WO1994019099A1 - Oxychlorination device - Google Patents

Abstract

In order to obtain high yields of 1,2-dichlorethane by reacting ethylene with hydrochloric gas and oxygen (oxychlorination), cross streams of the reactive components ethylene and oxygen are introduced into the catalyst fluidized bed and a horizontal component is imparted to one of the gas streams entering the fluidized bed. Advantageously, care is taken that the outflowing gas streams do not frontally hit each other and do not hit an adjacent gas inlet device.

Description

 description

Oxychlorination device

“Oxychlorination” means the reaction of ethylene with hydrogen chloride and oxygen or an oxygen-containing gas, where

1,2-dichloroethane (EDC) is formed. The hydrogen chloride obtained in the thermal cleavage of EDC to vinyl chloride is usually used as the hydrogen chloride.

For the oxychlorination, among other things, catalysts are used which contain metal halides, preferably copper chloride, on dust-fine supports such as aluminum oxide. The catalyst particles here have an average diameter of about 50 μm and form a fluidized bed which is either carried only by the reaction gas streams, if appropriate with portions of inert gas, or additionally by a recycle gas stream. In this process, the heat of reaction is distributed in the fluidized bed and dissipated on cooling surfaces, as a result of which a uniform temperature distribution in the fluidized bed reactor is achieved. The catalyst particles must have a high abrasion resistance. This property is essentially given by the carrier material, for which silica, kieselguhr or pumice stone are used in addition to the aluminum oxide already mentioned. If the abrasion resistance is insufficient, the catalyst particles are ground, in particular by the Gas jets of the gas introduction device, and the catalyst carrier dust thus occurring is discharged from the oxychlorination reactor by the upward gas stream. This not only causes a loss of catalyst, but also creates increased abrasion in the equipment.

On the other hand, the use of an abrasion-resistant carrier material leads to increased wear of the gas introduction devices, which leads to their frequent replacement, which means considerable effort and additional costs due to the interruption in production.

In addition to the necessary balance between the

The stability of the catalyst particles and the abrasion caused by them must also be ensured that the catalyst particles do not agglomerate, since clumping as a result leads to disruption of the fluidized bed. The consequences would be an uneven temperature distribution in the fluidized bed with a correspondingly more unfavorable reaction and possibly blockages at narrow points in the apparatus, for example in cyclones for dust separation above the fluidized bed or in downpipes for returning the dust from these cyclones to the fluidized bed. In addition to the nature of the catalyst and its distribution on the catalyst support, this tendency to clump depends in particular on the concentration of the reaction gases in the fluidized bed.

The invention relates to a device for oxychlorination, which is characterized by a Improved introduction of at least one of the gaseous reactants to be converted, at least one of the reactants being guided in such a way that the gas jet has a horizontal component (transverse to the flow direction leading upward in the entire fluidized bed). Due to its shape, the device according to the invention enables the reactor internals to be protected and the resulting long idle times, largely avoids clumping in due to its favorable gas distribution

Fluidized catalyst bed and allows such a favorable reaction that the yield of EDC is significantly increased by suppressing the formation of by-products and the undesirable combustion of ethylene with oxygen.

The distribution of the gas flows entering the fluidized bed over the entire reactor cross-section takes place via nozzles. In the case of larger reactor diameters in particular, a pressure loss which is controlled in these nozzles is important in such a way that the gas quantities of the reactants flowing in are kept as constant as possible at any point in the cross section. The speeds in the nozzles are necessarily so high to maintain the mentioned pressure loss that a high material removal takes place at these nozzles in a short time when there is carrier dust in the gas stream, which in turn is ground in a sharp gas jet at the nozzle outlet. This phenomenon occurs particularly with simple ones

Perforated plates, with perforated pipes and with nozzles, which are arranged at the end of gas supply pipes. The device for oxychlorination according to the invention is characterized by

- a reactor (1),

- a lower limit (2) for a fluidized bed ^■ - catalyst (3),

- a gas inlet (distributor pipe) (4) containing nozzles (5),

- Wherein the nozzles (5) open into tubes (6) which give the emerging gas stream a horizontal component in the flow direction, preferably by at the end of the tubes (6) baffles (7) with outlet openings (8) are arranged, and

- A gas inlet (9) below the limit (2).

A special embodiment of the device according to the invention is characterized by pipes (10) which are passed through the boundary (2), in which nozzles (11) are arranged below the boundary (2) but above the lower end of (10).

FIG. 1 shows a reactor according to the invention with the special configuration of the tubes (6) described above in cross section, which is shown in detail in FIG.

FIG. 3 shows a corresponding reactor in which the horizontal component in the gas flow direction is imparted by ends of the tubes (6) lying in front of or behind the plane of the drawing, as is shown, for example, in detail in FIG.

The deflection device (7) can be designed as a flat plate or curved, for example conical, so that the gas jets are deflected obliquely downwards. The tubes (6) themselves or the outlet openings (8) of adjacent tubes (6) are expediently arranged in such a way that the outflowing gas jets do not meet head-on and / or do not meet an adjacent tube (6).

The gas inlet (9) - as shown in FIGS. 1 and 3 - can be a tube directed towards the reactor floor, which is preferably curved. However, this embodiment is not essential to the invention. The gas can also be introduced in another form, for example by leading the gas inlet (9) vertically through the reactor floor and distributing it in the lower part of the reactor by means of a deflection device, for example a baffle plate. In any case, care must be taken to ensure that the reaction component (s) introduced or introduced by (9) reaches the fluidized bed (3) as evenly as possible through the inflow floor (2). A device as shown in FIGS. 1 and 3 is preferred.

The arrangement of the nozzles (11) in the tubes (10) is advantageously carried out on the basis of simple preliminary tests. An arrangement below half the height of the tubes (10) is preferred.

It is not expedient to extend the pipes (10) beyond the boundary (2) into the fluidized bed space, since this does not result in better gas distribution and an increased erosion can occur. In the case of an arrangement of the nozzles (11) according to FIGS. 1 and 3, the part of the tube (10) below the nozzle (11) forms an inlet section, which contributes to the alignment and equalization of the flow. The dimensions of the nozzles (5) in the tube (4) and the length of the tubes (6) are coordinated with one another in such a way that the pressure drop caused thereby ensures a uniform distribution of the gas over the cross section of the reactor (1). This dimensioning can easily be determined in individual cases using simple calculations.

In the device according to the invention, the oxychlorination reaction can take place due to the reduced

Abrasion or erosion run with long service lives. In particular in the preferred embodiment according to FIGS. 1 and 3 with the tubes (10) and the nozzles (11) arranged therein, the reaction can also be carried out very safely. The fact that the component entering through the lower boundary (2) first forms a mixing zone with the catalyst (3) before it comes into contact with the component or with the components which are introduced or are introduced through the distributor pipe (4). explosions can be safely prevented. If, for example, the ethylene is introduced through (9), it first forms a mixing zone above (2) with the catalyst fluidized bed (3) before it comes into contact with the one introduced through (4)

Comes into contact with oxygen or gas containing oxygen. In these cases, the hydrogen chloride can be added to one of the two components or both. On the other hand, the oxygen or the oxygen-containing gas, optionally in a mixture with hydrogen chloride, can be introduced through (9), again above (2) first forming a mixing zone with the catalyst in the fluidized bed (3) before contact with the other Mixing zone is possible, which is formed by the gas jets emerging from (6) or (8).

In each of the cases mentioned, an inert gas or cycle gas can be metered in in a manner known per se — expediently through the introduction pipe (9). Of course, it is also possible to feed the inert gas, a recycle gas or, for example, the hydrogen chloride as a separate component to the reactor (1) via separate inlet devices.

Through the particularly favorable introduction of the gases into the catalyst fluidized bed according to the invention, very uniform reaction conditions are ensured over the entire fluidized bed and higher yields are thereby achieved.

The invention is explained in more detail in the following examples.

example 1

An apparatus according to FIGS. 1 and 2 is used.

The reactants preheated to 160 ^β C are introduced in gaseous form into a reactor vessel (1) 0.5 m in diameter and 24 m high: a mixture of 190.5 kg / h of hydrogen chloride (HCl) and 45.2 kg / h of oxygen (0 ₂ ) flows through the line (4) via the nozzles (5) into the distributor pipes (6). From there, this gas mixture reaches the catalyst bed via the openings (8). The baffle plates (7) cause this to be deflected Horizontal gas flow. The openings (8) are arranged on the circumference of the distributor pipes in such a way that the gas stream emerging from the openings (8) in the fluidized bed does not cause any abrasion on the devices located therein. The energy of these gas jets swirls in the fluidized bed and causes an intimate mixing of the gases with the catalyst. 75.9 kg / h of ethylene (C ₂ H ₄ ) flow via the line (9) and the pipes (10) with the nozzles (11) through the distributor base (2). In the reactor vessel (1) there is copper (II) chloride as catalyst on an alumina carrier in the form of a fluidized bed (3). The above reactants are introduced into this fluidized bed. To fluidize the fluidized bed, a circulating gas flow of 280 kg / h additionally flows via the line (9) and the pipes (10) through the distributor plate (2) from below into the reactor vessel (1).

In the fluidized bed, the reactants are over the

Distributed reactor cross section and mixing zones are formed between the individual reactants and the catalyst. The reactants flow from bottom to top in the reactor. In this way they meet and react with the participation of the existing one

Catalyst to EDC and water. The resulting heat of reaction of 238.5 kJ / mol is dissipated via the fluidized bed (3) to the cooling coil (12), in which water evaporates at 183 ° C. The reaction temperature is 225 ° C at an overpressure of 3 bar in the reactor.

The gas stream at the reactor head, consisting of the reaction products and the cycle gas, leaves the reaction vessel (1) via two cyclones for further Processing. The two cyclones connected in series serve to separate the entrained catalyst dust from the gas stream at the reactor head above the catalyst fluidized bed.

The distribution pipes for the introduction of hydrogen chloride and oxygen are arranged at the lower end of the cooling coils (12). When all the reactants already mixed with the catalyst come together, the oxychlorination reaction begins here, and the heat generated in this way can be dissipated from here via the cooling coils (12). In this way it is excluded that higher temperatures occur in the fluidized bed below the cooling coil (12) if the reaction has already started there. A uniform temperature distribution throughout the reactor has a favorable effect on ethylene utilization and thus the EDC yield.

Example 2

An apparatus according to FIGS. 3 and 4 is used.

The reactants preheated to 160 ^# C are introduced in gaseous form into a reactor vessel (1) 2.8 m in diameter and 26 high: a mixture of 2 525 kg / h of ethylene (C ₂ H ₄ ) and 6 230 kg / h of hydrogen chloride (HCl ) via the lines (4) with the nozzles (5) and via the distributor pipes (6). 9,400 kg / h of air are passed through the

Line (9) through the pipes (10) with the nozzles (11) and the distributor plate (2) into the fluidized bed (3). In the reactor vessel (1) the catalyst copper (II) chloride is on an alumina carrier in the Form of a fluid bed (3). The above reactants are introduced into this fluidized bed. The gas flow of the reactants and the nitrogen content contained in the air flow cause fluidization of the fluidized bed. In this fluidized bed, the reactants are distributed over the cross section of the reactor and mixing zones are formed from the hydrogen chloride-ethylene mixture and the catalyst (3).

The reactants flow from bottom to top in the reactor (1). In this way, hydrogen chloride and ethylene meet with the air and react with the help of the catalyst to EDC and water. The resulting heat of reaction of 238.5 kJ / mol is dissipated via the fluidized bed (3) to the cooling coil (12), in which water evaporates at 189 ° C. The reaction temperature is 226 * C at an overpressure of 3.2 bar in the reactor. The gas stream at the reactor head, consisting of the reaction products and the nitrogen, leaves the reaction vessel (1) via three

Cyclones and a line for further processing. The three cyclones connected in series are used to separate the entrained catalyst dust from the gas stream at the reactor head above the catalyst fluidized bed.

The distributor pipes (6), which are directed downwards at an angle of 45 "to the vertical, for introducing the hydrogen chloride / ethylene mixture, result in a good distribution of this gas mixture over the

Reactor cross section without significant erosion due to the gas-catalyst mixture on the distributor pipes (6) or on the distributor base (2). For this purpose, the distributor tube (6) is across the cross section of the reactor distributed and offset from one another so that the gas stream emerging from the distributor tubes (6) in the fluidized bed does not cause any abrasion at the devices located therein. The energy of these gas jets swirls in the fluidized bed and causes an intimate mixing of the gases with the catalyst. This results in longer runtimes of the reactor between two shutdowns. While with conventional gas distribution systems this erosion limited the service life to an average of six months, the device according to FIGS. 3 and 4 results in service life of more than five years.

Claims

Expectations 1. Device for oxychlorination, characterized by - a reactor (1), - a lower limit (2) for a fluidized bed catalyst (3), - a gas inlet (distributor pipe) (4) containing nozzles (5), - The nozzles (5) open into tubes (6) which give the emerging gas stream a horizontal component in the direction of flow, and - A gas inlet (9) below the limit (2). 2. Device according to claim 1, characterized in that at the end of the tubes (6) deflection devices (7) with outlet openings (8) are arranged. 3. Device according to claim 1, characterized in that the tubes (6) point obliquely upwards or in the horizontal direction or obliquely downwards and these tubes (6) end freely in the catalyst bed (3). 4. Apparatus according to claim 1, 2 or 3, characterized in that the tubes (6) or the outlet openings (8) of adjacent tubes (6) are arranged so that the outflowing gas jets do not meet head-on and / or not an adjacent tube ( 6) meet. 5. The device, preferably according to one or more of the preceding claims, characterized by the boundary (2) Pipes (10) in which nozzles (11) are arranged below the boundary (2) but above the lower end of (10). 6. The device according to claim 5, characterized in that the nozzles (11) are attached below half the length of the tubes (10). 7. The device according to claim 6, characterized in that the nozzles (11) are mounted at a distance of approximately one diameter of the tubes (10) from the lower end of the tubes (10).