An Easy Evaluation Method for Reaction Hazard
Systematic methods and tools for managing the complexity
Safety & Risk Management Systems (T4-5)
Keywords: waste disposal, reaction hazard
In industry, the disposal of waste materials is potentially hazardous, as the blending of recycled chemicals (liquids etc) is gradually increasing. That is, unexpected chemical reactions could take place and fires and/or explosions could result.
Furthermore, the reactant mixtures in heterogeneous liquid-liquid reactions need to be agitated well in order for the chemical process to progress smoothly. Failure to control the mixing can cause unusual reactions and sometimes lead to situations that are out of control.
It could be useful to be able to explain the heat release behaviour under various agitation conditions better, as this would lead to a reduction in the risk of similar types of explosions, by calculations and/or laboratory scale screening tests. This is necessary because most of the companies concerned only have a small amount of capital and few experts available for safety evaluation experiments.
The heat release rate of a heterogeneous reaction can be estimated using the agitation conditions - agitating speed, etc., if it is diffusion controlled. On this assumption, some trials on the prediction of reaction heat in heterogeneous liquid-liquid reactions were carried out. To predict the maximum overall heat release rate, an equation has been proposed under the assumption that the rate is proportional to the contact area of the two liquid phases and the reaction rate per unit area.
A time profile calculation of the reaction heat release rate was also carried out. In the induction process of the equation for the model, the equation for the droplet size for the steady state was expanded. However, the time required to achieve a steady state is usually several hours, and the droplet size gradually decreases over time.
An equation to predict the heat release rate at any point in time has been proposed, using an empirical equation from the time versus droplet size and our experimental results obtained from a reaction calorimeter RC1. The hydrolysis of an anhydride was selected as a model reaction for our experiments.
The empirical equation depends on data with a smaller phi factor (volumetric fraction of the dispersed phase) than in our experiments. This is why some experiments to evaluate changes in the droplet size distribution with reaction time have been carried out using focused beam reflectance measurement (FBRM). The above factors are compared for heat release measurements obtained in a variety of sizes of reaction calorimeter. This information will be helpful for calculating heat release rates or for applying experimental data to actual situations in industrial plants
Presented Thursday 20, 11:00 to 11:20, in session Safety & Risk Management Systems (T4-5).
