A research team at the University of Nevada has developed a process takes de-watered sludge from a wastewater plant, and is able to efficiently dry it to the point that it can then be gasified into syngas, which can then be burned to produce electricity.
 Chuck Coronella, left, and Victor Vasquez, have developed a patent-pending fluid-bed system to dry wastewater sludge to be used for conversion to energy through a gasification and generation process. Photo by Mike Wolterbeek. |
I've been following the waste-to-energy field with interest for years. I was directly involved several years ago with Welton Myers trying to get a sewage-to-energy system installed in Ephraim, Utah (Ref.), which did not materialize because the technologies and connections between separate systems were not yet developed well enough.
So you can see why my interest was piqued today when I saw a story in the news about a University of Nevada research group headed by Chuck Coronella who are moving from the lab to the real world in a demonstration-scale system to turn wastewater sludge into electricity.
I phoned Dr. Coronella, associate professor of chemical engineering, to get some additional information and clarifications on the press release they issued last week.
He said that their process takes de-watered sludge from a wastewater plant, and is able to efficiently dry it to the point that it can then be gasified into syngas, which can then be burned to produce electricity.
This therefore solves two problems at once for the wastewater plant: it gets rid of the sludge, which is usually expensive to dispose of; and it produces electricity -- nearly half the amount needed to run the wastewater plant.
The process that Coronella's lab has been focusing on is a patent-pending fluid-bed system for drying of the sludge. The sludge typically contains around 80% water. But that goes down to around 20 - 30% after their process, making it suitable to then run through gasification.
Gasification is a well-known process, used in the coal industry, for example, in which carbonaceous material is partially combusted with a controlled amount of oxygen and/or steam at a relatively low temperature (compared to incineration or plasma), resulting in the production of syngas. The syngas, which consists primarily of hydrogen, carbon monoxide, and very often some carbon dioxide, can either be burned as fuel, or it can converted to synthetic natural gas. In this case, the syngas would be used to run a generator to produce electricity.
Some of the heat produced by the generator is used to facilitate the drying process.
Coronella said that though it is too early to predict accurately, he anticipates that the electricity will be produced in the range of 10 cents per kilowatt-hour, which is comparable to what the wastewater plant might be buying it for from the local utility, some places more than this, some less. He thinks the process could be commercially available in about two years.
In addition to sludge drying, Coronella expects that other applications might also eventually arise from their fluid-bed drying system, though they are focusing for now on the wastewater treatment industry.
The press release announced that the University of Nevada team's technology is scheduled to be set up in the Truckee Meadows Water Reclamation Facility next month following the recent signing of an interlocal agreement with the cities of Reno and Sparks.
"Our plan is to test the unit by about May 15," said Coronella. "We’re designing, building and assembling a continuous-feed system that will ultimately be used to generate electricity. We’ll run experiments throughout the summer, creating a usable dried product from the sludge."
The experimental carbon-neutral system will process 20 pounds of sludge per hour, drying it at modest temperatures into solid fuel that will be analyzed for its suitability to be used for fuel through gasification and, in a commercial operation, ultimately converted to electricity. The refrigerator-size demonstration unit will help researchers determine the optimum conditions for a commercial-sized operation.
"The beauty of this process is that it’s designed to be all on site, saving trucking costs and disposal fees for the sludge," Victor Vasquez, a University faculty member in chemical engineering said. "It uses waste heat from the process to drive the electrical generation. It also keeps the sludge out of the landfill."
Estimates, which will be further refined through the research, show that a full-scale system could potentially generate 14,000 kilowatt-hours per day to help power the local reclamation facility.
The demonstration-scale project is a collaboration with the cities of Reno and Sparks, operators of the wastewater plant. The city councils signed an interlocal agreement recently to allow the research to integrate into their operation, providing space for the experiments, the dewatered sludge and other resources to help make the project a success.
"Economically, this makes sense," Coronella said. "Treatment plants have to get rid of the sludge, and what better way than to process it onsite and use the renewable energy to lower operating costs." Coronella added, "This demonstration gives the University an opportunity to involve students in development of waste-to-energy technology, which ultimately will benefit the community. It's a win-win for everyone involved."
Installation of the system will begin in April, and the system will be tested mid-May. The project will last until fall 2010.
The University’s Technology Transfer Office, with assistance from the College of Business, is supporting the project with plans to make the system available to hundreds of communities around the country that operate water treatment plants.
For example, there are approximately 700,000 metric tons of dried sludge produced annually in California municipalities, which would sustainably generate as much as 10 million kilowatt-hours per day.
The project is funded through the Energy Innovations Small Grant Program, the California Energy Commission and the Department of Energy. This phase of the project was selected for funding by the Tech Transfer Office under a DOE grant to support transferring technologies from the lab to practical application.
The project is one of many of the University’s renewable energy research areas that have commercial potential to help Nevada’s economy grow.
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