US2334451A - Manufacture of metallic magnesium - Google Patents

Description

Nov. 16, 1943.. E, c. R; sPooNER MANUFACTURE OF METALLIC' MAGNESUM" Filed Dec. 50, 1942 FURNAGE SHOCK- cNlLLms come uefa/:Zar

Patented Nov. 16, 1943 UNITED STATES PATENT OFFICE MANUFACTURE F METALLIC MAGNESWM Edgar Clynton Ross Spooner, Swansea, Wales, as-

signor, by mesne assignments,to The Anglo y California National Bank of San Francisco, San Francisco, Calif., as trustee, a national banking association Application December 30, 1942, Serial No. 470,627 In Great Britain April 3, 1942 6 Claims.

This invention relates to the manufacture of metallic magnesium from magnesium oxide or from raw materials containing or yielding magnesium oxide by the reversible process according to which magnesium oxide and carbon yield magnesium and carbon monoxide.

The process for the production of the magnesium is carried out at high temperature and in order to prevent the reverse reaction taking place whereby the magnesium would revert to magnesium oxide, sudden chilling of the mixture lof magnesium and carbon monoxide must be effected.

According to one known process, this is secured by the addition to the reaction products immediately after leaving the hot reduction chamber of a substantial quantity of hydrogen or any other gas indiierent to or reducing magnesium.

In another process the cooling material now frequently referred to as a shock-chilling medium comprised liquid hydrocarbon oil brought into a state of ne division. The rst type of process which may be termed the hydrogen process has its advantages and its disadvantageaand the second type of process which may be termed the liquid oil process has also its advantages and its disadvantages.

An object of the present invention is tol provide an improved or modified shock-chilling system retaining largely the advantages ofthe above two systems and avoiding largely the disadvantages of those systems individually.- This can be secured'by the use of a suitable condensable gas as the shock-chilling medium.

The invention pertains to a process for manufacturing metallic magnesium by carbothermic reduction of magnesium oxide-containing prime material and shock-chilling of the resulting magnesium vapor-carbon monoxide mixture while using as coolant in a circuit a liquid inert to magnesium, said liquid being vaporzed before introduction as a coolant and the vapor egressing being subsequently liquifled for the purpose Of separating it from carbon monoxide before reintroduction. The improvement on said process according to the invention essentially consists in utilizing the heat content of the outflowing vaPOrgas mixture, preferably by contacting it with the returning cooling liquid, for vaporizing the liquid before its reuse as a coolant.

The accompanying diagrammatic drawing-illustrates apparatus suitable -for carrying the present invention into elect.

In carrying the invention into effect 1n the form illustrated by way of example there is introduced into the products leaving ythe furnace or hot reduction chamber a in which magnesium oxide and carbon are converted into magnesium and carbon-monoxide a condensable gas having a boiling point within the range +20 to 20 C. and especially butane. ,The butane or the like enters the shock-chilling apparatus, for instance, a shock-chilling cone b in the form of gas. This gas enters the cone b through apertures c, being led thereto by the shell d of the cone and an opening e. The products leaving the shock-chilling cone b pass to a drum or other cooler f, the metal being in the form of dry dust and the shock-chilling medium in the form of gas or' vapour. Thedust which falls to the bottom of the cooler passes out by way of an opening g and pipe h to a magnesium dust exit i. The mixture of dust and gas or vapour at the top of the cooler f passes by way of an opening :i and pipe 1c to a precipitation system l which may comprise dry.

bag lters or electrostatic precipitators, the exit condition of the dust beingdry and the exit condition of the medium being in the form of gas or vapour. The magnesium dust leavesthe cooler l at the base at m and then proceeds to the magnesium dust exit z' aforesaid. The hot gaseous productsl from the cooler pass by the pipe n to a heat exchanger o from which the cold gaseous products leave by way of the pipe p and pass to a cooling or refrigeration apparatus q. From this apparatus non-liquefied gas leaves at the top by Way of the pipe r and any liquefied product by way of the pipe s which goes back to the heat exchanger o from which cold gas ultimately leaves by the pipe t leading to the intake e to the shock-chilling cone referred to above. f Thus as' sation o the medium in the piping and other parts leading to the condensing system, it may be considered desirable to preserve the shock-chilling medium in the gaseous state at all temperatures'above normal atmospheric temperature.

These considerations in ,any given instance may indicate desirability of using a shock-chilling medium with a boiling point below 20 C. and preferably below C. y

As to the lower limit boiling point permissible, this is dictated mainlyXby matters of economy. Thus it may be more economic` to use a relatively cheap medium of boiling point 20 than an expensive medium of C. In general, 'however, the increase in condensation costs (refrigeration) as the boiling point falls below C. is such that the Alower boiling point limit may be taken as 20 C.-

Among suitable condensable gases, hydrocarbons represent a readily available group, butane as indicated being especially suitable as, for instance, it is a relatively cheap and abundant hydrocarbon, and has a boiling point Within the preferred range of 0 C. to 10 C.

The following table Acontains a number of chosenhydrocarbons:

Hydrocarbon Boiling point Z-methylpropane, 04H10 or ((CHmCH) 10.2 -2-methy1propene, CiHs or (CH=:C(CH;)CH3) 6 lbutene,.C4Hs or (CHaCHiCHzCHz) -5 1,3-butadlene, C1B or (CBnCHCHzCHzLH -3 Butane, Cillin o r (CHdCHzhCHs) -0 6 to 0.3 2-butene, 04H! cr (CHiCECHCHa) l to 2 5 (lyclobutene, CiHi or (CHzCHCHICHz) -3 to +1 Methyl-cyclopropane, 04H; or (CHaCHCHzCHz). 6

a-buten-i-yne, 04H. or (cn s comen.) 5 1butyl1e, CHa 0r (CH E CCHzCHi) 8.6 2,2di11}ethylpropane, Gillmor ((CHmC) 9.5 Butadlyne, 04H1 or (CH i CC E CH) 10.3 CyClOblltalle, CHs 0r (CHzCHnCHzCHz) 13 iabutadiene, ciu. or oH1=c;cHcH.----. 19

This alternative method of employing a shockchilling condensable gas simplifies the problem of condensing the medium for the release of the CO, that is to say the cooling or refrigeration unit q may take the form of a single gas cooler, for example with lbundles of pipes externally water cooled, but at the same time (i) the whole dust precipitation system must be kept hot in order-to prevent hydrocarbon condensation in the presence of the dust and (ii) it is necessary to heat andrevaporise the medium after condensation before re-using the medium in the gaseous condition for shock-chilling.

It must be understood that these latter disadvantages may outweigh, practically and economi-v cally, the advantages of the less costly condensa- .tion system in some instances.

tuated where condensation takes place over a wide range of temperature. v

Referring to the boiling point limits +20 C. to 20 C. quoted earlier, shock-chilling media within this range include not only those possess` ing single boiling points but any mixture of such media the boiling point range of4 which falls within these limits.

I claim: 1. In the Process for manufacturing metallic magnesium by carbothermic reduction of magnesium oxide-containing prime material and shockchilling of the resulting magnesium vapor-carbon monoxide mixture While using as coolantin a circuit a liquid inert to magnesium, said liquid being vaporized before introduction as a coolant and the egressing vapor being then liquified again for the purpose of separating the condensable gas from carbon monoxide before reintroducing it as the coolant; the step of utilizing the heat content of the outowing vapor-gas mixture for vaporizingthe liquid before the reuse as a coolant. 2. In the processfor manufacturing metallic magnesium by carbothermic reduction of magnesium oxide-containing prime material and shock-chilling of the resulting magnesium vaporcarbon monoxide mixture while using as coolant in a circuit a liquid inert to magnesium having a boiling point within the range minus .20 C. to plus 20 C., said liquid b'eing vaporized before introduction as a coolant and the egressing vapor being then liquified again for the purpose of separating itfrom carbon monoxide before, reintroducing it as the coolant; the step of utilizing the heat content of the outowing vapor-gas mixture by contacting it with the returning cooling liquid, for vaporizing the liquid before the reuse as `a coolant.

3. In the process for manufacturing metallic magnesium by carbothermic reduction of magnev sium oxide-containing prime material and shockchillingof the resulting magnesium vapor-carbon monoxide mixture while using as coolant in a circuit a liquid inert to magnesium having a. boiling point within the range minus 20 C. to plus 20 C., said liquid being vaporized before introduction as a coolant and the egressing vapor being then liquified again for the purpose of separating the condensable gas from carbon monoxide before reintroducing it as the coolant; the step -of utilizing the heat content of the outiiowing vapor-gas mixture, by contacting it'incountercurrent with the returning cooling liquid, for vaporizing the liquid before the reuse as a coolant.

4. A process as .claimed in claim 1, in which the condensable gas has a boiling point within the range +20 C. to 20 C.

5. A process as claimed in claim 1 in which the condensable gas is selected from the group of gases consisting of 2methylpropane; Z-methylpropene; 1-butene; 1,3-butadiene; butane; 2-butene; cyclobutene; methyl-cyclopropane; 3-buten-l-yne; l-butyne; 2,2-dimethyl-propane; butadiyne; cyclobutane; and 12-butadiene.

6. A process as claimed in claim 1 in which the condensable gas is butane.

EDGAR CLYNTON ROSS SPOONER.l

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