plants designed for lignite (brown coal) are increasingly used in locations as varied as germany, victoria, australia, and north dakota. lignite is a much younger form of coal than black coal. it has a lower energy density than black coal and requires a much larger furnace for equivalent heat output. such coals may contain up to 70% water and ash, yielding lower furnace temperatures and requiring larger induced-draft fans. the firing systems also differ from black coal and typically draw hot gas from the furnace-exit level and mix it with the incoming coal in fan-type mills that inject the pulverized coal and hot gas mixture into the boiler.