CA1329468C

CA1329468C - Hypochlorous acid reactor

Info

Publication number: CA1329468C
Application number: CA 614881
Authority: CA
Inventors: James Kenneth Melton; Garland Eugene Hilliard; John Holzworth Shaffer
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1988-10-07
Filing date: 1989-09-29
Publication date: 1994-05-17
Anticipated expiration: 2011-05-17

Abstract

ABSTRACT OF THE DISCLOSURE
An elongated, generally vertically extending cocurrent reactor vessel for the production of hypohalogenated acid by the mixing and reaction of a liquid alkali metal hydroxide and a gaseous halogen is provided wherein an atomizer is mounted near the top of the reactor vessel to atomize the liquid alkali metal hydroxide into droplets in the vessel. The vessel has a spraying and reaction zone immediately beneath the atomizer and a drying zone beneath the spraying and reaction zone. The reactor according to the invention is particularly useful for the production of hypochlorous acid.

Description

1 32~468 HYPOCHL~R~US AC~ REAC~OR

This invention relates generally to a reactor vessel and more specifically to a reactor vessel for the production of hypohalogenated acid by the mixing and reaction therein of an alkali metal hydro~ide and a gaseous halogen. ~ preferred product acid is i hypochlorous acid.
HypoGhlorous acid is used extensively in the preparation of chlorohydrin and chloramines.
Chloroisocyanurates ar~ typical examples. Hypochlorous acid has been produced by several processes or techniques. The use of dilute hypochlorous acid and large quantities of halogen to produce hypohalites, ' 15 such as sodium hypochlorite, is recent.
One technique employs the process in which chlorine, steam and air are bubbled through an aqueous solution of an alkali earth metal hypochlorite, such as calcium hypochlorite, to remove the resulting hypochlorous acid in vapor form. The hypochlorous acid is then co~densed and stored for use. This process, however, produces a large volume of undesirable , by-product, calcium chloride.
Another process uses a low concentration of aqueous caustic solution to scrub chlorine gas.
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However, the solution has an available chlorine content of about only 5% and, because of the chloride ion content, the hypochlorous acid that is formed quickly decomposes, most preferably to chloric acid.
Another related process prepares a solid mi~ture of alkali metal hypochlorite and alkali metal chloride by reacting chlorine gas with a spray of alkali metal hydro~ide, while drying with a g~s the reactants and product. Some cooling of the reacting chemicals and the drying gas may be done. The primary products of this process have very limited utility.
A more recent process, which produces ~ypochlorous acid vapor, sprays aqueous alkali metal hydroxide in droplet form or solid alkali metal -lS hydro~ide particles into gaseous chlorine. This approach attempts to utilize droplet sizes to attain the maximum surface to volume ratio possible. Droplets having an average diameter of less than about 1000 microns are employed.
These previous processes, and the apparatus employed to produce these processes, have suffered from not achieving substantially complete reactions between the chlorine and the alkali metal hydroxide. A
critical factor in determining the complete r~action is the droplet size of the alkali metal hydro~ide. It is also desirable that any hypochlorous acid produced and any water present be readily vaporizable. The salt particles produced as by-products in any process should be dry to facilitate handling. The salt particles should be sized so that they readily separate from the gaseous product mi~ture of hypochlorous acid. Prior 3 1 32q46~

processes have produced oversized alkali metal hydro~ide droplets that result in the undesired reaction of hypochlorous acid and the oversized particles to produce significant alkali metal chlorates. These oversized particles then retain excessîve moisture so that caking results and the caked mass adheres to the reactor surfaces. The presence of such alkali metal chlorates reflect reduced yields of the desired hypochlorous acid, while increasing the raw material and op~rating costs.
These problems are solved in the design of the present invention wherein a reactor vessel for the production of hy~ohalogenated acid is provided ~n.~ich the mi~ing and reaction of alkali metal hydro~ide and a gaseous halogen occurs.
It is an object of the present invention to provide a reactor vessel within which a gas phase controlled reaction can occur to produce a hypohalogenated acid.
It is another object of the present invention to provide a reactor vessel in which both a liquid-gas reaction and drying occur to produce a gaseous product and a .solid by-product.
It is a feature of the present in~ention that an atomizer is employed to produce small droplets of an alkali metal hydro~ide to ensure that the undesirable secondary reactions are minimized and that proper drying of the desired particles occurs.
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; ~4~ l 329468 It is another feature of the present invention that the reactor vessel permits the rapidly sequential events of absorption of gaseous halogen into the atomized particles of alkali metal hydroxide and water ` 5 evaporation to occur.
It is still another feature of the present invention that the atomizer is located near the top of the reactor vessel.
It is yet another feature of the present ~', 10 invention that heated halogen gas mi~ture is fed into the top of the reactor vessel.
It is an advantage of the present invention that the production of oversized alkali metal hydroxide droplets are avoided and that undesirable sscondary reactions are minimized.
It is another advantage of the present invention that manufacturing costs are substantially reduced.
These and other objects, features and advantages are provided in a reactor vessel for the production of hypohalogenated acid from the mixing and `~ reaction of an alkali metal hydroxide and a gaseous halogen in the reactor vessel, which is elongate and generally vertically positioned and the atomizer for atomizing the alkali metal hydro~ide is mounted within the reactor vessel above the spraying and reaction zone and the drying zone.
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~5~ 1 329468 In accordance with the present invention, there is thus provided a reactor for the production of hypo-halogenated acid from the mixing and reaction of an alkali metal hydroxide and a gaseous halogen, comprising in com bination:
a. an elongated, generally vertically extending reactor vessel having a top and an opposing bottom, and a central axis therebetweeni b. gas inlet means in the top of the reactor vessel;
c. flow directing means beneath the gas inlet connected to and inside the vessel effective to direct the gaseous halogen from the top to the opposing bottom;
d. infeed means mounted to the reactor vessel for feeding alkali metal hydroxide droplets in a spray into the vessel;
e. an alkali metal hydroxide feed line , connected to the infeed means in the reactor vessel i from a supply of alkali metal hydroxide;
f. a spraying and reaction zone beneath the 3 infeed means into which the alkali metal hydroxide is sprayed and reacts with the gaseous halogen to form reaction products including hypohalogenated acid;
g. a drying zone beneath the spraying and reaction 20ne to dry the reaction products; and h. outlet means below the drying zone and above the bottom for outletting gaseous halogen and product from the reactor vessel.
The present invention also provides, in another aspect thereof, a reactor for the production of a solid by-product and a gaseous product from the reaction of a gas and a liquid, comprising in combination:

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~ -6- 1 329468 a. an elongated, generally vertically extending reactor vessel having a top and an opposing bottom, and a central axis therebetween;
b. gas inlet means in the top of the reactor vessel to feed in a reactant gas;
c. flow directing means beneath the gas inlet connected to and inside the reactor vessel e fective to direct the reactant gas from the top to the opposing bottom;
d. a liquid feed line connected to the reactor vessel beneath the flow directing means;
e. infeed means mounted to the reactor vessel and connected to the liquid feed line for spraying the liquid;
-~ 15 f. a spraying and reaction zone beneath the infeed means into which the liquid is sprayed and in ~ which the liquid reacts with the reactant gas to form j the gaseous product and the solid by-product;
g. a drying zone beneath the spraying and reaction zone to dry the solid by-product;
h. outlet means below the drying zone for outletting the dried solid by-product from the reactor vessel; and i. a generally horizontally extending gaseous product outlet in the drying zone and above ~he opposing bottom to outlet product gas from the reactor and recycle any unreacted reactan~ gas.
~ eatures and advantages of this invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when it is taken in conjunction with the drawings wherein:

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~ 1 329468 FIGURE 1 is a side elevational view of the reactor vessel; and FIGURE 2 is a bottom perspective view of the ellipsoid inlet for the e~haust duct.
FIGURE l shows the reactor, indicated generally by the numeral 10, which reacts the liquid alkali metal hydro~ide, such as caustic, supplied by feed line 11 with the gaseous halogen, such as chlorine, to produce the solid salt crystals and the gaseous product, such as HOCl. Although the reactor will be discussed in terms of producing hypochlorous acid, it is to be understood that any halogen could be employed to produce hypohalogenated acid, for example, hypobromous or hypofluorous acid. The HOCl is condensed to produce liquid hypochlorous acid which, ~' for e~ample, can be mixed with a lime slurry to produce calcium hypochlorite. Gaseous chlorine, along with some chlorine mono~ide in the recycle system, is fed into reactor 10 via gas infeed 12 in the top 14. Top 14 is in the shape of an inverted funnel, that can be constructed of a suitable corrosion resistant material, such as titanium: coated titanium; an alloy of nickel, chrome, molybdenum, iron and other materials; tantalum;
and lined carbon steel or lined fiberglass reinforced plastic. The lining can be a suitable polyfluoro-' polymer.
Reactor vessel 15 has a perforated plate 16 atthe top between the reactor top 14 and the vessel 15.
The plate 16 is also made of a suitable corrosion resistant material, such as polytetrafluoroethylene or one oL the above mentioned materials with respect to , . , ,, , ~ , . . . . . . .

; top 14, and serves to create a straight cocurrent flow path for the chlorine gas flowing down from the top 14. Ethylene chlorotrifluoroethylene has also been used as a construction material for reactor vessel 15.
Vessel lS, similarly can be made from any suitable corrosion resistant material, such as carbon steel with a liner or coating of a suitable perfluoropolymer, such as that sold under the tradename TEPLON(R) PFA.
1 Reactor vessel 15 has a generally elongate 3 10 cylindrical central section 18 which tapers to a 3 conically shaped funnel bottom 19 to permit solid alkali metal halide salt, such as NaCl, product to ''f discharge out through a standpipe, not shown, for further processing. ~essel 15 has a caustic feed line 15 11 that enters through its side and provides the ¦ caustic to an atomizer nozzle 21. Nozzle 21 is mounted along the center line 22 of the vessel lS about six (06) inches below the top of vessel lS. Nozzle 21 creates caustic droplets of a desired size between about 50 to 200 microns which are of sufficient size to absorb virtually all of the gaseous chlorine feed while the chlorine and caustic react fast to produce the gaseous and solid products as shown in the equation: -NaOH t C12 ~ HOCl I NaCl i~ 25 The reac~ion occurs at a pH of about 4 to about 6 with a stochiometric ratio of about 30 to 1 chlorine to caustic. The gaseous HOCl is condensed between about 0 to about 10C after exiting the ¦ reactor to recover a concentrated HOCl solution.

~1 ~ 329468 Recycled gases, such as chlorine and chlorine monoxide, are exhausted from the vessel 15 through exhaust duct 24 and are fed back into reactor 10 via a recirculation loop, after passing through a heat e~changer (not shown) to achieve the necessary heat, when combined with the heat of reaction to evaporate the hypohalogenated acid, such as hypochlorous acid, and water phase to leave a dry sodium chloride or salt solid by-product. The desired reaction temperature 10 ranges from about 30 to about 100 centigrade.
The recycled gases are also used i~s reactant gases in the production of the hypohalogenated acid.
The recycled gases, for example chlorine and ; chlorine monoxide, enter the reactor vessel top 15 and disperse outwardly in the inverted funnel top 14 and pass through the flow directing means or perforated plate 16 to enter the reactor vessel 15 in a generally vertical flow orientation. Fresh halogen gas, for example chlorine, is fed in through chlorine feed line 20 through the reactor top 14 and is directed down over j the nozzle or atomizer 21.
~ ~ozzle 21 may be a single fluid atomizer, a ;~ two fluid nozzle or a wheel atomizer dependent upon the viscosity and density of the alkali metal hydro~ide being atomized and the amount of pressure to which the liquid is subjected. The materials of construction of the nozzle must be capable of withstanding the ~ harshness of the environment within the reactor.
j The vessel 15 has an outlet or e~haust duct 24 at the bottom of the drying zone 26 just above the funnel or conica1ly ~haped bottom 19 to remove the . ~ .

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" -~ 1 3~q468 product gas, the unreacted halogen gas and some by-product into the recirculation loop as previously described. Outlet or e~haust duct 24 exits through the side of vessel 15 generally horizontally and has an inlet 28 that is undercut such that the top overhangs or overlies and covers the bottom to preclude solid alkali metal chloride by-product, for e~ample sodium chloride, from falling directly into it. The preferred `r' shape of the inlet 28 is an undercut ellipsoid, as seen s 10 in FIGURE 2.
The vessel 15 has its central section 18 `' preferably cylindrically shaped, but it could also be ~ polygonal, as appropriate. The cylindrical design has dl a desired diameter and length. The length e~tends from 15 the top at the perforated plate 16 to the bottom of the drying zone 26, just above the funnel bottom 19. The dimensions of the len~th and the diameter can be selected so that the length to diameter ratio, l/d, can range from about 1 to 1 to about 1 to 5.
In operation the halogen gas, for e~ample chlorine, is fed into the reactor 10 through feed line 20 and is directed generally vertically downward over nozzle 21. Recycled gases are fed in from the recirculation system via gas infeed 12 into the reactor top 14 and are directionalized by perforated plate 16 down into reactor vessel 15. Vessel 15 has an elongate cylindrical section 18 which has a spraying and drying zone 25 adjacent the top surrounding nozzle 21 and a drying zone 26 therebelow.

The reacted gases e~it the reactor 10 through outlet or e~haust duct 29 for processing and recirculation, as appropriate. The solid by-product alkali metal halide, such as sodium chloride, exits the vessel 15 through the conically shaped funnel bottom 19 for processing. Bottom 19 is connected by conventional flanging to connecting pipes ~not shown).
The solid by-product alkali metal halogen is dried as it passes down through the drying zone 26.
The overhanging top portion of e~haust duct 24 prevents substantial quantities of the solid by-product from being drawn out through the undercut ellip60id inlet 28 with the product HOCl gas and the recycle gases.
While the preferred structure in which the principles of the pre~ent invention have been incorporated is shown and described above, it is to be I understood that the invention is not to be limited to ; the particular details thus presented, but, in fact, widely different means may be employed in the practice of the broader aspects of this invention. The scope of the appended claims is intended to encompass all I obviouæ changes in the details, materials, and ; arrangement of parts which will occur to one of skill in the art upon a reading of the disclosure.

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Claims

1. A reactor for the production of hypohalogenated acid from the mixing and reaction of an alkali metal hydroxide and a gaseous halogen comprising in combination:
a. an elongated, generally vertically extending reactor vessel having a top and an opposing bottom, and a central axis therebetween;
b. gas inlet means in the top of the reactor vessel;
c. flow directing means beneath the gas inlet connected to and inside the vessel effective to direct the gaseous halogen from the top to the opposing bottom;
d. infeed means mounted to the reactor vessel for feeding alkali metal hydroxide droplets in a spray into the vessel;
e. an alkali metal hydroxide feed line connected to the infeed means in the reactor vessel from a supply of alkali metal hydroxide;
f. a spraying and reaction zone beneath the infeed means into which the alkali metal hydroxide is sprayed and reacts with the gaseous halogen to form reaction products including hypohalogenated acid;
g. a drying zone beneath the spraying and reaction zone to dry the reaction products; and h. outlet means below the drying zone and above the bottom for outletting gaseous halogen and product from the reactor vessel.

2. The apparatus according to claim 1 wherein the reactor vessel further has an outlet in the bottom to remove solid reaction by-product.

3. The apparatus according to claim 1 wherein the reactor vessel bottom is generally conically shaped.

4. The apparatus according to claim 2 wherein the infeed means is mounted along the central axis of the vessel.

5. The apparatus according to claim 4 wherein the infeed means is further located below the flow directing means .

6. The apparatus according to claim 5 wherein the infeed means is further a single fluid pressure atomizer.

7. The apparatus according to claim 5 wherein the infeed means is a wheel atomizer.

8. The apparatus according to claim 5 wherein the infeed means is a two fluid nozzle atomizer.

9. The apparatus according to claim 5 wherein the reactor vessel is generally cylindrical above the vessel bottom .

10. The apparatus according to claim 5 wherein the reactor vessel is generally polygonal above the vessel bottom .

11. The apparatus according to claim 9 wherein the reactor vessel has a predetermined length and a predetermined diameter.

12. The apparatus according to claim 11 wherein the ratio of the reactor vessel length to the diameter ranges from about 1.0 to about 1.0 to about 1.0 to about 5Ø

13. The apparatus according to claim 5 wherein the gaseous halogen is selected from the group consisting of chlorine, bromine, fluorine and iodine.

14. The apparatus according to claim 13 wherein sodium hydroxide is used as the alkali metal hydroxide.

15. The apparatus according to claim 5 wherein the flow directing means is a perforated plate.

16. The apparatus according to claim 15 wherein the perforated plate is generally circular.

17. The apparatus according to claim 5 wherein the gas inlet means in the reactor vessel further includes a gaseous halogen infeed line connected to the reactor vessel above the flow directing means and below the gas inlet.

18. The apparatus according to claim 17 wherein the gas inlet means is connected to gas recirculation means to recirculate at least the gaseous halogen back into the top of the reactor vessel.

19. The apparatus according to claim 18 wherein the gas recirculation means further includes heater means to heat the recirculated gaseous halogen.

20. The apparatus according to claim 18 wherein the outlet means further extends generally horizontally from about the central axis of the reactor vessel through the reactor vessel and connects to the gas recirculation means.

21. The apparatus according to claim 20 wherein the outlet means further has an undercut ellipsoidally shaped inlet such that the top of the inlet overhangs the bottom of the inlet.

22. The apparatus according to claim 21 wherein the alkali metal hydroxide feed line extends generally horizontally into the reactor below the gas inlet means.

23. A reactor for the production of a solid by-product and a gaseous product from the reaction of a gas and a liquid, comprising in combination:
a. an elongated, generally vertically extending reactor vessel having a top and an opposing bottom, and a central axis therebetween;
b. gas inlet means in the top of the reactor vessel to feed in a reactant gas;
c. flow directing means beneath the gas inlet connected to and inside the reactor vessel effective to direct the reactant gas from the top to the opposing bottom;
d. a liquid feed line connected to the reactor vessel beneath the flow directing means;
e. infeed means mounted to the reactor vessel and connected to the liquid feed line for spraying the liquid;
f. a spraying and reaction zone beneath the infeed means into which the liquid is sprayed and in which the liquid reacts with the reactant gas to form the gaseous product and the solid by-product;
g. a drying zone beneath the spraying and reaction zone to dry the solid by-product;

h. outlet means below the drying zone for outletting the dried solid by-product from the reactor vessel; and i. a generally horizontally extending gaseous product outlet in the drying zone and above the opposing bottom to outlet product gas from the reactor and recycle any unreacted reactant gas.

24. The apparatus according to claim 23 wherein the reactor vessel has a generally cylindrical central section with a selected diameter and length.

25. The apparatus according to claim 24 wherein the length to diameter ratio is from about 1 to about 1 to about 1 to about 5.

26. The apparatus according to claim 23 wherein the infeed means is an atomizer.