Plasma-Arc Gasification

Plasma-Arc Gasification is a unique form of gasification that utilizes plasma torches to generate the highest temperatures of any type of gasifier. Plasma is an ionized gas that forms from high currents of electricity passing through the air across two electrodes. Plasma is sometimes called "the fourth state of matter" after solid, liquid, and gas. We see plasma in nature in the form of lightning bolts and also on the surface of the sun. The fundamental advantage of utilizing plasma is that it generates much higher temperatures than other technologies, and since it is electrically powered it can be fired up at the flip of a switch (a pretty big switch!) and attain operating temps almost immediately, and be shut down just as quickly. Plasma torches can generate heat up to 10,000 degrees.

Plasma gasification utilizes two primary techniques, the transferred torch and the non-transferred torch. The non-transferred torch has the electrodes inside the torch body and on the outside of the gasification reactor, air is blown through the torch across the plasma arc and into the gasifier. This it the type of system developed by Westinghouse-Plasma Corp which is the world leader today in gasifying MSW. I will detail the Westinghouse technology quite a bit in my blog.

A transferred torch places the electrodes inside the reactor and the arc is made inside the reactor. Proponents of this technique claim better heat transfer and electrical power efficiency, the downside may be greater wear on the torch because of the corrosive nature of the gases. Transferred torches are used in electric arc furnaces in the steel making industry. Heat also needs to be balanced between making sure there is enough to effectively break down all of your feed and the resulting tars while at the same time protecting the interior of your reactor and its refractory lining. Uncontrolled heats will damage the reactor.

Plasma torches have been used for many years to dispose of hazardous wastes and to melt foundry wastes and incinerator ashes. The military has also used the technology to destroy chemical weapons.