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Removed from the coal mine called coal mine entrance. The carbon thus obtained has very heterogeneous sizes, depending this on many factors. This coal is necessary to classification by grades and sizes. We will have to clearly define the limits of the qualities and sizes required for the application you are going to spend that coal. That is, it is making a most thorough possible classification of coal in order to give the different uses and applications it has. And all this is for what coal preparation is done.
The coal preparation process includes 7 stages:
l Separation of the types of coal by the looks of it
l Screening or particle sizing
l Crushing and breaking
l Mechanical washing
l Mixed coals
1. Separation aspect
Is applicable whenever there are well defined veins in the coal seam. The chopper is that it can be selected to thereby effect the separation.
Sieves are used to classify coal particle size. The sieves are square plates with grids of different sizes (mesh). This is what allows grading.
The sieves used industrially may be cylindrical or drum, oscillating (reciprocating screen). The latter are rectangular trays having a reciprocating motion. The velocity increases as the particle size decreasing.
3. Chosen hand
It applies to coals large. In a tape with 6 men chosen sterile at first glance to be detected are separated. The tape should have slow motion.
4. Crushing and destruction
It is smaller so better handling and outlet mall. The mechanical actions to be performed are:
l Wear or friction
In industrial equipment usually predominates an action, or several combined. According to the machine and the equipment used, they are obtained different sizes.
5. Wash Mechanic
This is to reduce the ash will give us the product in the combustion process. The cost of the manufacturing process after removal of ash and combustion lowers. Should take into account characteristics such as size, shape, elasticity, conductivity, humidictividad density.
Density is the most important in terms of sizing feature.
Washing processes can be dry and moist.
Dry: Based on the differences in density and dry friction. Also differences in elasticity
Wet: Based on the differences in size and shape. Also in the wet friction density and wettability and density.
Advantages and disadvantages of wet and dry washes and other aspects and photocopies
The so-called froth flotation process is the only process that goes for cleaning fine coal. Is to wet the coal particles with busrbujas foam. This foam will moisten the fine coal to thereby cleaning. The fine coal fleet with foam and impurities sink. This impure foam mass is passed through a filter to thus regain a more pure carbon.
The coal is mixed an auxiliary process within the preparation. The auxiliary processes can help complete the overall coal preparation. These auxiliary processes are:
l I drained
Flocculation is to recover water washing products of coal (fine powder coal ≤5 microns) and other products through the operation of certain elements that will precipitate. The most important function of this is to remove these products from the washing water and power and coal use in subsequent processes (pellets and briquettes). To this is added a kind of coagulant: starch, alginates, peptatos, alum (aluminum sulfate). Thus the flocs are formed. This process helps sometimes cyclones.
Dewatering involves removing part of the water with coals, because of the processes described above. To do this, go through sieves with metal grating. The size should be between 12-13 mm. For smaller sizes and centrifuged hoppers are used. For smaller sizes, vacuum filters and pressure filters are still used. The difficulty increases with decreasing size.
Mixing finally involves mixing various kinds of coals with different properties to the resulting mixture meets certain requirements that may be demanded by the end user.