Editorial - VGB PowerTech Journal 11/2014

Is pulverized coal firing still state of the art?

On one of our last family celebrations, after having discussed the usual topics such as holiday and diseases, we started talking about work. “What are you currently doing in your job?” I was asked. ”We are converting the start-up and co-firing system from fuel oil to pulverised coal,” I replied.

Of course I was told the usual stuff then. Pulverised lignite firing is nothing new, especially when wind farms and photovoltaic plants are being set up almost everywhere. Who needs the old coal-fired power plants in a world like that?

Good question – who really needs coal-fired power plants? According to media and quite a large number of people, coalfired power plants will vanished over the next few years.

Generally, I do not share this opinion and not only because I am an optimistic person. I pointed out the simple physical facts. Without the sun shining or the wind blowing, these plants generate 0.00 MW of power, even though their installed capacity could triple over the next few years. Of course, an energy storage facility could be the solution to store surplus power at times when generation exceeds demand. This is an approach, anyway. However, a solution for the huge storage capacity needed is still as far away as a working nuclear fusion reactor (approximately 2114, perhaps).

Of course I do not close myself to the general situation. As long as primary energy sources such as wind and sun are available, they should be used in order to preserve our limited resources of fossil fuels. If worldwide consumption remained constant, lignite deposits would last for the next approximately 5,000 years.

After surfing the internet for a while, you can also find quite good statistical data. One statistics, for example, deals with the average daily sun hours in Germany in 2013. They varied from state to state where we had between 1,360 hours and 1,690 hours of sunshine.
Similar data is also available for wind turbines. The average number of hours at full load amounts to approximately 1,500 annually over the last ten years.

The number of operating hours will surely increase, especially when more and more offshore wind farms will start operation.

Nevertheless, a year has 8,760 hours, so the question remains who will generate electricity for the remaining time of the year. According to operators, it will be the one who is able to optimally manage security of supply, production cost and environmental impact.

But let’s get back to the conversation with my friends. I told them something about the history of the Jänschwalde power plant. It was commissioned between 1976 and 1988 and retrofitted in the mid-1990s when it was equipped with a flue gas desulphurisation plant. Until 2010 it was operated mainly in base load, except during times when load was reduced at the weekends or at night.

Nowadays feed-in management is no longer a question of delivery contracts or being the cheapest supplier. Feed-in of energy generated from renewables has always priority and power plants are decommissioned or have to cut their output. To achieve this target with the older boilers at Jänschwalde, minimum load shall be reduced significantly by using a co-firing system based on pulverised lignite.

This solution allows use of locally-produced, less expensive pulverised lignite instead of fuel oil that has to be imported. By the way, pulverised lignite is ignited by a new plasma-based ignition system. This system had been tested at the Vattenfall Oxyfuel pilot plant.

I enthusiastically finished my explanations by referring to our VGB Symposium on “Fuel Technology and Combustion” where we deal with topics such as coal storage, processing, drying or combustion every other year.

From my point of view, pulverised coal firing is still state of the art and exiting, perhaps also due to the fact that we still have a certain “campfire mentality” in our genes.