DE580876C - Process for the pretreatment of carbonization gases for decomposition by compression and deep freezing - Google Patents

Description

Process for the pretreatment of carbonization gases fair through the decomposition Compression and Freezing The present invention relates to decomposition of carbonization gases through compression and deep freezing and aims to make the extraction more valuable To facilitate products made from such gases and to increase the quantity thereof. To the To achieve these purposes, the gases are subjected to a pretreatment before decomposition, which leaves its hydrocarbon content unchanged, the hydrogen content increases, while reducing that of carbon dioxide that is difficult to liquefy.

The pretreatment of the gases according to the invention takes place in a still warm, highly water vapor-containing state and consists in passing them over catalysts at about 500 ° in connection with subsequent liberation of the gases from hydrogen sulfide and carbonic acid after cooling. The treatment of the gases with catalysts brings about a conversion of a considerable part of the carbon oxide contained in the gases according to the well-known reaction equation CO + H20 - CO, + H .., whereby the water vapor contained in the hot gases can be used and due to the strong reduction in the carbon oxide content the precondition for the convenient implementation of the decomposition by compression and freezing is created as soon as the hydrogen sulphide and carbonic acid have been eliminated in a known manner. The carbon oxide content can be reduced to z to q by the treatment mentioned. ° 1o be reduced. Such a carbon oxide content is low enough to make a separation of the most difficult to liquefy hydrogen in the gas mixture unnecessary by a special fractionation step during the compression and freezing of the gases, especially if the hydrogen is not as such, but mixed with nitrogen for the ammonia synthesis should be used. The carbon oxide can then be washed out of the gas mixture remaining after the liquefaction of the hydrocarbons with liquefied nitrogen, a mixture of hydrogen and nitrogen remaining behind.

Compared to the process of direct separation of the carbonization gas components by compression and cooling results in the aforementioned partial implementation of the carbon dioxide in hydrogen and carbonic acid has the particular advantage that the im Heat of evaporation contained in the water vapor of the carbonization gases for the conversion process of the carbon monoxide is made usable and that the directly obtained from the carbonization gases Amount of hydrogen becomes much larger.

The pretreatment to be carried out according to the invention for the carbonization gases before Performing the process of separating the components by compression and deep freezing coincides with a method known for luminous gas, which works towards reducing the carbon dioxide content of the luminous gas as much as possible to be able to store this in a compressed state in steel bottles without contamination of the gas by iron carbonyl occurs, which occurs in the presence of somewhat larger amounts of carbon oxide in the luminous gas when the latter is stored forms in steel bottles. In the method according to the invention, the weight point is different the reduction of carbon monoxide to the point where harmful impurities can be avoided entirely by using iron carbonyl when stored in steel bottles because storage of carbon dioxide-containing carbonisation gas is out of the question at all comes because the gas mixture components anyway by compression and freezing from each other be separated. The previously known cleaning process for luminous gases put it accordingly in no way close to a method of separating the components of the carbonization gas a pretreatment of the still hot, steam-containing ones by compression and deep freezing Let gases enter, eliminating some of the carbon dioxide in the same way is converted into hydrogen and carbonic acid, as is the case with the cleaning process happens according to the older invention at luminous gas.

To carry out the conversion of the carbon monoxide with the steam The carbonization gases can be those already proposed for the reaction, from metal oxides existing catalysts are used, e.g. B. the oxides of iron, chromium, nickel, Zinc alone or in mixtures with one another and, if necessary, with joint use of activators such. B. alkalis and rare earths.

The new process can be implemented in various ways.

With some types of coal you can work in such a way that you can get all of them Carbonization gases without prior condensation directly over the catalysts at a suitable one Temperature, which is close to 500 °, passes through. In such cases it is sufficient often the water vapor escaping from the moisture of the raw coal to induce it the desired implementation, so that the use of live steam either entirely dispensable or only required in very small quantities.

The large amount of water vapor which such carbonization gases from the raw coal and which, by the way, for the conversion of the carbon dioxide into carbonic acid is required, causes even the hydrocarbons contained in the carbonization gases with several atoms of carbon, such as. B. ethylene, ethane and their homologues, which are known to be quite sensitive to heat, despite the relatively high Conversion temperature of about 5oo ° C are preserved and by far the largest Part remain undecomposed.

One can also work in such a way that one gets out of the smoldering gases first the more easily condensable by-products and the entrained by-products in the usual manner Separates water vapors, most of the hydrogen sulfide in one of the known ways and only then the carbonization gases, with a sufficient amount Water vapor mixed, passed through the iron-containing catalysts at around 500 ° C.

The nature of the shift in the composition taking place here of the gases can be seen from the following exemplary embodiments: Smoldering gases from further The composition reported below were at temperatures between 450 and 600 ° C passed over a catalyst, which by decomposition of a mixture of about 8.5 per cent iron nitrate and 15 per cent chromium nitrate were formed. As a carrier for this Pieces of pumice stone, potsherds and also slightly annealed bauxite pieces were the catalyst used.

The humidity of the raw gases to be treated was measured in such a way that it corresponded to a degree of saturation of the gases in humidity at 60 to 80 ° C and thus amounted to up to 700 g of water per 1 cbm of dry carbonization gas with a content of 18 to 24% carbon oxide . This amounts to about 1 to 3 parts of water vapor to 1 part of carbon dioxide.

Since the method of operation described here is based on a complete or even almost complete removal of the carbon dioxide does not matter, so you can get by with 1 to 1.2 parts of water vapor for 1 part of carbon oxide. A somewhat larger excess of water vapor disturbed the environment. setting not, a on the other hand, a very large excess reduced the conversion ratio.

A moderate content of sulfur and sulfur-containing compounds in the smoldering gases did not prove to be a hindrance to implementation.

In the list below, Ia, 11a, IIIa denote the composition of the original crude carbonization gas, Ib, Hb, IIIb denote the composition of the gases after the catalytic treatment and Ic, IIc, IIIc denote the composition. of the same gases after the carbonic acid and, if present, the hydrogen sulphide had been removed from them in some known manner: CO, C @ Hy C O H, C2H6 C11.4 N .; Ia io.8 @ 5.2 I8.4 35 3, II 2 =, I 6.1 Ib 2I, 3 4.6 4.2 42 3.6 I7.3 6, I. Ic - 5.8 5.3 53.0 4.5 22.0 7.7 Ha 2 0 , 7 4, I 22.8 2o, 6 3.3 23, I 4.2 IIb 3I, 1 3, I 6.6 30.5 3.5 20, I 5, I. IIc - 4.5 9.5 44.5 5.7 29.0 7.4 IIIa I7 4.8 23.9 22 3.9 23.5 4.6 IIIb 3I, 6 4 2.4 32.5 4, I 18, I 7.3 IIIc - 5.8 3.5 47.516, o 27.5 9.3 As can be seen from this, after the catalysis and removal of the carbonic acid, a gas mixture is obtained which contains between 45 and 55% hydrogen without the hydrocarbon content decreasing in any noteworthy manner.

Even if row b has a slightly lower content of hydrocarbons than row a, this reduction is more of an apparent nature, because the treated gas mixture has an increase in volume of about 15 % at the transition from row a to row b.

The gases catalyzed in this way are brought to air temperature in heat exchangers cooled, with the entrained, already contained before the catalysis as well any easily liquefiable hydrocarbons newly formed during catalysis and the water separates in liquid form. Thereupon the carbonic acid and the rest Hydrogen sulfide from the gases thus pretreated in a manner known per se removed by the carbonization gases, for example by means of brown iron ore, Luxscher mass or solutions containing iron oxide are treated. After removing the hydrogen sulfide the carbonic acid, be it by washing with water under pressure, be it by Treatment with caustic alkalis, freed from their carbonic acid content.

In view of the fact that the smoldering gases are already rich in themselves Are carbonic acid and even more carbonic acid due to the treatment described here are further enriched, it can easily happen that the total content of the carbonization gases of carbonic acid is around 3o to 40%. It may therefore be advisable to to technically utilize the carbon dioxide leached from the smoldering gases, be it. for the production of liquid or solid carbon dioxide, be it for chemical reactions.

The so pretreated and pre-cleaned gas, which now consists essentially of, for example, 26 % methane and homologues, ir % ethylene, ethane and their homologues, 6% carbon oxide, 53% hydrogen, r 0Io oxygen and 30% nitrogen Pressure from, for example, ten to thirty atmospheres. pre-cooled and then in the known gas separation apparatus, be it using an external cooling bath, be it by means of expansion with the performance of external work, cooled down so deep that the hydrocarbons in the liquefied state separate out completely and only hydrogen with very small amounts of nitrogen and carbon oxide in gaseous form remains.

The quantities that accumulate in each part of the apparatus liquid hydrocarbons can be expanded and gasified together; if it but it depends on the individual hydrocarbons e, such. B. propane, ethane, Ethylene, methane, etc., by themselves or at least in a highly enriched state one can get the fluids that accumulate in individual places subject to a single or multiple rectification.

Here the hydrogen can be obtained in a very pure state, if one cools it down in a known way so much that the small, Amounts of carbon dioxide and nitrogen carried along by it liquefy. It will come however, on using the hydrogen for ammonia synthesis, whereby it has to be mixed with nitrogen anyway, the carbon oxide can be used in a known manner Way completely removed by washing out the hydrogen with liquid nitrogen will. The method of operation, in particular the evaporation of the liquid Nitrogen and optionally the addition of gaseous nitrogen, regulated in this way be that the escaping carbon oxide-free gas mixture required for the synthesis @ usa.mmenstellung, z. B. 75 0% o hydrogen and 25 0lo nitrogen, and is therefore ready for catalysis.

Claims (1)

PATENT CLAIM: Process for the pretreatment of carbonization gases for the Disassembly by compression and freezing, characterized in that the still warm raw gases containing a lot of water vapor by passing over catalysts about 500 ° of the greater part of their carbon monoxide content and, after cooling, of hydrogen sulphide and be released from carbon dioxide.