Measuring online conductance

At the top end of the program monitoring scale is the use of online fluorescence tracing systems, whereby tracer dye polymers form part of the water treatment program and their concentration can be measured online at various locations throughout the boiler plant system. Much less expensive, handheld fluorometers are now available to conduct the same type of analysis at the laboratory bench or on the boiler house firing-floor. These tracer dye polymers can be used to determine ... 

Both the reactors are operated in batch, and the concentrations of components involved are measured online by electro-conductivity. Data interpretation is made by the kinetic equation of second order. The results obtained in the range of 25-45"C are given in Table 3. Again, the values for the rate constant measured in SCISR, ks, are S5 tematically higher than those in STR, ksr, by about 20%, and no significant difference betvi een the values for the active energy measured in SCISR and STR has been found. 

Figure 2 illustrates several cells with contacting electrodes. Cell designs are available for a variety of research, routine, and industrial applications. Routine measurements use conductivity cells of suitable size that may be directly immersed in beakers, flasks, etc. Water analysis and online industrial measurements may require immersion or flow-through cells for continuous monitoring. Precision measurements... 

AH, Z., Le, H.H., Ilisch, S., and Radusch, H.J. (2009) Morphology development in nanoclay filled rubber compounds and rubber blends detected by online measured electrical conductance. J. Mater. Sd., 44, 6427. 

In the most common method, the solution is irradiated with near-ultraviolet radiation (200-400 nm) to decompose organic matter by means of a radical formation mechanism. Then the generated CO2 is transported toward the detector with a carrier gas. In order to eliminate some ionic compounds that can interfere with the measurement, a membrane is placed before the detector. The detection is carried out either by the measurement of conductivity via a sensor or by a nondispersive infrared analyzer. In this online system, the sample analysis takes aroimd 6 min. Other systems based on the same principle have also been described. In this case the oxidation and detection are produced in the same chamber. In this "batch" apparatus the sample is trapped and analyzed for 3-30 min. With this latter system, some ionic species other than H and HCO3 can interfere with the conductivity readings. Species such as Ti02 [85,90] and persulfate [91,121] have been used as catalysts present as a diluted suspension in water. The TOC is obtained from the difference between the conductivities for the irradiated and nonirradiated samples. 

FIGURE 5.15 In situ method for measuring proton conductivity in Nafion membrane by using EC-AFM. The applied voltage induces water oxidation at the electrode. TTie protons are only transported through the membrane when the conductive AFM tip makes contact with an ion channel. These protons are used for the ORR at the AFM tip. [11,66,67]. (For color version of this figure, the reader is referred to the online version of this hook.)... 

Where-high purity MU is provided for higher pressure WT boiler plant FW, some form of continuous analyzers for measuring treated water pH and conductivity are almost always installed, as are sodium (Na) ion-selective electrodes for detection of sodium leakage. Automatic online silica analyzers also may be installed, but they measure only reactive (ionizable) silica (Si02), not colloidal or total silica, so caution is required where unforeseen silica leakage may present a problem. 

After the activation period, the reactor temperature was decreased to 453 K, synthesis gas (H2 CO = 2 1) was introduced to the reactor, and the pressure was increased to 2.03 MPa (20.7 atm). The reactor temperature was increased to 493 K at a rate of 1 K/min, and the space velocity was maintained at 5 SL/h/gcat. The reaction products were continuously removed from the vapor space of the reactor and passed through two traps, a warm trap maintained at 373 K and a cold trap held at 273 K. The uncondensed vapor stream was reduced to atmospheric pressure through a letdown valve. The gas flow was measured using a wet test meter and analyzed by an online GC. The accumulated reactor liquid products were removed every 24 h by passing through a 2 pm sintered metal filter located below the liquid level in the CSTR. The conversions of CO and H2 were obtained by gas chromatography (GC) analysis (micro-GC equipped with thermal conductivity detectors) of the reactor exit gas mixture. The reaction products were collected in three traps maintained at different temperatures a hot trap (200°C), a warm trap (100°C), and a cold trap (0°C). The products were separated into different fractions (rewax, wax, oil, and aqueous) for quantification. However, the oil and wax fractions were mixed prior to GC analysis. 

Any training conducted online must be performed in a controlled environment to ensure that production systems and data are not adversely impacted. Appropriate security measures must be taken to ensure that the training is isolated from the production environment. 

More recent findings suggest that the role of 5-HT reuptake in anxiety might be particularly critical during early development (26). The selective serotonin reuptake inhibitor (SSRI) fluoxetine given postnatally to wild-type mice for approximately 2 wk (between postnatal days 4 and 21) resulted in anxiety behavior when tested as adults, and this was similar to that of 5-HTT- - mice. Perhaps because these experiments were conducted in 5-HTT- mice on a 129 background, neither 5-HTT 7 nor postnatally SSRI-treated mice exhibited anxiety in the most typical measures of anxiety (see supporting online material [26]). 5-HTT- - and postnatal SSRI-treated mice did not demonstrate decreased center time in the open field or decreased open arm time or entries in the... 

This work was expanded in 2006, when the benzyl alcohol oxidation was conducted with cyclohexane as the solvent (Grunwaldt et al., 2006). The authors set out to address whether the active phase of the catalyst was oxidic or metallic palladium. The reaction conditions were as follows temperature 323 K reactant mixture, 200 p.1 of benzyl alcohol in 100 ml of cyclohexane saturated with 02. The catalytic activity was determined online by monitoring the intensity of the C=0 band in the benzaldehyde with IR spectroscopy. If the catalyst was not reduced in the XAFS reactor (by the H2-saturated cyclohexane), then no catalytic activity was measured, and the palladium remained oxidic. If the catalyst was prereduced, a highly active catalyst was obtained, and the XAFS data were found to be consistent with the presence of only metallic palladium. Thus, the conclusion was reached that palladium oxide exhibits hardly any activity at 323 K, whereas metallic palladium particles are much more active. 

Gas chromatographs equipped with flame ionization and thermal conductivity detectors gave detailed information on concentrations of oxygenated compounds, hydrocarbons etc., online in a semi-continuous manner. For the analysis of the hydrocarbons either a Varian Star 3400 CX or a Shimadzu GC-3BF with flame ionization detectors was used. N2, O2 and CO2 were measured with a Shimadzu GC-3BT equipped with a thermal conductivity detector. 

Eor tubular membranes, the permeation flux measurements are generally carried out by a shell-and-tube arrangement as shown in Fig. 13.2 [7]. Since the membrane is plated on the outside of the porous substrate, the feed gas flows upward through the outside of the membrane (shell side), and the permeate gas is collected on the tube side. A purge gas can also be used on the tube side if desired. The upstream pressure is monitored by a capacitance pressure transducer and the permeate side pressure is kept atmospheric. The gas permeation rate (the volumetric flow rate) is measured in the permeate side at atmospheric pressure and room temperature. For mixture experiments, the permeate and retentate can be analyzed by an online gas chromatograph equipped with appropriate detectors, such as Thermal Conductivity Detector (TCD), Flame Ionization Detector (FID) or others, depending on the specific gas mixture... 

Cells are available for sample volumes as small as 2 mL, while standard sample size is 25-50 mL. Special cells for highly accurate conductivity measurements are available for research purposes. Flow-through cells are available for online monitoring of process streams. The reference by Berezanski depicts several cell types. 

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