Apparatus and method for producing ammonia

Abstract

The invention relates to an apparatus and a method for producing ammonia, in which ammonia (NH3) is produced from synthesis gas in an ammonia reactor, in which the synthesis gas comprises hydrogen (H2) and nitrogen (N2), in which a nitrogen feed and a first heat exchanger are used, which are configured such that the hot ammonia (NH3) flowing out of the ammonia reactor heats the nitrogen used as synthesis gas in the nitrogen feed.

Description

Technical Field

[0001] The invention relates to an apparatus and a method for producing ammonia, wherein ammonia (NH 4) is produced from synthesis gas in an ammonia reactor. 3 ), wherein the synthesis gas comprises hydrogen (H 2 ) and nitrogen (N 2 ). Background Art

[0002] Known methods of producing ammonia generally require large amounts of energy. According to initial estimates, the production of ammonia requires about 1% of the energy produced today worldwide.

[0003] Ammonia produced from renewable energy sources is called green ammonia. Green ammonia is considered a rapidly growing energy carrier for hydrogen. In addition, ammonia is used in many industrial processes, especially in fertilizers. It is estimated that about 50% of the green hydrogen produced in the next few years will be processed directly into liquid ammonia for long-distance transportation of hydrogen, because the liquefaction of pure hydrogen is very energy-intensive.

[0004] In addition to the production of hydrogen by electrolysis and nitrogen by air separation plants, the largest energy and compression requirements are in syngas compression and cold boxes The synthesis gas compression compresses the nitrogen-hydrogen mixture to the pressure of 150-200 bar required for the synthesis process, and the cold box provides the refrigeration energy for liquefying and cooling ammonia to about -33°C at atmospheric pressure.

[0005] A preheating unit is usually required for heating the synthesis gas to the reaction temperature.

[0006] Currently, the nitrogen and hydrogen required to produce ammonia are usually compressed to the required synthesis pressure in a syngas compressor. The inlet pressure of this compressor is usually determined by the hydrogen pressure, which in green ammonia applications where electrolysis is performed on site is limited to the maximum outlet pressure of the electrolyzer (maximum 30-40bar).

[0007] The shaft power for the compressor is provided by a steam turbine, with the required steam being generated from the heat released during the ammonia synthesis process. Preheating of the synthesis gas must be accomplished by fuel-driven or electrically driven heaters or by recovering waste heat from the ammonia process, thereby reducing the amount of steam that can be generated for the steam turbine.

[0008] Liquefaction is achieved through the refrigerant cycle. Summary of the invention

[0009] It is an object of the present invention to provide an improved plant and an improved process for producing ammonia, in particular with regard to the use of energy required for producing the ammonia.

[0010] This object is achieved by a device according to claim 1 and a method according to claim 7 .

[0011] The present invention proposes an innovative solution for an environmentally friendly ammonia plant by integrating an electrolyser with renewable energy and an air separation plant utilizing refrigeration in order to reduce the overall energy demand and improve the overall economics.

[0012] The dependent claims reveal advantageous developments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above-mentioned characteristics, features and advantages of the present invention and the manner of achieving them are more clearly explained in conjunction with the following description of the embodiments, and the embodiments are explained in more detail in conjunction with the accompanying drawings.

[0014] In this case, identical components or components having the same function are provided with the same reference numerals. DETAILED DESCRIPTION

[0015] Embodiments of the present invention are described below with reference to the accompanying drawings. The drawings are not intended to show embodiments to scale, but rather are schematic and / or slightly deformed drawings for the purpose of illustration. For supplements to the teachings apparent in the drawings, please refer to the relevant prior art.

[0016] The Figure shows a schematic diagram of a plant for producing ammonia.

[0017] The figure shows a device 1 for producing ammonia. An important component of the device 1 is an ammonia reactor 2 constructed according to the prior art. Therefore, a detailed illustration of the ammonia reactor 2 is omitted here.

[0018] Synthesis gas is supplied to the ammonia reactor 2. The synthesis gas contains hydrogen H 2 and nitrogen N 2 Hydrogen (H 2 ) and nitrogen (N 2 ) reacts in the ammonia reactor according to the following chemical reaction formula

[0019] N 2 +3H 2 →2NH 3 +92KJ / mol

[0020] The chemical reaction is a highly exothermic reaction, that is, the ammonia NH formed in the ammonia reactor 3 has a relatively high temperature, wherein, according to the invention, the high temperature is used to preheat the nitrogen N 2 .

[0021] The device 1 has a nitrogen supply 3 for supplying nitrogen as synthesis gas. The nitrogen is supplied to a first pump 4 and from there to a heat exchanger 5. The nitrogen heated in the heat exchanger 5 reaches a further heat exchanger 6 and is further heated there. The nitrogen heated in the heat exchanger 6 reaches a further heat exchanger 7 and is further heated there.

[0022] The plant 1 comprises a supply 8 for the hot ammonia produced in the ammonia reactor. The hot ammonia flows successively through heat exchangers 7, 6 and 5, where it is cooled while the temperature of the nitrogen is increased.

[0023] Before the heated nitrogen flows into the ammonia reactor, the nitrogen is heated by a further heat exchanger 9 .

[0024] The plant 1 has an air supply 10 for supplying air. The air is supplied to a first compressor 11 and from there to a heat exchanger 9. The compressor 11 is part of an air separation plant and is therefore also referred to as a main air compressor (MAC). The air flows through the heat exchanger 9, where it is cooled and at the same time the temperature of the nitrogen is increased.

[0025] The nitrogen heated in the heat exchanger 9 reaches the ammonia reactor 2 .

[0026] The device 1 has a hydrogen supply 12 for supplying hydrogen. The hydrogen is supplied to a compressor unit 13 and from there to a heat exchanger 14. Air flows through the heat exchanger 9 from an air supply 10. The air cools there and at the same time the temperature of the nitrogen increases.

[0027] The device 1 has an oxygen supply 15 for supplying oxygen. The oxygen flows through two heat exchangers 16 and 17 and is heated there. The ammonia cooled in the heat exchangers 2, 3 and 4 is further cooled in the heat exchangers 16 and 17 so that the ammonia is finally in the liquid phase and can therefore be easily transported.

[0028] Therefore, the present invention proposes a solution for improving energy efficiency through three main ideas:

[0029] 1. Liquid N 2 Pumped from the air separation plant rather than compressed in the gas phase to reactor pressure.

[0030] 2. Use refrigeration energy from the air separation plant to partially liquefy and cool the NH 3 .

[0031] 3. Use the waste heat generated during air compression in the air separation plant to preheat the N 2 and H 2 .

[0032] The important features of the device 1 are described again below, wherein the reference numerals used below represent reference numerals associated with the components. Therefore, these reference numerals are marked in a rectangular or circular frame.

[0033] - Liquid N is produced in an air separation plant at atmospheric pressure and approximately -195°C 2 (material flow 1), which is pumped to the reactor pressure (150-210 bar) by means of a pump (pump 1) and subsequently, together with ammonia (material flow 7) and the hot air (material flow 13) produced in the main air compressor of the air separation plant (compressor 13), is heated to 250° C. (heat exchanger 2), evaporated (heat exchanger 3) and superheated (heat exchangers 4 and 5).

[0034] - Hydrogen is generated on site by electrolysis or supplied via a pipeline at a pressure between 1 and 60 bar (material flow 28) and subsequently in H 2 The H 2 The compressor can be a turbocompressor or a piston compressor and is subsequently preheated to 168° C. by hot air (stream 17 ) which is produced in the booster air compressors of the air separation plant (compressors 14 and 16 with heat exchanger 15 as intercooler).

[0035] - The actual ammonia reaction process remains unchanged, ie the heat of reaction is used to generate steam which can be used to generate electricity and / or to drive compression equipment, and the unconverted synthesis gas is recovered and recycled.

[0036] - NH leaving the liquid heater (water boiler) at 40-50℃ 3 (Stream 7) is cooled and partially liquefied (11%) in heat exchangers 12, 11, 4, 3 and 2 by cold nitrogen and oxygen from the air separation unit (ASU). The remaining 89% (stream 9) is fed to the refrigerant unit (heat exchanger 9) and liquefied there. The three liquid NH 3 The material flows (material flow 11, material flow 23 and material flow 27) are collected in storage containers for subsequent transport.

Claims

1. Equipment for the production of ammonia, The device comprises: an ammonia reactor configured to produce ammonia (NH3) from synthesis gas, wherein the synthesis gas comprises hydrogen (H2) and nitrogen (N2); A nitrogen feed section and a first heat exchanger configured so that hot ammonia (NH3) flowing out of the ammonia reactor heats nitrogen used as synthesis gas in the nitrogen feed section.

2. The device according to claim 1, The plant has a further heat exchanger which is designed in such a way that the air which has been heated in the air separation plant further heats the heated nitrogen coming from the first heat exchanger.

3. The device according to claim 1 or 2, The device has an electrolyser which is configured to produce hydrogen (H2) for use as synthesis gas, wherein: The hydrogen (H2) is heated using a compressor unit.

4. The device according to claim 3, The plant has a heat exchanger configured such that air heated in the air separation plant further heats heated hydrogen from the heat exchanger.

5. The device according to any one of the preceding claims, The plant has a heat exchanger configured such that oxygen produced in the air separation plant cools ammonia produced in the ammonia reactor.

6. The device according to any one of the preceding claims, in, Ammonia from the ammonia reactor is cooled via the heat exchanger such that the ammonia comprises a liquid phase.

7. A process for producing ammonia, in, producing ammonia (NH3) from synthesis gas in an ammonia reactor, wherein the synthesis gas comprises hydrogen (H2) and nitrogen (N2), Therein, a nitrogen feed section and a first heat exchanger are used, and the nitrogen feed section and the first heat exchanger are configured so that hot ammonia (NH3) flowing out of the ammonia reactor heats nitrogen used as synthesis gas in the nitrogen feed section.

8. The method according to claim 7, in, A further heat exchanger is used which is configured such that the air which has been heated in the air separation plant further heats the heated nitrogen from the first heat exchanger.

9. The method according to claim 7 or 8, in, An electrolyser is used, which is configured to produce hydrogen (H2) for use as synthesis gas, wherein the hydrogen (H2) is heated using a compressor unit.

10. The method according to claim 9, in, A heat exchanger is used which is configured such that the air heated in the air separation plant further heats the heated hydrogen coming from the heat exchanger.

11. The method according to any one of claims 7 to 10, in, A heat exchanger is used which is configured such that the oxygen produced in the air separation plant cools the ammonia produced in the ammonia reactor.

12. The method according to any one of claims 7 to 11, in, Ammonia from the ammonia reactor is cooled via the heat exchanger such that the ammonia comprises a liquid phase.

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