Characteristics of Solid Phase Grafting Reactor with Double Helical Ribbon Impeller

摘要

Polypropylene (PP) grafted maleic anhydride (MAH) is widely used in polymer modification. The research work on the solid phase grafting process is one of the most active fields in grafting processes. However, study of reactors for the solid phase grafting is to be intensified. The continuous solid phase grafting in a horizontal powder reactor with double helical ribbon impeller and its engineering scale-up problem are exhibited in this article.rnThe experimental results showed that several factors such as rotational speed, height of particle bed, particle size, and size and number of helical ribbon impeller, were the most important for power assumption, mixing time and heat transfer rate in a reactor with helical ribbons. The power assumption was linearly proportional to the rotational speed and bed height in the reactor, and arnpower number correlation, Np = 32.83 f~(1.22)(1 — 0.12Fr_s~(-0.38)), was proposed. Mixing time andrnresidence time distribution were studied by means of a tracer compound. The flow pattern in the reactor was similar to that in a continuous stirred tank. Heated by conduct oil, the reactor had heat transfer coefficient of 40-80W/m~2K, which was smaller than that in a fluidizing bed reactor. Arncorrelation of heat transfer coefficient, Nu = 0.267 Re~(0.77) f~(0.23), was obtained.rnContinuous grafting experiments were performed in the reactor. The effects of rotational speed , and particle size, as well as the residence time in the continuous reactor on graft levels were the most significant. The graft levels gradually increased with the rise of rotational speeds. But the bigger particle sizes had negative effect on graft levels. On continuously operating, the graft levels of the product were close to those from the smaller scale test, 1.3%.