Nitric acid plant for producing nitric acid

Abstract

The present invention relates to a nitric acid plant (S) for producing nitric acid, comprising a machinery train (M) with a drive device (2), in particular a steam turbine or an electric motor or possibly a gas turbine, an air compressor (1), a nitrous-gas compressor (3) and a gas expander (4), wherein the machinery train is a single-shaft machine, wherein the air compressor (1) is a compressor with an axial inlet (11) or an axial outlet (12), which is arranged at the end of the machinery train (M), and / or the gas expander (4) is formed with an axial inlet (41) or an axial outlet (42) and / or the nitrous-gas compressor (3) is formed with an axial inlet or an axial outlet.

Description

[0001] Nitric acid plant for the production of nitric acid

[0002] The present invention relates to a nitric acid plant for producing nitric acid according to the preamble of claim 1.

[0003] Nitric acid plants are used, for example, according to the single-pressure (also called mono-pressure) or dual-pressure process. For further details, please refer to EP 0 945 400 B1. However, the nitric acid plant is constructed similarly in both cases and essentially comprises a drive device, in particular a steam turbine (or electric motor or possibly a gas turbine), an air compressor, a nitrous gas compressor, and a gas expander. In the mono-pressure process, the nitrous gas compressor is omitted.

[0004] The aforementioned components are coupled to one another via a rotary transmission. The steam turbine is designed to drive the machine train using the resulting process waste heat. The air compressor compresses the required air, while the nitrous gas compressor compresses the NOx gas. The gas expander, located at the other end of the machine train, utilizes the residual gases and preferably also provides the necessary drive. The interrelationships, in particular the chemical and process engineering processes for producing nitric acid, are well known to those skilled in the art. Reference can also be made to EP 0 945 400 B1, among others.

[0005] According to the current state of the art, the sequence of the individual machines in a single-shaft turbomachine in a nitric acid plant, also known as an inline machine for dual-pressure nitric acid plants, was fixed due to the different speeds. For example, the following sequence had to be maintained: steam turbine, nitrous gas compressor, air compressor, gas expander. A nitric acid plant for producing nitric acid using the single-pressure or dual-pressure process, in which an air pre-compression stage, a NOx compression stage, and two expansion stages, each with a radial inlet and a radial outlet, are arranged in this order on a drive shaft and can optionally be connected to one another by gears, is known from WO 03 / 070634 A1.The invention described here builds on the invention according to utility model DE 20 2016 002 126 U1, since it now offers the possibility of variably arranging the individual machines of the turbomachine, designed as a single-shaft machine, in the nitric acid plant, and increasing the energy efficiency of a dual-pressure nitric acid plant through this invention. A nitric acid plant for producing nitric acid is known, for example, from DE 10 2016 003 950 A1. The essential aspect of the invention according to DE 10 2016 003 950 A1 is that the aforementioned components can be operated at a common speed and are thus coupled to one another without one or more speed-transmission gears for transmitting rotary motion.The advantage lies in particular in the elimination of the gearboxes that would otherwise be used and the associated cost savings and a reduction in maintenance effort, but also in an increase in the efficiency of the machine train and thus the yield of nitric acid, as well as the possibility of arranging the machines in any order within the machine train.

[0006] CN 203130565U also discloses a combined air and nitrous gas compressor for nitric acid production. Among other things, it describes that the impeller of the first stage of the air compressor unit, the impeller of the second stage of the air compressor unit, the impeller of the first stage of the nitrogen oxide unit, and the impeller of the second stage of the nitrogen oxide unit are to be semi-open impellers with high efficiency and axial air inlets. A radial compressor with axial intake is used as the air or nitrous gas compressor. This is a so-called geared turbo, also known as a multi-shaft machine, in contrast to the single-shaft machines mentioned in this patent. In a geared turbo, for example, shafts of different machines are driven at different speeds by a central gearbox.

[0007] Although the prior art already describes usable nitric acid plants for producing nitric acid by the dual-pressure process, comprising a machine train, there is still a need for improvement, in particular with regard to a further increase in efficiency.

[0008] This is where the present invention comes in and sets itself the task of proposing an improved nitric acid plant, in particular an improved machine train, designed as a single-shaft machine in a nitric acid plant according to the dual-pressure process, in which advantages can be achieved with regard to its efficiency.

[0009] According to the invention, this object is achieved by a nitric acid plant for producing nitric acid with the characterizing features of claim 1. Because the air compressor is a compressor for a nitric acid plant using the dual-pressure process with an axial inlet, which is arranged at the end of the machine train, a further increase in efficiency can be achieved, particularly compared to an air compressor of a single-shaft machine with a radial inlet. The end-side arrangement makes it possible to implement the axial intake in the simplest possible way. Due to the axial intake and the resulting reduction in flow (deflection) losses and optimization of the inflow profiles, the efficiency of the air compressor can be increased by, for example, 0.1% to 4%.This leads to improved energy efficiency of the entire nitric acid plant, making it more environmentally friendly and reducing operating costs.

[0010] Further advantageous embodiments of the proposed invention emerge in particular from the features of the subclaims. The subject matter and features of the various claims can, in principle, be combined with one another in any desired manner.

[0011] In an advantageous embodiment of the invention, it can be provided that the gas expander is designed with an axial inlet or an axial outlet, wherein the gas expander is arranged at the end of the machine train, in particular at the other end relative to the air compressor. This measure makes it easy to realize an axial inlet or outlet of the gas expander. This means, in particular, that the air compressor can be a compressor with an axial inlet. It is also possible for the air compressor to be a compressor with an axial outlet instead. The air compressor can, if necessary, also be a compressor with both an axial inlet and an axial outlet.

[0012] In a further advantageous embodiment of the invention, it can be provided that the air compressor, drive device, nitrous gas compressor, and gas expander are arranged in the aforementioned order, or the air compressor, nitrous gas compressor, drive device, and gas expander are arranged in the aforementioned order. Such an arrangement of the aforementioned components advantageously enables an axial inlet or outlet of the air compressor and / or gas expander (this can optionally also include a combination of axial inlet and axial outlet).

[0013] In a further advantageous embodiment of the invention, the nitrous gas compressor can be designed with an axial inlet or an axial outlet, with the nitrous gas compressor being arranged at the end of the machine train. This measure allows for a simple implementation of an axial inlet or outlet of the nitrous gas compressor (this may also include a combination of an axial inlet and an axial outlet).

[0014] In a further advantageous embodiment of the invention, it can be provided that the drive device, the air compressor, the nitrous gas compressor and the gas expander have a common drive shaft (the drive shafts of the individual machines are preferably connected by couplings) and thus a common speed. In such an arrangement, no gears are provided, so that, for example, efficiency losses due to gears can be eliminated. In this case, the machine train comprises machines such as an air compressor, steam turbine (or electric motor or gas turbine), nitrous gas compressor and gas expander, which run at a common speed and are connected by couplings, also known to those skilled in the art as "single-shaft machines" or "inline machines".

[0015] In a further advantageous embodiment of the invention, it can be provided that the drive device, in particular steam turbine or electric motor or possibly gas turbine, the air compressor, the nitrous gas compressor and the gas expander are designed to run at the same speed, wherein the speed value can be varied during operation.

[0016] In a further advantageous embodiment of the invention, an air filter can be installed upstream of the air compressor, in particular the air compressor inlet. This advantageously prevents unwanted suspended particles from being sucked into the air compressor.

[0017] In a further advantageous embodiment of the invention, the air filter can be aligned, in particular elevated, with the air compressor, in particular the air compressor inlet. This can further improve efficiency, particularly since the air intake path can be straightened and unwanted deflections can be avoided.

[0018] In a further advantageous embodiment of the invention, a supply pipe can be arranged between the air compressor and the air filter, in particular between the inlet of the air compressor and the air filter. The design of the supply pipe can influence the air flow.

[0019] Further features and advantages of the present invention will become clear from the following description of preferred embodiments with reference to the accompanying drawings.

[0020] Fig. 1 shows a machine train of a nitric acid plant according to the invention for producing nitric acid in a schematic representation with the sequence air compressor, drive device, nitrous gas compressor, gas expander;

[0021] Fig. 2 shows a machine train of a nitric acid plant according to the invention for producing nitric acid in a schematic representation with the sequence air compressor, nitrous gas compressor, drive device, gas expander;

[0022] Fig. 3 shows a nitric acid plant according to the invention with a machine train in a schematic representation.

[0023] The following reference symbols are used in the figures:

[0024] M Machine train

[0025] S Nitric acid plant

[0026] 1 air compressor

[0027] 2 Drive device, in particular steam turbine, alternatively electric motor or gas turbine

[0028] 3 Nitrogen gas compressor

[0029] 4 gas expanders

[0030] 5 input and output shafts with couplings

[0031] 6 Device for nitric acid process, especially ammonia oxidation

[0032] 7 Device for nitric acid process, in particular absorption and residual gas purification

[0033] 11 Inlet (suction) of the air compressor

[0034] 12 Air compressor outlet

[0035] 13 Air filter 14 Supply pipe

[0036] 15 Air filter pedestal

[0037] 41 Inlet of the gas expander

[0038] 42 Outlet of the gas expander

[0039] Features and details described in connection with a method naturally also apply in connection with the device according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other. Furthermore, a method according to the invention that may be described can be carried out with the device according to the invention. The order (Fig. 1 to Fig. 3) of the inlets and outlets of the steam turbine and the nitrous gas compressor is irrelevant.

[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a" and "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It will also be understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of the recited features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed elements.

[0041] A nitric acid plant S essentially comprises a machine train M.

[0042] The following description essentially refers to the actual machine train M and the components essential for understanding the invention. The other equipment of a nitric acid plant S, in particular its fluidic connections and other components, is sufficiently familiar to those skilled in the art. For further details, reference can be made, for example, to EP 0 945 400 B1. Reference is first made to Fig. 1.

[0043] A machine train M of a nitric acid plant S for producing nitric acid essentially comprises a drive device 2, in particular a steam turbine (electric motor or gas turbine), an air compressor 1, a nitrous gas compressor 3, and a gas expander 4.

[0044] The aforementioned components are connected to each other for transmitting rotary motion by means of input and output shafts 5 connected by couplings. In this patent, the individual input and output shafts of the individual machines are referred to as the "drive shaft." Preferably, a common rotational speed of the drive shafts 5 is considered. Reference can be made, for example, to DE 10 2016 003 950 A1, in particular to the resulting advantages.

[0045] The input and output shafts 5, connected by couplings, preferably rotate at the same speed. Essentially, the speed should be variable. However, it is also possible to provide for one or more gears to be interposed, particularly where a gradation of the speeds is required.

[0046] The drive device 2, preferably designed as a steam turbine, drives the machine train M accordingly.

[0047] The air compressor 1 and / or the nitrous gas compressor 3 is preferably designed as a single-stage or multi-stage compressor. The air compressor 1 and / or the nitrous gas compressor 3 can also be referred to as an air compressor and / or nitrous gas compressor.

[0048] The gas expander 4 is essentially a turbine in which a pressurized gas expands, thereby generating work. The gas expander 4 can also drive the input and output shafts 5, which are connected by couplings. The gas expander is preferably designed as a single- or multi-stage turbine.

[0049] As already explained above, the machine train M is part of a nitric acid plant S, which includes other components such as condensers, reactors, pipelines, etc. The interrelationships and additional components are known to those skilled in the art and need not be explained in detail. For further details, reference can be made, for example, to EP 0 945 400 B1.

[0050] According to the invention, the air compressor 1 is a compressor with an axial inlet 11 or axial outlet 12, which is arranged at the end of the machine train M, in particular that the air compressor 1 is arranged at the end of the machine train M and that the air compressor 1 is a compressor of a single-shaft machine with an axial inlet 11 in a nitric acid plant S according to the dual-pressure process (this can optionally also include a combination of axial inlet and axial outlet). A single- or multi-stage radial compressor with an axial inlet is also possible. This measure enables the sucked-in air to enter the air compressor 1 with lower flow losses.

[0051] In a compressor of a single-shaft machine with axial intake in a nitric acid plant S using the dual-pressure process, also called an axial turbocompressor, the gas to be compressed flows through the compressor in a direction essentially parallel, in particular parallel, to the drive shaft. The air compressor accordingly has the aforementioned inlet 11 for air, which can also be referred to as the intake, and an outlet 12 for the compressed air. The inlet 11 is accordingly aligned axially, while the outlet 12 can be aligned radially or axially.

[0052] It can further preferably be provided that the gas expander 4 is a gas expander of a single-shaft machine with axial intake in a nitric acid plant S according to the dual-pressure process. In a gas expander of a single-shaft machine of a nitric acid plant according to the dual-pressure process, the gas to be decompressed flows through the expander in a direction substantially parallel to the drive shaft, in particular parallel to the drive shaft. The gas expander has an inlet 41 and an outlet 42. The inlet or outlet are preferably also axially aligned.

[0053] In this context, it is further preferably provided that the gas expander 4 is provided at the other end of the machine train M, i.e., on the opposite side of the air compressor 1. This results in the following preferred sequence of the components of the machine train in the axial direction, namely air compressor 1, drive device 2, nitrous gas compressor 3, gas expander 4. Such an arrangement is shown, for example, in Fig. 1. An interchanged arrangement of nitrous gas compressor 3 and drive device 2 is also conceivable, i.e., air compressor 1, nitrous gas compressor 3, drive device 2, gas expander 4. Such an arrangement is shown, for example, in Fig. 2.

[0054] 1 and 2, it can be noted that, in principle, the machines, such as a steam turbine or NOx compressor, could be mirrored. This means that the inlets and outlets would be swapped. In principle, numerous arrangement options are conceivable, such as, in particular, the gas expander 4 being designed with an axial inlet 41 or an axial outlet 42, the gas expander 4 being arranged at the end of the machine train M, in particular at the other end relative to the air compressor 1, the air compressor 1, drive device 2, nitrous gas compressor 3, gas expander 4 being arranged in the aforementioned order or air compressor 1, nitrous gas compressor 3, drive device 2, gas expander 4 being arranged in the aforementioned order.For example, it can also be provided that the nitrous gas compressor 3 is designed with an axial inlet or an axial outlet, wherein the nitrous gas compressor 3 is arranged at the end of the machine train.

[0055] A nitric acid plant S with a machine train M is shown in Fig. 3.

[0056] It can preferably be provided that an air filter 13 is connected upstream of the air compressor 1, in particular the air inlet 11. Preferably, a supply pipe 14 with a defined dimension is provided between the air filter 13 and the air compressor 1, in particular the inlet 11 of the air compressor 1. The dimension of the supply pipe 14, in particular its length, can be used to influence the flow characteristics of the intake air.

[0057] Preferably, the arrangement of air filter 13 and air compressor 1, and in particular supply pipe 14, is arranged one behind the other in an axial direction and in particular horizontally or in alignment with one another. For this purpose, it can be provided, for example, that the air filter 13 is mounted on a corresponding pedestal 15, so that the air filter 13 and air compressor 1, in particular its inlet 11, form an alignment. In particular, it is intended to provide a supply pipe 14 that is as straight as possible in order to minimize flow losses and increase efficiency. However, mounting the air filter 13 away from the ground also has the advantage, even on dirty and dusty floors, that air is not sucked in close to the ground.It is further preferably provided that the nitric acid plant S comprises a device 6 for the nitric acid process, in particular ammonia oxidation, and a device 7 for the nitric acid process, in particular absorption and residual gas purification.

Claims

Claims 1. Nitric acid plant (S) for the production of nitric acid by the double-pressure process, comprising a machine train (M) with - a drive unit (2), in particular a steam turbine or electric motor or, if applicable, a gas turbine, - an air compressor (1), - a nitrous gas compressor (3), - a gas expander (4) - the machine train is a single-shaft machine, characterized in that - the air compressor (1) is a compressor with an axial inlet (11) or axial outlet (12) which is located at the end of the machine train (M).

2. Nitric acid plant according to claim 1, characterized in that the gas expander (4) is designed with an axial inlet (41) or an axial outlet (42), wherein the gas expander (4) is arranged at the end of the machine train (M), in particular at the other end with respect to the air compressor (1).

3. Nitric acid plant according to at least one of the preceding claims, characterized in that air compressor (1), drive unit (2), nitrous gas compressor (3), gas expander (4) are arranged in the aforementioned order or air compressor (1), nitrous gas compressor (3), drive unit (2), gas expander (4) in the aforementioned order.

4. Nitric acid plant according to claim 1, characterized in that the nitrose gas compressor (3) is designed with an axial inlet or an axial outlet, wherein the nitrose gas compressor (3) is arranged at the end of the machine train.

5. Nitric acid plant according to at least one of the preceding claims, characterized in that the drive unit (2), the air compressor (1), the nitrose gas compressor (3) and the gas expander (4) are single-shaft machines. Nitric acid plant according to at least one of the preceding claims, characterized in that the drive unit (2), in particular a steam turbine or electric motor or, optionally, a gas turbine, the air compressor (1), the nitrous gas compressor (3), and the gas expander (4) are configured to operate at the same speed, the speed of which can be varied during operation. Nitric acid plant according to at least one of the preceding claims, characterized in that an air filter (13) is arranged upstream of the air compressor (1), in particular the inlet (11) of the air compressor (1). Nitric acid plant according to at least one of the preceding claims, characterized in that one or more of the air filters (13) is aligned in line with the air compressor (1), in particular the inlet (11), and is in particular mounted on a frame.Nitric acid plant according to at least one of claims 7 or 8, characterized in that a supply pipe (14) is arranged between the air compressor (1) and the air filter (13), in particular between the air filter (13) and the inlet (11) of the air compressor (1).

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