CA1202485A - Slag fusion point modification - Google Patents
Slag fusion point modificationInfo
- Publication number
- CA1202485A CA1202485A CA000434141A CA434141A CA1202485A CA 1202485 A CA1202485 A CA 1202485A CA 000434141 A CA000434141 A CA 000434141A CA 434141 A CA434141 A CA 434141A CA 1202485 A CA1202485 A CA 1202485A
- Authority
- CA
- Canada
- Prior art keywords
- slag
- phosphate
- phosphate compound
- weight
- fusion point
- 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
Links
Landscapes
- Solid Fuels And Fuel-Associated Substances (AREA)
- Incineration Of Waste (AREA)
Abstract
ABSTRACT
Phosphate compounds have been found to be effective in raising the fusion point of the slag derived from the burning of coal or bark and thus to facilitate control of fireside deposit and corrosion in boiler units.
Phosphate compounds have been found to be effective in raising the fusion point of the slag derived from the burning of coal or bark and thus to facilitate control of fireside deposit and corrosion in boiler units.
Description
During combustion in a boiler furnace the reactions which occur between the fuel impurities lead to the formation of deposits which adhere to boiler surEaces. Such deposits upset khe normal operation conditions and cause such troublesome problems as (a) obstruction to gas flow; (b) interference with heat transfer due to the formation of deposits having thermal insulating properties; (c) damage to water tubes on the ash slopes due to bulk deposits falling; ~d) serious loss of metal tubes due to corrosion conditions accompanying deposi~s.
Deposit and corrosion buildup force unscheduled outages for cleaning (deslagging) or replacing of the failed tubes which can be costly.
Research and experimental work has been carried out on the problem of external fouling of boilers. ~hile there still remain a large number of problems unsolved, one of the methods for reducing boiler fouling is to use a fuel additive. Various additives have been used with some degree of success. On oil fired boilers, additives help prevent corrosion on the cooler part of the system, while on coal or bark fired boilers the emphasis has been to reduce external fouling.
Magnesium based additives are particularly effective and widely used in both oil and coal fired boilers. However, in a bark fired boiler, the slag contains mostly silica (up to 81%) and calcium oxide.
In this case, a phosphate compound was found to be one of the most effective additives which was able to increase the fusion temperature of slag. The slag deposit, when a phosphate material is used, becomes dry~
porous, and is in a friable form which is easier for removal by soot blowers.
~ombustion boiler efficiency is improved as the heat transfer surface become cleaner.
s This invention seeks to provide an additive that will redwce fireside deposit problems, and will control the nature of the slag deposited.
Alternatively this invention seeks to provide an additive that will raise the fusion point of the slag and also the softening temperatwre.
This invention comprises a method of raising the fusion point of slag, which is derived from firing solid fuel containing high amounts of silica (e.g. wood bark). This is accomplished by adding from 0.5 to 10.0%
by weight of a phosphate compound. The phosphate compound can be a monoammonium phosphate, an alkali-free phosphate, a diphosporous pentoxide, or a phosphoric acid. Preferably, monammonium phosphate is used. Although a wider range is useful, from 0.5 - 10% and, preferably, l.0 to 5.0% by weight of the slag is preferred. For convenience, the phosphate compound is in a 20% by weight solution. An alternate form of dosage is fronn 0.025 to 0.1% by weight of the solid fuel.
It is well known in the art that combustion catalysts have been used to reduce slag. By adding trace quantities of combustion catalysts, a light friable removed deposit was formed. The additive rearranges the crystal structure and instead of a heavy single crystal, it produces a large number of small crystals. Some of the combustion catalysts that have been found to be very useful are manganese chloride and manganese nitrate.
In accordance with the practice of this invention~ it has been found that the phosphate compound is even more effective in reducing slag formation when from 0.5 to 3.0% by weight of a combustion catalyst is added. Preferably, the combustion catalyst is manganese chloride or manganese nitrite.
Deposit and corrosion buildup force unscheduled outages for cleaning (deslagging) or replacing of the failed tubes which can be costly.
Research and experimental work has been carried out on the problem of external fouling of boilers. ~hile there still remain a large number of problems unsolved, one of the methods for reducing boiler fouling is to use a fuel additive. Various additives have been used with some degree of success. On oil fired boilers, additives help prevent corrosion on the cooler part of the system, while on coal or bark fired boilers the emphasis has been to reduce external fouling.
Magnesium based additives are particularly effective and widely used in both oil and coal fired boilers. However, in a bark fired boiler, the slag contains mostly silica (up to 81%) and calcium oxide.
In this case, a phosphate compound was found to be one of the most effective additives which was able to increase the fusion temperature of slag. The slag deposit, when a phosphate material is used, becomes dry~
porous, and is in a friable form which is easier for removal by soot blowers.
~ombustion boiler efficiency is improved as the heat transfer surface become cleaner.
s This invention seeks to provide an additive that will redwce fireside deposit problems, and will control the nature of the slag deposited.
Alternatively this invention seeks to provide an additive that will raise the fusion point of the slag and also the softening temperatwre.
This invention comprises a method of raising the fusion point of slag, which is derived from firing solid fuel containing high amounts of silica (e.g. wood bark). This is accomplished by adding from 0.5 to 10.0%
by weight of a phosphate compound. The phosphate compound can be a monoammonium phosphate, an alkali-free phosphate, a diphosporous pentoxide, or a phosphoric acid. Preferably, monammonium phosphate is used. Although a wider range is useful, from 0.5 - 10% and, preferably, l.0 to 5.0% by weight of the slag is preferred. For convenience, the phosphate compound is in a 20% by weight solution. An alternate form of dosage is fronn 0.025 to 0.1% by weight of the solid fuel.
It is well known in the art that combustion catalysts have been used to reduce slag. By adding trace quantities of combustion catalysts, a light friable removed deposit was formed. The additive rearranges the crystal structure and instead of a heavy single crystal, it produces a large number of small crystals. Some of the combustion catalysts that have been found to be very useful are manganese chloride and manganese nitrate.
In accordance with the practice of this invention~ it has been found that the phosphate compound is even more effective in reducing slag formation when from 0.5 to 3.0% by weight of a combustion catalyst is added. Preferably, the combustion catalyst is manganese chloride or manganese nitrite.
- 2 -24~1~
Many methods to minimize or control the formation of slag have been tried with mixed amounts of success. If fuel is carefully selected and contains no impurities, naturally there would be no slag problem. Although this is the surest method of control, it is economically unfeasible. In coal, the mineral matter is widely distributed. Modifying aerodynamics and furnace design factors to optimize the operating conditions is very costly and the existing system cannot be changed for at least a decade. ~he only alternative is the use of additives.
The exact mechanism of how the invention works is not complecely understood; and there are many different hypothesis about the action of additive compounds involving the chemical, physical or crystalline changes of the deposits. The additive may flux the slag deposit to reduce the fusion point or improve the flowability of the slag in a wet bottom furnace.
The additive may cause the minerals in the slag to change crystal structure (phase change) which would crack under the high temperature fluctuation or form a friable deposit. The additive may react with or destroy the bonding surface which causes the first sticky layer on the surface of a clean tube.
The additive might weaken the slag by forming gas bubbles with the slag.
To demonstrate the effectiveness of this invention a series of tests was run to measure softening temperature (ST) and fluid temperature (FT).
The fusibility or Cone-Fusion Test which is a standard mechod adopted by the American Society for Testing Material (ASTM) D 18S7-68 was used. This method provides an empirical observation of the gradual melting of 3/4 inch slag sample cones wich an equilateral-triangular base of 1/~ inch wide.
Ileated in a controlled-atmosphere furnace usually at a rate of 15.5F.
Many methods to minimize or control the formation of slag have been tried with mixed amounts of success. If fuel is carefully selected and contains no impurities, naturally there would be no slag problem. Although this is the surest method of control, it is economically unfeasible. In coal, the mineral matter is widely distributed. Modifying aerodynamics and furnace design factors to optimize the operating conditions is very costly and the existing system cannot be changed for at least a decade. ~he only alternative is the use of additives.
The exact mechanism of how the invention works is not complecely understood; and there are many different hypothesis about the action of additive compounds involving the chemical, physical or crystalline changes of the deposits. The additive may flux the slag deposit to reduce the fusion point or improve the flowability of the slag in a wet bottom furnace.
The additive may cause the minerals in the slag to change crystal structure (phase change) which would crack under the high temperature fluctuation or form a friable deposit. The additive may react with or destroy the bonding surface which causes the first sticky layer on the surface of a clean tube.
The additive might weaken the slag by forming gas bubbles with the slag.
To demonstrate the effectiveness of this invention a series of tests was run to measure softening temperature (ST) and fluid temperature (FT).
The fusibility or Cone-Fusion Test which is a standard mechod adopted by the American Society for Testing Material (ASTM) D 18S7-68 was used. This method provides an empirical observation of the gradual melting of 3/4 inch slag sample cones wich an equilateral-triangular base of 1/~ inch wide.
Ileated in a controlled-atmosphere furnace usually at a rate of 15.5F.
- 3 S
per minute, the cone goes through four melting stages as: 1) initial deformation temperature; 2) softening temperature; 3) hemispherical temperature; and ~) fluid temperature. This test has been used widely in coal-buying specifications. Strict observance of the test procedure is necessary to obtain reproducibility. Por each pOitlt, the difference for the critical point ~emperature between two separate runs shall not exceed 50~. (30C). Most of the users tend to use only the softening temperature and fluid tempera~ure. The softening temperature is the temperature at which the cone has melted to form a sphericalll~tp wi~h the height equal to the width of the base. The fluid temperature is the temperature at which the slag flows into a flat layer with a maximum height of 1/16 inch.
The results of the softening temperature and fusion temperature are given in Table 1 below.
The slag contained 81% silicon oxide, 9% calcium oxide, 3%
potassium oxide, and minor amounts of aluminum oxide, magnesium oxide, ferric oxide, and diphosphorous pentoxide. The dosage of additive was 5%
by weight of the slag.
In summary, phosphate compo~mds have been found to be effective in raising the fusion temperature or softening temperature of slag for coal and bar~ fired systems. By the use of these phosphate compounds, the slag formed by burning solid fuel can be controlled and causes less of a problem.
TABLE~ 1 SofteningFluid Treatment T~mperature 'I'eMperature Blank 2620P.2700f:.
Monoammonium Phosphate 2800 >2800 Phosphated alumina 2750 >2800 Magnesium oxide 2560 2700 Kaolin 2600 2700 ~A1203 2SiO2 2H20) TiO2 <2600 2700 CeCO3 <2600 2700 A12(SO4)3 <2600 2700 -- 5 _
per minute, the cone goes through four melting stages as: 1) initial deformation temperature; 2) softening temperature; 3) hemispherical temperature; and ~) fluid temperature. This test has been used widely in coal-buying specifications. Strict observance of the test procedure is necessary to obtain reproducibility. Por each pOitlt, the difference for the critical point ~emperature between two separate runs shall not exceed 50~. (30C). Most of the users tend to use only the softening temperature and fluid tempera~ure. The softening temperature is the temperature at which the cone has melted to form a sphericalll~tp wi~h the height equal to the width of the base. The fluid temperature is the temperature at which the slag flows into a flat layer with a maximum height of 1/16 inch.
The results of the softening temperature and fusion temperature are given in Table 1 below.
The slag contained 81% silicon oxide, 9% calcium oxide, 3%
potassium oxide, and minor amounts of aluminum oxide, magnesium oxide, ferric oxide, and diphosphorous pentoxide. The dosage of additive was 5%
by weight of the slag.
In summary, phosphate compo~mds have been found to be effective in raising the fusion temperature or softening temperature of slag for coal and bar~ fired systems. By the use of these phosphate compounds, the slag formed by burning solid fuel can be controlled and causes less of a problem.
TABLE~ 1 SofteningFluid Treatment T~mperature 'I'eMperature Blank 2620P.2700f:.
Monoammonium Phosphate 2800 >2800 Phosphated alumina 2750 >2800 Magnesium oxide 2560 2700 Kaolin 2600 2700 ~A1203 2SiO2 2H20) TiO2 <2600 2700 CeCO3 <2600 2700 A12(SO4)3 <2600 2700 -- 5 _
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of raising the fusion point of slag which comprises adding from 0.5 to 10.0% by weight of the slag of a phosphate compound selected from the group consisting of monoammonium phosphate, alkali free phosphate, diphosphorous pentoxide, and phosphoric acid.
2. The method of Claim 1 wherein the phosphate compound is added at from 1.0 to 5.0% by weight of the slag or from 0.025 to 0.1% by weight of the solid fuel.
3. The method of Claim 1 wherein the phosphate compound is monoammonium phosphate.
4. The method of Claim 3 wherein the phosphate compound is a 20%
aqueous solution.
aqueous solution.
5. The method of Claim 4 wherein the solution contains from 0.5 to 3.0% by weight of a combustion catalyst.
6. The method of Claim 5 wherein the combustion catalyst is selected from the group consisting of manganese chloride and manganese nitrate.
7. The method of Claim 1 wherein the phosphate compound is introduced into the boiler by mixing it with the solid fuel before firing.
8. The method of Claim 1 wherein the phosphate compound is injected into the furnace box prior to the deposit area.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US40660882A | 1982-08-09 | 1982-08-09 | |
| US406,608 | 1982-08-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1202485A true CA1202485A (en) | 1986-04-01 |
Family
ID=23608732
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000434141A Expired CA1202485A (en) | 1982-08-09 | 1983-08-08 | Slag fusion point modification |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1202485A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4759772A (en) * | 1987-07-22 | 1988-07-26 | Carus Corporation | Method of controlling self-ignition of low rank coal |
| WO2001005911A2 (en) * | 1999-07-16 | 2001-01-25 | Reatech | A method for reducing agglomeration, sintering and deposit formation |
| DE202011108946U1 (en) | 2011-12-13 | 2012-02-13 | Georg Dohmen | Additive for the improvement of ash and slag properties during the combustion of biogenic masses |
-
1983
- 1983-08-08 CA CA000434141A patent/CA1202485A/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4759772A (en) * | 1987-07-22 | 1988-07-26 | Carus Corporation | Method of controlling self-ignition of low rank coal |
| WO2001005911A2 (en) * | 1999-07-16 | 2001-01-25 | Reatech | A method for reducing agglomeration, sintering and deposit formation |
| WO2001005913A1 (en) * | 1999-07-16 | 2001-01-25 | Reatech | Phosphor addition in gasification |
| WO2001005911A3 (en) * | 1999-07-16 | 2001-08-09 | Reatech | A method for reducing agglomeration, sintering and deposit formation |
| US6615751B1 (en) | 1999-07-16 | 2003-09-09 | Raetech | Method for reducing agglomeration, sintering and deposit formation in gasification and combustion of biomass |
| DE202011108946U1 (en) | 2011-12-13 | 2012-02-13 | Georg Dohmen | Additive for the improvement of ash and slag properties during the combustion of biogenic masses |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP1375631B1 (en) | Fuel additive for preventing slagging and method for burning fuel | |
| US4498402A (en) | Method of reducing high temperature slagging in furnaces and conditioner for use therein | |
| US4372227A (en) | Method of reducing high temperature slagging in furnaces | |
| CA1169650A (en) | Vermiculite as a deposit modifier in coal fired boilers | |
| US4245573A (en) | Air heater corrosion prevention | |
| CA1257092A (en) | Method of conditioning fireside fouling deposits using super large particle magnesium oxide | |
| CA1202485A (en) | Slag fusion point modification | |
| CA2167991C (en) | Honeycomb regenerator | |
| US4428310A (en) | Phosphated alumina as slag modifier | |
| US3630696A (en) | Combustion adjuvant | |
| US4465000A (en) | Method of increasing the efficiency of cyclone-fired boilers using high sodium lignite fuel | |
| US4258017A (en) | Vanadium removal from furnace gases | |
| EP0208868B1 (en) | Catalytic cracking catalyst and process | |
| US2913319A (en) | Fuel oils | |
| US2843200A (en) | Fuel oils | |
| Marner et al. | A survey of gas-side fouling in industrial heat-transfer equipment | |
| US3078663A (en) | Residual fuels containing alkali metal and calcium, barium or strontium compounds | |
| US3127742A (en) | Petroleum fuel composition and process | |
| GB2142653A (en) | Method of binding vanadium compounds | |
| Bellan et al. | Fuel-composition effects on high-temperature corrosion in industrial/commercial boilers and furnaces: a review | |
| US2987884A (en) | Vanadium-containing residual fuels modified with calcium hypochlorite | |
| EP0130065A1 (en) | Improvements in and relating to combustion | |
| CLARKE | Vanadium ash problems in oil fired boilers | |
| CA1137704A (en) | Air heater corrosion prevention | |
| JPS6191416A (en) | Modifying method of scale produced upon combustion of oil coke |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |