Integration of heat pump circuits in distillation plants for polymeric substances.

Abstract

The present invention relates to a distillation plant for polymerizable substances, comprising a rectification column (1) having a reboiler (2) and a steam condenser (3), wherein a heat pump circuit with a compressor (7) fluidly connects both the reboiler (2) and the steam condenser (3), and wherein the reboiler (2) is heated by the heat pump circuit and the steam condenser (3) is cooled by the heat pump circuit during operation of the distillation plant. The heat pump circuit uses water as a working medium, and a mixing element (8) is arranged between the compressor (7) and the downstream reboiler (2), and the mixing element (8) is configured to add cooling water to the working medium during operation of the distillation plant in such an amount that a working medium temperature in the range of 80°C to 200°C can be established at the inlet of the reboiler (2). The distillation plant is configured such that the working medium partially serves as cooling water during operation of the distillation plant, and the working medium serving as cooling water is drawn from a small region of the heat pump circuit extending in the direction of the main flow of the working medium from the reboiler (2) to the steam condenser (3). The invention further relates to a process for producing (meth)acrylates, the use of the distillation plant and a method for operating the distillation plant.

Description

[Technical Field]

[0001] The present invention relates to a distillation plant for polymerizable substances, comprising a rectification column having a reboiler and a vapor condenser, wherein a heat pump circuit comprising a compressor fluidly connects both the reboiler and the vapor condenser, and wherein during operation of the distillation plant the reboiler is heated by the heat pump circuit and the vapor condenser is cooled by the heat pump circuit, the heat pump circuit using water as a working medium. [Background technology]

[0002] Distillation plants for polymerizable substances, especially (meth)acrylates, generally have the problem that excessively high temperatures of the polymerizable substances during operation of the distillation plant can lead to violent polymerization within the distillation plant. The reboilers of the distillation plants are often affected by violent polymerization and / or significant fouling due to high heating temperatures. Therefore, significant deposits can occur on the inner walls of the reboiler flow paths. Therefore, the flow paths of the polymerizable substances can be blocked during operation of the distillation plant, resulting in the reboiler losing its ability to function.

[0003] Due to the energy-intensive method of operating such distillation plants, heat pumps are generally the option to make the energy content of the vapor stream at least partially reusable for the distillation plant.

[0004] Patent Document 1 discloses a distillation plant for polymerizable materials in which a heat pump circuit with a compressor fluidly connects both a reboiler and a steam condenser. The reboiler is heated by the heat pump circuit, and the steam condenser is cooled by the heat pump circuit. Water is used as the working medium in the heat pump circuit. However, this disclosure has the disadvantage that compression of the working medium by the compressor can also excessively increase the temperature of the working medium, resulting in the downstream reboiler becoming too hot for the polymerizable material flowing through it.

[0005] Patent document 2 discloses a distillation plant for polymerizable materials, equipped with a replaceable heat pump. The distillation plant comprises a column and a heat pump operating between the column's reboiler and a steam condenser. The heat pump can be replaced by means connectable to the reboiler and the steam condenser, as needed. These alternative means include means for generating steam / refrigerant. However, this implementation, as well as the compression of the working medium by the compressor, has the disadvantage that when the heat pump is operated, the temperature of the working medium can be excessively increased, resulting in the downstream reboiler becoming too hot for the polymerizable material flowing through it. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 60-125201 [Patent Document 2] European Patent Application Publication No. 0965373 Summary of the Invention [Problem to be solved by the invention]

[0007] It is therefore an object of the present invention to ensure that an acceptable temperature range for polymerizable material in the reboiler is maintained during operation of the distillation plant.A further object of the present invention is to be able to adjust in a distillation plant the optimum temperature of the working medium in the reboiler for the prevailing operating conditions in a faster, more stable and more accurate manner. [Means for solving the problem]

[0008] These objects are achieved according to the present invention by a distillation plant according to claim 1, a process for producing (meth)acrylates according to claim 9, the use of a distillation plant according to claim 15, and a method for operating a distillation plant according to claim 16. The present invention further relates to preferred embodiments of the distillation plant according to claims 2 to 8 and to preferred embodiments of the process for producing (meth)acrylates according to claims 10 to 14.

[0009] According to the present invention, a distillation plant for polymerizable substances comprises a rectification column having a reboiler and a vapor condenser, a heat pump circuit comprising a compressor fluidly connecting both the reboiler and the vapor condenser and configured such that during operation of the distillation plant the reboiler is heated by the heat pump circuit and the vapor condenser is cooled by the heat pump circuit, the heat pump circuit uses water as a working medium, and a mixing element is arranged between the compressor and the downstream reboiler, the mixing element being configured such that cooling water is added to cool the working medium during operation of the distillation plant.

[0010] Cooling water is added to cool the working medium in an amount such that a temperature of the working medium in the range of 80°C to 200°C, preferably 100°C to 160°C, in particular 110°C to 160°C, can be established or is established or exists at the inlet of the reboiler.

[0011] Addition of cooling water to the working medium between the compressor and the downstream reboiler provides the advantage that the temperature of the working medium at the inlet of the reboiler can be controlled in a fast, stable and accurate manner. This makes it possible to avoid temperature peaks before they reach the reboiler by adding cooling water. Therefore, the acceptable temperature range for the polymerizable material in the reboiler is maintained during the operation of the distillation plant.

[0012] As used herein, the term "rectification column" should be understood to mean a general description of an apparatus in which heating produces vapor which rises and contacts a descending liquid phase.

[0013] The rectification column is known in its general configuration and is equipped with conventional devices, such as a column bottom evaporator, a high-boiling effluent evaporator, or a low-boiling effluent condenser, with the high-boiling substances preferably located in the bottom region of the rectification column and the low-boiling substances preferably located in the upper region. Typically, a portion of the mass flow of the high-boiling effluent is recycled to the bottom region of the rectification column. However, in principle, it is also possible for the bottom region to be heated, for example, via outer wall heating of the column in the bottom region, and / or for an evaporator to be integrated in the bottom region. A vapor stream is usually withdrawn from the top of the rectification column and fed to a condenser. This vapor stream is also commonly referred to as the low-boiling effluent. A portion of the vapor stream condensed in the condenser is recycled to the rectification column, and the remaining portion of the condensed vapor stream is discharged as distillate. The reflux ratio represents the ratio between the condensed vapor stream recycled to the column and the condensed vapor stream withdrawn as distillate. A reflux ratio in the range of 10% to 200% is generally established. Conceivable column internals for a rectification column include, in principle, all commonly used internals, such as trays, structured packing, and / or random packing. Preferred trays include bubble cap trays, sieve trays, valve trays, Thorman trays, and / or dual flow trays, and preferred random packings include those with rings, coils, saddles, or woven fabrics. The rectification column may also be equipped with additional standard components for control, such as pressure regulators, flow controllers, or sensors. In principle, it is also possible to connect two or more rectification columns together in series or parallel, which can function as a single "rectification column" in their integrated system.

[0014] In this specification, the term "reaction zone" should be understood to mean that a chemical reaction can occur in a zone, which may be, for example, in a reactor, in the bottom of a rectification column, or in a reactive distillation column. In the preferred case where the reaction zone is in a reactor, the reactor may have a column disposed thereon, and in the case of an esterification process carried out in a reactor, the column preferably performs distillative separation of water. The column itself is generally a distillation column or a rectification column equipped with internal structures. Such internal structures are trays, such as bubble cap trays, perforated trays, especially dual flow trays, random packing, structured packing, etc. The reactor may also be integrated into the rectification column so that the reaction can occur at the bottom of the rectification column.

[0015] In this specification, the term "reboiler" should be understood to mean a general heating element for a rectification column. A reboiler typically heats the bottom mixture from the rectification column so that the bottom effluent flows through the reboiler and is then returned to the bottom of the rectification column. A reboiler may also include additional standard components, such as control valves, pressure regulators, flow controllers, or sensors. Thus, an evaporator may also include control means. The term "reboiler" may also generally be understood to mean two or more evaporators connected to each other in series or parallel. Examples of suitable reboilers include thin film evaporators, Roberts evaporators, falling film evaporators, natural circulation evaporators, and forced circulation evaporators. The evaporators may be in the form of a shell-and-tube heat exchanger or a plate heat exchanger. Those skilled in the art are familiar with suitable evaporators, which are described, for example, in SPX, Evaporator Handbook, APV Americas, Engineered Systems, Separation Technologies, 4th Edition, available at https: / / userpages.umbc.edu / ~dfrey1 / ench445 / apv_evap.pdf (retrieved May 20, 2022). In the heat pump circuit, the reboiler functions as a condenser, which at least partially, preferably completely, condenses the working medium via the bottom effluent.

[0016] In this specification, the term "water separator" should be understood to mean a device capable of separating water droplets from, for example, a gas stream. Typical examples of water separators include demisters, in particular demisters comprising a knitted wire mesh, centrifugal droplet separators, or lamella separators. The water separator can be arranged in a water collection vessel or configured as a dedicated device.

[0017] In this specification, the term "vapor condenser" should be understood to mean a device for cooling and condensing the vapor stream from the distillation plant. Typical examples of vapor condensers include shell-and-tube heat exchangers, jacketed tube heat exchangers, or plate heat exchangers. The heat exchanger may be provided with a nozzle for injecting a solution containing a polymerization inhibitor to prevent polymer formation. In a heat pump circuit, the vapor condenser functions as an evaporator that at least partially, preferably completely, evaporates the working medium via the heat supply vapor stream.

[0018] In this specification, the term "mixing element" should be understood to mean a device that mixes a liquid flow with a further liquid flow. The mixing element is in particular a separate component from the compressor. Furthermore, the mixing element is preferably arranged downstream of the compressor. Typical examples of mixing elements include a steam jet, a Venturi mixer, one or more mixing nozzles, or a long tube that serves as a mixing channel. In the case of a tube several meters long, the mixing nozzles are arranged separately within the tube. Alternatively, the mixing nozzles are provided by a coaxial tube in the form of openings in the intermediate wall.

[0019] In this specification, the term "compressor" should be understood to mean a machine that compresses gas. An example of a suitable compressor is a geared turbocompressor, which generally has two or more compression stages and intermediate stages, each of which is provided with a device for intercooling.

[0020] In this specification, the term "working medium" should be understood to mean generally a fluid flowing through a heat pump circuit and in particular undergoing its local phase change capable of supplying or removing heat.

[0021] In this specification, "heat pump" should be understood to mean a machine that generally performs technical work, absorbing thermal energy from a reservoir having a relatively low temperature and transferring it as useful heat, together with propulsion energy, to a heated system having a relatively high temperature. The heated system may be, for example, a reboiler, and the reservoir having a relatively low temperature may be, for example, a steam condenser.

[0022] In this specification, the term "heat pump circuit" should be understood to generally mean a circuit through which a working medium circulates. The heat pump circuit includes a compressor, a condenser, and an evaporator, each of which is fluid-tightly connected to the heat pump circuit. In the heat pump circuit, the reboiler functions as a condenser in the heat pump circuit, and the vapor condenser functions as an evaporator in the heat pump circuit.

[0023] In this specification, the term "cooling water" should be understood to mean water used to cool the working medium in the compressor or at a point in the heat pump circuit between the compressor and the downstream reboiler. The cooling water may generally be supplied to the working medium from outside the heat pump circuit via a conduit to the heat pump circuit. According to the invention, the cooling water is supplied via a diversion of a partial flow of the working medium at a point in the heat pump circuit between the reboiler and the downstream steam condenser.

[0024] In this specification, the term "fluidly connected" should generally be understood to mean that two or more water-conducting components, such as two or more flow tubes, are connected to each other so that these connected components can conduct a fluid flow. Generally, when conducting a fluid flow, sufficient technical liquid-tightness should be ensured.

[0025] In a preferred embodiment of the distillation plant, the mixing element is configured such that cooling water having a temperature in the range of 1°C to 160°C, more preferably 105°C to 150°C, in particular 110°C to 140°C is added to the working medium during operation of the distillation plant to cool the working medium, the cooling water having a mass flow rate relative to the mass flow rate of the working medium in the range of 3% to 10%. This has the advantage that the optimum temperature of the working medium at the inlet of the reboiler can be adjusted in a fast, stable and accurate manner.

[0026] The distillation plant is configured such that the working medium partially serves as cooling water during operation of the distillation plant, and the working medium serving as cooling water is withdrawn from a small section of the heat pump circuit extending in the direction of the main flow of the working medium from the reboiler to the steam condenser. In particular, the distillation plant has a return conduit fluidly connecting the outlet of the reboiler in the heat pump circuit to the mixing element. The return conduit is particularly arranged in a small section of the heat pump circuit extending in the direction of the main flow of the working medium from the reboiler to the steam condenser. The working medium serving as cooling water is preferably withdrawn and / or returned at an absolute pressure ranging from 2 bar to 8 bar, more preferably from 4 bar to 6 bar. The working medium serving as cooling water is preferably withdrawn and / or returned at a temperature ranging from 105°C to 150°C, more preferably from 110°C to 140°C.

[0027] Surprisingly, it has been found that the working medium cooled by the reboiler can be partially used as cooling water. This technical implementation has the advantage that no additional external cooling water is required and the heat pump circuit is not interrupted by external cooling water except in exceptional cases. An example of an exceptional case is when the working medium is discharged from the heat pump circuit as a result of a leak or when the working medium requires partial replacement with fresh working medium. Complex safety devices, such as pressure valves or complex pressure damping means, become redundant. Furthermore, the efficiency of the heat pump is improved compared to cooling with a cooling medium external to the heat pump circuit.

[0028] In a preferred embodiment of the distillation plant, the steam condenser is a vertical shell-and-tube heat exchanger, which can save space in the distillation plant and makes the injection of the solution containing the polymerization inhibitor technically easy to achieve.

[0029] In a preferred embodiment of the distillation plant, the reboiler has a downstream condensate container in the heat pump circuit, and both the condensate container and the mixing element are adapted so that during operation of the distillation plant the working medium flows partially from the condensate container to the mixing element, acting as cooling water. If the working medium is collected in the condensate container downstream of the reboiler, this has the advantage that if the mass flow rate of the working medium is reduced, there is sufficient working medium present to act as cooling water.

[0030] In a preferred embodiment of the distillation plant, both the condensate container and the compressor are adapted so that during operation of the distillation plant, the working medium flows partially from the condensate container to the compressor, acting as cooling water. This has the advantage that it also cools the compressor without the need to use another fluid. The condensate container allows intermediate storage of the working medium, so that there is always enough working medium between the compressor and the downstream reboiler to act as cooling water for both cooling the compressor and cooling the working medium.

[0031] In a preferred embodiment of the distillation plant, the compressor comprises one compression stage or two or more compression stages, and the distillation plant is adapted so that, during operation of the distillation plant, cooling water, in the case of two or more compression stages, is at least partially added to the working medium via a respective inter-stage mixing element for each compression stage, each inter-stage mixing element being arranged between each adjacent compression stage of the compressor. Each inter-stage mixing element is preferably fluidly connected via a return conduit to the outlet of the reboiler in the heat pump circuit. In the case of multiple compression stages, this has the advantage that the working medium is cooled between the stages without the need to use another fluid.

[0032] In a preferred embodiment of the distillation plant, a droplet separator or tube having a length-to-diameter ratio of at least 10 is connected downstream of each inter-stage mixing element, which protects the downstream compression stages from droplets that could damage the compressor.

[0033] In a preferred embodiment of the distillation plant, the distillation plant is configured such that, to cool the working medium during operation of the distillation plant, cooling water having a temperature in the range of 1°C to 160°C, more preferably 105°C to 150°C, and in particular 110°C to 140°C, is added to the working medium at the inlet of the downstream compression stage via an intermediate-stage mixing element in such an amount that a temperature difference can be established between the temperature of the working medium and the temperature at which the working medium is in the form of saturated vapor under the absolute pressure that is present in the range of 2°C to 50°C, preferably 5°C to 20°C. In this embodiment, the cooling water is preferably added via the intermediate-stage mixing element at a mass flow rate relative to the mass flow rate of the working medium at the compressor inlet in the range of 3% to 10%. This has the advantage that cooling water is added to the working medium between the compression stages in an energy-efficient manner, so that only the required amount of cooling water is added.

[0034] In preferred embodiments of the distillation plant, the mixing elements and / or intermediate stage mixing elements are mixing nozzles, steam jets or venturi pumps. These variants result in an energy-efficient, robust and economical industrial implementation.

[0035] In a preferred embodiment of the distillation plant, the distillation plant is configured so that during operation of the distillation plant there is a further steam condenser downstream of the steam condenser, this further steam condenser being equipped with a downstream phase separator, which is configured so that during operation of the distillation plant both an aqueous phase and an organic phase can be produced, one of these two phases being preferably at least partially recycled to the rectification column, and very particularly preferably both phases being at least partially recycled to the rectification column, each separately, through two separate recycle conduits. This has the advantage that the amount of aqueous phase can be recycled to the rectification column regardless of the amount of organic phase, and vice versa.

[0036] In a preferred embodiment of the distillation plant, the vapor condenser and the further vapor condenser are vertical shell-and-tube heat exchangers, which have the advantage that the preferred addition of the solution containing the polymerization inhibitor can be more easily carried out in the inlet region of the shell-and-tube heat exchanger.

[0037] In a preferred embodiment of the distillation plant, a phase separator is connected downstream of the vapor condenser, and the phase separator is configured so that during operation of the distillation plant, both an aqueous phase and an organic phase are formed in the phase separator and these two phases are at least partially recycled to the rectification column, preferably via two separate recycle lines, which has the advantage that optimal separation in the rectification column is achieved in the case of processes with polymerizable substances.

[0038] In a preferred embodiment of the distillation plant, the distillation plant is configured such that the reboiler, through which the bottom mixture from the rectification column flows during operation of the distillation plant, has walls made of a corrosion- and acid-resistant material selected from the group consisting of zirconium, stainless steel and nickel-based alloys, which substantially, or even completely, prevents corrosion processes of the walls.

[0039] In a preferred embodiment of the distillation plant, the heat pump circuit includes a water separator, which is fluidly connected to the steam condenser so that the working medium flows from the water separator into the steam condenser and then flows back from the steam condenser to the water separator during operation of the distillation plant. The water separator serves as a collection vessel for the working medium, meaning that if the mass flow rate of the working medium decreases, there is enough working medium to both cool the steam condenser and for the compressor. Furthermore, the water separator damps potential pressure fluctuations in the heat pump circuit. Preferably, the water separator includes a demister to protect the downstream compressor from damage caused by liquid droplets.

[0040] In a preferred embodiment of the distillation plant, the distillation plant is configured such that, to cool the working medium during operation of the distillation plant, cooling water having a temperature in the range of 1°C to 160°C, more preferably 105°C to 150°C, and particularly 110°C to 140°C, is added to the working medium at the inlet of the reboiler via a mixing element in such an amount that a temperature difference between the temperature of the working medium and the temperature at which the working medium is in the form of saturated vapor in the range of 5°C to 50°C, more preferably 5°C to 20°C, can be established, where the absolute pressure is preferably in the range of 2 to 8 bar, particularly preferably in the range of 4 to 6 bar. In this embodiment, the cooling water is preferably added via the mixing element at a mass flow rate relative to the mass flow rate of the working medium in the range of 3% to 10%. This has the advantage that cooling water is added to the working medium between the compressor and the downstream reboiler in an energy-efficient manner. Only the amount of cooling water necessary is added so that the working medium transfers sufficient heat to the reboiler and the temperature of the working medium does not become too high.

[0041] The present invention further provides the use of a distillation plant according to the invention, wherein the distillation plant is used in a chemical process, in particular a process for producing (meth)acrylates, preferably n-butyl (meth)acrylate, or a process in which (meth)acrylates, preferably n-butyl (meth)acrylate, is obtained. The use of a distillation plant according to the invention in such a chemical process offers the advantage that polymer formation in the heat pump circuit is avoided.

[0042] The present invention further provides a method of operating a distillation plant.

[0043] According to the invention, in a method for operating a distillation plant, a liquid mixture is conveyed to a rectification column, and during the distillative separation, a vapor stream having a temperature in the range of 35°C to 120°C, in particular 50°C to 100°C, is generated at the inlet of the vapor condenser, and a bottom product having a temperature in the range of 80°C to 160°C, in particular 80°C to 130°C, is formed at the bottom of the rectification column, and the working medium from the reboiler is at least partially fed to the vapor condenser to be cooled, thus providing a vapor condenser. The working medium in the reboiler is heated, so that the working medium at the outlet of the steam condenser has a temperature in the range of 35°C to 120°C, particularly 50°C to 100°C, and an absolute pressure in the range of 0.1 bar to 0.9 bar, preferably 0.3 bar to 0.7 bar. The working medium is then compressed by a compressor, so that the working medium at the outlet of the compressor has a temperature in the range of 100°C to 300°C, preferably 150°C to 250°C, and an absolute pressure in the range of 1 bar to 10 bar. Cooling water is then added to the working medium via a mixing element in an amount such that a temperature at the inlet of the reboiler in the range of 80°C to 200°C, preferably 100°C to 160°C, more preferably 110°C to 160°C, is established.

[0044] The addition of cooling water to the working medium between the compressor and the downstream reboiler provides the advantage that the temperature of the working medium at the inlet of the reboiler is controlled in a fast, stable and accurate manner. Thus, by adding cooling water, it is possible to counter temperature rise peaks before they reach the reboiler. Thus, the acceptable temperature range for the polymerizable material in the reboiler is maintained during the operation of the distillation plant.

[0045] In the method for operating a distillation plant, it is preferred if cooling water is added to the working medium via a mixing element at a temperature in the range of 1°C to 160°C, more preferably 105°C to 150°C, in particular 110°C to 140°C, the cooling water having a mass flow rate relative to the mass flow rate of the working medium in the range of 3% to 10%.

[0046] Further preferred embodiments of the method for operating a distillation plant correspond to the above-mentioned preferred embodiments of the distillation plant according to the invention.

[0047] The distillation plant according to the invention is particularly suitable for producing (meth)acrylates. The invention relates to a process for producing (meth)acrylates by reacting (meth)acrylic acid with an alcohol, which corresponds to the (meth)acrylate, in the presence of an acid catalyst and a polymerization inhibitor, the process comprising: providing a rectification column having a reboiler and a vapor condenser, wherein a heat pump circuit including a compressor fluidly connects both the reboiler and the vapor condenser, the heat pump circuit using water as a working medium; carrying out an esterification in a reaction zone, in which the components (meth)acrylic acid and alcohol are used in a molar ratio ranging from 1.0:1.0 to 1.0:2.0, preferably from 1.0:1.1 to 1.0:1.5, and the esterification is carried out at a temperature ranging from 80°C to 150°C, preferably from 100°C to 130°C, and at an absolute pressure ranging from 0.2 to 5.0 bar, preferably from 0.4 to 1.5 bar, to obtain a resulting reaction mixture; a step of separating the water of esterification produced in the esterification from the reaction mixture in a rectification column, the reboiler being heated by a working medium flowing through the reboiler in a heat pump circuit; Discharging the gaseous vapor stream enriched with esterification water at the top of the rectification column; condensing the vapor stream in a vapor condenser to form an organic phase and an aqueous phase, the vapor condenser being cooled by a working medium flowing through the vapor condenser in a heat pump circuit, the working medium at the outlet of the vapor condenser having a temperature in the range of 35°C to 120°C, in particular 50°C to 100°C; supplying a working medium from the outlet of the steam condenser to a compressor, in which the working medium is compressed, and at the outlet of the compressor the working medium has a temperature in the range of 100°C to 300°C, preferably 150°C to 250°C, and an absolute pressure in the range of 1 bar to 10 bar, and a mixing element in the heat pump circuit is arranged between the compressor and a downstream reboiler, and in order to cool the working medium, cooling water having a temperature in the range of 1°C to 160°C, preferably 105°C to 150°C, in particular 110°C to 140°C, is added to the working medium via the mixing element in an amount such that at the inlet of the reboiler the working medium has a temperature in the range of 80°C to 200°C, preferably 100°C to 160°C, more preferably 110°C to 160°C; The present invention further provides a process comprising:

[0048] Adding cooling water to the working medium between the compressor and the downstream reboiler has the advantage that the temperature of the working medium at the inlet of the reboiler can be controlled in a fast, stable, and accurate manner. This makes it possible to avoid temperature rise peaks before the working medium reaches the reboiler by adding cooling water. Therefore, the allowable temperature range for the (meth)acrylate-containing polymerizable substance in the reboiler is maintained during the operation of the distillation plant.

[0049] In a process for producing (meth)acrylates, the working medium cooled by the reboiler is partially used as cooling water. This technical implementation has the advantage that no additional cooling water is required and the heat pump circuit is not interrupted by external cooling water except in exceptional cases. An example of an exceptional case is when the working medium is discharged from the heat pump circuit as a result of a leak or when the working medium requires partial replacement with fresh working medium. Complex safety devices, such as pressure valves or complex pressure damping means, become redundant as a result. Furthermore, it has surprisingly been found that the cooling water allows the specified temperature range of the working medium to be constantly observed, which means that there is no polymerization, contamination, and / or caking on the inner walls of the reboiler flow channels.

[0050] In the process for producing (meth)acrylates, cooling water is preferably added at a mass flow rate relative to the mass flow rate of the working medium in the range of 3% to 10%. In a preferred embodiment of the process for producing (meth)acrylates, cooling water is added at a temperature in the range of 1°C to 160°C, more preferably 105°C to 150°C, and particularly 110°C to 140°C, and at a mass flow rate relative to the mass flow rate of the working medium in the range of 3% to 10%. This has the advantage that cooling water is added to the working medium between the compressor and the downstream reboiler in an energy-efficient manner. Only the amount of cooling water necessary is added so that the working medium transfers sufficient heat to the reboiler and the temperature of the working medium does not become too high.

[0051] In the process for producing (meth)acrylates, the working medium partially serves as cooling water, and the working medium serving as cooling water is withdrawn from a small region of the heat pump circuit extending in the direction of the main flow of the working medium from the reboiler to the steam condenser. In particular, the working medium condensate formed in the reboiler is used as cooling water. The working medium serving as cooling water is preferably withdrawn and / or returned, in particular to the mixing element, at an absolute pressure ranging from 2 bar to 8 bar, more preferably from 4 bar to 6 bar. The working medium serving as cooling water is preferably withdrawn and / or returned, in particular to the mixing element, at a temperature ranging from 105°C to 150°C, more preferably from 110°C to 140°C.

[0052] In a preferred embodiment of the process for producing (meth)acrylates, the reboiler has a downstream condensate container in the heat pump circuit, and the working medium flows partly from the condensate container to the mixing element, acting as cooling water.

[0053] In a preferred embodiment of the process for producing (meth)acrylates, the working medium flows partly from the condensate vessel to the compressor, acting as cooling water.

[0054] In a preferred embodiment of the process for producing (meth)acrylates, the compressor comprises one compression stage or two or more compression stages, and in the case of two or more compression stages, cooling water is at least partially added to the working medium for each compression stage via a respective inter-stage mixing element, each inter-stage mixing element being arranged between each adjacent compression stage of the compressor.

[0055] In a preferred embodiment of the process for producing (meth)acrylates, a respective droplet separator is connected downstream of each inter-stage mixing element between each adjacent compression stage.

[0056] In a preferred embodiment of the process for producing (meth)acrylates, cooling water having a temperature in the range of 1°C to 160°C, more preferably 105°C to 150°C, and especially 110°C to 140°C, is added to the working medium via an intermediate-stage mixing element in an amount such that a temperature difference is established between the temperature of the working medium at the inlet of the downstream compression stage and the temperature at which the working medium is in the form of saturated vapor under the absolute pressure present in the range of 2°C to 50°C, preferably 5°C to 20°C. In this embodiment of the process, the cooling water is preferably added via the intermediate-stage mixing element at a mass flow rate relative to the mass flow rate of the working medium at the compressor inlet in the range of 3% to 10%. This has the advantage that cooling water is added to the working medium between the compression stages in an energy-efficient manner, so that only the required amount of cooling water is added.

[0057] In a preferred embodiment of the process for producing (meth)acrylates, the mixing elements and / or interstage mixing elements used are mixing nozzles, steam jets or venturi pumps.

[0058] In a preferred embodiment of the process for producing (meth)acrylates, a phase separator is connected downstream of the vapor condenser, and both an aqueous phase and an organic phase are formed in the phase separator, and these two phases are at least partially recycled to the rectification column, and the two phases are preferably recycled separately to the rectification column through two separate recycle conduits.

[0059] In a preferred embodiment of the process for producing (meth)acrylates, there is a further steam condenser downstream of the steam condenser, which further steam condenser is equipped with a downstream phase separator, in which both an aqueous phase and an organic phase are formed. It is preferred if one of these two phases is at least partially recycled to the rectification column. It is very particularly preferred if both phases are at least partially recycled to the rectification column, each separately, through two separate recycle lines.

[0060] In a preferred embodiment of the process for producing (meth)acrylates, the walls of the reboiler, through which the bottom mixture from the rectification column flows during operation of the distillation plant, are made of a corrosion- and acid-resistant material selected from the group consisting of zirconium, stainless steel and nickel-based alloys.

[0061] In a preferred embodiment of the process for producing (meth)acrylates, the heat pump circuit comprises a water separator, the working medium flows from the water separator to the steam condenser, and then the working medium flows back from the steam condenser to the water separator.

[0062] In a preferred embodiment of the process for producing (meth)acrylates, to cool the working medium, cooling water having a temperature in the range of 1°C to 160°C, more preferably 105°C to 150°C, and in particular 110°C to 140°C, is added to the working medium at the inlet of the reboiler via a mixing element in such an amount that a temperature difference can be established between the temperature of the working medium and the temperature at which the working medium is in the form of saturated vapor in the range of 5°C to 50°C, more preferably 5°C to 20°C, under the resulting absolute pressure, the resulting absolute pressure being preferably in the range of 2 bar to 8 bar, particularly preferably in the range of 4 bar to 6 bar. In particular, in this preferred embodiment, the cooling water is preferably added via the mixing element at a mass flow rate relative to the mass flow rate of the working medium in the range of 3% to 10%.

[0063] In a particularly preferred embodiment of the process for producing a (meth)acrylate, the (meth)acrylate is n-butyl (meth)acrylate.

[0064] A particularly preferred process for producing n-butyl (meth)acrylate is based on the reactants n-butanol and (meth)acrylic acid. In this document, "(meth)acrylic acid" is used to refer to a (meth)acrylic acid quality that preferably contains at least 98% by weight, more preferably at least 99.5% by weight, (meth)acrylic acid, even more preferably 0.2% by weight or less of water, and preferably 0.03% by weight or less of each of acetic acid, propionic acid, and isobutyric acid. It is preferred to use an n-butanol quality that contains at least 99.5% by weight of n-butanol, 0.05% or less of n-butanal, 0.02% or less of dibutyl ether, 0.1% or less of other alcohols, and 0.05% or less of water. Preferably, the color number is APHA 5 or less, and the acid number is 0.03 mg KOH / g or less.

[0065] Suitable polymerization inhibitors in the production of (meth)acrylates, which act as stabilizers, are, for example, N-oxides (nitroxyl or N-oxyl radicals, i.e. compounds having at least one NO group), such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (HO-TEMPO), 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 2,2,6,6-tetramethylpiperidine -N-oxyl, bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate, 4,4',4''-tris(2,2,6,6-tetramethylpiperidine-N-oxyl)phosphite or 3-oxo-2,2,5,5-tetramethylpyrrolidine-N-oxyl; monohydric or polyhydric phenols optionally having one or more alkyl groups, for example, alkylphenols, for example, o-, m- or p-cresol (methylphenol), 2-tert-butylphenol, 4- tert-Butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butylphenol, 2-tert-butyl-4-methylphenol, 2,6-tert-butyl-4-methylphenol, 4-tert-butyl-2,6-dimethylphenol or 6-tert-butyl-2,4-dimethylphenol; quinones such as hydroquinone, hydroquinone monomethyl ether, 2-methylhydroquinone or 2,5-di-tert-butylhydroquinone; hydroxyphenols such as catechol (1,2-dihydroxybenzene) or benzoquinone; aminophenols such as p-aminophenol; nitrosophenols such as p-nitrosophenol; alkoxyphenols such as 2-methoxyphenol (guaiacol, catechol monomethyl ether), 2-ethoxyphenol, 2-isopropoxyphenol, 4-methoxyphenol (hydroquinone monomethyl ether), mono- or di-tert-butyl-4-methoxyphenol;Tocopherols, such as α-tocopherol and 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran (2,2-dimethyl-7-hydroxycoumaran), aromatic amines, such as N,N-diphenylamine or N-nitrosodiphenylamine; phenylenediamines, such as N,N'-dialkyl-p-phenylenediamines (the alkyl groups may be the same or different, may each independently consist of 1 to 4 carbon atoms, and may be linear or branched), such as N,N'-dimethyl-p-phenylenediamine or N,N'-diethyl-p-phenylenediamine; hydroxylamines, such as N,N-diethylhydroxylamine; imines, such as methylethylimine or methylene violet; sulfonamides, such as N-methyl-4-toluene. sulfonamides or N-tert-butyl-4-toluenesulfonamide, oximes such as aldoximes, ketoximes or amidoximes such as diethylketoxime, methylethylketoxime or salicylaldoxime, phosphorus-containing compounds such as triphenylphosphine, triphenylphosphite, triethylphosphite, hypophosphorous acid or alkyl esters of phosphorous acid; sulfur-containing compounds such as diphenylsulfide or phenothiazine; metal salts such as copper or manganese, cerium, nickel, and chromium salts such as chlorides, sulfates, salicylates, tosylates, acrylates or acetates such as copper acetate, copper(II) chloride, copper salicylate, cerium(III) acetate or cerium(III) ethylhexanoate, or mixtures thereof;

[0066] The polymerization inhibitor or polymerization inhibitor mixture used in the production of (meth)acrylates is preferably at least one compound from the group comprising hydroquinone, hydroquinone monomethyl ether, phenothiazine, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl, bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)sebacate, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol, 2-methyl-4-tert-butylphenol, hypophosphorous acid, copper(II) acetate, copper(I) chloride, copper(II) chloride, copper(II) salicylate and cerium(III) acetate.

[0067] It is particularly preferred to use phenothiazine (PTZ) and / or hydroquinone monomethyl ether (MEHQ) and / or HO-Tempo as polymerization inhibitors in the production of n-butyl (meth)acrylate.

[0068] In the production of n-butyl (meth)acrylate, the polymerization inhibitor is preferably dissolved in one or more liquid organic compounds, which are preferably 2-butanol and / or n-butyl (meth)acrylate.

[0069] Suitable esterification catalysts for the production of (meth)acrylates include standard mineral acids and sulfonic acids, preferably sulfuric acid, phosphoric acid, alkylsulfonic acids (e.g., methanesulfonic acid, trifluoromethanesulfonic acid) and arylsulfonic acids (e.g., benzenesulfonic acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid) or mixtures thereof, although acidic ion exchangers or zeolites can also be used.

[0070] In the preparation of (meth)acrylates, it is particularly preferred to use sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, m-toluenesulfonic acid, o-toluenesulfonic acid or mixtures thereof.

[0071] It is very particularly preferred to use p-toluenesulfonic acid as an esterification catalyst in the production of n-butyl (meth)acrylate. Its content in the reaction zone, preferably in a reactor, based on the reaction mixture present therein is advantageously between 0.1% and 10.0% by weight, preferably between 0.1% and 6.0% by weight. Other organic sulfonic acids, such as methanesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, and / or sulfuric acid, can also be used. Their amount is equimolar to that of para-toluenesulfonic acid. Corresponding mixtures are also possible. The content of catalytically active acid in the bottom of the rectification column, based on the mixture present in the rectification column, can advantageously be between 2.5% and 50.0% by weight of para-toluenesulfonic acid or an equimolar amount of another organic sulfonic acid and / or sulfuric acid.

[0072] The invention will now be described in more detail with reference to the drawings, which should be considered as schematic representations, which do not represent limitations of the invention, for example with respect to specific dimensions or design variations. [Brief explanation of the drawings]

[0073] [Figure 1] FIG. 1 is a schematic process flow diagram of an exemplary distillation plant of the present invention for the production of (meth)acrylates using a heat pump. DETAILED DESCRIPTION OF THE INVENTION

[0074] FIG. 1 shows a schematic process flow diagram of an exemplary process of the present invention for producing polymerizable materials, preferably (meth)acrylates, in which the mixture obtained from the reaction zone is conveyed via conduit Z to fractionator 1.

[0075] A vapor stream is discharged from the top of the rectification column 1. In the downstream vapor condenser 3, the vapor stream is partially condensed to form an organic phase and an aqueous phase. The vapor condenser 3 in this case is a vertical shell-and-tube heat exchanger 3, and one or more polymerization inhibitors present in solution are added via conduit B in the inlet region of the shell-and-tube heat exchanger 3. Furthermore, the shell-and-tube heat exchanger 3 is equipped with a spray nozzle connected to conduit B. The spray nozzle disperses the polymerization inhibitors present in solution inside the tubes of the shell-and-tube heat exchanger 3. This directly stabilizes the vapor stream when condensation occurs and effectively prevents polymer formation.

[0076] A further steam condenser 4 downstream of the steam condenser 3 condenses any low boiling point materials remaining in the steam stream, resulting in complete condensation of the steam stream within the steam condenser 4 .

[0077] The condensate is then fed to a phase separator 5. The organic phase is at least partially returned to the rectification column 1 via conduit G, the remaining part of the organic phase being discharged from the distillation plant via conduit D. A separate conduit F is used to at least partially return the aqueous phase to the rectification column 1, the remaining part of the aqueous phase being discharged from the distillation plant via conduit E.

[0078] Reboiler 2 heats the bottoms from rectification column 1 in that at least a portion of the bottoms discharge flows through reboiler 2 and is then returned to the bottom of the column. The remaining portion of the bottoms discharge is discharged from the distillation plant.

[0079] The first vapor condenser 3 is cooled by the working medium flowing through it in the heat pump circuit. The working medium flows from the outlet of the vapor condenser 3 through a water separator 6 to a compressor 7, which includes a demister.

[0080] The compressor 7 comprises a first compression stage 15 and a second compression stage 12. The compressor 7 compresses the working medium, which then flows from the outlet of the compressor 7 via conduit P into the mixing element 8. The working medium then flows from the mixing element 8 via conduit Q to the inlet of the reboiler 2. The working medium then flows from the outlet of the reboiler 2 into the condensate container 9. A pump 14 conveys a partial flow of the working medium, which acts as cooling water, in conduit T to the mixing element 8. The mixing element 8 then adds the working medium, which acts as cooling water, to the working medium flowing from the compressor 7.

[0081] A conduit U is used to convey a further partial flow of the working medium, which serves as cooling water, from the condensate container 9 to the intermediate-stage mixing element 10 by means of a pump 14. A droplet separator 11, connected downstream of the intermediate-stage mixing element 10 and preferably comprising a knitted wire mesh, protects the second compression stage 12 from droplets.

[0082] A further partial flow of the working medium is conveyed by pump 14 from the outlet of condensate container 9 via conduit S to the inlet of water separator 6, where it is expanded by expansion valve 16 before, or preferably upon, entry into water separator 6. The working medium is then conveyed by pump 13 from water separator 6 to steam condenser 3.

[0083] In exceptional cases, it is also possible to add external steam acting as working medium to the conduit Q via the conduit V, in order to be able to increase the temperature of the working medium at the inlet of the reboiler 2. In exceptional cases, it is also possible to add external water acting as working medium to the water separator 6 via the conduit Y.

[0084] The working medium can be removed from the heat pump circuit via conduit X at any time, for example if too much pressure has built up in the heat pump circuit or if the working medium is to be exchanged.

[0085] Example The following example of a process for producing n-butyl acrylate is simulated by thermodynamic simulation. For this purpose, Aspen Plus® software (Aspen), which can be found on the website https: / / www.aspentech.com, was used. Aspen is a comprehensive simulation software package used for modeling, simulating, and optimizing chemical processes and plants in industry. Aspen has an extensive model database for modeling basic operations and a material database for the physical properties of many different materials.

[0086] Example 1 A thermodynamic simulation of an invention embodiment of a process for producing n-butyl acrylate using the distillation plant described in FIG. 1 was performed in Aspen and produced the following results:

[0087] The mixture obtained from the reactor is fed via conduit Z to rectification column 1 at a mass flow rate of 30010 kg / h and at a temperature of 105° C., the mixture having the following composition in parts by weight: Butanol 0.079 n-Butyl acrylate 0.650 Acrylic acid 0.070 Water 0.003 n-Butyl n-butoxypropionate 0.098 Balance 0.100

[0088] At the top of the rectification column 1, a vapour stream is discharged at a temperature of 88° C. The mass flow rate of the vapour stream is 37350 kg / h and the vapour stream has the following composition in parts by weight: water 0.381 Butanol 0.086 n-Butyl acrylate 0.526 Balance 0.007

[0089] The vapor stream is then condensed in a vertical shell-and-tube heat exchanger as vapor condenser 3 and in a further downstream vertical shell-and-tube heat exchanger as further vapor condenser 4 to form an organic phase and an aqueous phase. The condensate has a temperature of 32°C and an absolute pressure of 0.8 bar. In the inlet region of the vapor condenser 3, spray nozzles are provided, which dispense a solution containing one or more polymerization inhibitors into the inside of the tubes of the shell-and-tube heat exchanger. The mass flow rate of the solution here is 90 kg / h. Upon formation of the condensate, this directly stabilizes the condensate, thereby preventing polymer formation.

[0090] The condensate is then fed to phase separator 5. The resulting organic phase is returned to rectification column 1 via conduit G at a mass flow rate of 8062 kg / h and is discharged from the distillation plant via conduit D at a mass flow rate of 15250 kg / h. The resulting aqueous phase is returned to rectification column 1 via conduit F at a mass flow rate of 15590 kg / h and is separately discharged from the distillation plant via conduit E at a mass flow rate of 1855 kg / h.

[0091] The bottom effluent from the bottom of rectification column 1 with a mass flow rate of 377,400 kg / h and a temperature of 95° C. is heated by reboiler 2 to a temperature of 95° C. and returned to rectification column 1. A further bottom effluent with a mass flow rate of 16,330 kg / h and a temperature of 95° C. is discharged from the distillation plant.

[0092] The mixture in the bottom of the rectification column 1 now has the following composition in parts by weight: water 0.356 Acrylic acid 0.130 n-Butyl n-butoxypropionate 0.195 Acryloyloxyester 0.096 High boiling point substance 0.098 Balance 0.147

[0093] The steam condenser 3 is cooled by the working medium flowing through it in the heat pump circuit. The mass flow rate of the working medium here is 78,250 kg / h, and the working medium at the outlet of the steam condenser 3 is at a temperature of 80°C and an absolute pressure of 0.47 bar. In the simulation, the working medium used is water.

[0094] The working medium flows from the outlet of the steam condenser 3 via the droplet separator 6 to the compressor 7 at a mass flow rate of 17250 kg / h.

[0095] At the inlet of the compressor 7, the working medium has a temperature of 80°C and an absolute pressure of 0.47 bar. The compressor 7 comprises two compression stages 15, 12 and is a two-stage geared turbo compressor. The compressor 7 compresses the working medium so that at the outlet of the compressor 7, the working medium has an absolute pressure of 2.8 bar and a temperature of 206°C.

[0096] The working medium then flows from the outlet of the compressor 7 through conduit P to a steam jet nozzle, which functions as a mixing element 8. The working medium then flows through conduit Q from the steam jet nozzle to the inlet of the reboiler 2. The steam jet nozzle, inserted in between, adds a working medium serving as cooling water to the working medium, so that the working medium at the inlet of the reboiler 2, configured as a shell-and-tube evaporator, has a temperature of 140°C, an absolute pressure of 2.8 bar, and a mass flow rate of 19,980 kg / h. This is achieved by pump 14 conveying a partial flow of the working medium, serving as cooling water, from the outlet of the condensate container 9 through conduit T at a mass flow rate of 1,085 kg / h and a temperature of 131°C to the steam jet nozzle. The steam jet nozzle then adds the working medium serving as cooling water to the working medium flowing from the compressor 7.

[0097] A further partial flow of working medium is conveyed by pump 14 from the outlet of condensate container 9 at a mass flow rate of 1644 kg / h and a temperature of 131°C via conduit U to a further steam jet nozzle, which functions as an interstage mixing element 10 and is located between first compression stage 15 and second compression stage 12. The further steam jet nozzle adds working medium, which acts as cooling water, to the working medium entering from first compression stage 15. A droplet separator 11 downstream of the further steam jet nozzle protects downstream compression stage 12 from droplets. The temperature difference between the temperature of the working medium at the inlet to downstream compression stage 12 and the saturated vapor temperature of the working medium at the existing pressure is 10°C.

[0098] A further partial flow of the working medium is conveyed by pump 14 at a mass flow rate of 17250 kg / h and at a temperature of 131° C. from the outlet of condenser vessel 9 through conduit S to the inlet of droplet separator 6, where it is expanded by expansion valve 16 before entering droplet separator 6. Immediately before the working medium flows through expansion valve 16, the temperature of the working medium is 131° C. and the absolute pressure of the working medium is 4 bar.

[0099] A pump 13 then conveys the working medium from the droplet separator 6 to the vapor condenser 3 at a temperature of 80° C. and an absolute pressure of 1 bar.

[0100] Comparative Example 1 Except for the features specified below, this Comparative Example 1 is set up in the same manner as Example 1. Again, thermodynamic simulations were performed using Aspen software.

[0101] The working medium is not cooled by the mixing element 8 after leaving the compressor 7. As a result, the working medium at the inlet of the reboiler 2 is at a temperature of 260°C, instead of the 140°C temperature that occurs in Example 1. The mass flow rate of the working medium in conduit P in this comparative example is 18,890 kg / h, instead of the 19,980 kg / h mass flow rate in Example 1. The higher the temperature of the working medium, the higher the temperature in the reboiler 2. Therefore, as a result of the dynamic characteristics of the distillation plant, higher temperature peaks also occur, which overheat the bottom mixture flowing through the reboiler 2. In practice, this can result in fouling and / or polymer formation in the reboiler 2. In practice, the plant has to be shut down at shorter intervals for cleaning.

[0102] Comparative Example 2 Except for the specified features, this Comparative Example 2 is set up in the same manner as Example 1. Again, thermodynamic simulations were performed using Aspen software.

[0103] Compared to Example 1, the working medium acting as cooling water is not added to mixing element 8 nor to intermediate-stage mixing element 10. Instead, in this Comparative Example 2, the working medium is cooled at these two points by appropriate heat exchangers. The use of heat exchangers reduces the mass flow rate of the working medium leaving compressor 7 from 18,890 kg / h to 17,250 kg / h and the mass flow rate of the working medium entering reboiler 2 from 19,980 kg / h to 17,250 kg / h.

[0104] Under these conditions, a total of 1569 kW of heat is extracted from the heat pump circuit by the two heat exchangers. Due to the reduced flow of working medium through reboiler 2, less heat is transferred to the bottom mixture flowing through reboiler 2. Instead, an external heat carrier, e.g., heating steam, must be added to reboiler 2. This also reduces the efficiency of the heat pump circuit. [Explanation of symbols]

[0105] B Conduit for supplying polymerization inhibitor D Conduit for discharging the organic phase from the phase separator E. Conduit for discharging the aqueous phase from the phase separator F: A conduit for supplying the aqueous phase from the phase separator to the rectification column G. Conduit for feeding the organic phase from the phase separator to the rectification column P: A conduit for supplying the working medium from the compressor to the mixing element Q: A conduit for feeding the working medium from the mixing element to the reboiler S: A conduit for supplying the working medium from the condensate container to the water separator. T: Conduit for supplying the working medium from the condensate container to the mixing element U Conduit for supplying the working medium from the condensate container to the intermediate stage mixing element V. Conduit for supplying external working medium X Conduit for discharging the working medium from the heat pump circuit Y Conduit for supplying external working medium Z: A conduit for supplying the mixture obtained from the reactor 1 Rectification tower 2 Reboiler 3 First steam condenser 4 Second steam condenser 5 phase separator 6 Water separator 7 Compressor 8 Mixed elements 9 Condensate container 10 Interstage mixing element between two compression stages 11 Droplet separator between two compression stages 12 Second compression stage of compressor 13 Pump for conveying the working medium from the water separator to the steam condenser 14 Pump for conveying the working medium from the condensate container to the water separator 15 First compression stage of compressor 16 Expansion valve

Claims

1. A distillation plant for polymerizable materials, comprising a rectification column (1) having a reboiler (2) and a vapor condenser (3), a heat pump circuit comprising a compressor (7) fluidly connecting both the reboiler (2) and the vapor condenser (3), such that during operation of the distillation plant, the reboiler (2) is heated by the heat pump circuit and the vapor condenser (3) is cooled by the heat pump circuit; the heat pump circuit uses water as a working medium; a mixing element (8) is disposed between the compressor (7) and the downstream reboiler (2); the mixing element (8) is configured so that cooling water is added in an amount that allows a temperature of the working medium at the inlet of the reboiler (2) in the range of 80°C to 200°C to cool the working medium during operation of the distillation plant, The distillation plant is configured such that during operation of the distillation plant, the working medium partially serves as cooling water, the working medium serving as cooling water being withdrawn from a small region of the heat pump circuit extending in the direction of the main flow of the working medium from the reboiler (2) to the steam condenser (3).

2. The reboiler (2) has a downstream condensate container (9) in the heat pump circuit; 2. A distillation plant according to claim 1, wherein both the condensate container (9) and the mixing element (8) are adapted so that during operation of the distillation plant the working medium flows partially from the condensate container (9) to the mixing element (8) while acting as cooling water.

3. 3. A distillation plant according to claim 2, wherein both the condensate vessel (9) and the compressor (7) are adapted so that during operation of the distillation plant the working medium flows partially from the condensate vessel (9) to the compressor (7) while acting as cooling water.

4. The compressor (7) comprises one compression stage (15) or two or more compression stages (15, 12), the distillation plant is adapted such that, during operation of the distillation plant, the cooling water in the case of two or more compression stages (15, 12) is at least partially added to the working medium via a respective inter-stage mixing element (10) for each compression stage, 4. A distillation plant according to any one of claims 1 to 3, wherein each said inter-stage mixing element (10) is arranged between each said adjacent compression stages (15, 12) of the compressor (7).

5. 5. A distillation plant according to claim 4, wherein in the case of two or more compression stages (15, 12), a respective droplet separator (11) is connected downstream of each inter-stage mixing element (10) between said respective adjacent compression stages (15, 12).

6. 6. A distillation plant according to claim 1, wherein the mixing element (8) and / or the respective intermediate stage mixing element (10) present in the case of two or more compression stages (15, 12) is a mixing nozzle, a steam jet or a venturi pump.

7. a phase separator (5) connected downstream of the vapor condenser (3); the phase separator (5) is configured so that during operation of the distillation plant both an aqueous phase and an organic phase are formed in the phase separator (5) and these two phases are at least partially recycled to the rectification column (1); 7. A distillation plant according to any one of claims 1 to 6, wherein the two phases are preferably recycled separately to the rectification column (1) via two separate recycle conduits.

8. The heat pump circuit comprises a water separator (6), 8. A distillation plant according to any one of claims 1 to 7, wherein the water separator (6) is fluidly connected to the steam condenser (3) such that during operation of the distillation plant the working medium flows from the water separator (6) into the steam condenser (3) and then flows back from the steam condenser (3) to the water separator (6).

9. 1. A process for producing (meth)acrylates by reacting (meth)acrylic acid with an alcohol, corresponding to the (meth)acrylate, in the presence of an acidic catalyst and a polymerization inhibitor, comprising: providing a rectification column (1) having a reboiler (2) and a vapor condenser (3), wherein a heat pump circuit comprising a compressor (7) fluidly connects both the reboiler (2) and the vapor condenser (3), the heat pump circuit using water as a working medium; carrying out an esterification in a reaction zone, in which the components, said (meth)acrylic acid and said alcohol, are used in a molar ratio ranging from 1.0:1.0 to 1.0:2.0, preferably from 1.0:1.1 to 1.0:1.5, and said esterification is carried out at a temperature ranging from 80°C to 150°C, preferably from 100°C to 130°C, and at an absolute pressure ranging from 0.2 bar to 5.0 bar, preferably from 0.4 bar to 1.5 bar, to obtain a resulting reaction mixture; - separating the water of esterification produced in the esterification from the reaction mixture in the rectification column (1), the reboiler (2) being heated by the working medium flowing through the reboiler (2) in the heat pump circuit; - discharging the gaseous vapour stream enriched with esterification water at the top of the rectification column (1); - condensing the vapor stream in the vapor condenser (3) to form an organic phase and an aqueous phase, the vapor condenser (3) being cooled by the working medium flowing through the vapor condenser (3) in the heat pump circuit, the working medium at the outlet of the vapor condenser (3) having a temperature in the range of 35°C to 120°C; supplying the working medium from the outlet of the vapor condenser (3) to the compressor (7), in which the working medium is compressed, and at the outlet of the compressor, the working medium has a temperature in the range of 100°C to 300°C and an absolute pressure in the range of 1 bar to 10 bar, a mixing element (8) in the heat pump circuit being arranged between the compressor (7) and the downstream reboiler (2), and in order to cool the working medium, cooling water having a temperature in the range of 1°C to 160°C is added to the working medium via the mixing element (8) in an amount such that at the inlet of the reboiler (2) the working medium has a temperature in the range of 80°C to 200°C; Including, - The working medium partially serves as cooling water, and the working medium serving as cooling water is withdrawn from a small area of the heat pump circuit extending in the direction of the main flow of the working medium from the reboiler (2) to the steam condenser (3).

10. 10. The process of claim 9, wherein the cooling water is added at a temperature in the range of 1°C to 160°C and at a mass flow rate relative to the mass flow rate of the working medium in the range of 3% to 10%.

11. The compressor (7) comprises one compression stage (15) or two or more compression stages (15, 12), In the case of two or more compression stages (15, 12), the cooling water is at least partially added to the working medium via a respective inter-stage mixing element (10) for each compression stage; 11. The process of claim 9 or 10, wherein each said inter-stage mixing element (10) is disposed between each said adjacent compression stages (15, 12) of the compressor (7).

12. 12. The process according to claim 11, wherein the cooling water having a temperature in the range of 1°C to 160°C is added to the working medium via the intermediate stage mixing element (10) in an amount such that, at the inlet of a downstream compression stage, a temperature difference is established between the temperature of the working medium and the temperature at which the working medium is in the form of saturated vapor in the range of 2°C to 50°C, preferably in the range of 5°C to 20°C, under the absolute pressure occurring.

13. 13. The process according to any one of claims 9 to 12, wherein, in order to cool the working medium, cooling water having a temperature in the range of 1°C to 160°C is added to the working medium at the inlet of the reboiler (2) via the mixing element (8) in such an amount that a temperature difference can be established between the temperature of the working medium and the temperature at which the working medium is in the form of saturated steam in the range of 5°C to 50°C under the resulting absolute pressure, the resulting absolute pressure being preferably in the range of 2 bar to 8 bar, particularly preferably in the range of 4 bar to 6 bar.

14. The process of any one of claims 9 to 13, wherein the (meth)acrylate is n-butyl (meth)acrylate.

15. 9. Use of a distillation plant according to any one of claims 1 to 8, wherein the distillation plant is used in a chemical process, in particular in a process for producing (meth)acrylates or in a process in which (meth)acrylates, preferably n-butyl (meth)acrylate, are obtained.

16. 9. A method for operating a distillation plant according to any one of claims 1 to 8, comprising conveying a liquid mixture (Z) to a rectification column (1), During the distillative separation, a vapor stream having a temperature ranging from 35°C to 120°C is produced at the inlet of the vapor condenser (3) and a bottom product having a temperature ranging from 80°C to 160°C is formed at the bottom of the rectification column (1), The working medium from the reboiler (2) is at least partially fed to the steam condenser (3) to be cooled, and the working medium is heated in the steam condenser (3), and the working medium at the outlet of the steam condenser (3) has a temperature in the range of 35°C to 120°C and an absolute pressure in the range of 0.1 bar to 0.9 bar, preferably 0.3 bar to 0.7 bar, The working medium is then compressed by a compressor (7), so that the working medium at the outlet of the compressor (7) has a temperature in the range of 100°C to 300°C and an absolute pressure in the range of 1 bar to 10 bar; Cooling water is then added to the working medium via a mixing element (8) in such an amount that a temperature at the inlet of the reboiler (2) ranging from 80°C to 200°C, preferably from 100°C to 160°C, is established. method.

Images