US1653416A - Method and apparatus for treating fiber - Google Patents

Description

Dec. 20

RICHTER ET AL METHOD AND APPARATUS FOR TREATING FIBER 1 E z5 sean 9% 2 .5.2 nac Hmm nam m Q 3U tu; w w. V. l .w

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^ A. F. RICHTER ET AL METHOD AND APPARATUS FOR TREATING FIBER Filed July19. 1926 2 SheetsfSheet 2 HccuMuLnroR TANK Hom SUPPLY LINE To DIGEsTERs.

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l/steam1ng process of cooking is employed,

Patented Dec. 20, 1927.

UNITEDYA STATES l1.653.416 .PATENT OFFICE..

.AU'GUST F. RICHTER, 'OF WATERTOWN, AND FRANK A. AUGSBURY, OF OGDENSBURG',

NEW YORK, ASSIGNORS T0 STEBBINS ENGINEERING AND MANUFACTURING COI- u PANY, OF WATERTOWN, NEW YORK, A CORPORATION OF NEW YORK.

METHOD AND APPARATUS ron TBEATING FIBER..

is discharged from the digester during'- treatment.' 4

In general, where the quick cook or direct Ythe relief gases driven olif from the liquor in the digesters during the cooking process, are passed through relief gas coolers and after being cooled, this gas is passed into the bottom of the acid storage tank or it isv sometimes passed into the bottom of an absorption or recovery tower, the raw acid being sprayed into the top of the recovery tower and the gas, (in the case of the sulphite process, this is SO2 gas) iowing upward under pressure meets the down coming acid and is absorbed. Heretofore, it-

has been necessary to cool the sulphur dioxide gas in order that it might be absorbed by the'liquor. Due to this cooling, the acid, when pumped into the digester, requires an excess of steam to bring the temperature and pressure up in the digester.

It is also well known that quick cooks at high temperature have a destructive eiect upon the cellulose in the wood, and low temperature cooks, (which necessarily take a longer time) do not have as destructive effect upon the cellulose. Further, when cooking/is carried on at a comparatively low temperature, the yield of pure cellulose is higher. Our method and apparatus are applicable to both quick cook and slow cook systems.

In our process, no cooling of the gas from the digesters is required, as the gas is absorbed under pressure, thereby. conservingA thev heat units with the 'direct result that there is a considerable saving of steam during the cooking process.

' Briey, one phase of the present invention consists in passing the hot high andlow pressure relief `fases from the digesters into an accumulator tank where the gases are absulaton tion when it is applied to the fibrous material in the digester. l

The invention is illustrated in the accompanying drawings, in which,

Fig. 1 is a diagrammaticview of one a paratus forming the subject matter of tliie present invention.

Fig. 2 is a similar view of a modification.

Fig. 3 is a vertical sectional view of a detail taken on line 3-3 of Fig. 1.

In general, the apparatus consists of onev or more digesters, 1, 2, and 3,' an acid accumulator 4, and one or more-acid storage tanks 5 and 6.` 'Although three digesters have been illustrated in Fig. 1, the application can be employed'with any number vof digesters, orwith any number of acid storage tanks. In -this connection, it may be stated that itis general practice to emplo three acid tanks if three digesters are use' but only two acid storage tanks are used with the present invention, and these are combined with the acid accumulator 4.

The digesters employed are of the standard steel shell type now in common use, and' in the sulphite process these digesters are lined with an acid resisting metal. Also the acid storage tanks 5 and 6 maybe of steel or concrete with an acid resisting lining, or they may be made of wood. These pieces of apparatus are all in common 'use inrnany mills now operating. The acid accumulator is not now in use, but it may be of the saine general construction as each of the digesters and must be provided with an acid proof lining. We have shown the accumulator as arranged vertically, but it may be arranged horizontally and be as equally effective, provided that the same relative positions o f the inlet and outlet pipes are maintained. This accumulator may be of any shape found desirable. The digesters and acid accumulator may or may not be covered with a heat in- As these pieces of apparatus are lined, the lining acts as an insulator, but additional insulation may -be provided if necessary.

` process may be made in any known way and pumped from the acid system to the storage tanks by way of the pipe 7. p

The digesters are cooked in rotation, which is now common practice, and the wood chips or other fibrous material are introduced into the digesters from an overhead bin or chip conveyor (not shown) through sleeves 8 having covers 9. The liquid acid is forcedy into the bottom of the digester through pipe 10, either by an acid pump 11, or by applying steam pressure to the top of the accumulator 4, and driving the acid from the tank 4 through the pipe 12 and into the pipe 1Q. At this point, it will be noted that the pipe 10 is connected to the digesters by branch pipes 13, 14, and 15, each having a control valve 16, 17 and 18. The pipe 12 is also provided with a control valve 19, and the pump 11 is connected to the bottom of the accumulator tank by a pipe 20 having a control valve 21.

rIf the acid from the accumulator 4 is to be forced into the digester by `the pump 11, the valve 19 is closed and the valve 21 is opened, but ,if steam pressure is used instead of the pump, then the valve 21 is closed and the valve 19 is opened.

This method of forcing the acid into the digesters by pressure applied to the accumulator is new, and its advantages are that this steam pressure further heats up the acid, thereby assuring a better penetration of the acid into the chips before the cooking process is started. One of the desired results is thereby accomplished, as it is always advantageous to have the acid as hot as possible in order to secure quick penetration of the acid into the wood chips. The quicker this penetration is accomplished without carbonizing the chips, the better will be the pulp produced. besides" saving. time and investment. The pipe for introducing steam into the accumulator tank is shown at 22 and it is provided With a control valve 23.

During the cooking process, the gas from y the digesters is permitted to discharge into relief gas lines. In accordance with the present invention there are two rehef lines provided; one a high' pressure relief gas line" 24, and the other a low pressure line 25. The pipe 24 is connected to each digester by two branches 26, each having a control valve 27 therein. The low pressure pipe 25 is connected to each digester by two branches 28 each having a manually controlled valve 29 land an automatic check valve 30. Heretc 10W pressure line 25, which is connected to the upper portion of the accumulator tank at the point 31. As the digesters are worked in rotation, there is almost a. contant iiow of low pressure gas into the accumulator -1 when three o1' more digesters are employed. It three or more digesters are used, the cold acid from the storage tankNo. 5 is continuously forced by the pump 32 through pipe and sprayed into the top of the accumulator 4. This cold liquid showering in the tank 4 condenses and absorbs the hot incoming relief gas from the pipe 25. If only one or two digesters are connected up to the acid accumulator.l the pumping of acid is necessarily intermittent. Y

During the time that low pressure SO2 gas is being relieved from some of the digcsters into the top of the accumulator 4, SO2 gas at high pressure is being relieved into the high pressure lineA 24, and carried into the bottom of the accumulator/4 from the other digesters. This high pressure relief gas'passes into the tank 4 at the point 34 and bubbles up through the acid in the accumulator, and is thereby absorbed into the acid liquor, in this way building up the strength of the acid in the accumulator. A three way plug cock 35 is provided in the high pressure line 24 and is connected to the upper portion of the accumulator by a short pip-c 36, so that gas from thehigh pressure line can be admitted into thetop ofthe accumulator, when the pressure inthe latter drops to a point below that caused by the static head of the acid liquor in the accumulator. This is particularly necessaryl when the last cook is being finished preparatory to a shut down, and also at certain periods when the digesters get out of step from their regular sequence of operation. l

We will now assume that digesters Nos. 1 and 2 are already cooking, and No. 1 digester has been on for eight hours, and No. 2 for four hours. No. 3 digester has just been illedwith chips and acid, and the cooking process just started. At this time, digesters 1 and 2 Will both be relieving into the high pressure gas relief line 24. This gas passing into the bottom of the accumulator and bubbling up through Vthe acid and being absorbed thereby. Due to this, the acid liquor in the accumulator 4 is heated up so that this heated liquor may be forced by the pump 11 or by steam introduced through the pipe 22, from the accumulator 4 into -the lower end of the digester No. 3. As soon as the cook is started in digester No. 3, the valve to the low pressure relief gas'line is opened vand the gas is driven out by thc application ofsteam tothis digester. In ,thc event that the gaspressureon the top of the acid in the accumulator'is higher than the pressure in the digester` the check .valve 30 will close and prevent the flow of 'gas from lll) lli

Lesa-11e the accumulator back into the digester, but as. soon 'as the pressure in No. 3 digester is higher than that in the accumulator, the gas will flow from No. 3 digester into the top of the accumulator where it will be absorbed by the acid which is being pumped and sprayed into the accumulator from the storage tank by way of pipe 33. After the cold acid is pumped from the storage tank 5 into the accumulator, it will condense and absorb the gas in theaccumulaton Any gas that is not absorbed during this process will pass through the vent line 37, into the lower end of one or more of the digesters, or it may be passed through the pipe 38 into the lowerportion of the storage tank 5 where it will be absorbed by the acid liquor in this tank. Suitable valves 39 and 40 are provided in these pipes to control the flow. A vent line 41 is also provided for the storage tanks 5 and 6, this vent line being led to the acid system (not shown), so that the gas which Aforms on the top of theracid storage tanks,

will be absorbed in the acid making system, thus preventing the loss of gas.

As soon as No. 3 digester has been brought up to approximately pounds pressure, the valves 29 of that digester are closed, and the valves 27 of the same digester are opened, so that the high pressure gas is released into the line 24. At this time, the digester No.' 3

will have been cooked about four hours, and

No. 1 digester will be ready to be dropped in ressure. As soon as'the ressure in No. 1l digester drops, the'valves 2 of that digesf. ter will be closed and. the valves 29 of the same digester will be opened, to permit the low pressure gas to travel to the accumulator. The above disclosure is based on a total ,cycle from fill 'to fill of approximately 16 the accumulator, so that this liquor is 1n preheated condition before it enters a digester which is about to be started. The steam for cooking isi'ntroduced to the digesters by the well known means now generally employed. Y

y' In the modification illustrated in F ig. 2 we have illustrated two accumulators, and

i 51, hooked up with pressure or thermostatic control devices 52 and 53,v (these are both standard equi ment and can be purchased on the market so that the relief gases from.

the digesters, and liquor from the acid stor- I age tanks 54 and 55 are automatically changed, from one accumulator-to the other.-

That is, when one accumulator is up to a predetermined pressure, the gases and lliquor are automatically switched over to the other accumulator, leaving the first ready to discharge its contents into a digester whenever desired, this being automatically accomplished by opening the acid supply line leading into the digester. As the pressure and temperature in the irst accumulator drops, due to emptying its contents and filling the digester, steam is automatically admitted to the top of this accumulator, maintaining the proper 'pressure therein to force the acid to the digester which is being filled. During this period, the low pressure vent line at the top of the digester v undergoing filling, is opened. In this modification, 24a designates the high pressure 4relief gas line, which is provided with av control valve 24". Just be. low the valve 24", the pipe is branched at 24C, and' these branches are connected to the upper portion of the accumulator tanks. The pipe extends downwardly and is connected by valved branches 24d to the lower portions of the accumulator tanks. Thelow pressure relief gas line is 'designated 25, and is connected by branches 25b to the upper portion `of each accumulator tank.

The acid is supplied Vto the accumula-tor tanks by means of a pump 56 which forces the acid liquor -through a pipe 57 having `valved branches 58 connected to the l,tops of the accumulator tanks.

The acid is 'fed from' the accumulator tanksl to the digesters by means of a pipe .59'

which is connected by valved branches 60 `to the lower ends of the accumulator tanks.

Steam is supplied to the accumulator tanks "by means of a pipe 61 having valved'branches losA 62 connected to the tops of the accumulator tanks. l A

As soo`n as the digester has been from thefrst acid accumulator, the valve in the acid supply line to the digester is closed ,and the steam atthe top of the accumulator is shut oil by closing the valve in the branch 62. This causes the temperature and pressure Ain this particular accumulator to drop, and as soon as it has dropped suiiciently, the

automatic pressure or thermostatic controldevices 52, 53, automatically changes the valves, so that this accumulator-will again fill withacid from the storage tanks 54,55,

whilethe gas from the digesters is being recommonly called blow pits. `thus partially washed, and therefore does on the high pressure relief line is automatically opened. Such automatic regulation of valves is well known, and no specific means Afor accomplishing this need be illustrated.

Manual auxiliary control in this instance is also provided, so that digesters can be handled in this 'manner in case the automatic feature should for any reason fail to function. Occasionally, a check valve or an automatically controlled valve will stick, and under such circumstances, the digesters'may be controlled by manual valves, that is the reason why we prefer to use two valved branches 26, and two valved branches 28 for each digester. I.

Under our method of producing cellulose pulp, and handling digesters, we also prefer to provide a strainer at the bottom ofeach digester, so that when the cook is finished, the liquor is drawn of at the bottom of the digester through this strainer. In Figs. 1 and 3 we have illustrated such strainers and have designated the same 70. The strainer holds back fthe cooked pulp and allows the liquor to bledrained out and sent to the sewer "or else to thewaste liquor fuel recovery system, or wherever it is required. During the time the liquor is drained out of the digester, hot water is being pumped into the top through the line 71 which is providedwith valved branches 72. This water. drain.- ing down through thh pulp, partially washes same, so that when thewdumping valve, (not shown) is opened, the pulp is allowed to go into the drain pits (not shown), or what are Tho pulp is not contain much acid. As soon as the pulp has been partially washed in the digester,

this dumping valve or blow-od valve previ-` ously mentioned, is opened and the hot water entering the top of the digester will wash the contents of the digester Vout of the same and into the blow or draining pits. Due to this operation the fibers do not explode asis the case when the contents of the digester are blown out under pressure, therefore the ibersare not injured andthe pulp produced is of a better quality thanthat produced when the liquor is not drained out, and the liquor' and pulp are blown out into the blow pit by pressure applied to. the interior of the digester. We also prefer to arrange a hot water wash out line and that is commonly called the blow off elbow, so

that .this hot water comes in on a line par.

allel to the center line of the dischargepipe leading to the pits, thereby having a siphon effect in removing the contents' of the digester. In our method, the contents lof the digester are handled much more gently than under the old practice, both as regards the cooking andthe emptying, which produces a higher grade of pulp as above mentioned.

Our method of using the acid accumulator is applicable to both quick and slow cooks, as also 1s the method of dumping or emptying the dige ters, it only being necessary to so .and pressure, is accomplished lin the same manner now 4generally employed in quick cook systems. The advantages of our method, however, are that the heatsunits in therelief gas and liquor, are conserved and the pulp produced is of a higher and purer uality.

Although we have not s own it, aside relief valve for removing part of the liquor during the cooking process is also provided. This relief discharges the liquor removed from the digester during ythe cooking proc-` ess, back into the acid storage tanks, and this liquor is mixed with the\raw liquor from the acid system, as is standard practice at this time.

From the foregoing, it is believed that the construction and operation of our apparatus, and the novel steps of our method, may be clearly understood, and it will be apparent to those skilled in the art that changes may be made in the details disclosed, without'departing from the spirit of the-invention as expressed in the claims. v

`What we claim and desire to secure by Letters Patent is v 1. A method of treating fibrous material consisting in placing the same in .closed chambers, digesting the material in one of said chambers with acid under heat and pressure, liberating low pressure gas from,

liquor under pressure to absorb the gas and v heat the liquor, and introducing this heated liquor into the second chamber for digesting the material in that chamber.

2. A method of treatin fibrous material consisting in feeding acid liquor into the Aupper portion of an accumulator chamber, placin the fibrous material in first and second digester chambers, digesting the mate-` rial in the first chamber with acid under heat and pressure, releasing low pressure gas from the first digester chamber for a predetermined period of time and feeding the same into the upper portion of the accumulator chamber, subsequently releasing high pressure gas from the first digester'chamber and feeding the same into the lower portion .gases in the accumulator chamber wit the of the accumulator chamber, contactin said acid liquor to absorb the gas and heat the liquor, and feeding this heated liquor into the second digester chamber and contacting the same with the fibrous-material therein for digestion purposes.

3. In a method of treating fibrous material, digesting the material with acid in av z,consisting in placing the lmaterial in first and second digester chambers, digesting the material in one of said chambers with acid under heat and pressure, passing gas from thel first chamber to an accumulator chamber, contacting the as in the accumulator chamber with acid liquor to absorb the gas and heat the liquor, and introducing steam into the accumulator chamberV for heating liquor, and' heating the li uor by the gas enriched liquor and for forcing the. same in this heated condition `into contact with the material in the second chamber.

5. In an apparatus for treating fibrous material, aV digester and an accumulator, a high pressure relief gas line connecting the digesterto the accumulator,'a low pressure re ief gas line connecting the digester to the accumulator, valves arranged in said lines, means for feedin acid liquor Linto the accumulator for absorlingthe gas by the the gas and means for feeding t e gas enric ed heated liquor .from the accumulator into the digester.

or the other, means 'for feeding acidllquor len into the accumulator forabsorbing the-gas and heating the liquor, and means for' feed-f ing this gas enriched heated liquor to Vthedi ester.

An apparatus for treating fibrous material comprising a digester and an accumulator, said accumulator, means for feedlng relief as for the digester into the accumulator or contacting t e gas with the liquor, a conduit connecting the accumulator to the lowerl ortion of the digester, and means for feedlng aqueous steam from an outside source into t e upper portion of the accumulator Vhigh pressure relief tion o .jA'n apparatus for. treatingbrous maf. terial` comprising a digester and an accumumeans for feeding acid liquor into for forcing the liquor through ,the conduit into the dlgester. A

8. An apparatus for treating fibrous material com rising a digester, an accumulator, an aci storage tank, means for forcing and feeding acid. liquor from the storage Y tank to the accumulator'tank, a conduit for feeding acid liquor from the accumulator to the digester, a high pressure relief gas line connecting `the upper portion of the digester to the lower portion of the accumulator, a low pressure relief gas line connecting the 'upper portion of the digester to the upper portion of the accumulator, and means for forcing acid from the accumulator to said digester. .f

9. An apparatus-as-,claimed in claim 8 including a vent as pipe for leading vgas from the accumu ator to the storage tank. 10. An apparatus as'claimed in claim 8, including a by-pass pipe for connecting the I as line to the upper portion of the accumu ator,:.and a valve for controlling the passage of high .pressure relief gas to either the upper or lower porthe accumulator.

1l. A method of treating fibrous material, consistin in placing the material in a chamber, plac g acid liquor in a tank, introducing aqueous steam under pressure from an outside source into said tank for preheatin said `acid liquor, and utilizing the pressure ofthe steam for forcing the preheated acid liquor fromthe tank'v into said chamber and into contact with the material in the chamber.

its lower end, a -screen in said outlet, means for introducing acid liquor into said outlet beneath'the screen, and means for introducing hot ,liquid into the upper end of the digester for washing acid out of the materialin the digester and through-said screen. 13. A method of treating fibrous material, consisting in placing a raw material in first and second digester chambers, digesting the material inthe first chamber with acid under heat and pressure,-`releasing low pressure gas from the first vchamber for a predetermined period 'of time, subsequently releasing high` pressure gas from the first chamber for a predetermined period of time, contacting said gases with acid li uor under pressure to absorb the as and eat the liquor, and contacting the eated li uor with the fibrous material 1n the second igester chamber for digesting purposes.

14. A method oftreating fibrous materlal, consisting in feeding acid liquor into the upper portion of an accumulator chamber, placing the fibrous' material in a dlgester chamber, di stin the material in the chamber with acid un er heat and-pressure, releasing low pressure gas from the digester chamber for a predetermined period of time and feeding the same into the upper portion of the accumulator chamber, releasing at another period of time, high pressure gas fromV the digester chamber and yfeeding the same into the lower portion of the accumulator chamber, contacting said gases in the accumulator chamber with acid liquor under pressure to absorb the gas and heat the liquor, and contacting this heated liquor with fibrous material for digestion purposes. 15. In a method of treating fibrous material, digesting the material with a chemical solvent in a number of closed chambers under heat and pressure, releasing gas from the chambers and contacting the same in heated condition with pre-conditioned chemical solvent in an accumulator chamber under superatmospheric pressure to absorb the gas and heat the-solvent, releasing gas from one .of said chambers and contacting the same with fresh chemical solvent of 'a supply chamber arranged at a lower elevation than the top of 'the accumulator chamber, pumping pre-conditioned chemical solvent from the supply chamber into the accumulator chamber, and feeding the chemical solvent rom the laccumulator chamber, into one of said closed chambers. v

16. In -a liber treating method, digesting the fiber in a pluralityi of closed chambers under superatmospheric pressure with heated acid liquor, lreleasing acid ygas from said closed chambers and passing the same into a closed. accumulator chamber, contacting said gas"in the accumulator chamber with pre-conditioned acid liquor, releasing acid gas from one of said chambers and contacting the same with fresh acid liquor of a storage tank arranged at a lower elevation than the top of the accumulator chamber to pre-condition said fresh acid liquor, feeding the fresh acid liquor thus pre-conditioned from the storage tank into the accumulatorchamber, and passing the acid liquor from the accumulator chamber into one of said closed chambers. Y

17. In a liber treating method, digesting the liber in a closed chamber with a heated chemical solvent, releasing gas from said closed chamber and passing the same in its heated condition into. an accumulator chamtained in the iirst chamber, and utilizing ber, feeding fresh chemical solvent from a supply tank arranged at a lower elevation than the top of the accumulator chamber,

into the accumulator chamber, and contactrial. digesting the material with a chemical solvent in a closed chamber, releasing high pressure gas from said closed chamber foi` a period of time, and passing the same in heated condition into a second chamber, contacting said gas in the latter chamber with chemical solvent, releasing low pressure gas from said first Aclosed chamber for another period of time, and contactin said low pressure gas in heated condition with fresh chemical solvent, and feeding the solvent after it has been heated by said contact into a' closedchamber for digesting fibrous material.

'19. A method of treating fibrous material, consisting in placing the same in closed chambers, digesting the material in one of said chambers with acid under heat and pressure, liberating high pressure gas from the last mentioned chamber for a period of.

time, liberating low pressure gas from the last-mentioned chamber for a subsequent period of time, contacting these gases with acid liquor under ressure to absorb the gas and heat the liquor, introducing this heated liquor into the secondV chamber for digesting the material in that chamber, discharging the acid from the rst chamber while retaining the material therein, washing the material with liquid while it is cona liquid to wash the material out of the first chamber.

Executed June 16th, 1926.

AUGUST F. RICHTER.

FRANK A. AUGSBURY.

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