| Reactive precipitation is an important and common unit operation in the field of chemical engineering and has been widely used for producing solid particles of high purity from a liquid phase at low cost. For the purpose of practical application, the effective control of the precipitation must be achieved, since the quality of the product has crucial effect on the solid-liquid separation and the properties of particles, such as the specific surface area, the particle morphology, the particle size and the purity. For many precipitation applications, the particle size distributions (PSD) is of primary importance to the quality of the product. Quality requirements such as the mobility or the dissolution rate of the produced particles can be directly related to their PSD. Furthermore, the PSD directly influences the performance of the downstream separation units. From the viewpoint of industrial application, the key concerns are the refined control of the PSD, and notably the improvement on process reproducibility. During the precipitation process, the PSD is determined by a number of simultaneously occurring phenomena within the precipitator. The main phenomena are the primary nucleation of crystals, the subsequent growth and the agglomeration. Despite its industrial importance and long history, the design as well as the operation of continuous and batch precipitators still shows some difficulties, one of which is how to determine the operation conditions for obtaining the required PSD in continuous and batch precipitators. For the solution of such operation problems and obtaining a more thorough understanding of certain phenomena occurring in the reactive precipitation process, both experimental and numerical studies are carried out in present work. The mathematical modeling and numerical simulation have proven to be a valuable tool.The primary aim of present work is to develop a new method that can simulate the reactive precipitation process in a batch reactor. Based on the population balance and mass balance of reactive precipitation process, a numerical simulation model is developed to predict particle size distributions (PSD) and its evolution in a reactive precipitation process. The reaction-precipitation system of BaCl2 with Na2SO4 to prepare BaSO4 in aqueous solution is adopted to obtain ultrafine particles in a stirred precipitation reactor. The particle size distribution and the morphology of the particle are observed under Transmission Electron Microscope. It is illustrated by the experimental observation of the micrographs of BaSO4 particles obtained, that apparent agglomeration occurs between the particles, which phenomenon is taken into consideration in the present model. The population balance equation is solved by a discretization method to obtain the particle number and the particle size distributions. By implementing the model, the reactive precipitation process in a batch reactor including reaction, nucleation, growth and agglomeration is simulated. The simulation results are validated by the experimental data of BaSO4 precipitation and the literature data of NaBO3·4H2O precipitation. Further analysis is endeavored to explore the effects of some important operational parameters including the degree of supersaturation and precipitation time on particle size, particle size distribution, volume-based characteristic particle size and the variance of the particles. It is depicted that the particle size and particle size distributions are controlled by supersaturation, precipitation time and agglomeration between the particles. Stemming from the analysis in the context, the disciplinarian of the influences of these factors and the method for controlling particle size distributions are presented for the reactive precipitation process. Still further, the present model is expanded to model the reactive precipation in a continuous precipator with the system of BaCl2 and Na2SO4, which provideds a foundation and a new tool for following research in the field.
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