Impreglon Assists with Efficiency of Belt Dryer in Biogas Plant

A regional biogas plant needed to improve the efficiency of a belt dryer. The intention was to find a suitable coating for the screw conveyor to minimise the effort required for regular cleaning.

But first, a brief summary of how biogas energy is generated. Corn and the remains of rye plants, liquid manure and poultry excrement are mixed together and conveyed into large silos. The mixture remains in the silo for up to four weeks. The emitted gas is collected in large, flexible domes above the silo and then incinerated in large motors. A generator linked to the motor converts the rotational motion to electricity and feeds it to the power network. The energy that this regional plant (our customer) produces is enough to supply about 1,200 households with electricity.

In addition to the gas that is burned to generate electricity, another waste product is the digestate, which is later spread on fields as fertiliser. The digestate can be processed in only two ways. It can be collected untreated and used, or it can be dried (dry fermentation) to eliminate the high moisture content, thus reducing the weight substantially. The second method offers the advantage that less capacity is needed to store and transport the digestate.

Impreglon was asked for help and examined the equipment on site. Our suggestion was to coat the conveyor with PlasmaCoat® with an embedded polymer layer.

Our customer applies the second method, drying the digestate in a belt dryer. The fermentation residue from the digestate is wet and sticky, however, and it must be spread evenly on the belt with a screw conveyor. After even brief operation the screw became clogged with digestate, making it difficult to spread the material on the dryer belt. The equipment had to be stopped regularly. The heat from the adjacent dryer channel dried the residue onto the screw conveyor. It did not take long for the digestate to harden and stick so firmly to the conveyor that a crowbar had to be used to laboriously remove the residue in little pieces.

Impreglon was asked for help and examined the equipment on site. Our suggestion was to coat the conveyor with PlasmaCoat® with an embedded polymer layer. This coating system has excellent nonstick properties and it is also resistant to the abrasive forces of the digestate on the screw conveyor. The result is extremely satisfying.

The Impreglon coating does not completely prevent residue from adhering to the conveyor, but the process is much slower now. The equipment can run longer and removing the residue is quick and easy. The digestate layer just needs to be pried away in one place. Then, the dry, extremely solid mass can simply be pulled off the conveyor in one piece by hand.

More About This Company