CA1265784A - Method and apparatus for recovering heat from gases containing substances which contaminate heat transfer surfaces - Google Patents
Method and apparatus for recovering heat from gases containing substances which contaminate heat transfer surfacesInfo
- Publication number
- CA1265784A CA1265784A CA000415762A CA415762A CA1265784A CA 1265784 A CA1265784 A CA 1265784A CA 000415762 A CA000415762 A CA 000415762A CA 415762 A CA415762 A CA 415762A CA 1265784 A CA1265784 A CA 1265784A
- Authority
- CA
- Canada
- Prior art keywords
- hot gases
- heat exchanger
- gases
- temperature
- cooling chamber
- 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.)
- Expired - Lifetime
Links
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
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- 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
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Thermal Sciences (AREA)
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Environmental & Geological Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
- Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
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 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.
Description
~2~
The present invention is related to a method and apparatus for recovering heat from gase containing vaporized, ~olten 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 re-covery of heat from these gases is rendered difficult by the vaporized or lten components in the gases contaminating heat transfer surfaces. A
typical example of this are the waste gases of the pyrcmetallurgical industry. The cleaning of the heat transfer surfaces by means of the methods available at the mcment is in most cases extremely difficult, which leads to diminished usability of the plant and therefore also to considerable costs.
~ xperience has shown that the cleaning problems and most severe in that temperature range, where part of the solid compounds are in a eutectic state. As an example 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 ~hat the kest endurance values are obtained in such steam boilers m 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 blc~ers or mechanical
The present invention is related to a method and apparatus for recovering heat from gase containing vaporized, ~olten 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 re-covery of heat from these gases is rendered difficult by the vaporized or lten components in the gases contaminating heat transfer surfaces. A
typical example of this are the waste gases of the pyrcmetallurgical industry. The cleaning of the heat transfer surfaces by means of the methods available at the mcment is in most cases extremely difficult, which leads to diminished usability of the plant and therefore also to considerable costs.
~ xperience has shown that the cleaning problems and most severe in that temperature range, where part of the solid compounds are in a eutectic state. As an example 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 ~hat the kest endurance values are obtained in such steam boilers m 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 blc~ers or mechanical
2 ~ 7~
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.
It is an object of the present invention to further advance the efficiency of heat recovery from hot gases by further reducing the rate of contamination of the heat transfer surfaces.
In general terms and in one aspect of the invention, a method of recovering heat from gas containing moltPn components, said method comprising the steps of:
(a) directing hot gases having temperature in the range from about 800 C to about 1500-C from a furnace in a generally vertical direction;
(b) reducing the temperature of the hot gases to a temperature below the eutectic range of molten components contained in said hot gases b~ mixing into said hot gases recirculated solid particles;
(c) directing the mixture of the solid particles and of the hot gases having said reduced temperature to a heat exchanger and in the heat exchanger further reducing the temperature of said gases;
(d) the velocity of the gases passing through the heat exchanger being within the range of about 3 m/s (meters per second) to about 20 m/s and being selected, with respect to the volume of particles added to the hot gases upstream of the heat exahanger, such as to assure a generally pneumatic passage of the particles through the heat exchanger.
The invention also provides apparatus for reco~ering heat from gas containing molten aomponents, said apparatus compr.ising:
1~
, . ; ',, ' ": ~ ''' 2a ~ 2~i~7~
(a) generally vertical conduit means for directing hot gases having temperature in the range of about 800 C to about 1500-C from a furnace;
(b) said conduit means having an upper end portion communicating with a downstream end of a pre-cooling chamber disposed above the conduit means, which pre-cooling chamber further communicates with a discharge end of a feeding device of recirculated paxticulate material for admixing the particulate material into said pre-cooling chamber in amount sufficient to bring the temperature of the hot gases within the pre-cooling chamber to a temperature below the eutectic range of molten components contained in the respective hot gases;
(c) said pre-cooling chamber having a downstream end portion which merges with a heat exchanger chamber provided with heat exchange medium passage means whose heat transmitting surface means are exposed to the flow of a mixture of the pre-cooled hot gases and the particulate matærial;
(d) gas velocity control means adapted to generate and maintain the velocity of said gases in the heat exchanger chamber at a rate within the range o~ 3 m/s to 20 m/s, said rate being sufficient to assure a generally pneumatic passage of the particles of the particulate material through the heat exchanger chamber.
The cross-sectional area of the pre-cooling chamber taken across the flow of said hot gases may be generally equal to that of the heat exchanger chamber, whereby the velocity of gas flow ln both chambers is generally the same.
The term "pneumatic passage" with reference ta the particles means that the velocity o~ gases is selected, with 1[~
2b respect to the size and amount of the particles, to be sufficiently high to assure that the particles are carried along at generally the same speed as the velocity of the gas flow.
Experiments show that the speed within the mentioned range of 3 to 30 ~eters per second provides satisfactory results in practical applications.
The term "eutectic`' has the common meaning as set forth, for instance, in Webster~s New World Dictionary, Second College Edition, 1970, at page 484: "designating or of a mixture or alloy with a melting point lower than that of any other combination of the same components.
The drawing shows an embodiment according to the invention for heat recovery.
In the apparatus shown in the figure, hot gas containing vaporized and molten components flow 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 in pul~erous by nature and thus does not catch on the heat transfer ~urfaces. The sweeping eEfect re~uired 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 ~as entering the heat exchanger in point 3, the temperature of the mixture drops near the limit of the eutectio range.
After the m.ixing and the droppin~ of the temperature that occurred D
'7~
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 surfa oe s.
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 m the process or some other inexpensive material, such as sand, which is added to t~,e process through a pipe 9.
m e following advantages are obtained by means of the method accord-ing 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.
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.
It is an object of the present invention to further advance the efficiency of heat recovery from hot gases by further reducing the rate of contamination of the heat transfer surfaces.
In general terms and in one aspect of the invention, a method of recovering heat from gas containing moltPn components, said method comprising the steps of:
(a) directing hot gases having temperature in the range from about 800 C to about 1500-C from a furnace in a generally vertical direction;
(b) reducing the temperature of the hot gases to a temperature below the eutectic range of molten components contained in said hot gases b~ mixing into said hot gases recirculated solid particles;
(c) directing the mixture of the solid particles and of the hot gases having said reduced temperature to a heat exchanger and in the heat exchanger further reducing the temperature of said gases;
(d) the velocity of the gases passing through the heat exchanger being within the range of about 3 m/s (meters per second) to about 20 m/s and being selected, with respect to the volume of particles added to the hot gases upstream of the heat exahanger, such as to assure a generally pneumatic passage of the particles through the heat exchanger.
The invention also provides apparatus for reco~ering heat from gas containing molten aomponents, said apparatus compr.ising:
1~
, . ; ',, ' ": ~ ''' 2a ~ 2~i~7~
(a) generally vertical conduit means for directing hot gases having temperature in the range of about 800 C to about 1500-C from a furnace;
(b) said conduit means having an upper end portion communicating with a downstream end of a pre-cooling chamber disposed above the conduit means, which pre-cooling chamber further communicates with a discharge end of a feeding device of recirculated paxticulate material for admixing the particulate material into said pre-cooling chamber in amount sufficient to bring the temperature of the hot gases within the pre-cooling chamber to a temperature below the eutectic range of molten components contained in the respective hot gases;
(c) said pre-cooling chamber having a downstream end portion which merges with a heat exchanger chamber provided with heat exchange medium passage means whose heat transmitting surface means are exposed to the flow of a mixture of the pre-cooled hot gases and the particulate matærial;
(d) gas velocity control means adapted to generate and maintain the velocity of said gases in the heat exchanger chamber at a rate within the range o~ 3 m/s to 20 m/s, said rate being sufficient to assure a generally pneumatic passage of the particles of the particulate material through the heat exchanger chamber.
The cross-sectional area of the pre-cooling chamber taken across the flow of said hot gases may be generally equal to that of the heat exchanger chamber, whereby the velocity of gas flow ln both chambers is generally the same.
The term "pneumatic passage" with reference ta the particles means that the velocity o~ gases is selected, with 1[~
2b respect to the size and amount of the particles, to be sufficiently high to assure that the particles are carried along at generally the same speed as the velocity of the gas flow.
Experiments show that the speed within the mentioned range of 3 to 30 ~eters per second provides satisfactory results in practical applications.
The term "eutectic`' has the common meaning as set forth, for instance, in Webster~s New World Dictionary, Second College Edition, 1970, at page 484: "designating or of a mixture or alloy with a melting point lower than that of any other combination of the same components.
The drawing shows an embodiment according to the invention for heat recovery.
In the apparatus shown in the figure, hot gas containing vaporized and molten components flow 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 in pul~erous by nature and thus does not catch on the heat transfer ~urfaces. The sweeping eEfect re~uired 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 ~as entering the heat exchanger in point 3, the temperature of the mixture drops near the limit of the eutectio range.
After the m.ixing and the droppin~ of the temperature that occurred D
'7~
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 surfa oe s.
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 m the process or some other inexpensive material, such as sand, which is added to t~,e process through a pipe 9.
m e following advantages are obtained by means of the method accord-ing 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 co~pounds that have come to their surface in the vapo~ phase.
4. The amount of sulphur emissions can be decreased by arrang mg e.g. a Ca-based circulating material
5. The radi~tlon and convection heat exchan~e ar~ activa-ted.
. . . : .
~Q~G~784 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 800 to lS00 &
Temperature of outgoing gas S00 to 1200 C
Mean diameter of particles 100 to 2000 ~m Example 1:
The values of the offgases of a Cu-smeltery after the smelting furnace are:
gas flow mol/s 1740 dust content g/mol 2.7 temperature C 1400 The offgases are cooled by radiatlon cooling in the channel 1 to about 900 &, whereby a temperature range having difficult prcperties 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(molC) i.e. the thermal capacity flow is 66.1 kW/C. A preferable te~perature before the heat transfer surfaces of the heat exchanaer 2 is 700 & and after the heat transfer surfaces 550 &. Thus the circulating thermal capacity flow is 88.1 k~^1/C. The specific thermal capacity of the circula-ting material can be estimated to be about 0.8 kJ/(kgC), which gives a value of 110 kg/s for the circulating mass flow. Thus after the mixing the solid m~tter content of the gas is 63 g/mol (= 2.81 kg/Nm3~. In practise solid n~atter content~ of 900 to 1~00 g/mol have been used in a so called cir~ulating b~d reactor. A conc~ntrat~, fiand or a mixture of them i7~
can be used as the circulating material in a smeltery. Furthennore, particles included in the offgases are concentrated in the cooling circulationO
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 %
O3501 %
H 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 cambustion chamber, the flue gases ma~ contain even 50 ~ of the sulphur and 30 % of the sodium after the co~bustion zone. When the flue gases get cooler, the inorganic chemicals form mostly sodium sul~ate and sodium carbonate as well as sulphur dioxide. Depending on the com~osition 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 offg~s values in the ~ibove ccmbustion chamber are:
gas flow mol/s ~40 N~-~low molts 4.$6 S-fl~wmol/s 2.75 temperature C 900 dust (cond.~ g/mol 0.23 (10.3 g/~m3) Thermal capacity flcw of the gas 29.4 kl~/ C
Gas tem~eratures:
upstream of the exchanger 870 C
after mixing 700 &
downstream of the exchanger 550 &
Circulating thermal capacity flow 33.0 kW/C
Circulating mass flow (0.8 kJ/kg&~ 41.7 kg/s ~ust content of gas in the exchanger 50.0 glmol The circulation flcw comprises the Na2003-based dust of the flue gases and the Na2C03 or Na2$04 added to point 3.
Those skilled tn the art will appreciate that many mcdifications of the method and apparatus of the invention can be carried out within the context of the present invention. Accordingly, we wish to secure by letters patent which may issue on this application all such embodiments as properly fall within the scope of our contribution to the art.
:: .
. . . : .
~Q~G~784 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 800 to lS00 &
Temperature of outgoing gas S00 to 1200 C
Mean diameter of particles 100 to 2000 ~m Example 1:
The values of the offgases of a Cu-smeltery after the smelting furnace are:
gas flow mol/s 1740 dust content g/mol 2.7 temperature C 1400 The offgases are cooled by radiatlon cooling in the channel 1 to about 900 &, whereby a temperature range having difficult prcperties 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(molC) i.e. the thermal capacity flow is 66.1 kW/C. A preferable te~perature before the heat transfer surfaces of the heat exchanaer 2 is 700 & and after the heat transfer surfaces 550 &. Thus the circulating thermal capacity flow is 88.1 k~^1/C. The specific thermal capacity of the circula-ting material can be estimated to be about 0.8 kJ/(kgC), which gives a value of 110 kg/s for the circulating mass flow. Thus after the mixing the solid m~tter content of the gas is 63 g/mol (= 2.81 kg/Nm3~. In practise solid n~atter content~ of 900 to 1~00 g/mol have been used in a so called cir~ulating b~d reactor. A conc~ntrat~, fiand or a mixture of them i7~
can be used as the circulating material in a smeltery. Furthennore, particles included in the offgases are concentrated in the cooling circulationO
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 %
O3501 %
H 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 cambustion chamber, the flue gases ma~ contain even 50 ~ of the sulphur and 30 % of the sodium after the co~bustion zone. When the flue gases get cooler, the inorganic chemicals form mostly sodium sul~ate and sodium carbonate as well as sulphur dioxide. Depending on the com~osition 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 offg~s values in the ~ibove ccmbustion chamber are:
gas flow mol/s ~40 N~-~low molts 4.$6 S-fl~wmol/s 2.75 temperature C 900 dust (cond.~ g/mol 0.23 (10.3 g/~m3) Thermal capacity flcw of the gas 29.4 kl~/ C
Gas tem~eratures:
upstream of the exchanger 870 C
after mixing 700 &
downstream of the exchanger 550 &
Circulating thermal capacity flow 33.0 kW/C
Circulating mass flow (0.8 kJ/kg&~ 41.7 kg/s ~ust content of gas in the exchanger 50.0 glmol The circulation flcw comprises the Na2003-based dust of the flue gases and the Na2C03 or Na2$04 added to point 3.
Those skilled tn the art will appreciate that many mcdifications of the method and apparatus of the invention can be carried out within the context of the present invention. Accordingly, we wish to secure by letters patent which may issue on this application all such embodiments as properly fall within the scope of our contribution to the art.
:: .
Claims (9)
1. A method of recovering heat from gas containing molten components, said method comprising the steps of:
(a) directing hot gases having temperature in the range from about 800 C to about 1500°C from a furnace in a generally vertical direction;
(b) reducing the temperature of the hot gases to a temperature below the eutectic range of molten components contained in said hot gases by mixing into said hot gases recirculated solid particles;
(c) directing the mixture of the solid particles and of the hot gases having said reduced temperature to a heat exchanger and in the heat exchanger further reducing the temperature of said gases;
(d) the velocity of the gases passing through the heat exchanger being within the range of about 3 m/s (meters per second) to about 20 m/s and being selected, with respect to the volume of particles added to the hot gases upstream of the heat exchanger, such as to assure a generally pneumatic passage of the particles through the heat exchanger.
(a) directing hot gases having temperature in the range from about 800 C to about 1500°C from a furnace in a generally vertical direction;
(b) reducing the temperature of the hot gases to a temperature below the eutectic range of molten components contained in said hot gases by mixing into said hot gases recirculated solid particles;
(c) directing the mixture of the solid particles and of the hot gases having said reduced temperature to a heat exchanger and in the heat exchanger further reducing the temperature of said gases;
(d) the velocity of the gases passing through the heat exchanger being within the range of about 3 m/s (meters per second) to about 20 m/s and being selected, with respect to the volume of particles added to the hot gases upstream of the heat exchanger, such as to assure a generally pneumatic passage of the particles through the heat exchanger.
2. The method of claim 1, wherein said step of directing the mixture of the solid particles and of the hot gases to the heat exchanger is carried out at generally the same cross sectional area of the gas flow as that at the point upstream of the heat exchanger, of reducing the temperature of the hot gases by mixing into said hot gases recirculated solid particles, to provide said generally pneumatic passage of said particles and of the gases having a temperature below the eutectic range, through the heat exchanger.
3. The method of one of claims 1 or 2, wherein the temperature of gases upstream of the heat exchanger but downstream of the point at which the particles are admixed is about 700°C.
4. The method of one of claims 1 or 2, wherein the gases coming from said furnace are combustion gases of a soda boiler and wherein the reduction in temperature of the gases caused by said admixing of the solid particles is to about 700°C.
5. The method of one of claims 1 or 2, wherein the hot gases coming from said furnace are off gases of a and wherein the reduction in temperature of the gases caused by said admixing of the solid particles is to about 700°C.
6. Apparatus for recovering heat from gas containing molten components, said apparatus comprising:
(a) generally vertical conduit means for directing hot gases having temperature in the range of about 800°C to about 1500°C from a furnace;
(b) said conduit means having an upper end portion communicating with a downstream end of a pre-cooling chamber disposed above the conduit means, which pre-cooling chamber further communicates with a discharge end of a feeding device of recirculated particulate material for admixing the particulate material into said pre-cooling chamber in amount sufficient to bring the temperature of the hot gases within the pre-cooling chamber to a temperature below the eutectic range of molten components contained in the respective hot gases;
(c) said pre-cooling chamber having a downstream end portion which merges with a heat exchanger chamber provided with heat exchange medium passage means whose heat transmitting surface means are exposed to the flow of a mixture of the pre-cooled hot gases and the particulate material;
(d) gas velocity control means adapted to generate and maintain the velocity of said gases in the heat exchanger chamber at a rate within the range of 3 m/s to 20 m/s, said rate being sufficient to assure a generally pneumatic passage of the particles of the particulate material through the heat exchanger chamber.
(a) generally vertical conduit means for directing hot gases having temperature in the range of about 800°C to about 1500°C from a furnace;
(b) said conduit means having an upper end portion communicating with a downstream end of a pre-cooling chamber disposed above the conduit means, which pre-cooling chamber further communicates with a discharge end of a feeding device of recirculated particulate material for admixing the particulate material into said pre-cooling chamber in amount sufficient to bring the temperature of the hot gases within the pre-cooling chamber to a temperature below the eutectic range of molten components contained in the respective hot gases;
(c) said pre-cooling chamber having a downstream end portion which merges with a heat exchanger chamber provided with heat exchange medium passage means whose heat transmitting surface means are exposed to the flow of a mixture of the pre-cooled hot gases and the particulate material;
(d) gas velocity control means adapted to generate and maintain the velocity of said gases in the heat exchanger chamber at a rate within the range of 3 m/s to 20 m/s, said rate being sufficient to assure a generally pneumatic passage of the particles of the particulate material through the heat exchanger chamber.
7. Apparatus for recovering heat from hot gases exiting from a soda boiler, comprising:
(a) generally vertical conduit means for directing hot gases from a respective soda boiler and having temperature of about 800°C to about 1500°C from a furnace;
(b) said conduit means having an upper end portion communicating with a downstream end of a pre-cooling chamber disposed above the conduit means, which pre-cooling chamber further communicates with a discharge end of a feeding device of recirculated particulate material for admixing the particulate material into said pre-cooling chamber in amount sufficient to bring the temperature of the hot gases within the pre-cooling chamber to a temperature below the eutectic range of molten components contained in the respective hot gases;
(c) said pre-cooling chamber having a downstream end portion which merges with a heat exchanger chamber provided with heat exchange medium passage means whose heat transmitting surface means are exposed to the flow of a mixture of the pre-cooled hot gases and the particulate material;
(d) gas velocity control means adapted to generate and maintain the velocity of said gases in the heat exchanger chamber at a rate within the range of 3 m/s to 20 m/s, said rate being sufficient to assure a generally pneumatic passage of the particles of the particulate material through the heat exchanger chamber.
(a) generally vertical conduit means for directing hot gases from a respective soda boiler and having temperature of about 800°C to about 1500°C from a furnace;
(b) said conduit means having an upper end portion communicating with a downstream end of a pre-cooling chamber disposed above the conduit means, which pre-cooling chamber further communicates with a discharge end of a feeding device of recirculated particulate material for admixing the particulate material into said pre-cooling chamber in amount sufficient to bring the temperature of the hot gases within the pre-cooling chamber to a temperature below the eutectic range of molten components contained in the respective hot gases;
(c) said pre-cooling chamber having a downstream end portion which merges with a heat exchanger chamber provided with heat exchange medium passage means whose heat transmitting surface means are exposed to the flow of a mixture of the pre-cooled hot gases and the particulate material;
(d) gas velocity control means adapted to generate and maintain the velocity of said gases in the heat exchanger chamber at a rate within the range of 3 m/s to 20 m/s, said rate being sufficient to assure a generally pneumatic passage of the particles of the particulate material through the heat exchanger chamber.
8. Apparatus for recovering heat from hot gases exiting from a Cu-smeltery, comprising:
(a) generally vertical conduit means for directing hot gases from a respective Cu-smeltery and having temperature of about 800°C to about 1500°C from a furnace;
(b) said conduit means having an upper end portion communicating with a downstream end of a pre-cooling chamber disposed above the conduit means, which pre-cooling chamber further communicates with a discharge end of a feeding device of recirculated particulate material for admixing the particulate material into said pre-cooling chamber in amount sufficient to bring the temperature of the hot gases within the pre-cooling chamber to a temperature below the eutectic range of molten components contained in the respective hot gases;
(c) said pre-cooling chamber having a downstream end portion which merges with a heat exchanger chamber provided with heat exchange medium passage means whose heat transmitting surface means are exposed to the flow of a mixture of the pre-cooled hot gases and the particulate material;
(d) gas velocity control means adapted to generate and maintain the velocity of said gases in the heat exchanger chamber at a rate within the range of 3 m/s to 20 m/s, said rate being sufficient to assure a generally pneumatic passage of the particles of the particulate material through the heat exchanger chamber.
(a) generally vertical conduit means for directing hot gases from a respective Cu-smeltery and having temperature of about 800°C to about 1500°C from a furnace;
(b) said conduit means having an upper end portion communicating with a downstream end of a pre-cooling chamber disposed above the conduit means, which pre-cooling chamber further communicates with a discharge end of a feeding device of recirculated particulate material for admixing the particulate material into said pre-cooling chamber in amount sufficient to bring the temperature of the hot gases within the pre-cooling chamber to a temperature below the eutectic range of molten components contained in the respective hot gases;
(c) said pre-cooling chamber having a downstream end portion which merges with a heat exchanger chamber provided with heat exchange medium passage means whose heat transmitting surface means are exposed to the flow of a mixture of the pre-cooled hot gases and the particulate material;
(d) gas velocity control means adapted to generate and maintain the velocity of said gases in the heat exchanger chamber at a rate within the range of 3 m/s to 20 m/s, said rate being sufficient to assure a generally pneumatic passage of the particles of the particulate material through the heat exchanger chamber.
9. Apparatus as claimed in claim 6, 7 or 8 wherein the cross-sectional area of the pre-cooling chamber taken across the flow of said hot gases, is generally equal to that of the heat exchanger chamber, whereby the velocity of gas flow in both chambers is generally the same.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI813717 | 1981-11-23 | ||
| FI813717A FI64997C (en) | 1981-11-23 | 1981-11-23 | FOERFARANDE FOER TILLVARATAGANDE AV VAERME UR GASER INNEHAOLLANDE VAERMEYTOR NEDSMUTSANDE AEMNEN |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1265784A true CA1265784A (en) | 1990-02-13 |
Family
ID=8514888
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000415762A Expired - Lifetime CA1265784A (en) | 1981-11-23 | 1982-11-17 | Method and apparatus 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) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI76707C (en) * | 1984-09-14 | 1988-12-12 | Ahlstroem Oy | Process for the purification of gases containing condensable components |
| ES2093641T3 (en) * | 1988-12-20 | 1997-01-01 | Cra Services | MANUFACTURE OF IRON AND STEEL IN A DUPLEX MELTING CONTAINER AND A SOLID STATE OXIDE SUSPENSION PRE-REDUCER. |
| IE904007A1 (en) * | 1989-11-08 | 1991-05-08 | Mount Isa Mines | Condensation of metal vapours in a fluidized bed |
| FI93056C (en) * | 1991-07-23 | 1995-02-10 | Ahlstroem Oy | Method and apparatus for feeding process or flue gases into a gas cooler |
| 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 |
| FI93274C (en) * | 1993-06-23 | 1995-03-10 | Ahlstroem Oy | Method and apparatus for treating or recovering a hot gas stream |
| FI97424C (en) * | 1993-06-23 | 1996-12-10 | Foster Wheeler Energia Oy | Method and apparatus for treating or recovering hot gas |
| FI96436C (en) * | 1994-08-10 | 1996-06-25 | Ahlstroem Oy | Process and apparatus for treating waste |
| JP2002317915A (en) * | 2001-04-19 | 2002-10-31 | Ebara Corp | Gasifying melting furnace facility, and its operation method |
| EP1397521A2 (en) * | 2001-06-19 | 2004-03-17 | Voest-Alpine Industrieanlagenbau GmbH & Co. | Method and device for treating particulate material |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL80999C (en) * | 1952-12-18 | |||
| GB868368A (en) * | 1958-10-10 | 1961-05-17 | British Iron Steel Research | Improvements in or relating to heat exchangers |
| 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 |
| FR2279052A1 (en) * | 1974-03-01 | 1976-02-13 | Commissariat Energie Atomique | THERMAL ACCUMULATION PROCESS AND THERMAL ACCUMULATOR WITH LATENT HEAT OF FUSION AND DIRECT CONTACT |
| 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 |
| DE3205213C2 (en) * | 1982-02-13 | 1985-08-22 | Kronos Titan-Gmbh, 5090 Leverkusen | Device for cooling hot gas-TiO? 2? Suspensions from titanium dioxide production by vapor phase oxidation of titanium tetrachloride |
-
1981
- 1981-11-23 FI FI813717A patent/FI64997C/en not_active IP Right Cessation
-
1982
- 1982-11-05 DE DE3240863A patent/DE3240863C2/en not_active Expired
- 1982-11-17 CA CA000415762A patent/CA1265784A/en not_active Expired - Lifetime
- 1982-11-22 SE SE8206655A patent/SE454297B/en not_active IP Right Cessation
- 1982-11-22 JP JP57203816A patent/JPS6018000B2/en not_active Expired
-
1983
- 1983-05-18 GB GB08313711A patent/GB2140144B/en not_active Expired
- 1983-05-20 BE BE0/210815A patent/BE896801A/en not_active IP Right Cessation
- 1983-05-20 FR FR8308368A patent/FR2546288B1/en not_active Expired
- 1983-05-23 IN IN643/CAL/83A patent/IN158648B/en unknown
- 1983-05-23 AU AU14893/83A patent/AU553033B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| BE896801A (en) | 1983-09-16 |
| FI64997B (en) | 1983-10-31 |
| FI813717L (en) | 1983-05-24 |
| JPS58104498A (en) | 1983-06-21 |
| FI64997C (en) | 1986-01-08 |
| FR2546288B1 (en) | 1988-12-16 |
| DE3240863A1 (en) | 1983-06-01 |
| DE3240863C2 (en) | 1985-05-09 |
| AU553033B2 (en) | 1986-07-03 |
| IN158648B (en) | 1986-12-27 |
| JPS6018000B2 (en) | 1985-05-08 |
| SE454297B (en) | 1988-04-18 |
| GB2140144B (en) | 1986-08-20 |
| SE8206655D0 (en) | 1982-11-22 |
| FR2546288A1 (en) | 1984-11-23 |
| GB2140144A (en) | 1984-11-21 |
| SE8206655L (en) | 1983-05-24 |
| AU1489383A (en) | 1984-11-29 |
| GB8313711D0 (en) | 1983-06-22 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |