to a number of basic properties and relatively easy-to-obtain data. Based on these data, risk can be presented as a runaway graph (see Figure 2).
Data used to create the graph are determined by answering the following questions:
1. What is the heat evolution rate of the process as a function of time [qR equipment must handle?
(t)] that the
2. What temperature will be reached with the desired process running away, assuming an adiabatic condition for cooling failure (MTSR or MAT)?
3. When is MTSR maximal (the most critical instance for cooling failure)?
4. In what time ∆tDEC(T0 ) will a runaway
decomposition reaction develop, given the initial temperature T0 equal to MTSR)?
(with T0
5. In what time, at ∆tR be reached?
(Tp ), will MTSR typically being
6. What is the order of magnitude of an adiabatic temperature increase (∆Tad
, Dec
)
caused by the runaway of the secondary reactions (decomposition reaction) and what are the consequences?
To answer these questions adequately, data related to reaction mass energy potential, as well as data related to reactant accumulation and heat evolution, need to be determined. A reaction calorimeter, such as the industry- standard RC1e® from METTLER TOLEDO, is required. A reaction calorimeter such as this allows chemical reactions to be run under conditions that represent a specific process at scale (see Figure 3).
In these reactions, measurement of heat fl ow serves as a direct reaction-rate indicator, providing required basis data [qR
(t), ∆tR (Tp )].
Accumulation of reactants is calculated from the addition and conversion as a function of time. Energy accumulation is obtained by in- tegrating the heat fl ow curve from which ∆Tad MTSR, and MAT can be derived.
,
The energy potential of the reaction mass can be determined by microthermal analysis (e.g., diff erential scanning calorimetry, or DSC), where mixtures of starting materials and intermediate process phase samples are
Figure 3 – Diagram of the high-performance Thermostat RC1e, which enables fast, precise heating and cooling.
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AMERICAN LABORATORY • 19 • JUNE/JULY 2014
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