Method for producing organic isocyanate with improved sustainability

Abstract

By using a device for producing organic, aromatic isocyanate, said device at least containing a special production unit for providing nitric acid and superheated steam, a nitration unit, a hydrogenation unit, and a phosgenation unit, an improved use of sustainable energy sources can be achieved by utilizing waste heat as superheated steam for feeding heat energy to other utilization devices, in particular other units of the device. Parts of the aforementioned device are driven by an electric motor, as described in claim 1, in order to thus use the resources for process heat in the form of steam more effectively across the entire process chain of the device, whereby the use of energy is made more sustainable.

Description

[0001] Process for the production of organic isocyanate with improved sustainability

[0002] The invention relates to a device for the production of organic aromatic isocyanate, comprising at least a production unit for providing nitric acid and superheated steam, a nitration unit, a hydrogenation unit, and a phosgenation unit, wherein the device allows for improved utilization of sustainable energy sources by utilizing waste heat as superheated steam for the input of thermal energy into further utilization devices, in particular into further units of the device. The invention also relates to a process for the production of organic isocyanate with improved utilization of sustainable energy sources and the waste heat obtained from the process as regenerative energy, as well as the use of a special production unit for providing nitric acid and superheated steam for the supply of thermal energy, in particular to the nitration unit, hydrogenation unit, and phosgenation unit.

[0003] As is known from the prior art, organic aromatic isocyanates, such as toluene diisocyanate (TDI) or methylenediphenyl isocyanate (MDI), are usually obtained by phosgenation of aromatic amines, such as toluenediamine (TDA) or methylenedianiline (MDA), with phosgene.

[0004] The required aromatic amine can be prepared via catalytic hydrogenation of organic nitroaromatics, such as dinitrotoluene, with hydrogen under elevated pressure over a suspended, powdered catalyst (e.g., palladium on activated carbon or Raney nickel). This yields a product mixture containing, in addition to the desired aromatic amine, water, undesired isomers of the aromatic amine, high- and low-boiling byproducts, and optionally, added organic solvent. These byproducts must be removed before the aromatic amine is added for phosgenation.

[0005] As described in publication EP 0 757 034 A, the distillative purification and dehydration (also referred to as drying) of the organic aromatic amine required for phosgenation, as well as the distillative purification of the organic aromatic isocyanate as a product, requires thermal energy, which is usually introduced into the process in the form of superheated steam. As described in publication DE 19636191 A, superheated steam is likewise used to concentrate the sulfuric acid used for the production of organic nitroaromatics. By definition, superheated steam has a temperature above its boiling point at a given pressure.In most state-of-the-art processes, the superheated steam is largely generated in a steam boiler system with a superheater, using fossil fuels such as natural gas, coke, or petroleum-based fuels. However, generating this superheated steam requires a significant amount of energy, which, due to the use of fossil fuels, increases carbon dioxide emissions and is therefore not very sustainable.

[0006] The nitroaromatic used as a starting material in the catalytic reduction is in turn provided by a nitration of an organic aromatic compound, such as toluene, with nitric acid.

[0007] Nitric acid is first produced under increased pressure on a catalyst (e.g. platinum, platinum-rhodium) by reacting ammonia NH3 with oxygen, e.g. atmospheric oxygen, under oxidation according to reaction (1):

[0008] ( 1) 907.3 kJ heat of reaction

[0009] In this process, a large amount of heat energy is produced along with nitrogen monoxide (NO). The NO produced in this process is then further oxidized to nitrogen dioxide (NO2) according to reaction (2), releasing additional heat in the process.

[0010] (2) 113.1 kJ heat of reaction

[0011] The nitrogen dioxide NO2 produced in this way is then absorbed in water according to reaction (3) to obtain nitric acid and further heat:

[0012] (3) 4 HNO3256.9 / 93.3 kJ Heat of reaction

[0013] The absorption of NO2 occurs like the oxidation of ammonia at increased pressure, preferably at pressures between 4 and 14 bar.

[0014] The pressures required for the overall nitric acid production process are generated by compressing the process gases involved using a compressor. For this purpose, the oxygen required for ammonia oxidation, for example, is typically supplied as atmospheric oxygen in the form of compressed process air. This oxygen-containing process air is compressed by a compressor to a pressure suitable for both the oxidation reaction and the subsequent absorption reaction. The energy required for compression is partly obtained by expanding the residual gas exiting from the absorption reaction and also by utilizing the heat of reaction released during the reactions (1) to (3) mentioned above. This heat is used to generate steam, which is primarily used to drive the turbine of a turbo compressor for compressing the process gases used in nitric acid production.A suitable compressor is described, for example, in Fig. 1 of German patent DE 10 2022 201 476 A1. A nitric acid plant can be operated using the mono-high-pressure process. In this process, the combustion of the ammonia and the absorption of the nitrogen oxides occur at approximately the same pressure of about 10 bar. If large nominal capacities and / or higher acid concentrations are required, a nitric acid plant can be operated using the dual-pressure process. In the dual-pressure process, the combustion of the ammonia takes place at an elevated pressure that is lower than the elevated pressure prevailing during absorption.

[0015] For the production of organic isocyanates, the necessary organic starting materials, such as the organic nitro compound or the organic amine (see publication EP 0 757 034 Al), or nitric acid, can be delivered to the organic isocyanate production site. These starting materials are initially produced at a decentralized site, which is usually located so far from the phosgenation unit used for isocyanate production that the facilities cannot be connected by pipeline for material transport. The transport required for these deliveries, which must be carried out by means of transport (such as truck, rail, or ship), negatively impacts the sustainability of the overall process, i.e., the entire production process, due to the energy expenditure.

[0016] The object of the present invention was therefore to improve the sustainability of the overall production of organic isocyanate and, in particular, to reduce the carbon footprint of the manufacturing process. To this end, the energy requirements and the form of energy needed for each subprocess of isocyanate production were to be evaluated and incorporated into the optimization of the efficiency and sustainability of the overall process.

[0017] In accordance with the UN definition of sustainability ("sustainable development") as defined in the Brundtland Report of the World Commission on Environment and Development, the skilled person understands the "sustainability" of a process to mean that the implementation of the process in the present makes as little as possible, or even no contribution at all, to future generations of humanity being unable to satisfy their own needs, particularly needs relating to the use of resources such as fossil raw materials and especially those relating to the conservation of the environment, such as the protection of the Earth's atmosphere. The invention therefore aims to make the production of organic isocyanates, and polyurethanes produced therefrom, more sustainable than the production methods known from the prior art.The contribution of isocyanate and polyurethane production to a declining ability to meet the needs of future generations should be reduced or avoided. It has been found that, in particular, the energy requirements of the isocyanate production subprocesses can be met more sustainably if the process heat generated in the overall process is used as efficiently as possible and / or completely in the subprocesses in the form of steam.

[0018] A first object of the invention is thus a device for the production of organic aromatic isocyanate, comprising: at least one production unit for providing nitric acid and steam, wherein the production unit comprises: at least one compression unit, comprising at least one compressor for compressing oxygen-containing gas and at least one outlet for the compressed, oxygen-containing gas; and at least one supply device for providing ammonia; and at least one oxidation reactor for oxidizing the supplied ammonia in a mixture at least with oxygen from the compressed, oxygen-containing gas to a nitrogen oxide-containing product gas, providing heat; wherein the oxidation reactor has at least one outlet for nitrogen oxide-containing product gas;and at least one compression unit, comprising at least one compressor for compressing at least the nitrogen oxide from the product gas and at least one outlet for compressed, nitrogen oxide-containing product gas; at least one absorption reactor for reacting at least nitrogen oxide from the compressed product gas with water to form nitric acid; and at least one steam unit for providing superheated steam at a temperature of at least 200°C, wherein this steam unit includes at least one heat exchanger configured to remove heat from the oxidation reactor and / or from the product gas discharged from the oxidation reactor, in each case by transferring the heat to water, to provide the superheated steam;and at least one nitration unit for the nitration of organic aromatic compounds at least using nitric acid produced in said production unit and sulfuric acid to obtain at least organic aromatic nitro compounds and depleted sulfuric acid, wherein this nitration unit contains at least one unit for concentrating the depleted sulfuric acid obtained during the nitration and this nitration unit is connected to said production unit to provide the starting material nitric acid;and at least one hydrogenation unit for hydrogenating organic aromatic nitro compound produced in the nitration unit with hydrogen gas to obtain organic aromatic amino compound, wherein the hydrogenation unit comprises at least one hydrogenation reactor, at least one unit for dehydrating crude product and at least one distillation unit, and wherein this hydrogenation unit is connected to the nitration unit to provide the organic aromatic nitro compound as a starting material; and at least one phosgenation unit for phosgenating organic aromatic amino compound produced in the hydrogenation unit to obtain organic aromatic isocyanate compound, wherein this phosgenation unit comprises at least one unit for phosgene removal and at least one distillation unit, and wherein this phosgenation unit is connected to the hydrogenation unit to provide the organic aromatic amino compound;wherein the at least one production unit for providing nitric acid and steam additionally includes at least one electric motor, wherein the compressors of said compression units of the production unit are connected to the at least one electric motor for drive.

[0019] A connection between device components is typically formed to ensure a flow of material (e.g., reactants or intermediate products) from one device component to another. This connection is usually designed as a fluid connection, which is understood as part of a device that connects other device components and through which a substance, which can exist in any state of matter, can be transported as a flow from one device component to the next, for example, a supply line in the form of a pipe or other device components through which the substance is transported. The terms "connected" or "fluidly connected" mean that the named device components are connected to each other via such a connection or fluid connection.

[0020] The production unit according to the invention for providing nitric acid and steam comprises, as described above, at least one of the aforementioned compression units. This at least one compression unit is operated by at least one electric motor.

[0021] The use of an electric motor to operate at least one compression unit makes it possible to use the steam generated by the steam unit for purposes other than driving the compressor shafts.

[0022] Within the scope of the present invention, it is particularly preferred if, for the provision of green electric current, the electric motor is connected to a source of electric current from renewable energy, in particular from wind power, hydropower or solar energy. Those skilled in the art understand "renewable energy" to mean energy from an energy source that is not exhausted, such as wind energy, hydropower or solar energy.

[0023] In a further embodiment of the invention, it is preferred if the said compression units are combined into a single compression unit which contains at least the aforementioned compressors connected to at least one electric motor for drive. It is therefore particularly preferred according to the invention if the production unit for providing nitric acid and steam contains at least one compression unit comprising

[0024] (i) at least one compressor for compressing oxygen-containing gas; and

[0025] (ii) at least one compressor for compressing at least the nitrogen oxide from the product gas; and

[0026] (iii) a drive unit comprising at least one electric motor, which is connected at least via drive shafts to drive at least one compressor for compressing oxygen-containing gas and at least one compressor for compressing at least the nitrogen oxide from the product gas; and

[0027] (iv) at least one outlet for the compressed, oxygen-containing gas; and

[0028] (v) at least one outlet for compressed product gas containing nitrogen oxide; and, where appropriate, additionally

[0029] (vi) at least one gas expander. In the absorption reactor of the device according to the invention, a compressed residual gas is obtained from the compressed, nitrogen oxide-containing product gas after absorption and optionally purification. The gas expander (iv) of the compression unit is essentially a turbine in which the pressurized, compressed residual gas expands and thereby performs work. For this purpose, the gas expander has an inlet for the compressed residual gas and an outlet for the expanded residual gas, which remains compressed compared to atmospheric pressure. In this embodiment, the inlet for the compressed residual gas is connected to an outlet for the compressed residual gas located in the absorption unit.

[0030] The gas expander can also drive the drive shaft connected via couplings. The gas expander is preferably designed as a single- or multi-stage turbine.

[0031] It is particularly suitable to use a variant of the compression unit operated by an electric motor, as described in the publication DE 10 2022 201 467 Al or EP 0 945 400 A2, each with the provided inlets and outlets.

[0032] The production unit for the provision of nitric acid and steam, according to the invention, includes at least one provision device for the provision of ammonia. Such a provision device can, for example, be a storage tank for liquefied ammonia, which is connected to an ammonia production device via a compressor for filling with ammonia. Alternatively, the storage tank can be filled with liquid ammonia from transport containers such as tank trucks, which are used for delivery.In any case, in a preferred embodiment, it is advantageous to store such ammonia via the supply device as is the product of a manufacturing process in which hydrogen obtained by water electrolysis (using electrical energy from a renewable energy source) and nitrogen gas from the air (as described in the document WO 2024 / 017890 A2, hereby expressly and fully referenced) are converted to ammonia.

[0033] The production unit for providing nitric acid and steam comprises, according to the invention, at least one oxidation reactor for oxidizing the provided ammonia in the mixture with at least oxygen from the oxygen-containing gas compressed in the corresponding compression unit, wherein the oxidation reactor has at least one outlet for nitrogen oxide-containing product gas. Such oxidation reactors usable within the scope of the present invention are known to those skilled in the art, for example, from publications FR 2129012 A5 and Ullmann's Encyclopedia of Industrial Chemistry, Vol. 24, p. 177 (2012), to which explicit and full reference is hereby made.

[0034] To solve the problem, it has proven particularly effective if, in a preferred embodiment, the oxidation reactor of the device is designed such that it is capable of providing at least 20 MW of thermal energy, preferably at least 30 MW, during operation. This design of the oxidation reactor is easily implemented by a person skilled in the art by calculation, taking into account the process heats and varying the scaling of the reactor, e.g., the reactor size or, in the case of continuous reactors, the throughput, and is therefore not described in detail here.

[0035] According to the invention, the production unit for providing nitric acid and steam comprises at least one absorption reactor for reacting at least nitrogen oxide from the compressed product gas with water to form nitric acid. Such absorption reactors usable within the scope of the present invention are known to those skilled in the art, for example, from the publications in Ulmann's Encyclopedia of Industrial Chemistry, Vol. 24, p. 177 (2012), to which explicit and full reference is hereby made.

[0036] It is preferred according to the invention if said nitrogen oxide is selected from at least one compound selected from NO, NO2 or N2O4.

[0037] The production unit for providing nitric acid and steam according to the invention comprises at least one steam unit for providing superheated steam (preferably for providing a stream of superheated steam) at a temperature of at least 200°C, wherein this steam unit includes at least one heat exchanger configured to remove heat from the oxidation reactor and / or from the product gas discharged from the oxidation reactor, in each case by transferring the heat to water, to provide the superheated steam. Such steam units usable within the scope of the present invention are known in principle to those skilled in the art, for example, from the publications "Waste heat boilers for nitric acid plants": Borsig Process Heat Exchanger GmbH 05 / 2023, EP 2 336 635B1 and EP 1 261 548 B2, to which explicit and full reference is hereby made.

[0038] In a preferred embodiment, the steam unit is designed to generate a stream of superheated steam at an absolute pressure of at least 6 bar (preferably at least 11 bar) and a temperature of at least 200°C. It is particularly preferred that the steam unit is designed to generate a stream of superheated steam at an absolute pressure of at least 6 bar (preferably at least 11 bar) and a temperature of at least 200°C, and that the oxidation reactor of the device is designed to provide at least 20 MW, preferably at least 30 MW, of thermal energy to the steam unit during operation.

[0039] In a preferred embodiment of the invention, superheated steam produced in the nitric acid and steam production unit is to be utilized in at least one utilization device that is not part of the nitric acid and steam production unit and thus acts as a consumer for the superheated steam produced in the steam unit. For this purpose, at least one outlet of the steam unit for superheated steam is connected to said utilization device. At least one distillation unit and / or at least one dehydration unit and / or at least one heat exchanger and / or at least one steam turbine are particularly suitable as utilization devices.

[0040] In a particularly preferred embodiment of the device according to the invention, the device includes at least one utilization device for the superheated steam produced in the steam unit, wherein this utilization device is part of a unit selected from a nitration unit (including sulfuric acid concentration), a hydrogenation unit (including an associated distillation stage), a phosgenation unit (including an associated distillation stage), or a combination of at least two of these units. For this purpose, at least one utilization device of at least one unit selected from at least one unit of the group consisting of a nitration unit (including sulfuric acid concentration), a hydrogenation unit, and a phosgenation unit is connected to at least one outlet for superheated steam from the steam unit to provide the superheated steam.In a particularly preferred embodiment of the invention, at least one recovery device, selected from a distillation unit, dewatering unit, heat exchanger, or steam turbine, is connected to at least one unit, selected from a nitration unit (including sulfuric acid concentration), hydrogenation unit, or phosgenation unit, with at least one outlet for superheated steam from the steam unit to provide the superheated steam. In this embodiment, the distillation unit, dewatering unit, heat exchanger, or steam turbine from existing components of the nitration unit and / or hydrogenation unit and / or phosgenation unit thus function as a recovery device.In a further, particularly preferred embodiment, the nitration unit (including the sulfuric acid concentration), hydrogenation unit (including associated dehydration and / or distillation stage) and phosgenation unit (including associated distillation stage) are designed, in total, for the utilization of at least 25% of the total quantity of superheated steam that can be produced in the production unit for the manufacture of nitric acid and are connected to at least one outlet for superheated steam of the steam unit, in accordance with a planned steam utilization.

[0041] It is known that the nitration of organic aromatic compounds (such as benzene, toluene, xylene, and in particular the nitration of benzene to nitrobenzene) with nitrating acid, a mixture of sulfuric acid (e.g., oleum and / or sulfuric acid of varying concentrations), and nitric acid inevitably produces depleted sulfuric acid as a byproduct. The apparatus according to the invention comprises at least one nitrating unit for the nitration of organic aromatic compounds, at least using nitric acid produced in said production unit, and of sulfuric acid, yielding at least one organic aromatic nitro compound and depleted sulfuric acid. This nitrating unit is connected to said production unit for providing the starting material, nitric acid, and is equipped with a concentration unit for the depleted sulfuric acid.Nitrating units with sulfuric acid concentration units that can be used within the scope of the present invention are known to those skilled in the art, for example, from publications EP 1 508 563 A or Ullmann's Encyclopedia of Industrial Chemistry, 4th edition, Volume 17, p. 392, DE 19636191 A and US 2,256,999 A, to which explicit and full reference is hereby made. In general, the content of the depleted sulfuric acid obtained is approximately between 20 and 96 wt.%, in particular approximately 60 to 80 wt.% H₂SO₄, depending on the concentration of the sulfuric acid used in the nitrating acid and the amount of water of reaction produced per unit weight of nitrating acid during the nitration process, which is absorbed by the sulfuric acid.

[0042] In a preferred embodiment, the nitration unit (i.e., including the sulfuric acid concentration unit) is designed to utilize at least 25% of the total amount of nitric acid provided in the production unit and is connected to at least one nitric acid outlet of the absorption reactor. To further enhance sustainability, a variant of this embodiment is preferably implemented in which the oxidation reactor of the production unit is designed to provide nitric acid and steam such that it is capable of providing at least 20 MW, preferably at least 30 MW, of thermal energy during operation.The device according to the invention comprises at least one hydrogenation unit for hydrogenating organic aromatic nitro compound produced in the nitration unit with hydrogen gas to obtain organic aromatic amino compound, wherein the hydrogenation unit comprises at least one hydrogenation reactor, at least one unit for dehydrating crude product and at least one distillation unit, and wherein this hydrogenation unit is connected to the nitration unit for providing the organic aromatic nitro compound as a starting material.

[0043] The dewatering of the hydrogenation tubular product is very energy-intensive and is generally carried out in one or more stages using heated steam and, if necessary, under vacuum. The heat exchangers used can be gravity evaporators, immersion evaporators, kettle-type reboilers, shell-and-tube heat exchangers, or any other heat exchanger designs known to those skilled in the art. The water separation takes place in one or more distillation columns, which are preferably equipped with trays or structured packings. In a further preferred embodiment of the device according to the invention, the aforementioned at least one unit for dewatering the crude product is connected to at least one outlet for superheated steam from the steam unit for the supply of steam.

[0044] The purification of an aromatic amino compound typically takes place in single-stage or multi-stage distillation units to separate remaining water, low-boiling and / or high-boiling byproducts, and, if necessary, unwanted amine isomers. Rectification columns with trays, structured packings, or packings are generally used. Rectification can be performed under vacuum. The heat exchangers employed can be gravity evaporators, immersion evaporators, kettle-type reboilers, shell-and-tube heat exchangers, or any other heat exchanger designs known to those skilled in the art. In a further preferred embodiment of the device according to the invention, at least one distillation unit of the hydrogenation unit is connected to at least one outlet for superheated steam of the steam unit for the supply of steam.

[0045] Such hydrogenation units, including downstream destination and dehydration stages, which can be used within the scope of the present invention, are known to those skilled in the art, for example, from EP 2 263 997 A, EP 0 784 505 A, EP 1 602 640 A and EP 1 746 083 A, to which express and full reference is hereby made. The device according to the invention comprises at least one phosgenation unit for the phosgenation of organic aromatic amino compounds produced in the hydrogenation unit to obtain organic aromatic isocyanate compounds, wherein this phosgenation unit comprises at least one unit for phosgene removal and at least one distillation unit, and wherein this phosgenation unit is connected to said hydrogenation unit to provide the organic aromatic amino compound as a starting material.Such phosgenation units, including a downstream distillation stage, which can be used within the scope of the present invention, are known to those skilled in the art, for example, from the publications Six, Christian & Richter, Frank. (2003). Isocyanates, Organic: Ullmann's Encyclopedia of Industrial Chemistry, Vol. 20, pp. 63-82 (https: / / doi.org / 10.1002 / 14356007.al4_611), EP 1 371 636 A, WO 2011 / 003532 Al and EP 1 371 635 A, to which express and full reference is hereby made.

[0046] In the distillation and processing processes described in the prior art for the processing of organic isocyanates, heating steam is used for the evaporation and preheating of isocyanate, solvent, or phosgene. The heat exchangers used can be falling film evaporators, immersion evaporators, kettle-type reboilers, shell-and-tube heat exchangers, or any other heat exchanger designs known to those skilled in the art. The distillation processes can be carried out under vacuum. The distillative removal of solvent, low-boiling liquid, and / or high-boiling byproducts takes place in a single- or multi-stage distillation, optionally under vacuum. Rectification columns with trays, structured packings, or packed beds are typically used.In a further preferred embodiment of the device according to the invention, at least one distillation unit of the phosgenier unit is connected to at least one outlet for superheated steam of the steam unit for the supply of water vapor.

[0047] The apparatus of the first subject matter of the invention, as well as its embodiments, are each suitable for carrying out the inventive process for producing isocyanate. A further subject matter of the invention is therefore a process for producing organic aromatic isocyanate, comprising at least the following steps:

[0048] Production of nitric acid and superheated steam at a temperature of at least 200°C by at least the following steps:

[0049] Compression of an oxygen-containing gas to a compressed, oxygen-containing gas using at least one compressor of a compression unit, which is driven by at least one electric motor; mixing of ammonia with the compressed, oxygen-containing gas and subsequent oxidation of the ammonia to obtain nitrogen oxide-containing product gas and heat;

[0050] Conversion of the heat from the above oxidation using at least one heat exchanger into a stream of superheated steam with a temperature of at least 200°C;

[0051] Compression of the nitrogen oxide-containing product gas from the oxidation using at least one further compressor of a further compression unit, which is driven by an electric motor;

[0052] Reaction of nitrogen oxide from the compressed nitrogen oxide-containing product gas with water to form nitric acid;

[0053] Transport of the superheated steam through a transport unit to at least one unit for utilizing the steam flow;

[0054] Production of organic aromatic nitro compounds by reacting organic aromatic compounds with at least the previously produced nitric acid and with sulfuric acid;

[0055] Hydrogenation of the organic aromatic nitro compound with hydrogen gas to form an organic aromatic amino compound and processing of the crude product by at least distillation;

[0056] Phosgenation of the organic aromatic amino compound with phosgene to form an organic aromatic isocyanate compound and processing of the crude product by at least distillation; with the proviso that the unit for utilizing the steam stream is different from the previously mentioned units for compressing oxygen-containing gas and for compressing nitrogen oxide-containing gas.

[0057] To increase the supply of steam in the form of a steam stream, the inventive method involves driving at least one compressor of a compression unit by at least one electric motor. In a preferred embodiment, it is advantageous if the compression units are driven by at least one electric motor powered by electricity from renewable energy sources, in particular wind, hydro, or solar energy. Another preferred embodiment of the method is characterized in that the compression units are driven by at least the same electric motor.

[0058] For the provision of the steam stream, it has proven advantageous if, in a further preferred embodiment of the process, the heat provided during the oxidation of the ammonia has a thermal energy of at least 20 MW, preferably at least 30 MW.

[0059] For the transport and utilization of the steam stream generated in the process, it has proven advantageous if, in a further preferred embodiment of the process, the steam stream has an absolute pressure of at least 6 bar, preferably at least 11 bar.

[0060] The nitrogen oxide in question, of the nitrogen oxide-containing product gas, is preferably selected from at least one compound selected from NO, NO2 or N2O4.

[0061] In a preferred embodiment of the method, the stream of superheated steam is to be used in at least one unit for the utilization of the steam stream, which is different from the aforementioned units for the compression of oxygen-containing gas and for the compression of nitrogen oxide-containing gas and is selected from at least one unit selected from distillation unit, dehydration unit, heat exchanger, steam turbine.

[0062] In a preferred embodiment of the process, the crude product from the production of the organic aromatic nitro compound is further processed by distillation in a distillation unit, and steam from the transported steam stream is supplied to the operation of the distillation unit. Examples of suitable distillation units have been given to describe the apparatus of the first invention.

[0063] In a further particularly preferred embodiment, the inventive process additionally includes at least one step for concentrating the depleted sulfuric acid obtained as a by-product from the reaction of organic aromatic compound with at least the previously produced nitric acid and with sulfuric acid.

[0064] At least one step, selected from at least one of the aforementioned additional steps and / or at least one of the distillation steps that are mandatory in the process, can be carried out by operating a recovery device using the steam stream (in particular at least one recovery device selected from a heat exchanger and / or steam turbine).

[0065] To concentrate the depleted sulfuric acid obtained during the reaction of an organic aromatic compound with at least the previously produced nitric acid and with sulfuric acid as a byproduct, water can be removed from the depleted sulfuric acid in a distillation unit using the steam stream as a heat source via a heat exchanger of the distillation unit.

[0066] The distillation of the organic aromatic amino compound is subject to the same principles as the distillation of the raw product from the production of the organic aromatic amino compound within the scope of the first invention, mutatis mutandis.

[0067] In the context of processing the crude product during phosgenation, it is preferred according to the invention to first remove excess phosgene from the crude product (for example, by [method not specified]) and then at least to carry out the distillation of the organic aromatic isocyanate compound. The same applies to the distillation of the crude product from the phosgenation process as described in the first invention.

[0068] In a further particularly preferred embodiment of the method, it is carried out in a device of the first invention or its embodiments.

[0069] A third object of the invention is the use of the at least one production unit for nitric acid and superheated steam in a device of the first object of the invention for supplying at least one unit, selected from the group consisting of nitration unit, hydrogenation unit and phosgenation unit, with superheated steam at a temperature of at least 200°C to cover at least 25% of the heating steam requirement of these said units at an absolute pressure of more than 5 bar, in particular at least 6 bar, more preferably at least 11 bar.

[0070] The invention is illustrated by the following examples, without limiting the invention to the subject matter of these examples. Examples

[0071] Legend for Figures 1 and 2:

[0072] 1 production unit for the provision of nitric acid 7b and steam 8a

[0073] 2 Compression unit with compressor for compressing oxygen-containing gas

[0074] 2a Oxygen-containing reactant gas (e.g. air)

[0075] 2b compressed, oxygen-containing reactant gas (e.g. compressed air)

[0076] 3 Compression unit with compressor for compressing product gas containing nitrogen oxide

[0077] 3a compressed product gas containing nitrogen oxide

[0078] 4 Gas expanders for compressed residual gas (4a)

[0079] 4a compressed residual gas

[0080] 5. Ammonia supply device

[0081] 6 Oxidation reactor

[0082] 6a Product gas containing nitrogen oxide

[0083] 7 Absorption reactor

[0084] 7a Water

[0085] 7b Nitric acid

[0086] 8 steam units

[0087] 8a superheated steam with a temperature of at least 200°C

[0088] 9 heat exchangers

[0089] 9a Heat

[0090] 10 Nitriding Unit

[0091] 10a Sulfuric acid

[0092] 10b organic aromatic compound (e.g. benzene, toluene)

[0093] 10c organic aromatic nitro compound lOd depleted sulfuric acid lOe separated water

[0094] 11 Unit on Concentration

[0095] 12 Hydrogenation unit

[0096] 12a Hydrogen gas

[0097] 12b organic aromatic amino compound

[0098] 12c raw product

[0099] 13 Hydrogenation reactor

[0100] 14 Unit for drainage 14a Separated water

[0101] 15 distillation units

[0102] 16 Phosgenation unit

[0103] 16a organic aromatic isocyanate compound (e.g. TDI, MDI)

[0104] 17 Units for phosgene removal

[0105] 18 distillation units

[0106] 19 Electric motor

[0107] 19a Electricity from renewable energy

[0108] 20 steam turbine

[0109] 21 Steam generation using fossil fuels

[0110] 21a Steam from steam generation 21 and steam unit 8

[0111] In Figures 1 and 2, the connection between the individual compressor units 2, 3, the expander 4, and the electric motor 19, represented by the thick line, symbolizes a connection with corresponding coupling devices for driving the compressor units. Further lines between the individual components of the apparatus for the production of organic aromatic isocyanate represent connections designed to ensure a flow of material (e.g., reactants or intermediates) from one part of the apparatus to another. These connections are designed as fluid connections through which the corresponding substance intended for the connection (see respective markings) can be transported as a flow from one part of the apparatus to the next, for example, a feed line in the form of a pipe or other parts of the apparatus through which the substance is transported.The direction of flow is marked by an arrowhead.

[0112] Figures 1 and 2 each show an apparatus for the production of an organic aromatic isocyanate compound, comprising: a production unit 1 for providing nitric acid 7b and steam 8a, wherein the production unit 1 includes: a compression unit 2, comprising at least one compressor for compressing oxygen-containing gas 2a and at least one outlet for the compressed oxygen-containing gas 2b; and a supply device 5 for providing ammonia; and an oxidation reactor 6 for oxidizing the supplied ammonia in a mixture at least with oxygen from the compressed oxygen-containing gas 2b to a nitrogen oxide-containing product gas 6a, providing heat 9a; wherein the oxidation reactor 6 has at least one outlet for nitrogen oxide-containing product gas 6a;and a compression unit 3, comprising at least one compressor for compressing at least the nitrogen oxide from the product gas 6a and at least one outlet for compressed product gas 3a containing nitrogen oxide; an absorption reactor 7 for reacting at least nitrogen oxide from the compressed product gas 3a with water 7a to form nitric acid 7b; and a steam unit 8 for providing superheated steam 8a at a temperature of at least 200°C, wherein this steam unit 8 comprises at least one heat exchanger 9 configured to remove heat 9a from the oxidation reactor 6 and / or from the product gas 6a discharged from the oxidation reactor, in each case by transferring the heat 9a to water, to provide the superheated steam 8a;and a nitration unit 10 for the nitration of organic aromatic compound 10a at least using nitric acid 7b produced in said production unit and of sulfuric acid 10b to obtain at least organic aromatic nitro compound 10c and depleted sulfuric acid lOd, wherein this nitration unit 10 contains at least one unit for concentrating 11 the depleted sulfuric acid lOd obtained during the nitration and an outlet for the water lOe separated in the concentration 11 and this nitration unit 10 is connected with said production unit 1 to provide the starting material nitric acid 7b;and a hydrogenation unit 12 for hydrogenating organic aromatic nitro compound 10c produced in the nitration unit with hydrogen gas 12a to obtain organic aromatic amino compound 12b, wherein the hydrogenation unit 12 comprises at least one hydrogenation reactor 13, at least one unit 14 for dehydrating crude product, an outlet for the water 14a separated in the unit 14 and at least one distillation unit 15, and wherein this hydrogenation unit 12 is connected to the nitration unit 10 for the provision of the organic aromatic nitro compound 10c as a starting material;and a phosgenation unit 16 for the phosgenation of organic aromatic amino compound 12b produced in the hydrogenation unit 12 to obtain organic aromatic isocyanate compound 16a, wherein this phosgenation unit 16 contains at least one unit for phosgene removal 17 and at least one distillation unit 18, and wherein this phosgenation unit 16 is connected to the hydrogenation unit 12 to provide the organic aromatic amino compound 12b.

[0113] According to Fig. 2, the inventive embodiment of the device includes a production unit 1 for providing nitric acid 7b and steam 8a, and additionally an electric motor 19 powered by electricity from renewable energy 19a, wherein the compressors of the aforementioned compression units 2, 3 of the production unit 1 are connected to the electric motor 19 for drive. Furthermore, the production unit 1 of Fig. 2 additionally includes an expander 4 for compressed residual gas 4a from the absorption device 7. The gas expander 4 also contributes to the drive of the compression units 2, 3 via its gas turbine.

[0114] According to Fig. 1, the non-inventive embodiment of the device includes a production unit 1 for providing nitric acid 7b and steam 8a, and additionally a steam turbine 20 driven by the steam 8a. The compressors of the compression units 2, 3 of the production unit 1 are connected to the steam turbine 20 for drive. Furthermore, the production unit 1 of Fig. 1 additionally includes an expander 4 for compressed residual gas 4a from the absorption device 7. The gas expander 4 also contributes to driving the compression units 2, 3 via its gas turbine. According to Fig. 1, the remaining steam 8a generated in the production unit 1 is used together with superheated steam generated in a steam generator 21 using fossil fuels in the utilization units 11, 14, 15, 17, 18.

[0115] The following examples are given using the respective devices:

[0116] Example 1 (device according to Fig. 1, not according to the invention):

[0117] The apparatus shown in Fig. 1 for the production of organic aromatic isocyanate 16a comprises a production unit 1 for providing nitric acid 7b and steam 8a, which produces 70 t / h of 68% nitric acid, with the waste heat from the oxidation reactor 6 being generated in the form of 48 t / h of high-pressure steam 8a at an absolute pressure of 46 bar. Of these 48 t / h of steam 8a (abs. pressure 46 bar), 30 t / h are used for the internal steam turbine 20 to drive the compression units 2, 3 (corresponding to 6.3 MW of drive power) and 18 t / h are provided for further steam utilization by units 10, 12 and 16.

[0118] The total amount of nitric acid 7b produced (70 t / h) is dimensioned such that it more than meets the demand for the production of TDI 16a from toluene 10b, nitric acid 7b, hydrogen 12a, phosgene (COCE) using units 10, 12 and 16 of the apparatus.

[0119] The 18 t / h of steam 8a (abs. pressure 46 bar) provided for further steam utilization are fully used to cover the steam demand of the sulfuric acid concentration unit 11 of unit 10 of the TDI process chain, but are insufficient. In the concentration unit 11, water is distilled off the 75 wt% depleted sulfuric acid until the target concentration of 90 wt% is reached.

[0120] Since no further superheated steam 8a is available to meet the steam requirements of the process steps of units 10, 12 and 16 in the TDI process chain, this missing superheated steam is obtained from a steam generation 21 using external petrochemical sources.

[0121] Example 2 (device according to Fig. 2, according to the invention):

[0122] For the inventive device for the production of TDI as organic aromatic isocyanate 16a, illustrated in Fig. 2, production unit 1 for the provision of nitric acid 7b and superheated steam 8a is configured as follows. Production unit 1 produces 70 t / h of 68% nitric acid 7b in an electrified process. The steam turbine 20 used in Example 1 to drive the compression units 2, 3 is replaced by an electric motor 19 with a rated power of 6.3 MW, powered by electricity 19a from renewable energy. With the elimination of the steam turbine 20, the full quantity of the generated 48 t / h (abs. pressure 46 bar) steam 8a is available for energy-efficient steam utilization in the process chain of units 10, 12, and 16 downstream of production unit 1.

[0123] The total amount of nitric acid 7b produced (70 t / h) is dimensioned to exceed the demand for the production of TDI 16a from toluene 10b, nitric acid 7b, hydrogen 12a, and phosgene (COCE) using units 10, 12, and 16 of the apparatus. The 48 t / h of steam 8a (abs. pressure 46 bar) provided for energy-efficient steam utilization is used to 90% in the TDI process chain of units 10, 12, and 16, with the largest share going to the sulfuric acid concentration 11 of nitration unit 10, and a smaller share to the purification / determination and rectification units 14, 15, 17, and 18 of units 12 and 16.

[0124] In this example according to the invention, the available energy-efficient steam 8a from the nitric acid production 1 covers the entire remaining steam demand of the subsequent TDI process chain of units 10, 12 and 16.

Claims

P a t e n t a n s p r ü c h e 1. Apparatus for the production of organic aromatic isocyanate, comprising: at least one production unit (1) for providing nitric acid (7b) and steam (8a), wherein the production unit (1) comprises: at least one compression unit (2), comprising at least one compressor for compressing oxygen-containing gas (2a) and at least one outlet for the compressed oxygen-containing gas (2b); and at least one supply device (5) for providing ammonia; and at least one oxidation reactor (6) for oxidizing the supplied ammonia in a mixture at least with oxygen from the compressed oxygen-containing gas (2b) to a nitrogen oxide-containing product gas (6a) with the provision of heat (9a); wherein the oxidation reactor (6) has at least one outlet for nitrogen oxide-containing product gas (6a);and at least one compression unit (3) comprising at least one compressor for compressing at least the nitrogen oxide from the product gas (6a) and at least one outlet for compressed product gas (3a) containing nitrogen oxide; at least one absorption reactor (7) for reacting at least nitrogen oxide from the compressed product gas (3a) with water (7a) to form nitric acid (7b); and at least one steam unit (8) for providing superheated steam (8a) at a temperature of at least 200°C, wherein this steam unit (8) comprises at least one heat exchanger (9) configured to remove heat (9a) from the oxidation reactor (6) and / or from the product gas (6a) discharged from the oxidation reactor, in each case by transferring the heat to water, to provide the superheated steam (8a);and at least one nitration unit (10) for the nitration of organic aromatic compound (10a) at least using nitric acid (7b) produced in said production unit and sulfuric acid (10b) to obtain at least organic aromatic nitro compound (10c) and depleted sulfuric acid (1Od), wherein this nitration unit; (10) at least one unit for concentrating (11) the depleted sulfuric acid (1Od) obtained during nitration, and this nitration unit (10) is connected to said production unit (1) to provide the reactant nitric acid (7b); and at least one hydrogenation unit (12) for hydrogenating organic aromatic nitro compound (10c) produced in the nitration unit with hydrogen gas (12a) to obtain organic aromatic amino compound (12b), wherein the hydrogenation unit (12) includes at least one hydrogenation reactor (13), at least one unit (14) for dehydrating crude product, and at least one distillation unit (15), and wherein this hydrogenation unit (12) is connected to the nitration unit (10) to provide the organic aromatic nitro compound (10c) as a reactant;and at least one phosgenation unit (16) for the phosgenation of organic aromatic amino compound (12b) produced in the hydrogenation unit (12) to obtain organic aromatic isocyanate compound (16a), wherein this phosgenation unit (16) includes at least one phosgene removal unit (17) and at least one distillation unit (18), and wherein this phosgenation unit (16) is connected to the hydrogenation unit (12) for the provision of the organic aromatic amino compound (12b); characterized in that the at least one production unit (1) for the provision of nitric acid (7b) and steam (8a) additionally includes at least one electric motor (19), wherein the compressors of said compression units (2, 3) of the production unit (1) are connected to the at least one electric motor (19) for drive.

2. Device according to claim 1, characterized in that the nitriding unit (10), hydrogenation unit (12) and phosgenation unit (16) are designed in total to utilize at least 25% of the total quantity of superheated steam (8a) that can be produced in the production unit (1) and are connected to at least one outlet for superheated steam (8a) of the steam unit (8) according to a planned steam utilization.

3. Device according to claim 1 or claim 2, characterized in that said nitriding unit (10) is used to utilize at least 25% of the total amount of the in the Production unit (1) is designed to supply nitric acid (7b) and is connected to at least one outlet for nitric acid (7b) of the absorption reactor (7).

4. Device according to one of the preceding claims, characterized in that the electric motor (19) is connected to a source of electric current from renewable energy (19a), in particular from wind power, hydropower or solar energy.

5. Device according to one of the preceding claims, characterized in that said oxidation reactor (6) is designed to provide at least 20 MW of thermal energy (9a), preferably at least 30 MW of thermal energy (9a).

6. Device according to one of the preceding claims, characterized in that said device for generating a steam stream is suitable for generating said steam stream (8a) with an absolute pressure of at least 6 bar, preferably at least 11 bar.

7. Device according to one of the preceding claims, characterized in that superheated steam (8a) provided in the production unit (1) for the provision of nitric acid (7b) and steam (8a) can be used in a utilization device that is not a component of the production unit (1) for the provision of nitric acid (7b) and steam (8a), provided that at least one outlet of the steam unit (8) for superheated steam is connected to the said utilization device.

8. Device according to one of the preceding claims, characterized in that superheated steam (8a) provided in the production unit (1) for the provision of nitric acid (7b) and steam (8a) can be used in at least one utilization device, wherein the utilization device comprises at least one unit selected from a distillation unit, a dehydration unit, a heat exchanger, and a steam turbine, with the proviso that at least one outlet of the steam unit (8) for superheated steam (8a) is connected to said utilization device.

9. Device according to one of claims 7 or 8, characterized in that at least one of the recycling devices is part of a unit selected from the nitration unit (10), the hydrogenation unit (12), the phosgenation unit (16) or a combination of at least two of these units.

10. A process for the production of organic aromatic isocyanate, comprising at least the following steps: Production of nitric acid and superheated steam at a temperature of at least 200°C by at least the following steps: Compression of an oxygen-containing gas to compressed, oxygen-containing gas using at least one compressor of a compression unit, which is driven by at least one electric motor; Mixing ammonia with the compressed, oxygen-containing gas and subsequent oxidation of the ammonia to obtain nitrogen oxide-containing product gas and heat; Conversion of the heat from the above oxidation using at least one heat exchanger into a stream of superheated steam with a temperature of at least 200°C; Compression of the nitrogen oxide-containing product gas from the oxidation using at least one further compressor of a further compression unit, which is driven by an electric motor; Reaction of nitrogen oxide from the compressed nitrogen oxide-containing product gas with water to form nitric acid; Transport of the superheated steam through a transport unit to at least one unit for utilizing the steam stream; Production of organic aromatic nitro compounds by reacting organic aromatic compounds with at least the previously produced nitric acid and with sulfuric acid; Hydrogenation of the organic aromatic nitro compound with hydrogen gas to form an organic aromatic amino compound and processing of the crude product by at least distillation; Phosgenation of the organic aromatic amino compound with phosgene to form an organic aromatic isocyanate compound and processing of the crude product by at least distillation; with the proviso that the unit for utilizing the steam stream is different from the previously mentioned units for compressing oxygen-containing gas and for compressing nitrogen oxide-containing gas.

11. Method according to claim 10, characterized in that said compression units are driven by at least one electric motor which is powered by electric current from renewable energy, in particular from wind power, hydropower or solar energy.

12. Method according to claim 10 or claim 11, characterized in that said compression units are driven at least by the same electric motor.

13. Method according to one of claims 10 to 12, characterized in that said heat provided during oxidation has a thermal energy of at least 20 MW, preferably at least 30 MW.

14. Method according to one of claims 10 to 13, characterized in that said steam flow has an absolute pressure of at least 6 bar, preferably at least 11 bar.

15. Method according to one of claims 10 to 14, characterized in that the unit for utilizing the steam stream includes at least one utilization device selected from a heat exchanger and / or steam turbine.

16. Method according to one of claims 11 to 15, characterized in that it is carried out in a device according to one of claims 1 to 9.

17. Use of the at least one production unit (1) for nitric acid (7b) and superheated steam (8a) in a device according to any one of claims 1 to 9 for supplying at least one unit selected from the group consisting of a nitration unit (10), a hydrogenation unit (12) and a phosgenation unit (16), with superheated steam (8a) at a temperature of at least 200°C to cover at least 25% of the heating steam requirement of said units at an absolute pressure of more than 5 bar, in particular at least 6 bar.

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