JPH01501141A - Ammonia production method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Ammonia production method field of invention The invention relates to chemical technology, more particularly to the production of natural gas in plants of the nitrogen industry. When processing casing-head gas, The present invention relates to a method for producing ammonia from a nitrogen-hydrogen mixture.

Conventional technology A more effective prior art method for producing ammonia from nitrogen and hydrogen is The following reaction: N 2 + 3 Hz; = t2 N Hs + 10 to 35 MPa according to Q The process is carried out at temperatures up to 600'C and overpressures of up to 600'C.

The fact that the ammonia synthesis reaction is exothermic and reversible makes it possible to continuously control the temperature. Theoretically optimal ammonia concentration increases when reduced to Under the conditions, maximum yields of ammonia are achieved (E, Y Melnikov (E, Y a, Mel’　n1kov) iji” Handbook of Nitrogen Engine (Handbook of Nitrogen Worker), 1986. p. , 510: L. D., Kuznetsov et al. Synthesis of Ammonia, 198 2. “Khimiya” Publish-ers, Moscow, p. 296), for this reason modern ammonia production technology is It is desirable to provide temperature conditions close to theoretically optimal conditions. Furthermore, iron touch Temperatures above 550°C should not be used during the production of ammonia over medium. This is because at such temperatures the catalyst rapidly loses its activity. . Conversion rate of starting hydrogen-nitrogen feed to ammonia In general, a partially reacted hydrogen-nitrogen donor is used to increase The feed is repeatedly recycled from the outlet to the inlet of the synthesis reactor, and the resulting ammonia is An uncircumcised part of the feed is pumped out and purged. The recirculation ratio and pressure of the zero synthesis carrying out the Monia production process are based on economic parameters. Determined by

Ammonia production where the temperature and composition of the reactant gases do not change substantially over time. Methods are known in the art (L, D.

Kuznetsov (L, D.) et al., “Synthesis of ammonia (Synthesis of^-monia)”, 1982. “Himya (Kh iaiya)'' Publishers, Moscow, p, 296 ), the process involves the addition of a starting nitrogen-hydrogen mixture to the catalyst bed before the mixture is fed to the catalyst bed. The reaction can be carried out between the catalyst beds or directly within the catalyst bed by preheating the catalyst and using heat removal tubes. It involves intercooling the gas. When intercooling the nitrogen-hydrogen feed, The catalyst is arranged in 3-4 beds between which the nitrogen-hydrogen feed is introduced into the starting gas. Cooling is achieved by mixing with water or free M heat is generated by heating water or steam used for generation. This prior art method requires that the temperature conditions of the process be characterized by not fully complying with theoretically optimal conditions, and therefore starting nitrogen-hydrogen Insufficient conversion of n feed) to the desired product (approximately 16% of volume) was observed. Ru.

In addition, the practical implementation of the above method requires an elaborately designed, cumbersome, and sturdy counter. should be used.

Processes for producing ammonia carried out in a single bed of catalyst are known in the art. The catalyst is It is preheated to a temperature corresponding to the reaction temperature in the range 120-590°C.

The starting nitrogen-hydrogen feed is then heated to a temperature of 20 to 150°C. feed on top of the medium. After 5 to 30 minutes, reverse the direction of supply of the nitrogen-hydrogen mixture to the catalyst. change in the direction (SU, ^.

865796), the direction of feed of the nitrogen-hydrogen feed to the catalyst bed within equal time intervals. i.e. by varying the location of the nitrogen-hydrogen feed inlet and outlet. By making the changes occur intermittently, non-stationary conditions (non-stationary The continuous synthesis method of ammonia is carried out under the following conditions, and the temperature distribution is Moving along the catalyst bed, this temperature distribution is divided into three zones: nitrogen-hydrogen feed; heating zone, a hot zone within the center of the catalyst bed and a nitrogen-hydrogen feed from the catalyst bed. It is characterized by a temperature drop zone near the exit. The temperature drop zone is a cold gas mixture and Calculate the heat exchange of , which is formed for the preheat of the catalyst. Due to this temperature distribution, Generally allows a sufficiently high concentration of ammonia at the outlet from the catalyst bed .

However, in practical implementation, this method for producing ammonia encounter certain difficulties.

When carrying out this process, the nitrogen-hydrogen mixture at the outlet from the catalyst bed is Therefore, due to the different density of the catalyst bed packing, a low concentration of aluminum equal to 15.8% by volume ummonia is achieved. Structural heterogeneity of catalyst bed packing non-uniformities) are catalyst beds perpendicular to the direction of movement of the reaction mixture. 11) contributes to the formation of a superheated zone and a cooled zone, and The formation of eventually leads to overheating of the catalyst and loss of its activity.

As a result, as already mentioned above, the nitrogen-hydrogen at the outlet from the catalyst bed In the mixture, the ammonia concentration decreases.

Disclosure of invention By maintaining the temperature conditions of the process at a constant level, the present invention enables To provide a process for the production of ammonia which makes it possible to obtain the desired product It depends.

The purpose is to supply the nitrogen-hydrogen feed to a reactor with a temperature in the range of 420 to 590°C. into the medium bed, the feed direction of the feed is intermittently changed in the opposite direction, and then the production Nitrogen-hydrogen feed by removing ammonia and unreacted nitrogen-hydrogen feed from the catalyst bed According to the present invention, in a method for producing ammonia from at least two along the cross-section of the catalyst bed perpendicular to the direction of nitrogen-hydrogen feed feed. (in a catalyst bed divided into parts), between said parts, the next catalyst after the first part is The temperature gradient of the nitrogen-hydrogen feed at the inlet to the media section is equal to or less than 20°C. The feeds are mixed until the temperature is 20-250°C. carried out under a pressure of 10 to 100 MPa at an inlet temperature of the starting nitrogen-hydrogen feed of This is achieved by

According to the invention, nitrogen - about 20%, hydrogen - about 66%, alegone, methane, etc. A starting nitrogen-hydrogen supply containing approximately 10% inert gas and approximately 2% ammonia. Ammonia synthesis from feedstock compared to prior art methods for ammonia production reducing power consumption and general simplification of the process to produce the desired product. It is possible to obtain a concentration of 0% by volume.

Passing the starting nitrogen-hydrogen gas feed through a catalyst bed to reduce the temperature of this feed within the hot zone. In order to enable the mixing of ammonia and thus increase the ammonia yield, the present invention According to 0.5 to 1:1 in the cross section of the catalyst perpendicular to the feed direction of the starting feed. It is appropriate to use a catalyst divided into at least two parts with a volume ratio equal to It is.

According to the invention, it is suitable to use catalysts with a particle size of 15 to 501. Ru.

Further objects and advantages of the present invention are described in the following detailed description of the ammonia production method. It will now become more fully clear from the description and examples illustrating this method.

The process according to the invention uses as starting products the following composition: nitrogen - approx. 22%, hydrogen - approx. 66%, inert gases such as argon and methane - about 10% and ammonia - This is done by using a gas feed having about 2%. Synthesis of desired product is the result of the following reaction proceeding in the catalyst bed: N2 + BH4 = total 2NH, +Q It happens. Catalytic activity for ammonia synthesis is periodic. 5ystes+). However, most High catalytic activity makes it the most preferred cocatalyzed iron catalyst when carrying out the process according to the invention. Iron promoted catalysts. Than Specifically, the cocatalyzed iron catalyst has a slight excess of FeO above the stoichiometry. 90-98% magnetite and promoter additive (promotor adJitiv) es) (AI 20, Ca 01K20.5i (h and other oxides) 7~ Contains 10%.

The catalyst used is of fractional size, which is in the form of granular or crushed material. ion 5ize) is 1-3.3-5.5-7.7-1O510-15m theory be.

The method according to the invention has a fractionation size as defined above and a particle size of 15 to 5015 m. This was achieved using a catalyst that By using a catalyst with the above fractionation dimensions, filtration (filtering) The strength of the heat exchange between the initial nitrogen-hydrogen feed and the catalyst bed is As a result, the starting cold nitrogen-hydrogen feed is required to heat to a high temperature. The contact time will be long. During this contact time, the starting reactants (starti ng reagents) to enter the ammonia synthesis reaction and partially has time to enter the high temperature zone through which the reacted nitrogen-hydrogen feed passes; Therefore, the reaction takes place with less generation of heat, thus resulting in a lower maximum temperature. It will be done. In order to prevent slowing down of the diffusion of ammonia production reaction, large catalyst particles (la cloth that can be fed through holes in the rge-size particle) By equalizing, the temperature conditions of the process are close to the optimum conditions; The hydraulic resistance of is substantially reduced.

By using catalyst particles with a size of more than 50 mm, -pernitrogen-hydrogen feed (filtering nitrogen-hydrogen feed) The strength of the heat transfer and mass transfer processes between the medium and the Maintaining a high concentration of ammonia in the nitrogen-hydrogen feed at the exit from the media bed In order to achieve this, the amount of catalyst must be substantially increased, i.e. It is necessary to reduce the degree of

According to the present invention, the method for synthesizing ammonia is such that the ratio between the volumes of the parts to be divided is 0. ．． carried out in a catalyst bed divided into at least two parts equal to 5 to 1:1. It will be done. The synthesis method is carried out in a catalyst bed preheated to a temperature in the range of 420 to 590°C. It will be done. When this temperature is reached, the output of the above composition having a temperature of 20 to 250°C The reactant gas is fed into the catalyst bed under a pressure ranging from 10 to 100 MPa. The feeding direction of the 0 reaction gas is perpendicular to the cross section, and the catalyst bed is arranged along the cross section. It is divided into two parts.

In the method according to the invention, the direction of feed of the nitrogen-hydrogen feed to the catalyst bed is fixed. Periodically it is changed to the opposite direction (opposite).

The duration of such changes is generally equal to 1 to 30 minutes.

In the space between the sections of the catalyst bed formed during partitioning of the catalyst bed, the starting nitrogen - the hydrogen feed is nitrogen-water at the inlet to the next catalyst section after the first section of the catalyst; Mix until the temperature gradient of the elementary feed is equal to or less than 20°C.

The nitrogen-hydrogen feed mixture preferably accounts for about 1/3 of the total volume of the catalyst bed and It should be carried out in a high temperature zone located in the central part of the catalyst bed. high temperature range Mixing the nitrogen-hydrogen mixture on the outside considerably reduces its effectiveness. Already a headline As previously mentioned, for the most effective mixing of nitrogen-hydrogen gas, the volume of the catalyst bed should be It is necessary that the product ratio be equal to 0.5 to 1:1.

Temperature non-uniformity of nitrogen-hydrogen feed The homogenization of the firmities by mixing is associated with a pressure drop.

A temperature equal to or less than 20° C. at the inlet of the next catalyst bed section after the first catalyst bed section. During mixing of the nitrogen-hydrogen feed, the pressure drop increases considerably until the gradient Then, the power consumption for mixing (power eonsua+ption) is It increases considerably. At the above temperature gradient greater than 20°C in the catalyst bed, A hot zone and a cooling zone are formed, whereby nitrogen at the outlet from the catalyst bed The ammonia concentration in the hydrogen feed is reduced to a value of over 10%.

At a temperature of 20 to 250°C and under a pressure in the range of 10 to 100 MPa , a nitrogen-hydrogen feed is fed into the first portion of the catalyst bed along the motion of the gas stream. Ru. The supply of nitrogen-hydrogen feed at a temperature below 20° C. at the outlet from the catalyst bed does not result in any increase in ammonia concentration at temperatures above 250°C. The supply of this feed at a temperature of and the actual time between changes in the feed direction of the starting nitrogen-hydrogen feed. Due to the lack of ammonia in the nitrogen-hydrogen feed at the outlet from the catalyst bed, causing a decrease in near concentration. Under pressures below 10MPa and above 100MPa The efficiency of the ammonia synthesis method in In the hydrogen feed, the ammonia concentration is significantly reduced and the use of high pressures Significantly reduced by the fact that it requires expensive equipment. First part of the catalyst bed The nitrogen-hydrogen feed supplied from It has a high temperature of about 150 to 200°C. Nitrogen on the above mllIr surface The next catalyst bed after the first part of the catalyst bed in order to equalize the concentration of hydrogen feed. This is continued until the temperature gradient of this mixture at the inlet of the section is equalized below 20°C. The mixture of is mixed.

Structural non-homogeneity of the catalyst bed Temperature non-uniformity of the nitrogen-hydrogen feed caused by Characteristic time (character) to establish non-uniformity eristictise) due to changes in feed direction and changes in the starting nitrogen-hydrogen feed. Due to the fact that the time between The mixing of the materials leads to temperature homogenization in any cross-section of the catalyst bed perpendicular to the starting gas flow. inducing and thus generally allowing optimum conditions for the ammonia production process.

The change in the direction of feed of the nitrogen-hydrogen feed to the catalyst bed can vary from 1 to 1, as already mentioned above. It takes place every 30 minutes. The maximum period for which a change in the direction of supply of starting gas is allowed is In the short term, the ammonia in the nitrogen-hydrogen mixture at the outlet of the catalyst bed concentration decreases. In longer periods, the heat from the catalyst bed is The feed is removed and the ammonia production reaction is stopped.

Results of filtration of the starting nitrogen-hydrogen feed through the catalyst bed According to the invention, as already mentioned in detail above, ammonia is (nitrogen-hydrogen mixture) at a concentration of about 20% by volume. The generated Anne Monia and unreacted mixture are removed from the catalyst bed and by conventional techniques. It is sent for further separation and purification.

BEST MODE FOR CARRYING OUT THE INVENTION For a better understanding of the invention, some specific examples are given below.

Example 1 divided into two parts with a volume ratio equal to 1:1 and heated to a temperature of 500 °C A catalyst bed with a particle size of 3 to 5 was charged with nitrogen - 22% by volume, hydrogen - 66% by volume, inert A nitrogen-hydrogen feed containing 1% by volume of aqueous gases, 2% by volume of ammonia, At a temperature of 20°C and under a pressure of 32 MPa, a feed flow space velocity of 12,000 h-' Supply in degrees. the nitrogen-hydrogen feed to the next catalyst bed section after the first section of the catalyst bed; of the catalyst bed until the temperature gradient of this feed at the inlet of the catalyst bed is equal to 20°C. Mix between parts. Opposite to the feed direction of the starting feed The average yield of ammonia is 16.1%, with a change in ammonia every minute. The near gain is 14.1%.

Example 2 Synthesis of ammonia is carried out under conditions similar to those described in Example 1 above, however , the temperature of the nitrogen-hydrogen feed at the inlet to the catalyst bed is 100°C. departure supply A change in the direction of supply of material to the opposite direction takes place every 4 minutes. Average yield of ammonia is 19.7%, and the increase in ammonia is 17.7%.

Example 3 Synthesis of ammonia is carried out under conditions similar to those described in Example 1 above, however. , the temperature of the nitrogen-hydrogen feed at the inlet to the catalyst bed is 250°C. departure supply A change in the direction of supply of material to the opposite direction takes place every 5 minutes. Average yield of ammonia is 19% and the increase in ammonia is 17%.

Example 4 Synthesis of ammonia is carried out under conditions similar to those of Example 1, however, the starting nitrogen The pressure of the nitrogen-hydrogen feed was 10 MPa, and the nitrogen-hydrogen feed pressure was 10 MPa. The feed temperature is 100°C. Change in feed direction of starting feed in opposite direction is 5 minutes It is done every. The average yield of ammonia is 10% and the increase in ammonia is 8 %.

Example 5 Synthesis of ammonia is carried out under conditions similar to those of Example 1, however, the starting nitrogen The pressure of the hydrogen-hydrogen feed is 100 MPa. The average yield of ammonia is 32%. Yes, the increase in ammonia is 30%.

Example 6 Ammonia is synthesized under the same conditions as in Example 2 above.

However, the particle size of the catalyst is 15 mm. The average yield of ammonia is 20.2 %, and the increase in ammonia is 18.2%.

Example 7 Ammonia synthesis is carried out under conditions similar to those described in Example 2.

However, the average particle size of the catalyst is 50 cm. The average yield of ammonia is 16 %, and the increase in ammonia is 14%.

Example 8 Ammonia synthesis is carried out under conditions similar to those specified in Example 1, however , the catalyst bed is divided into two parts with a volume ratio equal to 0.5:1. Anmo The average yield of ammonia is 15.9% and the increase of ammonia is 13.8%.

Example 9 Synthesis of ammonia is carried out under conditions similar to those of Example 1, however, the catalyst bed is divided into two parts with a volume ratio of 0.6:1. Average yield of ammonia is 15.9%, and the increase in ammonia is 13.9%.

Example 10 Synthesis of ammonia is carried out under conditions similar to those of Example 1, however, the catalyst bed is divided into two parts with a volume ratio of 0.7:1. Average yield of ammonia is 14% and the increase in ammonia is 12%.

Example 11 Synthesis of ammonia is carried out under conditions similar to those described in Example 1 above, however , the catalyst bed is divided into two parts with a volume ratio of 0.8:1. of ammonia The average yield is 16% and the ammonia increase is 14%.

Example 12 Synthesis of ammonia is carried out under conditions similar to those of Example 1, however, the catalyst bed is divided into two parts with a volume ratio of 0.9:1. Average yield of ammonia is 16% and the increase in ammonia is 14.1%.

Example 13 Ammonia synthesis is carried out under conditions similar to those described in Example 1.

However, between sections of the catalyst bed, to the next section of the catalyst bed following the first section of the catalyst bed. This is continued until the temperature gradient of the nitrogen-hydrogen feed equals 10°C at the inlet of the Mix the feeds. The average yield of ammonia was 16.4%, and the increase in ammonia Addition is 14.4%.

Example 14 Synthesis of ammonia is carried out under conditions similar to those described in Example 1 above, however. , the starting nitrogen-hydrogen feed was: nitrogen - 20% by volume, hydrogen - 60% by volume, inert gas -15% by volume, and -5% by volume of ammonia. Opposite of feeding direction of starting feed Changes in the opposite direction occur every two minutes. The average yield of ammonia was 16.6%. The increase in ammonia was 11.6%.

Industrial applicability Ammonia, nitric acid, nitrogen-containing salts, urea, sodium bicarbonate, hydrocyanic acid , fertilizers, and the production of diazo-type photocopying materials.

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Claims (3)

[Claims] 1. A nitrogen-hydrogen feed is provided to the catalyst bed having a temperature within the range of 420 to 590°C. The feed direction of the feed is intermittently changed to the opposite direction, and then the generated ampere is supply by removing monia and unreacted nitrogen-hydrogen feed from the catalyst bed. In the process of producing ammonia from a starting nitrogen-hydrogen feed, in a catalyst bed that is divided into at least two parts in a cross section perpendicular to the feeding direction. between said portions, the nitrogen-hydrogen feed passes to the next catalyst after the first portion of the catalyst bed. Mix until the temperature gradient of the feed at the inlet to the bed section is equal to or less than 20°C. This method is carried out under a pressure of 10 to 100 MPa, at a pressure of 20 The method is characterized in that the process is carried out at a nitrogen-hydrogen feed inlet temperature of between 250°C and 250°C. Monia production method. 2. Volume equal to 0.5 to 1:1 in the cross section perpendicular to the feeding direction of the starting feed Claim characterized in that a catalyst is used which is divided into at least two parts in ratio The method described in item 1 of the scope. 3. The claim is characterized in that a catalyst having a particle size of 15 to 50 mm is used. The method according to scope items 1 and 2.