CA2027064A1 - Continuous production of potassium nitrate via ion exchange - Google Patents

Abstract

ABSTRACT
Potassium nitrate is produced by contacting nitric acid with a potassium loaded strong cationic exchange resin. In a preferred embodiment, a solution of potassium nitrate and dilute nitric acid is produced in a continuous liquid solid contacting apparatus. The preferred apparatus is formed of a plurality of resin filled chambers which rotate in and out of periodic fluid communication with fixed feed and discharge ports. The apparatus design allows for continuous supply of a nitric acid solution, potassium chloride regeneration solution, wash solutions, and air streams to ports arranged in zones, so that resin filled chambers pass through the zones to continuously produce a solution containing potassium nitrate and dilute nitric acid. In a preferred embodiment, the solution of potassium nitrate produced is neutralized with potassium hydroxide to convert residual nitric acid to potassium nitrate.

Description

2 ~3 '~
CONTINUOUS PRODuCTION OF POTASSIUM NITRATE
VIA ION EXCHANGE

FIELD OF THE INVENTION
This invention is directed to methods for producing potassium nitrate generally, and more particularly to methods for producing potassium nitrate via ion exchange, and to apparatus capable of producing potassium nitrate via ion exchange on a continuous basis.
BACKGROUND OF TH~ INVENTION
Potassium nitrate, otherwlse known as saltpeter or nitrate of potash, is important ln the production of fertllizers, explosives, glass, and numerous other industrial chemlcals. It is one of the oldest known "industrial"
chemicals. Potassium nitrate has been used on a large scale since around the year 1300, when the Chlnese dlscovered that saltpeter could be combined wlth sulfur and charcoal to produce the common exploslve known as black powder.
The ever growlng demand for potasslum nltrate for these and other such uses has resulted ln a prolonged search for lmproved potasslum nitrate production processes, and various methods have been invented to produce potassium nitrate. For example, large quantities of potassium nitrate are commercially produced by the reaction of potassium chloride wlth nitric acld in the presence of oxygen, yleldlng the following overall reaction:
2KCl + 2HNO3 + 1/2 2 ---> 2KNO3 + Cl2 + H2O.

The potassium chloride and nitric acid must be reacted at 100C to produce potassium nitrate, nitrosyl chloride and water as follows:
3KC1 ~ 4HN03 ---> 3KN03 + NOCl + C12 + 2H20.
The nitrosyl chloride is then oxidized to chlorlne and nitrogen peroxide, N02, with nitric acid. See Ghemical Process Industries, 4th Ed., Shreve and Brink, McGraw-Hill, Inc., New York (1977), pp. 272-273.
Smith et al, in U.S. Patent 2,963,345, herein incorporated by reference, disclose a process for producing potassium nitrate, which involves agitating solid particulate potassium chloride with liquid nitrogen peroxide under anhydrous conditions at a temperature of 15 C; excess nltrosyl chloride vapors produced by the reaction are continuously withdrawn to maintaln the reaction. Potassium nltrate and unreacted potassium chlorlde are then separated by addltion to a brine that contains dlssolved potasslum nitrate and potasslum chloride; the brine solution is heated to about 85 C to dissolve the potassium nitrate, but not the solid partlcles of potassium chloride. The solid partlcles o potassium chlorlde are then separated by flltratlon.
Large volumes of potasslum nltrate are also produced by the reactlon of ~odlum nltrate with potassium chlorlde, the overall reactlon belng:
XCl ~ NaN03 ---> XN03 ~ NaCl.
Thls process requlres that potasslum chlorlde be dlssolved in 2 ~
a hot solution of sodium nitrate; upon hea~ing, sodium chloride crystals are formed. The hot potassium nitrate solution is then run through the sodium chloride crystals forming at the ~ottom of the reaction vessel. However, a mixture of potassium nitrate and sodium chloride is formed, so additional processing operations are required to separate potassium nitrate.
Lehto, in U.S. Patent No. 3,983,222, herein incorporated by reference, discloses a continuous process for producing potassium nitrate, which includes the steps of extracting nitrate from aqueous solutions with an organic amine salt dissolved in an organic solvent, separating the organic phase containing the extracted nitrate from the aqueous phase, and stripping the organic base wlth a potassium salt stripping solution having a Ph of at least 0.5. The stripping solution also contains nitrate ions and potassium ions with the concentration oS potassium nitrate maintalned high enough to induce crystalllzatlon of potasslum nitrate from the stripping solutlon contlnuously.
Dotson et al, U.S. Patent No. 4,465,568, herein lncorporated by reference, uses an electrolytic process to produce chloride free mlxtures of sodium nitrate and potassium nitrate.
All of the prior art processes for producing potasslum nltrate are expenslve or dlfflcult to perform. Processes that utlllze nitric acld at elevated temperatures require speclally constructed equipment to handle the highly corrosive reactants, and further, elevated reaction temperatures require high energy inputs. Other prior art processes suffer from low yields of potassium nitrate or an impure product, while others involve the use or production of nitrogen peroxide, which is toxic, and poses a pollution problem.
Thus, there is a need for an inexpensive and continuous process for producing large quantities of potassium nitrate at ambient temperatures. There is also a need for a potassium nitrate production process which does not corrode reaction vessels, and thereby require expensive corrosion resistant construction materials. Further, there is a need for a safe potassium nitrate production process which produces by-products which are easy to handle, and dispose of.
Reaction of potassium chloride with nitric acid to produce potassium nitrate via ion exchange has not been attempted, since a potentlal hazard exlsts in the use of nitrlc acid ln ion exchange operatlons. There have been several accidents lnvolvlng the use of nltrlc acld as a regenerant or elutlon agent wlth lon exchange reslns. Nltrla acld ls a powerful oxldlzlng agent, and the reactlon of nitrlc acld wlth organlc ion exchange resins can result in a serious fire or exploslon. Further, whlle the use of dllute solutlons of nltric acld may reduce the rlsk of exploslon or flre, the presence of metals, such as copper, and absorbed organlc solutes ln any system contalnlng nltrlc acld can catalyze an ~ ~ ~J 7 ~
uncontrolled reaction. Even in dilute solutions, nitric acid is believed to have a negatlve effect on the useful life of exchange resins.
At dilute nitric acid concentratlons, larger volumes of resin are needed, with the resulting increase in cost, without a substantial decrease in the perceived potential for a fire or explosion. The necessity of using large volumes of expensive resin to achieve reasonable yields of product further discouraged the use of ion exchange to produce potassium nitrate.
The production of potassium nitrate by passing a neutral nitrate salt through a catlonic exchange resin was also not believed practical, since cationic exchange resins have an equal affinity for potassium and other monovalent ions.
Divalent ions, such as calcium, make regeneration of such a column difflcult, since large quantities of potassium are necessary to displace calcium bound to the resin. Yet, provided the aforementioned problems can be overcome, productlon of potassium nitrate via ion exchange offers a slmple, low cost and efficient alternative to the prior art method8.

SU~RY OF THE INVENTION
These and other ob;ects of the present invention are achieved by passing a solution of nitric acid through a potassium loaded strong cationic exchange resin to produce potassium nitrate. In a preferred embodiment, a fifteen per cent by weight nitric acid solution (15~ wt ~NO3(~q)) is passed through a potassium loaded strong catlonic exchange resin to produce a solution of about fifteen per cent by weight potassium nitrate (15~ wt KNO3(~q)) and about 0.5 per cent by weight of nitric acid; the solution of potassium nitrate and nltric acid is subsequently neutralized with potassium hydroxide (KOH) to produce a substantlally pure aqueous solution of potassium nitrate. High purity solid potassium nitrate (KNO3(~)) can then be produced by standard crystallization methods.
In a preferred embodiment, potassium nitrate is produced contlnuously through the use of a modlfled advanced separation devlce, ASD, such as that described ln U.S. Patent Nos.
4,764,276 and 4,522,726, ls8ued to Berry et al, and herein lncorporated by reference. Preferably the ASD is modifled to lnclude thlrty chambers, whlch are fllled with a catlonlc exchange resln, and whlch rotate about a circular path in perlodlc fluld communlcatlon wlth a serles of flxed feed and dlscharge ports connected to opposlte ends of the chambers.
Preferably, the feed ports and chambers are arranged 80 that each of the chambers 18 ln fluld communlcatlon wlth no ~J7 more than one feed port at a time, and each of the feed ports is in communication with at least one of the chambers at all times. The discharge ports are purposely arranged so that each of the chambers $s in fluid communication with no more than one discharge port at a time, and each of the discharge ports is in communication with at least one of the chambers at all times.
Preferably, a first feed port directs a continuous supply of a fifteen per cent by weight nitric acid solution, or first solution, into the rotating resin filled chambers in fluid communication therewith. Hydrogen ions are exchanged with potassium ions bound to the resin to produce a second solution of potassium nitrate and dilute nitrlo acid. The second solution flows into a first discharge port, which is in fluid communicatlon with the resin filled chambers in communication with the first feed port; the second solution from the first dlscharge port ls then dlrected to an adJacent second feed port. The second solutlon ls then passed through the resln in the chambers which are ad~acent to the chambers supplied with the irst solution, and flows out of the ad~acent second discharge port. The second solution flowlng from the second dlscharge port has a hlgher concentration of potassium nltrate and a lower concentration of nitric acid than the second solutlon flowlng from the first discharge port.
The second solution from the second dlscharge port is then dlrected lnto a thlrd eed port, through the resin ln the 2~2 ~3~

chambers which are adjacent to the chambers communicating with the second feed and discharge port, and flows out of a third discharge port. The second solution flowing from the third discharge port is then directed to an ad~acent fourth feed port, through the resin in the chambers filled with potassium loaded strong cationic exchange resin, and flows continuously out of a fourth discharge port. The solution of potassium nitrate and dilute nitric acid leaving the fourth discharge port is then neutralized with potassium hydroxide to convert the remaining nitric acid to potassium nitrate.
Preferably, the direction of flow of the first and second solutions is counter-current to the directlon of motion of the rotating resin filled chambers. Thus, chambers, filled with fresh potassium loaded strong cationic exchange resin, are first contacted with the second solution which is fed through the fourth eed port. Subsequently, the potassium loaded resin is sequentially sub~ected to the second solution fed from the third and second feed ports, with the second solution being fed to the chambers progresslvely havlng a hlgher nltric acld content and a lower potasslum nitrate concentratlon.
Thus, the potassium loaded resin will have been partially converted to its hydrogen loaded or acid form when it is contacted with the first solution of nitric acld provided by the first feed port. The resin in the chambers communicating with the irst eed port 19 substantially converted from the potassium loaded form to the hydrogen loaded form by contact d ~

with the first solution of nitric acid.
The chambers movlng from fluid communication with the first feed port are subsequently moved into fluid communication with a series of four wash water feed ports.
The rotating resin filled chambers are first moved sequentially into fluid communication with the last, or eighth feed port, of the four ports fed with wash water. The wash water is initially fed to a fifth feed port, flows through the resin filled chambers ln fluid communlcation therewith, exits 10 a fifth discharge port, is directed into a sixth feed port, and 90 on, until the wash water containing the highest concentration of potassium nitrate and nitric acid flows from the elghth feed port continuously. Thus, the fifth feed port directs substantially pure deionized water through the 15 hydrogen loaded resin to remove any resldual potassium nitrate and nitrlc acid on the resin in the chambers rotating into and out of fluld communication therewith. The "cleanest" wash water is used on the "cleanest" resin last, while the "dlrtiest" wash water 18 used on the ~dirtiest" resin first.
20 In a preferred process, the dilute wash solution of potasslum nitrate and nitrlc acid leaving the eighth dlscharge port is used to dilute a fifty-two per cent by weight nitric acid solution to form a fifteen per cent by weight nitric acld solution, which is fed to the first feed port.
The resin fllled chambers containing washed hydrogen loaded resin are then sequentially moved into and out of fluid 7 `~ ~ ~,S~

communication with a ninth feed port, which is fed a continuous stream of air. The air forces out any residual wash water on the resin in the chambers in communication with the ninth feed port. The resin filled chambers are then sequentially moved into and out of communication with six feed ports supplying a third solution of potassium chloride, or a fourth solution of potassium chloride and hydrochloric acid;
the fourth solution is produced by the conversion of the hydrogen loaded resin to the potassium loaded form.
Preferably, the third solution contains about ten to twelve per cent by weight potassium chloride, and is fed into a tenth and an eleventh feed port. The fourth solution produced in the chambers communicating with the tenth and eleventh feed ports is then directed from tenth and eleventh discharge ports into twelfth and thirteenth feed ports, and subsequently rom twelfth and thirteenth discharge ports to fourteen and fifteenth feed ports. Chambers filled with hydrogen loaded resln movlng from communlcatlon with the ninth feed port, or alr ln~ectlon port, are flrst moved lnto and out of communlcatlon wlth the flfteenth feed port, and are sequentially moved lnto and out of fluid communicatlon wlth the flfteenth, fourteenth, thlrteenth, twelfth, eleventh and tenth feed ports.
The chambers contalnlng potasslum loaded resln are then seguentlally moved lnto and out of fluld communlcatlon wlth four wash water feed and dlscharge ports, referred to as the '~2'~9~

sixteenth, seventeenth, eighteenth and nineteenth feed and discharge ports. Wash water fed to the sixteenth feed port is sequentially fed from the slxteenth discharge port through the ad~acent chambers via the seventeenth, eighteenth and nineteenth feed ports. Wash water fed to the sixteenth feed port is deionized, and substantially pure, while wash water enterlng the nineteenth feed port contains potassium chloride and hydrochloric acid rinsed from resin in the preceding chambers. The wash water leaving the nineteenth discharge port is preferably used to dilute incoming concentrated potassium chloride solutions, or it can be neutralized and disposed of.
A twentieth feed port dlrects alr lnto chambers moving from communication with the sixteenth feed port, and forces wash water from the resin.
Thus, in the preferred apparatus, each resin filled chamber i9 sequentially subJected to feed solutions of nitric acld, wash water, air, potassium ahlorlde, wash water, and alr.
BRIEF DESCRIPTION OF THE DRAWINGS
Flgure 1 ls a block dlagram lllustratlng the process of the present lnventlon.
Flgure 2 ls a front elevatlon vlew, with parts broken away, of the preferred apparatus for performing the method of the present lnvention.
Figure 3 is a cross-sectional vlew taken along llne 3-3 of Flgure 2.
Figure 4 is a cross-sectional view taken along line 4-4 of Figure 3.
Figure 5 is a cross-sectional view taken along line 5-5 of Figure 2.
Figure 6 is an exploded perspective view of parts of the apparatus shown in Flgure 5.
Figure 7 is a cross-sectional view with parts broken away taken along line 7-7 of Figure 5.
10Figure 8 is a cross-sectional view taken along line 8-8 of Figure 5.
Figure 9 is a cross-sectional view taken on line 9-9 of Figure 5.
Figure 10 illustrates a plant layout for performing the 15preferred embodiment of the present process.
Figure 11 is a schematic view illustrating a process for producing potassium nitrate using the apparatus of Figure 2.
DETAILED DESCRIPTION OF T~E INVENTION
The advanced separation device, ASD, disclosed ln U.S.
20Patent Nos. 4,765,276 and 4,522,726, has been used in various conflguratlons, and with numerous startlng materlals to produce valuable products on a small scale. For example, Berry et al, in U.S. Patent 4,704,263, disclose the production of potasslum phosphates by lon exchange using the ASD. The 25process involves passing a phosphate salt solution through a catlon exchange resin loaded with potasslum to form potasslum - ~ ~ ?J ~
phosphate, and after washing out residual salts, regenerating the cation exchange resin by addition of a potassium salt.
Preferably, the potassium salt is potassium chloride and the ion exchange resin is a strong cation exchange resin.
Phosphoric acid was not directly applied to the potassium loaded cation exchange resin to produce potassium phosphate.
In related U.S. Patent 4,704,262, ~erry d$scloses the use of the ASD to produce dialkali metal phosphates by ion exchange. The process involves passing an ammoniated phosphate solution through a weak cation exchange resin and the alkaline metal formed, so that the ammonium is exchanged with the alkaline metal to produce an ammonium loaded resin and a dialkali metal phosphate. In particular, the ammoniated phosphate solution is prepared by reacting ammonium with a water soluble phosphorus source, such as monocalcium phosphate or phosphoric acid, and the alkali metal salt is potassium 8ul fate, potassium chloride, sodium sulfate, sodium chloride, or sodlum carbonate.
It was desired to use the ASD in a similar fashion to Berry et al. to produce potassium nitrate via ion exchange.
Slnce additlon of nitric acid to a cation exchange resin was known to be dangerous, initlal experiments involved the conversion of neutral nitrate salts to potassium nitrate via ion exchange.
25Experiments were performed to determine if calcium nitrate could be converted to potassium nitrate by passage of

3~s~

a calcium nitrate solution through a potassium loaded strong cation exchange resin. The overall reaction is:

2Ca( NO3 ) 2 + 2RK - - - > 2KNO3 + Ca( NO3 ) 2 + R2Ca .
About ninety-five per cent of the calcium bound to the resin, but about five per cent calcium nitrate remained combined with the potassium nitrate produced. The calcium nitrate is difficult to separate, requiring substantial additional effort and expense to produce pure potassium nitrate. Further, upon attempting to regenerate the column from its calcium loaded form to its potassium loaded form, the exchange capacity of the resin was substantially reduced.
Thus, the following reaction proceeded to the right only about sixty per cent:

R2Ca + 2KCl - - - > 2RK + CaCl2 .
Attempts to pass sodium nitrate solutions through a potassium loaded column were discouraged because of the difficulty in obtaining hlgh yields of potassium nitrate.
Further, it was believed that the potasslum nitrate produced would be mixed wlth large amounts of sodlum nltrate. Finally, sodium nitrate is expensive in relation to other feed materlals such as calclum nltrate, indicating that the process would be expenslve as well as inefficient.
While it was believed that addltlon of nitric acid to a strong cationi~ exchange resln might pose a fire or explosion hazard, or could cause a substantial reduction in the useful life of the ion exchange resin used, the failure ln the oarller experlment~ to produce ~ vl~ble pot~e~ium nltrate lon exchan~e productlon method left ~ need for ~ better mothod for ~roducln~ potas~lum nltrate. Thu~, s~dltlonal ex~rlments were pQrforme~, ln whloh ~ oln~le f~xed aolumn wa9 f~lled wlth a ~ot~081um loaded stron~ c~t~onla exch~n~e re~ln, 801~ under the trade name DOWEX MONOSPHERE TG650C, ~nd a dilute solutlon of nltric acld w~ pa~Qa throu~h the rosln. 6urprl~1n~1y, th~ ~xchan~e ¢apeclty ~nd appearance of the re~n did not a~poar to be neg~tlvely effeated by the nltrla ~cld, and hl~h yl~ld~ of pota~slum nltrate reeulted. D~splte pr~dlatlon~
that nltrlo acld woul~ decay the ro~lns u~ed, ~urprleln~ly, ther~ was no resln dQcay noted, and consequently resln decay produot~ wer~ not noted ln the pot~81um nltr~te produced.
rùrthor, over the course of multlple ~xperlment~ wlth dilute lS nlt~lo ~cld, no flr- or explo~lon occurred. ~herefore, lt was dl-covored that pot~8slum nltrate could be produoed e~ly and ~t room t-mperature by pa~-ln~ nltrlc ~cl~ throu~h a pot~sslum lo~d d otron~ c~tlonlc ~xohang~ re~ln.
Ur- o~ a eln~l- 1x d bed ~xchano- column r~qulred a l~r~- ~mount o~ r~oln ln order to achleve ~r~ter th~n nlnety-~lv ~or c-nt oonverd on of nltrla ~old to pota~lum nltrate.
In order to produce puro pot~sslum nltrate, lt 18 necessary to neutr~llze tho excess nltrlc aold wlth pot~lum hydroxlde.
81nce ~otasslum hydroxlde le r~latlvoly expen~ive, the com~et~tlvo a~v~ntage of producln~ pot~-~lum nltr~te vl~ ion xch~n~e 1~ eub8tantl~11y reduced by th~ lnor~od c08t~

* Indicates a trade-mark throughout.

..

r~

involved in the purchase of large volumes of exchange resin to increase column yields, or the purchase of large volumes of potassium h~droxide to neutralize excess nitric acid.
Further, flxed bed exchange columns are not very efficient, since the ion exchange process cannct be carried out continuously. The flow of materials to the fixed bed must be frequently interrupted so the resin can be regenerated.
Fur~her, a large amount of resln ls wasted in fixed bed columns since the exchange zone in the fixed bed is relatively small compared to the size of the column bed. Finally, as the exchange zone nears the bottom of a column bed, the concentration gradient between the potassium ions bound to the resin and the hydrogen ions in the nitric acid feed solution has substantially diminished, which results in a reduction in the exchange efficiency.
The sùrprislng dlscovery that potassium nltrate could be produced by passing a nltrlc acld solutlon through a potassium loaded strong catlon exchange resln, wlthout causlng a flre or exploslon, or rapldly decompo~lng the resln, suggested that the ~uccess of Berry et al ln applylng the ASD to small scale productlon of alkall metal phosphates, such as potasslum phosphate, may posslbly serve as a model to produce potasslum nitrate vla lon exchange. Early experlments wlth a laboratory scale ASD or ion separation exchange process (ISEP) system produced by Advanced Separation Technologies, Inc. of Lakeland, Florida, were very successful; high yields of r~

potassium nitrate were produced on a continuous basis from continuous flows of nitric acid, potasslum chloride, and wash water.
Therefore, an industrial scale ASD, or ISEP, was constructed. The industrial scale ASD was essentially an enlarged version of the laboratory scale ASD. However, the industrial scale ISEP leaked so severely upon pressurization of the feed solutions, that it was not possible to use the apparatus effectLvely. Therefore, a critical valve, to be described in more detail later hereinbelow, was redesigned, and successfully tested; this resulted in a modified ASD
capable of producing over 5000 tons per year of potassium nitrate from contlnuous supplles of nltrlc acld and potasslum chloride.
With reference to Figure 1, a block diagram illustrating the overall process of the present invention is provided. The resin filled chambers of the ASD apparatus are represented in Flgure 1 by different zones. In practice, each of the resin fllled chambers is cycllcally passed through the different zones. Resln fllled chambers passlng through the potassium nltrate productlon zone are fllled with resln ln the potasslum loaded form, and a dllute nltrlc acld solution 2 ls passed through the resln. The nltrlc acld solutlon 2 is drawn from tank 4 by pump 6. The nltrlc acid solution 2 in tank 4 ls provided by combining a concentrated nltrlc acid source 8 with productlon wash water. A portlon of the dllute nitric acid 2 ~ ~J' ~
is combined with concentrated nltric acid solution 8 at static mixer 10. Thls ensures that a homogeneous nltric acid solution 2 ls provlded to the potasslum nltrate productlon zone. Preferably, the nitrlc acid is obtained as a fifty-two per cent by welght solutlon, and dlluted to approxlmately fourteen to sixteen per cent by weight nitric acid before it is pumped into the ASD.
It has been discovered that use of nltrlc acid at a lower concentratlon reduces the risk of flre or explosion, as well as reduces or substantially elimlnates $ast decomposition of the resin matrix. It is preferred that the nitric acid used be diluted below twenty-three per cent; at higher concentrations, clogging of the columns was noted, which is belleved to be due to preeipitation of nitrate salts in the resin ehambers.
The potassium nitrate solutlon 12 leaving the potassium nitrate produetion zone preferably eontalns about fifteen per eent by welght potassium nltrate and about 0.5 per eent by weight nltrle aeld. Preferably, thls eoneentration of resldual nltrle aeld 18 neutrallzed wlth potasslum hydroxlde.
The amount of potasslum hydroxlde used to neutrallze the exeess nltrle aeld 18 preferably small enough to make the present proeess eeonomleally eompetltlve wlth the prior art processes for produeing potasslum nltrate.
The ehambers leavlng the potasslum nltrate produetlon zone then pass to a potasslum nltrate produetlon wash zone.

7 ~ ~ ~
Wash water 14 is continuously passed through the resin in the chambers passing through the production wash zone to carry away residual potassium nitrate and nitric acid remaining on the resin. The effluent 16 from the production wash zone is directed to tank 4.
Chambers passing from the production wash zone then pass to the drain zone, where air from air source 18 forces any residual wash water from the resin in the chamber to prevent cross zone contamination. Preferably, the water drained from the resln is directed to a sewer 20, after any necessary environmental treatment steps are performed.
Preferably, the wash water 14 is deionized. Chambers leaving the drain zone which follows the production waæh zone, then enter a potassium chloride adsorption zone. The resin, whlch has been converted ln the potasslum nitrate production zone to its hydrogen loaded or acid form, is regenerated to its potasslum loaded form ln the potasslum chlorlde adsorption zone. A potasslum chlorlde ~olutlon 22 18 drawn from a tank 24, and fed by pump 26 lnto the chambers passlng through the potas~lum chlorlde adsorptlon zone. Preferably, the potasslum chlorlde eed 801utlon 22 is diluted in feed tank 24 to approxlmately a ten to fourteen per cent by weight solution of potasslum chloride wlth adsorptlon wash water exlting the potassium chloride adsorption zone. The exchange of potasslum ions for hydrogen ions bound to the resin in the potassium chlorlde adsorptlon zone results ln the productlon of hydrochloric acid. Preferably, the hydrochloric acid effluent 28 can be used in other chemical processes~ or neutralized with lime before disposing of the solution.
Chambers leaving the potassium chloride adsorption zone are then passed to an adsorption wash zone. Wash water 14 is passed through the chambers in the adsorption wash zone to remove residual potassium chloride and HCl. The effluent 30 from the adsorption wash zone is preferably combined in feed tank 24 with the concentrated KCl feed solution 32; this increases the efficiency of both KCl and water use. Finally, chambers leaving the adsorption wash zone enter a drain zone where air 18 forces any remaining water on the potassium loaded resin out of the chambers to prevent cross zone contamination. The air and water mixture 34 are forced from the chambers to a drain or sewer 36.
Referring now to Figure 2, there is shown a preferred apparatus 40 for continuously producing potassium nitrate via lon exchange in accordance wlth the hereln dlsclosed method.
Apparatus 40 ls posltloned wlthin an access framework 42, and comprises a dlsc-shaped rotating carousel 44, which supports a plurality of chambers 46, some of which are at the periphery of the disc-shaped rotating carousel 44. A plurality of generally radlally arranged feed hoses 48 deliver liquids to a feed distribution valve 50, and feed hoses 52 conduct liquids from the valve 50 to the chambers 46. Hoses 54 dellver llqulds from the chambers 46 to a dlscharge ' S~ ~

distribution valve 56, and hoses 58 conduct liquids from the discharge distrlbutlon valve 56. In a preferred embodiment, there are thirty chambers 46, the same number of feed hoses 52 and the same number of hoses 54. There are twenty of the feed hoses 48 and twenty of the hoses 58. As will be explained hereinbelow, some of the hoses 58 will be the same as or are connected to some of the feed hoses 48, to effect recycling of discharge liquid.
A control apparatus 60 is provided, and includes monitoring and control devlces and circuits for operating the apparatus 40 on a continuous basis. Also shown in Figure 2 are storage tank 62 for aqueous potassium chloride and storage tank 64 for nitric acld; tanks 62 and 64 are each connected by hoses to one of the feed lines 48.
lS Flgure 3 shows carousel 44 with chambers 46 thereon, and with eed hoses 48 connected to them. Note that some of chambers 46 are located lnwardly of the peripheral chambers 46. Feed hoses 48 are also connected to these inner chambers 46. Also shown ln Flgure 3 18 a shaft 66, whlch 18 conneated wlth carousel 44, so that rotatlon of shaft 66 rotates carousel 44, and vlce ver~a.
Referrlng to Figure 4, there is shown a cross-section of carousel 44 and a chamber 46, chambers 46 are preferably made of high denslty polyethylene. Feed hoses 48 enter through the top 68 of chambers 46 and dlscharge feed liquid into the ahamber 46, where it passes through an upper containment screen and ~upport pl~te 70. Wlthln ch4mb~r 46 thore i8 charge or body 72 of a strong c~tlonlo exchange r~sln, 8uch as th~t herelnelbove mentlone~. Above the bottom 74 of ah4mber 46 18 ~ ~upport plste an~ a lower contalnment screen 76, upon whioh re~ts reoln 72. Pr~forably, the ~cre~n~ ~re m~de of polypropylene, ~nd the 8Upport plate8 are m~de of polyvinyl ahloride, lt 18 preferred that su~ablo g~ket~ be loc~ted b~tween each of the8~ separ~te part~ wher~ver they sre Joined.
A ~referred gasket materl~l 18 sold under the trade name Hy~alon, and 1~ sold wlth A8Ds ~vallable from AS~ Inc. o~
Lakel~nd, Florld~. Connected to bottom 74 of each chamber 46 ~re ho~eE~ 5~. Also shown in Fi57ure 4 1~ ~ drlve motor 78.
Motor 78 ~rlves ~ plnlon 80, whlch 18 ln me~h with a r1n~ ~ear 82. As wlll be ~precl~ted, rotatlon of c~rou~el 44 may b~
o~ct~d ~y other mechanl~ms than th~t shown.
~eferrlng now to Flgure 5, there 1~ shown ~ cross-sectlon o~ dl~ah~rge dlstrlbutlon v41ve 56, lt beln~ und~r~tood that th- aon~tru~tlon o~ the feea dletrlbutlon valve 50 is ~ubetantially th~ oame, 81thou~h v-lve 50 18 po~ltloned ln ~pp~r4tu~ 40 so ~ to be lnverte~ wlth resp~ct to valve 56.
A pedestal 90, whlch ls of hollow conf~uratlon as shown, rests on ~ ba~e 92. At lts upper end, pedestal 90 18 provided wtth 4 serles o~ radl~ extendln~ ~butment plate~ 94 (see ~l~o ~igure 6) ~na the~e ~upport an lnner ~nnul~r ~l~te 96 ~n~
4n outer ~nnul~r plate 98, there beln~ an annulsr sp~ce between the ~l~tes 96 ~nd 98 Q8 shown ln Fl~ure~ 5 ~nd 6.

Extending downwardly ln alignment with the pedestal 90 is a drive shaft 100 having attached to it, as by a suitable keyway 101, a sprocket 102, located above the valve 56.
An inner valve housing ring 104 ls provided with a lower, lnwardly extending flange 106, and an annular series of bolts 108 secure flange 106 to the inner annular plate 96. Inner housing ring 104 is provided with an outwardly extending flange 110 at its upper end.
An outer housing ring 112 is concentric with inner hGusing ring 104 and has an outwardly extendlng flange 114 at its lower end; an annular series of bolts 116 secures the flange 114 to the outer annular plate 98. At its upper end, the outer housing ring 112 has an inwardly dlrected flange 118 which is ln spaced, opposing relationship to the flange 110.
As shown ln Figure 6, there is provided an annular body 120 having a radial width substantially the same as the space between the inner annular plate 96 and the outer annular plate 98. The body 120 is provlded wlth radially extending slots 122 whlch each recelves one of the gusset plates 94. An annular serle8 of L-shaped passages 124 are provided in the body 120, and the body 120 will be seen to have at lts top an outwardly extendlng annular flange 126 and an lnwardly extendlng annular flange 128. The vertlcal part 124A of the passage 124 extends to the upper surface 130 of the body 120:
~ody 120 18, as shown Flgure 5, of T-shaped vertlcal cross-sectlon.

3 ~ d~
On the upper surface 130 of body 120 there rests an annular crown plate 132. Crown plate 132 occupies the space above the body 120, and beneath the flanges 110 and 118 of the inner housing ring 104 and outer housing ring 112, respectively, and is between outer housing ring 112 and inner housing ring 104.
As shown in Figure 6, the bottom surface of the annular crown plate 132 has an annular series of evenly spaced ports 134. These ports 134 are each in fluid communication with a nipple 136, which extends upwardly from the annular crown plate 132. The number of ports 134 and their circumferential extent are such that at any given moment, each of the ports 134 is in fluid communication with at least one of the L-shaped passages 124. In a preferred embodiment, the centers of thirty ports 134 are separated by 12 lncrements, so that twenty of the L-shaped passages 124, which are distributed at 18 intervals about the annular body 120, will always be in fluid communiaatlon with at least one of the ports 134.
As shown in Flgure 7, the sprocket 102 has indentations 138 in it8 outer end which engage the nlpples 136, in spaaed groups o three, 80 as to drive the nipples 136 and the annular crown plate 13Z inside o valve 56.
The lower, horlzontal portions 124B of the L-shaped passages 124 are each in fluld communication with a hose 58.
Hence, fluid may pa88 into or out of nipples 136 to or from hose 54, into or out of the port 134, thence into or out of passage 124 in the body 120, and thence outwardly or lnwardly through hose 58.
To avold leakage, as shown in Figure 6, an annular outer bladder 140 underlies the flange 126, and an annular inner bladder 142 underlies the flange 128. The bladders 140 and 142 will be seen in Figure 5 to substantially occupy the spaces between the inner annular plate 96, the outer annular plate 98, the inner housing ring 104, the outer housing ring 112, the vertical portion of body 120 and the flanges 126 and 128 of body 120. Pneumatic pressure is provided in bladders 140 and 142 to urge the upper surface 130 of body 120 against the lower surface of the annular crown plate 132. Should any lea~age occur, it will be collected by a series of bores 144 extending through the inner housing ring 104, the bores being in fluid communication with nipples 146, which enable the bores 144 to be connected with a collection conduit 148, a drain conduit 150 being connected thereto.
Pneumatlc pressure can be adJusted in bladders 140 and 142 to mlnlmize wear of the valve component; suitable gauges and controls are preferably provlded to monltor and adJust bladder pressure. If bladder pressure is too low, leakage rom valves 50 and 56 wlll occur, and llqu:Ld will drain from conduits 150. Preerably, the inner bladders are malntalned at 75 PSI pressure, and the outer bladders are malntained at 70 PSI, with maximum recommended pressures belng 105 PSI and 100 PSI, respectlvely. Overinflation of the bladders will cause excessive torque to be required to rotate plate 132 in the valves 50 and 56. This could result ln rupture of the bladders, faster wear of the valves, or damage to the motor and drive mechanism.
In a preferred embodiment, the drive mechanisms are protected by a high torque lnterlock, which will turn off the drive motor and nitric acid and potassium chloride feed solutions when excessive torque is encountered. Preferably, the speed controller for motor 78 ls located inside the control apparatus 60. A preferred speed controller is sold under the name Speedstar JR; lt ls a varlable frequency drive, avallable from Electrical South Inc. of Greensboro, North Carolina, and requlres a 230 volt single phase power supply, converting lnput voltage to a 460 volt 3 phase output with a controlled frequency of 0-60 Hz.
In Figures 5 and 8, there will be seen a base plate 152 for pedestal 90, whl~h rests on the base 92. An ear 154 e$tends from pedestal 90, and 18 conneated to a hydraulia pump and motor 156 through piston 157. A seaond ear 158, having a 810t 160 thereln, extends from the base plate 152, and a bolt 162 passes through the slot 160. Bolt 162 may be loosened to permlt rotational movement of the pedestal 90 by the motor 156. This 18 effeated in order to obtaln ad~ustment of the valve 56, 80 that vertiaal parts 124A of passages 124 ln valve 56 are vertiaally allgned with vertlaal parts 124A of passages 124 ln valve 50. Thus, llqulds travelllng from a vertlaal part 124A in valve 50, through a chamber 46, and lnto the vertical part 124A in valve 56 which is in vertical alignment.
The effect of this ad~ustment is to annularly displace the pedestal 90, body 120, inner housing ring 104 and outer housing ring 112.
In Figure 7, there is shown the annular series of hoses 58, each pair of which is held by a support plate 164. There may be seen, also, the annular flange 118, the annular row of nipples 136, and inwardly thereof, the annular flange 110.
There is also seen the sprocket 102 with indentations 138 engaging spaced groups of three nipples 136. Also shown is the collection conduit 148, and shaft 100.
Flgure 9 dlscloses the plates 164, hoses 58, and the radially extending gusset plates 94 extending outwardly from the pedestal 90. Also shown is the shaft 100.
As noted above, valves 50 and 56 are substantially modlfied from previous ASD valves due to severe leakage problems encountered when using the prior art valves. Valves, such as 50 and 56 whlch lnclude body 120 have superior leak reslstance: thls ls due to the unitary constructlon of body 120, whlch is less likely to have its shape distorted by the rotation of crown plate 132. Further, slots 122 snugly fit over gusset plates 94 to prevent rotational slippage of body 120 in valves 50 and 56.
Hoses 58 are connected to the portlon of body 120 whlch pro~ects from between inner and outer annular plates 96 and 98 In order to re~uoe the pos~lble ~lexln~ or bendln~ of the proJect~n~ port~on of body 120 upon connectlon of hoses 58 to the horl~ont~ rt 12~B o~ ~-shaped p~ssa~es 12~, ho~es 58 ~re prefer~bly permanently attaohed to passa~es 124, and reln~orced wlth ~lates 164 Oulck rele~se connectore 166 enable r~p~d connection and dl~conn~otlon of extension~ of hose~ 58 w~thout ~tre~elng body 120, thereby resultin~ ln B
sur~rlslngly ~mproved le~k reslst~nt ~alve aonstructlon ~his v~lve constructlon allows ~or lar~e sa~le lndu~trlal ~roductlon of the pot~lu~ nltrats throu~h contlnuous oontact wlth tron~ c~tlonlc exoh~nge resln wlthout l~ak~e of nlt~lc 8cid ~eed ~olutlon or hydroohlorio aold disch~r~e ~olutlon Preferably, body 120 i8 molded ~rom ~ ~olld pl~tlc, which 18 cap~ble of resi~tin~ corrosion by the proce~s ro~atant~ 8n~ product~ A pr-ferre~ mat~rl-l for formin~ body 120 1- high ~n~ity poly thylene ~s~nles~ ~teel ~e known to roelot nltrlc acid, but hydroohlorlc ~cla produced in the ~ proc--~ lo ~nown to corrod~ ~t~lnlo~ ~t-el~ Thore~or~, in a pre~erred mbod~mont, rot~tln~ arown pl-te 132 i8 formed of an alloy ~old under ~he trade n~me Haetolloy "C22", sold wlth A8D~ ~vall~ble from A8T Inc of Lakelan~, Florid~ Oth~r m~ter~al~ may b~ u~ed, but may wear out f~ster The be~rln~s and other part~ of valve~ 50 ~nd 56 ~re ~ref~rably formed of ~olypropyl-ne, ~nd chlorlnated polyv~nyl chlorlde Prefe~ably, DOWEX MONOsPHERE TG650C* stron~ aatlon ~xch~n~e re~ln 1~ ~80~, whlah h~s a p~rtlale ~ of 20-40 ;,.. .
~ ,~

~ '~ ,f,;J ~

U.S. Standard Mesh. Preferably, chambers 46 are sufficiently large to hold a charge of 4.55 cubic meters of resin, and have enough space to allow for resin expanslon. The perforated resin support plate preferably has a 60 U.S. Standard Mesh screen thereon to contain the resin in the chambers. Note that, while the DOWEX MONOSPHERE TG650C resln ls preferred, any other strong cation exchange resin capable of producing potassium nitrate upon contact wlth nitric acid solution, is contemplated as being equivalent. Although individual chambers are used in a preferred embodiment, a large single chamber, divided into compartments, may be used in place of the separate chambers. Further, the number of compartments and feed ports may be changed. The preferred chambers are 61 cm ln diameter, having a resin bed depth of 61 cm, and allow for resin expansion of 15 cm.
As one of skill in the art will readily appreciate, a variety of procedures can be followed to optlmize operational parameters for apparatus 40. Further, a variety of modlflcations can be made to the apparatus to help ensure that the apparatus ls set up for and malntalned at peak efflciency.
In a preferred embodlment, valves 50 and 56 are kept in the same relative rotational positions with each other, in order to keep the zones of valve 50 synchronlzed wlth the zones of valve 56; mlsallgnment of the valves may cause cross-leakage ln the system. Therefore, lt ls preferred that anallgnment device (not shown) be utillzed to asslst ln the allgnment of the valves 50 and 56. For example, ln order to keep the fixed vertical passages 124A of valves 50 and 56 in vertical alignment, alignment indicator lights are preferably provided to assist in monitorlng valve alignment. Attached to valves 50 and 56, on crown plate 132, are fixed two magnetic pick-ups spaced at 180, which activate a sensor located on the fixed component of the valve. The sensors transmit a slgnal to the indicator lights when they are ln alignment with the magnetic pick-ups. When the valves 50 and 56 are in perfect alignment, the indicator lights for the upper and lower valves will light simultaneously. If the valves are out of allgnment, the lights wlll not be activated simultaneously.
In order to adJust allgnment of the valves, the necessary connections, such as bolt 162, are loosened, and pedestal 90, along with the components of valve 56 attached thereto, is rotated to align the vertical parts 124A of passages 124 in valve 56 with their corresponding parts in valve 50. Close vertlcal alignment o valves 50 and 56 is generally preferred for a carousel rotation rate of approximately fifty minutes to one hour per rotation; faster carousel rotation rates may requlre that vertlcal parts 124 in lower valve 56 lead the correspondlng parts ln valve 50. As one of skill ln the art can appreclate, the rotatlon rate of the carousel can be greatly increased or reduced depending upon solution flow rates and other process requlrements ln order to optlmlze the performance of apparatus 40.

With reference to Figure 10, a preferred plant layou~ Q
illustrated, which uses an apparatus, such as apparatus 40, to continuously produce potassium nitrate via contact of nitric acid with a strong cationic exchange resin. Solid potassium chloride is fed to hopper 200 where conveyor 202 directs them to a dissolution vessel 204. Solid potassium chloride is combined with water from line 206 in vessel 204, and stirred by an agitator 208, which is driven by motor 210. Pump 212 directs the concentrated potassium chloride solution to filter 214.
Preferably, the concentrated KCl solution in line 213 contalns about twenty per cent potassium chloride by weight.
The filtered potassium chlorlde solutlon in line 216 is then transferred by pump 218 to surge tank 220. Potassium chloride solution in tank 220 ls then directed to a potassium chloride eed tank 222 by pump 224. A sample point 226 enables samples to be drawn from potassium chloride solution line 216, so that its concentration and purity can be monitored. A control valve 228 regulates the amount o potassium chloride solution ln llne 216 belng ed to tank 222. A control loop 230 is provlded, and preferably lncludes a 1OW lndlcator quantity totallzer, a transducer to convert pneumatlc slgnals to electronlc signals, and a separate 1OW control whlch uses pneumatlc pressure to regulate control valve 228.
Potasslum chlorlde solutlon 216 is diluted in tank 222 through combination with adsorption wash effluent in line 232.

J ~
Preferably, potassium chloride feed solution in line 234 is directed from tank 222 to ports 6 and 7 of the potassium adsorption zone in Figure 11. Note that adsorption wash effluent 232 contains dilute potassium chloride and very dilute hydrochloric acid. Preferably, the potassium chloride feed solution in line 234 contains approximately twelve per cent potassium chloride by weight. As will be appreciated by one of skill in the art, potassium chloride solutions of greater and lesser concentration may be used.
A sample point 236 is provided to withdraw samples, and a separate pneumatic control loop 238, having similar parts and configuration to loop 230, is provided to control a solutlon recirculation loop 240; this ensures that a homogenous potassium chloride solution, having a stable concentration, is directed to apparatus 40.
Fresh deionized water is fed through line 242, and is stored ln a wash water tank 244. Preferably, tank 244 holds approxlmately 1300 gallons of water for a plant which produces approximately 5000 tons or more of potasslum nitrate per year, and a suficlent quantlty of water 18 malntained ln the tank through use o a float valve 246. Wash water ls then dlrected by pump 248 to lines 250 and 252. Line 250 dlrects water to the potasslum adsorptlon wash zone whlch lnltiates at port 2 in Flgure 11. Line 252 dlrects water to a potasslum nltrate productlon wash zone lnitiated at port 13 in Figure 11.
~ine 254 carries a solutlon of potasslum nltrate produced ~ ~ut~ J'i$1 ~ ia-~
in apparatus 40 from port 20 in Figure 11 where it i8 directed to a surge tank 2~6. Potasslum hydroxlde ls stored in tank 258 and pumped through line 260 to tank 256, where it is used to neutralize residual nitric acid in the potassium nitrate solution. Pump 262 directs neutralized potassium nitrate solution (the reaction of potassium hydroxide and nitric acid yielding a solution of potassium nitrate only), to a storage or surge tank 264. Preferably, pump 266 then directs the potassium nitra~e solution to a subsequent crystallization procedure. A pneumatic control loop 268 regulates valve 270 and valve 272 to ensure that the proper amount of potassium hydroxide solution from tank 258 is added to tank 256.
Line 274 carries production wash effluent from port 16, and directs it to tank 276 where it is combined with concentrated nitric acid from line 278. Flow of nitric acid in line 278 i8 regulated by control valve 280 which interacts with control loop 282. A density meter 284 interacts with control loop 282 for a purpose to be described below.
Nitrlc acid in line 278 is combined wlth a mixture of nltrlc acld and productlon wash water from tank 276, which is provided by llne 286 in static mixer 288. Pump 290 circulates solutlon from tank 276 through line 286, through static mixer 288, and lnto line 292 to ensure that a homogenous nitric acid solution is directed into line 294. Density meter 284 measures the density of the nitric acid solutlon passing through llne 286, and interacts with control loop 282 to ~ ~ 7~ J ~
thereby control the amount of solution flowing through lines 278, 286, 292 and 294.
Control loop 298 monitors and ad~usts for the volume of nltric acid solution in tank 276. Excess production wash effluent in line 274 is directed to a drain 300 by llne 302.
The production wash effluent in line 274 contains very dilute nitric acid and potassium nitrate. Preferably, the concentrated nitric acid is provided as a fifty-two per cent by weight solution and is diluted in tank 276 to an approximately twelve per cent by weight solution. Nitric acid in llne 294 is then directed to port 17 of the potassium nitrate productlon zone ln Figure 11.
The reactlon is generally carrled out at ambient temperatures, although some increase in temperature ls noted ln static mlxer 288 as a result of diluting the nitric acid.
Preferably, the temperature does not lncrease beyond about 110 F in statlc mlxer 288.
In a preferred embodiment, tanks 222 and 276 are formed of a plastlc materlal su¢h as those sold under the name Nalgene. Preferably, feed llnes are formed of two inch d~ameter polyvinyl chloride plplng, although any other materlal or slze tublng or plplng may be used, provlded lt does not interfer~ substantlally wlth the reaction process.
The electropneumatlc control loops can be replaced wlth other mechanlsms capable of automatlcally monltorlng and adJustlng solutlon concentratlons and flow, or the system can be run $
manually, although the later alternative is inefficient in comparison with automatic systems. A wash system (not shown) is preferably provided to perlodically rinse off apparatus 40.
With particular reference to Figure 11, note that line 304 provides compressed alr to ports 1 and 12 via lines 306 and 308, respectively (Please note that the numbers given to the ports is arbitrary). Nitric acid entering fixed feed port 17 passes into one or two chambers which are moving slowly into and out of periodic fluid communication with port 17.
The solution of nitric acid contacts potassium loaded strong cation exchange resin in the chambers to produce a solution of potasslum nitrate, while reducing the concentration of nitric acid. The solutlon of potassium nitrate and nitrlc acid flows out of the chambers in fluid communication with input port 17 lnto discharge port 17, and is sequentially dlrected to feed and dlscharge ports 18, 19 and 20.
As the nltrlc acld solutlon passes countercurrently to the chamber movement through ports 17 through 20, the concentration of nltrlc acld 18 reduced, whlle the concentratlon of potasslum nltrate ln the solutlon ls lncreased. Thus, freshly regenerated potasslum loaded strong catlon exchange resln ln the chambers movlng lnto and out of fluld communlcatlon wlth ports 20 ls contacted wlth a solutlon havlng a relatlvely hlgh concentratlon of potasslum nltrate and a low concentratlon of nltrlc acld.
Chambers passlng from the potasslum nltrate productlon 2~

zone pass to a production wash zone. Deionized water in line 252 is passed countercurrent to the chamber movement sequentially through ports 13 through 16. The effluent from discharge port 16 ~n llne 274 contains dilute potassium nitrate and very dilute nitric acid which is then directed to tank 276 where it is combined with concentrated nitric acid from line 278. Thus, nitric acid in line 294 will generally contain small quantities of potassium nitrate. Chambers passing from the production wash zone pass into fluid communication with air from line 308 through port 12 in a production drain zone. Air from line 308 forces residual potassium nitrate and nltric acid into discharge port 12 where it is subsequently disposed of from drain line 310.
Chambers passing from fluid communication with port 12 pass into a potassium adsorption zone, in which the hydrogen loaded resin formed in the potassium nitrate production zone i8 regenerated to its potassium loaded form. A potassium chloride solution in line 234 is directed into ports 6 and 7, and dlscharges through discharge ports 6 and 7. The solution discharglng from dlscharge ports 6 and 7 i8 preferably comblned, and is then directed to feed ports 8 and 9.
Preferably, the solution discharglng from ports 8 and 9 is combined, and fed to input ports 10 and 11. The concentration of potassium chloride in the solution decreases as the potassium chloride solution passes through the chambers in the potasslum adsorption zone towards the productlon draln zone.

2~2 ~

The adsorption of potasslum on the hydrogen loaded resin results in the formation of hydrochloric acid which ultimately discharges from ports 10 and 11 into discharge line 312.
Preferably, the hydrochlorlc acid is utillzed ln other chemlcal processes, or ls neutralized before dlsposal.
Chambers passlng from the potasslum adsorptlon zone then move to the adsorption wash zone where excess potassium chlorlde and hydrochloric acid are rinsed from the potassium loaded cation exchange resin. Note that wash water from llne 250 passes countercurrently to the dlrectlon of chamber movement through ports 2 to ports 5. Generally, feed solutlons are passed downwardly through the resin fllled chambers. However, lt is preferred that at least one feed solutlon be dlrected upward through the chamber ln order to redlstrlbute the resln ln the chamber. Thls avolds channelllng and other negatlve chromatographlc separatlon effects.
Note that the adsorptlon wash feed is preferably fed upwardly throùgh dlscharge port 5 and feed port S. The ad80rption wa8h zone effluent enters llne 232, where lt ls subsequently used to dllute potassium chlorlde feed solutlon ln tank 222. Chambers movlng from the adsorptlon wash zone then pass lnto fluld communlcatlon wlth feed port 1, where alr from llne 306 forces the resldual solutlon of dllute potasslum chlorlde and hydrochlorlc acld lnto dlscharge port 1; the dllute solutlon 18 then neutrallzed and sent to a sewer through line 314.
While twenty input ports and twenty dischar~e ports have been utilized in con~unction with thirty rotating chambers, it is contemplated that the various production zones represented in Figure 11 can be formed with as few as one input and discharge port for each zone, although this wlll require some modification of the valves. It follows that the number of chambers may be increased or decreased, or that multiple chambers may be replaced with a single chamber d$vided into a plurality of compartments.

The following non-limiting example provides an actual material balance for a potaQsium nitrate production plant uslng an apparatus such as described above. Other methods, materlals, and reactlons parameters than those descrlbed above or below can be used in the practlce or testlng of the present lnventlon. Table 1 below presents materlal lnput and output data for an ASD, such as descrlbed above, havlng thirty chambers fllled wlth a strong catlon exchange resln (DOWEX
MONOSPHERE ~G650C), which periodically rotate lnto and out of fluld communlcatlon wlth twenty vertically aligned feed and discharge ports; the solution flow pattern represented in Flgure 11 was followed.

r r~ r~ _ ~ .a _ _ o ~c r' r' ~ 1 N _ a N N r N _ ~ ~ ~1 ~1 ~ ~ ~ ~

__ _ ___ a '~^ ~ _ _ , , . _ . . . a __ ~ .~ .

~ii ;~ N ~5 ~ O~ O~ ~_ ~a ~ O rl ~ l L~ N N _ ~S N N _ rl o- r o o L~ ~ a ~ . 8 o ~ a a ~ ' ~ L~

Of particular significance ln Table 1 ls the row labled "KNO3 PRODUCT," showing that 15.9 metric tons per day of potassium nitrate were produced, with only 0.0068 metric tons per day being lost from the production drain zone. This 5quantity of potassium nitrate was produced from 15.12 metric tons per day of potassium chloride and 10.63 metric tons per day of nitric acid. This represents approximately a ninety-three per cent conversion of the nitric acid to potassium nitrate, with only a 0.1 per cent loss of nitric acid through 10the production drain zone. The remaining seven per cent nitric acid was subsequently neutralized with potassium hydroxide.
Although the resin utilized in Example 1 lost some of its color, no decrease in resin loading capacity was noted.
15Further, close examination of the resin beads continuously used for six months showed the beads to have maintained good sphericlty and strength. Thus, it appears that the resin may be used for long perlods of tlme wlthout any substantlal loss ln lts ablllty to reverslbly exchange potasslum and hydrogen.
20Please note that by ad~ustlng the concentration and flow rates of the varlous feed solutlons, alterlng the amount of resln ln the chambers, and adJusting the rotation rate of the carousel, that higher percentage converslon of nitric acid to potassium nitrate may be obtained.
25It i8 contemplated that the process descrlbed hereinabove 18 equlvalent to processes ln whlch the potasslum nltrate ~ 27`~
production zones, production wash zone, and production drain zones are not stationary, and the resin filled chambers are stationary, such that the feed and discharge ports are moved into and out of fluid communication with the stationary resin filled chambers. It is also contemplated that the continuous ion exchange process of the present invention can be performed by other apparatus, in which a plurality of stationary chambers or columns, filled with a strong cation exchange resin, are sequentially fed solutions of potassium chloride, wash water, nitric acid solution, and wash water solution, with air being in~ected into the columns following the adsorption wash and production wash solutions. There can be provided sufficient columns and control apparatus so that there are at least six columns, with each of the six columns undergoing a different step of the process than the other columns simultaneously. In this way, continuous production of potasslum nitrate from potassium chloride and nitric acid could also be produced.
Thus, it has been discovered that potassium nitrate can be easily and safely produced by contactlng a solutlon of nltrlc acld wlth the potasslum loaded strong catlon exchange resin, It is further posslble to achleved hlgh efflclency of this reactlon wlth minimal resln volume through the use of a contlnuous solid liquld contactlng apparatus, such as, but not limited to, that described above.
From the above teachings, it ls apparent that many ~J ;) ~J 7 1~

modifications and variations of the present invention are possible. It is therefore to be understood that the invention may be practiced otherwise than as specifically described.

Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the continuous production of KNO3 via ion exchange, comprising the steps of:
a) continuously passing a first solution comprising HNO3 through a first group of at least one potassium loaded strong cationic exchange resin bed to continuously produce a second solution comprising KNO3 and converting at least a portion of said resin to the hydrogen loaded form;
b) continuously passing a third solution comprising water through a second group of at least one resin bed having at least a portion of said resin in the hydrogen loaded form, said at least one bed also containing HNO3 and KNO3 formed in step a), to continuously form a fourth solution comprising HNO3 and KNO3;
c) continuously passing a fifth solution comprising KC1 through a third group of at least one resin bed having at least a portion of said resin in the hydrogenated form to continuously produce a sixth solution comprising HC1 and converting at least a portion of said resin to the potassium loaded form;
d) continuously passing a seventh solution comprising water through a fourth group of at least one resin bed having at least a portion of said resin in the potassium loaded form, said at least one bed also containing HC1 and KC1 formed in step c), to continuously form an eighth solution comprising HC1 and KC1; wherein - Page 1 of Claims -said steps a, b, c, and d are performed simultaneously;
said first, third, fifth and seventh solutions are continuously fed to said beds through feed ports in fluid communication with said beds;
said second, fourth, sixth and eighth solutions are continuously drained from drain ports in fluid communication with said beds;
said process further comprising simultaneously effecting relative movement between said beds and said ports so that said each of said first group of beds sequentially becomes a member of said second, third, fourth and first group of beds, each of said second group of beds sequentially becomes a member of said third, fourth, first and second group of beds, each of said third group of beds sequentially becomes a member of said fourth, first, second, and third group of beds, and each of said fourth group of beds sequentially becomes a member of said first, second, third, and fourth group of beds.

2. A process according to claim 1, wherein:
said fourth solution is combined with a ninth solution to form said first solution, said ninth solution comprising water and HNO3; and said sixth solution is combined with a tenth solution to form said fifth solution, said tenth solution comprising water and KC1.

3. A process according to claim 1, wherein:
said resin beds are all approximately equal in size;

- Page 2 of Claims -said first group of beds comprises at least two beds arranged in series, wherein said second solution formed in a first bed of said first group is fed to a second bed, the concentration of KNO3 in said second solution gradually increasing while passing through said second bed and any subsequent beds in said first group; and said third group of beds comprises at least two sets of two beds arranged in parallel, said sets of parallel beds being arranged sequentially, so said fifth solution is continuously and simultaneously fed to a first set of two beds in said third group, and said sixth solution obtained from said first set of beds is simultaneously and continuously fed to a second set of two beds in said third group, the concentration of said HC1 in said sixth solution gradually increasing while passing through said second set of beds and any subsequent sets of beds in said third group.

4. A process according to claim 1, further comprising the steps of:
e) continuously passing air through a fifth group of at least one resin bed containing said fourth solution to cause at least a portion of said fourth solution to drain from at least one bed of said fifth group;
f) continuously passing air through a sixth group of at least one resin bed containing said eighth solution to cause at least a portion of said eighth solution to drain from at least one bed of said sixth group;
wherein:

- Page 3 of Claims -said air is continuously fed to said fifth and sixth group of beds through feed ports in fluid communication with said fifth and sixth group of beds;
said fourth and eight solutions draining from said beds are drained from drain ports in fluid communication with said fifth and sixth group of beds;
said second group of beds sequentially become said fifth group of beds prior to becoming said third group of beds; and said fourth group of beds sequentially become said sixth group of beds prior to becoming said first group of beds.

5. A process according to claim 1, wherein at least about 85% of said HNO3 in said first solution reacts with said resin to form said KNO3.

6. A process according to claim 1, wherein:
said steps a, b, c, and d are performed at ambient temperatures; and said second solution comprises more than about 14% by weight of said KNO3, and less than about 1.0% by weight of said HNO3.

7. A process according to claim 1, wherein:
said strong cationic exchange resin comprises a sulfonated styrene-divinylbenzene copolymer; and the concentration of said nitric acid in said first solution is up to about 23% by weight.

- Page 4 of Claims -

8. A process according to claim 3, wherein:
each of said beds is placed in fluid communication with no more than one feed port at a time, and each of said feed ports is placed in fluid communication with at least one bed.

9. A process according to claim 8, wherein:
said first solution is continuously fed through a first feed port in fluid communication with at least one of said first group of beds, and said second solution is continuously drained from a first drain port in fluid communication with said first feed port through said at least one of said first group of beds;
said second solution is sequentially and continuously fed to and drained from second, third and fourth feed and drain ports in fluid communication with at least three other beds of the first group of beds, the direction of said flow of said first and second solutions being countercurrent to the relative direction of motion of said beds with respect to said ports.

10. A process according to claim 9, wherein:
said solutions are continuously fed and drained through twenty feed ports and twenty drain ports, each of said feed ports being in fluid communication with one of said drain ports, and each of said feed ports being sequentially placed in fluid communication with thirty beds.

11. A process according to claim 1, wherein:
said process is capable of producing at least 15.9 metric tons of KNO3 from about 10.6 metric tons of HNO3.

- Page 5 of Claims -

12. A process according to claim 11, wherein:
said process is capable of producing said at least 15.9 metric tons of KNO3 in about 24 hours from said about 10.6 metric tons HNO3 when said resin beds contain a combined total of at least about 4.5 cubic meters of said resin.

13. A process according to claim 10, wherein:
said process is capable of producing at least 15.9 metric tons of KNO3 from about 10.6 metric tons of HNO3.

14. A process according to claim 13, wherein:
said process is capable of producing said at least 15.9 metric tons of KNO3 in about 24 hours from said about 10.6 metric tons HNO3 when said resin beds contain a combined total of at least about 4.5 cubic meters of said resin.

- Page 6 of Claims -