SU963951A1 - Process for synthesizing ammonia - Google Patents

Description

The invention relates to methods for the synthesis of ammonia and can be used in the chemical industry.

A known method for the synthesis of ammonia by sequentially passing a gas through two catalytic zones. The gas entering the ammonia synthesis reactor passes a first catalytic zone in the radial direction after the preliminary heat exchanger, and as a result of the synthesis, the temperature rises from 410-420 to 510-520 ° C. Gas with a temperature of 510520 C enters the second catalytic zone and passes it axially. At the same time, heat of the ammonia synthesis reaction is removed, for which a heat exchanger is built in, which is built into the catalytic zone tl.

The disadvantage of this method is low product yield.

The closest in technical essence and the achieved result to the proposed method is the method of ammonia synthesis by successive passing of gas through three catalytic zones with the following temperature increase in the zones:

 - from 420-440 to 520-550 ° С And the zone - from 440-450 to 510-530 С IJJ zone - from 440-450 to 500-520 С and with heat removal of the reaction by cold bypass t-az, while the volume of the catalyst zones increase along the gas flow 2.

The synthesis of ammonia is carried out in a manner known per se in a reactor with an axial flow of gas through the reaction zone. The reactor consists of three catalytic zones, temperature. the mode in which is provided by the cold bypass gas.

The disadvantage of this method of ammonia synthesis is an increase in temperature from 440-450 to 500-520 ° C when the gas leaves the third catalytic zone, which, according to the equilibrium conditions of the ammonia synthesis reaction, makes it impossible to obtain a high content at the outlet (the real increase in ammonia is 12 about.%),

In addition, the amount of the main stream of the gas mixture passing through the catalytic zones, especially in the first zone, is reduced as a result. . separating most of the gas mixture into cold bypasses; The aim of the invention is to increase the efficiency of the process by increasing the yield of the finished product. The aim is to achieve that with the implementation of the synthesis process of ammonia by sequentially passing gas through three catalytic zones with temperatures ranging from 400-420 to 510-520 0 in the first and 440-450 to 500-520s in the second zones with simultaneous heat removal of the reaction by cold bypass gas in the third catalytic zone, the temperature is reduced along the course from 520-500 to 475-4bO ° C by including in the thermal scheme of the reactor yx conjugated controlled heat removal in the first and third catalyst zones. The difference of the proposed method lies in the fact that in the third catalytic zone, the temperature along the gas flow is reduced from 520-500 to 4 7 5-4 b O С by including conjugated regulated heat removal in zones I and III in the thermal scheme of the reactor. catalyst. In this method, ammonia synthesis is carried out in a reactor. The catalyst box of the reactor consists of three zones with a catalyst and one inlet of cold bypass gas between the first and second zones. In the first and third zones there are built-in heat exchangers. The distribution of the catalyst in the zones is as follows: 1030 vol.% In the first zone, 40-50 vol.% In the second and 30-40 vol.% In the third. The direction of flow of the gas mixture in the first and third zones is axial, and in the second - radial, which reduces the hydraulic resistance and intensifies the synthesis process. In the first and second zones of the synthesis. ammonia is carried out far from the equilibrium with increasing temperature, and in the third zone - with decreasing temperature. The synthesis of ammonia is carried out according to the scheme shown in the drawing, where arrow A shows the gas mixture entering the synthesis reactor, arrow B returns the converted gas from the reactor, arrow B shows the cold bypass gas injection. . The main gas flow enters the ammonia synthesis reactor through the (Top cover. Then the gas is directed down between the reactor vessel 1 and the catalyst box 2 and enters. In the annular space 3 of the pre-heat exchanger, where it is heated by the converter gas leaving the catalyst box From the pre-heat exchanger the main gas enters countercurrent tubes 4 of the third catalytic zone 5, where it is heated by the heat of the ammonia synthesis reaction. Then the gas mixture through the central tube b enters the interior 7, and then into the outer 8 heat exchange tubes of the first catalytic zone 9, where it is additionally heated to the temperature at the beginning of the reaction due to the heat of reaction, and then passes through the first catalytic zone in the axial direction. temperature is diluted with a bypass basin through the inlet line 10 and passes radially from the periphery to the center through the second catalytic zone 11. Then the gas mixture enters the third catalytic zone and passes through Cut the catalyst, located in the intertube space, in the axial direction. The ammonia synthesis process in the third catalytic zone proceeds at a decreasing temperature. The curved gas leaves the catalytic box 2 and passes through the tubes 12 of the preliminary heat exchanger, where it is partially cooled by a counter flow of the gas mixture passing through the annular space of this heat exchanger. From the latter, the gas mixture is directed to the condensation system. The temperature conditions in the third and first catalytic zones are controlled by the bypass gas supplied through lines 10 and 13. Example. Calculation of a real system with a reactor with a diameter of 1650 and a height of 15.8 m at a pressure of 320 atm, a circulation of 290000 nm, / h. The amount of cold bypass gas is 20% of the total flow, i.e. 588000 HMV4, and 80% is fed to the first catalytic zone, i.e. 232,000 nm7h When the content in the nitric mixture of 3.5% by volume of MPL, 4% by volume of Ar and 8% by volume of CH4, the following technological parameters were obtained: in the first zone with 3.4 m (22.55% of catalyst CA-1 fraction 3 The -6 mm temperature varies from 420 to 510 ° C, and the concentration of ammonia in the gas mixture varies from 3.5 to 13% by volume, i.e. the increase in ammonia is 9.5% by volume. After mixing with the cold bypass gas the concentration of ammonia at the inlet to the second catalytic zone is 13 0., 8 11.2% by volume. As a result of introducing 20% cold bypass gas with a temperature of 170 ° C, the temperature of the gas mixture at the inlet to the second catalytic zone decreases from 510 to. In the second catalytic zone, from 6.5 m (43.0%) of catalyst CA-1 of a fraction of 1-3 mm, the concentration of ammonia increases from 11.2 to 17.5% by volume as the temperature rises from 440 to C. Next, the gas mixture with an ammonia content of 17.5 O6v% and temperature enters the third catalytic zone with 5.2 m (34.4%) of catalyst CA-1 of a fraction of 8-12 mm without dilution with cold bypass gas. The synthesis of ammonia in this zone proceeds with an increase in the concentration of ammonia from 17.5 to 20.2% by volume, and the temperature decreases from 520 to. Thus, the increase in gamma is 20.23, 7% by volume.

Claims (2)

1.Patent of France 2141488 :, cl. Since 01 1/00, 1973. 2. Nitrogen, 1970, 63, p. 21.