Thermal destruction of polymers: analysis of the process physicochemical parameters

Abstract

This experimental study has confirmed that during thermal decomposition of polymeric waste samples at a temperature of 850 °C, without oxygen access, there is a 90 % drop in the mass of this waste with the release of a large volume of gaseous products. This feature should be taken into consideration in the engineering calculations of reaction chambers, reactors, and connecting gas pipelines. The analytical study was carried out by a method of thermodynamic analysis using the universal estimation system Astra (TERRA). It has been shown that with an increase in reaction temperature there is a change in the composition of the products of thermal destruction of polymeric waste by reducing the mole fraction of СН4 and increasing the proportion of Н2. The calorific value was calculated according to Mendeleev’s empirical formula. The experimental study (a pyrolysis-gas chromatography method) has confirmed the calculation results regarding an increase in the proportion of hydrogen in the gaseous products of destruction with an increase in process temperature. As a result, due to the lower volumetric heat of hydrogen combustion, the total caloric content of the synthesis gas obtained is significantly reduced. For the experiments, a laboratory installation of low-temperature pyrolysis of polymers with external supply of thermal energy was built, and synthesis gas was used as an energy carrier. At the experimental-industrial installation, by a low-temperature pyrolysis method, the synthesis gas of a stable composition with a lower heat of combustion of 24.8 kJ/m3 was obtained. The reliability of the results of the proposed estimation method to the results of instrumental measurements has been shown. Promising areas of further studies have been determined, including the optimization of processes of thermal destruction of chlorine-containing polymer waste; the effective use of hydrogen from the composition of the synthesis gas obtained.