GB2140144A - Method for recovering heat from gases containing substances which contaminate heat transfer surfaces - Google Patents

Method for recovering heat from gases containing substances which contaminate heat transfer surfaces Download PDF

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Publication number
GB2140144A
GB2140144A GB08313711A GB8313711A GB2140144A GB 2140144 A GB2140144 A GB 2140144A GB 08313711 A GB08313711 A GB 08313711A GB 8313711 A GB8313711 A GB 8313711A GB 2140144 A GB2140144 A GB 2140144A
Authority
GB
United Kingdom
Prior art keywords
gas
heat exchanger
heat
transfer surfaces
heat transfer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08313711A
Other versions
GB8313711D0 (en
GB2140144B (en
Inventor
Seppo Ruottu
Ari Halme
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ahlstrom Corp
Original Assignee
Ahlstrom Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ahlstrom Corp filed Critical Ahlstrom Corp
Publication of GB8313711D0 publication Critical patent/GB8313711D0/en
Publication of GB2140144A publication Critical patent/GB2140144A/en
Application granted granted Critical
Publication of GB2140144B publication Critical patent/GB2140144B/en
Expired legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D25/00—Devices or methods for removing incrustations, e.g. slag, metal deposits, dust; Devices or methods for preventing the adherence of slag
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
    • F22B1/18—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines
    • F22B1/1869—Hot gas water tube boilers not provided for in F22B1/1807 - F22B1/1861
    • F22B1/1876—Hot gas water tube boilers not provided for in F22B1/1807 - F22B1/1861 the hot gas being loaded with particles, e.g. dust
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J15/00—Arrangements of devices for treating smoke or fumes
    • F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
    • F27D17/001—Extraction of waste gases, collection of fumes and hoods used therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
    • F28D21/0001—Recuperative heat exchangers
    • F28D21/0003—Recuperative heat exchangers the heat being recuperated from exhaust gases
    • F28D21/001—Recuperative heat exchangers the heat being recuperated from exhaust gases for thermal power plants or industrial processes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28G—CLEANING OF INTERNAL OR EXTERNAL SURFACES OF HEAT-EXCHANGE OR HEAT-TRANSFER CONDUITS, e.g. WATER TUBES OR BOILERS
    • F28G1/00—Non-rotary, e.g. reciprocated, appliances
    • F28G1/12—Fluid-propelled scrapers, bullets, or like solid bodies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/30—Technologies for a more efficient combustion or heat usage
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P80/00—Climate change mitigation technologies for sector-wide applications
    • Y02P80/10—Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier
    • Y02P80/15—On-site combined power, heat or cool generation or distribution, e.g. combined heat and power [CHP] supply

Abstract

A method for recovering heat from a gas containing molten components by bringing it into contact with heat transfer surfaces of a heat exchanger, where upstream of the heat exchanger 2 the temperature of the gas is dropped below the eutectic temperature range by mixing in the gas solid, recirculated particles that have been cooled in the heat exchanger and separated from the gas, and possibly also other particles, e.g. sand. <IMAGE>

Description

SPECIFICATION Method for recovering heat from gases containing substances which contaminate heat transfer surfaces The present invention is related to a method for recovering heat from gas containing vaporized, molten and eutectic components by bringing it into contact with the heat transfer surfaces of a heat exchanger.
The process industry produces great amounts of hot gases. The recovery of heat from these gases is rendered difficult by the vaporized or molten components in the gases contaminating heat transfer surfaces. A typical example of this are the waste gases of the pyrometallurgical industry. The cleaning of the heat transfer surfaces by means of the methods available at the moment is in most cases extremely difficult, which leads to diminished usability of the plant and therefore also to considerable costs.
Experience has shown that the cleaning problems are biggest in such a temperature range, characteristic to each process, where part of the solid compounds are in a eutectic state. E.g.
often in non-ferrous metallurgic foundry processes small concentrations of Zn, As and Pb are enough to cause the eutectic behaviour of the entire dust. Dust in a eutectic state catches on the heat transfer surfaces and especially when crystallizing forms a dirt layer, the removal of which by means of the known cleaning methods (blowing or mechanical sweepers) is in some cases impossible. Field research has shown that the best endurance values are obtained in such steam boilers in which, due to the nature of the process, there has been natural erosion of the layers. It has also been possible to judge from the form of the dirt layers that even effective blowers or mechanical sweepers cannot considerably affect the dirt layers. On the other hand, erosion has kept the heat transfer surfaces parallel to the flow direction fairly clean.
From these observations rose the thought to use controlled erosion for the cleaning of heat transfer surfaces that are otherwise difficult to clean. The method according to the invention for heat recovery based on controlled erosion is characterized in that the temperature of the gas is dropped upstream of the heat exchanger below the eutectic temperature range of the molten components by mixing into the gas recirculated solid particles that have been cooled in the heat exchanger and separated from the gas and possibly also other particles.
The figure shows an embodiment according to the invention for heat recovery.
In the apparatus shown in the figure, hot gas containing vaporized and molten components flows through a channel 1 provided with radiation surfaces. When approaching a heat exchanger 2, the temperature of the gas is near the upper limit of the eutectic range. The temperature downstream of the heat exchanger is chosen to be sufficiently below the eutectic temperature range so that the dust contained by the gas is pulverous by nature and thus does not catch on the heat transfer surfaces. The sweeping effect required for keeping the heat transfer surfaces clean is acquired when the sweeping dust is concentrated in the heat exchanger so much that when mixing with the dusty gas entering the heat exchanger in point 3, the the temperature of the mixture drops near the limit of the eutectic range.
After the mixing and the dropping of the temperature that occurred in point 3, the suspension containing a sufficient amount of abrading particles flows through the heat exchanger 2 and thus by erosion prevents the forming of dirt layers on the heat transfer surfaces.
After the heat exchanger 2, the suspension has cooled below the eutectic range and is led tangentially through a channel 4 to a flow-through cyclone 5 from which the gases containing essentially no dust are discharged through a central pipe 6 and the separated solid material is returned through a pipe 7 to the gas flow to point 3 of the channel, upstream of the heat exchanger. An outlet 8 is disposed in the return pipe 7 for the circulating solid material. Thus the circulating solid material flow and the erosion effect can be regulated. The circulating material is preferably the solid material used in the process or some other inexpensive material, such as sand, which is added to the process through a pipe 9.
The following advantages are obtained by means of the method according to the invention: 1. The heat transfer surfaces are kept clean by means of a controlled erosion effect.
2. By mixing, the temperature can be rapidly dropped.
3. A so called dry washing effect is obtained, as the circulating solid particles condensate the compounds that have come to their surface in the vapour phase.
4. The amount of sulphur emissions can be decreased by arranging e.g. a Ca-based circulating material 5. The radiation and convection heat exchange are activated.
The operation ranges of the method according to the invention are the following: Gas velocity 3 to 20 m/s Particle content in gas 10 to 500 g/mol Temperature of incoming gas 300 to 1500 "C Temperature of outgoing gas 500 to 1 200 "C Mean diameter of particles 100 to 2000 sum Example 1: The values of the offgases of a Cu-smeltery after the smelting furnace are: gas flow mol/s 1 740 dust content g/mol 2.7 temperature "C 1400 The offgases are cooled by radiation cooling in the channel 1 to about 900 "C, whereby a temperature range having difficult properties as regards the contamination of the heat transfer surfaces is arrived at.The thermal capacity of the dusty offgas is about 1.7 kJ/(Nm3 "C)= 38 J(mol "C) i.e. the thermal capacity flow is 66.1 kW/'C. A preferable temperature before the heat transfer surfaces of the heat exchanger 2 is 700 "C and after the heat transfer surfaces 550 'C. Thus the circulating thermal capacity flow is 88.1 kW/'C. The specific thermal capacity of the circulating material can be estimated to be about 0.8 kJ/(kg C), which gives a value of 110 kg/s for the circulating mass flow. Thus after the mixing the solid matter content of the gas is 63 g/mol (=2.81 kg/Nm3). In practise solid matter contents of 900 to 1400 g/mol have been used in a so called circulating bed reactor.A concentrate, sand or a mixture of them can be used as the circulating material in a smeltery. Furthermore, particles included in the offgases are concentrated in the cooling circulation.
Example 2 The black liquor flow of a soda boiler is 5.6 kg/s and its dry matter content 0.60. A typical dry matter analysis is as follows: C 35.5% (of pulp) Na 20.8% S 5.2% 0 35.1% H ss 3.4% In case the combustion is carried out in a normal soda boiler, ca. 30% of the sulphur feed and 10% of the sodium feed follow the flue gases from the furnace partly as gaseous compounds and partly as small molten components. In case the combustion is carried out in a separate combustion chamber, the flue gases may contain even 50% of the sulphur and 30% of the sodium after the combustion zone. When the flue gases get cooler, the inorganic chemicals form mostly sodium sulfate and sodium carbonate as well as sulphur dioxide.Depending on the composition of the liquor and on the running circumstances, this may in some cases lead to the formation of a difficult sodiumpyrosulfate layer on the heat transfer surfaces.
The offgas values in the above combustion chamber are: gas flow mol/s 840 Na-flow mol/s 4.56 S-flow mol/s 2.75 temperature 'C 900 dust (cond.) g/mol 0.23 (10.3 g/Nm3) Thermal capacity flow of the gas 29.4 kW/'C Gas temperatures: upstream of the exchanger 870 "C after mixing 700 "C downstream of the exchanger 550 "C Circulating thermal capacity flow 33.0 kW/'C Circulating mass flow (0.8 kJ/kg C) 41.7 kg/s Dust content of gas in the exchanger 50.0 g/mol The circulation flow comprises the Na2CO3-based dust of the flue gases and the Na2CO3 or Na2SO4 added to point 3.

Claims (6)

1. Method for recovering heat from gas containing molten components by bringing it into contact with the heat transfer surfaces of a heat exchanger, characterized in that upstream of the heat exchanger the temperature of the gas is dropped below the eutectic temperature range of the molten components by mixing in the gas recirculated solid particles that have been cooled in the heat exchanger and separated from the gas, and possibly also other particles.
2. A method according to claim 1, characterized in that upstream of the heat exchanger, the temperature of the offgas from a Cu-smeltery is dropped to ca. 700 "C.
3. A method according to claim 2, characterized in that sand is added to the circulation flow.
4. A method according to claim 1, characterized in that upstream of a heat exchanger the temperature of the gas from a combustion chamber of a soda boiler is dropped to ca. 700 "C.
5. A method according to claim 4, characterized in that sodium sulfate and/or sodium carbonate is added to the circulation flow.
6. A method for recovering heat from gas containing molten components by bringing it into contact with the heat transfer surfaces of a heat exchanger substantially as herein described.
GB08313711A 1981-11-23 1983-05-18 Method for recovering heat from gases containing substances which contaminate heat transfer surfaces Expired GB2140144B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FI813717A FI64997C (en) 1981-11-23 1981-11-23 FOERFARANDE FOER TILLVARATAGANDE AV VAERME UR GASER INNEHAOLLANDE VAERMEYTOR NEDSMUTSANDE AEMNEN

Publications (3)

Publication Number Publication Date
GB8313711D0 GB8313711D0 (en) 1983-06-22
GB2140144A true GB2140144A (en) 1984-11-21
GB2140144B GB2140144B (en) 1986-08-20

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ID=8514888

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08313711A Expired GB2140144B (en) 1981-11-23 1983-05-18 Method for recovering heat from gases containing substances which contaminate heat transfer surfaces

Country Status (10)

Country Link
JP (1) JPS6018000B2 (en)
AU (1) AU553033B2 (en)
BE (1) BE896801A (en)
CA (1) CA1265784A (en)
DE (1) DE3240863C2 (en)
FI (1) FI64997C (en)
FR (1) FR2546288B1 (en)
GB (1) GB2140144B (en)
IN (1) IN158648B (en)
SE (1) SE454297B (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5019137A (en) * 1984-09-14 1991-05-28 A. Ahlstrom Corporation Method for cleaning gases containing condensable components
WO1993002331A1 (en) * 1991-07-23 1993-02-04 A. Ahlstrom Corporation A method of removing deposits from the walls of a gas cooler inlet duct, and a gas cooler inlet duct having a cooled elastic metal structure
WO1996005366A1 (en) * 1994-08-10 1996-02-22 A. Ahlstrom Corporation A recovery boiler where the flue gas is divided into two streams and a method therefore
US5505907A (en) * 1993-06-23 1996-04-09 A. Ahstrom Corporation Apparatus for treating or utilizing a hot gas flow
US5634516A (en) * 1993-06-23 1997-06-03 Foster Wheeler Energia Oy Method and apparatus for treating or utilizing a hot gas flow
WO2002086027A2 (en) * 2001-04-19 2002-10-31 Ebara Corporation Gasification and slagging combustion system
WO2002103063A2 (en) * 2001-06-19 2002-12-27 Voest-Alpine Industrieanlagenbau Gmbh & Co Method and device for treating particulate material

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0449891B1 (en) * 1988-12-20 1996-10-30 Cra Services Limited Manufacture of iron and steel in a duplex smelter and solid state oxide suspension prereducer
IE904007A1 (en) * 1989-11-08 1991-05-08 Mount Isa Mines Condensation of metal vapours in a fluidized bed
DE4131962C2 (en) * 1991-09-25 1998-03-26 Hismelt Corp Pty Ltd Method and device for treating hot gases with solids in a fluidized bed

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB743942A (en) * 1952-12-18 1956-01-25 Exxon Research Engineering Co Improvements in or relating to heat recovery in a gas fluidized-solids contacting operation
GB868368A (en) * 1958-10-10 1961-05-17 British Iron Steel Research Improvements in or relating to heat exchangers
GB1504794A (en) * 1974-03-01 1978-03-22 Commissariat Energie Atomique Method of thermal accumulation
GB2115132A (en) * 1982-02-13 1983-09-01 Kronos Titan Gmbh Device for the cooling of hot gaseous solids suspensions

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Publication number Priority date Publication date Assignee Title
DE1083058B (en) * 1959-07-10 1960-06-09 Schmidt Sche Heissdampf Process for keeping the heating surfaces of waste heat boilers clean and equipment for carrying out the process
US3080855A (en) * 1960-04-12 1963-03-12 Exxon Research Engineering Co Furnace flue gas composition control
GB1379168A (en) * 1972-02-18 1975-01-02 Babcock & Wilcox Ltd Use of heat exchanging furnaces in the recovery of heat in waste gases
US4300625A (en) * 1975-01-21 1981-11-17 Mikhailov Gerold M Preventing deposition on the inner surfaces of heat exchange apparatus
SE421145B (en) * 1978-02-23 1981-11-30 Stal Laval Apparat Ab DEVICE FOR SUPPLY AND DISTRIBUTION OF DUST-GAS
DE2841026C2 (en) * 1978-09-21 1983-03-10 A. Ahlström Oy, 29600 Noormarkku Combustion device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB743942A (en) * 1952-12-18 1956-01-25 Exxon Research Engineering Co Improvements in or relating to heat recovery in a gas fluidized-solids contacting operation
GB868368A (en) * 1958-10-10 1961-05-17 British Iron Steel Research Improvements in or relating to heat exchangers
GB1504794A (en) * 1974-03-01 1978-03-22 Commissariat Energie Atomique Method of thermal accumulation
GB2115132A (en) * 1982-02-13 1983-09-01 Kronos Titan Gmbh Device for the cooling of hot gaseous solids suspensions

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5019137A (en) * 1984-09-14 1991-05-28 A. Ahlstrom Corporation Method for cleaning gases containing condensable components
WO1993002331A1 (en) * 1991-07-23 1993-02-04 A. Ahlstrom Corporation A method of removing deposits from the walls of a gas cooler inlet duct, and a gas cooler inlet duct having a cooled elastic metal structure
US5443654A (en) * 1991-07-23 1995-08-22 A. Ahlstrom Corporation Method of removing deposits from the walls of a gas cooler inlet duct, and a gas cooler inlet duct having a cooled elastic metal structure
AU665959B2 (en) * 1991-07-23 1996-01-25 Foster Wheeler Energia Oy A method of removing deposits from the walls of a gas cooler inlet duct, and a gas cooler inlet duct having a cooled elastic metal structure
US5634516A (en) * 1993-06-23 1997-06-03 Foster Wheeler Energia Oy Method and apparatus for treating or utilizing a hot gas flow
US5505907A (en) * 1993-06-23 1996-04-09 A. Ahstrom Corporation Apparatus for treating or utilizing a hot gas flow
WO1996005366A1 (en) * 1994-08-10 1996-02-22 A. Ahlstrom Corporation A recovery boiler where the flue gas is divided into two streams and a method therefore
US5672246A (en) * 1994-08-10 1997-09-30 Ahlstrom Machinery Oy Increasing the capacity of a recovery boiler by withdrawing some of the exhaust gases from the furnace section
WO2002086027A2 (en) * 2001-04-19 2002-10-31 Ebara Corporation Gasification and slagging combustion system
WO2002086027A3 (en) * 2001-04-19 2003-05-08 Ebara Corp Gasification and slagging combustion system
WO2002103063A2 (en) * 2001-06-19 2002-12-27 Voest-Alpine Industrieanlagenbau Gmbh & Co Method and device for treating particulate material
WO2002103063A3 (en) * 2001-06-19 2003-12-11 Voest Alpine Ind Anlagen Method and device for treating particulate material
US7144447B2 (en) 2001-06-19 2006-12-05 Voest-Alpine Industrieanlagenbau Gmbh & Co. Method and device for treating particulate material

Also Published As

Publication number Publication date
FI64997C (en) 1986-01-08
JPS6018000B2 (en) 1985-05-08
FR2546288A1 (en) 1984-11-23
AU1489383A (en) 1984-11-29
FR2546288B1 (en) 1988-12-16
GB8313711D0 (en) 1983-06-22
FI64997B (en) 1983-10-31
IN158648B (en) 1986-12-27
SE8206655L (en) 1983-05-24
SE454297B (en) 1988-04-18
JPS58104498A (en) 1983-06-21
FI813717L (en) 1983-05-24
SE8206655D0 (en) 1982-11-22
DE3240863A1 (en) 1983-06-01
GB2140144B (en) 1986-08-20
BE896801A (en) 1983-09-16
CA1265784A (en) 1990-02-13
AU553033B2 (en) 1986-07-03
DE3240863C2 (en) 1985-05-09

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Legal Events

Date Code Title Description
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
PE20 Patent expired after termination of 20 years

Effective date: 20030517