US1923897A - Treating gases - Google Patents

Description

Aug 22 1933- G. F. UHDE TREATING GASES Filed March 1. 1929 Patented Aug. 22, 1933 jSTAT-:Es

TREATING- GASES `Greorg Friedrich Uhde, Bovinghausen, Germany, assignor to the firm Patentverwertungs A. G. Alpina, S. A. pour LExploitation de' Brevets Alpina, Patents Exploitation Cy. Alpina Ltd.,

Basel, Switzerland Application March 1, 192.9,seria1 No. 343,726, andv in Germany March 1, 1928 14 Claims.V (Cl. 23-199) My invention refers to means for carrying out chemical reactions in the gas or vapour phase. Ithas particular reference to the synthetical production of ammonia from its elements and more especially to means whereby a gas which shall take part in the reaction, can be heated up to a temperature at which it will be prepared to react with vanother gas under the influence of suitable catalysts.

As is well known to those skilledY in the art, gases containing hydrogen, when placed under high pressure and heated to temperatures near and above 400 C. are liable to act on iron and iron alloys, so that those parts of the reaction apparatus which consist of iron and iron alloys, will be gradually destroyed or at least their mechanical resistivity and strength will be impaired so that the life of such apparatus is shortened. Means have already been'devised for overcom- .20 ing these difficulties as far as those parts of the apparatus are concerned, such asthe autoclaves or converters, in which the gases react witheach other. However, hitherto those parts of the apparatus, in which the gases are heated up before Y Owing to the large surfacel of these pre-heating devices the transmission of heat couldnotbe rendered suiciently uniform to prevent local overheating to temperatures at which a speedy destructionof the apparatus takes place. If it was desired to obtain a certain average temperature, some parts of the apparatus had to be heated to a higher temperature.

According to the present invention I obviate these drawbacks by heating the gases up to the required temperature, which as a rule is below .500 C. by causing them to flow in countercurrent and in heat exchanging relation to a foreign hot inert g'as, for instance nitrogen, which is preferably placed under pressure. By the term foreign I wish to distinguish the hot inert gas, such as nitrogen, from the gases about to take partl other gases used in this reaction contain impurities which, when in Contact with the catalysts radiation must be supplied by heating the gases gases, such as nitrogen, do not exert such influence on iron. I prefer heating the inert gas,

rsuch as nitrogen, in a gas furnace either directly or by causing it to pass through a molten metal such as lead, Athe nitrogen or the like flowing through a heating coil immersed in a bath of molten lead which is maintained in molten condition and at the temperature required by means of some suitable furnace.

Preferably the heating-up of the reaction gases by means of lhot `nitrogen or the like is utilized only for bringing these gases, which have already acquired a temperature approaching reaction temperature, tothis reaction temperature so that the hot nitrogen is required to Vprovide only for the heating-up of the gases within a small range of temperature. To thisend the fresh gases designed to react. are preferably brought in heat exchanging relation, vpreferably in counter-current, with the hot gases escaping fromk the reaction chamber. Inl this manner the'` fresh gases are already heated up to a certain temperature approachingrreaction temperature, but, inthe case of gasescontaining hydrogen, remaining `below 400 C., at which temperature hydrogen does S0 not exert any detrimental action on iron. The gases which have thus been preheated to a temperature below 400"v C., are then brought in heat exchanging relation in, countercurrent to' the hot nitrogen'and are thus heatedfup to kthe tempera- 85 ture which is required for the carrying'through of the reaction. i 1

If this invention is applied to the synthetic production of ammonia, the new mode of .heating gases up, -apart from` being lapplied to the fresh gases entering the converters, may also be applied with particular advantage to the purifying step preceding reaction. As is well lnown to those skilledA in the art, the hydrogen and promoting reaction, are knownto exert a detrimental action on these catalysts,` whereby the catalysts are frequently deprived altogetherof their catalytic activity. Therefore the gases be- ,100

fore being heated up for reaction are as a rule subjected to a purifying process in order to remove all obnoxious impurities. ,This purifying action is obtained if the gases are passed at an 10F elevated temperature over special purication y f) catalysts and as the reaction which takes place in Contact with these catalysts, is only slightly exothermic, more especially if the percentage of impurities is not very great, the losses of heat by up again. This heating-up is preferably carried out also by means of hot nitrogen or some other inert gas.

I prefer placing the hot nitrogen or other inert gas under high pressure.

The reaction between ammonia and hydrogen, if high concentrations by volume are used, is connected with a great development of heat so that the gases leaving the converter have a far higher temperature than the gases entering same, and therefore in such cases the gases entering the converter can be heated up sufiicientlyby heat exchange with the gases leaving the converter. Therefore the heating-up by means of hot nitrogen or some other inert gas is particularly useful, as far as the reaction between hydrogen and nitrogen is concerned, mainly in those cases, where the gases are brought to reaction at low concentrations, where the heat developed in the reaction does not sufce for the heating-up of the entering gases. Similar conditions prevail, when the converters are being heated up before starting the synthetic process or when the contact mass in the converters is partly spent or less eiicient.

In the drawing aixed to this specification and forming part thereof an apparatus embodying my invention is illustrated diagrammatically by way of example.

Referring to the drawing, l is an ovenheated with a mixture of gas and air, the heating gas entering through the burner 2, while air `enters through a port 3. In the furnace is mounted a container 1i lled with lead and surrounded by a casing 5. The gases of combustion from this furnace pass through between the walls of the container 4 and the casing 5 and escape through an exhaust conduit 6. In the molten lead in the container Il is immersed a heating coil 7 into which nitrogen under high pressures substantially above atmospheric, for instance 100 atms. is introduced through a pipe 8l leading to acompressor 9. From the bottom end of the heating coil 7 a pipe 10 which is branched at 11, leads to the inlet pipes 12 of two heat exchangers 13, the exhaust pipes 14 of which are connected by means of a pipe 15 with a heat exchanging device 16 from which a pipe 17, on which a cooler 18 is mounted, leads to the suction side of the compressor 9. 19, 19 are pipes extending through the heat exchanging devices 13, 13. v20, 2) are re' ducing valves inserted in the pipes.

In the operation of this device nitrogen under pressure is forced by the compressor 9 through pipe 8 into the heating coil 7, where it is heated up to the temperature of the molten lead in the container 4. The hot nitrogen under pressure now passes through pipes 10 and 12 into the heat exchanging devices 13, heating up therein the hydrogen or other gas, which flows through the pipes 19 in countercurrent with the nitrogen. The hot nitrogen under pressureafter having transmitted part of its heat to the hydrogen, escapes from the heat exchanging device'through pipes 14- and pipe 15 into the heat exchanging device 16, to transmit the greater part of the heat still stored in it to the fresh nitrogen forced by the compressor 9 through pipe 8 into the heatn ing coil, this fresh nitrogen flowing in countercurrent to the spent nitrogen, which in returning to the compressor through pipe 17, is cooled down in the cooler 18.

In theV lead bath the nitrogen is for instance Vheated up to 320 C. and its temperature in the heat exchangers 13 is about 300 C. while on bdisclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

In the claims afxed to this specification no selection of any particular modification of the invention is intended to the exclusion of other modificationsthereof and the right to subsequently make claim to any modification not covered by these claims is expressly reserved.

I claimzj 1. In the synthetical production of ammonia Yby catalytic reaction the step of heating up the hydrogen by bringing same in heat exchanging relation with a foreign hot inert gas, While acting thereon with purifying means.

2. In the-synthetical production of ammonia by catalytic reaction the step of heating up the hydrogen by bringing same in heat exchanging relation with a foreign hot inert gas, while acting thereon with a purifying catalyst.

3. In the synthetical production of ammonia by catalytic reaotionthe step of causingthe hydrogen to flow in countercurrent and in heat eX- changing relation to foreign hot nitrogen under pressure over a purifying catalyst.

4. The method of carrying out reactions between gases or vapours in reaction chambers comprising conducting fresh gases or vapours first in heat exchange relation to hot gasesV leaving the reaction chambers and thereafter heating said preheated fresh gases up further by conducting same in heat exchanging relation with a foreign hot inert gas. j

5. The method of 'producing ammonia from hydrogen and nitrogenby catalytic action ina reaction chamber comprising conducting fresh hydrogen in heat exchanging relation and in countercurrent to hot gases escaping'from Ythe reaction chamber and then conducting the thus preheated hydrogen in heat exchanging relation and in countercurrent to foreign hot nitrogen under pressure.

6. In the treating and reacting at high temperatures of gases and vapors corrosive to metals 'at said temperatures, the step which comprises ino heating such a gas or vapor by bringing it into heat exchanging relation with a hot, confined stream of a foreign, non-corrosive gas under pressures substantially above atomspheric.

'7. The'process of claim 6 in which the heated foreign gas is passed countercurrent tothe gas or vapor to be heated.

8. The process of claim 6 in which the gas to be heated is hydrogen and the reaction is the synthetic production of ammonia.

9. In the synthetic production of ammonia by catalytic reaction, the step which comprises heating the hydrogen required in said reaction by bringing it into heat exchangingV relation with a hot, confined stream of a foreign gas under pressures substantially above atmospheric; theY said foreign gas being non-corrosive to metals at temperatures approaching reaction'temperatures.

13. The process of claim 9 wherein the foreign gas is nitrogen heated to a temperature ranging from about 300 to 400 C. and under high pressures ranging up to 100 atmospheres. n

14. The process of claim 9 wherein the foreign gas is heated by passing the same into heat exchanging relation with a bath of molten metal.

GEORG LFRIEDRICH UI-IDE.

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