SU1668297A1 - Ammonia synthesis - Google Patents

Abstract

The invention relates to chemical engineering and can be used in the production of ammonia. The method involves preheating the nitric mixture by heat exchange with the gas mixture passing through the catalyst layers, passing it through successive layers of the catalyst, maintaining optimum temperatures in the catalyst layers by cold bypassing the layers with the nitric hydrogen mixture selected before the preheating stage, cooling the gas mixture passing through the layers catalyst by heat exchange with the nitric mixture entering the first layer of the catalyst, the allocation of production ammonia aka and the return of unreacted nitric mixture to preheating, in which in order to increase the productivity of the process, hot bypassing of the catalyst layers by the nitric mixture that has been preheated is additionally carried out. 3 tab., 1 Il.

Description

This invention relates to chemical technology and can be used in the production of ammonia.

The aim of the invention is to increase the productivity of the process.

The drawing shows the diagram of the column for the synthesis of ammonia.

The synthesis column consists of a shell 1, inside which is placed a nozzle 2 consisting of four shelves filled with a catalyst. The shells 1 and nozzle 2 form between themselves a cylindrical gap 3 connecting the entrance to the column 4 with the inlet 5 into the annular space of the heat exchanger 6. The exit 7 from the annular space of the heat exchanger is simultaneously the gas inlet on the shelf I of the column nozzle. The outlet from the shelf IV of the nozzle through the central tube 8 is connected to the inlet 9 in the pipe part of the heat exchanger 6, and the outlet 10 from the pipe part of this heat exchanger is the outlet from the synthesis column.

Cold bypass gases are supplied to each of the catalyst shelves through line 11, which is connected to the gas inlet line to column 4.

Part of the gas after the annulus of the heat exchanger 6 enters the nozzles 12, which form a hot bypass on the shelves II, III, and IV of the catalyst.

The increase in the productivity of the ammonia synthesis column is due to the possibility of supplying an additional quantity of circulating gas while satisfying the upper limit value by the pressure differential.

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Lenich on the synthesis column due to removal of a part of the hot (after the preliminary heat exchanger) gas to the next shelves, which leads to a decrease in the pressure drop on the synthesis column,

The effect of uniform loss of catalyst actives is achieved by oi; one of a part of the circulating gas, Enriched with the content of initial components, for the ammonia synthesis reaction, from the gas line to the subsequent shelves of the hot bypasses In the well known LJTHOM method of supplying hungry bypasses solves the problem of cooling the reaction gas between the catalyst shelves. In the proposed method, a hot bypass leads to a substantial paralleling of the main gas flow, which allows to achieve the effect of uniform sweat When the activity of the column flanges catalyst | Inteza the interval campaign catalyst mileage.

The increase in ammonia co-synthesis productivity is achieved due to an increase in the supply of fresh nitric mixture to the circulation cycle of the synthesis sections. This enhancement of the load on the column is made possible by reducing the hydraulic resistance of the ammonia synthesis column, in parallel with the parallelization of the gas flow after a single heat exchanger of the synthesis column to all the shelves of the column. At the same time, a decrease in the ammonia concentration at the outlet of shelf IV with respect to the known method nevertheless leads to an increase in the productivity of the synthesis column due to an increase in the total volume of the circulating gas,

The ammonium synthesis colony, which implements the proposed synthesis method, worked as follows,

The circulating gas in a volume of not more than 900,000 H with a temperature of 195 ° C enters the inlet of the column 4 and further into the cylindrical gap 3, where the gas heats up to 50 ° C, 8 turn to take part of the heat of reaction and cool the loaded shell of the column Next, the gas enters through the inlet for 5 hours the intertubular space of the heat exchanger 6. where it is heated to 400 ° C by the reacted gases. The heated circulating gas successively passes through four shelves with a catalyst, in the presence of which the initial components i and - water / nitrogen interact with each other to form ammonia. The reacted gas enters the heat exchanger 6 through the central tube 8 and further to the exit.

In a known manner, at the beginning of the campaign, when the catalyst has high activity, the excess heat generated in the reaction bed is compensated for by

Bypassing cold circulating gas. At the end of the campaign, when the activity of the kalizayayura falls, cold bypassing 11 closes and nevertheless the temperature decreases steadily, reducing the yields () is low. In order to maintain the stability of the ammonia yield, it is necessary to reduce the amount of gas for processing, up to and including the disconnection of the column for catalyst overload.

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According to the proposed method, throughout the entire period of operation of the catalyst, jto / i II, HI and IV continuously supply heated heat exchange circulating gas.

0 At the beginning of the campaign, the supply of additional hot gas leads to the need for additional heat removal, which. necessitates an increase in the flow rate of the cold bypass supply on the shelves to

5 5-10%, depending on the selected technological mode.

At the end of the campaign, when the cold laips are closed, the effect of innovation is especially great. Arrival of what

0 bypass gas to the shelves leads to a relative increase in temperature along the shelves and a decrease in the hydraulic resistance of the column.

In addition, during the whole campaign is

5 leads to a shift in the equilibrium of the synthesis reaction towards the formation of ammonia, since the ammonia content in the feed gas decreases.

Consequently, conditions are created for

0 relative extension of the life of the catalyst and the column as a whole and an increase in the volume of ammonia from one weight unit of catalyst during the entire campaign. Performance and Efficiency

5 of the proposed method for the synthesis of ammonia is confirmed by calculating the material balance of the column when operating under new conditions, the data of which are given in Table. 1. Thus, with the introduction of hot

0 bypasses, the volume of circulating gases increases by 9.9%, and the productivity of the ammonia synthesis column increases by 605%.

5 In table. Figures 2 and 3 show examples in which the quantities of cold (5x 6.) and hot (Gr.6.) Bypasses and temperature - p (Tech) and output (Yours) on the first - fourth shelf of the column with the load on the V0 column are indicated. .

Claims (1)

Invention Formula The method of ammonia synthesis includes preheating the nitric mixture by heat exchange with the gas mixture that has passed the catalyst layers, passing it through successive layers of the catalyst, maintaining optimum temperatures in the catalyst layers by cold bypassing the mixtures with the nitric mixture selected before the preheating stage, cooling the gas mixture that has passed the catalyst layer by heat exchange with the nitric mixture entering the first catalyst layer, separating the pro-Auction ammonia and returning the unreacted nitric-hydrogen mixture to preheating, characterized by the fact that, in order to improve the performance of the process, hot bypassing is additionally performed catalyst layers nitric mixture, pre-heated. 0.0734 0.05584 0.0735 0.6588 0.0736 0.0568 0.1263 0.1223 0.6580 0.1254 0.123 0.0588 0.1232 6.6588 0.1261 0.124 0.0588 0,1056 0,0584 0.111 0.1050 0.05 SS 0.1056 0.0538 0.1059 0.0533 .Table 1 table 2 S4 66 66 one sixteen 455 355776 455 50i, 77 455 503.01 455 504.28 455 5L4, 55 449.02 498.65 447.87 498.41 498158 447.35 493.29 447.21 498.26 455.19 566.05 455.15 500.04 454.84 499.98 4S4.57 499.93 454.49 499.92 T a b l and c a3