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

Abstract

Rice husk has a great potential in its calorific value and silica content in ash which makes its valorization through combustion becomes important and interesting. 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. From this study, rice husk is devolatilized to form gases (63.37%), tar (8.69%), char (27.94%), and all of these are then oxidized to form flue gas. The realistic decomposition approach calculated that about 2.6 MJ/kg of specific combustion energy is produced, the maximum combustion temperature is up to 1457 o C for perfect insulation condition, and up to 1400 o C if there is a heat loss.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 o C. Furthermore, the thermodynamics simulation expressed that NO emission amount from rice husk combustion is negligible and there is still a probability for CO and H2 to be produced at above 500 o C due to Boudouard reaction and homogeneous water gas shift reaction (WGSR). The study showed that a realistic decomposition approach could predict the rice husk combustion performance with a reasonable and logical result. Supplying excess air of about 180-200% is advantageous to keep the combustion temperature at 700 o C in order to prevent silica crystalline formation which harms human 2 health, as well as suppressing NO emission and reducing CO emission from the simultaneous Boudouard and WGSR.

Optimization of purity and yield of amorphous bio‐silica nanoparticles synthesized from bamboo leaves

“…500 g of washed bamboo leaf powder was then combusted at 700°C for 2 h. The operating condition of combustion was chosen to avoid crystalline silica in the ash. [ 11,15 ] Subsequently, 100 g of the obtained ash was washed again for 1 h with 400 mL of 1 mol/L HCl. The washed ash was then rinsed with demineralized water.…”

“…[5,6] On the other hand, several crops can naturally convert mono-silicic acid from the soil to silica by the oxolation process. [7,8] Crops with rich silica content include bamboo (leaves), [9][10][11][12] rice and corn (husks), [13][14][15] and sugarcane (stems as bagasse). [16][17][18] Bamboo crops (Phyllostachys pubescens) are widely found in tropical countries.…”

Digitalized turbulent behaviors of air and rice husk flow in a vertical suspension furnace from computational fluid dynamics simulation

“…The typical excess air requirement for rice husk combustion is in the range of 40% to 100% 9 . This study selected 80% of excess air amount, and according to the study by Steven et al (2022), it gave to the mass ratio of air and rice husk of 10 37 . The air supply was then distributed to axial, tangential, and secondary air with ratios of 25:45:30, 25:51:24, and 25:60:15.…”

“…Process temperature was also varied at 25°C and 700°C. The temperature of 25°C represents the air and rice husk flow condition in absence of combustion phenomena (namely, cold flow modeling) 40 whereas the temperature of 700°C indicates the flow condition in the presence of combustion phenomena before the silica in rice husk ash transforms to crystalline phase 14,37,41 . Air density alleviates from 1.184 to 0.363 kg/m 3 , and air viscosity enhances from 1.84 × 10 −5 to 4.09×10 −5 Pa.s along with temperature change from 25°C to 700°C.…”

“…9 This study selected 80% of excess air amount, and according to the study by , it gave to the mass ratio of air and rice husk of 10. 37 The air supply was then distributed to axial, tangential, and secondary air with ratios of 25:45:30, 25:51:24, and 25:60:15. The particle size distribution followed Rosin-Rammler model with the range of 2-8 mm and varied at averaged diameters of 1, 2.5, and 4 mm.…”