US2192089A - Evaporator - Google Patents

Description

vuul vl l l aux/1H v U .L U U Cross Reference S. LONG EVAPORATOR Filed Nov. l, 1938 geb. 21, 1940.

2 Sheets-Sheet 1 ATTORNEYS Cross Referen S. LONG EVAPORATOR Filed Nov. l, 1938 2 Sheets-Sheet 2 ATTORNEYS Patented F eb. 27, 1940 UNITED STATES PATENT OFFICE 9 Claims.

The present invention relates to a new and improved evaporator especially designed for any non-salting evaporation, such as the concentration of clarified sugar beet or sugar cane juices.

In the process of evaporation, there are several factors which limit the capacity of a given piece of apparatus. One of these factors is the lm of water which collects on the heat transfer surface of the steam chamber and hinders the passage of heat from the steam to the evaporating chamber. Another factor is the film of vapor which forms on the heat transfer surface of the liquor chamber and also materially affects the transfer of heat. The depth of liquor in a large evaporator may often cause an appreciable increase in the boiling point of the liquor at the heat transfer surface due to hydrostatic pressure. Foaming and entrainment are also serious problems in some cases.

M In order to reduce the difficulties as outlined above, the primary object of -the present invention is to provide an evaporator in which the boiling liquor compartment and condensing steam compartment constitute spiral passages` ranged about a common axis amptedto be rotated at speed. SQ..that centrifugal force "lause the liquids to new toward the outer end of the spiral passages.

A further object of the invention is to provide an evaporator having a large heat transfer surface which is assembled within a comparatively small area combining the use of centrifugal force to aid in the removal of water film from the heat transfer surface.

A still further object of the invention is to provide a compartment for the liquor to be evaporated which is formed of spiral passages with a means of feeding the liquor thereto in a thin, rapidly moving film thereby materially reducing 4g the thickness of the vapor lm on the heat transfer surface, thus promoting surface evaporation rather than a boiling action.

The invention will be fully and comprehensively understood from a consideration of the following detailed description when read in connection with the accompanying drawings which form a part of the application.

In the drawings:

Figure 1 is a longitudinal sectional view through the evaporator and illustrating the principal details thereof;

Figure 2 is a vertical sectional View taken substantially on line 2-2 of Figure l;

Figure 3 is a fragmentary elevational view of a sheet of material employed for the forming of the spiral passages;

Figure 4 is a longitudinal sectional view taken substantially on line 4 4 of Figure 3;

Figure 5 is an enlarged fragmentary sectional 5 view of a. portion of the evaporator and illustrating an arrangement of valves for permitting the discharge of condensation and vapors, and

Figure 6 is an enlarged fragmentary sectional view of the steam discharge end of the evapolo rator. 3'1 il Referring to the drawings for a more detailed description thereof, the numeral III indicates a stationary casing adapted to house the apparatus which may be sealed and evacuated or kept under atmospheric pressure. A specially designed hollow shaft II extends transversely through the casing and is formed to provide non-communicating chambers I2 and I3 respectively, by means of the partition indicated generally at I4. 'I'he zo shaft II is free to rotate within the journals I5 mounted in the casing- II) and is driven by appropriate means such as a V belt and pulley I6. Each ond of the shaft II has a reduced portion I'l and I8 for the reception of a steam inlet pipe 25 I9 and exhaust vapor pipe 20. Each pipe I9 and 20 is attached to its respective end by means of suitable packing glands 2|, and the utility of each pipe will be more fully explained as the description proceeds. 30

As afore-indicated, the evaporator includes a liquor compartment and condensing steam compartment which constitute spiral passages arranged about a common axis and adapted to be rotated at high speed so that centrifugal force 35 will cause the liquids to flow toward the outer end of the spiral passages. The two compartments are formed by spirally winding two specially designed sheets of metal of the type illustrated in Figures 3 and 4 of the drawings. The sheets 40 of material indicated generally by the numeral 22 are formed with spaced ribs 23 and when spirally wound about the shaft I I form alternate rows of passages. Referring to Figure 1 of the drawings, the steam condensing passages are indicated at 24 and the liquor receiving passages are indicated at 25, and it will be readily understood that the depth of said passages is approximately equal to the sum of the thicknesses of the ribs 23. After the plates have been spirally wound about the shaft II the ends thereof Will terminate at diametrically opposed positions within the stationary casing Ill whereby the contents of the liquor receiving passages are discharged at one end of the casing and the steam condensate and 55 noncondensing gases are discharged at the other end of the casing.

The side Walls 26 of the spiral formation are sealed by any appropriate means such as solder or the' like and the multiplicity of spirals are preferably held in position by welding. The entire formation is then positioned within a suitable casing which may be secured thereto by any desired means and which is adapted to rotate with the formation. The casing includes a cylindrical hoop 21 and end plates 28, the end plates being keyed as indicated at 29 to the shaft EI, and may be bolted or otherwise secured to the hoop 21. This construction is provided to reduce strains due to variance of the speed of rotation.v

The hoop 21 is constructed with passages 3Il and 3| for receiving the condensed steam and thick liquor. By this construction the condensed steam, after traveling through the spirally formed steam passages, will be discharged within the collector passage 3| and likewise the liquor, after being driven by centrifugal force through the spirally formed liquor passages, will be discharged in the collector passage 30.

The side Walls 32 of the stationary casing have attached'. thereto hollow substantially ring shaped members 33 and 34 which are directly connected to the collector passages and 3|. The means for connecting the collector passage 30 with the ring 34 comprises a freely movable float valve 35 mounted in the upper end of the head plate 28 and the ring 33 is connected to the collector passage 3| by means of the thermostatic valve 36 and freely movable float valve 31 mounted in the other head plate 28, as clearly shown in Figure 1 of the drawings. Liquor is discharged from the end 39 of the ring 34 after passing from the collector passage 30, through the oat valve and into the ring 34. Likewise, steam condensate escapes through the float valve 31 from the collector passage 3| and into the ring 33 and is discharged through the end 40 of said ring 33. The non-condensible gases which represent the condition of the admitted steam after passing l through the spirally formed passages is discharged through the thermostatic valve 36Y into the ring 33.

Steam is admitted into the chamber I 2 through the inlet pipe I9 and extending from said chamber is a multiplicity of inlets 4| which cause the steam to be admitted to the spiral passages 24 and to circulate therethrough. The liquor to be evaporated is fedin a thin stream into the chamber |3 through the tube 42 which projects through the reduced encl I8 of the shaft H. The inlet liquor chamber i3 is formed with a row of minute orifices 43, which allow an even flow of liquor into the spiral liquor chamber 25. A small groove 44, see Figure 2 of the drawings, extends parallel to the row of orifices 43 to provide an even supply of liquor to all of the orifices. The supply of liquor when fed into the chamber I3, while being rotated, will be caused to deposit in the groove 44 and continual feeding, with the centrifugal action accomplished, will further cause the liquor to be supplied to the orices 43. Closely adjacent the groove 44 is provided a series of vaporoutlets 45. These outlets will be formed with raised edges 46 to prevent the flow of liquor therethrough from the chamber I3 to the spiral liquor passages 25. The vapor formed within said liquor passages will be expelled through the outlets 45 and will be exhausted at the end 41 of the pipe 20.

In operation, the evaporator rotor comprising the hollow shaft spiral compartments 24 and 25, hoop 21 and head plates 28, will be rotatedat a speed of 250 to 1500 R. P. M. Steam is admitted to the steam passage 24 through the com partment I2 of the shaft II. All condensate formed on the exterior walls of the steam passages will be discharged through the collector pasage 3| and float valve 31 and the non-condensible gases will escape through the thermostatic valve 36. The thin liquor, at the same time, is introduced into the compartment |3 of the hollow shaft and is driven by centrifugal force through the orices 43 which distribute it evenly among the sections of the liquor compartment or passages 25. The ports 45 allow the vapor from the evaporating liquor to pass back into the compartment |3 and be discharged through the exhaust end 46 of the pipe 2U. The thick liquor is then driven by centrifugal force to the collector passage 30 and thence through the float valve 35 into the collector ring 34 for discharge from the end 39 of said ring.

From the above description and operation it will be readily apparent that there is provided an evaporator so designed that the collection of a film of Water on the heat transfer surface of the steam chamber is eliminated. Means has also been provided for freeing and discharging the lm of vapor which normally forms on the heat transfer surface of the liquor chamber which materially hinders the ow of heat. The evaporating liquor is driven by centrifugal force to cause the liquor to flow toward the outer end of the evaporator and to be discharged therefrom'.

Also it will be understood, of course, by those skilled in the art that variations in the herein,- above described device involving the substitution of substantial equivalents for the devices de,- scribed are intended to be comprehended within the spirit of the present invention and that the invention is capable of extended application and is not confined to the exact showing of the drawings nor to the precise construction described and, therefore, such changes and modifications may be made therein as do not affect the spirit of the invention nor exceed the scope thereof as expressed in the appended claims.

What is claimed is:

l. A device of the character described ccmprising a stationary casing, a shaft rotatably disposed Within said casing and forming pair of nonecommunicating chambers, means for forming a multiplicity of spiral passages circumferentially of said shaft, said means including a ribbed sheet of metal. wrapped on said shaft and the ribs thereof being arranged perpendicular to the axis of the spiral, a cylindrical hoop-like member attached to said spiral and adapted to support the ribs on the outside thereof, head plates attached to each end of said spiral and forming with said hoop-like member an enclosing casing for said spiral passages, means admitting a heating medium to certain of said passages and means for feeding an evaporating liquid to other of said passages.

2. A device of the character described comprising a stationary casing, a shaft rotatably disposed within said casing, said shaft being hollow throughout its length, a multiplicity of spaced spirally formed walls defining spiral passages therebetween having communication with said shaft, one passage arranged in heat transfer relation with the other, means for admitting a heating medium from said shaft to certain of said passages and means for feeding an evaporating liquid from said shaft to the other of said passages.

3. A device of the character described comprising a stationary casing, a shaft rotatably disposed with-in said casing, said shaft being hollow throughoutits length and forming a pair of noncommupicating chambers, a multiplicity of spaced spirall' formed Walls defining spiral passages therebetween having communication with said shaitone passage arranged in heat transfer relation with the other, means for admitting a heating medium from one of-said chambers to one of said passages, and means for feeding an evaporating liquid from the other of said chambers to other of said passages.

4. A device of the character described comprising, aotativeiineliiber, a pair of sheet-like elements wound upon said memben rib-like means on said elements having contacting relation one with the other to support the sheet-like elements in predetermined spaced relation and cooperating therewith to provide two sets of conduits extending circumferentially about the axis of said member, with the two sets of conduits arranged in heat transfer relation with respect to each other, said sheet-like elements being fixedly related one to the other and with respect to said member for rotation therewith., one set of said conduits being adapted to circulate a heating fluid therethrough and the other set of said conduits being adapted to circulate a fluid to be evaporated, and meansl for controlling the inlet and exit of the respective iiuids with respect to said two sets of conduits.

5. A device of the character described con:- prising a otative member being hollow throughout its leng an'd``6ming a pair of non-communicating chambers, a pair of sheet-like elements wound upon said member, rib-like means on said sheet-like elements having contacting relation one with the other to support the sheet-like elements in predetermined spaced relation and cooperating therewith to provide two sets of conduits extending circumferentially about the axis of said member, with the two sets of conduits arranged in heat transfer relation with respect to each other, said sheet-like elements being xedly related one to the other and with respect to said member for rotation therewith, one set of said conduits being adapted to circulate a heating uid therethrough received from one of said chambers and the other set of said conduits being adapted to circulate a fluid to be evaporated and received from the other of said chambers, and means for controlling the inlet and exit of the respective iiuids with respectto said two sets of conduits.

6.,A device of the character described comprising a stationary casing, atsrlgyemably disposed Within said casing having formed therein a pair of non-communicating chambers, a multiplicity of spaced spirally formed walls dening spiral passages therebetween having communication with said shaft, one passage arthe other, enclosing ranged in heat transfer relation with a casing journalled on said shaft for said spiral passages, discharge means within said second casing and communicating with said passages, means for admitting a heating medium in, certain of said passages, and means for feeding an evaporating liquid to other of said passages.

7. A device of the character described comprising a stationary casing, a shaft rotaia bly disposed within said casing, said shaft being hollow throughout its length and forming a pair of noncommunicating chambers, a multiplicity of spaced spiraliy formed walls defining spiral passages therebetween having communication with said shaft, one passage arranged in heat transfer relation with the other, a casing journalled on said shaft and rotatable therewith for enclosing said spiral passages, said casing having a collector passage therein, collector' rings secured to each end of said stationary casing, means for admitting a heating medium to certain of said spiral passages, ine-ans for feeding an evaporating liquid to other of said spiral passages, and means within said second casing for permitting discharge of the evaporated liquid and heating medium.

8. A device of the character described comprising a stationary casing, a shaft rotatably disposed within said casing, said shaft being hollow throughout its length and forming a pair of non-communicating chambers, a multiplicity of spaced spirally formed walls defining spiral passages therebetween having communication with said shaft, one passage arranged in heat transfer relation with the other, a casing journalled on said shaft and rotatable therewith for enclosing said spiral passages, said second casing having a collector passage therein, collector rings secured to each end of said stationary casing, means for admitting heating medium to certain of said spiral passages, means for feeding an evaporating liquid to other of said spiral passages, and means within said second casing for permitting discharge of the evaporated liquid and heating medium, said means including a thermostatically controlled valve mounted in one end of said second casing and float waves mounted in each end of said second casing.

9. A device of the character described comprising a stationary casing, a shafmtggttably disposed within said casing, saidaft being hollow throughout its length and forming a pair of non-communicating chambers, a multiplicity of spaced spirally formed walls dening spiral passages therebetween having communication with said shaft, one passage arranged in heat transfer relation with the other, means for admitting steam to one of said chambers, means for admitting and discharging an evaporating liquid to the other chambers, said shaft having a plurality of orifices formed therein for admitting liquid to certain of said passages and having a second row of larger orifices for permitting the escape of vapor from said passages into one of the chambers within the shaft, said larger oriices having raised edges to prevent the ow of liquid therethrough.

SAM LONG.

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