US1466627A - Process of making cyanids - Google Patents

Description

7 'Aug. 28, I923. 1,266,627

. K. P. MGELROY PROCESS OF'MAKING CYANIDS Filed Jan. 25. 1922 2 Sheets-Sheet l VIP wi Aug. 28, 1923. 1,466,627 K. P. MCELROY PROCESS OF MAKING CYANIDS Fiied Jan. 25, 1922 2 Sheets-Sheet 2 [Mam/Ira? i P; M ma Patented Aug. 28, 1923.

UNITED STATES PATENT OFFICE.

KARL P. MOELROY, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO FERRO CHEMICALS INC., OF WASHINGTON, DISTRICT OF COLUMBIA, A CORPORATION OF DELAWARE.

I PROCESS OF MAKING CYANIDS.

Application filed January 25, 1922. Serial No. 531,614.

To all whom it may concern: Be it known that I, KARL POMERY MoEL- ROY, a citizen of the United States residing at \Vashington, in the District of Columbia, have invented certain new and useful Improvements in Processes of Making Cyanids, of which the following is a specification.

This invention relates to processes of making cyanids; and .it comprises a method wherein cyanid forming materials are fed to a suitable reaction chamber in which a dominant mass or pool of cyanid in the liquid and the vapor phase is maintained by aid of heat supplied by electrical means, the temperature being maintained above 1000. C. and cyanid being removed and recovered from the sphere of reaction as liquid or as vapor; all as more fully hereinafter set forth and as claimed.

The present invention is in part based upon a discovery that at temperatures above 1000 C. cyanid reacts with oxidized forms of alkali to form carbon monoxid, setting free nitrogen and alkali metal and that in making cyanid, the initial presence of cyanid itself in substantial proportions accelerates the conversion of alkali to cyanid in the presence of carbon and nitrogen. I have found that in systems comprising alkali, cyanid, carbon, nitrogen and carbon monoxid the conversion of alkali to cyanid is accomplished with what may be termed commercial velocity when the alkali and cyanid are present as vapor in substantial concentrations in the gas phase of the syS-.

tem, that is, at temperatures ranging above 1000 C. at about one or two atmospheres pressure.

Alkali, carbon and nitrogen when heated together form cyanid. The reaction is highly endothermic and most of attempts which have been made to utilize it technically have failed because of the inherent difficulty of supplying heat for the reaction -for the tendency of c anid to revert to alkali in presence of C at temperatures below those at which cyanid is formed.

In a copending application Serial No.

477,205, filed June 13, 1921, I havedescribed I and claimed a process of making cyanid from alkali, carbon and atmospheric nitrogen wherein these materials are heated together to a temperature well over 1000 C. lI1 a blast furnace such as is used for making pig iron, the operation of the furnace being so regulated that a dominant mass or pool of cyanid liquid and vapor is maintained in thehot zone of the furnace, the alkali being fed to such pool and cyanid removed therefrom at a rate proportioned to the supply of heat thereto. In the invention which is the subject matter of said application the source of heat used is the combustion of preheated carbon under gas producing conditions (that is to carbon monoxid) with preheated air, said combustion taking place in or in proximity to said dominant pool of cyanid. In said application the reinforcement of the combustion heat by electricall developed heat is described but not claime concentration of cyanid vapor is possible in the gases produced; the cyanid producing capacity of a furnace of given size being substantially increased over that which is possible when gasification of carbon with air constitutes the main supply of heat.

Since sodium cyanid is now the standard commercial form of cyanid and since sodium carbonate (soda ash) on account of its cheapness and its composition is an advantageous source of alkali for making cyanid, I shall describe the invention with particular reference to making sodium cyanid from sodium carbonate, it being understood,

that the invention is applicable to the pro-v duction of any other cyanid. I may use as the alkali of the process the oxid or carbonate (or compound capable of yielding these), of any alkali or alkaline earth or even the alkali or alkali earthmetals themselves and produce the corresponding metal cyanid.

For example potash, baryta, strontia, lithiav or even thallia are available in this connecrepresented by the reversible reaction The chemical energy involved in this reaction is, according to generally accepted data on heats of formation, 134320 calories, plus or minus. This quantity of heat is absorbed in the formation of cyanid from carbonate or is set free in the reversal of the reaction. The reaction comes to an equilibrium with a ratio of cyanid to carbonate depending partly upon the relative concentrations in the system of nitrogen and carbon monoxid and partly upon the temperature. Above 1200 C. cyanid is practically 100 per cent stable in the presence of ()0 alone and the conversion of carbonate to cyanid, with substantial proportions of initially present cyanid, takes place quickly and completely. From the practical standpoint therefore, the production of cyanid becomes a matter of an adequate supply of heat available for the reaction ata temperature around 1200 C. Since at these temperatures the vapor pressure of cyanid is quite large the cyanid formed is to a great extent in the vapor phase and heat for vaporization is required in addition to the heat of reaction. The total work of converting carbonate, carbon and nitrogento cyanid vapor at 1200 may be estimated to be, (per molecule NaCN):

Calories. 67160 23000 Heat absorbed in reaction Sensible heat of NaCN at 1200 Latent heat of fusion and vaporization 34500 Sensible heat 1% molecules CO 13400 The semi-combustion of carbon to form carbon monoxid evolves only about 30 per cent of the total heat of combustion of carbon but this amount is suflicient to raise all of the products of combustion to 1200 C. and leave a margin over available for making cyanid; that is for heating a certain further amount of carbon up to this temperature and producing cyanid from it. The greater the preheat which can be given air and carbon the greater is this margin; and contra, the greater the heat losses by radiation and the like, the less the margin. Radiation losses are proportional to temperature, time and area of exposed surface, and the faster the semi-combustion can be driven and the larger the furnace unit, the less the percentage loss of heat in this way. In large apparatus like a blast furnace or a big gas producer, using preheated blast and preheated fuel (see application Serial No; 477,205) the gasification of carbon with air may theoretically be as low as 0.3 to 0.5 pound per pound of cyanid produced in the gases in the vapor form. With lower tem- Y peratures giving slower reaction and with smaller apparatus, the figures are not so favorable. I

In the yield just mentioned, the cyanid is in the vapor form and this represents an expenditure of heat which, if the cyanid were delivered as liq'uid, would be available for the production of more cyanid. In the production of cyanid by semi-combustion of carbon with air as a source of heat, of necessity a large volume of gases is produced; this gas being carbon monoxid from the carbon and from the alkali carbonate and unused nitrogen. As sodium cyanid has a high vapor tension at 1200, with this bulk of gases the product exists in the vapor form. With a. less volume of gases, more or less of it occurs in the liquid form with a concomitant decrease in the amount of heat needed for cyanidation.

In one embodiment of the present invention I maintain a high concentration of cyanid vapor in the gases roduoed in the hearth or combustion zone oi a blast furnace or slagging gas producer by reinforcing the combustion heat by heat electrically developed in said zone. At the same time I so proportion the feed of alkali to the furnace and the withdrawal of gases at a low point in the furnace to the supply of heat to said hot zone that a dominant pool of cyanid, as liquid and vapor, is established and maintained therein, as more fully described in my application Serial No. 47 7 ,205. In so doing, the production of cyanid is smooth and regular and the capacity of a given furnace is increased over that which ispossible when combustion heat alone is used. Furthermore in working thus, the production of cyanid in a relatively small sized furnace becomes profitable whereas in very small furnaces, using combustion heat alone, the radiation and cooling factor is of such weight that the concentration of cyanid vapor in the gases may be small and the time yield concomitantly low. The proportion of combustion heat to electric heat may be as desired. I usually find it advantageous, on account, of the relative costs of combustion heat and electric energy, to have the proportion of combustion heat large and to apply electric energy in quantity sufficient merely .to overcome heat losses, therebv maintaining a high concentration of cyanid vapor without unduly' fast driving. ut I may in some cases rely principally upon electrical heating and make the combustion heat of subordinate weight, merely passing air into the reaction zone at a. rate sufiicient to maintain an excess of nitrogen therein. In one embodiment of the invention hereinafter described. I may use electrical heat alone and I may even pass nitrogen instead of air or mixed with air into the reaction zone. In this embodiment part of the cyanid is removed from the reaction zone in the liquid state, the use of electric heat serving to keep the volume of gases, and thereby the vaporization of cyanid, at a minimum.

In recovering cyanid from gases carrying it by condensing the vapor and depositing fume it is desirable to quickly cool such gases so as to pass rapidly through the temperature range at which cyanid tends to revert to alkali in the presence of CO and.

in this connection it makes for economy to have the concentration of cyanid vapor high and that of other gases low. When using electrical heat as above described, the temperature of the reaction zone maybe -con trolled independently of the speed of gas flow. The predominance of cyanid in the reaction zone is secured by this temperature control which results from proportioning the input of electric energy to the feed of cyanid forming materials going to the reaction zone and the withdrawal of cyanid and heated gases therefrom. The temperature is advantageously above 1000'C. and it is advantageous to keep it about 1200. In using fuels with high ash as a source of carbon it is advisable to run at an ash-slagging temperature with addition of lime, or other suitable flux, and the temperature may then be from 14009 to 1500; the gases may in this case be taken from the reaction chamber at lower temperatures.

The application of electric heat to the cyanid forming reaction zone .is accomplished by any suitable or convenient means.

In a shaft furnace provided with tuyeres near the bottom for blowing with hot air.

and with outlets for hot gases above the bosh or fusion zone, current may be supplied to the hot zone by meansof electrodes placed in suitable apertures through the furnace walls, the furnace charge, comprising charcoal or coke impregnated with cyanid and alkali serving as resistance material. Or the slag bath in the bottom of the furnace may be used as resistor, heat electrically generated therein radiating upwardly to the reaction zone. Or an electric furnace ofthe arc type with multiphase currents may be used, such furnace being provided with tuyeres for admission of hot air and having a superimposed shaft through which a regulated proportion of the cyanid laden gases from the hot zone passes upward in counter-current to a descending charge of alkalized fuel, and cyanid being condensed and recovered from a portion of said gases which are led from the furnace while they are at a temperature above 1000 and quickly cooled or otherwise treated for the separa tion of cyanid. A convenient method for supplying electric heat is by means of eddy currents induced in suitably prepared conducting linings provided in the hot zone, this zone being surrounded by heat insulating material and, outside of this, by a coiled electric conductor carrying high frequency alternatingcurrent. This method of apply-,

ing electric heat is of particular advantage with a small slagging gas producer Where it may be desirable merely to compensate losses by electrically developed heat and where the heat of gasification of preheated carbon with preheated air may be relied upon for the greater proportion of the necessary heat supply to the hot zone. The induction method may however also be conveniently utilized in a shaft furnace Where electric energy is the main source of heat, that is, where combustion heat is only incidental and considered merely as lessening the heat requirement of the cyanidreaction. It may here be noted that the use of air is usually preferable to that of nitrogen alone and that enrichment of the air with oxygen also makes for energy economy.

In the drawings annexed hereto I have shown, more or less diagrammatically, certain apparatus elements within the present invention and adapted for use in the opera tion of thedescribed method.

Fig. 1 is a view in central vertical section of an induction furnace;

an arc-heated the lining of the furnace. This is made of electric conducting material such as nichrome or other suitable refractory metal or it may be of graphitized carbon impreg.' nated and coated internally with magnesia or other suitable material. 5 represents a water cooled electrical conductor with electrical leads 6 carrying high frequency alternating currents by means of which heating currents are induced in the carbon cylinder 4 and in the alkalized and cyanized carbon which is in the furnace. The furnace is charged with material at the to by means of the charging hopper and bell The cylinder 4 isheat insulated by the material 8 consisting preferably of lamp black which is held in place by the casing 9 made of micanite or other electrical insulator. As shown, the bottom of the cylinder is inclined leads 15.

downwardly from the gas outlet toward the cyanid hole 3.

Fig. 2 depicts an electric resistance furnace in which the charge of alkalized and cyanized carbon constitutes the resistor. Elements 10 are air inlets, 11 the gas outlets, 12 the outlet for removal of molten material and 13 is a small carbon rod for carrying the starting current between the electrodes 14, supplied with current through electrical The furnace is fed with alkali and carbon through the charging devices 16 provided, as shown, with bells and hoppers. The furnace as shown is built with a flare or increasing cross sectional area toward the bottom so as to decrease the electrical resistance of this part of the charge and concentrate the heating effect of the current toward the top. The casing 17 may be made of magnesite or chromite brick work or of other suitable material. The conduit 18 carries cyanid laden gases to apparatus for recovery of cyanid, which may be such as that shown in Fig. 4.

Fig. 3 shows a furnace of the blast furnace type provided with bustle pipe and tuyeres 20 as air inlet, hot gas outlets 21,

- metal and slag outlet 22, and cool gas outlet 23 near the top. Inserted in the bosh walls through water cooled openings are electrodes 24 with electrical leads 25. The furnace has the usual charging device 26. The hot gas outlets 21 lead into an annular conduit 27 which is connected by conduits 28 to apparatus for cyanid recovery, here shown as comprising a water jacketed condenser 29 containing cooling pipes 30. This is a type of apparatus adapted for quickly cooling the hot cyanid laden gases through the temperature range below 1000, in which cyanid in presence of CO tends to revert to oxid and carbonate. Valves 31 and 32 are for the purpose of regulating the relative proportions of the furnace gases leaving the furnace through hot gas outlets 21 and passing up through the shaft and out by cold gas outlet 23.

Figure 4 shows another type of apparatus for quickly cooling cyanid laden gases; which may be used in connection with any of the furnaces herein described, being for example connected by inlet 35 to outlet 28 of the structure of Fig. 3 to outlet 18 of Fig. 2 or outlet 2 of Fig. 1. In this showing, inlet 35 is a conduit leading from the hot gas outlet of any cyanid furnace. Elements 36 and 37 are sheet metal towers connected at the bottom by conduit 38 and connected at the top by conduit 39. Conduit 38 is in the form of a hopper with a U-shaped bottom. In tower 37 are shown cooling pipes 40 in which air, water or other cooling medium circulates. Through the conduit 38 runs the conveyor 41 delivering into receptacle 42.

A thermal circulation of gases may be mainaaeaeav culation upwardly in 36 and downwardly in The 37. Cyanid is quickly condensed in 36, falls to the bottom and is removed by conveyor 38. As condensation is favored by nuclei, dustlike suspended particles are built up until they are large enough to fall freely.

The apparatus therefore gives or may be made to give, a granular product. Excess of gas passes out through pipe 43. Control of the volume of gas passing out of the apparatus and, therefore, of the volume of hot gas entering, is secured by adjustment of valve 44. A pyrometer 45 indicates the temperature resulting from the mixture of incoming hot gas with the mass of gas maintained in 36. The mass of hot gas which an apparatus of this type can handle is a matter of design. Usually the circulation through the towers is sufiiciently rapid without the aid of a fan in conduit 39, but such a fan (not shown) may be used. There may be as many of these coolers connected to the hot gas outlet of a. furnace as are required to handle the volume of hot gas required to be taken from the furnace in securing'the desired regulation thereof as described.

The apparatus of Figs. 1 and 2 are worked similarly. They differ mainly in the means provided for applying electric energy. Being filled with alkalized carbon in lumps (which may be charcoal, coke or other form of carbon impregnated with soda) the electric current is applied and the furnace brought When the alkali in-the furnace is .cyanided,

which can be tested by withdrawing a sample through 3 or 12, the air volume is increased and the feed of alkalized carbon through 7 or 16 is correlated with the air volume, both being properly proportioned with regard to the electric energy applied, thereb maintaining the temperature at the desire degree. The gases leaving the furnace through 2 or 11 now carry cyanid vapor in concentrations (below the saturation point) depending upon the ratio between the electric energy applied and the heat of combustion. .The latter is a function of the speed of driving (the volume of air per minute with the correlated alkali and carbon feed). With the speed of driving fixed the concentration of cyanid vapor in the gases varies directly with the electric alkali fed over that suflicient to saturate the gas as it leaves the furnace collects as cyanid in the molten state at the bottom of the furnace and is drawn ofi' from time to time through 3 or 12. The collectionof liquid cy-,

anid in this way is aided by the flare of the furnace shown in Figure 2 and by placing the induction coil 5 on the furnace of Fig;

1 well above the bottom, thus providing for a cooling effect and causing a condensation of cyanid from the gases before they leave the furnace. It is advisable with this type of furnace to keep the temperature at a minimum consistent with adequate speed 'of cyanid formation, thus minimizing heat con-- sumption and recovering in the molten state as described the maximum proportion of the cyanid formed in the furnace.

In the operation as above described I am in effect continuously gasifying carbon by sodium carbonate and by air, maintaining a temperature at which soda is vaporized and, in mixture with nitrogen and carbon monoxid, the soda vapor is contacted with carbon thereby forming cyanid, the conversion being accelerated by maintaining in the reaction zone substantial quantities of preformed cyanid serving as a dominant pool. With sufficiently fast driving, carbon dioxide may be first formed in the upper zones of the furnace, the heat of CO formation being partially absorbed in vaporization of soda; the soda vapor and CO together'with nitrogen, all at a'very high temperature, subsequently contact with carbon to form cyanid and CO with a drop in temperature as the gases proceed through .the reaction zone, Thev size of this zone should be greater, the greater the speed. of driving. The proportions of alkali and carbon to be used in the example, about 66 parts soda ash to 34 parts of charcoal of percent carbon. When using nitrogen alone heat would be supplied by electric power alone and the theoretical energy consumption may be estimated as about 1.5 kilowatt hours per pound of sodium cyanid vapor. The maximum concentration of cyanid vapor, corresponding to per cent fixation of the nitrogen passed into the furnace, would be 40 per cent by volume, assuming thevapo'r molecule to be represented by the formula NaCN. Using air in 100 per cent excess, that is with a 50 per cent fixation of its nitrogen, if the air be preheated to 7 50 and the gases taken off at 1200, the theoretical electric energy requirement, as estimated, would be reduced by about 9 per cent, the proportions of soda and charcoal would be 60. :40 and the equivalent maximum concentration of cyanid vapor in the gases 28 per cent. For that proportion of the cyanid removed from the furnace in the molten statean estimated saving of 20 per cent of theenergy requirement is indicated. Relying entirely upon combustion heat for .the cyanid reaction proper, using electric heat in proportion sufficient merely to balance heat-losses, the consumption of carbon with air preheated to say 750 and with the alkalized car-bon fed cold to the furnace, would be about 2.5 lbs. per pound cyanid, the ratio of soda in the alkalized carbon would be 28 parts to 72 of charcoal of 90 per cent carbon and the cyanid would be in a volume concentration of about 4 per cent in the gases. Something over 3 per cent of the air nitrogen would be fixed as cyanid at the expense of 34 per cent of the calorific value of the carbon used. In this case it may be said that 80 per cent of'the carbon is gasified by air and 20 per cent by soda. It will be seen from the foregoing that the procedure may be widely varied as desired to meet prices, scale of production, capital investment, demand for producer gas, etc. As heretofore noted, with an apparatus of given size or a fixed rate of gas flow, electric heating makes for a maximum time-yield and this tends to reduce all elements of overhead cost to a minimum,

Furnaces of the types shown in Figs. 1 and 2 may be operated 'discostinuously or batchsvise. In'batch operation, such a furnace may be charged with a mixture comprising carbon and alkali (alkalized charcoal works well) and, brought up to about 1000 or above by electric heat. Air or nitrogen, (preferably preheated) is then passed into the furnace and alkalize'd charcoal fed to the furnace at the same time, the proportion of alkali with the carbon being such, relative to the rate of gas flow, that alkali is fed and cyanid formed faster than the latter is removed from the furnace as vapor in the gases produced. As a result, cyanid accumulates in the furnace and the proportion of cyanid to residual charcoal may be brought to any desired concentration and the operation then discontinued. The furnace may then be cooled and the cyanized charcoal may be removed and utilized as such, or the cyanid may be separated 100 -,varying conditions as to power costs, fuel from the charcoal by suitable means such as leaching. Or the cyanid may be distilled or sublimed away from the furnace while the latter is still hot either under vacuum or by means of a circulating current of inert gas such as nitrogen, cyanid being deposited by cooling the efilux gases. Usually the continuous method of operation is preferable.

At about 1000 the vapor tensions of most alkalies and their cyanids is fairly small so that with a moderate feed of air or nitrogen (or air enriched in oxygen), a batch of alkalized charcoal in granular or lump form may be readily converted into cyanized carbon with a relatively small removal of cyanid or alkali in vapor form. With some alkalies, such as baryta, the temperature at which this is done can be higher than with potash or soda. The cyanized carbon will always contain some unconverted alkali; the amount depending upon temperature conditions.

Carbon being consumed in the reaction, the

proportion of cyanid and alkali (taken together) in the cyanized product is or may be greater than the proportion of equivalent alkali in the initial alkaliz ed charcoal. When using soda as alkali, the operation may be so managed as to yield cyanized charcoal containing a total alkali equivalent of from 40 to 80 per cent sodium cyanid. The proportion of cyanid (and alkali) in the product depends upon the masses of nitrogen and oxygen relative to those of the carbon and alkali. lBy regulation of these proportions the said proportion of cyanid may be as desired.

The operation of the furnaces shown in Figs. 1 and 2 may be reversed by introducing air or nitrogen at the bottom and taking away gases at the top; air inlets and gas outlets being simply reversed in function. In this event, the operation may then be so managed that all .or any part of the cyanid formed is removed from the furnace in the vapor state and recovered from the gases. When using air, furnaces of the types of Figs. 1 and 2 may be operated in a manner similar to the operation of the structure shown in Fig. 3.

In operating'the furnace of Fig. 3, charcoal, coke, coal or other carbonaceous matter, impregnated or mixed with soda together with flux for slagging the fuel ash are charged into the furnace through 26. The furnace being filled and the charge ignited, the materials descend slowly in countercurrent to a regulated portion of ascending gases produced in the hearth by the gasification of so preheated carbon with preheatedair introduced through 20. Gases produced in the furnace are withdraw through outlets 21 and 23 in relative proportlons definitely controlled in accordance with the furnace work; this control being effected by means of valves 31 or 4:4 and 32. Means ed to cyanid and preheated.

mecca-r for causingthe flow of gas through the furnace are not shown but may be either pressure applied to the inlet air line or differential suction applied to the respective outlet gas lines. The temperature in the hearth and combustion zone is kept very high, ranging from 2000 C. in the immediate vicinity of the tuyeres to about 1200, usually, at the level of the hot gas outlets 21. Electric heat is applied by means of current passing through the electrodes 24 placed, as shown, near the top of the bosh at opposite points on the circumference. Slag and metal if any be formed, are removed through 22 in usual ways. Cyanid is formed in the hot zone, passes upward as vapor with the gases and out of the furnace through 21, being recovered from the regulated portion of the furnace gases which is caused to flow through these outlets. The cyanid carried in the gas caused to pass up through the shaft is condensed, deposited and adsorbed in the descending alkalized carbon and the cyanid from the gas more or less reverts to oxid and carbonate in the cooler portion of the shaft. Thus the sensible heat of the CO and N and also the latent heat of vaporization of cyanid, and to a greater or less extent the sensible heat and the energy of reversion of the cyanid to oxid and carbonate are applied to the preheating of the soda and carbon and to the work of cyanid formation, so that the shaft delivers to the combustion zone alkali and carbon, with the alkali already to a greater or less extent deoxidized or convert- The proportion of the total work which is done in the shaft depends upon the regulation of the furnace operation, the principles of which may be illustrated as follows':The work of converting cold carbonte, carbon and nitrogen to cyanid vapor and CO at 1200 has been hereinbefore estimated at 138060 calories per molecule NaCN. Under the coun-' tercurrent stated action in the shaft of the furnace, the sensible heat of the CO formed in the cyanid reaction is recuperated by the descending alkali and carbon and the item of 13400 calories per molecule NaCN estimated as the sensible heat of 1:} molecules CO at 1200 may be left out of the calculation, leaving the total heat required at 124660 calorles per molecule NaCN or 2544 thermal units per pound cyanid. For purposes of illustration this work may be divided into three steps as follows (1) Conversion of carbonate .to oxid in the reaction, Na,CO -|-C:Na.,O+2CO, and preheating Na O+3C to 1200;

(2) Conversion at 1200 of liquid oxid to liquid cyanid in the reaction, Na O+3C+ N,':2NaCN+CO (3) vaporization of liquid cyanid at 1200 The chemical energy involved in (1) may be taken as 114480 calories and in (2) as per molecule N aCN With the molecular specific heat of 13 (1+0.00039 t) the sensible heat ofNa O at 1200 maybe estimated as about 23000 calories; the molecular heat of fusion is estimated at 4500 calories; and the molecular figures may be taken as about the same for cyanid. The heat in carbon at 1200 is 5832 calories'per gram-atom. Hence the'work involved in the three steps nay'be estimated to be: i

(1) 79238 calories per molecule or 1617 thermal units per pound cyanid.

(2) 15422 calories per molecule or 315 thermal units per pound cyanid. (3) 30000 calories per molecule or 612 thermal units per I I pound cyanid.

Total, 124660 2544 thermal units per pound cyanid. The relative proportions of the gas from the combustion zone caused to leave the furnace through hot gas outlet (21) of Fig. 3, and top gas outlet (23) respectlvely may be so adjusted that any desired proportion of the work involved in steps (1) and (2) may be done in the shaft. It is usually economical so to manage the operation that electric energy is utilized in quantity only sufiicient to compensate vheat losses; and to cause sufiicient gas carrying cyanid to pass I so upthrough the shaft in order toconvert all descending alkali to liquid cyanid preheated to about 1200; in other 7 words to;

' complete steps and (2) in the shaft leaving only step (3) or its equivalent to .be done in the combustion zone. So working, carbon is'needed in the hearth to be gasified with air atsay 750 to the extentof about 0.32 pound per pound of vaporized I cyanid. The corresponding volume concen- 40 tration of cyanid vapor is about 20 per cent of the mixed gases. About 55 per cent of these gases, caused to pass up through the shaft where they contact with descendin alkali and carbon, by virtue oftheir sensible heat and latent and potential energy developed in the condensation and partial cooling and reversion of cyanid and deposition of carbon is suflicient to complete the conversion to cyanid of sufficient alkali (which should be charged with the carbon) to replace the cyanid removed from the furnace in 45. per cent of the gases produced in the combustion zone. Such a proportionof said gases may bewithdrawn through the hot gas outlets 21. The consumption of car- 'bon in the gasification with air in the combustion zone is thus about 0.72 pound per pound of cyanid recovered from the per cent of the gases and 0.49 pound carbon is consumed in the cyaniding reaction; butfrom the percent of the gas going up through the shaft carbon is deposited in the decomposition of'CO' and with full (levelopment in thisiway of the latent energy of from he combust on zon the carbon s deposited may amount to 0.2 pound per pound of recovered cyanid, leaving the net carbon requirement about one pound per ratio in the top gas, increasing the proportion of hot gas withdrawn with rise of top temperature and fall of CO ratio and vice versa I may thus hold the top temperature and CO ratio at a desired point, corresponding to a desired degree of utilization inthe furnace of the fuel energy. Beyond a certain limit, the greater the .proportion of hot gas taken from the furnace at 21, the smaller the proportion of the fuel energy utilized in the furnace and hence, the application of electric heat. remaining suflicient to balance losses, the greater the consumption of carbon per pound cyanid. For example, with a hot gas withdrawal of about 58 per cent with 42 .per cent of the gases the shaft), the work devolving upon the combustion zone is about the equivalent of steps (2) and With electric heat compensating heat losses in the combustion zone, this work-requires the ,gasification of. about 0.49 pound carbon (preheated, to- 1200) with air at 750. An equatio f action might be written?) or the re-' I bon, sodium oxid and air in these proper; tions (the carbon'andsoda being preheated to 1200 and the air to 750) absorbsfnog heat and it follows that with air in-greater proportions, or if the materials be more;

highly preheated the reaction is exothermic. Putting it in another way: The theoretical temperature of the gasification of preheated carbon, 42 per cent by'preheated soda and 58 per cent by air preheated to 750 is about 1200. Some 13 per cent of-the air, nitro: gen is fixed as cyanid vapor in a concentration of about 14 per cent of the products of the gasificatiom With cyanid recovered from 58 per cent (by volume) of these prodnets and the other 42 per cent being utilized for preheating more soda and carbon, the total consumption of carbon is about 1.17 pound per pound cyanid produced. The proportions of soda and fuel (90% carbon) charged into the furnace should in this case be a t 5: 5. It may e noted that in a ca scowm any case these proportions should be carefully adjusted in correlation with the volume of hot gas withdrawn at 21 and the concentration of cyanid therein. Carbon may be introduced into the hot zone of the furnace in the form of liquid or gaseous hydrocarbons in volume so regulated as to adjust the proportions of alkali and carbon as desired. By increasing the electric energy applied the consumption of carbon may be reduced and a greater proportion of gas may be withdrawn through the hot gas outlet without reducing the concentration of cyanid in such gas. The regulation of the furnace operation is a matter .of coordinating the volume of hot gas withdrawn with the blast temperature and with the application of electric power, in conjunction with the proportions of alkali and carbon.

In applying the present invention to the general problem of nitrogen fixation, cyanid made as described is hydrolyzed to ammonia with recovery of alkali and this alkali may be returned to the furnace to be again cyanided. It is advantageous to practise the invention in a blast furnace in simultaneously producing cyanid and iron or action zone by aid of heat supplied by electrical means.

2. The process of making cyanids which comprises feeding air, alkali and carbon into a reaction chamber in which is maintained by aid of heat supplied by electrical means a mass of cyanized carbon at a temperature above 1000 C.

3. The process of makin cyanids which comprises feeding air, alkali and carbon into a reaction chamber in which is maintained by aid of heat supplied by electrical means a mass of cyanized carbon at a temperature above 1000 C. and removing cyanid from the sphere of reaction.

4. The process of making cyanids which comprises downwardly feeding air, alkali and carbon into a reaction chamber in which is maintained by aid of heat supplied by electrical means a mass of cyanized carbon at a temperature above 1000 C. and removing cyanid from the sphere of reaction.

5. The process of making cyanids which comprises downwardly feeding air, alkali and carbon into a reaction chamber in which is maintained by aid of heat supplied by electrical means a mass of cyanized carbon at a temperature above 1000 C. and removing cyanid from the bottom of said reaction chamber.

6. The process of making cyanid which comprises contacting a mass of alkalizcd carbon heated electrically to a cyanid forming temperature with a mass of nitrogen and oxygen so regulated that the proportion of cyanid and alkali in the resulting cyanized carbon is greater than the proportion of equivalent alkali in the initial alkalizcd carbon.

7. A process of making cyanid which comprises contacting alkali vapor and nitrogen with cyanized carbon maintained at a temperature above 1000 C. with the aid of heat supplied by electrical means.

8. A process of making cyanid which comprises feeding alkali, carbon and nitrogen into a reaction chamber to react with a mass of cyanid therein maintained at a temperature above 1000 C, removing cyanid laden gases therefrom and quickly cooling said gases to deposit cyanid substantially without reversion.

9. A process of making cyanid which comprises passing nitrogen into contact with alkali and carbon maintained at a cyanid forming temperature and quickly cooling resulting gases to deposit cyanid therefrom substantially without reversion.

10. A process of making sodium cyanid which comprises heating together to a cyanid-vapor-forming temperature sodium carbonate, carbon and nitrogen and quickly cooling resulting gases to deposit sodium cyanid substantially without reversion.

11. A process of making cyanid which comprises contacting nitrogen with alkali and carbon at a cyanid forming temperature maintained with aid of heat supplied to the sphere of reaction by means of electrical currents induced therein or in proximity thereto.

12. In nitrogen fixation the process which comprises contacting air preheated to substantially above 500 C, with alkalized and cyanized charcoal maintained at about 1200" C, by aid of heat supplied by electrical means.

13. In the manufacture of cyanids the process which comprises contacting at a temperature above 1000 C, preheated carbon and alkali under gas producing conditions with preheated air. recovering cyanid from a regulated proportion of the gases produced while preheating carbon and alkali with another regulated portion of said gases, and maintaining the temperature and a substantial concentration of cyanid vapor in the gases by aid 'of heat supplied by electrical means.

14. In the manufacture of sodium cyanid the process which comprises contacting at cyanid-vapor-forming temperatures preheated carbon and soda under gas producing conditions with preheated air, recovering sodium cyanid from a regulated proportion of the gases produced while preheating carbon and soda with another regulated 'portion of said gases, and maintainmg the temperature and a substantial concentration of cyanid vapor in thegases by aid of heat supplied by electrical means. l I

15. In cyanid making the process of cooling hot cyanid laden gases and depositing cyanid therefrom substantially without reversion which comprises leading such gases into a cooling chamber in which a relatively large mass of cooled gas is maintained.

16. The process of making sodium cyanid which comprises feeding nitrogen, soda and carbon into a reaction chamber in which is maintained by aid of heat supplied by electrical means a mass of cyanized carbon at a temperature above 1000 C.

17. In making cyanid vapor by heating together in a shaft furnace carbon, alkali and'air in the presence of cyanid, the proccess of providing in the hot zone a volume of heat available for work at cyanid forming temperatures which comprises reinforcing by heat electrically supplied the heat developed by CO formation from preheated air; and carbon preheated by counter-current contact in the shaft with a regulated prof I portion of cyanid-laden gases previously produced.

18. In the fixation in a blast furnace of nitrogen as cyanid vapor by gasifying carbon with soda and air at temperatures above 1000 C., the process of making the cyanid forming reaction exothermic which comprises regulating the relative proportions of alkali and carbon charged into the furnace in correlation with the blast heat and preheating said carbon and soda by counter current contact in the furnace shaft with a. regulated proportion of the cyanid-laden gases produced in the hearth, cyanid being recovered by quickly cooling another portion of such gases Withdrawn from the furnace 'at a level of high temperature.

7 19. In making cyanid from carbon, alkali and nitrogen 'in the presence of preformed cyanid in a shaft furnace heated by electrical means, the process of controlling the heat economy of the operation which comprises preheating the carbon and alkali descending through the furnace shaft to the electrically heated zone by counter current contact with a regulated cyanid-laden gases.

In testimony whereof, I have hereunto affixed 111 Si ature.

y K. P. MoELROY.

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