Formation of fly ash

From raw material to construction material

Fly ash is produced when hard coal is burned to generate energy. For the combustion process, the coal is ground in coal mills to particle sizes < 90 µm and injected into the boiler. Hard coal does not consist to 100 percent of carbon, however. Depending on the coal used, 5 to 35 percent non-combustible, mineral adjoining rock is also blown into the boiler and remains as ash.

At temperatures of 1200 °C in the combustion process, the non-combustible, mineral components do not become liquid. They merely melt on the surface and are swept along with the flue gas stream during injection into the boiler. The fly ash cools rapidly in the flue gas stream and forms spherical, predominantly amorphous particles.

To separate the fly ash, the flue gas stream is passed through multi-stage electrostatic precipitators and then transported via conveying lines to silos, where the fly ash is stored until being delivered to its destination by rail, ship or truck.

Storage and transport

In the construction and building materials industry, efficient and sustainable logistics chains are a key factor for success. Customers expect to receive products on time and in the quantity and quality they need.

Our flexible logistics strategies, a variety of storage options, and large silo capacities give us the expertise and the means to deliver our products quickly and reliably and ensure security of supply.

On the one hand, this enables us to meet our disposal obligations vis-à-vis our power plant customers, and on the other hand, access to large silo capacities and versatile transport routes mean we are able to ensure the best possible security of supply for our building materials customers – even in the months when power plants tend to produce less fly ash.

As complying with all environmental and safety standards is just as important to us as delivering reliably to our customers, we regularly review and optimize our logistics concepts. In doing so, we aim to

• shorten transport routes,
• link routes with each other and
• for example, utilize vehicles to the best possible capacity,

primarily to the benefit of the environment. Over the past five years, this has enabled us to reduce our emissions by 25 percent.