Abstract
This work discusses results on temperature profile, syngas composition, High Heating Value, and efficiency of a Coffee Husk counter-current fixed-bed gasification process, in which oxygen-steam blends were used as oxidizing agent. The experimentation was carried out for various Equivalence Ratio (ER) and Steam-Fuel Ratio (SF), whose ranges were [1.6 – 5.6] and [0.4 – 0.8] respectively. The results show that Increased steam (higher steam fuel ratios) improves the H2/CO molar ratio i.e., for a constant ER=3.7 and SF at 0.4, 0.6, and 0.8, the H2/CO ratio was 1.2, 1.4, and 1.8 respectively. Also, the addition of steam tends to increase the syngas Higher Heating Value, which ranged between 7714 kJ/m3 at ER = 1.6 and SF = 0.4 and 8841 kJ/m3 at ER = 3.2 and SF = 0.8. On the other hand, increased ER (lower oxygen) decreases the Net Cold Gasification Efficiency (CGENET) which was between 53 % at ER = 5.6 and SF = 0.6 and 82 % at ER = 1.6 and SF = 0.4. Results were also compared to results published before for gasification of the same biomass but using air-steam mixtures for partial oxidation. This comparison shows that the use of oxygen increases both the temperature profile in the bed and the yield of CO and H2 contained in the syngas.
Highlights
The continuous increase in both energy consumption and emissions, generated in the combustion of fossil fuels, around the world (International Energy Agency, 2016) has stimulated the study of new sustainable energy technologies to reduce the dependence of the population on fossil fuels
The economies of many countries are based on agro-industry, a sector that produces a lot of biomass residues that can be used as feedstock for the production of solid, liquid, and gas biofuels via Experimental Gasification of Coffee Husk thermochemical or biological gasification processes (Abbasi and Abbasi, 2010; Gírio et al, 2010; Yang et al, 2014; Aslan, 2016; Chen, 2016; Cutz et al, 2016; Joselin Herbert and Unni Krishnan, 2016; Bilgili et al, 2017; Toklu, 2017)
The empirical formula was determined based on the atom balance on components given by proximate and ultimate analyses, whereas the formation enthalpy was derived using the dry ash-free high heating value (DAF HHV) in order to perform an energy balance between reactants and products of the theoretical combustion of a kmol of biomass defined as the empirical formula (CH1.63N0.015O0.82S0.0024)
Summary
The continuous increase in both energy consumption and emissions, generated in the combustion of fossil fuels, around the world (International Energy Agency, 2016) has stimulated the study of new sustainable energy technologies to reduce the dependence of the population on fossil fuels. One of the most performed thermochemical processes is coal and biomass air-gasification have been used for a long time to produce syngas with a high heating value (HHV) ranging from 4 to 6 MJ/SATP m3 (Gordillo and Annamalai, 2010; Sandeep and Dasappa, 2014). In order to improve syngas quality (HHV and composition), the other gasification processes mentioned above have been studied. Biomass oxygen-steam gasification is a process used when it is required improving both gas composition and HHV of the mixtures produced
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