EP1154846A1

EP1154846A1 - Method and device to allow gaseous and solid reactants to react in a fluidized particle layer

Info

Publication number: EP1154846A1
Application number: EP00969437A
Authority: EP
Inventors: Gerhard Gross; Günter Lailach
Original assignee: Messer Griesheim GmbH
Current assignee: Messer Griesheim GmbH
Priority date: 1999-10-13
Filing date: 2000-10-06
Publication date: 2001-11-21
Also published as: WO2001026796A1; DE19949193C2; DE19949193A1

Abstract

In order to allow gaseous and solid reactants to react in a fluidized particle layer a fluidizing gas normally flows through a loose pile of primary particles lifting the pile and thereby creating a fluidized particle layer and reacting with said primary particles. A procedure whereby a solid powder loaded stream (11) is accelerated to supersonic speeds by means of a supersonic nozzle (4) and a carrier gas and is blown in transversally to the main stream direction of flow of the fluidizing gas in the fluidized particle layer is also known in prior art. In order to increase the solid load and the depth of penetration of the carrier gas stream (11), a carrier gas stream (11) which first exits the supersonic nozzle (4) and comprises a solid powder, is blown via a diffuser (2) disposed opposite to said supersonic nozzle (4) into a fluidized particle layer. In this invention a simple and operationally secure reactor is provided in order to perform said method characterized in that it has a supersonic nozzle (4) which lies opposite a direction of flow of a carrier gas-stream (11) and a diffuser (2) whereby a suction chamber (3) for a solid powder is provided between said supersonic nozzle (4) and a diffuser (2).

Description

Method and device for carrying out a reaction between gaseous and solid reactants in a fluidized particle layer

The invention relates to a method for carrying out a reaction between gaseous and solid reactants in a fluidized particle layer, wherein a fluidizing gas flows through a loose bed of primary particles, thereby raising the bed to form the fluidized particle layer and reacting with the primary particles, wherein a stream loaded with solid powder and accelerated to supersonic speed by means of a supersonic nozzle

Propellant gas is blown into the fluidized particle layer transversely to the main flow direction of the fluidizing gas.

Furthermore, the invention relates to a reactor for carrying out a reaction in a fluidized particle layer, with an inflow floor through which a fluidizing gas is introduced into a bed of primary particles located above the inflow floor for the purpose of producing the fluidized particle layer, and with a reactor wall surrounding the fluidized particle layer , in which at least one entry device is inserted above the inflow floor, which comprises a supersonic nozzle, by means of which a propellant gas is accelerated to supersonic speed with the formation of a propellant gas flow directed transversely to the main flow direction of the fluidizing gas.

The invention particularly relates to a process for producing metal chlorides such as TiCl ₄ , ZrCl and SiCl ₄ .

For the production of such metal chlorine, granular oxidic raw materials and granular petroleum coke are usually reacted at temperatures above 800 ° C. in fluidized bed reactors with the fluidizing gases chlorine and oxygen to form metal chlorides, CO ₂ and CO.

About 5 to 15% of the solid reactants are discharged as dust with the reaction gases after the grain size has been greatly reduced by the reactions is. These raw material losses due to dust discharge significantly increase the manufacturing costs for the metal chlorides.

The return of this dust to the fluidized bed reactors for the purpose of complete reaction has so far led to unsatisfactory results.

On the one hand, dusts are difficult to enter against the increased pressure prevailing in the fluidized particle layer in the fluidized bed reactor; that a large part of the dust is removed again.

It has been proposed to pellet the dust, but the effort is considerable and the success depends largely on the strength of the calcined pellets.

FIG. 5 shows an entry device for the entry of a solid into a reactor in the form of an injector, as are known from pneumatic conveying technology. Such injectors consist of an intake chamber (53)

Solid entry opening (55), a mostly conical nozzle (51) and a coaxial diffuser (52). With these injectors, finely divided solids can be conveyed from a lower pressure above the inlet opening (55) to a higher pressure (reactor) located behind the diffuser (52). The problem with this device is that the speed of the conveying gas stream (56) emerging from the nozzle (51) can only be varied within a relatively small range, because otherwise backflow occurs in the suction chamber (53). A loosening gas (54) can be blown through a sieve into the suction space (53) from below to avoid solid deposits in the suction space (53). The achievable solids loading of the conveying gas stream (56), the overcome

Back pressure in the space behind the diffuser (52) and the gas outlet speed from the diffuser (52) are relatively low. The system brings consequently also little advantage in solving the problem, dusts into the fluidized particle layer of ^'fluidized bed reactors write and distribute well in the film. DE-A197 22 570 discloses a method and a reactor according to the type mentioned at the outset. It is suggested that gas flows be injected into fluidized particle layers of a fluidized bed reactor by transversal injection at supersonic speed in order to avoid problems due to local concentration differences. It is also proposed to blow gas-solid mixtures into the fluidized particle layer in this way.

The technical implementation of this proposal is difficult, however, because in order to generate a gas jet at supersonic speed, the gas in front of the supersonic nozzle (hereinafter also referred to as the “Laval nozzle”) must have a pressure of several bars and both the compression of gases containing dust and the entry of dust into a compressed gas stream are extremely problematic, so the known method can only achieve a weak solid loading of the gas stream with a relatively small penetration depth into the fluidized particle layer.

In the fluidized bed reactor known from DE-A197 22 570, a slotted grate is provided, over which the fluidized particle layer is generated. This is surrounded by a reactor jacket in which Laval nozzles are installed. The Laval nozzles accelerate a gas stream laden with solids transversely to the main flow direction of the fluidizing gas in the direction of the fluidized particle layer to supersonic speed.

The invention has for its object a simple and economical

To provide a method in which, for the purpose of carrying out a reaction in a fluidized particle layer, a gas stream with a high solids loading and a large depth of penetration can be transversely blown into the fluidized particle layer. Furthermore, the invention has for its object to provide a simple and reliable reactor for performing the method.

With regard to the method, this object is achieved, based on the method mentioned at the outset, in that the propellant gas stream is loaded with the solid powder after leaving the supersonic nozzle and is blown into the fluidized particle layer via a diffuser opposite the supersonic nozzle. The propellant gas stream is first accelerated to supersonic speed by means of the supersonic nozzle and only then loaded with the solid powder. The compression and acceleration of the unloaded propellant gas stream presents no particular technical difficulties. A vacuum is created in the area behind the supersonic nozzle due to the high flow velocity of the propellant gas flow. This effect is intensified by the diffuser, so that the loading of the propellant gas stream in the area in front of the diffuser is facilitated by the solid powder being sucked into the propellant gas stream by the effect of the negative pressure. The above-mentioned difficulties with regard to the compression of dust-containing gases and the entry of dust into a compressed gas stream therefore do not occur in the method according to the invention.

Because the propellant gas stream exits the supersonic nozzle (Laval nozzle) and into the diffuser at supersonic speed, it is possible to convey the solid powder from a lower pressure space into the reactor, in which a higher pressure prevails. The method according to the invention enables a high solids loading of the propellant gas flow, a constant suction power and a high gas outlet speed from the diffuser and, as a result, a large depth of penetration of the solid powder into the fluidized particle layer.

In the fluidized particle layer, the solid powder reacts with the fluidizing gas introduced. The reaction can consist of a chemical reaction or a mechanical or thermal treatment. An example is the return of dust-like, solid raw materials into the fluidized particle layer of a fluidized bed reactor in the production of TiCI ₄ , ZrCI ₄ and SiCi ₄ , which have been discharged from the reactor by the flow of the fluidizing gas.

The diffuser is a component that is common in flow technology, by means of which a flow of high speed and low pressure is converted into a flow of lower speed and higher pressure. The Diffuser has a flow channel with an inlet opening and with an outlet opening for the flow medium.

The propellant gas stream enters the fluidized particle layer in a transverse direction - based on the main flow direction of the fluidizing gas. In this context, the expression “transverse” encompasses the directions running transverse to the main flow direction.

The solid powder is advantageously provided in a suction space and sucked in from there by means of the propellant gas stream. The intake chamber surrounds the gas outlet side of the supersonic nozzle. It can extend over the entire area between the supersonic nozzle and the diffuser and serve as a storage reservoir for a larger volume of the solid powder, thereby ensuring a uniform loading of the propellant gas stream.

Another improvement is to provide the solid powder in the suction space under increased pressure. This can be achieved, for example, by introducing the solid powder from locks into the suction space with increased pressure. The solids loading and the penetration depth of the propellant gas stream can thereby be increased still further.

In a particularly simple procedure, fluidizing gas is used as the propellant gas. Due to their identical chemical composition, propellant gas and fluidizing gas act in the same way on the solid powder.

A propellant gas containing chlorine and / or oxygen is preferably used to carry out chlorination reactions.

The method according to the invention has its full effect if the propellant gas is accelerated to a supersonic speed corresponding to at least 1.2 Mach, preferably 1.3 Mach to 3 Mach.

It has proven particularly favorable to generate a vacuum zone in the area of the gas outlet opening of the diffuser.

The additional zone of reduced pressure increases the depth of penetration of the laden propellant gas stream into the fluidized particle layer. This In particular in the case of fluidized bed reactors with a large diameter, the measure represents an alternative to the arrangement of a plurality of entry devices. It has proven useful to produce the vacuum zone by blowing in a propellant gas stream into a pressure reducing device connected to the diffuser. This makes it possible to increase the solids loading of the propellant gas stream several times over conventional processes. For example, the solids loading of the propellant gas stream in the method according to the invention can be two to three times as high as in the pneumatic conveying of the solids with conventional injectors mentioned at the outset, without backflow occurring.

In a preferred Verfa rens variant, raw material dust discharged from the fluidized particle layer is used as a solid powder. The method according to the invention makes it possible to return the dust discharged from the reactor in a manufacturing or processing process back into the reactor, in order to improve the economics of the process. The raw material dust is advantageously separated directly from the hot reaction gas in a dust separator and returned to the reactor by means of the process according to the invention. However, it is also possible to process these valuable raw materials first. For example, the raw material powders can be separated from the reaction gas of a fluidized bed reactor together with solid metal chlorides and dried after washing out the metal chlorides and then blown into the fluidized bed reactor.

In a further and equally preferred process variant, primary particles are used as solid powder. The primary particles to be treated in the fluidized particle layer are partially or completely introduced into the reactor using the method according to the invention. This measure, which is characterized by its economy, also makes it possible to use the raw material dust discharged from the fluidized particle layer as a solid powder in addition to the primary particles.

In a further advantageous process variant, waste dust is used as a solid powder. The waste dust is dust-like raw materials that arise in other processes. As an example, washed and dried Ti0 ₂ - Waste dusts called, which arise as insoluble residues when digesting titanium raw materials with sulfuric acid.

The propellant gas stream is preferably blown into the lower half, preferably into the lower quarter of the fluidized particle layer. The solid powder thus reaches a lower zone of the fluidized particle layer, so that a sufficient residence time for the reaction or treatment is ensured therein. To extend the residence time, the fluidized particle layer can contain additional particles of an inert material.

In the sense of a high solids loading of the propellant gas flow, an adjustment of the distance between the supersonic nozzle and the diffuser acts in such a way that the pressure in the intake space is minimal.

With regard to the reactor for carrying out this method, the above-mentioned object is achieved on the basis of the device according to the invention mentioned at the outset by the fact that the supersonic nozzle is opposite a diffuser in the flow direction of the propellant gas stream, that a suction space between the supersonic nozzle and the diffuser is provided for feeding a solid powder is provided.

Supersonic nozzle, diffuser and suction chamber are components of an entry device for the entry of a solid powder into the reactor. The propellant gas flow is accelerated to supersonic speed in the direction of the diffuser by means of the supersonic nozzle. An intake space is provided between the supersonic nozzle and the diffuser for the provision of a solid powder. In the simplest case, the supersonic nozzle extends into the intake space. As a suction space in this sense also acts as an outlet of a collecting container or a line for solid powder, which opens between the supersonic nozzle and the diffuser. Solid powder is sucked into the propellant gas stream from the suction chamber. The suction space can serve as a storage for a larger volume of the solid powder, so that a uniform loading of the propellant gas flow and thus a safe operation of the device is ensured. With regard to the method details and definition of terms, reference is made to the above explanations regarding the method according to the invention.

The reactor can be provided with several such entry devices for the entry of a solid powder.

The diffuser is a component that is common in flow technology, by means of which a flow of high speed and low pressure is converted into a flow of lower speed and higher pressure. The diffuser has a flow channel with an inlet opening and with an outlet opening for the flow medium. A reactor in which the diffuser is designed in the form of a Venturi nozzle is particularly simple and effective.

A further improvement of the reactor is achieved in that the diffuser has a gas outlet opening which is operatively connected to a pressure reducing device. A negative pressure is generated in the area of the gas outlet opening by means of the pressure reducing device. The additional negative pressure causes a greater depth of penetration of the loaded propellant gas stream into the fluidized particle layer. This measure represents an alternative to the arrangement of several entry devices, in particular in the case of fluidized bed reactors with a large diameter.

A pressure reducing device designed as an annular gap nozzle or swirl nozzle has proven particularly useful for this. An entry device can also be equipped with several such pressure reducing devices. The pressure reducing device succeeds in increasing the solids loading of the propellant gas stream several times over conventional methods.

The supersonic nozzle is preferably in the direction of the diffuser and in

Movable in the opposite direction. This makes it particularly easy to set the distance between the supersonic nozzle and the diffuser, which affects the negative pressure in the area of the outlet of the intake space and thus the intake power of the propellant gas stream. The process and reactor according to the invention are explained in more detail below on the basis of exemplary embodiments and a drawing. On the basis of sectional representations, the drawings show in detail:

FIG. 1 shows a first embodiment of an insertion device according to the invention for the introduction of a particle stream into a reactor in a side view

FIG. 2 shows a further embodiment of such an insertion device with an annular nozzle provided on the outlet side of the diffuser, in a side view,

FIG. 3 shows a side view of a diffuser provided with a swirl nozzle on the outlet side,

FIG. 4 shows a cross section through the diffuser according to FIG. 3 along the line A-A in a plan view, and

Figure 5 shows an entry device for the entry of a particle stream into a reactor according to the prior art in a side view.

The feed device shown in FIG. 1 is used to feed solid dust into a fluidized bed reactor. The insertion device comprises a Laval nozzle 4, a diffuser 2 in the form of a Venturi nozzle, and a suction chamber 3. The Laval nozzle 4 opens into the suction chamber 3. The diffuser 2 is located coaxially opposite the Laval nozzle 4 in the suction chamber 3. The Laval nozzle 4 accelerates propellant gas, which is symbolized by the directional arrow 11, to supersonic speed. The propellant gas 1 1 flows through the suction chamber 3 as a propellant gas stream. Solid dust is available in the suction chamber 3 and is to be introduced into the fluidized bed reactor. The solid dust is fed to the suction chamber 3 via the entry opening 5, as indicated by the directional arrow 12. The propellant gas stream sucks in the solid dust from the suction chamber 3 and arrives in the diffuser 2. From the diffuser 2, it enters the fluidized bed reactor (not shown in the figure) as a gas jet 13 containing solids. Depending on the operating parameters of the entry device according to FIG. 1, a different internal pressure is established in the area of the intake space 3. In order to keep this as small as possible, the distance between the Laval nozzle 4 and the diffuser 2 is adjusted by a corresponding displacement of the Laval nozzle 4 in the direction of the Diffuser 2 adjustable, as indicated by arrow 9. The input device is flanged from the outside to the reactor jacket in the region of the lower quarter of the fluidized particle layer of the fluidized bed reactor by means of the flange 1. For the purpose of loosening the solid dust, the suction chamber 3 is provided with a gas inlet for a purge gas 14.

In the illustration in FIG. 2, the same reference numerals are used to designate the same and equivalent components of the entry device as in FIG. 1.

In addition, the input device according to FIG. 2 is equipped on the output side to the diffuser 2 with a pressure reducing device in the form of an annular gap nozzle 6. The annular gap nozzle 6 is provided with a gas inlet by an additional one

Propellant gas stream 15 is introduced through the annular gap nozzle 6. The propellant gas stream 15 generates a pressure drop in the region of the gas outlet from the diffuser 2, which leads to the acceleration of the gas jet 13 emerging from the diffuser 2 and thus causes a greater depth of penetration into the fluidized particle layer.

A swirl nozzle 7 flanged to the diffuser 2 in the region of the gas outlet, as shown in FIGS. 3 and 4, has a similar effect. The propellant gas flow 15 is swirled by means of the tangential swirl nozzle 7. As an alternative to the swirl nozzle 7, guide vanes can also be used for swirling the propellant gas stream 15.

Injectors are known from pneumatic conveyor technology, which consist of a

Suction chamber with solids inlet opening, a, mostly conical, nozzle and a coaxial diffuser.

With these injectors, finely divided solids can be conveyed from a lower pressure space above the inlet opening to a higher pressure space behind the diffuser. The problem with this

The device is such that the speed of the propellant gas stream emerging from the nozzle can only be varied within a relatively small range, because otherwise there would be backflow in the intake space. The achievable solids loading of the conveying gas flow, the counterpressure that can be overcome in the space behind the diffuser and the gas exit velocity from the diffuser are relatively low. The The system therefore also has few advantages in solving the problem of introducing dust into the fluidized particle layer of fluidized bed reactors and distributing it well in the layer

The entry device shown in FIG. 5 in the form of an injector known from the prior art is described in more detail above

The method according to the invention is explained in more detail below using an exemplary embodiment and a comparative example with reference to the devices shown in FIGS. 1 and 5

Example 1 (comparative example)

An injector according to FIG. 5 was mounted on a fluidized bed reactor 30 cm above the inflow floor, as is usually used in pneumatic conveying technology when solids are required. The injector was flanged to the reactor wall with the gas outlet opening of the diffuser 52. The diffuser 52 had the shape of a ventun nozzle The gas outlet of the conical nozzle 51 had a diameter of 11 mm. Oxygen was used as the propellant 56, the pressure of which was reduced to 1.7 bar. The optimum distance between the nozzle 51 and the diffuser 52 was previously due to the dusty ore determined by a pipeline The pressure caused by the layer fluidized in the fluidized bed reactor pulsed in the area of the gas inlet connection between 1.15 and 1.20 bar.The ore dust was metered through a speed-controlled cellular wheel sluice into the suction chamber 53 At 1.7 bar propellant gas pressure 100 m ³ flowed O / h through nozzle 51 and Dif fusor 52 in the reactor In order to avoid solid deposits in the suction space 53, 5 m ³ 0 ₂ / h as a loosening gas 54 were blown through a sieve from below into the suction space 53. Under these conditions, a uniform vacuum could not be set in the suction space 53 if more than 400 kg Ore dust / h were dosed, the suction chamber became blocked. Even dosing was no longer possible from approx. 250 kg / h. The proportion of ore in the ore / coke dust mixture discharged from the reactor with the reaction gases was also at a dosage of 200 kg ore dust / h significantly increased (all volume data relate to m ³ in normal condition, all pressure data absolute pressure) Example 2

Instead of the injector used in Example 1, the feed device shown in FIG. 1 was flanged onto the fluidized bed reactor. From a design point of view, the conical nozzle 51 (FIG. 5) was essentially replaced by a Laval nozzle 4 (FIG. 1).

The Laval nozzle 4 had been calculated and manufactured in such a way that it generated a propellant gas velocity of 1.5 Mach at an oxygen admission pressure of 3.9 bar and 200 m ³ / h O ₂ . The distance between Laval nozzle 4 and diffuser 2 was optimized by means of the pneumatic delivery line. With this arrangement and the process parameters mentioned, 2.5 t / h of ore dust could be introduced into the reactor without excess pressure and solid build-up occurring in the suction space 3. With a dust input of up to 600 kg / h, the composition of the dust discharged from the reactor changed only insignificantly. Between 80% and 90% of the injected dust was converted in the reactor.

Claims

claims

1. A method for carrying out a reaction between gaseous and solid reactants in a fluidized particle layer, wherein a fluidizing gas flows through a loose bed of primary particles, thereby raising the bed to form the fluidized particle layer and reacting with the primary particles, one with solid powder loaded and by means of a supersonic nozzle accelerated to supersonic velocity stream of a propellant is blown transversely to the main flow direction of the fluidizing gas into the fluidized particle layer, characterized in that the propellant gas stream (1 1) after leaving the supersonic nozzle (4) loaded with the solid powder and via one of the Ultrasonic nozzle (4) opposite diffuser (2) is blown into the fluidized particle layer.

2. The method according to claim 1, characterized in that the solid powder is provided in a suction chamber (3) and is sucked in from there by means of the propellant gas stream (11).

3. The method according to claim 2, characterized in that the solid powder is provided in the suction chamber (3) under increased pressure.

4. The method according to any one of the preceding claims, characterized in that the fluidizing gas is used as the propellant gas.

5. The method according to any one of the preceding claims, characterized in that the propellant gas contains chlorine and / or oxygen.

6. The method according to any one of the preceding claims, characterized in that the propellant gas is accelerated to a supersonic speed corresponding to at least 1, 2 Mach, preferably 1, 3 Mach to 3 Mach.

7. The method according to any one of the preceding claims, characterized in that the diffuser (2) has a gas outlet opening, and that a vacuum zone is generated in the region of the gas outlet opening.

8. The method according to claim 7, characterized in that the vacuum zone is generated by blowing in a propellant gas stream (15) into a pressure reducing device (6; 7) connected to the diffuser (2).

9. The method according to any one of the preceding claims, characterized in that discharged from the fluidized particle layer

Raw material dust is used as a solid powder.

10. The method according to any one of the preceding claims, characterized in that primary particles are used as solid powder.

11. The method according to any one of the preceding claims, characterized in that waste dust is used as a solid powder.

12. The method according to any one of the preceding claims, characterized in that the propellant gas stream (1 1) is blown into the lower half, preferably in the lower quarter of the fluidized particle layer.

13. The method according to claim 2 or 3, characterized in that the distance between the supersonic nozzle (4) and the diffuser (2) is set so that the pressure in the suction chamber (3) is minimal.

14. Reactor for carrying out a reaction in a fluidized particle layer, with an inflow floor through which a fluidizing gas is introduced into a bed of primary particles located above the inflow floor for the purpose of producing the fluidized particle layer, and with one that fluidizes it

Particle layer surrounding reactor wall, in which at least one inlet device is inserted above the inflow floor, which comprises a supersonic nozzle, by means of which a propellant gas is accelerated to supersonic speed with the formation of a propellant gas stream directed transversely to the main flow direction of the fluidizing gas, characterized in that the supersonic nozzle (4) seen in the direction of flow of the propellant gas stream (1 1) is opposite a diffuser (2), and that between the supersonic nozzle (4) and the diffuser (2) a suction space (3) is provided for receiving a solid powder.

15. Reactor according to claim 14, characterized in that the diffuser (2) is designed in the form of a Venturi nozzle.

16. Reactor according to claim 14 or 15, characterized in that the diffuser (2) has a gas outlet opening which is in operative connection with a pressure reducing device (6; 7).

17. Reactor according to claim 16, characterized in that the pressure reducing device is designed as an annular gap nozzle (6) or as a swirl nozzle (7).

18. Reactor according to one of claims 14 to 17, characterized in that the supersonic nozzle (4) in the direction (9) on the diffuser (2) and in the opposite direction is movable.