HIGH PHOSPHORUS-CONTAINING SLAG, MANUFACTURING METHOD OF SLAG-BASED FERTILIZER, AND PHOSPHATE FERTILIZER

摘要

To provide a manufacturing method for providing high phosphorus-containing slag easy to use as a phosphorus resource, from steel slag.SOLUTION: A high phosphorus-containing slag is manufactured through: a first process for reduction treating steel slag containing phosphorous generated in a steel-making refining process, and reducing iron oxide in the steel slag to recover the same as a phosphorous-containing molten iron; a second process for dephosphorylation treating the phosphorus-containing molten iron obtained in the first process to recover resulting high phosphorus slag; a third process for heating the high phosphorus slag obtained in the second process at a temperature of 1500°C or higher to separate it into two liquid phases, and recovering ultra high phosphorus slag in an upper layer; and a fourth process for using the ultra high phosphorus slag obtained in the third process as it is, or conducting at least one of methods of a magnetic separation, a floatation separation, and a gravity separation to obtain a slag having phosphoric acid of 30 mass% or more, and an iron component of less than 10 mass% (in terms of Fe).SELECTED DRAWING: Figure 1