Analysis of Thermal Distillation Process for Digestate in the Aspect of Gas, Liquid and Solid Products of Thermal Conversion

The paper presents a case study for the process of thermal decomposition of digestate in order to obtain energy fractions. The aim of this work is to produce digestate and to indicate the potential of obtaining solid biofuel through thermal decomposition for the production of solid, gaseous and liquid products. In order to achieve the objective of the work, it was planned to produce digestate in mesophilic conditions, using a mixture of food and agricultural waste. The methanation process was carried out in accordance with the standard DIN 38 414 p.8. Thermal decomposition was carried out in the range of low-temperature pyrolysis at atmospheric pressure. The air-dried mass has been thermally decomposed. In the field of solid products, the acquisition of the form of carbonized biomass was assumed. The concentration of process gases was measured with the use of chemical and spectral sensors. In the scope of gas products, the observation of the emission of basic process gases (CO, CO₂, CH₄, H₂, NO_X, H₂S, O₂) was assumed. In the range of liquid products, the observation of moisture and tarry substances secretion was assumed. A case studie for digestate under dry thermal distillation conditions indicated insufficient emission of flammable gases (CO, CH₄) and the possibility of obtaining a flammable product in a low temperature range (from 200 ℃ to 300 ℃).