Lonesome Concentrator in Central Florida, USA

Florida is the nation's largest phosphate mineral, is the world's largest phosphate producing areas. The recoverable reserves are 2.6 billion tons, accounting for about 46% of its total reserves. In 1982, the output of phosphate rock reached 28.061 million tons, accounting for 75% and 23% of the total output of the United States and the world respectively.

Phosphate mining in the region is concentrated in the central and northern regions, with phosphate production in only Polk and Hillsborough counties accounting for 90% of total Florida production. There are 11 companies that mine the central phosphate rock and a company that mines the phosphate rock in the north. Currently, the region has a beneficiation plant up to as many as 24.

The Florida Phosphate deposit was formed during the Neogene to the Miocene, and the distribution ranged from the border of the state to the north and the half of the Nanzhao Peninsula. Mineral deposits of important economic value due to long-term exposure due to weathering are mainly found in the upper part of the northern Hawthorn group and the lower part of the central Bove Valley. In the lithology, the two layers of minerals are very similar, consisting of about one-third of each sand, clay and phosphate in the form of fine or pebbles.

Florida phosphate rock deposit types are: land psephitic phosphate rock, soft and hard phosphate rock, river gravel-like rock phosphate, aluminum phosphate, a phosphorus-containing dolomite Hawthorne layer of six, among them The difference is mainly due to the weathering and/or deposition of the primary ore. The current production of the phosphate rock in Florida is actually derived from the mining of gravel phosphorite.

The terrestrial gravel-type phosphorite ore has a soft texture and is round-oval. The particle size ranges from 25.4 mm to 0.44 mm, and the colors are gray, yellow, brownish green and black. The mineral composition is: 30% to 60% of phosphate, 12% to 25% of quartz sand, and 15% to 40% of clay.

The mining and selection processes used in each concentrator in the Florida area are roughly the same, which can be summarized as three major operations: washing, sorting and clay (tailing) treatment. The specific process is as follows: the topsoil is first stripped with a bucket shovel, the ore is discharged into a panning pit, rinsed into a slurry with a water gun, and pumped to a washing plant. The washing plant is provided with a fixed sieve and a tank washing machine. Equipment such as vibrating screens and hammer crushers . The ore is sieved, washed and classified to obtain a gravel-like phosphate product of about 14% (or +200 mesh) of 30% to 50% of the original ore (the product contains P ₂ O ₅ 30% to 35%, MgO 0.0). %~1%, Fe+Al 2%~3%). The undersize products of less than 14 mesh (or less than 20 mesh) are classified by a hydrocyclone, and the separated -150 mesh slime (containing P ₂ O ₅ to 15%) is discharged into the sedimentation tank; and -14 (or -20) ) ~-150 mesh underflow, that is, as the feed of flotation operation, the Chinese feed and then the "positive-reverse flotation" according to the coarse and fine fractions (that is, the anion collector is floated first to obtain coarse The ore is then subjected to reverse flotation by a cationic collector to remove residual silicon in the coarse concentrate to obtain coarse and fine phosphorus concentrate. This part of the flotation concentrate contains about 30% to 33% of P ₂ O ₅ , 0.0% to 0.5% of MgO, 0.1% to 5% of organic matter, and 2% to 3% of Fe + Al. The flotation reagent species employed, usually caustic soda, ammonia (liquid), sulfuric acid, fatty acid, amine salt, and coal oil, the amount varies depending concentrator. Take the Lonesom concentrator as an example to illustrate the generalization of the Florida phosphate rock by conventional anion-cation positive-reverse flotation.

The Lonersom concentrator was discovered in 1977. It has a design capacity of 249.5 to 27.22 million tons of raw ore per year, and an annual output of 136 to 1.54 million tons of flotation concentrate.

The mine began mining in 1913. The mine is located in the southeast corner of Hillsborough, Florida, about 25 kilometers from Tampa. The reserves of phosphate ore are 50 million tons, and the average P ₂ O _{5 is} close to 32%.

The mineral composition of the mineral is phosphate, quartz sand and phosphated clay, each accounting for about one-third. The main chemical components are: P ₂ O ₅ 9.1%, MgO 0.1%, and the rest are siliceous materials.

The main process engineering of the Lone Som concentrator is described as follows:

The ore mined by a 34m ³ bucket shovel is first prepared as a slurry and then transported to a screening station through a 2286m long pipe. +75mm material waste gas; -75mm+19mm material is crushed and mixed with pulp with a particle size of -10mm. The mixed -19 mm slurry is sent to a Ñ„ 600 mm hydrocyclone via another 610 m long pipe where the phosphated clay is removed and sent to the tailings storage area. The bottom of the hydrocyclone with a concentration of 70% after removal of the clay is discharged directly onto the conveyor belt and sent to the concentrator.

In the concentrator, the delimed material is washed, scrubbed and sieved in a scrubber to produce a final +16 mesh final ovate product (or sieve concentrate). The -16 mesh material is the flotation operation feed. (This part of the feed or the first classification after the coarse, fine-grained level of flotation, or mixed flotation). The feed after being sent to the flotation is first concentrated to a concentration of 75% by a hydrocyclone of Ñ„ 610 mm, and then selected by an anion collector to obtain a foam product (ie, a coarse concentrate); After the cyclone dehydration, sulfuric acid scrubbing and fresh water washing, it is selected with a cationic collector to obtain the product in the tank, which is the final phosphate concentrate. The final phosphate concentrate is dried to 2% moisture, which is the finished product. The tailings obtained in the sorting process are mixed with the clay waste, filtered by natural water, and then covered with the waste rock to form a stable reclaimed surface.

Concentrator flotation system: 4 columns of positive flotation, 2 slots per column. Solvent 14m ³ per tank. The flotation machine model is a Wemco type. The amount of flotation agent is (kg/t feed): fatty acid 1.0, amine salt 0.2, sulfuric acid 0.6, fuel oil 0.6.

According to the washing principle process shown in the figure below, the sieved concentrate (ie gravel product) contains P ₂ O ₅ 31% to 31.9%, flotation concentrate (ie coarse and fine phosphorus concentrate) contains P ₂ O ₅ 31.9%～33.74%, the content of comprehensive concentrate is MgO 0.3%. The tailings contain P ₂ O ₅ 0.9% to 1.4%. The total recovery rate of concentrate is 75%-85%.

Figure Florida Phosphorus Mine Washing Principle Process