US3112634A - Mixing tank - Google Patents

Description

N. KLYKKEN Dec. 3, 1963 MIXING TANK Filed July 2, 1962 N mm K mu WK 5 L m ATTORNEY.

United States Patent Office ddlld i Patented Dec. 3, 1%53 3,112,634 MEXENG TANK Nils Klyldren, Glens Falls, N.Y., assign-or to The Sandy Hill iron & Brass Works, Hudson Fails, N.Y., a corporation Filed July 2, 19-52, Ser. No. 2%,778 8 (llaims. (Ci. 68181) My invention relates generally to new and useful improvements and refinements in an apparatus for continuous chemical treatment, such as chlorine bleaching of wood pulp and the like, providing for a more complete and effective intimate mixing of the pulp suspension and the bleaching agent, preparatory to the passage of the resultant mixture to the next succeeding equipment, such as a bleach tower, the process comprehending the relation of several steps, and the apparatus envisioning features of construction and arrangements or" parts adapted to efiect such steps.

During the past few years, the paper industry has become increasingly aware of the importance of the chlorine stage in papermaking and has become greatly concerned with the aggravating problems of incomplete mixing. The instant invention envisions an effective dual-compartment construction to cope with this problem.

The main characteristic feature of the present invention lies in the fact that the pulp to be treated with chlorine or the like is continuously introduced, together with the chlorine, into a two-part circulating means comprehending a rising pipe or vessel through which the chlorine treated pulp moves upwards as it is circulated in a first part and is directed upwards into a second part where it is further circulated and thence deflected downwardly and is continuously removed from said second part after a suitable reaction period.

Herein, a lower or primary compartment of the structure provides a generally horizontal circulation by means of a circulation impeller, same having the advantage of producing a strong horizontal circulation to effectuate mixing of the stock, and an upper or secondary compartment, communicating with said lower compartment and having a circulation impeller disposed therein to provide a combination generally horizontal and vertical circulation and an additional mixing function.

A primary object of the construction is to provide means insuring the complete mixing of the bleaching agent and the pulp. By means hereof, any bleaching agent bubbles remaining in the stock following the mixing process in said lower compartment are dissolved upon the passage of the stock therefrom to the upper compartment through the single aperture between and centrally of the two compartments which is so strategically located as to lead the stock passing from the first compartment directly into the eye of an impeller within said upper compartment and to insure that no stock will by-pass the impeller wherefor additional mixing is guaranteed.

in the mixing of pulp and chemicals, a vigorous circulation is required in the mixing vat or container. Many of the known prior art constructions employ discs, mounted either vertically or horizontally, as the rotating elements. Others employ propellers, or specially-shaped rotors. The rotating element for all such machines serves two basic purposes: it circulates the pulp and the chemical, wherefore it may be denominated as a pump, While at the some time, it completely disintegrates the larger particles of the pulp and mixes them more thoroughly with the chemicals, Wherefore it may also be dominated as a mixer or agitator.

The structure hereof offers the advantage that the mixing means of the pair thereof may be, if desired, operated independently of each other.

Desirably, all of the stock will be part of a continuous flow pattern wherein all portions of the pulp and chemical will be caused to pass repeatedly through a pair of zones of action with the aid of discs or impellers which are disposed in separate, but interconnecting, compartments and which discs or impellers are disposed in planes at right angles as to each other.

By the use of the impeller or agitator in connection with the lower or primary compartment, the normal circulation achieved is a vertical type turbulence in that the pulp and chemical are thrown out by the vanes or impellers and pumped into the lower compartment to assume a circulatory motion along a generally horizontal, though slowly ascending, axis.

By the use of the impeller or agitator in connection with the upper or secondary compartment, the normal circulation achieved is a horizontal type turbulence in that the i ixed pulp and chemical are funther mixed and pumped in the upper compartment along another generally horizontal though slowly descending axis.

A zone of turbulence is established directly in front of each of the impellers in which. the pulp and chemical are swirled and generally subjected to a violent fraying action wherefore a quantity of stock, having been subjected to the mixing action in seriati-rn, first within one compartment and then within the other, is assured of a higher degree of agitation and mixing than has been heretofore obtainable. This is an especially desirable feature because of the conflicting requirements of distribution and mixing.

As a further distinct advantage hereof, I provide a dual compartment construction wherein communication between the upper and lower compartments is provided by means of a neck of restricted size, so positioned as to project the stock mixture from the lower compantrnen-t directly into the eye of an upper impeller disposed within the upper compartment, thus insuring that no stock can bypass the said impeller to the end that any bleaching agent bubbles remaining in the mixture as it passes into the upper compartment will be additionally mixed in the upper compartment.

Additionally, the neck afiording communication between rthe upper arid lower compartments and being constricted as aforesaid, restricts the quantity of the mixture admitted into the upper compartment, with the remainder of the mixture being forced to remain in the lower compartment for additional circulation and mixing.

Still a further object hereof is to provide a symmertical construction which will afford a good mixing action throughout the entire area of each of the respective compartm nts, even in mixing tanks of greatly increased diameters.

Stated otherwise, the fluent material is subjected to a strong turbulence by the lower impeller and flows in a horizontal path past a flow obstruction disposed within the lower compartment where this horizontal circulation is continued, the how obstruction serving additionally as a bafile to direct certain of the stock upwardly in circulatory motion through an opening of restricted size leading to the upper compartment where the stock is subj ected by an upper impeller to both vertical and horizontal components of flow to insure a further complete mixing action.

Another of the primary purposes hereof is to provide structural and operational improvements in devices of the class to which reference has been made, which improvements not only simplify the structure as such, it being a unitary, self-contained construction, but also provide important, distinct advantages in strength, durability and the like.

The characteristic features which are considered to be novel with this invention, as to its construction and organization, vill be better understood from a considera- '2 a tion of the following detailed description forming a part of this specification, and annexed hereto, when read in conjunction with the illustrations in the accompanying drawing, wherein like characters of reference are cur ploy-ed to designate like or corresponding par-ts throughout the several views and in which:

FIG. 1 is a vertical sectional View of the apparatus incorporating the structure of the invention; and

FIG. 2 is a sectional view taken on the line 22 of FIG. 1.

In said drawing annexted hereto and forming a part of this specification, I have shown but one embodiment of my invention which is deemed preferable. It is to be understood, however, that changes and modifications may be made in various respects and within the scope of the appended claims without departing from the spirit of the invention.

Briefly, and in its broadest aspect, my invention comprises the following principal parts:

A two-chamber circulating tank,

A flow obstruction in the lower chamber,

An impeller in the lower chamber, and An impeller in the upper chamber.

In the following description and claims, various details will be identified by specific names for convenience. These names, however, are intended to be as generic in their application as the art will permit.

Referring now to the drawing more in detail, I have shown, in FIG. 1, in section, a mixing tank or housing comprising a generally cylindrical outer wall or shell 1-9 with a major vertical axis and having a lowermost horizontally-disposed bottom wall or floor 12 and an uppermost roof 14 of generally inverted dish-shape at opposite ends thereof so as to provide an enclosure therewithin. Said mixing tank may be of any desired diameter and height.

Outer wall 14), bottom wall 12 and uppermost roof 14 of the structure will preferably be formed from steel plate.

They may be made in flanged sections as a practical convenience suitable for being bolted, riveted or otherwise secured together in place when the tank is set up.

Outer wall 14 bottom wall 12, and roof 14 will be lined on their inwardly-facing surfaces with a liner of ceramic tile 16 or equivalent.

I have found that one-half inch steel plate lined with three inch tile will produce a structure of desired strength which will resist the corrosive action of the bleaching agent and pulp mixed therein.

It will be apparent, however, that both the materials used and the dimensions thereof may be varied dependent upon the characteristics and quantities of the components being mixed.

The tank or housing interior is divided generally into a lower or primary mixing compartment 2t? and an upper or secondary mixing compartment 22 by means of a frusto-conical dividing wall 24 secured at its outer peripheral edge to the inner face of the outer wall It? of said tank or housing and provided with a centrally-located vertically-extending circular neck 26, through which a central opening 28, of restricted size, extends to afford communication between the two said mixing compartments.

Dividing wall 24 and neck 26 thereof will preferably be formed from steel pltae which will be lined on its opposite surfaces with ceramic tile 30, as shown. As with the outer housing, other materials may be substituted to meet the requirements of a particular mixing operation.

Said opening 28, being constricted, will limit the amount of the stock which may pass from said lower mixing compartment to said upper mixing compartment, thus insuring a more complete mixing of the stock, as will be subsequently more fully explained.

The upper wall or root 14 may be reinforced with radially arranged steel struts 1) in conventional manner.

a trance An additional means of egress and ingress into the lower compartment may be provided in the form of a conduit 23 extending thereinto through the side wall member, as shown.

in the lowermost portion of lower compartment 20, a flow obstruction, generally indicated by 4t), is provided, same being of generally circular configuration and rising upwardly from bottom wall or floor 12 on the mixers vertical axis and constructed with an outermost verticallyextending main cylindrical wall 4-2 capped by a conicallyshaped top wall 44 and including, additionally, a pair of outwardly-extending walls 45 and 4-3 tangentially joined at their inner ends to approximately diametrically-opposed sides of a lower half-portion of the vertically-extending cylindrical wall and converging toward each other and joining at their outer ends in the form of a so-called wing-like extension.

A horizontally-disposed roof 5%) extends outwardly from main cylindrical wall 42 in manner to be disposed between outwardly-extending walls 46 and 48 of the said wing-like extension, said roof 59 being spaced upwardly of the horizontal plane of bottom wall 12 and downwardly of the horizontal plane defined by the upper extremity of main cylindrical wall 42.

Preierentially, but not obligatorily, the wall members of the flow obstruction device will be of ceramic tile or like material, same having been found to be especially desirable for the practice of the invention in view of its capacity to withstand the injurious action of the normal constituents of the fiuent material employed herewith, particularly the bleaching agents, and to be readily, quickly and easily cleaned.

interiorly of main cylindrical Wall 42, top wall 44 and the walls of the wing-like extension, concrete 52 or equivalent reinforcing material may be provided to offer solidarity to the unitary llow obstruction.

By means of such flow obstruction, centrally of the tank, an upwardly open annular flow channel above bottom wall 12 is provided therearound.

At its lowermost portion, said cylindrical outer wall 1d, is cut away at one arcuate portion thereof, and generally tangentially-arranged and converging outer wall extensions 11 and 13 are substituted therefor, said wall extensions merging smoothly into said cylindrical wall 10.

Interiorly of said outer wall extensions 11 and 13, complemental generally tangentially-arranged tile wall extensions 17 and 13 of the ceramic tile liner 16 of said cylindrical outer wall will each merge into said ceramic tile liner 16 on diametrically opposite sides of the housing, and will converge generally toward each other, as shown.

Between the respective extensions 11 and 17 and extension 13 and 18, concrete 19 or equivalent reinforcement means will be provided.

The extension 17 of the housing and the extension 46 of the flow obstruction will be disposed generally in spaced parallel relationship to each other, and the extension 18 of the housing and the extension 48 of the flow obstruction will be likewise disposed generally in spaced parallel relationship to each other, as shown.

A secondary housing roof 21 is generally horizontally disposed over and connects between said extensions 11 and 13 as by weldments or the like so as to complete the housing enclosure and the outwardly projecting portion in the lower region thereof.

A horizontally-disposed stock inlet or conduit 66 is provided at one side of the m xing tank or housing and extends through suitably aligned openings in the wall 11, wall 17, and concrete 19 therebetween, immediately adjacent bottom v all or floor 12, to afford ingress of a continuous supply of the infed pulp into the tank or housing interior. Said inlet 6% may terminate at its outer extremity at a flange (not shown) for connection to a suitable pulp supply system.

A supply pipe 61 may be connected to said stock inlet or conduit 69 for supplying chemicals, such as chlorine gas, for the purpose of introducing the chemical agent into the pulp stream immediately prior to passage into the mixing tank.

It will here be stated that the stock inlet size is not critical, although it must be sufliciently large to accommodate the volume of pulp which must be continuously removed from the mixing apparatus for entry into the tower.

A lower rotatable impeller 76, stationarily secured upon the free end of a horizontally-disposed shaft 72 has an inner end disposed within the mixing tank or housing, same extending through a suitable opening in wall extension 13, immediately adjacent the bottom wall or floor l2 and adjacent stock inlet 59 and at right angles to the main axis thereof.

Said impeller will carry a vertically-disposed spider extending outwardly therefrom in concentric manner and carrying on its outer peripheral surface in equi-spaced relationship as to each other a plurality of vanes or blades 76, in a plane perpendicular to the axis of rotation of said impeller and each being tilted, relative to said plane, their purpose being to cause the fluid material in the tank, upon coming into contact therewith to be moved toward the outer perimeter of the locus defined by the outer edges of said vanes and outwardly therefrom in a horizontal directicn as the impeller is rotated.

The shaft '72 is suitably journalled and sealed in the housing.

Said shaft 72 is connected to and driven by any suitable means such as a motor 74, connected thereto.

Contrariwise, the shaft may be driven by means of V el ts and pulleys or the like.

The lower rotatable impeller housing is located at the bottom of the input chamber and is so located as to be tangentially arranged with respect to the lower compartment, and is separated from said lower compartment by means of an annular stoneware ring 78 disposed between the impeller and input chamber.

This allows the cylindrical construction of the lower compartment to be unitized and unbroken except for the entry from the input chamber.

Material enters the lower compartment through the stock inlet 6i? and is directed toward the vanes of the lower impeller 7 ii in the direction of the arrow :1, as shown in PEG. 2.

The stoneware ring 73 precludes the escape of the mixture from the area of the impellers 76 and directs the mixture into the passageway 30 bounded by the wall extension 13 of the tank and the wall 43 of the flow obstruction into the lower compartment 29.

The vertically circulating stock is deflected outwardly from impellers 76 of the lower impeller into passageway Si in the direction of arrow b, where it moves horizontally and upwardly into the mixing compartment 29.

The dividing wall 24, being cone-shaped, offers a baffle means within the lower chamber whereby the circulating stock is deflected downwardly therefrom as it impinges thereagainst in its circulatory movement within the lower chamber, while the upper wall 44 of the flow obstruction, which is also cone shaped, offers a similar baflle means whereby the circulating stock is deflected upwardly therefrom toward the opening 28 leading into the upper compartment 22.

The opening 28, being constricted as aforesaid, will admit only a small quantity of the bleaching agent and pulp mixture into the upper compartment, with the remainder of the mixture being forced to continue to circulate and further mix in the lower compartment.

That portion of the mixture which is admitted to the upper compartment 22 is directed into the eye of an upper rotatable impeller 90, depending from the uppermost roof 14 of the tank, carried by a vertically disposed shaft 92 which extends through and is suitably journalled in said uppermost roof as by antifriction hearings or the like,

and disposed in a horizontal plane. Said shaft 92 is connected to and driven by a motor 94 or any other suitable means, as previously described.

The upper impeller is provided with a plurality of vanes or blades 96, each being tilted from a radial line to provide maximum circulating action in manner as previously described with reference to lower impeller 70.

The zone of turbulence established directly in front of the upper impeller is both vertical and horizontal, with the rotating blades setting up a horizontal circulation of the upwardly or vertically moving stock passing into the upper compartment through the restricted opening 28.

In the upper compartment 22, the dividing Wall 24 and the uppermost roof 14-, both being cone-shaped, offer upper and lower bafile means whereby the swirling stock is directed therefrom as it impinges thereagainst toward a discharge means comprising a stock outlet 98 disposed in and extending outwardly from the outer wall 10 of the tank and providing egress for the treated pulp to other equipment such as a chlorine tower, not shown, for the bleaching action.

The stock outlet 98 terminates in a flange for connection to the tower means of conventional design and function.

Preferably, the stock outlet 98 is disposed entirely out side of the vertical plane of the inner wall of the cylindrical wall 16 so as to prevent interference with the movement of the mixture in a spiral path within the upper compartment preparatory to discharge into said stock outlet.

It is here to be noted that the infeed means, similarly to the discharge means, are of such configuration that the entire cross-sectional area of the mixing tank therebetween is free from obstructions, save for those specifically noted, thereby aiding in maintaining uniform flow.

in the cycle just described, the strong vertical circulation set up at the lower impeller 70 secures an even flow of pulp into the passageway 3% and throughout the entire area of the lower compartment and, with the pulp and bleaching agent thoroughly mixed, the stock mixture rises evenly without further agitation to the top of the lower compartment.

in addition to the satisfactory mixing function and the equalizing effect obtained due to the symmetrical construction of the lower compartment, and the baffle effects offered by the conical walls 24 and 39, the regllar upward flow of stock mixture through the mixer is secured over the whole section even with diameters exceeding 12 feet. It is notable that this is of special value as far as treatments at about 3% density are concerned, as the pulp has a tendency to separate and channel in this region.

The flow in the lower compartment is along a strong horizontal plane while the flow in the upper compartment is comprised of both Vertical and horizontal components of flow, so as to attain a unique mixing effectiveness.

The opening 23 provided in the neck 26 is so positioned as to project the stock mixture through the opening into the propeller eye of the upper impeller thereby insuring that no stock can by-pass the upper agitator. Thus, if any bleaching agent bubbles remain in the mixture, indicating an incomplete mixing, even after the strong horizontal mixing in the lower compartment, they will be completely dissolved in the upper compartment. There is both horizontal and vertical flow in the upper compartment which produces a final thorough mixing action unattainable in any of the prior art forms. The horizontal mixing in the lower compartment in conjunction with the movement of the stock mixture directly into the eye of the upper impeller, coupled with the horizontal and vertical mixing in the upper compartment, assures a complete mixing thereby providing a bleaching quality in the pulp heretofore unattainable.

The geometric configuration of the upper and lower compartments and of the flow obstruction provides an ideal flow medium for the impellers and contributes to the effectiveness of the design achieving the ultimate in 3,1 2 complete mixing. It is to be borne in mind that complete mixing prior to enry of the mixture into the bleaching tower is requisite, since such tower is essentially free of the agitation necessary for mixin The upper impeller 943 will move more slowly than lower impeller 70 as it necessitates more power.

Optimum impeller speed of either upper impeller 95 or lower impeller 79 will be according to the tonnage being directed through the mixer.

The mixer hereof is particularly adapted to complete mixing and will give smoothness and ease or" operation and reliability with minimum necessity for repair or maintenance on the part of the user.

This mixer is rugged and durable with a simplicity of design and offers protection against usual but hard conditions of practical use. Further, while the components are compact and of reliable construction, they are nevertheless readily accessible for maintenance and replacement purposes.

Having thus described the invention and the best manner of employment thereof what it is desired to claim and secure by Letters Patent of the United States is:

1. In apparatus for mim'ng chlorine and pulp stock in a bleaching operation, the combination of a dual compartment tank, a frusto-conical wall dividing said tank into upper and lower communicating compartments and having a passage therethrough, means providing ingress of stock into said lower compartment, means within said lower compartment for effecting the horizontal circulation of the stock Within said lower compartment, and means Within said upper compartment effecting the horizontal and vertical circulation of said stock projected thereinto from said lower compartment through said frustoconical wall.

2. In apparatus for mixing chlorine and pulp stock as set forth in claim 1 wherein said means within said lower compartment for effecting the horizontal circulation of the stock comprises a rotatable impeller mounted in said tank for rotative movement on a vertically disposed plane.

3. In apparatus for mixing chlorine and pulp stock as set forth in claim 1 wherein said means within said upper compartment for eifecting the horizontal and vertical circulation of the stock comprises a rotatable impeller mounted in said tank for rotative movement on a horizontally disposed plane.

4. A chlorine mixer comprising, an inflow, an enclosed lower compartment communicating with said inflow and containing a rotating impeller for inducing an agitated horizontal flow of stock within said lower compartment, a flow obstruction disposed Within said lower compartment for directing the flow of the stock mixture Within said lower compartment, an upper enclosed compartment containing a rotating impeller, a frusto-conical wall constituting the upper wall of said lower compartment and the lower wall of said upper compartment, a restricted aperture in said frusto-conical wall providing ingress of stool: mixture from said lower compartment to said upper compartment, and an outflow communicating with said upper compartment.

5. Apparatus for mixing a chemical agent and pulp stock comprising a dual compartment tank, a conicallyshaped wall dividing said tank into upper and lower intercommunicating compartments and having a passage therethrough, means providing infeed of stock and chemical agent into said lower compartment, means within said upper compartment for effecting the horizontal and vertical circulation of said stock projected thereinto from said lower compartment, and means providing discharge of the mixed stock and chemical agent from said upper compartment.

6. In apparatus for mixing chemical and pulp stock as set forth in claim 5 with means within said lower compartment r'or eifecting the horizontal circulation of the stock and comprising a rotatable impeller mounted in said tank on a vertically-disposed plane.

7. In apparatus for mixing chemical and pulp stock as set forth in claim 5 wherein said means within said upper compartment for effecting the horizontal and vertical circulation of the stock comprises a rotatable impeller mounted in said tank on a horizontally-disposed plane.

8. A mixer comprising, an input chamber providing means of ingress to an enclosed lower compartment having a rotating impeller disposed therein for providing horizontal flow of stock within said lower compartment, an upper enclosed compartment containing a rotating impeller, a frusto-conical wall separating said upper and lower compartments, a restricted aperture in said frusto-conical wall providing. ingress of the stock mixture from said lower compartment to said upper compartment, a flow obstruction disposed within said lower compartment for directing the fiow of the stock mixture circularly and upwardly within said lower compartment, and frusto-conical bafile m ans disposed within said upper compartment for directing the flow of the stock mixture circularly and downwardly within said upper compartment.

References tilted in the file of this patent UNITED STATES PATENTS

Claims (1)

1. IN APPARATUS FOR MIXING CHLORINE AND PULP STOCK IN A BLEACHING OPERATION, THE COMBINATION OF A DUAL COMPARTMENT TANK, A FRUSTO-CONICAL WALL DIVIDING SAID TANK INTO UPPER AND LOWER COMMUNICATING COMPARTMENTS AND HAVING A PASSGE THERETHROUGH, MEANS PROVIDING INGRESS OF STOCK INTO SAID LOWER COMPARTMENT, MEANS WITHIN SAID LOWER COMPARTMENT FOR EFFECTING THE HORIZONTAL CIRCULATION OF THE STOCK WITHIN SAID LOWER COMPARTMENT, AND MEANS WITHIN SAID UPPER COMPARTMENT EFFECTING THE HORIZONTAL AND VERTICAL CIRCULATION OF SAID STOCK PROJECTED THEREINTO FROM SAID LOWER COMPARTMENT THROUGH SAID FRUSTO-CONICAL WALL.

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