Lonersom Concentrator, Central Florida, USA
Florida is the nation's largest phosphate mineral, is the world's largest phosphate producing areas. The recoverable reserves amount to 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 Eocene to Miocene period, with a distribution from the northern border of the state to the south of the peninsula. Due to the long-term exposure and weathering, mineral deposits of great economic value are mainly found in the upper part of the northern Haethorn 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 phosphate rock in Florida is actually derived from the mining of terrestrial gravel phosphate rock.
The terrestrial gravel-like phosphorite ore is soft and round, with a granularity ranging from 25.4 mm to 0.044 mm. The colors are gray, yellow, brownish green and black. The mineral composition is: phosphate 30-60%, quartz sand 12-25%, clay 15-40%.
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 peeled off with a bucket shovel, the mined ore is discharged into the panning pit, rinsed into a slurry with a water gun, and the mill is transported by a pump. The washing plant is provided with a fixed sieve, a tank type washing machine vibrating screen and a hammer crusher . The ore can be sieved, washed and graded to a gravel-like phosphate product of about +40 mesh (or +20 mesh) containing about 30 to 50% of the original ore (the product contains P 2 O 5 30 to 35%, MgO0. 0 to 1%, Fe + Al2 to 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 5 to 15%) is discharged into the sedimentation tank; and -14 (or - 20) ~ +150 mesh underflow, that is, as the feed of the flotation operation, this feed is then subjected to "positive-reverse flotation" according to the coarse and fine fractions (ie, the anion collector is reversely floated to remove the coarse The residual silicon matter in the concentrate) gives coarse and fine-grained phosphorus concentrate. This part of the flotation concentrate contains about 31 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. Taking the Lonesom concentrator as an example, the general situation of the Florida phosphate rock by conventional anion-cation positive-reverse flotation method is described.
The Lone Som concentrator was built in 1977 with a design capacity of 249.5~2.722 million tons of raw ore per year and an annual output of 136-1.54 million tons of flotation concentrate.
The mine began mining in 1913. The mine is located in the southeast corner of Hillsborough, Florida. It is about 25 kilometers from Tampa. The phosphate ore reserves 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 of the Lonesom concentrator is described as follows:
The ore produced through a 34 m 3 dragline is first prepared as a slurry and then transported to a screening station through a 2,286 m long pipeline. The +75 mm material is discarded; the -75 mm + 19 mm material is broken and mixed with a slurry of -10 mm. 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 underflow of the hydrocyclone with a concentration of 70% after removal of the clay is directly discharged to 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 anionic collector to obtain a foam product (ie, a coarse concentrate); After the hydrocyclone 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 rows of positive flotation, 4 slots per column: 4 columns of reverse flotation, 2 slots per column. The volume per tank is 14 m3 . The flotation machine model is a Wemco type. The amount of flotation agent is (kg/ton feed): fatty acid 1.0, amine salt 0.2, sulfuric acid 0.6, fuel oil 0.6.
According to the washing process principle shown in the figure below, the sieve concentrate (ie gravel product) contains P 2 O 5 31.9～33.74%, and the integrated concentrate has 0.3% MgO content. The tailings contain P 2 O 5 0.9 to 1.4%. The total recovery rate of concentrate is 75-85%.
Florida Phosphate Mine Washing Principle Process Flow Chart
With straw as raw material, the production line can produce 1.0-10 tons of straw pellets with diameter of 6/8 mm. The core part of the production line is a SHD760 high-efficiency centrifugal pelletizer.
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