Pass Mountain Rare Earth Mine (USA)

I. Overview

The Mountain Pass rare earth mine is located in the southern part of California, USA and is one of the largest fluorocarbon strontium deposits in the world. The deposit was discovered in 1949 and 1951 for the United Petroleum Group Molybdenum Company (Molycrop.Inc.) All. A small amount of production began in 1952. After the 1954 flotation plant (Fig. 1) was completed and put into production, the annual production capacity of rare earth concentrates was converted into 4077 tons of rare earth oxides. The second phase of expansion was completed in December 1966, with a production capacity of 22,650 tons. In 1972, due to the promotion of rare earths in steel, the plant was expanded to 27,210 tons in 1973. In 1980, the production capacity has expanded to more than 40,000 tons. The products produced by the plant include: fluorocarbon antimony concentrate containing RE060%～63%; rare earth products containing RE068%～72% and rare earth products containing RE085%～90%.

Figure 1 US Pass Mountain Rare Earth Flotation Plant

Second, the nature of the ore

The Perth Mountain rare earth mine is distributed in a carbonate ore body with a length of 8 kilometers and a thickness of 2.4 kilometers, showing irregular veins. Calcite ore containing 40% to 60% barite and celestite containing 20% to 35%, containing 8% quartz and a small amount of apatite, galena, hematite and the like. The rare earth minerals in the ore are mainly bastnasite and contain a very small amount of monazite. The ore minerals in the ore are coarsely grained, and the average grade of rare earth is 7% to 8% REO.

    Third, the process flow and selection indicators

Mountain Pass rare earth ore beneficiation plant averaged 1,500 tons containing bastnaesite 10% (7% rare earth oxide) of ore per day. The process of the concentrator (Fig. 2) includes: the ore from the mine, which is broken by a two-stage closed circuit to -13 mm and sent to the grinding and floating workshop. Grinding uses a closed-loop process consisting of a rod mill, a ball mill and a hydrocyclone to grind the ore to -100 mesh for 80% of the flotation operation. Before the flotation, use 6 stirring tanks, stir under steaming conditions, add soda and sodium fluorosilicate in the first stirring tank, and add ammonium lignosulfonate in the third stirring tank, in the sixth Add C-30 Tal oil in a stirred tank, perform a rough selection, a single sweep, and four times to obtain a rare earth concentrate containing 60% to 63% of rare earth oxides under the condition of pH 8.8. The rare earth recovery rate is obtained. 65% to 70%. The rare earth flotation concentrate is further treated with an acid to obtain a rare earth product containing REO 68% to 72%; and after roasting, a rare earth product containing 85% to 90% of REO can be obtained.

Figure 2 Paceshan rare earth ore dressing process

The flotation reagent system and dosage of the Passhan Rare Earth Concentrator are listed in Table 1. The rare earth flotation indicators are listed in Table 2. The main equipment list is listed in Table 3.

Table 1 Flotation agent system and dosage

Table 2 Rare Earth Flotation Index

Table 3 List of main equipment