Mr. Obama rarely plays with other politicians - though he has played 7 times with Vice President Biden. In a fence-mending gesture, Mr. Obama invited then-House Speaker John Boehner to play on one occasion in June 2011 along with Gov. John Kasich, both Ohio Republicans.
Here are some ways to classify coal (by grouping it with similar types of rocks): Because slag formed from lava-like melted rock, it's sort of like an igneous rock -- but because humans made the melt, it's not a true igneous rock. So, we made up a new classification for slag: We call it a pseudo-igneous rock (pronounced SUE-doe ig-NEE-us).
Coal slurry is a mixture of solids and liquids produced by a coal preparation plant. As a slurry, coal is separated from non-combustable components and can be fractionated by particle size as well. Coal slurry can be transferred by pipeline or with specialised pumps such as a progressive cavity pump to pump the highly abrasive, corrosive and viscous coal slurry. The scale of water usage and hence potential costs and problems is large. More than 7 billion tons of coal are mined per year, using ap