Loop reactor and process for manufacturing an addition product

Abstract

The invention relates to a loop reactor and to a process for manufacturing an addition product.

Description

[0001] thyssenkrupp Intellectual Property GmbH

[0002] P148589PC00

[0003] Loop reactor and process for producing an addition product

[0004] The present invention relates to a loop reactor and a method for producing an addition product.

[0005] Chlorinated alkanes, in particular 1,2-dichloroethane (hereinafter: EDC), are predominantly obtained as an intermediate in the production of monomeric vinyl chloride (hereinafter: VCM). Hydrogen chloride (HCl) is produced during the reaction of EDC to VCM. EDC is therefore preferably produced from ethylene (C₂H₄) and chlorine (Cl₂) in such a way that a balanced ratio of hydrogen chloride (HCl) produced and consumed in the reactions is achieved, according to the following reaction equations:

[0006] CI2 + C2H4 — C2H4CI2 (pure EDC) + 213 kJ / mol (1)

[0007] C2H4CI2 (gap EDC) C2H3CI (VCM) + HCl - 71 kJ / mol (2) C2H4 + 2 HCl + 72O2 C2H4CI2 (crude EDC) + H2O + 238 kJ / mol (3)

[0008] The process for producing VCM with a balanced HCI balance, hereinafter referred to as the "balanced VCM process", includes: a direct chlorination in which part of the required EDC is produced from ethylene (C2H4) and chlorine (CI2) in the presence of a homogeneous catalyst and is released as so-called pure EDC;

[0009] • an oxychlorination reaction in which the other part of the EDC is produced from ethylene C2H4, hydrogen chloride HCl and oxygen O2 and is released as so-called crude EDC;

[0010] • A fractional EDC purification process in which the crude EDC, together with the recycled EDC from VCM fractionation and optionally with the pure EDC, is purified of the byproducts formed in oxychlorination and EDC pyrolysis to obtain feed EDC suitable for use in EDC pyrolysis. Alternatively, the pure EDC from direct chlorination can also be co-distilled in the high-boiling column of the EDC distillation.

[0011] • an EDC pyrolysis in which the feed EDC is thermally cracked; the reactor output mixture, called cracking gas, contains VCM, hydrogen chloride HCl and unreacted EDC as well as byproducts;

[0012] • a VCM fractionation in which the desired pure VCM product is separated from the cracking gas and the other essential cracking gas components hydrogen chloride HCl and unreacted EDC are recovered separately as valuable materials and recirculated as reusable input as return HCl or return EDC in the balanced VCM process.

[0013] In most industrially scaled direct chlorination processes, a circulating stream of the reaction product EDC serves as the reaction medium. This can be generated in a loop reactor with external or internal circulation. Furthermore, the circulating stream can be generated by forced or natural circulation. Iron(III) chloride is primarily used as the catalyst; sodium chloride, which reduces the formation of high-boiling compounds, can also be used as an additive.

[0014] Processes in which the reaction medium is circulated naturally prove to be particularly energy-efficient, as this eliminates the need for powerful pumps to generate the circulating flow.

[0015] The state of the art is illustrated, for example, by DE 27 24 045, EP 1 161 406, and DE 10 2008 020 386. DE 27 24 045 describes a process in which ethylene and chlorine are added in gaseous form to a reaction medium circulating naturally. This medium may contain not only EDC but also higher concentrations of other chlorinated hydrocarbons, such as 1,1,2-trichloroethane. The reactants dissolve in the circulating stream and react with each other to form EDC, which is fed in vapor form to a rectification zone. Here, the chlorine is added to the circulating reaction medium first, as it dissolves rapidly due to its high solubility. Advantageously, the ethylene is added downstream of the chlorine addition point with respect to the flow direction of the reaction medium, since the reaction then proceeds as reactive absorption: ethylene dissolves and reacts directly with the chlorine already in solution.However, the reactants can also be added simultaneously. The reactor then also serves to heat the rectification zone, from which cooled EDC is returned to the reactor.

[0016] In the process according to DE 27 24 045, all the heat of reaction is removed from the reactor by evaporating EDC. The amount of EDC evaporated is several times greater than the amount of EDC produced. DE 24 27 045 also discloses the feeding of recycled EDC and EDC from an oxychlorination process into the rectification zone in order to purify these two streams by distillation.

[0017] EP 1 161 406 and DE 10 2008 020 386 describe processes in which the reactants ethylene and chlorine react with each other in a homogeneous, liquid phase. In these processes, the reaction medium is also circulated naturally. EDC with a dissolved catalyst, e.g., iron(II) chloride, is used as the reaction medium; a larger proportion of other chlorinated hydrocarbons in the circulating reaction medium, as disclosed in DE 2427 045, is not provided for here.

[0018] To achieve a homogeneous reaction phase, gaseous ethylene is first added to the circulating reaction medium. This dissolves in the reaction medium and, after a certain time or after passing a specific distance above the ethylene addition point, is mostly present in dissolved form. Simultaneously, a liquid EDC partial stream is withdrawn from a suitable location in the reactor. In the process according to EP 1 161406, the withdrawal takes place in the downpipe of a loop reactor with external recirculation of the reaction medium; in the process according to DE 10 2008 020 386, the stream is withdrawn from the outer annular space of a loop reactor with internal recirculation. In both processes, the EDC partial stream withdrawn in this way is cooled by means of a heat exchanger and then used as a motive stream for drawing in gaseous chlorine by means of a liquid jet gas compressor.Due to the good solubility of chlorine in EDC, the chlorine is already in dissolved form at the outlet of the liquid jet gas compressor.

[0019] The EDC partial stream loaded with dissolved chlorine is now added to the circulating EDC main stream via a suitable distribution device at a point where the ethylene is already present in dissolved form. The reaction between chlorine and ethylene now proceeds largely homogeneously in the liquid phase.

[0020] This reaction process, disclosed in EP 1 161 406 and DE 10 2008 020 386, enables a significantly lower formation rate of high-boiling byproducts, particularly 1,1,2-trichloroethane, compared to processes carried out as reactive absorption. The resulting product quality is suitable for direct use in a downstream plant for the thermal cracking of 1,2-dichloroethane within a balanced VC IVI process and does not require prior distillative purification, especially for the separation of substances with higher boiling points than EDC.

[0021] A special feature of these processes is that the excellent product qualities are maintained at reaction temperatures of typically 120°C. This allows for economically viable heat recovery measures.

[0022] In the processes described in EP 1 161406 and DE 10 2008 020386, the produced EDC is withdrawn as vapor at the reactor head. The dissolved catalyst remains in the reactor. The processes described above are generally operated with a certain excess of ethylene to prevent the discharge of unreacted chlorine at the reactor head, which would lead to corrosion of downstream plant components and also to a deterioration of product quality. DE 2427 045 specifies ethylene excesses between 1 and 10 mol%. The added excess unreacted ethylene is discharged as gas at the reactor head and is a component of the reactor exhaust gas.

[0023] Other components of the reactor exhaust gas are inert admixtures of ethylene such as ethane with respect to the direct chlorination reaction, or similar admixtures of chlorine such as oxygen or - depending on the production process of the chlorine - hydrogen.

[0024] To prevent the formation of explosive gas mixtures in the reactor exhaust gas, which is possible due to the oxygen content, the reactor exhaust gas is diluted with an inert gas ("inertized"). Nitrogen or ethylene are most commonly used for this purpose. The criteria for the required quantity and location of the inert gas are known to those skilled in the art.

[0025] Particularly when using ethylene as an inerting medium, recovery of the unreacted ethylene contained in the reactor exhaust gas is necessary for economic reasons.

[0026] The processes described above are usually operated within the framework of a balanced VCM process. In this system, recovery can be achieved, for example, by adding the ethylene-containing exhaust gas from direct chlorination to the ethylene feed stream of an oxychlorination plant, where it is converted to 1,2-dichloroethane according to equation (3).

[0027] Another possibility for recovering excess ethylene is the installation of a post-reactor in which the ethylene-containing exhaust gas stream is reacted again with chlorine.

[0028] In addition to the direct chlorination plants operated within the balanced VCM process network, there are so-called "stand-alone plants," which are usually located near a chlor-alkali electrolysis plant and convert the chlorine produced in the latter to EDC (endoxic chemical). The EDC produced in this way can be transported as a safe "transport form" of chlorine to VCM plants operating in unbalanced mode. These unbalanced VCM plants either do not contain a direct chlorination section or are designed to process additional EDC from outside the plant boundaries, so-called "imported EDC," in addition to the EDC produced within the network through direct chlorination.

[0029] Operating a stand-alone plant offers the operator of a chlor-alkali electrolysis plant the advantage of not having to construct a complete VCM complex for further processing the resulting chlorine, which often also includes a downstream plant for the production of polyvinyl chloride (PVC). This can be the case when the main product of a chemical plant complex is caustic soda and the plant operator has no interest in the production of polyvinyl chloride.

[0030] Since no downstream system for processing excess ethylene, such as an oxychlorination unit, is available alongside a stand-alone direct chlorination unit, and the installation of a post-reactor with the corresponding equipment would entail significantly increased investment costs, nitrogen is inherently used as an inerting medium in such systems to minimize ethylene discharge via the exhaust gas. Simultaneously, the excess ethylene required to prevent free chlorine at the reactor outlet must be kept as low as possible to ensure the process's economic viability. Likewise, the resulting product quality must allow its use in an EDC cracking plant without prior distillation for the separation of high-boiling components.

[0031] Therefore, there is a need for an improved direct chlorination process that enables economical stand-alone operation under the boundary conditions described above, as well as a device with which this process can be implemented.

[0032] This problem is solved with respect to a device having the features of claim 1, and with respect to a method having the features of claim 16. The respective dependent claims represent advantageous and optional embodiments.

[0033] Surprisingly, it was found that the product quality of the processes described in EP 1 161 406 and DE 10 2008 020 386 can be significantly improved with the loop reactor and the process according to the invention when these are operated with modified process parameters.

[0034] Similarly, if the identified process parameters are adhered to, the required excess of ethylene for complete conversion of the chlorine can be reduced further, thus improving the economic efficiency of the process.

[0035] The invention thus relates in a first aspect to a loop reactor for the production of a reaction product, in particular a chlorinated alkane, comprising: a) at least one downpipe and at least one riser pipe, wherein the at least one downpipe and the at least one riser pipe each open at an upper end into a head zone and are in fluidic communication via this head zone, and are each connected to each other at a lower end via a deflection zone and are in fluidic communication via this head zone, b) at least one first feed device for a first reactant and at least one second feed device for a second reactant, wherein the at least one first feed device and the at least one second feed device enable the feed of the respective reactants into the at least one riser pipe, wherein the at least one first feed device is arranged below the at least one second feed device.wherein at least one pressure drop generator is arranged in the at least one riser pipe below the at least one first feed device. Preferably, the pressure drop generator is designed to generate, during nominal load operation of the loop reactor, such a pressure drop in the at least one riser pipe that the residence time of a circulating liquid reaction medium with the dissolved reactants in a reaction zone is between 30 and 120 seconds. A residence time between 40 and 100 seconds is particularly preferred.

[0036] The reaction zone is defined by a section in the at least one riser pipe from the second feed device to the exit from the at least one riser pipe.

[0037] The nominal load operation of the loop reactor can be determined by the rate at which reactants are added to the riser tube and / or the rate of gaseous reaction product that is drawn off from the top zone of the loop reactor, at which the nominal capacity of the loop reactor is reached.

[0038] By selecting the flow resistance of the pressure drop generator to match the nominal load operation of the loop reactor, the rate of the circulating reaction medium relative to the reactant addition rate is adjusted, and simultaneously, the total volume of media flowing into the riser pipe is controlled. The total volume of media flowing into the riser pipe determines the residence time of the liquid reaction medium and the dissolved reactants in the reaction zone. In a reduced partial load operation compared to nominal load, the reactant addition rate is reduced, resulting in a further increased residence time in the reaction zone.

[0039] The selection of the flow resistance of the pressure drop generator, adapted to the nominal load operation of the loop reactor, thus determines a lower limit for the residence time of the reaction medium in the reaction zone during operation of the loop reactor, which is not undercut even during partial load operation. Operating the loop reactor with such a long residence time in the reaction zone allows for a particularly significant reduction in the excess ethylene required for complete chlorine conversion.

[0040] An advantageous embodiment provides that the at least one pressure loss generator is designed as a flow straightener in the form of a plate provided with recesses or as a combination of a plate provided with recesses with further pressure loss generating or flow equalizing elements such as honeycomb structures, bundles of circular or non-circular channels, structured or disordered packings for mass transfer or static mixer packings.

[0041] Another advantageous embodiment provides that the at least one pressure loss generator is designed as a flow straightener in the form of pressure loss generating or flow equalizing elements such as honeycomb structures, bundles of circular or non-circular channels, structured or disordered packings for mass transfer or static mixer packings.

[0042] In particular, at least one pressure loss generator can be designed as a perforated plate with recesses of variable size.

[0043] Particularly advantageously, the at least one pressure loss generator comprises or is formed from a pair of perforated plates with an upper and a lower perforated plate, wherein the respective upper and lower perforated plates have at least a subset of recesses in projection of the upper and lower perforated plates onto each other, are open in projection of the upper and lower perforated plates onto each other in a first lateral position, and are partially or completely closed in a second lateral position of the upper and lower perforated plates onto each other when the upper perforated plate is moved laterally to the lower perforated plate.

[0044] For example, it may be provided that the upper or lower perforated plate of the pair of perforated plates is fixed in the riser pipe and the other perforated plate of the pair of perforated plates is laterally movable, for example by means of an actuator.

[0045] It may be provided that an element for influencing the flow, for example a limiting orifice or a controllable actuating element and / or a reduction, is arranged in the direction of flow upstream of the pressure loss generator.

[0046] Preferably, the ratio of the cross-sectional area of ​​the at least one downpipe to the cross-sectional area of ​​the at least one riser pipe is 0.07 to 0.45.

[0047] It is also preferred if at least one first static mixer is installed in the at least one riser pipe between the at least one first feed device and the at least one second feed device.

[0048] According to a further preferred embodiment, a withdrawal point for branching off at least one first partial flow is provided in the at least one downpipe, wherein the at least one first partial flow is fed into a mixer in which the second reactant is mixed into the partial flow and then flows into the at least one riser pipe via the at least one second feeding device.

[0049] For example, the partial flow can have at least one circulation pump and / or at least one heat exchanger.

[0050] It is also possible that the partial flow has a pressure relief valve and a downstream pressure relief tank, from which gaseous or liquid product can be drawn via a withdrawal point, which may have an upstream pressure relief valve.

[0051] It is also advantageous if at least one downpipe has a tap for branching off at least a second partial flow, which has at least one circulation pump and / or at least one heat exchanger and is returned to the at least one downpipe.

[0052] In particular, a second static mixer is installed in at least one riser pipe above at least one second feed device.

[0053] Preferably, the head section of the loop reactor further comprises at least one exhaust port for the extraction of a gaseous product. In the loop reactor, the at least one riser pipe can be arranged inside the at least one downpipe. Alternatively, the at least one riser pipe and the at least one downpipe can be designed as separate elements.

[0054] According to a further aspect, the present invention relates to a method for producing a reaction product by addition reaction of two reactants in a vertically oriented loop reactor according to the invention as described above, in which the loop reactor is connected with a liquid reaction medium and optionallya homogeneously dissolved catalyst is filled or is filled, such that the at least one downpipe, the at least one riser pipe and the deflection zone are completely and the head zone is at least partially filled with the liquid reaction medium, a first reactant is fed into the at least one riser pipe via the at least one first feed device and a second reactant is fed into the at least one riser pipe via the at least one second feed device, so that a natural circulation is formed, wherein in the at least one riser pipe the reaction medium with the reactants rises, is deflected in the head zone into the at least one downpipe and sinks there and is deflected again in the deflection zone and led into the at least one riser pipe.

[0055] According to the invention, it is provided that a circulating flow of the reaction medium is influenced by the at least one pressure loss generator upon entry into the at least one riser pipe.

[0056] According to a preferred aspect of the method, the flow is homogenized across the cross-section of the at least one riser pipe.

[0057] The first reactant is preferably an alkene, in particular ethene; the second reactant is a halogen, in particular chlorine; and the reaction product is a halogenated alkane, in particular 1,2-dichloroethane. Preferably, the reaction product and the reaction medium are identical. In preferred embodiments, the pressure drop generator, operating at nominal load in the loop reactor, creates a flow resistance in the at least one riser tube such that the residence time of the circulating liquid reaction medium with the dissolved reactants in a reaction zone is between 30 and 120 seconds, preferably between 40 and 100 seconds. The reaction zone is defined by a section in the at least one riser tube from the second feed device to the outlet of the at least one riser tube.

[0058] Furthermore, it is advantageous that in a section of at least one riser pipe from the second feed device to the exit from the at least one riser pipe (reaction zone) a flow velocity of the reaction medium with the reactants dissolved therein is defined as the empty pipe velocity of the liquid phase (e.g. based on the flow velocity of the reaction medium defined in this way), and / or a residence time of the reaction medium with the reactants dissolved therein is between 30 seconds and 120 seconds.

[0059] With respect to the cross-sectional area of ​​the at least one riser tube, the addition rate of the first reactant, which is in particular ethene, can be between 600 and 3,500 kg / (m²). 2 h), and / or the second reactant, which is in particular chlorine, between 1,400 and 8,000 kg / (m³) 2 h) are chosen.

[0060] The selected addition rate preferably corresponds to the nominal load operation of the loop reactor. Preferably, the circulating quantity of the reaction medium, based on the quantity of the first reactant added, is selected to be between 400 and 750 kg per 1 kg of the first reactant.

[0061] The first reactant can be completely dissolved in the reaction medium after passing through a mixing and dissolving zone that extends from at least one first feeding device to at least one second feeding device.

[0062] Likewise, the first reactant can be dissolved in a partial stream of the reaction medium and fed as a solution into the at least one riser tube via the second feed device, preferably the at least one partial stream being set to a temperature that is lower than the temperature of the reaction medium in the riser tube.

[0063] Preferably, the specific production quantity of the reaction product generated, based on the cross-sectional area of ​​the at least one riser pipe at the location of the second feed device, is between 2,000 and 10,500 kg / (m²). 2 h).

[0064] The reaction product is preferably withdrawn in gaseous form via the at least one exhaust vent in the head zone and / or in gaseous or liquid form via the extraction point.

[0065] The present invention is described in more detail below, in which specific and preferred embodiments are described using the example of the addition of ethylene and chlorine, without these being to be understood as limiting.

[0066] The invention relates in particular to a process for the direct chlorination of ethylene with chlorine using a circulating reaction medium and a catalyst, wherein ethylene and chlorine are supplied to the reaction medium. In this process, viewed in the direction of circulation of the reaction medium, ethylene is introduced into the circulating medium at an upstream point such that, after passing through a mixing and dissolution zone in the reaction medium stream, it is completely dissolved. The chlorine is dissolved in a cooled partial stream of the reaction medium and then supplied further downstream to the main stream of the reaction medium, the addition of the dissolved chlorine taking place at a point where the ethylene is also already in dissolved form.

[0067] The reactor comprises at least one riser pipe and at least one downpipe, wherein the at least one riser pipe and the at least one downpipe are connected to each other at their lower ends according to the principle of communicating vessels, and the at least one riser pipe and the at least one downpipe open into an evaporation vessel and a degassing vessel, respectively, at their upper ends. The addition points for ethylene and chlorine dissolved in the reaction medium are located in the at least one riser pipe. In particular, the length of the reaction zone is defined as the length of the riser pipe from the addition point for dissolved chlorine. The flow velocity in the reaction zone is preferably defined as the empty pipe velocity of the liquid phase. The residence time, based on the flow velocity of the liquid phase, is preferably between 30 seconds and 120 seconds.The chlorine addition density, based on the cross-sectional area of ​​the at least one riser pipe at the chlorine addition point, is preferably between 1400 kg / m. 2 h and 8000 kg / m 2 h. The ethylene addition density, based on the cross-sectional area of ​​the at least one riser pipe at the ethylene addition point, is preferably between 600 kg / m². 2 h and 3500 kg / m 2 h. Preferably, the circulating EDC quantity, based on the amount of ethylene added, is between 400 kg EDC / kg ethylene and 750 kg EDC / kg ethylene. The specific EDC production quantity, based on the cross-sectional area of ​​the at least one riser pipe at the chlorine addition point, is advantageously between 2000 kg EDC / m². 2 - h and 10500 kg EDC / m 2- H. In at least one riser pipe, at least one static mixer pack (reaction mixer) can be arranged above the chlorine addition point and at least one flow straightener below the ethylene addition point. The operating parameters mentioned above can be adjusted by dimensioning the internal components that generate pressure loss.

[0068] In one embodiment of the invention, no active actuators such as control valves, flaps, or similar devices are required in the flow path of the circulating EDC to adjust the operating parameters according to the invention. The operating parameters can be adjusted by appropriately dimensioning the pressure-loss-generating internals, such as static mixer packings and flow straighteners. The term "pressure-loss-generating internals" also extends to constrictions or narrowings of the reactor riser pipe and / or the reactor downpipe. However, the invention also includes arrangements in which additional active actuators are arranged in the flow path of the circulating EDC.

[0069] The operating state according to the invention with respect to natural circulation occurs when there is a force equilibrium between the driving force, caused by the mean density difference between the riser pipe and the downpipe on the one hand, and the sum of the pressure losses in the flow path of the circulating EDC on the other. The driving forces can be estimated both computationally and experimentally determined.

[0070] The pressure losses caused by the internal components can also be determined both mathematically and experimentally.

[0071] Methods for estimating or determining the driving forces or pressure losses are known to those skilled in the art.

[0072] In the following, the term "flow straightener" refers to a sheet metal plate with cutouts of any shape located in the flow path of the circulating 1,2-dichloroethane stream. However, the invention is not limited to this embodiment. In particular, more complex devices can also be used as flow straighteners, for example, devices consisting of parallel channels in the form of a honeycomb structure or parallel channels with arbitrarily shaped cross-sections. Static mixer packings can also be used. Furthermore, disordered packings for mass transfer, such as filler material or structured packings, can be used.

[0073] The more complex devices described above can be used alone or in combination with a plate provided with recesses. In a preferred embodiment, a combined apparatus consisting of a plate provided with recesses and one of the more complex devices described above is used, in which the plate provided with recesses is arranged upstream of the more complex device with respect to the flow direction of the reaction medium.

[0074] Other designs of flow straighteners are known to those skilled in the art.

[0075] In a further advantageous embodiment of the invention, a perforated sheet metal, analogous to a sieve tray of a distillation column, is used as a flow straightener. However, the design of the flow straightener is not limited to circular recesses, but can include recesses of any shape, such as rectangles, triangles, other polygons, or even ellipses. In this embodiment, the perforated sheet metal performs both the function of the flow straightener and the function of the pressure drop generator.

[0076] In a further advantageous embodiment of the invention, a combination of a sheet metal with recesses and a further pressure loss generator is used in series, wherein the sheet metal with recesses is arranged downstream of the further pressure loss generator with respect to the flow direction of the circulating 1,2-dichloroethane. In this embodiment, the functions of flow straightening and slowing down the circulating flow are decoupled insofar as the sheet metal with recesses primarily performs the function of the flow straightener and the further pressure loss generator primarily serves to slow down the circulating 1,2-dichloroethane flow.The additional pressure loss generator can be either a fixed flow resistance - for example, a limiting orifice - or an active actuating element - for example, a flap or another control valve that can be adjusted manually using auxiliary energy.

[0077] In this embodiment, the additional pressure loss generator can also be arranged spatially separate from the sheet metal with the recesses. For example, the additional pressure loss generator can be arranged in the reactor downpipe.

[0078] Furthermore, the additional pressure loss generator can also be arranged in a reactor section with a smaller pipe diameter than that of the reactor riser pipe, or in a constriction of the reactor riser pipe or reactor downpipe. The latter embodiment offers the advantage that smaller diameter actuators can be used, which are cost-effective and require lower actuating forces.

[0079] In a further advantageous embodiment of the invention, an additional static mixer pack is arranged above the ethylene injection point but below the chlorine injection point as an aeration mixer. When using such an aeration mixer, the installation of a flow straightener below the ethylene injection point is not strictly necessary, since the function of the flow straightener, both with regard to equalizing the flow and with regard to setting the desired pressure drop, can in this case be taken over by the additional static mixer pack.

[0080] In a further advantageous embodiment of the invention, the ratio of the cross-sectional area of ​​the downpipe associated with a riser pipe to the cross-sectional area of ​​the riser pipe is between 0.07 and 0.45.

[0081] In a further advantageous embodiment of the invention, vaporous EDC is obtained by at least partial flash evaporation of a liquid EDC stream taken from the reactor.

[0082] A further advantageous embodiment of the invention also relates to a process in which vaporous EDC is obtained by at least partial flash evaporation of a liquid EDC stream taken from the reactor, and the remaining liquid EDC stream, cooled by flash evaporation, is used, after optionally further cooling, to dissolve the chlorine used in the direct chlorination reaction. In a further advantageous embodiment of the invention, a flow straightener with a variable free cross-section is used, consisting of two superimposed, movable plates with recesses, the free cross-section of which is varied by moving one of the plates by means of an actuator.

[0083] Exemplary embodiments of the present invention are shown in the figures.

[0084] Figures 1a and 1b show the structure of a loop reactor 2 according to the invention, based on two possible embodiments. The same reference numerals denote identical device components.

[0085] Figure 1a shows a loop reactor with external liquid recirculation, and Figure 1b shows a loop reactor 2 with internal liquid recirculation. In both cases, liquid ethylene dichloride 1 (hereinafter referred to as EDC, the liquid reaction medium) flows in a closed loop through the loop reactor 2, which has a downpipe 3, a riser pipe 4, a lower deflection zone 5, and an upper degassing / evaporation zone 6. In the device shown in Figure 1b, the downpipe is designed as an annular gap between the outer vessel wall and the inner annular space (riser pipe 4). The term "riser pipe 4" therefore also includes this annular gap.

[0086] After passing through the deflection zone 5, the EDC 1 first flows through a flow straightener 7, which homogenizes the velocity profile of the flow across the cross-section of the riser pipe and whose pressure loss is preferably dimensioned such that the sum of the pressure losses of the flow straightener 7 and other internals located in the flow path of the circulating EDC leads to the setting of the operating parameters according to the invention at nominal load of the reactor.

[0087] In particular, it is preferably provided that the pressure loss generator 7, during nominal load operation of the loop reactor 2, generates such flow resistance in the at least one riser pipe 4 that the residence time of the circulating liquid reaction medium EDC with the dissolved reactants in a reaction zone is between 30 seconds and 120 seconds, preferably between 40 seconds and 100 seconds. The reaction zone is defined by a section in the at least one riser pipe 4 from the second feed device 20 to the outlet of the at least one riser pipe 4.

[0088] In the downstream direction of circulation of the EDC, gaseous ethylene 8 (first reactant) is added to the EDC, preferably via a feed or distribution device 9. The initially gaseous ethylene 8 then dissolves in the circulating EDC 1 as it travels upwards through the riser pipe. The dissolution process can be assisted by an (optional) static mixer 10 (e.g., aeration mixer, located below the second feed device).

[0089] A first EDC partial flow 12 is drawn from the downpipe 3 by means of a first EDC circulation pump 11 and cooled by means of a first heat exchanger 13. The first heat exchanger 13 can also symbolically represent a combination of at least two heat exchangers 13 connected in series, wherein at least one of these heat exchangers 13 heats a heat transfer medium, which in turn heats suitable heat sinks and thus serves to recover heat of reaction.

[0090] The cooled first EDC partial stream 14 now serves as a motive jet in a liquid jet gas compressor 15 (mixer) to draw in gaseous chlorine 16 (second reactant) and dissolve it in the cooled EDC partial stream 14. Due to the good solubility of gaseous chlorine in EDC, the chlorine is present in dissolved form at the outlet of the liquid jet gas compressor, except for any inert gases such as oxygen or hydrogen that may be present.

[0091] If the chlorine is already in liquid form, a distributor, combined with or without a static mixer, can be used for adding the chlorine 19 instead of the liquid jet gas compressor 15, as shown in Fig. 1c. In this embodiment, liquid chlorine 18 is mixed with the first cooled EDC partial stream using a distributor and the static mixer 19. Even if the available chlorine 18 has sufficient pressure to be fed into the reactor 2 without the use of a liquid jet gas compressor 15, a static mixer can be used for mixing and dissolving the chlorine 18 (not shown in the figures).

[0092] The partial stream 17 containing chlorine dissolved in EDC is preferably fed into the riser pipe 4 via a distribution device 20 at a point where the ethylene added upstream in the EDC's circulating direction has already dissolved. The two reactants, ethylene and chlorine, then react with each other in the liquid phase. The reaction is supported by a static mixer 21, referred to here as a reaction mixer. The heat of reaction increases the temperature of the circulating EDC stream.

[0093] After passing through the reaction mixer 21, the reaction mixture continues to flow upwards and begins to boil due to the decreasing hydrostatic pressure. Phase separation takes place in the evaporation / degassing zone 6 (top zone). Vaporous EDC is drawn off as product via the fume hood 22, while the liquid EDC 1 flows back into the cycle.

[0094] In addition to the first EDC partial stream 12, one or more further EDC partial streams 23 can optionally be extracted from the reactor, supplied to one or more heat sinks 25 for the recovery of reaction heat by means of one or more further EDC circulation pumps 24 and returned to the reactor.

[0095] The amount of vaporized EDC extracted via the exhaust 22 at the reactor head depends on the amount of heat removed via the liquid EDC circuit(s), with the minimum amount of EDC vaporized corresponding to the amount of EDC produced by the reaction. The main contribution of the buoyancy forces that cause and maintain natural circulation is due to the presence of gas phases – resulting from the addition of gaseous ethylene to the lower part of the riser tube on the one hand, and the vaporization of EDC in the upper part of the riser tube on the other (principle of the mammoth pump or gas lift reactor). The density difference between the liquid phase in the riser tube and the downpipe contributes only a small portion to natural circulation. Figure 2 shows further possible configurations of the reactor. Figures 2a and 2b schematically show reactors with external circulation in which the deflection zone 5 is not designed as a "U-tube".Figures 2a and 2b also indicate that the downpipe(s) 3 - also due to the arrangement of a flow straightener 7 in the riser pipe 4 - can have a significantly smaller diameter and thus a significantly smaller cross-sectional area according to the invention than the riser pipe 4.

[0096] With a significant reduction in the flow cross-section of the downpipe 3, the circulating EDC flows at high velocity into the deflection zone 5 and the riser pipe 4. Without the arrangement of a flow straightener 7 in the riser pipe 4, this would lead to a highly uneven velocity distribution in the area of ​​the ethylene distribution device 9 and thus to a negative impact on the ethylene dissolution. However, the flow straightener 7 ensures a uniform velocity distribution, so that the described disadvantage does not occur in the reactor according to the invention.

[0097] Figures 2a and 2b indicate that the reactor riser pipe 4 can optionally have a cross-sectional expansion in the area of ​​the evaporation / degassing zone 6. Figure 2b shows by way of example that several downpipes 3 can be associated with a riser pipe 4. Figure 2c shows by way of example that several reaction sections can be associated with an evaporation / degassing zone. However, the invention is not limited to these embodiments.

[0098] Figures 3a and 3b show further preferred embodiments of the invention. In the embodiment according to Figure 3a, a partial EDC flow is withdrawn from the reactor downpipe 3 and directed via a pressure relief valve 26 into a pressure relief vessel 27. The pressure in the pressure relief vessel 27 is regulated by means of a pressure-maintaining valve 28. In contrast to the previously described embodiments, vaporous EDC 30 is now no longer withdrawn from the reactor by boiling, but by flash evaporation. The unevaporated EDC fraction 30 is pumped back into the reactor downpipe 3 by the pump 31. In the embodiment shown in Figure 3b, vaporous EDC is also withdrawn from the reactor by flash evaporation. The liquid EDC, which has already been cooled by flash evaporation, is then further cooled by means of the heat exchanger 13, as already described in the explanation of Figures 1a and 1b, and used to dissolve the raw material chlorine.Any excess liquid EDC not required for dissolving the chlorine is returned to the reactor as partial stream 32. This partial stream 32 can also be returned to the reactor using a separate pump (not shown in Figs. 3a and 3b).

[0099] Figure 4 shows a flow straightener according to the invention with a variable free cross-section. Figure 4a shows the lower part of a reactor according to Figure 1b. EDC from the downpipe 3 flows around the lower edge of the riser pipe 4 and is deflected upwards. The flow straightener consists of an upper plate 32, which can be displaced relative to the lower plate 34 by an actuator 33. Figure 4a shows the fully open state of the flow straightener in a top view, using square recesses as an example. The recesses are aligned one above the other. Figure 4b shows the half-closed state. The upper plate 32 is displaced relative to the lower plate 34 and partially covers the recess of the lower plate. The arrangement shown is to be understood as an example. For example, the lower plate 34 can also be displaceable. Likewise, the actuator can be operated either with auxiliary power – e.g., pneumatically – or manually.Furthermore, the shape of the recesses is freely selectable and not limited to the square shape shown in Fig. 4. By selecting the shape of the recesses, the control characteristics can be well adapted to the control task. The use of an arrangement as shown in Fig. 4 is particularly advantageous when, under normal operating conditions, EDC is extracted from the reactor, cooled in an external heat sink, and returned to the reactor. If such a heat sink fails or is taken out of service, more EDC is vaporized at the top of the reactor, and the buoyancy force in the riser pipe increases due to the now higher gas content. In order to continue to maintain the operating parameters according to the invention, the EDC circulation flow can now be adjusted by adjusting the flow straightener.Figures 5a-5c show various embodiments in which the functions of flow straightening and pressure loss generation are decoupled from each other. For example, a sheet with recesses is used as a flow straightener, and an element for influencing the flow 37, such as a limiting orifice or an active (controllable) actuator, is used as an additional device for generating pressure loss. The active actuator is operated manually or with the use of an auxiliary energy source. The invention is not limited to the embodiments shown.

[0100] Fig. 5a shows the arrangement of a combination of flow straightener 36 and active actuator 37 in a loop reactor with inner circulation, wherein the active actuator is arranged in a narrowing of the reactor riser pipe 4.

[0101] Fig. 5b shows the arrangement of a combination of flow straightener 36 and active actuator 37 in a loop reactor with outer circulation, wherein the active actuator is arranged in a narrowing of the reactor riser pipe 4 and the diameter of the reactor downpipe 3 is smaller than the diameter of the reactor riser pipe 4.

[0102] Fig. 5c shows the arrangement of a combination of flow straightener 36 and active actuator 37 in a loop reactor with outer circulation, wherein the diameter of the reactor downpipe 3 is smaller than that of the reactor riser 4 and the active actuator is arranged in the reactor downpipe 3.

[0103] Fig. 5d shows the arrangement of a combination of flow straightener 36 and a limiting orifice 38 in a loop reactor with outer circulation, wherein the diameter of the reactor downpipe 3 is smaller than that of the reactor riser 4 and the limiting orifice is arranged in a narrowing of the reactor riser 4.

[0104] Fig. 5 shows the arrangement of a combination of flow straightener 36 and active actuator 38 in a loop reactor with outer circulation, wherein the diameter of the reactor downpipe 3 is smaller than that of the reactor riser 4 and the active actuator is arranged in a narrowing of the reactor downpipe 3.

[0105] legend

[0106] 1 Liquid EDC

[0107] 2-loop reactor

[0108] 3 downpipe

[0109] 4 riser pipe

[0110] 5 Deflection zone

[0111] 6 Evaporation / Degassing zone

[0112] 7 Flow straighteners

[0113] 8 Ethylen

[0114] 9 Ethylene distribution device

[0115] 10 fumigation mixers (optional)

[0116] 11 First EDC circulation pump

[0117] 12 First EDC partial current

[0118] 13 First heat exchanger

[0119] 14 First cooled EDC partial stream

[0120] 15 liquid jet gas compressors

[0121] 16 Chlorine, gaseous

[0122] 17 Chlorine, dissolved in EDC

[0123] 18 Chlorine, liquid

[0124] 19 Static mixer for chlorine addition (optional)

[0125] 20 EDC / Chlorine distribution device

[0126] 21 reaction mixers

[0127] 22 EDC in vapor form, during product withdrawal by boiling

[0128] 23 Additional liquid EDC substreams (optional)

[0129] 24 Additional EDC circulation pumps (optional)

[0130] 25 heat sinks for the recovery of reaction heat (optional)

[0131] 26. Relief valve

[0132] 27 relaxation containers

[0133] 28 Pressure holding valve 29 EDC, vaporous, during product withdrawal by flash evaporation

[0134] 30 EDC liquid, back to the reactor

[0135] 31 EDC return pump

[0136] 32 Upper plate of the flow straightener

[0137] 33 Actuator

[0138] 34 Lower plate of the flow straightener

[0139] 35 cutouts

[0140] 36 plates with cutouts as flow straighteners

[0141] 37 Actuating element, adjustment manually or by means of auxiliary energy

[0142] 38 Limiting orifice as a pressure loss generator

[0143] 39 Constriction (downpipe)

[0144] The present invention will be explained in more detail with reference to the following examples.

[0145] Example 1 (comparative example)

[0146] In a reactor according to Fig. 1a, but without flow straightener 7 and without aeration mixer 10, 9275 kg / h of ethylene react with 23041 kg / h of chlorine. The molar ethylene excess is 1.75%. The length of the reaction section is 7300 mm, and the diameter of the riser pipe is 2000 mm. The reaction product is drawn off as vapor at the reactor head and condensed. The following operating parameters are established:

[0147] Chlorine addition density [kg / m³] 2 h]: 7129

[0148] Ethylene addition density [kg / m³] 2 h]: 2821

[0149] Time spent [s]: 9.4

[0150] Ratio of circulating EDC / ethylene [kg / kg]: 1106

[0151] The resulting reaction product exhibits the following quality parameters:

[0152] Total light boiling points [wt. ppm]: 50

[0153] Total high-boiling compounds [wt. ppm]: 390 (excluding bromine compounds) Example 2 (Inventive process)

[0154] In a reactor according to Fig. 1b, but without aeration mixer 10, 4961 kg / h of ethylene react with 12477 kg / h of chlorine. The molar ethylene excess is 0.5%. The length of the reaction section is 12300 mm, and the diameter of the riser pipe is 2022 mm. The cross-sectional area ratio of the downpipe to the riser pipe is 0.41. The reaction product is drawn off as vapor at the reactor head and condensed. The following operating parameters are established:

[0155] Chlorine addition density [kg / m³] 2 h]: 3886

[0156] Ethylene addition density [kg / m³] 2 h]: 1545

[0157] Time spent [s]: 65

[0158] Ratio of circulating EDC / ethylene [kg / kg] : 491

[0159] The resulting reaction product exhibits the following quality parameters:

[0160] Total light boiling points [wt. ppm]: 20

[0161] Total high-boiling elements [wt. ppm]: 250 (Excluding bromine compounds)

[0162] Since the salt used for chlor-alkali electrolysis usually contains bromine, and this bromine is introduced into the direct chlorination process along with the chlorine produced during electrolysis, bromine compounds are inevitably formed as a byproduct of direct chlorination. Therefore, the bromine compound content is not used as a quality parameter.

Claims

thyssenkrupp Intellectual Property GmbH P148589PC00 Patentansprüche 1. Loop reactor (2) for the production of a reaction product, in particular a chlorinated alkane, comprising: a) at least one downpipe (3) and at least one riser pipe (4), wherein the at least one downpipe (3) and the at least one riser pipe (4) each open at an upper end into a head zone (6) and are in fluidic communication via this, and are each connected to each other at a lower end via a deflection zone (5) and are in fluidic communication via this, b) at least one first feed device (9) for a first reactant (8) and at least one second feed device (20) for a second reactant (16, 18), wherein the at least one first feed device (9) and the at least one second feed device (20) enable the feed of the respective reactants into the at least one riser pipe (4),wherein the at least one first feed device (9) is arranged below the at least one second feed device (20), characterized in that at least one pressure loss generator (7) is arranged in the at least one riser pipe (4) below the at least one first feed device (9).

2. Loop reactor (2) according to claim 1, characterized in that the pressure loss generator (7) is designed to generate, in nominal load operation of the loop reactor (2), such a flow resistance in the at least one riser pipe (4) that the residence time of a circulating liquid reaction medium with the reactants dissolved therein in a reaction zone is between 30 seconds and 120 seconds, wherein the reaction zone is defined by a distance in the at least one riser pipe (4) from the second feed device (20) to the exit from the at least one riser pipe (4).

3. Loop reactor (2) according to claim 1 or 2, characterized in that the at least one pressure loss generator (7) is designed as a flow straightener.

4. Loop reactor (2) according to one of the preceding claims, characterized in that the at least one pressure loss generator (7) is selected from the group consisting of perforated plates, bundles of parallel channels, static mixer packings, structured or unstructured packings for mass transfer or combinations of these devices.

5. Loop reactor (2) according to the preceding claim, characterized in that the at least one pressure loss generator (7) is designed as a perforated plate with size-variable recesses (35).

6. Loop reactor (2) according to the preceding claim, characterized in that the at least one pressure loss generator (7) comprises or is formed from a pair of perforated plates with an upper (32) and a lower (34) perforated plate, wherein each upper (32) and lower (34) perforated plate has at least a subset of recesses (35) in projection of the upper (32) and lower (34) perforated plate towards each other, is open in projection of the upper (32) and lower (34) perforated plate towards each other in a first lateral position and is partially or completely closed in a second lateral position of the upper (32) and lower (34) perforated plate towards each other when the upper (32) is moved laterally towards the lower (34) perforated plate.

7. Loop reactor (2) according to the preceding claim, characterized in that the upper (32) or the lower (34) perforated plate of the pair of perforated plates is fixedly mounted in the riser tube (4) and the other perforated plate of the pair of perforated plates is laterally movable, for example by means of an actuator (33).

8. Loop reactor (2) according to one of the preceding claims, characterized in that an element for influencing the flow (37), for example a limiting orifice or a controllable actuating element and / or a flow limitation (38, 39), for example a limiting orifice (38) and / or a reduction (39), is arranged in the flow direction upstream of the pressure loss generator (7).

9. Loop reactor (2) according to one of the preceding claims, characterized in that the ratio of a cross-sectional area of ​​the at least one downpipe (3) to a cross-sectional area of ​​the at least one riser pipe (4) is 0.07 to 0.

45.

10. Loop reactor (2) according to one of the preceding claims, characterized in that at least one first static mixer (10) is installed in the at least one riser pipe (4) between the at least one first feed device (9) and the at least one second feed device (20).

11. Loop reactor (2) according to one of the preceding claims, characterized in that a withdrawal point for branching off at least one first partial stream (12, 14, 17) is provided in the at least one downpipe (3), wherein the at least one first partial stream (12) is fed into a mixer (15, 19) in which the second reactant (16, 18) is mixed into the partial stream (12, 14, 17) and subsequently flows via the at least one second feed device (20) into the at least one riser pipe (4).

12. Loop reactor (2) according to the preceding claim, characterized in that the partial flow (12, 14, 17) has at least one circulation pump (11) and / or at least one heat exchanger (13).

13. Loop reactor (2) according to one of the two preceding claims, characterized in that the partial flow (12, 14, 17) has a pressure relief valve (26) and a downstream pressure relief vessel (27) from which gaseous gas is drawn off via a withdrawal point (29), which may optionally have a pressure relief valve (28) upstream. or liquid product can be extracted.

14. Loop reactor (2) according to one of the preceding claims, characterized in that a withdrawal point for branching off at least a second partial flow (24) is provided in the at least one downpipe (3), which has at least one circulation pump (24) and / or at least one heat exchanger (25) and is returned to the at least one downpipe.

15. Loop reactor (2) according to one of the preceding claims, characterized in that a second static mixer (21) is installed in the at least one riser pipe (4) above the at least one second feed device (20).

16. Loop reactor (2) according to one of the preceding claims, characterized in that the head zone (6) has at least one extraction point (22) for taking out a gaseous product.

17. Loop reactor (2) according to one of the preceding claims, characterized in that the at least one riser pipe (4) is arranged within the at least one downpipe (3) or the at least one riser pipe (4) and the at least one downpipe (3) are designed as separate elements.

18. A process for producing a reaction product by addition reaction of two reactants in a vertically oriented loop reactor according to one of the preceding claims, wherein the loop reactor (2) is filled or is filled with a liquid reaction medium (1) and optionally with a catalyst homogeneously dissolved therein, such that the at least one downpipe (3), the at least one riser pipe (4) and the deflection zone (5) are completely filled and the head zone (6) is at least partially filled with the liquid reaction medium (1), via which at least one first feed device (9) a first reactant (8) and via which at least one second feed device (20) a second reactant (16, 18) is introduced into the at least one riser pipe, so that a natural circulation is formed, wherein in the at least one riser pipe (4) the reaction medium with the reactants rises, is deflected in the head zone (6) into the at least one downpipe (3) and sinks there and is deflected again in the deflection zone (5) and led into the at least one riser pipe (4), characterized in that a circulating flow of the reaction medium is influenced by the at least one pressure loss generator (7).

19. Method according to the preceding claim, characterized in that the flow is homogenized across the cross-section of the at least one riser pipe.

20. Method according to one of the two preceding claims, characterized in that the first reactant is an alkene, in particular ethene, the second reactant is a halogen, in particular chlorine, the reaction product is a halogenated alkane, in particular 1,2-dichloroethane, and the reaction product and the reaction medium are identical.

21. Method according to one of claims 18 to 20, characterized in that in a section in the at least one riser pipe (4) from the second feed device (20) to the exit from the at least one riser pipe (4) (reaction zone) a flow velocity of the reaction medium with the reactants dissolved therein is defined as the empty pipe velocity of the liquid phase, and / or a residence time of the reaction medium with the reactants dissolved therein is between 30 seconds and 120 seconds.

22. Method according to one of claims 18 to 21, characterized in that the pressure loss generator (7) in a nominal load operation of the loop reactor (2) generates such a flow resistance in the at least one riser pipe (4) that a residence time of the circulating liquid reaction medium with the reactants dissolved therein in a reaction zone between 30 seconds and 120 seconds, wherein the reaction zone is defined by a distance in which the at least one riser pipe (4) extends from the second feed device (20) to the outlet of the at least one riser pipe (4) 23. Method according to one of claims 18 to 22, characterized in that, with reference to a cross-sectional area of ​​the at least one riser tube (4), an addition rate of the first reactant, which is in particular ethene, is between 600 and 3,500 kg / (m²). 2 h), and / or the second reactant, which is in particular chlorine, between 1,400 and 8,000 kg / (m³) 2h) is chosen.

24. Method according to one of claims 18 to 23, characterized in that the circulating quantity of the reaction medium, based on the quantity of the added first reactant, is selected to be between 400 and 750 kg per 1 kg of the first reactant.

25. Method according to one of claims 18 to 24, characterized in that the first reactant is completely dissolved in the reaction medium after passing through a mixing and dissolving zone extending from the at least one first feeding device (9) to the at least one second feeding device (10).

26. Method according to one of claims 18 to 25, characterized in that the first reactant is dissolved in a partial stream (12) of the reaction medium and is fed as a solution via the second feed device (10) into the at least one riser tube (4), wherein preferably the at least one partial stream (12) is set to a temperature that is lower than the temperature of the reaction medium in the riser tube (4).

27. Method according to any one of claims 18 to 26, characterized by net, that the specific production quantity of the generated reaction product, based on the cross-sectional area of ​​the at least one riser pipe (4) at the location of the second feed device (10) is between 2,000 and 10,000 kg kg / (m²) 2h).

28. Method according to one of claims 18 to 27, characterized in that the reaction product is withdrawn in gaseous form via the at least one extraction port (22) of the head zone (6) and / or in gaseous or liquid form via the extraction port (29).

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