Process for distillation of polymerizable substances

Abstract

The invention is related to a process for distillation of a feed mixture, comprising a polymerizable substance, in a device for production of the polymerizable substance, wherein the device for production of the polymerizable substance comprises at least one steam consumer, in particular at least one reboiler, and a distillation unit comprising a rectification column having a vapor condenser, wherein the feed mixture comprising the polymerizable substance is provided in the distillation unit, wherein a heat pump circuit having a compressor which fluidically connects the at least one steam consumer and the vapor condenser, the at least one steam consumer is heated by the heat pump circuit and the vapor condenser is cooled by the heat pump circuit and water is used as working medium in the heat pump circuit, wherein a working medium mix is fed to the compressor and the working medium mix is generated by withdrawing a first steam stream from the vapor condenser and addition of a second steam stream to the first steam stream, and wherein the second steam stream is withdrawn from a collection vessel of a condensation system, wherein at least one liquid condensate stream is depressurized and collected in the collection vessel. The invention is further related to a device for carrying out the process.

Description

[0001] 230819

[0002] 1

[0003] Process for distillation of polymerizable substances

[0004] Description

[0005] The present invention relates to a process for distillation of a feed mixture, which comprises a polymerizable substance, in a device for production of the polymerizable substance, wherein the device for production of the polymerizable substance comprises at least one steam consumer, in particular at least one reboiler, and a distillation unit comprising a rectification column having a vapor condenser. The feed mixture comprising the polymerizable substance is provided in the distillation unit and a heat pump circuit having a compressor fluidically connects the at least one steam consumer and the vapor condenser. The at least one steam consumer is heated by the heat pump circuit and the vapor condenser is cooled by the heat pump circuit, wherein water is used as working medium in the heat pump circuit.

[0006] Distillation plants for polymerizable substances, especially (meth)acrylates, generally have the problem that, during the operation of the distillation plant, high temperatures of the polymerizable substances are required but can lead to significant polymerization within the distillation plant. Frequently, the reboilers of the distillation plants, because of their high heating temperature, are affected by polymerization and fouling. Thus, considerable caking can form on the inner walls of the flow channels of the reboiler. The flow channels for the polymerizable substances can become blocked as a result in operation of the distillation plant, as a result of which the reboiler loses its ability to function.

[0007] Known examples of polymerizable substances are alkyl esters of (meth)acrylic acid, which are of significance, for example, as starting monomers for the preparation of aqueous polymer dispersions which find use, for example, as adhesives, paints or textile, leather and paper auxiliaries.

[0008] Typically, (meth)acrylates are produced by processes comprising an esterification step of esterifying (meth)acrylic acid with a feed alcohol to obtain a crude (meth)acrylate, and purification steps of purifying the crude (meth)acrylate to obtain the target product. In the purification steps distillation and stripping devices are applied, which are operated at an elevated temperature level and therefore require an extensive energy supply. The main energy consumers in those technologies are distillation columns.

[0009] Because of the energy-intensive method of operating such a distillation plant, it is an option to use a heat pump in order to make the energy content of the vapor stream at least partly reusable for the distillation plant.

[0010] EP 3769830 A1 is directed to a process for distilling a crude composition in a rectification plant including an indirect heat pump. A compressor is comprised in a vapor line, which connects the tube side of an overhead condenser with the shell side of a reboiler. 230819

[0011] 2

[0012] EP 0965373 A1 suggests a heat pump for a distillation device, wherein the heat pump is substitutable in case of compressor outage.

[0013] WO 2024 / 033149 A discloses an integration of a heat pump circuit into a distillation plant for polymerizable substances, wherein part of the working medium is used as cooling water and fed to a mixing element arranged downstream of the compressor of the heat pump.

[0014] Heat pump compressors can be damaged by condensation and droplet building within the compressor. Damages can be avoided by superheating the fluid which is fed to compressor. This can be done for example by returning the vapors from the pressure side of the compressor to the suction side of the compressor, but this causes additional load on the compressor and a higher energy consumption, resulting in a lowered efficiency. Thus, an alternative energy source for the superheating is of interest.

[0015] Typically, all condensate streams of a chemical plant, which are for example withdrawn from reboilers, are collected in flash steam drums. In the flash steam drum the pressure is reduced to ambient pressure. Thereby, hot condensate streams are flashed and generate flash steam at ambient pressure which is in general condensed in a heat exchanger via cooling water. This cooling water is then later again re-cooled via cooling towers or for example also by means of river water. In these cases the energy from the condensate streams is transferred to the environment and lost.

[0016] CN 111895381 A describes a steam flash drum, from which a discharge of the flashed steam is avoided.

[0017] In the documents mentioned above energy efficient measures to overheat the fluid fed to a compressor, which serves as heat pump in a distillation device, are not addressed.

[0018] It is an object of the present invention to protect the heat pump of a distillation plant from damage by means of superheating and to provide an energy efficient method for the superheating.

[0019] This object is achieved by a process for distillation of a feed mixture, comprising a polymerizable substance, in a device for production of the polymerizable substance, wherein the device for production of the polymerizable substance comprises at least one steam consumer, in particular at least one reboiler, and a distillation unit comprising a rectification column having a vapor condenser, wherein the feed mixture comprising the polymerizable substance is provided in the distillation unit, wherein a heat pump circuit having a compressor which fluidically connects the at least one steam consumer and the vapor condenser, the at least one steam consumer is heated by the heat pump circuit and the vapor condenser is cooled by the heat pump circuit and water is used as working medium in the heat pump circuit, wherein a working medium mix is fed to the compressor and the working medium mix is generated by withdrawing a first steam stream from the vapor condenser and addition of a second steam stream to the first steam 230819

[0020] 3 stream, wherein the first steam stream is provided at a first pressure level P1 and with a first temperature T 1 and the second steam stream is provided at a second pressure level P2 and with a second temperature T2, wherein the second pressure level P2 is higher than the first pressure level P1 and the second temperature T2 is higher than the first temperature T1 , and wherein the second steam stream is withdrawn from a collection vessel of a condensation system, wherein at least one liquid condensate stream is depressurized and collected in the collection vessel.

[0021] The invention is further directed to a device for carrying out the inventive process, wherein the device comprises at least one steam consumer, a rectification column having a vapor condenser, a heat pump circuit having a compressor, which fluidically connects the at least one steam consumer and the vapor condenser, and a condensation system with a collection vessel and a feed line which fluidically connects the collection vessel with the compressor. Preferably, the device comprises an expansion device such as a valve and / or baffle, in particular an expansion valve. Preferably, the expansion device, in particular the expansion valve, is arranged in fluidic connection between the collection vessel and the compressor. Preferably, the expansion device, such as the expansion valve, is configured to control the pressure in the collection vessel.

[0022] By the inventive process and system heat from already used utility condensation streams is efficiently recovered and used to superheat the feed stream to the compressor of the heat pump of the distillation unit.

[0023] Using low temperature heat recovery is most efficient when the energy is removed via evaporation of the working fluid water at low pressure. This evaporated working fluid from the vapor condenser, which provides the first steam stream in the inventive process, is at that stage typically at its dew point. Without any superheating before entry into the compressor it could cause damage to the compressor.

[0024] According to the invention the first steam stream is mixed with the second steam stream having a higher temperature and pressure level to protect the compressor from damage. Steam is understood as water present in gaseous form. Thus, the first steam stream and the second steam stream are at least partly gaseous streams. The second steam stream is withdrawn from the collection vessel in particular in gaseous form. Thus, the second steam stream is particularly in gaseous form when being withdrawn from the collection vessel. The second steam stream is withdrawn from the condensation system, such that energy from already used condensed utility streams can be recovered. Typically, the second steam stream is passed through an expansion device such as a valve and / or baffle, in particular an expansion valve, more preferably before being mixed with the first steam stream. Preferably, the second steam stream is expanded in the expansion device, in particular the expansion valve, such that the pressure of the second steam stream is reduced by passing the expansion device, in particular the expansion valve. In a preferred embodiment, the expansion device, in particular the expansion valve, is arranged downstream of the collection vessel, referring to the flow direction of the second steam stream. The expansion device, in particular the expansion valve, is preferably characterized by a pressure drop over the expansion device, in particular the expansion valve, of less than 600 hPa. Preferably, the expansion device, in particular the expansion valve, is arranged between the collection 230819

[0025] 4 vessel and the compressor. By means of the expansion device, such as the expansion valve, in particular the pressure in the collection vessel is controlled.

[0026] A typical waste heat source, namely the flash steam drum here also referred to as collection vessel, which is often present in chemical plants, is used according to the invention to improve the energy balance of a, in particular low temperature, heat pump system. The present invention enables the exploitation of the energy from the collected flash steam. The waste-steam from the flash drum is admixed to the feed stream of the compressor to ensure superheating at the entry of the compressor. By this means, moreover, an internal compressor recirculation can be avoided and the amount of energy which is recovered by the heat pump as well as the compressor efficiency are increased.

[0027] The term rectification column in this document is to be considered to be a general term for apparatuses in which vapors are generated by supply of heat, which ascend and come into contact with liquid phase flowing downward. Rectification columns are known in terms of their general design and have customary apparatuses, for example an evaporator in the bottom, an evaporator in the high boiler outlet or a condenser in the low boiler outlet, where the high boilers are preferably in the bottom region and the low boilers preferably in the top region of the rectification column. A portion of the mass flow from the high boiler outlet is typically fed back into the bottom region of the rectification column. However, it is also possible in principle that the bottom region is heated, for example, via an outer wall heating of the column in the bottom region and / or an evaporator is integrated into the bottom region. Typically, a vapor stream is drawn off at the top of the rectification column and fed to a condenser. The vapor stream is also typically referred to as low boiler output. A portion of the vapor stream condensed in the condenser is returned to the rectification column, whereas the remaining portion of the condensed vapor stream is drawn off as distillate. The reflux ratio here describes the ratio between the condensed vapor stream which is returned to the column and the condensed vapor stream which is drawn off as distillate. In general, a reflux ratio in the range from 10% to 200% is established. The column internals used for the rectification column may in principle be any standard internals, for example trays, structured packings and / or random packings. Among the trays, preference is given to bubble-cap trays, sieve trays, valve trays, Thormann trays and / or dual-flow trays; among the random packings, preference is given to those comprising rings, helices, saddles or braids. In addition, the rectification column may also comprise further standard components for regulation, by way of example pressure reducers, flow regulators or sensors. In principle, it is also possible to connect multiple rectification columns to one another by series or parallel connection, which can then also act collectively as a “rectification column”.

[0028] The at least one steam consumer is preferably at least one reboiler. The at least one steam consumer can comprise two or more reboilers. One of the two or more reboilers can be attached to other columns, in particular distillation columns, than the rectification column.

[0029] In addition to the at least one reboiler, the at least one steam consumer can comprise heat exchangers which are used for example for evaporation of water in an esterification step of the overall process. 230819

[0030] 5

[0031] The term reboiler, also referred to as evaporator concerning the processed product containing vapor, is understood to mean a general heating element for a rectification column. The reboiler typically heats a bottoms mixture from the rectification column, in that a bottoms output flows through the reboiler and is then returned back to the bottom of the rectification column. The reboiler may also comprise further standard components such as control valves, pressure reducers, flow regulators or sensors. The reboiler may therefore also comprise a closed-loop control. The term reboiler may also generally be understood to mean two or more evaporators which are linked in series or in parallel. Examples of suitable reboilers are thin-layer, Robert, falling-film, natural circulation or forced circulation evaporators. The at least one reboiler can be designed as shell-and-tube heat exchanger or plate heat exchanger Suitable reboilers are known to those skilled in the art and are described, inter alia, in: SPX, Evaporator Handbook, APV Americas, Engineered Systems, Separation Technologies, 4th edition. In the heat pump circuit, the reboiler functions as condenser, which at least partly, preferably fully, condenses the working medium using the bottoms output.

[0032] The term vapor condenser is understood to mean an apparatus that cools down and condenses a vapor stream from a distillation plant. Typical examples of a vapor condenser are a shell-and-tube heat exchanger, a jacketed-tube heat exchanger or a plate heat exchanger. In order to prevent polymer formation, the heat exchanger may be equipped with nozzles for injection of a solution comprising polymerization inhibitor(s). In the heat pump circuit, the vapor condenser functions as evaporator, which at least partly, preferably fully, evaporates the working medium using the heatsupplying product vapor stream from the rectification column.

[0033] The term compressor is understood to mean a machine that compresses gases. One example of a suitable compressor is a geared turbocompressor. The latter is generally designed with multiple compression stages and intermediate stages, and the respective intermediate stage is preferably equipped with an apparatus for intermediate cooling.

[0034] The term working medium is generally understood to mean the fluid that flows through the heat pump circuit and can especially add heat or remove heat by locally changing phase.

[0035] A heat pump is generally understood to mean a machine that absorbs thermal energy from a reservoir at relatively low temperature, expending technical work, and transfers it, at relatively high temperature, to a system to be heated as useful heat together with the driving energy. The system to be heated may, by way of example, be a reboiler and the reservoir at relatively low temperature may, by way of example, be a vapor condenser.

[0036] The term heat pump circuit is generally understood to 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 connected to the heat pump circuit in a fluid-tight manner. 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. 230819

[0037] 6

[0038] The expression fluidically connected is understood to mean that generally two or more traversable components, vessels or apparatuses, such as a plurality of flow tubes by way of example, are connected to one another in such a way that a fluid can flow through these connected components. In general, there should be a sufficient degree of technical imperviousness as a fluid flows through or into.

[0039] Preferably, the working medium mix has an inlet temperature TO at the inlet of the compressor and the inlet temperature TO is at least 1 °C, more preferably at least 2°C, even more preferably at least 3°C, higher than the dew point temperature Tdw of the working medium mix at the suction pressure P0 of the working medium mix at the inlet of the compressor.

[0040] Preferably, the at least one liquid condensate stream is at least partially evaporated in the collection vessel. More preferably, the at least one liquid condensate stream is partially evaporated in the collection vessel. The at least one liquid condensate stream, in particular all combined liquid condensate streams entering the collection vessel, comprise preferably more than 95 % by weight, more preferably more than 99% by weight, of water, based on all liquid condensate streams entering the collection vessel.

[0041] The condensation system can comprise or be any condenser which is arranged in fluidic connection with the collection vessel. In particular, the condensation system comprises the at least one steam consumer and / or the at least one additional steam consumer. The at least one steam consumer can be attached to the rectification column or deliver heat to any other apparatus such as reactors or columns, which might be at the same time part of production processes other than the production of the polymerizable substance. The at least one steam consumer can be the reboiler of the rectification column or be independent from the reboiler of the rectification column. Preferably, the at least one steam consumer is the reboiler of the rectification column.

[0042] Preferably, the at least one liquid condensate stream originates from additional steam consumers in the condensation system and / or from the at least one steam consumer, in particular of the distillation unit. More preferably, liquid condensate streams from at least two different steam consumers are collected in the collection vessel. The at least one steam consumer and optionally the additional steam consumers are in particular steam heated heat exchangers, in particular reboilers. The additional steam consumers are preferably part of the same production site as the rectification column. The additional steam consumers can be part of a different production plant or unit than the rectification unit. Typically, the additional steam consumers are arranged in spatial proximity to the rectification column, for example in a distance to the rectification column of less than 10 km, more preferably less than 5 km and even more preferably less than 1 km.

[0043] Preferably, one of the at least one steam consumer is a reboiler of the rectification column and the reboiler of the rectification column is heated by the heat pump circuit. At least part of the additional steam consumers can be heated by the heat pump circuit. 230819

[0044] 7

[0045] Preferably, the first pressure level P1 is at less than 1000 hPa, more preferably less than 900 hPa, even more preferably less than 800 hPa, even more preferably less than 700 hPa, even more preferably less than 600 hPa. Preferably, the second pressure level P2 is by at least 50 hPa, more preferably at least 100 hPa, even more preferably at least 200 hPa, even more preferably at least 300 hPa, even more preferably at least 400 hPa higher, than the first pressure level P1.

[0046] Preferably, the second temperature T2 is at least 1 °C, more preferably at least 5°C, even more preferably at least 10°C, even more preferably at least 15°C, higher than the first temperature T 1 . Preferably, the first temperature T 1 is less than 100°C, the second temperature T2 is less than 130°C and / or the at least one liquid condensate stream has a third temperature T3 at the inlet of the collection vessel, which is 90°C or higher. Preferably, the at least one liquid condensate stream is depressurized from a third pressure level P3 to the second pressure level P2 and the third pressure level P3 differs from the second pressure level P2 by at least 200 hPa. The third temperature T3 and the third pressure level P3 are in particular mass mean values over all liquid condensate streams entering the collection vessel.

[0047] The first temperature T1, the first pressure level P1 , the second temperature T2 and the second pressure level P2 are in particular given for the first steam stream and the second steam stream, respectively, referring to the condition directly before they are contacted with each other.

[0048] Preferably, the working medium mix consists to 50 wt.-% to 95 wt.-%, more preferably 70 wt.-% to 95 wt.-%, of the first steam stream and to 5 wt.-% to 50 wt.-%, more preferably 5 wt.-% to 30 wt.-%, of the second steam stream, referring to the total working medium mix.

[0049] Preferably, 5 wt.-% to 50 wt.-%, more preferably 10 wt.-% to 40 wt.-%, of the at least one liquid condensate stream, referring to the total of the at least one liquid condensate stream, is evaporated in the collection vessel, thus referring to all liquid condensate streams entering the collection vessel. Preferably, at least part of the remaining liquid condensate is fed from the collection vessel at least partially to the vapor condenser.

[0050] Preferably, a mixing element is disposed between the compressor and the at least one steam consumer, in particular the reboiler for example of the rectification column, wherein the working medium is cooled by adding a cooling water in such an amount that, at the inlet of the at least one steam consumer or the reboiler, a temperature of the working medium in the range from 100°C to 200°C, more preferably from 110°C to 200°C, even more preferably from 110°C to 160°C, is established. Preferably, the working medium serves partly as cooling water. More preferably, the working medium that serves as cooling water is taken from a subregion of the heat pump circuit that extends from the at least one steam consumer to the vapor condenser in the flow direction of the working medium, for example from the collection vessel. More preferably, the working medium that serves as cooling water is taken from the collection vessel. The working medium that serves as cooling water is even more preferably taken from the remaining liquid con- 230819

[0051] 8 densate from the collection vessel. Thus, the cooling water is particularly part of the remaining liquid condensate from the collection vessel, where the at least one liquid condensate stream is partially evaporated.

[0052] The cooling water allows an improved control of the stipulated temperature range of the working medium to be observed at all times. Thus polymerization, fouling and / or caking on the inner walls of the flow channels of the at least one steam consumer or reboiler can be reduced or avoided.

[0053] The working medium cooled by the at least one steam consumer or reboiler can be used partly as cooling water. This offers the advantage that no further external cooling water is required and the heat pump circuit is not disrupted by external cooling water. Complex safety devices such as pressure valves or costly depressurizing means become redundant. Moreover, the efficiency of the heat pump is increased by comparison with a cooling medium from outside of the heat pump circuit.

[0054] The term mixing element is understood to mean an apparatus that adds a further liquid stream to a fluid stream. The mixing element is, in particular, a component separate from the compressor. Moreover, the mixing element is preferably disposed downstream of the compressor. Typical examples of a mixing element are a steam jet, a Venturi mixer, one or more mixing nozzle(s) or a long tube serving as mixing zone. In the case of a tube of several meters in length, mixing nozzles are disposed individually in the tube. Alternatively, the mixing nozzles arise from a coaxial tube in the form of openings in the intermediate wall.

[0055] The term cooling water is understood to mean a water that serves to cool the working medium in the compressor or to cool the working medium at a point between the compressor and the downstream at least one steam consumer or reboiler in the heat pump circuit. Cooling water may generally be added to the working medium from outside the heat pump circuit via a conduit into the heat pump circuit. Preferably, the cooling water is provided by a branch of a substream of the working medium at a point in the heat pump circuit between the at least one steam consumer or the reboiler, and a downstream vapor condenser.

[0056] The addition of the cooling water to the working medium between the compressor and the downstream at least one steam consumer or reboiler offers the advantage that the temperature of the working medium at the inlet of the at least one steam consumer or the reboiler can be controlled quickly, stably and precisely. It is thus possible to avoid elevated temperature peaks by virtue of the addition of the cooling water, before they reach the at least one steam consumer or the reboiler. The permissible temperature range for a heat sensitive substance or the polymerizable substances in the at least one steam consumer or the reboiler is thus observed during the operation of the distillation plant.

[0057] Preferably, the mixing element is configured such that, during the operation of the distillation unit, the working medium is cooled by adding a cooling water to the working medium at a temperature in the range from 1 °C to 160°C, 230819

[0058] 9 further preferably from 105°C to 150°C, especially from 110°C to 140°C, where the cooling water has a mass flow rate relative to the mass flow rate of the working medium in the range from 3% to 10%. This results in the advantage that the optimal temperature of the working medium at the inlet of the at least one steam consumer or the reboiler can be adjusted quickly, stably and precisely.

[0059] In particular, the distillation unit has a recycling conduit that fluidically connects the outlet from the reboiler in the heat pump circuit to the mixing element. The recycling conduit is especially disposed in the subregion of the heat pump circuit which extends from the reboiler to the vapor condenser in the main flow direction of the working medium.

[0060] Preferably, the working medium that serves as cooling water is withdrawn, or recycled, at an absolute pressure within a range from 0.2 MPa to 0.8 MPa, further preferably from 0.4 MPa to 0.6 MPa. The working medium that serves as cooling water is preferably withdrawn, or recycled, at a temperature within a range from 105°C to 150°C, further preferably from 110°C to 140°C.

[0061] In a preferred embodiment, the vapor condenser is an upright shell-and-tube heat exchanger. In this way, it is possible to save space in the distillation plant, and injection of a solution comprising polymerization inhibitor(s) is readily implementable in technical terms.

[0062] In a preferred embodiment, the at least one steam consumer or the reboiler has a downstream condensate vessel, here the collection vessel, in the heat pump circuit, and both the condensate vessel and the mixing element are set up such that, during the operation of the distillation unit, the working medium flows partly from the condensate vessel to the mixing element, serving as cooling water. If the working medium is collected in a condensate vessel downstream of the reboiler, this results in the advantage that, in the case of a reduction in the mass flow rate of the working medium, sufficient working medium will be available to serve as cooling water.

[0063] In a preferred embodiment, both the condensate vessel and the compressor are set up such that, during the operation of the distillation unit, the working medium flows partly from the condensate vessel to the compressor, serving as cooling water. The condensate vessel enables intermediate storage of the working medium, which means that sufficient working medium will always be available to serve as cooling water both for the cooling of the compressor and for the cooling of the working medium between the compressor and the downstream at least one steam consumer or reboiler.

[0064] The compressor can comprise one compression stage or two or more compression stages. The distillation unit can be set up such that, during the operation of the distillation unit, the cooling water in the case of two or more compression stages is added at least partly to the working medium via one intermediate-stage mixing element for each compression stage, wherein the respective intermediate-stage mixing element is between the respectively adjacent compression stages of the compressor. The respective intermediate-stage mixing element is preferably fluidically connected by the recycling conduit to the outlet of the at least one steam consumer or the reboiler in the heat pump 230819

[0065] 10 circuit. In the case of multiple compression stages, this results in the advantage that the working medium is cooled between the stages, in particular without having to make use of other fluids.

[0066] In a preferred embodiment, a liquid droplet separator or a tube having a length-to-diameter ratio of at least 10 is connected downstream of the respective intermediate-stage mixing element. This further protects the downstream compression stage from droplets that can damage the compressor.

[0067] In a preferred embodiment, the distillation unit is configured such that, during the operation of the distillation plant, the working medium is cooled by adding a cooling water at a temperature in the range from 1 °C to 160°C, further preferably from 105°C to 150°C, especially from 110°C to 140°C, to the working medium via the intermediate-stage mixing element in such an amount that, at the inlet of the downstream compression stage, a temperature difference between the temperature of the working medium and the temperature at which the working medium under the existing absolute pressure takes the form of saturated steam in the range from 2°C to 50°C, preferably in the range from 5°C to 20°C, can be established or is established. In this embodiment, the cooling water is preferably added via the intermediate-stage mixing element with a mass flow rate relative to the mass flow rate of the working medium at the compressor inlet in the range from 3% to 10%. This results in the advantage that the cooling water is added in an energy-efficient manner to the working medium between the compression stages, such that only as much cooling water as needed is added.

[0068] In a preferred embodiment of the distillation plant, the mixing element and / or the intermediate-stage mixing element is a mixing nozzle, a steam jet or a Venturi pump. These variants bring about an energy-efficient, robust and economical industrial implementation.

[0069] In a preferred embodiment, the distillation unit is configured such that, during the operation of the distillation unit, there is a further vapor condenser downstream of the vapor condenser, and this further vapor condenser comprises a downstream phase separator, wherein the phase separator is designed such that, during the operation of the distillation unit, both an aqueous phase and an organic phase can form, wherein one of these two phases is preferably recycled at least partly to the rectification column, and wherein each phase is most preferably separately recycled at least partly to the rectification column through two separate recycling conduits. This results in the advantage that the amount of aqueous phase can be recycled to the rectification column irrespective of the amount of organic phase, and vice versa. Preferably, the vapor condenser and the further vapor condenser are an upright shell-and-tube heat exchanger.

[0070] Preferably, the rectification column comprises a second vapor condenser connected in series with the vapor condenser. The rectification column can comprises more than two vapor condensers connected in series. 230819

[0071] 11

[0072] In a preferred embodiment, a phase separator is connected downstream of the vapor condenser, wherein the phase separator is designed such that, during the 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 partly recycled to the rectification column, wherein the two phases are preferably recycled separately to the rectification column via two separate recycling conduits.

[0073] In a preferred embodiment of the distillation plant, a water separator is present in the heat pump circuit, wherein the water separator is fluidically connected to the vapor condenser in such a way that, during the operation of the distillation unit, the working medium flows from the water separator into the vapor condenser, and then the working medium flows back from the vapor condenser into the water separator. The water separator serves as collecting vessel for the working medium, which means that, in the case of a reduction in the mass flow rate of the working medium, there will be both sufficient working medium to cool the vapor condenser and sufficient working medium for the compressor. In addition, the water separator attenuates possible pressure fluctuations in the heat pump circuit. There is preferably a demister in the water separator, which protects the downstream compressor from damage by liquid droplets.

[0074] The term water separator is understood to mean an apparatus that can separate water droplets, for example, from a gas stream. Typical examples of a water separator are a demister, especially a demister with a wire mesh, a centrifugal droplet separator or a lamellar separator. The water separator may be present in a water collection vessel or be designed as a separate apparatus.

[0075] In a preferred embodiment, the walls of the reboiler are made from a nonrusting and acid-resistant material, in particular selected from the group consisting of zirconium, stainless steels and nickel-based alloys.

[0076] Preferably the distillation unit is used in chemical processes, especially in processes for formation or purification of a polymerizable substance or in processes in which a polymerizable substance occurs. The use of the distillation unit in such chemical processes offers the advantage that polymer formation in the heat pump circuit is avoided.

[0077] Preferably, the polymerizable substance is selected from the group consisting of (meth)acrylates, (meth)acrylic acid, styrenes and mixtures thereof. The polymerizable substance is more preferably a (meth)acrylate, in particular n-butyl (meth)acrylate. The particularly preferred process for preparing an n-butyl (meth)acrylate is based on the reactants n- butanol and (meth)acrylic acid.

[0078] The terms (meth)acrylic acid, (meth)acrylic ester or (meth)acrylate relate to acrylic acid, the corresponding acrylic esters or acrylates and / or to methacrylic acid, the corresponding methacrylic esters or methacrylates, respectively.

[0079] The feed mixture can be fed into the rectification column or the feed mixture, in particular the polymerizable substance comprised therein, can be formed in the rectification column. The feed mixture is preferably fed into the recti- 230819

[0080] 12 fication column. The feed mixture preferably comprises at least 30 wt.-%, more preferably at least 50 wt.-%, and typically less than 98 wt.-% or less than 95 wt.-%, of the polymerizable substance, referring to the total feed mixture.

[0081] Preferably, the process further comprises the following steps: conversion of (meth)acrylic acid with an alcohol to a (meth)acrylate by esterification in presence of an acidic catalyst and a polymerization inhibitor, wherein the feed mixture is obtained, providing the feed mixture comprising the (meth) acrylate in the rectification column, in particular separating the water of esterification formed in the conversion from the feed mixture within the rectification column, discharging a gaseous vapor stream, in particular enriched by the water of esterification, at the top of the rectification column, and condensing the vapor stream in the vapor condenser to form an organic phase and an aqueous phase, wherein the vapor condenser is cooled by the working medium, and the working medium at the outlet from the vapor condenser is at a temperature in the range from 35°C to 100°C, especially from 50°C to 100°C, and feeding at least part of the working medium from the outlet of the vapor condenser to the compressor together with the second steam stream, wherein the working medium mix is compressed within the compressor and the working medium mix at the compressor outlet is at a temperature in the range from 100°C to 300°C, more preferably from 150°C to 250°C, and an absolute pressure in the range from 1000 hPa to 10000 hPa, wherein optionally the mixing element cools the working medium mix by adding the cooling water at a temperature in the range from 1 °C to 160°C, more preferably from 105°C to 150°C, even more preferably from 110°C to 140°C, to the working medium mix in such an amount that, at the inlet of the at least one steam consumer, the working medium mix is at a temperature in the range from 100°C to 200°C, in particular from 110°C to 200°C.

[0082] In particular, the distillation unit is provided. The conversion is preferably performed within a reaction zone. The term reaction zone is understood to mean that a chemical reaction can take place within a zone, where the reaction zone may, for example, be in a reactor, in the bottom of the rectification column or in a reactive distillation column. In a preferred embodiment, wherein the reaction zone is in a reactor, the reactor may have a column on top, where the column, in the case of esterification processes taking place in the reactor, preferably separates off water by distillation. The column itself will generally be a distillation column or a rectification column having internals. Such internals are preferably trays, such as bubble-cap trays, perforated trays, especially dual-flow trays, random packings, structured packings or the like. In addition, the reactor may be integrated into the rectification column, such that the reaction can take place in the bottom of the rectification column.

[0083] Preferably, the (meth)acrylic acid and alcohol components are used in a molar ratio in the range from 1 .0:1.0 to 1 .0:2.0, more preferably in the range from 1.0: 1.1 to 1.0: 1.5. The conversion is preferably carried out at a temperature in the range from 80°C to 150°C, more preferably in the range from 100°C to 130°C, and at an absolute pressure in the range from 0.02 MPa to 0.50 MPa, more preferably in the range from 0.04 MPa to 0.15 MPa. Resulting from the conversion particularly a reaction mixture is obtained. 230819

[0084] 13

[0085] Preferably, a liquid mixture is conveyed into the rectification column, wherein, during the distillative separation, a vapor stream having a temperature in the range from 35°C to 120°C, especially from 50°C to 100°C, is formed at the inlet of the vapor condenser, and a bottoms product having a temperature in the range from 80°C to 160°C, especially from 80°C to 130°C, is formed in the bottom of the rectification column, and the working medium from the reboiler is fed at least partly to the vapor condenser to be cooled, as a result of which the working medium is heated in the vapor condenser, wherein the working medium at the outlet from the vapor condenser is at a temperature in the range from 35°C to 120°C, especially from 50°C to 100°C, and an absolute pressure in the range from 0.01 MPa to 0.09 MPa, preferably from 0.03 MPa to 0.07 MPa, and then the working medium is compressed by the compressor, as a result of which the working medium at the outlet from the compressor is at a temperature in the range from 100°C to 300°C, preferably from 150°C to 250°C, and an absolute pressure in the range from 0.1 MPa to 1.0 MPa. Then cooling water is preferably added to the working medium via the mixing element in such an amount that a temperature at the inlet of the reboiler in the range from 80°C to 200°C, more preferably in the range from 100°C to 160°C, further preferably in the range from 1 10°C to 160°C, is established. 230819

[0086] 14 cerium, nickel, and chromium salts, for example chlorides, sulfates, salicylates, tosylates, acrylates or acetates, for example copper acetate, copper(ll) chloride, copper salicylate, cerium(lll) acetate or cerium(lll) ethylhexanoate, or mixtures thereof.

[0087] The polymerization inhibitor or polymerization inhibitor mixture used in the preparation of (meth)acrylates is preferably at least one compound from the group of 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, hypo- phosphorous acid, copper(ll) acetate, copper(l) chloride, copper(ll) chloride, copper(ll) salicylate and cerium(lll) acetate.

[0088] Preference is given to using phenothiazine (PTZ) and / or hydroquinone monomethyl ether (MEHQ) and / or HO-Tempo as polymerization inhibitor in the preparation of n-butyl (meth)acrylate.

[0089] The polymerization inhibitor is preferably dissolved in one or more liquid organic compounds. The organic compound is preferably the alcohol and / or the (meth)acrylate.

[0090] Suitable esterification catalysts in the preparation of (meth)acrylates include 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, but acidic ion exchangers or zeolites are also usable.

[0091] Particular preference is given to using, in the preparation of (meth)acrylates, sulfuric acid, methanesulfonic acid, p- toluenesulfonic acid, m-toluenesulfonic acid, o-toluenesulfonic acid or mixtures thereof.

[0092] Very particular preference is given to using p-toluenesulfonic acid as esterification catalyst in the preparation of the (meth)acrylate, in particular n-butyl (meth)acrylate. In the reaction zone, which is preferably within the reactor, the content thereof based on the reaction mixture present therein is appropriately 0.1 wt.-% to 10.0 wt.-%, preferably 0.1 wt.-% to 6.0 wt.-%. Other organic acids such as methanesulfonic acid, benzenesulfonic acid, dodecylsulfonic acid and / or sulfuric acid are likewise usable. The amount thereof is preferably 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 therein may advantageously be between 2.5 wt.-% and 50.0 wt.-% of paratoluenesulfonic acid or an equivalent amount of another organic sulfonic acid and / or sulfuric acid.

[0093] An embodiment of the invention and comparative embodiments are illustrated in the figures and further described in the following. 230819

[0094] 15

[0095] The figures show:

[0096] Figure 1 a schematic process flow diagram of an illustrative distillation plant for preparation of a (meth)acrylate using a heat pump according to the state of the art,

[0097] Figure 2 an embodiment of a section of a device for production of a polymerizable substance, wherein different steam streams are combined and

[0098] Figure 3 a comparative embodiment of a device for production of a polymerizable substance.

[0099] Figure 1 shows a schematic view of a process flow diagram of an illustrative process according to the state of the art for preparing polymerizable substances such as a (meth)acrylate, in which a mixture resulting from a reaction zone is conveyed into a rectification column 1 .

[0100] At the top of the rectification column 1 , a vapor stream is discharged. In a vapor condenser 3, the vapor stream is partly condensed to form an organic phase and an aqueous phase. The vapor condenser 3 here is an upright shell- and-tube heat exchanger, wherein one or more polymerization inhibitor(s) present in a solution are added. The vapor condenser 3 is equipped with spray nozzles to distribute the polymerization inhibitor(s). This directly stabilizes the vapor stream on condensate formation, which efficiently prevents polymer formation.

[0101] A further second vapor condenser 4 downstream of the vapor condenser 3 condenses the low boilers remaining in the vapor stream, which results in complete condensation of the vapor stream in the second vapor condenser 4.

[0102] Subsequently, the condensate is fed to a phase separator 5. The organic phase is partly returned to the rectification column 1 and a remaining portion of the organic phase is discharged from the distillation unit 22. The aqueous phase is partly recycled to the rectification column 1 and a remaining proportion of the aqueous phase is discharged from the distillation unit 22.

[0103] A reboiler 2 heats the bottoms of the rectification column 1 . A portion of the bottom liquid flows through the reboiler 2 and is then returned back to the bottom. Part of the bottom liquid is withdrawn from the distillation unit 22.

[0104] The first vapor condenser 3 is cooled by the working medium that flows through it in a heat pump circuit 26. The working medium flows from the outlet of the vapor condenser 3 through a water separator 6 to a compressor 7. The water separator 6 includes a demister. The compressor 7 comprises a first compression stage 15 and a second compression stage 12. The compressor 7 compresses the working medium. The working medium then flows from the outlet of the compressor 7 into a mixing element 8. The working medium then flows from the mixing element 8 to the inlet of the reboiler 2. Subsequently, the working medium flows from the outlet of the reboiler 2 into a condensate vessel 9. A pump 14 conveys a substream of the working medium that serves as cooling water to the mixing element 8. The mixing element 8 then adds the working medium that serves as cooling water to the working medium that flows in from the compressor 7.

[0105] By means of the pump 14 a further substream of the working medium that serves as cooling water is conveyed from the condensate vessel 9 to the intermediate-stage mixing element 10. A liquid droplet separator 11 which is connected downstream of the intermediate-stage mixing element 10, and which preferably comprises a wire mesh, protects the second compression stage 12 from liquid droplets.

[0106] By means of the pump 14, a further substream of the working medium is conveyed from the outlet of the condensate vessel 9 to the inlet of the water separator 6, where the working medium is preferably expanded by means of an expansion valve 16 prior to entry or on entry into the water separator 6. Subsequently, the working medium is conveyed by a pump 13 from the water separator 6 to the vapor condenser 3.

[0107] It is also possible to add external steam, serving as working medium, upstream of the reboiler 2. Further, it is possible to add external water, serving as working medium, to the water separator 6.

[0108] A part of the working medium may be removed from the heat pump circuit 26 if, for example, too great pressure builds up in the heat pump circuit 26 or the working medium is to be exchanged.

[0109] Figure 2 shows an embodiment of a section of a device 19 for production of a polymerizable substance, wherein different steam streams 30, 32 are combined.

[0110] The device 19 for production of the polymerizable substance comprises at least one steam consumer 20, such as a reboiler 2, and a distillation unit 22 comprising a rectification column 1 having a vapor condenser 3 and a second vapor condenser 4. The at least one steam consumer 20 is heated by the heat pump circuit 26.

[0111] The feed mixture 24 comprising the polymerizable substance is fed into the distillation unit 22, wherein the heat pump circuit 26 having a compressor 7 which fluidically connects the at least one steam consumer 20 and the vapor condenser 3. The at least one steam consumer 20 is heated by the heat pump circuit 26 and the vapor condenser 3 is cooled by the heat pump circuit 26. Water is used as working medium in the heat pump circuit 26.

[0112] A working medium mix 28 is fed to the compressor 7 and the working medium mix 28 is generated by withdrawing a first steam stream 30 from the vapor condenser 3 and addition of a second steam stream 32 to the first steam stream 230819

[0113] 17

[0114] 30. The first steam stream 30 is provided at a first pressure level P1 and with a first temperature T 1 and the second steam stream 32 is provided at a second pressure level P2 and with a second temperature T2. The second pressure level P2 is higher than the first pressure level P1 and the second temperature T2 is higher than the first temperature T1.

[0115] The second steam stream 32 is withdrawn from a collection vessel 34 of a condensation system 36, wherein several liquid condensate streams 38 are depressurized and collected in the collection vessel 34. A feed line 44 fluidically connects the collection vessel 34 with the compressor 7. The second steam stream 32 is passed through an expansion valve 16. The liquid condensate streams 38 originate from additional steam consumers 40 in the condensation system 36 and from the at least one steam consumer 20 of the distillation unit 22. Part of the additional steam consumers 40 are heated by the heat pump circuit 26. The liquid condensate streams 38 are partially evaporated in the collection vessel 34. Part of a resulting remaining liquid condensate 42 is fed from the collection vessel 34 at least partially to the vapor condenser 3.

[0116] A mixing element 8 is disposed between the compressor 7 and the at least one steam consumer 20 and the working medium is cooled by adding a cooling water to the mixing element 8. The working medium partly serves as cooling water and is taken for this purpose from a subregion of the heat pump circuit 26 that extends from the at least one steam consumer 20 to the vapor condenser 3 in the flow direction of the working medium. Here, part of the resulting remaining liquid condensate 42 from the collection vessel 34 is taken as cooling water.

[0117] Figure 3 shows a comparative embodiment of a device for production of a polymerizable substance. The comparative embodiment corresponds to a large extend to the embodiment shown in figure 3. However, no steam is fed from the condensation system 36, namely the collection vessel 34, into the heat pump circuit 26 and the compressor 7. Nonetheless, remaining liquid condensate 42 from the collection vessel 34, for example originating from additional steam consumers 40 of the condensation system 36, might be used to refill the liquid level of the heat pump circuit 26. The second steam stream 32 is condensed by an additional condenser 48, which is attached to the collection vessel 34. The heat removed from the second steam stream 32 by the additional condenser 48 is release to the environment.

[0118] To ensure safe operation of the compressor 7 and superheating of the compressor feed 45, part of the compressed working medium is recycled via a compressor loop line 46.

[0119] Examples and comparative examples

[0120] As illustrative example, the process for production of n-butyl acrylate is simulated by thermodynamic simulations. For this purpose, the Aspen Plus® software (Aspen) can be used, which can be found at the website https: / / www.aspentech.com. Aspen is an extensive simulation software package which is used for modeling, Simula- 230819

[0121] 18 tion and optimization of chemical processes and plants in industry. Aspen has extensive model databases for modelling of basic operations and substance databases for the physical properties of many different substances.

[0122] Example

[0123] A thermodynamic simulation of an inventive embodiment of the process for preparing n-butyl acrylate using a distillation plant according to figure 2 gives the following results:

[0124] A feed mixture from a reactor is fed to a rectification column comprising dual flow trays. At the top of the rectification column, a vapor stream is withdrawn at a temperature of 95.2°C. The mass flow rate of the vapor stream is 39 860 kg / h and the vapor stream is condensed in two upright shell-and-tube heat exchangers. An organic phase and an aqueous phase are obtained in a phase separator and partly recycled into the rectification column. The condensate of the vapor stream has a temperature of 32°C.

[0125] The organic phase that forms is returned to the rectification column at a mass flow rate of 7 642 kg / h and withdrawn from the distillation unit at a mass flow rate of 17 230 kg / h. The aqueous phase that forms is returned to the rectification column at a mass flow rate of 16 500 kg / h and separately withdrawn from the distillation unit at a mass flow rate of 1 997 kg / h.

[0126] A bottom liquid from the rectification column is heated to a temperature between 110°C and 130°C by a reboiler and returned to the rectification column. A mass flow rate of about 15 t / h is withdrawn from the distillation unit at the bottom at a temperature between 110°C and 130°C.

[0127] The first of the two vapor condensers (vapor condenser 3) is cooled by the working medium that flows through the heat pump circuit. The mass flow rate of the working medium into the first vapor condenser is 1 819 t / h at a temperature of 84.7°C. The working medium downstream of the first vapor condenser is at a temperature of 85°C and an absolute pressure of 578 hPa. The working medium used is water.

[0128] Parts of the working medium flows from the outlet of the first vapor condenser via a liquid droplet separator to a compressor as a first steam stream.

[0129] In a collection vessel of a condensation system liquid condensate streams are depressurized, partly evaporated and collected. The resulting gaseous phase is withdrawn from the collection vessel as a second steam stream with a mass flow of 4 t / h, at a temperature of 99.8°C and at a pressure of 1 010 hPa; and led to the compressor. The second steam stream is expanded at an expansion valve and mixed with the first steam stream to form a working medium mix, which is fed to the compressor. The working medium mix entering the compressor has a temperature of 86.2°C, a pressure of 552 hPa and mass flow of 22 600 kg / h. 19

[0130] The compressor compresses the working medium mix such that the working medium is at an absolute pressure of 2 900 hPa and a temperature of 190°C at the outlet from the compressor.

[0131] The working medium flows from the outlet of the compressor to a steam jet nozzle that functions as mixing element. Subsequently, the working medium flows from the steam jet nozzle to the inlets of the reboilers. By virtue of the mixing element, part of the working medium that serves as cooling water is added, such that the working medium at the inlet of the reboiler of the distillation unit, designed as a shell-and-tube evaporator, is at a temperature of 150°C, an absolute pressure of 2 800 hPa and a mass flow rate of 21 580 kg / h. This is achieved in that a pump conveys a substream of condensate, serving as cooling water, from the collection vessel at a mass flow rate of 2 623 kg / h and at a temperature of 99.9°C to the mixing element and the compressor for interstage cooling. The temperature difference between the working medium being fed from the compressor into the mixing element and the working medium downstream of the mixing element is 40°C.

[0132] A remaining part of the working medium from the outlet of the mixing element, which is not conveyed to the reboiler of the distillation unit, is fed to two additional steam consumers with a mass flow of 3 648 kg / h.

[0133] Further, a substream of condensate from the collection vessel is conveyed at a mass flow rate of 18 600 kg / h and at a temperature of 98.9°C to the liquid droplet separator. Before the entry into the droplet separator this substream is added to the working medium, which is withdrawn from the first vapor condenser. In the liquid droplet separator, the working medium is present at a pressure of 569 hPa. From the liquid droplet separator, the first steam stream is led to the compressor together with the second steam stream.

[0134] An energy amount of 11 .3 MW is regained from the product stream at the first vapor condenser and the compressor is run with an energy demand of 2.6 MW.

[0135] Comparative example

[0136] A thermodynamic simulation of a comparative embodiment of a process for preparing n-butyl acrylate was effectuated, wherein a distillation plant according to figure 3 was applied. With the exception of the features specified hereinafter, this comparative example is set up in line with the example above.

[0137] The working medium withdrawn from the first vapor condenser is not mixed with steam from the collection vessel before entering the compressor. No steam is withdrawn from the collection vessel. Instead of mixing steam from different sources, part of the compressed working medium is recycled via a compressor loop line from the outlet to the inlet of the compressor in order to superheat the feed which enters the compressor. Thus, 326 kg / h of com- pressed steam at a temperature of 190°C and a pressure of 2 900 hPa is recycled back from the outlet of the compressor to the inlet of the compressor.

[0138] In this comparative example, 18 930 kg / h of the working medium withdrawn from the first vapor condenser enters the compressor with a temperature of 86.2°C and a pressure of 552 hPa. Accordingly, only a reduced mass flow of 20 790 kg / h of the working medium, having the required temperature of 150°C and absolute pressure of 2 800 hPa, is available to be fed into the reboiler of the distillation unit. No additional steam consumers are served with the working medium from the heat pump circuit of the distillation column and additional steam from the auxiliary supply net has to be conveyed to the reboiler of the distillation unit in order to achieve required temperatures in the bottom of the distillation unit. All other mass flows, temperatures and pressure levels given for the example above remain unchanged for the comparative example.

[0139] Compared to a total of 25 228 kg / h (21 580 kg / h + 3 648 kg / h) of compressed steam produced by the compressor, corresponding to 15.5 MW, as obtained in the example described above, the available amount of steam at the same energy level applying the comparative setup was reduced to 20 790 kg / h, corresponding to 12.8 MW.

[0140] In this comparative example, an energy amount of 11 .3 MW is regained at the first vapor condenser and at the compressor an energy input of 2.3 MW is required.

[0141] The overall difference of 2.4 MW ((15.5 MW - 2.6 MW) - (12.8 MW - 2.3 MW)) in terms of energy supply has to be additionally delivered from external energy sources to operate the reboiler of the distillation unit. The coefficient of performance (COP) of the heat pump is reduced from 6.0 to 5.6 in the comparative example.

[0142] All pressures are given in absolute pressures, where not stated otherwise.

[0143] 230819

[0144] 21

[0145] List of reference numerals

[0146] 1 rectification column

[0147] 2 reboiler

[0148] 3 vapor condenser

[0149] 4 second vapor condenser

[0150] 5 phase separator

[0151] 6 water separator

[0152] 7 compressor

[0153] 8 mixing element

[0154] 9 condensate vessel

[0155] 10 intermediate-stage mixing element between two compression stages

[0156] 11 liquid droplet separator between two compression stages

[0157] 12 second compression stage of a compressor

[0158] 13 pump for conveying the working medium from the water separator to the vapor condenser

[0159] 14 pump for conveying the working medium from the condensate vessel to the water separator

[0160] 15 first compression stage of the compressor

[0161] 16 expansion valve

[0162] 19 device for production of a polymerizable substance

[0163] 20 steam consumer

[0164] 22 distillation unit

[0165] 24 feed mixture

[0166] 26 heat pump circuit

[0167] 28 working medium mix

[0168] 30 first steam stream

[0169] 32 second steam stream

[0170] 34 collection vessel

[0171] 36 condensation system

[0172] 38 liquid condensate stream

[0173] 40 additional steam consumer

[0174] 42 remaining liquid condensate

[0175] 44 feed line

[0176] 45 compressor feed

[0177] 46 compressor loop line

[0178] 48 additional condenser

Claims

23081922Claims1 . Process for distillation of a feed mixture (24), comprising a polymerizable substance, in a device (19) for production of the polymerizable substance, wherein the device (19) for production of the polymerizable substance comprises at least one steam consumer (20), in particular at least one reboiler (2), and a distillation unit (22) comprising a rectification column (1) having a vapor condenser (3), wherein the feed mixture (24) comprising the polymerizable substance is provided in the distillation unit (22), wherein a heat pump circuit (26) having a compressor (7) which fluidically connects the at least one steam consumer (20) and the vapor condenser (3), the at least one steam consumer (20) is heated by the heat pump circuit (26) and the vapor condenser (3) is cooled by the heat pump circuit (26) and water is used as working medium in the heat pump circuit (26), wherein a working medium mix (28) is fed to the compressor (7) and the working medium mix (28) is generated by withdrawing a first steam stream (30) from the vapor condenser (3) and addition of a second steam stream (32) to the first steam stream (30), wherein the first steam stream (30) is provided at a first pressure level P1 and with a first temperature T 1 and the second steam stream (32) is provided at a second pressure level P2 and with a second temperature T2, wherein the second pressure level P2 is higher than the first pressure level P1 and the second temperature T2 is higher than the first temperature T 1 , and wherein the second steam stream (32) is withdrawn from a collection vessel (34) of a condensation system (36), wherein at least one liquid condensate stream (38) is depressurized and collected in the collection vessel (34).

2. Process according to claim 1 , wherein the working medium mix (28) has an inlet temperature TO at the inlet of the compressor (7) and the inlet temperature TO is at least 1 °C higher than the dew point temperature Tdw of the working medium mix (28) at the suction pressure P0 of the working medium mix at the inlet of the compressor (7).

3. Process according to claims 1 or 2, wherein the at least one liquid condensate stream (38) is at least partially evaporated in the collection vessel (34).

4. Process according to any of claims 1 to 3, wherein the at least one liquid condensate stream (38) originates from additional steam consumers (40) in the condensation system (36) and / or from the at least one steam consumer (20), in particular of the distillation unit (22).

5. Process according to any of claims 1 to 4, wherein liquid condensate streams (38) from at least two different steam consumers (20, 40) are collected in the collection vessel (34).230819236. Process according to any of claims 1 to 5, wherein the at least one steam consumer (20) and optionally the additional steam consumers (40) are steam heated heat exchangers, in particular reboilers (2).

7. Process according to any of claims 1 to 6, wherein one of the at least one steam consumer (20) is a reboiler (2) of the rectification column (1) and the reboiler (2) of the rectification column (1) is heated by the heat pump circuit (26).

8. Process according to any of claims 1 to 7, wherein the first pressure level P1 is at less than 1000 hPa.

9. Process according to any of claims 1 to 8, wherein the first temperature T 1 is less than 100°C, the second temperature T2 is less than 130°C and / or the at least one liquid condensate stream (38) has a third temperature T3 at the inlet of the collection vessel, which is 90°C or higher.

10. Process according to any of claims 1 to 9, wherein the at least one liquid condensate stream (38) is depressurized from a third pressure level P3 to the second pressure level P2 and the third pressure level P3 differs from the second pressure level P2 by at least 200 hPa.

11. Process according to any of claims 1 to 10, wherein the working medium mix (38) consists to 50 wt.-% to 95 wt.- % of the first steam stream (30) and to 5 wt.-% to 50 wt.-% of the second steam stream (32).

12. Process according to any of claims 1 to 11 , wherein 5 wt.-% to 50 wt.-% of the at least one liquid condensate stream (38), referring to the total of the at least one liquid condensate stream (38), is evaporated in the collection vessel (34).

13. Process according to claim 12, wherein at least part of the remaining liquid condensate (42) is fed from the collection vessel (34) at least partially to the vapor condenser (3).

14. Process according to any of claims 1 to 13, wherein a mixing element (8) is disposed between the compressor (7) and the at least one steam consumer (20), wherein the working medium is cooled by adding a cooling water in such an amount that, at the inlet of the at least one steam consumer (20), a temperature of the working medium in the range from 100°C to 200°C, in particular from 110°C to 200°C, is established, wherein in particular the working medium serves partly as cooling water and the working medium that serves as cooling water is taken from a subregion of the heat pump circuit (26) that extends from the at least one steam consumer (20) to the vapor condenser (3) in the flow direction of the working medium, for example from the collection vessel (34).

15. Process according to any of claims 1 to 14, wherein the polymerizable substance is selected from the group consisting of (meth)acrylates, (meth)acrylic acid, styrenes and mixtures thereof, in particular n-butyl (meth)acrylate.2308192416. Process according to any of claims 1 to 15, wherein the process further comprises the following steps: conversion of (meth)acrylic acid with an alcohol to a (meth)acrylate by esterification in presence of an acidic catalyst and a polymerization inhibitor, wherein the feed mixture (24) is obtained, providing the feed mixture (24) comprising the (meth) acrylate in the rectification column (1), in particular separating the water of esterification formed in the conversion from the feed mixture (24) within the rectification column (1), discharging a gaseous vapor stream, in particular enriched by the water of esterification, at the top of the rectification column (1), and condensing the vapor stream in the vapor condenser (3) to form an organic phase and an aqueous phase, wherein the vapor condenser (3) is cooled by the working medium, and the working medium at the outlet from the vapor condenser (3) is at a temperature in the range from 35°C to 100°C, and feeding at least part of the working medium from the outlet of the vapor condenser (3) to the compressor (7) together with the second steam stream (32), wherein the working medium mix (28) is compressed within the compressor (7) and the working medium mix (28) at the compressor (7) outlet is at a temperature in the range from 100°C to 300°C and an absolute pressure in the range from 1000 hPa to 10000 hPa, wherein optionally the mixing element (8) cools the working medium mix by adding the cooling water at a temperature in the range from 1 °C to 160°C to the working medium mix (28) in such an amount that, at the inlet of the at least one steam consumer (20), the working medium mix (28) is at a temperature in the range from 100°C to 200°C, in particular from 110°C to 200°C.

17. Device (19) for carrying out the process according to any of claims 1 to 16, comprising at least one steam consumer (20), a rectification column (1) having a vapor condenser (3), a heat pump circuit (26) having a compressor (7), which fluidically connects the at least one steam consumer (20) and the vapor condenser (3), and a condensation system (36) with a collection vessel (36) and a feed line (44) which fluidically connects the collection vessel (34) with the compressor (7).

Images