Carrier back pressure regulation

In this study, we used the modified Wicke-Kallenbach cell which is tubular membrane cell type. Permeation measurements were performed in the 293K-373K, Oatm-Satm range for H2, N2, CO2 and CH4. Feed gas and retentate gas were controlled by MFC(Mass Flow Controller, Tylan Co.) and BPR(Back Pressure Regulator). Permeate gas flux was measured by soap bubble flow meter, MFM (Mass Flow Meter, Teledyne Co.) and wet gas meter. Especially, MFM was used to measure kinetics of membrane permeation. Separated and retentate gas composition was analyzed by on-line GC(HP 5890 II, TCD type). Helium was used as carrier gas and sweeping gas. Temperature was detected by RTD(Hanyoung. Co.) at inlet, inner cell and skin of cell. Pressures were detected by pressure transducers(Deco Co.) at inlet and permeate part. 

When coupling a low-pressure detector such as the ELSD with SFC, detection takes place at atmospheric pressure, usually downstream of the back-pressure regulator [2]. Figure la shows a common SFC-ELSD interface with downstream pressure control. Factors affecting ELSD response in this configuration include nebulizer design, evaporation conditions, carrier gas flow rate, and the use of makeup fluid. 

Figure 2.48 Injector back pressure regulation. 1. Carrier gas inlet filter, 2. mass flow regulator, 3. electronic pressure sensor, 4. septum purge regulator, 5. solenoid valve, 6. electronic pressure control valve and 7. injector with column installed.

Fig. 3.2. System for double-column chromatography with intermediate trapping and re-injection, suitable also for direct injection of aqueous solutions. 1, carrier gas 2, pressure regulator 3, flow controller 4, vent for back-flushing S, injection port for heart-cut and back-flushing 6, precolumn (packed) 7, injection port for aqueous solutions 8, control flame ionization detector for pre-separation 9, vent for cutting 10. leak for make-up gas 11, trap 12, outlet of splitter 13, glass capillary column 14, flame ionization detector for main separation. Reproduced from [35].

The term back pressure describes the position of the EPC valve behind the injector in the split exit line, in combination with a mass flow controller in front of the injector (see Figure 2.48). In this widely used carrier gas regulation scheme for split/splitless injectors, the pressure sensor is typically found in the septum purge line close to the injector body to ensure a pressure measurement close to the column head. A filter cartridge may need to be used to protect the regulation unit from any carrier gas contamination. 

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