Wastes of the wastes, Part 3

So we have covered several wastes of anaerobic digestion, and one waste of gasification.  How about the other major waste of gasification, fly ash.  Why is it considered fly ash? Because it literally flies away with the gas stream.  Fly ash produced in the gasification process can be harmful to humans if inhaled.  In order to protect the public this fly ash must be collected and used in a productive way.  First after the gasification process has converted nearly all of the solid material to gases, some solids are left over, the fly ash.  Because the fly ash is so light in weight it travels out of the reactor with the gas stream.  In order to separate the ask from the gas stream a cyclone is used.  A cyclone is a device that changes the path of the flowing gas so that is is spun, like the motion of a tornado.  This high velocity path that the gas/fly ash stream takes cause there to be centrifugal forces acting on the heavier object.  Centrifugal force can be though of as the force that holds water in a bucket when the bucket is swung over your head.  The fly ash in this case has the most centrifugal force acting on it and travels to the outside of the cyclone.  Here the fly ash is allowed to exit the cyclone to be collected.

What is there to do with the fly ash once it has been collected?  One typical way of utilizing this fly ash is to use it as a component of concrete.   The fly ash when added to concrete can increase both the strength and durability of the concrete.  This is not just a recent technology either.  The ancient Romans used materials that contained volcanic ash to build a lot of their aqueducts and monuments.  One reason these structures are still standing is due the increased strength and durability added to the concrete by the volcanic ash present.