US2133496A - Gas generating process - Google Patents

Description

Patented Oct. 18, 1938 UNITED sTATEs PATENT or-'FlcE the-Rhine, Germany,

assigner: to I. G. Far-- benlndustrie Aktiengesellschaft, Frankfort-ontlie-Main, Germany Application November 16, 1934, Serial No. 753,317 In Germany November 16, 1933 7Claims.

The present invention relates to improvements in the carrying out of reactions in periodically heated chambers.

Many reactions taking place at high temperatures and in which carbonaceous materials are converted proceed with the deposition of carbon, which, depending on the conditions of the reaction is formed as graphite, carbon black or coke. These reactions, as for example the thermal splitting of gaseous hydrocarbons of the methane series or gaseous olefines or of oils or tars or their distillation orl conversion residues into gases rich in hydrogen, may be carried out in many case with advantage in periodically heated chambers provided with a heat-accumulating lling material, which if desiredI may also exert a catalytic action (said chambers being .called cowpers) since in these chambers the carbon deposited during the conversion period is burnt out in the heating period and may thus be made useful for the heating up of the chamber. Y

Sometimes, however, itis difllcult to burn outv the carbon from all places of the cowper in such a manner that a uniform heating up of the cowper takes place. This is especially the case when the carbon is deposited at different places of the cowper and in diiexent quantities. In order to avoid local overheating the cowpers hitherto were heated up in such cases in long heating periods and while at the same time cautiously adjusting the amount of the combustion air, which operation, of course, is uneconomica-l.

In order to attain a uniform temperature throughout the whole cowper it has already been proposed to add the oxygen-containing gases in stages and at different places `of the cowper to the heating gases.' However, also in this case difficulties are encountered by local overheating if the deposition of carbon during the reaction period is a large one.

We have now found that the aforesaid diniculties are removed and that a uniform temperature throughout the whole heat-regenerating chamber is attained in a sufciently short-time if these chambers are cooled before the conversion period, i. e. after havingvburnt out or while burning out -the deposited carbon in the heating period, by the additional supply of gases or vapors havinga lower temperature than the said chamber during the heating period or of gases or vapors capable of endothermically reacting with the deposited carbon or endothermically reacting in any other manner. These gases and vapors are hereinafter referred to as cooling gases and vapors. As such gases steam or carbon dioxide may be used with advantage. But also other gases or vapors may be successfully employed. The said cooling gases or vapors may be added -at different places and at each place l in different amounts, the addition being adjusted depending upon the particular local temperatures prevailing in the heat-regenerator in such a manner 'that a uniform heating of the whole heat-regenerator is secured. If the supply l0 of the cooling gases or vapors is to be eilected during the burning out of the deposited carbon it is preferable to employ `steam or carbon dioxide whereby combustible gases containing hydrogen and carbon monoxide are obtained at the l. same time. If the supply is eifected after the burning out also air may be used. In some cases it is also of advantage to add steam or carbon dioxide or inert gases together with oxygen-containing gases into the heat-regenerator at dif- 20 ferent places of the same. It is preferable to introduce the said additional gases, whether they enter with the deposited carbon into an endothermic reaction or not, directly into the zone or zones in which the carbon is deposited.

The above described manner of working is also useful in other reactions carried out with carbonaceous materials than those specically mentioned above provided that carbon is deposited at the high temperatures necessary for the conversion, since the process according to the present invention is not restricted to a particular reaction and relates more to the procedure in the period between two reaction periods. Thus the operation is also applicable to the production of olenes or aromatic hydrocarbons from methane or homologues of methane or gases containing the same if in these conversions substantial amounts of carbon are deposited.

We have also found that uniform temperatures in the heat-regenerators may also be established and that at the same time the carbon deposited in the chambers can be utilized by burning this carbon during the heating period by leading oxygen or air or other oxygen-containing gases di- 45 reetly into the zone of deposition, the resulting hot gases being led away through the cold parts of the chambers for the purpose of heating the latter. In this manner, the cooling of the still hot parts of the heat accumulator by the entering cold combustion air is prevented. Thus a considerable shortening of the heating period and consequently a considerable increase in the output are obtained. v

This manner of working may be carried out in different ways; for example after the reaction period, oxygen may be led directly into the commencement of the second half of the chamber (where the carbon has mainly been deposited) and the combustion gases may be led in the opposite direction to the previous flow of the initial materials to be decomposed and' out through the inlet for the latter, whereby the parts of the chamber cooled the most during the reaction period are heated.. The procedure may also be that the gases obtained by combustion of the deposited carbon are led in an attached Cowper apparatus the latter thus being heated. In some cases, carbon dioxide or steam may be mixed with the gases containing oxygen.

It is preferable to construct the insertions of heat-accumulating'. materials having a roughened surface and which, if desired, are catalytically active, as for example chamotte or materials which contain carbides, silicides, ferrites or chromites, so that the deposited carbon adheres well.

The process may be carried out at any desired pressure. y

The following examples, given with reference to the accompanying drawings which show diagrammatic vertical sections of arrangements of apparatus according to this invention, will further illustrate the nature of this invention, but the invention is not restricted to these examples or to the particular arrangements shown. The percentages are by volume.

Example 1 This example is given with reference to Figure 1 showing in a diagrammatic manner a vertical section of a cowper suitable for the conversion of oil residues into gases by cracking. In this Figure l, reference numerals I, 2 and 3 denote inlet pipes for oxygen containing gases. The pipes at the top of the cowper provided with valves are for the introduction of initial oil residue. The lateral outlets at the bottom are for the removal of the gas produced from the oil residues or of the waste heating gas respectively. The oil residues are sprayed from above into the heated cowper and are decomposed by the action of heat into gases rich in hydrogen, benzol, naphthalene, high temperature carbonization tar, coke and carbon black. The coke and the carbon black are deposited especially in the middle and in the lower half of the cowper. When the cowper is cooled down to a temperature no longer eieoting a. sufcient decompositionof the oil residues the cowper is heated with combustible gases and an excess of air both supplied from above to the cowper. Additional air or oxygen may be introduced through pipes I, 2 and 3 provided with nozzles. After some minutes the temperature rapidly rises to between 1400" and 1500" C. by the combustion of the carbon black and coke in the middle and lower part of the cowper. When adding after the combustion of the carbon suitable amounts of steam or carbon dioxide throughpipes I, 2 and 3 or through pipes 2 and 3 or through pipe 3 only the temperature in the middle and lower part of the cowper is reduced t0 between 1000 and 1100 C. I

Steam or carbon dioxide may also be added during the combustion of the deposited carbon, whereby, gases rich in hydrogen or carbon monoxide are formed while the cowper is cooled. By `the addition of the said cooling gases through pipes 2 and 3 the lower temperature of the upper part of the co'wper remains unchanged and the temperature of the middle part does not rise too high.

In this manner the time of heating for the thermal splitting of substances very liable to deposit carbon may be reduced to half that necessary in the .known processes, since it is possible to rapidly burn out the carbon without need for preventing local increases in temperature and for rapidly eliminating overheating. Thus the process is made much more economical.

As local cooling agents to be added before the conversion period there may also be employed gases or vapors which in the hot cowper are converted byan endothermic reaction, for example the conversion of methane or its homologues or natural gases or cracking gases or waste gases from the destructive hydrogenation 0I carbonaceous materials, into oleilnes and aromatic hydrocarbons in which case, however, it should be provided that no carbon is deposited, for example by employing a high rate of iiow or by the use of suitable refractory and checkerbrick. such as silicides or carbldes.

ing a diagrammatic vertical section of another' cowper. In this Figure 2 number Il denotes a nozzle for the introduction of initial crude oil residues. Nozzles I3 are for the introduction of gases containing oxygen. I 4 are outlets for the combustion gases, I5 and I6 gas pipes for the introduction of air and combustible gases. I'I is an outlet for the heating gases. Crude oil residues are sprayed through a nozzle II into the Cowper apparatus which is filled with bricks containing carborundum and heated to a mean temperature of 1000 C. Thermal splitting of the oil takes place whereby from each metric ton of oil, 900 cubic meters of a gas are obtained having the following composition:-

Per cent CO2 0.5 02H4 2.0 CO 0.5 H2 61.5 CH4 32.3 N2 3.2

After purication in the usual manner, this gas may be directly employed as illuminating gas. In addition to tar, there are also formed considerable amounts of carbon in the formv of carbon black, graphite and coke which settle mainly on the superiicially roughened bricks in the lower part I2 of the Cowper apparatus. When the reaction period is over, air is blown through nozzles I3 against the hot deposited carbon. Thereby the carbon is burned and the combustion gases, passing upwards, rapidly heat up the upper part of the Cowper apparatus the mean temperature of which has fallen ,to about 400 C. during the reaction period. .',The combustion gases leave at I4. lWhen the carbon has been completely burned, the heating up of the Cowper apparatus is completed by introducing gas and air through valves I5 and I6. These heating gases leave at I1.

Example 3 This example has reference to Figure 3 showing a diagrammatic vertical section of another Cowper apparatus. In this ligure numbers 24 and 28 denote two separate reaction chambers; 2| is a pipe for the introduction of initial crude oil residues; 23 denotes an air nozzle: 21 is a tained having the following composition:-

Per cent CO: 1.2 02H4 3.2 CO 11.2 Hz 55.4 CH4 25.5 Na 3.5

which leaves through the cowper 28 at a temperature of 900 C. and is subsequently subjected to cooling and washing. The carbon deposited on the bricks in the lower` part 22 of the cowper 24 is burned after the reaction period by blowing in air through nozzles 23 and the cowper 28 is brought completely to the reaction temperature by the hot combustion gases. When al1 the carbon has been burned, the valve 21 is closed and oil is thermally split in the cowper 28, while at the same time the cowper 24 is again heated to the reaction temperature by heating with gas (air valve 25, gas valve 26). The combustion gases leave at 29. The eilluent hot combustion gases may be employed for the preheating of oil and steam.

Example 4 This example has reference to Figure 4 showing a diagrammatic vertical section of another Cowper apparatus. In this figure numbers 3| and 32 denote two separate reaction chambers; 36 is a nozzle for the introduction of initial crude oil residues; and 48 are valves for the removal of hot reaction products or of hot combustion gases; 43 and 33 are valves for blowing in air; 38 and 39 are valves for the introduction of combustible gas and air respectively. In this Cowper apparatus the same reaction is carried out as described in Example 3. Firstly the ther- .malsplitting of the oil is effected in cowper 3|, oil and steam being sprayed in through a nozzle 36, while the hot reaction products leave `through the cowper 32 and the valve 35. During the reaction in cowper 3|, carbon is firmly deposited in large amounts on the bricks in the lower part 34. While the valve 35 is open, air is blown into cowper 3| through 33; burning of the carbon in 34' thus takes place and also strong heating of the lower part 31 of the cowper 32 to the reaction temperature. Any heat lacking is supplied to the cowper by means of gas and air through the valves 38 and 38, the valves 35 and 43 being closed and the valve 40 opened. The reaction is then carried out in the opposite direction,

heated to a temperature suicient for the conversion, to eiect the conversion and deposit the carbon on the filling material and after stopping the supply of said hydrocarbon material into said chamber heating it up again by combustion of thel deposited carbon, and passing from outside directly into the zone containing the main deposit of carbon a gas reducing the temperature of said zone so as to obtain a substantially uniform temperature throughout said chamber.

2. In the process as claimed in claim 1, the 4step of passing into the zone of the chamber in which carbon has deposited a gas having a lower temperature than that of said chamber during the heating period.

3. In the process as claimed in claim l, the step of passing into the zone of the chamber in which carbon has deposited a gas capable of ndothermically reacting with the deposited car- 4. In the process as claimed in claim 1, the step of passing into the zone of the chamber containing the main deposit oi? carbon a gas selected from the group consisting of steam and carbon dioxide.

5: -The process /tor' producing combustible gases by treatment of iluid hydrocarbon materials at a high temperature at which deposition of carbon takes place, which comprises passing said materials through a chamber provided with heat accumulating lling material and periodically heated to a temperature suilicient for the conversion, to effect the conversion and deposit carbon on the illling material and after stopping the supply of said hydrocarbon material into said chamber and between two normal conversion periods passing from outside directly into the zone containing the main deposit of carbon an endothermically reacting gas containing in addition oxygen and finally passing the gases resulting from the contact of the oxygen containing gas with the deposited carbon into the parts of the chamber having a lower temperature in said zone.

6. In the process as claimed in claim 5 the step of-passing oxygen into the zone containing the main deposit of carbon.

'7. In the process as claimed in claim 5 the step of passing air into the zone containing the main deposit or carbon.

FRITZ WINKLER PAUL FEILER.

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