How can coal slag protect the channel walls in an MHD generator?

In a coal-fired magnetohydrodynamic (MHD) generator, coal slag serves as a protective coating for the channel walls. Under the high-temperature conditions of the generator, the slag becomes molten and forms a layer that covers both the insulator and electrode walls.1

This slag layer provides several functional benefits:

• Thermal Protection: It reduces thermal losses to the channel walls, which more than compensates for any minor electrical losses caused by the presence of the layer.1
• Electrical Conductivity: The layer possesses sufficient electrical conductivity to facilitate conduction between the hot gas and the electrode structure. Crucially, this conductivity is not high enough to cause significant leakage of electric currents, which would otherwise result in power loss.1

By effectively insulating the structural components from the extreme heat of the combustion gases, the slag layer helps maintain the integrity of the generator channel during operation.1