Abstract:
A device for continuously decaffeinating raw coffee includes a first extractor having at least one cell for use in a first treatment stage where raw coffee is preswollen by a swelling fluid that is added to the raw coffee. The at least one cell receives the raw coffee that is to be preswollen and is defined by a bottom and a plurality of sidewalls that extend towards one another to define a wedge-shaped cell. Additional similarly shaped cells and receiving chambers positioned below the cells may also be provided with a perforated bottom separating each cell from its respective receiving chamber.

Description:
This application is a continuation of application Ser. No. 07/260,077, filed Oct. 20, 1988, now U.S. Pat. No. 4,922,812, issued May 8, 1990. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a device for decaffeinating raw coffee and more particularly, to a device for continuously decaffeinating raw coffee that is subjected to various treatment stages. 
     BACKGROUND OF THE INVENTION 
     EP-8-0,008,398 has disclosed a process for decaffeinating coffee, wherein caffeine is extracted from raw coffee by an aqueous fluid. The extraction fluid is passed over a preloaded activated carbon adsorber, the caffeine being adsorbed. 
     Since the raw coffee delivered usually has a water content of 7 to 15 g of water/100 g of dry matter, it absorbs water in an aqueous fluid. During this swelling process, up to 160 g of water/100 g of dry matter (usually 130 g of water/100 g of dry matter) can be additionally absorbed by the raw coffee bean, the volume of the raw coffee bean being approximately doubled. In order then to avoid block of the column apparatus, which is used normally for taking the raw coffee beans, the dumped charge is kept moving during the swelling process by special measures (fluidizing with water or preswelling in a mechanical mixer). During this movement of the beans, however, fine particles are detached from the surface of the beans (silvery pellicle), which particles are carried along by the fluid and cause blockage in the downstream activated carbon adsorber. 
     SUMMARY OF THE INVENTION 
     Starting from the state of the art described above, it is the object of the present invention to demonstrate a simplified device of the type mentioned at the outset, wherein the raw coffee beans can be treated less robustly hitherto, that is to say while substantially at rest. 
     This object is achieved by a device of the type mentioned at the outset, which comprises, at least in the first treatment stage, for receiving the raw coffee which is to be preswollen, a container with a bottom and side walls, a substantial part of the side walls extending at a mutual angle, forming a conical container space. 
     Surprisingly, it has been found that, in this case, no blocking of the raw coffee beans takes place while they absorb water or their volume increases, even if the dumped charge is not moved. However, as a result of the fact that the raw coffee beans are at rest, there is no detaching of particles on the surface of the raw coffee beans, so that the adsorber is not blocked. 
     Preferably, the container in the first treatment stage is constructed as a sector-type cell of a rotary extractor which has a multiplicity of similar cells and a stationary slotted bottom. The achievement of the object stated above by a container of such construction, in which only two cell walls are at a mutual angle and form a container space which conically widens in the horizontal direction is particularly surprising and at the same time advantageous, since rotary extractors with containers of such construction are available. 
     In a rotary extractor, the individual cells with their contents are rotated over a stationary slotted bottom, which is interrupted by a sector-shaped section so that the cell contents can drop through downwards in this section and be removed. In the description which follows, the individual cells are defined with respect to their function, it having to be taken into account that each cell successively undertakes the various functions. 
     The first treatment stage, in which the raw coffee is preswollen, is followed by the actual extraction stage which extends over several extraction cells. A separate (stationary) receiving chamber is here allocated to each cell. The rotary extractor of this construction operates preferably as a continuous percolation apparatus by the crossflow/counterflow from this process. In the individual extraction stages, the extract concentration thus rises (viewed in the direction opposite to that of coffee transport), the preswelling stage at the same time representing a first extraction stage with maximum extract concentration and the extraction fluid being passed from this first stage to the adsorber. 
     Preferably, the adsorber is also constructed as a rotary extractor which not only contains the adsorption stages (operated by the crossflow/counterflow process), but in which the adsorbent is also preloaded before the adsorption stages and washed after the adsorption stages. As a result of this construction, it is particularly easy to synchronize the extraction device with the adsorption device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features essential to the invention can be seen from the following description of preferred embodiments of the invention, wherein like elements bear like reference numerals and wherein: 
     FIG. 1 is a first diagrammatic perspective representation of a first rotary extractor, 
     FIG. 2 is a block diagram of the first treatment stage of the rotary extractor according to FIG. 1, 
     FIG. 3 is a block diagram of two extraction treatment stages of the rotary extractor according to FIG. 1, 
     FIG. 4 is the last treatment stages and discharge stage of the rotary extractor according to FIG. 1, 
     FIG. 5 is a diagrammatic block diagram of a rotary adsorber, 
     FIG. 6 is a diagrammatic vertical section through a treatment stage of the rotary adsorber according to FIG. 5, 
     FIG. 7 is a diagrammatic representation of the linkage between the rotary extractor and rotary extractor and rotary adsorber, and 
     FIG. 8 is a block diagram of the processes which can be carried out using the arrangement according to FIG. 7. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As can be seen from FIG. 1, a first rotary extractor 10 includes a housing 11, in which several cell walls are provided which extend radially from a common axis and of which only two cell walls are marked in FIG. 1 by the reference numbers 12 and 13. These first cell walls 12, 13 form diverging side walls of a first cell 14 1  which, furthermore, is bounded by an outer wall 15 and an inner wall 16. The stationary bottom consists of bars 18 which are spaced apart by slots 19. The slotted bottom 17 formed in this way is thus fluid-permeable, the dimensions of the slots 19 being adapted to the material which is to be treated. 
     Receiving chambers 20 1  to 20 m  are provided below the stationary perforated bottom 17,  m  corresponding to the total number of cells, The receiving chambers 20 are provided with partitions 21 and have a common outer wall 22. 
     For the sake of clarity, the housing 11 in the extractor 10 illustrated in FIG. 1 is shown as being open at the top, but preferably the housing is also closed at the top, so that the entire arrangement can be hermetically locked. 
     A diagrammatic representation of the structure and mode of action of the rotary extractor 10 according to FIG. 1 is given below by reference to FIGS. 2 to 4. The illustrations here show an instantaneous representation of an operational state with cells at rest, the cells being moved forward in a defined cycle by one chamber width or cell width each time. 
     In FIG. 2, the first cell 14 1  is shown diagrammatically, with a feedscrew 28 ending above it. Below the perforated bottom 17 of the first cell 14 1 , there is the first receiving chamber 20 1 , so that fluid dripping through the perforated bottom 17 can pass exclusively into this receiving chamber and not into adjacent receiving chambers. 
     The receiving chamber 20 1  communicates at its bottom with a suction branch of a pump 25, the delivery branch of which is taken via a line 31 through a heat exchanger 24 to a spray head 23 which is located above the cell 14 1 . The heat exchanger 24 is connected to a heating steam line 38 and a condensate line 39 and is constructed such that fluid withdrawn from the chamber 20 1  is heated to a defined temperature (preferably 80° C.) before it emerges from the spray head 23. 
     A counterflow line 30 and a swelling water line 36, which are described in more detail below, lead into the chamber 20 1 . A float 27, which controls a valve 26 between the outlet of the pump 25 and a caffeine extract line 32 in such a way that a defined level in the chamber 20 1  can be adjusted, is additionally provided in the chamber 20 1 . 
     The cell 14 1 , shown in FIG. 2, with chamber 20 1  is adjoined by several extraction cells with receiving chambers located below, of which only two are fully shown in FIG. 3. With respect to the wetting devices, consisting of pumps 25, lines 31, heat exchangers 24 and spray heads 23, these extraction cells are essentially identical to the wetting device for the first cell but the valve 26 which is controlled by the float 27 and one inlet of which communicates with the delivery branch of the pump 25, is connected by its other outlet to a counterflow line 30 which thus ends in the chamber 20 n-1  at the valve 26 associated with the chamber 20 n . Accordingly, the countercurrent line 30 of the chamber 20 n+1  leads into the chamber 20 n , and so on. The countercurrent line 30 shown in FIG. 2 thus carries fluid which originates from the chamber 20 2 . This arrangement produces a fluid flow which, on the one hand, represents a crossflow via the working device and, on the other hand, comprises a countercurrent in the direction opposite to that in which the cells 14 are transported (arrow P in FIG. 3). 
     Downstream of the last extraction cell 14 m-1  with a setting device constructed as described before, there is a washing cell 14 m , above which a spray head 23 is arranged which is connected via a valve 35 to a washing water line 34. The chamber 20 m-1  of the last extraction cell merges directly (without a partition) into the chamber 20 m  of the washing cell. A caffeine-free extract line 33, the connection of which is described in detail below, leads into this double chamber. 
     After the washing cell 14 m , the bottom 17 has a discharge cut-out 37 so that, when the cells are transported further, the cell content can drop down through this cut-out 37 into a discharge 29 and be removed by the discharge screw provided there. 
     The abovementioned caffeine extract line 32 (FIG. 2) is connected to an inlet of the adsorber, in which caffeine contained in the fluid flowing in, is adsorbed, so that caffeine-free fluid passes from the adsorber (described in more detail below) into the caffeine-free extract line and from there into the last double chamber. 
     The cell extractor is preferably constructed in such a way that the side walls 12, 13 (see FIG. 1) of each cell are at a mutual angle of at least 20°. The feed device 28 is constructed in such a way that, when raw coffee is filled in, the first stage can be filled with such a quantity that the dumped charge reaches up to a height which essentially corresponds to the external width of the sector. 
     In detail, the process proceeds as follows. During the cycle time which (preferably) is one hour, the cell walls forming a rotor are at a standstill and all pumps 25 are running. The raw coffee present in the washing cell 14 m  is sprayed with fresh water which passes into the receiving chamber located below, to which the extract, which is anyway free of caffeine, from the adsorber is fed via the line 33. Because of the preloading of the adsorbent, the caffeine-free extract contains substantially all the water-soluble constituents of the raw coffee, except for caffeine. 
     As a result of the additions of fluid (washing water, caffeine-free extract), the fluid level in the last double chamber rises up to a level at which the valve 26 is open by the float 27 and fluid is delivered from the double chamber via the pump 25, associated with the latter, into the receiving chamber located in front. At the same time, the fluid present in the chamber is passed, via the pump 25 (with simultaneous heating to about 80° C.) to the spray head 23 to form a crossflow and runs through the quantity of raw coffee present in the chamber 14 m-1 . With respect to its delivery rate, the pump 25 is here controlled in such a way that the spraying rate of recirculation rate is lower than the maximum percolation rate (flooding rate). 
     The result of the level controls in the receiving chambers, associated with the extraction cells located upstream is a fluid flow, the fluid having a caffeine concentration which rises from chamber to chamber. In the first receiving chamber 20 1  (FIG. 2), there is thus an extraction solution of maximum caffeine content, the fluid level in the first chamber 20 1  being kept constant by the valve 26 controlled by the float 27, since, at rising level, an extract rate corresponding to the fluid rate fed is passed via the line 32 to the adsorber and returns from the latter back into the receiving chamber associated with the last extraction cell. 
     Just before the end of the cycle time, all the pumps 25 are switched off and the level control in the receiving chambers is put out of action. Thus, the total fluid quantity in each stage is collected in the particular receiving chamber. After the fluid has dripped off, which takes an adjustable time, the drive of the extractor is switched on again and the cells are moved forward by one chamber. During the standstill time of the pumps 25, the valve 35 for controlling the washing water feed is turned off, while the fluid flow through the adsorber can be maintained. When the cells have reached their new position, all the pumps 25 are switched on again, the level control initially being kept inactive. After expiration of a time set by a control unit not shown in more detail, the level control is reactivated. Furthermore, after the cells have reached their new position, the first cell is filled--as described at the outset--with a fixed quantity of raw coffee. In addition, the heating steam lines 38 are isolated during the standstill time of the pumps 25. 
     The adsorber, which is located between the lines 32 and 33, is described in more detail below by reference to FIG. 5. 
     The adsorber comprises a second rotary extractor 100, above whose first cell 114 1  in inlet 128 is arranged, through which adsorbent (activated carbon) can be fed in. The receiving chamber 120 1  located below the first cell 114 1  is connected via an outflow line 140 to an outflow, so that washing water, which is sprayed via a line 134 and the spray head 123 from above onto the adsorbent which has been filled in, can be discarded directly. 
     The cell 114 2 , which follows the filling/washing cell 114 1 , is connected, together with its associated receiving chamber 120 2 , to a preparation/regeneration tank 141, the outlet lein of which is located at the suction connection of a lading pump 142, by means of which the adsorbent is sprayed by means of the spray head 123 with preloading fluid from the tank 141. The ingredients of the fluid used for preloading are described in more detail in the European Patent which was cited at the outset and which is herewith incorporated by reference. In any case, the fluid is adjusted in such a way that the purified activated carbon, fed via the feeder 128, is preloaded with the ingredients, or substances identical to the ingredients, which are not to be extracted from the coffee beans, so that the caffeine is adsorbed selectively on the adsorbent. 
     The preloading cell 114 2  is followed by a first adsorption cell 114 3  which is connected in countercurrent to the subsequent adsorption cells (up to 114 n ), the levels of the receiving chambers 120 3  to 120 n  having level control devices (float 127, valve 126, countercurrent line 130) and spraying devices (pump 125, crossflow line 131, heat exchanger 124, spray head 123) to form a crossflow/countercurrent. The arrangements are thus similar to those of the extraction cells of the first rotary extractor 10. 
     The caffeine extract line 32 from the receiving chamber 14 1  of the first rotary extractor 10 leads into the receiving chamber 120 n  of the last extraction cell 114 n . The valve 126, controlled by the float 127, of the first receiving chamber 120 3  of the first adsorption cell 114 3  controls the volumetric flow, taken via line 33 from the first chamber 120 3 , of caffeine-free extract, which is fed to the double chamber of the last extraction cell 14 m-1 . The adsorption cells 114 3  to 114 n  are adjoined by one or more washing cells 114 n+1  to 114 m  which carry a crossflow/countercurrent flow in the same way as described above, fresh wash being charged by a washing water line 134 to the last washing cell 114 m  and fluid being pumped via the level control of the first washing cell 114 n+1  into the line 36. This fluid is fed via the line 36 to the first (swelling) cell 14 1  or its chamber 20 1 . 
     Downstream of the last washing cell 114 m , the perforated bottom 117 of the second rotary extractor 100 is provided with a discharge cut-out 137, through which the adsorbent contained in this cell can drop down to a discharge screw 129. 
     The discharger 129 conveys the (washed) adsorbent to an oven which is not shown here in more detail and in which the activated carbon is reactivated at about 800° C., the substances adsorbed on the activated carbon being vapourized and being burned in a downstream burner. In addition, carbon dust is removed. Finally, a quantity of fresh activated carbon equivalent to the dust removed is added, so that the quantity of adsorbent in circulation remains constant. 
     FIG. 6 shows a diagrammatic longitudinal section of a cell of the adsorber 100. In these cells, ports 101, which lead via conduits 102 right down to the perforated bottom 117, are made in the side walls 113, 114. The ports 101 serve as overflow ports which pass that fluid quantity, which is delivered by the pumps 125 in excess of the percolation rate, directly down into the particular receiving chamber located below. In this way, the cells can be operated in the flooded state. 
     The overall process is described in more detail below by reference to FIGS. 7 and 8. Where &#34;cells&#34; are mentioned in this description, this expression also comprises at the same time the receiving chamber located below. 
     The rotary extractor 10 and the rotary adsorber 100 have the same number of cells and are operated in synchronized motion. Raw coffee via the feeder 28 and loaded washing water from a (single) washing cell 114 16  of the rotary adsorber 100 to the first cell 14 1  of the first rotary extractor 10. In addition, caffeine-loaded extract from the subsequent extraction cells 14 2  passes via the countercurrent lines into the first cell 14 1 . Caffeine-rich extract is pumped from the cell 14 1  via the line 32 into the last adsorption cell 114 15  of the adsorber 100, the rate corresponding to the fluid flows through the counter-current line 30 and the swelling water line 36 minus the quantity of fluid absorbed by the coffee beans on swelling. In the subsequent extraction cells 14 2  to 14 14 , the caffeine content of the coffee beans falls until it reaches its minimum in the last extraction cell 14 14 . Caffeine-free extract pumped out of the first adsorption cell 114 3  of the adsorber 100 is fed via the line 33 to this last extraction cell 14 14  . After the last extraction cell 14 14 , the cell content of the cell 14 15  is sprayed with washing water via a line 34, a dripping-off cell 14 16  also being provided downstream of this washing cell 14 15  in the arrangement shown in FIG. 7. After dripping-off, the cell content in a discharge cell 14 17  is passed to the discharge 29, the (decaffeinated) coffee discharge there then being dried in a dryer 40 by feeding air (L) as shown in FIG. 8. 
     In the absorber 100, a washing cell 114 16 , in which the adsorbent is sprayed via a washing water feed from a washing water line 134, is provided upstream (as viewed in the direction of transport of the adsorbent) of the last adsorption cell 114 15 . The substances not bound to the adsorbent are thus floated off, this fluid being used via the line 36 as swelling fluid. 
     Downstream of the washing cell 114 16 , the adsorbent in a discharge cell 114 17  is passed via a discharge 129 to the reactivator 103, from which the regenerated reactivated carbon is passed via a feeder 128 to the first cell 114 1  of the adsorber 100. In the next cell 114 2 , the activated carbon is preloaded, namely by spraying with a preloading fluid (lines 143, 144). 
     As shown by FIG. 8, the adsorbent is thus in a circulation which is &#34;disturbed&#34; only by the removal of carbon dust (arrow V) and the addition of fresh activated carbon (arrow K). 
     The drive of the rotary extractor 10 and of the adsorber 100, and their cell numbers, are chosen such that the adsorbent, which has been free of loading substances in the reactivator 103 for a period of about one hour, is preloaded for a period of about two hours, before it is used for a period of about six hours for adsorbing caffeine in the cells 114 3  to 114 15 . After the adsorption, the adsorbent is washed for a period of about two hours before it is regenerated once more. 
     The raw coffee fed to the rotary extractor via the feeder 28 is preswollen for a period of about one hour in the first cell 14 1  and then passes within a period of about six hours through extraction cells 14 2  to 14 14 . The decaffeinated raw coffee coming from the extraction cells is washed for a period of about 0.5 hours in the cell 14 15  and then drips off for a further 0.5 hours. After dripping-off, the decaffeinated raw coffee is then dried in a dryer 40 for a period of about 2.3  hours by feeding (warmed) air. 
     EXAMPLE 
     A rotary extractor having a total of 12 cells (segment angle 30°), an external diameter of about 1 m and an internal diameter of bout 0.45 m was filled with 8.7 kg of dry raw coffee per cell. In the dry state, the width/height ratio was here 0.19 m/0.21 m. The beans were sprayed with raw coffee extract having an extract concentration of about 14% at a flow rate which was lower than the flooding rate. The raw coffee was here swollen at 80° C. within one hour, without a blockage of the charge occuring.