Note: Descriptions are shown in the official language in which they were submitted.
CA 02337291 2001-02-16
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SHELL TUBE TYPE FILTER AND AUTO-CONTROLLED HEAT RECOVERY
SYSTEM OF WASTE WATER
Technical Field
The present invention relates, in general, to waste heat recovery systems
used for recovering heat from hot wastewater discharged from buildings or
factories and, more particularly, to a shell tube-type filter, having a
plurality of
tube-shaped micro-holes, and an auto-controlled waste heat recovery system
using
such shell tube-type filters.
Background An
As well known to those skilled in the art, buildings using a large quantity
of hot water or hot steam every day, such as spas or factories, discharge hot
wastewater laden with heat energy, and so a variety of waste heat recovery
systems
have been proposed and used for recovering and recycling heat from such hot
wastewater and thereby conserving heat energy.
Hov~~ever, such hot wastewater typically includes a variety of solids, such
as a variety of floating materials, reducing the heat recovering capacity of
the heat
exchanger of a waste heat recovery system, and so it is necessary to remove
such
solids from wastewater using filters prior to feeding the filter-processed
wastewater to the heat exchanger. During an operation of the waste heat
recovery
2 0 system, the filters are gradually deposited with solids thereon. It is
thus necessary
to remove the deposited solids from the filters through a repeated cleaning
process.
When such deposited solids are not removed from the filters periodically, the
filters are finally blocked with the solids. In such a case, the filters may
undesirably allow hot wastewater to directly flow to the heat exchanger
without
2 5 performing any filtering process of removing solids from the hot
wastewater, or
may block the water passage extending to the heat exchanger and prevent the
hot
wastewater from reaching the heat exchanger. This finally makes the waste heat
CA 02337291 2001-02-16
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recovery system unexpectedly stop its operation of recovering heat from the
hot
wastewater.
Net-type filters have been conventionally used in such waste heat
recovery systems. Hot wastewater, discharged from residential buildings and
large-scale buildings, such as spas, typically includes a large quantity of
long and
fine materials, such as hairs, waste threads, and waste yarns. When a
conventional net-type filter is used for filtering such hot wastewater during
a waste
heat recovering process, the hairs, threads and yarns are easily caught and
get
tangled in the net structure of the filter, thus finally blocking the filter.
It is thus
necessary to remove such hairs, threads and yarns from the net-type filter
periodically. However, it is almost impossible to automatically remove such
hairs, threads and yarns from the net-type filter since the hairs, threads and
yarns
are tightly wound on, firmly caught by and tangled in the net structure of the
filter.
Therefore, the hairs, threads and yarns have to be manually removed from the
filter
one by one, otherwise the filter, blocked with such hairs, threads and yarns,
has to
be replaced with a new one while forcing the owner to pay money for the new
filter.
Since the process of cleaning the net-type filters of conventional waste
heat recovery systems for recovering heat from hot wastewater has been
manually
2 0 performed as described above, it is impossible to automate such waste heat
recovery systems in the prior art.
In the conventional waste heat recovery system, scales are formed on the
external surfaces of the heat transfer tubes of a heat exchanger by a variety
of
precipitated materials and/or chemicals included in the hot wastewater flowing
2 5 outside the heat transfer tubes. Therefore, it is necessary to remove such
scales
from the external surfaces of the heat transfer tubes through a manual washing
process. However, such a manually operated washing process cannot be
precisely or effectively performed, and so the waste heat recovery system
cannot
be optimally operated. In order to recover heat from hot wastewater using the
3 0 conventional waste heat recovery system, the hot wastewater has to freely
flow
around the heat transfer tubes of a heat exchanger. During such a flowing of
the
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hot wastewater around the heat transfer tubes, heat of the hot wastewater is
transferred to working water flowing in the heat transfer tubes and preheats
the
working water. The preheated working water is fed to a target device, such as
a
boiler. It is thus possible to conserve heat energy or fuel in the amount of
recovered waste heat energy used for preheating the working fluid. However,
since the conventional waste heat recovery system is designed to be manually
operated, it is impossible to automatically operate the system, or to
automatically
measure the operational performance of the system, or to measure the amount of
recovered waste heat in an operation of the system. Therefore, people do not
want to purchase or install such conventional waste heat recovery systems in
their
buildings or factories. Even though a conventional waste heat recovery system
is
installed in a building, the system is not used at all, or is rarely used due
to the
above-mentioned defect of the system. This means that hot wastewater is
discharged as sewage, and it is a mere waste of excessive amounts of heat
energy.
In an effort to effectively recover and use such waste heat, many governments,
for
example, the Korean government, in 1994, established a law that requires any
person, wanting to construct a new building expected to discharge hot
wastewater
having a temperature not lower than 25°C, to install a waste heat
recovery system
in his building. However, such newly installed waste heat recovery systems
fail
2 0 to carry out desired operational functions in the same manner as that
described
above, and so the systems are not used, or are rarely used. Therefore, such
newly
installed systems merely increase the construction cost without effectively
recovering heat from hot wastewater discharged from buildings. This finally
results in a waste of money, a waste of energy and a waste of labor from a
national
2 5 point of view. The above-mentioned law now has become a mere scrap of
paper.
Disclosure of the Invention
Accordingly, the present invention has been made keeping in mind the
above problems occurring in the prior art, and an object of the present
invention is
to provide a shell tube-type filter for waste heat recovery systems, which is
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designed to be automatically cleaned by a flushing of pressurized wash water
flowing in a reverse direction when necessary, and so filtered solids, such as
hairs,
waste threads and waste yarns, are easily and automatically removed from the
filter
by the flushing of wash water. The present invention also provides an auto-
controlled waste heat recovery system, which uses such shell tube-type
filters, thus
being automatically operated during a waste heat recovering process.
Brief Description of the Drawings
The above and other objects, features and other advantages of the present
invention will be more clearly understood from the following detailed
description
taken in conjunction with the accompanying drawings, in which:
Fig. 1 is a circuit diagram, showing the construction and operation of an
auto-controlled waste heat recovery system in accordance with the preferred
embodiment of the present invention;
Figs. 2a and 2b are an exploded perspective view and a side sectional
view of a first filter unit included in the auto-controlled waste heat
recovery system
of the present invention;
Fig. 3 is an exploded perspective view of an assembly, consisting of a
vortex tank and a heat exchanger, included in the auto-controlled waste heat
recovery system of the present invention;
2 0 Fig. 4 is a side sectional view of the vortex tank of the present
invention;
and
Figs. Sa to Sc are a plan view, a side view and a bottom view of a
wastewater swirl nozzle included in the auto-controlled waste heat recovery
system
of the present invention.
2 5 Best Mode for Carrying Out the Invention
Reference now should be made to the drawings, in which the same
reference numerals are used throughout the different drawings to designate the
CA 02337291 2001-02-16
same or similar components.
Fig. 1 is a circuit diagram, showing the construction and operation of an
auto-controlled waste heat recovery system in accordance with the preferred
embodiment of the present invention.
5 As shown in the drawing, the auto-controlled waste heat recovery system
according to the present invention comprises a plurality of elements: a first
filter
unit 100, a second filter unit 400, a vortex tank 200, and a heat exchanger
300 that
are connected together by a pipeline. A plurality of automatic control valves
V 1
to V 10, and DV are provided at the inlets and outlets of the elements: the
filter
units 100 and 400, the vortex tank 200, and the heat exchanger 300, for
controlling
the flow of hot wastewater, working water, and pressurized wash water in the
system. The system also has a plurality of temperature sensors S l and S2, a
flow
meter S3, a pressure sensor S4. The system further comprises a control panel
AT
used for controlling the operation of the control valves, the temperature and
pressure sensors, and the flow meter.
In an operation of the waste heat recovery system according to this
invention, hot wastewater primarily flows into the first filter unit 100 so as
to be
primarily filtered. The primarily filtered wastewater is, thereafter, fed into
the
vortex tank 200, thus actively swirling within the tank 200 prior to being fed
to the
2 0 heat exchanger 300. Heat of the hot wastewater is transferred to low
temperature
working water flowing in the heat transfer tubes while the wastewater flows
around the heat transfer tubes of the heat exchanger 300, thus heating the
working
water. The processed wastewater is, thereafter, discharged from the heat
exchanger 300 to a drainage system or a sewage tank.
2 5 In the system of this invention, the second filter unit 400 is connected
to
the vortex tank 200 through a connection pipe with a control valve V 8. When
the
control valve V8 is opened, the swirling hot wastewater is fed from the vortex
tank
200 to the second filter unit 400, thus being secondarily filtered by the
filter unit
400. The secondarily filtered wastewater is, thereafter, returned from the
filter
3 0 unit 400 to the vortex tank 200 by a pump P.
In the operation of this system, the second filter unit 400 is periodically
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and intermittently operated. In such a case, the operational interval and
operational time of the second filter unit 400 is preset in accordance with
concentration of solids laden in the hot wastewater to be processed. That is,
the
second filter unit 400 is selectively used in the following cases. First, when
the
filtering process of the first filter unit 100 does not achieve a desired
filtering
effect, the primarily filtered wastewater is secondarily filtered by the
second filter
unit 400 prior to being returned to the vortex tank 200. Second, the second
filter
unit 400 is used for processing the wastewater when it is necessary to
actively
swirl the wastewater using a swirling nozzle 230 of the vortex tank 200 in
order to
finally prevent a depositing of precipitated materials of the wastewater onto
the
external surfaces of the heat transfer tubes of the heat exchanger 300 or to
prevent
the precipitated materials from blocking the passage of the wastewater.
The construction of the auto-controlled waste heat recovery system of this
invention will be described in more detail herein below.
Figs. 2a and 2b are an exploded perspective view and a side sectional
view of the first filter unit 100.
As shown in Fig. 2a, the first filter unit 100 comprises a hollow
cylindrical housing 110 with an open top, z top lid 120 covering the open top
of
the housing 110, and a shell tube-type filter 130 set within the housing 110.
2 0 Two upper spouts 111 and 112 outwardly extend in a radial direction from
the sidewall of the housing 110 at opposite positions. Of the two upper spouts
111 and 112, the first one 111 provided at the upper position is used as a
wastewater inlet spout, while the second one 112 provided at the lower
position is
used as a wastewater outlet spout, through which the primarily filtered hot
2 5 wastewater is discharged from the filter unit 100 to the vortex tank 200.
Two
control valves V 1 and V2 are provided at the two spouts 111 and 112. The
above
control valves V 1 and V2 are automatically controlled during an operation of
the
system.
One lower spout 114 vertically extends downwardly from the center of the
3 0 bottom wall of the housing 110. This lower spout 114 is used as a wash
water
inlet spout for introducing pressurized wash water into the first filter unit
100.
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The wash water inlet spout 114 is provided with a third control valve V3 for
controlling the flow of wash water relative to the first filter unit 100. A
sediment
drain pipe 115 is branched from the wash water inlet spout 114, and is
provided
with a drain control valve DV for selectively draining sediments from the
first
filter unit 100 to a drain tank.
The top lid 120 covers the open top of the housing 110, with a wash water
outlet spout 121 provided at the center of the top lid 120. The wash water
outlet
spout 121 is provided with a fourth control valve V4.
The shell tube-type filter 130 comprises a thick bed-shaped body with a
predetermined thickness. This filter 130 also has a circular cross-section,
and is
sized to be closely fitted in the housing 110 of the first filter unit 100,
and is
vertically and densely perforated from its upper surface 1305 to its lower
surface
130B, thus having a plurality of shell tube-type vertical holes 131 with a
small
diameter circular cross-section. When hot wastewater is introduced into the
filter
130 from the upper surface 1305, the wastewater flows down through the
vertical
holes 131 prior to being discharged from the lower surface 131 B of the filter
130.
When hot wastewater passes through the filter 130 as described above, a
variety of
solids, such as hairs, waste threads, waste yarns, and the other materials
having a
size larger than the diameter of the holes 131, in addition to precipitated
impurities
do not pass through the holes 131, but are removed from the wastewater and are
deposited on the top surface 131 S of the filter 130.
Particularly, different from conventional net-type filters, the shell tube-
type filter 130 of this invention prevents long and fine impurities, such as
hairs,
waste threads and waste yarns, from getting tangled together even though they
2 5 partially enter into the holes 131 during a wastewater filtering process.
It is thus
possible to easily remove filtered solids from the upper surface of the shell
tube-
type filter 130 through a flushing process and to use the filter 130 for a
desired
lengthy period of time.
That is, the shell tube-type filter 130 of this invention is automatically
3 0 washed by a flushing of pressurized wash water flowing in a reverse
direction
when necessary, and so the waste heat recovery system using such shell tube-
type
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filters of this invention is automatically operated.
During an operation of the waste heat recovery system of this invention,
hot wastewater flows into the first filter unit 100 through the wastewater
inlet
spout 111, and passes through the shell tube-type filter 130, thus being
primarily
filtered. The primarily filtered wastewater is, thereafter, discharged from
the first
filter unit 100 through the wastewater outlet spout 112, and is fed into the
vortex
tank 200. When the first filter unit 100 is used for a lengthy period of time,
the
shell tube-type filter 130 is finally blocked with filtered solids at its
holes 131, thus
being reduced in its filtering function. In such a case, it is necessary to
flush the
filter 130 using pressurized wash water so as to remove the filtered solids
from the
filter 130. When it is desired to flush the filter 130, the first and second
control
valves V 1 and V2 of the wastewater inlet and outlet spouts 11 l and 112 of
the
housing 110 are closed, while both the third control valve V3 of the wash
water
inlet spout 114 formed at the bottom wall of the housing 110 and the fourth
control
valve V4 of the wash water outlet spout 121 formed at the top lid 120 of the
housing 110 are opened so as to introduce pressurized wash water into the
housing
110. Therefore, the wash water flows in the reverse direction within the
housing
110 of the first filter unit 100, and forcibly removes the filtered solids,
such as
hairs, threads, yarns, solid materials and precipitated materials deposited on
the
2 0 upper surface 1305 of the filter 130, prior to being discharged along with
the solids
from the housing 110 to a sediment tank (not shown) through the wash water
outlet
spout 121. During such a flushing process of washing the filter 130, it is
possible
to almost completely remove solids from the holes 131 of the filter 130.
Fig. 3 is an exploded perspective view of an assembly, consisting of the
vortex tank 200 and the heat exchanger 300, included in the auto-controlled
waste
heat recovery system of this invention. Fig. 4 is a side sectional view of the
vortex tank 200.
As shown in the drawings, the vortex tank 200 comprises a hollow
cylindrical housing 210, which is opened at its upper and lower ends, and is
3 0 provided with both a top lid 220 and a wastewater swirling nozzle 230. The
housing 210 of the vortex tank 200 has the same diameter as that of the heat
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exchanger 300, and is concentrically mounted to the upper end of the heat
exchanger 300. In such a case, the interior of the housing 210 of the vortex
tank
200 communicates with the housing of the heat exchanger 300. The housing 210
of the vortex tank 200 is provided, at opposite positions of its sidewall,
with two
spouts used as a wastewater inlet spout 211 and a wastewater outlet spout 212.
The wastewater inlet spout 211 is connected to the first filter unit 100,
while the
wastewater outlet spout 212 is connected to the second filter unit 400.
The top lid 220 of the vortex tank 200 covers the open top of the housing
210, with an opening formed at the center of the lid 220. A wastewater inlet
spout 221 is vertically fitted into said opening of the lid 220, and is used
for
introducing secondarily filtered wastewater from the second filter unit 400
into the
housing 210 of the vortex tank 200. Mounted to the lower end of the wastewater
inlet spout 221 within the housing 210 of the vortex tank 200 is the
wastewater
swirling nozzle 230. This swirling nozzle 230 is a cylindrical member, which
is
closed at opposite ends thereof and is transversely arranged within the
housing 210
while being slightly inclined.
Figs. Sa to Sc are a plan view, a side view and a bottom view of the
wastewater swirling nozzle 230. As shown in the drawings, the swirling nozzle
230, comprising a hollow cylindrical body, is mounted to the lower end of the
2 0 wastewater inlet spout 221 at its central portion while communicating with
the
inlet spout 221 _ In such a case, the swirling nozzle 230 is slightly inclined
at a
predetermined angle of inclination relative to the vertical spout 221.
Two rows of orifices 231 are individually and axially formed along the
sidewall at each half part of the cylindrical nozzle 230 in such a way that
the two
2 5 rows of orifices 231 are linearly arranged at two positions, angularly and
equally
spaced apart from the bottom axial line of the nozzle 230 by an angle of
45° in
opposite directions.
During an operation of the system, secondarily filtered wastewater under
pressure from the second filter unit 400 flows into the swirling nozzle 230
through
30 the inlet spout 221, and is sprayed into the vortex tank 200 through the
orifices
231. In such a case, the secondarily filtered wastewater discharged under
CA 02337291 2001-02-16
pressure from the orifices 231 of the nozzle 230 is sprayed onto and mixed
with
the primarily filtered wastewater within the tank 200. This primarily filtered
wastewater already flowed from the first filter unit 100 into the tank 200
through
the wastewater inlet spout 211. Such spraying and mixing of the wastewater
5 within the vortex tank 200 causes the wastewater to swirl actively. In such
a
case, the object of the inclined arrangement of the nozzle 230 relative to the
inlet
spout 221 within the vortex tank 200 is to create a desired active swirling
action of
the wastewater within the tank 200.
When the wastewater swirls within the vortex tank 200 by the spraying
10 action of the swirling nozzle 230 as described above, it is possible to
almost
completely prevent an undesired attachment of any unfiltered impurities to the
external surfaces of the heat transfer tubes of the heat exchanger 300 during
a
flowing of the hot wastewater within the heat exchanger 300. This finally
prevents an unexpected reduction in the operational function of the heat
exchanger
300.
The heat exchanger 300 of this invention is shown in Figs. 1 and 4 in
detail. As shown in the drawings, the general construction of the heat
exchanger
300 remains the same as that of a conventional heat exchanger, but the
cylindrical
housing 310 of the heat exchanger 300 is open at its upper end so as to
2 0 communicate with the vortex tank 200. Therefore, wastewater naturally and
directly flows down from the vortex tank 200 into the housing 310 of the heat
exchanger 300 due to gravity, thus accomplishing a desired heat exchanging
action
between the hot wastewater and low temperature working water. After the heat
exchanging process, the wastewater is collected within a sewage collecting
tank
2 5 330 provided under the heat exchanger 300.
A plurality of heat transfer tubes 320, through which low temperature
working water flows, are set within the housing 310 of the heat exchanger 300
in
the conventional manner, thus forming a conventional lamellar structure.
During
an operation of the system, hot wastewater naturally flows through the gaps
3 0 between the tubes 320 due to gravity, and so heat is transferred from the
hot
wastewater to the low temperature working water within the tubes 320 through
the
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sidewalls of the tubes 320 made of a thermal conductive material, thus heating
the
working water to a desired temperature.
In such a case, the low temperature working water flows into the heat
transfer tubes 320 of the heat exchanger 300 through a working water inlet
spout
311 provided on the sidewall of the housing 310 at a lower position, and is
heated
by the hot wastewater prior to being discharged from the tubes 320 to a target
device, such as a boiler, through a working water outlet spout 312 provided
with a
fifth control valve V5. The two temperature sensors S1 and S2 are provided at
the two spouts 31 l and 312 of the housing 310, and are used for measuring the
temperatures of inlet and outlet working water, thus finally measuring the
quantity
of heat recovered by the working water. In addition, the flow meter S3 is
provided at the working water inlet spout 311, and is used for measuring the
quantity of inlet working water, or measuring flow rate of the inlet working
water.
In order to drain the processed wastewater from the sewage collecting
tank 330 to a sewage system, a wastewater drain spout 313 is provided at the
bottom wall of the tank 330. A wash water inlet spout 316, having a sixth
control
valve V6, is provided at the center of the bottom wall of the heat exchanger
300.
In addition, a sediment drain pipe 317 is branched from said wash water inlet
pipe
connected to the wash water inlet spout 316, and is provided with a drain
valve DV
2 0 for selectively draining sediments from the bottom wall of the heat
exchanger 300
to the drain tank.
The second filter unit 400 has a construction similar to that of the first
filter unit 100, but is used for secondarily filtering the primarily filtered
wastewater
from the vortex tank 200. The secondarily filtered wastewater is pumped up by
a
pump P, provi~'ed at an outlet spout 412 of the second filter unit 400, so as
to be
fed to the swirling nozzle 230 through the inlet spout 221 provided at the top
lid
220 of the tank 200, thus being sprayed onto wastewater within the tank 200
and
actively swirling the wastewater.
A pressure sensor S4 is provided on the housing 410 of the second filter
3 0 unit 400 for sensing pressure within the housing 410 and determining
whether the
shell tube-type filter 430 of the second filter unit 400 is desirably
operated. In an
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operation of the waste heat recovery system of this invention, the second
filter unit
400 is selectively operated under the control of the control panel AT.
In Fig. 1 showing the construction of the system including the second
filter unit 400, the reference numerals 410, 420, 411, 412, 421 and 414 denote
the
housing, top lid, wastewater inlet spout, wastewater outlet spout, wash water
outlet
spout, and wash water inlet spout of the second filter unit 400. In addition,
the
reference characters V7, V8, V9 and V 10 denote seventh to tenth control
valves
provided at the spouts of the second filter unit 400.
In the waste heat recovery system of this invention, a plurality of water
supply pipes are branched from the working water supply pipe of the heat
exchanger 300, and extend to the elements of the system, thus supplying a part
of
the working water under pressure to the elements so as to allow the elements
to use
the working water as wash water.
In an operation of the auto-cantrolled waste heat recovery system using
the shell tube-type filters, the system automatically senses the temperature,
pressure and flow rate of water using the sensors S1, S2, S3 and S4, and
automatically controls the control valves V 1 to V 10 and the pump P using the
control panel AT. The operation of the system is thus automatically
controlled,
different from conventional waste heat recovery systems.
2 0 That is, in the operation of the system, the control panel AT
automatically
controls the operational time of the elements of the system in accordance with
the
sensed temperature of heated working water and the temperature of discharged
wastewater. The control panel AT also controls the valves V1, V2, V3 and V4 of
the first filter unit 100, the pump P and valves V7, V8, V9 and V10 of the
second
2 5 filter unit 400, the valve VS of the vortex tank 200, and the valve V6 of
the heat
exchanger 300. In such a case, the operational time of the above-mentioned
pump and valves is automatically controlled by the control panel AT in
accordance
with concentration of solids laden in the hot wastewater. In addition, the
operational time of the drain valves DV of the elements 100, 300 and 400 is
3 0 automatically controlled by the control panel AT in accordance with the
concentration of solids laden in the hot wastewater. The control panel AT also
CA 02337291 2001-02-16
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automatically displays the quantity of recovered heat on a display device by
operating the signals output from the inlet and outlet working water
temperature
sensors S3 and S4 in addition to the signal output from the flow meter S4.
Industrial Applicability
As described above, the present invention provides a shell tube-type filter
and a waste heat recovery system using such shell tube-type filters. Different
from conventional net-type filters, the shell tube-type filter 130 of this
invention
prevents long and fine impurities, such as hairs, waste threads and waste
yarns,
from getting tangled together even though they partially enter into the holes
131 of
the filter 130 during a wastewater filtering process of the system. It is thus
possible to easily remove filtered solids from the upper surface 1305 of the
shell
tube-type filter 130 through a flushing process and to use the filter 130 for
a
desired lengthy period of time.
Particularly, the filtered solids are easily and automatically removed from
the upper surface of the shell tube-type filter by a flushing of pressurized
wash
water flowing through the holes 131 of the filter in a reverse direction from
the
lower surface 130B when necessary.
Therefore, the waste heat recovery system, using such shell tube-type
filters, is thus automatically operated during a waste heat recovering process
2 0 different from a waste heat recovery system using conventional net-type
filters.
The system of this invention is thus operated at low cost. In addition, the
operation of the elements of the system and the process of flushing the
elements of
the system using pressurized wash water are automatically controlled in
accordance with concentration of solids laden in hot wastewater, and so the
system
2 5 is improved in its operational durability and is convenient to users. In
addition,
the system of this invention has a vortex tank 200 and the second filter unit
400,
thus effectively filtering hot wastewater even though the wastewater is laden
with a
high concentration of solids. The present invention thus provides a very
effective
waste heat recovery system.
CA 02337291 2001-02-16
14
In addition, the control panel of the system of this invention is provided
with a display device for displaying the amount of recovered waste heat, and
so it
is possible to make a prediction about the amount of recovered heat energy and
to
effectively manage the consumption of energy. The display device also allows
the user of the waste heat recovery system to directly learn the amount of
recovered heat energy and the utility of the system. Although the preferred
embodiments of the present invention have been disclosed for illustrative
purposes,
those skilled in the art will appreciate that various modifications, additions
and
substitutions are possible, without departing from the scope and spirit of the
invention as disclosed in the accompanying claims.
