A New Twist on Gasification
A research team at SUNY Cobleskill has a giant undertaking ahead of it, demonstrating and developing applications for an innovative gasification technology prototype that holds promise for alternative and purposeful waste disposal.
As its name suggests, the rotary kiln gasifier facilitates a natural rotation providing agitation of the feedstock at high temperatures and allowing for a more complete conversion of all the feedstock to syngas. Contrary to traditional gasifiers, it sits horizontally and at a slight slope, allowing for a gravitational flow that moves the feedstock through the system, Goodale says. "The hope is that we don't turn too fast, but we turn fast enough to keep the feedstocks moving and we put it on a slight angle so that gravitational flow, along with the rotisserie, moves the feedstock from the point of entry to the point that they're totally transitioned from their biosolid state into a biogaseous state," he explains. "We control the speed and control the angle, and therefore control the rate of movement from entry to exit. We want it to be fast enough so it doesn't sit there in the chamber. We want it suspended." The primary approach is to establish a working 100-kilowatt (kW) prototype of the gasifier, dubbed TurnW2E, at SUNY to serve as a research demonstration, with installation of a 1-megawatt gasifier in the following phase. "This technology is innovative with the potential of revolutionizing the way biowaste is handled today," Goodale says.
W2E owns the rights and the technology to the TurnW2E prototype, but is sharing the license with Goodale and his SUNY team for use and research in SUNY's $4 million Environmental Science and Technology Center. The gasifier, which reaches temperatures up to 2,000 degrees, has not arrived on the campus yet, awaiting completion of the center. Once it is installed there, Goodale's team will focus on feedstock and syngas handling. Not only can the system take almost any type of feedstock, but those feedstocks can be fed separately or commingled. "We don't separate our materials," says Renee Comly, W2E CEO and director of business development. "We can take almost anything. I think every gasifier says that, but we can take almost any volume so our feedstock does not have to be at capacity and it can be used at lower volumes at different times of the day." Material is preprocessed for the gasifier, which has a 1:5 ratio for capacity, she adds.
As part of SUNY's Biowaste Conversion to Bioenergy Through Gasification project, Goodale will experiment with feedstocks such as paper, green waste, cafeteria waste and organic municipal solid waste in the rotary kiln gasifier. But will the system require reconfiguration to take all the different types? Goodale says no. "[W2E] believes they have it perfected to the point where it doesn't have to be reangled and they think that they have the speed of rotation where it needs to be for the feedstocks that we are putting into the kiln," he says. "I don't think this is going to need to be readjusted." The feedstock flexibility is a direct result of the slope and rotation of the kiln. Although modest, the slope controls the speed that feedstocks move from entry point to total gasification. "I don't know of any other gasifier or any other kiln or any other method of digestion that can handle this diversified feedstock stream," Goodale says.
Energy value will vary depending on feedstock, but an important aspect to consider, according to Goodale, is the project does not require growing crops and changing land mass.
W2E is in the process of launching the technology, with patents pending, and Comly is not comfortable releasing details about the happenings inside the chamber. She does share, however, that TurnW2E consists of different zones, giving it an efficient output. While SUNY's prototype will be for batch runs only, the rotary kiln gasification process is being used continuously at an industrial park in South Korea, where 100 tons per day of industrial waste from a mattress factory is converted to steam and sold to tenants of the park, Comly says. The system is also being installed in Cochin, India, where it will produce power from industrial and local wastes. In addition, a system is under construction at Eielson Air Force Base in Alaska that will serve as a demonstration and validation unit producing electricity from waste for the local grid.
Once the system reaches SUNY's laboratory, Goodale will evaluate the cleanliness of the syngas, expecting favorable results. "I'll be looking at how clean the gas pipe is and my hypothesis is that the pipe will be clean," he says. Because of the high temperatures, the system does not produce significant tar. "If not, we'll remove any tar and put it back through the kiln." Tar is a combustible, composed of hydrocarbons, and Goodale emphasizes that anything combustible will be used inside the kiln. "We want to do whatever is necessary to have a clean gas, as clean as possible, exiting the kiln.
"This is a very rich team in the sense of their knowledge base and we're really pioneers with this," he says. "No one has this prototype but W2E. Being one of a kind, we think it will make it possible for us to roll out this technology." During prototype batch runs at SUNY, the feedstock and syngas properties will be evaluated. His team will focus initially on electricity generation, but Goodale plans to explore liquid fuel options for the system in the future, under the assumption that the syngas can be turned into diesel and gasoline.
While there is no steadfast timeline, there is interest from government agencies in the scale-up and use of the rotary kiln gasifier. The U.S. DOE and the U.S. Department of Defense have issued grants to SUNY for the project and the DoD has a particularly significant interest in it. "The army certainly recognizes that wherever we have troops stationed, it is a substantial investment to care for our troops," Goodale says. "We have to care for them and that comes on the dollar of the taxpayer here in the U.S." Mess halls, for instance, produce substantial amounts of waste that usually winds up in landfills. The Military Academy at West Point, a project collaborator, sends its food waste to out-of-state landfills, Goodale says. That garbage can be converted to energy and used on-site for military operations. "That's why the U.S. Army has said, ‘Yes, let's put some money into the SUNY Cobleskill project,'" Goodale says.
"It has multiple applications as a stand alone, to generation of power to combined heat and power," says Philip Darcy, energy and environmental integrated production team leader for the DoD. The rotary kiln gasifier is an economic alternative to waste disposal, he adds. "It has the capability to reduce logistic support to forward application and recycle (thermal) wastes on installations, extending landfills and reducing costs of operations at the installations." The military is asking that the technology be transportable, allowing for easier deployment at multiple locations. Estimates by the Logistics Management Institute in a 2003 report indicated a cost of between $62 and $903 per ton for in-theater waste disposal and a cost to the DoD of $13 per gallon to deliver fuel to supply depots in-theater with additional transportation costs to battalion support areas, according to SUNY Cobleskill.
In agreement with Darcy, Goodale says the system is economic compared with other waste-to-energy processes such as anaerobic digestion (AD). AD systems are probably no pricier than rotary kilns as we've known them for years, but the gas they produce is not clean enough for internal combustion engines, so a backup engine is needed when the first one needs cleaning, Goodale says. The cylinders need to be cleaned and the residues need to be removed from the walls, representing added cost not necessary with rotary kiln gas, which is nearly free of methane. In addition, the payback period for AD systems tends to stay above 10 years, compared with between five and 10 for a rotary kiln, Goodale says, adding that that has yet to be proven. "I'm making a hypothesis that the rotary kiln gasifier will be very economic for these reasons: fairly short return on investment period, cleaner gas than the alternatives, and utilizing feedstock that is heretofore considered waste and not investing in growing a crop," Goodale lists. "This man believes that the system will prove itself to be very economic.
"Keep funding coming, DOE people, and we'll see if we can't do something that's going to, not at the end, but at some milestones, bring a real revolutionary method of handling both the military and society's waste streams," Goodale says. BIO
Lisa Gibson is a Biomass Magazine associate editor. Reach her at firstname.lastname@example.org or (701) 738-4952.