US1359652A

US1359652A - Process for the production of anhydrous magnesium chlorid or anhydrous double chlorids of magnesium

Info

Publication number: US1359652A
Application number: US317082A
Authority: US
Inventors: Ashcroft Edgar Arthur
Original assignee: Individual
Current assignee: Individual
Priority date: 1919-08-12
Filing date: 1919-08-12
Publication date: 1920-11-23
Anticipated expiration: 1937-11-23

Description

E. A. ASHCROF.

PROCESS FOR THE FRODUCUON F'ANHYDRUUS MAGNESIUM CHLRID GE ANHYDEOUS DUUBLE CHLORIDS 0F MAGNESIJM. AHUCATIGM FILED Aue. l2, 19m RENEWED om. 9.

2. .E Mal m 'Zvw P m Z m my.

E.y A. ASHCROFT.

PROCESS FOR THE PRODUCTION 0F ANHYDROUS MAGNESIUM CHLORID 0R ANHYDROUS DOUBLE CHLORIDS 0F MAGNESIUM. l

APPLICATION FILED AUG. I2. 1919. RENEwEUocT. 9. |920A 1,359,652.` l ymanned Nov. 23,1920.

3 SHEETS-SHEET 2.

E. A.:ASHCROFT. PROCESS FOR THE PRODUCTION OF ANHYOROus MAGNESIUM OHLORIO OR ANHYDOus DOUBLE OHLORIOS OF MAGNESIUM.

APPLICATION FILED AUG.I2, 15H9. RENEWED OCT. 9. 1920 1,359,652. Patented N0v.23,1920.

' h3 SHEETS-SHUT 3.

i 'STATES f-GFFICE? Encan ARTHUR Asircnori, di* LoNDoN, ENGDAND;

Appi'ieauon ined august 12,' 191e', sensi No, 317,082. Jzseaeygealoeiober e, i920. serial No. 415,951'.

- Tio all may concern:

Beit known-that'l, EneAaAnrHuii Asia:- ciioirr, a subject oi the King of Great Britaln resid at 65 London Wall, in the cityl of liondon, ngland, have invented new and' useful, improved Processes for the Production of Anhydrous Magnesium f chia-id, Oli-Anhydrous Dottie chinees 'Qi- Magnesium', of which -thefollowing is Va invention relatie-@principally to the proiliitionof anhydrous magnesium chlo lrid more especially from 'the ordinaryhydratedfm'agnesium chlorid of .'comnierce, which salt crystallizes from" its solutions containin the removalo water ofhydrationby ordinary lheat processes is attended by serious diiiiculties and that dehydration cannot be 'eii'ected by any linown process, available fori commercial purposes, the processes hitherto employed having1 been attended by serious decomposition -ot the neutral salt, loss 'of acid, and formation of basic residues.

From Afl). 1870 tov Aj. DI"1890`, or therevabout, manv'attempts were made to de- A' duction o iSolvay and others) more particularly with a view toiproviding processes for thepro- 'chlorin from the ma nesium chlorid of the 'Stassffurt deposits. n those processes itfhas, at various times, been sncf- .gested to use currents clair (hot, or cold or of other ases includinohydrochloric acid as, the latter havingz been suggested for t e purpose o' -improvingth .-eq'uilialso been proposed to raiseythe temperature brium lconditions according .to 'tie well known laws or mass reactions andit has ofthe salt progressively during treatment to avoid fusion' and therefore .indo not claim these operations tobe novel separately con- A sidered,`although l inalie use of themtiiej process according to' my present invention..

'ln spite oi? the aforesaid attempts and the considerable amount of worlrdone at A of themwere complete, or 4successful, from l a practical point-civica", because, throughv six molecular proportions of.- water'f'of ydration. lt is well lmown that troublesome operation), and in more recent years bythe treatment, with chlorin as, of

converter.

l' have invented novel means whereby the water of hydration can be entirely removed' .from hydrated magnesium chlorid without rnonucrioN or ANHYD'noUs riAeNE'siuMcHDomD oit ANi-iy.- i I .Ditous DOUBLE oHLoiiiDs or MAeNiisiUM. f

'spetmeaunn of Lettersintent i Patented Nov. 23,1920.

diiiiculty, and. at but small cost. According to my invention I employ the magnesium chloridin a suitable form as hereafter ex-y plained (preferably as needle crystalsyandf after removing'.suilicientl of the Awater 'of hydration byv'means of 1a voluminous current of heated air, which raises., the fusion ointl of the salt to above 250- centigrade,

treat the partically 'dehydrated 'crystals-- with a slow current of hydrochloric acid gas which vneed only be used 'in` suflicient quantity to combine with the waterliberated from the crystals, 'forming a strong'A solution thereof which is afterward completely re. I covered.; During the said treatment with .hydrochharie acid gas the vessel or retort, in` which the treatment takes place should be externally heated, and the temperature i should be slowly raised fromv a minimum oi 150 centigrade, orthereabout, to a maxi- -that fusion does not take place at any eriod of the treatment, but incipient tusionis produced toward the end of the said treatment and the material leaving the ap- 'mum or 650 centigrade, or thereabout, so

paratus then" assumes a partially crystalline formand consists of magnesium chlori'd 'of a very high degree oi purity, 98 to 99 percent. magnesium chlorid being possibleV if care be exercised in the operation.

-During the preliminary drying i with voluminous current of heated air the whole as this will prevent the usion or the 'charge o'l. the heatl is moet conveniently imparted tothe 'charge by heatin the air employed, 100 l which otherwise would take place. too' l readilyn When from three to tour molecular. proportions oil vwelter, out ci the total con-f tent of sin Amolecular proportions, have been removed from the salt the melting` point Awill be raised from about 80 cent1- iet grade, or thereabouajto about 250o` conti-` -a fused bathv ofthe initial compoun in a I sol ' however, the dehydration by means of air tion of the salt, and therefore no loss of the chlorin content, will have taken place.v If,

be pushed much further partial decomposition will ensue with evolution of hydrochloric acid gas.

Therefore, at this stage, a slow current of hydrochloric acidgas is substituted for the air current, and thereafter the temperatureis steadily raised as the water is removed from the charge.

I'have found that the action of the hy-l drochloric acid gas under these circumstances is not merely an improvement of the equilibrium condition, but 1s that of a powerful desiccator, and this to such an extent that very shortly after the application of the hydrochloric acid gas to the charge, and

at a temperature very little above 250D centigrade, the greater part of the water of hydration has been completely removed and carried over into'the condensing apparatus in the form of a strongsolution of hydrochloric acid. This solution condenses, .con-

taining about 2O per cent. hydrochloric acid. Thereafter, on continuing the same current of hydrochloric acid gas, while the charge 1s slowly raised to the maximum temperature of 650o centigrade, the remainder of the water-is carried over from the charge and, together with it, an excess of dry hydrochloric acidgas, which, as hereinafter eX'- plained, is immediately absorbed in the Water and partially saturated solution passinggthrough the absorbing apparatus.

y this means the whole of the hydrochloric acid gas employed in this treatment is recovered in the form of a strong solution containing say 33 per cent. of hydrochloric acid, and lcan be used again and again for the treatment of subsequent charges by expelling the gas by means of concentrated sulfuric acid, which also can be used again and again by reconcentrating the said sulfurie acid. Y

By this means it is found necessary to employ only a quantity of acid nearly equivalent to the weight ofthe salt underA treatment, such acid, as hereinbefore stated,

being completely recovered and available retorts, the discharge of which is continu-` Vous, land the charging of which may be inrceeding 50,000 cubic feet per hour per ton of charge, although it may be very much l greater, say as much as 500,000 cubic feet.

This stage is preferably carried on until such an amount (usually one third, or thereabout) of the total water has been removed from the initial material, so that the melting point is raised to say 250O centigrade,

or thereabout, no loss of chlorin from 'the salt ocurring. It may however (if preferred for any reason) be carried further, some hydrochloric acid then being given off and some magnesium oXid, or oxy'chlorid, remainingin the charge. In such case the subsequent treatment with hydrochloric acid will correct this effect and ,restore the neutrality of the salt, but with 'a corresponding consumption of hydroc loric acid gas.

In the second stagel of the process, treatment with a small, or slow, currentof hydrochloric acid gas is substituted for treatment with heated air (in the same, or another. vessel) and heat is applied Ato the charge, allowing sufficient time for fthe small, or Slow, current of hydrochloric acid gas to remove the reniaining water without decomposition of the salt, the temperature being slowly raised to say 650o centigrade. By this treatment a product having'98 per cent., or more, of pure anhydrous magnesium chlorid can be readily obtained. The

product is white and porous and remains in V105,-

that condition if the temperature does not exceed, say 5000 centigrade, but, as it is' steadily raised to about 650 centigrade, thet Aproduct becomes of a partially crystalline of weight, on fusion of the finished product i,sgopsa i' 'i .it is found to be eminently suitable for the electrolyticmanufacture of magnesium metal, or allo s. Y

'The following example is. the b est way with which I am acquainted of carrying out my invention in practice, but I do not limit myself to the precise detailsof this particm4 lar example.

Stage The magnesium c hlord is. pre-A pared in the form of needle crystals, which can conveniently bedone by allowing a solution, concentrated to a strength of about-80 Twaddell (1.400 specific gravity), to cool,

from say 50 centigrade to atmospherlc temperature, when more than half of the magnesium chlorid content will crystalline out and the crystals may be centrifugaled, orl drained, -in any suitable manner, and thenbe placed in the air drying apparatus and subjected to the aforesaid voluminous current of dry air at a temperature whichl must be lower than the fusion point ofthe initial hydrated charge, to commence with; for instance, in the case Wherev the heated air is passed in an upward direction incontact with'a descending charge, the air may be admitted at about 150 centigradc, and it will cool as it ascends until the incoming charge is met by air" at a temperature -low enough to prevent its fusion, but the air may, as the charge dries, be rather more strongly heated, say' up to 250 centigrade, the object of these regulations being in any case that the crystals shall not be caused'to fuse at any stage of the treatment but shall retain their form and dimensions notwithstanding the greatA loss of weight.

. The aforesaid conditions are automatically i brought about if an apparatus ha ving a (ontinuous discharge, as hereinafter described and illustrated, be employed, because, in thatvcase, the coolerair near the exit therefor from the apparatus will partially dry the descending charge, which,l in its turn, will be subjected to the hotter air at the lower part of the apparatus. ln such an np3 i paratus it is convenient to heat the air' to a higher degree, say up to '300' centigrade..

In the accompanying drawingsn Figure l represents in vertical sectionyan apparatus suitable' for use in carrying out the irst stage of the process;

Fig. 2 shows in vertical sectien an appa-i y ratus suitable for -use 1n carrying out 55 the second stage ofthe process; and hig. 3 is a more .or less diagrammatic elevation oi a complete installation torcarrying out the process.

The apparatus shownin Fig. l comprises a'vertical retort A, of iron, or other suitable metal, which may be enameled inside and is so'set as to be capable of retaining the heaty which is imparted to the charge by means of the heated air. This is shown as being done by surrounding-the retort by a casing B, containing a non-conductor ofheat Vsuch as slag-Wool. v y t The current 'ofy air is preferably intro- "duced at thelower end of the retort and, in

the drawing, this is shown as bei effected' by forming theoutlet in two'parts ,and D, -the part C dipping somewhatinto Vthe part D, with a gap abetween, this gap being surrounded byzan air lchannel E into which heated air is passed by the inlet Efrom any suitable source. The air passes up'throu h the descending charge and escapes at' 2,

'at d2 Jforming an air-tight joint, F is a 'while the treated material descendsinto any i suitable receptacle, such as a churn, whose .upper edge may lit 'against a resilient ring ribbed, or star, discharging wheel, the speed of rotation 'of which can be regulated, by

any, convenient means between say one `and sixteen revolutions per minute.l During the air `treatment it is convenient to desiccate the ingoing air, as, by this means, a somewhat better result-is obtained. Desiccation of the air however is not essential.l l have shown, at the upper end vci the retort A, a large cover a, orcleaning purposes' Aand a smaller cover a2 for charging purposes, both of whichcan be sealed air-tightly. The

lretort may also beV charged continuously, but

l prefer to introduce the charge intermittently, periodically removing the small door a2, -or that purpose, as the level of-the material in the retort falls.

Instead `of the aforesaid apparatus lv may v employ a similar apparatus which is charged anddischarged in hatches,ra grating being provided underneath for distributing the `carried too far, irst an evolution ci' hydrochloric acid gas talles place due to" the decomposition of thesalt at the high temper-v ature necessary for expellingv the bulk of the water of hydration, and finally, when the salt is nearly 'dry and the temperature has reached 200 to 250 centigrade an evolution of ,ehlorin willy take place. lt is neither necessary, nor desirable,' to carry the treatment so tar.

li' therefor now vproceed to the second stage of the process: i

Stage 2:-1This may be carried out in the same lapparatus as that in which the irst' stage of the process is carried out, or in another vessel, or retort, which may be similar to it with ,the difference that means are provided for heating .the charge to a tem# perature of 650 centigrade, or thereabout.

When the operation is carried out in the same vessel, or retort, flues are preferably provided around it for the purpose of this heating and, immediately afterthe treatment, according to the first stage, with a voluminous and rapid current of air, treatment by a slow current of dry hydrochloric acid gas is substituted for the air treatment, and heat-is applied'so as to slowly raise the temperature to 650 centigrade, or thereabout. As the hydrochloric acid gas has a strong aiiinity for water it will rapidly abn sorb the water of the charge while not causL ing any decomposition of the magnesium chlorid and, on leaving the hot vessel, or

retort, the moisture at once condenses and can be collected in the'condition'of a strong a separate apparatus and to arrange it that the material continuously discharged from the apparatus of the iirst stage of the treatment is intermittently introduced into the apparatus for the second stage of the treatment and then is continuously discharged from the last named apparatus. Y

Fig. 2 of the accompanying drawing lshows in vertical section a suitable apparatus which I have devised for this purpose. rl`he retort is shown as consisting of a bodypart G, made in two sections, and an upper part consisting of a closed hopper H, with a large cover h for cleaning purposes and a small cover 7b2. for charging and also an outlet I furnished with a discharge screw not 4shown into which outlet a depending part g projects and leaves a space at g2 into which hydrochloric acid gas passes by the pipe g3 and thence passes up through the descending charge and (accompanied by water vapor), away at h3, to any suitable place of discharge. The body-part G, depending part g,"and hopper and discharge parts (H and I) may be made of any suitable material.` For instance the body-part 'and depending part may be made of silicaglass and the hopper and discharge Vparts may be made of iron, enameled internally.

The heating of the retort is shown as being effected by ay furnace J, surrounding the body-part G, and heated by gas and air admitted at any suitable points, such as are shown for instance at K, the products of combustion passing ofi' by the chimney J2.

This treatment with the hydrochloric gas may continue for say three, or four, hours, p during which time the vaporized solution of hydrochloric acid will distil over at h3, and can, after condensation, drip through av sight-tube into a vessel provided for its retention, surplus hydrochloric acid gas being simultaneously absorbed in water in the-absorber. The hydrochloric acid absorber may consist of a series of lVoulfes bottles, or jars, terminating' in a tower of small diameter packed with any suitable packing and supplied with water.' By means of the sight-drip, and of a graduated vessel provided for receiving the acid, the progress throughout the period of .the treatment can be accurately observed which is very convenient in practice.

After the aforesaid treatment the chlorid will contain from ninety-eight, to ninetynine, per cent.` of pure magnesium chlorid and may be either fused to a dense crystalline snow-white, or water-white, salt, or

be used directly for any required purpose; for instance, it may be used in electrolytic cells for the production of magnesium and chlorid. The treated material is discharged into any suitable receptacle, and wherein any caked lumps, due to incipient fusion, are broken up, while being discharged.

Double salts of'magnesium chlorid; such,

for instance as carnallite, (the double chlohydrochloric acid employed is recovered,

for should even a small portion of acid be removed from the salt during the air treatf ment this can be readily absorbed by bubbling the escaping air through vessels containing water, and the dilute-solution of acid thus obtained can be employed in the absorbing apparatus for the hydrochloric acid plant. It will however iusually be found preferable to stop the air treatment before any acid has been liberated.

An example of a suitable arrangement of apparatus for the carrying out of my. process is illustrated on Fig. 3, which shows in outline an arrangement ofthe plant, in a building of two floors, the lower floor containing a pressure blower l the air from jectionable umes.

present) and escapes, while the charge of partially dried magnesium chlorid is again taken to the upper floor and charged, through a second hopper at 6LL into the continuously discharged aciddrier 6 from which the finished anhydrous magnesium chlorid produced may be continuously discharged into any suitable vessel. The hydrochloric acid generator 7 furnishes gaseous hydrochloric acidfor this acid-drier 6, which gas, after passing through the charge, escapes accompanied by the water eliminated from the crystals and is condensed, in the absorber plant 8, to a nearly saturated solution of hydrochloric acid for reuse, only' sufficient water being supplied to the small tower 8a of the absorbing plant 8 to produce a concentrated solution from all the hydrochloric acid which is absorbed. In the generator 7 concentrated sulfuric acid is used to again liberate the hydrochloric acid gas, the acid being used at approximately 1.840 specic gravity and discharged from the appa.

ratus at approximately 1.560 specific gravity, at which strength it will be found to contain only approximately three-tenths of one per cent. of hydrochloric acid. 7EL is a tank for hydrochloric acid and 7b iS a tank for.

sulfuric acid. The generator is preferably worked warm (say about 90o centigrade) and a current of air may be employed to expel the last of the hydrochloric acid so that the sulfuric acid can be again concentrated; for instance, in an ordinary cascade concentrator without the production of ob- This operation is very readily carried out. Two generators worked alternately maybe provided for each retort.

The process in accordance with my invention is very convenient and economical for use in conjunction with the process described in the specification of my application Ser. No. 317084 for Letters Patent, (of even date herewith) for the simultaneous production of metallic magnesium or its alloys and magnesium chlorate, which in turn is utilized for the production ofi other by-products, the material produced by my invention being eminentlysuitable for my improved electrolyt'ic process described in the specification of my. application Ser. No. 317803 for Letters Patent of even date herewith. What I cla-im is 1. In processes for the manufacture of any raised to above 250o centigrade and afterward applying a slow current of hydrochloric acid 'gas to' absorb and remove the remaining water of hydration.

2. In a process in accordance with claim 1; the removal of a portion of the water of hydration by a voluminous current of heated air and following such treatment by the application of a slow current of hydrochloric acid gas, substantially as hereinbefore described.

3. rIhe process in accordance with claim 1, the said process consisting in subjecting hydrated magnesium chlorid to a partial dehydrating process by means of heated air without applying external heat to the charge, completing the dehydrating by meansk of a slow current of hydrochloric acid gas, with the application of external heat to carrying out the first stage of thev process only until such amount of water has been removed from the initial material that the fusion point is raised to 250o centigrade, or thereabout, and no hydrochloric acid has been liberated.

6. In a process in accordance with claim 1, effecting the preliminary partial dehydration of the hydrated compound by means of a voluminous current of air in desiccated condition.

7. In a process in accordance with claim 1, effecting the preliminary partial dehydration of the hydrated compound by means of a voluminous current of air, halting said dehydration by the current of air before any decomposition, or liberation, of the hydrochloric acid has taken place, and thereafter employing the hydrochloric acid utilized for the main part of the'drying process in a cyclic manner by absorbing in water the acid which 'escapes from the generator to form a strong solution containing all the acid employed and expelling the dry hydrochloric acid from this solution by means of sulfuric acid, substantially as hereinbefore described. In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

EDGAR' ARTHUR ASHCROFT. Witnesses:

G. F. TYRoN, L. WALTER.