US3247888A - Electrically heated film evaporator - Google Patents

Electrically heated film evaporator Download PDF

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Publication number
US3247888A
US3247888A US290458A US29045863A US3247888A US 3247888 A US3247888 A US 3247888A US 290458 A US290458 A US 290458A US 29045863 A US29045863 A US 29045863A US 3247888 A US3247888 A US 3247888A
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United States
Prior art keywords
tube
evaporator
wall
solution
electrically heated
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US290458A
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English (en)
Inventor
Mueller Heinrich
Honsberg Werner
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BASF SE
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BASF SE
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Filing date
Publication date
Application filed by BASF SE filed Critical BASF SE
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Publication of US3247888A publication Critical patent/US3247888A/en
Anticipated expiration legal-status Critical
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
    • F24H1/10—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium
    • F24H1/101—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium using electric energy supply
    • F24H1/102—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium using electric energy supply with resistance
    • F24H1/105—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium using electric energy supply with resistance formed by the tube through which the fluid flows
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D1/00—Evaporating
    • B01D1/0011—Heating features
    • B01D1/0017—Use of electrical or wave energy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D1/00—Evaporating
    • B01D1/06—Evaporators with vertical tubes
    • B01D1/065—Evaporators with vertical tubes by film evaporating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D1/00—Evaporating
    • B01D1/30—Accessories for evaporators ; Constructional details thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D1/00—Oxides or hydroxides of sodium, potassium or alkali metals in general
    • C01D1/04—Hydroxides
    • C01D1/42—Concentration; Dehydration
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/0014—Devices wherein the heating current flows through particular resistances
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S159/00—Concentrating evaporators
    • Y10S159/01—Electric heat
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S159/00—Concentrating evaporators
    • Y10S159/34—Caustic

Definitions

  • This invention relates to an electrically heated evaporator. More specifically it relates to a film evaporator for vaporizing caustic alkali solutions.
  • Film evaporators of the type mentioned may consist for example of a vertical or substantially vertical tube preferably made of nickel.
  • the solution to be dehydrated flows down the inner surface of the tube as a coherent film. If at the same time-the tube is heated, and the amount of heat supplied and the solution fed in bear a certain relation to each other, it may be expected that the water will be vaporized for the most part and that a substantially anhydrous melt will be discharged at the lower end of the tube.
  • One prior art heating means comprises electrical heating elements arranged concentrically along the length of the evaporator tube.
  • the heat is transmitted from the heating elements via a heat-resistant protective layer to an inner tube of a nickelchromium-cobalt alloy which in turn heats the evaporator tube by radiation.
  • a heat-resistant protective layer Owing to the high heat resistance between heating element, protective layer, inner tube and evaporator tube, it is only after about four hours that thermal equilibrium is set up, because it is only after this period that the heating element has achieved its end temperature.
  • the specific loading of the heating surface of the evaporator tube is low, a tube having an external diameter of 125 mm. and a length of 3.96 m. handling only 72 kg./h. of 50% caustic alkali solution. An evaporation capacity of 19 kg./h.
  • Another disadvantage of this arrangement is that it is impossible to shut off the plant within a short time because the high temperature of the heating 3,247,888 Patented Apr. 26, 1966 trically heated film evaporator whose heating-up can be quickly and easily controlled.
  • Another object of the invention is to provide a film evaporator which can be heated within' a short period.
  • Yet another object of the invention is to produce different amounts of heat along the length of the evaporator tube according to the heat required in the tube.
  • the electrically heated film evaporator having a preferably vertically arranged evaporator tube. It is characterized by the following features: (a) the evaporator tube is arranged as an electrical resistor in the circuit; (b) a feed line is provided at or near the upper end of the tube for the supply of the material to be dehydrated to the inner wall of the evaporator tube; and, (c) the evaporator tube is provided at or near each end with a contact plate for the supply of electric current.
  • the evaporator tube may be tapped for uniform distribution of the liquid fed in.
  • a plurality of evaporator tubes may be provided, preferably connected in series.
  • the use of the evaporator tube as an electric conductor generating the heat within the wall of the tube is the most favorable solution because the tube has alternating current flowing either through its whole length or through only a portion thereof so that the tube is heated according to requirements.
  • the heat may be varied within wide limits by-regulation of the current and voltage.
  • the evaporator tube may be enveloped in suitable insulating material, for example mineral wool, to keep heat loss low.
  • the caustic alkali solution is supplied at or near the top of the evaporator tube, flows down on the inner wall of the tube and leaves at the bottom of the tube dehydrated to a greater or lesser degree, depending on the temperature -to which it has been exposed. Then it is collected.
  • the evaporated water flows in the opposite direction, passes through the upper end of the tube as vapor mixed with a small amount of air, and is passed to a condenser which condenses the water vapor.
  • the remaining air is blown into the atmosphere by the action of a fan.
  • the output of the fan is controlled so that the amount of air sucked in is just suflicient to prevent water vapor issuing from the lower end of the evaporator tube.
  • evaporator tube as an electric conductor offers the additional advantage that the metal cross-section of the tube may be varied at will by metals welded onto the tube or by the use of tubes having different wall thickness or unequal diameter. This makes it possible to vary the heat supplied to different parts of the tube.
  • the lower end of the heated portion of the tube for about 50 cm., has twice the metal cross-section of the remainder of the length of the tube and consequently, as compared with the rest of the tube, receives only one quarter of Joules energy. In this way it is possible easily to maintain any desired temperature of the effluent melt and to avoid overheating.
  • the use of the evaporator tube as an electric conductor otters great advantages in operation.
  • the heating-up period when starting up from cold is only a few minutes.
  • the temperature of the tube is not very much higher than the temperature of the solution. Therefore the risk of overheating is very slight.
  • Each nickel tube 1a, 1b and 1c are connected electrically in series by means of the contact plates 2, 3, 2 and 3 which are in elastic connection with each nickel tube, and an alternating current is supplied to the electrically connected tubes.
  • Each nickel tube is 7 In. in length and 70 mm. in internal diameter and has a wall thickness of 2.5 mm. in the upper portion and an increased wall thickness of mm. in the bottom portion extending about 50 cm. axially upwardly from the bottom of the heated portion of the tube.
  • Each tube as shown thus serves as an electrical conductor for about 6 m. of its length.
  • Caustic soda solution is introduced through a feed line 4a to the upper end of the nickel tube 1a and above the contact plate 2 (plate 2' in tubes 1b and 1c), is distributed along a tapped portion 5a of the inner wall 6a of the tube, flows down the inside of the tube as a uniform film and leaves the tube as a dehydrated melt at the lower end 7a thereof and can be collected there.
  • the roughened portion 5b of the inner wall 6b of tube 1b is likewise shown as a tapped thread, while this roughened portion 50 on the inner wall 6c of tube is in the form of a cross-notched area. In each case the roughened portion is about 100 mm. long in the axial direction and is located immediately downstream from the feed line.
  • Each evaporator tube is heat insulated with mineral wool 9a, 9b and 90.
  • the tube 1a is loaded with a current of 5000 amp, a voltage drop of about 12 volts is produced in the heated condition. At the same time about 100 kg./ h. of a 50% caustic soda solution is metered in through the feed line 4a. The solution is dehydrated in contact with the inner wall do. When the melt leaves the tube at 7a, it still contains about 0.5 to 1% of water. Its temperature is 380 to 400 C.
  • Each square meter of the inner surface of the tube 10 therefore evaporates 38 kg. of water per hour. This value is not however the maximum value. Loading of the tube wall with electric current is limited by the velocity of the vapor at the upper end and this should advantageously not exceed 10 m./sec.
  • Each of the tubes 1b and 1c can be operated in the same manner under the same conditions so as to handle a total feed to all three tubes of 300 kg./h. of the 50% caustic soda solution. While only three tubes are illustrated in the drawing, it is advantageous in an industrial plant to bank together six or more tubes of appropriate length since this -will give a satisfactory voltage drop when connected electrically in series.
  • the evaporator described is also suitable for dehydrating caustic alkali solutions having higher contents of caustic alkali, for example 71% caustic soda solution, which is to be regarded as a melt because it solidifies at room temperature. It is advantageous to heat up the caustic alkali solutions by cheaper sources of energy than electrical energy to a temperature at or near the boiling points prior to evaporation and only then to supply the solutions to the film evaporator. For example 50% caustic soda solution may with advantage first be concentrated to 71% by means of conventional mul-tipass evaporators and then dehydrated in the electrically heated film evaporator.
  • An electrically heated film evaporator for dehydrating caustic alkali solutions comprising: a substantially vertical evaporator tube, said evaporator tube being connected in an electrical circuit as an electrical resistance; means to uniformly distribute the solution to be dehydrated on the inner wall surface of said tube including (A) a feed line for supplying the solution at an angle to the axis of said tube to impinge on the inner wall of said tube in the neighborhood of the upper end of said tube and (B) a roughened portion on the inner wall of said tube extending over a short axial distance within said tube beneath and immediately downstream from said feed line; and means for supplying electric current to said evaporator tube.
  • An evaporator as claimed in claim 1 comprising a plurality of said evaporator tubes connected electrically in series.
  • An evaporator as claimed in claim 1 wherein a fan is connected in gaseous communication with the upper end of said evaporator tube for withdrawal of water vapor and air through said upper end.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Organic Chemistry (AREA)
  • Fluid Mechanics (AREA)
  • Inorganic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
US290458A 1962-06-27 1963-06-25 Electrically heated film evaporator Expired - Lifetime US3247888A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEB67832A DE1159413B (de) 1962-06-27 1962-06-27 Elektrisch beheizter Duennschichtverdampfer zur Entwaesserung von AEtzalkaliloesungen

Publications (1)

Publication Number Publication Date
US3247888A true US3247888A (en) 1966-04-26

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US290458A Expired - Lifetime US3247888A (en) 1962-06-27 1963-06-25 Electrically heated film evaporator

Country Status (5)

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US (1) US3247888A (da)
BE (1) BE634154A (da)
DE (1) DE1159413B (da)
GB (1) GB1039832A (da)
NL (1) NL294585A (da)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3370635A (en) * 1964-04-16 1968-02-27 Garrett Corp Evaporator tube assembly
US3604893A (en) * 1967-10-11 1971-09-14 Laporte Titanium Ltd Method and apparatus for electrically heating a fluid
US5220637A (en) * 1992-06-26 1993-06-15 Aai Corporation Method and apparatus for controllably generating smoke
EP0637723A1 (fr) * 1993-08-03 1995-02-08 Electricite De France Dispositif échangeur pour le chauffage d'un fluide visqueux
FR2797371A1 (fr) * 1999-08-05 2001-02-09 Cogema Thermosiphon par tube a passage de courant
US20050100709A1 (en) * 2003-11-06 2005-05-12 3M Innovative Properties Company Retroreflective elements comprising a bonded resin core and pavement markings
US20050155547A1 (en) * 2004-01-21 2005-07-21 Lenius Steven J. Disc coater
US20050158461A1 (en) * 2004-01-21 2005-07-21 3M Innovative Properties Company Methods of making reflective elements
CN105126368A (zh) * 2015-07-27 2015-12-09 上海中科易成新材料技术有限公司 一种降膜蒸发器
US20180134578A1 (en) * 2015-05-13 2018-05-17 Breakthrough Technologies, LLC Liquid Purification with Film Heating

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3629551A (en) * 1968-10-29 1971-12-21 Chisso Corp Controlling heat generation locally in a heat-generating pipe utilizing skin-effect current

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US568615A (en) * 1896-09-29 Apparatus for evaporating liquids
US912994A (en) * 1907-06-08 1909-02-23 Westinghouse Electric & Mfg Co Electric heating apparatus.
US1727585A (en) * 1927-08-23 1929-09-10 Robert A Carleton Fluid heating and vaporizing apparatus
US1932406A (en) * 1933-04-28 1933-10-31 Joseph W Harris Electric liquid-heating apparatus
GB482715A (en) * 1935-10-01 1938-04-01 Siemens Ag Improvements in or relating to electric steam generators or superheaters for high pressures and temperatures
FR891660A (fr) * 1938-03-05 1944-03-15 Wiener Locomotiv Fabriks Actie Installation de production de vapeur
US2873799A (en) * 1956-01-09 1959-02-17 Allied Chem Method and apparatus for dehydrating aqueous caustic solutions
US2891375A (en) * 1956-01-06 1959-06-23 Moulinage Et Retarderie De Cha Apparatus for the production of high-bulk yarn

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US568615A (en) * 1896-09-29 Apparatus for evaporating liquids
US912994A (en) * 1907-06-08 1909-02-23 Westinghouse Electric & Mfg Co Electric heating apparatus.
US1727585A (en) * 1927-08-23 1929-09-10 Robert A Carleton Fluid heating and vaporizing apparatus
US1932406A (en) * 1933-04-28 1933-10-31 Joseph W Harris Electric liquid-heating apparatus
GB482715A (en) * 1935-10-01 1938-04-01 Siemens Ag Improvements in or relating to electric steam generators or superheaters for high pressures and temperatures
FR891660A (fr) * 1938-03-05 1944-03-15 Wiener Locomotiv Fabriks Actie Installation de production de vapeur
US2891375A (en) * 1956-01-06 1959-06-23 Moulinage Et Retarderie De Cha Apparatus for the production of high-bulk yarn
US2873799A (en) * 1956-01-09 1959-02-17 Allied Chem Method and apparatus for dehydrating aqueous caustic solutions

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3370635A (en) * 1964-04-16 1968-02-27 Garrett Corp Evaporator tube assembly
US3604893A (en) * 1967-10-11 1971-09-14 Laporte Titanium Ltd Method and apparatus for electrically heating a fluid
US5220637A (en) * 1992-06-26 1993-06-15 Aai Corporation Method and apparatus for controllably generating smoke
WO1994000715A1 (en) * 1992-06-26 1994-01-06 Aai Corporation Method and apparatus for controllably generating smoke
EP0637723A1 (fr) * 1993-08-03 1995-02-08 Electricite De France Dispositif échangeur pour le chauffage d'un fluide visqueux
FR2708726A1 (fr) * 1993-08-03 1995-02-10 Electricite De France Dispositif échangeur pour le chauffage d'un fluide visqueux.
FR2797371A1 (fr) * 1999-08-05 2001-02-09 Cogema Thermosiphon par tube a passage de courant
US20050100709A1 (en) * 2003-11-06 2005-05-12 3M Innovative Properties Company Retroreflective elements comprising a bonded resin core and pavement markings
US20050155547A1 (en) * 2004-01-21 2005-07-21 Lenius Steven J. Disc coater
US20050158461A1 (en) * 2004-01-21 2005-07-21 3M Innovative Properties Company Methods of making reflective elements
US20180134578A1 (en) * 2015-05-13 2018-05-17 Breakthrough Technologies, LLC Liquid Purification with Film Heating
US10954138B2 (en) * 2015-05-13 2021-03-23 Breakthrough Technologies, LLC Liquid purification with film heating
CN105126368A (zh) * 2015-07-27 2015-12-09 上海中科易成新材料技术有限公司 一种降膜蒸发器

Also Published As

Publication number Publication date
NL294585A (da)
BE634154A (da)
DE1159413B (de) 1963-12-19
GB1039832A (en) 1966-08-24

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