How to separate sea beach sand monazite rutile zircon garnet ilmenite?
Separating sea beach sand is a complex, multi-step process. Its core lies in separating different minerals within the ore by utilizing the differences in their physical or chemical properties.
Generally, the separation process follows the principle of "coarse before fine, gravity before magnetic, physical before chemical," and can be summarized into the following core stages:
Stage 1: Pre-treatment The raw ore extracted from the mining area contains a large amount of useless material and must undergo pre-treatment to prepare for subsequent separation.
Screening: The raw ore is classified according to particle size using equipment such as vibrating screens. This improves the efficiency of subsequent separation equipment because different particle sizes require different separation parameters.
Crushing and Grinding: If the ore contains agglomerates or minerals are tightly bound to gangue, crushers or ball mills are needed to pulverize them, liberating the valuable minerals.
Washing: Washing machines or scrubbing machines are used to remove impurities such as clay and silt adhering to the ore surface.
Stage Two: Roughing (Primarily Gravity Separation)
This is the most crucial and core step in the separation of coastal placer deposits, primarily utilizing the density differences of minerals.
Principle: In coastal placer deposits, valuable minerals (such as ilmenite, rutile, zircon, monazite, etc.) typically have a much higher density than gangue minerals like quartz. Under the combined action of water flow and gravity, lighter minerals are carried away by the water flow, while heavier minerals settle and are collected.
Main Equipment:
Spiral Chute: This is the most commonly used and efficient roughing equipment. The slurry is fed from the top and flows within the spiral sluice. During this process, heavier minerals tend to move towards the inner side of the sluice, while lighter minerals move to the outer side. They are separated by a separator at the bottom of the sluice.
Spiral Chute
Shaking Table: Utilizing the reciprocating asymmetrical motion of the machinery and the water flow on the table surface, minerals are separated between the bed bars according to density and particle size, thus obtaining concentrate, middlings, and tailings. The separation accuracy is higher than that of the spiral sluice and it is often used for further refining of rough concentrate.
Shaking Table
After gravity separation, a "heavy mineral concentrate" is obtained, which is enriched with various useful minerals such as ilmenite, rutile, zircon, and monazite, but these are mixed together.
Third Stage: Fine Separation (Combined Operations of Magnetic Separation, Electrostatic Separation, and Flotation)
To separate single, qualified concentrates from the rough concentrate, it is necessary to utilize the differences in minerals' magnetic properties, electrical conductivity, and surface properties for combined separation.
Magnetic Separation
Principle: Utilizing the differences in magnetic properties among different minerals. When minerals pass through a magnetic field, strongly magnetic minerals are magnetized and adsorbed onto the magnetic separator, while non-magnetic minerals remain unaffected.
Dry Magnetic separator
Application:
First, a weak magnetic field separator separates strongly magnetic minerals, such as magnetite.
Then, a medium or strong magnetic field separator separates moderately magnetic minerals, such as ilmenite and monazite.
Finally, what remains are usually non-magnetic or weakly magnetic minerals, such as zircon and rutile.
Electrostatic Separation
Principle: Utilizing the differences in the conductivity of minerals under a high-voltage electric field. Minerals with high electrical conductivity (such as rutile) quickly lose their charge after acquiring it and are ejected by the centrifugal force of the drum; minerals with low electrical conductivity (such as zircon) are adsorbed onto the drum surface and carried to the back and brushed off.
Application: This is a key method for separating zircon (non-conductor) and rutile (good conductor).
Flotation
Principle: Utilizing the differences in the physicochemical properties of mineral surfaces. By adding specific "collectors," "inhibitors," and "frothers," the target mineral selectively adheres to air bubbles and floats to the surface of the slurry, where it is scraped off.
Application: Flotation is an effective separation method when minerals have very similar densities, magnetic properties, and electrical properties. For example, it is used for further purification of zircon or for separating certain fine-grained titanium minerals.
Fourth Stage: Refining and Tailings Treatment
Refining: The concentrate obtained after the above physical separation sometimes does not meet industrial requirements in purity, or needs further processing into higher-value products. At this stage, hydrometallurgical or pyrometallurgical methods are employed, such as:
Treating ilmenite with sulfuric acid or chlorine to produce titanium dioxide or sponge titanium.
Roasting and acid washing of zircon to improve its grade.
Tailure treatment: The large amount of tailings (mainly quartz sand) generated during the sorting process must be properly handled. Modern mines will:
Backfill the tailings into the mined-out area.
Reclaim and ecologically restore the tailings pond.
Investigate the secondary recovery of valuable components from the tailings or their use as building materials to achieve resource utilization.
Typical example of coastal placer beneficiation process (taking titanium-zirconium placer as an example):
Raw ore → Screening and washing → Spiral chute(gravity separation) → Obtaining heavy sand rough concentrate.
Rough concentrate → Drying → Medium/strong magnetic separation → Magnetic product is ilmenite concentrate; non-magnetic product proceeds to the next step.
Non-magnetic products → Electrostatic separation → Conductive products are rutile concentrate; non-conductor products are zircon concentrate.
(If necessary) The above concentrates are subjected to flotation or acid washing to improve their grade.
Radioactive minerals such as monazite (usually obtained in the intermediate magnetic separation section) separated from the concentrate need to be stored and managed separately.
In summary, sorting coastal placer deposits is a typical "combined process flow," using a series of physical methods such as gravity separation, magnetic separation, electrostatic separation, and flotation to gradually separate the mixed heavy minerals into various single, high-purity commercial concentrates. The specific process design depends on the specific mineral composition and economic value considerations of the placer deposit.
