CA2047500A1 - Process and apparatus for decaffeinating liquid, especially aqueous raw coffee extracts - Google Patents

Abstract

A b s t r a c t :

The invention relates to a process and an apparatus for decaffeinating liquid, especially aqueous raw coffee ex-tracts. The caffeine selective adsorbing agent is pre-ferably a molecular sieve, especially zeolite. This ad-sorbing agent is preferably arranged as a fixed bed in a column through which the raw coffee extract can be passed for decaffeination and through which subsequently at least one regenerating substance for regenerating the adsorbing agent for re-use can be passed. Preferably a plurality of such columns is inter-connected to a closed circuit, so that in a cyclic succession these columns can be connected to the adsorption process or the regeneration process. The columns can remain stationary in this process. The adsorbed caffeine is desorbed and, as a by-product, can be used for other purposes.

Description

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Process and appar~tus for decaffeindting l~qu~d, especlally aqueous raw coffQQ extracts D e s c r 1 ~ t ~ o ~ :

The invention relates to a process for decaffeinating liquid, especially aqueous raw coffee extracts, in which the caf-feine is adsorbed from the extract by means of an adsorbing agent. The invention further relates to an 5 apparatus for decaffeinating liquid, especially aqueous raw coffee extracts.

Different decaffeination methods are already in frequent use. Decaffeination can for example be conducted with 0 activated carbon acting as an adsorbing agent for caffeine.
For this purpose, the activated carbon has to be pretreated in a specific way to obta~n the required adsorbing pro-perties. In such a decaffeination process, an aqueous raw coffee extract is usually prepared and then contacted with the pretreated activated carbon for decaffeination.

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Such a decaffeination process is relatively complicated and expensive, especially because of the pretreatment of the adsorbing agent.

s The invention is therefore based on the object to propose a process for decaffeinating raw coffee extracts, which can be conducted in a more simple and economical manner. Accord-ing to the ;nvention, this object is attained, ;ndependent-ly of one another, by the features of cla;ms 1 and 19.

An apparatus accord;ng to the ;nvention for decaffeinat;ng l;quid coffee extracts, preferably for conducting the pro-cess according to the invention, is character;zed by the features of claim 19.

For the process accord;ng to the ;nvent;on for de-caffeinating raw cofFee extracts, a molecular sieve is used wh;ch ;s selective for caffeine. In an adsorption process, an extract of the coffee which is to be clecaffeinated is 20 contacted with this molecular sieve. The process according to the invention furthermore advantageously provides that the adsorbing agent is regenerated, especially by being liberated from the adsorbed caffeine, so that the adsorbing agent is re-usable for a following adsorption process.

Suitable adsorbing agents are molecular sieves, especially zeolites and particularly Y-zeolites. It is of advantage to use an aqueous raw coffee extract with a caffeine content of approxirnately 5 9/1.

The decaffeination process according to the invention is particularly economical to conduct, because practically no adsorbing agent is used. Instead, the adsorbing agent employed according to the invention is reprocessed after 35 the decaffeination of caffeine, so that it can be used almost indefinitely.

The adsorb;ng agent is regenerated by being liberated from the adsorbed caffeine. This desorbed caffeine can be isolated as a by-product of the decaffeination process according to the invention and can for example be used in 5 pharmaceutical products. This also reduces the costs of the decaffeination process according to the invention in an expedient way.

In the process according to the invention and according to o preferred embodimentsl the adsorbing agent can be re-generated at low costs, since the desorbing agents are easily and cheaply obtainable and the expenditure con-cerning the required apparatus installation is low.

15 Preferably, the adsorbing agent charged with caFfeine is first rinsed with an eluting agent, for example with water, to elute extract constituent substances - apart from caffeine - i.e. coffee residuals. The eluate obtained there-with con-tains extract constituents and can be used as a 20 swelling agent - which also reduces the costs - for pre-swelling or extracting raw coffee beans, so that the aqueous coffee extract which is to be decaffeinated can be economically prepared with this eluate.

25 After eluting the non-caffeine-constituents from the molecular sieve, the caffeine is desorbed from -the molecular sieve. For this purpose, a desorbing agent pre-ferably composed of 80% alcohol and 20% water is expedient-ly used. Passing the desorb;ng agent through the charged 30 adsorbing agent results in a solution of caffeine in the desorbing age~t. The desorbing agent and the caffeine can be separated to a large extent by d;stillation, so that the desorb;ng agent can be re-used for further desorption pro-cesses and ca~feine or aqueous caffein solution remains.

According to a further feature of the invention, desorption of caffeine ;s followed by a clean;ng step, in which residuals of the desorbing agent are displaced From the ~ ~ ~ 7 ~

adsorbing agent by means of a cleaning agent, preferably water or water vapor. Since the desorb;ng agent preferably also contains water, the desorbing agent and the cleaning agent can preferably be distilled off in a common 5 distillation process and be separated from the caffeine for reclaiming the desorbing agent and separating an aqueous caffeine solution.

The essent;al processes o~ the method according to the o invention are preferably conducted at a temperature ranging from between 50 and 100C, for example at about 75C.

~hen such an adsorbing agent is used, a pretreatment of the adsorbing agent, especially with regard to the selective 15 adsorptive capacity for caffeine, is advantageously not requ;red. Consequently, the decaffeination process according to the invention can be conducted in a more simple and economical way in this regard as well. Moreover, a molecular sieve can be used for a particularly long 20 period by way of reprocessing same. Furthermore, the adsorbed caffeine can be desorbed ;n a simple manner and with cheap desorbing agents.

The decaffeinating process or processes according to the 25 invention are thus particularly economical. Moreover, the process according to the invention can be automatized and conducted continuously in a particularly simple manner.

Separate protection is additionally claimed for a preferred 30 embodiment of the decaffeinating process according to the invention in which the process stages of the process are conducted in steps which are separate as regards the apparatus and are preferably identically designed. It is particularly advantageous to use individual steps or groups 35 of one or more steps simultaneously with adsorbing agents for difFerent process stages, but with each individual step passing in chronological succession through different pro-cess stages. The individual steps or groups of steps are preferably passed to the same respective process stage in cyclic continuation.

This means that an adsorption process can expediently be 5 conducted with some of the steps while simultaneously the adsorbing agent of the other steps is reprocessed. And the steps working in the reprocecessing stage can be in different phases at one time, for ;nstance some of them in the eluting phase, some in the desorbing phase or the o cleaning phase. Each of these steps passes through all existing stages in chronological succession.

If several steps are used in the same process stage, for example a group oF steps in the adsorption process, pre-15 ferably not all of these steps are passed to a followingprocess stage simultaneously, but rather in succession. It is for example preferred to use ten steps out of sixteen steps simultaneously for adsorption. As the adsorption process continues, only one of the ten adsorption steps is 20 taken out of the adsorption process and transferred to the reprocessing stage. This removed step is then replaced, pre-ferably cyclically, by a freshly reprocessed step.

The coffee extract which is to be decaffeinated is pre-zs ferably passed through all adsorption steps successively,first passing through the adsorpt;on step which out of all the involved steps has been in the adsorption process the longest and therefore has the lowest capacity to absorb caffeine, so that at the end the last remainder of caffeine 30 in the coffee extract to be decaffeinated is removed, i.e.
adsorbed by the most effective and freshly reprocessed adsorption step particularly efficiently. This ensures a particularly efficient and complete decafFeinat;on of the coffee.

An apparatus according to the invention for deca-Ffeinating liquid, especially aqueous raw coffee extracts comprises at least one chamber (process step) with a fixed bed of ad-sorb;ng agent, preferably of molecular s;eve, arranged there;n, and through wh;ch the l;quid or gaseous substances can be passed. Said chamber also comprises feed and drain connections for ;ntroduc;ng and w;thdrawing raw coffee ex-5 tract and at least one further agent for regenerating theadsorbing agent.

The chamber ;s preferably a column. Preferably, there ;s a f;xed bed of a molecular s;eve (for example 2 kg) located o ;n such a column through which the respective liquid or gaseous agent can be passed or is passable. The feed and withdrawal of the different agents used can be conducted in a particularly specific way by providing separate connections and l;nes for these agents, with preferably s several chambers in this line system being connected parallel to one another. It is preferred to use closed circuit lines with Forward and return flow.

Herew;th, the apparatus accord;ng to the ;nvent;on has the 20 part;cular advantage that the chambers ;tself do not have to be moved for conduct;ng ;nd;vidual processes of the decaffe;nat;ng process. The chambers and the adsorb;ng agent located therein do expediently not change location.
Instead, d;fferent agents are introduced to the chambers in 25 a spec;f;c way.

A group of chambers ;s preferably connected ;n ser;es for conducting the adsorption process or other processes. The agent needed for this process is then success;vely passed 30 through the chambers of sa;d group (from chamber to chamber).

Further advantageous embodiments of ~he process according to the invention and the apparatus according to the 35 invention follow from the subclaims.

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Exemplary embodiments which present further features of the invention are shown in the drawings, in which:

Fig. 1 shows a block diagram to illustrate the prin-s ciple structure of a decaffeinating apparatus according to the invention and the operation of the decaffe;nating process according to the ;nvention, o Fig. 2 shows a schematic side view of several apparatus steps of an apparatus according to the invention in the form of columns, Fig. 3 shows a perspective side view of the columns according to Fig. 2, Fig. 4 shows a circuit of a first embodiment of a de-caffeinating apparatus according to the in-vention, Fig. 5 shows the circuit of a second embodiment of an apparatus according to the invention, Fig. 6 shows the circu;t of a third embodiment of an apparatus according to the invention and Fig. 7 shows a top view of an example of a principle arrangement of the apparatus steps of a de-caffeinating apparatus according to the in-vention.

Fig. 1 shows a block diagram of the principle structure of an embodiment of a decaf~einating apparatus according to the invention and for the operation of an example of a de-35 caffeinating process according to the invention.

Field 10 in the block diagram represents the preparat;on ofa liqu;d, espec;ally an aqueous raw coffee extract wh;ch ;s to be decaffeinated, i.e. it represents an extraction.

5 The raw coffee extract prepared in this way is fed to an adsorption process according to f;eld 11, in which the caffeine is removed from the raw coffee extract with an adsorbing agent. The adsorbing agent is preferably a molecular s;eve, namely a zeolite, preferably a Y-zeol;te, which is suitable for a selective adsorption of caF-feine.

The raw coffee extract may pass through t~e adsorption pro-cess several times for decaffeination. After adsorption, the decaffeinated raw coffee extract is withdrawn and s further processed, which is not shown in Fig. 1.

The adsorbing agent used in adsorption 11 is reprocessed after the adsorption process so it can be re used in a following adsorption process 11. For this purpose, several 20 chronologically successive processes are conduc-ted, namely an elution process 12, a desorption process 13 and a clean-ing process 14.

Water is preferably used for the elution process, which is 25 to remove the raw cof~ee extract remainders or residuals from the adsorb;ng agent. Th;s water ;s passed through the adsorb;ng agent, ;f necessary several t;mes. The water, wh;ch is containing coffee extract residuals after the elution 12, can be used as swelling water for swelling the 30 raw coffee beans in the extraction process 10.

In the desorption 13, wh;ch follows the elut;on 12, a de-sorbing agent ;s passed through the adsorb;ng agent charged with caffe;ne. This desorb;ng agent ;s preferably composed 35 of 80% alcohol and 20% water. In th;s desorpt;on process 13, the desorb;ng agent may be repeatedly passed through the adsorb;ng agent as well.

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The desorbing agent desorbs the caffeine from the adsorbing agent, i.e. the adsorbing agent is liberated from caffeine.
The desorbing agent withdrawn from the desorption process 13 contains caffeine. The desorbing agent and the caffeine 5 or aqueous ca~feine solution are separated by means of a distillation process 15. After reprocessing, the desorbing agent, separated from the caffeine by means oF
distillation, can be re-used in a following desorption pro-cess. After the distillation process 15, the aqueous caffeine solution is wi-thdrawn and fed to a caffeine pro-cessing process 16 to obtain caffeine as a b~-product o~
the decaffeinating process.

A cleaning process 14 is conducted after the desorption process 13 in order to liberate the adsorbing agent from residuals of the desorbing agent. Preferably water vapor or water is used as cleaning agent. The desorbing agent is displaced from the adsorbing agent by means of this water vapor. After the cleaning process, a desorbing agent/clean-20 ing agent mixture is withdrawn and also fed to thedistillation process 15. Since water vapor or water is used as cleaning agent, the alcohol and water composition of the liquid which is fed to the distillation process 15 is not changed qualitatively. The quant;tative composition of the 25 reclaimed desorbing agent can be controlled via the para-meters of the distillation 15.

The sequence of processes 11..14 in the block diagram according to Fig. 1 is to be understood chronologically.
30 But at the same time, fields 11..14 in the hlock diagram also represent the arrangement of chambers containing ad-sorbing agents. Each of the chambers employed passes in chronological succession through the processes 11..14. Con-sequently, the block diagram according to F;g. 1 can also 35 be understood spatially insofar as some of the chambers are operating in one of the process stages according to pro-cesses 11..14 simultaneously and spatially side by side. I-t follows that while some of the chambers and the adsorbing agent located therein conduct the adsorption process 11, the adsorbing agent of other chambers ;s at the same t;me reprocessed with the three processes 12..14, some chambers being in the elution process 12, some already in the de-5 sorption process 13 and others already in the cleaning pro-cess 14. Preferably sixteen chambers with adsorbing agent are used for the decaffeinat;ng process, w;th ten chambers being simulateneously in the adsorption process 11, one chamber in the elution process 12, four chambers in the o desorption process 13 and one chamber in the cleaning process 14.

~hen the cleaning process 14 is completed in the latter chamber, i.e. when the last stage in the process of repro-cessing the adsorbing agent is completed, this chamber is again transferred to the adsorption process 11. At the same time, the chamber which has been in the adsorption process 11 the longest is transferred to the elut;on process 12, the chamber prev;ously used for the elut;on process 12 ;s 20 transferred to the desorption process, and the chamber wh;ch has been in the desorption process 13 the longest is transferred to cleaning process 14. Consequently, the chambers cyclically pass from one process to the o-ther, such that the number of chambers in any process advantage-25 ously always remains constant.

As a result, the chambers used in the adsorp-tion process 11 ha~e for example been in this process for different lengths of time. Preferably, the adsorption process of fresh raw 30 coffee extract ;s started in that chamber wh;ch has been in the adsorption process the longest, i.e. which has an adsorbing agent which is charged the most w;th caffeine and is therewith the least capable of receiv;ng or adsorbing caffeine. In the course of the adsorption process, the raw 35 coffee extract ;s passed through all (ten) chambers, and finally through the chamber which has been freshly trans-ferred from the cleaning process 14 -to the adsorption pro-cess 11, i.e. which has the adsorhing agent with the highest capacity of adsorbing caffeine. Consequently, even the last res;dual of caffeine is effectively removed from the raw coffee extract.

5 It is an advantage that the chambers do not ha~e to change locat;on for being transferred from one process to the next. Instead, the chambers remain in a fixed location and only the agents needed for the respect;ve process are intro-duced to the chambers. Consequently, each chamber ;s o connected to the appropriate substance lines of the re-spective process. The apparatus for conducting the process only has to provide a parallel connection of the chambers and a suitable valve control.

I5 Preferably 20 l/h of raw coffee extract is fed to the adsorption process 11, using preferably aqueous raw coffee extract with 5 g/l caffeine. Taking into account the pro-cess sequence, the adsorbing agent of each individual chamber is thus charged with 100 9 caffeine during the 20 adsorption process 11.

The individual processes 11..14 have to be in chronological coordination. The elution process 12 can For instance be conducted in three steps o~ 10 min each, so that the whole elution process 12 takes 0.5 h. Altogether 6 l eluting agent are for instance used in this process. After el~tion, the eluted chamber can remain on stand-by for ~7.5 h before being transferred to the desorption process 13. The de-sorp-tion process may take 1 h for each chamber. Thereafter, the chamber is transferred to the cleaning process 14. The actual cleaning ;n the cleaning process 14 may for instance take 0.5 h. This may also be followed by a stand-by period of 0.5 h. Accordingly, in 1 h of adsorpt;on process 11, other chambers go through the elution process 12 (;ncluding a stand-by period3, the desorption process 13 or the clean;ng process 14 (including a stand-by period). Sub-sequently, one chamber from one process ;s cyclically trans-ferred -to the following process. The adsorpt;on process 11 A ~

can thus be conducted near enough continuously with only short ;nterrupt;ons for d;sconnect;ng and connecting a chamber.

s Fig. 2 shows a schemat;c side view of chambers with ad-sorbing agents, as they can be used for the processes 11..14 accord;ng to F;g. 1. F;g. 2 shows three of pre-ferably altogether s;xteen chambers.

o Perpend;cularly or;ented columns 17 are used as chambers.
These columns are filled w;th zeolite (for example 2 kg) act;ng as adsorbing agent, approximately up to a level 18.
The zeolite in the column 17 rests on a permeable sieve bottom 19 and forms a solid bed of adsorbing agent on th;s sieve bottom 19. The successive columns 17 are connected to one another via connection lines 20, such that agents are introduced to a column 17 from above, withdrawn from the column 17 at the bottom and introduced to the following column 17 again from above. Each connect;on l;ne 20 has an 20 actuable shutoff valve 21 to d;sconnect the preced;ng column 17 from the follow;ng group of columns ;f required.
The agents are moved in the connection l;nes 20 w;th pumps 22. Samples can be withdrawn via sample valves 23.

25 Each column 17 has a double wall 24 by means of which the wall of the column 17 is heatable by a heat;ng med;um. Such a heat;ng medium may be passed through the double wall Z~, as indicated by the arrows 25. The heating medium can be passed through the double wall in counterflow to the sub-30 stance lines through the columns 17. The columns l7 arepreferably heated to temperatures of 60 to ~0C, pre-ferably to approx;mately 75C. The temperature can be ad-justed to optimize -the respective process to be conducted or ;t may be relevant as regards for example prevent;ng the 35 raw coffee extract from spo;lage.

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Fig. 3 shows the three columns 17 accord;ng to F;g. 2 ;n a schemat;c perspect;ve v;ew.

F;g. 4 shows the c;rcuit according to a -First embodiment of 5 a decaffeinating apparatus according to the invention.

In Fig. 4 and the following figures, sim;lar structural elements are designated by the same reference numerals as in Fig. 2.

Fig. 4 shows several columns 17. To simplify matters, only five out of preferably sixteen columns are shown. The columns 17 are connected to one another in a circuit via a connection line 20a and further connection lines 20.

Each of the columns 17 has connections for agent feed lines 26a..29a and for drain lines 26b..29b. The columns 17 are connected in parallel with respect to these agent lines 26..29. A by-pass line 30 is provided to by-pass a de-zo fective column 17 or to reverse the direction of flow ofthe agents through the columns 17.

Adjacent columns 17 can be connected or disconnected from one another by means of the shutoff valves 21, so that 25 groups of one or more columns 17, which are separated from one another, can be formed. Each culumn 17 can be connected to one of the substance lines 26..23 by means of four for-ward flow valves 31 and four return flow valves 32, with the columns 17 of one column ~roup being connected to the 30 same substance line 26..29.

Raw coffee extract which is to be decaffeinated is provided in a raw coffee tank 33. The raw coffee extract can be passed through defined columns 17 via the line 28 and can 35 be withdrawn after decaffeination in the direction in-dicated by arrow 34. For an adsorp~ion of the caffeine from the raw coffee extract, a ~roup of preferably ten colums 17 is used as an adsorbtion group and is interconnected via ~ 3 the connection lines 20 or shutoff valYes 21, and at the same time shut off from the other columns 17. Only the first column 17 of this adsorpt;on goup ;s connected to the feed line 28a for the extract and only the last column 17 5 is connected to the drain line 28b for the extract. Thus, the extract to be daffeinated enters the first column 17 of this group and passes through each following column 17 via the connection lines 20 tfrom column to column) up to the last column 17 and from there into the dra;n line 28b.
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After such a run of the extract through the group of ad-sorption columns, the column 17 which has been in this adsorption group the longest is disconnected from this adsorption group by shutting off the preceding and the 15 following shutoff valve 21. The forward Flow and return flow valves 31, 32, which also belong to the line 28, are shut off as well. By open;ng the valves 31, 32 to line 29, this column 17 is connected to the elution cycle to conduct an elution process. The elut;ng agent feed line 29a is connected to a tank 35 w;th eluting agent. The eluting agent is withdrawn from this eluting agent tank 35 and passed through the column 17 which is to be eluted. After elution, the eluting agent which has passed through the column 17 and which is enriched with the extract con-25 stituent substances can be introduced to a second elutingagent tank 36. This eluting agent from -the eluting agent tank 36, which contains extract constituents separated from the adsorption agent, can be used for a second elution and can be finally withdrawn in the direction indicated by 30 arrow 37. The elut;ng agent, containing extract con-stituents separated from the adsorbing agent, can be re-used as a swell;ng liquid for swelling raw coFfee beans, to prepare a raw coffee extract from raw coffee beans. This raw coffee extract is used for decaffeination and intro-35 duced to the raw coffee extract tank 33.

The column 17 which has passed through an elution is dis-connected from the line 29 by means of operat;ng the valves 31, 32 accordingly and is connected to the desorbing agent line 27. Preferably four columns are always ;n the de-5 sorption process at any time. The desorbing agent is storedin a desorbing agent tank 38 connected to the desorbing agent line 27 and could flow through the columns 17 of the desorption group via connection lines 20 simultaneously or success;vely. AFter the desorbing agent has passed through ~o the columns 17 of the desorption group, it reaches an inter-mediate tank 40 via the desorb;ng agent drain line 27b and a cooler 39. From this tank it is fed to a distillation unit 42 by means of a pump 41. The withdrawn desorbing agent contains the desorbed caffeine which has been 15 desorbed from the adsorbing agent o-F the columns 17 of the desorption group. The desorbing agent ;s separated from the caFfeine in the distillation unit 42 by being distilled off and cooled down with a cooler 43. A pump 44 re-turns the reclaimed and cooled desorbing agent into the desorb;ng 20 agent tank 38 via a return line 45. An aqueous caffeine solution rema;ns in the lower port;on o~ the d;st;llat;on un;t 42. This solution can be concentrated by means of a circulation evaporator 46 and can be withdrawn via a drain line 47.

Preferably four columns 17 are s;multaneously in the de-sorption process 17, and in a deF;ned success;on one column 17 From the preceding elut;on is connected to the de-sorption group and simultaneously one already desorbed 30 column 17 is disconnected from the desorption group so the number of columns 17 in this group remains constantly four.
Via a pump 48 and a heat exchanger 49, Fresh desorbing agent is pumped from the desorbing agent tank 38 into the column 17 of the desorption group which has been desorbed 35 the most. For example 4 l desorbing agent is pumped for 40 min into this column 17. At the same time, used-up de-sorbing agent is pumped out of the column 17 of the de-sorption group which belongs to the desorption group the - 16 ~
shortest and into which the desorbing agent from the (now) oldest desorption column is introduced via the connection lines 2~. The used-up desorbing agent is pumped into the distillation unit 42. The column 17 provided with fresh desorbing agent is meanwhile completely desorbed and is pumped empty within a period of 20 min, with the desorb;ng agent be;ng fed to the following column 17 of the de-sorption group. Thereafter, the desorbed column 17 is dis-connected from the desorpt;on group. The column 17 leav;ng o the elution process is connected to the desorption group and receives the desorbîng agent from the preceding desorpt;on group column 17 wh;ch desorbing agent ;s ;n the end d;splaced therefrom by the relatively fresh desorb;ng agent com;ng from the column wh;ch has just been dis-s connected from the desorpt;on group. Thus, each column rema;ns ;n the desorpt;on group for four hours.

The column disconnected from the desorpt;on group is connected to the cleaning agent line 26 as a single column after being shut off from the other columns by the shutoff valves 21.

Water vapor is used as a clean;ng agent and ;s fed into the cleaning agent feed line 26a ;n the direction indicated by arrow 50 and passed through the column 17 which i5 to be cleaned. The vapor which has displaced the last residual of desorbing agent from the cleaned column 17 is withdrawn from this cleaned column 17 via the cleaning agent drain line 26b and, together with this desorbing agent residual, reaches, via a cooler 51, -the intermediate tank 40 which also receives used-up desorbing agent. Accordingly, a desorb;ng agent/water vapor mixture wh;ch contains dis-solved caffeine is reprocessed in the distillat;on unit 42 and separated ;nto fresh desorb;ng agent and aqeuous caffeine solution.

~,9 After the clean;ng process, the adsorbing agent of the cleaned column 17 ;s again adsorptive and can be re-connect-ed to the adsorption group of ten columns. The place of this column in the elution is taken by the adsorption 5 column which is used-up the most.

Consequently, there are always ten out of sixteen columns in the adsorption process, one column in the elution pro-cess, four columns in the desorption process and one column o in the cleaning process, with only one column of one group being cycl;cally transferred from one group to the next in an intermittent manner. This ;s made possible by a simple control of the valves 21 and 31, 32.

~5 A complete cycle, in which one column passes through all possible process stages, from the youngest adsorption column to the oldest adsorption column, to the column in the cleaning process, from ~he youngest desorption column to ttle olded desorption column and finally to the cleaning 20 column, takes 16 h. Each switching cycle, in which one column is cyclically transferred to the following group of columns takes 1 h.

Fig. 5 basically shows a circu;t like that of Fig. ~, the 25 only difference being an additional third eluting agent tank 52 in the circuit of Fig. 5.

Coming from the first elut;ng agent tank 35, fresh eluting agent passes through the column 17 of the elution process 30 and into the second eluting agent tank 36. From this second tank, eluting agent is withdrawn for a second elution of the column 17 and is passed through the column 17 and into the third eluting agent tank 52. The eluting agent from the third eluting agent tank 52 is used for a th;rd elut;on and 35 thereafter is w;thdrawn ;n the direction indicated by arrow 37. The eluting agent circuit comprises a pump 53 and heat exchangers 54, 55.

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F;g. 6 shows a c;rcuit s;m;lar to those of F;gs. 4 and 51 especially of Fig. 5. F;g. 6 add;tionally shows a vapor tank 56 and tanks 57 and 58 for used-up elut;ng agent and decaffeinated extract. Two intermediate tanks 40a and 40b 5 are provided instead of just the one ;ntermediate tank 40.
The distillation unit 42 is followed by a caffeine pro-cessing unit 59.

Fig. 7 shows a schemat;c top plan v;ew of s;xteen columns o 17. These columns 17 are distributed essent;ally evenly over the per;phery of a rectangle by means of column holders 60. Fig. 7 also ind;cates that the columns 17 are connected to a closed c;rcuit system via lines 20, 20a and 26..29.

Claims (28)

1. A process for decaffeinating liquid, especially aqueous raw coffee extracts, wherein the caffeine is ad-sorbed from the extract by an adsorbing agent, cha-racterized in that a molecular sieve is used as adsorbing agent and in that the process of regenerating the adsorbing agent, especially the desorption of adsorbed caffeine com-prises at least one further process step for a re-usability of the adsorbing agent.

2. The process as claimed in claim 1, wherein zeolite is used as a molecular sieve.

3. The process as claimed in claim 2, wherein the zeolite is a Y-zeolite.

4. The process as claimed in one of claims 1 to 3, wherein the molecular sieve charged with caffeine is treat-ed with a liquid desorbing agent to attain a desorption of the caffeine.

5. The process as claimed in claim 4, wherein the de-sorbing agent is an alcohol-water mixture.

6. The process as claimed in claim 5, wherein the de-sorbing agent is composed of 80% alcohol and 20% water.

7. The process as claimed in one of claims 1 to 6, wherein the whole or part of the process is conducted at a temperature of approximately 50°C to 100°C, preferably at approximately 75°C.

8. The process as claimed in one of clams 1 to 7, wherein after desorption the molecular sieve is treated with a cleaning agent, preferably with water or water vapor, to remove residuals of the desorbing agent.

9. The process as claimed in one of claims 1 to 8, wherein, prior to desorption, the molecular sieve charged with caffeine is treated with an eluting agent, preferably water, for eluting sustaining non-caffeine-constituent substances.

10. The process as claimed in one of the preceding claims, whereon the process steps, comprising at least the adsorption of the caffeine by a molecular sieve and the regeneration of the molecular sieve, are conducted in steps being separate in apparatus terms and preferably having the same design.

11. The process as claimed in clam 10, wherein in-dividual steps or groups of one or several steps with molecular sieves are used for different process stages at one time, but each individual step passes through different process stages in a chronological succession.

12. The process as claimed in claim 11, wherein in a group of several steps being in the same process stage, the substance (raw coffee extract, eluting agent, desorbing agent, cleaning agent) which corresponds to the process stage successively passes through the steps of this group.

13. The process as claimed in claim 11 or 12, wherein sixteen steps are used, ten steps of which being simultaneously kept as a group in the process stage of adsorption, and the other six steps being kept in the regeneration process.

14. The process as claimed in claim 13, wherein four steps are kept in the process stage of a desorption of the caffeine from the molecular sieve of these steps.

15. The process as claimed in claim 13 and 14, wherein one step at a time is kept in the process stage for eluting the molecular sieve prior to desorption and one step in the process stage for cleaning the molecular sieve after desorption.

16. The process as claimed in one of claims 10 to 15, wherein each step is a column containing the molecular sieve.

17. The process as claimed in one of the preceding claims, wherein approximately 20 l/h of liquid raw coffee extract is passed through the molecular sieve for the caffeine desorption.

18. The process as claimed in one of the preceding claims, wherein the raw coffee extract is used in a con-centration of approximately 5 g/l.

19. An apparatus for decaffeinating liquid, especially aqueous raw coffee extracts, preferably for conducting a process as claimed in one of claims 1 to 18, comprising at least one chamber (apparatus step) with a -fixed bed of adsorbing agent arranged therein through which liquid or gaseous substances can be passed, said chamber having feed line and drain line connections for introducing and with-drawing raw coffee extract and at least one further agent for regenerating the adsorbing agent.

20. The apparatus as claimed in claim 19, wherein the chamber is part of a column (17).

21. The apparatus as claimed in claims 19 or 20, wherein the chamber comprises Four feed line connections and four drain line connections, specifically one feed and drain line connection each for a raw coffee extract line (28), a line for an eluting agent for an elution (29), a line for a desorbing agent for a desorption (27) and for a line (26) of a cleaning agent for a cleaning process.

22. The apparatus as claimed in claim 21, wherein the desorbing agent line (27) is designed as a closed circuit line starting from a desorbing agent tank (38), leading to the chamber and from the chamber to a distillation unit (42) for reclaiming the desorbing agent and which passes the cleaned desorbing agent from this distillation unit (42) back into the desorbing agent tank (38).

23. The apparatus as claimed in claim 21, comprising three eluting agent tanks (35, 36, 52) connected to one another via the eluting agent line (29), such that the chamber (column 17) can be eluted three times, the first eluting agent tank serving for receiving fresh eluting agent prior to a first run, the second tank serving for holding eluting agent after the first run and the third eluting agent tank serving for holding eluting agent after a second run and the eluting agent (eluate) reaching the drain line after a third run.

24. The apparatus as claimed in one of claims 19 to 23, comprising a plurality of chambers, especially sixteen chambers.

25. The apparatus as claimed in claim 24, wherein the chambers are connected in parallel with respect to the substance lines (26..29).

26. The apparatus as claimed in claim 24 or 25, wherein each chamber is connected to a following chamber via a connection line (20, 20a).

27. The apparatus as claimed in claim 26, wherein the connection line (20, 20a) connects the drain of one chamber with the feed connection of a following chamber.

28. The apparatus as claimed in one or more of claims 24 to 27, wherein the chambers are inter-connected to a closed circuit via a connection line (20a) between the last chamber and the first chamber.