Bubble column application on purification of biogas and production of nano-calcium carbonate in continuous process

Abstract

Purification of biogas by removing carbon dioxide content has been developed to increase its calorific value. The CO₂  contained in biogas was absorbed by contacting Ca(OH)₂ solution and CO₂ in the bubble column to produce high purity of biogas and generated precipitated calcium carbonate (PCC) simultaneously. Two sources of CO₂ were used in this work, which were CO₂ contained in biogas and pure CO₂. Pure CO₂ was used as a benchmark in this study to show the effect of the presence of methane contained in biogas on the absorption process. The investigation was done in a continuous process. The results showed that the highest absorption of CO₂ was obtained in biogas at 79.34 %. PCC with calcite phases was successfully formed in 225–270 nm. Rhombohedral calcite phase was formed by the use of pure CO₂ and biogas as a source of CO₂. The use of CO₂ contained in biogas and pure CO₂ in the absorption process did not have an effect on the crystalline phase and morphology of calcite formed. Several factors that significantly affected the absorption of CO₂ were gas flow rate, absorbent flow rate, CO₂ concentration in the gas inlet, and the initial liquid level in the bubble column.