Clean Coal Processing
Because of its low cost and abundance, coal comprises almost 50% of the U.S. generation portfolio. Coal, like other fossil fuel supplies, takes millions of years to create, but releases its stored energy within only a few moments when burned to generate electricity. Because coal is a finite resource, and cannot be replenished once it is extracted and burned, it cannot be considered a renewable resource.
Usually, coal is utilized to convert water into steam in boilers. Coal is pulverized into fine powder, for proper combustion, and then it is fed to boilers for steam generation. The steam is then used to drive steam turbines. The turbine shaft is coupled to a generator shaft which generates electricity.
Wet Drum Magnetic Separator
Wet drum magnetic separators are employed in the preparation plant to recover the magnetite used in the heavy media separation circuit. Recent innovations in both magnetic circuit design, and materials of construction, have been applied to wet drum magnetic separators to maximize magnetite recovery and minimize wear and maintenance.
The magnetic element is the most important feature of a wet drum separator. In the design of a magnetic separator, the magnetic field intensity, and the magnetic field gradient, are two first order variables that affect separation response. Although there are several variables influencing magnetic separation, the magnetic field strength is indisputably the foremost variable for high levels of magnetite recovery.
There have been recent technological advancements in the design and modeling of magnetic circuits. Precise magnetic circuit modeling and optimization is now carried out using multi-dimensional finite element analysis. The North American industry standard is the Eriez 950 gauss Interpole magnetic element. This magnetic element maximizes the magnetic field strength and gradient resulting in high levels of magnetite recovery.
The counter-rotation wet drum tank style is preferred for heavy media applications. The drum rotates against the slurry flow in the counter-rotation tank style. Any magnetite that is not immediately collected will pass through to a magnetic scavenging zone. The short path that the magnetic material must be conveyed ¨C between the feed entry point and the magnetics discharge lip combined with the magnetic scavenging zone ¨C results in high magnetite recoveries.
Essentially all wet drum tanks used in heavy media applications have leveling spigots and a full width overflow that must be maintained during operation. A deviation in the overflow may result in inefficiencies in the performance and the loss of magnetite. A modification of the counter-rotation wet drum tank represents a recent development in technology for heavy media wet drum magnetic separators. The self-leveling tank has no discharge spigots to adjust or monitor and maintains a constant slurry level at any flow rate.
When a wet drum magnetic separator is properly applied, the magnetite loss will be less than 0.25g of magnetiteter of effluent. This generally equates to a magnetite recovery in the 99.8% to 99.9% range.
Modern Magnetic Separation
Modern magnetic separation equipment is essential in the removal of tramp iron for coal processing. Since pull strength of today¡¯s magnets is much greater than its predecessors, magnetic separators are an even more effective tool for preventing costly damage and shutdowns. Through the installation of advanced magnetic separation equipment, coal processing operations are running more efficiently than ever before.
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