Chalmers University researchers have discovered that a certain bed material improves the combustion efficiency of waste and biomass. The material decreases operating and maintenance costs significantly. In collaboration with the energy supplier Eon, the researchers have proven the concept in today’s commercial boilers.

The Chalmers team’s findings make combined heat and power (CHP) technology much more interesting both from a profit and a climate perspective, and start engineering smarter next generation designs.

The team’s discovery of how metal oxides’ oxygen-carrying properties can be used in circulating fluidized bed (CFB) boilers has been verified and scaled up from the lab to commercial reality within record time.

During last winter, from November 2014 to May 2015, the Chalmers researchers and Eon personnel conducted long-term testing with the new bed material in a state-of-the-art combined heat and power (CHP) plant, Händelöverket in Norrköping.

In one of the plant’s five boilers, P14, a 75 MW CFB boiler, the silica sand normally used was replaced with an ilmenite-based bed material. Bed material in the form of sand is used to even out heat fluctuations and make the combustion of the fuel more efficient.

Chalmers University of Technology. Image Credit: Chalmers University of Technology. Click image for the latgest view.

Chalmers University of Technology. Image Credit: Chalmers University of Technology. Click image for the largest view.

The iron-titanium mineral ilmenite and other metal oxides have a clear advantage compared to regular sand: they can transport oxygen inside the combustion chamber from places where there is an abundance of oxygen to places where there is a depletion in oxygen. When oxygen-carrying bed material is circulated inside the chamber mixing with the fuel, the oxygen is distributed evenly in time and space.

Fredrik Lind, PhD at the Department of Energy and Environment and project coordinator at Chalmers University of Technology points out the advantages, “This brings forth an array of positive effects, which testing completed in Norrköping confirms. The combustion becomes more uniform and efficient. The boiler’s total efficiency increases. The emission of carbon monoxide is lowered radically, as are problem related to ash fouling.”

“We are now sure that we are able to significantly lower the operational and maintenance costs in most of the thousands of fluidized bed combustor plants that are currently in use internationally,” he said.

It is too early to speculate in the exact gains but it is clear that the profit margin of each CHP boiler will improve significantly.

Eon is hoping to start using the new ilmenite-based bed material in two boilers in Norrköping this year, and have several other plants in line. Eon will also use its gathered experience to start offering a service concept that enables a transition to the new bed material.

Bengt-Åke Andersson, Adjunct Professor in combustion technology and Senior Specialist at Eon, who has worked with fluidizing bed technology for a long time said, “This is the biggest improvement I have experienced. A little like placing a turbo charge to the process. One of the advantages is that it enables the burning of difficult fuels like coarse waste. This could become crucial in the future, if we are to meet our climate goals.”

Professor Henrik Thunman got the idea to test metal oxides as bed material from another project where ilmenite was used as a catalyst to clean gas from tar in the biomass gasifier at Chalmers University of Technology. Suddenly he found himself with a solution for a problem that had eluded researchers and boiler producers for a long time: How to avoid unburned fuel in a commercial boiler?

The first scientific results were published in June 2013. Since then, the research has sped ahead toward being implemented in a real application.

Thunman said, “This shows the importance of having a critical mass of researchers and quickly being able to scale up basic and applied results. The concept is an offshoot from more than one hundred man years of research combined with the experiences we have built up under more than 10-15 years within energy technology.”

Last winter’s full-scale trial is the last in a long run of tests that have taken place over a period of two to three years, first in the Chalmers Power Plant, and from 2014 paralleled in Eon’s commercial plant. A key success factor is the fact that the Chalmers power plant contains the world’s largest research boiler. Another critical factor is this type of industry academy collaboration, which Chalmers and Eon have pioneered since 2007. As of today, Chalmers University of Technology collaborates with more than ten other global companies in similar manners.

Stefan Bengtsson, president and CEO of Chalmers University of Technology said, “Our work always focuses on specific challenges associated with sustainability, which requires systems thinking and multi-linked cooperation. This allows for long-term challenges to be at the core of specific cooperative projects, involving both research, education and utilization. This type of cooperation between Chalmers University of Technology and our industry partners favors the creation of new knowledge and a speedy innovation process. We can renew and be fast-moving together.”

Fredrik Rosenqvist, Head of Business Innovation at Eon Sverige confirmed Bengtsson’s view saying, “The knowledge developed in cooperation between Chalmers University of Technology and Eon is fostered by many years of research. Without this on-going close contact and Chalmers University of Technology’s fundamental understanding of industry needs, we would not be where we are today. Bringing along experience built up throughout the years, Eon now takes the leap from successful research to commercialization, giving the market access to a solution that not only favors the environment but also the economy.”

This work is for a narrow but very important set of people generating heat for power and heat for other uses. While not seemingly directly connected to daily life this work will impact utility bills for millions of people as boilers get upgraded.

There is more information available at the press release link above.  A research paper is expected to publish soon as well.

One does wonder, the discovery of how to avoid unburned fuel, the basic problem in pollution control, just how will this new view affect other combustion processes? This story is likely at the beginning.


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