Abstract: A distillation column is arranged so that a liquid hole which allows liquid containing a polymerizable organic compound to flow from on a tray supporting member downward is formed in a part of the tray supporting member, for example, a support ring, so that substantial retention of the liquid on the tray supporting member is avoided. Therefore, the liquid, such as crude acrylic acid, is allowed to smoothly flow down from on surfaces of a tray and the tray supporting member, thereby causing no substantial retention of the liquid. As a result, polymerization which tends to occur when the liquid is retained on the surfaces of the tray and the tray supporting member thereby being heated is effectively prevented, and the polymerizable organic compound is efficiently purified.

Abstract: A method and apparatus for recycling and recovering potentially explosive solvents includes providing a contaminated solvent to a distillation tank, vaporizing the solvent in the distillation tank, thereby producing solvent vapor, condensing the solvent vapor, and adding a free radical scavenger substance to the distillation tank during the heating step. The vapor is then condensed and collected in a clean solvent tank where additional free radical scavenger substance is added to the clean solvent tank. Preferably, contaminated solvent is introduced into the solvent recovery system by providing contaminated solvent into contaminated solvent tank which is connected to the distillation tank, and an oxygen displacer substance is provided to the contaminated solvent tank and the clean solvent tank so as to minimize the amount of free oxygen in the tanks.

Abstract: A method of distillation having the steps of drawing a volume of untreated water containing impurities into a container, applying a vacuum to the container, applying an oscillating electric charge to the untreated water thereby producing water vapor from the untreated water, capturing the water vapor in a vapor pipe, and condensing the water vapor back into a liquid form in a collecting chamber. An oscillating frequency of 2.6 gigahertz, either by sonic or electric charge, displaces the hydrogen bonding between water molecules. This displacement permits distillation at a low temperature without the infusion of large amounts of energy common in previously known methods.

Abstract: A process for the purification of pentafluoroethane (F125) containing chloropentafluoroethane (F115). The F125-F115 mixture to be purified is subjected to an extractive distillation, the extractant being a C.sub.5 -C.sub.8 perfluoroalkyl halide.

Abstract: A distiller control circuit includes a power bus with first and second lines and a fan circuit connected across the lines and having a fan motor and a fan thermostat in series. There is also a heater circuit connected across the lines and having a heater and a heater thermostat in series. The fan thermostat is normally open, closes at an elevated temperature and automatically re-opens when the temperature subsides. The heater thermostat is normally closed, opens at an elevated temperature and must be manually reset to the closed position.The raw water vessel has a reset mechanism with a pivot-mounted bar and a contact surface on the bar. When the contact surface is depressed, the bar is urged to the second position for resetting the heater thermostat. The heater circuit terminates in a two-stud male connector and the platform has a two-slot female connector. The studs slide into electrically-conductive engagement with the slots when the raw water vessel is inserted into the condensing platform.

Abstract: A device for distilling a liquid feed which includes a core pipe and a first fluid in a series of helically wound tubes or vanes employing the core pipe as a mandrel. The liquid to be distilled passes over a series of interstices which are created by the helically wound tubes or vanes and a distillate recovered as a consequence.

Abstract: A method and apparatus for separating components from a mixture includes a condensing surface located in a high vapor concentration region above the source of evaporated liquid. The evaporated liquid is condensed on the condensing surface. The condensed liquid is removed from the condensing surface while it remains liquid, using substantially capillary forces. A plurality of open grooves are formed on the condensing surface. The grooves channel the condensed liquid on the condensing surface away from the mixture. The grooves can be capillary grooves which satisfy the Concus-Finn Inequality.

Abstract: A solvent extraction apparatus which includes a heating plate, a vessel for containing a solvent, an extraction thimble to obtain a sample to be extracted from said vessel and a cooler for condensing evaporated solvent vapors. The cooler is connected to the vessel for containing the solvent, preferably by an adaptor. A lifting rod is provided which passes through the cooler which, at its lower portion, is provided with a drip rim on which the extraction thimble is detachably fixed. The thimble can be moved vertically by the lifting rod and the flow of solvent into and out of the cooler can be regulated by the lifting rod.

Abstract: A portable distiller convertible between an operating mode and a storage mode which permits easy transport includes a boiler vessel, a condenser, and a collection container. The condenser is mounted on a two-way lid which engages the top of the boiler in an operating mode to support the condenser over the boiler. The lid is insulated to prevent the transfer of heat from the boiler to the condenser. The lid is reversible to allow the condenser to be inserted into the boiler vessel for storage. The container may also be stored in the boiler, and preferably receives the condenser for storage.

Abstract: A method of concentrating chemicals for semiconductor devices, which includes the steps of heating a sample container by using a high-energy light source, vaporizing the chemicals by injecting a high-temperature gas into the sample container through an injection opening in the sample container and discharging the vaporized chemicals by the pressure of the gas through a gas outlet formed on the sample container. An apparatus of concentrating chemicals for semiconductor devices includes a sample container having a sample-supply window, a gas-injection opening and a gas outlet. A high-energy light source heats the sample container and a gas-supply source supplies the gas through a gas-injection opening in the sample container. A gas-heating device located between the sample container and the gas-supply source heats the gas provided by the gas-supply source.

Abstract: Improved kugelrohr or apparatus for distilling or separating liquids. It includes a rugged, reliable air oven and drive unit with numerous safety features. One or more external guards eliminate burn hazard and risk of accidental contact. A thermal isolation support isolates the oven from its rest surface. A grounded heating element eliminates shock hazards. The oven is fitted with a grommet or bushing to support a flask connected to one or more additional flasks in a series. The outlet of the last flask in the series is connected to a drive tube via a flexible coupling. The drive tube is connected to a rotary bearing assembly mounted on a drive unit. The oven and the flasks may include impellers for circulating air to enhance heating efficiency.

Abstract: A process for preparing and/or extracting samples by heating them together with a solvent in a container under pressure, using a Soxhlet apparatus. The samples are dried by heating in a container; and the resultant vapors are drawn off to generate a vacuum in the container.

Abstract: A process is provided for the isolation of (meth)acrylic acid from a mixture containing (meth)acrylic acid as the main component and lower aldehydes as secondary components by rectification in a rectification column having a stripping section and a rectification section, wherein the starting mixture containing the (meth)acrylic acid to be isolated by rectification is not fed directly to the rectification column but is first passed into a heated dwell vessel which is connected to the vapor side of the rectification section of the rectification column and in which the starting mixture is kept at the boil and, instead of the starting mixture as such, the bottom liquid of the dwell vessel is fed to the rectification column.

Abstract: The water distiller 10 includes a plurality of housings 12, 14, 16 each mounted below a support plate 32. A voltage regulator 144 maintains a desired voltage potential between heating probes 34 and 36 within a heating bowl 46. An operator selector 142 automatically regulates the flow of water through inlet valve 70 to control the incoming water flow rate to the heating bowl. Area contact between water in the heating bowl and a substantially horizontal plate 42 at the lower end of each heating probe determines the electrical power used by the distiller, and maintains water in the heating bowl at substantially a constant level. An improved particle trap 80 and vent valve 100 provide reliable and safe operation of the distiller. Heating bowl 46 and a water inlet line 76 may be easily removed for cleaning the distiller.

Abstract: Use of labels for labelling rubber parts, in particular tires, comprisinga) a base layer comprising a laser-inscribable, co-vulcanizable, pale rubber blend whichb) contains an additive which produces a color change on laser irradiation,c) is, if desired, covered by a protective covering which is transparent in the visible region and in the near IR region, andd) is, if desired, coated on one side with a self-adhesive composition whiche) is, if desired, covered by a release paper or a release film.

Abstract: Water distillation apparatus for convenient domestic use including a housing containing a condenser coil and having a vapor inlet and a distillate outlet. A fan cools and condenses vapor. A boiler is releasably connected to the housing by a vapor discharge outlet in the form of an inwardly-directed cylinder and the vapor inlet has a cooperating spigot termination so that the boiler may be moved away from the vapor inlet and filled with water for batch distillation. The distilland water is heated with an electric heating element and the distillate is discharged through a carbon filter into a discrete glass pitcher adjacent to the boiler. The arrangement permits easy removal of the boiler from the housing for filling with distilland or cleaning, as well as the convenient replacement of the boiler in the housing afterwards.

Abstract: A method for concentrating a clay slurry by subjecting the slurry to indirect heat exchange within a heat exchanger to elevate the temperature of the slurry while specifically suppressing boiling of the liquid within the heat exchanger. The heated slurry is subsequently subjected to a rapid pressure reduction which causes flash evaporation of part of the liquid. The rapid pressure reduction can occur in a separation vessel.

Abstract: A microwave distillation apparatus is provided. The apparatus includes a microwave heating chamber having a plurality of walls. A vessel is located within the chamber for containing a liquid to be distilled. The vessel has a mouth for receiving the liquid. A connecting tube extends though an opening formed in one of the plurality of chamber walls. The connecting tube has a first end thereof for sealably engaging the mouth of the vessel, and a second end thereof extending outwardly from the chamber. A biasing assembly is located outside of the chamber, and engages the connecting tube with a biasing force to maintain the seal between the connecting tube and the mouth of the vessel. A distillate capture assembly is connected to the connecting tube for receiving vapors emitted from the liquid when heated, and for condensing the vapors into a liquid distillate for capture and storage.

Abstract: A distilling apparatus which includes a water chamber to receive cold water from an external water supply source, a heating chamber having an electric heater controlled to heat water to the boiling point, a guide pipe connected between the bottom side of the water chamber and the bottom end of the heat chamber to guide water from the water chamber to the heating chamber, a radiating coil pipe connected to a distilled water drain pipe outside the apparatus, and a steam pipe connected between the steam chamber and the radiating coil pipe and passing through the water chamber to guide steam from the heating chamber to the radiating coil pipe, permitting steam to be condensed into distilled water and heat to be absorbed by water in the water chamber.

Abstract: A water purification apparatus positionable on an existing dispenser has a valve control member positionable in the water plenum of the dispenser to control release of purified water from the apparatus to the dispenser. A feedwater tank receives supply water which is fed to a water level control tank to maintain the water level in the boiler of the apparatus above the heating element. The control tank includes a partition separating a main reservoir from a de-foamer control chamber within which anti-foaming agent may be added. A condenser is coiled into a number of convolutions about a central opening and has external heat exchanger fins. An end cap assembly closes the central opening except for a small portion through which air is blown by a fan so that substantially all of the air flows over the fins. The boiler is a cylindrical container having a peripheral lip about an open end on which a lid having a steam outlet tube is positioned.

Abstract: Inhibition of the formation of unsaturated carbon compounds during the heating of 141b by the use of a vessel pre-treated with HF to form an iron fluoride coating on the internal surfaces of said vessel.

Abstract: A distilling device has an undistilled water tank to contain undistilled water, a cover covering the tank, a water heating area communicating with the tank, a high-frequency oscillator disposed under the water heating area, a heater disposed above the water heating area, a cooling area beside the heater, and a water collecting can disposed under the cooling area. The cooling area and the water heating area are separated by a separating plate.

Abstract: A distillation device with a rotating evaporator flask disposed within a heated bath. The heated bath is movable down and away from the evaporator flask to provide space for an evaporator flask support below the evaporator flask. The evaporator flask support holds the evaporator flask while it is connected or disconnected from the rotary drive. In addition, a U-shaped case accommodates the collecting flask and/or evaporator flask. The case supports the flask in an upright manner and facilitates positioning and transporting of the flask.

Abstract: An apparatus for converting seawater or other contaminated water into pure water for reuse including: a source of the contaminated water; a first horizontal housing connected to the source of contaminated water and having a heat exchanger therein for vaporizing the contaminated water therein; a vertical housing connected to the distal end of the first horizontal housing for fluid communication therebetween; a second horizontal housing connected at its proximate end to the vertical housing for fluid communication therebetween, the second horizontal housing having a heat exchanger therein for condensing vapor therein; a weir vertically mounted in the first housing for retaining a portion of the contaminated water in the first housing and allowing the other portion of the contaminated water to pass through the heat exchange evaporator from the proximate to distal end of the first housing.

Abstract: The water distillation system according to the invention recaptures and utilizes the inherent heat of transformation in converting from the vapor to the liquid states. The water distillation system efficiently removes volatile gases and impurities from the distillate and recaptures and reuses the heat from the impurities. A water seal is created to seal the drive shaft aperture of the compression housing and the rotating drive shaft of the compression rotor. In addition, the compression rotor is assembled of ultra-light, strong member in such a manner to significantly reduce the manufacturing and maintenance costs of the compression rotor drive mechanism.

Abstract: A vapor compression distillation/product concentration device includes an evaporator/condenser core, with alternating boiling and condensing chambers with edge manifolds such that substantially the entirety of each plate surface is used as a heat transfer surface. Seals are conveniently formed between adjacent plates by laying a bead of liquid gasketing material such that as the plates are laid atop each other and cured, a waffle-like seal is formed surrounding the contact points between adjacent plates which interlocks the seal with the plates. A truly perpendicular fluid flow is achieved between the alternating boiling chambers and condensing chambers as each fluid traverses the entirety of each chamber in a unidirectional flow as it passes through the evaporator/condenser core.

Abstract: A water distillation apparatus and method include an improved control system for operation and maintenance, condensers with plastic to metal seals between a plastic condenser manifold and metallic cooling tubes, and a filter with steam bypass to allow for easy sterilization of the filter and remaining distillation system. The control system includes a three pronged probe assembly for monitoring conditions within an evaporation chamber. One of the three probes monitors steam conductivity and provides a steam fault signal to indicate an upper level of contaminants in the steam. A purge pump is responsive to fault signals, including the steam fault signal, to pump water from the evaporation chamber. Improved techniques are also provided for periodically dumping a portion or all of the water in the heating pan to reduce contamination of the system.

Abstract: A compact, transportable and self-contained apparatus for treating wastewater containing as impurities and pollutants various non-volatile (at water boiling points) fluids such as greases, oils and soaps, having a vessel/evaporator for receiving the wastewater, a heater below the evaporator to heat the wastewater admixture and boil off the water, a collector to draw off the non-volatile fluids from substantially the entire height of the water evaporator, and automatic refill/shutdown control devices for the apparatus.

Abstract: A water purification method and apparatus is described which distills a contaminated water supply having contaminants dissolved therein with electrically powered spaced apart immersion electrodes. When connected to a source of alternating electrical current, the electrode members cooperate to distill water by heating while concurrently removing the contaminants as solid precipitates in the contaminated remaining water.

Abstract: A distilled water supply device including a stand, a condensing unit mounted on the stand and separated by a partition wall into an upper chamber, which receives water from an external water source, and a bottom chamber, which condenses steam into distilled water, a heating unit detachably mounted inside the stand below the condensing unit and controlled to heat water from the upper chamber into steam, permitting steam to be guided into the bottom chamber for condensing, a vertical guide pipe for guiding water from the upper chamber to the heating unit, a vertical steam pipe for guiding steam from the heating unit to the bottom chamber for condensing.

Abstract: A method for increasing the rate of evaporation of water in a humid atmosphere by providing a high frequency electric field at the evaporating surface of the water. The method is an energy-efficient alternative to attempts to lower the humidity of the air surrounding water to be evaporated.

Abstract: A plate-type distillation/condensation apparatus and a method of using same to separate at least two volatility-differing liquid or vapor components from a mixed fluid stream thereof are disclosed, wherein the apparatus contains at least one flow plate having formed on a common facial surface thereof at least one distillation/condensation chamber containing an inlet port for the mixed fluid stream; a primary flow channel in fluid communication with the inlet port; one heat exchange conduits, wherein (i) a first heat exchange conduit for a first cooling fluid is disposed in a first heat exchange contact with the primary flow channel sufficient to condense at least a portion of a first vapor component into a first condensate phase, or (ii) a first heat exchange conduit for a heating fluid is disposed in a second heat exchange contact with the primary flow channel sufficient to boil at least a portion of a first liquid component into a first vapor phase, and a second heat exchange conduit for a second cooling fl

Abstract: Volatile acids containing metal salt impurities, such as metal pickling solutions-are regenerated by a process in which the acid is subjected to sulfuric acid distillation. Resulting volatile acid vapor is condensed and recycled to the pickle tank, while the residual acid mixture is treated in an acid sorption unit, preferably of the acid retardation type. Acid sorbed in the acid sorption unit is periodically eluted with water and recycled, while metal impurities are rejected in a deacidified by-product solution.

Abstract: A distilling apparatus for distillation of water, including a condensing chamber divided into an upper holding space for receiving water from a water source and a lower holding chamber for condensing steam into water, a heating chamber controlled to heat water from the upper holding space into steam and having a steam outlet connected to the lower holding space for guiding steam into the lower holding space for condensing, a hot water chamber, which receives condensed water from the lower holding space of the condensing chamber, and a cold water chamber, which receives distilled water from the hot water chamber and cools it down by an electronic cooler.

Abstract: An evaporator, which includes a water chamber for receiving water to be evaporated. A plurality of evaporator tubes which when heated, and when water is on an inner wall of a tube, evaporates at least a portion of that water. A plurality of distributors spatially connecting the water chamber with the evaporator tubes in a manner so that each distributor uniformly and distributes the water from the water chamber to an inner wall of a corresponding evaporator tube. A heat source, which heats the plurality of tubes to an evaporation temperature. Apparatus distills the water vapor resulting from the water evaporation to provide distilled water.

Abstract: A method for the separation and recovery of volatiles from a sludge containing about 1 to 80% by weight liquid solvents and 20 to 99% by weight solids, in which said sludge is fed with a reagent powder material in an amount effective to form a mixture having a high surface area to a distillation vessel, said mixture is heated to a temperature up to about 350.degree. C. while said mixture is advanced through the vessel for a time sufficient to distil a sufficient portion of the solvents to yield a solid residue powder, distilled solvents are condensed, and the solid residue powder recovered. The vessel preferably is a mechanical fluidized bed distillation vessel and said mixture is fluidized while being heated therein under a partial vacuum in a non-oxidizing atmosphere. The effective amount of reagent powder material includes about 5 to 70 wt % of the reagent powder material.

Abstract: A process for the removal of organic impurities and dissolved salts from hydrazine hydrate and aqueous solutions thereof by distillation of the hydrazine hydrate under reduced pressure, passing the hydrazine hydrate vapor through an adsorbent, and condensing the vapor.

Abstract: A water distillation apparatus and method include an improved control system for operation and maintenance, condensers with plastic to metal seals between a plastic condenser manifold and metallic cooling tubes, and a filter with steam bypass to allow for easy sterilization of the filter and remaining distillation system. The control system includes a three pronged probe assembly for monitoring conditions within an evaporation chamber. One of the three probes monitors steam conductivity and provides a steam fault signal to indicate an upper level of contaminants in the steam. A purge pump is responsive to fault signals, including the steam fault signal, to pump water from the evaporation chamber.

Abstract: A rotary evaporator is described utilizing a magnetically driven fluorocarbon cylinder, operating within a solvent container, to create a thin solvent film for rapid evaporation without the usual requirement for rotating the entire solvent container assembly. Infra-red heating is employed for efficient evaporation rates. Solvent heating is controlled during evaporation by a single temperature probe, turning the infra-red heater on and off on demand of the probe. Over heating of the product is prevented by maintaining a solvent residue at or near the conclusion of an evaporation.

Abstract: A pollution control apparatus (10) for controlling water-based liquid waste includes a vacuum distillation vessel (14) for separating water-based liquid waste into a distilled water component and a pumpable sludge component. A pH control system (12) allows the vacuum distillation vessel (14) to operate at maximum efficiency, and a purification system (22) allows the distilled water component to be purified to a level capable for reuse in chemistry, or else suitable for direct discharge into a municipal sewer. A microprocessor allows the apparatus (10) to operate automatically.

Abstract: In isolating fullerenes from fullerene-containing soot the soot is heated by using microwaves to from 300.degree. to 800.degree. C. and the evaporating fullerenes are condensed.

Abstract: A process and apparatus for stripping a volatile component from a liquid. The volatile component is destroyed by exothermic reaction with an active component in the gas phase, typically over a catalyst. Heat generated by the reaction of the volatile and active components is transferred to a fluid contact zone in which the organic component is stripped from the liquid stream by a stripping gas. Transfer of heat to the fluid contact zone increases the equilibrium partial pressure of the volatile component in the gas phase and thus increases the driving force for mass transfer in the stripping operation. Preferably, the volatile component is reacted with the active component in a regenerative heat transfer reaction system.

Abstract: A concentrator for reducing the volume of a mixture containing a solvent and various dissolved and/or undissolved solids includes a chamber adapted to receive the mixture and a heater coupled to the chamber for applying heat to the mixture within the chamber, the heat being provided at a temperature sufficient to vaporize the solvent. A condensing tower receives the vapors from the chamber and including a first stage and at least one second stage. A plurality of walls included in each of the first stage and the second stage of the tower direct the vapors along a torturous path including at least one reversal of direction in each of the stages. A coolant is provided to cool the second stage of the tower but not the first stage in order to facilitate condensation of the vapors in the second stage but not in the first stage of the tower. The coolant may include water in order to facilitate the processing of aqueous solutions.

Abstract: Process and apparatus for reclaiming or concentrating waste aqueous solutions of gas treating chemicals, such as alkanolamines, used for removing acid components or water vapor from natural gas. The process involves heating the waste solution under a high vacuum to form a vapor and a liquid residue. The temperature and vacuum can be varied to form a vapor consisting mainly of water vapor or a vapor containing both water vapor and vaporized gas treating chemical. The vapor is subsequently condensed or passed through a wash column to produce a concentrated solution. The liquid residue is heated by passing it through a single pass, generally co-current heater at a rate which avoids localized overheating of a liquid to a temperature above the decomposition temperature of the gas treating chemical. The heated liquid residue is then used to heat the feed waste solution by being thoroughly mixed with it, thus avoiding overheating of the feed solution.

Abstract: A home water distillation device for converting tap water to distilled water largely free of dissolved minerals and gases. A tubular shaped boiler with an electrical heating unit provides steam to a condensation coil immersed in an open top reservoir into which tap water is admitted under the control of a standard metering valve. The unit utilizes condensation heat to drive off chlorine and the like into the atmosphere, so that the steam is free of dissolved gases and the distillate product is corresponding free and therefore of increased palatability.

Abstract: Process for reclaiming or concentrating waste aqueous solutions of gas treating chemicals, such as alkanolamines, used for removing acid components or water vapor from natural gas. The process involves heating the waste solution under a high vacuum to form a vapor and a liquid residue. The temperature and vacuum can be varied to form a vapor consisting mainly of water vapor or a vapor containing both water vapor and vaporized gas treating chemical. The vapor is subsequently condensed or passed through a wash column to produce a concentrated solution. The liquid residue is heated by passing it through a single-pass, generally co-current heater at a rate which avoids localized overheating of a liquid to a temperature above the decomposition temperature of the gas treating chemical. The heated liquid residue is then used to heat the feed waste solution by being thoroughly mixed with it, thus avoiding overheating of the feed solution.

Abstract: In the representative leachate treatment system disclosed in the specification, leachate is supplied to a submerged combustion gas evaporator having a downwardly-directed central burner supplying combustion gases through a downcomer to a combustion gas distributor in an evaporation zone. A conical baffle beneath the gas distributor separates the evaporation zone from a quiescent settling zone in a conical bottom of the distributor from which leachate concentrate and sludge are removed. The leachate supplied to the evaporator is preheated by exhaust gases from the evaporator and combustion air supplied to the burner is preheated by leachate concentrate and sludge removed from the evaporator. Landfill gases may be used to fuel the burner and the sludge may be further concentrated and liquid from the concentrator returned to the evaporator.

Abstract: There is described an apparatus for distilling liquids in a vacuum, having a receptacle for a liquid that can be connected to a vacuum pump, a heating arrangement for heating the receptacle causing the liquid to evaporate, a condenser for condensing the vapour, and a collecting vessel for the condensate. To be able to handle the apparatus quickly and more simply and to make it overall more economical and make it possible to carry out continuous distillation, the heating arrangement includes a vacuum-tight receiving chamber (1) for the receptacle (2) and a microwave generator (13, 13.

Abstract: An apparatus for removing non-volatile residues and impurities from a used solvent includes a self-scrubbing heating distillation subassembly for separating purified solvent for reuse and a controlled waste collector subassembly for overflowing concentrated residues and impurities stripped from the used solvent into an easy-to-service container. The apparatus may be disposed in a parallel in-line relationship with a circulating solvent flow circuit, such as in a dry cleaning operation, to continuously withdraw and purify aliquot portions of the circulating solvent stream, returning good solvent back to the flow circuit and concentrating non-volatile residues and impurities to a removable, environmentally sound serviceable container.

Abstract: A highly efficient distillation unit is provided for heating water and condensing the generated steam to remove the contaminants from the water. Efficiency is enhanced by providing a compact air cooled fin-and-tube heat exchanger which removes heat from the steam, with a powered blower passing air by the fins. A removable bowl which houses the evaporating water is suspended from a rod biased toward its upper position. Mechanical linkage interconnects the rod and a valve which controls incoming water flow to the bowl. The valve closure member is incrementally moved from an opened position to a closed position as a function of the weight of the water in the heating bowl. A low density electrical heating element is powered with from 40 to 55 watts per square inch of submerged heating element exterior surface. The bowl is configured to have a large surface area of heated water to heater input power, thereby further maximizing efficiency.