CO2 Measurement of Synthetic Biogas by Passing It through Dilute NaOH Solution

Abstract

The feasibility of measuring CO2 content in biogas was evaluated in this research. Firstly, Curtipot pH simulator was used to visualize the titration behaviors of various percentages of dissolved CO2 in a wide range of concentrations of NaOH solution. As a general output of those simulations, it was shown that when the titration curves of different CO2 content samples are separated enough, titration can provide precise information about the value of dissolved CO2. Also, when the ratio of the molar concentration of NaOH to the molar concentration of CO2 is in the range of 1 to 2(equivalent to the stoichiometric ratio of bicarbonate and carbonate), the separability of the curves is enough satisfactory to be used for precise determination of CO2; Outside this range, the accuracy of data segregation by titration diminishes. Moreover, when the ratio of the molar concentration of NaOH to CO2 is between 1 and 2, by only a one-time probing, it is possible to determine the concentration of CO2 in the standard NaOH solution. In this case, titration over a wide range of pH does not provide more reliable and accurate information. The effects of temperature CO2 measurement shows that a difference of even 10 °C can only cause less than 1% decrease in CO2 estimation. Finally, a comparison between gas chromatography and pH measurement was performed and the experimental results showed closeness the results of our proposed method with that of GC(less than 0.05% relative error). This method can be used in designing a non-expensive measuring method that would pave down the road for developing countries.