Abstract: The invention relates to a method of preparing a mineral melt in a cupola furnace that uses at least one plasma torch to provide heat energy to the furnace. The plasma torch uses nitrogen, carbon monoxide, carbon dioxide, or a mixture thereof as the carrier gas. The invention also relates to a cupola furnace for the preparation of the mineral melt, and the use of a plasma torch in a cupola furnace to reduce the amount of NOx and/or hydrogen in the furnace off-gas.

Abstract: The present invention concerns a method and an apparatus (12) for measuring the temperature of a fluid stream (11), said apparatus comprising a movable frame (13, 14) having first end facing towards the fluid stream to be measured and an oppositely directed second end; a beam splitter (9) which is movably arranged in the frame for advancement into said fluid stream to open the fluid stream; an optical temperature measurement device (8) for determining the temperature of the fluid stream by measuring the thermal radiation from the fluid stream; and control means for controlling the movement of the frame and the beam splitter and controlling the performance of the optical temperature measurement device.

Abstract: The present invention concerns a method and an apparatus (12) for measuring the temperature of a fluid stream (11), said apparatus comprising a movable frame (13, 14) having first end facing towards the fluid stream to be measured and an oppositely directed second end; a beam splitter (9) which is movably arranged in the frame for advancement into said fluid stream to open the fluid stream; an optical temperature measurement device (8) for determining the temperature of the fluid stream by measuring the thermal radiation from the fluid stream; and control means for controlling the movement of the frame and the beam splitter and controlling the performance of the optical temperature measurement device.