DE492230C - Process for the decomposition of gas mixtures by liquefaction and rectification - Google Patents

Description

Process for the separation of gas mixtures by liquefaction and rectification To completely dismantle one composed of several components To carry out gas mixtures by liquefaction and rectification, it is necessary to in each rectification stage at the boiling point of the higher-boiling component Apply heat and a corresponding amount of heat at the boiling point of the lower remove the boiling component. The heat of condensation of the components to be broken down is in the. generally not sufficient for this, especially if the purity and Yield high demands are made, and you therefore have a special one Circulation of an auxiliary used, which the latter at a higher temperature and condensed under higher pressure to give off heat and under lower pressure and evaporates again at a correspondingly lower temperature while absorbing heat. Of the Temperature range over which heat transfer with such a circuit (Y can be carried out is often limited above by the critical temperature the auxiliary material used; downwards the limit is given by the fact that the suction of the auxiliary material under lower steam pressure because of the large to conveying volumes and the difficulty of heat transfer practically difficulties caused, so that one is reluctant to fall below div temperature at which the Vapor pressure of the auxiliary i at is. The simple auxiliary circuit is sufficient no longer works when -the boiling points of the components to be separated are very far apart, what especially when dismantling one consisting of three or more substances Mixture will often be the case.

The present invention enables such mixtures to be decomposed in a simple manner. Instead of one additive, two or more are used used whose evaporation areas are as far apart as the rectification of the mixture required. So now to avoid the big complication. which the arrangement would require several separate circuits with different auxiliary gases, wherein for each auxiliary gas a special compressor and different fee flow heat exchangers would be required, according to the present invention, a mixture of the various Used excipients that compress with a single compressor and in one single counter-flow is cooled. However, upon condensation, the mixture becomes decomposed using a partial condensation with rectification effect. As a result of this decomposition, several condensates of different types are obtained from the mixture Boiling temperature; each condensate is evaporated separately after expansion, namely at different temperatures, according to the different composition, so there (:, the condensation and evaporation practically have the same temporal range spanned as when using separate individual circuits. First night of \ 'crdampfun;.; the components are brought together again and together compressed.

The implementation of the procedure will be carried out by hand from the drawing for the decomposition of a mixture of three gases, e.g. 13. Methane, ethylene and propylene. explained. The boiling points of the three components are i i i, S ° and 169.33, respectively or 225.4- abs. So if you liquefy the mixture by compression and cooling t and first the most volatile component in a first rectification column - Separate the CH4 and in a second rectification column the remaining two components want to separate, a heat transfer of 112` abs. to 225- abs. necessary that cannot be achieved with a simple gas cycle.

In the figure, let i be the first rectification column, in which the mixture, which has been precooled by the expansion products in a (not shown) countercurrent heat exchanger and possibly liquefied at _; entry. An evaporation vessel 4 is provided below the column and a condenser 5 is provided above it. At 6 the . abe -separated, lower-boiling component -1lethane - from. The mixture of the higher-boiling components emerges in liquid form at 7 and is introduced at S into the second rectification column 2, which is again equipped with an evaporator 9 and a condenser 10. The most volatile component - propylene - leaves the column at ii, the ethylene exits at 12.

To carry out the rectification, according to the present invention an auxiliary mixture of two substances, e.g. B. methane and ethylene, in a compressor promoted to a suitable D: ruclc. Compressor and Gegenstxo-mer are for simplification the drawing, omitted above. The gate-cooled compressed mixture occurs at 13 into the condenser i4, which is located in a bath of liquid propylene. Of the \ -eriquid is set up so that the ver tlüssigren shares against the rising Gas flow after. flow downwards and interact with your gas over a large surface step. so that if the length of the condenser is sufficient, it can be dismantled to a large extent of the mixture enters and essentially pure ethylene in the lower part becomes liquid accumulates and can be removed at 15. After relaxation through valve 16 is this ethylene as a coolant in the condenser; it leaves the same at Sator .o a-17 in a gaseous state.

The remainder of the mixture in gaseous form, which is essentially ordered from methane, is called hot i S from the \ @ erd.unpftitigs; "efäf :,, led out andin a bath of liquid: \ ethylene that is in the 4. container. in the spiral i9 liquefied. To. Relaxation in valve 2o is used to charge the condenser 5 and occurs at 2 1 in gaseous form. The components emerging at 1 7 and 2 1 of the llilfsgeinisches are just like the components exiting at 6. i i and 12 of the bag to be dismantled in order to recover the cold in countercurrent heat exchange brought with warm, compressed gas.

The pressure at which the auxiliary mixture is to be conveyed must be so high be that both pure ethylene boil in a bath of below about i at pressure Propylene as well. pure methane turns into ethylene boiling under the pressure of the column can liquefy. For the former condensation a pressure of about i2ata sufficient, however, the second condensation requires a pressure of 24 ata if the methane boils in under i ata. If you work in the rectifil: ation column i and the evaporation: gsgefäß 4 with an overpressure of, for example, 1 all to the condensation to favor the methane in the reflux condenser 5, the pressure for the second Condensation in the spinals 19 can be increased to at least 35 atmospheres. On the latter So pressure is to compress the circulating mixture.

Any other gas mixture can be separated in the same way are executed. Should the dismantling be carried out in more than two stages. so can the second condensation instead of (as described) as total condensation as partial Condensation can be carried out with rectification, i.e. the spiral i9 through a return condenser. similar to 14, is replaced. The decomposition into The latter can be completed by the fact that under the gas inlet 13 a rel: tification column is provided in which the h; erabrieselude liquid is freed from the last fractions of the lower-boiling components. To this The purpose is then a heater - z. B. by, the condensing cycle mixture, before it enters the cutting facility at 13 - to protrude because the for the expulsion of the lower-boiling components in the necessary vapors generated by the rectification column. The reflux condenser 14 can also be replaced by a rectification column. in which the in a separate condensation device (which can again be used to heat the column) recovered liquid in known Way is rectified.

as cycle gas, any one of two or more components existing mixture are used, its components in your The temperature range required for the dismantling will condense and evaporate. E, s is particularly useful, B.estan: dteile, which in the gas to be decomposed itself are included to use, as then inevitable losses of the circulating Gases can easily be replaced by placing the decomposition facility at suitable points Gcmische removes the desired composition. The relationship in which the Components of the auxiliary gas are mixed., Depends on the heat b @ aw. Cold b.eda.rf of the individual relctification columns, which will be very different, depending on the demands placed on the purity and yield of the products and as the case may be, the heat content of the gas to be decomposed for itself to make the heating of the individual pillars usable. There is another special feature here Advantage that the present procedure compared to your already much more complicated one the use of managed auxiliary circuits. Namely, the requirements change of the purity of the products, so must those in the various districts adhere to gas mixtures, what for given machines for each circuit is not possible without further ado, in the case of the present procedure, however, by amendment the mixing ratio can be achieved in the simplest way.

The auxiliary circuit described can also be used for this purpose in order to fully or partially cover the cooling capacity required to cover the losses to effect. Is used, as in the example described above, for the auxiliary circuit Gases with a very large Joule-Thomson effect can be achieved by throttling the same has a very considerable cooling effect. It may therefore be sufficient under certain circumstances be to compress the mixture to be disintegrated only to moderate pressure.

Claims (1)

PATEN TA NSPRÜCI3E: -i. Process for the decomposition of gas mixtures by liquefaction and rectification, characterized in that the supply of heat required to carry out the rectification is wholly or partially through a. Auxiliary gas conveyed in the circuit, composed of two or more components, is effected, the components of which are separated by rectification angle in the fractional liquefaction under pressure and then reunited after separate evaporation, the start of condensation of the auxiliary gas mixture and the evaporation temperature of its lower-boiling component remaining so far apart As for the heating and cooling of the rectificadon (control equipment is required. For example, the method according to claim 1), characterized in that decomposition products of the processed gas mixture are used as the auxiliary gas and are constantly fed to the auxiliary circuit to the extent that it is due to losses or the removal of gases 3. The method according to claims i and z, characterized in that the auxiliary circuit is also used at the same time to cover the cooling requirement of the cutting plant.