US2884147A - Method of shipping celulose pulp in bulk - Google Patents

Description

DESTINATION April 28, 1959 METHOD OF Filed June 14, 1957 FORMING CONTINUOUS PARTIALLY D EWATERED SHEET OF PULP SHREDDING PULP SHEET INTO PARTICULATE FORM LOADING PULP IN PARTICULATE FORM INTO CARGO SHIP RESLUSHING OF PULP IN sI-IIP's HOLD AT HYDRAULIC UNLOADING OF PULP DEWATERING OF UNLOADED PULP CONVEYING OF PULP TO STORAGE OR CONVEYING STATION R. o. HUNT T AL 2,884,147

SHIPPING CELLULOSE PULP IN BULK 2 Sheets-Sheet l INVENTORS REED o HUNT EI NARW. ERICKSON I WILBUR J. LOWNDES JAMES D. WETHERN JAMES COMA- R. o. HUNT ETAL METHOD OF SHIPPING CELLULOSE PULP IN. BULK Filed June 14, 1957- April 28, 1959 I 2SheetsSheet2 Du S 0 N T 0 N SN A W m O lumnu wwc o mss DR EE ET 'IIIIIIIII III (I), III III IIIIIIIIIIII I ATTQRNEY nited States METHOD OF SHIPPHNG CELLULOSE PULP 1N BULK Reed 0. Hunt, San Rafael, and Einar W. Erickson, Hillsborough, Calif., and Wilbur J. Lowndes, Kent, James D. Wethern, Camas, and James G. Coma, Vancouver, Wash., assignors to Crown Zellerbach Corporation, San Francisco, Calif., a corporation of Nevada Application June 14, 1957, Serial No. 665,799

6 Claims. (Cl. 214-152) improved method whereby pulp in large quantities can be transported over long distances at minimum cost. More specifically stated, the general object of the invention is to provide a satisfactory and practical method fortransporting or shipping pulp in bulk so that the pulp can be produced at the source of the raw material for the pulp, and then, by employment of the improved method of the present invention, can advantageously be transported to desired and more suitable locations with respect to the consuming market for conversion there into the paper or other products for which it is to be used. Heretofore various methods have been used to some extent for transporting pulp, in one form or another, from the raw material sources. In general such methods have involved cumbersome and relatively expensive operations. One such Well known method consists in shipping the pulp in sheet form, the sheets of pulp being substantially died in order to have a dry fiber content of approximately 90%. Such pulp sheets are shipped either in baled form, the dried sheet being rolled or cut into sections for baling, or the sheets are folded several times and piled on pallets and transported in that manner. In either case considerable labor is involved in the handling, carting and shipping of such pulp sheets. Subsequently, upon arrival at destination, in order for the pulp in this form to be utilized, the substantially dry pulp sheets must be mechanically defiberized in the presence of Water, thus, for example, defiberized in heaters. One of the disadvantages of this defiberizing of the dry sheets is that some detrimental effect on the fibers results.

A particular object of the present invention is to provide an improved method of shipping pulp in bulk which will take the place of the shipping of the pulp in sheet form.

A related object is to provide an improved method of shipping pulp which will considerably reduce the amount of manual labor heretofore required in the handling of the pulp for shipment, and thereby reduce the cost of pulp shipments.

Another object of the invention is to provide a practical method of handling and shipping pulp in bulk form which will eliminate the necessity of using substantially dried pulp sheets inasmuch as such sheets then require subsequent mechanical defiberizing in the presence of water, as mentioned above.

A further and important object of the invention is to provide an improved method of shipping pulp in bulk with the employment of cargo ships, in place of having such shipments made by rail or motor transport, and to enable the transporting of the pulp to be handled on the basis of volume instead of on the basis of gross weight while enabling maximum capacity of shipboard space to be utilized at minimum cost.

2,884,147 Patented Apr. 28, 1959 The manner in which these objects and other advantages are achieved through the method of the present invention will be readily understood from the following explanation and description. Reference is to be made to the accompanying drawings in which:

Figure 1 is a diagram chart listing the successive steps involved in the carrying out of the method or process of the invention;

Figure 2 is a diagrammatic cross sectional elevation of a compartment in the hold of a cargo ship showing the same employed for the transportation of pulp in accordance with the present invention;

Figure 3 is a diagrammatic sectional elevation similar in part to Figure 2 but drawn to a larger scale to indicate more clearly the water-distributing nozzles at the bottom of the hold in the cargo ship together with the outlet through which the slushed pulp is pumped from the ships hold in the unloading of the pulp cargo; and

Figure 4 is a fragmentary sectional elevation, drawn to a still larger scale, showing an agitator in the bottom of the compartment in the ships hold employed as an aid in the slushing of the pulp and in preventing clogging of the outlet and pump.

As indicated in the chart of Figure 1, the first step in the method, which occurs at the location where the pulp is produced, involves the partial dewatering of the pulp with the forming of a continuous blanket or sheet from the pulp. Thus the pulp, after standard processing operations in the pulp mill, is delivered by pump or gravity head in fluid slurry form for the partial dewatering operation. The dewatering operation can be done satisfactorily on a modified Kamyr machine, or a machine corresponding in part to a paper making machine with the drying section entirely omitted. Rotary press rolls are used with the cylinder former to produce a continuous pulp sheet having the consistency of from 20% to 50%, with the preferred consistency range being from 25% to 40%. Such a modified Kamyr machine of the type mentioned, that is, a machine in which no drying, as distinguished from partial dewatering, takes place, is capable of high-capacity production with only a minimum of cellulose damage.

The continuous pulp blanket or sheet is then shredded into particulate form, as the second step in the carrying out of the method. Preferably the last press roll feeds the pulp sheet over a bed plate serving as a breaker edge for the shredding operation. A suitable and satisfactory shredder can be made with a plurality of spaced discs secured on a common shaft. ,T he peripheries of the discs are formed with blunt teeth, preferably spaced from 3 to 6 inches apart in the circumferential direction, the teeth being from /s to /8 of an inch in width and the shredder discs being spaced from /a to 1 /2 inches apart on their common shaft.

The shaft and discs are rotated at sufiicient speed so that the peripheral speed will be adequate relative to the rate at which the pulp sheet is fed over the bed plate to the shredder. For example, with the shredder made as described and with the rate of sheet feed over the bed plate at from 50 feet to 250 feet per minute, the peripheral speed of the shredder discs can range from 1800 feet to 7000 feet per minute, with the preferred speed near 3200 feet per minute. Such a shredder will shred the pulp sheet into particles having their largest dimension from inch to 2 inches and with minimum particle flufiing.

It will be readily understood that shredder performance;v

in general will be governed by the number and spacing of shredder teeth and the speed at which the shedder is operated.

The pulp sheet, as fed to the shredder, is in very satisfactory condition for shredding into the desired particulate form. There is essentially no cellulose a U damage as a result of such shredding. The moisture content of the pulp sheet keeps airborne dust loss to a minimum during the shredding and also during the subsequent handling of the pulp in particulate form. Furthermore, the shredded particles lend themselves readily to subsequent further slushing.

It is important that the consistency of the pulp sheet as it is shredded should be within the 20% to 50% range previously mentioned, or, in other words, that the moisture content of the sheet should not be less than 50% nor more than 80%. Lower moisture content decreases the cellulose quality, makes subsequent further slushing more difiicult, and increases fiber dust problems. On the other hand, higher moisture content will cause increased particle finding as a result of the shredding, and increased fluffing in turn results in decreased cellulose capacity in storage.

The shredder throws the pulp particles preferably into a chute leading to a moving belt conveyor. The pulp is carried on this belt conveyor to a stock pile. A drag conveyor or other means, together with another moving belt, are used for delivering pulp from the stock pile into chutes which lead to compartments in the ships hold when the pulp is to be loaded into the ship.

The particulate form of the shredded pulp lends itself very well to mechanical conveying to and from storage stock piles and to the transport loading site. Mechanical conveying, such as belt conveying, of the shredded pulp is preferable to pneumatic conveying since the latter would aggravate the fiufiing problem and detract from maximum cellulose capacity in the cargo ship.

The cargo ship, by which the pulp, in bulk and in particulate form, is conveyed to the desired location for the plup utilization, has its cargo hold not only preferably divided into separate compartments, but is provided at the bottom with Water-delivery nozzles, whereby water is supplied for slushing the pulp and for forming a pool at the bottom of the pulp mass when the pulp cargo is to be unloaded hydraulically as later explained.

As the shredded pulp is dropped down by the chutes into the various compartments in the hold of the ship, the pulp compacts to a considerable extent under its own weight, since in its particulate form the pulp is compressible. If necessary, a standard ships trimmer is used to fling the pulp into out of the way corners of each hold compartment during the ship-loading operation. A ships trimmer is a device which is well known and is standard ship-loading equipment, and operates to fling particulate material horizontally as it is being loaded into a. ships hold. The depth of the ships hold causes considerably more self-compaction of the pulp to take place than would occur in much shallower bins or compartments, such as those of trucks or railway freight cars. This compaction also is an important factor in the efi'icient utilization of cargo space, and contributes in enabling transportation of the pulp by ship to be carried out at maximum capacity and minimum cost. Generally the shredded pulp containing 50% to 80% moisture (thus with the consistency of 20% to 50% as previously mentioned), will be sufliciently self-compacting in a ships hold to require no further aid in the securing of the desired compaction for transportation. However, if the moisture content is near the minimum limit specified then optionally water may be sprayed onto the pulp by hoses as it is being dumped into the ships hold. In such case, however, the amount of water sprayed onto the pulp must be carefully controlled so as not to give too much compaction, and obviously an excessive amount of Water added to the pulp would considerably increase the bulk density of the mass without a sufiiciently corresponding increase: in the cellulose content per unit of volume. Also, whether any Water is required to be sprayed onto the pulp as the pulp is being loaded into the ship will de pend on the depth of the compartments in the ships.

4: 7 hold which are being filled with the pulp. The loading of the pulp into the ships hold completes the third step in the method, as indicated in Figure 1, and the loaded pulp in each compartment may be considered as indicated at P in Figure 2 with the ships hull indicated at 10 in this figure.

The fourth step in the method takes place after the ship, with its cargo of pulp, arrives at its destination where the pulp is to be unloaded and subsequently converted. Hydraulic unloading of the pulp is an essential feature of the method. in order for the pulp to be unloaded hydraulically from the ship the pulp must be mixed with water to reduce the consistency to such extent that the mixture can be pumped out from the ships hold in a satisfactory and efiicient manner. To accomplish this properly the consistency of the mixture, when it is to be drawn out by the pumps, should be reduced down to from 1% to 9%, the preferred consistency range for such pumping being from 2% to 5%. For this purpose, of reducing the pulp consistency or increasing the amount of water in the mixture, the ship is equipped with water-discharging nozzles 11 (Figure 3) on the inside of the bottom of each hold compartment in which the pulp is carried. These nozzles 11 are mounted on suitable conduits or pipes 12 which in turn are provided with suitable connections (not shown) so that they can be connected by hose lines with a suitable source of water under pressure at the unloading dock. The number of water-discharging nozzles required in the bottom of each compartment will depend on the nozzle water capacity, the compartment size, and the rate at which it is desired to have the reduction in consistency or the slushing of the pulp at the bottom of the compartment take place. The nozzles should be so arranged that uniform slushing takes place in the bottom of each compartment. Also, the velocity of the water jets from these nozzles should be sufliciently high .-to provide enough energy for creating a turbulence in the introduced water in the bottom of the compartment and thus be effective in slushing the pulp as it is contacted by the water from the nozzles. A desirablewater pressure for the supply to the nozzles should be at least about 50 pounds per square inch, and preferably between to pounds per square inch.

For effectively carrying out this slushing of the pulp in the bottom of the compartment, it has also been discovered that there should be a shallow pool, of from 1 to 5 feet in depth, formed in the bottom of the compartment and maintained constantly during the discharging or pumping of the slushed pulp from the compartment. The turbulence in this pool produces an even distribution of the pulp in the pool from the bottom of the pulp mass and the pulp mass gradually drops as a plug into the turbulent pool zone. Generally the existence of this desired pool in the bottom of the compartment will be indicated by the appearance of some water at the top of the sides of the Pulp mass, as indicated at 13 in Figure 2. If it is desired to assist the bottom nozzles in creating and maintaining this pool in the bottom of a compartment additional water may be delivered into the compartment on top of the pulp by means of hoses, alhough it is preferable to have all the water, for maintaining the bottom pool and for slushing the pulp in the bottom of the compartment, delivered through the nozzles at the bottom of the compartment since the turbulence produced by the water from these nozzles is an important factor in obtaining the rapid and thorough slushing of the pulp from the bottom of the pulp pile in preparation for withdrawal by the pump.

Preferably also agitating means, such as the driven rotating propeller indicated at 14 in Figure 4, is provided in the bottom of each compartment to aid in the slushing of the pulp by breaking up any lumps of pulp in the pool, and such an agitator also serves to minimize the possibility of any plugging occurring in the suction linet'othe pump (the pump not being shown), Such an agitator preferably is positioned close to the intake of the suction pipe (indicated at 15 in Figure 4) through which the pulp is drawn by the pump from the bottom of the compartment.

In addition to the stationary water nozzles in the bottom of each compartment, a swing nozzle, indicated at 16 in Figure 3, is also preferably provided in each compartment. Such a swing nozzle helps additionally to wash the last remnants of pulp from the compartment during the completion of the unloading. The use of swing nozzles or rotating nozzles in other installations is well known, as for example, for the washing of the interior of tanks, and a description of such a nozzle therefore is unnecessary here.

The pool at the bottom of each compartment should be constantly maintained during the unloading operation. This can be done by regulating the rate at which the slushed pulp is discharged to correspond with the rate at which water is delivered by the nozzles, or vice versa. Thus if the discharge rate is too low in comparison with the delivery rate of water through the nozzles the fluid pool at the bottom will build up, the jet energy from the nozzles will be smothered, and eventually the slushing of the pulp will practically cease and the pulp plug will merely float on the rising water. On the other hand, if the discharge rate is too high in comparison with the delivery rate through the nozzles, the fluid pool in the bottom of the compartment will gradually disappear, causing the compressed pulp to drop sufiiciently to plug the suction pipe to the pump or else cause water channeling through the pulp from the nozzles to the suction line with very little pulp slushing. Maintenance of the shallow pool in the bottom of the compartment and sufficient turbulence in the pool, with the rate of discharge properly regulated, will enable the pulp to be discharged efliciently while also enabling the consistency of the pulp as discharged to be kept within the desired narrow range previously mentioned.

The discharging pumps deliver the slushed pulp mixture to shore facilities where partial dewatering of the mixture takes place. The dewatering of the unloaded slushed pulp comprises the sixth step in the method, as indicated in Figure 1. This dewatering of the discharged pulp is done in a conventional manner preferably on vacuum deckers, and the consistency of the discharged pulp is increased from to 30% and preferably to about 20%. In other words, the Water content of the slushed pulp is now reduced by such shore facilities to about 80%. The water which is removed from the slushed pulp during this step in the method, (such water frequently being referred to as white water), is preferably utilized by being returned with additional water to the nozzles in the ships hold for the slushing of the remaining pulp there. This reuse of the white water for further slushing operation minimizes fiber loss in the slushing and related dewatering process.

The dewatered or thickened pulp is then generally placed in storage until it is to be converted into paper or into any other cellulosic products for which it is needed. This dewatering of the pulp prior to its final conversion also minimizes the storage tank volume.

Thus the present invention provides a practical and very economical method of transporting large volumes of cellulose pulps from the raw material sources, where the pulps can be prepared, to accessible locations near consuming markets, where the pulps can be more advantageously converted into the desired market products. The invention enables the pulps to be handled in large quantities at comparatively low transportation costs with the expenditure of only a minimum amount of time and labor on the part of the operators in the actual handling of the pulp throughout the entire procedure, and the fact that the pulp is delivered at the destination in a highly 6. satisfactory condition for converting is a further important advantage achieved in the shipping of pulp in the manner herein described and explained.

We claim:

1. The improved method of shipping cellulose pulp in bulk by ship including forming the pulp into a partially dewatered pulp sheet, shredding said pulp sheet into particles, loading the shredded pulp into the hold of the ship, subsequently, at the ships destination point, adding water beneath the pulp mass in the ship so as to reduce the consistency of the pulp at the bottom of the pulp mass to a condition suitable for pumping, and removing the pulp from the ship by pumping the low-consistency pulpv from beneath the pulp mass at approximately the same rate as the rate at which the water is added beneath the pulp mass so as to enable the pulp to be withdrawn from the ships hold without flooding the hold.

2. The improved method of shipping cellulose pulp in bulk by cargo ship comprising forming the pulp into a pulp sheet having a consistency of from 20% to 50%, shredding said pulp sheet into particles, loading the shredded pulp into the hold of the cargo ship, subsequently, at the ships destination point, adding water beneath the pulp mass in the ship suflicient to reduce the consistency of the pulp at the bottom of the pulp mass down to from 1% to 9%, removing the pulp from the ship by pumping the low-consistency pulp from beneath said pulp mass, regulating the rate at which the low-consistency pulp is pumped from the ship and the rate at which the water is added at the bottom of the pulp mass in the skip so as to maintain uniform consistency in the pulp as pumped from the ship, and finally dewatering the unloaded pulp to a higher consistncy.

3. The improved method of shipping cellulose pulp in bulk by cargo ship which comprises forming the pulp into a pulp sheet having a consistency of from 25% to 40%, shredding said pulp sheet into particles having their largest dimension from A of an inch to 2 inches, loading the shredded pulp by mechanical means into the hold of the cargo ship, subsequently, at the ships destination point, adding water beneath the pulp mass in the ship suflicient to reduce the consistency of the pulp at the bottom of the pulp mass down to from 2% to 5%, removing the pulp from the ship by pumping the lowconsistency pulp from beneath said pulp mass, regulating the rate at which the low-consistency pulp is pumped from the ship and the rate at which the water is added at the bottom of the pulp mass in the ship so as to maintain uniform consistency in the pulp as pumped from the ship, dewatering the unloaded pulp to a higher consistency suitable for storage preparatory to being converted, and reusing the water obtained from said dewatering by returning said water to the bottom of the pulp mass in the ships hold.

4. In the shipping of cellulose pulp wherein the pulp in particulate form is transported by cargo ship, the improved method of unloading the pulp at the ships destination point which includes adding water beneath the pulp mass in the cargo ship sufficient to reduce the consistency of the pulp at the bottom of the pulp mass down to from 1% to 9%, removing the pulp from the ship by pumping the low consistency pulp from beneath said pulp mass, and regulating the rate at which the low consistency pulp is pumped from the ship and the rate at which the water is added at the bottom of the pulp mass in the ship so as to maintain uniform consistency in the pulp as pumped from the ship and so as to enable the pulp to be withdrawn from the ship without requiring the flooding of the ships hold.

5. In the shipping of cellulose pulp wherein the pulp in particulate form is transported by cargo ship, the improved method of unloading the pulp at the ships destination point which includes adding water beneath the pulp mass in the cargo ship suflicient to reduce the consistency of the pulp at the bottom of the pulp mass down to from 2% to 5%, maintaining a pool of water of a depth of from one to five feet beneath the pulp mass and providing means for keeping saidpool agitated so as to aid in slushing the pulp at the bottom of the mass, removing the pulp from the ship by pumping the low-consistency pulp from beneath said pulp mass, and regulating the rate at which the low-consistency pulp is pumped from the ship and the rate at which the water is added to the pool at the bottom of the pulp mass in the ship so as to maintain uniform consistency of the pulp as pumped from the ship and so as to enable the pulp to be withdrawn from the ship without the flooding of the ships hold.

6. The improved method of shipping cellulose pulp in bulk which comprises forming the pulp into a partially dewatered pulp sheet having a. consistency of from about 20% to 50%, shredding said pulp sheet into particles having their largest dimension from of an inch to 2 inches, loading the shredded pulp into the hold of a cargo ship, spraying the pulp with water if necessary during the loading of the ship to reduce the consistency to not less than approximately 20%, subsequently, at the ships destination point, adding water beneath the pulp mass in the ship so as to reduce the consistency of the pulp at the bottom of the pulp mass to a condition suitable for pumping, maintaining a pool of water of from one to five feet in depth beneath the pulp mass in the ship and providing means for keeping said pool agitated to aid in slushing the pulp, removingv the pulp from the ship by pumping the slushed, low-consistency pulp from beneath said pulp mass, regulating the rate at which the pulp from beneath said pulp mass is pumped from the ship and the rate at which the Water is added to the pool at the bottom of said pulp mass so as to maintain uniform consistency in the pulp as pumped from the ship, and then dewatering the unloaded pulp to a higher consistency suitable for storage preparatory to being converted.

References Cited in the file of this patent UNITED STATES PATENTS

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