US2559404A - Art of pumping mercury - Google Patents

Description

July 3, 1951 R. B. COX

ART OF PUMPING MERCURY Filed June 1, 1946 Brine Inlet Patented July 3, 1951 ART OF PUMPING MERCURY Robert B. Cox, Wyandotte, Mich., assignor to Wyandotte Chemicals Corporation, Wyandotte, Mich., a corporation of Michigan Application June 1, 1946, Serial No. 673,762

6 Claims. (Cl. 103-260) The present invention relates to an improved method of pumping liquid mercury, and a pumping system for same.

Considerable difiiculty has arisen in the past in producing a forced flow, i. e. in pumping liquid mercury or an amalgam having the same physical characteristics as the liquid mercury itself. Due to the relatively high specific gravity of the mercury, it has previously been thought necessary to use a positive displacement type of mechanical pump, or one whose moving parts act directly on the mercury. Mercury, however, has the tendency to amalgamate with, or dissolve, many other metals and elements. See British Chemical Abstracts, Applied Chemistry, 1927, page 304.

Therefore, in the art of pumping mercury, the severe problem of amalgamation of the fluid mercury with the metallic parts of a mechanical displacement type of pump, has always been present. This problem is particularly acute in the industrial electrochemical art in the operation of mercury cathode brine cells where it is necessary to handle and transfer a large volume of mercury, both in the form of sodium amalgam (sodium being soluble in mercury to the extent of about 8 parts in 1000) and in its denuded form.

My present invention is therefore particularly well suited for use with such a mercury cathode electrolytic cell as disclosed in my co-pending application Serial No. 576,041 filed February 3, 1945.

I have discovered that mercury in its liquid form can be entrained in a rapidly flowing stream of relatively lighter liquid which is inert and substantially non-reactive with respect to mercury. Such lighter liquid may be water or an aqueous solution containing other dissolved chemical compounds, such as a caustic soda solution, or it may be an organic liquid such as a liquid hydrocarbon having a specific gravity and viscosity equivalent to that of water. The mercury is thereby transported or pumped along with the lighter vehicular stream to a desired point of delivery. Due to the relatively great differences in the specific gravities of mercury and the vehicular liquid, they can then be readily separated from each other, prior to contact of the mercury with the parts of a mechanical pump, so that it is possible to use an ordinary water. pump in my mercury pumping system,

My invention possesses the additional advantage, in that the conduits in which the mercury or sodium amalgam is flowed, can be made from a material such as glass, .or a synthetic resin so that there is no danger of the mercury or sodium amalgam dissolving or reacting with the conduit elements with which it does come in contact.

My invention is of particular advantage when used in conjunction with a sodium-amalgam electrolytic process, as it renders possible an unusual reduction in the amount of mercury required for operation of the process, since the volume of mercury that would otherwise be necessary to fill pumps, conduits, reservoirs, etc., is greatly reduced and because such volume is primarily occupied by the vehicular liquid. It has been found that my invention renders it possible to reduce to about one-half the mercury volume requirement (representing a large proportion of the material cost) of a moving mercury cathode cell, such as disclosed in my aforesaid co-pending application.

I have also made the discovery that the rate of flow of the water stream with which the mercury is entrained, must be at or above a certain specified critical velocity, in order to effect satisfactory operation.

Additional objects and advantages of my invention shall become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends and to enable any person skilled in the art readily to understand and practice the invention, the following full and concise description and annexed drawing set forth the best mode in which I have contemplated applying the principle of my invention.

In said annexed drawing Fig. 1 is more or less a diagrammatic view illustrating the mercury pump system embodying the principle of my invention and;

Fig. 2 is a top plan View of the chamber for separating the entrained mercury from the vehicular water stream.

Now referring more particularly to the drawing, there are shown therein a conduit I leading from a source of mercury supply and connected at the point 2 to the conduit 3, the latter being part of the vehicular water stream or loop. A

stream of water is introduced to the conduit 3 3 from the conduits 4 and 5 leading from the water pump P. The velocity of the water stream in the conduits 3, 4 and 5 is much greater than that of the mercury in the conduit I. As substantially illustrated in Fig. 1, the mercury, on entering the water stream, is broken up and en-' trained in the form of elongated globules 6 and thus lifted or pumped to a higher elevation.

In Fig. 1, the source of mercury entering the conduit l is shown as derived from the sodium amalgam outlet 1 in the bottom of the vertical, electrolytic brine decomposition cell 8, such as shown and described in greater detail in my aforesaid co-pe'nding application. Fresh mercury,

derived from the stripping or denuding cell where the sodium amalgam is reacted to form caustic soda, hydrogen and mercury, is introduced through the inlet 9 and the electrode nozzles ID to the top of the cell 8. I

A flared or diverging connection 'll leads from the conduit 3 to the inlet 12 on the outer periphery of the separating chamber 13. The latter chamber I3 is preferably of a circular shape. .Its bottom is dished inwardly to form a central raised portion, as indicated at M, and thus forming a ring-like space around the outside portion of the bottom of the chamber l3 where the mercury or sodium amalgam is collected as indicated at [5 whence it is drained out through the outlet I6 connected through a suitable U-tube trap to the outlet conduit ll. From the conduit 11, the sodium amalgam may suitably be lead to a stripping or denuding cell.

The heavier mercury is thus separated from the Water stream in the chamber l3. Due to the fact that the velocity of the Water stream is substaneffect of the vehicular stream velocity to entrain such mass.

The mercury-free water rises up through .the

central neck or constricted portion I4 of the chamber [3 whence it passes through the connecting conduit l9 back to the pump P.

The conduit with a suitable valve connected therein, leads from a water supply source (not shown) to the conduit IQ for the purpose of replenishing the amount of water which might be required from time to time in the water circuit or loop. A gas conduit 2| is connected in the upper end of the separating chamber neck l3 for leading off any small amount of gas that might be generated.

' I have discovered that the linear velocity of the lighter fluid, such as the water in the conduit 3,

must be at or above a critical minimum of 19 inches per second. A practicable velocity, to accommodate line surges and maintain uniform :operation, is about 50% greater than this critical minimum, or 28.8 inches per second. Of course, a slight pressure or head must be maintained on the mercury in the conduit I, which is at least equal to the pressure of the vehicular water stream in the conduit 3. A mercury pressure or head of about 5 inches in the conduit I will renderit possible to lift or pump the liquidmer- 4 cury to a height of several feet in the conduit 3. It will be apparent to those skilled in the art, that my above described invention may be equally well used for pumping fiuid mercury or fluid amalgams in environments other than in connection with a sodium-amalgam electrolytic cell,

and that other vehicular liquids may be employed beside the water referred to in the foregoing detailed description. Thus, a weak caustic soda solution will operate equally as Well as Water in the system described.

In the appended claims, the term liquid mercury is intended to include in its scope liquid mercury containing dissolved or amalgamated metals or elements, as long as the resultant body maintains essentially the physical characteristics of liquid mercury itself.

Equivalent modes of practicing my invention may be followed provided that they are within the scope and purview of the appended claims.

I, therefore, distinctly claim and particularly point out as my invention:

1. The method of pumping mercury which comprisesintroducing liquid mercury into an aqueous stream moving at a linear velocity greater than 19 inches per second, the head of said mercury being at least equal to that of said aqueous stream at the point of entrainment.

2. The method of pumping mercury which comprises entraining a body of liquid mercury in a rapidly flowing aqueous stream said stream being of substantially constant pressure and velocity throughout its vehicular length, introducing said mercury into said stream at a head at least equal to that of said stream, separating the mercury from such stream by decreasing the velocity thereof, increasing the velocity of said stream and recycling it to the pumping system.

3. The method of pumping mercury which comprises inducting the liquid mercury into a conduit containing a rapidly flowing aqueous stream said stream being of substantially constant pressure and velocity throughout its vehicular length, introducing said mercury into said stream at a head at least equal to that of said stream, introducing such stream into the bottom .of :an enlarged chamber, therein separating out a the mercury therefrom and returning the mercury-free stream to the pumping system.

4. The method of pumping mercury which comprises inducting the liquid mercury into a conduit containing an aqueous stream flowing at a linear velocity of greater than 19 inches per second, the head of said mercury being at least equal to that of said aqueous stream at the point of entrainment, introducing the mercury-entrained stream into the bottom of a circular chamber having a larger cross-sectional area than that of said conduit, withdrawing the mercum from the'bottom of said chamber, and withdrawing the mercury-free stream from the top of said chamber.

.5.'The method of pumping mercury which comprises introducing a bod of liquid mercury, at a given point of elevation, into an upwardly flowing vehicular stream of relatively lighter liquid, said stream being of substantially constant velocity throughout its vehicular length, the head of said mercury body at such point of introduction being at least equal to that of said stream, entraining said mercury body in said vehicular stream, and lifting the so-entrained mercury to a second point of elevation higher than that attainable by the head of said mercury body itself.

6. The method as in claim 5 including the additional steps of introducing the mercuryentrained stream at said second point of elevation into the bottom of an enlarged chamber, imparting a rotary motion to the path of flow of said stream in said chamber, and maintaining said stream at such a linear velocity that the resultant centrifugal and gravitational forces exerted thereon operate to separate the mercury therefrom.

ROBERT B. COX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 619,349 Reicken Feb. 14, 1899 734,499 Baker et a1 July 28, 1903 Number Number OTHER REFERENCES British Chemical Abstracts, Applied Chemistry, 1927, page 304.

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