US1250088A - Process and apparatus for separation of suspended particles from gases. - Google Patents

Description

, H. A. BURNS. PROCESS AND APPARATUS FOR SEPARATION OF SUSPENDED PARTICLES FROM GASES. APPLICATION FILED APR. I8, [914.

1,250,088. Patented DeD. 11, 1917.

- ED STA PATENT orrion.

HERBERT ALEXANDER BURNS, OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO IN'TER- NATIONAL PRECIPITATION COMPANY, OF LOS ANGELES, CALIFORNIA, A CORPORA- MON OF CALIFORNIA.

PROCESS AND APPARATUS FOR SEPARATION OF SUSPENDED PARTICLES FROM GASES.

Specification of Letters Patent.

Patented Dec. 11, 1917.

Application filed April 18, 1914. Serial No. 832,892.

, by electrical action. In such apparatus the gas to be cleaned is passed through an electri c field in which a silent discharge is maintained, thereby causing the particles to be charged and to migrate under the action of the electric field, transversely to the current of gas, so as to be separated or precipitated therefrom. For effective precipitation it is desirable that the migration should proceed in one direction only or substantially so,

- and this requires that the electric field shall be unidirectional and that the discharge shall proceed in such manner as to charge all the particles similarly. In order to produce such a discharge, the electrodes between which the discharge is maintained are so constructed as to facilitate discharge from certain of the electrodes, herein re ferred to as the discharge electrodes, and to minimize the discharge from the'other electrodes, herein termed the collecting electrodes. For this purpose the discharge electrodes are formed in such manner as topresent relatively small surface and sharp con vexity, so that adjacent to such electrodes the electric field is comparatively strong, and correspondingly strong ionizing and discharge effects are produced, and the collecting electrodes are formed with fiat or con-' cave surfaces of relatively large extension, so that the field intensity ionization and discharge at such surfaces is comparatively small. It is, of great importance that the surface of'the collecting electrodes should be smooth, or free from sharp projections or roughness of any kind, since such projections concentrate the electric field adjacent thereto and form centers of ionization and discharge, with the result that the normal migration of suspended particles toward these electrodes is interfered with by the reverse charges imparted. to the particles through the ionization of the gas adjacent to the collecting electrodes. I have found that, in many cases, the material precipitated on the collecting electrodes tends to build up thereon, so as to form projections which act as centers of discharge and interfere, in the manner stated, with complete and effective migration of the particles in the gas passing through the apparatus, with the result that a considerable proportion of such particles fail to reach the collecting electrodes and are swept through the apparatus, by the current of gas, without precipitation. An important object of the present invention isto maintain the collecting electrodes'in such condition as to present surfaces of minimum roughness so as to avoid, as" far aspossible, any interference with efi'ective precipitation of the particles. This object I attain by maintaining a film or layer of liquid on the surface of the electrode, so

that the surface exposed to the electric field is in efiect a liquid surface, which automatically retains a smooth condition. I also fprefer to provide for continual movement 0 the liquid over the surface of the electrode,

whereby any material deposited on the electrode is washed away, either by the en-' training action of the stream of liquid, or by actual solution ofx the material in the liquid.

A further object of the invention is to provide, in certain cases, for selective separation of certain constituents of the suspended matter, by solution insuch liquid at the collecting electrodes.

Anotherobject of thevinvention is to provide for separation from the gas being treated, of any constituents capable of absorption in the liquid on the electrodes, either by physical or chemical action.

Other objects of the invention will appear hereinafter.

The invention may be carried out in any suitable apparatus, for example in the apparatus illustrated in the accompanying drawing, wherein:

Figure 1 is a partly broken plan view of a treater having cylindrical collecting elece trodes.

Fig. 2 is a vertical section of the treater shown in Fig. 1.

Fig. 3 is a vertical section, transverse to Fig. 2 of the lower electrodes.

portion of the collecting Fig. 4 is a view similar to Fig. 3 showing another construction of the drainage means.

Fig. 5 is a vertical section of a treater having plane electrodes.

ig. 6 is aside elevation of one of the collecting electrodes shown in Fig. 5.

Referring to Figs. 1 and 2, the treater comprises cylindrical collecting electrode members 1, which may be connected at their lower'ends'to a header 2, and discharge electrodes 3 which may be formed as fine wires suspended from an insulated support 5 so as to,extend axially within the cylindrical electrodes 1. Weights 6v are provided for holding the fine wire electrodes taut, and a spacing frame 7 rests on said weights and is connected by means of a rod 7 to an insulated support 8, so as, to retain the fine wire electrodes 3 in proper position. The cylindrical electrode members 1 are preferably arranged so as to extend vertically and they may discharge at their upper ends into the open air, or into a suitable header 9 leading to a flue 9 for conducting away the cleaned gas.

Supply means, such as pipes 10, are provided at the upper part of the collecting electrodes 1, for supplying water or other liquid to said electrodes. These pipes preferably discharge tangentially into theupper part of the electrode members 1, in order to equalize the stream of liquid around the inside of the cylindrical walls of said electrode members, and in order to further equalize such stream, said electrode-members may be enlarged at their upper ends; to form shelves 0r ledges 11, on to which the liquid is dis charged from the pipes 10, so that by the tune the liquid reaches the cylindrical body portion of the electrode member itis distributed around the same in a uniform layer or film. v

Any suitable means may be provided at the lower ends of the collecting-electrodes, for carrylng away the liquid flowing from such electrodes. For this purpose, the header 2 connected to the lower ends of the electrode members -1 and to the flue 12 for supplying the gas to be treated may extend below the surface of a body of liquid 14 in a tank 14, having an overflow-outlet 15. In order to prevent shortcircuiting action at the spaclng means for the discharge electrodes, by the liquid running down from the collecting electrodes, annular troughs 16 may be provided at the bottom of electrode members 1, said troughs being inclined so as to drain the liquid to outlets 16 which are so located that-the liquid descends therefrom at a distance from the spacing'means 7. Said troughs are formed in a top member 2' for member 2, said member 2 having apertures 13' for passage of the gas into cylindrical members 1, and the walls of these apertures being convexly rounded as shown at 13'. The rounding of these walls 13 and the ensage of the gas from the header 2 to the collecting electrode members 1, these 0penings being surrounded by walls 19, for directing the liquid to space above the roof member 17, whence the accumulated material may be removed by drainage to the tank 14, or by flushing with liquid supplied through a pipe 23.

To maintain the required difference of potential between the electrodes 1 and 3, the

electrodes 1 maybe grounded, and the electrodes 3 connected to wire 24 leading through a rectifier 25 to a step-up transformer 26, which receives alternating current from a suitable supply circuit.

My process is carried out in the above described apparatus as follows: The gas to be treated is led through the flue 12 and header 2 and passes upwardly through the cylindrical electrode members 1. A. suitable liquid, for example. water, is supplied through pipes 18 and flowing tangentially from said pipes over the shelves 11, is distributed uniformly over the inner surfaces of the electrode members 1 forming a liquid film electrode surface on each electrode member 1. The discharge electrodes 3 are raised to 'a suitable potential difference, relatively to the collecting electrodes, by means of the supply connections shown, so as to cause ionization of the gas in the vi cinity of electrodes 3 with the result that the particles suspended in the gas adjacent -to said electrodes are charged similarly to electrodes 3 by the discharge carried by the ions proceeding from said electrodes. The particles so charged are driven transversely of the current of gas, toward the collecting electrodes, by the action of the electric field between the electrodes, and by reason of the absence of any counter-ionization or countor-discharge at the collecting electrodes, the particles are enabled to reach the collect-' ing electrodes without interference and are completely precipitated on the liquid film surface thereof. The absence of counterionization at the. electrodes 1 is due largely to the fact that the liquid film, by reason. of its surface tension, maintains a smooth, even surface and prevents concentration of the electric field at any point. Moreover, the liquid being continually supplied at the top of the electrodes 1 flows downward in a steady film-stream, which continually carries away the matter deposited on the electrodes, thereby maintaining the electrodes in clean, smooth condition, so that the precipitating operation proceeds effectively, without interference due to roughening of these electrodes by the precipitated matter. The water or other liquid, carrying the deposited matter, passes away through the outlet means at the bottom of the electrodes, and the cleaned gas passes away through the flue 9.

In case the solid material precipitated from the gas contains a constituent which is soluble in. the liquid supplied to the electrode 1, this constituent is taken up in solution in such liquid, and may thereby be removed or separated, not only from the gas, but from the remainder of the solid precipitate, which is allowed to settle, or is otherwise removed from the solution. For example, by treating flue gases containing sugar dust together with water-insoluble dust, in the above described manner, using water as the liquid for the film electrode, I may recover the sugar content of the dust, the solution being drawn ofi', settled and the sugar recovered therefrom in any usual manner.

My process may also be applied to the separation of gaseous constituents from a mixed gas, in case such constituents are capable of being dissolved in the liquid used, or of reacting with the same to form a soluble compound. This application of the process is of particular advantage when the gas contains dust or solid or liquid suspend ed matter, in addition to the soluble gaseous constituent. In this connection the operation of the electric field serves not only to precipitate the suspended material, but also aids in the absorption of the gaseous constituent, the gases being forced into contact with the liquid on the collecting electrodes by the action .of the electrical wind or convection, proceeding from the discharge electrodes.

By maintaining a liquid film electrode, such as above described, I am enabled to overcome many of the difficulties usually encountered in cleaning gases by electrical action, and the gases can be passed through the apparatus at higher velocity than with solid collecting electrodes under the usual conditions.

Under certain conditions it may not be necessary to maintain the liquid film continuously, the liquid being then supplied intermittently, or from time to time, whenever the accumulation of material on the collecting electrodes is such as to require it. This will be the case, for example, when the amount of precipitated material is small, and it will be particularly the case when the precipitated material is soluble in the liquid used, since in such case any deposit may be readily washed away after it is formed.

In case the precipitated material is not capable of being readily dissolved or washed away by the liquid, it is desirable to maintain continuously, a liquid surface at the collecting electrode, to prevent deposition of an adherent coating of such material.

members 28. Under certain conditions,

some of the particles carried by the gases under treatment may also be precipitated on the discharge electrodes and my inven-' tion may also provide for supply of washing liquid to such electrodes. Thus, as shown in Fig. 5, a nozzle 33 may be provided adja cent each discharge electrode 29, through which water or other cleaning liquid may be supplied, from time to time, to such electrodes, so as to keep the same sufficiently clear of accumulated deposits to maintain maximum efliciency of discharging action of the electrode, the electrical current being shut off while the discharge electrode is being cleaned in this manner.

The liquid supplied to the electrodes may be of any suitable nature. It may be water, or a liquid having special chemical properties enablin it to dissolve certain of the const-itutents o the precipitated material, or of the gases. In special cases it may be found .ing a current of such gas between a discharge electrode surface, of relatively limited area, and a liquid collecting electrode surface, of relatively extended area, and maintaining between such electrode surfaces, sufficient unidirectional potential difference to produce a discharge from such discharge electrode surface and thereby charge the suspended particles and cause them to move across the-current of gas and into contact with the liquid collecting electrode.

2. The process of separating suspended particles from gases, which consists in passing a current of such gas adjacent to a dis surface, and continually by the motion of the liquid, carrying away the particles so collected by the liquid and. to thereby maintain a smooth liquid electrode surface adapted to minimize discharge therefrom.

3. The process of separating from a gas, suspended particles, whose constituents are partly soluble and partly insoluble in a liquid, which consists in maintaining a moving stream of such liquid, of relatively extended area, passing a current of the gas past said stream, passing an electric discharge into said gas to charge theparticles, forcing the charged particles into contact with such liquid stream, by the action of an electric field, so as tocause the soluble particles to be dissolved and the insoluble particles to be suspended in such liquid, carrying away the material of the particles by the move- ,ment of the liquid, and subsequently separating the soluble from the insoluble material.

4. The process of separating from a gas, a constituent which is soluble in a liquid, which consists in passing the gas adjacent to the surface of a stream of such liquid, and passing an electric discharge through the gas to cause convection of the gas toward the liquid surface so as to bring the gas into efl'ective contact with the liquid.

5. In an apparatus for electrical separation of suspended particles from gases, the combination of liquid supply and distributing means adapted to maintain a moving liquid stream of relatively extended surface, a discharge electrode of relatively small surface arranged opposite the surface of said stream, means for maintaining'between such discharge electrode and stream suflicient unidirectional potential difference to produce electric discharge, and means for passing the gas to be treated through such discharge.

6. In an apparatus for electrical separation of suspended matter from gases, an electrode member formed as a vertical pipe, means for supplying liquid tangentially to the upper part of said pipe to form a liquid film electrode at the interior surface of said pipe, and a discharge electrode extending axially in said pipe and insulated therefrom.

7. In an apparatus for electrical precipitation of suspended matter from gases, the combination with collecting electrode means racemes .charge therefrom, of means for directing liquid onto the upper part of said discharge electrode means in such manner as to cause the liquid-to run down on said discharge electrode means to clean the same.

8. In an apparatus for electrical precipitation of suspended particles from gases, a vertically extending flue, a discharge electrode extending therein, means for passing liquid downwardly along the walls of said flue and means for passing gas upwardly through said flue.

9. In an apparatus for electrical precipitation of suspended particles from gases, vertically extending flue means, header means at top and bottom' of said flue means for conducting gas therethrough, the lower header means being provided with a water seal and overflow at its bottom, and discharge electrodes extending within said flue means. n

10. In an apparatus for electrical precipitation of suspended particles from gases, the combination with vertically extending collecting electrodes, an insulated support, a plurality of discharge electrodes suspended from said support and extending downwardly past said collecting electrodes, a retainin frame connected to and supported on "said discharge electrodes below said collecting electrodes, and insulating means for holding said frame from lateral displacement.

11. The process of promoting chemical or physical action between a liquid and a gas which consists in distributing the liquid over an electrode surface and maintaining an electrical field between such electrode surface and an opposing electrode so as to produce electrical windage and thereby bring the gas in effective contact with said li uid.

12. The process of promoting action between gaseous and non-gaseous materials which consists in distributing said non-gaseous material over an electrode surface. and bringing said gaseous material into contact with the non-gaseous material by the action of electrical windage.

13. In an apparatus for electrical separathereto to form a liquid film on its inner lower end of said pipe for catching the liqsurface, an insulated support extending over .uid descending on said pipe and directing said pipe, a discharge electrode hung from it aWa-yfrom said retaining means.

said insulated support and extending axially HERBERT ALEXANDER BURNS. in said pipe, an insulated retaining means Witnesses:

extending below said pipe and engaging WM. N. DREW,

said discharge electrode, and means'at the MAIY T. REDDY.

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