Abstract: A method is disclosed for controlling or monitoring the injection of one or more solids in a system, process, unit or apparatus by mathematically modeling the independent injection of the solids to maintain a determined or pre-determined ratio, percentage, fraction or relative amounts of total solids injected. The model uses historical process data, current process data and/or data from an external source to adjust set points in the master controller to maintain a predetermined amount of solids to be injected within a given period of time. In accordance with the process of the invention, new set-points are generated in the master controller using variables other than a unit or system response variable as input into the model.