US1424992A - Evaporator - Google Patents

Description

W. H. P. CREIGHTON.

EVAPORATOR.

v APPLICATION HLED DEC-30, 1920.

1 9 9 gg a I Patented Aug. 8, 1922.

ATTORNEYS.

EVAEORATOR.

To all whom it may concern:

Be it known that I, W'iLLIAM H. P.

, Gnnrenroma citizen of the Unitedtitates,

residing at New Orleans, in the parish of Orleans and State of Louisiana, have invented certain new and useful Improvements in Evaporators; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

1 The density of sugar and other juices or liquids is increased by successive boiling, usually at pressures belowthat of the atmosphere, in a series of vessels called, collectively, a multiple effect.

In a multiple effect the first vessel is supplied with steam from an external source, usually the exhaust from the main engines. Economy is attainedby using the steam which rises from the boiling liquid in the first heater or effect as the heating agent in the To operate in this mannerthe vaporpressures on the liquid surfaces of the different effects must differ, the highest-pres sure being that on the surface of the liquid in the first effect. This difference of pressure in two adjacent effects is essential for the transfer of heat, and it also furnishes the force to move the liquid from one effect to the next.

The density of the liquid is increased by partial evaporation in each effect; and the greatestdensity of the liquid is in the last effect, from which the liquid is pumped, or carried off by gravity, in the usualway.

Standard vertical effects are divided into belts, the lowest, into which the liquid enters, is called the bottom belt; above it is the steam belt which eitherv receives steam from the" engines or from the vapor belt of a preceding effect, and distributes it to the intertubular heating space. Above the steam belt, are the vapor belt, the dome and the top.

The object of this invention is toincrease the rate of evaporation per unit of heating surface in any effect or vacuum pan having vertical or inclined juice tubes between tube sheets, by certain alterations inthe design of the steam belt.

Specification of Letters Patent.

Patented Aug, E5, 1922.

Application filed December 30,1920. Serial No..434,08 8. i

To secure the highest rate of heat transmissionthrough heating surfaces, the most recent experiments show that, among other requirements, it is essential;

1) To obtain the highest possible average velocity ofboth the heating and heated fluids past the heating surfaces;

(2) That the amount of incondensable gases must be kept to the irreducible minimum. V

The design of evaporators now generally in use violates these requirements; as will be hereinafter shown:-

To better illustrate my invention I have shown two effects connected together, the

first of the present standard make now generally in use, and the second the same general type modified according to my inven tion.

Reference is had to the accompanying drawings, in which Figure 1, is a diagrammatic view'of two effects connected together, one of the oldand the other of my improved construction, parts being shown in central vertical section, and parts beingomitt ed for the sake of clearness in the drawings; H

FigureQ shows a half sectional view along the line 2-2 of Figure 1, and looking in the direction of the arrows; parts beingomitted, and

Figure 3 shows a half sectional view along the line 3-3 of'Figure 1,-parts being omitted for the sake of clearness' in the drawings.

Like parts are indicated bysimilar'reference symbols throughout the several views.

A represents an effect of the present standard make suppliedwith heating'fluid through the pipe B, and provided with the pipe B for carrying off the vapor evapo rated; this pipe B is connected to the pipe B as shown in dotted lines, whereby the vapor rising fromthe effect A is delivered to the heating chamber of the effect A, -the vapor rising from the latter being carried series or to the the effect A, improved form ofsteam belt H is illustrated. Each steam. belt is surrounded with an annular chamber h Referring first to the well known cons. struction of the steam belt H, shown to the right of Fig. l, the heating surface com-.

prises a large numbern o'f vertical tubes h of small diameter secured in the tube sheets 3 and 7, in which tubes the liquid in boiling moves, upwards, and of one central v downconier D, wl1ich the'liquid move downwards or returns to the bottom belt. Steam afterentering the belt at Bpasses to the right and left in the chamber h and enters the undivided intertubulai space through the vertical openings, p, 22 10 etc.

in the inner'hwall of the'annular belt. Similarports should be provided onthe other side o tthe apparatus.

Much more steam. enters. the ports 79 directly opposite the pipe B, and p", where the currents (moving in opposite directions) I me et',jthan enters any. intervening port on eitherside; Opposite each port, especially pand 327, a few. tubes receive a strong current of steam for their entire length. These tubes are especially efficient, at the expense of a much larger number'of tubes. not so v favorably placed. I

After the steam enters the intertubular space, itsvelocity low and its direction fluctuating. The various currents moving radially from the ports interfere withone another, and so neutralize the velocity past.

the heating surfaces.

"To be able to remove. air or other incondensable gas, it is essential to accumulate it in one spot continuously. With the ever varying and uncertain movement of? the steam in the undivided intertubular space,

' this is not possible- Hence there is much guess work in the positioning of a, pipe K, perforated in the steam belt and connecting to the. vapor belt, partially opening a valve X,-the incondensable; gasesand some vapor are supposedto pass into the vapor belt 1 due to the lower pressure therein.

It will beof course understood that the water, of condensation =will be drawn off from the steam belt H, but there are various ways well known in the art, for accomplish; ing-this result, and the said feature ,not be ingE'a-part ofmy. present inventionis not showntllfirein; s

i In the etlect A", shown to the left of Fig;

1, the heating surface comprises numerous vertical tubes h of small diameter in which the liquidwrises, and a few tubes of larger diameter fa'vorablyplaced in each section,

to; act as downcomers instead of the large central downcomer vD of the steam belt H.

a'The steam belt-.H is'divided into cylindrical sectors thin vertical plates V, V V V5 extending from the tube sheet f to the tube sheet f and from the inner wall of the annular belt to a contral exhaust pipe T, which is provided with'openings t, t, and 1 t for each sector, with an escape passage #2 This pipe T serves as an eduction pipe from the effect for condensate, for incondensable gases, and,when robbing the effect of con.- siderable steam. What is meant by robbing the eiiect will be hereinafter explained. Similar radial plates corresponding to V" to 3 should of course be provided on the opposite side of the apparatus. l 3

The inner wall of the annular belt H" is perforated opposite. each-sector by one or more horizontal openings S, the principal ones "being below the levelbfthe-liquid maintained in the; efiect, as the most intense circulation is obtained in a" tube applying heat asnear the bottom of the'tube as possible.

follows: p I

The pressure in the e ducti'on" tube T being low, steam will tend to enter each'section, from the annular chamber it"; The major steam current will be strong andlow The operation of the steam belt l-l is as 1 down and will induce a'high liquidcurre'nt in the tubes. A; very large number oftubes are affected by this cur-rent ineachfsector.

Losing heat the steam decreases in volume. However, in its passage. to the central e2;- haust pipe T, the vertical cross section of the steam path rapidly decreases, so that that steam velocity perpendicular to'the tubes is substantially 'maintained. The construction calls for a short, direct and almos't'radial movement of the steam, incondensable gases,

and condensate to the exit zfi ,wheretheyjcan be] separated and sent to heaters, otheri'effccts,"orto sweetwater pumps. I

' The upper part ofthe liquid tubesis fi-lled withsteam which absorbs heat slowly; It is well to have some steam sweep the upper part of th'e'tubes to carry incondensable gases toth'e exit as well as evaporate the liquid film clinging to the inside o'fthetubes."

Since steam at lo wpressure contains. al-

' steam is removed before it enters the efr'ect.

Inthe new constructionpit would be taken off this is not true o'f the vertical slots shown in the prior art. v

To sum up. This construction will cause high grade steam to impinge on more'tubes and on that part of each tube that will induce thehighest velocity of the liquid in the tube. Further the condensate and incondensable gases are not allowed to remain in the heating chamber, but are swept in a short direct path to the exit. '7 p r 7 While the drawings and description refer to cylindrical efl'ects,.the improvements are applicable to multiple effects and vacuum pans of any shape where vertical are inclined tubes between tube-sheets areused, with the heating mediumin the intertubular space. The annular .beltmay' bereplaced by conduits of steam, and the single central exit forall sectors may be replaced byan exit for each sector or wedge especially when vessels of rectangularor approximately rectangular steam belts are, used.

It will also be obvious that various other modifications might be made in the herein described apparatus, and in the construction, combination and arrangement of parts,

which could be used without departing from the spirit of my invention and I do not mean to limit the. invention. to such details except as pointed'out'in the claims. p a

I have used in the claims the term radial plate referring to the partition plates V to V which in a cylindrical evaporator would preferably be radial; in an evaporator of a polygonal shape these plates would be diagonally disposed, and not true radii; but I mean to cover such alternative, construction in the term radial plates aforesaid.

Having thus described my invention, what I claim and desire to secure by Letters Patent of the Unitedcltates is 2- 1. A vacuum pan or effect provided with a steam belt having transverse tube sheets, tubes for the passage of liquid, connecting said tube sheets and opening therethrough; a series of radial partition plates separating the heating space into a series of wedge shaped chambers, each containing a group of said tubes, means for supplying steam to the outer portions of said chambers, and means for carrying off the heating fluid from the contracted inner portions of said CllHIflbers.

2. A vacuum pan or efl'ect provided with a steam belt having transverse tube sheets, a

series of groups of tubes, each group consists ing of small tubes for the passageof liquid upwards, and of larger tubes for the flow of liquid downwards, connecting said'tube sheets and opening therethrough, a series of radial partition plates separating the heating space into a series of wedge shaped chambers, each containing a group of said tubes, means for supplying steam to the outer portions of said chambers, and means for carrying oil the heating fluid from the contracted inner portions of said chambers.

3. A vacuum pan or effect provided with a steam belt having a series of circumferen-l tially arranged ports forlthe admission of steam, transverse tube sheets above and be low said ports, tubes for the passage Of liquid connecting said tube sheets and opening therethrough, a series of radial partition plates separating the heating space into a I series of wedge shaped chambers, each'coni taining a group of said tubes, means for. supplying steam to said ports and through them to the outer portions of said chambers, and means for carrying off the heating fluid from thecontracted inner portions of said chambers. v

4:. A vacuum pan or effect provided with a steam belt having a series of circumferentially arranged ports for the admission of steam, transverse tube sheets above andbelow said ports, tubes for the passage of liquid connecting said tube sheets and opening therethrough, a series of radial partition plates separating the heating space into a series of wedge shaped chambers, each containing a group of said tubes, means vfor supplying steam to said ports and through them to the outer portions of said chambers, ace'n tral exhaust pipe with ports opening into the various chambers for carrying ofi the heating fluid from the contracted inner portions of said chambers.

5. A vacuum pan or effect provided with of said wedge shaped chambers, and means I for carrying ofi the heating fluid from the contracted inner portions of said chambers.

6. A vacuum pan or effect provided with a steam belt having transverse tube sheets, tubes for the passage of liquid connecting said tube sheets and opening therethrough, a series of radial partition plates separating the} heating space into a series oi edge shaped chambers; each containing a group 'offsaid'tuhes, means for supplying steam to the outer portions. of said chambers, and a central exhaust pipe'with ports opening into the various chambers for carrying ott thefheatiiig; fluid from thecoiitr-aeted inner portions of. said chambers.

, l. A vacuum pan or efiect; provided With a steambelt having transverse, tube sheets,

I a seriesiof' groups of tubes, eaoh'group consistingoi small tubes Jior the passage or liqid upwards, and of larger tubesfor the flow of liquid dow niizards, connecting said tube sheets and openingtherethrougi a series ofradial partition plates, separz-iting the heatii g space into a series of wedge shaped chambersieaehi containing a group of said tubes; means forsupp1ying stean to the outer portions ofsaid 'chambers, and a central exhaust pipe .with ports opening into the wrists chambers for carry ng off the heating fluid from the contracted irir er; portioiis of, said chambers.

a steam belt; having; a series of circumfere itiallyarranged ports for the adm ss on of steam, transverse tube sheets above and below said ports, tubes for the passage of 'iiquid connecting said tube sheets and opening therethrough, a series of radial part tion plates separating heating space into a ser es of wedge shaped chambers, each containing a a group of said tubes,'means for supply ng steam to. said ports and through them to the outer portions. of said chambers and :1 cent al ex au t p p with. ports pe g nt the various chambers for; carryii g off the h a ng luid om the contrac ed inn p tiorus oi-said chambers,

8, A 'vacuumpan. or effect pro zided with A v c um pan orfieet p qvided with a steam belt haying a series of circumfere y ly ged pore. rt e adr ii 's en it t ans s tube sheets a e e and. e; 10W said ports, a seriesof groups of tubes, each group consisting ofsmall tubes fiorthe p s ag o iq i pw rds, nd Of rger tubes for thefiow of liquid downwards, con;

necting said tube sheets ar d opening there{ al y'arrallsed p sf f the m s i of e m, t ans s tub Sh sav an be low said ports, tubes for the passage of Hid onn c i g, Sa tu sh e an p n therethrough, a series of radiai partition p esv sep ating he h tin P 9 "int series of Wedge shapedchambers, each conv tai ing a group of said tubes, auai r uiari hollow chamber surrounding said ports, means for supplying steam to said hollow chamber and through it tot-he outer portions of said Wedge shaped chambers, and a central exhaust pipewith. ports, opening into the various chambers for carrying o'fi' heating fluid from the contracted iIifIlQl portions of said chambers. v

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