Char derivation from date palm biomass and microalgae; characterization, thermal and economic analysis

Ing. Ali Akhtar

Doctoral thesis

Abstract:

Waste-derived products are considered to address the question of sustainability in a variety of projects and applications. These products provide a consistent source of raw materials as well as cope with the waste handling dilemma. Waste derived carbon is one of these products which not only has gained serious consideration from an environmental point of view but also proven to be useful in soil amendment, wastewater treatment and production of nano-materials. This study provided a thorough approach to the production of optimised carbon materials from date palm biomass and wastewater derived microalgae. Their individual and co-pyrolysis behaviour with product performance in energy application including combustion and pyrolysis presented thoroughly. Slow pyrolysis of the date palm branches (DB) and wastewater derived microalgae (WMA) was conducted in the temperature range (HTT) of 400-600 °C. Mass yield decreased; whereas, ash content increased with the increase in HTT. Algae biochar (AB) char showed higher mass yield and ash content and reduced heating values as compared to DB samples. DB chars, however, showed higher stability than AB chars. Combustion of both types of the char samples found to degrade through a two-stage devolatilization process whereas char pyrolysis showed one stage devolatilization. DB samples at 400 and 500 °C and, AB samples at 500 and 600 °C showed lower activation energy during combustion than their feedstock. Similarly, co-pyrolysis of date palm branches and wastewater derived microalgae was conducted between 400-600 °C for multi-stage pyrolysis. Char aromaticity increased, and mass yield decreased substantially with the increase in treatment temperature in both single stage pyrolysis and two-stage pyrolysis from 40% to 30% by weight. Nitrogen concentration was decreased with the increase in temperature, which determines its transformation to the gas phase. Combustion of the feedstock and the char samples produced at 400 °C and 500 °C showed two-stage degradation. The optimum treatment temperature for two-stage pyrolysis to gain the lowest activation energy is found to be 500 °C during combustion, moderate heating values and lowest price. The economic analysis showed a decrease in price with the increase in treatment temperature for two-stage pyrolysed biochar due to a decrease in energy content. It can be concluded that co-pyrolysed char from multi-stage pyrolysis process contains the superior properties and complements each other. The obtained product may be useful for potential applications in multiple areas such as energy and adsorption than individual pyrolysis of each of the concerned feedstock which has certain limitations.

Keywords

Biomass, Kinetic Modelling, Combustion, Pyrolysis

Jazyk práce: English

Datum vytvoření / odevzdání či podání práce: 14. 6. 2019

Obhajoba závěrečné práce

• Vedúci: doc. Ing. Vladimír Krepl, CSc.
• Oponent: Jan Malaťák, doc. Ing., Ph.D., Petr Hutla, DiS., externi, Karel Svoboda, externi

Czech University of Life Sciences Prague

Faculty of Tropical AgriSciences

Doctoral programme / odbor:
Agricultural Specialization / Sustainable Rural Development in the Tropics And Subtropics