US1951867A - Apparatus for cleaning gas - Google Patents

Description

March 20, 1934. J. P. GRILL! APPARATUS FOR CLEANING GAS Filed April 11, 1931 3 Sheets-Sheet l March 20, 1934. J. P. GRILL! APPARATUS FOR CLEANING GAS 3 Sheets-Sheet 2 Filed April 11, 1931 March 20,- 1934.

J. P. GRILL] APPARATUS FOR CLEANING GAS Filed' April 11, 1951 3 Sheets-Sheet 3 fizz/8%:

Patented' Mar. 20, 1934 UNITED STATES APPARATUS FOR CLEANING GAS John P. Grilli, Chicago, Ill., assignor to H. A.

Brassert & Company, Chicago, 111., a corporation of Illinois Application April 11, 1931, Serial No. 529,340

4 Claims.

This invention relates to a new apparatus for cleaning gas and more particularly comprises an apparatus whereby the gas is subjected'to the combined eifect of washing and electrical precipitation. This combination results in providing a simple means of cleaning gas to a high degree of cleanliness with a minimum expenditure of power.

Heretofore the fine cleaning of gases has been caused bymechanical means requiring considerable horse power, or by electrical precipitation, such as the Cottrell system. The electrical precipitation method requires much less power than mechanical washers, but has not yet been perfected to the point of uninterrupted operation. The present electrical precipitator consists of chambers containing anodes and cathodes, the former consisting of chains or other elements suspended between cathodes which usually consist of metal plates or concrete walls arranged vertically and spaced at sufficient distance from each other to prevent continuous electrical discharges from the positive to the negative elements. The gases pass vertically or horizontally through the spaces between the cathodes and the dust particles are ionized and gradually move toward the negative plates or walls. Because of the necessary wide space between the elements to avoid electrical discharges, considerable .time is required to completely clean the gas. Also this type of precipitator has been found to have a very small overload capacity. In case of cleaning blast furnace gas, which varies greatly in temperature and dust content due to irregularities in the working of the furnace, the electrical precipitator at times becomes inoperative due to excessive dust and moisture content in the gases. Furthermore, the accumulation of dust on the cathodeshas to be periodically cleaned oif, resulting in intermittent operations in any chamber.

Electrical precipitators have been designed to handle both liot and cold gases. In case of using hot gases the difiiculties are greater because of the variation, in gas temperatures and velocities inherent to any furnace operation. In order to preserve at least part of the sensible heat of the gases and at the same time decreasing the operating problems, systems have been developed whereby gases are first pre-cleaned and cooled and then heated in heat interchangers, the hot gas giving oiT its heat to the -cool gas. Serious dificulties have arisen in the operation of such plants owing to the building up of dirt in the heat interchangers. Furthermore, such apparatus is expensive in first cost, maintenance and supervision, and also occupies a great deal of space.

which is not often available around industrial plants.

Plants have also been designed in which the gas is completely cooled regardless of the loss of sensible heat. Here the gas is first washed in tower Washers of the usual type. The washed gas is then taken to the precipitator chamber where thedust is deposited on the cathodes, which are more or less wetted by the entrained water taken from the gas. The dust which accumulates in spite of the presence of water has still to be periodically cleaned out as the dust collects irregularly on the very large surfaces and it is difiicult to equally fiush all parts of cathode surfaces. These operations have not been successful. Interruptions in the continuity of the operation occur and the installation of duplicate apparatus is required with an expensive system-of valves to controlthe flow of the gases through the one chamber and the other. This makes a very costly installation, as well as operation.

Owing to the large number of parallel passages through which the gas can travel in all known precipitation, a uniform distribution of the gases through the system is extremely diflicult and this is one of the features causing unequal deposits, which, in turn, infiuence the distribution.- It is well known that gases will choose the path of least resistance and this cannot be predetermined and counteracted on account of the number of variables present.

It is an object of the present invention to provide a new and improved gas cleaning apparatus utilizing electrical precipitation.

It is a further object to provide apparatus of this character in which both anode and cathode may extend across the gas flow, both said elements being permeable to the flow of gas.

It is an additional object to provide an apparatus, of this type in which the unequal de- It is also an object to' provide an apparatus adapted to take care of considerable overload and rushes of gas and'dust.

It is an additional object to provide constructions and supporting arrangements for cathodes and anodes of such structures.

Other and further objects will appear as the description proceeds.

I have shown certain prefered embodiments of my invention in the accompanying drawings, in which- Figure 1 is a vertical section through a gas washer and precipitator;

Figure 2 is a horizontal section taken on lin 2-2 of Figure 1;

Figure 3 is a vertical'transverse section taken on line 3-3 of Figure 1; and

Figure 4 is a vertical transverse section taken on line 44 of Figure 1.

My invention comprises a new method of precipitation, in which the gases instead of traveling lengthwise or parallel to the anode surfaces pass through a permeable anode and cathode at right angles. The anode is charged by a unidirectional current, which ionizes the dust and water particles in the gases. Thereafter I pass them through a cathode section in which solids and water particles are attracted to the deionizing surfaces. This process may be repeated as often as necessary to reach the requisite degree of cleanliness.

Referring to the form of construction shown in the drawings, the precipitator housing 11- is provided with the inlet passage 12 and outlet passage 13. Adjacent the inlet is located the anode 14, which comprises a metallic screen permeable to the gas flow. This anode is supported on insulators 15 and is connected by the wire 16 with a suitable source of electrical power to properly charge the anode. As best shown in Figure 3, the anode screen 14 is connected laterally adjacent its lower edges to the insulators 17 to prevent swaying of the screen under the influence of the gas fiow. The upper insulators 15 are housed in a chamber 18 and the lateral insulators in chambers 19.

Adjacent the anode 14 is located the cathode structure 20 which in the form shown in the drawings, consists in closely placed corrugated members alternately placed. The corrugations on alternate members run vertically and on intermediate alternate members run horizontally. This construction is permeable to the gas flow but serves to deflect and disturb the flow so as to cause a thorough contact between the gas and the cathode surfaces. These cathode assemblies are not insulated from the shell 11 and consequently are grounded with respect to the anode 14 which is insulated from the shell and at a high potential.

The upper end of the cathode 20 is covered by a closed chamber 21 containing a plurality of water spray nozzles 22. These nozzles are so designed and related that the entire upper surface of the cathode may be subjected to a Water spray. The water runs down over the cathode surfaces to a sump 23 provided with a water seal outlet 24 at a level such that the water covers the lower edge of the cathode preventing gas from flowing below this edge.

Adjacent the cathode 20 is located a second anode 25 which is similar to the anode,14 and is similarly supported by insulators 26 located in chamber 27. This anode also has lateral supports similar to anode 14. A second cathode 28 of corrugated members similar to cathode 20 is located adjacent anode 25. The chamber 29 is located above cathode 28 and contains nozzles 30 adapted to cover the cathode surfaces with water.

The passage 31 leads from the outlet side of the precipitator housing 11 to a fan 32 which discharges through passage 33 to a heat exchanger 34. The heated clean gas passes through passage 35 to branch passages 36 and 3'7 to chambers 26 and 18. Branch passages 38 and 39 lead to the lower insulator containing chambers. The flow of warm gas through the insulator chambers keeps the insulators dry and thus minimizes electrical losses. The heated gas flows from these chambers back into the precipitator 11.

As the gases flow through the anode grids, the

dust and moisture particles are electrically charged or ionized. If the velocities of the gases are such that one screen will not suffice to properly ionize the particles of dust and moisture, then additional screens may be employed one above the other at short distances. Satisfactory ionization will be accomplished by this system much more rapidly -and certainly than with the present methods, as I break up the gas into many small and uniform streams, the size of which may be regulated by the size of the screen openings, but the smaller the mesh, the more rapid and complete will be the ionization. As my anode structure is permeable to the gas flow and is all of the same polarity, the mesh can be very small and is only limited by the permissible gas pressure drop.

The maximum amount of ionization can be ac complished without danger of arcing. In this lies an important advantage of my invention. The cathode or deionizing element in my invention is entirely separated from the anode section, and may be either a screen or grid, similar to the anode, or is preferably made of corrugated sheets to present to the particles of dust and water ample surfaces to discharge their electrical charge and deposit themselves. The entrained moisture so deposited tends to wash down such dust, but additional water is provided through sprays to periodically flush'the cathode.

In the forms of construction shown current may be shut ofi during the short period required for such flushing, or the flow of Water may be continuous.

While I have shown certain preferred embodiments of my invention, these are to be understood to be illustrative only, as I contemplate such changes and modifications as come within the spirit and scope of the appended claims.

I claim:

1. In an electrical precipitator, a cathode comprising a plurality of sheets of corrugated iron secured together with the corrugations on alternate sheets in angular relation to each other and so placed relative to the gas flow that the gas flows between said sheets.

2. In an electrical precipitator, an anode, a cathode parallel to the anode and comprising a plurality of sheets of corrugated iron secured together with the corrugations of alternate sheets at right angles to each other, and so placed relative to the gas flow that gas flows between said sheets.

3. In an electrical precipitator, an anode, a cathode parallel to the anode and comprising a plurality of sheets of corrugated iron secured together with the corrugations of alternate sheets at right angles to each other and so placed relative to the gas flow that gas flows between said sheets, and means for causing a flow of water over said sheets.

4. In an electrical precipitator, an anode, a cathode parallel to the anode and comprising a plurality of sheets of corrugated iron secured together with the corrugations of alternate sheets at right angles to each other, and so placed relative to the gas flow that gas flows between said sheets, and a water seal covering the lower edge of said sheets.

JOHN P. GRILLI.

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