CA1107510A - Method and apparatus for preparing molten glass - Google Patents
Method and apparatus for preparing molten glassInfo
- Publication number
- CA1107510A CA1107510A CA294,126A CA294126A CA1107510A CA 1107510 A CA1107510 A CA 1107510A CA 294126 A CA294126 A CA 294126A CA 1107510 A CA1107510 A CA 1107510A
- Authority
- CA
- Canada
- Prior art keywords
- pellets
- borates
- bed
- furnace
- wet
- 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
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B1/00—Preparing the batches
- C03B1/02—Compacting the glass batches, e.g. pelletising
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
- C03C1/02—Pretreated ingredients
- C03C1/026—Pelletisation or prereacting of powdered raw materials
-
- 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
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Treating Waste Gases (AREA)
- Glass Compositions (AREA)
- Glass Melting And Manufacturing (AREA)
Abstract
ABSTRACT OF THE INVENTION
Volatile borates and/or fluorides are removed from the hot stack gases of a glass furnace by passing the hot stack gases up through a layer of wet pellets containing ions of an alkaline earth metal or an alkali metal. The pellets may contain solid borates and/or fluorides as part of the feed to the glass furnace, and still absorb volatile materials from the stack gases, so long as the borates and/or fluorides in the pellets are in, or are converted to, a less soluble and volatile form than are the volatile materials in the stack gases. Ca(OH)2 is a preferred material for converting the volatiles into an essentially nonvolatile form. Ion exchange materials, such as clay, can also.
he used to capture these volatiles.
Volatile borates and/or fluorides are removed from the hot stack gases of a glass furnace by passing the hot stack gases up through a layer of wet pellets containing ions of an alkaline earth metal or an alkali metal. The pellets may contain solid borates and/or fluorides as part of the feed to the glass furnace, and still absorb volatile materials from the stack gases, so long as the borates and/or fluorides in the pellets are in, or are converted to, a less soluble and volatile form than are the volatile materials in the stack gases. Ca(OH)2 is a preferred material for converting the volatiles into an essentially nonvolatile form. Ion exchange materials, such as clay, can also.
he used to capture these volatiles.
Description
11~7510 The present invention relates to new and improved methods of removing volatiles, and particularly borates and fluorides, from hot furnace gases.
In the manufacture of glass, fluxing materials are added to silica and/or hi~h melting silica-tes, as for example the aluminum silicates, in order to produce an initial molten stage which hastens the dissolving of the silica and/or silicates, and in addition to provide a manageable low melting temperature for the final glass product. Soda is an extensively used material for accomplishing these purposes, but soda by itself produces glasses that are leachable in water and so have poor weathering characteristics. Soda glass i5 in fact so leachable that it can-not be used as the sole fluxing agent for glasses from which glass fibers are made, and so other fluxing materials, such as borates and/or fluorides, are used to lower the melting tempera-ture of the silicates, and to provide silicates of sufficiently low solubility in water that they have acceptable weathering characteristics.
Glasses that contain borates and/or fluorides, when in the molten state, liberate borates and/or fluorides, and these materials go out with the stack gas of the furnace. What is more, sodium borates and/or sodium fluorides by themselves have appre-ciable vapor pressure at their melting temperatures so that a sig-nificant amount of these materials is lost when batches containing these materials are heated during the charging operation of glass furnaces. Borates and fluorides produce ecological problems when they exit with stack gas and so it has long been desired to find an economical way of extracting these ~olatile materials from th~ -stack gas.
It has been suggested heretofore that cooling air be mixed - 1 - ~
11~751~) with the stack gas to lower its temperature to the point where the volatile borates and fluorides condense into particulate matter which can be extracted from the gas by means of bag filters and/or electrostatic precipitators. This method of extraction is not economical, however, because the cooling air lowers the stack effect to such an extent that fans must be used to move the stack gas through the ba~ filters and/or electrostatic precipitators.
The cooling air that is introduced into the stack gas must be so voluminous that the fan size becomes enormous, and the method uneconomical.
Prior to the present invention no process has been known for extracting volatile borates and/or fluorides from stack or effluent gas that is sufficiently simple, efficient, and economi-cal to carry out as to warrant commercial usage of the process.
According to one aspect of this invention there is pro-vided a method of-removing borates and/or fluorides from hot effluent gases liberated by a gas producing furnace comprising pelletizing with water batch materials containing borates and/or fluorides and including less than about 3% by weight Na2O, charging the pellets to the charging end of a pellet treatment bed having charging and discharging ends, conducting hot effluent gases from a glass producing furnace to a region of the pellet treatment bed adjacent its discharging end, maintaining a layer of wet pellets at the charging end of the pellet treatment bed, and causing the effluent gases to pass through the pellet treat-ment bed including the layer of wet pellets at the charging end of the pellet treatment bed to preheat the pellets, and charging pellets from the discharge end to said furnace.
According to another aspect of this invention there is provided a method of removing borates and/or fluorides from hot . - -, ':
~1~751~
effluent gas li~erated by a glass producing furnace comprisingpelletizing with water batch materials containing borates and/or fluorides and an ionizable alkali metal and/or alkaline earth metal material, said batch materials including less than about 3% by weight Na2O, charging the wet pellets to the charging end of a pellet treatment bed having charging and discharging ends, conducting the hot effluent gas from a glass producing furnace to a region of the pellet treatment bed adjacent its discharging end, maintaining a layer of wet pellets at the charging end of the pellet treatment bed, and causing the furnace effluent gas to pass through the pellet treatment bed including the wet layer of pellets to remove at least some of the volatile borates and~or fluorides from the furnace effluent gas and to preheat the pellets, and charging pellets from said discharge end to said furnace.
The preferred method described and illustrated herein fa-cilitates preventing the escape of volatile borates and/or fluorides from the batch material during the time that the tempera-ture of the batch materlal is being raised to the temperature of complete fusion, and furthermore facilitates heating wet pellets of batch material without destroying the pellets before they reach their molten state.
The invention will be further understood from the follow-ing description by way of example with reference to the single figure of the drawing which illustrates a gas fired glass melting system embodying principles of the present invention.
Figure 1 illustrates a gas fired glass melting system 10 having raw material storage bins lla, llb, llc, and lld which for example contain such raw materials as sand, limestone, feldspar or any other necessary constituents to the batch formulation. The basic raw materials are drawn from the storage bins and mixed in Ç'.i .~., ~ . .
.
.
751i~
proportions in accordance with the desired batch formulation by any known batch formulation mixing apparatus represented in Figure 1 as a mixing valve V. The formulated batch is preferably pelletized into batch pellets of approximately 1/4" to 5/8" in diameter. In the preferred method used by the applicant, 90% of the pellets produced have a diameter in this 1/4" to 5/8" range.
Any known dry material pelletizer such as the four foot diameter pelletizing disc manufactured by Dravo Corporation of Pittsburgh, Pennsylvania may be used. It is preferable to add approximately 20~ by weight of water to the batch formulation. The pellets are then fed into the top of a pellet heating chamber 13 within which the moist pellets are dried and pre-heated to the desired tempera-ture as they gravitate downward through the chamber 13. The chamber 13 as shown provides a vertical pellet treatment bed.
The high temperature flue gas exhausted from a gas fired melter 15 is conveyed from an exhaust stack 16, via appropriate piping 17, into the bottom of the pellet heating chamber 13. The hot flue gas, having entrained therein exhaust products from the gas fired melter 15, is percolated upward through the gravitating ~pellets. Located at the top of the pellet heating chamber 13 is an exhaust fan 18 to assist in maintaining the proper flue gas flow rate through the pellet heating chamber 13. As the flue gas percolates upward through the gravitating batch pellets, heat is ~ ~ -transferred from the hot gas to the pellets. As a result thereof the fluorides and borates entrained in the flue gas precipitate out and collect as condensables upon the batch pellets. Further, because of the precipitating fluorides and borates and sulfates coupled with the filtering effect of the pellet bed, entrained dust particles or particulate matter are also effectively removed from the flue gas. The percolating flue gas also reduces compac-.. , - .
~;
- - : ..
, ~ - ' 11~751~) tion of the pellet bed thereby assisting movement of the pellets downward to the chamber exit 19.
The most efficient transfer of heat from a hot gas per-colating upward through a pelletized bed occurs at the point of bed fluidization. However, complete fluidization of the pellet bed causes disintegration of the batch pellets by elutriation.
Therefore, it is preferred to maintain the pellet bed in a semi-fluid state thereby obtaining maximum heat transfer without pellet disintegration.
- 4a -F
. , . - .
: .
.
~1qP751~
A system melting a typical E-type glass formulation of:
CONSTITUENT PERCENT BY WEIGHT
Si2 55.0 A123 15.0 CaO 22.0
In the manufacture of glass, fluxing materials are added to silica and/or hi~h melting silica-tes, as for example the aluminum silicates, in order to produce an initial molten stage which hastens the dissolving of the silica and/or silicates, and in addition to provide a manageable low melting temperature for the final glass product. Soda is an extensively used material for accomplishing these purposes, but soda by itself produces glasses that are leachable in water and so have poor weathering characteristics. Soda glass i5 in fact so leachable that it can-not be used as the sole fluxing agent for glasses from which glass fibers are made, and so other fluxing materials, such as borates and/or fluorides, are used to lower the melting tempera-ture of the silicates, and to provide silicates of sufficiently low solubility in water that they have acceptable weathering characteristics.
Glasses that contain borates and/or fluorides, when in the molten state, liberate borates and/or fluorides, and these materials go out with the stack gas of the furnace. What is more, sodium borates and/or sodium fluorides by themselves have appre-ciable vapor pressure at their melting temperatures so that a sig-nificant amount of these materials is lost when batches containing these materials are heated during the charging operation of glass furnaces. Borates and fluorides produce ecological problems when they exit with stack gas and so it has long been desired to find an economical way of extracting these ~olatile materials from th~ -stack gas.
It has been suggested heretofore that cooling air be mixed - 1 - ~
11~751~) with the stack gas to lower its temperature to the point where the volatile borates and fluorides condense into particulate matter which can be extracted from the gas by means of bag filters and/or electrostatic precipitators. This method of extraction is not economical, however, because the cooling air lowers the stack effect to such an extent that fans must be used to move the stack gas through the ba~ filters and/or electrostatic precipitators.
The cooling air that is introduced into the stack gas must be so voluminous that the fan size becomes enormous, and the method uneconomical.
Prior to the present invention no process has been known for extracting volatile borates and/or fluorides from stack or effluent gas that is sufficiently simple, efficient, and economi-cal to carry out as to warrant commercial usage of the process.
According to one aspect of this invention there is pro-vided a method of-removing borates and/or fluorides from hot effluent gases liberated by a gas producing furnace comprising pelletizing with water batch materials containing borates and/or fluorides and including less than about 3% by weight Na2O, charging the pellets to the charging end of a pellet treatment bed having charging and discharging ends, conducting hot effluent gases from a glass producing furnace to a region of the pellet treatment bed adjacent its discharging end, maintaining a layer of wet pellets at the charging end of the pellet treatment bed, and causing the effluent gases to pass through the pellet treat-ment bed including the layer of wet pellets at the charging end of the pellet treatment bed to preheat the pellets, and charging pellets from the discharge end to said furnace.
According to another aspect of this invention there is provided a method of removing borates and/or fluorides from hot . - -, ':
~1~751~
effluent gas li~erated by a glass producing furnace comprisingpelletizing with water batch materials containing borates and/or fluorides and an ionizable alkali metal and/or alkaline earth metal material, said batch materials including less than about 3% by weight Na2O, charging the wet pellets to the charging end of a pellet treatment bed having charging and discharging ends, conducting the hot effluent gas from a glass producing furnace to a region of the pellet treatment bed adjacent its discharging end, maintaining a layer of wet pellets at the charging end of the pellet treatment bed, and causing the furnace effluent gas to pass through the pellet treatment bed including the wet layer of pellets to remove at least some of the volatile borates and~or fluorides from the furnace effluent gas and to preheat the pellets, and charging pellets from said discharge end to said furnace.
The preferred method described and illustrated herein fa-cilitates preventing the escape of volatile borates and/or fluorides from the batch material during the time that the tempera-ture of the batch materlal is being raised to the temperature of complete fusion, and furthermore facilitates heating wet pellets of batch material without destroying the pellets before they reach their molten state.
The invention will be further understood from the follow-ing description by way of example with reference to the single figure of the drawing which illustrates a gas fired glass melting system embodying principles of the present invention.
Figure 1 illustrates a gas fired glass melting system 10 having raw material storage bins lla, llb, llc, and lld which for example contain such raw materials as sand, limestone, feldspar or any other necessary constituents to the batch formulation. The basic raw materials are drawn from the storage bins and mixed in Ç'.i .~., ~ . .
.
.
751i~
proportions in accordance with the desired batch formulation by any known batch formulation mixing apparatus represented in Figure 1 as a mixing valve V. The formulated batch is preferably pelletized into batch pellets of approximately 1/4" to 5/8" in diameter. In the preferred method used by the applicant, 90% of the pellets produced have a diameter in this 1/4" to 5/8" range.
Any known dry material pelletizer such as the four foot diameter pelletizing disc manufactured by Dravo Corporation of Pittsburgh, Pennsylvania may be used. It is preferable to add approximately 20~ by weight of water to the batch formulation. The pellets are then fed into the top of a pellet heating chamber 13 within which the moist pellets are dried and pre-heated to the desired tempera-ture as they gravitate downward through the chamber 13. The chamber 13 as shown provides a vertical pellet treatment bed.
The high temperature flue gas exhausted from a gas fired melter 15 is conveyed from an exhaust stack 16, via appropriate piping 17, into the bottom of the pellet heating chamber 13. The hot flue gas, having entrained therein exhaust products from the gas fired melter 15, is percolated upward through the gravitating ~pellets. Located at the top of the pellet heating chamber 13 is an exhaust fan 18 to assist in maintaining the proper flue gas flow rate through the pellet heating chamber 13. As the flue gas percolates upward through the gravitating batch pellets, heat is ~ ~ -transferred from the hot gas to the pellets. As a result thereof the fluorides and borates entrained in the flue gas precipitate out and collect as condensables upon the batch pellets. Further, because of the precipitating fluorides and borates and sulfates coupled with the filtering effect of the pellet bed, entrained dust particles or particulate matter are also effectively removed from the flue gas. The percolating flue gas also reduces compac-.. , - .
~;
- - : ..
, ~ - ' 11~751~) tion of the pellet bed thereby assisting movement of the pellets downward to the chamber exit 19.
The most efficient transfer of heat from a hot gas per-colating upward through a pelletized bed occurs at the point of bed fluidization. However, complete fluidization of the pellet bed causes disintegration of the batch pellets by elutriation.
Therefore, it is preferred to maintain the pellet bed in a semi-fluid state thereby obtaining maximum heat transfer without pellet disintegration.
- 4a -F
. , . - .
: .
.
~1qP751~
A system melting a typical E-type glass formulation of:
CONSTITUENT PERCENT BY WEIGHT
Si2 55.0 A123 15.0 CaO 22.0
2 3 7.0 F2 0.5 Na2O 0.5 in a conventional gas fired melter supplying 15 tons of molten glass per day may be expected to produce a sufficient quantity of hot flue gas to adequately pre-heat the batch pellets. It has been determined that by introducing 1,500F flue gas tO the pellet heating chamber and percolating it upward through the gravitating pellet bed 14 having a 46% porosity at a pore velocity of 200 feet per minute the pellets may be heated from ambient temperature to approximately 1,400F prior to exiting the chamber. The maximum flue gas velocity that may be maintained through the pellet bed 14 without causing pellet dusting is the velocity which produces fluidation of the bed. Preferably, the velocity should be at least 75% of the fluidizing velocity. For pellets between 1/2" and 5/8" in diameter a pore velocity between 200 feet per minute and 600 feet per minute will be acceptable. Heat balance calculations indicate that approximately 880,000 BTU per ton of the batch pellets processed may be reclaimed from the percolated flue gas by this process. This represenis a 10 to 15 percent fuel saving for the melter 15. It is preferred that the exhaust gas exit temperature at the fan 18 be sreater than 250F to prevent water condensation within the pellet bed 14 or pellet heating chamber 13.
In operation the system establishes an equilibrium state whereby the batch constituents normally lost to the atmosphere are -5~
~ .
, 75~
re-claimed and returned to the melting process. ~ence, the batch formula must be adjusted to compensate for the re-claimed consti-tuents. In actual practice an electric melt bach formula may be effectively used in a gas melter embodying the invention. Thus, in a glass plant operation having both electric and gas fired melters one batch formula may be used in both types of melter.
Example 1 By way of further example, the following materials, with-in the ranges indicated in parts by weight below, are charged to the pelletizer of the drawing for making E-glass:
- SiO2 20 to 35 Al2O3.2siO2.2H2O (Kaolin)20 to 35 ` CaCO3 15 to 25 2CaO.3B2O3.H2O (calcined Colemanite) 10 to 25 Na2SiF6 (Any inorganic fluoride) 0.2 to 5 NaNO3 0 to 1 CaSO4.2H2O (Gypsum) 0 to 1 Water 15 to 25 with the total sodium and/or calcium salts that are ionizable in water at room temperature (NaNo3 and/or gypsum) being at least 0.10% by weight. Aluminum silicates are of course clays which are plasticized by water into ion change materials when in the non-` sintered wet condition. These materials also act as a binder for the wet pellets. As previously indicated, the flue gas from the furnace contains ~aporized borates which are believed to be H3BO3 and/or H2B4O7. Inasmuch as the pellets at the top of the bed of ; pellets 14 are wet, and these borates are soluble, the borates are extracted from the gas and go into solution. The burnt colemanite is only slightly soluble, so that the water of the pellets being charged is not saturated with borates. In addition, the solubility .
~ - 6 -75~) of these borates increases with temperature, so that more and more of the borates in the gas are picked up by the wet pellets as the pellets proceed down through the layer of wet pellets at the top of the pellet bed. It will further be seen that the pellets contain some ionizable alkali metal salts and/or alkaline earth salts. These ions react with boric acids to form much less soluble alkali metal borates and/or alkaline earth borates which also are much less volatile and higher melting. The borates which are extracted by the wet pellets are thus captured and converted to a generally nonvolatile phase before the pellets reach the tem-perature at which the acid borates are boiled off. In addition,by converting the borates into the preferred alkaline earth bo-rates, the borates can be kept from fusing at the 740C range where the sodium tetraborates melt; and so the pellets can be heated safely to a higher temperature to remove more heat from the stack gas without the pellets being rused together.
If it is desired to use a sodium borate as a raw material for the pellets, it will be advantageous also to have some calcium ion and preferably Ca(OH)2 in the wet pellets to react with the sodium borate and convert it into a less soluble and less volatile calcium borate before the pellets leave the wet layer at the top of the pellet bed.
It can be readily determined from the abovementioned list of ingredients that the amount of Na2O in the batch is less than about 3% by weight.
Vaporization of borates from the hot lower region of the pellet bed is captured by passing the gas through the upper sur-face of the wet layer of pellets. Preferably the gas leaves the wet pellets below 300F and above 212F, and most preferably at ; 30 approximately 250 F.
11'~751~) When cldy is used in the pellets, it not only acts as a wet binder for the pellets but aids in extracting borates and/or fluorides by ion exchange. Fluorides are also dissolved out of the hot gas by the water on the surface of the pellets; and what has been said about the capture of borates also applies to the fluorides. In general, the alkaline earth fluorides are less soluble than the alkali metal fluorides and they react with the ~` alkaline earth metal ions to be taken out of solution. The alkaline earth fluorides are quite nonvolatile, so that the cap-tured fluorides are retained through the preheated step until they reach the molten glass in the glass furnace. Conversion of the borates and fluorides to the alkaline earth form has the fur-ther advantage in that the pellets can be raised to a higher temperature before melting and fusing together. This allows more heat to be absorbed by the pellets without plugging equipment and thereby a greater thermal efficiency. Not only does the process of the present invention effectively remove borates and fluorides from furnace stack gas, but it is economical to carry out commer-cially, because the cost of the equipment that must be added to a glass furnace is largely offset by the savings in energy which the process provides.
In some instances, it may be desired to provide an addi-tional gelling agent to batch materials before pelletizing to pro-vlde a green binder for the pellets. Any type of organic or inor-ganic gelling agent can be used so long as it does not upset the chemical balance of the desired glass. This will usually not be a problem, however, because only a small amount of gelling agent is - needed; usually from 0.5~ to 4% of the water is all that is neces-sary. Examples of inorganic gelling agents are: refined attap~
gite (3MgO.1.5A1203.8SiO2.9H20); and Benagu (a highly beneficiated ~"
i~751~) hydrous magnesium montmorillionite sold by the National Lead Co.J
Organic gellinc3 agents are, of course, fugitive, and are burned off without altering the chemical composition of the batch. Suit-able examples are Carbopol (a trademarked material produced by B.
F. Goodrich Co. under U.S. Patent 2,789,053); Kelzan* (a poly-saccharide gum produced by fermentation of an alginate with xan-thomonas comphistris bacterium and sold by the Kelco Co.); and any good methyl cellulose or other organo substituted cellulosic gelling agent.
While the invention has been described in considerable detail, it is not limited to the particular embodiments shown and described, and many adaptations, modifications, and arrangements thereof are possible without departing from the scope of the in-vention as claimed in the following claims.
f * Trade Mark :
In operation the system establishes an equilibrium state whereby the batch constituents normally lost to the atmosphere are -5~
~ .
, 75~
re-claimed and returned to the melting process. ~ence, the batch formula must be adjusted to compensate for the re-claimed consti-tuents. In actual practice an electric melt bach formula may be effectively used in a gas melter embodying the invention. Thus, in a glass plant operation having both electric and gas fired melters one batch formula may be used in both types of melter.
Example 1 By way of further example, the following materials, with-in the ranges indicated in parts by weight below, are charged to the pelletizer of the drawing for making E-glass:
- SiO2 20 to 35 Al2O3.2siO2.2H2O (Kaolin)20 to 35 ` CaCO3 15 to 25 2CaO.3B2O3.H2O (calcined Colemanite) 10 to 25 Na2SiF6 (Any inorganic fluoride) 0.2 to 5 NaNO3 0 to 1 CaSO4.2H2O (Gypsum) 0 to 1 Water 15 to 25 with the total sodium and/or calcium salts that are ionizable in water at room temperature (NaNo3 and/or gypsum) being at least 0.10% by weight. Aluminum silicates are of course clays which are plasticized by water into ion change materials when in the non-` sintered wet condition. These materials also act as a binder for the wet pellets. As previously indicated, the flue gas from the furnace contains ~aporized borates which are believed to be H3BO3 and/or H2B4O7. Inasmuch as the pellets at the top of the bed of ; pellets 14 are wet, and these borates are soluble, the borates are extracted from the gas and go into solution. The burnt colemanite is only slightly soluble, so that the water of the pellets being charged is not saturated with borates. In addition, the solubility .
~ - 6 -75~) of these borates increases with temperature, so that more and more of the borates in the gas are picked up by the wet pellets as the pellets proceed down through the layer of wet pellets at the top of the pellet bed. It will further be seen that the pellets contain some ionizable alkali metal salts and/or alkaline earth salts. These ions react with boric acids to form much less soluble alkali metal borates and/or alkaline earth borates which also are much less volatile and higher melting. The borates which are extracted by the wet pellets are thus captured and converted to a generally nonvolatile phase before the pellets reach the tem-perature at which the acid borates are boiled off. In addition,by converting the borates into the preferred alkaline earth bo-rates, the borates can be kept from fusing at the 740C range where the sodium tetraborates melt; and so the pellets can be heated safely to a higher temperature to remove more heat from the stack gas without the pellets being rused together.
If it is desired to use a sodium borate as a raw material for the pellets, it will be advantageous also to have some calcium ion and preferably Ca(OH)2 in the wet pellets to react with the sodium borate and convert it into a less soluble and less volatile calcium borate before the pellets leave the wet layer at the top of the pellet bed.
It can be readily determined from the abovementioned list of ingredients that the amount of Na2O in the batch is less than about 3% by weight.
Vaporization of borates from the hot lower region of the pellet bed is captured by passing the gas through the upper sur-face of the wet layer of pellets. Preferably the gas leaves the wet pellets below 300F and above 212F, and most preferably at ; 30 approximately 250 F.
11'~751~) When cldy is used in the pellets, it not only acts as a wet binder for the pellets but aids in extracting borates and/or fluorides by ion exchange. Fluorides are also dissolved out of the hot gas by the water on the surface of the pellets; and what has been said about the capture of borates also applies to the fluorides. In general, the alkaline earth fluorides are less soluble than the alkali metal fluorides and they react with the ~` alkaline earth metal ions to be taken out of solution. The alkaline earth fluorides are quite nonvolatile, so that the cap-tured fluorides are retained through the preheated step until they reach the molten glass in the glass furnace. Conversion of the borates and fluorides to the alkaline earth form has the fur-ther advantage in that the pellets can be raised to a higher temperature before melting and fusing together. This allows more heat to be absorbed by the pellets without plugging equipment and thereby a greater thermal efficiency. Not only does the process of the present invention effectively remove borates and fluorides from furnace stack gas, but it is economical to carry out commer-cially, because the cost of the equipment that must be added to a glass furnace is largely offset by the savings in energy which the process provides.
In some instances, it may be desired to provide an addi-tional gelling agent to batch materials before pelletizing to pro-vlde a green binder for the pellets. Any type of organic or inor-ganic gelling agent can be used so long as it does not upset the chemical balance of the desired glass. This will usually not be a problem, however, because only a small amount of gelling agent is - needed; usually from 0.5~ to 4% of the water is all that is neces-sary. Examples of inorganic gelling agents are: refined attap~
gite (3MgO.1.5A1203.8SiO2.9H20); and Benagu (a highly beneficiated ~"
i~751~) hydrous magnesium montmorillionite sold by the National Lead Co.J
Organic gellinc3 agents are, of course, fugitive, and are burned off without altering the chemical composition of the batch. Suit-able examples are Carbopol (a trademarked material produced by B.
F. Goodrich Co. under U.S. Patent 2,789,053); Kelzan* (a poly-saccharide gum produced by fermentation of an alginate with xan-thomonas comphistris bacterium and sold by the Kelco Co.); and any good methyl cellulose or other organo substituted cellulosic gelling agent.
While the invention has been described in considerable detail, it is not limited to the particular embodiments shown and described, and many adaptations, modifications, and arrangements thereof are possible without departing from the scope of the in-vention as claimed in the following claims.
f * Trade Mark :
Claims (22)
1. A method of removing borates and/or fluorides from hot effluent gases liberated by a glass producing furnace com-prising pelletizing with water batch materials containing borates and/or fluorides and including less than about 3% by weight Na2O, charging the pellets to the charging end of a pellet treatment bed having charging and discharging ends, conducting hot effluent gases from a glass producing furnace to a region of the pellet treatment bed adjacent its discharging end, maintaining a layer of wet pellets at the charging end of the pellet treatment bed, and causing the effluent gases to pass through the pellet treatment bed including the layer of wet pellets at the charging end of the pellet treatment bed to preheat the pellets, and charging pellets from the discharge end to said furnace.
2. The method of claim 1 wherein the effluent gases are controlled to provide a temperature of the gases exiting from said wet layer below approximately 300°F.
3. The method of claim 2 wherein the batch material con-tains borates and an ionizable alkali metal and/or alkaline earth metal material and wherein the borates of the batch material are caused to be relatively insoluble compared to the borates in the effluent gas.
4. The method of claim 3 wherein the borates in the batch material are calcined Colemanite.
5. The method of claim 1 or 2 wherein the pellets in-clude an ionizable alkali metal and/or alkaline earth metal salt.
6. The method of claim 1 wherein said pellet treatment bed is positioned with said wet layer at the top and said dis-charging end at the bottom.
7. The method of claim 6 wherein said effluent gas is passed through said bed at a velocity between 75% and 100% of the velocity which fluidizes the bed of pellets.
8. A method of removing borates and/or fluorides from hot effluent gas liberated by a glass producing furnace comprising pelletizing with water batch materials containing borates and/or fluorides and an ionizable alkali metal and/or alkaline earth metal material, said batch materials including less than about 3%
by weight Na20, changing the wet pellets to the charging end of a pellet treatment bed having charging and discharging ends, con-ducting the hot effluent gas from a glass producing furnace to a region of the pellet treatment bed adjacent its discharging end, maintaining a layer of wet pellets at the charging end of the pellet treatment bed, and causing the furnace effluent gas to pass through the pellet treatment bed including the wet layer of pellets to remove at least some of the volatile borates and/or fluorides from the furnace effluent gas and to preheat the pellets, and charging pellets from said discharge end to said furnace.
by weight Na20, changing the wet pellets to the charging end of a pellet treatment bed having charging and discharging ends, con-ducting the hot effluent gas from a glass producing furnace to a region of the pellet treatment bed adjacent its discharging end, maintaining a layer of wet pellets at the charging end of the pellet treatment bed, and causing the furnace effluent gas to pass through the pellet treatment bed including the wet layer of pellets to remove at least some of the volatile borates and/or fluorides from the furnace effluent gas and to preheat the pellets, and charging pellets from said discharge end to said furnace.
9. The method of claim 8 wherein the effluent gas is controlled to provide a temperature of the gas exiting from said wet layer below approximately 300°F.
10. The method of claim 8 wherein the batch material con-tains borates and wherein the borates in the batch material are caused to be relatively insoluble compared to the borates in the effluent gas.
11. The method of claim 10 wherein the borates in the batch material are calcined Colemanite.
12. The method of claim 1 wherein the wet pellets are dried as they move towards said discharge end of said treatment bed, the borates in the batch material are sodium borates, and the wet pellets contain alkaline earth metal ions to preci-pitate alkaline earth borates during drying of the pellets.
13. The method of claim 8 wherein clay is used as a binder in the step of pelletizing said batch materials.
14. The method of claim 8 wherein said pellet treatment bed is positioned with said wet layer at the top of the bed and said discharging end at the bottom of the bed.
15. The method of claim 14 wherein said effluent gas is passed through said bed at a velocity between 75% and 100% of the velocity which fluidizes the bed of pellets.
16. The method of claim 14 wherein 90% of the pellets which are charged to said bed have a diameter between approximately 1/4" and approximately 5/8".
17. The method of claim 13 wherein said batch material comprises the following materials in the approximate weight per-centages indicated:
Limestone from 15 to 25 Silica from 20 to 35 Alumina Silicate from 20 to 35 Burnt Colemanite from 10 to 25 Inorganic Fluoride from 0.2 to 5 Calcium Sulfate 0 to 1 Sodium Nitrate 0 to 1.
Limestone from 15 to 25 Silica from 20 to 35 Alumina Silicate from 20 to 35 Burnt Colemanite from 10 to 25 Inorganic Fluoride from 0.2 to 5 Calcium Sulfate 0 to 1 Sodium Nitrate 0 to 1.
18. The method of claim 8 wherein a gelling agent is used in a sufficient amount to provide a wet binder for the pellets.
19. In a process of producing glass by charging to a melting furnace and melting therein a batch having the composi-tion:
with the total of the sodium and calcium salts that are ionizable in water at room temperature (NaNO3 and CaSO4 . 2H2O) being at least 0.10% by weight, the improvements of pelletizing the batch materials using water, charging the wet pellets containing free water onto the upper surface of a vertical pellet treatment bed having a lower discharge end communicating with the furnace, sub-stantially simultaneously (1) withdrawing pellets through said lower discharge end for charging to the furnace, (2) moving the remaining pellets by gravity downwardly through the bed, (3) passing the hot furnace effluent gas upwardly through the bed to heat the pellets therein, and (4) drying the wet pellets on the upper surface of the bed by the spent effluent gas which has al-ready passed through the bed, the sequential performance of steps (3) and (4) on the effluent gas being effective (a) to remove at least some of the boron from the effluent gases, (b) to remove at least some of the fluorine from the effluent gases, and (c) to remove at least some of the particulate matter from the effluent gases, and the presence of the wet particles at the surface of the bed enhancing the performance of steps (3) and (4).
with the total of the sodium and calcium salts that are ionizable in water at room temperature (NaNO3 and CaSO4 . 2H2O) being at least 0.10% by weight, the improvements of pelletizing the batch materials using water, charging the wet pellets containing free water onto the upper surface of a vertical pellet treatment bed having a lower discharge end communicating with the furnace, sub-stantially simultaneously (1) withdrawing pellets through said lower discharge end for charging to the furnace, (2) moving the remaining pellets by gravity downwardly through the bed, (3) passing the hot furnace effluent gas upwardly through the bed to heat the pellets therein, and (4) drying the wet pellets on the upper surface of the bed by the spent effluent gas which has al-ready passed through the bed, the sequential performance of steps (3) and (4) on the effluent gas being effective (a) to remove at least some of the boron from the effluent gases, (b) to remove at least some of the fluorine from the effluent gases, and (c) to remove at least some of the particulate matter from the effluent gases, and the presence of the wet particles at the surface of the bed enhancing the performance of steps (3) and (4).
20. A process as defined in claim 19, wherein at least some of the vaporized boron compounds in the furnace effluent gas is removed during the performance of steps (3) and (4) as alkaline earth metal borates.
21. A process as defined in claim 19, wherein at least some of the gaseous fluorine in the furnace effluent gas is re-moved during the performance of steps (3) and (4) as alkaline earth metal fluorides.
22. In a process of producing glass from a batch material for forming a glass containing less than about 3% by weight Na2O
and containing a volatile borate in a furnace which liberates hot effluent gases including volatile borates and solid contaminant particles, the improvement comprising: pelletizing the batch materials using water and an ionizable alkali metal and/or alka-line earth metal salt present in the batch, charging the wet pellets containing free water to the charging end of a pellet treatment bed having charging and discharging ends, maintaining a layer of wet pellets at the charging end of the pellet bed, and conducting the hot furnace effluent gases through the bed and through the layer of wet pellets, the step of conducting being effective to remove at least some of the volatile borates and the solid particles from the furnace effluent gases.
and containing a volatile borate in a furnace which liberates hot effluent gases including volatile borates and solid contaminant particles, the improvement comprising: pelletizing the batch materials using water and an ionizable alkali metal and/or alka-line earth metal salt present in the batch, charging the wet pellets containing free water to the charging end of a pellet treatment bed having charging and discharging ends, maintaining a layer of wet pellets at the charging end of the pellet bed, and conducting the hot furnace effluent gases through the bed and through the layer of wet pellets, the step of conducting being effective to remove at least some of the volatile borates and the solid particles from the furnace effluent gases.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US76492277A | 1977-02-02 | 1977-02-02 | |
| US764,922 | 1977-02-02 | ||
| US84983977A | 1977-11-09 | 1977-11-09 | |
| US849,839 | 1977-11-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1107510A true CA1107510A (en) | 1981-08-25 |
Family
ID=27117536
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA294,126A Expired CA1107510A (en) | 1977-02-02 | 1977-12-30 | Method and apparatus for preparing molten glass |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5398318A (en) |
| CA (1) | CA1107510A (en) |
| DE (1) | DE2804498A1 (en) |
| FR (1) | FR2379487A1 (en) |
| GB (1) | GB1555920A (en) |
| IT (1) | IT1089325B (en) |
| NL (1) | NL7714629A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4248616A (en) * | 1979-04-19 | 1981-02-03 | Owens-Corning Fiberglas Corporation | Pollution abating, energy conserving glass manufacturing apparatus |
| US4298369A (en) | 1980-03-31 | 1981-11-03 | Owens-Corning Fiberglas Corporation | Glass manufacturing process having boron and fluorine pollution abating features |
| JP2021091571A (en) * | 2019-12-10 | 2021-06-17 | 日本電気硝子株式会社 | Manufacturing method of alkaline earth aluminoborosilicate glass |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1469109A (en) * | 1965-12-27 | 1967-02-10 | Saint Gobain | Intermediate product for the manufacture of glass and other silicates, and process and apparatus for its manufacture |
| US3529979A (en) * | 1966-10-26 | 1970-09-22 | Ppg Industries Inc | Method of preparing alkali sand products |
| US3728094A (en) * | 1971-07-15 | 1973-04-17 | Bowman And Ass Inc | Process of making glass |
| US3924030A (en) * | 1971-12-15 | 1975-12-02 | Nippon Soda Co | Method for production of glass-forming materials |
| US3788832A (en) * | 1972-08-25 | 1974-01-29 | Inst Gas Technology | Process for pre-treating and melting glassmaking materials |
| US3880639A (en) * | 1972-12-13 | 1975-04-29 | Owens Illinois Inc | Sulfur recovery from glass melting and refining |
| FR2238678B1 (en) * | 1973-07-24 | 1979-01-26 | Saint Gobain | |
| US4026691A (en) * | 1975-11-03 | 1977-05-31 | The Dow Chemical Company | Making a pelletized glass batch for soda-lime glass manufacture |
| NL181989C (en) * | 1976-11-08 | 1987-12-16 | Ppg Industries Inc | PROCESS FOR PREPARING A COLEMANITE-CONTAINING GLASS FIBER GLASS MIX. |
-
1977
- 1977-12-30 IT IT31513/77A patent/IT1089325B/en active
- 1977-12-30 CA CA294,126A patent/CA1107510A/en not_active Expired
- 1977-12-30 GB GB54342/77A patent/GB1555920A/en not_active Expired
- 1977-12-30 FR FR7739865A patent/FR2379487A1/en not_active Withdrawn
- 1977-12-31 JP JP15854277A patent/JPS5398318A/en active Pending
- 1977-12-31 NL NL7714629A patent/NL7714629A/en not_active Application Discontinuation
-
1978
- 1978-02-02 DE DE19782804498 patent/DE2804498A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB1555920A (en) | 1979-11-14 |
| FR2379487A1 (en) | 1978-09-01 |
| NL7714629A (en) | 1978-08-04 |
| IT1089325B (en) | 1985-06-18 |
| JPS5398318A (en) | 1978-08-28 |
| DE2804498A1 (en) | 1978-08-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4358304A (en) | Method for preparing molten glass | |
| US4184861A (en) | Energy efficient apparatus and process for manufacture of glass | |
| US4225332A (en) | Energy efficient pollution abating glass manufacturing process with external recovery of heat from furnace flue gases | |
| EP0145350A2 (en) | Vitrification of asbestos waste | |
| CA1107509A (en) | Method of preparing colemanite-containing glass batch | |
| US4338112A (en) | Method for controlling particulate emissions from a glass furnace | |
| CA1107510A (en) | Method and apparatus for preparing molten glass | |
| US4347073A (en) | Method of producing glass from agglomerates which include organic coated scrap glass | |
| CA1073932A (en) | Method of preparing boric acid containing glass batch | |
| US4362543A (en) | Method for controlling particulate emissions | |
| CA1073933A (en) | Method of preparing anhydrous boric acid containing glass batch | |
| TWI267495B (en) | Methods of forming particulate glass batch compositions and reducing volatile components from an exhaust stream | |
| CN101260012B (en) | Method for producing composite particle slow release silicon fertilizer | |
| CN1321202C (en) | Poison eliminating profit increasing method of antimony smelting arsenic alkali slag and high temperature energy-saving smelting furnace | |
| US4330314A (en) | Apparatus and process for predrying and preheating glass batch agglomerates before melting | |
| CN109279782B (en) | System for preparing microcrystalline glass by using chlorine-containing titanium extraction hot slag | |
| AU550283B2 (en) | Directed flow, thin layer glass fusion | |
| JP3746111B2 (en) | Method for producing sodium silicate cullet | |
| WO2017179364A1 (en) | Method for manufacturing glass product | |
| CN109133650A (en) | A method of devitrified glass is prepared using titanium slag is mentioned containing chlorine | |
| AU519499B2 (en) | Pollution abating, energy conserving glass manufacturing process | |
| CN109133651A (en) | It is a kind of by mentioning the devitrified glass that titanium slag is prepared containing chlorine | |
| AU2018202993B2 (en) | A system and a method for fabrication of arsenic glass | |
| US11168014B2 (en) | System and method of fabrication of arsenic glass | |
| JPS60221327A (en) | Preheating method of glass raw material |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |