New Bed Material Enhances Efficiency of CHP Technology

A recent discovery by a team of researchers at Chalmers University of Technology reveals that a particular bed material is capable of enhancing the efficiency of biomass and waste combustion, while at the same time minimizing maintenance and operational costs.

The Chalmers team partnered with energy supplier Eon to prove their theory using real-world boilers.

The research findings give new interest to combined heat and power (CHP) technology in terms of both profit and environmental impact, and paves the way for the development of smart, next-gen designs.

The team was successful in proving that circulating fluidized bed (CFB) boilers gain from the metal oxides’ oxygen-carrying properties. This concept was not just proved but scaled up to commercial level from the lab in a very short span of time.

Between November 2014 and May 2015, the Chalmers and Eon teams were involved in detailed testing of a new bed material in an advanced CHP plant, Händelöverket, Norrköping.

Out of the five boilers at the CHP plant, the P14 75 MW CFB boiler was chosen for the testing. Here, instead of the silica sand usually used, an ilmenite-based bed material was used.

Sand-form bed material is used to balance heat fluctuations in order to achieve more efficient fuel combustion. However, ilmenite, an iron-titanium mineral, and other metal oxides are more advantageous than sand. They are able to carry oxygen from places oh high concentration to those of lower concentration within the combustion chamber.

By circulating the oxygen-carrying bed material within the combustion chamber along with the fuel, the oxygen gets spread evenly across the space.

“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,” says Fredrik Lind, PhD at the Department of Energy and Environment and project coordinator at Chalmers University of Technology.

“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 says.

Ilmenite – The Bed Material of the Future from Chalmers Univ. of Technology on Vimeo.

Quick commercialization and climate win

Although the precise amount of profit cannot be ascertained at this time, it is certain that the profit for each CHP boiler will increase to a great extent.

Eon plans to apply the new bed material in two boilers in Norrköping, with other plants in the pipeline. Using the expereince gained from the research, Eon will be offering a service concept to enable a smooth transmission to the new bed material.

“This is the biggest improvement I have experienced. A little like placing a turbo charge to the process,” says Bengt-Åke Andersson, Adjunct Professor in combustion technology and Senior Specialist at Eon, and expert in fluidizing bed technology.

“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,” Fredrik Lind adds.

Professor Henrik Thunman borrowed the idea to test metal oxides as bed material from a project that used ilmenite as a catalyst to clean gas from tar present in a biomass gasifier. He derived a solution to the challenging query of how unburned fuel can be avoided in a commercial boiler. The initial findings were published in June 2013. From then onwards, the team worked towards applying the concept in reality.

“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,” Henrik Thunman says.

A product of Chalmers University of Technology’s take on industrial collaboration

The full-scale trial was the final in a series of tests carried out over two or three years, beginning at the Chalmers Power Plant and moving on to Eon’s commercial plant. The Chalmers Power Plant has the largest research boiler in the world, which proved to be a major advantage for the success of this project.

The industrial-academic partnership between Chalmers and Eon was another crucial factor. The Chalmers University of Technology continues this trend and currently partners with over ten other companies globally.

“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,” says Stefan Bengtsson, President and CEO of Chalmers University of Technology.

He adds “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.”

Eon confirms this view.

“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,” says Fredrik Rosenqvist, Head of Business Innovation at Eon Sverige.

The full-scale trial results will soon be reported scientifically.


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