WO2009034408A1 - Method for melting glass in a recuperative glass melting furnace - Google Patents

Method for melting glass in a recuperative glass melting furnace Download PDF

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Publication number
WO2009034408A1
WO2009034408A1 PCT/IB2007/002962 IB2007002962W WO2009034408A1 WO 2009034408 A1 WO2009034408 A1 WO 2009034408A1 IB 2007002962 W IB2007002962 W IB 2007002962W WO 2009034408 A1 WO2009034408 A1 WO 2009034408A1
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WIPO (PCT)
Prior art keywords
glass
air
furnace
fuel
pulverized fuel
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PCT/IB2007/002962
Other languages
French (fr)
Inventor
Miguel Angel Olin Nunez
Roberto Cabrera Llanos
Iván Jorge SOLIS MARTINEZ
Rafael Valadez Castillo
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Vitro Global, S.A.
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Application filed by Vitro Global, S.A. filed Critical Vitro Global, S.A.
Priority to PCT/IB2007/002962 priority Critical patent/WO2009034408A1/en
Publication of WO2009034408A1 publication Critical patent/WO2009034408A1/en

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    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/235Heating the glass

Definitions

  • the present invention is related to a method for melting glass in a recuperative glass melting furnace and, more specifically to a method for melting glass in a recuperative glass melting furnace using a pulverized fuel. 10
  • Unit melter furnaces have been used to melt glass (by
  • each regenerator has a lower chamber, a refractory structure above the lower chamber and an upper chamber above the structure.
  • Each regenerator has a respective port connecting the respective upper chamber with a melting and refining chamber of the furnace.
  • the main purpose of these regenerative chambers is to increase the amount of heat recovered from hot flue gases in order to heat up the incoming combustion air after the firing cycle change, that is taking place every 20 or 30 minutes for this type of furnaces.
  • recuperative furnace Another type of furnace similar to the regenerative type that take advantage from the flue gases and recovers the heat using a recuperator device is the recuperative furnace. It is well known that, to operate a recuperative glass melting furnace, a plurality of burners using different fuels (gas, oxy-gas, liquid fuels) are disposed side-by-side.
  • the furnace heated by recuperative means consists on the preheating of the combustion air through the recuperators which are made mainly of special steel or ceramics as the double shell or the tubes bundle type.
  • the typical burner for this kind of furnace uses an inlet specially designed in order to have the same distribution for the combustion air surrounding the burner nozzles.
  • the melting and refining chamber is fed with glass making materials at one end thereof at which is located a doghouse and has a molten distributor disposed at the other end thereof.
  • the burners to produce the heat released by the fuel such as natural gas, liquid petroleum, heavy and light fuel oil or other gaseous or liquid fuels which are suitable for use in the glass melting furnace and thereby supply heat for melting and refining the glass making materials in the chamber.
  • the melting and refining chamber is fed with glass making materials at one end thereof at which is located a doghouse and has a molten distributor disposed at the other end thereof, which comprises a series of ports through which molten glass may be removed from the melting and refining chamber.
  • the burners may be mounted in a number of possible configurations, for example in the case of regenerative furnaces: a through-port configuration, a side-port configuration or an under-port configuration.
  • Fuel e.g. natural gas
  • Fuel is fed from the burner into the incoming stream of pre-heated air coming from each regenerator during the firing cycle, and the resultant flame and products of combustion produced in that flame extend across the surface of the melting glass, and transfer heat to that glass in the melting and refining chamber.
  • the regenerators in a regenerative type furnace are cycled alternately between combustion air and exhaust heat cycles. Every 20 minutes, or 30 minutes, depending on the specific furnaces, the path of the flame is reversed.
  • the objective of each regenerator is to store the exhausted heat, which allows a greater efficiency and a higher flame temperature that could otherwise be the case with cold air.
  • the burners operates continuously in both sides of the furnace sending the flue gases directly to the recuperator, this heat will be used to preheat the air, this means that this kind of furnace does not cycle alternately between combustion air and exhaust heat cycles.
  • the preheated air by the recuperators increase the efficiency of the furnace without storing the heat in a chamber made by breaks as in the regenerative type furnace, the recuperators instead, release the heat to the combustion air reaching lower temperatures and saving less energy as compared for example with a regenerative furnace.
  • the present invention is related to the application of different technologies to reduce the melting cost, using a solid fuel coming from the petroleum residuals of distillation towers, such as petroleum coke, in order to be used for glass production in an environmentally clean way.
  • the volatiles are extracted from the top of the coking drums and the remaining material in the drums is a hard rock make of around 90 percent of carbon and the rest of all the impurities from the crude oil used.
  • the rock is extracted from the drums using hydraulic drills and water pumps.
  • a typical composition of petroleum coke is given as follow: carbon about 90%; hydrogen about 3%; nitrogen from about 2% to 4%; oxygen about 2%; sulphur from about 0.05% to 6%; and others about 1 %.
  • Use of Petroleum Coke Petroleum solid fuels have already been used in cement and steam power generation industries. According to the Pace Consultants Inc. the use of petroleum coke in years 1999 for cement and power generation were between 40% and 14% respectively.
  • the burning of petroleum coke is used as a direct fire system, in which the atmosphere produced by the combustion of the fuel is in direct contact with the product.
  • a rotary kiln is needed in order to provide a thermal profiled require by the product.
  • a shell of molten cement is always formed avoiding the direct contact of the combustion gases and flames with the refractories of the kiln, avoiding attack thereof.
  • the calcined product (cement) absorbs the combustion gases, avoiding the erosive and abrasive effects of vanadium, SO3 and NOx in the rotary kiln.
  • the glass industry use several kinds of refractory materials, and most of them are used to accomplish different functions, not only the thermal conditions but also the chemical resistance and mechanical erosion due to the impurities contained by fossil fuels.
  • a fossil fuel as the main energy source represents an input to the furnace of different kinds of heavy metals contained in the fuel, such as: vanadium pentoxide, iron oxide, chromium oxide, cobalt, etc.
  • heavy metals such as: vanadium pentoxide, iron oxide, chromium oxide, cobalt, etc.
  • vanadium pentoxide In the process of combustion most of the heavy metals evaporate because of the low vapor pressure of the metal oxide and the high temperature of the melting furnace.
  • the chemical characteristic of the flue gases coming out of the furnace is mostly acid because of the high content of sulphur from the fossil fuel.
  • the vanadium pentoxide presents an acid behavior such as the sulphur flue gases.
  • Vanadium oxide is one of metals that represents a source of damage to basic refractories, because the acid behavior of this oxide in gaseous state. Is well known that the vanadium pentoxide reacts strongly with calcium oxide forming a dicalcium silicate at 1275°
  • the dicalcium silicate continues the damage to form a phase of merwinite and the to monticelite and finally to forsterite, which reacting with vanadium pentoxide to form a low melting point of tricalcium vanadate.
  • One way to reduce the damage caused to basic refractories is the reduction of the amount of calcium oxide in the main basic refractory in order to avoid the production of dicalcium silicate that continues reacting with vanadium pentoxide until the refractory may fail.
  • Vanadium Pentoxide the action of Vanadium Pentoxide with Sodium Oxide and the Action of Vanadium Pentoxide with Calcium oxide. They concluded that: 1. — Mullite resisted the action of vanadium pentoxide at temperatures up to 1700°C.
  • -Vanadium pentoxide may act as a mineralizer during the slagging of alumino-silicate refractories by oil ash, but it is not a major salgging agent.
  • 4.-Low-melting compounds are formed between vanadium pentoxide and sodium or calcium oxides, specially the former.
  • the U.S. Pat. No. 6,789,396 issued to Miguel Angel Olin-Nunez et al, on Sep 14, 2004, describes a method of producing commercial glass in a glass melting furnace using the combustion of pulverized fuel as a heating source for melting raw materials for producing glass.
  • This invention uses a mix of pulverized fuel with a first flow of air or gas for producing a pulverized fuel-air or gas mixture to be supplied to a plurality of burners in a glass melting region of the glass melting furnace and also, uses simultaneously a second flow of air or gas together with the pulverized fuel-air or gas mixture in each of said burners to provide a combustion flame with high thermal efficiency to carry out a controlled heating for melting the commercial glass.
  • a pollution control system is adapted in a waste gas outlet of the glass melting furnace for reducing and controlling the air pollution to the atmosphere.
  • the present invention is related with the use of a low cost solid fuel, from petroleum distillation residual (petroleum coke) in order to produce commercial glass in an environmentally clean way, reducing the risk of damage in the refractories of the glass furnace and reducing the emissions of contaminant in the atmosphere.
  • combustion equipment for feeding and burning petroleum coke was developed in order to perform an efficient combustion.
  • the invention also contemplates an emissions control system, which was located following the furnace in order to clean the flue gases to avoid the emission of impurities from the fuel, such as SOx 1 NOx and particulates.
  • the present invention lies in the design of several systems placed in a single process in order to produce commercial glass in a recuperative type glass furnace.
  • pulverized fuel is burned for melting glass raw materials for the manufacture of glass sheets, containers, fiber glass or others.
  • Means for supplying the pulverized fuel are fed in at least a burner or a series of burners arranged in a staged or opposite distribution by means of controlling the length of flame for burning the pulverized fuel continuously for melting glass, said glass melting furnace including special metals means at the recuperative devices of the glass melting furnace for resisting the chemical attack of the carryover from the batch, the corrosive action of combustion gases provoked by the burning of said pulverized fuel in the furnace.
  • the right selection of refractory material within the glass furnace can reduce the impact of the impurities contained in the fossil fuel, based on the thermodynamic analysis and the chemical composition of the impurities and the chemical compounds forming the refractories.
  • the present invention can be implemented in an existing furnace with traditional recuperative system, giving the opportunity to reach economic benefits of less expensive fuels like petroleum coke
  • a first objective of the present invention is to provide a method for melting glass for supplying in a controlled manner a pulverized fuel-air or gas mixture to each of a plurality of burners in a glass melting region of the recuperative glass melting furnace for a continuous operation of that said burners.
  • Is an additional objective of the present invention to provide a method for melting glass, which provides a more stable combustion due to continuous burning process compared to the reversal cycles on a regenerative type furnace
  • An additional objective of the present invention is to provide a method for melting glass which produces an optimal mixture between the pulverized fuel-air or gas mixture, reducing the NOx gases
  • Another additional advantage of the present invention is to provide a method for melting glass that diminishes the consumption of pulverized fuel, due to a better combustion and higher thermal efficiencies
  • An additional objective of the present invention to provide a method for melting glass ⁇ wherein pulverized fuel is fed directly to a recuperative glass melting furnace in a fuel-air ratio around 16% to 30% of air in excess with respect to a stoichiometric air.
  • Another objective of the present invention is to provide a method for melting glass in a recuperative glass melting furnace, which also can be simultaneously melted with two or three types of fuel.
  • Series of burners can be arranged in the melting chamber for burning independently petroleum coke, gas or fuel oil.
  • Another objective of the present invention is to provide a method for melting glass, wherein the pulverized fuel is fed by means of pneumatic means, with a elevated relation solid-air.
  • FIG. 1 is a schematic plant view of an end recuperative type glass melting furnace
  • FIG. 2 is a schematic view of the system for feeding and burning a pulverized fuel in accordance with the present invention
  • FIG. 3 is a schematic view of the system for feeding and burning a pulverized fuel in accordance with the present invention.
  • the figure 1 illustrates a plant view of a schematic recuperative glass melting furnace wherein the glass melting is melted.
  • the recuperative glass melting furnace 10 is signed by the preheating of the combustion air through heat exchangers or recuperators 12, 14, normally made of steel as double shell type or tube bundle type.
  • the furnace 10 can be designed as cross fired type or end fired type (figure 1 ).
  • the waste gas outlet opening is located above the bumers in order to have the flame in a shape of a horizontal standing "LJ".
  • the waste gas opening can be situated at the front wall as well as at the side wall.
  • the recuperative furnaces are suitable for glass melting between 4 - 60 t/d, in some special cases also up to 150 t/d.
  • the typical glass melting furnace 10 includes an elongated glass tank having an upstream end wall 16 and a downstream end wall 18, sidewalls 20, 22, a floor (not shown) and a roof (not shown) all made from appropriate refractory materials such as alumina, silica, alumina- silica, and the like. At least one pair of the opposing burners 24, 24A, 26, 26A, 28, 28A and 30, 3OA, are positioned in a side-by-side relation in the sidewalls 20, 22 over the unmelted glass batch, for melting the glass.
  • a fuel feeding system FFS is shown in accordance with the present invention.
  • pulverized petroleum coke is received in a single feeder 32.
  • Each feeder 32 includes a silo or tank 34.
  • the single feeder 32 comprising a conical section 36 for discharging a constant flow of the pulverized coke toward each one of the burners 24, 26, 28, 30 or 24A, 26A, 28A and 3OA, as will be described later.
  • the pulverized material is stored in the feeder 32 and it is discharged in a continuous form through an air lock rotary valve 38 attached to the lower section of the conical section 36 for continuously discharge the pulverized material toward a main pipe 40.
  • An air blower 44 is associated with the air lock rotary valve 38 and the main pipe 40 to convey the pulverized material that is being provided from the feeder 32 through of the main pipe 40.
  • the main pipe 40 is connected respectively to a first plurality of pipes 42, 44, 46 and 48, for feeding the supply of an air-fuel mixture toward each of the burners 24, 26, 28 and 30.
  • Each first plurality of pipes 42, 44, 46 and 48 includes return pipes 50, 52, 54 and 56, for returning back in an individual way the pulverized coke toward the silo or tank 34.
  • the feeder 32 will supply a pulverized air-fuel mixture in one side of the glass meting furnace 10, which will be connected to a plurality of burners 24, 26, 28 and 30.
  • the feeder 32 will feed the required amount of pulverized fuel to all the burners 24, 26, 28 and 30. So, in case that any burner be changed (i. e by maintenance, fuel change, etc.), the flow of the air/ pet coke mixture will be maintained in a constant way, returning back the air/ pet coke mixture by means of the corresponding return pipes 50, 52, 54 and 56 toward the silo or tank 34.
  • This operation condition permits that the feeding of the pulverized fuel does not affect the other burners that are being maintained in operation.
  • the fuel feeding system performs automatically refilling, when a level of pulverized fuel is reached, and there is not necessity of interrupt the feeding of the fuel in each of the burners.
  • the feeding of pulverized fuel can feed continuously to each one of the burners, for example, for the case of recuperative furnaces.
  • a similar arrangement of pipes can be carried out.
  • the fuel feeding system can be charged during the alternate operation cycle.
  • the behavior of the opposite side of the furnace is of similar manner, however the fuel feeding system has the capacity of delay, advance or uniform in the feeding time in accordance with the operation requirements of the furnace
  • the embodiment of the figure 1 shows a similar arrangement of fuel feeding system FFS, which is located in the side 22 of the furnace 10.
  • the burners 24A, 26A, 28A and 3OA are placed in the opposite side 22 of the furnace 10, but maintaining a front separation region with respect to the burners 24, 26, 28 and 30, to avoid that the flames of each burner to collide one with the other, when all the burners are in operation over both sides of the furnace.
  • the burners can be placed on the roof of the furnace (not shown), to produce a flame on the surface of the glass.
  • the figure 2 shows a second embodiment of the system for feeding the pulverized fuel in accordance with the present invention.
  • an individual fuel feeding system FFS1 , FFS2, FFS3 and FFS4 is placed by each burner 24, 26, 28 and 30.
  • each fuel feeding system FFS1 , FFS2, FFS3 and FFS4 includes a feeder 32A, and a silo or tank 34A.
  • Each feeder 32A comprising a conical section 36A for discharging a constant flow of the pulverized coke toward one of the burners, for example burner 30..
  • the pulverized material is stored in each feeder 32A and it is discharged in a continuous form through an air lock rotary valve 38A attached to the lower section of the conical section 36A for continuously discharge the pulverized material toward a main pipe 42A.
  • An air blower 44A is associated with the air lock rotary valve 36A and the main pipe 42A to convey the pulverized material that is being provided from the feeder 32A through of the main pipe 42A.
  • the main pipe 42A is directly connected to the burner 30 to the supply of the air-fuel mixture toward the burner 30.
  • the main pipe 42A including a return pipe 52A, for returning back the air/ pet coke mixture by means of the corresponding return pipes 52A,toward the silo or tank 34A.
  • each feeder can be rechargeable in accordance with the process necessities.
  • the method for melting glass using a pulverized fuel comprises, a) feeding a controlled flow of a mixture of pulverized fuel and air or gas under pressure from at least a feeding means; b) discharging the mixture of pulverized fuel and air or gas from the feeding means toward at least one distribution means; c) regulating in a controlled manner the pulverized fuel-air or gas mixture from the distribution means to each of a plurality of burners in a glass melting region of the recuperative glass melting furnace; d) preheating a combustion air through of at least a recuperator of the recuperative glass melting furnace; and, e) mixing the preheating combustion air and mixture of pulverized fuel and air or gas in the glass melting region of said glass melting furnace to provide a combustion flame with high thermal efficiency to carry out the melting of the glass.

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  • Engineering & Computer Science (AREA)
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  • Glass Melting And Manufacturing (AREA)

Abstract

The present invention is referred to a method for producing glass in a recuperative glass melting furnace. A controlled flow of a mixture of pulverized fuel and air or gas under pressure is feed to a series of feeding means. The mixture of pulverized fuel and air or gas is discharged from the feeding means toward at least one distribution means, wherein the pulverized fuel-air or gas mixture is regulated in a controlled manner from the distribution means to each of a plurality of burners in a glass melting region of the recuperative glass melting furnace. Combustion air is preheated through of at least a heat exchanger of the recuperative glass melting furnace, and the preheating combustion air and mixture of pulverized fuel and air or gas is simultaneously mixed in the glass melting region of said glass melting furnace to provide a combustion flame with high thermal efficiency to carry out the melting of the glass.

Description

A METHOD FOR MELTING GLASS IN A RECUPERATIVE GLASS
MELTING FURNACE.
BACKGROUND OF THE INVENTION 5 1. Field of the Invention
The present invention is related to a method for melting glass in a recuperative glass melting furnace and, more specifically to a method for melting glass in a recuperative glass melting furnace using a pulverized fuel. 10 2. Related Prior Art
Melting glass has been done in different kinds of furnaces and using different types of fuels, depending on the final characteristics of the
•-.- product and also with regard to the thermal efficiency of the melting and refining processes. Unit melter furnaces have been used to melt glass (by
15 means of gas fuel). These furnaces have several burners along the sides
7; pf the furnace, and the whole unit looks like a closed box where there is a chimney that can be placed either in the beginning of the feeder or at the very end of the furnace, in other words, going downstream. However there \s an enormous heat loss in the glass leaving high-temperature
20 operating furnaces. At 2500° F., for example, the heat in the flue gases is
62 percent of the heat input for a natural gas fired furnace.
In order to take advantage of the remaining heat of the flue gases, a more sophisticated and expensive design came into being, named as the regenerative furnace. It is well known that, to operate a regenerative glass melting furnace, a plurality of gas burners is associated with a pair of sealed regenerators disposed side-by-side. Each regenerator has a lower chamber, a refractory structure above the lower chamber and an upper chamber above the structure. Each regenerator has a respective port connecting the respective upper chamber with a melting and refining chamber of the furnace. The main purpose of these regenerative chambers is to increase the amount of heat recovered from hot flue gases in order to heat up the incoming combustion air after the firing cycle change, that is taking place every 20 or 30 minutes for this type of furnaces.
Another type of furnace similar to the regenerative type that take advantage from the flue gases and recovers the heat using a recuperator device is the recuperative furnace. It is well known that, to operate a recuperative glass melting furnace, a plurality of burners using different fuels (gas, oxy-gas, liquid fuels) are disposed side-by-side. The furnace heated by recuperative means consists on the preheating of the combustion air through the recuperators which are made mainly of special steel or ceramics as the double shell or the tubes bundle type. The typical burner for this kind of furnace uses an inlet specially designed in order to have the same distribution for the combustion air surrounding the burner nozzles. The melting and refining chamber is fed with glass making materials at one end thereof at which is located a doghouse and has a molten distributor disposed at the other end thereof. The burners to produce the heat released by the fuel, such as natural gas, liquid petroleum, heavy and light fuel oil or other gaseous or liquid fuels which are suitable for use in the glass melting furnace and thereby supply heat for melting and refining the glass making materials in the chamber. The melting and refining chamber is fed with glass making materials at one end thereof at which is located a doghouse and has a molten distributor disposed at the other end thereof, which comprises a series of ports through which molten glass may be removed from the melting and refining chamber. The burners may be mounted in a number of possible configurations, for example in the case of regenerative furnaces: a through-port configuration, a side-port configuration or an under-port configuration. Fuel, e.g. natural gas, is fed from the burner into the incoming stream of pre-heated air coming from each regenerator during the firing cycle, and the resultant flame and products of combustion produced in that flame extend across the surface of the melting glass, and transfer heat to that glass in the melting and refining chamber.
In operation, the regenerators in a regenerative type furnace are cycled alternately between combustion air and exhaust heat cycles. Every 20 minutes, or 30 minutes, depending on the specific furnaces, the path of the flame is reversed. The objective of each regenerator is to store the exhausted heat, which allows a greater efficiency and a higher flame temperature that could otherwise be the case with cold air. In the case of the recuperative type furnace, the burners operates continuously in both sides of the furnace sending the flue gases directly to the recuperator, this heat will be used to preheat the air, this means that this kind of furnace does not cycle alternately between combustion air and exhaust heat cycles. The preheated air by the recuperators increase the efficiency of the furnace without storing the heat in a chamber made by breaks as in the regenerative type furnace, the recuperators instead, release the heat to the combustion air reaching lower temperatures and saving less energy as compared for example with a regenerative furnace.
It is well understood that the thermal efficiency of a regenerative furnace is larger than for example a unit melter furnace. However, for low capacity glass melters is not always economically feasible to built regenerator chamber due to the high investment cost associated with larger amount of refractory bricks required to build such regenerators chamber. In these cases, it is normally to use a unit melter or a recuperative glass furnace instead
In the past, the fuel used to melt glass was fuel oil, coming from distillation of petroleum. For many years this kind of fuel was used, but the tighten of environmental regulations have been pushing for reduction of fuel oil, since this kind of oil has impurities coming from the petroleum crude oil, such as, sulphur, vanadium, nickel, and some other heavy metals. This kind of fuel oil produce pollutants such as SOx, NOx and particulates. Recently the glass industry has been used natural gas as a cleaner fuel. All the heavy metals and sulphur coming in the liquid stream of petroleum residuals from distillation are not contained in natural gas. However, the high temperature produced in the flame of natural gas has been very effective for producing more NOx than other pollutants. In this sense, a lot of effort has been done in order to develop low NOx burners for firing natural gas. Additionally, different technologies have been developed to prevent the NOx formation. An example of this is the Oxy- fuel Technology, which utilizes oxygen instead of air for the combustion process. This technology has the inconvenient of require a unit melter furnace with a special preparation of the refractories since air infiltration need to be prevented. The use of oxygen also produced a higher temperature flame, but with the absence of nitrogen the NOx production is drastically reduced.
One inconvenient of oxy-fuel process is the cost of the oxygen itself. In order to make it cheaper it needs to place an oxygen plant besides the furnace in order to feed the required oxygen by the melting process.
However, the continuing upward spiral of energy costs (primarily natural gas) have forced the major float glass manufacturers to add
"surcharges" to truckloads of flat glass. Natural gas prices have increased over 120% this year (in Mexico only or elsewre), far above previous estimates.
The general consensus among glass industry insiders is that distributors will be forced to take a close look at these new 'surcharges', and most likely be forced to pass them along. Taking into account the previous art, the present invention is related to the application of different technologies to reduce the melting cost, using a solid fuel coming from the petroleum residuals of distillation towers, such as petroleum coke, in order to be used for glass production in an environmentally clean way.
The main difference of this type of fuel regarding fuel oil and natural gas is the physical state of the matter, since fuel oil is a liquid phase, natural gas is a gas phase while petroleum coke for instance is a solid. Fuel oil and petroleum coke have the same kinds of impurities, since both of them are coming from residuals of distillation tower of crude oil. The significant difference is the amount of impurities contained in each of these. Petroleum coke is produced in three types of different processes called delayed, fluid and flexi. The residuals from the distillation process are placed in drums and then heated up to from 900. degree, to 1000° Farenheit degrees for up to 36 hours in order to take out most of the remaining volatiles from the residuals. The volatiles are extracted from the top of the coking drums and the remaining material in the drums is a hard rock make of around 90 percent of carbon and the rest of all the impurities from the crude oil used. The rock is extracted from the drums using hydraulic drills and water pumps.
A typical composition of petroleum coke is given as follow: carbon about 90%; hydrogen about 3%; nitrogen from about 2% to 4%; oxygen about 2%; sulphur from about 0.05% to 6%; and others about 1 %. Use of Petroleum Coke Petroleum solid fuels have already been used in cement and steam power generation industries. According to the Pace Consultants Inc. the use of petroleum coke in years 1999 for cement and power generation were between 40% and 14% respectively. In both industries, the burning of petroleum coke is used as a direct fire system, in which the atmosphere produced by the combustion of the fuel is in direct contact with the product. In the case of cement production, a rotary kiln is needed in order to provide a thermal profiled require by the product. In this rotary kiln, a shell of molten cement is always formed avoiding the direct contact of the combustion gases and flames with the refractories of the kiln, avoiding attack thereof. In this case, the calcined product (cement) absorbs the combustion gases, avoiding the erosive and abrasive effects of vanadium, SO3 and NOx in the rotary kiln.
However, due to the high sulfur content and the presence of vanadium, petroleum coke as fuel is not commonly used as a fuel in the glass industry, due to the negative effect negative on the structure of the refractories and to environmental problems. Problems with the Refractories
The glass industry use several kinds of refractory materials, and most of them are used to accomplish different functions, not only the thermal conditions but also the chemical resistance and mechanical erosion due to the impurities contained by fossil fuels.
Using a fossil fuel as the main energy source represents an input to the furnace of different kinds of heavy metals contained in the fuel, such as: vanadium pentoxide, iron oxide, chromium oxide, cobalt, etc. In the process of combustion most of the heavy metals evaporate because of the low vapor pressure of the metal oxide and the high temperature of the melting furnace. The chemical characteristic of the flue gases coming out of the furnace is mostly acid because of the high content of sulphur from the fossil fuel. Also the vanadium pentoxide presents an acid behavior such as the sulphur flue gases. Vanadium oxide is one of metals that represents a source of damage to basic refractories, because the acid behavior of this oxide in gaseous state. Is well known that the vanadium pentoxide reacts strongly with calcium oxide forming a dicalcium silicate at 1275°C.
The dicalcium silicate continues the damage to form a phase of merwinite and the to monticelite and finally to forsterite, which reacting with vanadium pentoxide to form a low melting point of tricalcium vanadate.
One way to reduce the damage caused to basic refractories is the reduction of the amount of calcium oxide in the main basic refractory in order to avoid the production of dicalcium silicate that continues reacting with vanadium pentoxide until the refractory may fail.
On the other hand, another problem with the use of the petroleum coke is related with the high sulfur and vanadium content, which have a negative effect on the structure of the refractories in the furnaces. The foremost requirement characteristics of a refractory is to withstand exposure to elevated temperature for extended periods of time. In addition it must be able to withstand sudden changes in temperature, resist the erosive action of molten glass, the corrosive action of gases, and the abrasive forces of particles in the atmosphere. The effect of the vanadium on the refractories has been studied in different the papers, i.e. Roy W. Brown and Karl H. Sandmeyer in the paper "Sodium Vanadate's effect on superstructure refractories", Part I and Part II, The Glass Industry Magazine, November and December 1978 issues. In this paper the investigators tested different cast refractories which were centered on overcoming the vanadium attack in the flowing cast compositions, such as alumina-zirconia-silica (AZS), alpha-beta alumina, alpha alumina and beta alumina, which are commonly used in glass tank superstructures.
J. R. Mclaren and H. M. Richardson in the paper "The action of Vanadium Pentoxide on Aluminum Silicate Refractories" describe a series of experiments in which cone deformation were carried out on sets of ground samples from bricks with alumina content of 73%, 42% and 9%, each sample containing admixtures of vanadium pentoxide, alone or in combination with sodium oxide or calcium oxide. The discussion of the results were focused on the action of
Vanadium Pentoxide, the action of Vanadium Pentoxide with Sodium Oxide and the Action of Vanadium Pentoxide with Calcium oxide. They concluded that: 1. — Mullite resisted the action of vanadium pentoxide at temperatures up to 1700°C.
2.-No evidence was found of the formation of crystalline compounds or solid solutions of vanadium pentoxide and alumina or of vanadium pentoxide and silica.
3. -Vanadium pentoxide may act as a mineralizer during the slagging of alumino-silicate refractories by oil ash, but it is not a major salgging agent.
4.-Low-melting compounds are formed between vanadium pentoxide and sodium or calcium oxides, specially the former.
5.-In reactions between either sodium or calcium vanadates and alumino-silicates, lower-melting-point slags are formed with bricks high in silica than with bricks highs in alumina.
T. S. Busby and M. Carter in the paper "The effect of SO.sub.3, Na.sub.2SO.sub.4 and V.sub.2O.sub.5 on the bonding minerals of basic refractories", Glass Technology Vol. 20, No. April, 1979, tested a number of spinels and silicates, the bond minerals of basic refractories, in a sulphurous atmosphere between 600 and 1400. degree. C1 both with and without additions of Na.sub.2SO.sub.4 and V.sub.2O.sub.5. It was found that some MgO or CaO in these minerals was converted to the sulphate. The reaction rate was increased by the presence of Na.sub.2SO.sub.4 or V.sub.2O.sub.5. Their results indicate that the CaO and MgO in basic refractories can be converted to the sulphate if they are used in a furnace where suphur is present in the waste gases. The formation of calcium sulphate ocuurs below 1400°C. and that of magnesium sulphate below about 11000 C.
However, as was described of the above, the effect of the vanadium on the refractories produce a great amount of problems in the glass furnaces, which has not solved in its totallity
Notwithstanding the above the inventors of the present invention have already considered the burning of petroleum coke for the melting of glass raw materials seeing of all the factors above described, such the high sulfur and vanadium contents, which have a negative effect on the structure of the refractories in the furnaces and also serious problems with the environment.
For example, the U.S. Pat. No. 6,789,396 issued to Miguel Angel Olin-Nunez et al, on Sep 14, 2004, describes a method of producing commercial glass in a glass melting furnace using the combustion of pulverized fuel as a heating source for melting raw materials for producing glass. This invention uses a mix of pulverized fuel with a first flow of air or gas for producing a pulverized fuel-air or gas mixture to be supplied to a plurality of burners in a glass melting region of the glass melting furnace and also, uses simultaneously a second flow of air or gas together with the pulverized fuel-air or gas mixture in each of said burners to provide a combustion flame with high thermal efficiency to carry out a controlled heating for melting the commercial glass. A pollution control system is adapted in a waste gas outlet of the glass melting furnace for reducing and controlling the air pollution to the atmosphere. Considering all the processes described above, the present invention is related with the use of a low cost solid fuel, from petroleum distillation residual (petroleum coke) in order to produce commercial glass in an environmentally clean way, reducing the risk of damage in the refractories of the glass furnace and reducing the emissions of contaminant in the atmosphere.
So, in order to utilize of this invention effectively, combustion equipment for feeding and burning petroleum coke was developed in order to perform an efficient combustion. The invention also contemplates an emissions control system, which was located following the furnace in order to clean the flue gases to avoid the emission of impurities from the fuel, such as SOx1 NOx and particulates. By the integration of developed equipment, selecting the right configuration of equipment and systems, it is possible to use a low cost fuel, produce commercial glass and generate flue gases within environmental regulations.
From the above, the present invention lies in the design of several systems placed in a single process in order to produce commercial glass in a recuperative type glass furnace. So, in a glass melting furnace, pulverized fuel is burned for melting glass raw materials for the manufacture of glass sheets, containers, fiber glass or others. Means for supplying the pulverized fuel are fed in at least a burner or a series of burners arranged in a staged or opposite distribution by means of controlling the length of flame for burning the pulverized fuel continuously for melting glass, said glass melting furnace including special metals means at the recuperative devices of the glass melting furnace for resisting the chemical attack of the carryover from the batch, the corrosive action of combustion gases provoked by the burning of said pulverized fuel in the furnace. Finally, means for controlling the air pollution in a waste gas outlet after that the combustion of the pulverized fuel in the glass melting furnace has been carried out, said means for controlling the air pollution reducing the emissions of sulfur, nitrogen vanadium, iron and nickel compounds at the atmosphere.
The right selection of refractory material within the glass furnace can reduce the impact of the impurities contained in the fossil fuel, based on the thermodynamic analysis and the chemical composition of the impurities and the chemical compounds forming the refractories.
The present invention can be implemented in an existing furnace with traditional recuperative system, giving the opportunity to reach economic benefits of less expensive fuels like petroleum coke
Also, the present invention allow the use of existing preheating combustion air systems and facilitate the use of alternative fuels like petroleum coke in easy way after adding the new equipment. SUMMARY OF THE INVENTION In accordance with the present invention a first objective of the present invention is to provide a method for melting glass for supplying in a controlled manner a pulverized fuel-air or gas mixture to each of a plurality of burners in a glass melting region of the recuperative glass melting furnace for a continuous operation of that said burners. Is an additional objective of the present invention to provide a method for melting glass, which provides a more stable combustion due to continuous burning process compared to the reversal cycles on a regenerative type furnace An additional objective of the present invention is to provide a method for melting glass which produces an optimal mixture between the pulverized fuel-air or gas mixture, reducing the NOx gases
Other additional advantage of the present invention is to provide a method for melting glass that diminishes the consumption of pulverized fuel, due to a better combustion and higher thermal efficiencies
Another additional advantage of the present invention is to provide a method for melting glass that provides high flexibility and lower investment
It is another objective of the present invention to provide a method for melting glass, wherein a mix of pulverized fuel in combination with air or gas is injected in each one of the burners.
An additional objective of the present invention to provide a method for melting glassτ wherein pulverized fuel is fed directly to a recuperative glass melting furnace in a fuel-air ratio around 16% to 30% of air in excess with respect to a stoichiometric air.
Another objective of the present invention is to provide a method for melting glass in a recuperative glass melting furnace, which also can be simultaneously melted with two or three types of fuel. Series of burners can be arranged in the melting chamber for burning independently petroleum coke, gas or fuel oil.
Other objective of the present invention is to provide a method for melting glass, wherein the pulverized fuel is fed by means of pneumatic means, with a elevated relation solid-air.
These and other objectives and disadvantages of the present invention will be evident to the experts in the field from the following detailed description of the invention, which is illustrated in the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic plant view of an end recuperative type glass melting furnace;
FIG. 2 is a schematic view of the system for feeding and burning a pulverized fuel in accordance with the present invention; and, FIG. 3 is a schematic view of the system for feeding and burning a pulverized fuel in accordance with the present invention. DETAILED DESCRIPTION OF THE INVENTION
The figure 1 illustrates a plant view of a schematic recuperative glass melting furnace wherein the glass melting is melted. The recuperative glass melting furnace 10 is signed by the preheating of the combustion air through heat exchangers or recuperators 12, 14, normally made of steel as double shell type or tube bundle type. The furnace 10 can be designed as cross fired type or end fired type (figure 1 ). At the end fired type system the waste gas outlet opening is located above the bumers in order to have the flame in a shape of a horizontal standing "LJ". At the cross fired type the waste gas opening can be situated at the front wall as well as at the side wall. The recuperative furnaces are suitable for glass melting between 4 - 60 t/d, in some special cases also up to 150 t/d.
The typical glass melting furnace 10 includes an elongated glass tank having an upstream end wall 16 and a downstream end wall 18, sidewalls 20, 22, a floor (not shown) and a roof (not shown) all made from appropriate refractory materials such as alumina, silica, alumina- silica, and the like. At least one pair of the opposing burners 24, 24A, 26, 26A, 28, 28A and 30, 3OA, are positioned in a side-by-side relation in the sidewalls 20, 22 over the unmelted glass batch, for melting the glass.
Making now reference to the Figure 2, a fuel feeding system FFS is shown in accordance with the present invention. In this embodiment, pulverized petroleum coke is received in a single feeder 32. Each feeder 32 includes a silo or tank 34. The single feeder 32 comprising a conical section 36 for discharging a constant flow of the pulverized coke toward each one of the burners 24, 26, 28, 30 or 24A, 26A, 28A and 3OA, as will be described later. The pulverized material is stored in the feeder 32 and it is discharged in a continuous form through an air lock rotary valve 38 attached to the lower section of the conical section 36 for continuously discharge the pulverized material toward a main pipe 40. An air blower 44 is associated with the air lock rotary valve 38 and the main pipe 40 to convey the pulverized material that is being provided from the feeder 32 through of the main pipe 40. In this embodiment the main pipe 40 is connected respectively to a first plurality of pipes 42, 44, 46 and 48, for feeding the supply of an air-fuel mixture toward each of the burners 24, 26, 28 and 30. Each first plurality of pipes 42, 44, 46 and 48, includes return pipes 50, 52, 54 and 56, for returning back in an individual way the pulverized coke toward the silo or tank 34.
As was described in the first embodiment, the feeder 32 will supply a pulverized air-fuel mixture in one side of the glass meting furnace 10, which will be connected to a plurality of burners 24, 26, 28 and 30. The feeder 32 will feed the required amount of pulverized fuel to all the burners 24, 26, 28 and 30. So, in case that any burner be changed (i. e by maintenance, fuel change, etc.), the flow of the air/ pet coke mixture will be maintained in a constant way, returning back the air/ pet coke mixture by means of the corresponding return pipes 50, 52, 54 and 56 toward the silo or tank 34. This operation condition permits that the feeding of the pulverized fuel does not affect the other burners that are being maintained in operation.
The fuel feeding system performs automatically refilling, when a level of pulverized fuel is reached, and there is not necessity of interrupt the feeding of the fuel in each of the burners. With this arrangement, the feeding of pulverized fuel can feed continuously to each one of the burners, for example, for the case of recuperative furnaces. In case of regenerative furnaces a similar arrangement of pipes can be carried out. By means of this type of furnaces, the fuel feeding system can be charged during the alternate operation cycle.
The behavior of the opposite side of the furnace is of similar manner, however the fuel feeding system has the capacity of delay, advance or uniform in the feeding time in accordance with the operation requirements of the furnace, The embodiment of the figure 1 shows a similar arrangement of fuel feeding system FFS, which is located in the side 22 of the furnace 10. However as can be observed in the figure 1 , the burners 24A, 26A, 28A and 3OA, are placed in the opposite side 22 of the furnace 10, but maintaining a front separation region with respect to the burners 24, 26, 28 and 30, to avoid that the flames of each burner to collide one with the other, when all the burners are in operation over both sides of the furnace. However, in one additional embodiment of the present invention, the burners can be placed on the roof of the furnace (not shown), to produce a flame on the surface of the glass.
The figure 2 shows a second embodiment of the system for feeding the pulverized fuel in accordance with the present invention. In this case an individual fuel feeding system FFS1 , FFS2, FFS3 and FFS4 is placed by each burner 24, 26, 28 and 30. In this second embodiment each fuel feeding system FFS1 , FFS2, FFS3 and FFS4 includes a feeder 32A, and a silo or tank 34A. Each feeder 32A comprising a conical section 36A for discharging a constant flow of the pulverized coke toward one of the burners, for example burner 30.. As was previously described, the pulverized material is stored in each feeder 32A and it is discharged in a continuous form through an air lock rotary valve 38A attached to the lower section of the conical section 36A for continuously discharge the pulverized material toward a main pipe 42A. An air blower 44A is associated with the air lock rotary valve 36A and the main pipe 42A to convey the pulverized material that is being provided from the feeder 32A through of the main pipe 42A. In this embodiment the main pipe 42A is directly connected to the burner 30 to the supply of the air-fuel mixture toward the burner 30. The main pipe 42A including a return pipe 52A, for returning back the air/ pet coke mixture by means of the corresponding return pipes 52A,toward the silo or tank 34A.
By means of this arrangement, there is possible to generate different thermal profiles within the furnace 10, adjusting the feeders to different operation conditions of the furnace. Each feeder can be rechargeable in accordance with the process necessities.
From the above the method for melting glass using a pulverized fuel comprises, a) feeding a controlled flow of a mixture of pulverized fuel and air or gas under pressure from at least a feeding means; b) discharging the mixture of pulverized fuel and air or gas from the feeding means toward at least one distribution means; c) regulating in a controlled manner the pulverized fuel-air or gas mixture from the distribution means to each of a plurality of burners in a glass melting region of the recuperative glass melting furnace; d) preheating a combustion air through of at least a recuperator of the recuperative glass melting furnace; and, e) mixing the preheating combustion air and mixture of pulverized fuel and air or gas in the glass melting region of said glass melting furnace to provide a combustion flame with high thermal efficiency to carry out the melting of the glass. From the above, a method for melting glass has been described and will apparent for the experts in the art that many other features or improvements can be made, which can be considered within the scope determined by the following claims.

Claims

WE CLAIM:
1.- A method for producing glass in a recuperative glass melting furnace, the method comprising: a) feeding a controlled flow of a mixture of pulverized fuel and air or gas under pressure from at least a feeding means; b) discharging the mixture of pulverized fuel and air or gas from the feeding means toward at least one distribution means; c) regulating in a controlled manner the pulverized fuel-air or gas mixture from the distribution means to each of a plurality of burners in a glass melting region of the recuperative glass melting furnace; d) preheating a combustion air through of at least a heat exchanger of the recuperative glass melting furnace; and, e) mixing the preheating combustion air and mixture of pulverized fuel and air or gas in the glass melting region of said glass melting furnace to provide a combustion flame with high thermal efficiency to carry out the melting of the glass.
2.- A method as claimed in claim 1 , wherein the method comprises placing the burners in the furnace in a opposite relation one in front to the other, but maintaining a parallel separation region with respect to each other to avoid that flames of each burner to collide one with the other, when all the burners are in operation in the furnace.
3.- A method as claimed in claim 1 , wherein the method comprises: operating continuously all the burners during the melting of the glass.
4.-. The method as claimed in claim 1 , wherein step b) comprises discharging the fuel-air or gas mixture with one feeding means to supply the pulverized fuel-air or gas mixture to all the burners.
5.-. The method as claimed in claim 1 , wherein step b) comprises discharging the fuel-air or gas mixture individually for each burner.
6.-. The method as claimed in claim 1 , wherein the pulverized fuel is petroleum coke.
7.-. The method as claimed in claim 1 wherein the step b) includes returning the flow of pulverized fuel-air or gas mixture from the distribution means to step a) while maintenance of the burners are carried out, maintaining a constant flow of the pulverized fuel and air mixture in the distribution means.
8.- The method as claimed in claim 1 wherein the furnace is a cross fired type.
9.- The method as claimed in claim 6 further comprises: generating different thermal profiles within the furnace, adjusting the discharging step to different operation conditions of the furnace.
PCT/IB2007/002962 2007-09-12 2007-09-12 Method for melting glass in a recuperative glass melting furnace WO2009034408A1 (en)

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
GB2525942A (en) * 2014-05-07 2015-11-11 Linde Ag Hot spot burner and reversing lance for end port regenerative furnace

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US4006003A (en) * 1975-10-29 1977-02-01 Owens-Illinois, Inc. Process for melting glass
US20020134287A1 (en) * 2001-03-23 2002-09-26 Olin-Nunez Miguel Angel Method and system for feeding and burning a pulverized fuel in a glass melting furnace, and burner for use in the same
EP1634856A1 (en) * 2004-09-10 2006-03-15 Air Products and Chemicals, Inc. Combustion method with staged oxidant injection

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
US4006003A (en) * 1975-10-29 1977-02-01 Owens-Illinois, Inc. Process for melting glass
US20020134287A1 (en) * 2001-03-23 2002-09-26 Olin-Nunez Miguel Angel Method and system for feeding and burning a pulverized fuel in a glass melting furnace, and burner for use in the same
EP1634856A1 (en) * 2004-09-10 2006-03-15 Air Products and Chemicals, Inc. Combustion method with staged oxidant injection

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2525942A (en) * 2014-05-07 2015-11-11 Linde Ag Hot spot burner and reversing lance for end port regenerative furnace

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