Safety in Emulsion Polymerization Reactors: An Experimental Study

Abstract

Summary: The risk parameters of the high‐solids‐content emulsion copolymerization of vinyl acetate/butyl acrylate/acrylic acid (78.5/18.5/3 wt.‐%) were studied. The effect of the polymer/monomer ratio, the total solids content, the initiator/monomer ratio, the non‐swollen polymer particle size, and the process temperature on the onset temperature for runaway, the adiabatic temperature increase, and the maximum temperature and pressure achieved was studied. These data are needed to determine the safety limits for the variables of this system considering the worst case scenario; namely, a runaway reaction under adiabatic conditions. It was found that the onset temperature is always below the typical process temperature for this system (70–80 °C). Therefore, in the case of a cooling system failure (i.e., electrical failure) the runaway reaction will take place. Relatively high pressures (up to 6 bar) were monitored during the runaway.Evolution of the maximum pressures reached during all the experiments versus the polymer‐to‐monomer ratio ‘r’ and the process temperature ‘Twork’.magnified imageEvolution of the maximum pressures reached during all the experiments versus the polymer‐to‐monomer ratio ‘r’ and the process temperature ‘Twork’.

Life in the E‐Sphere

“…Comparing the kinetics with the laboratory scale experiments by Azpeitia et al,3 it can be seen that the kinetics seem to start much faster. While in those experiments an initial temperature increase rate of around 1–2 K · min −1 is observed, only after an adiabatic temperature increase of more than 20 K does the reaction accelerate.…”

“…In addition, these can be used to estimate the time available for recognition and addition as well as mixing in of a stopper solution to inhibit the runaway reaction. Unfortunately, only few reports are published on runaway kinetics for emulsion polymerization 3…”

Reactor Fouling in Emulsion Polymerization

“…Fortunately, the range 0−20 wt % is the most significant because at industrial scale, the semicontinuous emulsion polymerizations are carried out at this range of monomer concentrations. Higher concentrations reduce the controllability of the polymer quality (e.g., copolymer composition and molar mass distribution 22 ) and might create a safety issue (large amounts of monomer in the reactor are prone to cause thermal runaways 23 ). The increase in the wet fouling with the monomer concentration may be in part due to the decrease in the T g of the monomer swollen polymer and in part due to the lower coverage of the monomer swollen particles by the surfactant.…”

Lumped Kinetics of Self-Heating Runaway Reactions: A Statistical Treatment

“…The greater the sensitivity of the calorimeter, the lower the detectable onset will be. 15 The onset temperatures of self-heating reactions are usually lower than the starting temperatures of many commercial exothermic processes, 16 so potential runaway situations always lurk. Good process-safety practices require the knowledge of T o .…”