A method of reducing the amount of unreacted ammonia coming out of the reactor in the process of producing acrylonitrile, and a method of producing acrylonitrile

 

(57) Abstract:

Describes how to reduce the amount of waste generated during the manufacture of Acrylonitrile, which is the introduction of an additional quantity of oxygen-containing gas, preferably air, at essentially the absence of any oxygen-containing compounds, in the upper part of the reactor with a fluidized bed of catalyst, to communicate at least some part of unreacted ammonia, to reduce the amount of unreacted ammonia present in the stream exiting the reactor. 2 C. and 15 C.p. f-crystals, 5 PL.

The present invention is directed to a significant reduction in the amount of unreacted ammonia and the corresponding decrease of ammonium sulfate and final waste generated from apraregulated ammonia in the production of Acrylonitrile by the direct ammoxidation /oxidative ammonolysis/ unsaturated or saturated hydrocarbon, preferably propylene or propane, ammonia and oxygen in a reactor with a fluidized bed containing a catalyst for the ammoxidation /oxidative ammonolysis/. In particular, the present invention napravleniyaner layer to significantly reduce the amount of ammonia, remaining in the gaseous flow coming out of the reactor with a fluidized bed in the Acrylonitrile process. This process is carried out in the absence of any additional oxygen-rich hydrocarbon compounds, such as methanol. A significant reduction in the formation of ammonium sulfate in the production of Acrylonitrile leads to considerable advantages from the point of view of Economics and environmental protection.

There are several patents that have addressed the introduction of methanol into the reactor fluidized bed in the manufacture of hydrogen cyanide. In addition, these studies also revealed the introduction of methanol in the Acrylonitrile reactor fluidized bed with the aim of obtaining hydrogen cyanide in the production of Acrylonitrile. For example, in U.S. patents 3911089 and 4485079 discusses the ammoxidation /oxidative ammonolysis/ methanol to obtain hydrogen cyanide with the introduction of methanol into the reactor with a fluidized bed containing a catalyst for the ammoxidation /oxidative ammonolysis/ acceptable for the production of Acrylonitrile. In addition, Japanese patent application 74-87474, 79-08655 and 78-35232 belong to the same methods povy it is also assumed, the secondary effect of this technique lies in the reduction of sulfuric acid used for neutralization. All of these patents relate primarily to the production of additional quantities of hydrogen cyanide. Finally, U.S. patent 5238473 and nevadasiena on the simultaneous consideration of the application USA N series 08/137425, filed January 23, 1994, and application USA N series 03/104752, filed August 11, 1993, the transmitting powers of the present invention is directed to a significant decrease in the amount of unreacted ammonia coming out of the reactor with a fluidized bed, which uses oxygen-containing compounds, such as methanol, whereas in Chinese patent CN 1032747 /Sun et al/ disclosed multistage air supply to the reactor to increase conversion to Acrylonitrile.

In U.S. patent N 4.070.393 disclosed a method of producing Acrylonitrile, including passing through the fluidized bed of catalyst ammonia, oxygen-containing gas and the hydrocarbon with the oxygen.

The present invention relates to a special method of introducing oxygen-containing gas, preferably air, into the fluidized bed reactor in order to achieve things is m in the Acrylonitrile process without reducing the yield of the latter. This method is carried out in the absence of any oxygen-rich hydrocarbon compounds, such as methanol.

Brief description of the invention

The main purpose of the present invention is a significant decrease in the number of ammonium sulfate formed during the production of Acrylonitrile.

Another objective of the present invention is a significant reduction in the production of Acrylonitrile amount apraregulated ammonia in the effluent from the reactor flows.

Additional objectives, advantages and novel elements of the present invention will be partially set out in the following description of the invention and will become apparent to a skilled in this area specialists in the study of the following or may be understood when implementing the present invention in practice. Objectives and advantages of the present invention may be realized and obtained by means of the methods and combinations detailed in the attached claims.

To achieve the above objectives of the present invention that are implemented and described in this application, the method of the present invention includes the introduction in the lower part ready propylene and propane, to interact in the presence of a fluidized bed of the catalyst in order to obtain Acrylonitrile, the introduction of additional quantities of oxygen-containing gas, practically free of any oxygen-containing compounds, in the upper part of the fluidized bed reactor, in a place where additional oxygen is no significant impact on the reaction of formation of Acrylonitrile, but reacts at least part of the unreacted ammonia and propylene present in the reactor, to reduce the amount of free ammonia present in the reactor flow coming from the above reactor, the transmission of the stream exiting the reactor and containing Acrylonitrile, in abruptly cooling the column to cool the effluent from the reactor, the flow of the water in order to remove undesirable impurities, and the allocation of Acrylonitrile from the specified /tempering/ columns. Two additional positive aspects gained through the implementation in practice of the present invention lies in the fact that /1/ is formed more acrolein, unwanted by-product in the production of Acrylonitrile and /2/ create additional amounts of cyanide the m variant of the method of the present invention the oxygen-containing gas is air.

In a preferred variant of the method of the present invention, the point of introduction into the reactor additional oxygen-containing gas is at a point above at least 50% of the calculated height of the expanded fluidized bed of catalyst, preferably above at least 70% of the calculated height of the extruded catalyst layer, most preferably above 85%, and especially preferably the introduction of gas at a level above 90%.

In another preferred embodiment of the present invention the additional amount of oxygen-containing gas is introduced at a level above 100% of the calculated height of the extruded catalyst layer.

According to another aspect of the present invention, which is performed and described below, the method of the present invention includes the introduction of ammonia, oxygen-containing gas and a hydrocarbon selected from the group comprising propylene and propane, in the lower part of the fluidized bed reactor containing a fluidized bed of catalyst for the ammoxidation /oxidative ammonolysis of/ to interact in the presence of the above catalyst with getting Acrylonitrile, where the improvement lies in the introduction of dopolnitelnoi in the upper part of the fluidized bed reactor at a point where oxygen does not have a significant effect on the reaction of a hydrocarbon, ammonia and oxygen-containing gas to produce Acrylonitrile, but interacts with at least some of the unreacted ammonia present in the reactor, in order to reduce the amount of ammonia exiting the reactor.

In the preferred embodiment of the present invention additional oxygen-containing gas is introduced into the upper part of the reactor at a point above at least 70% of the calculated height of the expanded fluidized bed of catalyst.

In yet another preferred embodiment of the present invention additional oxygen-containing gas is introduced into the upper part of the fluidized bed reactor at a point at least above 80% from the calculated height of the expanded fluidized bed of catalyst.

In accordance with another embodiment of the invention the additional oxygen-containing gas is introduced into the upper part of the fluidized bed reactor at a point at least above 90% from the calculated height of the expanded fluidized bed of catalyst.

In another predpochtitel ooriginal layer, is sufficient for interaction with at least 15% of the unreacted ammonia present in the upper part of the reactor, preferably at least 25%, more preferably at least 40%.

The term "oxygen-containing compounds" as used in the present invention include carboxylic acids, ketones, alcohols, esters and mixtures thereof. The present invention differs in that in the process of the present invention is not present significant amounts of such compounds.

The value of the method in accordance with the present invention is that this method creates a simple and cost-effective method of significantly reducing leakage of ammonia /i.e. unreacted ammonia/ in the reactor with a fluidized bed along with the attendant benefits that are /1/ reducing ammonium sulfate formed as a by-product during the manufacture of Acrylonitrile /2/ achieving reduction of leakage of ammonia without the use of expensive oxygen-containing compounds and /3/ progress reducing leakage of ammonia without additional quantities of undesirable by-products. These prla, if it is not possible to implement deep injection. Currently, the waste stream arising from the columns of the rapid cooling, contains /NH4/SO4in high concentrations, which makes very difficult the destruction of this thread economical and acceptable from the point of view of safety to the environment way. Minimization of the content of ammonium salts in this thread can make it acceptable for processing by means of waste treatment technologies that do not require stringent conditions or the use of expensive construction materials /for example, calcining,/, or, if you cannot spend the deep injection, leading to a significant economic effect and to increase safety for the environment.

Described in more detail below, the preferred embodiment of the present invention.

Detailed description of the invention

The present invention reduces the formation of ammonium sulfate in the production of Acrylonitrile by adding additional quantities of oxygen-containing gas, preferably air, practically does not contain oxygen-containing compounds, preferably in the absence of any such connection, in rsbatch ammonia, present in the reactor, with an additional amount of oxygen without significant effect on the efficiency of the production of Acrylonitrile. It is important to note that the introduction of oxygen-containing gas in the upper part of the reactor is the actual introduction of additional oxygen into the reactor over the amount, which is added at the bottom of the reactor under normal operating conditions used in the process of producing Acrylonitrile. That is, if under normal operating conditions in the lower part of the reactor is required ratio of air to propylene 9.5:1, this ratio will be preserved by the introduction of additional oxygen in the upper part of the reactor. The decrease in the amount of ammonium sulfate in the waste stream leaving the column rapid cooling installations for the production of Acrylonitrile, can dramatically improve the environmental safety of production and its economy.

In a preferred implementation of the present invention the air is introduced into the reactor with a fluidized bed in the upper part of the reactor in a catalytic zone /at least to the point corresponding to 50% of the height of the extruded catalyst/ or higher /that is, a point u is de he will be able to respond with a significant amount of excess ammonia, but will not compete with the main reaction ammoxidation /oxidative ammonolysis/ propylene, which flows in the lower part of the catalytic layer. In the present invention the term "fluidized bed reactor" means not only a conventional fluidized bed reactor catalyst, but also any reactor capable of supporting the catalyst in a liquid state, such as, for example, circulating fluidized bed reactors, transport-linear reactors, ascending the reactor or reactors with recycle. Additional oxygen may be introduced into the reactor in any direction, although it is preferable introduction angled down. The air distributor can be made from conventional materials such as steel/alloy steel/ with a number of nozzles, which are enough to ensure good mixing without affecting the flow distribution in the reactor.

In another preferred embodiment of the present invention the point of introduction of additional oxygen-containing gas should be at the level corresponding to 70% of the height level of expanded catalyst layer, preferably from 80 to 90% of the height of expanded catalyst layer, and the pre is aqueous catalyst layer", which is used in this description, means the height of the catalyst bed when the catalyst is in a fluidized condition, i.e. the height of the catalyst layer, when in the fluidized bed reactor gaseous components are present and mixed with a catalyst.

Each catalyst for the ammoxidation /oxidative ammonolysis/ propylene/propane to obtain maximum yield in Acrylonitrile and/or economic point of view works partly with different ratios of raw materials and operating conditions. Excess ammonia coming out of the reactor, where it flows ammoxidation /oxidized ammonolysis/ propylene will vary depending on the used catalyst. The number of additional oxygen-containing gas, which must be added to the reactor, will also vary depending on the catalyst and the nature of the reactor. Accordingly, in the practical implementation of the present invention, the amount of additional oxygen-containing gas introduced into the reactor will be determined by the conditions and the catalyst. Usually any catalyst for the ammoxidation /oxidative ammonolysis/ can be used Osom the ratio of oxygen/ propylene /for example, above 9,3:1/. For example, acceptable for use in this invention are the catalysts described in U.S. patents 3642930, 4485079, 3911089, 4873215, 4877764, and in Japanese patent applications 74-874774 and 78-35232, which are included in the description as a reference.

As mentioned previously, each catalyst for the ammoxidation /oxidative ammonolysis/ will work for different ratios of raw materials and different working conditions. When implementing the present invention standard operating conditions under which works propylene/propane catalyst should not be changed, but can vary depending on the feedstock and the catalyst utilized. Normal operating conditions and the ratio of supply of raw materials in the production of Acrylonitrile are presented in U.S. Patent 3911089 and 4873215, which are included in the description as a reference.

The present invention is illustrated using examples in which the author describes the method of the present invention.

Example 1

Approximately 12.5 tons of ammoxidation catalyst /oxidative ammonolysis/ propylene loaded into the fluidized bed reactor to obtain Acrylonitrile. After a few days of keeping the Torah 12 pounds/square inch /0.816 ATM/ hour flow rate /Czos/ 0.085 h-1miss air/ammonia/propylene in a molar ratio 9.3/1.21/1.0. After 24 h after establishing the ratio of the raw material and the temperature of the reactor core experience selection /table 1/ shows the conversion of propylene 98.1%, conversion to Acrylonitrile to run 80.49% to HCN - 4.98% to acrolein - 0.7%, to acrylic acid is 1.3%. From the presented results we can see that 8% of supplied ammonia burns, breakthrough of ammonia is 0.22 g/cubic ft STD. /7.86 g/m3/ and the consumption of sulfuric acid to neutralize the excess of ammonia in countercurrent operation quick cooling is 0.22 Gal/min /0.83 l/min/.

Example 2

In the conditions of Example 1 and without the introduction of vapor of methanol /oxygen-containing compound through the air distributor in the point layer, located at the level of 90% of the height of expanded catalyst layer, introducing air at a molar ratio of dilution air to propylene 0.52. Experience highlight /table 1/ gives the total conversion of C3= 99.1%, the conversion of propylene for the run up to the Acrylonitrile - 80.5% to HCN = 5.43% to acrolein - 0.6%, and to acrylic acid 1.3%. From the presented results we can see that 7% of supplied ammonia burns and consumption of sulfuric acid falls from 0.22 to 0.16 gpm /from 0.83 to 0.52 l/min/, h is without introducing vapors of methanol /oxygen-containing compound through a separate air distributor in the point layer, the corresponding 90% of the height of expanded catalytic layer, introducing air at a molar ratio of dilution air to propylene /MOIT/ 0.51. The lower the molar ratio of the air/C3= then reduced from 9.3 to 9.1 to show whether it is possible to reduce the total ratio air/C3= without negative influence on the yield of Acrylonitrile /DCA/ or HCN and while maintaining the reduced consumption of sulfuric acid. Experience highlight /table 2/ gives the total conversion of C3= 99.2%, the conversion of propylene to run to the Acrylonitrile - 79.9% to HCN and 5.6%, to acrolein - 0.6%, and to acrylic acid 1.3%. From the presented results we can see that 13% of supplied ammonia burns, and the consumption of sulfuric acid to centralize ammonia falls from 0.22 to 0.17 Gal/min /from 0.83 to 0.64 l/min, which corresponds to the reduction of leakage of ammonia by 23% compared to the experience without separate air /see table 2/. This shows that the General attitude of air/C3= can be reduced from 10 to 9.48 without a significant reduction in output by DCA or HCN, reducing the negative impact for the higher ratio of the dilution air.

Examples 4-9

The next series of experiments aimed at quantifying the positive impact OTDELENIE. Under the conditions of Example 1, except that the ratio of supply of raw materials air/ammonia/ propylene is 9.4/1.22/1.0. The initial basic experience and the ultimate basic experience /examples 4 and 5, table 3/ show the conversion of propylene 98,7%, conversion to Acrylonitrile to run 80.7% to HCN - 5.1% to acrolein - 0.8%, to acrylic acid is 1.7%. From the presented results we can see that 5% of supplied ammonia burns, breakthrough of ammonia is 0.18 g/cubic ft STD. /6.43 g/m3/ and the consumption of sulfuric acid to neutralize the excess of ammonia in countercurrent operation quick cooling is 0.17 gpm /0.64 l/min/. Without the introduction of vapor of methanol /oxygen-containing compound through a separate air distributor in the point layer, located at the level of 90% of the height of expanded catalyst layer, introducing air at a molar relationship dilution air and propylene 0.1, 0.2, 0.4 and 0.6. The average of four experiments highlight /example 6-9, table 3/ at elevated relationship dilution air show overall conversion of C3= 99.2%, conversion to Acrylonitrile to run 80.7% to HCN - 5.4% to acrolein - 0.8%, to acrylic acid - 1.5%. From the presented results we can see that 15% of supplied ammonia is adding dilution air to 0.12 Gal/min /0.45 l/min/ /decrease the leakage of ammonia at 30% to 0.10 Gal/min /0.38 l/min/ /decrease the leakage of ammonia 40%/. The relationship between the ratio of dilution air to propylene and consumption of sulfuric acid while maintaining the other parameters constant /for example, the air/propylene in the lower part of the reactor, the ammonia/propylene, the temperature of the catalytic layer, the pressure in the upper part of the reactor, and the parameters of catalyst/ presented in table 3.

Examples 10 to 14

This series of experiments designed to show the applicability of the diluted air phase /additional quantity of air supplied in a raised point reactor/ within a broader interval of the ratios of ammonia. The experiments of examples 4-9 repeated, except that use low ammonia/propylene equal to 1.17. In the examples 4-9, except for the supply of raw materials at a molar ratio of the air/ammonia/propylene 9.3/1.17/1.0, the average value of the two basic experiments highlight /examples 10 and 11, table 4 shows the conversion of propylene 98.7 %, conversion to Acrylonitrile to run 80.2% to HCN - 5.0% to acrolein - 1.2%, to acrylic acid is 1.8%. From the presented results we can see that 10-13% of supplied ammonia burns, breakthrough of ammonia is 0.06 g/cubic ft STD. /2.14 g/m3/ and the consumption of sulfuric kN/. Without the introduction of vapor of methanol /oxygen-containing compound through a separate air distributor in the point layer, located at the level of 90% of the height of expanded catalyst layer, introducing air at a molar relationship dilution air and propylene 0.1, 0.2 and 0.3. The average value of three experiments highlight /examples 12-14, table 4/ at elevated relationship dilution air show overall conversion of C3= 99.2%, conversion to Acrylonitrile to run 80.1% to HCN - 5.1% to acrolein - 1.1%, to acrylic acid was 1.9%, From the presented results we can see that 15% of supplied ammonia burns, and the consumption of sulfuric acid with increasing addition of dilution air drops to 0.06 Gal/min /0.22 l/min/ /65% reduction of leakage of ammonia/, up to 0.05 Gal/min /0.19 l/min/ /decrease the leakage of ammonia by 71%/ and to 0.04 Gal/min /0.15 l/min/ /decrease the leakage of ammonia by 76%/ relative consumption of acid in a base of experience with a ratio of ammonia to propylene equal to 1.22. The relationship between the ratio of dilution air to propylene and consumption of sulfuric acid while maintaining the other parameters constant /for example, the air/propylene in the lower part of the reactor, the ammonia/propylene, the temperature ASS="ptx2">

Examples 15-18

This series of experiments is conducted with the decrease in the ratio of the air/propylene in the lower part of the reactor with increasing ratio dilution air phase with the aim to show whether it is possible to reduce the total ratio of the air/propylene without adverse effect on the yield of Acrylonitrile or HCN while maintaining the reduced consumption of sulfuric acid. In the examples 4-9 in the point located at the level of 90% of the height of expanded catalyst layer, introducing dilution air phase at a molar ratio of dilution air to propylene 0.2, 0.4 and 0.6, with a simultaneous decrease of the ratio of the air/propylene in the lower part of the reactor 9.1 to 8.9, 8.7 and 8.6, respectively. Thus, the total ratio of the air/propylene is maintained approximately constant 9.3 - 9.4.

The average value of three experiments highlight /Examples 15-17, table 5/ at elevated relationship dilution air show overall conversion of C3= 88%, conversion to Acrylonitrile to run 80.4% to HCN - 4.8% to acrolein - 0.9% to acrylic acid is 1.4%. From the presented results we can see that 15% of supplied ammonia burns, and the consumption of sulfuric acid is increased from 0.19 Gal/min /0.72 l/min/ up to 0.21 gpm /0.79 l/min/ Rel is the ratio of dilution air to propylene and consumption of sulfuric acid while maintaining the other parameters constant /for example, the relationship of the air/propylene in the lower part of the reactor, the ammonia/propylene, the temperature of the catalytic layer, the pressure in the upper part of the reactor, and the parameters of catalyst/ presented in table 5.

These experiments show that the General attitude of the air/propylene can be maintained constant, however, as the reduction ratio air/propylene in the lower part of the reactor there is a decrease in the conversion of propylene, which has a negative effect on the yield of HCN and Acrylonitrile. Moreover, the consumption of sulphuric acid cannot be reduced by adding dilution air under the scheme. This indicates that without negative influence on the distribution of the reaction products and their output valid only small decrease of the ratio of the air/propylene in the lower part of the reactor.

1. A method of reducing the amount of unreacted ammonia coming out of the reactor in the production of Acrylonitrile obtained by the introduction into the fluidized bed of catalyst ammonia, oxygen-containing gas and a hydrocarbon with an extra supply of oxygen-containing gas, characterized in that use hydrocarbon selected from propane and propylene, and introduce ammonia, oxygen is rasego gas, essentially free of any oxygen-containing compounds, in the upper part of the fluidized bed reactor at a point where additional oxygen is no significant impact on the reaction of formation of Acrylonitrile, but reacts with at least part of the unreacted ammonia present in the reaction stream coming from the specified reactor, pass the reaction effluent stream containing Acrylonitrile, through the column of rapid cooling to cool the effluent from the reactor stream with water to remove undesirable impurities and produce the Acrylonitrile from the column of rapid cooling.

2. The method according to p. 1, characterized in that the oxygen-containing gas is air.

3. The method according to p. 1, wherein the point of introduction into the reactor additional oxygen-containing gas is higher than at least 50% of the calculated height of the expanded fluidized bed of catalyst.

4. The method according to p. 3, characterized in that the point of introducing into the reactor additional oxygen-containing gas is at a level above at least 70% of the calculated height of the expanded fluidized bed catalyst is asego gas is at a level higher at least 90% of the calculated height of the expanded fluidized bed of catalyst.

6. The method according to p. 1, characterized in that the amount of additional oxygen-containing gas introduced into the reactor is sufficient for interaction with at least 15% of unreacted ammonia.

7. The method according to p. 1, characterized in that the amount of additional oxygen-containing gas introduced into the reactor is sufficient for interaction with at least 25% of unreacted ammonia.

8. The method according to p. 1, characterized in that the amount of additional oxygen-containing gas introduced into the reactor is sufficient for interaction with at least 40% of unreacted ammonia.

9. The method according to p. 1, characterized in that the hydrocarbon is a propylene.

10. The method of producing Acrylonitrile by the introduction into the fluidized bed of catalyst ammonia, oxygen-containing gas and a hydrocarbon with an extra supply of oxygen-containing gas, characterized in that use hydrocarbon selected from propane and propylene, and introduce ammonia, oxygen-containing gas and the hydrocarbon in the lower part pseudouridines rasego connection in the upper part of the fluidized bed reactor at a point where additional oxygen is no significant impact on the reaction of formation of Acrylonitrile, but reacts with at least part of the unreacted ammonia present in the reaction stream coming from the specified reactor.

11. The method according to p. 10, characterized in that the additional oxygen-containing gas is injected into the upper part of the reactor at a point above at least 70% of the calculated height of the expanded fluidized bed of catalyst.

12. The method according to p. 10, characterized in that the additional oxygen-containing gas is injected into the upper part of the reactor at a point above at least 80% of the calculated height of the expanded fluidized bed of catalyst.

13. The method according to p. 10, characterized in that the additional oxygen-containing gas is injected into the upper part of the reactor at a point above at least 90% of the calculated height of the expanded fluidized bed of catalyst.

14. The method according to p. 10, characterized in that the amount of additional oxygen-containing gas introduced into the re>15. The method according to p. 10, characterized in that the amount of additional oxygen-containing gas introduced into the reactor is sufficient for interaction with at least 25% of unreacted ammonia.

16. The method according to p. 10, characterized in that the amount of additional oxygen-containing gas introduced into the reactor is sufficient for interaction with at least 40% of unreacted ammonia.

17. The method according to p. 10, characterized in that said hydrocarbon is a propylene.

 

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SUBSTANCE: present invention relates to a reactor for producing hydrogen cyanide using Andrussov's method, and a method of producing hydrogen cyanide, which is realised using the disclosed reactor. The reactor has a reservoir (2), at least one gas inlet (3) which has a gas inlet region (4), a reaction product output (5) and a catalyst (6), which is characterised by that inside the reservoir (2), between the gas inlet region (4) and the catalyst (6) there is at least one mixing element (7) and at least one gas-permeable intermediate layer (8), said mixing element (7) lying between the gas inlet region (4) and the gas-permeable intermediate layer (8).

EFFECT: very simple and cheap production of hydrogen cyanide, high output, efficiency and longer service life of the catalyst.

26 cl, 3 dwg, 1 tbl, 4 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method for combined production of acrylonitrile and hydrogen cyanide by treating a combined stream obtained by combining an acrylonitrile product stream and a stream containing hydrogen cyanide, where said streams are obtained concurrently in separate reactor systems. The method comprises steps (a) to (e). Step (a) involves obtaining acrylonitrile and providing an acrylonitrile product stream. Step (b) involves obtaining hydrogen cyanide and providing a stream containing hydrogen cyanide. Step (c) involves combining the stream containing hydrogen cyanide and the acrylonitrile product stream in an absorption column with water to obtain a combined product stream having the ratio of the acrylonitrile product stream to the stream containing hydrogen cyanide of about 9 to 1 or less. Step (d) involves treatment of the combined product stream successively in a recovery column, a decantation tank having an aqueous layer and an organic layer, and a column for separating head fractions, where pH is controlled by adding an acid to pH 7.0 or lower in the absorption column and the recovery column and to pH below 4.5 in the decantation tank and the column for separating head fractions. Step (e) involves separating the stream of crude HCN from the stream of crude acrylonitrile in the column for separating head fractions, treating the stream of crude HCN in a column for distilling HCN and treating the stream of crude acrylonitrile in a drying column. The pH in the column for distilling HCN is kept below 4.5, and temperature in the decantation tank is below 50C.

EFFECT: method increases output of hydrogen cyanide and prevents polymerisation thereof.

8 cl, 1 dwg, 2 ex

FIELD: chemistry.

SUBSTANCE: invention can be used in chemical and metallurgical industry. The method of producing hydrogen cyanide involves preparing gaseous formamide by evaporating liquid formamide in an avaporator. The dwell time of formamide in the evaporator is less than 20 s. The evaporator used is a micro-evaporator which is in form of multiple parallel microstructured sheets of evaporation and heating channels arranged alternately one above the other. Each sheet is a flat structural unit and has a large number of parallel channels having hydraulic diameter of 5-4000 mcm and form a flow path from one side of the sheet to the other. The obtained gaseous formamide is subjected to catalytic dehydration to obtain hydrogen cyanide.

EFFECT: invention enables to obtain hydrogen cyanide with high degree of selectivity, as well as at pressure close to or higher than atmospheric pressure.

12 cl, 2 dwg, 5 ex

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