One ISU researcher plays an important role in designing the future of next generation biofuel technology. Nicholas Creager, graduate student in mechanical engineering, designed and built a prototype gasifier, which combines elements from gasification and fast pyrolysis to produce transportation fuels.
This gasifier is part of a two-step process. The first step is to convert bio-oil into a gas mixture called synthesis gas or syngas and the second step is to synthesize the product into transportation fuel, said Song-Charng Kong, associate professor in mechanical engineering.
”We are focusing on the first step,” Kong said. “We gasify bio-oil to produce syngas.”
Traditionally, gasification uses a biomass feedstock, such as corn stover, corn cobs or wood chips, and exposes the material to high temperatures of 700 C or greater with controlled amounts of oxygen and/or steam to produce a mixture of gases called synthesis gas, Kong said. The end product can be processed into transportation fuels.
Fast pyrolysis, on the other hand, works by exposing a feedstock to brief amounts of extreme heat in the absence of oxygen to produce a liquid called bio-oil. A catalyst, such as microbes, then converts the bio-oil into transportation fuels.
This new gasifier combines elements from both approaches. Bio-oil produced from pyrolysis is loaded into a gasifier which produces syngas.
Creager said the concepts for this prototype originate from a proposal written to the U.S. Department of Energy in 2008 by Robert Brown, director of ISU-based Bioeconomy Institute and the Anson Marston distinguished professor of engineering, and the late Victor Shang-Yi Lin, professor of chemistry. Creager said in 2009 the project was awarded to the chemistry department, which put the ISU-based Center for Sustainable Environmental Technologies in charge of building the gasifier. About this time, Creager was just joining the program.
“I started my graduate program in 2009,” Creager said. “My project is to design, build and test the gasifier.”
Several specifications were laid out in a U.S. Department of Energy grant for the gasifier design, Creager said. Taking those design parameters, Creager laid them out in sequential order of importance and reaction order for the system to function. From there, Creager spent the next two years researching and designing the gasifier.
“I looked a lot into literature of other gasifiers that had been built and really looked into how they were built and what properties they had that made them functional and incorporated them into the design,” Creager said.
Through dedication and hard work, Creager built the gasifier in January 2012 and has been running tests since June. The next phase in the project: building it on a commercial scale.
Brown said one problem associated with gasification is that gasifiers are typically built in giant scale with fairly expensive equipment. The large scale reactors are built with extra external equipment for preliminary processing. A series of lock hoppers, choppers, grinders and dryers turn biomass feedstocks into a more manageable form, such as pellets, which is then fed into the gasifier reactor to produce syngas.
This new concept removes the preliminary processing step. Biomass is first sent through a fast pyrolysis machine which produces bio-oil, Brown said. The liquid is then fed directly into the gasifier reactor. This concept supports smaller reactor sizes which reduces construction and maintenance costs.
“We are really focusing on the scalability of this gasifier to make sure it does represent a large scale system,” Creager said. “It gives you a better insight of what will be possible in the future if they were to scale this bio-oil gasifier up and use it for full production.”