Note: Descriptions are shown in the official language in which they were submitted.
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Description
The invention concerns a cleaning apparatus for the adsorptive
cleaning of propellent gas for the drive of a gas engine, which contains an
adsorption agent which is formed in particular by activated carbon.
Cleaning apparatuses of that kind are employed in particular in
relation to the use of biogas as a propellent gas, in order to make it
possible to use exhaust gas catalytic converters for the exhaust gases
from the gas engine. The adsorption agent of the cleaning apparatus
provides for filtering out trace agents which are contained in the biogas
and which would otherwise quickly severely adversely affect operation of
the engine and in particular any exhaust gas catalytic converter that may
possibly be fitted.
As the adsorption agent, for example activated carbon, has only a
limited absorption capability for the pollutants and contaminants which are
to be filtered out, it is necessary from time to time either to replace the
adsorption agent or to regenerate it, in particular by heating. In order to
ensure that in that case the pollutants or contaminants which are liberated
still do not nonetheless pass into the engine, the adsorption agent is
desirably flushed during the regeneration procedure with a flushing gas
which entrains the liberated substances and which is subsequently burnt
off.
A cleaning apparatus of that kind is known from EP 0 818 617 A1.
In that case, it is also possible to provide two cleaning apparatuses for a
single gas engine so that, upon regeneration of one of the two cleaning
apparatuses, the gas engine can continue to be operated with the second
cleaning apparatus. A respective regeneration procedure for a cleaning
apparatus is implemented in each case after a given period of operation of
the gas engine, after which experience has shown the cleaning efficiency
of the cleaning apparatus begins to fall (which can be established by the
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measurement of residual gas components in the biogas in preliminary
experiments). As the degree of contamination of the biogas with
pollutants and contaminants can vary very greatly, the interval between
two cleaning operations cannot be selected to be too great, in which
respect however the possibility cannot be completely excluded that a
higher level of contamination of the propellent gas than expected means
that saturation of the adsorption agent is already achieved at an earlier
time.
The object of the present invention is to exactly determine the
interval for the service life of the adsorption agent or between two
regeneration operations in order to reduce a potential threat to the engine
and the exhaust gas catalytic converter as a consequence of saturation of
the adsorption agent.
In an apparatus of the kind set forth in the opening part of this
specification, in accordance with the invention, that is achieved in that to
measure the loading of the adsorption agent with adsorbed pollutants,
there is provided a capacitor which as a dielectric contains adsorption
agent through which propellent gas flows.
In that respect the invention is based on the realization that the
dielectric constant of the adsorption agent is a function of the loading
thereof with adsorbed substances. The loading of the adsorption agent
can therefore be detected and monitored on the basis of a measurement
of the dielectric constant of adsorption agent through which propellent gas
flows. If adsorption agent through which propellent gas flows is used as
the dielectric of a capacitor which is embedded in the adsorption agent of
the cleaning apparatus, it is therefore possible to deduce the loading of
the adsorption agent with adsorbed substances from a measurement of
the capacitance of the capacitor, in which case when a maximum
permitted loading which is close to saturation of the adsorption agent is
reached, a regeneration operation or replacement can be implemented.
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Further advantages and details of the invention are described
hereinafter with reference to the accompanying drawing in which:
Figure 1 is a diagrammatic view of an engine arrangement which
includes a cleaning apparatus according to the invention,
Figure 2 is a diagrammatic view of the cleaning apparatus, the
housing containing the adsorption agent being shown in a perspective
section through the longitudinal central plane, and
Figure 3 is a diagrammatic perspective view of a part of the cylinder
capacitor provided for measurement of the loading.
In the engine arrangement shown in Figure 1 reference numeral 1
diagrammatically indicates an internal combustion engine which is
operated with gas (gas engine) and which is supplied by way of a
propellent gas feed line 2 with biogas (in particular sewage or sludge gas
or waste dump gas). The gas engine can be in particular a large
i5 stationary gas engine. An exhaust gas catalytic converter 4 can be
provided in the exhaust tract 3 of the gas engine while arranged in the
propellent gas feed line 2 to the gas engine 1 is a cleaning apparatus 5 for
the adsorptive cleaning of the propellent gas.
The cleaning apparatus 5 can advantageously contain activated
carbon as the adsorption agent. The use of such a cleaning apparatus 5
makes it possible substantially to increase the service lives for the engine
and the exhaust gas catalytic converter 4, whereby the use of such an
exhaust gas catalytic converter 4 in relation to gas engines which are
operated with biogas is 1=trst made meaningfully possible. A reduction in
the total discharge of pollutants can in turn be achieved by way of the
exhaust gas catalytic converter 4.
Figure 2 diagrammatically shows a cleaning apparatus according to
the invention, wherein the housing containing the adsorption agent is
shown in longitudinal section and without the adsorption agent contained
therein, in order better to illustrate the components disposed therein. The
housing 51 can completely correspond to that shown in EP 0 818 617 A1,
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with the exception of the capacitor 52 to be described hereinafter, and it
can be filled with the activated carbon described in that specification, as
the adsorption agent. The regeneration operation is also effected in the
manner described therein, and does not have to be repeated in detail
here.
As shown in Figure 3, the cylinder capacitor includes the two
cylindrical electrodes 10, 11 which are held at a spacing by suitable spacer
portions 12 of electrically insulating material (for example plastic
material). Advantageously those spacer portions are of a configuration
such as to be beneficial to a flow therearound. The electrodes which are
made for example from steel are provided with a protective layer, for
example enamel, to afford protection from corrosion and/or chemical
influences.
A capacitor of that kind is arranged in the housing 51 as shown in
Figure 2 and is embedded there in the adsorption agent which in particular
fills the intermediate space between the electrodes 10, 11 of the capacitor
and thus forms its dielectric. In that respect, besides the temperature
obtaining and the frequency of the ac voltage applied to the capacitor, the
dielectric constant of that dielectric also depends on the loading of the
2o adsorption agent with adsorbed components. The capacitor 52 is
connected to a measuring device 53 which evaluates the dielectric
constant of the dielectric of the capacitor. The measuring device 53
substantially comprises a capacitive measuring bridge which is supplied
with ac voltage and which determines the capacitance of the capacitor 52.
In that connection, the frequency of the ac voltage can be in the range of
between 10 Hz and 10 MHz.
When the cleaning apparatus is brought into operation, the
activated carbon adjoining the region of the propellent gas feed line 2
initially adsorbs the major part of the contaminants or pollutants. It is
only when the adsorption capability of that part of the activated carbon
decreases as a result of approaching saturation, that the part of the
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activated carbon which is at the outlet side suffers from an increased level
of loading, and the approach thereof to the saturation condition thus
indicates the attainment of the total maximum possible loading of the
activated carbon. For that reason the capacitor is preferably arranged in
the region of the activated carbon, at the outlet side.
In a very simple embodiment attainment of the maximum
permissible level of loading could be indicated optically or acoustically by
the measuring device 53, whereupon a regeneration operation or
replacement of the adsorption agent could be implemented manually. In
the illustrated embodiment the measuring device 53 outputs its output
signal to a control device 54. When the maximum permissible level of
loading is reached, the control device 54 automatically initiates and
implements a regeneration operation. For that purpose (as described in
EP 0 818 617 A1) the activated carbon is heated by way of the heating
elements 55, 56 for example to a temperature of between 350°C and
450°C. At the same time the activated carbon is flushed with small
amounts of a combustible flushing gas, in particular a cleaned and pre-
heated propellent gas. For that purpose the valves 6, 7, 8, 9 are suitably
actuated by the control device 54. As also described in EP 0 818 617 A1,
it is advantageously also possible to provide two cleaning apparatuses for
a single gas engine so that the gas engine can continue to be operated
during regeneration of one of the two cleaning apparatuses.
Instead of a cylinder capacitor it would in principle also be possible
and viable to use another capacitor whose dielectric is formed by
adsorption agent through which propellent gas flows, for example a plate
capacitor.
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