The heterogeneity of waste tire pyrolytic char associated
with
ash composition and distribution is explored to understand the effect
of ash on gasification. In this paper, high-ash tire tread (TT) and
low-ash sidewall (SW) were separated to study gasification kinetics
and the influence of ash on char physicochemical morphological evolution
during CO2 gasification. Morphological development and
characterization of chars were studied using N2 adsorption
and scanning electron microscopy coupled with energy dispersive X-ray
analysis. Isothermal gasification kinetics were derived from a thermogravimetric
analyzer and described by the shrinking core model (SCM), volumetric
model (VM), and the random pore model (RPM). The results showed that
TT char has silica-based ash clusters which inhibit gasification,
particularly at high conversions. Moreover, TT ash suppresses surface
area development and forms an inherent skeletal structure that inhibits
particle size reduction during the reaction. In contrast, SW char
exhibited significant particle size reduction, and surface area development
was more pronounced compared to that for TT char. The surface area
for SW char increased until 75% conversion and decreased thereafter,
albeit insignificantly, while the TT char surface area decrease was
more pronounced after 50% conversion. All chars exhibited significant
internal structure development, thus eliminating the SCM as an appropriate
model. All models yielded kinetic parameters of nearly the same magnitude,
and the RPM was selected as the most suitable model. The activation
energy for TT and SW were found to be 177.1 and 163.6 kJ mol–1, respectively. The model-free method confirmed the reliability of
the results. These findings further confirmed the inhibiting nature
of tire ash.
Disaster-hit and/or un-electrified remote areas usually have electricity accessibility issues and an abundance of plant-derived debris and wood from destroyed wooden structures; this can be potentially addressed by employing a decentralized ultra-small biomass-fed gasification power generating system. This paper presents an assessment of the technical viability of an ultra-small gasification system that utilizes densified carbonized wood pellets/briquettes. The setup was run continuously for 100 h. A variety of biomass was densified and carbonized by harnessing fugitive heat sources before charging into the reactor. Carbonized briquettes and furnished blends exhibited inferior gasification performance compared to the carbonized pellets. In the absence of tar blockage problems, steady-state conditions were achieved when pre-treated feedstock was used. Under steady-state conditions for carbonized pellets gasification operated at an equivalence ratio of 0.32, cold gas efficiency and carbon conversion achieved 49.2% and 70.5%, respectively. Overall efficiency and maximum power output of 20.3% and 21 kW were realised, respectively. It was found that the system could keep stable while the low heating valve of syngas was over 4 MJ/m3 on condition that avoiding tar blocking issues. The results indicate that the proposed compact ultra-small power generation system is a technically feasible approach to remedy power shortage challenge. In addition, process simulation considering carbonized wood gasification combined power generation was formulated to produce syngas and electricity. Woody pellets with the flow rate of 20 kg/h could generate a 15.18 kW power at the air flow rate of 40 Nm3/h, which is in a good agreement with 15 kW in the 100 h operation. It is indicated that the gasification combined power generation cycle simulated by Aspen simulator could achieve reliable data to assist the complicated experiment operation.
The influence of inherent tire char ash during co-gasification with coconut hydrochar prepared at different intensities was investigated by thermogravimetric analysis to ascertain the extent to which synergistic interaction, reactivity, and activation energy reduction were altered. High-ash tire tread (TT) and low-ash sidewall (SW) both exhibited enhanced synergy, reactivity, and activation reduction upon cogasification with hydrochars; however, the extent of promotion was more pronounced in SW-hydrochar blends. This difference was caused by the inhibiting nature of TT inherent ash, particularly the role of Sicontaining compounds. Inhibition in TT-hydrochar blends was mainly due to the promotion of alkaline and alkaline earth metal transformation into inactive silicates, and to a lesser extent, the mass transfer effect caused by accumulated ash, especially at conversions higher than 70%. The extent of enhancement correlated well with the concentration of available alkaline and alkaline earth metals. The findings may be useful in justifying the exclusion of high ash tire char as gasification feedstock to mitigate ash-related problems.
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