Adsorption medium reactors with a continuous fluidised bed of a granular absorption medium are known to be used in various ap- plications. Usually, a permeable bottom wall provides a through- flow of the liquid through the reactor. This permeable wall is equipped with a mesh wjdth withholding small particles. In chro- matographic applications, this mesh should be small enough to withhold the gel filling the reactor and large enough to let pass the particles to be distributed in the columns. This is a complicated procedure and there are no satisfactory results with the reactors of the prior art.

US 3,298,793 relates to a fluidised bed reactor, wherein the fluid to be treated is a gas stream. Therefore the flowing ve- locities are very high. Another reactor of such a kind is known from US 3,933,445, mentioning a gas inlet velocity of 50 to 500 feet per second. A third prior art document in this respect is US 3,974,091 showing the relevant stream velocities within Fig.

1.

Therefore the approach of US 5,549,815 is not usable by someone skilled in the art to prepare a reactor with a fluidised bed.

Furthermore, it is not suitable for food and drug applications or chromotographic applications as it is unsanitary, i. e. it has dead zones where particles can collect and which are difficult to clean without disassembling the device.

It is therefore an object of the invention to provide for a sim- ple reactor with a fluidised bed, with means for reliably pre- venting a particle exchange without inhibiting the liquid flow.

In the present invention this object is solved by providing an reactor according to the preamble of claim 1, characterised in that one or more outlets in to the reactor for the liquid to be treated are provided inside the reactor at a distance from, but near to, the bottom of said reactor and directed mainly towards said bottom of said reactor.

In a preferred embodiment of the present invention the tube guiding the liquid towards the outlets has an inner cross- sectional area which is equal to the sum of the inner cross- sectional area of all outlets connected thereto and in that the tube is divided in a multitude of portions leading to identical outlets arranged in a symmetrical way in respect to the tube.

Such a scale up design can only be achieved through the inven- tion. The cited prior art would not work with liquids, nor sani- tary requirements would be fulfilled.

Advantageous further developments of the invention may be taken from the dependent claims. In the following, the invention will be explained in detail with the aid of the embodiments repre- sented schematically in the drawings. The drawings show: Fig. 1 a schematical perspective view through a fluidised bed reactor with first embodiment of an outlet, in accor- dance with the present invention ; Fig. 2 an enlarged cross-section through the bottom of a re-

actor according to a second embodiment of the present invention having the inlet coming from below the bot- tom of the reactor; Fig. 3 a schematical view on two possibilities of spiderlike distribution of outlets in the reactor in accordance with the present invention ; and Fig. 4 a schematical view of two further embodiments of dis- tribution of liquid for the fluidised bed inside the reactor in accordance with the present invention.

Fig. 1 shows a schematical perspective view of an embodiment of an adsorption medium reactor 1 with a cylindrical wall 2 and a bottom 3. The bottom 3 is a disk, preferably coated with Teflon (by DuPont) or another smooth surface or it is a polished metal- lic surface. Alternatively, the bottom 3 can be equipped with a mesh (as described above) to allow combinations of flux and to allow elution of adsorbed material in packed bed mode. The space 4 between the walls 2 is filled with the medium creating the fluidised bed (not represented in the Fig.). In the central region of the reactor 1 is placed a rigid tube 5 extending along the longitudinal axis of the reactor 1 vertically from the top of the reactor 1 close to the bottom 3. The end 6 of the tube is directed towards the bottom 3 of the reactor 1. Between the lower. end 6 of the tube 5 and the bottom 3 of the reactor 1 is a gap 7 allowing the flow of liquid 8 descending through the tube 5 to be distributed equally in all directions around the outlet 6. The diameter of the reactor 1 can be in the range of several centimeters. The diameter of the tube 5 is e. g. 5 millimetres.

The relationship between both diameters may be chosen to be be- tween 1: 5 and 1: 20. An practical upper limit is given through the fact that the liquid descending within the tube 5 must also reach the fluidised bed near the reactor wall 2 and this depends on the velocity of the liquid, the horizontal distance to the

reactor walls 2 and the kind of liquid.

The very narrow distance to the bottom results in a complete fluidization. There is not necessarily a so called dense zone which is effectively necessary e. g. in US 5,549,815 to get plug flow. Typical flow velocities being applied are 200 to 400 cen- timeters per hour linear flow velocity.

The gap 7 between the bottom 3 of the reactor 1 and the lower end 6 of the tube 5 may be chosen between 1 and 5 millimetres preferably between 2 and 3 millimetres. This gap 7 gives the liquid descending the tube 5 enough space to follow the horizon- tal direction of the arrow 8 long enough and to enter the fluid- ised bed over the whole cross-section of the reactor 1. However, the particles of this bed are prevented from entering and block- ing the bottom 6 of the tube 5. The diameter of the reactor 1 can be chosen between several centimetres and 32 to 40 centime- tres. The diameter of the tube 5 can be chosen between 2 and 10 millimetres and preferably in the range of 6 millimetres.

Larger vessels can be constructed by arranging several reactors 1, one beside another without intervening walls so that only the outer circumferential wall remains. This forms the reactor em- bodiments as shown in Fig. 3 and 4.

Another way to distribute the liquid, as shown in Fig. 2, is to place a tube 15 beneath the reactor 1 which tube extends through the bottom 3. Then the tube 15 is directed into one or more horizontal branches 16. These horizontal branches 16 are ori- ented parallel to the bottom 3 until the point where they are bent in a zone 17 to a lower end with an outlet 18 parallel to the bottom 3 to of the reactor 1. The gap between the bottom 3 and the outlet 18 is similar to the gap between the bottom 3 and

the outlet 6 shown in Fig. 1. With directions and branches 16 and outlets 18 similar to tube 5 and end 6, respectively, the diameter of the reactor 1 according to Fig. 2 is chosen prefera- bly to be twice the diameter of the reactor 1 of Fig. 1, so that every tube portion 16 with outlet 18 gives rise to similar liq- uid flows 8 as in Fig. 1.

Fig. 3 shows schematical views from above of a reactor 1 with sidewalls 2 which are rectangular. The edges of the circumfer- ence wall should be rounded in order to achieve a minimal of dead zones in larger vessels. The tube 5 can be directed from above or can come from below as indicated in the upper part on the right side of Fig. 3. The tube 5 or 15 has four tube por- tions 16 with a combined cross-sectional area which is equiva- lent to the cross-sectional area of tube 5 or 15. These tube portions 16 end in a bent portion 17 with an outlet directed to- wards the bottom 3 of the reactor 1. Every circle 20 in Fig. 3 relates to the zone which is covered by every outlet of the por- tions 16. The diameter of the active laminar flow distribution circle 20 can be calculated from the gap 7, the diameter of the outlet 6, the kind of fluidised bed and the liquid and its pres- sure. As can be seen from this example the single reactor 1 of Fig. 1 can be replaced by a multiple reactor 11 in Fig. 3 which is a. directly scalable device.

In the lower part of Fig. 3 another distribution of tube outlets 16 is demonstrated, wherein six portions 16 are distributed to guide the liquid coming from tube 5. The zones 21 beyond the circles 20 are zones which are more distant from the outlets 18 than twice the distance between two outlets 18. The laminar flow of liquid is therefore not so strong. Nevertheless the fluidised bed also receives liquid in these regions.

It is a significant advantage of the invention in industrial ap- plications, that there is this possibility of cellular scale-up.

Fig. 4 shows two other schematical views of distribution of out- lets. The outlets 28 are at the end of the tubes 16 and create a stabilised laminar flow of liquid especially in the circles 20.

The left part of Fig. 4 shows a tube 5 with six horizontal tube portions 16 together with one central outlet just below the tube 5. This outlet must be chosen smaller or to be reached after an additional way in a tube portion below one of the tube portions 16 in order to have the same pressure of the outgoing liquid as in all other end portions 28.

Another possibility of distribution is shown with the triangular distribution as demonstrated on the right hand side of Fig. 4.

Both embodiments of Fig. 4 have the advantage in comparison with the embodiments of Fig. 3 that the surface of the space 21 be- tween the circles 20 is smaller. Therefore the distribution of liquid is more uniform.

The incoming stream of liquid is directed perpendicularly, i. e. right angled, onto the bottom 3 of the respective reactor 1.

However, angles different to 90° may be chosen with the result of less symmetry of the reactor 1. The main principle of all shown embodiments is the upflow behaviour of the liquid with an initial downflow onto the bottom 3 of the reactor 1.

The reactor 1 can be used for all kind of experimental stages from equilibration to cleaning. It is especially possible to provide reactors 1 for a laboratory scale since the reactor 1 is directly scalable. The outlets 8 or 18 are placed at a fixed po- sition some millimetres above the sedimented bed within the re- actor 1, so that a multitude of similar outlets within a bigger

reactor (see Fig. 3 or 4) behave as the one outlet within reac- tor 1 of Fig. 1.

The combination of common chromatography column design with the idea described in the present applciation leads to the possibil- ity of building a reactor where packed bed (downflow) and fluid- ised bed (upflow) applications can be combined by simply using a mesh or a photo-edged metal foil at the bottom. The mesh size maximum may be one third of the size of the smallest particles of the stationary phase in the column. In case of the use of a photo-edged metal foil the size of the holes can be similar as in the case of a mesh.

Typically, the fluidised bed is used for applying the feed (re- actants) and for washing. Packed bed is used for elution of ab- sorbed material and similar steps where a minimum of liquid should be used. With the mesh or foil at the bottom, the upward flow can be achieved either via the net or the tubes or a combi- nation of both. Especially for cleaning the reactor without emp- tying it (so called cleaning in place), a combination of both inlet possibilities can lead to superior results.

In food and drug production, all equipment and especially the reactors must be designed in a sanitary way. This means, that there must not be any dead zones (i. e. zones that are not flushed by the liquid) within the whole system. It is clear, that the described dense zone (see e. g. US 5,549,815) is inhibi- tory for applications in food and drug production, especially where biological material is applied.

The above mentioned combination (net/foil and tubes) are allow- ing for best sanitary design and scale up.

The reactor is filled with particles. Applications, where a strict control of the hydrodynamics is required, ask for spe- cially designed particles and of course plug flow of the liquid.

The special properties of the APB Streamline Gel, which may be used within such a reactor, are: -Spherical particles -Particle size: polydispers (leading to a size gradient) -Particle density: non homogenous (leading to a particle density gradient) Each of the spherical particles with different sizes and densi- ties theoretically has its own hydrodynamic property and subse- quently its predefined place in the reactor. This leads to a stable fluidised bed. Other types of gel or particles are suit- able for the application within the reactor.