In-situ gasification-activation system with staged oxidizer supply for generation of activated carbon and intrinsic hydrogen rich by-product gas from coconut shells

A bottom-lit open top packed bed In-situ Gasification-Activation System with Staged Oxidizer Supply (IGAS-SOS) for co-generation of activated carbon (AC) and intrinsic hydrogen rich producer gas from coconut shells in a single step is demonstrated. Primary air is used for gasification. Superheated steam, in conjunction with secondary air, is employed for activation by injecting it directly into the char bed and distributing it evenly. It is identified that volatile equivalence ratio between 2.1 and 2.5, steam temperature ( \(T_{steam}\) $T_{\mathit{steam}}$ ) of \(\sim \) $\sim$ 700 \(^\circ \) ${}^{\circ }$ C, and \(t_{act}\) $t_{\mathit{act}}$ of \(\sim \) $\sim$ 3 h are critical for char-steam reaction to be kinetically controlled. Increase in \(T_{steam}\) $T_{\mathit{steam}}$ from 250 to 700 \(^\circ \) ${}^{\circ }$ C increases both maximum activation and intrinsic H \(_2\) ${}_2$ yield from 624 m \(^2\) ${}^2$ /g and 16 g/kg of biomass to 965 m \(^2\) ${}^2$ /g and 27 g/kg of biomass, respectively without much compromise in AC yield. Further, the preferred configuration of oxidizer supply also ensures tar-free exit gas, with higher hydrocarbon levels below 2.5 g/kg of biomass. \(SA_{BET}\) $S{A}_{\mathit{BET}}$ and yield are enhanced at least twofold compared to earlier works on in-situ physical activation.