamber. However, as the 'nnpi'eghating chamber c'or'itains liquor, the temperature within this chamber is not as high 'aswould be the case if the chips were subjected to the temperature corre sponding to saturated steam pressure of perhaps one hundred fifty pounds. For example, the liquid within the chamber may he only approximately 240 F. within the chamber 31 although the temperature or satur'ated steam at one hundred twenty-five pounds pressure is approximately 344 F. Thus the chips are soaked uhder hydrostatic steam pressure within the liquid and the chips are thoroughly impregnated without becoming cooked or without danger of being overheated at the outside raw and uncooked at the center.

The heating chamber 15 may be maintained at any desiredste'am pressure at or lower than that found in the impregnating chamber. However, it is usually desirable to maintain the chips at a temperature somewhat below that in the cooking chambers if the heating chamher is large enough so that the chips remain therein for any substantial period of time.

It will be seen that with this system the feed through the impregnating chamber will remain substantially constant as the type of apparatus employed produces a substantially constant feed. As long as the rotary valve 11 provides an adequate supply of chips in the heating chamber '15, no difficulty will be involved in the event the rotary valve does not feed the same amount during each rotation. The steam supply in the heating chamber 15 may be through the rotary valve element 12 to assist in emptying the pockets thereof or may be directly into the chamber 15 as desired. 7

The system described may use the types of liquors described in my previous application and may produce the pulps described therein. The iiiaiii difference in v the present invention resides in the particular form of feed for supplying the impregnating chamber with chips.

In accordance with the patent statutes, I have described the pririciples of construction and operation of my method of preparing paper pulp,- and while I have endeavored to set forth the best embodiment thereof, I desire to have it understood that obvious changes may be made Within the scope of the following claims without departing from the spirit of my invention.

I claim: I

l'. A feed mechanism for wood chips and the like oomp'rising a rotary transfer valve, a sealed heating chamber connected to the transfer valve to receive chips therefrom, a tubular passage into which chips pass from said heating chamber, a tapered end on said-passage, a screw conveyor within said tubular passage, and a tapered end on said screw conveyor, and a chip immersion chamber into which said tubular passage extends.

2. The construction described in claim 1 and in which the heating chamber is positioned above the tubular passage so that chips may drop by gravity into said passage.

3. The structure described in claim. 1 and in which the heating chamber is generally vertical and the tubuIar passage is generally horizontal and below said heating chamber. I

.4. A wood chip impregnating apparatus including an elongated liquid containing immersion chamber, an out:-

let at one end of said chamber extendin upwardly therefrom, a tubular passage tapering toward the other end of said chamber and communicating therewith, a spiral conveyor in said tubular passage having a tapered end in said tubular passage, a heating chamber above said passage and a rotary valve connected to said heating chamber and arranged to deliver chip thereto.

5. The structure described in claim 4 and including means for maintaining hydrostatic pressure upon the liquor within the impregnating chamber.

6. A Wood chip impregnating apparatus including an impregnating chamber, an inlet extending downwardly into said chamber, said inlet including a feed valve through which the wood chips are fed, a preheatin chamber beneath the level of said feed valve, a second feed means extending from said preheating chamber to said impregnating chamber through which the chips pass while maintaining a pressure differential between said impregnating chamber and said preheating chamber, conveyor means for conveying the chips longitudinally of said impregnating chamber, an outlet at the end of said impregnating chamber remote from the second feed means, said outlet extending upwardly from said impregnatin chamber, and steam supply means for subjecting the liquid within said impregnating chamber to steam pressure, the impregnating liquor within said impregnating chamber being maintained thereby at a temperature substantially below the correspondin temperature of saturated steam at the steam pressure upon the liquid, whereby the chips passing through the impregnating chamber may be soaked at a temperature below steam temperature and at a pressure substantially above atmospheric pressure.

References Cited in the file of this patent UNITED STATES PATENTS 1,505,934 Olier Aug. 19, 1924 1,679,336 Dunbar July 31, 1928 1,922,313 Mason Aug. 15, 1933 1,938,802 Braun et al Dec. 12, 1933 1,954,012 Lemberger at al Apr. 10, 1934 1,982,130 Wollenberg Nov. 27, 1934 2,024,689 Groombridge et a1 Dec. 17, 1935 2,323,194 Beveridge et al June 29, 1943 2,396,587 Lowgren et al Mar. 12, 1946 2,427,495 Deuchler Sept. 16, 1947 2,474,862 Richter July 5, 1949 2,542,801 De La Roza Feb. 20, 1951 2,623,820 Messing Dec. 30, 1952 2,673,690 Segl Mar. 30, 1954 2,709,652 Plunguian May 31, 1955 2,744,012 Bylund May 1, 1956 FOREIGN PATENTS 537,088 France May 13, 1922 551,013 France Dec. 23, 1922 857,307 Germany Nov. 27, 1952 OTHER REFERENCES Paper Trade 1., Nov. 6, 1947, p. 77.