The present invention relates to a method for production of amorphous silica from particulate materials containing at least 50% elemental silicon, where the silicon-containing material is supplied to a combustion reactor which is heated by an oil- or gas burner and where amorphous silica is recovered after the outlet from the combustion reactor. Based on the first torque target value and the second torque target value, the torque command value calculator calculates the torque command value. 1060% by weight, and ethylene glycol diethyl ether in an amount of 0. An elongate center electrode has a body extending between opposite ends, wherein the body is compacted and sintered of a conductive or semi-conductive ceramic material.