FGD gypsum: indexing belt filter deployed in Scandinavia

November 2020

The reference at a glance


Production of FGD gypsum as a by-product of a power plant


Indexing belt filter

Operating site





Gypsum slurry washing


Reduction of residual moisture and removal of corrosive compounds through cake washing

BHS-Sonthofen is helping a power plant in Scandinavia transform a waste product back into a raw material: high-purity FGD gypsum with a residual moisture content of 10% (90% solids) can be resold directly to the construction materials industry. Since 2007, the power plant has been operating a flue gas cleaning system that uses a BHS indexing belt filter (BF). An additional filter has now been ordered. The combustion processes produce flue gas that is contaminated with sulfur compounds. Milk of lime is used to remove the sulfur compounds. Gypsum slurry is produced as a by-product, the residual moisture content of which must be brought down to 10% and any corrosive compounds need to be removed. The BHS indexing belt filter performs both of these tasks using its efficient cake washing. The system has been running smoothly since it was installed.

The BHS indexing belt filter installed in 2007 ensures a low residual moisture content, which in turn guarantees a high-quality FGD gypsum. The production process starts the necessary desulfurization of the flue gas. This is done by spraying milk of lime into the flue gas flow. The sulfur compounds in the flue gas react with the milk of lime, which are then absorbed. The gypsum slurry obtained through this process has a moisture content of 90%, which is dried down to 45-50% using a cyclone. This is where the BHS indexing belt filter comes in: it not only reduces the moisture content to the 10% that is required, but it also uses effective cake washing to remove corrosive compounds that have a negative impact on the gypsum’s suitability to be used as a construction material. The dried and purified FGD gypsum can then be sold as a final product.

In this application, it is especially important that the filters have high throughput rates. The solution from BHS-Sonthofen ensures this while also conserving resources, since the water used to operate the vacuum pump is also used for the cake washing, which saves fresh water. The Scandinavian customer is incredibly satisfied with the belt filter and is planning to partner with BHS-Sonthofen again for its upcoming capacity expansion.