The method of obtaining pure hydrocarbons from a mixture containing aromatic and non-aromatic hydrocarbons

 

(57) Abstract:

Describes a method of obtaining pure hydrocarbons from a mixture of hydrocarbons containing aromatic and non-aromatic hydrocarbons, in particular, of a mixture of hydrocarbons enriched in aromatic hydrocarbons by extractive distillation extractive distillation column. Between the upper and lower parts of the column provides the first input to the solvent for the first stream portion of the selective solvent. As the selective solvent used is N-substituted morpholine. From the head part of the extractive distillation column as a product of refining output, mainly non-aromatic hydrocarbons, and from the bottom of the extractive distillation columns to extract as output, in the main, aromatic hydrocarbons and the selective solvent. In the upper part of the column above the first input of the solvent in the extractive distillation column via a second input serves the second stream of selective solvent. The amount of solvent, submitted together with the second stream is less than 50% of the total amount of the solvent. The technical result - the development of a simple and nedavah products. 6 C.p. f-crystals. 2 Il.

The invention concerns a method of obtaining pure hydrocarbons from a mixture of hydrocarbons containing aromatic and non-aromatic hydrocarbons, in particular, of a mixture of hydrocarbons, rich in aromatic hydrocarbons by extractive distillation extractive distillation column, and between the upper and lower parts of the column through the first input to the solvent in the extractive distillation column enter the first thread portion of the selective solvent, and at least N-substituted morpholine is used as the selective solvent from the head of column output as a refined product, mainly non-aromatic hydrocarbons, and from the bottom of the distillation column to extract as output, in the main, aromatic hydrocarbons and the selective solvent. Extractive distillation of various mixtures of hydrocarbons containing aromatic and non-aromatic hydrocarbons by N-substituted morpholines as selective solvent is used in large-scale process plants for obtaining very pure aromatic hydrocarbons. As mixtures of prevalidated contain along with various aromatic hydrocarbons and even non-aromatic portion which, in particular, consists of paraffins, cycloparaffins, olefins, diolefins and organic sulfur compounds. By using extractive distillation of a mixture of hydrocarbons separated, aromatic hydrocarbons, on the one hand, and non-aromatic hydrocarbons, on the other hand. Thus, this extractive distillation suitable for obtaining pure aromatic hydrocarbons and to produce a clean non-aromatic hydrocarbons, such as olefins and diolefins. In the process of extractive distillation of aromatic hydrocarbons from used a mixture of hydrocarbons enriched by a large number of selective solvent in the lower portion of the extractive distillation column as an extract. Nonaromatic hydrocarbons from used a mixture of hydrocarbons concentrate on the contrary, at the head of the distillation columns in the form of product refinement. In practice, it is known that when carrying out the extractive distillation selective solvent is served at the head of the distillation column. This leads to the fact that the product of the refining of the head of the column does not contain residues of solvent, which could be neglected. This part rastvortsev, which is an expensive operation.

In the known method of the above type according to the invention (DE 4040145 A1), compared with the method known from practice, as extractive distillation and removal of residual solvent from the product of the refining is performed in a single column. For this purpose extractive distillation column has an additional top, and the selective solvent is introduced into the extractive distillation column via the input for the solvent below the top of the column. This introduced the solvent flows down the plates of the column down, he collects aromatic hydrocarbons in the lower part of the extractive distillation column. Nah the hydrocarbons of the mixture used, on the contrary, the rise in the distillation column up in the form of steam. The upper part of the column located above the input solvent is used to remove residual solvent from these non-aromatic hydrocarbons. Known from the application Germany - DE 4040145 A1 - way, mostly paid off, however it needs to be improved. This known method has, in particular, the disadvantages, if you use a mixture of hydrocarbons with a high sterjantov about 85% or pre-purified benzene content of aromatic hydrocarbons of more than 95%. When using such mixtures of hydrocarbons, the share of non-aromatic hydrocarbons in relation to the amount of selective solvent is very small. When extractive distillation of aromatic hydrocarbons are absorbed served on top of a selective solvent and sent to the bottom of the extractive distillation column. Nonaromatic hydrocarbons rise, as it has already been stated, in vaporous form in the head of the distillation column. On separate plates of the distillation column establishes the equilibrium, which depends in particular on the temperature and the concentrations of the substances. If extractive distillation according to the method, there are variations in the heating system of the column, or if you have changes the set temperature of the solvent or changing the number of summed solvent, then this equilibrium is disturbed. These imbalances are reflected in particular in the extractive distillation of a mixture of hydrocarbons with a very high content of aromatic hydrocarbons, as for example, pre-purified benzene content of aromatic hydrocarbons of more than 95%. The high content of aromatic hydrocarbons and low levels or disturbance to what is present in high concentration of aromatic hydrocarbons due to unbalance is not already popadayutsa fully selective solvent and transported in the lower part of the column. Moreover, in particular, easily boiling benzene, which is compared with non-aromatic hydrocarbons of lower boiling point, can flow into the upper part of the column through the input of solvent. As a result, in particular, benzene enters the head of the distillation column, so that the head part is a mixture of aromatic and non-aromatic hydrocarbons. Already a small amount of aromatic hydrocarbons, which due to the above-mentioned oscillation enters the upper part of the column (above the first loading solvent) results in relatively small quantities nah, expected, to a relatively high content of aromatic hydrocarbons in the product refining. Additionally they indicate losses in the yield of aromatic hydrocarbons.

In contrast, the basis of the invention is the technical challenge is to develop a simple and inexpensive ways, the features, temperature and concentration, however, achieves a clean separation of aromatic and nonaromatic hydrocarbons and, accordingly, a high yield of aromatic and non-aromatic hydrocarbons.

The goal of the project is achieved by the method of the mentioned type which is characterized in that the upper part of the column above the first input of the solvent in the extractive distillation column via a second input for solvent serves a second partial stream of selective solvent, and the amount of solvent, filed with the second stream is less than 50% of the total quantity of solvent submitted together with the first and second threads. Scope of the invention includes particularly enriched in aromatic hydrocarbons with a mixture of aromatic hydrocarbons above 85% for use in the method according to the invention. Preferably, use pre-purified benzene content of aromatic hydrocarbons of more than 85% and/or raw coke oven benzene content of aromatic hydrocarbons of from about 85%. However, in the scope of the invention can be used pyrolysis gas with a content of aromatic hydrocarbons around the Xia, in the framework of the method according to the invention can also be used, and mixtures of these hydrocarbons. Typically, a mixture of hydrocarbons containing aromatic hydrocarbons with 6 to 8 carbon atoms. Preferably, as a selective solvent serves N-substituted morpholines with not more than 7 carbon atoms in the substituent. According to a preferred form of execution of the invention as a selective solvent serves N-formyl-morpholine.

The proposed solution comes from the fact that according to the method known from the application Germany - DE 4040145 A1, in part of the column located above the input for the solvent, there is no supplied selective solvent, and therefore, in this part of the column, basically, we have the conditions for distillation and there are no conditions for extractive distillation. For this reason, the head of the column may come easily, for example the boiling benzene in the above-described deviations of the conditions of the extractive distillation, and therefore at the head of the column, the benzene is mixed with non-aromatic hydrocarbons, which represents a drawback. Further, the invention is based on the fact that by feeding the second stream of selective solvent through the second input is Italia can be created conditions for extractive distillation. This additional site columns with the terms and conditions of the extractive distillation can help to ensure that aromatic hydrocarbons and particularly benzene can no longer get into the head of the column. Aromatic hydrocarbons are washed away in the lower part of the column. Also with large variations of temperature and concentrations in the column extractive distillation of this result is achieved thanks to an additional area of extractive distillation between the two inputs to the solvent. It is enough that through the second input solvent was served only a relatively small amount of selective solvent. In accordance with paragraph 1 of the claims is the amount of solvent supplied through the second input to the solvent should be less than 50% of the total amount of the solvent. Preferably this amount of solvent is from about 0.5 to 10% of the total amount of the solvent. However, the specialist is not clear that by supplying relatively small quantities of selective solvent through a second input for solvent aromatic hydrocarbons can be effectively removed from the head of the column. Due to the additional flow of the contents of aromatic hydrocarbons in the head of the column. A relatively small amount of solvent also leads to the fact that the second thread can be set and adjusted more precisely. Between the upper and lower parts of the column extractive distillation can be brought, for example, heat through boiler of boiling water.

The result according to the method according to the invention achieves a clean separation of aromatic hydrocarbons, which are concentrated in the lower part of the column, and non-aromatic hydrocarbons, which are at the head of the column. In accordance with this achieves a high output as a pure aromatic hydrocarbons and pure nah. It should be emphasized that these benefits can be realized in a simple and inexpensive way. Compared to the extractive distillation column, which is used According to the method according to the application Germany - DE 4040145 A1, extractive distillation column according to the invention has a greater height, and she more than approximately 5 to 10 theoretical plates or separation steps. In addition to the second input of the solvent, additional equipment costs for installation is not required. Compared with the known method does not require the plants used amount of solvent is divided into two partial flow, which is introduced into the extractive distillation column through both input solvent.

Moreover, it is clear that in the framework of the method according to the invention between the second input of the solvent and the head part of the extractive distillation column in the upper part of the column provided for the area in which you implement the conditions of distillation and which serves the purpose distillative branch of the selective solvent from the non-aromatic hydrocarbons. In particular, there are many possibilities for implementing the method according to the invention. The invention provides that the extract of the aromatic hydrocarbons and the selective solvent is extracted from the bottom of the extractive distillation column is fed into the distant column, in which the aromatic hydrocarbons are separated from the selective solvent. It is advisable to outrun the column to maintain vacuum conditions, while the aromatic hydrocarbons are highlighted in the head part distant columns as a by-product. This selective solvent moves to the bottom of distant columns. In accordance with a preferred form of execution of the invention the selective solvent is extracted from the bottom of charites is returned to the extractive distillation column. For this purpose suitable selective solvent, formed in the bottom of distant columns, through the first and second inlets for supplying solvent to reintroduce in the extractive distillation column. It is reasonable inferred from the distant columns of the solvent be channeled through the respective heat exchanger for cooling the selective solvent and establishing the desired temperature of the solvent. Preferably the amount of solvent supplied to the second stream through the second input of the solvent is 0.5-10% of the total amount of the solvent supplied together with the first and second threads.

The invention provides that used a mixture of hydrocarbons before the introduction of the extractive distillation column can be brought into thermodynamic equilibrium in the separation tank and separated into liquid and vapor phases. Then both phases can be separately introduced into the extractive distillation column. When this vapor phase is introduced into the extractive distillation column below the level of the liquid phase.

It is understood that in the method according to the invention the temperature input selecting the existing heat exchangers. Heating of the extractive distillation column is carried out in the usual way.

Below the invention is explained in more detail on the drawing representing an example implementation. It schematically:

in Fig. 1, the device for implementing the method of obtaining pure hydrocarbons in accordance with the prior art,

in Fig. 2, the device for implementing the method of obtaining pure hydrocarbons according to the invention.

In Fig. 1 and 2 shows a device for implementing the method of obtaining pure hydrocarbons from a mixture containing aromatic and non-aromatic hydrocarbons, in particular, of a mixture of hydrocarbons enriched in aromatic hydrocarbons. According to the method takes place extractive distillation in the extractive distillation column 1, in which between the upper part 2 of the column and the lower part 3 of the column posted by enter 4 for the solvent, in which the selective solvent is introduced into the extractive distillation column 1. The upper part 2 of the column can be performed in separate columns. As the selective solvent used, preferably, N-formylmorpholine. By adding a selective solvent in extractive distill the cities are shifted relative to each other so what possible their separation in the extractive distillation column. Aromatic hydrocarbons are using a selective solvent in the lower part 5 of the extractive distillation column 1. Extract from the aromatic hydrocarbons and the selective solvent is selected in the lower part 5 of the extractive distillation column 1, enter and serve in distant column 6. Nonaromatic hydrocarbons rise to the extractive distillation column 1 in vaporous form up and stand out as a product of refining in the head part 7 of the extractive distillation column 1, whence can be derived. In the distant column 6 separated from the lower part 5 extract comprising aromatic hydrocarbons and the selective solvent is separated, preferably in a vacuum on aromatic hydrocarbons and the selective solvent. Aromatic hydrocarbons are highlighted in the head part 8 of distant column 6, where it can be selected. Selective solvent, on the contrary, isolated in the lower part of the distant column 6. From the lower part 9 of the selective solvent output and input for solvent 4, 10 again introduced into the extractive distillation column 1. Now, with the heat exchangers for cooling the selective solvent to a predetermined temperature before re-introduction into the extractive distillation column 1. As shown in Fig. 1, and in Fig. 2 shows the above input 4 for supplying solvent to the upper part 2 of the column in the form of Packed columns, which often has a smaller diameter than the lower part 3 of the extractive distillation column.

In Fig. 1 shows a device for implementing the method according to the application Germany - DE 4040145 A1, from which the invention proceeds. There is only one single input 4 for supplying solvent that is located between the upper part 2 of the column and the lower part 3 of the column. On top of the 2 columns on the input 4 to the solvent provided, in General, the conditions for distillation, and this upper part of the column is used for the selective removal of the solvent from the non-aromatic hydrocarbons, which are concentrated in the head part 7 of the column.

As shown above, this method offers the drawback consisting in the fact that when the deviation of the current conditions of the extractive distillation, in particular, when the deviations in the heat of the extractive distillation column 1, the temperature of the solvent and/or filed with the quantity of the selective solvent in the upper part 2 of the column can get aromatic hydrocarbons and to mix so regulatel what follows, in particular, when the known method used a mixture of hydrocarbons enriched in aromatic hydrocarbons.

In Fig. 2 shows a device for implementing the method according to the invention. In accordance with the invention in the upper part 2 of the column above the first input 4 of solvent fed through the second input 10 in the column for extractive distillation of a second thread portion of the selective solvent. Supplied with a second flow amount of solvent is mainly 0.5 to 10% of the total amount of the solvent supplied through the inlets 4, 10. Through this relatively inexpensive technique to achieve that under the above deviations in the conditions of the extractive distillation of aromatic hydrocarbons are fully concentrated in the lower part 5 of the extractive distillation column 1, and nonaromatic highly purified hydrocarbons, respectively, are highlighted in the head part 7 of the extractive distillation column. These benefits can in particular be achieved in the case of mixtures of hydrocarbons nah content less than 15% or nah content less than 5%. On the second input 10 for solvent shown of the selective solvent from nah.

The result according to the method according to the invention have the benefit of aromatic and nonaromatic hydrocarbons with high yield and high purity. Additional in comparison with the known method the amount of solvent used in a loop is not required.

The method can be carried out with relatively small consumption of energy.

1. The method of obtaining pure hydrocarbons from a mixture containing aromatic and non-aromatic hydrocarbons, in particular, of a mixture of hydrocarbons enriched in aromatic hydrocarbons by extractive distillation extractive distillation column using N-substituted of the research as a selective solvent, in the upper part of the extractive distillation column via the first input of the selective solvent serves first partial stream of selective solvent and from the head part of the extractive distillation column as a product of refining output, mainly non-aromatic hydrocarbons, and from the bottom of the extractive distillation column to extract as output, mainly aromatic hydrocarbons and the selective solvent, autopodium through the second input of the selective solvent of the second partial stream of selective solvent, moreover, the amount of solvent, filed with the second partial stream is less than 50% of the total quantity of solvent submitted together first and second partial streams.

2. The method according to p. 1, characterized in that use enriched in aromatic hydrocarbons mixture of hydrocarbons with an aromatic content of hydrocarbon above 85%.

3. The method according to p. 1 or 2, characterized in that as the selective solvent used is N-substituted morpholine with not more than 7 carbon atoms in the substituent.

4. The method according to one of paragraphs.1 to 3, characterized in that as the selective solvent used is N-formylmorpholine.

5. The method according to one of paragraphs. 1 to 4, characterized in that the extract of the aromatic hydrocarbons and the selective solvent selected from the bottom of the extractive distillation column, served in a distant column, in which the aromatic hydrocarbons are separated from the selective solvent.

6. The method according to one of paragraphs.1 to 5, characterized in that the selective solvent selected from the bottom of the extractive distillation column, served in the circulation loop through the entries for solvent return again the scent of the solvent, supplied with the second partial stream is 0.5 to 10.0% of the total amount of the solvent supplied together with the first and second partial streams.

 

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