At present, dense medium cyclone coal preparation is recognized as an efficient coal preparation method in the world. Because of its large capacity and high separation efficiency, the dense medium cyclone is especially effective for the raw coal which is difficult to be separated or extremely difficult to separate. Its main working principle is: using high density dense medium suspension medium, under the action of centrifugal force, raw coal is mainly separated into gangue, clean coal or medium coal in dense medium cyclone according to density.
The coal preparation technology of dense medium cyclone is various. Among them, dense medium cyclone separation 0 ~ 50 mm raw coal process is widely used. At present, it has been applied well in some large and medium-sized coal washing plants in Shanxi, Guizhou and Anhui provinces, and has been recognized by users. The inlet pressure is one of the main variables that affect the performance of dense medium cyclone. If the inlet pressure is too small, the fluid rheology is not stable, and a large proportion of medium is diverted to the bottom flow, resulting in the clean coal misplaced into the gangue. Therefore, how to maintain the inlet pressure of hydrocyclone is a key problem. This puts forward higher requirements for the selection of the feed pump of the dense medium cyclone. Only the selection of feed pump is accurate and reasonable, can the inlet pressure of hydrocyclone be guaranteed, the separation effect and separation efficiency can be guaranteed.
Attention should be paid to the following aspects when selecting the feeding pump of dense medium cyclone
First, reasonable outlet diameter. The nominal diameter of the outlet pipeline should be the same as or slightly larger than the outlet diameter of the pump, and the flow rate in the pipe should be between 2.0 ~ 3.0m3/s; if the size of the inner diameter of the pipeline is too large, the flow rate of the pipeline will be too low, resulting in solid precipitation and blocking of the pipeline; if the pipe diameter is too small, the pipeline resistance is too large, which will consume the pump head and cause the inlet pressure of the cyclone to drop.
Second, the reasonable choice of pump speed. Due to the high density of the slurry transported, and if it is pressurized feeding, the particle size of raw coal is larger and the pump is seriously worn, so the pump with lower speed should be selected. The speed of 590? 730r / min is reasonable.
Third, the reasonable selection of pump impeller flow path. Because in the pressurized feed, the heavy medium contains a large number of large particles of raw coal, so the impeller flow path of the pump should be wider to facilitate the raw coal to pass through.
Fourth, the consideration of the height of back irrigation. In general, it is easy to ignore when selecting the type. However, in the case of relatively short conveying pipeline and strict inlet pressure requirement of hydrocyclone, the height of 2-4.5min should be considered.
Fifth, the understanding and calculation of the pressure value of the cyclone inlet pressure gauge. Understanding of the inlet pressure value of dense medium cyclone in the calculation process: this pressure value can be directly calculated by adding the clean water head and pipeline loss.
In addition to several other points for attention, the selection of feeding pressure of cyclone is the most important. It has been proved by practice that when selecting the parameters of feed pump, the pressure value required at the inlet of hydrocyclone (i.e. pressure gauge value) is directly added to the calculated pipeline loss according to the clean water head. In this way, the feeding pressure required by the hydrocyclone can be ensured in actual operation, and the ideal state of coal preparation effect can be ensured.