Abstract: A mixing apparatus which prevents erosion of left and right side walls 12a 12b for a flow path 12 for a molten substance of high temperature M and homogenizes the molten substance of high temperature while occurrence of air bubbles is prevented, wherein there are a plurality of mixing units 11 in the flow path 12; an even number of pairs of mixing units 11 are arranged symmetrically with respect to the center line in a longitudinal direction of the flow path 12 and the gap s between a left side wall or a right side wall and an outer peripheral edge of a mixing blade 14 is determined to be 0.04-0.1 times as much as the distance W between the left and right side walls 12a, 12b.

Abstract: A secondary air humidity controller comprising a humidity sensor which detects a humidity in secondary air for combustion in a glass melting furnace; and a humidifier which is arranged upstream of the humidity sensor, and which supplies moisture to the secondary air so that an output from the humidity sensor reaches a predetermined value.