US2067480A - Process of manufacture of pulp - Google Patents

Description

J. 12, 1937. I J DE LA RQZA' s 2,067,486

PROCESS OF MANUFACTURE OF PULP Filed July 18, 1935 I INVENTOR JoaqumJu/ioak/a/Paza 5/? Patented Jan. 12, 1937 UNITED sures PATENT OFFICE PROCESS OF MANUFACTURE OF PULP Joaquin Julio de la Rosa, Sr., Great Neck, N. 1.,

assignor to de la Rosa Corporation, Wilmington, Del., a corporation of Delaware Application July 18, 1935, Serial No. 32,016

11 Claims.

My invention relates to a process of manufacture of pulp from wood, fibrous or cellulose bearing materials and more particularly to improvements in the art of digestion of such materials with chemicals at elevated temperatures chips present. Since the quantity of cooking liquor to be used must be governed by the bone dry weight of chips, it is obvious that there will be changes in the liquor ratio with resultant ungo economic operation from the standpoint of liquor waste, heat load required and accurate predetermination of the cooking time required.

Irrespective of the economic disadvantages of variation in moisture content, other disadvan- 25 tages exist with respect to present modes of pulp i is preferableto remove the coloring matters wholly or in part before digestion at elevated temperatures and pressures, in order to avoid fixing them within the cellulose.

40 In addition to those features to which Ihave already referred, the manufacture of a high grade of pulp such as is produced by the so-. called Mischterlisch Process requiresa cooking time up to seventy-two hours for a single 45 batch. Generally, the sulphite process employs a mixture of chemicals consisting of lime water and sulphurrdioxide which forms a compound or mixture called calcium bisulphite". In that process, a digesting vessel is filled with wood 50 chips and a chemical and, after the cover "is bolted on, heat is applied'slowly. The object in this is to allow the calcium part of the chem ical to penetrate the chips thoroughly before the temperature is raised suificiently high to digest 55 the material. This is due to the fact that cellulosic raw material which is impregnated thoroughly with a base will not be adversely affected by the acid cooking liquor at the maximum temperatures employed in digestion. If the chips are not thoroughly penetrated with lime 5 or some other base and the digester temperature is raised to the normal cooking temperatures, the acid part of the chemical will decompose the cellulose as well as the incrustants.

All but one or two hours of the total time required in this process is employed in slowly penetrating the chips with the base and the remainder in the actual digesting operation wherein the acid plays the part of hydrolytic agent.

It will be apparent therefore that if the cellu- 16 losic raw material were first impregnated with a base in some rapid and expeditious manner, that the overall cooking time either in a batch or continuous process would be materially lessened.

It is an object of my invention to provide a 20 method for obtaining a uniform moisture content in material to be digested.

It is another object of my inventionto provide a method for preparing material for treatment in a digesting zone which will permit more exact determination of the quantitiesof cooking liquor needed in the digesting zone and closer control of the digesting conditions.

It is a further object of my invention to provide a method for accurately determining the quantity of bone dry material being passed to the cooking zone in a continuous digesting operation.

It is still another object of my invention to provides. method for treating material'prior to digestion by an acid cooking process which will thereby secure a very high grade of pulp, and appreciably reduce the cooking time.

It is also an object of my invention to provide a method of treating fibrous or cellulose bear- 4 ing, material before a digesting operation to remove large quantities of coloring and other undesirable materials in the material whereby an imprcved'yield of pulp of better strength and color will be obtained.

Other and further objects of my invention will appear from the following description and the appended claims.

In the accompanying drawing which forms part of the instant specification and is to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in thevarious views;

Figure 1 is an elevation of one mode of apparatus capable of carrying out the process of my invention.

Figure 2' is a sectionalv view on an enlarged scale of. a portion of the digester and the. inlet assembly of the apparatus shown in Figure 1.

In general, the establishment of a uniform moisture content in wood chips, fibrous or cellulose bearing materials to'be digested is carried out by means-eta reciprocatingpiston type of press such as-is shown in my Patent No. 1,991,- 244 bearing date on the twelfth day of February, 1935; I prefer to term wood chips in which a uniform moisture content has been established as being uniformly impregnated. This will perhaps be'more-easily' understoodgby reference to a simple illustration. 'If'a block of wood having a" certain normal moisture content is permitted to float in a body of water for a...

sumcient period of time, the pores or interstices of the wood will eventually absorb the water until ,nna y. as a result of complete saturationor ,uniform impregnation",' the wood" being water-logged, willsink. In my process uniform impregnation isacliieved, but in a much more rapid-manner.

The wood chips or' other material to be digestedare placed in the hopper of a press and wett'ed withaliquid which may be either hot or cold. Preferably 'when uniform impregna-.

tion' is all that is desired, water wilLbeused. The wetted chips will be compressed .by the force; appl ed by the piston, the excessliquid being. squeezed out of the chips andthe mass of chips formed" into adense body ofv material confined by the'restrictive choke of the press to a uni directional movement. The applied intensity} of the: force in conjunction the resistance to forward movement caused, by friction of the choke will force the wetting liquid' throughout the poreSof the fmate'rial to thereby uniformly" distribute the liquid 1 in. the material. j j As the, uniformlyimpregnated material is--' sues from the choke, of the press it falls into a hopperwhich is provided at its bottom portion withahinge'd' gate: arranged to open and close] I automatically to feed a predetermined weight of chips from the" hopper. The" weight of bone dry chips in? any givenweight: of uniformly im- D egnated' chips mayeasily be determined by distilling the liquid from I the v impregnated chips. and weighing the bone dry chips remaining."

Obviously, therefore," for a given compressive force andagiven restrictive action of the choke, all chips leaving the press will be uniformly impregnated and have the same 'moisture content. 1 The weight of bone dry material in the body of the impregnated chips. will thus bear a pre cise relation; to the total weight' of chips and liquid" contained in' the chips'and the amount of cooking liquor required may be readily "ar- V The impregnated chips are discharged from a weighing hopperonto a. moving belt which carries. the chips -forwardovert-a weighing device and 'drops'them intokthe hopper ofasecond press serve ing as the'feeding device for a continuous digester such as is shown in my Patent No. 1,991,244 to which I have previously referred.

In this second press .ti' e chips are wetted in the-hopper with a -solution of a. base, preferably veryhot lime. water, although the solution may be'vva'i'm,v or even cold. Other solutions cointaining abase-such asl compounds of calcium, sodiurm magnesium, potassium, or ammonium,

from the impregnating zone.

,trate the chips before the cooking alone or in any mixture with each other, as economics and other factors may dictate, may

be used as the wetting liquid. The piston of this press applies a. compressing force to the wetted material sufncient in conjunction with the restrictive force of the choke to uniformly impregnate the chips with the solution of a base, squeeze the excess liquid from the chips, and to form an internally 'unreinforced plug of a "density su'filoient' of itself to withstand the pressure existing in the digesting chamber to which this press is connected. This press as well as the first press is provided with a drain by which the excess of liquid expressed from the material and escaping backwardly around the surface of the piston may be withdrawn Thematerial now uniformly impregnated with the solution of a base is-intermittently advanced by the piston,

into the digesting chamber of the continuous digester. The material may be digested in this chamber with plain sulphur dioxide gas, sulphurous acid, bisulphite of lime, .or any acid cooking liquor. I prefer. to cook with sulphurous' acid madeby passing sulphur dioxide into water. The actual cooking time required in the digesting chamber will, not vary more than from a fewniinutes to a. few hours, depending upon the material and process employed, as compared to the maximum of seventy-two hours required in the Mischterlisch Process" previ ously referred to while producing an even highor grade of pulp thanthe highest grade produced by this latter process. I

Instead of using water as an impregnating liquid in the first press my inventionv also con-- templates the use of sulphurous or otheracid I to subject the material before digestion to a decolorizing operation.- The dilute hot acid solution used willremove a substantial amount of the coloring matters from the material before digestion at elevated temperatures and pressures is carried out. The decolorizing may be effected by either a single ordouble pressing operation.

Inthe single pressing operation, a dilute acid solution is added to the chips at "the hopper of the diges'ter inlet press. The piston compresses the chips'forcing the acid solution through the chips andthus dissolving the coloring materials. The excess of solution containing dissolved coloring materials isjexpressed from the body of chips, escapes backwardly around the piston and is withdrawn from the impregnating zone through the drain; provided. The acid impregnated pulp is then forced by the piston into the digesting chamber of the continuous digester and cookedat an elevated. temperature and pressure to form pulp. The cooking liquor in.

this case will contain-an alkali, calcium bisul phite for example, and the time of cooking will be relatively long. This follows, since in accordance with usual practice, the calcium part of the cooking liquor musthave time to peneliquor is brought to the final high temperature.

In the double pressing operation: the chips are thoroughly wetted with preferably a hot dilute acid solution in the hopper of a first press, the acid being forced into the chips by the piston, and the excess with dissolved coloringmatt rs escaping backwardly around the piston and being removed thro'ughthe drain provided. The acid impregnated chips after being weighed are then transferred to they hopper of a digester inlet press wherein they are wetted with water to which may be added small-amounts'of a base. Preferably, I employ hot water orwsolution' of ;a .base

although warm or even acoldliquid may be-em-Q "ployed. The piston .of the second press iforces the water or solution of .a base through the .chips, washing but additional amounts .ofwthe acid with dissolved coloring "matters, the liquid expressedand that inexcess escaping backwar'dly around the piston and being removed through the drain provided. .By employing ,a solution of .a-base :as the wetting liquid in .thesecond. press,

, .I am enabled to employ a :short cookingtime scribed Lhereinafter.

dining .the subsequent digesting operation :under heat and pressure. The chips benniformly impregnated with thesolution of a" base permit- :ting immediate cooking at high temperature with-an acid cooking liquor without danger of destruction of'the cellulose. On theotherihand,

.ings, awstearn engine i drives reciprocating plunger 2 :through any suitable transmission of gearing or the like. The cellulose bearingamaterial to be 'pulpedis fedinto hopper -S' by any suitable means inotshown) A supply pipe :4 which-may be oif any desired-shape; Tsupplieswa tor :forestablishing moisture content "of .Lthe

chips *:or :sulphurousacid or other bleaching medium, "the :supply beingrcontrolled by -valve :5. The liquid material and the fibrous =material which may be wood chips or the like, :pass through conduit-8 where they are forcedthrough conduit :I by the plunger-=2.. Thev conduit 'l is provided with forming .a. passageway ofconstantly :decreasingfcross section, to .a point, and "then r'diverging'as will be more 'iully de- The excess liquid :is squeezed .from'the rmaterial "tobe 'digested, and is drained through connection I. "lhe impreg- .nated material passes into a hopper -tandxis deposited on "a .conveyor belt 10.. The conveyor belt .is provided witha device II for weighing :thematerial. The assembly may be that which is made by :the Merrick Scale Manufacturing Company of Passaic, New Jersey, known-as the Merrick Conveyor Weightometer! The conveyor belt -.I I conveys :the material toahopper 12,

into which pipe i 3, controlled by 'valve cil, leads.

provided with liners 12,..23, and 24.

Through pipe l3,'I-'may-inject .an alkaline solu- $101110! water for washing out bleaching acid.

.Asteam engine i5 drives reciprocatingplunger "through a suitable transmission of gears or the like, similar to that which drives plunger .2. A drain l'l, similar to drain I, is provided for carrying .ioflc the excess vIliquid. The plunger IO 'forcesthe bleached and preimpregnatedchips ;or

other fibrous material througha passageway ll which is provided with liners forming a con-. verging-diverging passageway. By referring to Figure'2, :it will be observed that the passageway 18 is formed of threesections, i9, 20,.1and 2i, Linerin is of constantly decreasing cross section .in the direction of movement of .thematerial. Liners 23 and -24 are of constantly increasingfcross sectionalzarea so that the assembly forms a conobjects .of :my invention. method of digesting fibrous material to obtain vergingediverging passageway. The structure of the'gpassageway II shown .infFigure 2 is similar to roi' passageway]. The preimpregnated material .passeslto the digester which comprises .axshellJiZS andz'an "inner rotary shell 26 which *rotated bymotor 2-1 .throughgears 28, 29, 30, andringgear"3i=secured or formed upon rotary shell '26. The :cookiiigliquor is injected into the ..digester vzthrough connection .32. The cooking liquormay be 'sulphurous acid foran acid cook,

or calcium hyposulphite for an alkaline cook.

in the case of anacid cook, water is injected throughpipe 4 for establishing the moisture content of the chips andthe basic solution is injected through pipe I; for impregnating. In the case .ofzan alkali cook,.sulphurous acid or other bleaching acid is injected through pipe ,4 and 'water one :base solution is injected through pipe is :for:washing out the bleaching agent.

Itwill be seen that I have accomplished the I havexprovided a pulp in'which :a .uniform moisture content isobtained in the material to be digested. By-preimpregnating the digesting material .and weighing'.the same before passing it into the digester .a more exact determination of the quantities of cooking liquor needed in the digesting zone can be made and a closer control of digesting conditions can..bexexercised. The cooking time is considerably .reducedsand 1a very-highisrade .of;pulp.isobtained. IiLarge quantities of color- .ing'matter and undesirable materials are removed :prior atoentering the .material in the di-.

.gesting zone and an improved-yield 'is obtained of pulpaofabetter strengthand color.

.It will be understood that certain features and subcombinationsare of utility :and may benemxployed without reference to other features and sub-combinations. is contemplated by and .is .within .the 'scopeiof my claims. It is further obvious that various changes "may be made in details within the scope of .my claims without :departing from the spirit .of invention. kit is, therefore, .to ,beaunderstood that my invention isrnot to-"be limited to therspeciilc details shown Having .thus described invention, what *1. A -'processiforthe manufacture of :pulp from Jilbrous or. cellulose bearing material comprising,

wetting the :material with a bleaching liquid,

subjecting am of the wetted material to a pressuresumcient to' uniformly impregnate the vmaterial with the bleaching. liquid, wetting the "uniformlyhzimpregnated .material with a wash r-liqu'id, subjecting the uniformly impregnated material to a pressure suflicient :to displace the greater portion .of the bleaching liquid andadissolved rmatterwith the wash liquid and then .digesting the material with .a cooking liquor to produce pulpv ofimprovedcolorand strength.

.2. .A process'for the manufacture of pulpfrom aflbrous oncellulwe bearing material comprising,

uniformly impregnating .the material with an .acid solution by pressing, impregnating the acid impregnated material with a hot base solution byv pressing and then 'digesting the material by "an alkaline process.

'3. :Aprocess for the-manufactureaofpulp from *fibrous .or cellulose bearing material comprising wetting the material with that. amount of dilute acid solution necessary to completely impregnate ithe "material, applying. a compressing force to the wettedamaterial gwhile confining the body of jhlaterial' to" a uni-directionalrestricted moveiiientffsaid'torce having an applied intensity sii'm'cient' in conjunction with the restrictive force touniiormly impregnatethe material with the acid solution, wetting the'impregnatedmaterial with asolution containing a base, applying a compressing force to the impregnated wetted material while confining the body of material to a'uni-directional restricted movement into a'digestin'g chamber, said last mentionedcolor and strength.

4. The process of claim 3, said confined body of base impregnated material forming an internally 'unreinforced plug of a density sufl'iciently high to withstand the pressure existing within the-digesting zone." I.

5. The process of claim 3' including the step of withdrawing from the zone of impregnation the liquids displaced from the material during the base impregnating step. i r

6.: A process for the manufacture of pulp from fibrous or cellulose bearing material comprising, wetting the material with a dilute acid solution, pressing the wetted materialto impregnate the material with the acid soluion-and to dissolve the coloring matter ofthe material in the acid solution, withdrawing the .excess liquid and dis-' solved coloring mattersfrom the impregnating zone, feeding the acid impregnated material into a digesting zone and cooking the material therein with an alkali liquor for a period of time suflicient to form pulpof improved strength and color.,

7. A process for the manufacture of pulp from fibrous; or cellulose bearing material comprising, wetting the material with a hot dilute solution ofysulphurous acid, applying a compressingforce to the wetted material'while confining the body of material to a uni-directional restricted movement, into a digesting chamber, said force havaocvQcao ing an applied intensity suiflcient in conjunction with the restrictive force to uniiormly impregnate the material with the dilute acid solution, withdrawing the expressed liquid with its dis solved coloring material from the impregnating fibrous or cellulose bearing materialcomprising,

wetting the material with that amount of liquid necessary to completely impregnate the material, applying a compressing force to the wetted material while confining the body of material to a uni-directional restricted movement, said force having an applied intensity suflicient in conjunction with the restrictive force to uniformly impregnate the material with the. liquid, wetting the impregnated material with a chemical solution, applying a compressing force to the impregnated wetted material while confining the body of material to a uni-directional restricted movement into a digesting chamber, said last mentioned forcehaving an applied intensity suflicient in conjunction with the restrictive force to uniformly impregnate the material with the chemical solution and form a material body of high density, and digesting the material under pressure in the digesting chamber witha predetermined amount of cooking liquor to produce pulp of improved color and strength.

10. The process of claim 9, said confined body of chemically "impregnated material forming an internally unreiniorcedplug of a density sufllciently high to withstand the pressure existing .within the digesting zone.

,11. The process of claim 9, including the step of withdrawing i'rom the impregnating zones the

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