Kureha Kagaku Kogyo Kabushiki Kaisha

Ngk Insulators, Inc.

Toshikatsu Haga

Hiroyuki Fukuda

Saburo Hori

Hiroshi Shinoda

Hideharu Hayakawa

Yukio Ito

Stabilized zirconia refractories comprising fine block crystals of zirconia, having a high bulk density due to their dense texture and a higher bending strength than the conventional calcined zirconia refractories are disclosed. The stabilized electrocast zirconia refractories are obtained by pouring an electrofused melt of a blend of a zirconia-base material and a stabilizing agent into a mold and solidifying the poured melt from its lower portion by cooling the bottom part of the mold forcibly. Also the method for producing the stabilized electrocast zirconia refractories is disclosed.

Stabilized electrocast zirconia refractories

Disclosed herein is the reinforced electrocast zirconia refractories showing an extremely high bending strength obtained by the heat-treatment of stabilized electrocast zirconia refractories under the specified conditions.

Reinforced electrocast zirconia refractories

This invention relates to a burning furnace of hot gas recirculation type for minimizing fuel cost. The furnace includes a cyclone which receives dust-containing exhaust gases. One or more secondary air-introducing nozzles are provided for the cyclone at top of or in close proximity to the upper end of the cyclone leading concentrically to a flue gas passage such as funnel. Upon introducing secondary air under pressure into the cyclone, a downwardly directing swirling air flow is formed therein for the separation of heavier dust together with part of the fed exhaust gases. The thus separated air-hot gas mixture including heavier dust particles is returned to initial stage of the furnace for the recirculation through the furnace. Lighter combustible soot or the like particles are burnt in a flame curtain formed in the cyclone and finally discharged together with main and substantially dust-free exhaust gas portion constituting an upwardly directing swirling core flow in the downwardly directing and swirling outer air flow, into the flue gas passage.

Hot gas recirculation type burning furnace

Hot gas is introduced into a heat treatment furnace 10 through a plurality of nozzles 11 on the furnace wall to form a conical, downwardly swirling gas flow which is convergent at the top and divergent at the bottom. Such a gas flow pattern both heats the bed below, and acts to contain and oxidize any particles blown or splashed up out of the bed. Exhaust gas is discharged up through the conical apex of the swirling flow. The downward angle .alpha. that each nozzle axis forms with the vertical furnace wall is defined by 0&lt;.alpha..ltoreq.30.degree., and the inclination angle .beta. of each nozzle axis with a horizontal line tangent to the furnace circumference is defined by 45.degree..ltoreq..beta..ltoreq.85.degree..

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Iwaki, Japan

Toshikatsu Haga