RU2291851C1 - Method of methanol production - Google Patents

Abstract

FIELD: chemical industry; methods of production of methanol.

SUBSTANCE: the invention is pertaining to method of production of methanol. The method provides for: mixing of the main stream of the synthesis gas with the circulating gas; partition of the gained mixture into two streams; heating up of one of the streams of the gas mixture up to the starting temperature of the synthesis; the passage of the both streams through the reactor of the methanol synthesis, consisting of four or five adiabatic catalyst layers; at that the heated stream is fed to the inlet of the first layer and the cold stream is divided and fed in the form of the cold by-passes between the layers of the catalyst; refrigeration of the reacted gas; separation of the condensed crude methanol and division of the non-condensed gas stream into the blowdown gas, which is withdrawn from the system, and the gas stream, which is compressed in the compressor and fed to the circulation. At that in the existing by-passes of the last two layers of the catalyst they introduce the additional stream of the synthesis gas, and the total percent of the additional stream of the synthesis gas introduced into existing by-passes of two last catalyst beds is introduced into the existing by-passes of the last two catalyst layers, in respect to the main stream of the synthesis gas varies from 36.3 % at the high activity of the catalyst up to 3.6 % at the lowered activity of the catalyst and the distribution of the additional stream of the synthesis gas between the layers varies from 10 up to 90 %. The method allows the fullest usage of the catalyst activity in its last layers.

EFFECT: the invention ensures the fullest usage of the catalyst activity in its last layers.

1 tbl, 11 ex, 1 dwg

Description

The present invention relates to the field of chemical technology and can be used in factories producing methanol.

A known method for the production of methanol is described in the copyright certificate SU 1375311 and involves the implementation of a methanol synthesis process in a multi-shelf catalytic reactor in which a coolant is used to cool the circulation gas between the layers, supplied to a heat exchanger-cooler, and then cold bypass is fed into the synthesis gas.

The closest in technical essence to the claimed is the method described in the book Karavaev M. Technology of synthetic methanol. M .: Chemistry, 1984 and involving the implementation of a methanol synthesis process in which only cold bypasss are used to cool the circulation gas between the catalyst beds.

The disadvantages of this method include:

1. incomplete use of the activity of the catalyst in the last layers due to a decrease in the concentration of reagents CO, CO ₂ , H ₂ and an increase in the concentration of reaction products of methanol and water on the last layers of the catalyst;

2. for the existing methanol synthesis unit, there is a limit on the load of fresh gas associated with problems of heat removal from the reaction on the first shelves.

Overcoming these disadvantages is possible if the maximum activity of the last catalyst layers is used. The task is achieved by additional supply of synthesis gas to the existing bypasses of the last catalyst layers with a constant supply of fresh gas. However, this is possible with a sufficiently high activity of the catalyst in the first layers. As the unit operates, the activity of the catalyst decreases mainly in the first layers, while the temperature of the onset of the reaction on the first shelf should increase. For the current unit, the possibility of increasing the reaction onset temperature on the first shelf is limited by the surface of the regenerative heat exchanger. Therefore, with a decrease in catalyst activity, the possibility of additional supply of synthesis gas to existing bypasses of the last catalyst layers is reduced.

The invention in a method for producing methanol, which includes:

- mixing the main stream of synthesis gas with circulating gas;

- dividing the resulting mixture into two streams;

- heating one of the streams of the gas mixture to the initial synthesis temperature;

- passing both streams through a methanol synthesis reactor consisting of four or five adiabatic catalyst beds, the heated stream being fed to the inlet of the first layer, and the cold stream being separated and supplied as cold bypasses between the catalyst layers;

- cooling of the reacted gas;

- the release of condensed crude methanol;

- separation of the non-condensed gas stream into two: circulation and purge, which is removed from the system;

- compression of the circulating non-condensed stream in the circulating compressor,

lies in the fact that in the existing bypasses, starting from the penultimate, an additional stream of synthesis gas is introduced. At the same time, the percentage of additional synthesis gas flow entering the existing bypasses in relation to the main synthesis gas flow varies from 36.3% with high catalyst activity to 3.6% with reduced catalyst activity. The distribution of the additional synthesis gas flow between the layers varies from 10 to 90%.

The technological scheme (figure 1) of the proposed method is as follows: the synthesis gas is compressed in the compressor pos.6 to a pressure of 10.0-5.0 MPa and is divided into two streams 1 and 13. Stream 1 is fed to a mixture with circulating gas (stream 2). The resulting stream 3 is divided into two streams - 4 and 5. Stream 5 enters the synthesis reactor pos.2 as cold bypasses between the adiabatic catalyst layers. Stream 13 is divided into two streams 14 and 15, which are mixed with the last cold bypass. Stream 4 is sent to a recuperative heat exchanger pos.1, where it is heated to the temperature of the beginning of the reaction and then (stream 6) enters the synthesis reactor pos.2. The reacted gas after the synthesis reactor (stream 7) is sent to the recuperative heat exchanger pos.1, where it is cooled, losing heat to the gas mixture (stream 6) entering the reactor pos.2. After the recuperative heat exchanger, the cooled stream 8 enters the refrigerator-condenser pos. 3 and then to the separator pos. 4, in which the liquid methanol-raw material (stream 9) is separated from the non-condensed gas stream 10. Then, the exhausted non-condensed gas stream 10 is discharged purge gas (stream 11) in order to maintain a certain concentration of inert components in the synthesis cycle. The remaining circulating gas (stream 12) is sent to the circulating compressor pos.5.

Technical implementation of the invention is confirmed by the following examples. For all calculations of the examples, the following constant values were adopted:

The composition of fresh synthesis gas, vol.%:

СО - 18.904, CO ₂ - 9.162, H ₂ - 70.064, CH ₄ - 1.047, N ₂ - 0.574, Ar - 0.249

The pressure of the synthesis gas is 90 bar.

The load on the main synthesis gas is 11000 nm / h; for these process conditions it is the maximum possible.

The load on the circulation compressor is 53000 nm / h. The volume of catalyst in the reactor is 8 m ³ , the number of layers is 4 or 5.

The methanol condensation temperature is 40 ° C.

The additional stream of synthesis gas entering the last two bypasss is divided in a percentage of 10 to 90% per layer. The temperature of the inlet of the circulation gas to the first layer cannot exceed 225 ° C, which is due to the surface of the regenerative heat exchanger.

Examples 1, 2, 2a, 2b, 3, 3a, 3b, 4, 4a, 4b are made for the same reactor with 4 catalyst layers, and in example 5 with 5 catalyst layers.

Example 1. The calculation of the base case without additional supply of synthesis gas. The activity of the catalyst adopted at the beginning of the campaign.

In the remaining examples, the activity of the catalyst decreases as its service life increases.

Example 2, 2a, 2b. Calculation of options with an additional supply of synthesis gas in an amount of 4000 nm ³ / hour, with 90, 50, 10% of the total amount being supplied to the last layer. The activity of the catalyst adopted at the beginning of the campaign.

Example 3, 3a, 3b. The calculation of the option with an additional supply of synthesis gas in an amount of 2400 nm ³ / hour, with 90, 50, 10% of the total amount being supplied to the last layer. The activity of the catalyst in the first layer is 63.3% of the initial, and on the rest - remained unchanged.

Example 4, 4a, 4b. The calculation of the option with an additional supply of synthesis gas in an amount of 400 nm ³ / hour, with 90, 50, 10% of the total amount being supplied to the last layer. The activity of the catalyst in the first layer is 63.3%, in the second layer 93.3% of the initial one, and on the rest it remained unchanged. Example 5. The calculation of the option with 5 layers and an additional supply of synthesis gas in an amount of 4000 nm ³ / hour in equal parts. The activity of the catalyst adopted at the beginning of the campaign.

Table Examples Additional synthesis gas, nm ³ / h The distribution of additional synthesis gas in layers,% % additional synthesis gas from the main Methanol productivity, t / h Productivity in methanol,% The temperature at the entrance to the first layer The activity of the catalyst in layers one - - - 4.296 one hundred 215.6 100, 100 100, 100 2 4000 10/90 36.3 4.988 116.1 216.2 100, 100, 100, 100 2a 4000 50/50 36.3 4.923 114.6 216.4 100, 100, 100, 100 2b 4000 90/10 36.3 4.925 114.4 216.5 100, 100, 100, 100 3 2400 10/90 21.8 4.703 109.5 224.4 63.3, 100 100, 100 3a 2400 50/50 21.8 4.7 109.4 224.5 63.3, 100 100, 100 3b 2400 90/10 21.8 4.636 107.9 224.5 63.3, 100 100, 100 four 400 50/50 3.6 4.418 102.8 224.1 63.3, 93.3, 100, 100 4a 400 10/90 3.6 4.418 102.8 224.1 63.3, 93.3, 100, 100 4b 400 90/10 3.6 4.418 102.8 224.1 63.3, 93.3, 100,100 5 4000 50/50 36.3 5.448 126.8 212.9 100, 100, 100, 100.100

As can be seen from examples 1, 2, 2a, 2b, 3, 3a, 3b, 4, 4a, 4b, 5, tabulated, for an active catalyst, the additional supply of synthesis gas to the existing bypasses of the last catalyst beds is 36.3%, while performance in the four-shelf unit increases by 16.1%, and in the five-shelf unit - by 26.8%. With a decrease in the activity of the catalyst, it is necessary to gradually reduce the supply of additional synthesis gas up to 3.6% so as not to exceed the maximum permissible temperature of entry into the first layer.

Claims (1)

A method for producing methanol, including mixing the main stream of synthesis gas with circulating gas, dividing the resulting mixture into two streams, heating one of the streams of the gas mixture to the initial synthesis temperature, passing both streams through a methanol synthesis reactor consisting of four or five adiabatic catalyst layers, moreover, the heated stream is fed to the inlet of the first layer, and the cold stream is separated and supplied in the form of cold bypasss between the catalyst layers, cooling the reacted gas, and the formation of scondes raw methanol and separation of the non-condensed gas stream into a purge gas that is discharged from the system and a gas stream that is compressed in the compressor and sent to the circulation, characterized in that an additional synthesis gas stream is introduced into the existing bypasses of the last two catalyst layers, the total percentage of the additional synthesis gas stream introduced into the existing bypasses of the last two catalyst layers, in relation to the main synthesis gas stream, changes from 36.3% at high activity isator to 3.6% with reduced activity of the catalyst and the distribution of the additional stream of synthesis gas between the layers varies from 10 to 90%.