US1760014A - Process of preparing ammonia-factor gases - Google Patents

Description

May Z7, 1930. F. H. sNYDER ET AL PROCESS OF PREPARING AMMONIA VFACTOR .GASES Filed July 22, 1927 uw. v .nu

i Patented May 2.7, 1930 u/NITED STATES PATENT ori-ICE FRANCIS H. SNYDER AND EDGAR D. NEWKIRK, OF SYRACUSE, NEW YORK rnocnss oF PREPARING' Application iled July 22,

. This invention relates to the manufacture of ammonia and more particularly. to a method of and apparatus for preparing in an extremely simple, eflicient, and economical lmanner .gaseous mixtures ofhydrogen and nitrogen particularly suitable for use in the synthetic production of ammonia.

The principal object of this invention isy to provide a simple and eiii'cient process of preparing substantially pureammonia factor gas mixtures at a cost which is suiiiciently loW to render the use of such gasmixtures in `the synthetic production of ammonia commercially practical. f

Another object of this invention is to provide a process of preparing ammonia factor gases by contacting air and steam With sponge iron at an elevated temperature.

A further object of this invention is to provide a continuous process of preparing substantially pure ammonia factor gas mixtures by contacting mixtures of air and steam' in suitable proportions With sponge iron at an elevated temperature and subsequently removing the impurities present in the resultinor gasv mixture.

A fiirther object of this invention is to provide aI continuous process of preparing ammonia factor gas mixtures by intimately contacting a current of steam and air with a current of sponge iron at an elevated temperature, the flow of the current of the steam and air mixture With respect to the flow of the current of sponge iron being regulated in such a manner that the amount of the steam and air mixture in excess of the amount required to oxidize a given amount of the sponge iron will contact with unoxidized sponge iron.

A furtherobject of this invention is to provide a continuous and thermally self-sustaining process of preparing hydrogen andv nitrogen by intimately contacting a current of steam and air with a current of sponge iron in the form of nodules at an elevated temperature.

' A further object of this invention is to provide/an economical and efficient process of preparing hydrogen by contacting a current of steam with a current of spongeiron AMMONIA-FACTOR GASES 1927. Serial No. 207,743.

at an elevated temperature and separating and removing the reaction-products formed.7

A further object of this invention is to provide ,an economical and elcient process of preparing hydrogen by intimately contacting a current of steam with a current of sponge iron in the form of nodules at an elevated temperature, the flow of the current of steam With respect to the ilovv of the current of sponge iron being regulated in such a manner that the amount of steam iny our process.

Other objects and advantages of the invention will become apparent during the course of the following description.

Various processes have been proposed heretofore for producing hydrogen from steam and iron by the alternate oxidation and reduction of the iron in situ, hydrogen and iron oxid being produced in one phase and, by gaseous regeneration ory reduction, iron sponge being produced in the other phase. These methods have not met with any practical success principally because of tvvo major dillicu'lties or disadvantages in the processes. In the first place during the alternate'oxidation andreduction of the iron in situ the chemical activity of the iron is continuallyl diminished. Secondly, the processes have not been successful because of the inefficiency of the reducing phase, the reducing process being limited to the equilibrium reactions involved. Vle propose to overcome these difficulties by intimately contacting a current of nodules of sponge iron of'a selected size and of a high degree of purity With a counter current of steam to produce hydrogen and iron oxide or preferably with a. counter-current of a mixture of steam and air in suitable proportions to produce a mixture ofhydrogen and nitrogen suitable for use inthe synthetic production 'of ammonia. The reactions are carried out at an elevated temperature in a closed chamber which is preferably `'completely iilled with nodules of sponge iron in order that the steam or steam and air mixture will come into very intimate contact with the sponge iron. The sponge iron preferably passes downwardly through a vertically arranged treating chamber at a predetermined rate and the steam or steam and air mixture is passed upwardly through the apparent volume'occupied by the sponge iron, the rate of flow of the current of sponge iron being regulated in such a manner that the steam or steam and air mixture in excess of the amount required to oxidize the iron will contact with unoxidized sponge iron. These .reactions are highly exothermic and are thermally self-sustaining and by the treatment indicated the heat of combustion is localized with the result that the oxidation is substantially complete and the troublesome equilibrium factors are substantially eliminated. Moreover, by regulating the flow of the current of sponge iron inthe manner indicated and removing the iron oxid formed the yield of hydrogen or hydrogen and nitrogen is substantially constant.

In the accompanying drawing We have shown in diagrammatic form a preferred embodiment of apparatus particularly adapted for use in the practice of our process.

Referring to the drawing, the reference numeral 10 designates generally a factor gas generator which preferably consists of a metal shell 11 which is provided throughout a portion of its length with a refractory lining 12. The upper portion of the generator 10 is provided with a suitable closure 13 having a centrally disposed opening 14 about which is arranged a trap feeder 15 communieating with a hopper 16. The lower portion of the generator 10 is disposed in a water seal 17 which is preferably provided with an inclined portion 18. The trap feeder 15 is adapted to feed nodules of sponge iron 19 from the hopper I16 into the generator 10, which is designed to be completely filled with sponge iron as indicated in the drawing. After the nodules of sponge iron are oxidized in the mannerl hereinafter described they are removed from the water seal 17 by any suitable means such as by raking-them up the inclined portion 18 but preferably by means of an automatic ash remover of ordinary construction ('not shown) arranged adjacent 'the outlet end of the generator 10.

The upper portion of the. generator 10 is provided with an outlet opening 20 communieating with the outlet pipe 21. Adjacent the lower portion ofthe generator l() is arranged an annular manifold or tuyre 22' provided with a plurality of spaced openings 23 communicating with the interior of the generator 10. A plurality of thermo-couples 24 are arranged at spaced points in the gen- A erator 10 between the tuyre 22 and the top of the generator and a plurality of sight glasses 25 are' arranged in the wall of the generator 10 in the upper portion thereof.

A heater 26 similar in construction to a hot air furnace is arranged adjacent the ber of the heater 26 is connected by the pipe 29 to the tuyre 22 and the upper portion of the outer chamber of the heater 26 is connected by means of a pipe 30 to a heat interchanger designated generally by the numeral 31.

The heat interchanger 31V is of the usual tube boiler construction and is provided with an outer casing 32 and a pair ofheaders 33 connected by a plurality of tubes or pipes 34. The lower portion of the heat interchanger 3l is provided with an inlet pipe 35 and the outer portionof the heat interchanger 31 below the upper of the headers '33 is provided with a pip 36 communicating with the opening 20 1n the generator 10. The

outer portion of the heat interehanger 31 v above the lower of the headers 33 is provided With an outlet pipe 37 communicating with the lower portion of a counter-current scrubber 38 in which is preferably disposed a body of sponge iron nodules 39. The upper portion of the scrubber 38 is provided with a liquid inlet pipe 39 having a control valve 40 and the lower portion of the scrubber 38 is provided with an outlet pipe 41 having a control valve 42. The liquid inlet pipe 39 is preferably provided with la suitable nozzle 43 which is adapted to deliver a spray of liquid on to the sponge iron A39. The upper portion of the scrubber 38 is provided with an outlet opening communicating with the pipe 44 which is connected to a pump 45 designed to deliver gases under pressure through the pipe 46 into the ammonia water counter-current scrubber 47. The scrubber 47 is provided with a plurality of staggered baiiie plates 48 over which is delivered liquid A from the tank 49 which is connected to the scrubber 47 by means of the'pipe 48. The tank 49 is provided with a gas outlet opening 50 in the upper portion thereof, a gauge 51, and an inlet pipe 52 arranged adjacentthe lower portion of the tank 49. The lower portion of the scrubber 47 is provided with a liquid outlet pipe 53 having a control valve 54 and the upper portion of the scrubber 47 is provided with a gas outlet pipe 55 communicating with the gasholder or gasometer 56. f 1

The gas holder- 56 is connected by the pipe 57 to the'compressor 58' which is in turn connected by the pipe 59 to the oil separator 60 provided at-the bottom thereof with a blow-off or discharge pipe 61 having a control valve 62. A pipe 63 connects the upper portion of the oil separator '60 with a coil 64 arranged in a brine tank 65 and which is connected by means ofy a pipe 66 with a rose nozzle 67 arranged in a liquid ammonia receiver 68. The upper portion of the receiver 68 is provided with a gas outlet pipe 69 communicating with a rugged or sacrilice catalyst converter 70 which is connected by the pipe 71 to a trap 72 which servesto prevent liquid ammonia from surging back into the converter 70. A pipe 73 connects the trap 72 with a coil 74 arranged in the brine tank 65. The coil 74 is connected by means of a pipe 75 to the union 76 which is connected by the pipe 77 to the coil 78 arranged in thefbrine tank 65. The coil 78 is connected by the pipe 79 to a rose nozzle 80 arranged in a second liquidy ammonia receiver 81. The receiver 81 is connected by the pipe 82 to the ammonia converter 83 which is connected by the pipe 84 to the coil 85 arranged in the brine tank 65. The coilA 85 is' connected by a pipe 86 to the circulating pump 87 which is in turn connected by the pipe 88 to the union 76.

The lower portion of the liquid ammonia l receiver 81 is provided with an outlet pipe 89 which communicates with the receiver 68. The receiver 68 is provided adjacent the lower portion thereof with an outlet pipe 90 connected to an expansion valve 91 which communicates with a coil 92 arranged in the brine tank 65. The coil 92 is connectedby the pipe 93 to the ammoniagas outlet pipe 94 which is provided with a control valve 95. The pipe 93 also communicates with the pipe 96, having a control valve 97, which is adapted to deliver ammonia gas to the gas and liquid mixer 98. The mixer 98 is also provided with a water inlet pipe 99 having a control valve 100. The mixer 98 is connected by the pipe 52 to the tank 49 into which it is adapted to deliver ammonia water.

In the preferred practice of our process nodules of sponge iron preferably of the size of a hens egg, are delivered from the hopper 16 by the trap feeder 15 into the gas generator 1() which is filled with such sponge iron nodules. A mixture of steam and air in suitable proportions to form a mixture of hydrogen and nitrogen adapted for use in the synthetic production of ammonia, and preferably'in the proportions of 24 volumes of steam to 6 volumes of air is introduced into the inlet pipe 35 of the heat interchanger 31 where it passes through the tubes 34 and is preheated by the hot gases discharged into the heat interchanger 31 from the pipe 36 when the process is in operation. The mixture of gases is then passed into the outer or air chamber of the furnace 26 where it passes downwardly and is discharged therefrom through the pipe 29 into the tuyre 22 from which it is discharged through the openings 23 into the generator 10. v i

In the gas generator 10 the hot gaseous mixture of steam and air reacts with the sponge iron to oxidize the iron and produce hydrogen and nitrogen. The general reactions of steam and air with iron at an elevated temperature are indicated by the following equations: v

However', since in actual practice of our process We find that both ferrous-ferrie oxid (Fe304) and ferrie oxid (Fe203) are formed, it is believed that the steam first reacts with the sponge iron to form ferrous-ferric oxid and that a portion of this oxid is reduced by the air to form ferrie oxid, the reactions probably taking place according to the following equations:

In order to insure rapid and com plete oxidation of the sponge iron the temperature within the generator 10 is preferably maintained at approximately 500 C., and the steam and air mixture is introduced into the generator 10 from the furnace 26 at preferably not more than 2000 C., below the reaction temperature. At the beginning of the process it is necessary to preheat the incoming air and steam, and the furnace 26 is fired and maintained at the desired temperature. After the process is in operation the reaction is more than thermally self-sustaining and for each cubic foot of the hydrogen and nitrogen mixture produced approximately 66 B. t. us are produced. The fire in the furnace 26 is then extinguished or permitted to die out and the temperature in the generator 10 is controlled by regulating the draft openings 28 to admit cold air therethrough.

The temperature at various points in the gas generator l0 is ascertained by the thermocouples 24 connected to suitable recording instruments (not shown) and the conditions within the generator may be viewed through the sight glasses 25.

It will be apparent that during this operation of the process the sponge iron immediately above the tuyre 22 will be first oxidized and if the material is not removed the zone ofl oxidation will move upwardly through the generator 10. However, We prefer that the upper limit of the zone of oxidation does not advancematerially above the center portion ofthel generator. Hence the iron oxid is removed through the bottom of tain the upper limit of the zone of oxidation at a given point in the generator, and unoxidized sponge iron is fed from the hopper 16 at the same rate at which the iron oxid is being removed in order that the generator 10 w'ill be filled at all times.

The hydrogen and nitrogen in the generator 10 together with minor impurities are discharged through the pipe 21 into the outer chamber of the heat interchanger 31 from which the gases are discharged into the counter-current scrubber 38. A spray of water is delivered from the nozzle 33 downwardly through the scrubber and the action of water on the hot gases entering through the pipe 37 causes the water'in the lower portion of the scrubber 38 to be converted/into the steam whereby the unoxidized sponge iron nodules disposed in the scrubber 38 are heated to an elevated' temperature at which the sponge iron will react with certain of the impurities present in the incoming gases, such, for example, as small amounts of carbon monoxide and these impurities are removed in this manner from the gas mixture. If any solid particles such as iron oxid dust from the generator 10 are entrained in the gases these particles are removed during the passage of the gases through the counter current scrubber 38.

The gases are cooled by the Water in the scrubber 38 and discharged therefrom into the pipe 44 from which they are conducted to the compressor 45 which forces the gases upwardly through the counter-current scrubber 47 in intimate Contact with the ammonia water which passes downwardly over `the baflle plates 48 and which is discharged through the pipe 53 at the desired rate. The ammonia water is delivered to the countercurrent scrubber 47 from the tank 49, which is fed by the pipe 52 from the gas and liquid mixer 98.v Any oxygen present in the water is, due to the presence of ammonia, liberated from the water and discharged from the tank 49 through the opening 50. The hydrogen and nitrogen mixture passing upwardly through the scrubber 47 is freed from impurities such as carbon dioxid and other impurities capable of reacting with the ammonia water to form soluble compounds and the mixture, completely purified except for minor amounts of water vapor is discharged from the scrubber 47 into the gas holder 56 where it is retained for use in the ammonia synthesis unit hereinafter described.

The ammonia factor gas mixture is conducted from the gasometer or gas holder 56 through the pipe 57 to the compressor 58 wherein the hydrogen-nitrogen mixture is compressed to about fron 1,000 to 10,000 pounds per square inch, preferably about 4,500 pounds per square inch, and forced into the oil separator 60 where any oil from the -compressor 58 'entrained in the gas mixture and the bulk of water vapor present in the gas mixture is removed. The factor gases are then conducted through the cooling coil 64 into the liquid ammonia receiver 68 which contains a predetermined amount of liquefied ammonia gas therein. The gases are discharged into the body of the liquefied ammonia gas in the form of small bubbles from the rose nozzle 67 whereby any water vapor and other minor impurities remaining in the gases are to a large extent removed. The gases are then conducted through the pipe 69 into the rugged or sacrifice catalyst converter 70 which serves both to convert a portion of the gases into ammonia and to further purify the gases in the usual and well known manner. The uncombined factor gases and the ammonia formed in the converter 70 are conducted through the cooling coil 74 to the union 76 where the gases are mixed with the ammonia which has been produced in the converter 83. and ammonia is conducted through the cooling coil 78 wherein the bulk-ammonia present is condensed and the resulting mixture is delivered through the rose nozzle 80 into the liquid ammonia receiver 81. The liquid ainmonia delivered into the receiver 81 passes therefrom through the pipe 89 into the lower portion of the receiver 68. The uncombined factor gases now completely purified are del liveredithrough the pipe 82 into the converter 83 where, in the usual and well known manner, a certain proportion of the factor gases are combined in the presence of a suitable catalyst to form ammonia and this gaseous This mixture of factor gases ammonia is discharged through the pipe 84 into the cooling coil 85 wherein the bulk of ammonia is condensed and is circulated by means of the circulating pump 87 which is lubricated by the liquid ammonia passing therethrough to the union 76 where it mixes with the new factor gases introduced through the pipe 75 and the mixture of ammonia and uncombined factor gases passes through the coil 78 where any gaseous ammonia present is condensed and into the receiver 81 where it is collected. f

The level of the liquid ammonia in the receiver 68 is preferably controlled by the expansion valve 91 to which the liquid ammonia is delivered by the pipe 90 and by whichthe.- i

liquid ammonia is expanded into the cooling coil 92 where with the absorption of heat the ammonia serves to lower the temperature of the brine in the brine tank 65 to cool the cooling coils arranged in the brine tank. The gaseous ammonia from the -coil 92 is discharged into the pipe 93 and the major portion of the ammonia is discharged into suitable gas holders (not shown) through the pipe 94. A small portion of the gaseous ammonia 4is conducted through the pipe 96 to the ammonia and Ywater mixer 98 where it is mixed with water introduced through the pipe 99.

This ammonia water is delivered. through the pipe 52 into the tank 49 which feeds the ammonia water scrubber 47 and from which it is discharged through the pipe 53 for use preferably as a source of commercial ammonia compounds..

As heretofore stated our process is applicable to the production of hydrogen on a very economica-l and practical basis. In the preparation of hydrogen steam is introduced into the inlet 35 of the heat interchanger 31 and is conducted through the furnace 26 into the gas generator 10 where the steam reacts with the sponge iron at an elevated temperature to form hydrogen and iron oxid. As in the case of preparing ammonia factor gases, the iron oxid produced is discharged from the generator 10 at the desired rate and unoxidized sponge iron is delivered through the trap feeder 15 into the generator 10 at the same rate at which the iron oxid is being removed in order to keep the generator 10 completely iilled with sponge iron. The iron oxid discharged from the generator 10 is removed and is'preferably employed in the manufacture of steel or is reduced in the usual manner and reused in the practice of our process.

In the practice of our process we have found that ,from six tons of sponge iron which may be obtained at approximately $4.00 per ton we are able to produce approximately one ton of the hydrogen-nitrogen mixture, such mixture therefore costing approximately $24.00 a ton or 241;*l per cubic feet of gas. It will be readily apparent that this amount is several times less the present cost of am-l monia factor gases. Moreover, the gas mixture is substantially pure with the result that a materially greater life is afforded the catalyst employed in the ammonia converter, whereby a material saving in expense is effected.

While we have described in detail the preferred practice of our process and the preferred form of apparatus to be used in connection therewith it is to be understood that the shape, size and arrangement of parts of the apparatus and that the details of procep dure and proportions of ingredients in the practice of our process may be widely varied Without departing from the spirit of the invention or the scope of the subjoined claims.

We claim 1. The process of producing hydrogen and nitrogen which comprises contacting iron in activated form with steam and air at an elevated temperature.

2. The process of producing hydrogen and nitrogen which comprises intimately contacting a current of nodules of iron in' activated form with a current of steamand air at an elevated temperature.

3. The process of producing hydrogen and nitrogen which comprises intimately con,- tacting a current of nodules of sponge iron 5. The process of producing hydrogen and nitrogen which comprises'passing a current of sponge iron through a chamber, passing a current of steam and air through the apparent volume occupied by said sponge iron, and maintaining an elevated temperature in said chamber.

6. The process of producing hydrogen and nitrogen which comprises passing-a current of sponge iron through al chamber, passing la current of steam and air counter-current- Wise through the apparent volume occupied by said sponge imm-maintaining an elevated temperature in said chamber, and conducting olf the gaseous products formed.

7. The process of producing hydrogen and nitrogen Which comprises intimately contacting a current of iron nodules with a current of steam and air at an elevated temperature, and regulating the flow of the current of iron with respect to the flow of the current ofp steam and air in such manner that the steam and air in excess of the amount required to oxidize a given amount of iron willcontact with unoxidized iron. i

8. A process of producing ammonia factor gases which comprises contacting a mixture of steam and air with sponge iron at an elevated temperature, the steam and air being present in such proportions that the hydrogen and nitrogen produced will occur substantially in the proportions of three volumes of the former to one volume of the latter.

9. A continuous process of producing ammonia factor gases which comprises malntaining a ilow of a current of sponge iron and a counter-current flow of a current of steam and air in intimate contact therewith at an elevated temperature, ing present in such proportions that the hydrogen and nitrogen produced will occur substantially in the proportions of three volumes of the former to one volume of the latter.

10. A process of the character described which comprises intimately contacting steam and air with nodules of sponge iron at an elevated temperature, separating the iron oxid from the hydrogen-nitrogen gas mixture formed, and washing said gas mixture with water and ammonia to remove substantially all of the impurities present.

In testimony whereof we affix oursignathe steam and air be-

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