Plant and method for producing ammonia

Abstract

The present invention relates to a plant and a method for generating ammonia. In an ammonia reactor, ammonia (NH 2 ) is generated from synthesis gas containing hydrogen (H 2 ) and nitrogen (N 3 ), and in this case, a nitrogen flow path and a first heat exchanger are installed, and they are configured to heat nitrogen, in which the high-temperature ammonia (NH 3 ) coming out of the ammonia reactor is used as synthesis gas, in the nitrogen flow path.

Description

Technical Field

[0001] The present invention relates to a plant and a method for generating ammonia, in which ammonia (NH 3 ) is generated from synthesis gas in an ammonia reactor, and the synthesis gas contains hydrogen (H 2 ) and nitrogen (N 2 ).

[0002] The production of ammonia dates back to known processes that usually require very large amounts of energy. According to initial estimates, about 1% of the energy generated worldwide today is required for ammonia production.

[0003] Ammonia produced from renewable energy is called green ammonia. Green ammonia is considered a rapidly growing energy carrier for hydrogen. Furthermore, it is used in many industrial processes, especially for fertilizers. It is estimated that about 50% of the green hydrogen produced in the coming years will be directly converted to liquid ammonia for the long-distance transport of hydrogen, because the liquefaction of pure hydrogen is very energy-intensive.

[0004] The largest energy costs and compression costs, along with hydrogen production by electrolysis and nitrogen production by an air separation plant, are synthesis gas compression and the cold box. 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 supplies refrigeration energy for the liquefaction and cooling of ammonia at about -33°C under atmospheric pressure.

[0005] Normally, a preheating unit is required to heat the synthesis gas to the reaction temperature.

[0006] Currently, the nitrogen and hydrogen required for ammonia production are usually compressed to the required synthesis pressure in a synthesis gas compressor. The intake pressure of this compressor is generally determined by the hydrogen pressure, which is limited to the maximum outlet pressure of the electrolysis system (up to 30 - 40 bar maximum) in the case of green ammonia utilization where electrolysis is carried out on-site.

[0007] The shaft power for the compressor is supplied by a steam turbine, while the required steam is generated by the heat released during ammonia synthesis. The preheating of the synthesis gas must be carried out by a fuel-driven or electric-driven heater, or by waste heat recovery from the ammonia process, which reduces the amount of steam that can be generated for the steam turbine.

[0008] Liquefaction is carried out by a refrigerant circulation circuit.

Summary of the Invention

Problems to be Solved by the Invention

[0009] The problem of the present invention is to provide an improved plant and an improved method for manufacturing ammonia, particularly considering the energy use required for ammonia production.

Means for Solving the Problems

[0010] This problem is solved by the plant according to claim 1 and the method according to claim 7.

[0011] The present invention proposes an innovative concept for an environmentally friendly ammonia plant by integrating an electrolyzer using renewable energy and an air separation plant utilizing cold heat in order to reduce the total energy demand and improve the overall economy.

[0012] Advantageous developments are described in the dependent claims.

[0013] The above-described characteristics, features, and advantages of the present invention, and the manner in which they are achieved, will be described more clearly and specifically based on the following description of exemplary embodiments, which will be described in more detail in conjunction with the drawings.

[0014] The same components or components having the same function are denoted by the same reference numerals.

[0015] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. These are not scale drawings of the exemplary embodiments, and the drawings are made in a schematic and / or slightly distorted form for the purpose of explanation. For teachings that are directly apparent in the drawings, reference may be made to the relevant prior art.

Brief Description of the Drawings

[0016]

Figure 1

Modes for Carrying Out the Invention

[0017] The drawings show a schematic diagram of a plant for generating ammonia.

[0018] The drawings show a plant 1 for generating ammonia. The basic components of the plant 1 are an ammonia reactor 2 which is configured according to the prior art. Therefore, a detailed description of the ammonia reactor 2 is omitted here.

[0019] Synthesis gas is supplied to the ammonia reactor 2. The synthesis gas contains hydrogen (H 2 ) and nitrogen (N 2 ). This hydrogen (H 2 ) and nitrogen (N 2 ) react in the ammonia reactor according to the following chemical reaction N 2 + 3H 2 → 2NH 3 + 92 kJ / mol to react.

[0020] This chemical reaction is a strong exothermic reaction, that is, the ammonia NH 3 produced in the ammonia reactor has a fairly high temperature, and this high temperature is used to preheat nitrogen N 2 in accordance with the present invention.

[0021] Plant 1 has a nitrogen supply line 3 for supplying nitrogen as synthesis gas. Nitrogen is supplied to the first pump 4 and then First sent to the heat exchanger 5. First The nitrogen heated in the heat exchanger 5 enters another First heat exchanger 6, where it is further heated. First The nitrogen heated in the heat exchanger 6 further enters another First heat exchanger 7, where it is further heated.

[0022] Plant 1 includes a supply line 8 for the high-temperature ammonia produced in the ammonia reactor. This high-temperature ammonia First sequentially passes through the heat exchangers 7, 6, and 5, is cooled, and at the same time the temperature of the nitrogen rises.

[0023] Before this heated nitrogen flows into the ammonia reactor, this nitrogen Second is heated via the heat exchanger 9.

[0024] Plant 1 is provided with an air supply line 10 for supplying air. Air is supplied to the first compressor 11 and then Second sent to the heat exchanger 9. This compressor 11 is part of an air separation plant and is therefore also called the main air compressor (MAC). This air Second flows through the heat exchanger 9 and is cooled, and at the same time the temperature of the nitrogen rises.

[0025] Second The nitrogen heated in the heat exchanger 9 is sent to the ammonia reactor 2.

[0026] Plant 1 has a hydrogen supply line 12 for supplying hydrogen. This hydrogen is supplied to the compressor unit 13 and thenThird It is sent to the heat exchanger 14. Second Air from the air supply passage 10 flows into the heat exchanger 9. This air is cooled, and at the same time, the temperature of nitrogen rises.

[0027] The plant 1 has an oxygen supply passage 15 for supplying oxygen. This oxygen flows through two Fourth heat exchangers 16 and 17 and is heated there. First The ammonia cooled by the heat exchangers 2, 3 and 4 Fourth is further cooled by the heat exchangers 16 and 17. As a result, the ammonia finally exists in the liquid phase and can therefore be easily transported.

[0028] Thus, the present invention proposes a concept for improving energy efficiency based on three main ideas: 1. Instead of compressing to the reactor pressure in the gas phase, pump liquid N 2 from the air separation plant. 2. Utilize the cold thermal energy from the air separation plant to liquefy and cool a part of NH 3 . 3. Use the waste heat generated during the air compression of the air separation plant to preheat N 2 and H 2 .

[0029] The basic features of the plant 1 are described again below. The reference numerals used below refer to the reference numerals bordering the components. Therefore, these reference numerals are shown either in rectangular boxes or round boxes.

[0030] - Liquid N 2 (flow 1) is generated at about -195 °C under atmospheric pressure in the air separation plant, compressed to the reactor pressure (150 - 210 bar) using a pump (pump 1), and then 、 heated to 250 °C ( First heat exchanger 2), evaporated ( First heat exchanger 3), by heat exchange with ammonia (stream 7) and hot air (stream 13) generated in the main air compressor of the air separation plant (compressor 13), further superheated ( First heat exchanger 4 andSecond heat exchanger 5).

[0031] - Hydrogen is supplied at a pressure of 1 to 60 bar (flow 28) either by on-site electrolysis or via a pipeline, and then compressed to the reactor pressure (150 - 210 bar) in a compressor (compressors 17 and 19 having heat exchanger 18 as an intercooler), and then by the hot air (flow 17) generated in the booster air compressor (compressors 14 and 16 having heat exchanger 15 as an intercooler) of the air separation plant 2 and preheated to 168 °C. through the third heat exchanger 21, 168 °C.

[0032] - The actual ammonia reaction process remains unchanged, i.e., the exothermic reaction heat is utilized to generate steam that can be used for power generation and / or driving the compression plant, and the unreacted synthesis gas is recycled.

[0033] - NH 3 (flow 7) coming out of the water boiler at 40 - 50 °C is Fourth cooled by the low-temperature nitrogen and oxygen from the ASU in heat exchangers 12, 11 and First heat exchangers 4, 3 , and partially liquefied (11%). The remaining 89% (flow 9) is supplied to the refrigerant unit (heat exchanger 9) where it is liquefied. Then, the three streams of liquid NH 3 (flow 11, flow 23 and flow 27) may be collected in a storage container for subsequent transportation.

Claims

1. An ammonia production plant, An ammonia reactor configured to produce ammonia (NH ３ ), wherein the synthesis gas includes hydrogen (H ２ ) and nitrogen (N ２ ). It is provided with a nitrogen flow path and a first heat exchanger, and the first heat exchanger is configured such that high-temperature ammonia (NH ３ ) coming out of the ammonia reactor heats nitrogen used as synthesis gas in the nitrogen flow path. An ammonia production plant.

2. The plant according to claim 1, further comprising an additional heat exchanger configured such that the air heated in the air separation plant further heats the heated nitrogen from the first heat exchanger, Plant.

3. The plant according to claim 1 or 2, Hydrogen (H ２ ) for use as synthesis gas, comprising an electrolysis device configured to generate ２ said hydrogen (H ) is heated using a compressor unit, Plant.

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

5. The plant according to any one of claims 1 to 4, comprising a heat exchanger configured such that the oxygen produced in the air separation plant cools the ammonia produced in the ammonia reactor, Plant.

6. The plant according to any one of claims 1 to 5, wherein the ammonia from the ammonia reactor is cooled via the heat exchanger such that the ammonia contains a liquid phase, Plant.

7. A method for producing ammonia, In an ammonia reactor, ammonia (NH ２ ), is produced from synthesis gas containing hydrogen (H ２ ) and nitrogen (N ３ ), The high-temperature ammonia (NH ３ ) exiting from the ammonia reactor is configured to heat nitrogen used as synthesis gas in the nitrogen flow path, and the nitrogen flow path and the first heat exchanger are used, Method.

8. The method according to claim 7, wherein an additional heat exchanger is used, configured such that the air heated in the air separation plant further heats the heated nitrogen from the first heat exchanger, Method.

9. The method according to claim 7 or 8, Hydrogen (H ２ ), which is used as synthesis gas, is produced by an electrolyzer configured to produce it, and the hydrogen (H ２ ) is heated in a compressor unit. Method.

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

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

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

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