US3170007A - Apparatus for cleaning dust-laden gases - Google Patents

Description

Feb. 16, 1965 E. KRANTZ APPARATUS FUR CLEANING DUST-LADEN GASES Filed June 11, I963 HEATER mvzu'ronz EVERT K RANTZ ATTYS.

United a O 3,170,007 APPARATUS FOR DUST-LADEN Evert Krantz, Stockholm, Sweden, assignor to Aktiebolaget Svenska Flaktfabriken, Stockholm, Sweden, a corporation of Sweden Filed June 11, 1963, Ser. No. 287,017

Claims priority, application Sweden, Dec. 23, 1960, 12,498/ 60 4 Claims. (Cl. 261-136) This invention relates to an apparatus for cleaning dustladen gases and has for an object theprovision of improvements in this art. Cleaning is efiected by wet-purification which produces an agglomeration of dust particles by a special use of finely atomized washing liquidinto the dust-laden gas and the subsequent precipitation of the agglomerated dust and liquid particles. This application is a continuation-in-part of my copending application Serial No. 161,017, filed December 21, 1961, now abandoned; In part the invention makesv use of apparatus which is similar to that disclosed in my Patent No. 2,883,167.

In order to obtain an optimum efiiciency in the separation of dust particlesfrom theentraining gas it is essential in gas purifiers of the above-mentioned type that intimate mixing of the washing liquid with the gas be obtained and also thatthe largest possible contact surface be obtained. This means that the washing liquid which is supplied must be broken up into very fine particles since the efiiciency of the action increases as the particle size is reduced.

With centrifugal apparatus or compressed air nozzles heretoior'e used for the atomization of liquid, there are diificulties in securingthe very small particle size whichis desired Without unreasonably great power consumption.

and other disadvantages." To "be effective for removing I very fine dust particles from gases, it is necessary to provide liquid particles'in the .orderof' about 20a. In order 2 plies to humidifying by circulating Water .at 26 C. If the elficiency of cooling be taken to be 50%, this means that approximately 6 g. or 6 cm. of water/ kg. of gas is converted during condensation into particles of a size in the order M10 If 1 g. or 1 cm. of water is broken up into particles of this size, it will provide a total external.

. to 2.0 m? or a total of 12 m? of contactsurface/kg. of

to obtain particles of this small size by means of-cen-Q trifugal nozzles it is necessary to use a nozzle pressure as high as 150 kg./cm. and for compressed air nozzles the air must have a working pressure as high as 0.7 kg./crn.

V the nozzles if they are to withstand the wear and avoid clogging. The latter requirement is the most difficult to 1 meet and it has been found practically impossible to produce a reliable compressed air'nozzle for dust separation. The present invention eliminates the above-mentioned gas. In order to obtain particles of the last-mentioned size with the aid of centrifugal nozzles, a working pressure of not less than about 1000 l g./cm. would be required.

The invention will now be described more in detail with reference to the'accompanying drawing wherein:

The single figure is a somewhat diagrammatic vertical axial section through the gas inlet and liquid mixing portions of a wet purifier with liquid supply in two stages.

In the. drawing, the numeral 1 designates a collection chamber with a gas outlet 1a at the top, a trapped liquid overflow 1b, and a sludge clean-out chamber 1c. The,

numeral Z'designates, in general, the multi-stage venturitype gas purifier provided in accordance with the present invention.

An inlet pipe '3 provides for the introduction of raw hot dust-laden gas to be purified into an expansion chamber 4 having a cylindrical upper portion 4a and a lower funnel-shaped portion 4b The upper portion 4a has a diameter much greater than the diameter of the pipe 3 and the'pipe 3 at the lower end terminates below the upper endof the funnel-shaped portion 4b but fully clear of the sides thereof. I

An .outlettube 5 of considerably smaller diameter than the inlet pipe 3 is connected to and extends down from thebottom of the funnel-shaped portion 4b. An annular sharp-edged ledge 12 is provided at the lower end of the i n V funnel-shaped portion 4b to cause gas and liquid flowing This places very exacting requirements on the design of g and other difiiculties by supplying liquid in at least two separate stages by specialized, apparatus-of a simple, sturdy, effective and reliable character.

In the first stage hot liquid is supplied into a gas ex- 1 pansion space in such a way that the moisture from the waterfexists'largely in the form-of vapor. This has" the highly desirable efiect of producing an effective temperature drop of'the-incoming hot gas so that the gas, independently of its inlet temperature, will always enter the next stage of treatment with a-substantially constant temperature and volume.

In a subsequent stage, after the hot gas has been "-reduced to'substantially constant temperature and volume and a substantially saturated condition in the first stage and supplied by a small-size tube into a second expansion chamber, the gas is cooled by the intermixingtherewith of finely divided particles of cold water to produce a condensation of the vapor from the steam phase and a consequent increase of the effective contact surface.

With the present treatment a considerable increase of the contact surface of the liquid with the gas is obtained, as the following example'will illustrate. If the incoming gas'has a temperature of C. and a water content of 10 g./kg. of gas, the water content can be increased'to 21 g/kg. of gas-an increase of ll'gi/kg. of gas. This apdownward thereover to flow inward with violent turbu lence, as disclosed in my patent referred to above, to break A lower expansion chamber 6 has a cylindrical portion 6a which extends down from the top' end of the funnelshaped portion -4b and at the lower end of the cylindrical portion 6a there is provided a funnel-shaped portion 6b. The lower end of the tube 5 terminates below the upper end of the funnel-shaped portion 6b but fully clear'of the sides thereof.

An outlet difi'user tube 7 of the venturi type, and having an upperend considerably smaller than the tube 5, is connected to the lower end of and extends down from the funnel-shaped portion 6b. An annular sharp-edged ledge 13 is provided at the lower end of the funnel-shaped portion 6b to cause gas and liquid flowing downward thereover to flow inward with violent turbulence to break the liquid up into very fine particles and mix them thoroughly with the gas. The lower end of the downwardly outfiaring tube 7 discharges liquid and gas below the surface of the body of liquid which is collected in the chamber 1. The tube 7 expands downwardly to-reduce the velocity of the gas and avoid undue turbulence in the liquid in the'tank 1.

Liquid is supplied to the downflowing gas in two stages, I,

each into a body of expanding gas.

In the first stage, hot liquid is supplied through an inlet pipe 8 into, an annular trough 10 above the upper end of the funnel-shaped portion4b to flow down in'anannular sheet along the, conical surfaceof the funnel-shaped portion 4b and discharge over the inner edge of the annular flange 12 into the body of fast-moving gases. An annular space is left between the'innerside of the annular trough 10 and the outside of the inlet pipe 3. The liquid flowing down the funnel-shaped portion 412 builds up in radial thickness above the annular flange 12 to assist in forcing the liquid inward into the high-velocity stream of gas. Means for heating the water is indicated at 14.

In the second stage, cold liquid is supplied through an inlet pipe 9 into an annular trough 11 above the upper end of the funnel-shaped portion 6b to flow down in an annular sheet along the conical surface of the funnelshaped portion 6b and discharged over the inner edge of the annular flange 13 into the body of fast-moving gases. An annular space is left between the inner side of the trough 11 and the outside of the outlet tube 5. The liquid flowing down the funnel-shaped portion 611 builds up in radial thickness above the annular flange 13 to assist in forcing the liquid inward into the high-velocity stream of gas.

When the liquid flows down and inward over the sharpedged flanges 12 and 13 it is broken up violently by the turbulence of the high-velocity gases flowing at a velocity in the order of 30 to 125 m./ sec.

The liquid supplied in the first stage is at a relatively high temperature so that it readily vaporizes in the hot gas to form very fine vapor particles. The presence of this body of vapor at approximately the state of saturated steam, having a very large heat-storage capacity, brings the mixture, of gas and vapor substantially to a constant temperature regardless of the temperature of the entering gas. Since the temperature is constant, the volume per unit of weight of the saturated gas will be substanti'ally constant.

Since the saturated gas provided in the first mixing chamber is at an approximately fixed temperature it is readily chilled and condensed by the cold water in the second stage, with good agglomerationof the fine particles of liquid on the dust particles, which provides almost complete separation when the gas is flowed out through the water both maintained in the tank 1, pure clean gas flowing out at In for such uses as may be desired.

Because of the fact that the gas is cooled at each stage, its volume is reduced and the channels 3, and 7 of decreasing diameter are selected accordingly-to maintain the flow of gas at all stages near the same velocityfor the better turbulence and break-up and mixing with the water which is introduced.

The water at each stage is supplied at a reduced throat location where, on account of the restricted throat size the gas velocity is momentarily at a maximum to produce the greatest turbulence, followed by an expansion which causes good assimilation of the fine vapor particles formed here and cooling of the gas by expansion.

It will now be seen that by the apparatus of use provided by the invention the dust separation is very effectively produced by extremely simple and inexpensive means. The hot dry gas which may. be supplied at varying dry bulb temperatures is effectively saturated and brought to constant temperature in the first stage and condensed and the'dust particles agglomerated in the second stage. This provides gas flow at substantially constant rate at each mixing point, a condition favorable to the most effective particle break-up and difiusion.

While one embodiment of the invention has been described for purposes of illustration, it will be understood that there may be various embodiments and modifications within the general scope of the invention.

1 claim:

1. Apparatus for the wet-purifiction of hot dust-laden gases, comprising in combination: a first expansion chamber, a gas supply conduit extending down into said first expansion chamber, a second expansion chamber disposed below' said first expansion chamber, a convergent bottom for said first expansion chamber, a first mixing conduit extending from the bottom of said convergent bottom into said second expansion chamber, a convergent bottom for said second expansion chamber, a second mixing conduit extending downward from the bottom of the second expansion chamber, inwardly projecting flanges at the upper ends of each of said mixing conduits,'means to supply hot liquid around the outer periphery of said first expansion chamber above the upper end of said convergent bottom to flow down in an annular film over said convergent bottom and inward over said flange to break up in the violent turbulence of the hot gas flowing at high velocity over said flange, and means to supply cold liquid around the outer periphery of said second expansion chamber above the upper end of said convergent bottom to flow down in an annular film over said convergent bottom and inward over said flange to break up in the violent turbulence of the gas flowing at high velocity over said flange, the entire flow of gas and liquid being confined to pass through said mixing conduits, said conduits being successively of smaller size downward to take account of reduced gas volume and provide high velocity gas flow through said conduits.

2. Apparatus as set forth in claim 1, further characterized by the fact that said second mixing conduit has its lower end formed of increasing size downward and has its lower end submerged in liquid.

pansion chamber having a funnel-shaped lower end por tion and a restricted bottom outlet tube with an inwardly projecting annular flange at its upper end; means for supplying hot water to the top of said funnel-shaped portion to flow downward in an annular film thereon and over said annular flange, said outlet tube being of a smaller diameter than said supply pipe to compensate for cooling of the gas and provide high velocity flow past said annular flange to atomize the water and mix it in said gas; a second expansion chamber having a funnel-shaped lower end portion and a restricted lower bottom outlet tube with an inwardly projecting annular flange at its upper end; means for supplying cold water to the top of said funnel-shaped portion to flow downward in an annular film thereon and over said annular flange, said lower outlet tube being of a smaller diameter than the first said outlet tube to compensate for cooling of the gas in said second expansion chamber and provide high velocity flow past said. anular flange to atomize the water and mix it with the gas, and means providing a body of water for the outflow of gas from said lower outlet tube.

4. Apparatus for cleaning hot dry dust-laden gases,- oomprising in combination, a gas supply pipe, a first expansion chamber having a funnel-shaped lower end portion anda restricted bottom outlet tube with an inwardly projecting annular flange at its upper end; means for supplying hot water to the top of said funnel-shaped portion to flow downward in an annular film thereon and over said annular flange, a second expansion chamber having a'funnel-shaped lower end portion and a restricted lower bottom outlet tube with an inwardly projecting annular flange at its upper end; means for supplying cold water to the top of said funnel-shaped portion to flow downward in an annular film thereon and over said annular flange, and means providing a body of water for the outflow of gas from said lower outlet tube, said lower outlet tube expanding in diameter downward to minimize turbulence in the body of water at its outlet.

References Cited by the Examiner UNITED STATES PATENTS 1,182,543 5/16 Ferguson 5590 1,844,851 2/32 Harmon 5594. 2,883,167 4/59 Krantz 261-46,

NORMAN YUDKOFF, Primary Examiner. REUBEN FRIEDMAN, Examiner.

Claims (1)

1. APPARATUS FOR THE WET-PURIFICATION OF HOT DUST-LADEN GASES, COMPRISING IN COMBINATION: A FIRST EXPANSION CHAMBER, A GAS SUPPLY CONDUIT EXTENDING DOWN INTO SAID FIRST EXPANSION CHAMBER, A SECOND EXPANSION CHAMBER DISPOSED BELOW SAID FIRST EXPANSION CHAMBER, A CONVERGENT BOTTOM FOR SAID FIRST EXPANSION CHAMBER, A FIRST MIXING CONDUIT EXTENDING FROM THE BOTTOM OF SAID CONVERGENT BOTTOM INTO SAID SECOND EXPANSION CHAMBER, A CONVERGENT BOTTOM FOR SAID SECOND EXPANSION CHAMBER, A SECOND MIXING CONDUIT EXTENDING DOWNWARD FROM THE BOTTOM OF THE SECOND EXPANSION CHAMBER, INWARDLY PROJECTING FLANGES AT THE UPPER ENDS OF EACH OF SAID MIXING CONDUITS, MEANS TO SUPPLY HOT LIQUID AROUND THE OUTER PERIPHERY OF SAID FIRST EXPANSION CHAMBER ABOVE THE UPPER END OF SAID CONVERGENT BOTTOM TO FLOW DOWN IN AN ANNULAR FILM OVER SAID CONVERGENT BOTTOM AND INWARD OVER SAID FLANGE TO BREAK UP IN THE VIOLENT TURBULENCE OF THE HOT GAS FLOWING AT HIGH VELOCITY OVER SAID FLANGE, AND MEANS TO SUPPLY COLD LIQUID AROUND THE OUTER PERIPHERY OF SAID SECOND EXPANSION CHAMBER ABOVE THE UPPER END OF SAID CONVERGENT BOTTOM TO FLOW DOWN IN AN ANNULAR FILM OVER SAID CONVERGENT BOTTOM AND INWARD OVER SAID FLANGE TO BREAK UP IN THE VIOLENT TURBULENCE OF THE GAS FLOWING AT HIGH VELOCITY OVER SAID FLANGE, THE ENTIRE FLOW OF GAS AND LIQUID BEING CONFINED TO PASS THROUGH SAID MIXING CONDUITS, SAID CONDUITS BEING SUCCESIVELY OF SMALLER SIZE DOWNWARD TO TAKE ACCOUNT OF REDUCED GAS VOLUME AND PROVIDE HIGH VELOCITY GAS FLOW THROUGH SAID CONDUITS.

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