About process control of polypropylene

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In the next few years, the apparent consumption of polypropylene will still maintain a high growth rate, and imports will increase. The polypropylene industry has broad prospects in China. For now, polypropylene is a deep-processed product of refinery companies. At present, the production process of polypropylene can be divided into five categories according to the polymerization type: solution method, slurry method, bulk method and gas phase method, and bulk method-gas phase combined process. On their production lines, the quality parameter of viscosity or molecular weight is generally collected to judge the reaction of materials, so as to control production in a timely manner. However, as far as we know so far, most manufacturers use offline laboratory sampling and analysis, which has a certain time lag. Therefore, online detection of viscosity has great guiding significance. The general principle is as follows (the specifics will depend on the working conditions): 1. In order to improve the reaction effect in the kettle, almost all polymerization reaction kettles are equipped with a stirring device. For the specific reaction device, the torque required for stirring is related to the material viscosity, temperature, density, liquid level height in the kettle, stirring speed and other parameters. ； 2. Unlike usual viscous Newtonian fluids, the viscosity of polymers changes with changes in shear rate and must be modeled using liquid rheology principles. ； 3 The model requires only three input parameters (the introduction of other parameters will have a small improvement in measurement accuracy and can be ignored): Torque (stirring power), which indicates the work consumed by stirring. ； Stirring speed, this parameter characterizes the shear rate ； Polymer temperature, the influence of temperature on viscosity also shows a serious non-linear relationship, and compensation and correction must be carried out. The biggest advantage of this online viscosity detection system is that it is installed directly on the production line and does not require sampling, so there will be no problem of blocking the sampling pipeline. You are all experts on the production line. Please give us some valuable suggestions!