Mining Publication: Low Temperature Limits for Mixing Recycled Oil, Diesel Fuel, and Ammonium Nitrate to Make ANFO-Type Blasting Agents

Research was conducted to determine the safe operating conditions for using recycled (used) lubricating oil from mining equipment as a partial replacement for diesel fuel to make ANFO-type blasting agents. The use of recycled oil (RO) saves energy, reduces oil imports, and reduces mining costs. Low ambient temperatures may cause these recycled oils to become too viscous for proper absorption by ammonium nitrate (AN) prills and result in poor blast performance, safety hazards, and environmental problems. To help quantify and resolve these issues, viscosity, mixing, and performance tests were done at various temperatures. Diesel fuels No. 1 and No. 2 were studied separately and in blends with 25%, 50%, and 75% RO. Good quality ANFO mixes (94-6) were produced with dry absorbent prills and blended fuel (No. 1 diesel plus RO) at temperatures as low as -40 deg F (-40 deg C) with 75% No. 1/25% RO and at -20 deg F (-29 deg C) with 50/50. Diesel fuel No. 2 also made good mixes as low as -30 deg F (-34 deg C) with 75% No. 2/25% RO and at 0 deg F (-18 deg C) with 50/50. Reference detonation velocity tests were conducted in 1.4-in (3.6-cm) diameter steel pipe at 70 deg F (21 deg C) on No. 1 diesel ANFO (94-6), giving an average value of 9,722 ft/sec (2,964 m/sec). Comparison tests showed good ANFO performance at low temperatures. Blended fuel ANFO (75% No. 1/25% RO) mixed, loaded, and tested at -40 deg F (-40 deg C) produced an average velocity of 9,247 ft/sec (2,818 m/sec). A 50/50 blend gave a velocity of 8,083 ft/sec (2,464 m/sec) at -20 deg F (-29 deg C). Based on these results, a practical field method has been developed to help evaluate whether a specific oil blend will mix properly with AN at a low ambient temperature. This method will help to promote the safe and reliable use of RO ANFO at low temperatures with adequate performance.