Abstract: This application concerns methods and apparatus for use in industrial waste recovery operations such as recovery of non-consumed chemicals in industrial processes, with recovery of quick lime in a wood pulp process being an example. In some embodiments, methods comprise baking lime sludge in a kiln and controlling a temperature in a calcining zone of the kiln to be above about 2250° F. to vaporize sodium contained in the lime sludge. Interaction of the vaporized sodium with SOx can deter accumulation of one or both of CaCO3 and CaSO4 on one or more inner surfaces of the kiln. In some embodiments, lime sludge can be rinsed to generate a filtrate comprising dissolved NaOH, and the filtrate can charge a scrubber for removing SOx from an exhaust from the kiln. Embodiments of co-fired burners for heating such kilns by burning petroleum coke and natural gas are also disclosed.