Analysis of the products of low-temperature microwave pyrolysis of peat

To increase the efficiency and intensity of processing of organic natural caustobiolite or peat, a prototype laboratory microwave reactor with an increased loading volume of the processed material has been developed. The modernized experimental setup is a microwave reactor under reduced pressure with a constant removal of pyrolysis gases through a trap with liquid nitrogen into a gas sampler. The increase in the volume of the microwave reactor was achieved through the use of additional systems for transporting microwave radiation and a special system of absorption of reflected power from the reactor volume. The reactor was connected to a microwave source (industrial magnetron) with a frequency of 2.45 GHz, with a total power of 1 kW. The duration of microwave irradiation of peat in the reactor was 16 minutes. As a result of a series of experiments, samples of three fractions – solid, liquid, and gaseous – were obtained and analyzed. A comparative analysis of the products of low-temperature pyrolysis of bog sphagnum peat obtained by heating based on heat transfer from the walls of the reactor (conventional thermal heating) and heating by microwave radiation. The main difference between heating by radiation and heat transfer is that in the first case there is an increase in temperature throughout the volume, and not just in the zone of the phase boundary, which increases the intensification and the efficiency of the process. This is especially evident when heating solid objects in which there is no heat transfer by convection. Comparison of the products of the three fractions obtained was carried out using gas chromatography analysis data with massspectrometric detection, as well as using the results of elemental analysis. The study has shown that microwave heating causes a deeper destruction of the initial substrate – to the carbon residue and low molecular weight products of inorganic and organic nature. In addition, the surface of the solid fraction was examined using a scanning electron microscope; the presence of porous structures with pore sizes from 5 to 7 μm has been detected.

peat, microwave pyrolysis, microwave reactor, carbon residue, low molecular weight products of inorganic and organic nature, high-tech peat processing