Process and apparatus for regenerating a moist adsorption medium

A process and an apparatus for processing an adsorption medium which, by means of a hot gas, is freed of an agent, particularly moisture, adsorbed in the adsorption medium and is then cooled by a stream of gas or air. In order to avoid undesired heating of the exiting gas stream and/or of the drying air, a stream of cooling gas emerging from the hot adsorption medium is conducted through a heat accumulator for receiving the heat from the hot adsorption medium and then is recirculated through the adsorption medium.

BACKGROUND OF THE INVENTION 
This invention relates to a process for processing an adsorption medium 
which, by means of hot gas, is freed of an agent, particularly moisture, 
adsorbed therein, and is then cooled by means of a stream of gas. The 
invention further relates to an apparatus for carrying out the process of 
the invention. 
A moisture-laden gas stream is formed, for example, as the exit gas from a 
hopper in which plastic granules are dried by a stream of drying air. In 
such a case, for example, as described in Graeff, U.S. Pat. No. 4,870,760, 
the exit gas is conducted through one or more drying vessels filled with 
an adsorption medium, whereby the adsorption medium extracts the moisture 
from the gas so that the resulting dry gas can be used again as a drying 
gas for drying plastic granules. 
When the adsorption medium in a drying vessel is saturated with moisture, 
the drying vessel is transferred to a regeneration phase in which heated 
outside air is conducted through the adsorption medium and thereby takes 
up and carries away the moisture which was adsorbed therein. At 
approximately 250.degree. C., the temperature of the hot air used for 
regenerating the adsorption agent is significantly higher than the 
temperature of the exit air to be dried, which is normally 60.degree. C. 
When a drying vessel, after it has been regenerated, is used again to 
adsorb moisture from the exit gas, it initially fails to dry the exit gas 
because the temperature of the adsorption medium is too high. In addition, 
the exit gas which flows through the hot adsorption agent is heated to a 
temperature which is above the temperature desired for the drying air. 
Measures have therefore been suggested to cool the adsorption medium, which 
is still very hot at the end of a regeneration phase, and to delay making 
the absorption medium available for adsorbing moisture from the exit air 
until after the absorption medium has been cooled. Published European 
Patent Application No. EP 162,537 discloses two drying vessels connected 
in parallel, one of which is in the regeneration phase when the other is 
in the adsorption phase. In order to cool the hot adsorption medium, a 
partial stream of the exit gas is directed through the hot adsorption 
medium at the end of the regeneration phase and is then admixed with the 
drying gas exiting from the other drying vessel. This has the disadvantage 
that the partial flow of the exit gas which is used for cooling the 
adsorption medium is not dried, and consequently the moisture content of 
the drying air is adversely affected. In addition, the drying air is 
heated considerably by the partial stream of exit gas used to cool the 
adsorption medium, and this heating of the drying air is undesirable in 
many applications. 
Roth, Published German Patent Application No. DE 3,412,173, discloses using 
a partial stream of drying air for cooling the hot adsorption medium and 
then after the partial stream has passed through the hot adsorption 
medium, returning the partial stream to the stream of supplied exit air. 
This arrangement has the disadvantages that, during the cooling phase, 
only a smaller amount of drying air is available to the drying stage, and 
that the temperature of the exit gas to be processed is increased to a 
value which reduces the efficiency of the adsorption. 
Despite the efforts of the prior art, there remains a need for a better 
method and apparatus for regenerating a moist adsorption agent. 
SUMMARY OF THE INVENTION 
It is therefore the object of the invention to provide an improved method 
and apparatus for regenerating a moist adsorption medium. 
Another object of the invention is to provide a method and apparatus which 
avoids excessive heating of the exit gas or the drying air. 
A further object of the invention is to provide a method and apparatus 
which effectively cools a regenerated adsorption medium. 
These and other objects of the invention are achieved by providing a 
process for regenerating an adsorption medium which is freed of an agent 
adsorbed therein by treatment with a hot gas and thereafter cooled by a 
stream of cooling gas, wherein a warmed stream of cooling gas emerging 
from the hot adsorption medium is conducted through a heat accumulator for 
taking up heat from the hot adsorption medium and then recirculated 
through the adsorption medium. 
In accordance with a further aspect of the invention, the objects are 
achieved by providing an apparatus for regenerating an adsorption medium 
in which the adsorption medium is freed of an adsorbed substance by 
treatment with a hot treatment gas, the apparatus comprising at least one 
dryer vessel containing a charge of an adsorption medium for the 
substance, a supply line for a gas containing the substance, a connecting 
line leading from the supply line to the at least one vessel, an outlet 
line for exhausting gas from the at least one vessel, a regeneration line 
communicating between the connecting line and the outlet line, a heater 
associated with the at least one vessel for heating a gas flowing 
therethrough, a heat accumulator associated with the regeneration line for 
absorbing heat from a hotter gas or releasing heat to a cooler gas 
traversing the regeneration line, valve means for selectively switching 
gas flow in the apparatus between a drying circuit comprising the supply 
line, the connecting line, the at least one vessel containing the charge 
of adsorption medium, and the outlet line, and a regenerating circuit 
comprising the regeneration line, the heat accumulator, the heater, the at 
least one vessel containing the charge of adsorption medium, and the 
connecting line, and fan means operable to convey gas through the drying 
circuit or through the regenerating circuit. 
In accordance with the invention, a stream of cooling gas emerging from the 
hot adsorption medium is conducted through a heat accumulator for 
absorbing the heat from the hot adsorption medium, and after passing 
through the heat accumulator, the stream of cooling gas is recycled 
through the hot adsorption medium. As a result, the hot adsorption medium 
cannot have any influence on the drying operation and/or the drying air. 
In addition, the heat contained in the hot adsorption medium is not lost. 
Instead, during the adsorption phase following the regeneration, this heat 
may be extracted from the heat accumulator for other uses. This 
significantly improves the energy balance of the processing of the 
outgoing gas. The heat accumulator is virtually maintenance free and is 
therefore a very low-cost accessory for the dryer. 
In an advantageous further embodiment of the invention, the heat contained 
in the heat accumulator is used at the beginning of the subsequent 
regeneration step to heat the gas used for the regeneration, whereby 
heating energy is saved. 
In order to avoid a decrease in the flow of drying air during the 
regeneration, it is preferred to use outside air for regenerating the 
adsorption medium. 
If, in accordance with a preferred embodiment of the invention, the gas 
stream which emerges from the hot adsorption medium is repeatedly 
recirculated through the heat accumulator and the adsorption medium until 
the adsorption medium is sufficiently cooled, then there is no possibility 
that the gas stream used to cool the adsorption medium will deposit 
moisture back into the adsorption medium, which would occur if fresh 
outside air were used to cool the adsorption medium. 
If in accordance with a further preferred embodiment of the invention, a 
material, such as metal, which has a high specific heat and/or high 
thermal conductivity, is used as the storage medium, then the space 
requirement for the heat accumulator will be reduced. The use of glass or 
rocks as a storage medium facilitates easy replacement of the storage 
medium if the medium becomes contaminated by deposition of foreign matter 
carried along with the gas. Furthermore, for this purpose it is also 
recommended to improve the heat transfer between the hot dry gas and the 
storage material by appropriately shaping the storage material and/or 
increasing the flow rate of the gas through the heat accumulator. The use 
of spherical storage materials made of iron or glass or small rocks which 
have an average diameter of approximately 2 to 10 mm has proved 
particularly suitable. 
The amount of the storage medium should preferably be selected such that 
the product of the weight of the storage material and its specific heat is 
approximately equal to or greater than the product of the weight of the 
adsorption medium to be cooled and its specific heat. 
In order to carry out the process, an apparatus may be used having a drying 
air dryer which comprises at least one drying vessel filled with an 
adsorption medium, a fan connected in series with the drying vessel, a 
regeneration line with a heating device connected through controllable 
valves to an outlet line for the drying gas, and an exit gas supply line 
for the drying air dryer. This apparatus is further characterized by the 
fact that the regeneration line is provided with a heat accumulator for 
receiving the heat from the hot adsorption medium which is connected 
through another controllable valve with the outgoing gas feed line. 
In a preferred embodiment of the apparatus of the invention, the heat 
accumulator contains a heat storage medium which comprises a material 
having a high specific heat, such as glass, metal or rocks. The storage 
material is preferably spherical, and the balls of storage material 
advantageously have diameters of about 2 to about 10 mm.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
A charge of plastic granules 2 is introduced, continuously or 
intermittently, through an upper feed opening (not shown) into a drying 
hopper 1, where the granules are dried. After drying, the granules are 
discharged from the drying hopper through a lower discharge opening 3 and 
are supplied, for example, to an apparatus for manufacturing plastic 
articles (not shown). In order to dry the charge 2, a drying-air supply 
line 5 extends into the drying hopper 5 and ends in a distributor 6 
adjacent the discharge opening 3 of the hopper. Drying air, which has been 
heated to a required temperature of 80.degree. C. or more, is introduced 
through line 5 into the drying hopper 1 and flows upwardly through the 
charge 2 in the hopper and exits the hopper through an exit air line 8 
emanating from the lid of the drying hopper 1. 
The moisture-laden air exiting from drying hopper 1 is conducted by the 
exit air line 8 to a drying air dryer, designated generally by reference 
numeral 10, in which the entrained moisture is extracted from the exit 
air. In the drying-air drier 10, the exit air from line 8 passes through a 
first solid filter 12 and a flap valve 14 to the intake line 16 of a fan 
18 whose pressure line 20 leads to an outer annular chamber 22 of a drying 
vessel 24. The moist exit air flows radially through an adsorption medium 
26 contained in the drying vessel 24. The adsorption medium 26 may 
comprise, for example, silica gel and/or a molecular sieve, which extracts 
the moisture from the air. The dried air which flows from the adsorption 
medium 26 into a central duct 28 of the drying vessel 24, passes to an 
outlet line 30 which leads out of the drying vessel 24 and in which a 
heating device 7 is installed. 
The drying air feed line 5 branches off from the outlet line 30 outside the 
drying vessel 24, and a flap valve 29 is disposed in the drying air feed 
line 5. Another line 32 also branches off from the section of outlet line 
30 which extends out of the drying vessel 24. This branch line 32 also 
comprises a flap valve 31, and leads to a heat accumulator 50. Heat 
accumulator 50 takes the form of a box which is closed with the exception 
of the feed and discharge lines and in which a heat storage medium 55 is 
housed between oppositely disposed screens 52 and 54. Heat storage medium 
55 may consist of glass balls, rocks or iron balls or even of a mixture of 
screws, nuts and similar metallic hardware or metal shavings. A gas line 
34 leads into the heat accumulator 50 at the end opposite branch line 32. 
Line 34 branches into a line 33 which leads to an intake filter 36 and a 
gas line 38 on which a reversing valve 40 is disposed. When the valve body 
of valve 40 is in the position illustrated by broken line 42, the valve 
connects the line 38 with a line 35 leading into line 16 through a flap 
valve 37, which thereby connects line 38 with fan 18. When the valve body 
of valve 40 is in the position illustrated by solid line 44, the reversing 
valve connects line 35 with a short chimney section 39 leading to the open 
air. 
During the adsorption phase, flap valve 14 opens and flap valve 37 closes, 
while fan 18 draws exit air from drying hopper 1 through line 8 and filter 
12 and forces the exit air through line 20 into the annular outer chamber 
22 of the drying vessel 24. The exit air passes radially through the 
adsorption medium 26 in the drying vessel 24. In the illustrated preferred 
embodiment, the adsorption medium 26 comprises a layer of silica gel and a 
layer of molecular sieve. The air dried by the adsorption medium 26 passes 
radially into the central duct 28 and from thence into the outlet line 30, 
where the air is heated by the switched-on heating device 7. The heated 
air is then guided through open flap valve 29 and line 5 back into the 
drying hopper 1 as drying air, while the flap of flap valve 31 remains 
closed. 
When the adsorption medium 26 becomes saturated with moisture, which can be 
sensed if desired by sensors in the adsorption medium and transmitted to a 
control device (not shown), the control device reverses the direction of 
rotation of the fan 18 so that then, because of the changed pressure 
conditions in lines 5, 8, 16, 32, the flap valves 31 and 37 will open up 
while the flap valves 14 and 29 will close. The reversing valve 40 is in 
position 44. Fan 18 draws in outside air through filter 36 which passes 
via lines 34 and 32 through accumulator 50, thereby bringing the 
accumulator 50 to the temperature of the outside air. The outside air then 
arrives in line 30 where it is heated by the switched-on heating device 7 
to a temperature of, for example, 250.degree. C. The heated air then flows 
radially outwardly from central duct 28 through the adsorption medium 26 
into the annular outer chamber 22, and in the process picks up the 
moisture from the adsorption medium 26, after which the air leaves the 
drying vessel 24 through line 20 and is exhausted by fan 18 though lines 
35 and 39. 
When all moisture has been driven out of the adsorption medium 26, which 
has a temperature of, for example, about 250.degree. C., the regeneration 
phase is concluded so that the cooling phase can begin. If desired, the 
moisture level in the adsorption medium can be determined by a suitable 
sensor (not shown). Entry into the cooling phase is accomplished by 
switching the valve 40 from position 44 to position 42 and switching off 
the heating device 7. The hot outside air which then leaves the drying 
vessel 24 is forced by the fan 18 through line 35 into line 38 and from 
line 38 through line 34 into the heat accumulator 50, where the heat 
storage material 55 absorbs the heat carried by the hot gas. The gas is 
recirculated by fan 18 through lines 32, 30, 20, 35, 38 and 34 several 
times so that gradually (e.g. over a period of several minutes) the 
quantity of heat which was contained in the adsorption medium 26 is 
transferred to the heat accumulator 50. The pressure conditions existing 
in lines 38 and 34 prevent new outside air from being taken in. Thus, 
during the cooling, the adsorption medium 26 is not exposed to any 
additional moisture beyond that originally present in the circulating 
outside air because no new outside air is taken in for the cooling. This 
so-called residual moisture is extremely low. If necessary, another 
reversible valve may be installed in branch line 33 which extends from the 
junction of lines 38 and 34 to filter 36. 
After completion of the cooling phase, the direction of rotation of fan 18 
and the position of reversible valve 40 are again reversed by the control 
device so that a new adsorption phase can begin. 
At the start of the subsequent regeneration phase, the heat contained in 
the heat accumulator is used to heat the outside air taken in through 
filter 36 so that the quantity of heat stored in the accumulator may be 
used for heating the hot gas required for the regeneration so that the 
heating device 7 may be switched on at a later point in time, thereby 
saving energy. 
FIG. 2 illustrates an apparatus comprising two drying vessels 24a and 25 
which are connected in parallel and which are operated alternately in the 
adsorption and regeneration cycles. The structural components in the 
apparatus of FIG. 2 which correspond in function to the structural 
components of the apparatus of FIG. 1, are identified by the same 
reference numbers with the suffix "a". 
The exit air from the granule drying hopper 1a passes through line 8a, 
filter 12a and connecting line 16a to a fan 18a, whose pressure line 20a 
leads to a first reversing valve 62. In the illustrated position of the 
valve body 66, the exit air passes through line 70 and past a heating 
device 23 to drying vessel 25 which still contains sufficiently dry 
adsorption medium 27. The heating device 23 is therefore switched off, and 
the gas flowing into the drying vessel 25 passes through the adsorption 
medium 27 contained therein, which extracts moisture from the exit gas. 
The dry gas leaves the drying vessel 25 through discharge line 72 which 
leads to another reversing valve 60. In the illustrated position of the 
valve body 64, the drying air from line 72 passes through supply line 5a, 
and through heating device 74 which is mounted thereon, into the drying 
hopper 1a. 
Simultaneously, a fan 17 draws in outside air through intake filter 36a, 
line 34a and heat accumulator 50a which is mounted on line 34a and which 
is brought to the temperature of the outside air as the air passes 
therethrough. Fan 17 forces the air through pressure line 32a, reversing 
valve 62, line 76 connected behind it and a switched-on heating device 7a, 
into the second drying vessel 24a, where the outside air, which has been 
heated to approximately 250.degree. C., flows through the adsorption 
medium 26a and picks up the moisture contained in the adsorption medium. 
The moisture-laden hot air then passes through discharge line 78 of drying 
vessel 24a and through an additional reversing valve 60 in line 35a from 
where the moisture-laden air, as a result of position 44a of the valve 
body of the reversing valve 40a, is exhausted through line 39a. 
When the regeneration is concluded, the cooling phase is entered during 
which the valve body of reversing valve 40a is changed to the position 
shown by broken line 42a so that the hot, now dry air stream from line 35a 
passes through reversing valve 40a to line 38a which leads into line 34a 
between the intake filter 36a and the heat accumulator 50a, so that the 
hot gas can deposit the heat carried therein in the heat accumulator 50a. 
The gas is circulated by the running fan 17 through lines 32a, 76, 78, 
35a, 38a and 34a until the adsorption medium 26a is sufficiently cooled. 
Then reversing valves 60, 62 and 40a are reversed so that drying vessel 25 
can enter the regeneration cycle and drying vessel 24a can enter the 
adsorption cycle. As the regeneration of drying vessel 25 commences, the 
outside air drawn in through outside filter 36a by fan 17 is heated in the 
now hot heat accumulator 50a so that, as in the embodiment of FIG. 1, the 
heat contained in the adsorption medium 26a at the start of the cooling 
can be used to heat outside air to produce hot gas for regenerating the 
adsorption medium 27 at the start of the regeneration phase. 
The drying air dryer shown in FIG. 3 associated with the drying hopper 1b 
is of the "carousel" design disclosed in U.S. Pat. No. 3,757,492. In this 
illustrative embodiment, the carousel contains five drying vessels 25b, 
65, 75, 85 and 24b which are mounted in opposing openings of a lower valve 
disk 82 and an upper valve disk 84 and which can be rotated together with 
the upper and lower valve disks by means of a shaft 89 driven by a motor 
90. Three lower stationary valve chambers 86, 93, 99 are associated with 
the lower valve disk 82, while the upper valve disk 84 cooperates with 
three stationary upper valve chambers 87, 95, 97. The five drying vessels 
are arranged on a circular path which is concentric to the shaft 89, and 
the six valve housings are constructed along concentric arcs of a circle. 
A fan 18b draws in moisture-laden exit gas from an exit gas line 8b 
through a filter 12 and conveys it as shown by the arrows through lower 
valve housing 86 to the openings corresponding to the drying vessels 25b, 
65, 75, 85 and into the drying vessels, which are in the adsorption phase. 
Moisture is extracted from the wet exit gas by the adsorption medium 
contained in drying vessels 25b, 65, 75 and 85, so that drying air leaves 
the drying vessels 25b, 65, 75, 85 through the openings corresponding with 
the upper valve housing 87, is heated to the required temperature by 
heating device 83, and is supplied to drying hopper 1b through a drying 
air line 5b as shown by the arrows. 
The fifth drying vessel 24b is in the regeneration phase during which 
outside air is drawn in by fan 17b through intake filter 36b, line 34b and 
heat accumulator 50b and is supplied via a duct 76b and a heating device 
7b, to a connecting line 91 of valve chamber 93. From valve chamber 93, 
the hot air passes as shown by the arrow through an opening into the 
interior of drying vessel 24b and then flows through the 
moisture-saturated adsorption medium 26b, where the hot gas picks up 
moisture. The gas then leaves drying vessel 24b through line connecting 
line 35b and valve chamber 95, from where it is discharged through chimney 
39b. 
During the cooling phase, which follows the regeneration phase, the 
carousel comprising the five drying vessels and the associated valve disks 
82 and 84 is rotated further around the axis 89 so that the connecting 
line 35b is situated above the valve chamber 97 and an inlet line 92 is 
situated above the valve chamber 99. Valve chamber 97 is connected by line 
38 to connecting line 34b. Fan 17b then forces the hot gas which flows out 
of the drying vessel 24b into valve chamber 97 and through lines 38b and 
34b into heat accumulator 50b, which absorbs the heat from the hot gas. 
Since the intake line 92 is no longer situated above valve chamber 93 but 
above valve chamber 99, the air delivered by the fan 17b can only pass 
through branch duct 94 into valve chamber 99 and from there through an 
opening (not shown) in the intake line 92 and thence into drying vessel 
24b. In its further course, the air which passes through the adsorption 
medium 26b in order to cool it, is forced through outlet line 35b and an 
opening (not shown) into the valve housing 97 and then is conveyed through 
ducts 38b and 34b back to the heat accumulator 50b. 
When the adsorption medium 26b has been sufficiently cooled, the drying 
vessel 24b is transferred back to the adsorption phase by an appropriate 
rotation of the carousel, while one of the other drying vessels 25, 65, 75 
or 85 is transferred by the turning of the carousel into the regeneration 
phase in the position previously occupied by drying vessel 24b in FIG. 3. 
Through intake filter 36b, fan 17b will then draw in cool outside air 
which is heated in the heat accumulator 50b, and after the heat content of 
the accumulator is exhausted, is further heated by the heating device 7b 
to the required temperature of 250-300.degree. C. 
EXAMPLE 
Drying air dryer for 200 m.sup.3 /hour of drying air. 
In the carousel dryer described above, one of the drying vessels may remain 
in the adsorption phase approximately 60 minutes. The subsequent 
regeneration phase may last approximately 10 minutes, and the subsequent 
cooling phase may last approximately 5 minutes. Each drying vessel may 
contain a filling of from 2 to 4 kg of a molecular sieve. The throughput 
of regeneration air may amount to 50-100 m.sup.3 /hour. The regeneration 
air temperature (hot gas temperature) may be between 180.degree. C. and 
250.degree. C. The heat accumulator may contain from 4 to 8 kg of steel 
balls having an average diameter of 2 to 10 mm. The flap valves mentioned 
in the specification are preferably check valves. The drying air dryer may 
be designed for a drying air quantity of 20 to 2,000 m.sup.3 /h. 
FIG. 4 illustrates a honeycomb dryer used for removing moisture from air. A 
charge of plastic granules 2 is continuously or intermittently introduced 
into a drying hopper 1, where it is dried. After drying, the granules are 
discharged from drying hopper 1 through lower discharge opening 3. In 
order to dry the granules 2, a drying air supply line 5 extends into the 
drying hopper 1 and ends in a distributor 6 adjacent discharge opening 3. 
Drying air, which has been heated to the required temperature of 
80.degree. C. or more, is introduced through line 5 into the drying hopper 
1, flows upwardly through the charge 2 in the hopper, and leaves the 
hopper through an exit air line 8 emanating from the lid of the drying 
hopper 1. The moisture-laden exit air from the drying hopper 1 is 
conducted through exit air line 8, a filter 100 and a delivery pump 101 to 
a drying air dryer 102. This dryer is designed as a so-called honeycomb 
dryer, i.e. it comprises a rotary disk which rotates approximately 1 to 3 
times per hour. By means of three stationarily arranged sealing strips 
103, 104, 105, the honeycombs--typically folded paper or fiber glass which 
is coated with a molecular sieve--are divided into three areas. In area 
106, the moisture in the return air coming from the drying hopper 1 is a 
absorbed. In section 107, moisture adsorbing agent is regenerated by 
blowing heated outside air therethrough. The outside air reaches this 
section 107 through a filter 108 and a fan 109 as well as a heating device 
110. In section 111, cool outside air is blown in for cooling purposes 
through line 112. Then the thus treated honeycombs rotate into the 
adsorption part. The honeycomb disk rotates continuously. The three 
operations--absorpticn, heating and cooling, take place adjacent each 
other in a continuous manner. A honeycomb dryer can, for example, also be 
found in the publication "Multi Function System, Multi Jet II" of Matsui 
Corp. 
FIG. 5 shows the use of a heat accumulator with such a honeycomb dryer. The 
cooling zone 111 shown in FIG. 4 has been omitted. Instead, the heating 
for the purpose of regeneration and the subsequent cooling occur in the 
same section, specifically in section 113. During a heating and cooling 
cycle, the honeycomb body is stopped. After the conclusion of the heating 
and the cooling, the honeycomb body is rotated further by an amount which 
moves the regenerated and cooled honeycomb part into the adsorption zone 
114 and, at the same time, moves a moisture-saturated honeycomb part into 
the regeneration zone 113. 
As also illustrated in FIG. 4, the adsorption zone receives the 
moisture-laden exit air from the drying hopper 1. After a honeycomb part 
enters the regeneration zone 113, during a time period of typically 2 to 6 
minutes, outside air is drawn in through filter 108, conducted through 
heat accumulator 115, and heated by the regeneration heating device 116 to 
the required regeneration temperature. This heated air is conducted 
through the regeneration zone where it adsorbs the moisture contained 
there and then the resulting moisture-laden air is exhausted through valve 
117. When, the moisture is driven out of the adsorption medium, which has 
a temperature of approximately 250.degree. C., the regeneration phase is 
concluded so that the cooling phase may begin. 
The cooling phase is initiated by reversing the valve 117. The hot outside 
air which then leaves the regeneration zone is forced by the fan 109 into 
the heat accumulator 115. The heat storage material of the accumulator 
absorbs the heat carried by the hot gas. The gas is then repeatedly 
circulated by the fan so that gradually, e.g. over the course of several 
minutes, the heat contained in the adsorption medium is transferred to 
heat accumulator 115. In this case, no outside air is taken in. Thus, the 
adsorption medium in the honeycomb dryer is not exposed to any additional 
moisture beyond that which was originally present in the circulating 
outside air because no new outside air is taken in for the cooling. As 
described above, at the conclusion of the cooling phase, the honeycomb 
body is rotated further by an amount and a new regeneration cycle is 
started. 
FIG. 5 illustrates a modification of the regeneration circulating system. 
In this modification, a bypass valve 119 is provided and a bypass line 118 
is arranged in parallel with the heating device 116. This bypass line 118 
is connected during cooling of the regeneration zone so that the heat 
content of the heating device 116 will not be lost, i.e so that the 
heating device will not be cooled down. In this way, further savings with 
respect to the thermal energy required for the process can be achieved. 
In order to activate the bypass according to FIG. 5b, a switching valve 119 
is provided. The regeneration air is thereby conducted through the heater 
during the heating stage, and diverted along a parallel path around the 
heater during the cooling stage. 
The overall arrangement with brief stops by the honeycomb dryer has the 
advantage that a new portion of the honeycomb does not need to be 
regenerated before it is sufficiently saturated with water. A sensor 120, 
which is arranged in the supply line (i.e. the drying air line), is 
provided for measuring, for example, the dew point of the just dried air. 
By means of this measurement, the moisture adsorption capacity of the 
adsorption agent can be optimally utilized. In addition, the length of the 
adsorption stage is thereby controlled with reference to the amount of 
moisture which is adsorbed. Of course, it is also possible to determine 
the amount of adsorbed moisture by gravimetrically measuring the honeycomb 
body or by means of a thermosensor which monitors the temperature of the 
adsorption medium. 
If the moisture content of the dried air falls outside a predetermined 
limiting value, then the honeycomb body is rotated an amount corresponding 
to the size of one segment. This means that the honeycomb body is only 
rotated when it is actually necessary to regenerate the adsorption medium. 
The foregoing description and examples have been set forth merely to 
illustrate the invention and are not intended to be limiting. Since 
modifications of the disclosed embodiments incorporating the spirit and 
substance of the invention may occur to persons skilled in the art, the 
invention should be construed to include everything within the scope of 
the appended claims and equivalents thereof.