Microwave-induced plasma gasification technology makes headway

By Bryan Sims | February 17, 2011

As rapid accumulation of MSW continues to stress landfills, many municipalities across the U.S. are in search of cost-effective, energy efficient technologies capable of converting millions of tons of this waste into saleable products. Plasma arc gasification is one technology that has gained a lot of attention in recent years as a solution.

Edinburg, Texas-based plasma gasification technology developer Plasma2Energy, along with its holding company Plasma Gasification Corp., intends to be part of the solution by deploying its patented version of plasma gasification units across the U.S.

While plasma gasification isn’t new technology, much of the developments in the field have centered on improvements to existing or older technologies. Traditionally, plasma gasification uses an arc or torch where temperatures can exceed that of the Sun’s surface, essentially vaporizing the incoming MSW material to make syngas that can be converted into electricity, biofuels and other products.

According to chemical engineering graduate and Plasma2Energy vice president Teo Tijerina, the company took a different approach for its technology. Instead of going by the traditional electrical plasma arc concept, Plasma2Energy’s “ABA Process” utilizes high intensity microwave induction to create a plasma field, which Tijerina said is a key factor that makes the plasma gasification reactor more energy efficient.

“The technology is able to convert a much higher yield in terms of energy in a reactor and, secondly, it has improved parasitic consumption, which is how much electricity the reactor needs to produce electricity,” Tijerina told Biorefining Magazine. “In old [plasma gasification] technology, the parasitic consumption is very high—anywhere from 40 percent to 80 percent, depending on the process. We’re in the 10 percent or lower parasitic consumption range.”

Traditional plasma arc gasification technologies inherently carry a heavy price tag when it comes to operating expenses and capital expenditure, but because Plasma2Energy’s ABA process uses lower electricity consumption, Tijerina said the investment placed on the technology by a municipality would pay for itself.

“We’re not as competitive obviously as oil, but at least we have a product now where a municipality can make money on it and not have to subsidize a product,” he said.

Based on batch and pilot reaction calculations, Plasma2Energy’s microwave-induced plasma gasification technology, according to Tijerina, is capable of converting one ton of MSW into approximately 2,000 to 2,200 kilowatt hours of electricity. This is substantially higher compared to other plasma gasification systems currently on the market, which typically convert up to 815 kilowatt hours, according to research Tijerina cited in a book titled, “Municipal Solid Waste to Energy Conversion Processes,” authored by Gary C. Young.

In addition to being converted into electricity, the syngas can go through a Fischer-Tropsch secondary process to be transformed into products such as diesel, gasoline and kerosene. In power generation applications, the syngas produced can also be piped into gas turbines at an average of 33,000 Btu per pound of waste. For a reactor of 120 metric tons per day, this translates into a generation of more than 17 MW. The ABA process itself takes up about 2 MW, leaving an excess of almost 87 percent of energy that can be internally used or sold to the public grid.

Additionally, MSW doesn’t need to be pretreated or finely-crushed, or require the separation of metals or soils. It can also contain oils and other petroleum-derivatives and include high levels of humidity, such as those found in feedstocks in sugarcane bagasse or pulp and paper waste.

“One of the main differentiating aspects of our technology compared to plasma arc or torch technologies is that it utilizes water contained inside the waste, where the water actually becomes part of the chemical reaction to produce the syngas,” Tijerina said. “We can bring damp waste into our reactor and in some cases we might even inject water to increase the conversion yield of the waste.”

Another product that is produced in the process is synthetic oil, which forms when the gas is cooled and condensates. The oil can be collected and re-fed into the process conversion to syngas, or it can be collected in its raw form and refined into various biochemicals or fuels, similar to how petrochemical refiners process crude oil, said CEO Rodolfo Sanchez.

“Depending on the composition of the feedstock, the plasma gasification reactors can produce between 40 and 50 percent synthetic oil per ton of MSW,” Sanchez said. “What we have seen on the characterization of MSW in Texas, it should be 45 percent oil in the first cycle of the process. If we convert all the material to produce syngas, we can generate at least 2.2 MW hours of electricity per metric ton of processed feedstock.”

Like other plasma gasification technologies, Plasma2Energy’s produces a residual, vitrified slag material as a result of the melting of metals and other silicates found in MSW, which account for roughly 1 percent of the coproduct stream. The slag material can be sold as an aggregate for road construction.

Currently, PG Corp. has a 150 metric ton per day pilot facility under construction in Monterrey, Mexico, along with a 10 metric ton per day batch reactor that’s being validated by Monterrey-Tech University in Mexico. According to Tijerina, Plasma2Energy is looking to deploy a larger plasma gasification facility in Texas, which would ultimately serve as demonstration and training grounds prior to commercial roll-out.

“We want to become primarily a licensing company, where our initial plant would be a demonstration plant that conducts trial runs, training as well as operations to prove out the efficiencies that our calculations show to prove commercial viability,” Tijerina said. “And then, thereafter, we really want strategic partners to get the technology deployed as quickly as possible. We think that there’s a huge opportunity out there for everyone, and we also believe that it’s in our national interest to use more waste for energy and wean ourselves from foreign oil.”