AU651315B2

AU651315B2 - Waste heat recovery apparatus

Info

Publication number: AU651315B2
Application number: AU55845/90A
Authority: AU
Inventors: Marcel Sultan
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-05-26
Filing date: 1990-05-23
Publication date: 1994-07-21
Anticipated expiration: 2010-05-24
Also published as: EP0473654A1; AU5584590A; WO1990014556A1; EP0473654A4

Description

65131 PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: .'Cmplete Specification-Lodged: Accepted: Lapsed: Priority: Rke~ated Art: Published: TO BE COMPLETED BY APPLICANT Name of Applicant: MARCEL SULTAN Ac~dress of Applic, Actual Inventor: Address for Servic 11 Pretoria Street LEICHHARDT 2O'4I- SYDJNEY N.S.W. AUSTRALIJ -w 2 JI~.j Complete Specification for the invention entitled: The following statement is a full description of this invention, including the best method of performing it known to Note: The description is to be typed in double spacing, pica type face, in an area not exceeding 250 mm in depth and 160 mm in width, on tough white paper of good quality and it is to be inserted inside thir form.

14599/78-L 14599/78-L ~Printed bY C. J.THOMPS ON. CoMpnn -,'.thrk P.4r-- The present invention relates to an energy conservation apparatus to recover the waste energy in various industrial processes.

Conventionally, large amounts of heat energy are wasted in industrial processes by being eliminated into the atmosphere in the form of heated (flue gas between 2000 40000).

The heated exhaust flue gas can for example, be produced through the operation of a superheated steam boiler from a electricity power station and a saturated steam :0 boiler used by large industrial processes such as in Petro- Chemical, Hospital, Paper pulp making, Brewery and Laundry.

0 9 Commonly, boilers make effective use of only about 50% and 55% of the input energy. Fuel with most of the 15 remaining percentage being transfered into heated exhaust flue gas, through the chimney which produces high velocity draft to balance the pressure drops into the boilers combustion chamber.

With tho uso of "Eonomiser" (hoat trc-nsfer u-nitpositioned in any hot duct, it is poss capture of waste heat ener e exhaust flue gas converted to ater or chemicals, from 20°-900C, liquids S ndheat transfer oil from 100°o3120G ud for ye- I 1 The prior water heater economizer with low efficiency is common in many types of industrial applicas tions which is found to have a deficiency, namely the waste of energy (flue gas) via exhaust pipe of dryers and steam boiler chimneys.

Existing energy saving devices in this field have 2 been found to achieve on average only about 5% saving in energy cost. The installation of such devices is high to the minimal saving in energy cost.

It is an object of the present invention to provide an improved and particularly more efficient, system for recovering energy from flue gas.

According to one aspect of the present invention there is provided a flue gas energy recovery system, adapted for connection to a combustion chamber operatively heating a vessel for the production of hot liquids and/or gases, comprising a heat exchanger arranged to receive combustion gases from said chamber at one end, and to exhaust said gases into the atmosphere at the other 10 end, while transferring heat to said liquids and /or gases, characterised in that one or more temperature sensors are provided in said heat exchanger which *ee* i: operatively send signals to a control unit, said heat exchanger further including a draft fan for controlling the rate of gas flow through said heat exchanger, said fan being controlled by said control means, the arrangement being such that said control unit controls said fan so as to increase the rate of flow through said heat exchanger when the temperature of the gases increases, and vice versa, so as to maintain a substantially constant pressure in said heat exchanger.

With the use of a heat exchange unit according to the present invention positioned in any hot duct, it is possible to capture 90% of waste heat energy to the exhaust flue gas converted to heat water or chemicals, from 200 90 oC, liquids and heat transfer oil from 100o 312oC00 used for dryer.

The present invention may achieve a saving of up to 90% of wasted energy from the exhaust ducts of dryers, incinerator, steam boilers, electricity power stations superheated steam boilers, gas turbine and other suitable plant and equipment for only a small capital outlay.

Discharge temperature can be reduced to a maximum of, say, 600 to 800oC into the atmosphere.

According to one embodiment suitable for use in an industrial process employing a boiler by feeding heated water produced by the heat transfer unit back into the feed water tank to 85oC temperature and the excess of the hot water can be discharged through to the underground tank to redirect into the 4 -1 o a lam r d .a oer o ne r r r oe t ft ft s 1 ft. f industrial process, therefore a reduction in consumption of fuel at approximately to bring the water into the boiler to reach boiling point of 100 oC.

The present invention may also be used to pre-heat the water or chemicals by a two stage heat transfer unit, the first stage heat transfer unit will pre-heat the water or chemicals, to 400 45oC and second stage heat transfer unit will increase the temperature from 850 0 90oC of hot water or chemicals.

The two stage heat transfer units according to the present invention can be heated with two different liquids at the same time at different degree of temperature At this time discharged flue gas temperature through the atmosphere may be 600C maximum.

The heat transfer system is provided with an electronic variable speed fan inverter to balance the pressure drops into the boiler combustion chamber e.g.

when the boiler stack temperature is being increased the inverter speed up the 15 fan and passing more flue gas through the high efficiency heat transfer system.

If the stack temperature decreased the inverter reducing the speed of the fan and the remaining heat will be conserved into the boiler to save the energy cost.

The prior natural exhaust chimney required long lengths and large diametre to balance the pressure drops into the boiler, and it was difficult to control the discharge flue gas through the chimney.

With the use of the preferred embodiment of the present invention, the lengths of the flue may be reduced by 75% compared with prior exhaust chimneys. According to the present invention, the discharge flue gas is controlled by electronic speed inverter controlling a fan.

In a preferred form of the invention, the control of the supply of heated water or chemicals form the heat transfer units to energy utilizing function of the process is provided by an insulated below ground pre-heated 40o-45oC

I

4- -4tank, and hot water 85°C tank is adapted to store the heated water at a pre-determinated temperature until required by the said energy utilization function.

Where the energy utilization function is a boiler, heated water from the tank may be pumped into a boiler feed water tank to 850C from where it is fed the boiler so that less energy is consumed to bring already heated boiler water to saturated steam at 10000. A similar result may be achieved where heated water from heat transfer units is fed directly to the boiler feed water tank.

c. a fFurther feature and advantages of the invention will become evident from the following detailed description when read in conjunction with the accompanying drawings in which: 0 0 Fig.1 is a schematic diagram representing the single stage "Economizer" with operational installations,storage underground tanks, and electronic controller.

*f 0 Fig.2 is a schematic diagram representing the two stage "Economizer" with operational installations,storage 20 tanks, and electronic controller.

Fig.3 is a cross cut section A A of the fan impeller and case.

Fig.4 is a cross cut section C C of the heat transfers tubes, tubes plate, vessel and external insulation,of the first stage pre-heatind unit.

is a cross cut section B B of the heat transfer tubes, tube plates, vessel and external insulation of the second stage 85 C 90 C liquids heating unit.

Fig.6 is a cross cut section E E of the heat transfer tubes, tubes plates, vessel and external inculation I 7, Z I of the single stage 85°C 900C liquids heating unit.

Fig.7 is a cross cut section D D of the fan impeller and case.

Fig.8 is a sectional integrated representation of the two stage "Economizer" heat transfer units and variable speed axial fan.

Fig.9 is a sectional integrated representation of a single stage 'economizer heat transfer unit and the vari- S able speed axial fan.

In the operational installation shown in Fig.1 the 1 single stage "Economizer"1 intake the exhaust flue gas from boiler 54 which generates steam to drive an indus- 'trial process supply by line 94, exhaust heat energy (flue gas) from boiler 54 is used to heat water circulation into economizer heat transfer 1. The hot water produced is passed to storage tank 55, through solenoid valve 10, non return valve 11 and pipe 92, pressure valve 13, with non ret.'n valve 13a, discharges the excessive water pressure from "Economizer" 1 into line 92. Line 96 to top up the water level of storage tank 55a, through gate valve 90, solenoid valve 100 and check 101.

j Multi-stage pump 86 under control direct of solar SQ"j water pump controller 82 is connected to suction pipe 88a having a check valve 88 and filter 87, multy-stage pump 86, pumps the water into line 97 through to non return valve 102,gate valve 103, non return valve 70 from solar panel 71, check valve 73, solenoid valve 72 and line 93 straight to solenoid valve 17 and check valve 16 into "Economizer" heat transfer unit 1. Solenoid valve 17 is unider direct control of solar temperature controller K-ysi (0 6 9including solenoid valve 72, thermostatic sensor 74, solenoid 67: When solar energy is available solenoid valve 72 and 17 are open and solenoid valve 67 remains closed, if solar energy is not available.

Water level sensing device 84 is controlled by controller 83, solar water pump 86 which supply the water through line 97 is controlled by controller 82, and controller 75; The storage hot water tank 55 is provided with pump 56 filter 58 and non return valve 57 which is installed on the suction pipe 57a.

r* 01

I)

S

t t" Pump 56 delivery the hot water through line return valve 69, solenoid valve 68 and feed water tank when the feed water tank 65 is full the water level float control 66 gives a signal to controller 77 to cutoff the water supply by solenoid valve 68. Hot water line provides the processing plant with water also.

When pressure in line 95 reaches a pre-determinated high level by pressure gauge 80 which has setup pressure switch 78 under control direct of water pump controller 79 to shut off pump 56. A further alternative means of relieving an excessive water pressure in the line 95, but without shutting off pump 56 is provided by pressure relief valve 85. The main cold water line 89, tops up the level into hot water tank 55 through line 99 via non return valve 98 and solenoid valve 81 which is controlled by water level sensor 64 and controller 115.

Feed water tank 65 supplies boiler 54 with 85C hot water which is passed through line 91; To maintain the temperature constant inside hot water tank 55 is provded with steam injector 63 temperature sensor 60 and self acting steam valve 59. Steam line 94 supplies through to r- *1-t 7 valve 61 and non return valve 62 with saturated steam and self acting steam valve 59.

That temperature range of water is maintained by termostatic sensor 9 when it detects the desired range of water temperature it sends a signal to the "Economizer" controller 76 to open solenoid valve 10.Thus discharging water heated of setup range of temperature into line 92, from where it may be discharged into underground storage tank In order to maintain a high efficient heat transfer into unit 1, thermocouple 15 ad 15a sends a signal to economizer controller 76 to increase or decrease the excess air produced by variable speed fan 14, which maintain the So. balance of pressure drops into the boiler exhaust flue gas.

0 0@ 15 In the operational installations shown in Fig.2,the two stage economizer 29 and 29 a, intakes exhaust flue gas from boiler 541- which generates steam to drive in industrial process supply by line 94. Exhaust heat energy(flue 4Q gas) from boiler 54 is used to heat water circulating into "Economizer" heat transfer heat transfer 29 and 29a.This water produced is passed to storage tank 55 through solenoid valve 36, non return valve 37, and line 92. The pressure relief valve means of relieving an excess water pressure in line 92. Second stage "Economizer" 29 pre- 25 heats the cold water supply from tank 55a. Pump 86 delivery through line 111 to inlet solenoid valve 34 and check valve 35 into "Economizer heat transfer 29.

Multi-stage pump 86 under direct control of preheated water pump controller 113 is connected to suction pipe 88a having check valve 88 and filter 87. Main cold P -I 9water line supplies the line 113a with water to tops up the level storage tank 55a. Water level sensor 84 sends a signal to water level controller 113 to open or close solenoid 109 which is provided with non return valve 110.

Main cold water line 89 feeds water into "Economizer" 29 through solenoid valve 33 and check valve 32 under control of heat transfer controller 76.

Hot water storage tank 55 operates by multi-stage water pump 56 under direct control of controller 79 is connected to suction pipe 57a having a check valve 57 and filter 58 acting on the submerged part of suction pipe 57a.

Water pumped from tank 55 through check valve 69, I" gate valve 105, solenoid valve 68 into feed water tank t' which supplies boiler 54 from line 91. Feed water tank 15 float level control 66 under direct control of controller 77 opens or closed solenoid valve 68 connected to line gate valve 106 and 107 supplies the hot water to the processing plant It; t

''IC

I I i, i *i a

I

4*4* ai A further alternative means of relieving excesive 20 water pressure in line 95 without shutting off pump 56 is provided by pressure relief valvo 85 which discharges excess pressure through tank 55. In order to maintain the constant level into hot water tank 55, cold water line 99 supplies water through solenoid valve 81 and valve 25 98 under control of multi-level sensor 64 an controller 104.

To maintain the constant temperature of hot water tank 55, internal steam injector 63 is placed in the bottom of tank. The steam passes from line 94, gate 61, check valve 62 and supplies self acting steam valve 59 cr .'f q 4 0 at a0 P *0 a a*p P a04 through injector 635 "Economizer"heat transfer unit 29 is provided with pressure relief valve 18 to relieve the excessive pressure through line 114.

In order to maintain a high efficient heat transfer into units 29 and 29a, thermocouple 19 and 23 send a signal to "Economizer" controller 76a to increase or decrease the excess air produced by variable speed fan which maintains the balance of pressure drops into the boiler combustion chamber.

The temperature range of water is maintained by thermostatic sensor 51 and 21, when it detects the desired range of water temperature, sends a signal to economizer controller 76a to open the solenoid valve 30 and 36.

Thus discharging water heated of setup range temperature into line 92 and 114, from where it may be discharged into underground storage tanks 55 and In Fig. 3 is shown a cross cut section A A with impeller 24 and fan case section In Fig.4 is represent by cross cut section C-0 of 20 the heat transfer tubes 44, 44a, 44b with baffles 43,43b and 43a, tube 47 with baffles 48 are welded into tubes plates 46 and vessel 29, outside insulation which provides thermal insulation 28.

In Fig.5 the cross cut section B-B shown are the 25 large hea transfer tubes 38, 38a and 38b with baffles 39, 39a and 39 b which improves the pressure drops on the heat transfer system. The small diametre heat transfer tubes with twisted baffles 41 provides the high efficiency heat transfer. Tube plate 53 is welded with tubes 40,38, 38a, 38b and vessel 46b,outside insulation 28a provides the thermal insulation.

a a 0~ a a a a a a Ba a a* a 0 67 as a 0 a a a Pe@ In Fig.6 the cross section E-E of heat transfer tubes 4a, 4b 4tc with baffles 4, Lkd and 4e, improves the pressure drops op- the heat transfer system. The small diametre heat transfer tube 5 with twisted baffles 6, provides the high efficiency heat transfer. Tube plate 2 is welded with tubes 5,4a,4b,4c and vessel 1, outside insulation 3 provides thermal insulation.

In Fig. 7 is shown a cross cut section fl-f with impeller 14a and fan case section 14.

In Fig. 8 represents the integrated assembly of a two stage Economizer "heat transfer unit 26 is provided with tube 38 and twisted baffles 39 tube 40 an:! mwisted baffles 47, tube plates 52 which are welded to heat trasfer tubes 38 and 40, the exhaust flue gas passed through the tubes to heat the water or chemicals to 850- 90 0

C.

The pre-heated or cold water is directed to inlet solenoid valve 34 and check valve 35. When the water is ±.eated to setup temperature control by thermostatic device 21, the solenoid valve 36 with check valve 37, discharges the hot water into the storage tank. Pressure vessel 26 is provided with safety relief valve 22 and check valve 22a, excess pressure,which is discharged through I To control flue gas temperature intou heat transfer unit 26a, thermocouple 21 and 23 are fitted, gate valve 42 is provided for service, flange 49 is connected L CI Ii~ to lw boilor- exhaust flange. Heat transfer unit 29 prosvides the pre-heated water or chemicals to unit 26 to a setup temperature 45 0-50 0 C the excess of the flue gas from heat transfer unit 26 is passed through the variable speed axial fan 25,with impeller 24 and case 25a which directs the flue gas into unit 29, heat transfer tubes 44 and 47 with twisted baffles 43 and 48. The tube plates 45 and 46 are welded to heat transfer tubes 44 and 47 Inlet cold water or chemicals is directed to inlet solenoid alve 33, and check valve 32 into vessel 29,- When the water is heated to setup temperature control by thermostatic device 51 solenoid valve 30 with check valve 31, discharges the pre-heated water into storage tank 55a, ready to supply unit 26.

To control flue gas temperature into heat transfer unit 29 and 29a ,thermocouple 19 23 are fitted, heat transfer unit 29 is provided with safety pressure relief valve 18 and check valve 18a to relieve excess pressure 15 which is discharged through the storage tank 50 is connected to the exit chimney.

0 0 9Q In Fig.9 represent the general assembly of the single stage "Economizer" heat transfer unit 1 is provided with tube 4 and twisted baffle 4c, tube 5 and twisted baffle 6 tube plates 2 2a which are weld to heat transfer tubes 4 and 5. The exhaust flue gas is passed through the tubes to heat the water or chemicals to 852900°, the ,pre.-heated or cold water is directed to inlet solenoid valve 17, check valve 16 and pipe 8. When the water is heated to setup temperature control by thermostatic device 9, solenoid valve 10 with check valve 11, discharges the hot water into the storage tank Pressure vessel I is provided with safety valve 13 i 'which relieves the excess pressure which is discharged through the storage tank 55.To control flue gas temperature into heat transfer unit 1, thermocouple 15 and are fitted. Variable speed fan 14 with i,mpeller 14a intakes the exhaust heat (flue gas) from the boiler which increases or decreases the excess air and provides high efficiency heat transfer which maintains the pressure drops into boiler combustion chamber.

1 2 The "Economizer" is provided with thermal insulation 3 and clading to prevent the loss of themperature. Flange 12 is connected to the boiler exhaust stack flage, and flange 12a which is connected to the exit chimney of unit 1.

Various modifications may e made with details of the scope and ambit of the invention.

DATED THIS 26 DAY OF MAY 1990 NAME OF THE APPLICANT, MARC SULTAN a o a 9

I

Claims

1. A flue gas energy recovery system, adapted for connection to a combustion chamber operatively heating a vessel for the production of hot liquids and/or gases, comprising a heat exchanger arranged to receive combustion gases from said chamber at one end, and to exhaust said gases into the atmosphere at the other end, while transferring heat to said liquids and lor gases, characterised in that one or more temperature sensors are provided In said heat exchanger which operatively send signals to a control unit, said heat exchanger further Including a draft fan for controlling the rate of gas flow through said heat exchanger, said fan being controlled by said control means, the arrangement being such that said control unit controls said fan so as to increase the rate of flow through said heat exchanger when the temperature of the S gases increases, and vice versa, so as to maintain a substantially constant pressure in said heat exchanger,

2. A system according to claim 1, wherein said heat exchanger Is adapted to produce output liquids and/or gases at two or more different temperatures, the outpi temperatures being controlled by said control unit.

3. A system according to claim 1 or claim 2, wherein said control unit Is S adapted to control the exhaust gas temperature.

4. A system substantially as hereinbefore described with reference to the accompanying figures. IGNATE MARCEL SULTAN DATE C. *A

9. 9- «•O L-l- II ABSTRACT Conventionally, large amounts of heat energy are wasted in industrial processes by being eliminated into the atmosphere in the form of heated (flue gas between 2000 400 C). The "Universal liquids heat transfer economizer can saving up to 90% wasted energy from exhaust ducts of dryers, incinerators, steam boilers, electricity power station superheated steam boilers, gas turbines and other suitable plant and equipment for only a small capital outlay. With the new"economizer" installed, the new dis- charge temperature would de reduced to a maximum of 60° 80 C into the atmosphere. t The reduction in consumption of fuel at 50% to bring the water into the boilers to reach boiling point of 100 0 C. t