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| Home > Publications database > Enabling mass loss measurement for controlled atmosphere experiments in a tube furnace |
| Poster (After Call) | FZJ-2021-02235 |
; ; ; ;
2021
Please use a persistent id in citations: http://hdl.handle.net/2128/27853
Abstract: In fire safety science, the thermogravimetric analyzer (TGA) is used for determining materialand reaction parameters for fire modeling with Computational Fluid Dynamics (CFD) codes,e.g. the Fire Dynamic Simulator (FDS). The kinetic parameters describing the decompositionreactions of a material, are determined based on the mass loss rate of the material asfunction of the temperature measured by a TGA device. In the TGA, it is assumed that thesample is in thermal equilibrium with the furnace temperature. For this assumption to hold,the sample needs to be sufficiently small. So far, it is not clear whether these small samplesare in general good representatives to predict bench and real scale experiments, e.g. conecalorimeter. For example, for small samples bubbling is very inhomogeneous, while for largesamples bubble formation is more homogeneously distributed on the sample surface.However, a TGA has precisely controllable boundary conditions: the gas flow rate andcomposition, the furnace temperature and a homogeneous exposure of the sample to theheat flux. Therefore, it would be beneficial to have an experimental device with theadvantageous properties of the TGA which can handle more representative samples sizes.Consequently, the tube furnace is proposed as experimental set-up to conduct definedbench scale tests. The tube furnace allows for sample sizes in the order of 100 g.Standard tube furnaces, e.g. described in DIN 19700, do not measure the mass loss.Therefore, the design of a balance within the tube furnace is outlined in this contribution.Mass loss curves from tube furnace experiments can then be used to determine the kineticsof the reaction and compare the results to kinetic parameters predicted using TGAexperiments. In order to evaluate the measurement technique, the integral mass loss forsamples exposed for different periods of time in the tube furnace will be measured andcompared to the time resolved mass loss data. These experiments will be done prior to thebalance experiments. The results of the initial experiments, i.e., exposing samples fordifferent time lengths to a certain heating rate, are presented and compared withthermogravimetric data from the literature as well as own experimental data in thiscontribution.The tube furnace, for which the balance will be constructed, consist of a quartz glass tubewith an inner diameter of 90 mm and a length of 80 cm, inside an oven with radial heatingelements. A sample can be placed inside the oven in a quartz glass specimen boat.Experiments can be performed under well-defined atmosphere; the composition and theflow rate of the gas can be controlled. Both isothermal experiments, by moving the sampleinto the furnace after preheating, as well as experiments under dynamic conditions, byheating the furnace while the sample is inside, are possible. The tube furnace has amaximum heating rate of 5 K/min and can heat up to 1000˚C. CO, CO2 and O2concentrations are measured, allowing to determine the heat release rate for materials withknown combustion processes.
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