SECHOIR A AIR, PARTICULIEREMENT POUR LA PRODUCTION D'OZONE

AIR DRYING APPARATUS, IN PARTICULAR FOR THE PRODUCTION OF OZONE

Abrégé anglais

A B S T R A C T
An air drying apparatus has a pair of columns containing a drying
agent, e.g. silica gel. One column is used for drying air whilst the other is
regenerated by air heated by a heater at the end thereof. A valve arrangement
enables air to be dried to be drawn through the columns in turn in the direc-
tion of their heater ends, and enables air for regeneration to be blown into
the heater ends of the columns. The air to be dried and the air for regene-
ration are passed through the columns in opposite directions. A good output
of dried air is obtained. Having the heaters mounted in the columns, and the
absence of any requirement for the valve arrangement to handle hot air gives
a simple and economic construction.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An air drying apparatus which comprises a pair of substantially
vertical columns each containing an air drying agent, a heater at the lower
end of each column, passage means connecting the upper end of each column
directly with the atmosphere, a common outlet for air dried by passage
through the columns from their upper to their lower ends, an air suction
pump in said common outlet, a common inlet for drying air to be heated by
the heaters and regenerate the drying agent by passage through the columns
from their lower to their upper ends, a blower in said common inlet, and a
four-way valve arrangement coupled to the lower ends of the two columns, to
the common outlet and to the common inlet, for connecting the lower end of
one column with the inlet and the lower end of the other column with the
outlet and vice versa.
2. Apparatus according to Claim 1 in which the heaters are electrical
heaters.
3. A process for drying air which comprises passing the air downwardly
through a pair of substantially vertical columns used alternately, each of
which columns contains a drying agent and has a heater at its lower end,
and passing the thus dried air to a common outlet, the air-flow downwardly
through the columns being drawn from the atmosphere by a suction pump in the
common outlet, and regenerating each column, whilst air is being dried by
downward passage through the other column, by blowing drying air upwardly
therethrough so that it is heated by the heater thereof and is discharged at
the upper end of the column after drying-contact with the drying agent, the
blowing air being taken from atmosphere by a common inlet provided with a
blower, and the connection of the two columns with the common inlet and the
common outlet being effected by a four-way valve arrangement operable to
connect the lower end of one column to the common outlet whilst the lower
end of the column is connected with the common inlet and vice versa.
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Description

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The present invention relates to the drying of air, e.g. for use in
the production of ozone, and has as objects the provision of an apparatus and
a method therefor.
It is known to provide air drying apparatus having t~o columns,
containing a drying agent, e.g. of the silica gel type~ A change-over valve
arrangement is provided whereby the dried air can be led to an output and
drying air from a blower can be passed through the columns as required.
One column is used to produce the dried air while the other is
being regenerated by passing a current of heated air therethrough from the
blower in order to extract the moisture which has been removed in producing
the dried air. In this way, the apparatus produces a continual supply of
dried air.
~ The columns are fitted at their tops with heaters for heating the
air used for drying. At the top end of each column is an entrance pipe
equipped with a blower. At the lower end is a connection to the change-over
valve arrangement for venting the flow to atmosphere or directing it to the
output as required. Usually the output is equipped with its own air pump,
so that the blower on a column is only switched on to provide air for
regenerative drying. Drying air for regeneration and the processed air pass
2~ through the column in the same direction.
In accordance with the present invention, there is provided an air
drying apparatus which comprises a pair of substantially vertical columns
each containing an air drying agent, a heater at the lower end of each
column, passage means connecting the upper end of each column directly
with the atmosphere, a common outlet for air dried by passage through the
columns from their upper to their lower ends, an air suction pump in said
common outlet,a common inlet for drying air to be heated by the heaters
and regenerate the drying agent by passage through the columns from their
lower to their upper ends, a blower in said common inlet, and a four-way
3n valve arrangement coupled to the lower ends of the two columns, to the
common outlet and to the common inlet, for connecting the lower end of
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one column with the inlet and the lower end of the other
column with the outlet and vice versa.
Further in accordance with the present invent-lon, there
is provided a process for drying air which comprises passing
the air downwardly through a pair of substantially vertical
columns used alternately, each of which columns contains a
drying agent and has a heater at its lower end, and passing
the thus dried air to a common outlet, the air-flow downwardly
through the columns being drawn from the atmosphere by a
suction pump in the common outlet, and regenerating each
column, whilst air is being dried by downward passage through
the other column~ by blowing drying air upwardly therethrough
so that it is heated by the heater thereof and is discharged
at the upper end of the column after drying-contact with the
drying agent, the blowing air being taken from atmosphere by a
common inlet provided with a blower, and the connection of the
two columns with the common inlet and the common outlet being
effected by a four-way valve arrangement operable to connect
the lower end of one column to the common outlet whilst the
lower end of the column is connected with the common inlet and
vice versa.
In further describing the invention, reference will be
made to a pair of columns but it is to be understood that more
than two columns may be provided, if desired, and operated so
that any single column is used periodically for drying air and
; regenerated whilst one or more other columns is used for the
drying.
It is characteristic of the apparatus and method of
the invention that the air for regeneration and the processed
air pass through the columns in opposite directions. The
column being usea to produce processed air accumulates
moisture at the entrance end but this is quickly removed when
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the regenerating air is passed through in the opposlte
direction.
Preferably the columns are substantially vertical
columns and the heaters are at the bottoms of the columns.
Heaters at the bottoms of the columns can be arranged to
produce convection currents which, together with the flow
produced by the blowers, provide an enhanced regenerative
effect. It can be arranged that the blowers and the heaters
co-operate to heat the
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drying agent near the heater~ends o~ the columns so that the dried air is
obtained at an elevated temperature and correspondingly reduced humidity.
Damage to the apparatus by over-heated air is minimised in the present
arrangement. During regeneration, the blowers and the valves are upstream of
the heaters and therefore not affected thereby. The heated drying air for
regeneration affects only the columns themselves before being discharged to
atmosphere. With the heaters at the bottom of vertical columns, the regene-
rating air rises through the columns irrespective of whether it is forced by
the blower or rises by convection and so cannot affect other parts of the
apparatus.
The apparatus may be of very simple and economic construction. A
simple change-over valve assembly formed of four valves suffices. The valves
do not have to be capable of withstanding high temperatures since they have
only to pass cold or slightly warmed air. No separate housing for the heaters
is required since they may simply be built into the columns. Conveniently, a
single blower is provided for supplying the drying air to both columns via the
valve arrangement, this arrangement giving a very simple construction.
The following description in which reference is made to the accompany-
ing diagrammatic drawing of a preferred embodiment of the apparatus is given
in order to illustrate the invention.
The apparatus shown in the drawing has two columns 1 and 2. Each has
fitted within its bottom end, an electric heater 3. Above the heater is a
perforated plate 4 which supports a filling 5 of a drying agent, for example
a silica gel of commercially available type.
At the upper end of each column is an entrance pipe 6~ open at its top
to atmosphere. At the lower end a pipe 7 connects the column with a change-
over valve assembly 8 which consists of four separate valves 9, 10, 11 and 12.
A connection leads to between valves 9 and 10 from a blower 14. From between
valves 11 and 12, an outlet pipe 15, constituting the output of the drying
apparatus, connects to apparatus 16, e~g. an o~one apparatus. Suction pump 17

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is associated with th0 apparatus 16 to draw air downwardly through the columns.
A control unit 18 serves the four valves 9 to 12 and the blower 14. It con-
sists of a clock arrangement ~o make the change-overs at previously selected
intervals. Alternatively, it can be controlled by a temperature and/or mois-
ture detector 19 in the outlet pipe 15. Detector 19 can be preset to any de-
sired values of temperature or moisture content.
With valve 11 open and the suction pump 17 working, atmospheric air
is sucked through the entrance pipe 6 into the column 1 and, after being dried
by the drying agent 5, passes through the outlet pipe 15 to the apparatus 16.
After a predetermined time, chosen by experience or by measuremen~s, valves 9
and 12 are opened and valves 10 and 11 closed, or if already closed, remain
closed. The heater 4 in column 1 and the blower 14 are now started. Air
dried in column 2 now passes to apparatus 16 while the blower 14 feeds air
upwardly over the heater 3 in column 1. The heated air serves as a drying
agent and carries moisture extracted by the drying agent 5 to atmosphere up-
wardly through the top of column 1 and pipe 6. After an adequate drying period,
the heater 3 of column 1 and the blower 14 can be turned off so that the drying
agent 5 can cool off. After a further period, the valves arrangement can be
operated so that column 1 is again used for drying air whilst column 2 is re-
generated.
It will be understood that the foregoing description of specificapparatus is given for purposes of illustration only and that various modi-
fications such as may occur to those skilled in the art may be made without
departing from the spirit and scope of the invention.
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