OCR Text |
Show The gas blending system is a set of rotameters using the "dilution blending system" (9). This allows preparing flowing gas mixtures of several components, the amount of each component being accurately known and readily varied in the range of several percent, down to a few ppm. Controlled amounts of CH3 0H vapor were added to the flowing gas mixture by passing Ne at a measured flow rate through a saturator filled with methanol and kept at a controlled temperature (usually -16oC) and mixing this methanol containing flow with the main flow. As shown in Figure 1, the addition of HeO and 503 to the flowing gas mixture is done just upstream of the reactor. A dilute aqueous solution of HeSO~ is pumped via a preC1Slon metering pump to a vaporizer. The rate of pumping is chosen so as to provide the desired value of [HeO] in the gas mixture. On .vaporization and heating above 3000C, HeSO~ is converted to HeO and 503 and the concentration of HeSO~ in the solution is chosen so as to provide the desired value of [503 ] in the gas mixture going into the reactor. The construction of this system is such that the acid and its vapors never see any materials other than quartz and Teflon. Once the appropriate gas mixture is prepared, it goes into the reactor, a length of quartz tubing inside a three zone electric furnace. This quartz tube reactor has three sections, an input leg of 1 mm 10, a center section of 10 mm 10 and an outlet leg of 1 mm 10. The lengths of these three sections are chosen in such a manner that the input and outlet legs are in th~ portion of the electric furnace in which there is a temperature gradient and the center section is in the portion of the furnace in which the temperature is uniform. The reactor thus provides an accurately defined time-attemperature. After leaving the reactor, the flowing gas mixture is analyzed. NO, CO, SOe and De were measured respectively by a Thermoelectron' Chemiluminescent NOx meter, a Thermoelectron Gas Filter Correlation CO analyzer, a rhermoelectron Pulsed Florescence 502 analyzer, and a Teledyne 02 analyzer. The first three of these instruments were calibrated daily with calibration gas mixtures purchased from Matheson, while lab air was used to calibrate the fourth. Three different procedures were used to determine [503 ] in the post reaction gases. In procedure A a sample trap is used. The inlet end of this trap is inside the three zone electric furnace so that the gases . enteriag.the .trap are at .a .temper&tur.e .well above their dew point. The body of the trap was immersed in boiling water. As discussed by Wendt et al.(lO) SOa may be quantitatively recovered from flue gas by condensation as HeSO~ at 90 to 100oC. By using the three way valve the entire gas flow was passed through this hot trap for a predetermined time, after which all flows were stopped and the amount of HeSO~ collected was measured by the procedure of Fritz and Yamamura (11), i.e., by titration with an. BOY. alcohol/20Y. water solution of barium perchlorate with thorin indicator. This sampling procedure has the advantage of eliminating a number of potential sources of error, i.e. the fraction of.SOa remaining in the post reaction gas 1s simply the amount of HeSO~ collected in the trap divided by product of the rate at which the precision metering pump inputs acid and the collection time. In procedures Band C the extent to which the input 503 was converted to SOe was determined for reaction mixtures in which SOe was not initially present by using the amount of SOe produced by the reaction with the Pulsed Florescence SOe meter. In procedure B, then, the conversion of the SOa was calculated as the ratio of SOe output measured by the SOe meter to S~ input calculated from the known rate at which the metering pump delivered sulfuric ··acid to the boiler. |