A method controls mass and heat loading of sludge feed into a fluidized bed combustor (FBC) controlled via regulation of a polymer dosage or a sludge feed rate including: continuously monitoring at least one performance characteristic of the FBC; producing an input signal characteristic; analyzing the input signal and determining a first rate of change of the characteristic; generating an output signal based on the first rate of change to control addition of polymer to the FBC; generating a second output signal to control addition of sludge feed to the FBC; and determining a transition point between the addition of polymer and addition of sludge, which transition point is an upper limit of a first rate change to maintain flow so that the value of the characteristic is maintained proximate at the upper limit.