US2207347A - Crystallizing evaporator - Google Patents

Description

July 9, 1 B. s. HUGHES CRYSTALLIZING EVAPORATOR Filed April 10, 1937 2 Sheets-Sheet l.-

Trim; M 741. 414,

July 9, 1940- B. s. HUGHES 7,347

CRYSTALLI Z ING EVAPORATOR Filed April 10, 1937 2 Sheets-Sheet, 2

Patented July 9, 1940 oars'ramzmo EVAPORATOR Burton SuH ughes, Buffalo, N. Y., assignor to Zaremba Company, Buffalo, N. Y., a corporation of Maine Application April 10, 1931, Serial No. 136,172 eolaims. (01. 159-45) This invention relates to evaporating methods and apparatus particularly adapted for crystallizing substances out'of aqueous solutions byremoving part of the water through evaporation.

One of the methods heretoforeknown comprises subjecting a solution to heat, causing the solution to flow upwardly to cause crystals to become separated and suspended in thesolution, and withdrawing and returning a portion of the solution for reheating and retreatment.

A general form of apparatus which has been employed for carrying out thistype 011 method includes an evaporator: bodyassociated with an external heater for the solution and a pumpfor withdrawing, circulating and returning the solution. i

In the usual apparatus of this characterboiling occurs in the tubes of the heater and in contact with the walls of the evaporator and crystals :are deposited in the heater tubes; the crystals obtained are of inferior size; and the capacity and output of the apparatus are materially reduced by the presence of incrusted crystals in the heatertubes and circulation pipes and by the necessity of frequent stopping for boiling out to remove the incrustations.

One of the principal objects of my invention is to provide apparatus in which no boiling occurs in the heater tubes and in which there is no deposit of crystals in the tubes, on the surface of the evaporator shell, or in the pipes connectinggthe heater and evaporator. 1

Another object or, the invention isthe provision of an evaporator method by which a solution,,preliminarily heated, is so proportioned to and mixed with a solution of adiflerenttemperature as toproduce thedeposit of crystals of largesize and quantity.

Another object is the provision of an evaporator system in which the solution is circulated and recirculatedthrough the heater tubes and evaporator, the circulation system being hydrostatically balanced and itsoperation requiring only the amount of power necessary to overcome friction. f

Another object isthe provisionof an improved method of and means for regulating the tem-,

perature and condition of the solution and maintaining a hydrostatic balance.

o A turther object is the provision of improved means for distributing the solution within the evaporator and effecting intimate mixing of the incoming solution with the contents of the evaporator, resulting in uniform ebullition withu out explosive spouting and spraying or the solution in the evaporator,- thorough circulation within the evaporator, and the building up of crystals of. large size out of contact with the or effect, whether used as a single unit or in multiple. For the sake of convenience and to avoid unnecessary duplication only a single system .or efiect is represented in the drawings.

The drawings illustrate a preferred form of 15 the apparatus or system which constitutes a part of my invention and which is adapted for the carrying out of my improved method.

In the drawings:

Figure 1 is a vertical, sectional elevation of 20 my apparatus embodied in a single efiect evaporator. Figure 2 is a top plan view thereof. Figure 3 is an enlarged horizontal section taken on line 3-,3, Figure 1.

Similarzoharacters of reference indicate corresponding parts throughout the several views.

\Generally speaking, my apparatus or system comprises an evaporator In, a heater ll located beneath the evaporator and connected to the discharge of a pump l2, a suction pipe 13 connecting the evaporator with the suction of the pump, a return pipe ll connecting the discharge side of the heater with the evaporator, means within theevaporator for mixing the heated solution, supplied by the pipe H with the solution contained in the evaporator l0 and provision for free upward and downward circulation of the solution within the evaporator.

The heater ll may 'be of any suitable form or type of construction. The structure illus-, trated is conventional, consisting of a heating chamber 15 containing a .nest of heater tubes It, the tubes being connected at their respective ends with an inlet chamber I! in communication with the discharge of pump l2 and a dis- 5 body Ill adapted to contain a quantity of aqueous solution to be treated, and is provided at its lower end with an inverted conical section 2| to which the upper end of the pipe I3 is connected. Openlugs 22 and 23 are provided at the upper end of the body l0 and at the lower end of conical section 2|, respectively, for the release of steam and the discharge of crystals. 'The opening 22 may be connected with a condenser (not shown) or with the succeeding body of a multiple etiect evaporator (not shown). Disposed concentrically within the conical lower end of the evaporator body is a like-shaped sleeve-like partition or conical member forming a chamber or separator 24 which is open at the top" and defining or constituting a substantially annular partition which is spaced from the walls thereof to provide an annular space or passage 25 for the circulation of the solution, and disposed at the lower end of the separator in communication with the pipe I4 is a distributor indipipe l4 as well as from the passage 25 into the conical chamber 24, the latter separating the ascending current of solution inside the chamber fromv the descending current exteriorly thereof. To this end, this distributor consists of a central spreader. 21 in the form of an inverted cone which preferably terminates at its lower end immediately above the open end of pipe I4, and extending from this spreader are hollow, thin walled radial arms .or spokes 28 which may be permanently secured in any appropriate manner to the upper end of such pipe l4. These arms merge at their upper ends into the top side of the conical spreader to provide intervening spaces or ports 29, and their inner edges are substantially upright and coextensive with the inner wall of the pipe I4, while their closed bottom edges may be inclined outwardly to merge into the contiguous wall of the conical chamber 24. Formed in the arms '28 areslots 30 which converge upwardly and through which the heated solution is circulated upwardly and discharged in thin sheets from the pipe l4 into the chamber 24, while the solution contained in the evaporator body is circulated downwardly through the passage 25 and thence upwardly through the spaces 29 between the slotted arms. The solution issues from the slots at such-a velocity that part of its energy is imparted to the solution into which it issues, thus causing circulation of solution upward through the ports 29 and inner cone 24 and its return downward through the annular space 25. There is also a thorough commingling of the heated'solution from the slots with the cooler solution contained inthe evaporator. The upper end of the chamber 24 is open and preferably disposed below the normal level of the solution, as indicated in Figure 1. It will also [be noted in this figure that the spreader forms a closure for the top 01' the pipe l4 to divert the ascending current oi. solution into the hollow arms 28.

V The apparatus is so proportioned that the solution covers the top of the distributor 26 to such depth that boiling does not occur until after the space 25. The apparatus is also so proportioned that the combined area 01' the ports 29 is greater than the combined area of the discharge ends of the arm-slots.

In the operation of the apparatus, the solution to be treated is continuously supplied to evaporator HI, at the rate required to maintain the desired level. Pump I2 is operated continuously, and the solution is drawn through pipe l3, forced through heater tubes l6 and return pipe I4 and discharged into the body of liquid in the evaporator through slots 39. As the solution passes through the tubes I5 it is heated by the steam or otherheating medium in the chamber" l5 and enters the evaporator III at a temperature several degrees above the temperature of the solution contained in the evaporator, which has a temperature corresponding to the boiling point of such a solution at the absolute pressure maintained in the evaporator.

The temperature increase of the solution passing through heater tubes I5 is derived from the temperature diiTerence betwen the heating me dium surrounding the heater tubes l6 and that of the liquid in the tubes. The higher temperature of the heating medium may be obtained in various ways. When steam is used it will be at a pressure higher than the pressure in evaporator l0. 7

To insure the maintenance of the desired temperature difference and rate of heat transfer, accumulation of condensate and/or gases in the heated shell II is prevented by their removal through outlet20.

After being heated in the tubes 16, the solution passes through pipe I4 into the interior of the evaporator I0, issuing in thin sheets from the slots 30 and entraining liquid from the-body of solution in the inner cone 24, which entrained liquid moves upwardly and is replaced by liquid flowing through the passages or ports 29. The conicalchamber 24 separates the ascending current of solution from the current descending through the intervening passage 25. The circulation thus produced is accelerated by the formation of steam bubbles within the conical chamber 24 and the consequent unbalancing oi the ascending and descending columns of liquid.

Since the heated solution supplied by pipe I 4 mixes with a much larger volume of cooler or relatively unheated solution within the evaporator ill, the temperature of the mixture is much lower than that of the heated solution alone and violent boiling is thus avoided. No boiling or ebullition occurs until the heated solution rises to a level where the hydrostatic head is reduced to a value which will permit boiling under the existing temperature and pressure conditions, and at this level the boiling which occurs is distributed over the entire area within the conical chamber 24 and is quiet and uniform and out of contact with the shell of the evaporator. As a consequence, there is no accumulation of crystals on the surface of the evaporator shell. Similarly, there is an absence of deposit in the heater tubes because the solution isin continual circulation, enters the heater tubes at saturation,

through the chamber 24 until they attain a size that causes them to settle into the bottom or the evaporator from which they may be removed through opening in the usual manner," continously or otherwise, Suitable connections may be' provided Ior'silpplying additional solution to replace losses by evaporation and for the removal of crystals.

Anyfsuitable" means may be provided for effecting the removal of crystals and the replacement of solution to maintain the desired level in the evaporator, and continuously or intermittently operatingv means may be employed for these purposes, such means being well known and forming no part of my invention.

The continual circulation and repeated passage of crystals through the zone in which material is thrown out of solution by evaporation is favorable to-the building up of crystals or large size. The power required for circulation in the system is .a minimum,'the system being hydrostatically balanced and requiring only suflicient power to overcome .friction. Furthermore, by my construction of evaporator, the circulation is such as to carry the crystals around and around so that crystals of large size can be produced and-the operation is quiet and regular and can be operated for long periods without interruption.

I claim as my invention:

1. Anevaporator comprising a casing adapted liquid through saidseparator member, and

lower portion of said container in spaced relation to its surrounding wall to provide a downcirculating passage for the liquid and opening at its upper and lower ends into said container for providing for the upward circulation of the liquid through said separator member, and means'for supplying heated liquid directly into the lower end of said separator member and for causing the entrainment therewith of liquid within the container to eflect a circulation of such liquid upwardly through said separator member and downwardly through said surrounding circulating passage, said means including a slotted portion for discharging the heated liquid in thin sheets upwardly into the interior of said separator member and an intervening ported portion 1or establishing induced circulation through the down-circulating passage and upwardly through said separator member.

3. An evaporator, comprising a container for liquid having a concentrically arranged, partition-like wall therein defining a main chamber for the upward circulation oi. liquid and an annular secondary passage for the downward circulation of the liquid, means for supplying heated liquid to the container, and a distributor connected to'the lower end oi said partition-like wall and having a discharge in communication with said liquid-supplying means fordntroducing the heated liquid directly into said-main chamber, said distributor having ports therein adjacent its discharge'i'or establishing induced circulation of the liquid downwardly through said secondary passage and thenceupwardly' into the main chamber.

' 4. An evaporator, comprising a container for liquid having 'a concentrically arranged, partition-like wall therein defining a main chamber for the upward circulation of liquid and an "annular secondary passage for the downward circulation of the liquid, means for supplyingheated liquid to the container, anda' distributor connected to the lower end 10! said partition-like wall and having a plurality of discharge ports therein establishing communication between said liquid supply means and said main chamber, said distributor having intervening ports be-- tween said discharge ports ior establishing communication between the lower ends of the main portion of said container a substantially. coneshaped partition disposed concentrically within the like-shaped portion of said container and deflning a main chamber for the upward circulation of the liquid and an annular secondary-passage for the downward circulation of the liquid, and a distributor means interposed between the discharge end oi said pipe and the opposing lower end of said conical partition, said distributor means having a plurality of ports therein for introducing the fluid in stream-like fashion from said pipe into said main circulating chamber and having intervening spaces between said ports for establishing induced down circulation of the fluid from said secondary passage into said main chamber.

6. An evaporator, comprising a container for the liquid, a substantially sleeve-like partition disposed in said container with its top edge below the level of the liquid therein and spaced from the container wall for defining an inner chamber for upward circulation of liquid and an annular outerchamber for downward circulation oi liquid, a pipe for conveying heated liquid to said container and having its discharge end in communication with said inner chamber, and a distributor at the discharge end of said pipe having ports and deflecting means for directing the heated liquid in thin sheets into the lower portion of the upward circulation chamber and having passages adjoining said ports for establishing induced circulation between the lower portions of said inner and outer circulating chambers.

'7. An evaporator, comprising a container for the liquid having means therein below the liquidlevel for defining an inner chamber for the upward circulation of the liquid and an outer chamber for the downward circulation of the liquid, a heater for heating the liquid, 9. pump interposed between the container and the heater including pipes for circulating the liquid from the container through the heater and returning it from the heater to the inner, upward circulation chamber of said container, and means interposed between the discharge endoi the return-circulating pipeand said chamber-defining means for controlling the flow o i -heated-.1iqu1d from said return pipe into said inner chamber and forcontrolling induced circulationpi the fluid in said container, said means including ports for directing the heated liquid in thin sheetsinto the lower end of said upward circulation chamber and other ports disposed in cooperative, relation to said first-named ports for establishing communication between the-lower ends of said downward and upward circulationchambers. j

8. An evaporator, comprising a container including-means therein dividing it intosubstantially concentrically-disposed, circulating chambers for the upward and downward circulation of the liquid in a predetermined zone, a pipe for conveying heated liquidvto saidcontainer, and a distributor disposed between the discharge end of I said pipe and said chamber-forming means including a member having a plurality of spaced hollow arms opening at their lower ends into the discharge end of said pipe and at their upper ends into the lower end of said upward-circulating chamber, the spaces between said arms providing for the circultion of the fluid from the lower end of the downward circulating chamber to the companion end of the upward circulating chamber.

9. An evaporator, comprising a container for theliquid having means therein defining a predetermined circulating zone, a pipe for supplying liquid under pressure to said circulating zone andmeans for heating the liquid in said pipe, the discharge end of said pipe being provided with a distributor head having radially-spaced, slotted arms for issuance of heated liquid therefrom into said circulating zone and the resulting spaces between said arms establishing communication between the interior and exterior of the circulating zone-defining means for causing the entrainment, with the heated liquid, of liquid within the container to effect mixture and circulation of the heated liquid and the body of liquid in said container.

, BURTON S. HUGHES.

CERTIFICATE OF" CORRECTION. Patent No. 2,2o7,3L v July 9, 191m.

' BURTON s. HUGHES.

It is hereby certified that error appears in the printed specification of the ahove' nunbe z fed'pat ent x equjining correction as follows: Rage 5, first colnmn line 50,- claim 2 ,strike out the words "liquid through said sepsrator me'mfber l nd and insel t instead --liquid,*aseparator'member disposed within the-. the' ssio. Letters Potent should be read with this correctibn therein t n mayyonfqm cord of the case in the Patent D ffi ceQ Signed and sefl edathijs 27th day'of Angust, V A. 1;. 191m;

Henry Van Arsdale (Seal) 1 Acting Commissioner of Patents.

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