Method and apparatus for producing aqueous solution containing urea

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing an aqueous solution containing urea, meant for use when removing nitrogen oxides from gaseous combustion products and flue gases. The method involves steps for: using carbon dioxide to wash at least a portion of concentrated aqueous urea solution obtained directly from or downstream the urea extraction section of an apparatus for producing urea and containing residual free ammonia, to obtain a first vapour phase containing carbon dioxide and possibly ammonia and concentrated aqueous urea solution containing carbamate and essentially not containing free ammonia, and dilution of said concentrated aqueous urea solution containing carbamate and essentially not containing free ammonia with water until the required urea concentration in the aqueous solution is achieved. Also disclosed is an apparatus for producing an aqueous solution containing urea (versions) and a method of modernising existing apparatus for producing urea (versions).

EFFECT: invention significantly reduces power consumption.

21 c, 2 dwg

 

The present invention relates, in General, to a method for producing an aqueous solution containing urea, intended for use in the removal of nitrogen oxides (Nox)present in the gaseous combustion products through their recovery with gaseous ammonia.

In particular, the present invention relates to the aforementioned method, in the exercise of which urea is produced by synthesis from starting materials ammonia and carbon dioxide.

The present invention relates also to an apparatus for obtaining an aqueous solution containing urea, which is the above method.

As you know, international laws on emissions resulting from the combustion of fossil fuels (gaseous products of combustion or flue gases) is constantly greater demands a radical reduction of pollutants in the above gaseous emissions, including, in particular, oxides of nitrogen (Nox), as it is believed that they are caused by the so-called acid rain.

For this purpose various methods for cleaning gaseous emissions from the burning of fossil fuels. In particular, the widely used method of selective catalytic reduction of nitrogen oxides (Nox), better known as SLE (eng. SCR), to the which provides the removal of significant amounts of NO and NO 2from gaseous emissions by converting them into compounds that are neutral to the environment, such as nitrogen and water vapor.

This method is used, in particular, to radically reduce the content of nitrogen oxides in the emissions from heavy duty vehicles, especially cars with diesel engines or diesel engines with turbocharging.

The method of SLE is based on the following sequential chemical reactions, leading to the removal of nitrogen oxides by reaction with ammonia and oxygen in the stream, to be clear:

4NO + O2+ 4NH3= 4N2+ 6H2O

6NO2+ 8NH3= 7N2+ 12H2O

NO + NO2+ 2NH3= 2N2+ 2H2O

All the above reactions are very exothermic, and estimates the temperature of the stream of gases containing Nox in the amount of 1000 ppm million, in the process of chemical transformation increases on average at 10-11°C.

The optimal temperature range for the method of SLE is within 180°C-350°C. At temperatures below 180°C chemical transformation is not complete, and therefore cannot normally required to provide the results of removal of nitrogen oxides, while at temperatures above 350°C between ammonia and oxygen contained in the gas stream, adverse reactions occur, the AK that at 400°C we have the loss of about 5-10% ammonia, mainly in the following reaction.

The reactions, antagonistic in relation to the reactions associated with the treatment, at temperatures above 350°C and the practical need to avoid lowering the temperature below the minimum operating temperature 200°C causes the need to use to implement this method, an appropriate catalyst system or catalyst; heavy duty vehicles of the latest generation, such as, for example, heavy trucks with engines meeting Euro 4 or Euro 5, usually equipped with such a catalytic system or catalytic Converter.

With regard to the supply of ammonia required for implementing the method of SLE, it is known to use ammonia or urea in an aqueous solution with a concentration typically in the range of 15-35 wt.% on the weight of the solution.

This aqueous solution using spray nozzles inject into the stream of cleaned gas on the inlet side of the catalytic system of SLE (or catalyst). On the inlet side of the catalytic system can also be installed more static mixing device which provides the necessary turbulence of the flow of gases contributing to the distribution of the reagent.

Particularly common is the use of urea is in an aqueous solution as a reagent for the implementation of the above method, as this excludes risks associated with the transportation or storage of ammonia or aqueous solutions. In this case, the ammonia needed for the cleaning of flow of the gases produced by decomposition of urea in place the following reaction:

N2H4CO + H2O = 2NH3+ CO2

The decomposition reaction is endothermic and the necessary heat is provided by the cleaned gases (typically having a temperature above 300°C), what allows to reduce the temperature of the gas to the optimal values for implementing the method of SLE, above.

As far as getting the urea in the aqueous solution used to remove oxides of nitrogen, prior art provided by the first receiving urea is synthesized in molten form or in the form of granules in the usual units for production of urea, and then the dilution of the urea water to achieve in the obtained aqueous solution of the desired concentration of urea.

This way you can get the final product (urea in aqueous solution), which is particularly pure and does not contain free ammonia (ammonia is undesirable because of its unpleasant smell and impact on the environment), due to the fact that by synthesizing get urea (in molten form or in pellets) with a very high grade is Yu purity (purity - not less than 99%).

However, the above method is associated with a high consumption of energy, since the removal of ammonia in the process of obtaining the fused or granular urea of high purity should be concentrated urea solution obtained by the synthesis in order to completely remove the solvent (water), and then re-enter the above solvent at the stage of dilution molten or granulated urea. A method of obtaining a water stream containing urea, disclosed for example in WO 2006/096048.

Accordingly, the technical problem underlying the present invention is to develop and provide a method of obtaining an aqueous solution containing urea, for use in removal of nitrogen oxides from gaseous products of combustion or flue gases, based on the aqueous solution of urea, obtained by synthesis, which eliminates the aforementioned disadvantages of the known prior art, in particular, the above-mentioned method, in the exercise of which there is a possibility, mainly to remove ammonia from the above aqueous solution of urea, obtained by synthesis, with lower energy consumption compared with conventional methods.

In accordance with the present invention, this technical problem is solved by time is abode method of producing an aqueous solution, contains urea, which is used for removal of nitrogen oxides from the gaseous combustion products and the flue gas, which is characterized in that it comprises the following stages:

- flushing with carbon dioxide at least part of the concentrated aqueous solution of urea containing residual free ammonia obtained directly from the partition extraction of urea or below in the direction of flow of the section extraction of urea on the plant for urea, with the first vapor phase containing carbon dioxide and possibly ammonia and concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia;

- dilution of the above concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia water to obtain an aqueous solution of the desired concentration of urea.

The above-mentioned desired concentration of urea in aqueous solution is preferably in the range of 15-35 wt.% by weight of solution.

In a particularly preferred embodiment of the present invention a concentrated aqueous solution of urea containing residual free ammonia being at least partially flushing with carbon dioxide, is obtained directly from the section extracted what I urea on the device for producing urea.

In another embodiment, the method includes processing the aqueous solution obtained in section synthesis unit for production of urea and containing urea, ammonium carbamate and free ammonia to decompose ammonium carbamate, possibly in the presence of inert gas Stripping section to remove urea, obtaining, thus, the second vapor phase containing ammonia and carbon dioxide, and the concentrated aqueous solution of urea containing residual free ammonia. The method may further include a recirculation of the specified second vapor phase containing ammonia and carbon dioxide, in the form of condensate in the section of the synthesis of urea.

The expression "section of the extraction of urea" is used to refer to parts of the plant for producing urea containing essentially a standard device for the purification of aqueous solutions of urea, obtained by synthesis, with the aim of reducing the content in these solutions carbamate and free ammonia. Such devices include at least one device for decomposition of carbamate or Stripping apparatus which is an apparatus thermal action or, preferably, operates using an inert gas used for evaporation of the solution. Moreover, the pressure in the extraction of urea is generally lower than is ecchi synthesis, in which the ammonia and carbon dioxide are urea.

In another preferred embodiment of the invention a concentrated aqueous solution of urea containing residual free ammonia being at least partially flushing the carbon dioxide comes from the evaporation section below in the direction of flow of the above section extraction urea unit for production of urea.

To this end the above-mentioned concentrated aqueous solution of urea containing residual free ammonia being at least partially flushing with carbon dioxide, preferably obtained from the evaporator in the above sections evaporation used for evaporation of concentrated urea solution coming from the section of the extraction of urea on the device for producing urea and containing residual free ammonia.

Thanks to the present invention a concentrated aqueous solution of urea, obtained on the device for producing urea directly from partition retrieve urea or below in the direction of flow in this section and still containing free ammonia, mainly subjected to, at least partially, flushing with carbon dioxide, not evaporation, as in the implementation of known methods, by mentioning is mentioned above.

This allows you to get great advantages relative to the prior art, including a significant reduction in energy consumption, due to the fact that the energy consumption for flushing with carbon dioxide is less than that required by evaporation.

Moreover, flushing with carbon dioxide mainly allows you to remove a greater quantity of free ammonia contained in the above solution, turning it into safer carbamate (from the point of view of impact on the environment) and possibly turning it partially in the vapor phase by evaporation using the above carbon dioxide.

Therefore, a concentrated aqueous urea solution obtained by washing with carbon dioxide, basically does not contain free ammonia and mainly can be used for removal of nitrogen oxides from gaseous products of combustion after diluting it with water until the desired concentration of urea in aqueous solution (15-35 wt.% by weight solution) and the ammonia content is below the threshold value of the sense of smell, preferably below 150 ppm million

In addition, it should be noted that the ammonium carbamate contained in the above aqueous solution of urea, while using the above solution to remove Nox from gaseous products sharemyplaylists decomposes along with urea, thus, the newly forming carbon dioxide and ammonia, the latter is used to remove Nox.

The above-mentioned technical problem is solved by creating the installation to obtain an aqueous solution containing urea, used for removal of nitrogen oxides from gaseous products of combustion or flue gases, in which the above-described method proposed in the invention.

In accordance with one embodiment of the invention, the installation includes a section of the synthesis of urea and the section of the extraction of urea, communicating with each other, and characterized in that it further includes:

section flushing with carbon dioxide below in the direction of flow of the above-mentioned section of the extraction of urea;

- supply pipe mounted between the above section extraction of urea and above the washing section, for supplying at least part of the concentrated aqueous urea solution obtained in the above section the extraction of urea and containing residual free ammonia in the above section leaching;

the pipeline for the supply of carbon dioxide in the above section leaching;

the pipeline for release of the concentrated aqueous solution of urea containing carbamate and essentially not containing free the ammonia, from the above sections, rinsing, and

pipe for water supply which is connected with the above pipeline for release from the washing section, for diluting the above-mentioned concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, to obtain the desired concentration of urea in aqueous solution.

In accordance with another embodiment of the invention, the installation includes a section of the synthesis of urea, the section extraction of urea and the evaporation section, including the first evaporating device and the second evaporating device; and the above section are communicated with each other, and the setup is different in that it further includes:

section flushing with carbon dioxide below in the direction of flow of the above-mentioned section of the extraction of urea;

- supply pipe mounted between the above first evaporation apparatus and the above-mentioned washing section, for supplying at least part of the concentrated aqueous urea solution obtained in the above first evaporation apparatus and containing residual free ammonia in the above section leaching;

the pipeline for the supply of carbon dioxide in the above section leaching;

the pipeline for release of concentrated water dissolve the and urea, containing carbamate and essentially not containing free ammonia, from the above sections, rinsing, and

pipe for water supply which is connected with the above pipeline for release from the washing section, for diluting the above-mentioned concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, in order to obtain the desired concentration of urea in aqueous solution.

Proposed in the present invention, the device for producing an aqueous solution containing urea, can be performed on a new project or preferably can be created on the basis of already existing equipment for production of urea by synthesis.

In the latter case, in accordance with another feature of the present invention provides a method of modernization (reconstruction) of an existing unit for production of urea from ammonia and carbon dioxide, including the sections of the synthesis of urea and the section of the extraction of urea, communicating with each other, which differs in that it comprises the following stages:

- installation section of flushing with carbon dioxide below in the direction of flow of the above-mentioned section of the extraction of urea;

- installation of the connecting pipeline between the above section extraction of urea and the above section promilk is, designed to supply at least part of the concentrated aqueous urea solution coming from the above sections, extraction of urea and containing residual free ammonia in the above section leaching;

- installation of pipeline for supply of carbon dioxide in the above section leaching;

- installation of pipeline for production of a concentrated solution of urea containing carbamate and essentially not containing free ammonia, from the above sections leaching; and

- installation of pipeline for water supply connected to the above-mentioned exhaust manifold to dilute the above concentrated solution of urea containing carbamate and essentially not containing free ammonia, to obtain in an aqueous solution of the desired concentration of urea.

In accordance with another embodiment of the invention a method of modernization (reconstruction) of an existing unit for production of urea from ammonia and carbon dioxide, including the sections of the synthesis of urea, the section extraction of urea and the evaporation section, including the first evaporating device and the second evaporation apparatus, and the above section are communicated with each other, characterized in that it comprises the following stages:

- installation section of flushing with carbon dioxide lower voltage is to making a thread above section extraction of urea;

- installation of the connecting pipeline between the aforementioned first evaporation apparatus and the above section rinsing, designed to supply at least part of the concentrated aqueous urea solution obtained in the above-mentioned first evaporation apparatus and containing residual free ammonia in the above section leaching;

- installation of pipeline for supply of carbon dioxide in the above section leaching;

- installation of pipeline for production of a concentrated solution of urea containing carbamate and essentially not containing free ammonia, from the above sections, rinsing, and

- pre-installation of pipeline for water supply connected to the above-mentioned exhaust manifold to dilute the above concentrated solution of urea containing carbamate and essentially not containing free ammonia, to obtain in an aqueous solution of the desired concentration of urea.

Other features and advantages of the method of producing urea in aqueous solution proposed in the present invention, will be apparent from the following description of the preferred variants of its implementation, given as an illustrative and non-limiting example, with reference to the accompanying drawings, on which:

figure 1 presents a flowchart of the known installation to obtain an aqueous solution, contains urea, which is intended for use in the removal of nitrogen oxides from the gaseous combustion products;

figure 2 presents the block diagram of the proposed in the present invention is setup to obtain an aqueous solution containing urea, intended for use in the removal of nitrogen oxides from the gaseous combustion products.

As can be seen from figure 1, a known device for producing an aqueous solution containing urea, intended for use in the removal of nitrogen oxides from gaseous products of combustion, generally designated by the reference numeral 1.

A method of producing urea in aqueous solution, obtained by setting 1, based on receiving urea is synthesized in molten form and the subsequent dilution of the molten urea with water to obtain in the resulting aqueous solution of the desired concentration of urea.

In particular, the installation 1 includes section 2 of the synthesis of urea, operating at a predetermined high pressure (for example, 135-175 bar), section 3 extraction of urea, operating at a predetermined low pressure (for example, 1-10 bar), section 4 evaporation and section 5 cleaning/condensation of vapors derived from section 4 of evaporation, and the above section are communicated with each other.

In addition, the installation 1 includes pipelines 6 and 7 for the filing, respectively, carbon dioxide and ammonia, which are necessary for the synthesis of urea in section 2 of the synthesis. In this section, 2 in the reactor, the ammonia and carbon dioxide react with obtaining an aqueous solution containing urea, ammonium carbamate and free ammonia, which pipe 8 serves in section 3 extraction of urea.

In section 3 we extract urea above solution containing urea, ammonium carbamate and free ammonia, processed with the purpose of decomposition of the ammonium carbamate in the respective, essentially, a standard device, such as a Stripping apparatus, the apparatus for distillation (stills) and others, getting a vapor phase containing ammonia and carbon dioxide, and concentrated urea solution (with concentration of urea equal to, for example, 70 wt.% by weight solution)containing residual free ammonia.

Vapor phase, leaving section 3 extraction of urea and ammonia and carbon dioxide, respectively, recycle pipeline 9 in section 2 of the synthesis for further conversion into urea, while the concentrated urea solution leaving the above section 3 extraction of urea and containing residual free ammonia, the pipe 10 serves in section 4 evaporation.

In particular, the above-mentioned vapor phase, the soda is containing ammonia and carbon dioxide, recycle section of the synthesis is preferably in the form of condensate (with the formation of a solution containing ammonium carbamate) using a condensing fluid (usually a recirculating solution of carbamate), essentially, in the conventional capacitor in section 3 extraction of urea.

The stream of gases containing inert gases (e.g. nitrogen, hydrogen, oxygen etc), usually present at the feeding of carbon dioxide to protect the reactor section 2 synthesis from corrosion, also diverted from section 3 extraction of urea through the pipeline 11.

In section 4 evaporation of the above concentrated solution of urea containing residual free ammonia, the solvent is evaporated (water) and remove residual free ammonia using essentially conventional devices such as, for example, multiple evaporators, etc., receiving molten urea and steam phase containing water and ammonia.

Accordingly, the vapour phase leaving section 4 evaporation and containing water and ammonia via the pipeline 12 is fed to the processing section 5 (treatment), in which there are a number of conventional devices for its condensation and the allocation of water residual gaseous components (mainly ammonia and carbon dioxide).

Then the output section 5 processing pipeline 13 to receive the flow of fluid, mainly consisting of water for future use and the flow of gases, consisting mainly of ammonia and carbon dioxide, which pipe 15 recycle in section 3 extraction of urea.

In section 3 we extract urea above the stream of gases mainly consisting of ammonia, may be subjected to regular cleaning and returned, preferably in the form of condensate, in section 2 of the synthesis.

Instead, the molten urea is obtained in section 4 evaporation/distillation, emerges from the above sections 4 through the pipe 16 and is mixed with water circulating in the pipe 17, soobshayem with tubing 16 to release the molten urea, obtaining, thus, an aqueous urea solution with the required concentration of urea, for example, concentration equal to 32 wt.% by weight of solution.

Figure 2 is proposed in the present invention, the device for producing urea in aqueous solution, designed for use in the removal of nitrogen oxides from gaseous products of combustion, and this installation generally designated by reference numeral 20.

In particular, the proposed invention in installing 20 provides the obtaining by the synthesis of urea and urea in aqueous solution, which can be used to remove nitrogen oxides from the gaseous products of combustion, as is more fully explained below in the present description.

ELEH the coefficients installation 20, structurally and functionally equivalent to the corresponding elements described above setup 1, are denoted by the same numerals for references. Moreover, for brevity, the description of these elements is then missing.

Installation 20, as described above, the installation 1 includes section 2 of the synthesis of urea, operating at a predetermined high pressure (for example, 135-175 bar), section 3 extraction of urea, operating at a predetermined low pressure (for example, 1-10 bar), section 4 evaporation and section 5 cleaning/condensation of vapors derived from section 4 of evaporation; and the above section are communicated with each other.

In particular, in the present embodiment, the section 4 evaporation includes a first evaporation apparatus 4A and the second evaporating device 4b installed in series and communicating with each other and with section 3 extraction of urea (through the first evaporation apparatus 4A).

In addition, in accordance with the present invention, the installation 20 includes a section 22 flushing with carbon dioxide below in the direction of flow of the section 3 extraction of urea and line 23 is mounted between the section 3 extraction of urea and section 22 of the washing, for diversion of a portion of the concentrated aqueous urea solution coming from section 3 extraction of urea and containing residual free ammonia in the above section 22 promilk is.

In particular, the pipe 23 communicates with the pipe 10 for the issue of the above concentrated aqueous solution of urea containing residual free ammonia, from section 3 extraction of urea, which the rest of the above concentrated aqueous solution of urea containing residual free ammonia, is fed into the section 4 evaporation.

In section 22 of the washing of the above concentrated aqueous solution of urea containing residual free ammonia, is subjected to washing with carbon dioxide supplied in section 22 on the appropriate pipe 24, which generally leads to the transformation contained in the above solution residual free ammonia carbamate and possible removal of part of the ammonia in the vapor phase by Stripping with a gaseous stream of carbon dioxide supplied to the section 22 wash.

To this end, the section 22 of the washing includes some of the standard device for mass transfer between the liquid phase and the gaseous phase, such as, for example, scrubbers for gas purification, plate distillation columns, etc.

As a result, at the output of section 22 of the washing obtain a concentrated aqueous solution of urea containing carbamate and, basically, not containing free ammonia, and steam phase containing dio is led carbon and perhaps ammonia.

In accordance with the present invention a concentrated aqueous urea solution obtained in section 22 of the washing and containing carbamate and, basically, not containing free ammonia, diluted with water circulating in the pipe 17 which communicates with the pipe 25 to the issue of the above solution from the washing section, and thus, the desired concentration of urea in aqueous solution, for example, the concentration of urea equal to 30 wt.% by weight of solution.

Vapour phase coming out of the section 22 of the washing and containing carbon dioxide and possibly ammonia, serves in section 3 extraction of urea by pipeline 27, mounted between the section 22 and rinsing section 3 extraction of urea, for further essentially normal processing, for example, in order respectively to ensure its recirculation in section 2 of the synthesis is preferably in the form of condensate.

It should also be noted that carbon dioxide for washing, supplied in section 22 of the washing can mainly be part of the source of carbon dioxide supplied in section 2 of the synthesis of urea. Alternatively, carbon dioxide can come from other parts of the plant proposed in the invention, or from external sources. Preferably, carbon dioxide for washing serves in section 22 in isback is in relation to the content of ammonia in a concentrated urea solution, in order to carry out mainly in quantitative terms, the transformation of the above-mentioned ammonia carbamate.

In addition, it should be noted that in accordance with the present invention, the remaining portion of the concentrated aqueous solution of urea containing residual free ammonia emerging from section 3 extraction of urea and not directed in section 22 of leaching, mainly served by pipeline 10 in the first evaporation apparatus 4A section 4 distillation, and from there through the connecting conduit 31 to the second evaporation apparatus 4b. From the first evaporator 4A receive more concentrated aqueous urea solution, still containing residual free ammonia, while the second evaporation apparatus 4b, the solvent is removed completely, and thus, the molten urea, which emerges from the evaporator 4b through the pipeline 16. In addition, from the evaporators 4A and 4b receive the vapor phase containing water and ammonia, which on the respective pipes 12A and 12b are sent to the processing section 5, above.

In one of the embodiments of the invention (not shown in the drawings) may be provided to supply all of the concentrated aqueous solution of urea containing residual free ammonia section 22 washing with carbon dioxide is kind, in order to ensure that only an aqueous solution containing urea, to remove oxides of nitrogen. In this case, is not required section 4 evaporation and section 5 processing, or these sections, if they exist, can be removed (for example, in the case of reconstruction of the plant for producing urea).

In another embodiment of the invention (shown by the dashed line in figure 2) may be provided for feeding part of the concentrated aqueous urea solution leaving the first evaporator 4A and containing residual free ammonia, through the connecting conduit 30 in section 22 wash. This can be done alternatively with respect to the feeding section 22 washing the concentrated aqueous urea solution coming from section 3 extraction of urea and containing residual free ammonia, or in addition to this filing.

Therefore, the method and installation proposed in the present invention, a high operational flexibility, since there is the possibility to select an aqueous solution containing urea and residual ammonia, for submission to the leaching in different and additional locations, to meet the special and depending on certain circumstances requirements.

Another advantage of the invention concludes what I is in the case of reconstruction of existing facilities, the volume of conducted interference in the work is minimal and does not require a high cost, since it is only necessary to design the washing section and the corresponding connecting lines between this section and section extraction of urea or evaporation section of the existing installation.

Of course, the person skilled in the art to meet specific and depend on specific circumstances, requirements, may make numerous modifications and to make various modifications to the above-described method and a device for producing an aqueous solution containing urea, covered by the scope of protection of the present invention defined in the attached claims.

1. The method of obtaining an aqueous solution containing urea, for use in the removal of nitrogen oxides from gaseous products of combustion and flue gas, characterized in that it includes a stage on which exercise:
flushing with carbon dioxide at least part of the concentrated aqueous solution of urea, obtained directly or from below in the direction of flow of the extraction section of the urea plant for obtaining urea and containing residual free ammonia, obtaining, thus, the first paragraph is the global phase, containing carbon dioxide and possibly ammonia and concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, and
the specified dilution of the concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia water to obtain an aqueous solution of the desired concentration of urea.

2. The method according to claim 1, characterized in that said concentrated aqueous solution of urea containing residual free ammonia being at least partially flushing with carbon dioxide, is obtained directly from section (3) extraction of urea unit for production of urea.

3. The method according to claim 1, characterized in that said concentrated aqueous solution of urea containing residual free ammonia being at least partially flushing the carbon dioxide comes from section (4) evaporation below in the direction of the flow section (3) extraction of urea unit for production of urea.

4. The method according to claim 3, characterized in that said concentrated aqueous solution of urea containing residual free ammonia and subjected to at least partially flushing with carbon dioxide, is obtained from the evaporation apparatus (4A) in section evaporation used in the of pariwana concentrated aqueous solution of urea, coming from section (3) extraction of urea unit for production of urea and containing residual free ammonia.

5. The method according to claim 1, characterized in that the desired concentration of urea in aqueous solution is in the range of 15-35 wt.% by weight of solution.

6. The method according to claim 1, characterized in that it includes processing the aqueous solution obtained in section (2) of the synthesis unit for production of urea and containing urea, ammonium carbamate and free ammonia to decompose ammonium carbamate, possibly in the presence of inert gas Stripping section (3) extraction of urea, obtaining, thus, the second vapor phase containing ammonia and carbon dioxide, and the concentrated aqueous solution of urea containing residual free ammonia.

7. The method according to claim 1, characterized in that it includes the submission of the specified first vapor phase containing carbon dioxide and possibly ammonia, in section (3) extraction of urea.

8. The method according to claim 6 or 7, characterized in that it includes a recirculation of the specified second vapor phase containing ammonia and carbon dioxide, in the form of condensate in section (2) synthesis of urea.

9. The method according to claim 1, characterized in that all of this concentrated aqueous solution of urea containing residual free ammonia, is subjected promisc what carbon dioxide.

10. The method according to claim 1, characterized in that it includes the evaporation part of the concentrated aqueous solution of urea containing residual free ammonia which is not subjected to washing with carbon dioxide, in section (4) evaporation of receiving, thus, the molten urea.

11. Device for producing an aqueous solution containing urea, for use in the removal of nitrogen oxides from gaseous products of combustion and flue gas comprising communicating with one another partition (2) synthesis of urea and section (3) extraction of urea, characterized in that it also includes
section (22) flushing with carbon dioxide below in the direction of the flow section (3) extraction of urea,
the supply pipe (23), mounted between the section (3) extraction of urea and the above-mentioned section (22) of washing, to supply at least part of the concentrated aqueous urea solution obtained in section (3) extraction of urea and containing residual free ammonia section (22) flushing,
pipe (24) for supplying carbon dioxide section (22) flushing,
the pipe (25) to release the concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, from section (22) leaching, and
the pipe (17) for water supply, reported the specified pipe (25) for the release of the section (22) washing, for a specified dilution of the concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, to obtain in an aqueous solution of the desired concentration of urea.

12. Installation according to claim 11, characterized in that it comprises a pipe (27) between the above section (22) washing and section (3) extraction of urea to supply the vapor phase, leaving a section (22) washing and containing carbon dioxide and possibly ammonia, in section (3) extraction of urea.

13. Installation according to claim 11 or 12, characterized in that it also includes
section (4) evaporation below in the direction of the flow section (3) extraction of urea,
the connecting pipe (10) between the section (3) extraction of urea and section (4) evaporation to supply part of the concentrated aqueous urea solution obtained in section (3) extraction of urea and containing residual free ammonia, in section (4) evaporation,
the pipe (16) for release obtained by the synthesis of urea in molten form from section (4) evaporation.

14. Device for producing an aqueous solution containing urea, used for removal of nitrogen oxides from gaseous products of combustion or flue gases, including section (2) synthesis of urea, section (3) extraction of urea and section (4) flash steam is tion, including the first evaporating device (4A) and the second evaporating device (4b), and these sections (2, 3, 4) communicate with each other, characterized in that it also includes
section (22) flushing with carbon dioxide below in the direction of the flow section (3) extraction of urea,
the supply pipe (30)mounted between the first evaporation apparatus (4A) and the above-mentioned section (22) of washing, to supply at least part of the concentrated aqueous urea solution obtained in the first evaporation apparatus (4A) and containing residual free ammonia section (22) flushing,
pipe (24) for supplying carbon dioxide section (22) flushing,
the pipe (25) to release the concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, from section (22) leaching, and
the pipe (17) for supplying water which is connected with the specified pipe (25) release of the section (22) washing, for specified dilution of the concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, to obtain in an aqueous solution of the desired concentration of urea.

15. Installation according to 14, characterized in that it comprises a pipe (27) between the above section (22) washing and section (3) extraction of urea to supply the vapor phase, ahadada of the section (22) washing and containing carbon dioxide and perhaps ammonia, in section (3) extraction of urea.

16. Installation 14 or 15, characterized in that it also includes
section (4) evaporation below in the direction of the flow section (3) extraction of urea,
the connecting pipe (10) between the section (3) extraction of urea and section (4) evaporation to supply part of the concentrated aqueous urea solution obtained in section (3) extraction of urea and containing residual free ammonia, in section (4) evaporation,
the pipe (16) for release obtained by the synthesis of urea in molten form from section (4) evaporation.

17. Installation according to 14, characterized in that it includes
the connecting pipe (10) between the section (3) extraction of urea and the first evaporation apparatus (4A) in section (4) evaporation for supplying the concentrated aqueous urea solution obtained in section (3) extraction of urea and containing residual free ammonia in the first evaporating device (4A),
a connecting pipe (31) between the first evaporation apparatus (4A) and the second evaporating unit (4b) in section (4) evaporation for diversion of a portion of the concentrated aqueous urea solution obtained in the first evaporation apparatus (4A) and containing residual free ammonia, the second evaporating device (4b), and
the pipe (16) for vypuskatrehbukvennuyu urea from the second evaporator (4b).

18. The way of modernization (reconstruction) of an existing plant for producing urea from ammonia and carbon dioxide, comprising communicating with one another partition (2) synthesis of urea and section (3) extraction of urea, characterized in that it includes a stage on which exercise:
the mounting section (22) flushing with carbon dioxide below in the direction of the flow section (3) extraction of urea,
installation of connecting pipe (23) between the section (3) extraction of urea and the above-mentioned section (22) leaching to supply at least part of the concentrated aqueous urea solution leaving section (3) extraction of urea and containing residual free ammonia section (22) flushing,
pipeline Assembly (24) for supplying carbon dioxide section (22) flushing,
installation of pipeline (25) to release the concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, from section (22) leaching, and
installation of the pipeline (17) for water supply, connected to the specified pipe (25) for release to specified dilution of the concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, to obtain in an aqueous solution of the desired concentration of urea.

19. The way of modernization on p different those who, what carry out a preliminary installation of the pipeline (27) between the section (22) washing and section (3) extraction of urea to supply the vapor phase, leaving a section (22) washing and containing carbon dioxide and possibly ammonia, in section (3) extraction of urea.

20. The way of modernization (reconstruction) of an existing plant for producing urea from ammonia and carbon dioxide, including the sections (2) synthesis of urea, section (3) extraction of urea and section (4) evaporation, including the first evaporating device (4A) and the second evaporating device (4B), and these sections (2, 3, 4) communicate with each other, characterized in that it includes a stage on which exercise:
the mounting section (22) flushing with carbon dioxide below in the direction of the flow section (3) extraction of urea;
installation of connecting pipe (30) between the first evaporation apparatus (4A) and the above-mentioned section (22) leaching to supply at least part of the concentrated aqueous urea solution obtained in the first evaporation apparatus (4A) and containing residual free ammonia section (22) flushing,
pipeline Assembly (24) for supplying carbon dioxide section (22) flushing,
installation of pipeline (25) to release the concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, section and (22) washing, and
installation of the pipeline (17) for water supply, connected to the specified pipe (25) to issue, to dilute mentioned concentrated aqueous solution of urea containing carbamate and essentially not containing free ammonia, to obtain in an aqueous solution of the desired concentration of urea.

21. The way to modernization in claim 20, characterized in that conduct pre-installation of pipeline (27) between the section (22) washing and section (3) extraction of urea to supply the vapor phase, leaving a section (22) washing and containing carbon dioxide and possibly ammonia, in section (3) extraction of urea.



 

Same patents:

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

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 a method of producing1,1-1,6-hexamethylene-3,3,3',3'-tetrakis(2-oxyethyl)-bis-urea, which can be used in medicine. The method involves reacting 1,6-hexamethylene diisocyanate with diethanolamine in an aqueous medium, where diethanolamine is taken in stoichiometric amount ranging from 1.001 to 1.01 and after synthesis, excess diethanolamine is removed on a cation exchange resin, which is added to the reaction mixture in amount ranging from 5 to 10% of the mass of initial components while stirring until pH of the reaction mixture falls to a value ranging from 7.0 to 7.2.

EFFECT: simplification of the method and increased output of the end product.

1 cl, 3 ex, 1 tbl

FIELD: equipment of synthesis stage of process for producing urea from ammonia and carbon dioxide.

SUBSTANCE: apparatus includes high-pressure section operating practically at the same pressure values of synthesis reactor and condenser arranged inside said reactor. Condenser includes large number of flat plate like practically rectangular heat exchangers whose long sides are parallel to reactor axis. Each heat exchanger is made of two placed one onto other metallic sheets mutually joined by welding along their perimeter and forming inside heat exchanger preset-width cavity between them. Sheets from which heat exchangers are made are mutually joined by spot welding and they define in cavity of heat exchangers wavy path for fluid flowing. Said path includes mutually connected portions communicated through branch pipes for inlet of flowing heat transfer agent to heat exchangers and outlet of said agent from it. Preferable ducts for distributing flowing heat transfer agent fed to heat exchanger and for collecting outlet heat transfer agent are formed by means of tubes arranged in inner cavity of heat exchanger and secured to its mutually opposite long sides. At least one heat exchanger has internal partition passing from its one side to other opposite side and spaced from said opposite side by some distance for forming in cavity of heat exchanger U-shaped path for flowing heat transfer agent. Said path has descending and raising portions communicated with respective branch pipes passing outside from heat exchanger. Portions of U-shaped path have smoothly increased cross section area.

EFFECT: simplified design of zone for synthesis and condensation of reaction mixture for producing urea at improved efficiency of the whole process.

15 cl, 7 dwg

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

SUBSTANCE: the invention is pertaining to chemical industry, in particular, to the method and the installation for preparation of the carbamide solution applied as the agent for purification of nitrogen oxides from the exhaust gases of the combustion engines. The method of preparation of the carbamide solution provides for the dilution with the desalted water up to the necessary solution strength of the carbamide formed in its production process, desorption of the dissolved gases from the solution at its air blasting and the subsequent absorption of the impurities from the air by the solid adsorbent. If necessary the solution may be added with the agent to lower its freezing temperature. The installation for realization of the method consists of: the container of the source solution of the carbamide, the apparatus with the stirring device, the desorber, the adsorber, the means for feeding of the carbamide solution from the container of the source solution of carbamide into the apparatus with the stirring device, the means for feeding of the desalted water into the apparatus with the stirring device, the means for feeding of the carbamide solution from the apparatus with the stirring device into the desorber, the means for feeding of the air from the desorber into the adsorber, a means for feeding of the air into the desorber, the means for feeding of the air from the desorber into the adsorber. The technical result of the invention is development of the method and creation of the installation for preparation of the carbamide solution meeting the specification requirements for purification of nitrogen oxides from the exhaust gases of the combustion engines.

EFFECT: the invention ensures development of the method and creation of the installation for preparation of the carbamide solution meeting the specification requirements for purification of nitrogen oxides from the exhaust gases of the combustion engines.

4 cl, 1 dwg

The invention relates to improvements in the technology of production of urea from ammonia and carbon dioxide

The invention relates to a method of neutralizing ammonia in installations for the production of urea

The invention relates to the production of urea, in particular a highly efficient method for the synthesis of urea from ammonia and carbon dioxide as a source of reagents

The invention relates to the production of mineral fertilizers, in particular to a method of obtaining crystalline urea, which provides effective environmental clean its use in agriculture, chemical industry, etc

The invention relates to chemistry, in particular to technology for granulated urea, suitable for bulk transport and storage in bulk

FIELD: engines and pumps.

SUBSTANCE: device for treatment of exhaust gases of internal combustion engines operating on lean flammable mixture of internal combustion engines for automobiles containing decomposition catalyst of reducing agent by, in particular, catalyst hydrolysis in stream of exhaust gas, and doser for injection of reducing agent, in particular, for injection of water solution of urea upstream in exhaust pipeline, at that one additional catalyst device, in particular, one SCR-catalyst is connected in succession to decomposition catalyst of reducing agent, at that before decomposition catalyst (9) of reducing agent inlet section (10) for exhaust gas is included, it has area (15a, 15b) of flow turn and is designed so that exhaust gas is injected radially from outside of inlet pipe (14) connected to decomposition catalyst (9) of reducing agent to part (11a, 11b) of housing around inlet pipe (14) and passes in contraflow through end inlet hole (15) of inlet pipe (14) to decomposition catalyst (9) of reducing agent, at that reducing agent is injected in area (15a) of turn of exhaust gas flow, the area relates to inlet hole.

EFFECT: quantitative improvement of decomposition of reducing agent, reducing dimensions of device.

12 cl, 4 dwg

FIELD: engines and pumps.

SUBSTANCE: invention refers to device containing exhaust system including catalyst-adsorbent NOx (NAC) and catalytic soot filter (CSF). Essence of invention: device contains: (i) internal combustion engine operating on lean mixture; (ii) exhaust system for treatment of exhaust gas from engine, at that the system includes: (a) the first monolithic basis containing catalyst-adsorbent for NOx (NAC); (b) catalytic soot filter (CSF) including filter basis; and means for enrichment of exhaust gas with periodic obtainment of enriched composition of exhaust gas during normal functioning of engine with lean mixture to remove sulphate adsorbed by catalyst-adsorbent NOx, at that exhaust system includes: (c) chemical compound located downstream of at least some part of catalyst-adsorbent NOx, which is effective for removal and/or converting of at least some part of hydrogen sulphide containing in enriched exhaust gas obtained from removed sulphate adsorbed by catalyst-adsorbent NOx. Also transport device containing device and method of desulfation of catalyst-adsorbent NOx (NAC) in exhaust system.

EFFECT: reducing ejection of H2S, desulfation of NAC under conditions of enriched mixture.

32 cl, 3 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to methods of producing catalysts for cleaning diesel engine emissions. Described is a method of producing a catalyst for diesel soot after-burning, involving mixing a copper extract in n-caprylic acid and a molybdenum extract in isoamyl alcohol in a ratio which ensures content of metals in the obtained mixture which corresponds to the composition CuMoO4, subsequent removal of the solvent from the obtained mixture and pyrolysis thereof on air, wherein the obtained mixture of extracts is brought to total concentration of metals of 1.5-2.0 wt % using isoamyl alcohol; the diluted mixture is deposited on a substrate made from titanium or alloy thereof, which is treated by plasma-electrolytic oxidation in an aqueous electrolyte; the solvent is removed by heating the titanium substrate with the deposited mixture of extracts to 150°C for not less than 1 hour; subsequent pyrolysis is carried out at temperature 540-550°C for not less than 1 hour.

EFFECT: simple method of producing a catalyst on a metal substrate and high efficiency thereof while simultaneously improving quality and efficiency of the obtained catalyst.

2 cl, 3 dwg, 3 ex

FIELD: engines and pumps.

SUBSTANCE: inventions may be used in production of engines. Device is intended for preparing gas mix containing, at least, one of the following substances: reducing agent and its precursor. Proposed device comprises supply tank for water solution 45 of reducing agent precursor communicated with evaporation chamber 24, device to dispense said solution 45 into evaporation chamber 24 and evaporation chamber heater 27. Evaporation chamber is heated to 350-450°C whereat said water solution is completely evaporated. Hydrolysis catalyst 17 is arranged downstream of evaporation chamber 24. Hydrolysis catalyst 17 is furnished with means 31 to maintain uniform temperature therein. Heat capacity of hydrolysis catalyst 17 does not exceed 60 J/K.

EFFECT: ruled out local cooling, efficient hydrolysis.

12 cl, 24 dwg, 1 ex

FIELD: process engineering.

SUBSTANCE: invention relates to vanadium-free catalyst for reduction of aluminium oxides by ammonium or compound decomposing thereto. It relates also to activation of homogeneous mixed cerium and zirconium oxides for nitrogen oxide reduction. Proposed catalyst comprises catalytically active coat applied on inner carries body. Note here that said coat consists, partially or completely, of homogeneous mixed cerium and zirconium oxides with cerium amount varying from 10 wt % to 90 wt % per total weight of said mix, activated for reduction by introducing transition metal. Transition metal is selected from the group including chromium, molybdenum and mixes of said transition metals or combinations thereof.

EFFECT: high-activity, vanadium-free, cheap and effective reduction catalyst.

19 cl, 9 dwg, 1 tbl, 13 ex

FIELD: process engineering.

SUBSTANCE: invention may be used in chemical industry. Device 1 and method are used to evaporate, at least, one of the following reagents, i.e. solution of reducer precursor and reducer precursor. Device comprises, at least, one electrically heated heating zone 2. Said heating zone 2 comprises, at least, one electrical heater 3 with heating resistor 4 self-adjusted nearby significant temperature. Electrical resistor 4 is characterised by electric resistance variation curve related to temperature and having, at least, one kink point. Curve of derivative of said electric resistance variation curve, in temperature range related to said kink point, features full width at the level of semi-peak, equal to not over 40 K. In the range of significant temperatures, said electric resistance variation curve features rise exceeding 1 Ohm/K.

EFFECT: simplified and fast adjustment of evaporation.

10 cl, 5 dwg

FIELD: engines and pumps.

SUBSTANCE: cylinders of engine running on lean mixes are proposed to be divided into two groups to discharge waste gases via pipelines assigned to each said group. Each said pipeline incorporates carbon-black filter. Said exhaust pipelines are integrated into one common exhaust pipeline at its inlet. Said common exhaust pipeline accommodates catalyst for nitrogen dioxide removal. Said filters are regenerated to limit waste gas temperature in common exhaust pipeline by mean temperature of waste gases in operating conditions and at filter recovery to protect aforesaid catalyst from thermal damages.

EFFECT: higher efficiency.

16 cl, 3 dwg

FIELD: engines and pumps.

SUBSTANCE: catalytically activated filter designed to filtrate solid particles from spent gases (SG) of a diesel engine and having a filtering element and an oxidising-active catalytic coating, and also one more coating catalytically active in the reaction of selective catalytic reduction (SCR-reaction), containing a material that accumulates ammonia, besides, the specified coatings are arranged in the order, in which SG exposed to neutralisation or reduction of toxicity first go through a coating that is catalytically active in the SCR-reaction, and then through the oxidising-active catalytic coating.

EFFECT: simplified and cheaper system of SG neutralisation or toxicity reduction designed to remove nitrogen oxides and solid particles from SG from engines operating at depleted fuel mixtures, and also minimised backpressure of SG.

20 cl, 9 dwg

FIELD: transport.

SUBSTANCE: invention may be used in engine production. Engine exhaust gas containing NO2 is brought in contact with catalyst. Said catalyst is active in reducing NO2 to NO and comprises, at least, one platinum group metal provided that platinum metal is not platinum. Catalyst comprises, at least, one metal oxide active in redox reactions for NO2 reduction to NO in reaction with CO, hydrocarbons and/or carbon black present in exhaust gas. Proposed device comprises engine exhaust system provided with above described catalyst.

EFFECT: reduced emission.

12 cl, 2 tbl, 3 dwg, 2 ex

FIELD: chemistry.

SUBSTANCE: invention relates to chemical industry and catalyst systems which can be used particularly in processes for oxidation of hydrogen chloride to molecular chlorine, oxychlorination of methane, partial oxidation of (C1-C4) lower paraffins to alcohols and aldehydes (oxygenates). The invention can also be used in processes for producing valuable chemical products and semi-products, as well as when processing different gaseous and liquid wastes. Described is a catalyst system for heterogeneous reactions, which is a geometrically structured system containing microfibre of a high-silica carrier with diameter of 5-20 mcm, which is characterised by presence of hydroxyl group absorption bands in the infrared spectrum with wave number ν=3620-3650 cm-1 and half-width 65-75 cm-1, has specific surface area measured using a BET method based on thermal desorption of argon, SAr=0.5-30 m2/g, has surface area measured using an alkaline titration method SNa=5-150 m2/g with ratio SNa/SAr=5-50, and at least one active element, characterised by that the active element is made either in form of a MezOxHaly composite or in form of a NwMezOxHaly composite, where element N in the composite NwMezOxHaly is selected from a group comprising alkali, alkali-earth elements or hydrogen, element Me in composite NwMezOxHaly and composite MezOxHaly is selected from a group containing iron, cobalt, nickel, ruthenium, rhodium, vanadium, chromium, manganese, zinc, copper, silver, gold, or one element from lanthanum and lanthanides, and element Hal in composite NwMezOxHaly and composite MezOxHaly is one of halogens: fluorine, chlorine, bromine and iodine.

EFFECT: higher activity of the catalyst system and high resistance to deactivation in aggressive media in oxidation, chlorination and oxychlorination reactions.

3 cl, 3 ex

FIELD: gas treatment catalysts.

SUBSTANCE: invention, in particular, relates to internal combustion engine exhaust gas neutralizers. Method of invention comprises rolling refractory metallic tape into block by way of overlapping its smooth and corrugated sides to form channels, performing ultrasound-assisted chemical cleaning of thus rolled tape in alkali solution followed by joining alternate layers of metallic tape with each other by diffusion welding in vacuo within a range of 5·10-5-1·10-5 mm Hg using stepwise heating to 1250 ± 10°С and isothermal exposure to this temperature for 12-17 min to form monolithic structure consisting of triangular and trapezoidal channel at density up to 600 channels per 1 inch2. Invention further describes carrier for catalytic exhaust gas neutralizers representing monolithic metallic structure in the form of cylindrical block or block with oval cross-section, which block consists of parallel channels, 200-600 per 1 inch2, density of channels varying along the cross-section of carrier: from center and extending to 0.55 0,7 diameter if cylindrical block or large axis of oval cross-section, density of channels is 400-600 per 1 inch2 and farther it decreases to 200 or 400 channel/inch2, respectively.

EFFECT: simplified manufacture technology and increased strength of monolithic cellular structure.

4 cl, 4 dwg, 1 tbl

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