US3790369A

US3790369A - Method for enhancing the reaction of a species of a liquid with a fluid substance

Info

Publication number: US3790369A
Application number: US00148672A
Authority: US
Inventors: R Olsson; E Turkdogan
Original assignee: United States Steel Corp
Current assignee: United States Steel Corp
Priority date: 1971-06-01
Filing date: 1971-06-01
Publication date: 1974-02-05
Anticipated expiration: 1991-02-05

Abstract

A liquid stream is caused to disintegrate in a spray of fine droplets, thereby markedly increasing the amount of surface area available for reaction. The liquid is forced through an orifice into a chamber of lower pressure; prior to its entrance into the chamber, fine bubbles of a gas are entrained within the liquid. After entry into chamber, the individual bubbles expand radially, causing the stream to be broken into sheets of fine droplets, which then react with a gas or liquid in the chamber and/or with injected gas.

Description

United States Patent [191 [111 3,790,369 Olsson et al. [45] F b, 5, 1974 [54] METHOD FOR ENHANCING THE 1,323,583 12/1919 Earnshaw 75/60 X RE N OF A SPECIES OF A LIQUID 3/133; gilt lierow M le/354% e ou WITH A FLUID SUBSTANCE 2,059,230 1l/l936 Hall et al. 75/0.5 C [75] Inventors: Robert G, Olsson, Edgewood 3,116,999 l/ 1964 Arrnbruster 75/49 Borough; T. Turkdogan 3,606,291 Schneider X Pittsburgh both of Pa 860,929 7/1907 Merrell et al. 159/48 R 1,406,381 2/1922 Heath et al. 159/48 R [73] Assignee: United States Steel Corporation, 3,166,613 1/1965 Wright et al. 159/48 R Pittsburgh, Pa, 3,615,723 10/1971 Meade 159/48 R Y [22] Filed: June 1971 Primary Examiner--L. Dewayne Rutledge [21] Appl. No.: 148,672 Assistant Examiner-Peter D. Rosenberg v Attorney, Agent, or Firm-Arthur Greif [52] US. Cl 75/491,5795//1589,27 053//6409, [57] ABSTRACT [51] Int Cl (321C 7/10 Bo'ld U16 F26b 3/12 A liquid stream is caused to disintegrate in a spray of [58] Fieid 'gg l 75/49 59 0 159/48 fine droplets, thereby markedly increasing the amount of surface area available for reaction. The liquid is 203/49 forced through an orifice mto a chamber of lower pressure; prior to its entrance into the chamber, time [56] g g g g gz bubbles of a gas are entrained within the liquid. After entry into chamber, the individual bubbles expand ra- Rozian causing the strea n to. be broken into sheets of S fine droplets, which then react with a gas or liquid in orenz I 2,997,384 8/1961 Feichtinger.... 75/59 the chamber and/or h mjected 3,031,261 4/1962 Vogel et al 159/48 R 14 Claims, 6 Drawing Figures I I: III: 2

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ROBERT a. OLSSO/V and ETHEM r rumrooamv Artur ey PATENTEDFEB 51924 3.790.369

snm 2 OF 3 FIG 20.

N0 6148 INJECTION By a Afforney METHOD FOR ENHANCING THE REACTION OF A SPECIES OF A LIQUID WITH A FLUID SUBSTANCE This invention relates to a method of causing a liquid to disintegrate into a spray of fine droplets, whereby an impurity or other species within the liquid may be reacted to form a useful product or one which is easily separated.-

Reactions of gaseous substances with a component of a liquid generally require vigorous stirring of the bath, since only the portion of such component at the surface of the liquid is available for reaction. Such stirring keeps the surface from being saturated with reaction product and from being depleted of the reactant species. This is especially true in molten metals, since the hydrostatic pressure of the liquid a short distance below the surface is generally greater than the partial pressure of the reaction product. Thus, a method for atomizing the liquid and thereby markedly increasing the surface to volume ratio would be highly desirable. The instant invention is directed to a relatively simple and inexpensive method for effecting such a desirable disintegration and atomization of a liquid. This invention is based on the utilization of a relatively small amount of gas, in the form of fine bubbles, which is dispersed in the liquid prior to its being discharged into a region of lower pressure. Gas injected in this manner will break the discharged liquid stream into a spray of fine droplets, even when there is no evolution of dissolved gas from the liquid. The fine droplets are then reacted with the injected gas and/or with a bleed gas maintained within the lower pressure region. The process having diverse utility, thus it may be employed for the production of high surface area particles (e.g., alumina catalysts, in which the liquid is molten aluminum and the bleed gas is oxygen) as well as in the purification of liquids wherein only the impurity reacts with the bleed gas and is thereby removed (e.g., purificationof molten iron wherein the impurities are reacted with an oxygen bleed gas).

The objects and advantages of the invention will be better understood by referring to the appended claims and the following description and Figures, in which:

FIG. I is a schematic diagram of the apparatus employed in the experiments;

FIGS. 2A and 2B show the effect of gas injection on a mercury stream;

7 FIG. 3 is a graph depicting the fractional removal of sodium as a function of initial sodium concentration and gas injection rate;

FIG. 4 compares the effectof 0; vs. Ar injection on removal of sodium; and

FIG. 5 shows the increased effect provided by gas injection, on fractional removal of sodium.

Experiments were performed on the purification of sodium amalgams A schematic diagram of the apparatus employed is shown in FIG. 1. The mercury flowed in a single pass from a reservoir 1 through a nozzle and into the vacuum tank 2. The upper portion of this tank was an 18 in. X IS in. diameter glass cylinder 3 through which the sprays could be observed and photographed. Gas was injected 4 through an 0.5 mm id hypodermic needle, at a metered rate. The vacuum was maintained by a two-stage vacuum pump 5; the desired pressure being obtained by augmenting the gas flow through the needle with a metered gas bleed 6 directly into the vacuum chamber.

The initial amalgams were prepared by adding sodium chips to the mercury under an inert atmosphere. The sodium oxide formed during an experiment, rapidly separated from the mercury and was deposited in the interior of the vacuum tank or could be skimmed from the surface of th mercury after it was withdrawn from the system. Experiments were conducted within the following range of variables:

Tank pressure PFFIO torr (ins injection rate G ll-2 l/min(S'I'P) Total gas rate (injection and l-l() l/min (S'I'P) bleed) Liquid flow rate 3.54.85 l/min Initial liquid composition C,=l [-540 ppm Na In some experiments, both the injected and the bleed gases were oxygen; in others, argon was introduced at one of these positions.

Sprays formed by the manner of this invention are discontinuous with a very definite structure. Highspeed still and motion pictures were taken of many of the sprays; the exposure time for the still photographs being about 3 X 10' sec. Droplet velocities and sizes, and rates of bubble formation were measured from these pictures. The effect of bubble injection is shown in FIGS. 2A and 2B (facsimile tracings of these photographs), wherein 2A shows the mercury with no gas injection. In 2B, gas was injected at a pressure of 1,280 torr. The stream of mercury is disintergrated by the very rapid expansion of the gas bubble as the liquid entersthe vacuum chamber. This creates discrete, uneven sheets of droplets, with the spread and expansion of the spray increasing as the gas injection rateis igcreased.

FIG. 3 shows the fractional removal of sodium (for gas injection rates, G, of 0, l, and 2 l/min) as a function of initial sodium concentration for experiments in which oxygen was used both as the injected and bleed gas. The fractional removal (F) is defined as F c, cg/c,

where C and C are the initial and final sodium concentrations respectively. It may be seen that the fractional removal of sodium increases with increasing gas injection rate and decreasing sodium concentration, but is not affected to any great extent by vacuum tank pressure, P Later experiments, have however shown that significant increases inthe ratio of pressure of the reservoir to that of the vacuuml chamber (i.e., P lP will effect an increase in the removal rate by decreasing the mean droplet size of the spray.

In FIG. 4, F vs. C is shown for experiments in which either the injected or the bleed gas was argon with G 1 l/min. The solid line represents the correlation from FIG. 3B, i.e., in which oxygen was used for both purposes. There is good agreement between all the experiments for C ppm. At greater values of initial sodium concentration. the data for argon injection fall above the line. while those for oxygen injection (argon bleed) fall below. indicating that for these latter data..

the rate of oxidation of sodium is being restricted by a shortage of oxygen. In the other experiments, there was always a surplus of oxygen. On the other hand, the argon injection data would be expected to be somewhat higher than the all-oxygen" line'of FIG. 38, since 3 argon does not react with the sodium prior to its emergence from the nozzle, and is therefore totally available for stream breakup. At high gas injection rates, this effect decreases because the formation of spray is less sensitive to the rate of injection.

As seen from FIG. 3A, there is considerable sodium removal even with no gas injection. The removal being low and relatively constant for sodium values greater than 50 ppm. It is believed that the oxidation occurred when the pool was formed and stirred during each experiment (about 1.5 min.) and during the time for release of the vacuum and draining of the mercury (about 2-3 min.) prior to sampling. If it is assumed that the fractional removal with no gas injection is equal to that occurring in the pool when there is spray formation, one may determine the degree of enhanced removal by subtracting the values in 3A from 38 and 3C. These values are given in FIGS. 5A and 58 respectively, except that for the region where C 100 ppm, the data for spray formation with argon injection (i.e., no oxygen starvation) were used in place of-those with oxygen injection. It is seen that the fractional removal in the spray region also increases as the initial sodium concentration decreases. This is attributed to coverage of the available surface by clumps of solid reaction product, Na O; i. e., limited by diffusion of sodium to the droplet surfacefBy fufther inc'iesifi 'EE75665 rate and decreasing the radius of injected bubbles, the

mean radius of the droplets in the spray could be further decreased, thereby increasing thefraction of oxide-free surface available for reaction. In the above experiments, the average distance from the nozzle orifice to the pool surface was 79 cm, providing a contact time for flight of droplets of about 0.15 sec. By providing longer spray'fall heights, the contact time would increase and even greater removal could be achieved.

The enhanced disintegration of the liquid, by utilization of the instant process, is effected by causing the liquid (with its entrained bubbles) in the vessel in which it is contained to be suddenly accelerated, as it passes through a nozzle orifice of substantially reduced cross-sectional area and into the zone of reduced pressure. Referring again to to FIG. 1, where A, represents the cross-sectional area of vessel 1, and A the area of the orifice, it is preferred that the ratio of A /A be at least 2:1. With this acceleration of the liquid there is acorrei o5difiuddh drop in pressure from that at the base of the vessel to that of the reduced pressure zone. Entrained gas bubbles are rapidly taken from the high pressure region to the low pressure region where bubble expansion results in the radial spread of the liquid stream and an ensuing spray of fine, large surface area droplets.

To achieve an efficient utilization of gas bubbles for such expansion, the gas should be injected at a point wherein the liquid is at a pressure considerably higher than that of the reduced pressure zone. Thus, the gas may be injected at any point within the containment vessel above the nozzle, where the pressure within the bubble will be approximately that of the surrounding liquid. However, it is most efficiently injected at a point sufficiently proximate to the orifice (as depicted) so as to cause a substantial portion of the bubbles to be entrained within the increment of liquid entering the reduced pressure zone.

The length of the nozzle should be short (for purposes of this invention, the term nozzle" is considered to be a device for converting the pressure and potential energy of a fluid into kinetic energy and will therefore also include a knife edgeorifice) so that the passage of liquid with its entrained bubbles will be sufficiently rapid, thereby preventing the bubbles from expanding to a substantial extent prior to the time the liquid has left the nozzle. Consequently, substantially all the gaseous expansion will be available for spray formation.

The maximum nozzle length will depend on a number of factors. Thus, the diminished expansion caused by a relatively long nozzle could be overcome to some ex-' tent by increasing the ambient pressure of the liquid and/or by increasing the force by which the liquid is forced through the nozzle. These latter expedients serve to increase the velocity of liquid through the nozzle and to increase the initial stored energy in the bubbles. Thus, to prevent such substantial expansion of the bubbles within the nozzle, with its consequent loss of available energy, it is considered desirable to limit the residence time of the incremental portion of liquid within the nozzle. This time limit is basically a function of the pressure of the liquid at the point of gas injection (and hence the pressure inside the bubbles prior to any expansion). It is, therefore, preferred that the liquid be urged through the nozzle with sufficient force so that the resistance time of the liquid within the nozzle is defined by the equation:

where t= residence time in seconds, and

P,= pressure in atmospheres, of the liquid, at the point of gas injection.

To achieve such desirable short residence times, the liquid is preferably accelerated through the nozzle orifice by the application of a force in addition to, and acting in concert with the atmospheric force. Thus, in FIG. 1, the head of liquid (gravity) and the atmosphere both aid in forcing the liquid through the nozzle. However, the instant method need not rely on gravitational (i.e., downward flow) or atmospheric forces. Thus, for example, a piston device may be employed to force the liquid into a region of reduced pressure.

The choice of fluid employed'will be dependent on the desired reaction. Thus, in the purification of molten steel by oxidation of the impurities, it will, of course, be necessary to employ an oxygen-containing gas as the reactive fluid, whereas in the removal of Zn from molten lead, a gas such as chlorine would be employed as the reactive gas. The reactive fluid need not, of course, be a gas, thus a liquid may be employed in the reduced pressure region to react with the separated species.

Since the disintegration of the liquid stream is not dependent on saturating'or dissolving a gas within the liquid, any non-deleterious gas may be injected for purposes of spray formation. Thus, in addition to argon or other gases classified as inert," any gas may be em-' ployed which does not react detrimentally with the liquid being treated. Thus, inmany instances, inexpensive air injection may be employed.

We claim:

l. A method for controlling and enhancing the reaction of a component of a liquid with a fluid reactant capable of reacting with said component to form a product which is easily separable from said liquid, which comprises;

passing the liquid from the vessel in which it is contained, through a nozzle opening, the crosssectional area of which is less than 0.5 the crosssectional area of said containment vessel, and into a zone maintained at a pressure substantially lower than the pressure of the liquid within said vessel, said zone containing said fluid reactant;

injecting a gas into said liquid at a rate by which spaced apart bubbles are formed, said bubbles being of a diameter substantially smaller than the effective diameter of the nozzle opening, the point of said gas injection being in a region of the liquid, prior to its passage through said nozzle, where the pressure of the liquid is substantially higher than that of said low pressure zone;

urging said liquid through said nozzle by theapplication of a force acting in addition to and in concert with the force exerted by the atmosphere ambient to said containment vessel so that the passage of the liquid with its entrained bubbles will be sufficiently rapid to prevent the bubbles from expanding to a substantial extent prior to the time the liquid has left the nozzle whereby the resultant expansion of said bubbles enhances the disintegration of said liquid, thereby materially increasing the surface available for reaction, reacting said component with saidreactant fluid to form said easily separable product, removing said product and collecting the resultant refined liquid.

2. The method of claim 1, wherein said point of injection is sufficiently proximate said nozzle, so as to cause a major portion of said bubbles to be entrained within the increment of liquid entering said nozzle.

3. The method of claim 2, in which said reactant fluid is a gas.

4. The method of claim 3, in which the surface of liquid available for reaction is increased, by increasing the flow rate of injected gas.

5. The method of claim 4, in which the surface of liquid available for reaction is increased, by decreasing the radius of injected bubbles.

6. The method of claim 5, in which the surface of liquid available for reaction is increased, by increasing the pressure in said containment vessel, in relation to the pressure in said low pressure zone.

7. The method of claim 6, in which said additional force is supplied by. a mechanical pistonf 8. The method of claim 6, in which said additional force is that of gravity.

9. The method of claim 8, in which said injected gas is other than said reactant gas.

10. The method of claim 9, in which the concentration of reactant gas is maintained by a bleed of said gas into said zone.

11. The method of claim 8, in which said injected gas contains said reactant gas.

12. The method of claim 11, in which the concentration of reactant gas is augmented'by an additional bleed of said gas in said zone.

13. The method of claim 8, in which said liquid is molten iron and said gaseous reactant is an oxygen containing gas.

14. The method of claim 13, in which said components are impurities which are removed by, reaction with said oxygen containing gas.

Claims

2. The method of claim 1, wherein said point of injection is sufficiently proximate said nozzle, so as to cause a major portion of said bubbles to be entrained within the increment of liquid entering said nozzle.
3. The method of claim 2, in which said reactant fluid is a gas.
4. The method of claim 3, in which the surface of liquid available for reaction is increased, by increasing the flow rate of injected gas.
5. The method of claim 4, in which the surface of liquid available for reaction is increased, by decreasing the radius of injected bubbles.
6. The method of claim 5, in which the surface of liquid available for reaction is increased, by increasing the pressure in said containment vessel, in relation to the pressure in said low pressure zone.
7. The method of claim 6, in which said additional force is supplied by a mechanical piston.
8. The method of claim 6, in which said additional force is that of gravity.
9. The method of claim 8, in which said injected gas is other than said reactant gas.
10. The method of claim 9, in which the concentration of reactant gas is maintained by a bleed of said gas into said zone.
11. The method of claim 8, in which said injected gas contains said reactant gas.
12. The method of claim 11, in which the concentration of reactant gas is augmented by an additional bleed of said gas in said zone.
13. The method of claim 8, in which said liquid is molten iron and said gaseous reactant is an oxygen containing gas.
14. The method of claim 13, in which said components are impurities which are removed by reaction with said oxygen containing gas.