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Fire Hazards and Associated Terminology
Published in Asim Kumar Roy Choudhury, Flame Retardants for Textile Materials, 2020
Thermal decomposition precedes combustion and ignition of the material. Combustion is an exothermic process that requires three components, namely heat, oxygen, and fuel. When left unchecked, combustion becomes self-catalyzing and will continue until the oxygen, the fuel supply, or excess heat is depleted.
Cultivation and Conversion of Algae for Wastewater Treatment and Biofuel Production
Published in Sonil Nanda, Prakash Kumar Sarangi, Dai-Viet N. Vo, Fuel Processing and Energy Utilization, 2019
Priyanka Yadav, Sivamohan N. Reddy, Sonil Nanda
Combustion is an exothermic process in which different organic components react with oxygen to generate heat energy and steam that can be used to turn turbines to generate electricity. Gasification is thermal degradation of organic matter with a limited supply of oxygen to produce combustible synthesis gas (a mixture of CO and H2). Pyrolysis is the thermal degradation of organic substances in an inert atmosphere to produce bio-oil, biochar, and gases. Liquefaction is a biomass-to-liquid conversion technology that mostly produces bio-oil and traces of tar and char. The bio-oil obtained from liquefaction contains less oxygen and moisture compared to pyrolysis-derived bio-oil, which results in its high-energy value (Nanda et al. 2014). Hydrothermal liquefaction is basically a hydrothermal conversion technique that uses hot-pressurized water acting as the reaction medium to solubilize the biomass directly to bio-oil. In the hydrothermal gasification process, the reaction temperature is greater than 350°C in the absence of an oxidizing agent, which generates a gas phase containing H2, CO, CO2, CH4, and C2+ components. Hydrothermal gasification also uses subcritical and supercritical water to hydrothermally decompose algae to produce H2-rich syngas. Hydrothermal carbonization transforms biomass into hydrochar at a comparatively lower temperature in the range of 180°C–250°C and pressures of 2–10 MPa.
Basic Processes of Internal Combustion Engines
Published in K.A. Subramanian, Biofueled Reciprocating Internal Combustion Engines, 2017
In contrast, combustion is an exothermic process in which heat energy is released. Flame velocity influences the performance of spark-ignition engines. If the flame velocity is higher, the heat release rate would be higher, resulting in enhancement of the degree of constant volume combustion. Note that thermal efficiency increases with an increase in the degree of constant volume combustion. An increase in flame velocity increases the in-cylinder temperature and the quality of heat, resulting in better conversion from heat to work.
Analysis of moisture re-adsorption behavior of dried lignite: Inherent and extrinsic factors
Published in Drying Technology, 2022
Lulu Fan, Xianliang Meng, Ruizhi Chu, Guoguang Wu, Xiao Li, Peng Liu
By fitting the adsorption isotherms (Figure 8), model parameters were listed in Table 6. Then, the model parameters were substituted into Eq. (7) and Eq. (8) to obtain the first layer (Figure 12) and second layer (Figure 13) adsorption, respectively. Obviously, these change tendencies are consistent with Figure 11. The first layer adsorption is mainly affected by the surface oxygen-containing functional groups, while the second layer adsorption mainly occurs between water molecules. As the samples were treated in the same way, their nature will not differ greatly. In view of this, the difference was mainly due to the re-adsorption temperature. Combined with the thermodynamics analysis (Section “Moisture re-adsorption thermodynamics analysis”), moisture re-adsorption is an exothermic process, accompanied with rising adsorption binding energy. Hence, increasing the temperature is not beneficial to the moisture re-adsorption process. The rise of re-adsorption temperature can reduce the moisture re-adsorption ability of the dried lignite.
Preparation of colloidal hydrated alumina modified NaA zeolite derived from rice husk ash for effective removal of fluoride ions from water medium
Published in Journal of Asian Ceramic Societies, 2020
Colloidal hydrated alumina modified NaA zeolite with solid loading of 5% was prepared at 70°C under stirring for 2 h maintaining pH 6–7. It shows specific surface area of 54 m2 g−1 comprising micropores and mesopores. The atomic % of aluminum, silicon, sodium and oxygen in the product was found to be 17.99, 5.77, 0.65 and 75.59%, respectively as evidenced from X-ray photoelectron spectroscopy. Comparing unmodified NaA zeolite, the drastic fall of sodium content and increase of aluminum content in modified NaA zeolite helps facilitate adsorption of fluoride ions in aqueous solution. The synthesized materials showed efficient adsorption capacity for the removal of fluoride. Within a very short time (20 min), the adsorption % reached ≥90%. The adsorption % sharply increased with decrease in pH and increase in adsorbent dose. Among the co-existing ions, phosphate ions affect significantly for fluoride adsorption because of larger hydrated ionic radius to compete with fluoride ions for the same active sites of the adsorbent. The maximum efficiency of fluoride adsorption remained practically unchanged up to three cycles of the regenerated samples. The adsorption studies showed pseudo-second-order kinetics and Langmuir isotherm model to be fitted well. The amounts of fluoride adsorbed at equilibrium increased with decreasing adsorbent dose. The thermodynamics study indicates spontaneous and exothermic process of adsorption.
First-principles energy and vibration spectrum simulations of Cr/V interacting with H in W-based alloy in a fusion reactor
Published in Journal of Nuclear Science and Technology, 2018
Song Gao, Yue-Lin Liu, Zhen-Hong Dai, Quan-Fu Han, Fang Ding
Employing Equation (1), we calculate the formation energies of H in the TS with the increasing temperature in W–Cr and W–V alloys. For comparison, we also show the corresponding results in pure W, as plotted in Figure 2. The H formation energies in the TS increase with the increasing temperature in W and W-based alloys (Figure 2(a)). This demonstrates that the heat of solution of H dissolving in W and W-based alloys will increase with the increase of temperature. In other words, the dissolution of H becomes more and more difficult with the increasing temperature. The definition of formation energy states that the negative formation energy should be an exothermic process, while the positive formation energy represents an endothermic process. According to the current results from Figure 2(a), one sees that all the formation energies are positive over the whole temperature range from 300 to 2100 K, meaning that the solution process of H in W and W-based alloys is always endothermic with the considered temperature range. Furthermore, we note that with the increasing temperature, the H formation energy is always lower in dilute W–Cr alloy than in dilute W–V alloy as well as pure W, and the energy difference between H in W–Cr and W–V alloys is close to 0.04 eV. This means that the dissolution of H becomes easier in the vicinity of Cr than in the vicinity of V in W. While the formation energy difference of H in W–V alloy and pure W is very small and only ∼0.015 eV, suggesting that the presence of AE V can hardly enhance the H dissolution over the whole temperature regime. Therefore, the appearance of AE Cr in W should be favorable for the H dissolution, while V has little effect on the dissolution of H in W.