Thermodynamics Simulation Performance of Rice Husk Combustion with a Realistic Decomposition Approach on the Devolatilization Stage

• Published in: Waste and biomass valorization 2022-05, Vol.13 (5), p.2735-2747
• Main Authors: Steven, Soen, Hernowo, Pandit, Restiawaty, Elvi, Irawan, Anton, Rasrendra, Carolus Borromeus, Riza, Abrar, Bindar, Yazid
• Format: Article
• Language: English
• Subjects: Air temperature; Ash; Calorific value; Carbon monoxide; Combustion; Combustion efficiency; Combustion temperature; Decomposition; Decomposition reactions; Devolatilization; Emission analysis; Emissions; Emissions control; Engineering; Environment; Environmental Engineering/Biotechnology; Flue gas; Fugacity; Heat loss; Ideal gas; Industrial Pollution Prevention; Insulation; Mathematical analysis; Original Paper; Renewable and Green Energy; Rice; Shift reaction; Silica; Silicon dioxide; Simulation; Thermodynamics; Waste Management/Waste Technology; Water gas
• ISSN: 1877-2641; 1877-265X
• DOI: 10.1007/s12649-021-01657-x

The high calorific value of rice husk and rich silica content in rice husk ash make its valorization becomes attractive. This study presents the thermodynamics simulation performance of rice husk combustion using a realistic decomposition approach. A non-ideal gas approach and fugacity coefficient were also considered in the calculation. In this study, devolatilization of rice husk is simulated to form gas (64.78%), liquid/tar (7.28%), solid/char (27.94%), and all of these are then oxidized with 100% excess air to form flue gas. From the calculation, about 2.6 MJ/kg of specific combustion energy is produced. The maximum combustion temperature in the furnace is up to 1457 °C for perfect insulation and up to 1400 °C if there is a 5% heat loss due to radiation. Furthermore, the thermodynamics simulation expressed that NO X emission amount from rice husk combustion is negligible and there is still a probability for CO and H 2 to be produced at above 500 °C due to Boudouard reaction and homogeneous water gas shift reaction (WGSR). It is found that combustion equipped with larger excess air could quench the heat produced and reduce the combustion efficiency but could maintain the temperature at 700 °C. Supplying excess air of about 180–200% is advantageous to keep the combustion temperature at 700 °C to avoid silica crystalline formation which harms human health, as well as suppressing NO X emission and reducing CO emission from the simultaneous reaction of Boudouard-WGSR. Finally, the study concluded that a realistic decomposition approach could predict the rice husk combustion performance with reasonable and logical results. Graphical Abstract