US1632779A - Apparatus for cooking pulp - Google Patents

Description

June 21, 1927.

. 1,632,779 C. H. ALLEN APPARATUS FOR COOKING PULP Filed Jan.l8. 1922 4 Sheets-Sheet l I 1 J Inventor.

June 21,1927. 1,632,779

C. H. ALLEN APPARATUS FOR COOKING PULP Filed Jan. 18, 1922 4 Sheets-Sheet 2 Inventor Q1/1613? (2/4 A June El, 1927. 1,632,779

C. H. ALLEN APPARATUS FOR COOKING PULP Filed Jan.18. 1922 4 Sheets-Shget 3 Jun 21 1927. v-

e c. H. ALLEN APPARATUS FOR COOKING PULP Filed Jan. 18. 1922 -4 Sheets-Sheet. 4

Inventor:

.Patented June 1927.

- CARLTON H. ALLEN, on drums FALLS,

NORTHERN PAPER COMPANY, mAmE.

NEW YORK, ASSIGNOB or ONE-HALF To GBEA'J; or MrLLmocKEr, mAnvE, A coaPoaA'rron or APPARATUS {FOR COOKING PULP.

Application Med January 18, 2922. Serial lie. 630,140.

The usual process of cooking chemical pulp consists in introducing wood in the torm of chips into a suitable digester to gether 'with the proper chemicals. The'digester is then tightly closed an steam is admitted into the bottom of the digester at av variable rate and for a period of time more or less indefinite.

This addition of heat produces a chemical reaction inthe charge of pulp making materials which separates the celluloge from the lignin and other pitchy substances in the wood, and effects the so-called ,digesting process. The reaction also results in liberl5 ating sulphur dioxid in considerable quantities, and this gas produces apressure in the digester which rises to apoint :in excess of that of the steam at the same tempera ture. Consequently, in order to make room for the introduction of more steam, and to keep the digester pressure within practical limits, the pressure is relievpd at intervals or continuously by allowing some of the fluids to escape from the digester. The conditions within the digester are indicated by temperature and prezsure recoriiens, and ac cording to themost approved practice, the

attendant is given detailed instructions as to the temperature and pressure conditions which should be maintained at succeeding intervals of time during the cooking Lopera:

tionh He tries to produce these conditions through the-adjustment of hand valves.

This process, while generally followed 1B the better pulp mills, is open to theobjection that the success of the process depends to a very great extent onthe experience, care and skill of the attendant. So far asconditions existing within the digester are concerned,

40 the attendant has only the temperature and pressure recorders to guide him. Thermometers placed within the digster give only a very rough indication otthe conditions there.-

in since the volu-me of material within the digester is very large, the circulation is. sluggish and is constantly changing so that one part of the,digester may be much hotter than another. The variations in pressure in the digester also. affect the steam flow with a given setting of the steam control valve.

Consequently, the indications. which guide the attendant are unreliable. The result of these conditions is a considerable variation in the quality of the pulp produced by suc conditions existing in the digester,

cessive cooks, a very I irregular rate of steaming, thus producing. wide fluctuations 1n the load on the boilers, and a wide difi'erence in the length of time required to cook 7 individual charges.

With theseconditions in mind, it is the chief object of the present invention to, improve apparatus for cooking pulp with a view especially to producing .more uniform results, ity of the pulp and eliminating the care and skill required on the part of, the attendant.

The nature of the invention will be readily understood fromthe following description when read in connection with the accompanying'drawings, and the novel features will be particularly pointed out in the appended claims.

, ,Referring now to the drawings,

Figure 1 is a view, somewhat diagram- .matic, illustrating a pulp cooking or digesting apparatus embodying the invention in the form at present preferred;

f Fig. 2 is a side elevation of the more important parts of the apparatus that controls 'steam to the digester, certain of the parts being shown in cross section;

Fig. 3 isa plan view of the apparatus ,shown in Fig. 2;

Fig. 4. is a perspective view showing certain portions of the apparatus shown in Figs. 2 and 3; and Fig.- 5 is a perspective view that actuates the valve, operating mechanism, thisview showing also the part that is driven by the pawl; Y

Preliminary to a detailed description of the construction shown in the drawingsfit improving the production and qual-' of the pawl may be stated that according to the present invention the cooking operation is controlled, not by reference to temperature and pressure but instead, by predetermining the quantityof heat required to cook a given charge, and

,thendelivering heat to said charge at a sub{ stantially predetermined rate until sald quantity has been delivered. The quantity of heat required 'to cook a cord, or other measured quantity of chips, can readily be determined so that it is a matter of simple arithmetic to determine the amount of heat required to cook the charge placed in the digester. Incalculating this quantity, the heat losses under the conditions obtaining during the process must also be included. The drawings show both a novel organization of pulp cooking or digesting apparatus designed especially for use in practicing this process, and also a novel apparatus for-con: trolling automatically the flow of stea'mvto the digester.

Referring first to Fig. 1, the construction shown comprises a digester 2, which may be of the usual type, and means for supplying steam to said digester, including a steam sup ply line 3, a valve 4.;controlling the flow of steam throu h said line, and an automatic apparatus, w ich Will be described later, for operating said valve.- The steam supply line delivers steam to the lower" end of the digester 2, and a drain pipe- 5 also is'connected to this end of the digester through a valve 6. Leading from the upper end of the digester is a discharge pipe 7, and the d1scharge of fluidsthrough this pipe is cona threaded section I in either direction will trolled by an automatic pressure relief valve 8. r

The invention includes a novel apparatus for controlling both the rate of flow of steam to the digester and also the length of time during which said flow shall continue, this apparatus being best shown in Figs. 2, 3 and 4.

Referring to said figures, and particularly to Ifig. 2, it will be seen that the valve he opposite ends of this element, however, eing so proportioned that the valve has a constant tendency to-close when the steam pressure is on it. The valve stem includes connection with another part 13, and these two sections" being keyed or splined together so that they are compelled to rotate in unison, but can have a relative longitudinal movement. A bevel gear 14 is secured fast onthe upper end of the part 13 and meshes with another bevel gear 15 fast on one end of a horizontal shaft 16 which carriesa worm ear 17 meshing with a worm 18 fast on a s aft 19, Fig. 3. These shafts, and the arts 12 and .13, are supported in. suitable a wheel 20 having a series of pins 21 projectin forward from the face thereof. It is evi ent that rotation of the pin wheel 20 be transmitted through the mechanism just described to raise or lower the valve element 10, depending upon the direction of said rotation.

or the purpose of producing this rotatlve movement of the pin wheel 20, a double actin vide recte dogs 23 and 24, either one of which may be made to engage the pins 21. This pawl has an upwardly extending arm 25 which is connected to the lower end of a" 12 having a telescoping earings, and the shaft 19 carries crank arm 23, the upper end of this arm being connected to a crank 'pin or eccentric pin 27 mounted on a disk 28, secured fast on the end of a shaft 30. A guide link 31 connected to the joint between the parts 25 and 26 causes the pawl 22 to reciprocate substantially in a straight line. The shaft 30 carries a worm wheel 32 which is driven by a worm 33 secured on a shaft 34 driven by an electric motor 35. ,j

The-position; of a pawl 22 is controlled by a bent rod 37, Fig. 2, which is connected to a bell crank lever 38 mounted in a bracket 39. One arm of this lever carries a weight 40, while the other arm normally bears against one end of a horizontal rod 41 Which is supported in suitable guides for longitudinal sliding movement. The weight 40 is suflicient, when it'is free to control the pawl 22, to hold this pawl in its right-hand position, Fig.2, where it will cause a counter clockwise movement of the pin wheel-20, and thus will operate through its connections with the valve element 10 to close this element.

The mounting of the pawl22 enables it to be moved into either a position in which it actuates the connections with the valve 10 to close said valve, or into another position in which it opens said valve, or in an intermediate or neutral position in which it by-a time mechanism, and by a mechanism which is responsive automatically to changes in the .rate' of steam flow. In other words, the controlling apparatus includes a mechanism which is driven at a constant speed, another mechanism which is automatically responsive to changes in the rate of steam flow, and means for correlating the opera- 'tions of these two mechanisms to cause them to exert a joint control over the valve operating mechanism.

The time element or mechanism just referred to includes the motor 35, a worm 43 fast on the shaft 34 which the motor'drives, this worm driving a worm wheel 44 fast on a shaft 45, and carrying an additional worm '46 driving a worm wheel 47 fast on theupper end of a vertical shaft 48. This shaft ,is threaded for the greater part of its length, as clearly shown in Fi 2, and carries a nut or follower 50 whic engages with the threads of the shaft 48. A controller 51 consisting of a plate of suitable shape, Fig.' 4), is removably secured to the follower 50 by means of a pin or thumb screw 52 which enablesthe plate or controller to swing freely relatively tothe screw. This controller is so supported that it bears agamst. the left-hand end of the rod 41. previously referred to. A lip or flange 53 projecting from one edge ofthe part 50 en-' ,gageswith a stationary part 54 of the frame (see llii;

' this tank tube 65 down stream, direction of steam flow. The tube 64 is conand prevents the slide from rotating onthe s aft 48.. 1

The mechanism responsive to variations in the steam flo'w comprises abeam fast on a shaft 56, this shaft being machined at'opposite sides of the beamto form knife edge earings which rest on plates 57-57 secured to the machine frame. -Two receptacles designated, respectively, at 58 and 59 are secured fast to the beam, the receptacle 58, being lower and closer to the fulcrum or axis on which the beam tips than the recep-' tacle 59. A pipe 60 connects the lower ends of these two receptacles, and the rece tacle 58 and the pipe connection 60 preferab y are substantially filled with mercury, or some other heavy and relatively non-volatile liquid. A spring 61, connected at one end of the right-hand end of the beam 55 and at its other end adjustably secured to the frame by means of a bolt 62, tends to hold the beam v normally in the position in which is shown in Figs. 2 and 4. The upper ends of the two receptacles or containers 58 and 59 are connected, respectively, to spaced points in the steamconducting pipe or conduit 63, between which points a differential pressure exists that varies with the rate of steam flow. In the present instance Petot tubes 64 and 65, respectively, Fig. 4, are located. in the steam pipe 63, the open end of the tube 64 being directed up stream and that of the with reference to the nected to the container 58 by means of a. pipe 66 leading into a vertical tank 67, a U- shaped pipe 68 leading from the bottom of and connected bv a flexible tube 69 to piping70 leading into the top of the container '58. The connections from the Petot tube 65 to the container 59 are similar to those just. described, and com rise :3. pi e 71, tank 72, U-shaped pipe 73, Hexible tub ing 74, and pipin I 75, all arranged as clearly shown in i2. 4. The lengths of flexible tubing69 and 7 4 are coiled spirally about the shaft 56 so that they exert only a very slight opposition to the tipping or rocking movement of the beam 55 on its ful crum, this tippin movement merely wind ing up or unwinding slightly the coils 69 and 7 4. A bracket 76 issecured fast to the shaft 56 and has spaced armsthrough which adjusting screws 77 and 78 are threaded,

these screws bearlng' agalnst the opposite sides of an arm 80 mounted loosely on the end portion of the shaft 56. The end of this.

arm has an extension on which is mounted a roll, grooved as shown at-81, Fig. 4, to re" ceive the edge of the controller plate 51, this part of the arm bearing against the controller plate at a point directly opposite the point of engagement therewith of the rod 41. v The differential pressurebetween the Petot tubes 64 and 65 varies with the square ofthe velocit of the steam flowing throu h the pipe 63. his differential pressure tlllSdS m osed through the" connections above described on the body of mercury in, the connected receptacles 58 and 59, and tends to force mercur out of the. receptacle 58 through the'plpeconnection 60 and into the receptacle 59. Obviously the quantity of the connections and prevent the flow of live steam into the containers 58 and 59. This apparatus thus is capable". of. producing a relatively powerful movement of the arm 80. If this arm were mounted to move over a suitable scale, the apparatus would consti tute a steam'flow meter.

Assuming now that a charge of chips, and other. pulp forming materials, has been placed in the digester 2, and that the valves 6. and 10 are both closed, the cooking operation is begun by switching current on to the motor 35. The parts at this time are in the positions in which they are shown in Fig. 2, the double acting pawl or actuator 22 being reciprocated up and down in its neutral or idle position. As soon as the shaft 34 begins to rotate, the slide orfollower 50 will begin to rise slowly, being drawn upwardly on the threaded shaft48. The end 81 of the arm of the rod 1 41; and the result of this upward movement of the controller is to slide the rod 41 toward the right, Fig, 2, thus acting through the bell crank lever 38 androd37 to" move the double acting pawl 22 toward the left, Fig. 2. This movement renders the dog 24, Fig. 5, opera-' tiveto act on the pins 21 to rotate the pin wheel 20 step b step in a clockwise dir ecs tion, and there ore to open the valve element 10. Steam begins to flow through the conduit 63 andpipe line3 to the digester 2 as soon as the valve 10 isopen, and this flow establishes a differential pressure on the body of mercury "in' the, connected containers 58. and 59, forcing a part of the mercury from the former into the latter container, and thereby tip ing the beam 55 in a clockwise direction a out its fulcrum. This move:

Ill)

plate, 51 to an extent determined by the degree of tipping of the beam. If this movement sjso small that the edge of theconwhere it will simply reciprocate idly without changing the setting of the valve element 10. If the .part 81 is moved com-- pletely out of contact with the controller plate 51, the weight will swing the pawl 22 toward the right, Fig. 2, far enough to bring the dog 23 into operationon the pin wheel, thus producing'a closing movement of the valve plunger: 10. This will result in a very short time in swinging the arm 80 backagain inn counter clockwise direction and causing the art 81 to bear again against .the edge of t e controller plate 51 withthe results above described.- The rate of steam 'flow thus will depend on the. shape of the controller plate 51. Usually a relatively large steam flowis desired during the early stages of the cooking of a charge, and i the flow is gradually decreased as the cooking operation progresses. For this. reason the plate is made wide at its upper end, as shown, and is gradually decreased in width toward its lower end. The plate is drawn upwardly at @510 but constant rate, and when the end of the plateis withdrawn from between the parts 81 and 41 the/flow of steam is automatically shut off, as.will

readily be understood. Usually; however,

the steaming is stopped by the attendant before this action takes place. The blank space at the upper end of the shaft 48 p -events the slide 50 from rising too far. 1

89 fast on a transverse shaft 90. An arm 91'is fixed to the end of this shaft and is adapted to engage a pin 92 which is secured in an extension 93 of the pawl 22, as best shown in Fig. 5. Consequently, when the valve operating mechanism has been in operation long enough to cause the arm 91 to, make substantially a complete rotation, it will engage the pin 92 and thereby return the pawl 22 to its neutral position. The maximum adjustment of the valve lunger 10 (in either direction thus is effectua ly limite As above stated, it is-necessary to relieve the pressure in the digester at intervals during the cooking operation, and for this purpose I prefer to use a pressure relief valve which will open automatically upon a rise in pressure above a' substantially predetermined point. 1

Referring to Fig. 1, the valve there shown comprises a valve plunger 95 mounted in a valve casing 96 having a suitable seat for said plunger. The plunger is supported by a valve stem 97, secured to a flexible diaphragm 98 which is clamped between the upper and lower members 99 and 100, respectively, of a hollow casing, the upper member of this casing'being connected to the valve casing 96 through a tube 101 that encircles the valve stem 97. The digester pressure thus is imposed directly on the upper surface of the diaphragm 98 and this pressure is opposed by a coiled spring 102 which bears against the lower surface of'the diaphragm and is backed up by an adjusting screw 103 threaded through the casing 100. Consequently, when the digester pressure overcomes the combined pressure of the spring 102 and the fluid pressure exerted on the lower face of the will be lifted off its seat and the surp us pressure allowed to escape, or blow. The

gpressure at which this action will take place The controller plate 51 is removably atcan be varied by adjusting the screw 103.

tached to the slide 50 by a thumb screw 52 so'that other plates can be used, as desired, for different batches on conditions.

In order to facilitate the resetting of the slide 50 after a cookhas been completed, it is split and the two split portions are held in operative relationshlp to the threaded rod 48 by means of a thumb screw 85. By loosenin this thumb screw, therefore, the parts are disengaged from the threads of the rod 48 and the slide 50'-may be lowered, to its original or initial position, as sbpwn in Fig. 2.

An automatic mechanism also is provided to limit the maximum adjustment of the valve plunger 10 that can be made by the valve operating mechanism.

Referring to Figs. 2 and 3, it will be seen that the shaft 16 has a bevel gear 88 at the inner end thereof meshing with another gear It will now be evident that the pulp cooking apparatus above described will operate automatically to deliver steam to the digester at a predetermined but variable rate for a predetermined length of time, and that the pressure in the digester will be automatically relieved whenever it 'rises above'a prer etermined point. This apparatus, therefore,eliminates entirely the uncertain manual controlwhich heretofore has been required, and avoids any necessity for relying on the experience, care, or attention on the part 'of the attendant. I have demonstrated thata better average quality of pulp is produced by this process, and that the yield of-pulp from a given quantity of material is increased. Furthermore, the sudden anlwidefluctuations in steam flow which are produced by the manual control are avoided, thus making it very much easier lunger 95, this plun erfor the boilers to carry the steam load. A'n especially important advantage of this process and apparatus is that the average time required to-cook a charge is substantially reduced. 7 a.

By properly designing the controller plate 51, almost any condition encountered in actual practice can besatisfactorily handled. It may also be noted here that this plate 10 forms the connecting link or eldment between the time mechanism and the mechanism; responsive to changes in the rate of steam flow. That is, both of these mecha- T nisms act through thisplate to, exert a joint control over'the action of the'valve operating mechanism. While I'have herein shown and described the best embodiment of the invention of which I am at present aware, it will be appreciated' that the invention susceptible L of embodiment in many forms of apparatus differing in details from the construction shown without departing from the spirit or scope of this invention.

in part, of my prior application Serial No. 348,059, filed Dec. 29, ,1919. Claims on the sub'ect matter common to the two cases are made, however, in this application, the

.claims in the earlier case being restricted to subject matter which is not disclosed in this application. r The flow controlling mechanism disclosed in ,this ap lication claimed in my divisional" application Serial No. 44,258, filed July 17, 1925, claims in the present application being directed to the pu p cooking apparatps.- 11 A I I Having thusdescribed my invention, what 0 I desire to claim as new is: 7

, 1. A pulp cooking apparatus comprising, in combination, a digester, a steam supplyline leading to said digester, and means for controlling the flow of steam to said digester and operative automatically ,to deliver a' substantially predetermined? quantity of steam thereto at a predetermined rate and ina substantially predetermined time.

2. A pulp cooking apparatus comprising, in comblnation, a-digester, a steam supply line leading to siiid digester, and means for controlling the flow of steam to said digester and operative automatically to supply steam to said digesten at a substantially predetermined but variable rate and for a substantiallf predetermined length, of time, where r tel-val of time. The present appllcationils-a contlnuation,

- valve, and means controlled jointly by time by itwill deliver a predetermined quantity 015 steam to said digester. p I 3. A pulp cooking apparatus comprising', in combination, a digester, a steam supply line leading to said digester, means for controlling the fiow of steam to said digesterand operative automatically to deliver a substantially predetermined quantity. of steam thereto at a predetermined rate and in a substantially predetermined time, and means for ahtomatically relievinglthe pres-v sure in said digestenwhen it rises above a substantiallyprrdeterminedpoint,

pulp cooking apparatus comprising, in combination, a digester, a steam supply line leading to said digester, a valve controlhug the flow of steam therethrough, and automatic means for operating said valve controlled jointlybytime and the 'rate of steam flow through'said supply line, whereby steam may be supplied automatically to, said digesteiat a substantially predetermined but variable rate during a given in- 5. A pulp, cooking apparatus comprising, in combination, a digester, means for sup plyino steam to said digester, means for antomatically wcontrolling the supply of steam to said digestr to cause the cooking operation to proceed in .a substantially predeterminedmanner, and additional means for automatically controlling the discharge of fluids from said digester.

' 6, A pulp cooking apparatus comprising, in combination, a digester, a steam supply linealeadin to said digester,a valve controlling the flow of steam through said line, power-driven mechanism fdradjusting said and by the rate of steam flow through said supply; line for automatically controllingthe operation ohsaid" valve adjusting mechanism. q 7. A pulp cooking apparatus comprising, in combination, adigester, a steam supply line leading to said digester, a 'valve controlling theflow of steam through said line, ,pow'er driven mechanism for opening and closing saidvalve, said mechanism including a pawl and ratchet, and automatic mecli anism-controlled jointly by time and by th rate of flow of steam through said supply linefor controlling" the operation ofsaid pawl and ratchet. 1

CARLTON H.

Images