1. A physicochemical process modelling system comprising a data processor, a user input interface, an output interface, a memory, and a data storage device, wherein, the storage device stores a library of initial models each having code for modelling a physicochemical process, said initial model library having a hierarchical structure with initial models at leaf nodes of the structure and physicochemical selection criteria at upper levels of the structure; the processor is programmed with: a model editor having an input interface for prompting user input of chemical species component data, a process description, and experimental data, the process description being in a natural language, a validation function for parsing the inputs, for performing semantic, contextual, consistency, and tolerance checks, and for automatically building equations according to rules associated with the process description, a simulator function for executing and integrating the equations built by the validation function, a fitting function for operating exclusively with data of the edited and validated model to fit physical and/or chemical rate constants to achieve a best fit with the experimental data, and an optimisation function for iteratively executing the fitted model with different process condition inputs until an output parameter is optimized; and the output interface outputs a simulation of a modelled physicochemical process to a user.