US2215267A - Gas treater - Google Patents

Description

Sept. 17, 1940- c. w. J. HEDBERG Er Al.. 2,215,267

GAS TREATER Filed Nov. 22, 1938 2 Sheets-Sheer l I I I I I I I I I I III l/ f f/ llI\\ ///r\\|/(\\\\ l f f l\ //l /l|\ l l l I l Sept 17, 1940- c. w. J. HDBx-:RG ETAL 2,215,267

GAS TREATER Filed Nov. 22, 1938 2 `Sheets-Sheet 2.

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llllllll/lll/l/ll Patented Sept. 17, 1940 UNITED STATES PATENT OFFICE GAS TREATER New York Application November 22, 1938, Serial No. 241,862

3 Claims.

This invention relates to the electrical insulation of high potential members in apparatus for the treatment of gases containing constituents condensible to form electrically conductive,

corrosive, inflammable or otherwise troublesome substances. The invention is particularly applicable to electrical precipitators used in cleaning hot phosphorus-containing gases such as are produced in the electrothermic or blast furnace l reduction of phosphate materials.

A principal purpose of the invention is the provision of means for the eective electrical insulation of high potential members of apparatus for treating gases containing condensible substances.

A further object of the inventio-n is to prevent the contamination of liquid sealing substances used in electrical precpitators by condensible components of the gases being treated.

It has been found that these and other desirable objects and advantages may be attained by providing a liquid seal structure including a body oi insulating liquid positioned to insulate electrically the high tension members of a gas treatl5 ing apparatus 'from the low tension members thereof and to prevent free flow of gas between the interior and the exterior of the apparatus and by providing means whereby the surface of said body of liquid which communicates with the 0 interior of the apparatus may be flushed or screened by a stream of inert gas. It has been found to be advantageous to provide also means whereby the temperature of the protective gas and of the body of liquid may be differentially maintained.

When applying the invention to the cleaning of gases containing, for example, phosphorus, it is particularly desirous that the flushing gas be maintained at a temperature above the dew l0 point of any phosphorus that may be contained therein or diffuse thereinto from the gases being treated. It is further desirable to maintain the sealing liquid at a relatively low temperature to reduce the solubility of phosphorus 15 therein and the rate of diffusion of dissolved phosphorus therethrough.

For the purpose of illustration the invention will be more particularly described as applied to ro an electrical precipitator for the cleaning of hot phosphorus-containing gases, with reference to the accompanying drawings in which:

Fig. l is an elevation in partial section of the upper portion of an electrical precipitator em- 55 bodying the invention;

Fig. 2 is atop view in partial section of the precipitator of Fig. l; and

Fig. 3 is an enlarged fragmentary detail in elevation of a portion of Fig. 1.

In the drawings, numeral I0 designates the -5 shell of an electrical precipitator having inlets I2 and outletsl I3. The shell is insulated as indicated at I4 and is divided into a downpass portion and an uppass portion by vertical partition I5. l0

Positioned over opening I6, in top plate II of shell I0, is oil seal I8.

The oil seal comprises an annular trough consisting of a cylindrical outer wall 20 welded at 22 to inner wall and bottom member 2l, and an 1I apron 46 positioned so that the bottom rounded edge 41 of the apron is submerged in the oil I9 within the annular trough. Wall 20 is surmounted with a ring 26 to eliminate any tendency for discharge from the edge to members of 20 different potential. Member 2| is also surmounted with a rounded member, in this instance a hollow torus ring 23. Apron 45 is formed as a cup which is suspended in inverted position from discharge electrode suspension member 50, being held to member 50 by clamp 48.

Beneath and inside trough member 2I is a hollow walled assembly comprising annular members 28 and 29 with gas space 30 between them and heat insulation 38, preferably attached to $0 member 28, to heat insulate member 28 from trough member 2l. This assembly is held in position in cylinder 2G by spot welding at contact line 21 and also where members 23 and 29 contact at 23. Gases are admitted to space 30 35 through inlet connection 40. They leave space 30 through holes 33, which permit portions of the gases to issue directly into the annular space around member 50, and through holes 34 which permit other portions of the gases to pass through space 31 above insulation 38 through holes 35 into ring 23 and thence through holes 25 in ring 23 to the space directly over the oil I9. Oil is admitted to the seal through feed pipe 4I, annular distributing pipe 42 and outlet noz- 45 zles 43. An outlet pipe 44 carries the oil back to storage or to settling tanks or other conditioning means (not shown), an overflow Weir 44 in pipe 44 being used to maintain the oil in the seal at the desired height, and a valve 44 be- 50 ing provided for the purpose of draining the seal.

Mounted on cylinder 20 of oil seal I8 is an oval-shaped insulator compartment with floor 56, side Wall and top 51. Two pedestal type insulators 60, resting on oor plate 56, support 55 a horizontal composite beam 6l which extends over oil seal iS and supports rod 50, xed collars 62 and 63 on rod 50 being used to maintain the rod in the desired position. About each insulator Gil, is a conical shaped enclosure l0 with upper end open which is for the purpose of keeping any condensible vapors which may evaporate from the outer portion of the surface of oil i9, or other conducting material, from reaching the surface of the insulator. A purging gas (clean, dry air, for example), is introduced from a suitable source (not shown) through pipe l2 into the bottom of enclosure 70, annular pipe li with holes spaced about its top surface and positioned about the base oi insulator 60 being used to liberate and distribute the gas within the enclosure. The high voltage electrodes 53 hanging from members 52, which in turn are supported by frame work 5l and rod 50, are energized through a conductor which is introduced through the center of insulator 60 and makes electrical contact with beam Si. The collecting electrodes (not shown) and the shell of the precipitator are grounded as indicated at 85.

Mounted on top of rod 50 is a box Sl! containing rapping means operated through a shaft 5l' by a mechanism (not shown) which is attached to iianged opening Held by couplings 55 on shaft 6l is an insulating link member 65 usually of electrical porcelain which insulates the ground end of shaft Si and the mechanism which turns it from box which is at high' potential, being in contact with rod Insulator is protected from foreign matter by an enclosure in the same manner in which insulator is protected, the piuging gas being supplied through pipe il to distributor lli. Enclosures 'ifi and are made in halves can be pulled apart when the insulators are to be inspected and cleaned. The

insulator compartment can be entered t'L 'ough eas outlet lf3 with damper ill manholes Sil. A L controls the gas pressure within the insulator compartment.

The precipitator embodying the invention is operated as follows when gases carrying phosphorus vapors are to be cleaned as they leave the furnace at about 230 C. (4A-6 E). The shell and contents oi the precipitator heated, preferably by surface heating ur ts, to a temperature above the phosphorus dew point oi the gases. rThe phosphorus dew point is usually about 180 C. (356 FJ, and the precipitator is commonly heated to slightly over 200 C. before the gases to be cleaned are turned into it. Before or while the precipitator is being heated it is purged with a non-combustible gas such as carbon dioxide.

The insulator compartment is not heated to as high a temperature as the remainder of the precipitator because the oil seal prevents the gases from circulating into and. permitting phosphorus vapors to condense in that part of the precipitator. Clean air, at a temperature well above its dew peint, is introduced through pipes 'l2 and 'll to gas ush insulators G0 and respectively. This air escapes through opening 85, although other openings can be provided.

When the furnace gases are introduced into the precipitator, it is advisable to simultaneously introduced heated carbon dioxide or other gas, which is relatively inert to both phosphorus and its carrying gas, into the oil seal through pipe 40. This gas is preferably heated indirectly with high pressure steam or by electric heaters to about 160 to 180 C. After the furnace gases are cleaned in the precipitator and cooled in condensers and the phosphorus removed, they may be reheated and used as purge gases on the interior surface side of the oil seal. The use of carbon dioxide is then discontinued. Some phosphorus vapor may remain in the gases, which comprise principally carbon monoxide, returned from the phosphorus condensers but it is in such small amounts that the phosphorus dew point will in general be below 70 C. The purge gas must be heated to above its phosphorus dew point but it need not be heated to the phosphorus dew point of the raw furnace gases. With steam at pounds per square inch, the returned gases for purging can be heated to about 150 C. and this has been found to be a very satisfactory temperature for those gases.

The temperature drops through the precipitator are, in an illustrative example, as follows: Raw gas to be cleaned, 230; purging gas iiowing into oil seal, 150; oil leaving oil seal, 90; and air in insulator compartment, about 40 C. These controlled temperature drops keep all gases containing phosphorus above their phosphorus dew points, respectively, keeps the oil well below its flash point, which may be between and C., and keeps the air or gas in the insulator compartment in motion and at a temperature which minimizes evaporation of phosphorus from the oil and condensation of that phosphorus on insulating surfaces.

We claim:

l. In the electrical treatment of gases containing a readily condensible component, the improvement which comprises providing an insulating liquid seal between the high tension and the low tension portions of the treating apparatus having a free liquid surface in communication with the interior of the treating apparatus, directing a current of an inert gas maintained at a temperature above the dew point of the condensible component of said flushing gas over the interior surface of the sealing liquid, and maintaining the sealing liquid at a substantially lower temperature than that of the ushing gas.

2. in the electrical treatment of gases containing phosphorus the improvement which comprises providing an insulating liquid seal between the high tension and the low tension portions of the treating apparatus having a free liquid surface in communication with the interior of the treating apparatus, directing a current of an inert gas maintained at a temperature above the phosphorus dew point of said ilushing gas over the interior surface of the sealing liquid and maintaining the sealing liquid at a substantially lower temperature than that of the ushing gas.

3. In the electrical treatment oi gases containing phosphorus, the improvement which comprises providing an insulating liquid seal between the high tension and the low tension portions of the treating apparatus having a free liquid surface in communication with the interior of the treating apparatus, and directing a current of an inert gas maintained at a temperature above the phosphorus dew point of said flushing gas out below the phosphorus dew point of the gas being treated over the interior surface of the sealing liquid.

CARL W. J. HEDBERG. LOUIS N. BONACCI.

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