CA2120526A1

CA2120526A1 - Plant for recuperating heat from waste water

Info

Publication number: CA2120526A1
Application number: CA002120526A
Authority: CA
Inventors: Egmont Bartl
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-10-04
Filing date: 1992-10-02
Publication date: 1993-04-15
Also published as: EP0605580A1; EP0605580B1; JPH06511078A; AT400268B; AU2646992A; ATA198491A; WO1993007424A1; DE59207019D1

Abstract

The invention concerns a plant for recuperating heat from preferably discontinuously arising waste water from, in particular, domestic households, commercial and industrial premises, etc. The plant comprises at least one counter current-flow heat exchanger through which the waste water flows and which is connected in circuit with at least one hot-water tank or boiler. The invention calls for a sensor (6), designed to detect the arrival of waste water, to be fitted in the line (10) carrying the waste water, the sensor being connected to at least one pump (1) or to a control unit (8) which controls the pump(s). When the sensor generates a signal indicating the arrival of waste water, the pump (1) is switched on and sucks the waste water in the line (10) out of the line and through the heat exchanger (3).

Description

. WO 93/07424 212 0 S 2 6 PCT/A~92~00125 System for Recovering Heat from Waste Water The invention pertains to a system for recovering heat ~rom waste water which arises, preferably discontînuously, from, in particular, households, houses, commercial ente ~ rise~, etc., which include~ at least ~ counter-flow heat exchanger ~hrough which the waste water flows, and which is con~ected in the circuit of at least one warm water reservoir or a water hea~er.

Such sy~tems for recovering heat from waste water are generally known.

It is th~ object of the i~vention to further develop such 3y8tems such that they are enabled to process all h~usehold-conventional waste watérs in chemically and mechanically clean or s~lightly soiled form a~ well as in strongly soiled orm, i.e. when soap,~ grease, hairs, detergent~, chemical ~: ~ clean~ers~ ood leftovers, etc. are contained in the waste wat r. Further~or~, uch:a system should operate fully aut~matically, ~hould be largely m~intenance-fr~e, it should ~ be~prQvldcd~in a~structurally simple apparatus with a :~ : 20~ buil*-in unit:concept,~and~t should have a degree of efficiency as~ high as possible.

; These ob~ects are ~ttained, in accordance with the invention, with~a~system of:the foregoing kind in that a : ~ :

, , . ., ~ , . . Wo 93/07424 PCT~AT92/00125 -2- 2120~26 ~ensor i~ provided in the discharge line for the waste water which is responsive to incoming waste water, which sensor is connected to at least one pump or to a control device controlling the pump(s), with which waste water is drawn off when the pump is turned on upon the occurrence of a signal indicating ~urther waste water in the waste wate~r_line~which is then guided or pumped through the heat exchang~r.

In a preferred embodiment it is envisioned that tempera~ure sensors are provided for determining the temperature o~ the waste water and the storage water flowing into and from th~
heat exchanger~ particularly in the immediate vicinity of ~he corresponding connections of the heat exchanger, which tempera~ure sensor~ are connected to the control device, with which the amount of the velocity o~ throughput of.the pump and/or the pumping amount of the pump in the loop *or the storage water can be controlled in dependence of the measur~d:or calculated te~perature diference between th~
inlet at the heat exchanger for the waste water and the ~:~ outlet ~or ~he ~torage water and/or at the inlet for the s~orag~ water:and at the o~tlet for the waste water~

A fuxther ad~antageous embodiment is characterized in that a : ~ pipe~ection orlan a~sembly unit i~ pr~vided ~or connection in~a co~ventional waste water line in which the waste water ~` sensor(~) are disposed and with which the intake line of the pump or the waste wa er outlet line (downstream) of the Xeat ex~hanger communicate.

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'W0 93/07424 212 0 5 26 PCT/AT92/00125 With the sensor which registers the occurrence o~ water, the pump is always turned on when waste water is available for processing; when the water ~tops, the pump is turned offO
Due to the controlled supply of the warm waste water and the controlled ~upply of the stora~e water to be heat~d to the heat exchanger, optimized heat exchange is enabled, so that ~he heat content o~ the waste water can be optimally utilized. Finally, the ~y~tem can be delivered in the form o a compact unit, which is aonnected between a water heater and a waste water line which is easily connected into the waste water pipe~

.

Pr~ferrad embodiments can be found in the following description, in the drawing and in the patent claim~.

The drawin~ depiots a schematic CQnstruction of the syst~m according to ~he invehtion.

he system a~cording to the invention is essentially divid~d into~th~ee~individual ~omponents, namely a wat~r haater 17, a main:unit,;which is schematically re~erenced at 18, and tie-in unit~10~

20~ : The water haater 17 inaludes a cold water supply line 19 and a: line~ 10 le~ding the a user. An arbitrary heating de~ice, or instance~electrical heating rods, are indicated at 2~ in the upper~region of the watér hPater. ~he feed to the line 20 leading to ~he users is effected via a motor mixer 70 ts :~:

:

W0 93/07424 212 0 5 2 fi P~T~AT92/00125 which a hot water conducting line 22 and a line 23 conducting water heated by the waste water. The temperature in the line 20 is sensed by means of a temperature probe S
and it is evaluated with a control de~ice or a control compu~er 8; the motor mixer 7 is also controlled~wi~h the control device 8.

A further essential device is the tie-in unit 10 which can be inserted into any arbitrary waste water pipe or a w~ste water line and which has a corresponding cross-section adapted to that of the non-illustrated was~e water line. The main unit 18 includes as essential components the control unit 8, a cyclone 2, a pump 1, a heat exchanger 3, a further : pump 4 and possibly a check val~e 9.

The ~ie-in unit 10 has a downwardly directed recess or a :: bulge 26, into which a suction pipe ~1 opens which leads to the pump lr q~he bulge ~6 :is closed off on top with a filter or: a filter si~ve 15;: so that waste water entering the tie-in unlit ~lO: ~lows through the filter 15 in orde~ to reach the suction opening OI the line 11 and it is prsfiltere~ in tha~way. ~ctually, the~lines, sensors and components whi h form the~tie-in~}unit:lO could aiso be formed or disposed in a~waste wa~er line. ~: ~

:: ~ : :
The warm waste water aspirated by the pump 1 is supplied_ .into the cyclon 2 in which a float 12 is disposed which aarries a rod 27 at its upper side, with which a ventilation 'WO 93/07424 2 1 2 0 5 2 ~ Pc~/AT92/ool25 flap 13 for a ventilation line 16 can be adjusted. Dep~nding on the amount of air aspirated with the waste water in the line 11, the water level 28 in the cyclone 2 rises or falls;
while the water level 18 rises, the ventilation flap 13 is closed; when the flap 13 is open, air is fed bac~ via the line 16 to the tia-in unit 10, i.e. to a location upstream of the suction line 11, so as to maintain the incoming waste water at temperature by means of the v~ry warm air and so as not to waste the heat content in the air. ~he pres~ure of the waste water in the cyclone s~parator 2 is controlled with the float -12 and the ventilation ~lap 13, whiah waste water is fed through a line 29 to a corresponding ~upply connector 30 in~o the heat exchanger 3 and w~ich leaves the ~heat exchang~r at 31 through the line 14. The line 14 issues into th~ ti~-in unit downstream of the filter 15; it is pos8ible to proYide a pipe 32 in order to introdu~e the returning,~cooled~waste water into the tie-in unit as far from the suction line 11 as possible, and to prevent a~y : back~low.

0:~ ~h~ heat exah~nger~is~further supplied with cool water at a supply~openin~ 32, which water is withdrawn from the lower part Qf:~the wat~r:heater 17, or'with cold~water from the line 19 Yia a pump 4~ Tha~ water which ~lows ~hrough the heat: exchanger lea~es the same at the ou~let opening 33 and :: : ~ `: : :

it reaches the upper part of the water heater ~7 through_a : lin~25 and: the cheok valve 9, whereby a stra~i~ication of W0 93/07424 212 0 5 2 ~ PCT~AT92~00125 the water forms in the water heater 17 according to its temperature.

In accordance with the withdrawal of warmed water ~rom the water heater 17 through the line 20, cold water ~an flow in through the cold water line 19 into the heat exchanger 3 or into the water heater 17, i.e. into its lower part~

The control device 8 is connected to water sensors 6, to temperature sensors 5 and to the pumps 1 and 4O ~he water sensor 6 ups~ream of the suction line 11 serves to detect incoming waste water and, upon receiving a corresponding signal from the senso~, the control device 8 places the pump 1 into operation for drawing off the available waste water.
: The temperatur~ o~ the waste water is simultane~usly measured with ~he appropriate temperatur~ probe 5.

A water ~eel~r 6' is disposed downstream o~ the suction line 11 with whiah it is det~rmined whether waste water ha~

:
: tr~v~rsed ~cros~ the filt~r 15 while the pump 1 operated; if :~ this is affirmatîve~ it is an indiaation that the filter 15 is plugged up~ In that case, the control device 8 re~erses .

~1 20~ ~he:pumpi~g direction o~ the pump 1 and pushes already :
aspirated water through the line 11 into the ~ulgQ 26 and thereby flushes the:filter 15 counter tv its filtering direct~ion~ so as to provide free passage for the waste water in_o t~e bulge 26 for aspiration through the line 11; the flushing is maintained for a period of time, so as to allow WO 93/07424 212 0 5 ~ 6 PCT/~T92/00125 the f lushed~out dirt to be removed, th t is to say that after the flushing, waste water is not immediately aspirated again, but instead it is used for removing the flushed-out dirt .

The control device further monitors the temperatures ~t the inlets 30 and 32 of the heat exchanger 3 and/or at its outlets 31 and 33. The control device forms the difference of the temperature values at the heat exchanger ~r D~ean~; of appropriate calculation units, i.e. the difference at the 10 inlet 30 for the waste water and at the outlet 33 ~or warm water and/or th difference at the outlet 31 for waste water and at th~ inl~t 32 for cold water from the water heater 1 :: or the cold water line 19.

ne te~pe~ature dif ~Eerentials ~T at the respecti~e inlet~;
~nd outIets is a measure for the heat krans~er from the warm waste w~te:r to the cool wate:r 8upplied from the water heater 17 or ~Erom t:he cold water li~ 19. The tem~eratuxe diffe~en~ials ~thus d~termined are preferably maintained equal; ~or~ ~hat purpose: it i5. provided that khe am~:sunt of 20: warm waste water and the amount of ool water fl~ing througlh the water heater~correspond to ona another in terms : o~ volume. The~cor~esponding volumes aan be adjusted by controlling he pump~1 and/or the pump 4, in that ths : ~ throughp~t o~ the wasta water and/or of t~ cool water is regulate~, *or the purpose o~ mutually adjusting th~ amounts of water circulating through the heat exchang~r in ~he :

W0 93/07424 21 2 0 5 2 ~ PcT/AT92/ool25 respecti~e divisions for waste water and for cc)ld water per unit time.

The measurement of the 1:emperature dif ferences ~T is pra::tically done with t:wo differential controllers, for instance with PID properties, whose voltage values are processed by the control device 8.

The tie-in unit 10 se~fes several functions; it serves to withdraw the wa~:te water flowing in the discharge pipelines, as we~l as the back~eed thereo~ after the heat exchange 10 proc:ess~; furthe~ore, the air is disposed of through this c:onnector segment 10 which had been aspiral~ed.

Nagnetically inductive sensors may be provided fc3r detecting .
wat~r supply ~and the water temperatures.

q~he dimensions of the entire tie-in unit 10 are aimed at a imple assQmbly into,existing discharge pipes; the maximum built-in depth ~below the discharge level, :IEor instanGe, iE;
about 2 cm; connec~tor~ are pro~ided in the tie-in unit for th~ entry of~ wasts water:, for the diss:~h~rge o:E waste water, Eor~ a æuc~ion cc::nnection to the`main unit, and for a water rel:urn a~ r the heat exchang~ proces~; as well a~ ~or an air return~

The main unit 18 can be conf igllred as a built-in uLnit, so that an unproblematic: assembly into, for instance, kitchen , , . s W0 93/07424 212 0 5 2 6 PCT/AT92/00125 _ g _ cabinets below an exist'ng counter is enabled; the housing measurements correspond *o the usual norm for household appliances o~ ~0 x 60 cm and are easily attained. The main unit 18 also allows for the necessary operational management which is required in order to withdraw a maximum in heat energy from the soiled waste water and thus to warm up the cold fresh water.

The assembled system components are acoustically dampened and built into th~ main unit; connectors exist compatibls with the tie-in unit~ -~he pumps 1 and 4 provided in the ~ain unit 18 can be~orce-feeders and they are pre~erably infinitely ~ariable, :~ so as to assure corresponding control response.
: :

~rhe water reservoir or water heater 17 is preferable loaded by the main unit 18 under consideration Qf the heat strati:fication:~in the: uE~?er third of i*s volume; reheating with the rsheating deYice 21 is preferably effected in the ~up~er~third o~f the:wa~er heater 17.

For ~ptimizing the~degree~of ef~iciency of the system, the , 20~ eleotronically controlle~ three-way mixer 7 adjusts the withdrawal:temp~ra~ure onto a rated value; this concept leads to ~he ~act tha~, when any arbitrary amount of warm wa~er is withdrawn ~hro-~gh the line 20, an e~ual amount of fresh cold water flows into the water heater 17 fro~ below, ~ ;
: :

WO 93/07424 212 0 ~ 2 ~pCT/AT92/00125 which again leads to a cooling of the entire amount of waste water during ~he heat recovery to the temperature level of the fresh water and corresponding hea~ recovery.

~hen waste water arriv~s in the tie-in unit 1~, the arrival is de~ermined by means of the magnetic inductiYe feeler 6 and tha t~mperature is measured with the sensor 5~ From these measured values the control de~ice 8 in the main unit 18 forms a ~tartoff argumentO In the case of a start, the entire amount o~ waste water is drawn o~ through the backflushable ~ilter sieve 15 by means of the pump 1, The air which i~ necessarily conducted from the disch~rge system in this proces~ ~s well disturbs for various reasons, because when the system is at a stillstand this can lead ~o incrustation fro~ dried dirt. Also, water with detergent foams vexy sltrongly ~ Iring the wi~hdrawal suation from the ewer, especially when air is present. A water-air mixture :
(foam~ ha~; an entirely different specific heat capacity a~
c:c~mpared to wat:er alone,: which would make the control o~ ~he throughput in the h~at exchan~er 3 or the ~Ere~hwater pu~p 4 very difficult in terms of :a~taining equal flow speeas for wa~te water and :~Eresh water in the heat exchanger 3O

In order to realize the separation o~ water and air effQctively,: fast, and withou~ large voIumes of re~;t water which would ac~ol d~wn during stillstand and thus reduce the fficiency o~ ~he system, we h~ve E,rovlded the relati~ely .
::~ small cyclone separator ~ with correspondiny dimen~ions. The : ~ .

~W0 93/07424 PCT/AT92~00125 ~loat-controlled ventilation or hinged valve 13 leads to a pressure at the heat exchanger 3 which corresponds ~o the throughput volume (air and water~ of the pump 1, or to the water level in the cyclone 2, which conducts the wast~ water through the w~ste water part of the heat exchanger 3. The the water level rîses, this is an indication of a flow speed through the heat exchanger 3 which is too low, so that the pressuxe in the cyclone 2 should be raised, for which purpose the ventilation opening of the cyclone 2 is closed with the flap 13 by means of the rising float 12 7 The water l~vel could also be measured with the control device 8 and the air ventilation could be controlled accordingly.

The construction of ~h~ heat exchanger 3 is ~uch that designed partial turbulences are c~used th~rein ~hich absolutely prevent ~he deposit of grease and similar impurities present in the waste water during the cooling process, even if no grease solven~s are present in the waste water.

The cooled-down was~e water and the air from ~he v2ntilation 20~ are conduc~ed bac~ to the tie-in unit lO and thus ~o the sewage; ~yst~m;~air and water are separately conducted so as not to have to settle for an efficiency loss in ~he case of a:~mall amoun of waste water per unit time (a lot o~f air is :~ condu~ted), since the air produced in the ventilation ::~ contains heat which would be los' if it were conduct~d back ~ together with the coolded-down waste water.

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~W0 93/07424 212 n 5 2 5 PCT/AT92/00125 The cleaning of the filter sieve 15 is provided so as to maintain this filter sieve pervious, which becomes soiled at variable intervals; bath water hardly soils a filter sieve;
w~hing machine water soils relatively quickly due to the lînt contained therein. As soon as the filter si~e besomes impervious to the waste water, the same is bypassed, leading to the presence of water in the tie-in unit 10 i~mediately downstream (as seen in the direction of flow) of the filter sieve 150 The ~urther water det~ctor 6' placed at that location sends a corresponding signal.to the control device, which then reverses the pump 1 for a shor time with regard to i~s-pumping direction and thus effects an extremely e~fective backflushing of the ~ilter sieve 15, whereby the bac~lushed water is discharged through the tie-in unit 10 a~d conducted into the sewer~A short st~p of ~he suction, : i.e. o~ the pump 1, p~ior to a renewed start in the normal conYey~ ng di~rection of the pump 1 allows the dirt to flow by the ~iev~ 15 together wi~h the waste water simultaneously wing through the tie-in un:it 10, which prevents the :: 20 :~lushed-out impurit~eæ :Erom being re-aspirated right away ~ and~rom plugging the ~ilter 15.

~ . :
T~e total degree of efficiency Of the system in cooperation wi~h the di~fering and~mu~ually ind:ependent w~rm water withdrawal ahd discharge amounts occurring in a household, as-well: as the instants and tim~ intervals thereof, c:an .Q.nly be optimized when the amount~ of discharg~n~ w~ste water and freshwater to be heated are adapted to one another, and are .

.. .. ... .. .. ..

`W0 93/07424 212 ~ 5 2 6 PCT/AT92/00125 pre~erably equal, since that assures optimal heat tr~nsfer and optimal heat recovery. In order to fulfill this re~uirement, the control device measures all temperatures at the heat exchanger 3, which is operated in counterflow, and controls the infinitely adjustable pump 1 and/or ,~he pump-4 in a manner such that a preferably equal absolute temperature differential Q~ results between the measurement points 30 and 33 for the warm waste water and the warm ~resh water, as compared to the measurement points 31 and 32 for the cold waste water and the cold fresh water~

The equilibrium of the amounts of water is attained virtually perfectly by controlling the flow velocity; the :~ diameters of the ~ipes and of the heat exchanger are known, ~o that the~flow v~locity (i.e. ~he water pressure3 is the only par~meter to be controlled.
:
~: The spring-biased check~valve 9 tied into ~he feed line 25 ~: to~the water heater, pri~vents an unwanted circulation through the usable~water~part o~ the syst~m which i~

, ~ : .
connected in ~he by-pass~configuration with the water 20~ heater;~ Guch circulation~would destroy the ~tratification in : the wat~r:heater ~7:during stil~stand and an unde~ireable admixing of cold water~duri~g a withdr~wal of warm water.

~arious sie~es or~sieY2 materials may be utilied for the_ ~, filter sieve 17, for instance ~abric sieves with d mesh width of about lOO:~m.

~ ~ .

Claims

P a t e n t C 1 a i m s :

1. System for recovering heat from preferably discontinuously arising waste water from, particularly, households, houses, businesses, etc, comprising at least one heat exchanger (3) through which the waste water flows, which operates in counterflow and which is connected in the circulation cycle of at least one warm water reservoir or water heater (17), whereby a sensor (6) is provided in the discharge line (10') conducting the waste water which responds to the arrival of waste water and which is connected to at least one pump (1) or to a control device (8) controlling the pump(s) (1), with which pump the waste water detected in the waste water line (10') is removed or drawn off in the case of a signal from the sensor which indicates the arrival of waste water and conducted or pumped through the heat exchanger (3), characterized in that the control device (8) and the pump (1) transporting the waste water adjust the waste water throughput through the heat exchanger (3), and the control device (8) and the pump (4) disposed in the circulation loop of the reservoir (16) adjust the reservoir water throughput through the heat exchanger (3) to one another, and control or adjusts the same to a mass ratio, or to a throughput ratio, or to a flow velocity ratio of between 0.8 and 1.2, preferably of about 1:1.

2. The system according to claim 1, characterized in that the sensor (6) in the discharge line (10') is disposed upstream of the connection of the suction line (11) of the forced-flow pump (1).

3. The system according to claim 1 or 2, characterized in that a cyclone separator (2) is disposed between the pump (1) and the heat exchanger (3) for separating air conducted with the waste water.

4. The system according to claim 3, characterized in that for the purpose of air discharge from the cyclone separator (2) and for pressure adjustment of the waste water exiting the cyclone separator (2) a vent line (16) issuing from the upper end of the cyclone (2) is closable with a ventilation flap (13) which is adjustable with the water level in the cyclone (2), for instance by means of a float (12).

5. The system according to one of the claims 1 to 4, characterized in that temperature sensors (5) are provided for determining the temperature of the waste water and the storage water flowing into and out of the heat exchanger (3), particularly in the immediate vicinity o* the corresponding connections (30, 31, 32) of the heat exchanger (3), which temperature sensors (5) are connected to the control device (8), with which the throughput amount or the throughput flow velocity of the pump (1) and/or of a pump (4) disposed in the circulation cycle for the storage water are controllable in dependence of the measured or calculated temperature differentials (.DELTA.T) between the inlet (30) at the heat exchanger (3) for the waste water and at the outlet (33) for the storage water and/or at the inlet (32) for the storage water and at the outlet for the waste water (31).

6. The system according to one of the claims 1 to 5, characterized in that a pipe section or a tie-in unit (10) is provided which can be inserted into a conventional waste water line (10'), in which the waste water sensor (6) is disposed and into which the suction line (11) of the pump (1) issues and downstream thereof the waste water discharge line (14) of the heat exchanger (3).

7. The system according to claim 6, characterized in that a downwardly projecting flat pan or bulge (26) is formed in the lower region of the pipe section or the tie-in unit (10) into which the pipe (11) reaches which leads to the pump (1).

8. The system according to claim 6 or 7, characterized in that the flat pan or bulge (26) is separated from the volume of the pipe section or tie-in unit (10) by means of a filter or filter sieve (15).

9. The system according to one of the claims 1 to 8, characterized in that the pump (1) is disposed in the housing (18) in front of the cyclone separator (2).

10. The system according to one of the claims 6 to 9, characterized in that the waste water is supplied to the suction line (11) of the pump (1) through a filter or a filter sieve (15).

11. The system according to one of the claims 6 to 10, characterized in that a further water sensor (6') for detecting waste water which flows over the filter (15) and which has not been drawn off is provided in the tie-in unit or in a pipe section (10) downstream of the suction line (11) and of the filter (15), which further sensor (6') is connected to the control unit (8), with which the pumping direction of the pump (1) is reversible for a certain period of time in the case of a corresponding signal for flushing the filter (15) with already aspirated waste water.

12. The system according to one of the claims 3 to 11, characterized in that the air ventilation line (16) connected to the upper end of the cyclone separator (2) issues into the tie-in unit or into the pipe section (10) upstream of the suction line (11) for the pump (1).

13. The system according to one of the claims 1 to 12, characterized in that the tie-in unit (11) is disposed at a lower level than heat exchanger (3) and the water heater or the warm water reservoir (16).

14. The system according to one of the claims 1 to 13, characterized in that the interior of the heat exchanger (3) is provided with turbulence inducing devices or whirling chambers for preventing grease deposits.

15. The system according to one of the claims 8 to 14, characterized in that a fabric sieve filter is used as a filter (15) with a permeability of 50 - 200 µm, preferably of about 100 µm.

16. The system according to one of the claims 6 to 15, characterized in that the pipe section or the tie-in unit (10) is disposed at a level below the housing (18).