Abstract: A reference voltage generating circuit in a DC power supply includes a differential amplifier for detecting a difference voltage between a reference voltage and the output voltage, and a voltage control circuit which is responsive to an output signal from the differential amplifier so as to control the DC power supply output voltage to limit the difference between the output voltage and the reference voltage to zero. More specifically, the reference voltage generating circuit includes a reference voltage source, a first variable resistor connected in parallel with the reference voltage source, a second variable resistor connected to the negative side of the reference voltage source, a third variable resistor connected to the positive side of the reference voltage source, and a switching circuit for connecting a movable contact piece of the first variable resistor to either the second or third variable resistors, or to neither of them.

Abstract: Method and apparatus for processing reduced iron in which granular iron oxide charged into a vertical furnace is reduced by a reducing gas comprising mainly carbon monoxide and hydrogen, a substantial portion of the waste gas generated in the reduction process being regenerated in a recirculating system. The reduced iron which has been reduced in the vertical furnace is continuously discharged at a temperature above 500.degree. C under isolation from the exterior atmosphere and is received in a plurality of air tight, sealable component adjusting receptacles. The reduced iron received in the receptacles is subjected to component adjustment at a temperature ranging from 700.degree. to 1100.degree. C by using the regenerated reducing gas and, thereafter, it is discharged from the receptacles under isolation from the exterior atmosphere so as to be received in air tight sealable cooling receptacles thereby cooling the same to a temperature lower than 100.degree.

Abstract: A method of raising the temperature of a reducing gas containing a CO component for avoiding the problems caused by soot inevitably generated in raising the temperature of the reducing gas. In heating the reducing gas to a temperature higher than 500.degree.C, the rate of raising the temperature of the reducing gas is kept higher than 350.degree.C/sec. during the time the temperature of the gas is being raised through the range of 500.degree. - 750.degree.C, while the flow velocity of the reducing gas is kept higher than 7 m/sec.