Quality evaluation of solid biofuels based on rice straw waste biomass

Bc. Monika Špunarová

Master's thesis

Abstract:

Biomass from plants, specifically agricultural waste and residues, can serve as a promising energy alternative to fossil fuels. It is an environmentally friendly and renewable source of energy even for solid biofuel production. Nowadays, there are huge amounts of produced agricultural biomass residues, particularly rice straw, which are not properly utilized and processed. This thesis demonstrated a possible way of processing rice straw and tested the appropriateness of the densification method in terms of pelletizing that transform these abandoned bio-wastes into pellets, products with a higher energy value. Generally, densification increases the bulk density of original biomass material which leads to the production of solid fuels uniform in size and shape. It brings with it the advantages of cheaper transportation and storage, as well as easier and more efficient handling. Rice straw material obtained from Cambodia was grinded and subsequently pelleted. The main mechanical, physical and chemical properties (moisture content, calorific value, mechanical durability, amount of heavy metals, C-H-N analyse, volatile matter, ash content and ash melting behaviour) were determined. Since rice straw exhibited a large production of ash during combustion, special emphasis was put on understanding the role of ash melting behaviour. This is because during the combustion of straw occurs ash sintering which can result in the damaging of the heating facilities. This negative aspect can be overcome by the addition of additives based on calcium. The additives containing calcium may be effective for certain biomass material but ineffective, or even with the opposite effect, for other types of biomass material. The effectiveness is also dependent on other conditions. Based on the research, additives of calcium hydroxide and calcium carbonate were mixed with rice straw. Generally, the pellet samples with the addition of calcium carbonate showed a better ability to abate the sintering of the rice straw ash. Thus, the present investigation was carried out in order to research the potential abatement of ash melting behaviour by using calcium carbonate additives in different ratios. The pellets quality was evaluated by comparing their properties with the current EN and ISO technical standards and findings of other authors of scientific papers.

Keywords

ash melting behaviour, calcium additive, pellets, rice straw, pressing process, standards

Language used: English

Date on which the thesis was submitted / produced: 22. 4. 2016

Thesis defence

• Supervisor: Ing. Tatiana Ivanova, Ph.D.

Czech University of Life Sciences Prague

Faculty of Tropical AgriSciences

Master programme / field:
Tropical Agriculture / Sustainable Rural Development in the Tropics and Subtropics