How coal-and-oil combination firing worked

How did a coal-and-oil-fired warship use both fuels?

Often by spraying oil over a coal fire to intensify combustion, gaining power at the cost of additional machinery wear.

The label could describe separate coal- and oil-fired boilers, but Almirante Latorre used oil sprayers over a coal bed. Injected oil intensified the fire and raised steam production quickly. That boost could produce valuable extra power without rebuilding the plant around a single fuel. The additional heat also damaged furnaces and boilers more rapidly, increasing the need for reconditioning. The system offered useful supply flexibility to a navy whose access to either fuel could vary.