Evaluation of Activated Carbon from Raphia Palm Nut Endocarp as Adsorbent for Solid Adsorption Refrigeration

Abstract

Activated carbon was produced from powdered Raphia palm nut endocarp (REAC) using H3PO4 and CaCl2 as activators before carbonization, and the responses studied to investigate its suitability for solid adsorption refrigeration applications. Temperature, resident time, concentration, and impregnation ratio, were the parameters used and ash content, carbon yield and surface area were the responses. The effect of preparation sequence was evaluated. The efficiency of the activated carbon on the adsorption of methanol was investigated an experimental rig. 100 g of sample was carbonized at 200, 400 and 600oC, and the carbonized samples were used for solid adsorption refrigeration to determine the optimum carbonization temperature. Carbonization times (30, 60, 90, and 120 minutes), activating agent concentrations (25, 50, 75 and 100%) and impregnation ratios (1:1, 1:2, 1:3, and 1:4 precursor to activating agents) at the optimum temperature were used to determine the optimum resident time, concentration and impregnation ratio. The results revealed that H3PO4 activated samples at optimum conditions of 500˚C temperature, 50% concentration, 60 minutes resident time and 4 ml/g impregnation ratio yielded better response with low percentage of ash content (2.25%), high carbon yield (73.63%) and large surface area (2857.51 m2/g) activated carbon were obtained at the optimum conditions. The adsorbing efficiencies of the carbons prepared through activation with H3PO4 achieved 0.084 and 14.5 of Coefficient of Performance (COP) and Specific Cooling Power (SCP) respectively. The results indicated that the carbon is activation before carbonization is well suited solid adsorption refrigeration applications.