BG62436B1 - Device and its application for oxychlorination - Google Patents

Abstract

The device relates to the production of 1,2-dichloroethanefrom ethylene, hydrogen chloride and oxygen, or oxygen-containinggas (oxychlorination), respectively, which favourably results in areactor (1) having lower limitation (2) for the catalyst fluidizedbed (3). A gas pipeline (distribution piping) (4) is fitted abovethe limitation (2) and inside the catalyst fluidized bedcontaining nozzles (5) distrubuted along the entire cross sectionof reactor (1). Nozzles (5) end in pipes (6) which to a greatextent are directed to outgoing gas flow into a counterflow to thegas flow which fluidized the catalyst and is supplied by means ofa delivery gas pipeline (7) fitted under limitation (2).8 claims, 1 figure

Description

Technical field

The invention relates to an oxychlorination device and its application. Oxychlorination is understood to mean the interaction of ethylene with hydrogen chloride and oxygen or oxygen-containing gas to give 1,2 dichloroethane (EDC). Hydrogen chloride is generally used which is released by thermal cleavage of EDC when converted into vinyl chloride.

For oxychlorination, catalysts are used which, on powdered carriers, such as aluminum oxide, contain metal halides, preferably copper chloride. The catalyst particles have an average diameter of about 50 µm and form a fluidized bed, which is maintained either only by the reaction gas streams containing optionally inert gas, or additionally by a single circulating gas stream. In this method, the reaction heat is distributed in the fluidized bed and transferred to cooling surfaces, thereby achieving a uniform temperature distribution in the fluidized bed reactor. In this case, the particles in the catalyst must have high abrasion resistance. This property is mainly determined by the carrier, in addition to the alumina already mentioned, silica, kieselguhr or pumice stone is used. With insufficient durability, the catalyst particles are ground, especially from the gas jets of the gas supply device, and the resulting dust from the catalyst carrier is withdrawn from the reactor from the upstream gas stream. This causes not only the loss of catalyst, but also increased wear of the equipment.

On the other hand, the use of wear-resistant material as a carrier leads to increased wear and tear on gas supply units and their frequent replacement, which means significant costs and additional costs due to production interruption.

In addition to the necessary balance between the stability of the catalyst particles and the wear caused by them, the catalyst particles must not agglomerate, as the resulting lumps cause fluid bed disturbances. The consequences would be an uneven temperature distribution in the fluidized bed with a corresponding unfavorable reaction, as well as possible blockages in narrow sections of the apparatus, for example, in a cyclone to remove dust over the fluidized bed or in the outflow tubes to return the cyclone dust into the fluidized bed. layer. Apart from the characteristic features of the catalyst and its distribution on the catalyst carrier, this tendency to aggregate depends especially on the concentration of the reaction gases in the fluidized bed.

BACKGROUND OF THE INVENTION

EP 0 446 379A discloses a reactor for the preparation of α-β unsaturated nitriles, at the bottom of which is provided a horizontally spaced olefin or tert-butyl alcohol gas feeder. A large number of nozzles are located at the bottom of the gas supply unit. Below this gas supply device and in parallel thereto is a second gas supply device for supplying gas containing oxygen. The distance between the two gas feeders is 25 to 300 mm. A smaller distance between the two gas feeders can lead to their damage by melting due to an unusual reaction, whereas at larger distances, the olefin or tert-butyl alcohol will not mix properly with the oxygen-containing gas, which will reduce the yield of nitrile.

GB 1 265 770A discloses a fluidized bed reactor with a distribution plate at the bottom of the reactor under which a gas supply device is provided, and otherwise provided at the ends of the reactor jacket above and adjacent to the distribution plate. gas supply device. This other gas feeder helps the catalyst not settle at the ends of the reactor. These precautions are necessary in particular in order not to reduce the catalyst. An additional gas supply device may be provided in the fluid bed, which is located at the bottom of the reactor in order to carry out extensions.

52436 ro fluidized bed based mixing of reactants.

WO 94/19099 discloses an oxychlorination facility consisting of a lower limitation reactor 1 for the catalyst fluid bed 3, gas pipeline / distribution pipe / 4, which has nozzles 5 terminating in tubes 6 which supply the outgoing gas stream horizontal component in the direction of flow. Under the restriction 2 a gas pipeline 9 is foreseen.

According to one embodiment of said apparatus, said tubes 6, in which the nozzles 5 terminate, have guides with outlet openings at their end, and according to another embodiment, these tubes 6 are pointed obliquely upwards, horizontally or obliquely downwards, with the tubes 6 terminating. freely in the catalyst bed. It is also possible that these tubes or the outlet openings of adjacent tubes are so arranged that the outgoing gas jets from them do not meet frontally with each other and / or do not hit the adjacent tube. Other preferred embodiments include tubes which have been passed through the restriction, in which nozzles are located, located below the orbit, but above the lower end of the tubes. These nozzles are preferably placed less than half the length of the respective tubes, in particular at a distance of almost one diameter of the tube from its lower end.

This well-known facility exhibits wear and tear with prolonged operation and high switching speeds, ie. at high gas velocities in the pipeline.

SUMMARY OF THE INVENTION

This wear does not occur or occurs to a very small extent when the tubes in which the nozzles end direct the gas flow substantially against the gas stream which maintains the catalyst as a fluidized bed.

The invention relates to an oxychlorination device comprising:

- a reactor having a lower limit for the catalyst fluid bed, a gas pipeline located below the lower limit, pipes passed through the lower limit, a gas pipeline (distribution pipes), located above the lower limit and including pipes.

According to the invention, the gas pipeline (nozzles) contains nozzles distributed along the entire cross-section of reactor 1 and terminating in its tubes, directing the gas stream leaving them substantially in countercurrent to the gas stream, which fluidizes the catalyst, which is formed between the upper edges of the reactor. the pipes in the structure and the lower ends of the pipes of the gas pipeline / distribution pipes, the mixing zone is sized so that it is possible to mix the outputs coming out of the pipes mentioned here. substances with catalyst, excluding the mixing zone from 25 to 300 ppm.

In a preferred embodiment, there are nozzles in the tubes passing through the lower restriction located below the restricted but above the lower end of the tubes. The doses should be located at a distance from the lower end of the pipes, which is approximately equal to the diameter of the pipes.

In another preferred embodiment, the nozzles of the pipeline (distribution pipes) are of different diameters and are distributed so that the amount of gas passed through the pipeline is distributed evenly across the cross section of the reactor.

According to the invention, the device must be designed so that the same number of tubes in the pipeline disposed above the restriction are arranged against the pipes in the restriction, and the tubes are evenly distributed along the cross section of the reactor. By arranging, respectively, one of said tubes, the amounts of reacting gases exiting each of these tubes are substantially adjusted accordingly.

In another embodiment of the device according to the invention, an equal number of tubes of the restriction and of the pipeline above it are disposed one against the other. This geometry determines the lowest possible erosion of the pipelines from the gas stream upstream of the restriction pipes. In addition, with this arrangement of tubes, the reactants leaving them and entering the catalyst fluid bed immediately come into full contact with the catalyst. This favors the desired reaction in the direction of EDC formation and suppresses side reactions such as heating ethylene with oxygen.

Another embodiment of the device allows for greater freedom for its parameters and construction. For example, the number of pipes in the pipeline above the limit is different from the number of pipes in the limit. However, in this case it is also important that these pipes are positioned as evenly as possible along the cross section of the reactor. This form allows the number of pipelines in one reactor to be changed without at the same time adjusting the tubes to the limit, which would entail high costs.

Examples of carrying out the invention

The invention is explained in more detail in the following example, shown in the accompanying figure, which is a schematic representation of an oxychlorination device.

The apparatus includes reactor 1, which in the particular example is 2.8 w in diameter and 26 t in height. . Above the lower restriction 2 there is a pipeline 4 which contains nozzles 5 terminating in tubes 6. A mixture of 5974 kg / h hydrogen chloride and 1417 kg / h oxygen is fed through pipeline 4, which passes through the nozzles 5 and tubes 6 into the catalyst boiling. layer 3. The nozzles 4 are of different diameters to achieve the most uniform distribution of gas across all the nozzles 5 and thus the cross section of the reactor 1. The nozzle diameter 5 increases in the direction of flow in the gas line 4 from 8.6 mm, 9.3 mm and further 10 mm to compensate for various pressure losses along the length of the pipeline 4 to the respective nozzles 5. The tubes 6 are an internal diameter of 40 mm and a length of 300 mm. Under the lower limitation 2 in the reactor 1 is a feed gas line 7 through which 2380 kg / h of ethylene is fed. Pipes 8 with nozzles 9 were inserted through the lower limitation 2. Ethylene fed through the gas line 7 passes through the tubes 8 and nozzles 9 into the catalyst fluid bed 3. Copper (II) chloride is supported on the carrier alumina in the form of a catalyst fluid bed as a catalyst. The starting materials mentioned above are fed into this catalyst fluid bed 3. For fluidization of the fluidized bed, an additional circulating gas flow of 8780 kg / h is supplied to the reactor 1 through the gas line 7 and the pipes 8 of the lower limit 2. The upper ends of the pipes 8 are connected aligned with the lower limit 2. Thus, the distance between the lower limit 2 and the lower ends of the pipes 6 amounts to 400 mm. In this section, the starting materials are distributed along the cross section of reactor 1 and mixing zones are formed between the individual starting materials and the catalyst. In reactor 1, upstream ethylene and circulating gas jets, which meet with hydrogen chloride and oxygen and react with the assistance of the available catalyst to obtain EDC and water. The resulting reaction heat of 238.5 kJ / mol is passed through the catalyst fluid bed 3 to a cooling coil 12 in which water is evaporated at 183 ° C. The reaction temperature in reactor 1 is 225 ° C at an overpressure of 3.2 bar. The gas flow at the top of reactor 1, consisting of the reaction products and the circulation gas, exits reactor 1 through three cyclones (not shown in the figure). The three cyclones in series serve to separate entrained catalyst dust from the gas stream in the upper part of reactor 1 above the catalyst fluid bed 3.

Claims (5)

Claims 1. An oxychlorination device, comprising: - a reactor / 1 / having a lower limitation / 2 / for the catalyst fluid bed / 3 /, - supply gas pipeline / 7 / located below the lower limit / 2 /, - pipes / 8 / passed through the lower limit / 2 /, - gas pipeline / distribution pipes / / 4 / located above the lower limit / 2 /, which contains pipes / 6 /, characterized in that the gas pipeline / 4 / contains nozzles / 5 /, distributed along the entire cross section of the reactor / 1 / and ending in the pipes / 6 /, 62430 directing the outgoing gas stream substantially in countercurrent to the gas stream, which fluidizes the catalyst, whereby the gas formed between the upper ends of the pipes (8) passed into the lower limit (2) and the upper ends of the pipes (6) of the pipeline / 4 (mixing zone) is dimensioned such that it is still possible to mix the effluent (8) and (6) exiting the said tubes with the catalyst, excluding the mixing zone from 25 to 300 mm. A device according to claim 1, characterized in that there are nozzles (9) extending below the restriction (2), but below the restriction (2), but above the lower end of the tubes (8). Device according to claim 2, characterized in that the nozzles (9) are located at a distance from the lower end of the pipes (8), which is approximately equal to 5 one pipe diameter / 8 /. A device according to claim 1, characterized in that the nozzles (5) are of different diameters and are distributed so that the amount of gas passed through the pipeline (4) is evenly distributed along the cross section of the reactor (1). Use of the device according to claims 1 to 4 for the reaction of ethylene with hydrogen chloride and oxygen or oxygen-containing gas to obtain 1,2-dichloroethane.