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1、Rubber SeptumJ Rotameter30wt% HfOTo HoodGlass FritInfrared DetectorInjectionPortN2 Carrier GasFigure 3.3: Schematic of Total Inorganic Carbon (TIC)MgClOgDessicantComputer with PicoLog SoftwareapparatusTotal Inorganic Carbon (TIC) measurementThe concentration of CO2 in amine solutions was determined
2、by the measurement of the total inorganic carbon present in the sample as developed previously (Critchfield, 1988; Hilliard, 2008; Lee, 1986). A schematic of the TIC apparatus is shown in Figure 3.3. The apparatus consists of a rotameter type gas flow meter, glass injection tube with injection port
3、and frit, two glass cylinders used as desiccant tubes, CO2 detector, and a computer. CO2 loading throughout this thesis is reported in units of moles CO2 per mole alkalinity. This unit is defined for amine alkalinity, or equivalence of amine, based on the number of amino functions on the parent amin
4、e and is used for convenience in the field of CO2 capture. This definition is not based on an alkalinity result from a titration procedureTo set up the apparatus for use, two 3/8 inch diameter glass tubes were first filled with magnesium perchlorate (MgClO4) desiccant. To fill the tubes, a small bal
5、l of glass wool was placed approximately one-half inch from one end of the tube. Large pieces of desiccant were added to the tube to fill the tube until one-half inch from the other end of the tube. Another piece of glass wool was placed at the top of the tube to securely hold the desiccant in place
6、. A new septum was placed on the injector port for each new analysis. Using a 3 mL syringe, 1 to 1.5 mL of phosphoric acid (H3PO4) was injected through the septum to fill the injection chamber. The nitrogen (N2) gas was then turned on at the source and the rotameter was adjusted to achieve the desir
7、ed flow rate. Usually the rotameter was maintained at a reading of 12 or 13. The rotameter was periodically checked throughout the measurements to ensure that the N2 flow was maintained.To begin the analysis, the samples were first gravimetrically diluted 10, 50, or 100X, depending on the expected c
8、oncentration of CO2. The dilute sample was injected into the injection port on the side of the first glass tube using a syringe pressed through the septum. This injection tube had a glass frit below the injection port that allows the carrier N2 to pass through the frit, through the acid, and up the
9、tube but did not allow the acid to fall through. The injected sample entered the system in the pool of acid and was quickly acidified. This acidification released all of the CO2 present in solution.The released CO2 entered the N2 carrier gas stream that traveled through the two desiccant tubes befor
10、e finally reaching the Horiba PIR 200 infrared detector (Horiba, Irvine, CA, USA). The resulting change in voltage detected by the infrared detector produces peaks that were recorded with PicoLog software (Pico Technology, Cambridgeshire, United Kingdom). The infrared detector is very sensitive to a
11、ny water vapor that reaches it, so two tubes of desiccant were always used. The first tube was replaced for every run while the second tube was replaced less often, approximately every 5 to 7 runs or as needed. Not shown in Figure 3.3 is a stand that supports the three tubes on a metal plate with tu
12、be holders where the tubes can snap into place. An airtight seal is maintained with Swagelok ultra-torr vacuum fittings (Arthur Fluids System Technologies, a Swagelok Distributor, Austin, TX).A calibration curve was prepared at the end of each analysis using a 1000 ppm standard inorganic carbon solu
13、tion, which was a mixture of K2CO3 and KHCO3 (Ricca Chemical Company, Arlington, TX). The TIC method quantified the CO2, carbonate (CO3-2), bicarbonate (HCO3-), and carbamate (PZCOO-, PZ(COO-)2, etc.) species present in solution. These species are in equilibrium in the series of reactions shown in e
14、quation 3.9 below.CO32 + 2H+ HCO3 + H+ H2CO3 CO2 + H2O (3.9)Acidification shifted the equilibrium toward CO2 which bubbles out of solution and was detected in the analyzer. CO2 loading is reported throughout this thesis as moles of CO2 per mole of alkalinity or moles of CO2 per equivalence of PZ, wh
15、ere there are two moles of alkalinity per mole PZ.At the end of a run, the N2 flow was turned off at the rotameter and the source. The data recorded by PicoLog, a set of time versus voltage data, were exported to excel and saved. The first desiccant tube was removed from the apparatus and emptied. I
16、f the second desiccant tube was not wet, it remained in the apparatus for the next user. The acid in the injection port was removed using the 3 mL syringe and placed in the appropriate acid waste container. The injection port and first desiccant tube were then washed with distilled water.In order to calculate CO2 concentration, the areas of each peak were first calculated for the samples and the calibration pe
