Device and method for the preparation of process medium

Abstract

Device for the treatment of water-based process media (pm) by evaporation, comprising a primary evaporator (1) configured to separate the process medium (pm) into distillate (d) and pre-concentrate (vk); and a secondary evaporator (2) configured to separate the pre-concentrate (vk) into vapors (b) and concentrate (k), characterized by the fact that the primary evaporator (1) is heated by isobaric recirculation of the vapor (b) generated in the secondary evaporator (2), the isobaric recirculation is carried out by isobaric guidance of the vapor (b) into the primary evaporator (1) or a heat exchanger (4) thermally coupled to the primary evaporator (1), so that the primary evaporator (1) is heated with the energy of the vapor (b) generated in the secondary evaporator (2), and the primary evaporator (1) and, if applicable, the secondary evaporator (2) comprises an atmospheric evaporator designed to operate at atmospheric pressure up to a negative or positive pressure in the range of -100mbar to 100mbar.

Description

[0001] The present invention relates to a device and a method for the treatment of water-based process media by evaporation, in particular vapor compression.

[0002] Water-based process media originate from industrial plants and / or product manufacturing and are mixed with oils, salts, detergents, or similar substances. Examples include cooling lubricant emulsions, die-casting emulsions, floor cleaning water, washing and degreasing baths, rinsing baths, or paint pretreatment systems, as well as wastewater from pickling processes for metal surface treatment.

[0003] Conventional processes and systems for treating water-based process media, such as those known from DE 10 2012 203 439 A1, DE 3 935 892 A1, EP 0 022 181 A2, or DE 419 432 A, use single- or multi-stage evaporators to separate the process medium into a distillate and a concentrate. The distillate can be returned to the process or discharged. In conventional single-stage evaporators, the concentrate can contain, for example, approximately 65 to 40% water and approximately 35 to 60% residues such as oils and salts.

[0004] There are generally two different approaches to separating aqueous process media using evaporators: atmospheric evaporation and evaporation under (partial) vacuum. In conventional atmospheric evaporators, the energy required to evaporate the process water is supplied mechanically by compressing the vapor and thermally by means of a heater. Atmospheric evaporators operate at atmospheric pressure up to a negative or positive pressure of ±100 mbar. In vacuum evaporators, the required energy is supplied through compression, but usually without thermal energy being supplied by means of a heater. This requires a greater volume change than atmospheric evaporation but usually eliminates the need for additional thermal heating.

[0005] A characteristic of conventional evaporators is the required additional heating, which requires a high energy input. Attempts to achieve higher concentrate concentrations through increased evaporation of the process medium using a multi-stage evaporator setup significantly exacerbate this disadvantage.

[0006] The present invention is therefore based on the object of providing a device and a method for the treatment of water-based process media by evaporation, in particular vapor compression, in order to increase the concentration of the concentrate in an economical manner compared to the known solutions.

[0007] This object is achieved according to the invention by the features of the independent claims. Preferred embodiments of the invention are the subject of the dependent claims.

[0008] A device according to the invention for the treatment of water-based process media by evaporation / vapor compression comprises a primary evaporator which is configured to separate the process medium into distillate and pre-concentrate and a secondary evaporator which is configured to separate the pre-concentrate into vapors and concentrate, wherein the primary evaporator is heated by isobaric recirculation of the vapors generated in the secondary evaporator.

[0009] Isobaric vapor recirculation, in the context of the present invention, means that the vapor is conducted under virtually identical pressure conditions, i.e., without any active pressure change. In other words, isobaric recirculation means the removal of vapor from the secondary evaporator without an intermediate compressor arrangement or stage. Depending on the energy loss during vapor conduction, for example, in a vapor line, a pressure drop of a few mbar is inevitable during vapor recirculation. In any case, the vapor pressure is at least not actively changed by means of a compressor arrangement or the like.

[0010] The decisive factor in the context of the present invention is to recycle the energy of the vapor generated in the secondary evaporator to heat the primary evaporator, wherein the recovery of the energy stored in the vapor takes place under isobaric guidance (i.e. without active pressure change) of the vapor.

[0011] This creates a multi-stage evaporator arrangement that can be operated without any significant additional energy consumption compared to single-stage evaporators. At the same time, greater concentration is achieved. On the one hand, the provision of the secondary evaporator requires additional energy. However, because the vapor is recirculated from the secondary evaporator, the additional energy stored in the vapor can be fed back into the process. This means that when the vapor condenses again, condensation heat is released, which previously had to be introduced as heat of evaporation in the secondary evaporator. Only a small amount is lost as heat in the concentrate and as system-related waste heat. Compared to conventional solutions, the heating is essentially outsourced to the downstream secondary evaporator.

[0012] Thus, a higher concentration of the concentrate can be achieved in an economical way.

[0013] A preferred option for isobaric recirculation is the direct isobaric flow of the vapor into the primary evaporator. This is achieved, for example, by directly coupling the primary evaporator with the secondary evaporator on the vapor side. This allows a natural pressure gradient to be utilized without the need for an additional compressor, which would require additional energy. The primary evaporator can be heated with the energy of the vapor generated in the secondary evaporator, for example, by condensing the vapor in a heat exchanger located in or on the primary evaporator, which then feeds the released condensation energy into the process medium treatment process.

[0014] However, the energy recovery from the vapor does not necessarily have to take place directly in or at the primary evaporator, but can also occur via vapor recirculation. This means that during isobaric recirculation, the vapor can be isobarically guided into a heat exchanger thermally coupled to the primary evaporator, which can also be located outside the primary evaporator. This thermal coupling ultimately allows the primary evaporator to be heated using the energy from the vapor generated in the secondary evaporator.

[0015] Energy recovery is therefore achieved by extracting energy from the vapor directly in / at the primary evaporator or during recirculation.

[0016] After energy recovery, the vapor condensate is preferably discharged together with the distillate separated in the primary evaporator and / or introduced into the process medium to be treated for redistillation.

[0017] Particularly in the treatment of cooling lubricant emulsions, increasing concentration of the pre-concentrate can lead to increased vapor contamination. If this vapor were introduced directly into the distillate circuit of the primary evaporator, this could degrade the quality of the distillate. This can be prevented by introducing the (reliquefied) vapor into the process medium being treated. Alternatively, the (reliquefied) vapor can be discharged with the distillate discharged from the primary evaporator. This would be preferable in terms of a favorable material balance. In principle, the discharge or discharge of the (reliquefied) vapor can be determined depending on quality requirements, economic aspects, and the type of process medium being treated.

[0018] Preferably, the primary evaporator is heated exclusively by the energy from the vapor generated in the secondary evaporator. This avoids additional heating of the primary evaporator by completely outsourcing the heating to the secondary evaporator.

[0019] Further preferably, the concentrate has a residual water content of a maximum of 50%, preferably a maximum of 20%, even more preferably between 10 and 15%. In principle, the achievable concentration varies depending, among other things, on the type of process medium or on economic considerations. In the case of cooling lubricants, for example, a concentration to the aforementioned residual water content leads to a significantly increased oil content in the concentrate. A concentrate with such a high concentration can then be thermally recycled in cement production or waste incineration. Due to the low residual water content, an economically viable material recycling of, for example, oils and salts in the concentrate can also take place. This allows the concentrate to be put to further use in an economical manner and does not have to be disposed of expensively by waste disposal companies or processed in further process steps.

[0020] According to the invention, the primary evaporator and, optionally, the secondary evaporator comprise an atmospheric evaporator. This is configured to operate at approximately atmospheric pressure down to a negative or positive pressure in the range of -100 mbar to 100 mbar, preferably up to an overpressure of approximately 50 mbar, more preferably 30 mbar. As already described, conventional vacuum evaporators operate in a vacuum and use a large portion of the input energy for compression. This means that, compared to atmospheric evaporators, significantly less energy is required in the form of heating power. Atmospheric evaporators require more heating power and less compression power. Therefore, with atmospheric evaporators, excess energy in the form of heat can be utilized more efficiently, particularly in the primary evaporator.

[0021] The device according to the invention preferably comprises a throttle / nozzle system downstream of a heating element with flow around it, preferably designed as an annular gap, in order to separate the pre-concentrate as a superheated medium in the secondary evaporator into vapors and concentrate, in particular by flash evaporation. The pre-concentrate to be concentrated can be conveyed via a heating element, for example, using a circulation pump. The throttle / nozzle system arranged downstream of the heating element prevents evaporation of the pre-concentrate from occurring at the heating element. In particular, the pre-concentrate heated to a temperature above its evaporation point or superheated can be injected into a container via a throttle valve, whereby water evaporates. The residual concentrate returns to the circuit until the desired concentration is reached.Consequently, a high pressure above the vaporization point is built up before the throttle / nozzle. Downstream of the throttle / nozzle, the pre-concentrate expands suddenly and is immediately vaporized. This type of vaporization is called "flash vaporization" or "expansion vaporization."

[0022] The further preferred provision of an annular gap prevents the risk of deposits and incrustations forming due to the concentrated process medium. In other words, with increasing concentration of the process medium, or with decreasing residual water content, the risk of incrustations and deposits forming increases. In this regard, the provision of an annular gap offers a cleaning effect around the heater due to high flow velocities and shear forces.

[0023] Even more preferably, the device according to the invention further comprises a buffer which is interposed between the primary evaporator and the secondary evaporator and is configured to temporarily store at least a portion of the pre-concentrate. Firstly, such a buffer can compensate for production fluctuations of the upstream primary evaporator, thereby enabling constant and consistent operation of the secondary evaporator. This is particularly advantageous in order to be able to provide the required amount of vapor for heating the primary evaporator. Secondly, during a start-up process of the device according to the invention, the secondary evaporator can initially be operated (exclusively) with pre-concentrate from the buffer. This allows heat to be generated for preheating the primary evaporator without it having to be operated under cold-start conditions from the outset.Thus, the start-up process of the device according to the invention can also be energetically optimized.

[0024] A further aspect of the present invention relates to a method for treating water-based process media by evaporation / vapor compression, with a device according to one of the preceding aspects, the method comprising the following steps: - Separation of the process medium in a primary evaporator into distillate and pre-concentrate; and - Separation of the pre-concentrate into vapors and concentrate in a secondary evaporator, whereby the primary evaporator is heated by isobaric recirculation of the vapors produced in the secondary evaporator.

[0025] The process medium is separated in the primary evaporator and optionally the pre-concentrate in the secondary evaporator at atmospheric pressure up to a negative or positive pressure in the range of -100 mbar to 100 mbar, preferably up to an overpressure of about 50 mbar, more preferably 30 mbar.

[0026] More preferably, the primary evaporator is heated exclusively by the isobaric recirculation of the vapor generated in the secondary evaporator.

[0027] It may prove advantageous if the pre-concentrate is separated into vapors and concentrate in the secondary evaporator as a superheated medium by flash evaporation, in particular after passing through an annular gap.

[0028] Further preferably, at least a portion of the pre-concentrate is temporarily stored in a buffer before being separated into vapors and concentrate in the secondary evaporator. When starting up the treatment of the process medium, the pre-concentrate initially temporarily stored exclusively in the buffer is preferably separated into vapors and concentrate in the secondary evaporator. Short description of the characters

[0029] They show: Fig. 1 is a schematic block diagram of an inventive device according to a first embodiment of the present invention. Fig. 2 a schematic block diagram of an inventive device according to a second embodiment of the present invention. Fig. 3 is a schematic block diagram of an inventive device according to a third embodiment of the present invention. Detailed description of preferred embodiments

[0030] A first preferred embodiment of the invention will be described below with reference to the attached Fig. 1 described in detail.

[0031] Fig. Figure 1 shows a schematic block diagram of a two-stage evaporator arrangement with which a water-based process medium pm, such as a cooling lubricant emulsion, can be treated. The process medium pm, for example, has a water content of approximately 95%.

[0032] The evaporator arrangement comprises two evaporators, ie an upstream primary evaporator 1 and a secondary evaporator 2 downstream of the primary evaporator 1. In the present preferred embodiment, both evaporators 1, 2 are atmospheric evaporators in which the medium to be evaporated is essentially evaporated by supplying heat under atmospheric pressure (up to a slight overpressure of, for example, about 30 mbar).

[0033] The process medium pm is first introduced into the primary evaporator 1 via an inlet and circulates therein, preferably by means of a mechanical drive, such as a circulation pump. With the addition of heat energy, the process medium pm in the circuit of the primary evaporator 1 is separated into distillate d and pre-concentrate vk. A portion of the process medium pm evaporates and, after reliquefaction, can be discharged as distillate d. This can be returned to industrial plants for reuse. As soon as the pre-concentrate vk reaches a typical residual water content, for example, 65%, it is discharged and introduced into the secondary evaporator 2.

[0034] In the secondary evaporator 2, the pre-concentrate vk to be concentrated is heated in a heating circuit and conveyed, for example, with the help of a circulation pump via a heating element. The preferential provision of an annular gap reduces the risk of deposits and incrustations forming due to the high concentration of the process medium. The heating element heats the pre-concentrate vk to a temperature above its evaporation point or sprays it into a container as a superheated medium via a throttle valve. Consequently, a high pressure above the evaporation point is built up upstream of the throttle / nozzle. Downstream of the throttle / nozzle, the superheated medium suddenly expands and is immediately evaporated. This type of evaporation is also referred to as "flash evaporation" or "expansion evaporation". During this process, the pre-concentrate vk to be concentrated is evaporated.More precisely, a portion evaporates, which is discharged as vapor b, and the residual concentrate is then returned to the circuit of the secondary evaporator 2 until a desired (final) concentration is reached. This residual concentrate contains, for example, a residual water content of a maximum of 50%, preferably a maximum of 20%, more preferably between 10 and 15%, i.e., for example, an oil content of 70-90%. Once the desired final concentration is reached, the concentrate k is discharged from the circuit of the secondary evaporator 2.

[0035] The vapor b generated in the secondary evaporator 2 is fed to the primary evaporator 1. According to the invention, this occurs under essentially isobaric conditions. This means that the vapor b generated in the secondary evaporator 2 is passed through a line without active recompression, i.e., without the aid of a compressor stage or the like, into a heat exchanger located in the primary evaporator 1. There, the vapor b condenses, allowing the process medium pm in the primary evaporator 1 to be heated by the condensation heat released from the vapor b.

[0036] The energy introduced into the secondary evaporator 2 for evaporating the pre-concentrate vk is stored almost entirely in the vapor b. Only small amounts are lost through residual heat from the concentrate k and through plant-specific waste heat. Thus, a large portion of the energy that must be introduced into the secondary evaporator 2 for evaporating the pre-concentrate vk can be recovered through the condensation of the vapor b described above. This enables the generation of the heating power required in the primary evaporator 1 to be outsourced, preferably completely, to the downstream evaporator stage, i.e., to the secondary evaporator 2.

[0037] After the condensation heat has been released, the (reliquefied) vapor b can preferably be introduced as distillate into the process media circuit of primary evaporator 1 to be treated. Particularly when treating cooling lubricant emulsions, increasing concentration of the preconcentrate vk can lead to increased contamination of the vapor b. If this were introduced directly into the distillate circuit of primary evaporator 1, this could impair the quality of distillate d. This can be prevented by introducing the (reliquefied) vapor b into the process media circuit of primary evaporator 1.

[0038] However, this procedure is not mandatory. Alternatively, the (reliquefied) vapor b can be introduced into the distillate d, which is discharged from the primary evaporator 1. This would be preferable in terms of a favorable material balance.

[0039] In principle, the discharge or introduction of the (reliquefied) vapor b can be determined depending on economic aspects and the type of process medium pm to be treated.

[0040] In the following, a modification of the above-described embodiment will be described with reference to the Fig. 2. Except for the differences described below, the device and the method within the modified embodiment correspond to the first embodiment.

[0041] In order to respond to possible operating fluctuations and further improve energy efficiency, an additional buffer 3 can be provided.

[0042] This is located downstream of the primary evaporator 1 and upstream of the secondary evaporator 2. At least a portion of the pre-concentrate vk discharged from the primary evaporator 1 is temporarily stored in buffer 3. The pre-concentrate vk temporarily stored in buffer 3 can be fed into the secondary evaporator 2 as needed.

[0043] Preferably, pre-concentrate vk can continue to be fed directly from the primary evaporator 1 to the secondary evaporator 2 without being temporarily stored via the buffer 3. However, it is also conceivable to supply the pre-concentrate vk discharged from the primary evaporator 1 to the secondary evaporator 2 exclusively via the buffer 3.

[0044] Buffer 3 can be used to compensate for production fluctuations (output fluctuations) of the upstream primary evaporator 1, ensuring a constant supply of pre-concentrate vk to the secondary evaporator 2. This enables constant and consistent operation of the secondary evaporator 2.

[0045] Furthermore, when the device according to the invention is switched on, the secondary evaporator 2 can first be operated by introducing the pre-concentrate vk from the buffer 3. As a result, as described above, vapor b is generated in the secondary evaporator 2, which can provide the heating energy required for the primary evaporator 1. The operation of the primary evaporator 1 can then be started. This makes it possible to provide heat for preheating and starting the primary evaporator 1 in an energy-efficient manner. This allows not only the ongoing operation but also the start-up process of the device according to the invention to be energetically optimized by also outsourcing the generation of the heating energy required for preheating and starting the primary evaporator 1 (at least partially, but preferably completely) to the secondary evaporator 2.

[0046] A further modification of the embodiments described above will be described below with reference to the Fig. 3. Except for the differences described below, the device and method within the scope of the third embodiment correspond to the first embodiment.

[0047] As already described, it is not absolutely necessary to recover the energy stored in the vapor b by directly returning the vapor b to the primary evaporator 1. As in Fig. As shown in Figure 3, the vapor b can be fed under isobaric conditions, ie, without an intermediate compressor arrangement, into a heat exchanger 4, in which it condenses. Depending on quality requirements or economic aspects, the resulting vapor condensate bk can either be introduced into the process medium pm to be treated for redistillation or added to the distillate d.

[0048] The energy stored in the vapor b, which is released in the heat exchanger 4 by condensation of the vapor b, is returned to the primary evaporator 1 by thermal coupling of the heat exchanger 4 with the primary evaporator 1 in order to heat it. As in Fig. 3, this can be achieved by passing pre-concentrate vk from the primary evaporator 1 through the heat exchanger 4 and back into the primary evaporator 1.

[0049] The third embodiment may also comprise a buffer 3 as described above with respect to Fig. 2 and the second embodiment are described. List of reference symbols 1 primary evaporator 2 secondary evaporators 3 buffers 4 heat exchangers b vapors bk vapor condensate d distillate k Concentrate pm process medium vk pre-concentrate

Claims

[1] Device for the treatment of water-based process media (pm) by evaporation, comprising a primary evaporator (1) configured to separate the process medium (pm) into distillate (d) and pre-concentrate (vk); and a secondary evaporator (2) which is designed to separate the pre-concentrate (vk) into vapors (b) and concentrate (k), characterized by , that the primary evaporator (1) is heated by isobaric recirculation of the vapor (b) generated in the secondary evaporator (2), the isobaric recirculation is carried out by isobarically guiding the vapor (b) into the primary evaporator (1) or a heat exchanger (4) thermally coupled to the primary evaporator (1), so that the primary evaporator (1) is heated with the energy of the vapor (b) generated in the secondary evaporator (2), and the primary evaporator (1) and optionally the secondary evaporator (2) comprise an atmospheric evaporator which is designed to operate at atmospheric pressure up to a negative or positive pressure in the range of -100 mbar to 100 mbar. [2] Device according to claim 1, characterized by that the primary evaporator (1) is heated exclusively by the energy of the vapor (b) generated in the secondary evaporator (2). [3] Device according to one of the preceding claims, characterized by that the concentrate (k) has a residual water content of a maximum of 50%, preferably a maximum of 20%, more preferably between 10 and 15%. [4] Device according to one of the preceding claims, characterized by that the primary evaporator (1) and / or the secondary evaporator (2) is arranged to operate at atmospheric pressure up to an overpressure of about 50 mbar, more preferably 30 mbar. [5] Device according to one of the preceding claims, comprising a throttle / nozzle system after a flow-around heating element, preferably designed as an annular gap, in order to separate the pre-concentrate (vk) as a superheated medium in the secondary evaporator (2), in particular by flash evaporation, into vapors (b) and concentrate (k). [6] Device according to one of the preceding claims, further comprising a buffer (3) which is interposed between the primary evaporator (1) and the secondary evaporator (2) and is arranged to temporarily store at least a part of the pre-concentrate (vk). [7] Method for the treatment of water-based process media (pm) by evaporation, with a device according to one of the preceding claims, comprising the steps: Separation of the process medium (pm) in a primary evaporator (1) into distillate (d) and pre-concentrate (vk); and Separation of the pre-concentrate (vk) in a secondary evaporator (2) into vapors (b) and concentrate (k), characterized by , that the primary evaporator (1) is heated by isobaric recirculation of the vapor (b) generated in the secondary evaporator (2), the isobaric recirculation is carried out by isobarically guiding the vapor (b) into the primary evaporator (1) or a heat exchanger (4) thermally coupled to the primary evaporator (1), so that the primary evaporator (1) is heated with the energy of the vapor (b) generated in the secondary evaporator (2), and the process medium (pm) in the primary evaporator (1) and, if applicable, the pre-concentrate (vk) in the secondary evaporator (2) are separated at atmospheric pressure up to a negative or positive pressure in the range of -100 mbar to 100 mbar. [8] Method according to claim 7, characterized bythat the process medium (pm) in the primary evaporator (1) and / or the pre-concentrate (vk) in the secondary evaporator (2) are separated at atmospheric pressure up to an overpressure of about 50 mbar, more preferably 30 mbar. [9] Method according to claim 7 or 8, characterized by that the primary evaporator (1) is heated exclusively by the energy of the vapor (b) generated in the secondary evaporator (2). [10] Method according to one of claims 7 to 9, characterized by that the pre-concentrate (vk) is separated in the secondary evaporator (2) as a superheated medium by flash evaporation, in particular after passing through an annular gap, into vapors (b) and concentrate (k). [11] Method according to one of claims 7 to 10, characterized by that at least a part of the pre-concentrate (vk) is temporarily stored in a buffer (3) before it is separated into vapors (b) and concentrate (k) in the secondary evaporator (2). [12] Method according to claim 11, characterized by that when the treatment of the process medium (pm) is started up, pre-concentrate (vk) temporarily stored exclusively in the buffer (3) is separated in the secondary evaporator (2) into vapors (b) and concentrate (k).

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