US1991245A - Process for producing cellulose - Google Patents

Description

Feb. 12, 1935. J. DE L A ROZA, 92 1,991,245

PROCESS FOR PRODUCING CELLULOSE Original Filed Dec. 17, 1931 W U a i l g w INVENTOR A TORNEY Patented Feb. .12,

rnoonss FOR rnonuomo oammnosn This invention relates Joaquin Julio de is.

Roza, Sn, Plandome, N. Y., assignor to de la Roza Corporation, Wilmingto Del., a corporation of Delaware Original application December 17, 1931,

Divided and this application Jan- Serial nary 4, 1934, Serial No. 705,210

to the process for producing cellulose, and is a division of my copending application Serial No.

ber 17, 1931.

It has for an object uous treatment of cellulose.

as to accomplish the 581,636, filed Decemto provide for the continbearing material so production of cellulose therefrom at a greatly accelerated rate.

Another object consist s in providing for treatment of cellulose bearing material at a much higher volumetric density than has heretofore been are greatly enhanced.

practical, whereby the efli'ciency and output providing means for uniform penetration of chemical into the raw material prior to heating to maximum temperature, whereby the treatment time is reduced and the quality of the product improved.

Another object consists in providing apparatus which is relatively simple and inexpensive to manufacture and yet highly productive and efll cient in operation.

A further object consists in providing certain improvements in the form,

construction and ardiagrammatically represented when taken in connection which representation,

in the drawing,

with the following description, will set forth my invention for the clear skilled in the art.

In the treatment of understanding of those cellulose bearing materials,

such as wood and various members of the grass family, it has been treating vessels or customary to charge the digesters with a mixture of the fibrous material and chemical solution, in-

troduced together or separately;

the treatment,

to apply heat for and thereafter then discontinue the heat, discharge the contents, and repeat the operation by again charging, etc.

This procedure arising from the has involved serious limitations interruption of treatment at the time of each discharge, from the lack of uniform quality in the product due to defective and uneven penetration the chemical, and from fibrous of the raw material by the limited amount of cellulose bearing material treated in a given vessel or digester at a single time. My invention overcomes these limitations by for continuous treatment which may proprovidceed for hours or months, if desired; and for greatly increasing the the charge during charge containing dry material per cubic tially the. maximum in treatment. about nine pounds of bone volumetric density of Heretofore a foot has been substan-' the case of wood, and

about half of that in the case of bagasse, cornvides for charging to a volumetric density of, say, twelve to fifteen, or even twenty pounds of bone dry material per cubic foot.

Referring to the drawing, which includes one diagrammatic figure, I a treating vessel or digester is denoted by 1. The form of this vessel is quite unusual but its general construction may substantially follow any well known or approved kind of digester. It should be provided with any usual or desirable equipment such, for instance, as gauges, valves, thermometers, 'heating appliances, etc. The vessel may either be stationary or of the rotating type.

At one end a valve 2 is provided which is operable by the handle 3 for discharging the contents from the vessel. This valve may be of usual or suitable form, construction and operation.

The representation of the vessel in the drawing is broken away intermediate its ends to ind icate that it is intended to have a greater proportionate length than shown in the drawing;

and I may say that I prefer to make this vessel of relatively great length and small diameter. This may be illustrated by a length of, say, a few hundred feet, and a diameter of, say, a few feet. Such a proportion greatly facilitates the continuous procedure which features my invention and tends to insure that all the material is uniformly treated and occupies a uniform period of time vessel. It will be understood that the particular dimensions and proportions of the vessel may be varied to suit different factors arising from various methods of treating various materials.

during passage through the treating,

The end of the vessel opposite the valve 2 is provided with an opening 4 which is in com- The larger end of the tube communicates with a cylinder 6 in which is located a piston 7 that is designed to be 'reciprocated by suitable mech-'- I anism, not shown. Two positions of the piston are representei by way of-example, in full and dotted lines. This mechanism is illustrated as one of many suitable kinds adaptable for the purpose of feeding the material.

The cylinder 6 has a port 8 which is in reg-' ister with a feedor hopper 9,, which may be of any well known or a proved form. Q

in which are located strainers 13 and 14, check valves 15 and 16, and manual valve 17. The check valve 15 operates so as to permit entry into the vessel and the check valve 16 operates so as'to permit movement from the vessel. The valve 17 is operable so as to permit movement in either direction. The particular construction and arrangement of these circulating andfeeding parts may, of course, be varied to suit different conditions. In the drawing 1 have shown only one pipe 12, but it will be understood that additional pipes, correspondingly arranged, may be provided to connect additional ports in the vessel. As the construction of such additional pipes and ports would, naturally, be the same as that shown, it is deemed unnecessary to illustrate them. This pipe 12 permits circulation of the solution from near the discharge end of the vessel to near its inlet end and thus facilitates the action of the chemical and the movement of the material. It also has a certain advantage by way ofproviding means for affecting the temperature within the vessel. The valve 17 may be used for the injection of chemical into the vessel, as may be required,

- from the vessel of an excess of chemical, if

conditions call for it, though it will be understood that, during the operation of the apparatus, the valve 17 is normally closed. The strainers 13 and 14 are calculated to withhold the passage of any large particles of the material through the circulating pipe '12.

vThe parts hereinabove mentioned are intended to be connected by suitable means such as, for example, flanges and bolts, which are diagrammatically represented in the customary way, and which it is regarded as unnecessary to designate by reference numerals.

In operation, the fibrous cellulose bearing ma-' terial, such as bagasse, cotton linters, cotton stalks, flax stalks or waste, wood, or any of the suitable. undergrowth-woods, grasses orcanes, etc., may be broken up or shredded in any of the many well known or approved manners and conveyed, for instance by a conveyor belt, to the hopper 9. This material may be mixed with the desired chemical solution, as by use of a tank or spraying apparatus, prior to its conveyance to the hopper; or it may be mixed with such solution at the time it is deposited in the hopper; or otherwise. I prefer to spray it as it enters the hopper because, the less the mixture is exposed to the air, the less will be the oxidation.

The material is continuously passed into the hopper and drops therefrom into the cylinder 6 at a point in front of the piston '7 when the latter is wholly or partly retracted. The reciprocating action of the piston will continuously force the material through the tube toward and into the vessel 1. The frictional resistance of the tube 5 will cause the material to be more tightly compacted orcompressed as it is urged through the tube so that it will enter the vessel in a condition of quite high volumetric density, e. g., about twenty to thirty or more pounds of dry material to the cubic foot. This density will vary according to different conditions existing in different treating procedures, but I ordinarily prefer to usesomething over thirty pounds to allow an abundant mar- ,gin of safety against blow-outs. In order to facilitate this compacting ofthe material, I prefer to, atthe outset, drop a somewhat compact wad of material through .the hopper into the cylinder, which wad will act as a plug in the tube 5 and thusinitiate the compressing or compacting action described. Such a wad may be made either manually or by any suitable compressing device'which is at hand. Compression of the material to substantially the density indicated will cause each successive charge or batch advanced by the piston to act as a sort of plug or cork while in the tube, 5.and the entrance to the vessel 1 so as effectively to prevent any escape of the contents from the vessel back into the tube under the influence of the pressure within the vessel. On the other hand, after each successivebatch of the material has been forced into the vessel, it will expand or break up so as better to circulate and 'intermix with the chemical solution. In these respects, the relative cross sectional size of the apparatus at the cylinder v6, the opening 4 and the body of the vessel 1 are of some importance with respect to the best operation of the apparatus and I have found that the said proportions, substantially as shown in the drawing, are satisfactory although, of course, various changes in these factors as well as in the particular shape of the parts may be made while retaining the apparatus in operative form and arrangement. It will be observed that, in the drawing, the diameter of the body of the vessel 1 is about twice the diameter of.

the opening 4, so that the cross sectional area of the former would be about four times that of the latter. Experimental test and practical operation has proved this ratio of one to four to be well within the preferred limits which, for the best operation, should not greatly vary from the ratio named.

This action of the piston on the material not only compacts and moves the material toward and into the vessel 1, but it also brings about a thorough mixing of the chemical solution with. the fibrous material by forcing the chemical through pressure into the cells, so as to insure that the chemical has access to' and reaches every portion of the material, prior to heating to maximum temperature, thereby preventing injury to the material, expediting the operation, and improving the quality of the product.

As the material is thus compacted ,and forced through the tube 5, the action ma become so severe as to press or squeeze some the chemical solution out of the material: in which event this solution may escape: backwardly between the piston and the walls of the cylinder 6.

At the outset of the operation the discharge valve 2 is closed and it is retained in closed position until the vessel has been charged to the intended degree or density, which condition may be indicated by a suitable thermometer pressure gauge or other recording instrument provided on the vessel. When this stage is reached, the vavle 2 is opened and regulated so that it remains open the proper amount to insure the same rate of discharge, during the continuous operation of the apparatus, as the rate of charge of the vessel through the tube 5.

It should also be said, though it will probably be understood, that the heating appliances for the vessel are set in operation at the outset of the procedure so that a proper treating temperature is maintained within the vessel, as by injection of steam, other approved way.

menace iacketing, electricity, or, any If the vessel is of the rotatingtype, as hereinahove indicated, the rotary motion, which may be either continuous in one direction or oscillatory, will have a substantial tendency to agitate the contents of the vessel and thereby promote the treatment.

It will be seen that. as already indicated, chemical solution may be admitted or discharged through the valve 1'7 to or from the vessel 1, so that the predetermined and desirable proportionof the mixture of material and chemical solution, is maintained in the vessel.

It will be observed that this apparatus, through the cooperation of the feeding device and the frictional resistance of the tubular inlet, compacts the material to such a density as satisfactorily to establish a seal during operation while permitting the continuous feed of the material into the digester. The apparatus also permits digestion at a very high density which promotes .eiilciency by, among other things, preventing the fresh material from mixing with the partly digested material; and promotes economy in various respects including a saving in heating medium, chemical, recovery'processes, radiation losses, labor, time, and avoidance of the re-use of chemical in the form of black liquoror the like. The form of inlet which I have shown complements the form of feeding device to enable a very rapid compacting of the entering material and, thus, the prompt formation of a very satisfactory seal, while likewise permitting. the ready passage ot. the material through the inlet. and into the digester proper.

The above described apparatus and method provide for a continuous procedure whereby the material is fed into the hopper 9 and forced by the piston 7 through the treating vessel under predetermined conditions as to'treating chemical, volumetric density, and temperature or pressure. I contemplate that the apparatus may be operated both day and night for any reasonable period of time. 7 The treated material, as it is discharged from the vessel, may be subjected to the ordinary steps, or to a further chemical treatment, or may be shipped to some other mint for use or further treatment. In

case an additional treatment under the action of chemical and temperature is desired, the discharged material may be fed into another simi= lar apparatus and wntlnuously treated as here inabove dmcrihed.

I do not intend the invention to be limited to the particular kind of cellulose 1-1 :1 "i ma terial treated, or as to chemical or temmrature employed, but intend the same to have broad application as a continuous procedure in the manufacture of cellmose, preferably under con= ditions of very. volumetric density oi charge. Furthermore, it will he undo mi that various changes may he rmomd to m the form, commotion, and orrmgommt oi the several parts, and in the stage followed, without do from the spirit and scene oi my inven tion; and hence I do not intend'to he limited to the details herein shown or described, except they may in the clothes.

thus described my invention, What l;

claim is: v

l. A continuous method of producing cellulose including the sten oi treating cellulose imaterial with a chemical in a digestion lag a volumetric density in excess of 12# per cubic foot (dry basis) g 2. A continuous method of producing cellulose including the steps of continuously charging and discharging a digesting vessel with cellulose 5 bearing material and maintaining the charge in said vessel at a volumetric density substantially in excess of 12#. per cubic foot (dry basis).

3. A continuous method of producing cellulose including the step of charging the cellulose m bearing material successively through compression and digesting steps and treating the material with a chemical in the digestion step at a volumetric density in excess of l2# per cubic foot (dry basis). 15

4. A continuous method of producing cellulose comprising the step of charging the cellulose bearing material in a compressed column to a digestion stage wherein the column is disintegrated, and treating the material with a chemi- 20 cal while maintaining said material at a volumetric density in excess of l2# per cubic foot (dry basis). g

5. A continuous me hod of producing cellulose including the steps of charging the cellulose 25 hearing material in a compressed column to a digestion stage wherein the column is disintegrated, and exhausting the occluded air from the material in the compression step, and treating the material with a chemical at a volumet- 3o ric density in excess of l2# per cubic foot (dry basis) in the digestion step.

6. A continuous method of producing cellulose including the steps of spraying the material with the liquid at a low temperature and exhausting the occluded air from the material in a compression. step, introducing the material thence into, an elongated digestion step and subiecting the material to the digestion action of chemicals at a higher pressure relatively lower than the pressure existing in the compression step.

l. A continuous process for digesting fibrous or cellular material comprising the steps of adding a digesting liquor in a preliminary step, passing the material thence to a digesting step in which the material is subjected to a digesting items at a higher temperature than that in the ou m 1-: step, and maintaining the material under digmtion at a volumetric density in excess oi 121% per cubic feet (dry basis) during. the digestion therwi.

o. A continuous method oi continuously dinesting fibrous or cellular material comprising the steps of changing the material to be digested 5, to a digestion siege, adding a chemical thereto, checting the digestion oi the material at a vol= umetric demity excess of l2#' per cubic loot (dry basis), and discharging the digested material irons. the digmtlon stage, and controlling m the input and dlscharge of material to be oilgcsted to maintain predetermined digestion conolitions. w

e. A mmhod oi" continuously digesting fibrous @l' cellular material comprising the steps oi the material to digmted to a di section stage, adding a chemical thereto, sheet the digestion oi" the material at a volumetric density in oi per cubic foot (dry temperature and at a M

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