Predictive design of nano-particle production via precipitation requires that the different steps through which particle formation occurs are deeply understood in order to control the final product properties and quality. In this work nano-particle precipitation in a confined impinging jet reactor (CIJR) is studied from the modelling point of view. The mathematical model, based on computational fluid dynamics (CFD), includes a micro-mixing model, the interchange by exchange with the mean (IEM) model coupled with the direct quadrature method of moments (DQMOM) approach, and solves the population balance equation (PBE) with the quadrature method of moments (QMOM). Eventually CFD predictions are compared with experimental data and good agreement is found.