This article presents a comprehensive study on simulation, estimation and control of size distribution in aerosol processes with simultaneous chemical reaction, nucleation, condensation and coagulation. Initially, a typical aerosol process is considered and a detailed population balance model is presented which describes how the aerosol size distribution evolves with time. The population balance is complemented with mass and energy balances that describe the evolution of the continuous phase species and temperature of the system. Sectional representations and unimodal lognormal moment approximations of the population balance model are then derived and solved, It is found that the moment model provides reasonably accurate estimates of the average properties of the aerosol size distribution computed by the sectional model for long times. Then, a nonlinear state estimator is constructed on the basis of the moment model. which employs measurements of the geometric average particle diameter to compute the evolution of the average properties of the aerosol size distribution. Finally, a nonlinear controller is designed on the basis of the moment model and is implemented on the sectional model to achieve an aerosol size distribution with desired geometric average particle diameter. The robustness properties of the nonlinear estimator and controller with respect to significant parametric model uncertainty are successfully tested through computer simulations.