Steam superheater for a system for producing ammonia

Abstract

The invention relates to a steam superheater (10) for generating superheated working steam in a system for producing ammonia from hydrogen and nitrogen without a front end for generating a synthesis gas by means of a reforming process, comprising a chamber body (12) for delimiting a chamber volume (14), an inlet opening (24) formed in the chamber body (12) for supplying hot product gas from an ammonia converter, an outlet opening (26) formed in the chamber body (12) for discharging cooled product gas, and a protective layer (34) which is applied onto the chamber body (12) inner face (36) outside the inlet opening (24) and the outlet opening (26), the inner face delimiting the chamber volume (14), in order to protect the material of the chamber body (12) from surface corrosion due to hydrogen and nitrogen. By means of the protective layer (34) of the chamber body (12), corrosion promoted by the temperature and the pressure of the product gas can be cost-effectively and simply avoided such that a high durability of a system for producing ammonia is cost-effectively facilitated, wherein in particular a front end for generating a synthesis gas by means of a reforming process can be obviated while nevertheless allowing superheated working steam with a high energy content to be generated.

Description

[0001] thyssenkrupp Uhde GmbH / thyssenkrupp AG

[0002] Our reference number: 24021 IPIOWO

[0003] Steam superheater for an ammonia production plant

[0004] Description

[0005] The invention relates to a steam superheater with which working steam can be generated from the waste heat produced in an ammonia production plant, as well as to the use of such a steam superheater and a method for manufacturing such a steam superheater. In particular, the invention is applicable in ammonia production plants where there is no front end with a steam reforming unit for producing the synthesis gas for ammonia production, so that no thermal energy from steam reforming is available for steam superheating.

[0006] From WO 2021 / 105060 Al, a plant for the production of ammonia from hydrogen and nitrogen without a front end for the production of synthesis gas by reforming natural gas is known. The plant has a first ammonia converter and a second ammonia converter located downstream of the first. The product gas exiting the first ammonia converter is first passed through a steam superheater and then through a heat recovery steam generator located downstream of the steam superheater. Steam is produced in the heat recovery steam generator before the product gas mixture is fed to the second ammonia converter. The steam generated in the heat recovery steam generator is fed to the steam superheater to produce superheated steam as working steam for a turbine. The product gas mixture exiting the first ammonia converter has a temperature of approximately 500°C and a pressure of approximately 200 bar.

[0007] There is a constant need to improve the durability of an ammonia production plant in a cost-effective manner.

[0008] The purpose of the invention is to demonstrate measures that enable a high durability of an ammonia production plant in a cost-effective manner.

[0009] The problem is solved by a steam superheater with the features of claim 1, a use with the features of claim 10, and a method with the features of claim 14. Preferred embodiments are specified in the dependent claims and the following description, each of which, individually or in combination, can represent an aspect of the invention, the scope of protection being determined by the claims. When a feature is presented in combination with another feature, this serves only to simplify the presentation of the invention and is in no way intended to imply that this feature cannot also constitute a further development of the invention without the other feature.

[0010] One aspect of the invention relates to a steam superheater for generating superheated working steam in a plant for producing ammonia from hydrogen and nitrogen without a front end for generating synthesis gas by reforming, comprising a chamber body for limiting a chamber volume, an inlet opening formed in the chamber body for supplying hot product gas from an ammonia converter, an outlet opening formed in the chamber body for removing cooled product gas, and a protective layer applied outside the inlet opening and outside the outlet opening on an inner surface of the chamber body limiting the chamber volume to protect the material of the chamber body from surface corrosion by hydrogen and nitrogen.

[0011] If a front end for generating synthesis gas for ammonia production by reforming natural gas or naphtha is available, synthesis gas production can be carried out using various methods. Sufficient waste heat is available to generate working steam with a target temperature of approximately 470°C. However, if this front end is not present or not required, particularly because the reactants nitrogen and hydrogen for ammonia production are already available in sufficient quantity and purity, or are produced using electricity generated from renewable energy sources, the working steam cannot be generated using heat energy from the front end. It is possible, however, to use the waste heat from the ammonia converter, which already requires cooling, to generate the superheated working steam instead of the waste heat from the front end used for synthesis gas production.Since the ammonia converter is typically operated at a maximum temperature of 470°C to 480°C, it is necessary to operate the converter in such a way that at least one outlet temperature of the converter is approximately 500°C or significantly higher. This is required to superheat the steam introduced into the steam superheater sufficiently to generate working steam at a temperature of approximately 470°C, particularly at a pressure of approximately 70 bar or 75 bar. Simultaneously, it is advantageous to operate the ammonia converter at the highest possible pressure to shift the reaction equilibrium towards the product side. This allows the product gas to be supplied to the steam superheater with a correspondingly higher enthalpy, thus improving the heat transfer from the product gas to the steam being superheated.

[0012] However, it was recognized that, when the front end is replaced by the ammonia converter for generating working steam, the product gases leaving the ammonia converter and entering the steam superheater can have a corrosive effect at such high operating temperatures and pressures. Unconverted hydrogen contained in the product gas can have such a high partial pressure that it can cause hydrogen embrittlement and cracking on metallic surfaces, which would not occur, or at least not to such a significant extent, at lower temperatures and pressures. It is also assumed that the very high

[0013] The temperature of the product gases from the ammonia converter, due to their nitrogen content, promotes nitriding of the steel, especially low-alloy steel, leading to material loss and cracking. Therefore, the temperature and pressure levels of the product gas can cause damage to the steel material of the steam superheater's chamber body.

[0014] High-temperature corrosion (nitriding) and pressurized hydrogen attack / hydrogen embrittlement can occur. This can reduce the service life / durability of the system. System damage and unplanned shutdowns can result.

[0015] The damage mechanisms described above are also referred to, for the sake of simplicity, as “surface corrosion” or “corrosion” within the scope of the present invention.

[0016] It was also recognized that the damage mechanisms triggered by hydrogen and nitrogen can be prevented by coating the chamber with a protective layer, particularly one containing nickel. Since the chamber body can have a relatively simple shape, it is possible to upgrade the steam superheater to meet the particularly high demands of generating working steam using a very hot product gas from the ammonia converter at a high pressure level by applying a relatively simple and cost-effective coating of the chamber body with the protective layer, without this having a significant impact on the system downstream of the steam superheater.It is possible to leave the outer surface of the chamber body, which borders the feedthroughs, uncoated and to utilize the fact that the pipes inserted into the feedthroughs already provide sufficient protection for the chamber body material. The protective coating on the chamber body allows for the cost-effective and simple prevention of corrosion accelerated by the temperature and pressure of the product gas, thus enabling a cost-effective and long service life for an ammonia production plant, particularly one with a front end for generating a...

[0017] Synthesis gas can be saved through reforming, yet superheated working steam with a high energy content can still be generated.

[0018] The steam superheater is specifically designed to heat an already vaporous fluid to an even higher temperature level in order to generate superheated working steam. The steam superheater can operate, for example, as a heat exchanger and can be operated on either a counterflow or coflow principle. Specifically, the product gas is introduced into the chamber volume of the superheater, while the fluid to be superheated is separated from the product gas and passed through the chamber volume via a piping system.

[0019] The working steam should have a temperature of approximately 500°C and a pressure of approximately 70 bar or 75 bar. Preferably, the working steam's properties meet a predetermined requirement or standard to enable its industrial use at a specific energy level, particularly in ammonia production plants. For example, the working steam can be fed to a turbine to drive a machine and / or generate electrical energy.

[0020] A plant for the production of ammonia (NH₃) from hydrogen (H₂) and nitrogen (N₂), in which the steam superheater according to the invention is preferably used, preferably does not have a front end for the production of synthesis gas by reforming. Preferably, the nitrogen required for the production of ammonia is taken from the ambient air, wherein the nitrogen is separated from the oxygen and / or carbon dioxide and / or other gases in the ambient air, for example by separation during air liquefaction. The hydrogen required for the production of ammonia can be obtained, in particular, by the electrolysis of water, preferably using a battery. The system uses stored electrical energy, generated renewably, particularly from solar and / or wind power. This makes it possible to design the system for the production of so-called "green ammonia." Preferably, the system can produce ammonia without using fossil fuels as an energy source and / or without using natural gas or naphtha as raw materials. The system can preferably be designed and further developed as described in WO 2021 / 105060 A1, the contents of which are hereby incorporated by reference as part of the invention.

[0021] The chamber body defines the chamber volume and may have passages for the product gas and for the steam to be superheated. The chamber body has an inner surface that defines the chamber volume and may be interrupted by the passages, in particular the inlet and outlet openings for the product gas. The chamber body may be multi-part, for example, two-part. Preferably, the chamber body is made of a steel, in particular a low-alloy steel in which the sum of the alloying elements does not exceed 5% by mass. This allows the chamber body to be manufactured cost-effectively and provides a sufficient base for the protective layer to be securely attached or applied, in particular by weld overlay, in a manner that is sufficiently resistant to peeling and temperature fluctuations.In particular, it is provided that, with regard to the chamber body, the protective layer is only provided on the inside of the chamber body facing the chamber volume.

[0022] The inlet opening and / or the outlet opening can be designed as a through-hole in the chamber body material. Preferably, the inlet opening and / or the outlet opening is incorporated into the chamber body after the protective layer has been applied. In this way, the coating, for example applied by weld overlay, can be applied to the closed, uninterrupted inner surface of the chamber body, and the inlet and outlet openings are subsequently created, for example, by drilling. The inlet opening and / or the outlet opening can in particular, it should be designed in a circular or circular-cylindrical shape to accommodate a pipe with a circular outer contour.

[0023] The product gas consists in particular of ammonia, hydrogen, and nitrogen, wherein the product gas is composed of more than 95% by mass, preferably more than 97% by mass, and most preferably more than 99% by mass of ammonia, hydrogen, and nitrogen. The product gas is present at the outlet of the ammonia converter and / or at the inlet of the steam superheater at a temperature of approximately 510°C ± 15 K and / or a pressure of approximately 220 bar ± 50 bar. In particular, at most a pipeline, but preferably no further process equipment, is provided between the ammonia converter and the steam superheater.The intensive state variables of the product gas at the outlet of the ammonia converter and / or at the inlet of the steam superheater are therefore almost identical, with only convective heat losses to the environment and / or heat conduction effects along the system and / or a pressure loss along the line between the ammonia converter and the steam superheater occurring.

[0024] The protective layer can be selected to prevent surface corrosion in the presence of product gas at the temperatures and pressures expected within the chamber volume of the chamber body. In particular, the protective layer is made of a high-alloy steel in which the content of at least one alloying element exceeds 5% by mass. Preferably, the protective layer contains nickel as an alloying element, preferably at least 5% nickel by mass.

[0025] In particular, it is provided that an inlet pipe for supplying the hot product gas is inserted into the inlet opening, wherein insulation between the inlet pipe and the inlet opening thermally protects the chamber body, and / or an outlet pipe for removing the cooled product gas is inserted into the outlet opening, wherein insulation between the outlet pipe and the outlet opening thermally protects the chamber body.

[0026] In one embodiment, the inlet pipe is welded to the outer surface of the inlet opening and / or the outlet pipe is welded to the outer surface of the outlet opening in a media-tight manner. Preferably, the inlet pipe is welded to the coating applied in the inlet opening, thereby creating a media-tight seal.

[0027] The inlet pipe itself is made of a material that already provides sufficient protection against the aforementioned damage mechanisms, so that a coating of the inlet pipe is not necessary.

[0028] According to one embodiment, the inlet pipe and / or the outlet pipe has a flange surface for pressing a flanged pipeline against it, the flange surface being coated with the protective layer. This also protects the joint between the pressed-together flange surfaces from surface corrosion.

[0029] Preferably, the inlet pipe and / or the outlet pipe has a sleeve made of a ceramic fiber material for insulating the material of the inlet pipe and / or the outlet pipe. The ceramic fiber material of the sleeve can provide thermal resistance to at least reduce heat losses through convective heat dissipation on the outside of the respective pipe. At the same time, the sleeve can protect the material of the respective pipe from surface corrosion. The sleeve, designed for thermal insulation, can thus simultaneously provide corrosion protection by being located on the inside rather than the outside of the respective pipe.

[0030] Particularly preferably, the chamber body has a base and a pot placed on the base, the pot having a base-facing contact surface that is at least partially annular and coated with the protective layer. In particular, the pot and at least partially the base are coated with the protective layer. Preferably The base is attached to the pot, for example by screwing it on using a seal, so that the contact force achieves the sealing effect, or alternatively a welded seal can be used.

[0031] In particular, the protective layer is produced by an additive coating process, preferably by weld overlay. According to one embodiment, the protective layer comprises at least two independently applied layers. This allows the protective layer to be built up cost-effectively and with very precise thickness to provide sufficient protection.

[0032] Preferably, the protective layer contains a nickel-containing alloy and / or has a layer thickness of at least 8 mm. This allows the protective layer to provide sufficient protection against surface corrosion and / or high-temperature corrosion and hydrogen embrittlement.

[0033] Another aspect concerns the use of a steam superheater, which can be designed and further developed as described above, in a plant for the production of ammonia from hydrogen and nitrogen without a front end for generating synthesis gas by reforming, for the purpose of generating superheated working steam at the energy level at an outlet of the ammonia converter using the product gas of the ammonia converter. The steam superheater according to the invention makes it possible to provide a plant for the production of ammonia from hydrogen and nitrogen without a front end for generating synthesis gas by reforming, in which superheated working steam with a high energy content can nevertheless be generated without significant corrosion effects occurring.The protective layer of the chamber body allows corrosion, which is promoted by the extreme state variables of the product gas, to be avoided cost-effectively and easily, thus enabling a high durability of an ammonia production plant in a cost-effective manner, in which in particular. A front end for generating synthesis gas through reforming can be saved, yet superheated working steam with a high energy content can still be produced.

[0034] Hydrogen is preferably produced by the electrolysis of water using renewably generated electricity, particularly solar and / or wind power, with at least some of the electrical energy being temporarily stored in a battery system. This makes it possible to produce "green ammonia," the production of which does not require burning fossil fuels. The rechargeable battery allows sufficient electrical energy to be stored to continue ammonia production even in unfavorable weather conditions, without having to resort to fossil fuels in the interim.

[0035] In particular, the product gas is supplied at a temperature T of 400°C < T < 600°C, in particular 450°C < T < 550°C, preferably 480°C < T < 520°C, and at a pressure p of 150 bar < p < 250 bar, in particular 180 bar < p < 220 bar, preferably

[0036] 190 bar < p < 200 bar, supplied to the steam superheater. With these intense state variables for the product gas, working steam can be generated at a sufficiently high energy level.

[0037] Preferably, the product gas leaves the steam superheater with a temperature difference AT of 2 K < AT < 60 K, in particular 5 K < AT < 20 K and preferably 10 K < AT < 15 K. This allows the product gas to leave the steam superheater at a temperature at which subsequent process engineering steps are not affected, high-temperature corrosion downstream of the steam superheater is unlikely, and at the same time, working steam can be generated at a sufficiently high energy level.

[0038] Another aspect concerns a method for manufacturing a steam superheater, which can be designed and further developed as described above, in which the chamber body is provided, the protective layer is applied to the inside of the chamber body, subsequently the inlet opening and the outlet opening are introduced into the chamber body, the inlet pipe is inserted into the inlet opening and the outlet pipe into the outlet opening, and after insertion, the inlet pipe and / or the outlet pipe is sealed to the chamber body, in particular by welding with the protective layer. In particular, it is possible to produce the inlet opening and the outlet opening in the chamber body after the protective layer has been applied, preferably by a machining and / or separating process. The production of the protective layer is thus not interrupted by gaps in the inside surface to be coated.The protective layer of the chamber body allows for cost-effective and simple prevention of corrosion promoted by the extremely intense state variables of the product gas, thus enabling a cost-effective high durability of an ammonia production plant, in which, in particular, a front end for generating synthesis gas by reforming can be saved and yet superheated working steam with a high energy content can be generated.

[0039] It is particularly advantageous to coat a flange surface of the inlet pipe and / or the outlet pipe with the protective layer. This also protects the joint between the pressed-together flange surfaces from surface corrosion.

[0040] In particular, the protective layer can be produced by an additive coating process, especially by a welding process.

[0041] The invention is explained below by way of example with reference to the accompanying drawings and preferred embodiments, wherein the features shown below, both individually and in combination, represent an aspect of the

[0042] The invention can be represented, the scope of protection being determined by the claims. If a feature is shown in the merely exemplary drawings and the accompanying description in combination with another feature, this serves only to simplify the presentation of the invention and is in no way intended to imply that this feature cannot also be a further development of the invention without the other feature. The following are shown:

[0043] Fig. 1: a schematic sectional view of a steam superheater,

[0044] Fig. 2: a schematic cutaway detail view of the steam superheater from Fig. 1 and Fig. 3: another schematic cutaway detail view of the steam superheater from Fig. 1.

[0045] The steam superheater 10 shown in Fig. 1 can be provided in a plant for the production of ammonia from hydrogen and nitrogen, wherein the plant does not have a front end for the production of synthesis gas by reforming and the steam superheater 10 is connected via a pipeline directly downstream of an ammonia converter operated at an elevated temperature and / or pressure. The steam superheater 10 has a chamber body 12 that defines a chamber volume 14. For this purpose, the chamber body 12 has a base 16 and a pot 18, wherein the pot 18 is placed on the base 16 by its own weight via a contact surface 20 and is pressed into place by means of screw connections 22. The chamber body 12 has an inlet opening 24 and an outlet opening 26, which are produced in the pot 18, for example, by a machining process and / or a separation process.The inlet opening 24 and the outlet opening 26 have, in particular, a circular cross-section and / or a circular-cylindrical shape. The inlet opening 24 and the outlet opening 26 can each be axially extended by a nozzle 30 attached to an outer surface 28 of the chamber body 12. A pipe 32 can be flanged to the steam superheater 10 on the inlet side and outlet side of the nozzle 30, respectively.

[0046] Since the plant, which is specifically intended for the production of green ammonia, does not have a front end for generating the synthesis gas as a feedstock for the ammonia converter, The steam superheater 10 cannot be fed with the synthesis gas, which is otherwise present at a very high temperature, but is fed with the product gas from the ammonia converter. For this purpose, the ammonia converter is operated at a particularly high temperature so that the product gas leaving the ammonia converter and being supplied to the steam superheater 10 can superheat steam to approximately 500°C in the steam superheater 10 in order to generate the desired working steam with the desired intensive state variables. According to the invention, high-temperature corrosion of the steam superheater 10, which is further promoted by the hydrogen content in the product gas, is prevented by a nickel-containing protective layer 34 on an inner surface 36 of the chamber body 12, applied in particular by weld overlay.

[0047] An inlet pipe 38 is inserted into the inlet opening 24, which extends through the inlet opening 24 into the chamber volume 14. An outlet pipe 40 is inserted into the outlet opening 26, which also extends through the outlet opening 24 into the chamber volume 14. The inlet pipe 38 and the outlet pipe 40 may be welded to the protective layer of the inlet opening 24 and 30, or to the protective layer of the nozzle 30.

[0048] As shown in Fig. 2, the inlet pipe 38 and / or the outlet pipe 40 can be lined on the inside with a sleeve 42 made of a ceramic fiber material. In particular, the protective layer 34 can extend into the area of ​​a flange surface 44, so that the protective layer 34 can be press-fitted between the nozzle 30 and the pipe 32 on the nozzle side by means of a seal 32 to create a media-tight seal.

[0049] As shown in Fig. 3, the protective layer 34 applied to the inside 36 of the pot 18 can also form at least part of the contact surface 20 facing the base 16. The protective layer 34 can thus be welded between the pot 18 and the base 16 in a media-tight manner or pressed in a media-tight manner by means of a seal 46. Optionally, the base 16 can also form the protective layer 34 and / or a separate

[0050] have a seal 46 and / or a cover on a top surface 48 facing the chamber volume 14.

Claims

Patent claims 1. Steam superheater (10) for generating superheated working steam in a plant for the production of ammonia from hydrogen and nitrogen without a front end for generating synthesis gas by reforming, comprising a chamber body (12) for limiting a chamber volume (14), an inlet opening (24) formed in the chamber body (12) for supplying hot product gas from an ammonia converter, an outlet opening (26) formed in the chamber body (12) for removing cooled product gas, and a protective layer (34) applied outside the inlet opening (24) and outside the outlet opening (26) on an inner surface (36) of the chamber body (12) limiting the chamber volume (14) for protecting the material of the chamber body (12) from surface corrosion by hydrogen and nitrogen.

2. Steam superheater (10) according to claim 1, wherein the inlet pipe (38) is welded to the outer surface of the inlet opening (24) and / or the outlet pipe (40) is welded to the outer surface of the outlet opening (26) in a media-tight manner.

3. Steam superheater (10) according to one of claims 1 to 2, wherein the inlet pipe (38) and / or the outlet pipe (40) has a flange surface (44) for pressing on a flanged pipe (32), wherein the flange surface (44) is coated with the protective layer (34).

4. Steam superheater (10) according to one of the preceding claims, wherein the inlet pipe (38) and / or the outlet pipe (40) has a sleeve (42) made of a ceramic fiber material for insulating the material of the inlet pipe (38) and / or the outlet pipe (40).

5. Steam superheater (10) according to one of the preceding claims, wherein the chamber body (12) has a base (16) and a pot (18) placed on the base (16), wherein the pot (18) has a contact surface (20) that is at least partially ring-shaped, coated with the protective layer (34), and points towards the base (16).

6. Steam superheater (10) according to one of the preceding claims, wherein the protective layer (34) is produced by an additive coating process, in particular a welding process.

7. Steam superheater (10) according to claim 6, wherein the protective layer (34) preferably has at least two independently applied layers.

8. Steam superheater (10) according to one of the preceding claims, wherein the protective layer (34) contains a nickel-containing alloy and / or has a layer thickness of at least 8 mm.

9. Use of a steam superheater (10) according to one of claims 1 to 8 in a plant for the production of ammonia from hydrogen and nitrogen without a front end for the production of synthesis gas by reforming for the purpose of generating superheated working steam with the product gas of the ammonia converter at the energy level at an outlet of the ammonia converter.

10. Use according to claim 9, wherein the hydrogen is produced by electrolysis of water using electrical energy generated by renewable energy, wherein the electrical energy is at least partially stored in a battery system. - 17 - 11. Use according to claim 9 or 10, wherein the product gas is supplied at a temperature T of 400°C < T < 600°C, in particular 450°C < T < 550°C, preferably 480°C < T < 520°C, and a pressure p of 150 bar < p < 250 bar, in particular 180 bar < p < 220 bar, preferably 190 bar < p < 200 bar, is supplied to the steam superheater (10).

12. Use according to any one of claims 9 to 11, wherein the product gas leaves the steam superheater (10) with a temperature difference AT of 2 K < AT < 60 K, in particular 5 K < AT < 20 K and preferably 10 K < AT < 15 K.

13. Method for manufacturing a steam superheater (10) according to one of claims 1 to 7, in which the chamber body (12) is provided, the protective layer (34) is applied to the inside (36) of the chamber body (12), subsequently the inlet opening (24) and the outlet opening (26) are introduced into the chamber body (12), the inlet pipe (38) is inserted into the inlet opening (24) and the outlet pipe (40) is inserted into the outlet opening (26) and is welded to the protective layer (36) in a media-tight manner.

14. Method according to claim 13, wherein a flange surface (44) of the inlet pipe (38) and / or the outlet pipe (40) is coated with the protective layer (34).

15. Method according to one of claims 13 to 14, wherein the protective layer (34) is produced by an additive coating process, in particular by a welding process.

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