Coal preparation includes coal blending, homogenization, size reduction, grinding, screening and processing. The most important step is coal preparation or cleaning. The cost of coal preparation depends on the method used and the degree of beneficiation required, which largely depends on the market demand for the product. Almost all coal used for electric power generation and industrial boilers is ground or crushed and sized before combustion. The presence of incombustible substances or ash increases the net heat content, but it reduces dust, ash, transportation and shipping costs. The ash content will also increase the wear of coal grinding equipment and boilers.
Therefore, coal can be cleaned to varying degrees, and according to its type, its utilization takes into account the cleaning cost. Extremely dirty coal containing a large amount of foreign minerals must undergo extensive cleaning to meet market specifications. The final selling price of these coals is determined by the cost of the cleaning step.
Washing or cleaning of coal
Washing of coal is the most important step in the coal preparation process. Raw coal must undergo selective qualitative and quantitative analysis to find the most suitable coal cleaning operating conditions to obtain the required quality. Among these analyses, the washability test is the most important.
The main purpose of coal preparation is:
(1) Remove impurities in raw coal, reduce ash and sulfur content, improve coal quality, and meet the needs of users.
(2) Divide coal into products of different quality and specifications to meet the needs of users in order to effectively and rationally use coal and save coal.
(3) After coal is washed, the gangue can be discarded on the spot, which can reduce ineffective transportation and create conditions for the comprehensive utilization of coal gangue.
(4) Coal washing can remove most of the ash and 50% to 70% of pyrite sulfur, reducing the pollution of the atmosphere from coal burning. It is the premise of clean coal technology.
How is coal washed?
There are two main methods for washing coal, one is density separation, and the other is froth flotation. Both processes depend on the fact that the particles from which the coal sample is made have different densities. For example, when water is added to the sample, the particles will sink to different depths according to their density. In this way, the various components of the sample can be separated from each other.
Fengwang provides coal washing machine, which is a air chamber jig under sieve, used for the separation of lump coal or unsorted raw coal. In view of the status of coal in the global energy framework and the reasonable environmental concerns associated with it, the technology to produce clean coal is essential to achieve efficient energy production and reduce environmental footprint.
