System for Measurement CO₂ Adsorption on the Fly Ashes

Abstract

Adsorption capacity at a defined temperature and pressure of the adsorptive is a key parameter determining applicability of the material for carbon dioxide capture. A laboratory apparatus allowing measurement of up to 12 samples in parallel under the same conditions was designed for this purpose. The adsorbers are installed in a thermally insulated box equipped with recuperation heating/cooling allowing measurements in the temperature range of 10–40 °C. The gas flow is controlled and recorded using the thermal mass flowmeter/controller Bronkhorst EL-FLOW Prestige. Achieving the equilibrium CO₂ concentration between gaseous and solid phase is detected by the IR analyzer Horiba PG-250. Four materials were subjected to the sorption capacity measurements using the gas mixture of 14 molar % CO₂ in nitrogen: two fly ashes from coal-fired power plants and two adsorbents synthesized from the same fly ashes. The synthesis was based on melting with NaOH followed by a hydrothermal treatment of the intermediate. The optimal conditions of the synthesis were evaluated primarily on the basis of the specific surface of the products. The sample with higher percentage of albite (41 wt. %) melted at 550 °C with NaOH using weight ratio 1:1.5 exhibited the highest sorption capacity of 3.6 g/100 g at 10 °C.