Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B3/00—Charging the melting furnaces
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
  • C03B5/12—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture in shaft furnaces

Definitions

• the present invention relates to a method of melting rock material into a smelt used for manufacturing mineral fiber.
• the method according to the invention is implemented by performing the melting in a shaft furnace in which the rock material and the amount of fuel proportionated according to the quantity of the rock material is fed into the furnace via an inlet at the top thereof .
• the rock material is crushed to a proper particle size.
• the particle size of coke conventionally used as the fuel is selected appropriately.
• the rock material and coke are charged into this type of furnace in layers, whereby the pile of layered raw materials sinks in the furnace downward as the lower end of the pile melts in the melting zone formed in the bottom part of the furnace and is discharged from the furnace bottom.
• air is injected upward at a suitable height from the furnace bottom into the mixture of rock material and fuel.
• the flue gases formed in the fuel combustion process rise through the pile of rock material and fuel until reaching the top of the furnace to be discharged therefrom.
• the particle size in the pile must be sufficiently large to provide an appropriate free space about the particles.
• injection nozzles of a special construction are used to feed the combustion air into the melting zone.
• the melt formed is collected on the furnace bottom into a pool of suitable height by allowing the excess melt to discharge over a weir disposed slightly above the level of the furnace bottom.
• This pool formation serves to equalize the short-term fluctuations of the melt qualities.
• the average composition of the melt must be controlled by adjusting the composition of the raw materials to be melted, that is, by adding suitable ingredients to the in- feed material mix.
• the composition of materials being melted is controlled by sampling the melt, and based thereon, adding the required raw material components to the top of the furnace, into the infeed mix of rock material and fuel.
• a melt control technique is primarily hampered by the finite transport delay of the added component along with the rock material to the bottom of the furnace. This delay brings about a significant uncertainty factor to the material composition control and, in spite of predictive calculations and estimations, inaccuracy of control results.
• the composition of the melt is difficult to keep within the set limits.
• the additive ingredients tra- veiling downward in the raw material pile will be subjected to a relatively long period in contact with the hot flue gases, which leads to loss of additive ingredients 3 through evaporation. Particularly apatite and boron compounds are problematic in this respect.
• some of the additive ingredients such as bauxite and titanium compounds are slowly melting requiring their grinding to a substantially smaller particle size than the rock material and the fuel .
• the fine particulate matter causes problems to the passage of flue gases through the material pile as well as loss of material due to entrained transport of material dust, whereby the elimination of these problems necessitates briquetting of additive ingredients into sufficiently large agglomerates.
• additive ingredient can be introduced along with a carrier medium directly into the melting zone or its immediate vicinity.
• the additive ingredient can be introduced into the furnace along with the combustion air.
• the additive ingredient can be mixed with an auxiliary fuel which may be a gaseous, liquid or fine-ground solid fuel.
• the combinations of the above carriers can be used for introducing the additive ingredient.
• the melt composition can be primarily controlled using conventional coarse control techniques, so that the initial charge of 4 basic materials known beforehand to be in short supply in the melt and also known to behave rather unproblematical- ly in the melting process, are added slightly undercompensated into the melting furnace. Then, the special cha- racter of the present invention can be utilized for fine control of the melt composition and the introduction of hard-to-melt additive ingredients.
• the introduction of the additive ingredient along with its carrier medium can be complemented by feeding enriching oxygen into the melting zone, whereby the feed rate of oxygen addition is adjusted compatible with the actual composition of additive ingredients thus creating advan- tageous conditions for the melting thereof in melting zone. Due to the presence of carbon, the overall conditions in the melting zone are reducing. The degree of reducing conditions can be decreased by the oxygen addition, or even reversed into oxidizing conditions if the excess amount of oxygen addition is sufficiently large.
• the introduction of the enriching oxygen is advantageously carried out separately from the introduction of additive ingredients and also is provided with an independent control facility. This can be accomplished by different types of injection nozzle constructions having separate channels on one hand for the additive ingredient (s) and its carrier and on the other hand for the enriching oxygen.
• melt viscosity is primarily affected by the melt composition and temperature.
• the available raw material and/or the raw material 5 mix giving the desired melt composition may be such that melts at a high temperature requiring the melt to kept at a high melt temperature, too.
• This melt pool temperature may be excessively high to maintain the optimal viscosity, which subsequently causes problems in the fi- berizing stage.
• the method according to the invention can offer a solution to problem by allowing the introduction of such an additive ingredient that has no significant effect on the melt composition.
• the mel- ting of such an additive ingredient binds heat thus lowering the melt temperature.
• One useable additive for this purpose is recycled fiber, preferably in milled form.
• the control of melt composition by virtue of the method according to the invention may also be used for controlling the composition-dependent viscosity of the melt.
• the implementation of the invention may be accomplished by means of conventional infeed equipment based on, e.g., the use a carrier gas flow into which solid particulate matter is introduced with the help of a separate feed apparatus .
• the feed apparatus in an embodiment of such equipment comprises a rotating compartmental feeder adapted centrally in a cylindrical container, said feeder having its compartments bordered by the cylindrical shell of the container and its end surfaces.
• the carrier gas flow is provided with opposite aligned inlet and outlet nozzles, respectively, at the opposite ends of the cylindrical container thus permitting the carrier gas flow to entrain the solid particulate matter loaded in the com- partments as they sequentially meet the opposed nozzles.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=8551405

Family Applications (1)

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Family Cites Families (4)

• 1998
  • 1998-03-27 FI FI980710A patent/FI980710A/fi unknown
• 1999
  • 1999-03-26 EP EP99913327A patent/EP1089944A1/de not_active Withdrawn
  • 1999-03-26 AU AU31489/99A patent/AU3148999A/en not_active Abandoned
  • 1999-03-26 WO PCT/FI1999/000249 patent/WO1999050196A1/en active Application Filing

Non-Patent Citations (1)

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