BE1030481B1 - Ammonia converter for fluctuating partial load operation - Google Patents

Abstract

The present invention relates to an ammonia converter 10, wherein the ammonia converter 10 has a shell 20, wherein the ammonia converter 10 has a reactant inlet 30 and a product outlet 40, wherein the ammonia converter 10 has at least a first catalyst bed 50 and a second catalyst bed 60, wherein the first catalyst bed 50 and the second catalyst bed 60 are flowed through radially from the outside towards the center, the ammonia converter 10 having at least one first heat exchanger, the first heat exchanger being designed as a first tube bundle heat exchanger, the first tube bundle heat exchanger having a central tube 70 and a plurality of heat exchange tubes 80 , wherein the heat exchange tubes 80 are arranged parallel to the central tube 70 and around the central tube 70, the first tube bundle heat exchanger having a deflection device 90, the deflection device 90 being arranged between the central tube 70 and the heat exchange tubes 80, the first tube bundle heat exchanger being annular the first catalyst bed 50 is surrounded, characterized in that the educt inlet 30 is connected directly to the heat exchange tubes 80 in terms of gas flow, the central tube 70 being connected directly to the space between the shell 20 and the first catalyst bed 50 in terms of gas flow.

Description

1 BE2022/5308

Ammonia converter for fluctuating partial load operation

The invention relates to an ammonia converter that is designed to function reliably even with fluctuating utilization. Fluctuating loads occur, for example, when the hydrogen is produced using renewable sources

Energy is generated by electrolysis and the available educts are therefore subject to large fluctuations depending on the weather situation.

From EP 3 497 392 B2 is the use of a plate heat exchanger and one

Synthesis device for the production of ammonia in particular is known.

A synthesis device and a method for producing ammonia in particular are known from EP 3 497 058 B1.

During ammonia synthesis, energy is released through the conversion. The higher the

The higher the temperature, the further the equilibrium shifts towards the reactants. And if the temperature exceeds a certain level, damage can of course occur

Device arise. Therefore, implementation usually takes place in two or more

Stages. Between two stages, the excess energy is transferred to cooler incoming educt using a heat exchanger.

For a normal synthesis, the heat exchanger is designed for maximum efficiency, as it can be made particularly small, which in turn allows more catalyst in the converter, which in turn increases conversion.

If a conventional converter is now confronted with a fluctuating educt stream, it can happen that the educt stream cools the product stream to such an extent that it is no longer warm enough at the next stage, for example below 370 °, to be further implemented, the reaction comes to a standstill. However, if the heat exchanger were to be made smaller, either the cold incoming gas would not be heated sufficiently, so that the reaction would come to a standstill, or the converter could overheat at full load because the gas emerging from the previous stage is not cooled down sufficiently.

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The object of the invention is to provide a converter that works reliably both at full load and at the lowest possible partial loads.

This task is solved by the ammonia converter with the features specified in claim 1. Advantageous further training results from the

Subclaims, the following description and the drawing.

The ammonia converter according to the invention has a shell. The shell is relevant for the high pressures usual for ammonia synthesis and at the same time must be for the

Hydrogen-containing atmosphere and elevated temperatures must be designed. The ammonia converter also has an educt inlet and a product outlet. Additional by-product inlets can be provided, for example to cool

For example, to be able to supply the educt gas mixture directly to the second catalyst bed in order to be able to regulate the temperature, for example. Through the

The educt inlet is the mixture of hydrogen and nitrogen (if necessary with others

Components such as ammonia or argon). This is done via the product outlet

Product gas mixture of ammonia, hydrogen and nitrogen from the

Ammonia converter removed. The ammonia converter has at least a first

Catalyst bed and a second catalyst bed. Within the catalyst beds, the conversion of hydrogen and nitrogen to ammonia takes place on the surface of the catalyst. The first catalyst bed and the second catalyst bed are flowed through radially from the outside towards the center. The gas mixture to be converted is therefore supplied from the outside from a space between the shell and the catalyst bed

Catalyst bed supplied. The gap between the shell and the catalyst bed is used

Distribution of the gas mixture along the catalyst bed. The ammonia converter has at least a first heat exchanger. The first heat exchanger is designed as a first tube bundle heat exchanger. The first tube bundle heat exchanger has a central tube and a plurality of heat exchange tubes. The

Heat exchanger tubes are flowed through in the opposite direction to the flow through the central tube. The heat exchange tubes are arranged parallel to the central tube and around the central tube. The heat exchange tubes thus surround the central tube. The first tube bundle heat exchanger has a deflection device.

The diverter is fluidly connected between the central pipe and the

Heat exchange tubes arranged and leads the gas flow from one to the other.

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The first tube bundle heat exchanger is surrounded in a ring by the first catalyst bed, and is therefore arranged in the inner core of the first catalyst bed. As a result, the gas mixture heated by the reaction in the first catalyst bed becomes the

Tube bundle heat exchanger is supplied and thus heats the gas mixture inside the

Tube.

According to the invention, the educt inlet is directly connected to the gas flow

Heat exchange tubes connected and the central tube is connected directly to the space between the shell and the first catalyst bed in terms of gas flow. That the

Educt inlet is directly connected to the heat exchange tubes in terms of gas flow technology, which means in particular that the central first tube is not arranged between the educt inlet and the heat exchange tubes. Likewise means that the central

Pipe gas flow directly with the space between the shell and the first

Catalyst bed is connected, which is not connected between the central tube and the space between the shell and the first catalyst bed

Heat exchange tubes, This is the first heat exchanger

DC heat exchanger. In common converters the heat exchanger is called

Countercurrent heat exchanger operated, as this reduces the size of the heat exchanger, which in turn increases the amount of catalyst and thus the maximum

Plant capacity increased. Therefore, a direct current heat exchanger appears inefficient. The

However, direct current heat exchangers have a technical advantage. Due to the direct current, both gas flows have the same output at maximum heat transfer

Temperature. This means that not too much heat can be transferred; both gas streams have the temperature that is required to further convert each of the gas streams when fed to the next catalyst bed and thus maintain the reaction.

This results in a maximum at the expense of a certain proportion of the maximum capacity

Flexibility for partial loads is achieved, making the ammonia converter ideal for use in producing so-called green ammonia using renewable sources

Energy.

In a further embodiment of the invention, the ammonia converter has a third

Catalyst bed. The third catalyst bed is arranged between the first catalyst bed and the second catalyst bed. The first heat exchanger has a first partial heat exchanger and a second partial heat exchanger. The first

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Partial heat exchanger is surrounded in a ring by the first catalyst bed and the second partial heat exchanger is surrounded in a ring by the third catalyst bed. The

The path of the gas flow is therefore from the educt inlet through the first heat exchanger, more precisely through the heat exchange tubes of the first partial heat exchanger, then through the

Heat exchange tubes of the second partial heat exchanger, then through the central tube. From there the gas stream is passed between the shell and the first catalyst bed and then through the first catalyst bed. From there it passes through the first heat exchanger between the shell and the third catalyst bed and is then passed through the third

Catalyst bed guided. From there it passes through the first heat exchanger between the shell and the second catalyst bed and is then guided through the second catalyst bed. The gas stream is then passed through the product outlet.

In a further embodiment of the invention, the entire surface is the

Heat exchange tubes for sufficient heat transfer for one

Partial circulation gas quantity of 10% of the maximum circulation gas quantity is designed at full load. The lower the possible partial load, the greater it is

Heat exchanger can be carried out. On the other hand, the ammonia converter can also be used with very small amounts of renewable energy available

Energy can continue to be operated so that switch-off times are reduced, which in turn avoids start-ups with high losses.

In a further embodiment of the invention, the ammonia converter has a maximum system capacity of 50 to 700 tons of ammonia per day. That's it

Invention particularly preferred for comparatively small systems

Ammonia synthesis. Conventional systems reach a capacity of 3000

tons per day and more. However, if you want to use renewable energies, they are subject to change over time. On the other hand, this is also the case

Production is regularly limited, for example by the space available for solar or wind turbines. It can therefore be assumed that systems that

Production of green ammonia is planned to be comparatively small

Need converter. However, there is a synergy with the invention here. Since the

Converters are built in a pressure-resistant shell, which usually have certain characteristics

sizes. This means that in comparatively small systems there is additional space in the converter. The disadvantage of the increased space requirement for the first heat exchanger according to the invention is therefore not a disadvantage.

In a further embodiment of the invention, the first heat exchanger has radially arranged guide elements on the side around which the gas emerging from the first catalyst bed flows in order to produce a flow that crosses the heat exchange tubes

Flow arranged. This zigzag guidance optimizes the exchange.

Below is the ammonia converter according to the invention based on one in the

Drawing illustrated embodiment explained in more detail.

Fig. 1 Ammonia converter

In Fig. 1 an exemplary ammonia converter 10 is shown in a schematic cross section. The representation is not to scale and serves to illustrate the

Invention.

A mixture of hydrogen and nitrogen is supplied via an educt inlet 30.

The gas mixture is passed into the heat exchange tubes 80 and flows downwards and is heated in the process. The heated material is extracted from the heat exchange tubes 80

Gas mixture is brought together by means of the deflection device 90 and into the central tube 70. There the gas mixture flows upwards and then reaches the gap between the shell 20 and the first catalyst bed 50 via the upper area. There the

Gas stream is guided radially through the first catalyst bed 50, converted there and heated up in the process. The gas stream emerging from the first catalyst bed 50 releases its excess heat to the heat exchange tubes 80 and is fed into the gap between

Shell 20 and third catalyst bed 100. There the gas stream is guided radially through the third catalyst bed 100, converted there and heats up in the process. The gas stream emerging from the third catalyst bed 100 releases its excess heat to the heat exchange tubes 80 and is fed into the gap between the shell 20 and the second

Catalyst bed 60 guided. There the gas flow is radial through the second

Catalyst bed 60 guided, implemented there and heated up. The one from the second one

The gas stream emerging from the catalyst bed 60 is led to the product outlet 40.

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Reference number 10 ammonia converter 20 shell 30 educt inlet 40 product outlet 50 first catalyst bed 60 second catalyst bed 70 central tube 80 heat exchange tube 90 deflection device 100 third catalyst bed

Claims (5)

7 BE2022/5308 patent claims 1. Ammonia converter (10), wherein the ammonia converter (10) has a shell (20), wherein the ammonia converter (10) has a reactant inlet (30) and a product outlet (40), wherein the ammonia converter (10) has at least a first catalyst bed ( 50) and a second catalyst bed (60), wherein the first catalyst bed (50) and the second catalyst bed (60) are flowed through radially from the outside towards the center, the ammonia converter (10) having at least one first heat exchanger, the first heat exchanger is designed as a first tube bundle heat exchanger, the first tube bundle heat exchanger having a central tube (70) and a plurality of heat exchange tubes (80), the heat exchange tubes (80) being arranged parallel to the central tube (70) and around the central tube (70), wherein the first tube bundle heat exchanger has a deflection device (90), the deflection device (90) being arranged between the central tube (70) and the heat exchange tubes (80), the first tube bundle heat exchanger being surrounded in a ring by the first catalyst bed (50), characterized in that the educt inlet (30) is connected directly to the heat exchange tubes (80) in terms of gas flow, the central tube (70) being connected directly to the space between the shell (20) and the first catalyst bed (50) in terms of gas flow. 2. Ammonia converter (10) according to claim 1, characterized in that the ammonia converter (10) has a third catalyst bed (100), the first heat exchanger having a first partial heat exchanger and a second partial heat exchanger, the first partial heat exchanger being annularly separated from the first catalyst bed ( 50), the second partial heat exchanger being surrounded in a ring by the third catalyst bed (100). 3. Ammonia converter (10) according to one of the preceding claims, characterized in that the entire surface of the heat exchange tubes (80) is designed for sufficient heat transfer for a partial circulation gas quantity of 10% of the maximum circulation gas quantity at full load. 8 BE2022/5308 4. Ammonia converter (10) according to one of the preceding claims, characterized in that the ammonia converter (10) has a maximum system capacity of 50 to 700 tons of ammonia per day. 5. Ammonia converter (10) according to one of the preceding claims, characterized in that the first heat exchanger has radially arranged guide elements for generating a flow crossing the heat exchange tubes (80) on the side around which the gas emerging from the first catalyst bed (50) flows.