Method for producing sodium tungstate, method for collecting tungsten, apparatus for producing sodium tungstate, and method for producing sodium tungstate aqueous solution

A method for producing sodium tungstate from a tungsten containing material, said method comprising the steps of:

• continuously or intermittently supplying at least one of said tungsten containing material and an oxidant made of one of sodium nitrate and sodium nitrite;
• heating at least one of said oxidant and said tungsten containing material;
• and
• continuously producing a reaction product by bringing said tungsten containing material and said oxidant into contact with each other in an atmosphere containing oxygen, in the step of continuously producing said reaction product, said tungsten containing material is contained in a holding container and at least a part of said tungsten containing material contained in said holding container is immersed in a melt containing at least one of said oxidant and said reaction product, said holding container having a side provided with a plurality of openings and a bottom provided with a communication hole, said openings and said communication hole each being sized so as to prevent passage of said tungsten containing material, said holding container being immersed in said melt such that at least half of said tungsten containing material is immersed in said melt.