EP2462054A1

EP2462054A1 - Method for producing chlorine by gas phase oxidation of hydrogen chloride in a fluidized-bed reactor

Info

Publication number: EP2462054A1
Application number: EP10737322A
Authority: EP
Inventors: Martin Karches; Kati Bachmann; Martin Sesing; Lothar Seidemann; Michael Pilz
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2009-08-05
Filing date: 2010-07-28
Publication date: 2012-06-13
Also published as: WO2011015503A1; CN102482082A; JP2013500926A; US20120134913A1; KR20120054616A; BR112012002613A2

Abstract

The invention relates to a method for producing chlorine by gas phase oxidation of hydrogen chloride on a heterogeneous, particulate catalyzer in a fluidized-bed reactor, obtaining a product gas mixture that is freed of any carried catalyzer particles in cyclones (1) disposed in the upper region of the fluidized-bed reactor, comprising a cylindrical upper part (2) having a tangential or spiral inlet (3) for the product gas mixture and narrowing at the lower end thereof via a conical part (4) into a cyclone downpipe (5), and a central immersion pipe (6) in the upper region of the cyclone (1) for diverting the product gas mixture freed of the carried catalyzer particles, characterized in that one to seven cascades of two to five cyclones each connected in series are used, wherein the cyclones (1) of each cascade, except for the cyclone (1) first permeated, which is designed that approximately 90 to 99% by weight of the carried catalyst particles are precipitated, each comprise a trickle valve (7) at the lower end of the cyclone downpipe (5) comprising an angled pipe terminator (8) and a loose flap valve (9) suspended at an angle α to the vertical, wherein the angle α and the weight of the flap valve (9) are designed so that the torque of the flap valve (9) based on the diameter of the outlet opening out of the angled pipe terminator (8) is in the range of 2 to 300 N/m².

Description

Process for the production of chlorine by gas phase oxidation of hydrogen chloride in a fluidized bed reactor

description

The invention relates to a process for the production of chlorine by gas phase oxidation of hydrogen chloride in a fluidized bed reactor.

The production of chlorine by gas-phase oxidation of hydrogen chloride on a heterogeneous, particulate catalyst by the so-called Deacon process is known and can be carried out industrially, for example in fluidized bed reactors, as described in WO 2005/092488.

The mass transfer in a fluidized bed and thus also the conversion of the reactants is significantly influenced, in particular, by catalyst particles of a size in the range from about 15 to 45 μm (compare Chemical Reaction Eng., Proceedings of the Fifth European / Second International Symposium on Chemical Reaction. , Amsterdam, 2, 3 and 4 May, 1972) Known devices for retaining catalyst particles from the product gas stream from fluidized bed reactors, in particular cyclones or filters, catalyst particles, in particular catalyst particles in the order of magnitude of about 15 to 45 microns particularly important for the mass transfer , with limited restraint. However, as far as possible, catalyst particles in the above-mentioned order of magnitude which are particularly important for the mass transfer and which are entrained with the product gas stream should be recycled back into the fluidized bed. Preferably, smaller catalyst particles, with an average particle size <15 microns should be collected as much as possible in order to recover the expensive catalyst and to prevent them interfere in subsequent system components, in particular lead to coverings on heat exchanger tubes and possibly also to bonds. This finer fraction should not be recycled unchanged in the fluidized bed.

It was therefore an object of the invention to provide a process for the production of chlorine by gas phase oxidation of hydrogen chloride on a heterogeneous particulate catalyst in a fluidized bed reactor, of the catalyst particles discharged from the fluidized bed, in particular the fraction of the order of magnitude of about 15 is returned to 45 microns in the fluidized bed. The object is achieved by a process for the production of chlorine by gas phase oxidation of hydrogen chloride on a heterogeneous, particulate catalyst in a fluidized bed reactor, to obtain a product gas mixture in cyclones, which are arranged in the upper part of the fluidized bed reactor, of entrained catalyst particles is freed, comprising a cylindrical upper part with a tangential or spiral inlet for the product gas mixture, which tapers at its lower end via a conical part in a cyclone downcomer, and a central dip tube in the upper part of the cyclone for discharging the entrained catalyst particles freed product gas mixture , characterized in that one to seven cascades of two to five cyclones connected in series are used, the cyclones of the cascade, with the exception of the respective first cyclone, which is designed so that there in which at least 90% by weight of the entrained catalyst particles are deposited, each having a trickle valve at the lower end of the cyclone downcomer, comprising an angled pipe end and a loose flap suspended at an angle α to the vertical, the angle α and the weight of the flap Flap are designed so that the torque of the flap based on the diameter of the outlet opening from the angled Rohrendstück in the range of 2 to 300 N / m ² . The gas phase oxidation of hydrogen chloride with an oxygen-containing gas stream in the presence of a heterogeneous, particulate catalyst by the so-called Deacon process is known.

The Deacon process can be carried out in various apparatus, in particular also in fluidized bed reactors, as provided by the present invention. Fluidized bed reactors generally have an at least approximately rotationally symmetrical, in particular a cylindrical, geometry. The starting materials, hydrogen chloride and an oxygen-containing gas stream are fed to the fluidized-bed reactor from below via a gas distributor, in particular a perforated bottom or a bottom with gas distribution nozzles arranged therein, the process conditions being set such that a heterogeneous, particulate catalyst forms a fluidized bed.

As catalysts, supported catalysts are preferably used which comprise one or more metal components on an oxidic support. Metal components are, for example, ruthenium or copper compounds. Alumina, in particular γ-aluminum oxide or δ-aluminum oxide, zirconium oxide, titanium oxide or mixtures thereof can be used as oxidic supports. When using the fluidized bed reactor for the oxidation of hydrogen chloride to chlorine, for example, the catalysts based on ruthenium known from GB 1, 046,313, DE-A 197 48 299 or DE-A 197 34 412 can be used. Furthermore, the catalysts described in DE-A 102 44 996 are suitable based on gold, containing on a support 0.001 to 30 wt .-% gold, 0 to 3 wt .-% of one or more alkaline earth metals, 0 to 3 wt .-% of one or more alkali metals, 0 to 10 wt .-% of one or more rare earth metals and 0 to 10 wt .-% of one or more other metals selected from the group consisting of ruthenium, palladium, osmium, iridium, silver , Copper and rhenium, each based on the total weight of the catalyst.

For the preparation of the catalyst, a γ-alumina powder is preferably impregnated with an aqueous solution of ruthenium chloride hydrate corresponding to the water absorption of the support, then dried at 100 to 200 ^° C. and finally calcined at 400 ^° C. under an air atmosphere. The ruthenium content of the catalyst is preferably 1 to 5 wt .-%, in particular 1, 5 to 3 wt .-%.

The process is preferably carried out as described in WO 2005/092488 by controlling the temperature distribution within the fluidized bed by arranging one or more heat exchangers in the fluidized bed in such a way that the temperature profile in the main flow direction, along the axis of rotation of the fluidized bed reactor, a temperature difference between the lowest and highest temperature of at least 10 Kelvin. The product gas mixture, which leaves the fluidized bed at its upper end, entrains a part of the catalyst particles with it. In order to minimize the loss of entrained catalyst particles, one to seven cascades of in each case two to five cyclones connected in series are provided by the process according to the invention in the upper region of the fluidized-bed reactor. Here, as a cascade, as usual, an arrangement of devices connected in series, in this case cyclones understood.

Each cyclone comprises in the manner known to those skilled, a cylindrical upper part with a tangential or spiral inlet for the mixture to be separated, in this case the product gas mixture, wherein the cylindrical upper part tapers at its lower end via a conical part into a cyclone downcomer. Due to the tangential or spiral inlet, the product gas mixture to be separated is imparted with a spiral downward movement, the catalyst solid particles contained therein depositing on the walls of the cyclone and be discharged via the cyclone downfall pipe. The gas stream cleaned off in the cyclone leaves the same in its upper area via a central dip tube.

According to the invention, at least one cascade of in each case two to five cyclones connected in series is used, the cyclone of each cascade flowing through first being designed such that at least 90% by weight of the entrained catalyst particles are precipitated therein.

The cyclone design is carried out according to the manner known to the person skilled in the art, as a rule according to the model by Barth-Muschelknautz, in particular taking into account the pressure loss and the degree of separation, which primarily depend on the peripheral velocities inside the cyclone (see VDI Warmestlas, 8th edition, 1979, Lja1-Lja1 1). The cyclone of the one or more cascades, which is flowed through first, is in particular designed such that the cyclone downcomer is submerged in the fluidized bed. This prevents a bypass of product gas mixture via the cyclone downcomer, or ensures that the product gas mixture passes through the cyclone exclusively or almost exclusively via the tangential inlet.

Advantageously, at the lower end of the cyclone downpipe of the cyclone first flowed through the one or more cascades connect an angled lower pipe end. In a further preferred embodiment, a baffle plate can be arranged below the lower end of the cyclone downcomer.

The further, one to four cyclones of each cascade are each equipped with a trickle valve at the lower end of the cyclone downcomers, each of which, as usual, has an angled pipe end and a loose, at an angle α to the vertical, which is different from 0, has suspended flap. The flap must lie completely on the angled, adjoining the cyclone downpipe lower pipe end; thus, this must be angled beyond the vertical position. The lower end of the cyclone downcomer is closed with a trickle valve to reduce or prevent gas bypass over it.

The inventors have recognized that it is possible to design the flap so that the separated solid additionally seals the flap against a gas bypass, while at the same time ensuring that the cyclone is not flooded by separated solid matter. Contrary to the view held in the trade publication "Hydrocarbon Processing", May 2007, pp. 75-84 that the flap weight has no influence on the gas bypass, it was found that the torque of the flap, wherein the angle of attack of the flap to the vertical and enter the flap weight, in the above range of about 2 to 300 N / m ² a minimal gas bypass and thus a minimal loss of expensive catalyst results.

For the above values for the torque of the flap, the angle α of the flap to the vertical is set in particular in a range between 1 and 5 ° and can vary in a relatively large range, from about 0.1 to 100 kg, because of the flap size depends, which in turn depends on the outlet opening of the tube.

Preferably, the flaps are designed so that they have a torque in the range between 10 and 200 N / m ² , in particular in the range between 30 and 100 N / m ² . More preferably, the flaps are designed so that they have an increasing torque with increasing position of the corresponding cyclone in the cascade. Preferably, one to five cascades of cyclones are used, in particular two to three cascades of cyclones.

In particular, each cascade comprises two to three cyclones. Within a cascade, identical cyclones can be used. In case of several cascades these can be identical to each other.

For a further separation of catalyst solid particles, the product gas stream, which is already largely purified in one or more cascades of cyclones, can additionally be conducted via a filter arranged outside the fluidized-bed reactor. This may in particular be designed so that it retains catalyst particles with a diameter <15 microns. In addition, nickel chloride, which can form during the reaction, is retained in the external filter. The process is advantageously carried out under the injection of inert gas. Preferred is in the equipped with flaps cyclones - At the inner wall of the angled Rohrendstückes, at the point A, where the extension of the center line of the cyclone downcomer pipe meets the inner wall and / or - at a point B, which is located downstream of the point A, and / or

- At a point C at the cyclone downcomer, preferably flushed at the lower end of inert gas. The flushing of inert gas has the following advantages:

Very fine solid particles seal the flap, it comes to complete or partial defluidization of the catalyst solid, the solid particles are based on the wall and form solid bridges. Then, no sufficient force can be applied to the flap to open it, i. the flap is blocked. The gassing loosens the solid particles and opens the flap.

Inert gas sparging may be carried out at any of the three sites A to C alone or in any combination of sites A, B and C.

A further advantage of inert gas flushing is that it is possible to check the function of a trickle valve via a differential pressure measurement between two gassing lines or a differential pressure measurement between a gassing line and the reactor head, since the pressure loss is a measure of the separation between the two measuring points Amount of solids is.

The invention is explained in more detail below with reference to a drawing and an embodiment.

In the drawing show in detail

FIG. 1 shows the schematic illustration of a preferred embodiment of a cyclone for use in the method according to the invention,

2 shows a preferred embodiment of a trickle valve with representation of the suspension for the flap, with partial representation of the suspension for the flap in Figure 2A, Figure 3 is a schematic representation of a plan view of a flap, Figure 4 is a schematic representation of a pilot plant, the one to

Implementing the method according to the invention used nachstellt cyclone downpipe, and the

FIGS. 5 to 7 show the results of tests with the pilot plant shown in FIG. 4, with different flap weights.

In the figures, like reference characters designate like or corresponding features.

Figure 1 shows schematically a cyclone 1 with a cylindrical upper part 2 with tangential inlet 3 for the product gas mixture, which tapers via a conical part 4 to a cyclone downfall tube 5, with central dip tube 6 in the upper part of the cyclone for the discharge of entrained catalyst particles liberated product gas mixture, as well as with a trickle valve 7 at the lower end of the cyclone downcomer 5, comprising an angled pipe end 8, which is formed in two pieces in the preferred embodiment shown in the figure, as well as a loosely suspended at an angle α to the vertical flap 9th

FIG. 2 shows an enlarged view of the lower end of a cyclone downpipe 5 with a Trickle Valve 7 adjoining it, which comprises an angled pipe end piece 8. At the point A, at which the central axis of the cyclone downpipe 5 meets the inner wall of the angled pipe end piece 8, an inlet pipe for inert gas is arranged by way of example. The angled pipe end 8 terminates at an angle α, the slightly, in the present example by 3 °, deviates from the vertical. At the lower end of the cyclone downpipe 5 is a suspension device 10 for the flap, not shown in Figure 2 (reference numeral 9 in Figure 1) is provided. FIG. 2A shows an enlarged view of the suspension device 10.

Figure 3 shows the schematic representation of a preferred embodiment of a flap 9, with two exemplary openings 11 in the upper region of the flap 9, via which the flap 9 is suspended in corresponding suspension devices 10.

Figure 4 shows the schematic representation of a pilot plant that simulates a cyclone downpipe 5 with trickle valve 7. About a solids dosage 12 solid is metered into the cyclone downcomer, the pressure maintenance 13 simulates the negative pressure in the cyclone downcomer and the separated solid is weighed on the balance 14.

Figures 5 to 7 show the results of the embodiments, which were carried out on a pilot plant shown in Figure 4.

embodiments

In tests A and B, the product is metered into the downpipe at a rate of 30 kg / h at a set and regulated vacuum of 850 mbar. In addition, a small amount of gassing of about 200 L / h is added via the gassing. The difference between the two tests lies in the flap or its weight.

In experiment A (see diagram experiment A), only the flap (about 3 kg net weight) without additional weight is used. After about 1, 2 - 1, 3 h opens the flap and it flow out about 35 kg of product. The drop tube is thus empty after each opening and accordingly the amount of leakage gas is high.

In experiment B (see diagram experiment B) this flap with 10 kg additional weight is now used. Again, the door will open after about 1 - 1, 3 h. The outflowing amount of product amounts in each case to 25 - 35 kg. The downpipe is also here almost empty after the opening process. If one compares the leakage gas quantities of both experiments, then one notes a difference. In experiment B, this gas quantity is on average slightly smaller than in experiment A. However, since these gas quantities are to be further minimized, in the next experiment C an additional 10 kg are applied to the valve (total weight now approx. 23 kg).

In experiment C (see diagram experiment C), the particles are also metered in at 30 kg / h and gassed at about 200 L / h. From about 1 - 1, 5 h, the solid trickles out continuously but slowly out of the cyclone downpipe. During this time, there are no significant fluctuations in pressure or in the amount of leakage gas. This means that the particles held by the heavy flap in the cyclone downcomer seal the flap opening.

Claims

claims

1. A process for preparing chlorine by gas phase oxidation of hydrogen chloride on a heterogeneous particulate catalyst, in a fluidized bed reactor, to obtain a product gas mixture, which is freed of entrained catalyst particles in cyclones (1), which are arranged in the upper part of the fluidized bed reactor comprising a cylindrical upper part (2) with a tangential or spiral inlet (3) for the product gas mixture, which tapers at its lower end via a conical part (4) into a cyclone downpipe (5), and a central immersion tube (3). 6) in the upper area of the

Cyclone (1) for discharging the entrained catalyst particles freed product gas mixture, characterized in that

- One to seven cascades of two to five cyclones (1) connected in series are used, wherein the cyclones (1) of each cascade, with the exception of the first through-flow cyclone (1), which is designed so that therein at least 90 wt. -% of entrained catalyst particles are deposited, at the lower end of the Zyklonfallrohrs (5) each have a Trickle valve (7) comprising an angled Rohrendstück (8) and a loose, at an angle α to the vertical suspended flap (9), said Angle α and the weight of the flap (9) are designed so that the torque of the flap (9) based on the diameter of the outlet opening from the angled Rohrendstück (8) in the range of 2 to 300 N / m ² .

2. The method according to claim 1, characterized in that the cyclone downpipe (5) of the respective first cyclone (1) formed by each of the one to seven cascades is immersed in the fluidized bed.

3. The method according to claim 1 or 2, characterized in that below the lower end of the cyclone downpipe (5) of the first arranged in the one to seven cascades cyclone (1) a baffle plate, spaced from the lower end of the cyclone downpipe (5) is arranged ,

4. The method according to any one of claims 1-3, characterized in that the cyclone downpipe (5) of each cyclone flowed through the first to seven

Cascades having an angled lower pipe end.

5. The method according to any one of claims 1-4, characterized in that one to five cascades of cyclones are provided.

6. The method according to any one of claims 1-5, characterized in that two to three cyclones (1) are provided per cascade.

7. The method according to any one of claims 1-6, characterized in that the cyclones (1) are constructed identical within a cascade.

8. The method according to any one of claims 1-7, characterized in that the cascades are formed identical to each other.

9. The method according to any one of claims 1-8, characterized in that the torque of the flap (9) based on the diameter of the outlet opening in the range of 10 to 200 N / m ² .

10. The method according to claim 9, characterized in that the torque of the flap (9) based on the diameter of the outlet opening in the range of 30 to 100 N / m ² .

1 1. A method according to any one of claims 1-10, characterized in that the angle α of the flap (9) to the vertical in the range of 1 to 5 °.

12. The method according to any one of claims 1-1 1, characterized in that the torque of the flap (9) increases with ascending position of the respective flap (9) associated with the cyclone (1) in the cascade.

13. The method according to any one of claims 1-12, characterized in that downstream of the one to seven cascades of cyclones (1), a filter is provided.

14. The method according to any one of claims 1-13, characterized in that in the flaps (9) equipped with cyclones (1)

- On the inner wall of the angled Rohrendstückes (8), at the point A, at which the extension of the center line of the cyclone downcomer pipe (5) meets the pipe inner wall and / or

- At a point B, which is located downstream of the point A, and / or

- At a point C at the cyclone downcomer, preferably flushed at the lower end of inert gas.

B09 / 0003PC