APPARATUS AND PROCESS FOR CONTINUOUS ADSORPTION

Abstract

The invention relates to an apparatus for the continuous production of a particulate adsorption product, the apparatus comprising: a mixing drum having an elongated cavity for receiving a particulate adsorbent material, an adsorbent inlet and a product outlet, wherein the mixing drum is arranged such that the cavity is inclined in flow direction of the particulate material, and wherein the cavity comprises an initial transport zone adjacent to the inlet and a mixing zone following the initial transport zone; a rotating member extending through the cavity in a longitudinal direction, wherein the rotating member comprises a helical conveying blade at longitudinal positions corresponding to the initial transport zone and mixing instruments at longitudinal positions corresponding to the mixing zone; and one or more injection nozzles for injecting a liquid adsorbate to the mixing zone. The invention further relates to a process for the continuous production of a particulate adsorption product using such apparatus.

Claims

1. An apparatus for the continuous production of a particulate adsorption product, the apparatus comprising: a mixing drum having an elongated cavity for receiving a particulate adsorbent material, an adsorbent inlet and a product outlet, wherein the mixing drum is arranged such that the cavity is inclined in flow direction of the particulate material, and the cavity comprises an initial transport zone adjacent to the inlet and a mixing zone following the initial transport zone; a rotating member extending through the cavity in a longitudinal direction, wherein the rotating member comprises a helical conveying blade at longitudinal positions corresponding to the initial transport zone and mixing instruments at longitudinal positions corresponding to the mixing zone; and one or more injection nozzles for injecting a liquid adsorbate to the mixing zone.

2. The apparatus of claim 1, wherein the mixing instruments comprise mixing paddles that are preferably distributed over the length of the mixing zone.

3. The apparatus of claim 2, wherein the operative surfaces of the paddles are slanted backwards.

4. The apparatus of claim 1, wherein the cavity further comprises a terminal transport zone adjacent to the outlet and wherein, at longitudinal positions corresponding to the terminal transport zone, the rotating member comprises a further helical conveyor blade.

5. The apparatus of claim 1, wherein the cavity further comprises a resting zone following the mixing zone and, at longitudinal positions corresponding to the resting zone, the rotating member is devoid of mixing instruments or conveyor blades.

6. The apparatus of claim 5, wherein the cavity further comprises an intermediate transport zone between the mixing zone and the resting zone, or within the mixing zone, and wherein, at longitudinal positions corresponding to the intermediate transport zone, the rotating member comprises another helical conveyor blade.

7. The apparatus of claim 5, wherein the resting zone extends over at least 10%, at least 15% or at least 20% of the length of the cavity and/or has a longitudinal extension that is equal or greater than the longitudinal extension of the initial transport zone, the terminal transport zone, the intermediate transport zone, or one of the mixing zones.

8. The apparatus of claim 1, wherein the incline angle is between 15 and 45° and/or wherein the L/D ratio of the cavity is between 2 and 10, preferably between 3 and 7.

9. The apparatus of claim 1, wherein the incline angle and the length and diameter of the mixing zone are such that there are longitudinal positions within the mixing zone whose entire cross-section remains below the level of product removal, and preferably such that longitudinal positions whose entire cross-section remains below the level of product removal account for at least 30% of all longitudinal positions within the mixing zone.

10. The apparatus of claim 9, wherein the incline angle, the length of the mixing zone and the positions of the injection nozzles are such that all injection nozzles are located below the level of product removal.

11. The apparatus of claim 1, wherein the apparatus comprises a lifting device for adjusting the incline of the cavity, preferably comprising one or more hydraulic cylinders.

12. A process for the continuous production of a particulate adsorption product using an apparatus of claim 1, the process comprising the steps of: continuously feeding a flowable particulate adsorbent material into the initial transport zone of the cavity through the inlet; continuously injecting a liquid adsorbate into the mixing zone of the cavity through the nozzles; and continuously operating the rotating member to propagate the adsorbent through the initial transport zone to the mixing zone and to agitate the adsorbent and the adsorbate in the mixing zone.

13. The process of claim 12, wherein the rotating member is operated at a rotational speed such that the peripheral speed of the helical conveying blade and the mixing instruments is 1 m/s or less.

14. The process of claim 12, wherein the particulate adsorbent materials is a silica, charcoal or zeolite material and/or wherein the particulate adsorbent material is a porous material having a specific surface area of at least 100 m.sup.2/g and/or wherein the liquid adsorbate is a liquid biologically active component or a liquid solution or dispersion of a biologically active component.

15. The process of claim 12, wherein the feed rate of particulate adsorbent material and the rotational speed of the rotating member are adjusted such that the average residence time of the particulate material is between 2 and 20 minutes, preferably between 5 and 10 minutes.

16. The process of claim 12, wherein the cavity volume unoccupied by the particulate material is filled with ambient air.

17. The apparatus of claim 3, wherein the cavity further comprises a terminal transport zone adjacent to the outlet and wherein, at longitudinal positions corresponding to the terminal transport zone, the rotating member comprises a further helical conveyor blade.

18. The apparatus of claim 2, wherein the cavity further comprises a terminal transport zone adjacent to the outlet and wherein, at longitudinal positions corresponding to the terminal transport zone, the rotating member comprises a further helical conveyor blade.

19. The apparatus of claim 18, wherein the cavity further comprises a resting zone following the mixing zone and, at longitudinal positions corresponding to the resting zone, the rotating member is devoid of mixing instruments or conveyor blades.

20. The apparatus of claim 17, wherein the cavity further comprises a resting zone following the mixing zone and, at longitudinal positions corresponding to the resting zone, the rotating member is devoid of mixing instruments or conveyor blades.

Description

[0038] Further details and advantages of the invention will be explained in the following with reference to the figures and working examples. The figures show:

[0039] FIG. 1: a schematic longitudinal section of an illustrative embodiment of an inventive apparatus;

[0040] FIG. 2: a flow diagram illustrating the process of the invention;

[0041] FIG. 3: a longitudinal section of the mixing drum of a concrete embodiment of an inventive apparatus;

[0042] FIG. 4: a longitudinal section of the mixing drum of another concrete embodiment of an inventive apparatus; and

[0043] FIG. 5: an assay showing the surface loading of an adsorbate over process time at different residence times.

[0044] In FIG. 1 an apparatus of the invention is schematically illustrated. The apparatus 10 comprises, as a key constituent, a tubular mixing drum 11 having an elongated tubular cavity 12 of essentially circular cross-section for receiving a granular adsorbent material. On the upstream end of the cavity 12, an adsorbent inlet opening 13 is provided on the upper side of the cavity wall. On the downstream end of the cavity 12, a product outlet opening 14 is provided on the lower side of the cavity wall.

[0045] The inlet opening 13 may be connected to a feeding apparatus for continuously introducing a controlled amount of granular adsorbent material to the cavity 12, such as a suitable gravimetric loss-on-weight type powder feeder. Such is apparent from the flow diagram of FIG. 2, where the mixing step 101 that is carried out in the apparatus 10 is preceded, on the one hand, by a step 201 of charging a feeder from a granular adsorbent material reservoir and a step 202 of feeding the granular adsorbent material to the inlet 13.

[0046] A rotating shaft 15 extends through the cavity in longitudinal direction. The shaft 15 is arranged in the center of the circle defined by the cross-section of the cavity 12 and is operably connected to an electric motor 16 for driving the shaft 15 at a desired rotation speed.

[0047] The rotating shaft 15 comprises two types of rotating annexes that are distributed over the length of the cavity 12, namely a helical conveying blade 17 and mixing paddles 18. The helical conveying blade 17 is arranged around the shaft 15 in the initial section of the cavity 12 that is adjacent to the inlet opening 13. The mixing paddles 18 are distributed over the remaining length of the shaft 15 in the subsequent part of the cavity 12. Owing to these two different types of annexes, the cavity can be divided in two main longitudinal sections, namely an initial transport zone 12a that is adjacent to the inlet 13 and a subsequent mixing zone 12b that extends from the initial transport zone 121 to the outlet 14. A discharge zone 12z follows the mixing zone 12b at the downstream end.

[0048] The apparatus 10 further comprises injection nozzles 19 for injecting a liquid adsorbate to the cavity 12, and more specifically to an early position within the mixing zone 12b of the cavity 12. The injection nozzles 19 are connected to a suitable liquid supply that includes a tank, a heating, a liquid pump and a volume flow meter whose signal is used to regulate pump operation. Such, again, is apparent from the flow diagram of FIG. 2, where the mixing step 101 is also preceded by a step 301 of suctioning liquid adsorbate from a liquid adsorbate tank and, optionally, preheating the liquid adsorbate to a desired temperature, a step 302 of pumping the liquid adsorbate to the nozzles 19 and a step 303 of measuring the volume flow towards the nozzles 19.

[0049] The outlet opening 14 can be connected to a suitable packaging apparatus for weighting and packaging the product. Also this is apparent from the flow diagram of FIG. 2, where the mixing step 101 is followed by a packaging step 401.

[0050] Still further, the apparatus comprises a lifting means including suitable swivel joints 20 and a hydraulic cylinder 21 for lifting the end section of the tubular mixing drum 11 to adjust a certain incline of the tubular cavity 12. In consideration of the incline, the mixing zone 12b of the cavity 12 can further be subdivided in a fully filled section 12b.sub.1 and a partially filled section 12b.sub.2. Specifically, owing to the essentially fluid behavior of suitable granular adsorbent materials, the materials will form an essentially planar surface 22 within the cavity 12, which is symbolized in FIG. 1 with a dotted line. The surface level corresponds essentially to the level of the exit opening 14, as any fluidly behaving material that reaches the level of the exit opening 14 will flow out of this opening 14. The longitudinal position of the boundary between the fully filled section 12b.sub.1 and the partially filled section 12b.sub.2 hence depends on the ratio of length L(12b) to diameter D of the mixing zone 12b as well as on the incline angle α. In the schematic illustration of FIG. 1, these parameters are such that the length of the fully filled section 12b.sub.1 corresponds approximately to the length of the partially filled section 12b.sub.2.

[0051] In this regard, it is preferred that the injection nozzles 19 are arranged at an early position within the mixing zone 12b, that is fully filled in operation. The section of the mixing zone where the liquid adsorbate is injected hence constitutes a subsection of the fully filled section 12b.sub.1, and is symbolized in FIG. 1 by reference numeral 12b.sub.1-1.

[0052] In FIG. 3 a mixing drum of a concrete embodiment of an inventive apparatus is illustrated. Identical reference numerals as in FIG. 1 are used for corresponding parts.

[0053] The mixing drum 11, rotating shaft 15 and rotating annexes are all made of stainless steel. The mixing drum 11 consists of two halves, a base 11a and a lid 11b. The inlet opening 13 and the injection nozzles 19 are arranged at the lid 11b. The rotating shaft 15, motor 16 and the outlet opening 14 are arranged at the base 11a. The overall length L of the cavity 12 is 140 cm and the diameter D is 20 cm, accounting for an L/D ratio of 7.0 and a total chamber volume of 0.044 m.sup.3.

[0054] The regular rotation direction of the shaft 15 is counterclockwise, when looking in the direction of the product flow that is symbolized in FIG. 3 by arrow P.

[0055] As opposed to the apparatus schematically illustrated in FIG. 1, the apparatus of FIG. 3 is more complex as far as the rotating annexes of the shaft 15 and, correspondingly, the zones of the cavity are concerned. Specifically, between the initial transport zone 12a and the discharge zone 12z of the cavity, there are, in consecutive arrangement, a mixing zone 12b, an intermediate transport zone 12c, a resting zone 12e and a terminal transport zone 12y.

[0056] In the mixing zone 12b the shaft 15 carries a number of mixing instruments. These mixing instruments comprise two pairs of mixing paddles 18, wherein the individual paddles 18 of the pairs are slightly offset in longitudinal direction. Between the pairs there are arranged two helical mixing blade fragments 18b that, in contrast to the helical conveying blade 17 of the initial transport zone 12a, does not comprise a closed surface but is rather an open construction such as to limit the feeding forward action. The nozzles 19 are arranged at a longitudinal position corresponding to the upstream pair of mixing paddles 18.

[0057] In the intermediate transport zone 12c, a helical conveying blade 17c whose blade shape and angle corresponds to the helical conveying blade 17 of the initial transport zone 12a is arranged around the shaft 15. The intermediate transport zone 12c is rather short and the number of full rotations of the helical conveying blade 17c around the shaft 15 is less than two.

[0058] In the resting zone 12e, the shaft 15 comprises no mixing or conveying annexes.

[0059] Finally, in the terminal transport zone 12y, another helical conveying blade 17y is arranged around the shaft 15, whose blade shape and angle again corresponds to the helical conveying blade 17 of the initial transport zone 12a.

[0060] In an experimental setup, the apparatus as in FIG. 3 was loaded with a particulate silica material with a nominal median particle size of between 200-400 μm and a liquid of essentially pure E vitamins (TATG; tocopheryl acetate technical grade) having a viscosity of approx. 1000 mPa.Math.s at 37° C. as liquid adsorbent material. The weight ratio of the granular silica material and the liquid adsorbent material was 48/52. The inclination of the cavity 12, i.e., the angle α was set to 33°. The rotation speed of the shaft was set to 45 rpm, which led to a peripheral speed of the conveying and mixing instruments of around 0.5 m/s. Nozzle pressure was 4.5 bar and liquid temperature was 37° C. Silica temperature was 27° C.

[0061] Using these settings, the filled chamber volume was determined at 0.015 m.sup.3, corresponding to approx. 34% of the total chamber volume. The feed rates (granular material) necessary to attain certain average residence times (standard deviation is about 40%) as determined in this experiment are outlined in Table 1 below.

TABLE-US-00001 TABLE 1 Residence time Feed rate 10 min 52 kg/h 15 min 35 kg/h 20 min 26 kg/h

[0062] Where the mean residence time was set to 15 minutes, a dry product of good homogeneity was obtained. It can thus be expected that a 10-15 minutes residence time would be sufficient in the given setting. Accordingly, scaling calculations would suggest that an output of several tons of product per hour would be attainable with bigger mixers having a chamber volume of, for example, between 0.1 and 2 m.sup.3. Such scaling calculations for commercially available mixers are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Pilot Mixer Ruberg DLM 350-1500 Ruberg DLM 800-3000 L [m] 1.4 1.5 3.0 D [m] 0.2 0.35 0.8 L/D 7.0 4.3 3.8 chamber [m.sup.3] 0.0044 0.144 1.507 volume filled [%] 34 34 50 75 34% 50% 75% chamber [m.sup.3] 0.015 0.049 0.072 0.108 0.512 0.754 1.130 volume feed rate at residence time [kg/h]  5 min 104 342 502 752 3.566 5.246 7.868 10 min 52 171 251 376 1.783 2.623 3.934 15 min 35 114 167 251 1.189 1.748 2.623 20 min 26 85 125 188 892 1.311 1.967

[0063] In FIG. 4 another mixing drum of a concrete embodiment of an inventive apparatus is illustrated. Again, identical reference numerals as in FIG. 1 are used for corresponding parts.

[0064] The mixing drum 11 of FIG. 4 differs over the mixing drum of FIG. 3 in that the resting zone 12e is replaced by a secondary mixing zone 12d that comprises a number of mixing paddles 18d that are offset in longitudinal direction. The configuration and shape of these paddles 18d is identical to the configuration and shape of the paddles 18 of the primary mixing zone 12b.

[0065] In an experimental setup, the apparatus as in FIG. 4 was loaded with a particulate silica material with a nominal median particle size of between 45-50 μm and a solution of 23% of 3-Nitrooxypropanol (3NOP, a drug given to ruminants to reduce methane emission) dissolved in 77% propylene glycol solvent as liquid adsorbent material. The weight ratio of the granular silica material and the liquid adsorbent material was 50/50. The inclination of the cavity 12, i.e., the angle α was set to 33°. The rotation speed of the shaft was set to 45 rpm, which led to a peripheral speed of the conveying and mixing instruments of around 0.5 m/s. Nozzle pressure was 6 bar and liquid temperature was 15° C. Silica temperature was 27° C.

[0066] Using these settings, the filled chamber volume was determined at 0.017 m.sup.3, corresponding to approx. 38% of the total chamber volume. The feed rates (granular material) necessary to attain certain average residence times (standard deviation is about 40%) as determined in this experiment are outlined in Table 3 below.

TABLE-US-00003 TABLE 3 Residence time Feed rate 2 min 30 sec 249 kg/h 5 min 124 kg/h 7 min  89 kg/h 10 min   62 kg/h

[0067] In FIG. 5 an assay is shown that illustrates the surface loading of 3NOP over process time at different residence times. While it would be expected that lowering the residence times have a negative impact on the adsorption homogeneity, the assay shows indeed very good adsorption homogeneity even at an average residence time of only 2 min 30 sec. Accordingly, scaling calculations would suggest that an output of several tons of product per hour would be attainable with bigger mixers having a chamber volume of, for example, between 0.1 and 2 m.sup.3. Such scaling calculations for commercially available mixers are shown in Table 4 below.

TABLE-US-00004 TABLE 4 Pilot Mixer Ruberg DLM 350-1500 Ruberg DLM 800-3000 L [m] 1.4 1.5 3.0 D [m] 0.2 0.35 0.8 L/D 7.0 4.3 3.8 chamber [m.sup.3] 0.0044 0.144 1.507 volume filled [%] 38 38 50 75 38% 50% 75% chamber [m.sup.3] 0.017 0.055 0.072 0.108 0.573 0.754 1.130 volume feed rate at residence time [kg/h] 2.5 min 249 816 1.073 1.610 8.522 11.214 16.820   5 min 124 408 537 805 4.261 5.607 8.410   7 min 89 291 383 575 3.044 4.005 6.007  10 min 62 204 268 402 2.131 2.803 4.205

[0068] Similar assays have demonstrated no difference in loading and homogeneity between adsorbate temperatures of 15° C., 25° C. and 35° C.

[0069] It is understood that the apparatuses of FIGS. 4 and 5, i.e., with mixing zone or secondary mixing zone, could interchangeably be used for both experiments described above.