WO2000061860A2 - A method for reducing the risk for coatings and cloggings of heat absorbing surfaces present above the black liquor sprayers in a recovery boiler - Google Patents
A method for reducing the risk for coatings and cloggings of heat absorbing surfaces present above the black liquor sprayers in a recovery boiler Download PDFInfo
- Publication number
- WO2000061860A2 WO2000061860A2 PCT/SE2000/000710 SE0000710W WO0061860A2 WO 2000061860 A2 WO2000061860 A2 WO 2000061860A2 SE 0000710 W SE0000710 W SE 0000710W WO 0061860 A2 WO0061860 A2 WO 0061860A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- black liquor
- increased
- boiler
- recovery boiler
- reducing
- Prior art date
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C11/00—Regeneration of pulp liquors or effluent waste waters
- D21C11/12—Combustion of pulp liquors
Definitions
- the following invention refers to a method for reducing in a recovery boiler the risk for coatings and clogging of heat absorbing surfaces following after the combustion.
- a phenomena, which increases carry-over of physical matter depends on that non-combusted liquor droplets are carried along.
- the liquor is supplied to the boiler via black liquor sprayers equipped with nozzles.
- the liquor droplets, which are formed in the nozzle are first subjected to an intense heating, which evaporates all water. Thereupon the exterior of the drop is heated and the drop begins to pyrolyse. This takes place very swiftly but the interior parts of the drop are cooler and the exterior surface will have time to pyrolyse so rapidly that all oxidative gases, including water, will be kept away. This means that the exterior surface will carbonize and radicals that have been formed are recombinated with polymerisation as a result. The external surface becomes almost tight but elastic.
- the interior of the drop will continue to be pyrolysed, but the pyrolytic gases can not escape. An overpressure is created, which makes the black liquor drop swell up as a popcorn. This makes it especially sensitive to be carried along at high gas speeds and explains why also noncombusted black liquor drops are transported to the upper parts of the boiler .
- the other type of coating is caused by the chemical dust, which is formed in the upper regions of the boiler when gaseous sulphur and sodium compounds are combined and condensate.
- This dust is often named "fume” and is a dust which is comparatively easy to sweep as long as the chemical composition is the right and the melting point of the dust exceeds the temperature of the surrounding gas.
- the factor mainly influencing -the chemical composition of the dust is the amount of evaporated sulphur and sodium, which in turn are controlled by the temperature in the lower part of the combustion chamber. A high temperature gives a big evaporation of alkali resulting in big volumes of dust and a high portion of carbonate in the dust, which increases the pH-value of the dust. Normally the chloride discharge from the bed will also increase with increasing temperature.
- a concentration of chlorides in the dust will lower the melting point of the dust and make it "stick” and make it more difficult to sweep dust also at lower gas temperatures in the upper region of the boiler. If the temperature in the lower combustion chamber is too low, i.e. if the boiler is driven too cold, the result will be a high sulphur discharge in relation to the sodium discharge, which lowers the pH- value of the dust. This to gives raise to a sticky dust, which can be difficult to sweep away at too high surrounding temperatures in the upper part of the boiler.
- Normally air registers are used above the black liquor sprayers in a recovery boiler in order to obtain final combustion, so called overfire air registers.
- the overfire air is fed into the boiler under high pressure through especially designed air ports.
- the air is accelerated in the air port in that the static pressure is transformed to an impulse which increases the linear speed of the air.
- Inside the boiler the air is slowed down in that the impulse is transferred to gas present in the path and it will flow with an upward movement and in that other gas being sucked into the jet and admixed with the air.
- the fuel which is sucked in will oxidize very rapidly as the concentration of oxygen is high.
- the impulse from the air port has been reduced the oxygen molecule will move at about the same speed as other molecules in the gas.
- the transport of oxygen up to the fuel is now controlled by diffusion, convection and chemical reaction (through the temperature effects) .
- the speed of combustion will be very strongly dependent of the concentration of oxygen and fuel .
- a purpose of the present invention is to provide a method for minimizing in a recovery boiler the risk for coatings and clogging of heat absorbing surfaces situated above the black liquor sprayers, and this has been achieved mainly therein that the oxygen concentration in the recovery boiler is raised at at least one level above said black liquor sprayers for the purpose of increasing the combustion speed for the pyrolytic gases and thereby reducing the gas temperature prior to its entrance in the superheater area.
- Other purposes and features according to the present invention are defined in the sub claims.
- a recovery boiler 1 of the type used in connection to the method according to the invention is illustrated schematically in the drawing figure .
- the recovery boiler 1 incorporates in a conventional manner a lower combustion chamber 2 and an upper combustion chamber 3 in which final combustion takes place.
- a number of black liquor sprayers 4 are provided in the boiler wall for supply of black liquor, which shall be burned.
- supply means 5 for staged supply of final, oxygen enriched combustion air, in the embodiment shown arranged in three burning-off registers, situated between the black liquor sprayers and the superheater part 6 of the boiler.
- An ordinary recovery boiler was furnished with the possibility of supplying oxygen to the overair system of the boiler. Then oxygen was charged to the air channel under control and in especially designed nozzles for obtaining a good stirring before the oxygen enriched air is supplied to the boiler via air ports (5) .
- the physical carry-over was measured by especially installed carry-over meters in the upper part of the boiler.
- the gas temperature profile was measured with installed IR pyrometers before the superheater, and with protected thermoelements before the set of tubes and after the economiser .
- the carry-over meters were positioned at the rear wall of the boiler and at the right hand side wall at noose level.
- the physical measuring principle was based on the number of sparks measured.
- the combustion speed is also very strongly dependent of the fuel concentration. By increasing the fuel concentration in the gases, which arrive to this final combustion zone it is possible to increase the combustion speed still more and thereby is achieved still lower gas temperatures into the superheater section.
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU44446/00A AU4444600A (en) | 1999-04-14 | 2000-04-14 | A method at recovery boiler |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE9901331A SE9901331L (en) | 1999-04-14 | 1999-04-14 | Soda boiler procedure |
SE9901331-0 | 1999-04-14 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2000061860A2 true WO2000061860A2 (en) | 2000-10-19 |
WO2000061860A3 WO2000061860A3 (en) | 2001-02-08 |
Family
ID=20415213
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE2000/000710 WO2000061860A2 (en) | 1999-04-14 | 2000-04-14 | A method for reducing the risk for coatings and cloggings of heat absorbing surfaces present above the black liquor sprayers in a recovery boiler |
Country Status (4)
Country | Link |
---|---|
AU (1) | AU4444600A (en) |
CO (1) | CO5700179A1 (en) |
SE (1) | SE9901331L (en) |
WO (1) | WO2000061860A2 (en) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4823710A (en) * | 1987-10-13 | 1989-04-25 | Canadian Liquid Air Ltd.- Air Liquide Canada Ltee. | Non-peripheral blowing of oxygen-containing gas in steam generating boilers |
US4857282A (en) * | 1988-01-13 | 1989-08-15 | Air Products And Chemicals, Inc. | Combustion of black liquor |
US5007354A (en) * | 1989-02-20 | 1991-04-16 | Oy Tampella Ab | Combustion air supply system for a recovery furnace |
EP0905308A1 (en) * | 1997-09-26 | 1999-03-31 | L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude | Methods of improving productivity of black liquor recovery boilers |
-
1999
- 1999-04-14 SE SE9901331A patent/SE9901331L/en not_active Application Discontinuation
-
2000
- 2000-04-14 AU AU44446/00A patent/AU4444600A/en not_active Abandoned
- 2000-04-14 CO CO00027874A patent/CO5700179A1/en not_active Application Discontinuation
- 2000-04-14 WO PCT/SE2000/000710 patent/WO2000061860A2/en active Application Filing
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4823710A (en) * | 1987-10-13 | 1989-04-25 | Canadian Liquid Air Ltd.- Air Liquide Canada Ltee. | Non-peripheral blowing of oxygen-containing gas in steam generating boilers |
US4857282A (en) * | 1988-01-13 | 1989-08-15 | Air Products And Chemicals, Inc. | Combustion of black liquor |
US5007354A (en) * | 1989-02-20 | 1991-04-16 | Oy Tampella Ab | Combustion air supply system for a recovery furnace |
EP0905308A1 (en) * | 1997-09-26 | 1999-03-31 | L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude | Methods of improving productivity of black liquor recovery boilers |
Also Published As
Publication number | Publication date |
---|---|
SE9901331D0 (en) | 1999-04-14 |
WO2000061860A3 (en) | 2001-02-08 |
AU4444600A (en) | 2000-11-14 |
CO5700179A1 (en) | 2006-11-30 |
SE9901331L (en) | 2000-10-15 |
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