US2257362A - Apparatus for treating liquidsolids mixtures - Google Patents

Description

Sept. 30, 1941. E. c. zlTKowsKl APPARATUS FOR TREATING LIQUIDSOLIDS-MIXTURES Filed July l, 1940 2 Sheets-Sheet l L ege/vd Ffa] . s. W L mm wm j@ Ab. Y MM, B E 9, VUIl 2 Patented Sept. 30, 1941 N UNI-reo. STATES PATENT OFFICE APPARATUS Fon TREATING LIQUID- soLIDs MIXT-URES Emil C. Zitkowski, San Mig-ucl, Tarlac, P. I. Application July 1, 1940, Serial N o. 343,372 -s claims'. (o1. es zvo) This invention relates to counter-current 1de- 4cantation and apparatus for performing `the same, and `more ,particularly relates to countercurrent decantation `operations -employed in the `sugarrening process.

In the'manufacture .of sugar, precipitates `are vformed `in the purification stages. v While the ex-A traction requires the 'separation ofthe liquids `and solids, Y,there 4is a considerablejquantity of sugar content `in the form of solutionjadhering to the precipitates vat vthe vseparation stage. ,To prevent losses otherwise occurring, a countercurrent decantation operation has been employed in which the solid contentis Washed to 4recover therefrom as much as possible of the adhering solution.`

While u,various means-may -be employed for effecting such separations, clarifying tanks or fthickeners have been used extensively for this purpose. Some thickeners may be of the Washing, multi-tray type in uwhich a descending bed of solids is subjected ;to Washing by `a risingcolr umn of liquid in limited areas, usually wells, proi vided for this purpose. As such `apparatus requires a quiescent treatmentzone forpromotion of settling, the Washing action, of necessity, `must r 'be conducted in such a limited `way as to avoid widespread agitation.

As a consequence, the `operations heretofore employed in the art have not brought the washing liquid in direct contact with any great amount lof the surfaces of the solids content :in order to prevent disturbance of the sludge bed.

lIt is an object of the'present invention to pro- "vide a `countercurrent `decantation `operation in which Ta sludge Vbed is ldivided between its zone Y `o'f formation and its point of discharge and Asubjected at the `point of division to thorough penetration by a `countercurrent flow of washing liquid. y i Another `object `of the 'inventionis the provifsionlof means for dividing a sludge bed during its: gravitational descent through a settling zone to expose surfaces of thefsolids content to washing influences A.wit'llout vproducing undue agita-A tion. Y

Afurtherobject of the invention is the provi- ,sion `iof a zoneLof contact of relatively large superficial area for c'o-.mingling streamsof mate- Rrial :in Ha countercurrent decantation operation.`

Other objects reside `in novel ,combinations and arrangements of parts :and novel steps and treatments, all -of which kwill appear `more ffully in the-course of the following description.`

To afford a better understanding, reference is `made tothe accompanying `drawings ,illustrating apparatus embodying features of the present invention. In the drawings, inthe several 4views of which like parts have been designated similarly: s

Figure 1 is a vertical central section through thickener apparatus embodying features of the present invention;

Figure 2 is an enlarged fragmentary view of the deck or partition dividing the tank of Figure 1 intor a plurality of compartments;

Figure 3 is aseotiontaken alongthe line 3-3 of Figure '1; and Figure 4 is a `section taken along the line 4--4 of Figure 1.

Referring first to Figure `1, settling apparatus of the ,thickener type has been designated gen` erally 4bythe reference numeral 5 and comprises a `tank divided-by a partition 6 into lower and upper settling compartments 'i (and 8 respectively. The bottomof the tank ,preferably is in-` clined and terminatesin a vconical sump portion lEl h'avinga discharge outlet i0 at its lower end.

A rotary shaft I2 supported in bearings i3 and i4 at its upper and lower ends carries rake elements yland l-^6 respectively. AA feed Well H is *provided in the upper portion of` compartment `8 for the reception of feed delivered through any suitable conduit, such as the ohute I8. A 'launder i9 v4extends around the upper edge of tank 5 for the reception Yof solution overowing yits top, and a suitable `discharge outlet 2U is provided for the removal of clear liquid collected in the laun'der. A suitable manhole and iuidtight cover 2l' is providedin compartment 'l to permit access `thereto for cleaning or repair.

Shaft l2 is driven by any suitable mechanism, here illustrated as a gear 22 driven through the intermediary of a pulley 23 connected with a suitable prime movennot shown. It will be apparent tothose skilled in the art vthat any suitable form of driving mechanism may be employed, and if desired, elevating mechanism of the type usually associated with thickeners may be provided for elevating the rakeswhen starting up.

Preferably, `such mechanism after shutdowns. will T'be mounted onV superstructure indicated generally by the `reference numeral 24.

in compartment I at a suflicient velocity to move it to the periphery of deck 6 without interruption. However, the control of velocity is necessary to prevent undue turbulence, for which reason the valve 26 is provided as a means of controlling such flow.

The deck or partition 6 is fitted in close proximity to shaft I2 to prevent the passage of material from one compartment to theV other centrally of the tank. Preferably, a stumng box will be provided for this purpose. The partition 6 terminates in spaced relation to the walls of tank 5, as indicated by the reference numeral 28. The periphery of deck or partition 6 is serrated, as shown at 29, in Figure 2, and in conjunction with space 28, provides an irregularly shaped passage through which sludge moving down i wardly along deck 6 must pass to enter compartment IL l This irregularly shaped passage serves to break up and loosen the descending bed of sludge without producing an undue amount of agitation, and the wash liquid flowing from nozzle 21 toward the periphery of tank 5 rises through the descending solids coming in contact with substantially all the surfaces thereof by reason of the loosened character of the sludge body.

In order to provide for a "progressive movement of settled solids, the rakes I and I6 are provided with suitable scraping blades 39 to act on the bed of solids deposited along the bottom surfaces of the respective compartments. As the solids in compartment 8 move from the center toward the periphery, whereas the solids in compartment 1 move from the periphery to the central sump 9, it is necessary to have the blades 36 of scraper I6 disposed in the direction oppositeitothe blades 30 of scraper I5.

To insure uniformity of overow, the upper rim ofv tank 5 is provided with a serrated edge 3I of the same character as the edge 29 of deck 6. With this arrangement, channeling due to irregularities is prevented and only clarified solution overflows into launders I9 and pas-ses to the discharge 20. n -V While the present invention has been illustrated' in connection with a single deck, twocompartment tank, it will be obvious that where f desired, the action in the first two compartments may be repeated in a second or more groups of compartments through which the sludge passes in a progressive movement. In such a multideck arrangement, the wash liquid'entering the f bottom of the tank will be required to pass alternately through peripheral and central passages in` its ascending movement through the respective compartments, or in the alternative, a clear liquid withdrawal through the side of the tank might be provided in the upper portion of the second compartment lfrom the bottom, as well as any other corresponding thereto.

AWhile the present invention is adapted for use in -a variety of treatments where countercurrent decantation is employed, it is particularly suited for use in the sugar refining process because of the character of the materials treated.V The solids of the sludge being a combination of organic and inorganic substances, tend to pas-s into a state of suspension in liquid followingI anyV appreciable agitation, for which reason the loosening of the sludge bed has to be accomplished in a relatively gentle action'to avoid turbulence.

The 'operation ofV the mechanism 'with kreference to the treatment of a sludge containing sugar will now be described, it being understood that similar operating methods will be employed for any pulp or sludge treated in the apparatus.

Pulp or sludge from any suitable source (not shown) is fed into the feed well I1 of tank 5 through chute I8. On filling the compartments 1 and 8, a relatively quiescent condition is developed, with the result that solids ysettle through the liquid body standing in compartments 'I and 8 and form a sludge bed on the bottom of tank 5 and along deck 6.

After the sludge beds are formed, the outlet I0 is opened to permit removal of sludge and I the action thereafter is continuous.

Shaft I2 is rotated at slow speed, causing the Scrapers I5 and I6 to impart a progressive movement to the sludge beds. The sludge bed on partition 6 moves toward the periphery, while the sludge bed at the bottom of tank 5 moves centrally until discharge into sump 9 from which it passes from the tank through outlet IIJ.

4During rotation of shaft I2, a wash liquid, usually water, is delivered through the shaft from reservoir 25 to outlet 21 and discharges from the nozzle at controlled velocity determined byv regulation of valve 26. This wash liquidiiows in the mannerV indicated by the directional a1'- rows in Figure 1 to the passage 28 where it penetrates through the sludge bed, passing across the serrated edge 29 of partition 6 and in passage 28 to wash the individual solid particles and recover therefrom adhering solution having considerable sugar content. I

As a further safeguard Vagainst turbulence in passage 28, an annular rim 32 is provided above such passage to prevent the direct descent of settling solids and at the. same time requiring lan undulating movement ofthe ascending liquid stream, insuring greater surface contact thereby in its movement through the sludge bed.

y Upon rising through the bed of sludge, the wash liquid is free to rise directly along the sides of the tank to the serrated overflow 3I, with the clarified liquid carrying the sugar content in solution passing across the overiiow into launder I9 for subsequent removal from the treatment through-outlet 2U. l

In this way, the solids forming the sludge bed in the upper compartment 8 are thoroughly Washed during the descent into compartment 1 and the sugar content passes in solution with the wash liquid for continuous removal by overiiow across serratedV edge 3| into launder I9.

At'the same time, solids already washed and relieved of the adhering sugar content move to sump 9 and thence out of the apparatus through discharge outlet I0 in a continuous action.

' 'I'he provision of the peripheral washing Vzone of' large superficial area and the loosening of the sludge bedV from its movement over and through the serrated-edge 29 serve to bring substantially all surfaces of the solids content in contact with wash liquid without producing undue turbulence in the settling. zones. The'valuable constituents comprising the sugar content dissolve readily in the Wash liquid and pass with the same in the form of solution directly to the overflow for removal from the treatment. i

Thus, it is apparent that a high degree of efliciency in the recovery of valuable constituents adhering'to solids is attained in the operation described. :While such thickeners are used primarily in fthickened'sludges derived therefrom.

1Likewise, in other treatments lwhere -countercurrent fdecantation iis employed, such as the 'cyanide treatment innmetallurgical operations, Athe apparatus and `methods Idescribed will be eilicacious.

`Whi1e the apparatus described "and illustrated is particularly suited i'oriattainingg the objects `of the present` invention, `that -various structural -modifications may be Ait l will be understood employed within Ithe spirit and scope of `the 'invention. For example, the `discharge 'ofjwashing liquid vmay lbe accomplished by providing :a pipe in place of nozzle 21, which will extend from shaft I2asubstantialdistance or even adjacent the passage 28. Similarly, the velocity control of the wash liquid may be attained by means other than valve 26.

However, a low velocity iiow is necessary to prevent undue turbulence resulting from the washing action, and consequently regulation of the ow of wash liquid to and through passage 28 is recommended.

Under some conditions it may be desirable for this purpose to eliminate the outlet through nozzle 21 and substitute a plurality of restricted discharge outlets in the shaft I2 immediately below deck 6. Preferably, these outlets will be spaced ninety degrees about the shaft, although the number and location may be varied to satisfy operating requirements.

Control of the sludge removal through the provision of suitable pumps is within contemplation of the invention and it will be apparent to those skilled in the art that regulation of discharge to balance feed is necessary in connection with continuous operation.

The number and arrangement of scraper arms will be a matter of choice, as well as the position and arrangement of blades on the scraper elements.

Where the expressions break up or breaking are used in the description and claims, they are intended to designate an action in which the continuity of matter is destroyed rather than to suggest a violent severance.

What I claim and desire to secure by Letters Patent is:

l. Apparatus of the character described, comprising a tank, a partition in the tank dividing the same into a plurality ofv superposed settling compartments and spaced from the sides of the tank to provide a peripheral passage, means for delivering a liquid-solids mixture into the upper compartment of the tank, means for removing clear solution from the upper portion of the tank, meansfor removing settled solids from the lower portion of the tank, means for moving solids settling into the` upper compartment to the peripheral passage, said partition having radially projecting serrations at its periphery for breaking the solids body descending into the peripheral passage and thereby exposing the individual surfaces of the solids constituents, and means for discharging wash liquid into the lower compartment in a position to rise through the peripheral passage countercurrent to the separated solids descending therethrough.

2. Apparatus of the character described, comprising a tank, a partition in the tank dividing compartmentsand spaced from the sides of the tankito provide a peripheralpassage, meansffor the same Linto la Aplurality of -superposed settling Adelivering:a-liquid-solids mixture into the upper compartmentof the tank, means for removing `clear solution `iromthe upperportion of the-tank,

means for removingsettled solids ifrom the lower `portion-of the ltank, ymeans for `moving solids settling into 4the uppercompartment to the peripheral passage, said partition having radially .projecting'serrations at its periphery fori breaking the solids body descending into the peripheral passage and thereby exposingthe'individual surfaces of the solids constituents, vmeans for discharging wash liquid into the lowerlcompartment ina positiontolrisethrough the peripheral passage countercurrent to-thefseparated solids descending therethrough,` and means for regulating the .veloci-ty off'the washliqiiid so introducedinto said lowercompartment.

3. Apparatus of the character described, comprising a tank, a partition in the tank dividing the same into a plurality of superposed settling compartments and spaced from the sides oi' the tank to provide a peripheral passage, means for delivering a liquid-solids mixture into the upper compartment of the tank, means for removing clear solution from the upper portion of the tank, means for removing settled solids from the lower portion of the tank, means for moving; solids settling into the upper compartment to the peripheral passage, said partition having serrations projecting outwardly in a substantially horizontal direction at its periphery for breaking the solids body descending into the peripheral passage and thereby exposing'Y the individual surfaces of the solids constituents, and means for discharging wash liquid into the lower compartment in a position to rise through the peripheral passage countercurrent to the separated solids descending therethrough. Y

4. Apparatus of the character described, comprising a tank, a partition in the tank dividing the same into a plurality of superposed settling compartments and spaced from the sides of the tank to provide a peripheral passage, means for delivering a liquid-solids -mixture into the upper compartment of the tank, means for removing clear solution from the upper portion of the tank, means for removing settled solids from the lower portion of the tank, a scraping element for moving solids settled in the upper compartment to the peripheral passage, a scraping element for moving settled solids in the lower compartment to the solids removal means, said partition having radially projecting serrations at its periphery for breaking the solids body descending to the peripheral passage and thereby exposing the individual surfaces of the solids constituents, means for discharging wash liquid into the lower compartment in a position to rise through the peripheral passages countercurrent to solids descending therethrough, and blades disposed on the scraping elements in the respective compartments with the blades in the upper compartment directed oppositely to those in the lower compartment.

5. Apparatus of the character described, comprising a tank, a conical partition in the tank dividing the same into a plurality of superposed settling compartments and spaced from the sides of the tank to provide a peripheral passage, means for delivering a liquid-solids mixture into the upper compartment of the tank, means for removing clear solution from the upper portion of `collecting surface ving in thevform of an inverted cone, means for thetank, the bottom ofythe tank providing the for the lower compartment beremoving settled solids from the lower portion of the tank, means formoving solids settling into the ,upper compartment to the ,peripheral passage, vsaid partition having radially projecting serrations at its periphery for breaking the solids body descending hinto the peripheral passage and thereby exposing the individual surfaces of the solids constituents, and means for discharging wash liquid into the lower compartment in a position to risel through the peripheral passage countercurrent to the separated solids descending therethrough.

6, Apparatus of the character described, comprising a tank, a partition in the tank dividing the same into a plurality of superposed settling compartments and 'spaced from the sides of the tank to provide a peripheral passage, means for delivering a liquid-solids mixture into lthe-upper compartment oi` the tank, means Afor removing clear solution from the upper portion of the tank, means for removing settled solids from the lower portion of the tank, a hollow rotary shaft in the tank; means mounted on s aid shaftrfor moving solids settlinginvthe upper compartment to the peripheralpassage, said partition having 'radiallyprojectingserrations at its periphery for breaking the solids body descending intopthe lpevripheral :passage and thereby exposing-the individual surfaces of the-solids constituents, said

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