MXPA00012865A - Melting furnace having cullet preheating and rear crown vent with support system - Google Patents

Abstract

A glass melting furnace (10) that simultaneously preheats and removes volatile substances from glass making material being introduced into the furnace (10). The glass making material, consisting of cullet and scrap glass, is introduced on a shelf (68) located at a rear portion of the furnace (10). A vertically-oriented crown vent (34) is also located at the rear portion of the furnace (10). The shelf (68) is at such an elevation above the glass line (14) to allow sufficient time for the cullet and scrap glass to be heated by the exhaust gases exiting through the crown vent (34). The furnace burners (44) also oxidize the binder and other organic materials in the scrap glass. The furnace (10) also includes a crown vent support system that independently supports the refractory stack (74) such that the refractory stack (74) can be repaired or replaced while the furnace (10) is operating.

Description

FUSION OVEN THAT HAS PRE-HEATING OF ROTARY GLASS WASTE AND CROWN VENTILATION POSTERIOR WITH SUPPORT SYSTEM TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION This invention relates generally to the manufacture of glass and in particular to a glass melting furnace with a pre-heating system for broken glass debris and posterior crown ventilation , with an independent steel support system to optimize the use of fuel while allowing the oxidation of the waste glass and the removal of pollutants from the exhaust gases. BACKGROUND OF THE INVENTION The manufacture of glass involves the mixing of various ingredients in batches, generally including silica sand, dry powders, granular oxides, carbonates and other raw materials (depending on the type of glass desired) and heating them to a temperature of about 1500 ° C (2730 ° F) where they melt and acquire a homogeneous nature. During the melting of the batch from which the liquid glass is formed, various hot gases are formed which are vented from the furnace. As a measure of heat conservation, these gases have been vented from a corona in the rear portion of the furnace and pass through a heat recuperator. Substantial amounts of heat are required for the fusion process, usually supplied by fossil fuel combustion. In a typical glass melting furnace, the heat supplied to the melt is predominantly provided by natural gas in admixture with preheated combustion air. The resulting flame is burned over the melt and the heat transfer to the melt is by irradiation of the furnace enclosure and the flame. In addition, some furnaces increase the heat with an electrical reinforcement. The main attraction of an electrical reinforcement, is that it allows an increase in the production of an existing furnace by providing a source of additional heat to the fusion. A method for increasing the amount of heat that can be added to a furnace while avoiding the high cost of operating an electrical reinforcement comprises pre-heating the feed material - that is, the constituents of the glass batch and broken glass waste. . The broken glass waste is fragmented pieces of glass that are added to the other ingredients of the lot and charged to the melting furnace. A certain minimum proportion of the total lot is required to be broken glass waste in order to provide adequate melting characteristics, generally in the range of 10 to 20%. The waste of broken glass normally used for this purpose is generated with the glass factory, either breaking the product during the manufacturing process or casting of molten glass during product changes. Recent emphasis on waste recycling has resulted in the collection of large quantities of what is known as ecological broken glass waste. That is, generally glass bottles that are returned to recycling centers. With proper processing such as color sorting, removal of foreign substances and breaking into smaller sized pieces, the waste of ecologically broken glass can be made suitable to remelter the new glass. Currently, there are a number of glass factories with glass melting furnaces where approximately 80 to 90% of the batch feedstock is waste of broken ecological glass. As the use of broken glass waste increases, the pre-heating of broken glass waste offers an important alternative to electrical reinforcement. In addition, due to furnace economy and state legislation that encourages the recycling of waste glass, the use of broken glass waste will most likely increase in the near future to the point where it can be the predominant feed material in container furnaces. in many parts of the country. Nowadays, the maximum amount of glass that can be extracted from an existing furnace is limited by the amount of energy that can be applied in the furnace to melt the feed material. This limit is reached when the furnace is at an intense burn, which results in a maximum flow of combustion products. However, additional energy can be applied in the furnace by pre-heating the glass waste to provide a more productive and efficient glass manufacturing process. When using a pre-heater of broken glass waste, it is convenient to heat the broken glass waste at a temperature just below that in which it starts to become sticky and agglomerate. Tests have shown that with a pre-heater inlet gas temperature of 899 ° C (1650 ° F), broken glass debris can be heated to 593 ° C (1100 ° F) which is ideal. For example, for a furnace operating with a feed material that is 70% by weight of broken glass waste, the pre-heat broken glass waste at a temperature of approximately 593 ° C (1100 ° F) (a fair temperature below that in which it starts to get sticky and agglomerate) can provide an increase in productivity as much as 30%. Due to the relatively poor thermal transfer of the hot combustion gases to the molten glass tank, the temperatures of the process exhaust gases are usually quite high despite the various types of heat recovery equipment employed. In addition, pollutants of various types of the fusion process are emitted together with the exhaust gases. In this way, the glass industry requires a cost-effective and simple system, where it can increase the productivity of glass melting furnaces by pre-heating their waste material from broken glass waste before the melting process, while that pollutants are removed simultaneously from the exhaust gases of the melting furnace and by reducing the waste glass from the melting process. COMPENDIUM OF THE INVENTION The above objectives as well as other objectives not specifically listed, are achieved by a melting furnace that improves the process of and apparatus for glass melting. Another object of the invention is to provide a melting furnace having a pre-heating system for broken glass debris and a rear crown vent with an independent chimney support. Still another object of the invention is to provide a method, as before, which simultaneously allows removal of particulate pollution emissions from the exhaust gases of the glass furnace. Still another of the invention is to provide a method, as before, which simultaneously allows reducing organic waste glass materials from the melting process. These and other objectives are achieved by providing an apparatus for glass melting. The apparatus comprises a tank portion or receptacle for containing molten glass to a glass line. The receptacle includes a bottom wall, a rear end wall, a front end wall and side walls. A feeding mechanism provides means for introducing a batch of glass as a layer onto the molten glass in a first region of the receptacle. The glass batch may include raw materials, broken glass waste and glass waste. The molten glass is removed from a second region of the receptacle. The glass batch is heated using a mixture of fuel and oxygen. A crown covers the receptacle and forms a space on the layer. A corona ventilation is oriented vertically from the crown and is located in the first region of the receptacle to vent exhaust gases from the space. The glass batch introduced in the first region is pre-heated by the exhaust gases that are vented by the corona ventilation from space.

In another embodiment of the invention, the apparatus comprises a tank for containing molten glass to a glass line, a mechanism for feeding glass batch in a first region of the tank, means for removing molten glass from a second region of the tank, means for heat the glass batch, a crown to cover the tank and form a space on the glass line, and a vertically oriented crown vent to vent exhaust gases from the space. The corona ventilation includes a first section, a second section positioned on the first section and a third section positioned between the first and second sections to independently hold the second section. The second section can be repaired or replaced during operation of the device. Various objects and advantages of this invention will be apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional side elevation view of the melting furnace according to a preferred embodiment of the invention. Figure 2 is a top plan view of the melting furnace of Figure 1, showing the feeder screws and ports for the glass batch for broken glass waste and glass waste. Figure 3 is a cross-sectional view of the melting furnace taken on line 3-3 of Figure 2. Figure 4 is a cross-sectional view of the melting furnace taken on line 4-4 of Figure 2. Figure 5 is a side elevational view showing the feeder screw and port for the broken glass and waste glass and the corona ventilation located at the rear end of the melting furnace and an independent support system for corona ventilation according to the preferred embodiment of the invention. DETAILED DESCRIPTION AND PREFERRED MODALITIES OF THE INVENTION As illustrated in Figures 1 and 2, a furnace 10 for melting glass, comprises a receptacle for containing molten glass 12 to a line of glass 14 and batch of glass 16, on at least a portion of that line of glass 14. The receptacle is illustrated as a tank portion 18 that includes a bottom wall 20, side walls 22 and 24, rear end wall 26 and front end wall 28. Side walls 22, 24 support an arch roof or refractory crown 30 on the tank portion 18 and the glass line 14 to circumscribe a space 32 on the molten glass 12. A crown vent 34 is located at a rear end or first region of the furnace 10, to allow gases to pass through the tank. exhaust gas damper 36 and a chimney 38 and into the atmosphere, after treating it to protect the environment. The posterior crown ventilation is discussed in more detail below. The oven 10 includes a plurality of burners 44 distributed over the oven 10 conveniently to provide means for heating the oven 10. In the preferred embodiment, the burners 44 use a mixture of oxygen and natural gas to heat the oven 10. The oven 10 may also include a set of electrodes 46 distributed over the oven 10 conveniently, to provide Joule heating of the molten glass 12. Typically, the electrodes 46 are formed in pairs, in rows over the length of the oven with an outer electrode on one side of the center line connected to an inner electro on the other side of the center line. Three phase alternating current is used as the electric current with similar phases in each row of electrodes. If electrical reinforcement is actually used, it can be controlled through the physical rotation of the secondary winding in the transformer (not shown), varying the number of secondary turns and therefore, voltage or secondary voltage, or through current control. Current control with direct current suppression is by any convenient means such as phase-controlled combustion of back-to-back SCRs (not shown) or proportional control of time through convenient gate means. Other electrode arrangements may be used, as will be appreciated by a person skilled in the art. Batch material comprising raw materials, is introduced into the rear portion or first region of the furnace 10 through the gates 48 and 50, located in the side walls 22 and 24, respectively, when using respective feeder screws or feeders 52 and 54 having an elevation above the floor of floor 40, such that the material of the lot is introduced lightly on the glass line 14, typically approximately 10.16 to 20.32 cm (4 to 8") above the line of glass. glass 14. For protection of the heat of the furnace 10, the feeding screws 52 and 54 are preferably recessed in the side walls 22 and 24. The batch material is fed in the rear portion or first region of the oven 10 to a such speed that it forms and maintains a layer of the glass batch 16 on the surface of the molten glass 12. This layer essentially extends over the two thirds of the rear surface of the glass fu It is floated in the molten glass 12 and evenly distributed over it by temperature profiling, using the gas / oxygen profile distribution between the various oxygen / fuel burners 44. This layer of the batch is aided to hold on the back, allowing a better residence time of fusion, by the pile of broken glass broken rear cold that acts as a thermal collector to keep the back of the furnace 10 cooler than the front of the furnace 10, helping to establish the well-known thermal pump and the roller or thermal wheel cells thus developed. This greatly helps in the melting efficiency of the furnace 10. Glass streams in the molten glass 12 and the progressive advance of the batch material of the feed screws 52, 54, develop flow of the glass batch from the rear portion or first region towards a front portion or second region of the furnace 10. The molten glass 12 is directed from the front end wall 28 through a groove 56 in the front end wall 28 and passes over the channel 58 to a forehearth (not shown) which is used to form the desired product such as glass fibers. The material for production of glass, such as waste from broken glass and waste glass, can also be charged in the furnace 10 through a gate 60, preferably located in the rear end wall 26 when using a feeder screw 62 to minimize the dusting of fine particles. A storage hopper 64 can be used to provide the waste material of broken glass and waste glass to the screw feeder 62 through a discharge outlet 66. In a manner well known in the art, the rotation ratios of the feeder screws 52, 54 and the feeder screw 62, can be controlled so as to adequately provide the amount of batch material and the amount of material Waste of broken glass and waste glass entering the furnace 10, respectively. Similar to the feeder screws 52, 54, the feeder screw 62 can also be recessed in the rear end wall 26 to protect it from the heat of the furnace 10. Now with reference to Figure 5, the furnace 10 includes a shelf, generally shown in FIG. , to temporarily contain the broken glass and scrap glass waste as it enters the oven 10 through the gate 60. The shelf 68 includes a shelf block 69 to support a rear part of the shelf 71 and a pair of side blocks at an angle 73. Preferably, the shelf block 69 extends horizontally approximately 30.48 to 35.56 cm (12 to 14") inside the oven 10, such that the rear end wall 26 of the oven 10 is vertically divided to a portion U, and a lower portion L, the upper portion U has a greater distance to the front end wall 28 than the lower portion L. It will be noted that the angled side blocks 73 cause the waste material of broken glass and waste glass to form a stack as they are introduced into the furnace 10. Preferably, the shelf block 69, the rear shelf part 71 and the angled side blocks 73, can be made of a well-known corrosion resistant material, such as Zirchrome 50 and the like The shelf 68 may also include a layer 75 preferably made of AZS material and having an approximate thickness of 7.62 cm (3") placed on the shelf block 69 to provide protection against opening. erosion and additional corrosion of the broken glass waste and waste glass that is introduced into the furnace 10. An important aspect of the invention is the elevation of the gate 60 and the screw feeder 62 xon with respect to the glass line 14. As seen in Figure 5, the elevation of the feeder screw 60 for the waste of broken glass and waste glass, is at a much higher distance on the glass line 14 than the elevation of the feeder screws 52, 54 for the material of the lot. Specifically, gate 60 and feeder screw 62, preferably are at a lifting distance d, approximately 76.20 to 106.68 cm (30 to 42") from the centerline of gate 60 to glass line 14, and more preferably about 91.44 cm (36") on the glass line 14, compared to a typical distance of 10.16 to 20.32 cm (4 to 8") for the feeder screws 52, 54 for the batch material, as previously mentioned, the angled side blocks 73 of the shelf 68 cause the waste of broken glass and waste glass to form a stack in the shelf 68 as they are introduced into the oven 10. Because the gate 60 and the feed screw 62 raise the distance d, with respect to the glass line 14, the waste of broken glass and waste glass will form an inclined surface 70 extending from the shelf 68 to the glass line 14 when the broken glass waste and waste glass is introduced into the furnace 10. As a result of the formation of the inclined surface 70, Waste of broken glass and waste glass will slowly fall down the inclined surface 70, since waste of broken glass and waste glass is introduced. in the oven 10. As a result of this falling action, the waste glass is exposed to the burners 44, to flame and oxidize the binder and other organic material present in the waste glass. Also, this dropping action allows the broken glass waste to have a length of time sufficient to absorb energy from the exhaust gases passing in a counter flow direction (indicated by arrows 77 in Figure 5) to the crown vent 34. It should be considered that the location of the gate 60 and the crown vent 34, both in the rear portion or first region of the furnace 10, provide an optimum arrangement for the recovery of heat from the exhaust gases to pre-heat waste from broken glass and the oxidation of the binder and other organic material from the waste glass. However, it should also be considered that the location of the damper 60 and the crown vent 34 can be conveniently located in the furnace 10 in order to optimize the heat recovery of the exhaust gases to pre-heat glass waste. broken and oxidize the waste material divided. Another important aspect of the invention is the arrangement of crown ventilation 34 for the removal of exhaust gases from the combustion process of furnace 10. As seen in Figure 5, the crown vent 34 generally includes a first or lower section 72 also known as an orbeling, and a second or upper section 74 also known as a refractory chimney. The korbeling section 72 and the refractory chimney 74 are separated by a support ring 76. A ring or refractory ring 78 preferably made of refractory insulation resides in the crown 30 and defines the exhaust gas gate 36. Preferably, korbeling 72 it is mounted on the refractory ring 78. Korbeling 72 protects the support ring 76 from the heat of the exhaust gases and preferably includes approximately 4 strips of refractory brick arranged in a square-shaped arrangement with a total height of approximately 30.48 cm (12") In the preferred embodiment, each section has an approximate exterior dimension of 127 cm (50") and an interior dimension of approximately 66.04 cm (26"). It should be noted that each section can be rotated approximately 90 ° to avoid tip alignment In the preferred embodiment, the refractory chimney 74 preferably includes approximately 17 sections of refractory brick arranged in a substantial assembly. circular entity with a total height of approximately 127 cm (50"). Refractory chimney 74 has an outer diameter of approximately 111.76 cm (44") and an approximate internal diameter of 66.04 cm (26"). The refractory chimney 74 may include an opening 80 located at a convenient distance on the crown 30, to allow cushion air to enter the refractory chimney 74. Preferably, the opening 80 is located approximately two-thirds of the way through the refractory chimney 74. through sections 11 and 12 of the refractory brick. Alternatively, the opening 80 can be removed and the damping air can enter from the top of the refractory chimney 74. Temperature sensing means 82 such as a thermocouple and the like, can also be located at a convenient distance above the opening 80 for measuring the temperature of the exhaust gases in the refractory chimney 74. It will be understood that the temperature sensing means 82 can be located at any convenient location on the refractory chimney 74 in order to provide an accurate indication of the exhaust gas temperature in the refractory chimney 74. It will also be understood that the invention is not limited by the aforementioned dimensions for refractory section 72 and chimney 74 and that the invention can be practiced with any dimensions that are capable of maintaining the exhaust gas temperature above approximately 1150 ° C (2100 ° F). It will be noted that the temperature of exhaust gas within refractory chimney 74 is an important design consideration, especially for furnaces used to melt glass containing volatile substances such as sodium or borate, on the surface of the glass production material. The normal use of ports, combustion gases and chimneys located adjacent to the furnace 10, can cause the refractory brick of the refractory chimney 74 to fall below about 1150 ° C (2100 ° F). As a result, the sodium and borate released from the glass and during the melting process can condense and form liquid slag in the refractory brick. In conventional horizontally oriented piles, this liquid slag causes premature wear and corrosion of the refractory brick and requires periodic scraping of the refractory brick. On the other hand, the corona ventilation 34 of the invention virtually eliminates the formation of liquid slag in the refractory brick of the refractory chimney 74, by allowing the burners 44 to adequately heat the refractory brick at about 1150 ° C (2100 ° F), while still allowing a sufficient amount of cushion air to be blown into the refractory chimney 74 to maintain a slightly positive pressure in the furnace 10. Maintaining a slightly positive pressure in the furnace 10 prevents air filtration in the furnace 10, thus limiting the formation of NOx and increase fuel economy. This is achieved by designing a vertically oriented crown vent 34 with a very short height, preferably less than 3 meters (10 feet), compared to conventional horizontally oriented stacks having a length of 6,096 meters (20 feet) or more. As a result, any slag that forms in the refractory chimney 74 of the corona ventilation 34 of the invention falls vertically into the furnace 10 and is eventually assimilated by the molten glass 12. In addition, the thermocouple 82 located over the opening 80 for the air The damper can be used to check the exhaust gas temperatures and this information can be used to control the air flow damper to ensure that the brick of the refractory chimney 74 is maintained at approximately 1150 ° C (2100 ° F) to prevent condensation from the volatiles that cause corrosion. It should be noted that the dampening air can be used in conjunction with water-cooled or non-water-cooled plates (not shown) located in the upper part of the refractory stack 74. The plates (not shown) can be used in a well-known manner in the art to limit the amount of cushioning air needed to maintain the refractory chimney 74 in control of the pressure in the furnace 10 and the temperature in the refractory chimney 74 in order to prevent condensation of volatiles in the brick. Another important aspect of the invention is the independent support system for crown ventilation 34. In the preferred embodiment, this independent support system is achieved by a support ring 76 that independently supports the fire stack 74 in such a way that the refractory chimney 74 does not rest on the korbeling 72. This configuration allows the refractory chimney 74 to be repaired or completely removed while the furnace 10 operates. The support ring 76 is preferably made of 253MA and can be cooled by any convenient fluid such as water, in a manner well known to those skilled in the art. Preferably, the support ring 76 is mounted on an expansion ring 84 filled with a fiber layer material that allows thermal expansion of the korbeling 72 and the refractory chimney 74 in the vertical direction.

Chimney joint strips and corresponding clamps (not shown) may also be used to hold the upper section 74 of the crown vent 34 in a well known manner. As described above, the oven 10 of the invention allows the pre-heating of the broken glass and waste glass waste by the exhaust gases and the oxidation of the organic material in the waste glass by the burners 44 of the oven 10. In addition, the crown vent 34 is placed in the rear portion of the furnace 10 and the broken glass debris is introduced into the furnace 10 at a higher elevation than conventional furnaces, thereby increasing the energy efficiency of the furnace 10. In addition, the independent support system for crown ventilation 34 allows the thermal expansion of the crown vent 34 in the vertical direction and allows the refractory chimney 74 to be repaired or replaced while the furnace 10 operates, thereby also increasing the efficiency of the furnace 10. The principle and mode of operation of this invention have been described in their preferred embodiments. However, it should be noted that this invention can be practiced otherwise than as illustrated and described specifically without departing from its scope,

Claims (11)

1. CLAIMS 1.- An apparatus for melting glass, characterized in that it comprises: a receptacle for containing molten glass to a glass line, the receptacle includes a bottom wall, a rear end wall, a front end wall and side walls; a layer loader for introducing a glass production material, which includes glass batch constituents that incorporate organic impurities as a layer on molten glass in a first region of the receptacle against the rear end wall; a shelf located on the rear end wall and extending horizontally in the receptacle below the layer loader and on the glass line to contain glass production material introduced by the layer loader; a throat for removing molten glass from a second region of the receptacle adjacent the front end wall; at least one fuel / oxygen burner located in a side wall of the receptacle on the glass line to heat the glass production material in the receptacle; a crown that covers the receptacle and that defines a space on the glass line; and a crown vent to vent exhaust gas from the fuel / oxygen burner from the space defined by the crown, the crown vent is oriented vertically from the crown within the first region of the receptacle, thereby in use, exhaust gases of the fuel / oxygen burner pass through and in this way pre-heat the glass production material contained in the rack, before being ventilated by the corona ventilation.
2. 2. - Apparatus in accordance with the claim 1, characterized in that the shelf divides the rear end wall into an upper portion and a lower portion, the upper portion has a greater distance to the front end wall than the lower portion.
3. 3. - Apparatus in accordance with the claim 1 or claim 2, characterized in that the shelf includes a shelf block for supporting a pair of angled side blocks and a rear shelf part.
4. 4. - Apparatus according to any of claims 1 to 3, characterized in that the lid loader is at an elevation of 76 to 107 cm (30 to 42") on the glass line
5. 5. - Apparatus in accordance with any of claims 1 to 4, characterized in that it also comprises a feeding mechanism for feeding the glass batch in the receptacle at an elevation of 10 to 15 cm (4 to 6") on the glass line.
6. 6. Apparatus according to claim 1 or claim 5, characterized in that the feeding mechanism feeds batches of glass to the first region of the receptacle.
7. 7. - Apparatus according to any of claims 1 to 6, characterized in that the crown ventilation includes a first section, a second section placed on the first section and a support ring placed between the first and second sections to independently hold the second section.
8. 8. An apparatus for melting glass, characterized in that it comprises: a receptacle for containing molten glass to a line of glass; a batch loader for feeding glass production material in a first region of the receptacle; means for removing "molten glass from a second region of the receptacle, at least one fuel / oxygen burner on the glass line for heating the glass production material, a crown for covering the receptacle and defining a space on the glass line and a vertically oriented crown vent for venting exhaust gas from the fuel / oxygen burner from the space defined by the crown, the crown vent includes a first section, a second section placed on the first section and a support ring placed between The first and second sections for independently holding the second section
9. 9. - Apparatus according to any of claims 1 to 8, characterized in that the crown ventilation has a height of less than 3 meters from the crown. claim 1 or claim 9, characterized in that the support ring comprises metal 253MA. 1. Apparatus in accordance with the claim 9 or claim 10, characterized in that the crown ventilation further comprises an expansion ring placed between the support ring and the first section, the expansion ring is filled with fiber material to allow thermal expansion of the first section and the second section in a vertical direction.