Primary coal crusher keeps pace with demands of customer
27 July, 2013 at 6:48 am in Buy & Sell
The process of crushing coal to a more manageable size is an important step in the processing chain. Primary crushers reduce a wide range of large Run of Mine (RoM) coal to either a marketable product or a range that can be more easily handled by the preparation plant. More recently, as large mines try to crush RoM coal to a saleable product, the industry has seen the size of primary crushers grow. Moreover, crusher manufacturers are making improvements to the equipment that extends the life of the rolls and the average time between maintenance.
In the eastern U.S., where a majority of the coal production is washed, primary crushers are usually reducing a 20- to 24-inch feed to a more easily conveyed 4- to 6-inch top size. In the West, especially at large surface mines such as those found in the Powder River Basin (PRB), the raw feed to the primary crusher can be as high as 60 to 70 inches. Because the RoM characteristics, these mines do not wash coal and they are looking to create a direct-ship, 2-inch product. Employing some of the largest primary coal crushers, they are reducing 20- to 70-inch RoM coal to 2 inches in a single pass.
Another concern that surrounds the crushing process is the generation of fines. More than a dust control nuisance, excessive fines can be a safety issue. More mines are becoming cognizant of the fact that fines only create more headaches downstream, according to Mike Hamby, vice president-sales, Gundlach Equipment Corp. “In the past, the mines did not worry about generating fines,” Hamby said. “Fines are now viewed as wasted material and the mines are taking accountability all the way to the face. Fines represent product that is lost the moment it’s extracted.” Gundlach manufactures a single-stage, two-roll and double-stage, four-roll crusher. Editor’s note: Although feederbreakers and sizers could be considered primary crushers, this article defines primary crushers as single roll crushers and two stage crushers.
Real estate comes at a premium in coal country and another noticeable trend is that the mines want one piece of equipment that could do the job without multiple stages of handling in the smallest footprint possible, Hamby explained. Today’s crusher manufacturers are seeing more larger applications, 500 to 800 tons per hour (tph), rather than the traditional smaller installations (150 to 200 tph)
As far as improvements, Hamby sees a number of refinements being implemented to make today’s machines better. Gundlach has a coupling-mounted roll that allows quick removal and replacement. The company also offers a gear box that allows for the timing of the rolls to eliminate or dramatically grinding and reduce fines generation.
Wear materials is another area that Hamby says crusher manufacturers have made great improvements. “We just replaced a set of rolls in the PRB that had 50 million tons of life,” Hamby said. “As little as 15 years ago, we were very happy to get 8 million tons out of that same application.”ore separating line: http://www.china-mills.com/p36.html