Furnaces – Process
Reexamination Certificate
2002-08-06
2004-04-20
Rinehart, Kenneth (Department: 3749)
Furnaces
Process
C110S1010CD, C110S1010CD, C110S105000, C110S1010CC, C110S1010CD, C110S293000
Reexamination Certificate
active
06722294
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a method and apparatus for feeding a pulverized material for a glass melting furnace and, in particular to a method and apparatus for feeding a pulverized material for a glass melting furnace which can continuously operate with a back pressure during the unloading of the pulverized material.
2. Related Prior Art
Melting glass has been done in different kinds of furnaces and of the types of fuels, depending on the final characteristics of the product and also regarding the thermal efficiency of the melting and refining processes. Unit melter furnaces have been used to melt glass (by means of gas fuel), these furnaces have several burners along the sides of the furnace, the whole unit looks like a close 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, it means, in the downstream of the process. However there is an enormous heat loss in the glass leaving high-temperature 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 come out, named as the regenerative furnace. It is well known that, to operate a regenerative glass melting furnace, a plurality of gas burners are 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 burners are arranged to burn fuel, such as natural gas, liquid petroleum, 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 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 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.
For operating the glass melting furnace, the fuel fed to the burners and the combustion air supplied is controlled by measuring at the port mouth and the top of the structure, the quantity of oxygen and combustible material present so as to ensure that within the melting chamber or at points along the melting chamber, the combustion air fed is controlled in excess to that is required for combustion of the fuel being supplied, to ensure a complete combustion of the fuel.
However, due to the continuing upward spiral of energy costs (primarily natural gas), this have forced that the major float glass, containers and tableware manufacturers to add “surcharges” to truckloads of flat glass, bottles and other glass articles. Natural gas prices have increased over 120% this year (in México), far above previous estimates.
Taking into account the above, the present invention is related to the use a pulverized material as a source of fuel for melting glass and more specifically to a method and apparatus for metering a pulverized material to a furnace for melting glass.
Apparatuses for the continuous gravimetric metering of pourable material are know in the art. Gravimetric metering systems are generally adopted in application when the exact measurement and control of the material in question are of fundamental importance (pharmaceutical industry, chemical industry, cement industry, glass industry, food industry, etc.) or where the flows involved are so small that the error which occurs if a volumetric metering system is used is not tolerable.
Examples of the gravimetric metering apparatuses for pourable material are illustrated in the U.S. Pat. Nos. 4,528,848, 4,661,024, 5,184,892, 5,353,647, 5,670,751 and 6,041,664.
For example the U.S. Pat. No. 4,528,848 of Hans Häfner is related to a device for continuous, gravimetric metering and pneumatic conveying of pourable material provides that a material stream is conveyed over a measuring path while charging a load measuring device and the product of moment load and conveying speed is formed. The conveyor is in the form of a rotor having an essentially vertical axis and conveyor pockets in the form of chambers or cells which are moved with the rotor in a circular orbit over the measuring path. A housing surrounds the rotor in a pressure tight manner and includes a charging aperture and an emptying aperture which are rotationally displaced from one another. A load measuring device is connected to the housing and a tachometer is provided for measuring the angular velocity of the rotor. A pneumatic conveying system is provided which has feed lines respectively communicating with an air feed aperture in the housing and the emptying aperture.
The U.S. Pat. No. 4,661,024 of Hans W. Häfner is related to a method for operating an apparatus for continuous gravimetric metering and feeding of pourable material conveyed by a conveyer through a metering path, the conveyer including a rotor provided with conveyer pockets, having an essentially vertical axis and being arranged within a housing in a tightly sealed manner, the housing being provided with a charging station and a discharging station the latter including ports for connecting a pneumatic feeding system, wherein a gas is supplied to spaces within the housing and the rotor outside the metering path.
The U.S. Pat. No. 5,184,892 of Hans W. Häfner is related to a system and a method for continuous gravimetric metering, pneumatic conveying and/or mixing of pourable materials using metering apparatuses of a type such as e.g. disclosed in U.S. Pat. No. 4,528,848.
The U.S. Pat. No. 5,353,647 of Ludger Toerner is related to an apparatus for measuring a bulk material mass flow by measuring Coriolis forces that are caused by the mass flow passing through a winged wheel. The mass flow is introduced centrally onto the winged wheel, which rotates with a constant r.p.m. and diverts the mass flow radially outwardly. The Coriolis forces and thus the corresponding reaction torques which are proportional to the mass through-flow are measured with the aid of a torque joint interposed between a housing of the winged wheel and a drive motor for the shaft that drives the wheel. Force sensor elements, preferably in the form of bending beams, are incorporated into the torque joint and are deflected by the reaction torque moment applied to the motor housing. These bending beams provide an output signal that is proportional to the mass through-flow through the apparatus.
Other apparatus related to a gravimetric metering of bulk material is claimed in the U.S. Pat. No. 5,670,751 of Hans Wilhelm Häfner which includes a weighting container which is supported on at least one weighing cell connected to a weighing electronics and is connected by flexible connections to a bulk material feed line and a discharge line, wherein a pressure sensor is provided on the weighing con
Cabrera-Llanos Roberto Marcos
Solis-Martinez Iván Jorge
Valadez-Castillo Rafael
Abelman ,Frayne & Schwab
Rinehart Kenneth
Vitro Global, S.A.
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