Physio-chemical treatment of pyrolysis aqueous phase : a study of COD and TOC removal
Filenko, Vladislav (2025)
2025
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-202505069347
https://urn.fi/URN:NBN:fi:amk-202505069347
Tiivistelmä
Fast pyrolysis is a thermochemical conversion process, in which lignocellulosic biomass is being thermally converted into bio-oil. Bio-oil comes in the form of a highly oxygenated liquid; the strong presence of oxygen hinders the potential of the bio-oil. To improve the usability of the bio-oil, vapour product from fast pyrolysis is catalytically upgraded resulting in improved characteristics of bio-oil. However, as a side effect of the catalytic upgrading, an aqueous stream is separated from the upgraded bio-oil. The aqueous phase is a complex mixture of water and organic compounds, with no further use for the aqueous phase it is disposed of.
The recovery of chemicals from the aqueous stream, while having its appeal, usually requires preliminary treatment and does not appear to be economically feasible. The right treatment of catalytic fast pyrolysis aqueous phase is, therefore, the first step towards disposal or valorisation of the aqueous phase. Usual treatment includes solvent extraction with application of activated sludge process as a biological treatment. However, in case of many industrial water effluents and catalytic fast pyrolysis, the performance biological treatment may be impaired by the contents of treated waters. Improvements can be made by implementing pre-treatment to ease the chemical load on the biological treatment. Coagulation-flocculation and electrochemical oxidation are environmentally friendly and low costing treatments that have proven to reduce organic load from the industrial water effluents and make them more suitable for biological treatment.
A combination of coagulation-flocculation and electrochemical oxidation treatments was utilized in treatment of two catalytic fast pyrolysis aqueous products. After going through the full treatment, the aqueous products have experienced 84% and 59% total COD removal for AP1 and AP2 respectively, as well as a 52% total TOC removal in both aqueous products. It was established that the organic compounds in the two aqueous products studied differ in quantity, composition and biodegradability. This study examines the potential of the physiochemical treatment of the aqueous phase, and while the aqueous products were not completely treated, with further development of the treatment complex, it can become the first step towards aqueous stream remediation or valorisation.
The recovery of chemicals from the aqueous stream, while having its appeal, usually requires preliminary treatment and does not appear to be economically feasible. The right treatment of catalytic fast pyrolysis aqueous phase is, therefore, the first step towards disposal or valorisation of the aqueous phase. Usual treatment includes solvent extraction with application of activated sludge process as a biological treatment. However, in case of many industrial water effluents and catalytic fast pyrolysis, the performance biological treatment may be impaired by the contents of treated waters. Improvements can be made by implementing pre-treatment to ease the chemical load on the biological treatment. Coagulation-flocculation and electrochemical oxidation are environmentally friendly and low costing treatments that have proven to reduce organic load from the industrial water effluents and make them more suitable for biological treatment.
A combination of coagulation-flocculation and electrochemical oxidation treatments was utilized in treatment of two catalytic fast pyrolysis aqueous products. After going through the full treatment, the aqueous products have experienced 84% and 59% total COD removal for AP1 and AP2 respectively, as well as a 52% total TOC removal in both aqueous products. It was established that the organic compounds in the two aqueous products studied differ in quantity, composition and biodegradability. This study examines the potential of the physiochemical treatment of the aqueous phase, and while the aqueous products were not completely treated, with further development of the treatment complex, it can become the first step towards aqueous stream remediation or valorisation.