A method of producing urea plant for its implementation (options), upgrade install (options)

 

(57) Abstract:

Urea is produced by interaction of ammonia and carbon dioxide in the reaction space with obtaining a reaction mixture comprising urea, carbamate and free ammonia in aqueous solution. At the stage of decomposition in the reaction mixture partially carbamate is decomposed and partially separates the free ammonia in aqueous solution in the form of a first stream comprising a pair of ammonia and carbon dioxide, and produces a flow comprising urea and residual carbamate in aqueous solution. The first stream to partially condense and get the flow of the first portion of carbamate in aqueous solution, which is recycled to the reactor. The flow of urea and residual carbamate in aqueous solution refer to the section extraction of urea, where separating urea from the rest of the carbamate with getting the flow of the second portion of carbamate in aqueous solution, which is also a process for the partial decomposition of the carbamate. Thus separated second stream of vapors of ammonia and carbon dioxide with impurities, which is partially condensed, and receive the third flow of carbamate in aqueous solution, is also recycled to the reactor. The decomposition of the second flow of carbamate in aqueous solution are the, first desorber to partial decomposition of the carbamate obtained in the reaction mixture from the reactor, the equipment for the partial condensation of the vapors of desorber and recycling the first stream of carbamate in aqueous solution in the reactor section of the extraction of urea, which receive the second flow of carbamate in aqueous solution. In addition, the installation includes a second desorber to partial decomposition of the carbamate in the second thread section of the extraction of urea. When this selected pair is sent optionally installed in the condenser, which is connected with the reactor for recycling in him the third part of carbamate in aqueous solution. The way of modernization of the plant for producing urea is feeding the reaction mixture from the reactor for the synthesis of urea in the first desorber for the partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the reaction mixture, and subsequent at least partial condensation of the vapors taken from the first desorber, condenser and recycling the first portion of carbamate in aqueous solution in the reactor. This serves stream containing urea and residual carbamate in aqueous solution, from the first desorber in section extraction o optionally set the second desorber for the partial decomposition of at least part of the second portion of carbamate in aqueous solution, and install the equipment in which condense at least part of the vapor taken from the second desorber, and are recirculated to the reactor of the third part of carbamate in aqueous solution. As a result of increased purity and yield of the final product. 6 C. and 8 C.p. f-crystals, 3 ill.

The invention relates to a method for producing urea.

In particular the invention relates to a method for producing urea, which comprises the following stages:

conducting interaction between ammonia and carbon dioxide in the reaction space with obtaining a reaction mixture comprising urea, carbamate and free ammonia in aqueous solution;

- processing the obtained reaction mixture, consisting of partial decomposition of carbamate and partial separation of free ammonia in aqueous solution to obtain the first stream consisting of vapors of ammonia and carbon dioxide, and flow comprising urea and residual carbamate in aqueous solution;

processing the first containing vapors of ammonia and carbon dioxide stream, which consists in grainpro part of the carbamate in the reaction space;

- flow comprising urea and residual carbamate in aqueous solution, in the section extraction urea;

- separation section of the extraction of urea residue of the carbamate from the urea and receiving the second part of an aqueous solution of carbamate.

The present invention relates also to an apparatus for implementing the above method and to a method of upgrading an existing installation to obtain urea to create on its basis proposed in the present invention is installed.

As you know, currently in the production of urea significantly increased the need for plants with, on the one hand, high productivity and technological flexibility, and on the other hand, requiring for their small investment and low production costs, in particular energy consumption.

Currently developed and implemented in practice different ways of obtaining urea based essentially on hold in the reaction space of interaction between fed to him by ammonia (NH3) and carbon dioxide (CO2with recycling in this reaction space unreacted ve the carbon dioxide and carbamate in aqueous solution (see EP 0212744).

Technological scheme of such a method of producing urea is shown in Fig. 1, and in this scheme there is a reaction space, equipment for the decomposition of carbamate and section extraction of urea, in which the urea solution are being entered into the interaction and again returned into the reaction space a substance (see EP 0266840).

On the one hand, this recirculation can be almost fully use such a valuable source products, such as ammonia and carbon dioxide, however, on the other hand, it requires a transfer in the reaction apparatus of large quantities of water (H2O), which reduces the overall yield of the conversion of carbon dioxide into urea, which is when this method of obtaining a urea varies typically in the range from 59 to 63%.

The technical problem to be solved by the present invention is directed, is to develop a method of producing urea, having a high conversion yield, relatively simply implemented in practice at low investment and low production costs.

In the present invention this problem is solved by using a method, which comprises the following stages:

processing at least part of the second part of an aqueous solution of carbamate obtained in section extraction of urea, which consists in the partial decomposition of the carbamate to obtain a second stream consisting of vapors of ammonia and carbon dioxide, and a stream containing residual carbamate in aqueous solution;

processing the second containing vapors of ammonia and carbon dioxide gas stream consisting of at least partial condensation of the vapour receiving a third portion of carbamate in aqueous solution;

- recycling the third part of carbamate in aqueous solution in the reaction space.

In accordance with the invention, at least part of the aqueous solution of carbamate selected from the section extraction of urea, it is advisable to process consisting in the partial decomposition of carbamate and the selection is not entered into the interaction of ammonia and carbon dioxide from containing a large amount of water solution of the residual carbamate.

Together with not entered into interaction with the substances in the reaction space is returned to a very small amount of water, which can significantly reduce the consumption of water supplied into the reaction space, and ensure the part of the second part of an aqueous solution of carbamate its decomposition is useful to pressure, essentially equal to the pressure in the reaction space.

For more efficient condensation and selection section of the extraction of urea have not entered into the interaction of substances stream containing residual carbamate in aqueous solution, it is advisable to send after partial decomposition of the second portion of carbamate in section extraction of urea.

Another option proposed in the present invention the method includes the following stages:

- the flow of the reaction mixture containing urea, carbamate and free ammonia in aqueous solution, in the apparatus for decomposition;

- feeding apparatus for decomposition of at least part of the second part of an aqueous solution of carbamate and partial decomposition of the reaction mixture and the second part of the carbamate takes place in the same apparatus for the decomposition with the formation therein of the first and second streams of vapors of ammonia and carbon dioxide, and a stream containing urea and residual carbamate in aqueous solution.

In this embodiment proposed in the invention, a method of obtaining urea from a technical point of view is very simple, because it eliminates the need for installation on existing facilities, additional equipment is ractice quite satisfactory results can be obtained, providing partial decomposition of at least 50%, preferably at least 60% of the second part of an aqueous solution of carbamate.

Another object of the present invention, which aims at solving the above technical problem, is to install, which is the above-described method of producing urea and which includes:

reactor for the synthesis of urea;

the first desorber, which is taken from the reactor the reaction mixture is subjected to a treatment consisting in the partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the reaction mixture;

- equipment for at least partial condensation of the vapors taken from desorber, and recirculation in the reactor of the first part of carbamate in aqueous solution;

section extraction of urea, which is a stream containing urea and residual carbamate in aqueous solution selected from the first desorber, and in which the separation obtained in the urea reactor from the second portion of carbamate in aqueous solution;

characterized in that it provides:

second desorber, in which there is a partial decomposition of at least part of the second part of Cais second desorber, and recirculation in the reactor of the third part of carbamate in aqueous solution.

In accordance with another variant of the invention proposes a device for producing urea, which includes:

reactor for the synthesis of urea;

- desorber in which the processing of the reaction mixture taken from the reactor, consisting of partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the reaction mixture;

- equipment for at least partial condensation of the vapors taken from desorber, and recirculation in the reactor of the first part of carbamate in aqueous solution;

- section extraction of urea, which is a stream containing urea and residual carbamate in aqueous solution selected from the specified desorber, and in which the separation obtained in the urea reactor from the second portion of carbamate in aqueous solution;

characterized in that it contains:

- equipment for submission to desorber at least part of the second portion of carbamate in aqueous solution.

In accordance with the present invention installed for the implementation of the proposed methods for obtaining urea can be made in the form of the newly create and improve performance in relation to energy consumption.

Another object of the present invention is a method of upgrading equipment for production of urea, containing:

reactor for the synthesis of urea;

the first desorber, which is taken from the reactor the reaction mixture is subjected to a treatment consisting in the partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the reaction mixture;

- equipment for condensing at least part of the vapor taken from the first desorber, and recirculation in the reactor of the first part of carbamate in aqueous solution;

section extraction of urea, which is a stream containing urea and residual carbamate in aqueous solution selected from the first desorber, and in which the separation obtained in the urea reactor from the second portion of carbamate in aqueous solution;

characterized in that it includes:

- adding a second desorber for processing at least part of the second portion of carbamate in aqueous solution, lies in its partial decomposition;

- installation of equipment for condensing at least partially taken from the second desorber vapors and recycling to the reactor of the third part carbama the stop of the present invention includes:

- the installation of the second desorber for processing at least part of the second portion of carbamate in aqueous solution, lies in its partial decomposition;

- installation of equipment for supplying vapor taken from the second desorber, in equipment designed for condensing vapors taken from the first desorber.

Another option proposed in the present invention a method upgrade the present invention includes:

- installation of equipment for feeding at least part of the second portion of carbamate in aqueous solution in desorber.

Other distinctive features and advantages of the present invention are discussed below in the description of preferred but not limiting the scope of the invention examples of its implementation with reference to the appended drawings.

Fig. 1 is a block diagram of the technological process of production of urea in a known manner.

Fig. 2 is a block diagram of the first variant of the technological process of obtaining urea proposed in the invention method.

Fig. 3 is a block diagram of a second variant of the technological process of production of urea proposed in the invention method.

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This diagram shows the reaction space 1, in which at high pressure is the synthesis of urea supplied to him by the pipelines 21 and 22 of the gas streams consisting essentially of pure ammonia and carbon dioxide, respectively.

Usually while working in the reaction space are supported on the following conditions:

The molar ratio of NH3/CO2input - 2,9-3,4

The molar ratio of H2O/CO2input - 0,4-0,7

Conversion output CO2in urea, % - 59-63

Pressure, bar abs. - 150

The temperature of the reactionoC - 185-190

In Fig. 1 shows the unit 2 high pressure decomposition of carbamate, section 5 of the granulation of urea and the capacitor 6 high pressure.

The apparatus 2 for the decomposition of the carbamate and the capacitor 6 typically operate at a pressure equal to the pressure in the reaction space 1.

Blocks 3, 4, 7 and 8 are included in the composition section extracting urea. Blocks 3 and 4 represent the desorbers or stills, and blocks 7 and 8 capacitors.

The final product, which is obtained in block 4 represents in this case the solution, which contains up to 99.7% of urea.

In block 8 includes devices is but blocks 3 and 7 operate at medium pressure (18 bar), and blocks 4 and 8 operate at low pressure (4 bar).

On line 23 of the block 1 is selected, the flow of the liquid reaction mixture comprising urea and not entered into the interaction of substances, in particular of carbamate and free ammonia in aqueous solution.

On line 23, the liquid enters the unit 2, which is its processing, consisting in a partial decomposition of carbamate and partial separation from solution of free ammonia.

The apparatus 2 for the decomposition of the carbamate is generally desorber that as the Stripping reagent through the pipeline 30 is supplied taken from the pipeline 22 carbon dioxide.

Formed in desorber 2 pairs of ammonia and carbon dioxide are removed from desorber pipeline 24; at the same time through the pipeline 25 of desorber enters the liquid stream containing urea and residual carbamate in aqueous solution.

The pipe 24 passes through the condenser 6, in which a pair of ammonia and carbon dioxide are condensed to form the carbamate in aqueous solution, which is fed back into the reaction space 1.

The pipe 25, which has a liquid consisting of urea and Astok of carbamate in aqueous solution is decomposed and separated from the urea solution.

Typically, the urea concentration in the stream flowing through the pipeline 25 fluid after block 3 is 70-72%, and after the block 4 is about 99%.

Located in the gaseous ammonia and carbon dioxide passes from the distillers 3 and 4 in the pipes 26 and 27 respectively.

The pipe 27 passes through the condenser 8, in which a pair of ammonia and carbon dioxide are condensed to form the carbamate in aqueous solution, which is applied to the capacitor 7, accelerating flowing in it the process of condensation flowing through the pipeline 26 of the gas flow.

Similarly, the pipe 26 passes through the condenser 7, in which a pair of ammonia and carbon dioxide are condensed to form the carbamate in aqueous solution, which is applied to the capacitor 6, accelerating the process of condensation flowing from pipe 24 of the gas flow.

Part of the water contained in the aqueous solution formed in the condenser 8, is subjected to further processing and purification from all traces of ammonia and urea in a special part of the condenser 8 of the apparatus. After purification of waste water through the pipeline 28 is drained from the installation.

The urea solution through the pipeline 25 is supplied from the dis is Truboprovod 29.

In another embodiment, this method as unit 7 uses a column for the separation of ammonia, in which pure liquid ammonia, which together with the ammonia supplied to the plant by pipeline 21, served in the reaction space 1 shown in Fig. 1 highway 31.

As shown in Fig. 1, in a known process of obtaining urea containing all the carbamate solution, separated from the urea is recycled back into the reaction space 1, and this solution contains a large amount of water, which is necessary for condensation of vapor and transfer have not entered into the interaction of the reactants.

In Fig. 2 and 3 show block diagrams of technological processes respectively of the first and second options proposed in the present invention a method of producing urea.

Shown in these drawings, the circuit elements are similar in structure and operation principle of the circuit elements shown in Fig. 1, are denoted by the same positions as in Fig. 1, and will not be considered.

It is shown in Fig. 2 unit 9 is designed for a decomposition of the carbamate apparatus which operates at high pressure, equal pressure is I an aqueous solution of carbamate with a high water content, subjected to the processing, consisting in a partial decomposition of the carbamate.

The pipes 32 and 33 of the device 9 enters the gas stream containing vapors of ammonia and carbon dioxide, and the liquid flow comprising urea and residual carbamate in aqueous solution.

Taken from the apparatus 9 through the pipe 32, the gas stream with a very high content of ammonia and carbon dioxide and very low water content (of the order of a few percent) passes through the condenser 6, in which ammonia and carbon dioxide are condensed to form the carbamate in aqueous solution, which pipe 24 is returned into the reaction space 1.

In the form shown in Fig. 2 technological scheme of the whole carbamate in aqueous solution, separated from the urea in the extraction section of the urea treated (decomposition) in block 9. However, quite satisfactory results can be obtained in the case of the feed block 9 only part of a carbamate selected from the section extraction of urea. It is preferable to return to the processing in block 9 at least 50% of the total quantity produced in it carbamate.

On offer in the present invention method as a result of interaction ammian and free ammonia in aqueous solution, which is supplied to the processing unit 2 decomposition, in which there is a partial decomposition of carbamate and partial separation of free ammonia in aqueous solution. From the block 2 the decomposition of the pipe 24 enters the first flow of vapors of ammonia and carbon dioxide, and the pipe 25 is given to the flow of urea and residual carbamate in aqueous solution. Through the pipe 24, the vapor stream is passed to the block 6, in which there is at least partial condensation of the vapor and forms a first portion of carbamate in aqueous solution, which is returned to the reaction space 1. Liquid through the pipe 25 is fed into the extraction section of urea (blocks 3, 4, 7 and 8), in which occurs the separation of urea from the second portion of carbamate in aqueous solution, which flows to the pipe 26.

In the technological scheme proposed in the invention method of producing urea at least part of the liquid in the pipe 26, is subjected to partial decomposition in block 9 with the education received in the tube 32 of the second stream of vapors of ammonia and carbon dioxide and into the pipe 33 stream containing residual carbamate in aqueous solution. The pipe 32 is connected to the block 6, in which there is at least partial condensation of the vapor and forms the in 1.

This scheme provides high conversion yield in the reaction space, because it returns a highly concentrated solution of the carbamate with a very low water content.

Proposed in the invention is a method of obtaining urea allows to achieve conversion of the output of carbon dioxide in the urea from approximately 70 to 75%, which far exceeds the conversion output of the known methods for producing urea.

In addition, such a high conversion yield and the almost complete absence of water returned to the reaction space 1, significantly reduce the number of substances to be separated from the urea solution, resulting in improved functioning and increased characteristics of desorber 2 and distillers 3 and 4 sections extraction of urea.

In the form shown in Fig. 2 diagram of the fluid flow, which flows through a pipe 33 and contains a very large amount of water is returned to the section extraction of urea, accelerating its processes of condensation and highlight formed in the distillers 3 and 4 are not entered into the interaction of substances.

The pipe 33 is preferably pass through the distiller 10, Vor, served in the block 8.

From the distiller 10 also departs pipe 34, which consists of the remaining ammonia and carbon dioxide steam flow with a small water content is fed to the condensation in block 7 section extraction of urea.

This scheme forms a closed circuit process water, which accelerates the process of condensation of ammonia and carbon dioxide in blocks 7 and 8 and is not returned to the reaction space 1, without negative impact on flowing in the reaction space of the interaction of ammonia with carbon dioxide.

In the alternative proposed in this invention method, the technological scheme of which is shown in Fig. 3, the fluid in the pipe 26 which communicates with the section extraction of urea, in particular with the capacitor 7 is not connected, as known in the scheme, directly into the reaction space 1 through the block 6, and is fed into the apparatus for the decomposition shown in the diagram in block 2, in which is formed a stream of vapors of ammonia and carbon dioxide, which pipe 24 is returned into the reaction space 1, before passing it through the condenser 6.

In this scheme, the partial is I, in which the decomposition of flowing through the pipeline 26 of the reaction mixture, allowing proposed in the invention method on the same equipment, which consists of the existing installation, operating under well-known technological scheme.

As the Stripping reagent in the apparatus 2 for the decomposition can also use part of the ammonia fed to the reaction space. Alternatively, the unit 2 can operate in the mode imagesarray, when to accelerate decomposition of the carbamate is used evaporating the ammonia.

In addition, the section extraction of urea can be performed in only two devices 4 and 8, working at low pressure. In this case, the flow comprising urea and residual carbamate in aqueous solution, is served after the decomposition of the unit 2 directly in the block 4, which is the final separation of the urea solution from entering into co-agents.

The following describes an installation for producing urea, working on the proposed in the present invention method.

Device for producing urea consists of a reactor for the synthesis of urea, shown in the form of blokadaya shown in blocks 3, 4, 7 and 8 vehicles, and related devices for condensation and recirculation in the reactor vapor taken from the first and second desorbers.

In the installation process scheme is shown in Fig. 2, the device for condensing vapors taken from the second desorber 9, is preferably in the form of a device for condensing vapors taken from the first desorber 2, which is shown in the diagram in block 6.

In this embodiment, between the second desorber and section extraction urea installed distiller, shown as block 10.

In the device for producing urea, the technological scheme of which is shown in Fig. 3, there is a lead line, made in the form of pipe 26 connecting section of the extraction of urea with desorber 2. In this case, there is no need to use desorber 9 and distiller 10.

The installation for carrying out the present invention a method of producing urea can be done in the form of newly created installation or setup, obtained by upgrading an existing installation, such as installation, technological scheme of which is shown in Fig. 1.

In the first case before the internals of the second desorber (block 9) to decompose at least a portion of carbamate in aqueous solution, taken from section extraction of urea (via pipeline 26);

- installation of equipment for condensing at least part taken from the second desorber vapors and recycling to the reactor (unit 1) obtained by this highly concentrated carbamate in aqueous solution.

In another embodiment proposed in this invention upgrade includes:

- installation of equipment for supplying vapor taken from the second desorber (block 9), shown as block 6 equipment designed for condensing vapors taken from the first desorber (2).

The preferred option proposed in the present invention a method of upgrading an existing installation to obtain urea provides:

installation tools (line 33) for feeding the remainder of carbamate in aqueous solution from the second desorber (block 9) in section extraction of urea.

In one of the preferred variants of the present invention proposed therein upgrade includes:

installation tools (line 26) for feeding at least part of the solution of the carbamate from partition retrieve urea shown in the diagram in the form of blocon to increase the conversion yield of the existing reactor for the synthesis of urea, but to increase its performance.

In fact, in the proposed scheme, in the reactor 1 is returned, a very small amount of water that can increase the amount fed to the reactor ammonia and carbon dioxide, without overloading not only the reactor, but desorber 2 and stills 3 and 4 sections extraction of urea.

The following examples, which are illustrative only and not limiting the scope of the invention and helps to compare the conversion outputs of the units that are on offer in the invention method, or obtained as a result of modernization of existing facilities proposed in the invention method, with the conversion output units operating according to the method.

Example 1. As a result of upgrading an existing installation, which works by a known method and technological scheme of which is shown in Fig. 1, was created, which works on offer in the invention method and technological scheme of which is shown in Fig. 2.

The work of the existing installation is based on the so-called process of imagesarray ammonia when in apparatus for the decomposition shown in the diagram in the TES on imagesarray scheme pipeline 30 is missing.

Before the modernization of the reactor for the synthesis of urea worked in the following modes:

The molar ratio of NH3/CO2at the entrance to 3.2

The molar ratio of H2O/CO2input - 0,6

Conversion output CO2in urea, % - 61

Pressure, bar abs. - 150

TemperatureoC - 190

Performance, tons of urea/day - 1800

After upgrading an existing installation by adding the second desorber 9, in which one of the sections of the extraction of urea was applied to 77% of a solution of carbamate, and the flow of vapor from the second desorber through the condenser 6 in the reaction space 1 (see Fig. 2) the reactor was operating in the following modes:

The molar ratio of NH3/CO2at the entrance to 3.2

The molar ratio of H2O/CO2at the entrance to 0.19

Conversion output CO2in urea, % - 70

Pressure, bar abs. - 150

TemperatureoC - 190

Performance, tons of urea/day 2500

Proposed in the present invention method led to a 9 % increase in the conversion yield and 700 tons, i.e. more than 39%, to increase the performance of an existing installation.

A significant increase in the conversion yield and decrease the amount of water returned to the modernization and low capital investment. In addition, the increase of the conversion output after the upgrade has allowed to reduce the amount expended on the installation of energy.

Example 2. As a result of upgrading an existing installation, operating well-known scheme, shown in Fig. 1, at its base, created a new working under proposed in the invention method, the installation process scheme is shown in Fig. 2.

Existing installation mode desorption of carbon dioxide gas when the flow of carbon dioxide as a Stripping reagent is served (by pipeline 30) in the apparatus for the decomposition shown in the diagram in block 2. When working in this mode in the scheme does not require the pipe 31, and the unit 7 is not required apparatus for separation of ammonia. In this scheme does not require the devices 3 and 7, and section allocation urea may only consist of working at low pressure devices 4 and 8.

Before the modernization of the reactor for the synthesis of urea worked in the following modes:

The molar ratio of NH3/CO2at the entrance to 3.0

The molar ratio of H2O/CO2input - 0,5

Conversion output CO2in urea, % - 60

Pressure, bar abs. About 145
the setup portion of the installation by adding the second desorber 9, in which section of the extraction of urea was applied 70% solution of carbamate, and the flow of vapor from the second desorber through the condenser 6 in the reaction space 1 (see Fig. 2) the reactor worked in the following new mode:

The molar ratio of NH3/CO2at the entrance to 3.0

The molar ratio of H2O/CO2input - 0.25 to

Conversion output CO2in urea, % - 66

Pressure, bar abs. - 150

TemperatureoC - 190

Performance, tons of urea/day 2500

Proposed in the present invention method led to a 6 % increase in conversion output and 600 tons, i.e. more than 32%, to increase the performance of an existing installation.

However, in addition, the increase in productivity and conversion yield was achieved with very little upgrading an existing installation and low additional investment.

Example 3. In this example, the increase of the conversion output of the reactor was achieved by his work in the newly created installation, which was implemented proposed in the present invention method, technological scheme of which is shown in Fig. 2.

As in example 2, the installation is served by pipeline 30 as a Stripping agent into the apparatus decomposition, shown in the diagram in block 2. In this case, the scheme does not require pipelines 22 and 31, and the unit 7 is not required apparatus for separation of ammonia. In section extraction of urea required to have the devices 3, 4, 7 and 8 medium and low pressure.

The reactor composition proposed in the present invention the plants for urea worked in the following modes:

The molar ratio of NH3/CO2at the entrance to 3.2

The molar ratio of H2O/CO2input - 0,1

Pressure, bar abs. - 150

TemperatureoC - 190

Performance, tons of urea/day - 400

Conversion output of carbon dioxide into urea in the running in this mode, the reactor was very high and reached 72%. The quantity of water returned to the reactor a solution of the carbamate was quite small.

A small amount of water and not entered in the interactions of the substances contained in the reaction mixture entering the apparatus for decomposing and then in section extraction of urea was determined by comparison with existing installations, the reduction of the load on the used hardware and provided for reducing power consumption and reducing the required kapitalanlagen is itnow calculation.

1. A method of producing urea, including the interaction between ammonia and carbon dioxide in the reaction space with obtaining a reaction mixture comprising urea, carbamate and free ammonia in aqueous solution; treating the resulting reaction mixture, consisting of partial decomposition of carbamate and partial separation of free ammonia in aqueous solution to obtain the first stream consisting of vapors of ammonia and carbon dioxide, and flow comprising urea and residual carbamate in aqueous solution; treating the first containing vapors of ammonia and carbon dioxide flow, consisting of at least partial condensation of the first portion of carbamate in aqueous solution; recycling a first portion of carbamate in the reaction space; a flow comprising urea and residual carbamate in aqueous solution, in the section extraction urea; Department section extraction urea residue of the carbamate from the urea and receiving the second portion of carbamate in aqueous solution, characterized in that it further includes the following stages: processing at least part of the second portion of carbamate in aqueous solution,

obtained in section extraction of urea, C is an acidic gas, and stream containing residual carbamate in aqueous solution; treating the second containing vapors of ammonia and carbon dioxide gas stream consisting of at least partial condensation of the vapors and receiving a third portion of carbamate in aqueous solution; and recycling the third part of the carbamate in the reaction space.

2. The method according to p. 1, characterized in that the partial decomposition of at least part of the second part of the residual carbamate in aqueous solution is performed at a pressure, which essentially corresponds to the pressure in the reaction space.

3. The method according to p. 1, characterized in that it also includes stage feed stream containing residual carbamate in aqueous solution formed after partial decomposition of the second portion of carbamate in section extraction of urea.

4. The method according to p. 1, characterized in that it includes the flow of the reaction mixture containing urea, carbamate and free ammonia in aqueous solution, in the apparatus for decomposition; feeding at least part of the second portion of carbamate in aqueous solution in said apparatus for decomposition, with partial decomposition of the reaction mixture and the second part of the carbamate is carried out in the same apparatus for razlozhennosti of carbamate in aqueous solution.

5. The method according to p. 1, characterized in that at least 50% of the second portion of carbamate in aqueous solution is subjected to a treatment consisting in the partial decomposition.

6. The method according to p. 5, characterized in that at least 65% from the second portion of carbamate in aqueous solution is subjected to a treatment consisting in the partial decomposition.

7. Device for producing urea-containing reactor for the synthesis of urea; the first desorber, which is taken from the reactor the reaction mixture is subjected to a treatment consisting in the partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the reaction mixture; equipment for condensing at least part of the vapor taken from desorber, and recirculation in the reactor of the first part of carbamate in aqueous solution; section extraction of urea, which is a stream containing urea and residual carbamate in aqueous solution selected from the first desorber, and in which the separation obtained in the urea reactor from the second portion of carbamate in aqueous solution; characterized in that it is provided by the second desorber, in which there is a partial decomposition of at least part of the second the second desorber, and recirculation in the reactor of the third part of carbamate in aqueous solution.

8. Installation according to p. 7, characterized in that the equipment for condensing vapors taken from the second desorber, is equipment for condensing vapors taken from the first desorber.

9. Installation according to p. 7, characterized in that it also contains equipment for feed stream containing residual carbamate in aqueous solution from the second desorber in section extraction of urea.

10. Device for producing urea-containing reactor for the synthesis of urea; the first desorber, which is taken from the reactor the reaction mixture is subjected to a treatment consisting in the partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the reaction mixture; equipment for condensing at least part of the vapor taken from desorber, and recirculation in the reactor of the first part of carbamate in aqueous solution; section extraction of urea, which is a stream containing urea and residual carbamate in aqueous solution selected from desorber, and in which the separation obtained in the urea reactor from the second portion of carbamate in aqueous rastoder solution in desorber.

11. The way of modernization of the plant for producing urea by feeding the reaction mixture from the reactor for the synthesis of urea in the first desorber for the partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the reaction mixture, and subsequent at least partial condensation of the vapors taken from the first desorber, condenser and recycling the first portion of carbamate in aqueous solution in the reactor by feeding a stream containing urea and residual carbamate in aqueous solution, from the first desorber in section extraction of urea for the Department received in the reactor urea from the second portion of carbamate in aqueous solution, characterized in that which further establish the second desorber for the partial decomposition of at least part of the second portion of carbamate in aqueous solution, as well as installing equipment designed for condensing at least part of the vapor taken from the second desorber, and for recirculation in the reactor of the third part of carbamate in aqueous solution.

12. The way of modernization of the plant for producing urea by feeding the reaction mixture from the reactor for the synthesis of urea in the first desorber for partial razloga and subsequent at least partial condensation of the vapor, taken from the first desorber, condenser and recycling the first portion of carbamate in aqueous solution in the reactor by feeding a stream containing urea and residual carbamate in aqueous solution, from the first desorber in section extraction of urea for the Department received in the reactor urea from the second portion of carbamate in aqueous solution, characterized in that it further establish the second desorber for the partial decomposition of at least part of the second portion of carbamate in aqueous solution, and install the equipment with which submit vapor taken from the second desorber, equipment for condensing vapors, taken from the first desorber.

13. The method according to p. 11 or 12, characterized in that install the equipment for feed stream containing residual carbamate in aqueous solution from the second desorber in section extraction of urea.

14. The way of modernization of the plant for producing urea by feeding the reaction mixture from the reactor for the synthesis of urea in desorber for the partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the reaction mixture, and subsequent at least partial core the reactor at flow, contains urea and residual carbamate in aqueous solution, of desorber in section extraction of urea for the Department received in the reactor urea from the second portion of carbamate in aqueous solution, characterized in that it further set up the equipment for feeding at least a second portion of carbamate in aqueous solution in desorber.

 

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FIELD: chemical technology.

SUBSTANCE: invention relates to producing urea from ammonia and carbon dioxide. Method involves preparing products of reaction in the synthesis zone as a solution containing urea, ammonium carbamate and unreacted ammonia. Part of solution obtained in synthesis of urea (preferably 10-60 wt.-%) is fed from the synthesis zone to additionally assembled zone of treatment under mean pressure at 1-4 MPa wherein gas flow is separated and subjected for absorption with ammonium carbamate solution of low pressure supplying from the section for isolation and treatment of urea. As a variant of method the invention proposes to use the combined reactor in the synthesis zone representing vertically installed or combined reactor. Enhancement of output of existing processes in synthesis of urea is achieved by feeding part of urea solution synthesized in the synthesis reactor to additionally installed zone for treatment of mean pressure including the dissociation zone, desorption zone of mean pressure and the condensation zone of mean pressure. Invention provides enhancement of output of unit for producing urea being without modification of section of high pressure.

EFFECT: improved method for producing urea.

10 cl, 4 dwg

FIELD: chemical technology.

SUBSTANCE: invention relates to technology for preparing urea. Method involves interaction of pure ammonia and carbon dioxide in reaction space to obtain reaction mixture containing urea, carbamate and free ammonia in an aqueous solution that is treated in evaporator (1) to obtain partially purified mixture that is fed to section for isolation of urea. Diluted solution of carbamate removing from the urea isolating section is subjected for treatment in evaporator (2) and at least part of vapors formed in it is recovered to the reaction space and/or into evaporator (1). Significant part of carbamate in aqueous solution is subjected for decomposition under pressure that corresponds essentially to pressure value in reaction space. Part of decomposition products including ammonia and carbon dioxide in vapor phase is recovered into reactor and/or into the first evaporator (1) and carbamate after its partial decomposing is fed into section for isolating urea. Device for preparing urea consists of the synthesis reactor, evaporators (1) and (2) for partial decomposition of carbamate and for separation of free ammonia and carbon dioxide in vapor phase, apparatus for condensation of vapor flow, pipe-line for recover of carbamate part in aqueous solution into reactor and section for isolation of urea from its aqueous solution. Preferably, pipe-line is fitted with ejector and evaporators are fitted with apparatus for feeding carbon dioxide as a evaporating agent. Invention provides enhancing yield of urea, reducing energy consumptions and investment due to updating the technological schedule of the process.

EFFECT: improved preparing and updating methods.

30 cl, 4 dwg

FIELD: chemical industry; methods and the devices for production of carbamide from ammonia and carbon dioxide.

SUBSTANCE: the invention is pertaining to the field of chemical industry, in particular, to the methods and the devices for production of carbamide from ammonia and carbon dioxide. The method of production of carbamide includes the interaction of ammonia and carbon dioxide in the zone of synthesis at the heightened temperatures and pressures with formation of the melt of the carbamide containing carbamide, water, ammonium carbamate, ammonia and carbon dioxide. The carbamide melt distillation conduct at the heat feeding on the two stages of pressure preferentially at 15-25°C and 2-5 kgf/cm2. The carbamide melt distillation on the first step of the pressure conduct sequentially in two zones. In the first zone the distillation is conducted adiabatically or at the heat feeding, and in the second zone - at the heat feeding in the stream of carbon dioxide. The condensation-absorption process at refrigeration of the gases of the distillation is conducted with utilization of the aqueous absorbers. The formed aqueous solutions of the carbon- ammonium salts are recycled from the stage of the condensation-absorption of the gases of the distillation of the second step to the stage of the condensation-absorption of the gases of distillation of the first step, and also from the stage of the condensation-absorption of the gases of distillation of the first step into the zone of the synthesis. The evaporation of the aqueous solution of carbamide is exercised in some steps at the heat exchange between the gases of the distillation of the first step and the aqueous solution of carbamide at the stage of the preliminary evaporation. The installation for production of carbamide consists of: the reactor of the carbamide synthesis; the device with the heat feeding from the external source for distillation of the carbamide melt produced in the reactor of the carbamide synthesis at the first step of the pressure and consisting of the column of distillation melt of the first step and the film-type heat exchanger; the device with the heat feeding for the distillation of the carbamide melt on the second step of pressure; apparatuses for evaporation at heating of the aqueous solution of the carbamide produced on the second step of distillation. The devices for condensation-absorption at refrigeration of the gases of the distillation of the both steps switch on the heat exchanger-recuperator for heat interchange between the gases of the distillation of the first step and the aqueous solution of carbamide. The installation also contains a means for feeding of ammonia and carbon dioxide into the reactor of synthesis of carbamide, feeding of the carbamide melt from the reactor of synthesis into the column of distillation of the first step, from the column of distillation of the first step into the film-type heat exchanger and from the film-type heat exchanger into the device for distillation of the second step, the aqueous solution of carbamide from the device for distilling of the second step into the heat exchanger-recuperator and from the heat exchanger-recuperator - into the apparatus for the subsequent evaporation; the gases of distillation from the device for distilling of the first step - in the heat exchanger-recuperator and from the heat exchanger-recuperator - into the device for condensation-absorption of the gases of distillation of the first step; the gases of distillation from the apparatus for distillation of the second step - into the device for condensation-absorption of the gases of distillation of the second step; the solution of the carbon-ammonium salts from the device for condensation-absorption of the gases of distillation of the second step - into the device for condensation-absorption of the gases of distillation of the first step and from the device for condensation-absorption of the gases of distillation of the first step - into the reactor of synthesis, a means for feeding of carbon dioxide into the film-type heat exchanger. The technical result of the invention is the increased degree of the heat recuperation of the production cycle and reduction of he quantity of the heat exchangers using the heating steam from the external sources.

EFFECT: the invention ensures the increased degree of the heat recuperation of the production cycle and reduction of he quantity of the heat exchangers using the heating steam from the external sources.

8 cl, 3 ex, 3 dwg

FIELD: chemical industry; methods of production of carbamide from carbon dioxide and ammonia.

SUBSTANCE: the invention is pertaining to the method of production of carbamide from carbon dioxide and ammonia. The method of production of carbamide is realized in the reactor of synthesis with the subsequent thermal distillation from the reaction mixture of the carbamate and partially ammonia in the high-pressure apparatus at heat input by means of the steam. The separated gas phase is directed for condensation into the high-pressure condenser, where gas condensation heat is transferred to the heat-carrier with formation of the steam A. The carbamide solution from the high-pressure apparatus is fed for the ammonium carbamate decomposition into the apparatus at the average pressure with usage of the heat carrier. At that as the heat carrier use the steam condensate produced after the high-pressure apparatus in the combination the steam A. The high-pressure condenser represents the submerged condenser. The installation for production of carbamide includes the reactor of the synthesis of carbamide, the high-pressure apparatus for the thermal distillation of the carbamate and ammonia from the solution of synthesis of carbamide with the heat supply by means of the heat carrier, and also contains the apparatus for ammonium carbamate decomposition at the average pressure. As the high-pressure condenser used for the gas phase condensation the installation contains the submerged condenser. The method of the installation upgrade consists that the existing high-pressure condenser is substituted for the submerged condenser. The technical result of the invention is reduction of the power inputs due to upgrade of the equipment and the combined usage of the scheme of recuperation of the heat of the heat carriers.

EFFECT: the invention ensures the reduced power inputs, the upgrade of the equipment, the combined usage of the scheme of recuperation of the heat of the heat carriers.

12 cl, 2 dwg

FIELD: chemical industry; methods and devices for production of carbamide.

SUBSTANCE: the invention is pertaining to the methods and devices for production of carbamide from ammonia and carbon dioxide. At realization of the method the reaction mixture from the synthesis reactor is fed in the stripper for the partial decomposition of the ammonium carbamate in the flow of the source carbon dioxide at the pressure practically equal to the pressure in the synthesis reactor. The stream of the source carbon dioxide is divided into two parts, one of which is routed into the stripper, and the other part is used as the working stream for injection of the gas stream from the stripper into the vertical condenser. The liquid stream from the stripper is fed at the stage of the subsequent decomposition of the ammonium carbamate, and the gaseous stream from the stripper is injected into the lower part of the vertical condenser for its mixing with source liquid ammonia. The liquid stream from the vertical condenser is fed into the synthesis reactor, butt from the gaseous stream absorb ammonia and carbon dioxide. The installation for production of carbamide consists of: the synthesis reactor; the scrubber for purification of the gaseous streams from the reactor from ammonia and carbon dioxide; the stripper for the partial decomposition of the ammonium carbamate; the vertical condenser, in which the mixing of the gas stream from the stripper with the source liquid ammonia takes place. The stripper is connected to the lines of feeding of the fluid stream from the reactor and the stream of the source carbon dioxide, and also is equipped with tool for injection of the gaseous stream from the stripper into the vertical condenser by the part of the stream of the source carbon dioxide. By the liquid stream the stripper is linked with the apparatuses for the subsequent decomposition of the ammonium carbamate and extraction of carbamide. The method of upgrading of the installation for production of carbamide consists in connection of the reactor of the synthesis to the stripper for the partial decomposition of the ammonium carbamate in the flow of the source carbon dioxide, in equipping the stripper with the tools for injection of the gaseous stream from the stripper into the vertical condenser with the part of the stream of the source carbon dioxide, and also in the availability of the lines of delivery of the gaseous mixture after the injector and the feeding line of the source liquid ammonia into the lower part of the vertical condenser. The technical result of the invention is the increased degree of conversion of the source reagents into carbamide at reduction of the scale of recirculation of the non-converted reactants.

EFFECT: the invention ensures the increased degree of conversion of the source reagents into carbamide at reduction of the scale of recirculation of the non-converted reactants.

11 cl, 2 ex, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to production of urea from ammonia and carbon dioxide. A reaction mixture is obtained in a synthesis reactor at given high pressure as a result of a reaction between NH3 and CO2, where the said reaction mixture contains urea, ammonium carbamate and free ammonia in aqueous solution, from which ammonium carbamate and ammonia are extracted and subsequently returned to the synthesis reactor. Ammonium carbamate and ammonia are extracted from the reaction mixture on process steps for decomposing ammonium carbamate to NH3 and CO2 and their stripping and on the next process step for their re-condensation to obtain ammonium carbamate which is returned to the synthesis reactor. The reaction mixture obtained as a result of the reaction between ammonia and carbon dioxide is taken to the process steps for decomposition and stripping using a pump.

EFFECT: changing production capacity by changing pump parameters, possibility of horizontal assembling, reduced expenses on servicing and increased safety.

12 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to obtaining urea from ammonia and carbon dioxide. As a result of ammonia and carbon dioxide interaction at high pressure in reactor obtained is water solution, which contains urea, ammonium carbamate and ammonia. From obtained water solution carbamate and ammonia are separated by decomposing carbamate and thermal evaporation of ammonia and carbon dioxide in stripping apparatus, obtaining ammonia and carbon dioxide, which after that are again condensed in condenser obtaining carbamate, which is returned to reactor. All stages together with reaction of synthesis are carried out in fact at one and the same pressure. In addition, into reactor additionally supplied is passivating oxygen, obtained as a result of interaction waste gases, which contain carbon dioxide, ammonia and passivating oxygen which did not take part in the reaction, are removed from reactor and are supplied into bottom part of stripping apparatus for passivation of at least part of its internal surfaces. Installation for obtaining urea contains communicating with each other and forming closed high pressure contour reactor, stripping apparatus, condenser, section of final urea purification and pipelines for supply into reactor of carbon dioxide and ammonia. It is equipped with pipeline for supply into reactor of passivating oxygen and pipeline for connecting upper part of reactor with bottom part of stripping apparatus.

EFFECT: ensuring even and efficient passivation of all apparatuses of high pressure contour.

13 cl, 2 dwg

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