HMS and DMS are acronyms for Heavy (Dense)Medium Separation and is applied to the process of pre-concentration of minerals mainly the production of a high weight, low assay product, which may be rejected as waste. In principle it is the simplest of all gravity processes and is a standard laboratory method for separating minerals of different specific gravity. Fluids of suitable density are used so that the minerals lighter than the fluid float and those denser sink.
Closely sized samples are required for optimum separation. The ore sample to be tested is crushed to the required top-size and screened at at appropriate sizes (we and dry screening is carried out at 38-75 microns if these sizes are to be examined). A typical size distribution on crushed drill core would be 2440, 850, 300, 106 and 38 microns from a top-size of 3350 microns.
Dense medium separation (or heavy medium separation (HMS), or the sink-and-float process) is applied to the pre-concentration of minerals, i.e. the rejection of gangue prior to grinding for final liberation. It is also used in coal preparation to produce a commercially graded end-product, clean coal being separated from the heavier shale or high-ash coal.
In principle, it is the simplest of all gravity processes and has long been a standard laboratory method for separating minerals of different specific gravity. Heavy liquids of suitable density are used, so that those minerals lighter than the liquid float, while those denser than it sink (Figure 11.1).
Since most of the liquids used in the laboratory are expensive or toxic, the dense medium used in industrial separations is a thick suspension, or pulp, of some heavy solid in water, which behaves as a heavy liquid.
The process offers some advantages over other gravity processes. It has the ability to make sharp separations at any required density, with a high degree of efficiency even in the presence of high percentages of near-density material. The density of separation can be closely controlled, within a relative density of 0.005 kg l -1 and can be maintained, under normal conditions, for indefinite periods. The separating density can, however, be changed at will and fairly quickly, to meet varying requirements. The process is, however, rather expensive, mainly due to the ancillary equipment needed to clean the medium and the cost.
Warning ORGANIC HEAVY LIQUIDS ARE TOXIC. INHALATION OF FUMES IS EXTREMELY DANGEROUS AND A THE FUME CUPBOARD WITH DOWNDRAFT VENTILATION MUST ALWAYS BE USED. SKIN CONTACT MUST ALSO BE AVOIDED (USE RUBBER GLOVES). HOWEVER, IF THE SAFETY PRECAUTIONS ARE STRICTLY ADHERED TO, THE OPERATION IS QUITE SAFE.
In the production of the diamond plant, heavy medium separation/ dense medium separation processing technology is very important, directly related to energy utilization, resource conservation, and production efficiency, considered to be one of the most effective methods of gravity separation. DMS technology can be used for coal washing and separation of diamonds and other precious stones, recovery of gold and platinum group metal (PGM), and treatment of copper, lead, zinc and other metal ores. In recent years, with the continuous improvement of peoples awareness of environmental protection, traditional mineral processing technology is increasingly unable to meet the actual needs of protecting the ecological environment. As a technology that has an important impact on Chinas sustainable development, innovation and improvement of heavy medium mineral processing technology and management are very necessary. The article outlines the process flow of heavy medium mineral processing technology. Overview of the process flow of heavy medium mineral processing technology (1) Sorting of heavy minerals in lump ore. This process is mainly to separate the ore and ore bodies and to place mixed mineral materials in the heavy medium cyclone. Because the heavy medium sorting machine has a high precision advantage, can process mineral materials in large quantities, it is used in separating and mixing mineral materials. It has great advantages and improves the efficiency of mineral material sorting. This process is generally applicable to large-scale concentrators. At present, the process problems in this process are mainly reflected in the difficulty of management and the difficulty in recycling, which affects the improvement of production efficiency. (2) Jig rough selection. In the jigging process, the refuse discharging density is usually guaranteed at 1180 kg per square meter, the jig machine adopts pre-exhaustion can effectively reduce the strontium content in the mineral resources. The influence of the previous sorting process avoids the wear damage caused by the krypton content of the cyclone, meanwhile, ensures the service life of the cyclone, which has a certain superior effect on the technical upgrading of the jig sorting system and the large fluctuation of the ore body.
(3) Mine body jigging. In this process, mainly through the mineral-heavy medium cyclone separation process, sorting and processing of mineral products, the process has the advantages of high precision, large processing capacity, and low cost, but there are also some shortcomings, mainly reflected in low yield and low separation efficiency. Therefore, the process is more suitable for concentrators with stable minerals. (4) Secondary separation of the heavy medium cyclone. In the secondary sorting process of the cyclone, the process flow is firstly operated by the quarrying stone technology, and the crushed mineral product is secondarily sorted with the concentrate. Since the two products are simultaneously sorted, the process flow It is more complicated, and two sets of media recovery equipment are needed in the process. This also shows that the operation cost and construction cost of the process itself is high, and the daily management and maintenance involved are also more. (5) Two-product heavy medium cyclone sorting. The heavy products and minerals are effectively sorted by a low-density cyclone, and the heavy products are sorted again after sorting to obtain minerals. The two-product heavy medium cyclone sorting process itself has high raw material requirements, so the process operation is also difficult and the operability is relatively low, so this process is not common in Chinas mineral processing work.
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The dry dense medium separation of iron ore based on floating and sinking of ore particles in a gassolid fluidized bed was investigated using zircon sand as the fluidized medium. The float-sink of ore particles with mean size Dave=23.6mm was investigated as the fluidizing air velocity and the float-sink time were varied. It was found that gangue with density less than 2850kg/m3 which float is able to be separated from valuable ore with density greater than 2850km/m3 which sink. The set point (density where half the particles float and half the particles sink) decreases with increasing the air velocity, and that the float-sink separation is completed within 2min. The influence of different sized ore particles in the float-sink experiments was also investigated. As a result, the iron ore with Dave17.6mm are successfully separated. As Dave decreases below 17.6mm, the ore particles with density near the set point tend to scatter in the fluidized bed without floating or sinking, resulting in separation efficiency which decreases with decreasing Dave. This indicates that the size of the ore particles is one of the major factors to achieve high separation efficiency.