Study on Heat Transfer in Scale-up of Stirred Tank Reactor Using Maxblend^R Impeller for Continuous Bulk Polymerization

Abstract

A Maxblend^R (MB) impeller was adopted in the mixing reactor for a continuous polymerization reaction. When the liquid level was lower than the top of the impeller and the upper shell cover of the reactor was cooled, the monomer vaporization was accelerated to exceed the amount of the heat transfer from the jacket surface, which offered an effective means to remove the heat of reaction. The rate of monomer vaporization (v) by a Maxblend^R impeller changed as a function of the 1.4 th power of the impeller speed, the 0.4 th power of the impeller diameter and the 0.45 th power of the nitrogen flux.
The value of the overall coefficient of heat transfer (U_j) and v were estimated as 304 kJ/m²h°C and 26.7 kg/m²h, respectively for the commercial scale reactor under conditions of P_v = 1. 5 kw/m³ (73 rpm) from the experimental value of U_j = 460 kJ /m² h°C and v=67 kg/m²h determined from the heat balance of the pilot scale reactor. Based on those values, a commercial reactor with a productivity of 750 kg/h was designed assuming the difference between the jacket temperature and the reaction temperature (Δt_j) =-12.8°C. Parameters were found to be U_j =326 kJ/m²h°C, v=31 kg/h (at the purge gas rate of 1/7 that of the pilot scale) and Δt_j =-12.5 for the commercial reactor, suggesting that the ability of heat transfer of the commercial reactor was designed conciderably larger than the estimated value.