DE1519598A1 - Process for breaking down a mixture of substances by rectification - Google Patents

Description

Process for the decomposition of a mixture of substances by rectification

The invention relates to a method for decomposing a material skeleton by rectification, whereby the differences in the boiling behavior of a genetic component or a group of mixture components on the one hand and the rest of the mixture on the other hand, are large.

Such methods are known. With them, the mixture of substances to be broken down becomes liquid in a rectification column Abandoned head as reflux liquid. The steam flowing in the opposite direction to the return flow is heated by heating the bottom of the rectification column generated. The task of the liquid mixture at the top of the column is due to the different boiling behavior

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of the substances contained in the liquid mixture. Because even if the mixture has a significant high boiling point, that is in equilibrium with the boiling mixture standing gas phase, i.e. the top product of the column, is so poor High boiling point, so that no intolerable losses arise from it.

In the known methods, however, occur thermodynamic Difficulties that can be attributed to the large differences in the boiling behavior of the mixture components.

Because due to the large differences, the occurring

Temperature differences between the top and bottom of the rectification column tend to be very large. For example, in the case of a low-temperature rectification the sump liquid - almost pure high boiling - can be evaporated at a temperature which is considerable is above the temperature at which that fed to the column at the top Mixture of substances was condensed, i.e. cold must be available at a much lower temperature than it can be recovered upon evaporation of the bottom liquid. Therefore, one is forced in the known method, in addition to arrange a heat pump, with the help of which the cold can be transformed.

The invention is based on the problem of the thermodynamic difficulties occurring in the known processes significantly reduce and thus the investment and operating costs for carrying out a process for dismantling

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generation of a mixture of substances by rectification, with the differences in the boiling behavior of a mixture constituent or a group of mixture constituents of one and the rest of the Mixtures of substances are large, to be reduced significantly.

This object is achieved in that a part of the liquid mixture evaporates and into the foot of a rectification column blown in and the remainder is given up at the top of this rectification column as reflux.

So it is not the entire liquid mixture of the column is given up at the top as reflux liquid, but only still part of it. The other part is evaporated and blown in vapor form into the rectification column at the foot. The in The vapor rising from the column is no longer caused by evaporation of the bottom liquid, but by evaporation a part of the mixture of substances generated. But this e.g. in the case of a low temperature rectification, the cold is no longer obtained at the relatively high evaporation temperature of the sump, but at the sliding evaporation temperature of the mixture, which is on average much lower than that of the swamp. As a result, the method according to the invention requires - opposite the known methods - much less expensive means of transforming the cold. That and the cheaper ones Heat exchange ratios possible use of smaller heating surfaces result in a considerable reduction in investment and operating costs. The same applies accordingly

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for rectification carried out at higher temperatures.

As a result of the advantageously very different boiling behavior of a mixture constituent or a group of mixture constituents on the one hand and the rest of the mixture of substances on the other hand, the one at the foot of the rectification column is old The liquid which is in equilibrium with the steam blown in and which runs off into the sump is so rich in high-boiling substances that it does not meet high purity requirements as a product

If there are several mixture fractions with different high-boiling content, the portion is advantageous of the mixture, which is to be evaporated and blown into the rectification column, formed from the mixture fraction, dl is richest in the high-boiling mixture component or the high-boiling group of mixture components so that in this case to win possible purest high boilers.

According to one embodiment of the invention, thank you * may b «i the production of nethane from a mixture, as in the Cooling of coke oven gas occurs in liquid form at low temperatures, part of the mixture is evaporated in the heat exchange with coke oven gas.

According to a further development of the inventive conception, in the production of nethane from coke * ofeogts the ti «f bed parts pulling away from the head of the rectiflcation column directly to the cold reetgae draw ·«! * ») *

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Further advantages and details of the invention can be found in the exemplary embodiment shown schematically in the drawing. The exemplary embodiment shows the part of a coke oven gas decomposition plant that is important for the production of methane from coke oven gas for obtaining a hydrogen-nitrogen chemical for the synthesis of ammonia.

The pre-cooled coke oven gas is fed to the system via line 1 and further cooled in heat exchangers 2 and j5. A part of the coke oven gas condenses in the process, essentially CH ^, CO and H ₂ . This condensate is separated from the remaining coke oven gas in the liquid separator 4 and fed in two parts to the rectification column 5 in different ways. One part is fed directly to SSuIe 5 through line 6 as reflux liquid. The other part is conducted via line 7 to heat exchanger 3, where it is evaporated and blown into the SHuIe 5 ex fut As a result of the favorable boiling ratio of CH ^ on the one hand and CO + K ₂ on the other hand, it is very strongly enriched with methane and can therefore be sailed as a product directly at the foot of the slope with line 8.

If there is a 60% methane fraction, part of which evaporates and is poured into the rectification column, the liquid in equilibrium with this vapor is at ee. 95 # enriched with methane

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In this case, proper procedures could at most 95 # Deliver methane.

The product is then evaporated at a relatively high temperature (boiling point of the moderately pure methane) in the heat exchanger 2; thus only supplies cold at a relatively high temperature. The condensate separated in the liquid separator must, however, be formed in the heat exchanger 3 at a lower temperature. In order to achieve the “asu”, part of the condensate is also evaporated in heat exchanger 3. Since the condensate still contains a substantial proportion of CO and M ₂ , its mean boiling temperature is significantly lower than the boiling temperature of the bottom liquid or the product, ie the evaporation of one part of the condensate provides 3 cold in the heat exchanger at a lower temperature.

The residual gas withdrawn from the top of the column 5, consisting of “CO” V ₂ and small parts of methane, is added to the reed gas flowing through the line 9 upstream of the heat exchanger 3 and the reed gas coming upstream of the nitrogen water of the coke oven gas decomposition plant and flowing through the line 9 heated together with him in heat exchangers 3 and 2. The hydrogen-nitrogen mixture coming from a nitrogen scrubber is also passed through this heat exchanger with the line 10.

For example, the invention can also be particularly advantageous in the furnace recovery of ethylene are used where the boiling ratios between ethylene on the one hand and methane on the other • use · for the production of a moderately pure product · «favorable are.

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Claims (4)

r; r> LINDE AKTIENGESELLSCHAFT (H 275) ^. H CS / OCC 9/21/1965 Ste / Pi claims 1. Process for the decomposition of a mixture of substances by rectification, whereby the differences in the boiling behavior of a mixture constituent or a group of mixture constituents on the one hand and the rest of the mixture on the other, are large, characterized in that part of the liquid Mixture evaporated and in the PuB of a rectification column blown in and the remainder is given up at the top of this rectification column as the return flow. 2. Method ^ for breaking down a mixture of substances according to claim 1, characterized in that when several mixture fractions are present, the part of the mixture which evaporates from the Geaisch fraction is formed, which is richest in the high-boiling Geaisch constituent or the high-boiling group of Geraisch constituents 1st. 3. The method for decomposing a substance mixture according to claim 1 and 2, in particular for the production of methane from a Gejfiedh, such as 4er cooling of Kofcsofeagftg at deep temperatures, which means that the part of the ÖSilsohäS in the WärweaustsusjCii with 009809 / _ "_. _;% LINDE AKTIENGESELLSCHAFT 4. A method for breaking down a mixture of substances according to claim 1 to 3i in particular for the production of methane from a Mixture, as is obtained in liquid form when cooling coke oven gas at low temperatures, characterized in that the more volatile constituents withdrawn from the top of the rectification column are mixed directly into the cold residual gas will. 009 809/1 318