An adsorber device for drying compressed gas comprises a first
and a second chamber which operate alternately on drying and on
regenerating the desiccant contained in the chambers. Regenerating
is accomplished by branching-off a partial flow of dried gas at
the outlet side of the chamber operating on drying and supplying
the partial gas flow to the chamber working on regenerating. Means
are provided for limiting the branched-off partial gas flow to the
gas volume actually needed for regenerating. Embodiments are described
wherein this gas limiting is accomplished with a constant partial
gas flow prevailing between the two chambers and, further, embodiments
are described wherein this partial gas flow is adjusted in accordance
with the main gas flow through the chamber working on drying.
What is claimed is:
1. An adsorber device with a desiccant for drying compressed gas
and for regenerating the desiccant in a continuous operation in
mains between a gas compressor and a gas consumer, the device comprising
a first and a second chamber having inlet and outlet sides loaded
with the desiccant, and a pressure-operated pneumatic changeover
valve each at the inlet side and at the outlet side of the chambers
for alternately connecting one of the chambers to the gas flow to
be dried between the compressor and the consumer, a first solenoid
relief valve at the inlet side of the first chamber and a second
solenoid relief valve at the inlet side of the second chamber, a
timing mechanism for generating electric pulses for operating the
relief valves, and a choke connection between the outlet sides of
the first and second chamber for branching off and supplying a portion
of the dry gas for regenerating the desiccant in the respective
other chamber, the alternate connection of the chambers into the
flow of gas to be dried being accomplished by alternately opening
and closing the solenoid relief valves, thereby generating alternating
pressure conditions in the first and the second chamber for reversing
the operating positions of the pneumatic changeover valves,
wherein the improvement comprises
a. a gas metering member arranged ahead of the pneumatically operated
changeover valve at the inlet side of the first and second chamber
for measuring the rate of gas flow,
b. a totalizing mechanism included in the gas metering member,
the mechanism generating electric pulses when the gas flow through
the metering member reaches a predetermined volume,
c. a latching relay connected between the totalizing mechanism
and the first and second solenoid relief valve, the relay opening
alternately the first and the second valve upon receiving a pulse
from the totalizing mechanism,
d. a first and a second timing mechanism connected to the first
and the second solenoid relief valve, respectively, for closing
the valve after a predetermined time phase has elapsed after valve
opening, the timing mechanism being started to run by the valve
the arrangement being such that (1) the choke connection between
the outlet sides of the first and second chamber is adjusted for
branching off and conducting a partial flow of the dry gas to the
chamber operating on regenerating that is capable of accomplishing
complete desiccant regeneration within that period of time that
is required to reach the predetermided volume to which the totalizing
mechanism is set when the maximum rate of gas flow is transmitted
through the chamber operating on drying, and (2) the time phase
to which the timing mechanism is set for closing the solenoid relief
valve after opening is equal to the said period of time.
2. The adsorber device as claimed in claim 1 wherein the volume
to which the totalizing mechanism is set for generating electric
pulses is adjustable.
3. The adsorber device as claimed in claim 1 wherein the gas metering
member is a partial flow meter connected in parallel to the changeover
valve and wherein an orifice plate is arranged in the gas mains.
4. The adsorber device as claimed in claim 3 wherein a further
orifice plate is provided ahead of the partial flow meter.
5. The adsorber device as claimed in claim 1 wherein the gas metering
member is a partial flow meter connected in parallel to an adjustable
changeover valve being arranged in the gas mains.
6. The adsorber device as claimed in claim 5 wherein a further
adjustable valve is arranged ahead of the partial flow meter.
BACKGROUND OF THE INVENTION
The present invention relates to a device for adsorptive drying
compressed gas in an adsorber and regenerating the desiccant contained
therein in a continuous operation.
Adsorbers of this type are known to comprise a first chamber and
a second chamber, both of which containing the desiccant for adsorptive
gas drying. One of the chambers is always connected to the gas flow
from the compressor to the consumer while the other undergoes a
regenerating phase of the desiccant.
This is accomplished by a first pneumatic changeover valve which
connects the inlet of either the first chamber or the second chamber
to the mains conveying the gas to be dried, and by a second pneumatic
changeover valve which connects the outlet of either the first chamber
or the second chamber to the mains through which the dry gas flows
to the consumer.
Further, there is provided a choke joint interconnecting the outlet
sides of the first and second chamber. The inlet side of each chamber
is provided with a solenoid relief valve.
These elements, in combination with a timing mechanism for controlling
the solenoid valves, permit a continuous drying and regenerating
operation in cycles in such a way that always one chamber is engaged
in gas drying while, at the same time, the desiccant in the other
chamber is regenerated. During this operation, reversal of the pneumatically
operated changeover valves is tripped, utilizing control pulses
transmitted from the timing mechanism, closing the relief valve
of the chamber being in the regenerating cycle and opening the relief
valve of the chamber being in the drying cycle.
In a known device of this type cycle reversal is accomplished in
such a manner that the timing mechanism, once the preset operating
time has elapsed, causes the closing of the relief valve of the
unpressurized regenrating chamber, so as to enable a working pressure
to build up above the choke joint. Thereafter, the relief valve
of the drying chamber (under working pressure) opens, so as to admit
pressure release in this latter chamber.
Inversion of the pressure conditions on both sides of the changeover
valves obtained in this manner ensures that the valves are automatically
pressed into their reverse operating positions.
The timing mechanism is set to an operating cycle just sufficient
to provide drying of the max. gas volume with the max. rate of flow
or resp. output from the consumption circuit, for which the desiccant
charge is rated. Accordingly the choke joint is designed to be capable
of branching off a partial dry gas flow sufficient to regenerate
the moisture-laden (and saturated) desiccant within the preset cycle.
This means that in a practically applicable case the working cycle
is 5 minutes and the partial flow is 0.15 of the max. rate of flow
at a prevailing working pressure of 7 bar.
Devices of this type have, however, the following disadvantage:
Occurence of the max. rate of flow is quite rare in practice. The
actual rates of gas flow during the fixedly preset cycle are essentially
lower and, as a matter of fact, vary between 30% and 70% of the
max. rate of flow. This means likewise that the desiccant is loaded
to an accordingly less substantial extent. On the other hand, the
dry gas flow branched off for regenerating, the volume of which
depending on the fixed outlet of the choke and on the constant working
pressure prevailing in the drying chamber, has always the constant
value ##EQU1## wherein p represents the working gauge pressure in
bar. Consequently only a fractional part of the branched off gas
flow is utilized regularly for regeneration. The result is a comparatively
high loss of gas and thus a waste of expensive energy.
It is, therefore, the object of the invention to adapt the regenerating
gas flow R to the actually consumed volume of gas Q and thus to
achieve savings in energy cost.
SUMMARY OF THE INVENTION
According to the invention, the above stated object is attained
in a device for adsorptive gas drying of the above indicated type
by connecting a metering member ahead of the pneumatic changeover
valve at the adsorber inlet side. This metering member measures
the rate of gas flow through the chamber just operating on drying
and, depending thereupon, adapts operating cycles or respectively
rates of gas flow between the two chambers in such a way as to avoid
branching off surplus dry gas to the chamber in the regenerating
In a first embodiment of the invented device the metering member
is a gas meter of which the totalizing mechanism is adjustable to
a desired rate of flow, which is preferably the max. rate of flow.
Once same is reached, this mechanism opens the solenoid relief valve
of the chamber in the drying cycle, after previously the timing
mechnism set to the actual duration of regeneration cycle has closed
the solenoid relief valve of the regenerating chamber.
This makes the operating cycles of the respective drying chamber
variable in dependence on the gas meter. Preferably the cycles are
so dimensioned that the max. rate of flow Qmax is obtained. Thus
the max. regenerating rate R can be admitted to the regenerating
chamber. The regenerating chamber cycle is, however, maintained
to the required fixed value, in dependence on the timing mechanism.
The regenerating cycle thus obtained is practically always shorter
than that of the drying chamber, which in the case of low consumption
rates remains essentially longer in operation.
In a further embodiment of the invention the metering member, instead
of totalizing, measures the rate of gas flow being passed through
in the moment, and instead of the fixed choke a butterfly valve
is provided which is constantly readjusted according to the flow
To this end an orifice plate may be connected ahead of the changeover
valve at the adsorber inlet side, whereof the differential pressure
pneumatically adjusts the butterfly valve in the opening and closing
sense, for example, over a pneumatically connected controller.
In a still further embodiment a control flap may be accomodated
in the gas stream as the measuring element. Under the influence
of the gas stream the flap performs variable deflections which,
in turn, accordingly influences the butterfly valve, for example,
over a mechanical control arrangement.
In the last two embodiments, with decreased gas consumption, the
partial stream for regeneration is decreased accordingly. As a result
the two solenoid valves can be operated by the timing mechanism
at short intervals, one after the other, without consuming an expensive
surplus of regenerating gas.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more readily comprehended from the following
description when taken in conjunction with the appending drawings,
FIG. 1 shows schematically a drying device according to the prior
FIG. 2 shows a first embodiment of the invented device,
FIGS. 3 and 4 show two modifications of the embodiment of FIG.
FIG. 5 shows a further embodiment of the invented device, and
FIG. 6 shows a third embodiment of the invented device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, the prior art drying adsorber shown
in FIG. 1 operating on pressure cycling, comprises a first and
a second chamber A1 and A2 alternating on drying and regeneration.
Over a pneumatically controlled changeover valve Ve at the adsorber
inlet side the gas to be dried is passed into one of the chambers,
for example into chamber A2 under a given working pressure. In
the chamber the gas is dried to a pressure dew-point of at least
-40.degree. C. (233 K), whereupon it is passed to the consumers
mains over the pneumatically controlled changeover valve Va at the
A partial dry gas flow serving for regeneration is released in
pressure down to atmospheric pressure by a nozzle or resp. choke
FE and is then passed over the desiccant to be regenerated in the
chamber A1. Thereafter the gas leaves the chamber, saturated, over
the solenoid controlled relief valve S1 and a silencer D1. For parallel
chamber A2 there is a relief valve 52 and a silencer D2. The gas
stream continuously branched off for regeneration, over the choke
FE, depends on the working pressure and the choke design, which
means that it is constant. The choke design is based on the assumption
that the drying chamber A2 is operating on max. gas volume Qmax
to be handled by the desiccant charge is to be passed through it
within the shortest possible period of time, within which the regeneration
of the desiccant in the chamber A1 has to be performed, too.
Drying in A2 and regenerating in A1 are therefore finished after
the elapse of the said cycle as preset by the timing mechanism M.
This is achieved by pulses of current from the timing mechanism
M which closes the solenoid relief valve S1 and opens the solenoid
relief valve S2 shortly thereafter. This causes a pressure rise
in A1 and a pressure drop in A2 and means an inversions of the pressure
conditions prevailing on both sides of the changeover valves Ve
and Va. Thereby these valves are pneumatically changed over. As
a result, drying starts in A1 and regeneration in A2.
A synchronous motor in the timing mechanism M drives cam discs
having adjustable contact transmission. The cam discs control the
solenoid relief valves S1 and S2 over pulses of current, thus determining
the operation cycles. Since pressure cycling, which is a heat-less
process, is a surface adsorption with short charging periods, the
operation cycle of the adsorber is approximately 10 minutes, i.e.
5 minutes for drying and 5 minutes for regeneration.
The embodiment of the invention shown in FIG. 2 is characterized
in that the two solenoid relief valves S1 and S2 are alternately
actuated by the gas meter Z, the totalizing mechanism of which being
equipped with a pulse transmitter, via a latching relay C. Additionally
each one is depending on one timing mechanism T1 or T2 respectively.
The arrangement is such that, as soon as the fully laden desiccant
in chamber A1 for example, is readily regenerated, its relief valve
S1 is being closed by the timing mechanism T1 so that the working
pressure is obtained in this adsorber. This condition is then maintained
over a certain, possibly longer, period of time, till the adsorber
in the drying cycle A2 has received the volume of gas as preset
by the gas meter Z. Thereupon the relief valve S2 of same will be
opened by pulse from the gas meter Z over the relay C. The pressure
in the chamber will then be released.
At this very moment, changeover of the changeover valves Ve and
Va is taking place as described above, whereupon rich gas (wet gas)
is admitted to the chamber A1 and a partial stream of dry gas is
guided to the chamber A2. This partial stream is again proportioned
in such a way that regeneration in chamber A1 will be performed
within the shortest possible time required for passing-through of
the total volume in the case of max. consumption in the chamber
A2. This partial stream is, however, interrupted after finalizing
of regeneration so that, in spite of continued load of the desiccant
in Chamber A2 no surplus of regenerating gas will be consumed in
FIG. 3 shows a modification of the embodiment shown in FIG. 2.
Instead of a meter to which the full gas flow is admitted, a partial
flow meter Z1 of some known make is provided. This partial flow
meter is arranged in parallel connection with an orifice plate B1
and allows the use of a meter of accordingly smaller design. An
orifice plate B2 ahead of the partial flow meter Z1 represents the
inherent resistance, however it may be omitted in this arrangement.
In the embodiment shown in FIG. 4 the orifice plates B1 and B2
are replaced by valves V1 and V2. These valves are adjustable and
allow the adapting of the partial flow meter Z1 to an unlimited
main gas stream.
In a quite identical manner as in case of the meter in the embodiment
shown in FIG. 2 the partial flow meter Z1 is equipped with a pulse
transmitter PT being arranged subsequent to the totalizing mechanism
TM. This transmitter, over a latching relay C opens the solenoid
relief valve S1 or S2 of the chambers A1 or A2 respectively, whichever
is operating on drying. Closing of the chamber A1 or A2 whichever
is at the moment operating on regenerating, is performed by the
associated timing mechanism T1 or T2 respectively.
In the embodiments according to the FIGS. 5 and 6 the fixed choke
FE of the embodiments of FIGS. 1-4 has been replaced by adjustable
butterfly valves FE1 or FE2 respectively. These valves are designed
to vary the rate of the gas flow branched off for regeneration in
a constant or resp. proportionate way with respect to the main gas
According to FIG. 5 this is achieved by means of an orifice plate
B being connected ahead of the inlet changeover valve Ve. The orifice
plate B provides resetting of the butterfly valve FE1 for example,
over a pneumatically connected control element H.
In the embodiment of FIG. 6 instead of the orifice plate B there
is arranged a control flap K1 ahead of the inlet changeover valve
Ve, reacting on flow variations by variation of its angle of deflection.
The flap K1 controls the butterfly valve FE2 for instance over
a mechanical coupling K1-K2.
In both modifications the solenoid valves S1 and S2 of the two
chambers depend on the timing mechanism M, from where they are actuated
in conformity with a fixed operating cycle, i.e. they are opened
and closed resp. in the required sense. Duration of this operating
cycle of the two chambers is preferably based on the time being
sufficient or resp. required to charge and regenerate the desiccant
charge with the full rate of flow. The time for drying and regenerating
may be equally long. In this instance, no unnecessary surplus consumption
of regenerating gas will occur, since the volume of the regenerating
gas is always preset to be proportional to the drying gas volume.
The invention includes the possibility of applying the effectively
consumed volume of gas according to the embodiments of the FIGS.
2 3 and 4 also for use in adsorptive dryers with heat regeneration.