US2045818A - Method of and apparatus for producing paper pulp - Google Patents

Description

June 30, 1936. F. w. ADAMS ET AL 2,045,813

METHOD OF AND APIARATUS FOR PRODUCING PAPER PULP Filed June 26,- 1934 2 She ets-Sheet 1 Egi ' June 30, 1936. I F. w, ADAMS ET AL 2,045,818

METHOD OF AND APEARATU S"FOR PRODUCING PAPER PULP Filed June 26, 1954 2 Sheets-Sheet 2 //\/l/ENTORSI -%4'ATTORNE Patented June 30, 1936 METHOD OF AND APPARATUS FOR PRODUCING PAPER PULP Frederick W. Adams, Stoneham, Mass, and George S. Witham, Jr., Lincoln, N. H.

Application June 26, 1934, Serial No. 732,456

8 Claims.

This invention relates to the production of chemical woodpulp. It has for its general objects to improve the quality of the pulp obtained from a given grade of wood, and to effect economies in the pulp producing process.

As is well understood by those skilled in this art, the commercial methods of producing pulp of this character include the cooking of wood chips in a large digester. At the completion of the cook, the pulp and digester liquor are discharged into a pit or vat, the discharging operation being commonly referred to as 'blowing the digester, and the pit or vat usually being called a blow pit. When the charge is ready to be blown, it is under considerable pressure, say for example, between 40 and 120 lbs. per square inch, and its temperature is high, ranging from, perhaps, 270 to 350 F. The blowing operation consists simply in opening the blow valve and allowing the pressure in the digester to force the entire charge through a pipe line into the blow pit, where the pressure is substan tiallyatmospheric. Consequently, when the pulp is discharged, the pressure on the fibers is released very quickly. This sudden release of pressure produces an effect on the fibers similar to that purposely created in a similar manner in some industries for the purpose of exploding the product under treatment. In the case of pulp, however, the result is to weaken the fiber and, consequently, to reduce the strength of the paper ultimately made from the fiber.

In addition to this effect, the practice just described also results in producing large volumes of steam which are discharged into the surrounding atmosphere through the vomit stack leading from the blow pit. Small proportions of sulphurous acid are carried ofi with the steam and gases so evolved and create a nuisance, due partly to their disagreeable smell and partly, also, to their tendency to attack metal roofings and other exposed metal parts of adjacent buildings.

The present invention is especially concerned with these considerations, and it aims to improve processes of handling the pulp in connection with the cooking operation with a view to avoiding the objections just described and conserving the heat contained in the cooked charge, and which, according to the customary process, is wasted.

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

In the drawings,

Figure 1 is a side elevation, partly in section, showing somewhat diagrammatically those features of an apparatus with which this invention is-more especially concerned;

Fig. 2 is an end view on a larger scale of the 5 float operated valve illustrated in Fig. 1; and

Fig. 3 is a vertical, sectional view of parts of the apparatus shown in Fig. 1.

The apparatus illustrated in the drawings comprises a digester 2, from the bottom of which the usual pipe line or blow line 3 leads into the blow pit 4. Included in the blow line is the usual blow-oil valve 5. So far as these features of this arrangement are concerned, they may be of any usual or convenient'iorm. According to the present invention, an injector 6 is included in the blow line 3, and the intake leg 1 of this injector leads into a well or reservoir 8 which iskept constantly filled to a substantially predetermined level with cold water the valve fails, for any reason, to operate properly.

When the cook has been completed and the valve 5 is opened to blow the charge, the kinetic energy of the outgoing mixture of pulp and waste digester liquor flowing through the injector creates a suction in the intake leg 1, serving to cause a flow of water from the well 8 through the leg 1 and into the injector where it becomes mixed with the pulp and digester liquor flowing through the pipe line 3. By selecting an injector of a design and capacity suited to the requirements of the individual digester with which it is to be used, and properly controlling the head through which the cooling water must be raised, I the proportion of water mixed with the outgoing charge can be predetermined within limits surficiently accurate for all practical purposes. The quantity of water so mixed with the discharged stock should be sufficient to prevent the forma tion of any objectionable quantity of steam during practically the entire blow. When the valve 5 is first opened there is a brief instant during which the discharged stock will not be mixed with water, but this interval of time is only momentary, as will readily be appreciated, and is simply long enough to enable the flow of stock to set up the necessary vacuum required to start the flow of water through the injector. There; after the stock will be dischargedinto the blow pit in a hot condition but at a temperature below the boiling point'of water. With this arrangement, therefore, the explosion of the fiber, and the consequent weakening action on it, is avoided and the creation of large volumes of steam also are prevented.

The mixing of the water with the discharged stock serves not only to cool the pulp, as above described, but it also initiates the pulp washing operation, the water added to the stock being utilized for this purpose. In addition, it permits the washing of the pulp at a higher temperature than that ordinarily used so that this operation is made more effective, more uniform, and proceeds more rapidly. Thus the heat which has been wasted by former processes is conserved and made toserve a useful purpose.

The foregoing operations are typical of those used in the production of chemical wood pulp by the sulphite process. The invention is equally applicable to the sulphate and soda processes. In the latter, however, the water usually will be replaced with black liquor. Here, the invention produces the additional advantage of assisting in the evaporation of the water constituent of the liquor incidental to the usual recovery process.

Preferably a check valve [4, Fig. 3, is located at the intake port of the injector, or at some point in the intake leg 'I, where it will prevent any flow downwardly through this leg.

While we have herein shown and described a procedure embodying this invention which is typical of one process of producing pulp, and an apparatus suitable for use in said process, it will be evident that the invention may be embodied'in other forms and practiced in other ways without departing from the spirit or scope thereof.

Having thus described our invention, what we desire to claim as new is:

1. The combination with a pulp digester, a blow-off line leading therefrom and a blow-off valve in said line, of means for mixing a sumcient quantity of a suitable liquid with the charge of stock and waste liquor while the stock is flowing through said lineto prevent any substantial explosion of the fiber as the latter is discharged from said line.

2. The combination with a pulp digester, a

blow-oil line leading therefrom and a blow-ofl valve in said line, of means for mixing a sum-- cient quantity of a suitable liquid with the charge of stock and waste liquor while the stock is flowing through said line to prevent the discharge of anysubstantial quantity of steam from said line during the blowing of a charge.

3. The combination with a pulp digester, a blow-oi! line leading therefrom and a blow-off valve in said line, of an injector in said line, and 10 a supply of relatively cool liquid with which the intake leg of said injector is connected.

4. The combination with a pulp digester, a blow-off line leading therefrom and a blow-oil valve in said line, of an injector in said line, and 15 7 means for conducting relatively cool liquid to the intake port of said injector.

5. The combination with a pulp. digester, ablow-off line leading therefrom and a blow-off valve in said line,of an injector in said line, a '20 well for holding a supply of relatively cool liquid, an intake pipe leading from the intake port of said injector into said well, and a check valve in said pipe serving to prevent any substantial flow of liquid through the pipe from the injector to. the well.

6. That improvement in methods of producing chemical wood pulp, which consists in cooking the pulp, blowing the charge at the end of the cook, and causing the kinetic energy of the charge to mix a cooling liquid withthe outgoing charge before the charge is liberated.

7. That improvement in methods of producing chemical wood pulp, which consists in cooking the pulp, blowing the charge at the end of the cook, and causing the kinetic energy of the charge to mix a suiiicient proportion of a suitable cooling liquid with the outgoing charge, while 4 said charge is still under pressure, to substantially prevent the discharge of steam at the final delivery. 7

8. That improvement in methods of producing chemical wood pulp, which consists in cookin the pulp, blowing the charge at the end or the cook, and, during said blowing operation mixing a suflicient proportion of relatively cool liquid with the stream of pulp 3am discharged to prevent explosion of the fiber upon its final delivery. FREDERICK W. ADAMS.

GEORGE S. WI'I'HAM, Jn.

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