Performance prediction and validation of equilibrium modeling for gasification of cashew nut shell char

Abstract

-Cashew nut shell, a waste product obtained during deshelling of cashew kernels, had in the past been deemed unfit as a fuel for gasification owing to its high occluded oil content. The oil, a source of natural phenol, oozes upon gasification, thereby clogging the gasifier throat, downstream equipment and associated utilities with oil, resulting in ineffective gasification and premature failure of utilities due to its corrosive characteristics. To overcome this drawback, the cashew shells were de-oiled by charring in closed chambers and were subsequently gasified in an autothermal downdraft gasifier. Equilibrium modeling was carried out to predict the producer gas composition under varying performance influencing parameters, viz., equivalence ratio (ER), reaction temperature (RT) and moisture content (MC). The results were compared with the experimental output and are presented in this paper. The model is quite satisfactory with the experimental outcome at the ER applicable to gasification systems, i.e., 0.15 to 0.30. The results show that the mole fraction of (i) H 2 , CO and CH 4 decreases while (N 2 + H 2 O) and CO 2 increases with ER, (ii) H 2 and CO increases while CH 4 , (N 2 + H 2 O) and CO 2 decreases with reaction temperature, (iii) H 2 , CH 4 , CO 2 and (N 2 + H 2 O) increases while CO decreases with moisture content. However at an equivalence ratio less than 0.15, the model predicts an unrealistic composition and is observed to be non valid below this ER.

Gasification of Miscanthus x giganteus Pellets in a Fixed Bed Pilot-Scale Unit

“…To determine the equilibrium constants described in Equation (1), it is necessary to rely upon the following intermediate reactions occurring during gasification (Schuster et al, 2001;Ramanan et al, 2008):…”

“…Outputs of such models have been shown to be accurate (Pandey et al, 2013). Different thermodynamic equilibrium models exist in the literature, however, these have also been limited in relying upon small, laboratory-scale, experimental data (Schuster et al, 2001;Zainal et al, 2001;Altafini et al, 2003;Ramanan et al, 2008;Pandey et al, 2013). It is therefore, necessary to determine if such kinetic models can accurately predict conversion when based upon pilotscale data for conditions comparable to actual industrial-scale applications.…”

Syngas production through gasification and cleanup for downstream applications — Recent developments

“…Lignite [24] Anthracite [24] Petcoke [3] Heavy residue [25] Wheat straw [3] CNS [26] Pine wood [3] Olive tree [3] MSW [22] Moisture ( bed gasifiers are the extent of carbon conversion and the carryover of particles having high carbon content. Hence, to achieve high overall conversions, the carried-over fines are collected and recycled back in the gasifier with fresh feedstocks (Fig.…”

Biomass gasification with CHP production: A review of state of the art technology and near future perspectives

“…For the model developed in this project, the following assumptions are made [27][28][29][30]: (1) biomass is represented by general formula CHxOyNzSr, (2) residence time of reactants is high enough to reach chemical equilibrium, (3) reactions are at thermodynamic equilibrium, (4) reactions proceed adiabatically, (5) reaction temperature and residence time for reactants are sufficiently high to reach chemical equilibrium, (6) there is no tar in the gasification zone, (7) ash is inert and it is not involved in any reactions, and (8) gasification products contain CO 2 , CO, H 2 , CH 4 , N 2 , and H 2 O (there is no oxygen in syngas -during the process of gasification only 20-40% of stoichiometric air is used); With reference to all these assumptions, the most important one is that the residence time of reactants is high enough to reach chemical equilibrium; this hypothesis is confirmed by other authors [24,28,31].…”