NOVELTY - System for optimizing and controlling particle size distribution and for scale-up of nanoparticle production in an aerosol flame reactor comprises aerosol flame reactor integrated with process instruments, where the reactor further comprises burner; precursor/reactant fed to aerosol flame reactor; stream input fed along with precursor or reactant to aerosol flame reactor; simulation tool with programmed instructions to cause the processor to couple flame dynamics model and particle population balance model.    USE - As system for optimizing and controlling particle size distribution and for scale-up of nanoparticle production in an aerosol flame reactor (claimed); where the nanoparticles are suitable for applications in the fields of ceramics, catalysis, coatings, electronics, chemical and mechanical polishing, data storage, and fuel cells.    ADVANTAGE - The system optimizes and controls the particle size distribution of nanoparticles; provides scale-up of production of nanoparticles with desired properties; provides cost effective and time saving method and system for optimizing and controlling the particle size distribution and scale-up of production of nanoparticles; reduces the number of trials or experiments to be conducted for scale-up, if not avoid them completely; provides details about the internal condition of the process equipment and insight into the phenomena that occur during the process.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) simulation tool with programmed instructions to cause the processor for optimizing and controlling mean particle size and specific surface area and for scale-up of nanoparticle production in an aerosol flame reactor integrated with process instruments, where the improvement in the simulation tool comprises coupling flame dynamics model with particle population balance model; and    (2) optimizing and controlling the mean particle size and specific surface area and for scale up of nanoparticle production in an aerosol flame reactor, involving determining the operating data for physical process parameters from the process instruments integrated with aerosol flame reactor, the mixing characteristics of the precursor or reactant at a particular concentration and the stream input fed to the burner of aerosol flame reactor with the process instruments; feeding the determined data to the simulation tool with the programmed instructions to obtain the simulated data for optimizing and controlling the mean particle size and specific surface area and for scale up of nanoparticle production, implementation of the simulated data obtained from the simulation tool; i) estimating the rate kinetics of the precursor oxidation reaction using the precursor to product conversion kinetics coupled to particle population balance model of the simulation tool with programmed instructions, obtaining the output as product particle size and specific surface area of the reactor from the simulation tool with the programmed instructions to optimize and control the particle size distribution and for scale up of nanoparticle production in an aerosol flame reactor integrated with the process instruments.