Abstract: To provide a method for producing molten glass, whereby formation of dust can be suppressed when the molten glass is produced by an in-flight melting method. Granules containing silica sand and satisfying the following conditions (1) to (3) are used. (1) In a particle size distribution curve obtained by measuring the granules passed through a sieve having 1 mm openings by a dry laser diffraction scattering method, D50 representing the cumulative volume median diameter is from 80 to 800 ?m. (2) The average particle size of the silica sand in the granules is from 1 to 40 ?m. (3) In a particle size distribution curve obtained by measuring water-insoluble particles to constitute the granules by a wet laser diffraction scattering method, the ratio of D90/D10 is at least 10.

Abstract: A glass-melting furnace, which suppresses the effect of exhaust gas on molten glass quality, a process for producing molten glass, and a process and apparatus for producing glass products. The glass-melting furnace containing: a raw glass material particle feed portion disposed downwardly at a furnace wall portion in an upper portion of the glass-melting furnace; a heating unit provided under the feed portion, which forms a gas phase portion for converting raw glass material particles into liquid glass particles; a flue inlet disposed on the upstream side of the gas phase portion in a flow direction of the molten glass liquid; a furnace-bottom portion, which accumulates the liquid glass particles that produce the molten glass liquid; and a discharge portion, which discharges the molten glass liquid.

Abstract: The present invention provides a process for producing a molten glass which can produce a molten glass having a good quality, a glass-melting furnace, a process for producing glass products and an apparatus for producing glass products. While an oxygen combustion burner 20 is rotated by a motor 38, glass raw material particles (not shown) are dropped into a high-temperature gas phase atmosphere produced by a flame F of the oxygen combustion burner 20, to be changed into liquid glass particles. By rotation of an outlet (nozzle) of the oxygen combustion burner 20, the falling position of the liquid glass particles 26, changes with time. Accordingly, generation of bubbles caused by continuous fall of the liquid glass particles in a particular position on a molten glass liquid surface is prevented. Accordingly, it is possible to produce a molten glass having a good quality with few bubbles.

Abstract: Glass raw material particles are dropped from an oxygen combustion burner 24, and the glass raw material particles are heated by a flame F of an oxygen combustion burner 24 and a thermal plasma P, to melt the particles. Liquid glass particles 30 produced by the melting fall downwardly in a melting tank 12, and fall on a surface of a molten glass liquid G in the melting tank 12. Then, an upper layer G1 of the molten glass liquid G is heated by electrodes 40, 40 of a heating apparatus 38 provided in the melting tank 12. By this method, air and residual gas generated in the molten glass liquid G and the liquid glass particles 30 fallen onto the surface of the molten glass liquid G, become bubbles, surface and are smoothly discharged.

Abstract: Glass raw material particles are dropped from an oxygen combustion burner 24, and the glass raw material particles are heated by a flame F of an oxygen combustion burner 24 and a thermal plasma P, to melt the particles. Liquid glass particles 30 produced by the melting fall downwardly in a melting tank 12, and fall on a surface of a molten glass liquid G in the melting tank 12. Then, an upper layer G1 of the molten glass liquid G is heated by electrodes 40, 40 of a heating apparatus 38 provided in the melting tank 12. By this method, air and residual gas generated in the molten glass liquid G and the liquid glass particles 30 fallen onto the surface of the molten glass liquid G, become bubbles, surface and are smoothly discharged.

Abstract: A glass-melting furnace, which suppresses the effect of exhaust gas on molten glass quality, a process for producing molten glass, and a process and apparatus for producing glass products. The glass-melting furnace containing: a raw glass material particle feed portion disposed downwardly at a furnace wall portion in an upper portion of the glass-melting furnace; a heating unit provided under the feed portion, which forms a gas phase portion for converting raw glass material particles into liquid glass particles; a flue inlet disposed on the upstream side of the gas phase portion in a flow direction of the molten glass liquid; a furnace-bottom portion, which accumulates the liquid glass particles that produce the molten glass liquid; and a discharge portion, which discharges the molten glass liquid.

Abstract: An apparatus for producing molten glass, a process for producing molten glass, an apparatus for producing a glass product and a process for producing a glass product, which are capable of preventing deterioration of the quality of molten glass caused by deposition of scattered particles on a furnace wall or a flue. In the present invention, together with the operation of introducing and melting glass material particles by an oxygen combustion burner, glass cullet pieces are dropped from glass cullet pieces-introducing tubes to form a substantially cylindrical enclosure around a flame by a flow of glass cullet pieces. That is, glass cullet pieces are dropped from eight glass cullet pieces-introducing tubes to partition off the furnace wall from the flame. And, particles scattering from the flame are captured as deposits on the surface of falling glass cullet pieces and dropped into a glass melt in the melt reservoir.

Abstract: The present invention provides (i) a glass melting furnace, (ii) a process for producing molten glass, (iii) an apparatus for producing a glass product, and (iv) a process for producing a glass product, which are capable of preventing deterioration of the quality of molten glass caused by deposition of particles floating on a wall of the furnace. The melting furnace described herein includes a melting tank in which a flue located substantially at the center of a ceiling wall and a number of first heating units are disposed, such that particles floating in the furnace are suctioned off by a suction power of the flue and discharged from the furnace without being directed to a surrounding furnace wall. This drastically reduces the amount of floating particles deposited on the furnace wall, which prevents damage to the furnace wall and deterioration of the quality of glass produced therein.

Abstract: The present invention provides a glass-melting furnace etc. which can maintain homogeneity of molten glass in an apparatus and a process for producing molten glass by melting glass raw material particles and glass cullet pieces. In the present invention, glass raw material particles are dropped from a glass raw material particle heating unit 14 constituted by oxygen combustion burners 34, 34 . . . and a glass raw material particle feed portion, and the glass raw material particles are changed into liquid glass particles 38, 38 . . . in high-temperature gas phases produced by flames 32, 32 . . . of oxygen combustion burners 34, 34 . . . . In the step of heating and melting the glass raw material particles, glass cullet pieces 30, 30 . . . are feed by an feed means 40 of a glass cullet piece feed portion 12 so as to be spread radially toward the plurality of flames 32, 32 . . . around the feed portion.

Abstract: The present invention provides a process for producing a molten glass which can produce a molten glass having a good quality, a glass-melting furnace, a process for producing glass products and an apparatus for producing glass products. While an oxygen combustion burner 20 is rotated by a motor 38, glass raw material particles (not shown) are dropped into a high-temperature gas phase atmosphere produced by a flame F of the oxygen combustion burner 20, to be changed into liquid glass particles. By rotation of an outlet (nozzle) of the oxygen combustion burner 20, the falling position of the liquid glass particles 26, 26 . . . changes with time. Accordingly, generation of bubbles caused by continuous fall of the liquid glass particles in a particular position on a molten glass liquid surface is prevented. Accordingly, it is possible to produce a molten glass having a good quality with few bubbles.

Abstract: A DC/DC converter includes a main switching element and a subordinate switching element, and is arranged to supply power to load via a coil. The ON-time of a subordinate switching element in a succeeding cycle is controlled based on a period of time tdif from the time when the subordinate switching element is turned off until the time when voltage at the point of connection of the two switching elements reaches a predetermined threshold value.

Abstract: A DC/DC converter includes a main switching element and a subordinate switching element, and is arranged to supply power to load via a coil. The ON-time of a subordinate switching element in a succeeding cycle is controlled based on a period of time tdif from the time when the subordinate switching element is turned off until the time when voltage at the point of connection of the two switching elements reaches a predetermined threshold value.

Abstract: A control circuit for a DC/DC converter which includes a main switching element, a sub switching element, and a reactor in order to convert a DC input voltage to a DC output voltage. The control circuit comprises a clock signal generator for generating a clock signal during a blank period in which both the main and sub switching elements are off; a comparator for comparing a reference voltage and a voltage at a connection point between the main and sub switching elements and for outputting a comparison signal indicating a relation of magnitude between the reference voltage and the voltage at the connection point; and an operation mode switching section for monitoring the comparison signal at a timing corresponding to the clock signal in order to detect a voltage state at the connection point, and controlling the sub switching element in accordance with the voltage state.

Abstract: A control circuit for a DC/DC converter which includes a main switching element, a sub switching element, and a reactor in order to convert a DC input voltage to a DC output voltage. The control circuit comprises a clock signal generator for generating a clock signal during a blank period in which both the main and sub switching elements are off; a comparator for comparing a reference voltage and a voltage at a connection point between the main and sub switching elements and for outputting a comparison signal indicating a relation of magnitude between the reference voltage and the voltage at the connection point; and an operation mode switching section for monitoring the comparison signal at a timing corresponding to the clock signal in order to detect a voltage state at the connection point, and controlling the sub switching element in accordance with the voltage state.