A partial oxidation feed system (10) and a method are provided. The system (10) includes a slag additive slurry feed system (31) configured to combine a slurrying agent (24), a mineral slag additive (22), and a liquid slurrying medium (25) to generate a stabilized mineral slurry (26). The slurrying agent (24) is configured to increase a viscosity of the stabilized mineral slurry (26). The system (10) also includes a partial oxidation system (12) configured to receive the stabilized mineral slurry (26), a feedstock (16), and oxygen (14) into a gasifier reaction chamber (27). The partial oxidation system (12) is configured to partially oxidize the feedstock (16) to produce a gaseous product (18) and a solid product (20).