Black liquor recovery design

Black Liquor Recovery Boilers Many special boiler designs have been developed around the world for the pulp and paper industry, including black liquor recovery boilers. 

Various permutations of the black liquor recovery boiler design are used to combust soda liquors in the soda pulping process and alkaline earth liquors and ammonium liquor (red liquor) in the sulfite pulping process. 

Black liquor is not an ideal fuel, partly because of its moisture and partly because of the very high ash content, i.e. the inorganic elements. It has been difficult to achieve steam temperatures above 480°C, compared to 540°C with coal. The ability to generate electricity can be achieved only with higher combustion temperatures by burning at a higher solids content (80%). Newer steels and designs can limit corrosion from small amounts of chlorides and potassium. New recovery furnaces can have rated capacities of over 2500 tonnes of dry solids per day. 

Loutfi H., Blackwell B., Uloth V, Lignin recovery from kraft black liquor prehminary process design, Tappi J., 74(1), 1991,203-210. 

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