Water column, head pressure

FIGURE 14.1 One-minute fast elution of three small molecules from a 5 cm x 1 mm column packed with 5 /tm C18 particles. Column head pressure at 180 /tL/min flow rate is 2800 psi. Solvent composition is 60 40 water acetonitrile. 

FIGURE 14.9 Performance of short column ultrahigh pressure nano LC system at 10 /rL/min for the separation of tranylcypromine sulfate, perphenazine, and their impurities. Nano LC may be operated at 10 times optimum column flow rate and achieve ultrahigh throughput and reproducibility. Short column (3 cm x 150 /mi inner diameter) was packed with 1.8 /im C18 particles. Solvent A was water with 0.4% ammonia solvent B was acetonitrile with 0.4% ammonia. Gradient 0 to 1 min, 3 to 10% B 1 to 1.3 min, 10 to 35% B, 1.3 to 3.5 min, 35 to 90% B held at 90% B through 4.9 min and then returned to 3% B. Column head pressure was 7200 psi. 

FIGURE 14.10 Comparison of benzene (1), naphthalene (2), and biphenyl (3) test probes eluted from a 3 cmx 75 (Xm inner diameter column packed with 1.8 flm C18 particles. Trace A was obtained at 1.2 /ll./min flow rate and trace B was obtained at 10,000 psi column head pressure (10 /il./min flow rate). Mobile phase was 60 40 acetonitrile water. 

Supercritical fluid chromatographic pumps must have both a wide range of compensation and use dynamic compressibility compensation to produce accurate and reproducible flow and composition. Whereas water has a compressibility factor of 75 x 10 /bar, methanol is more compressible at 120 X 10 /bar. Carbon dioxide has widely varying compressibility from 95 to 395 X 10 /bar at 5°C, depending on the pump delivery pressure (column head pressure). The viscosity of pure carbon dioxide is 1 /20 the viscosity of pure methanol. During composition programming, the viscosity of the mixed fluid and the column head pressure increases as the modifier concentration increases. Without dynamic compensation, the actual delivery of the carbon dioxide would roll off. The total flow would be less than the set points and the modifier concentration would be more than the set points. 

The column headed 1 gives the volume of the gas (in milliliters) dissolved in 1 mL of water when the pressure of the gas plus that of the water vapor is 760 mm. 

Pneumatic systems use the wave motion to pressurize air in an oscillating water column (OWC). The pressurized air is then passed through an air turbine to generate electricity. In hydrauhc systems, wave motion is used to pressurize water or other fluids, which are subsequendy passed through a turbine or motor that drives a generator. Hydropower systems concentrate wave peaks and store the water dehvered in the waves in an elevated basin. The potential energy suppHed mns a low head hydro plant with seawater. 

Bertole et al.u reported experiments on an unsupported Re-promoted cobalt catalyst. The experiments were done in a SSITKA setup, at 210 °C and pressures in the range 3-16.5 bar, using a 4 mm i.d. fixed bed reactor. The partial pressures of H2, CO and H20 in the feed were varied, and the deactivation, effect on activity, selectivity and intrinsic activity (SSITKA) were studied. The direct observation of the kinetic effect of the water on the activity was difficult due to deactivation. However, the authors discuss kinetic effects of water after correcting for deactivation. The results are summarized in Table 1, the table showing the ratio between the results obtained with added water in the feed divided by the same result in a dry experiment. The column headings refer to the actual experiments compared. It is evident that adding water leads to an increase in the overall rate constant kco. The authors also report the intrinsic pseudo first order rate-coefficient kc, where the overall rate of CO conversion rco = kc 6C and 0C is the coverage of active... 

Figure 11.3 Water column exerting 1 psig of head pressure (1 psig = 28 in of water).

A column of water 28 inches high exerts a head pressure of 1 psi, as shown in Fig. 11.3. To determine the pressure drop of water flowing through a hole, in pounds per square inch, we would calculate... 

Water was used as the liquid phase. The liquid delivery system consists of a feed tank, pump, and a flow indicator. Water is recycled, as well as added if necessary, to maintain a constant suction head at the pump. The in-house air system was used as the gas delivery system through a rotameter. Air enters the setup at a point below the packing. Two taps are mounted at the inlet and outlet of the packed column for pressure drop measurement. 

Conventional high pressure NICI spectra were obtained using a Hewlett-Packard 5985B quadrupole GC/MS, as described previously (1). Methane was used as the Cl reagent gas and was maintained in the source at 0.2-0.4 torr as measured through the direct inlet with a thermocouple gauge. A 200 eV electron beam was used to ionize the Cl gas, and the entire source was maintained at a temperature of 200° C. Samples were introduced into the spectrometer via the gas chromatograph which was equipped with a 25 meter fused silica capillary column directly interfaced with the ion source. For all experiments, a column coated with bonded 5% methyl phenyl silicon stationary phase, (Quadrex, Inc.) was used and helium was employed as the carrier gas at a head pressure of 20 lbs. Molecular sieve/silica gel traps were used to remove water and impurities from the carrier gas. 

The impurities of propylene carbonate that have been identified by gas chromatography85 include C02, water, propylene oxide, allyl alcohol, 1,2-propylene glycol, 1,3-propylene glycol, and lesser amounts of unidentified materials. The solvent may be purified readily by vacuum fractional distillation, with a reflux ration of 10 1 at 0.5-1 torr. At this pressure the column head temperature is 72-75°C. Another suggestion is to heat propylene carbonate with sodium carbonate and potassium permanganate (both 10 g L 1) for 2 h prior to vacuum distillation. 

Answer If the surface pressure for the water column is 700 kPa, or 0.7 MPa, then we can estimate the bottom hole pressure using the hydrostatic head equation (see Chapter 8). First, assume the density of water is 1000 kg/m3. 

Plinke process In this process sulfuric acid is distilled at atmospheric pressure with indirect heating by natural gas and oil combustion (combustion chamber temperature 800 to 1100°C). This process is predominantly used in Europe. The to be concentrated waste acid is fed in at the top of the distillation column into boiling 96% sulfuric acid at atmospheric pressure and 320°C in a cast iron boiler. Water is expelled at the column head leaving a 96% acid. By adding nitric acid, which is mainly reduced to nitrogen, organic impurities can be removed oxidatively. 

The analytical procedure for extraction and class separation was adapted from Venkatesan et al. (1987) and consisted of repeated ultrasonic solvent extractions using hexane/acetone followed by saponification of the free fatty acids in KOH/methanol. The organic extract was then divided into three fractions containing aliphatics (w-alkanes), PAH and n-alcohols, and sterols using open column chromatography on 10% water-deactivated silica. Free fatty acids and n-alcohols were derivatized by BSTFA prior to analysis on GC-MS. All determinations were performed using a Hewlett Packard 5890 series 11 gas chromatograph equipped with a split/splitless injector and an electronic pressure control. The column was a 30 m X 0.25 mm ID coated with a 0.25 /rm, 5% phenyl-methylsilicone phase (J W DB-5MS) at a head pressure... 

In view of the fact that the water content in the bottoms product of the pressurized column is twice that of the prerun column, the hydrocarbons transferred ftom the prerun column into the pressurized column will reliably be found in the bottoms product, i.e. they are transferred to the atmospheric distillation column. Thus, ethanol becomes the key component for the pressurized column. Since the bottom product of the pressurized column - unlike that of the atmospheric column - does nOt have to meet certain purity requirements, this column need not have a side outlet for ethanol, but the ethanol is quantitatively transferred to the atmospheric columit. The high methanol content in the bottom of the pressurized column facilitates ethanol separation. Nevertheless, for the same number of trays, the pressurized operation of this column leads to a higher reflux than in the atmospheric column. The bottoms product ftom the pressurized column is transferred to the atmospheric column at approximately 125-35°C. The overhead product is obtained at approximately 115-125°C, condensed in the reboiler of the atmospheric column, and fed to the reflux drum of the pressurized column. From there, some of the overhead product is withdrawn by way of an after-cooler as on-spec methanol while the rest is pumped back uncooled as reflux to the column head. 

It is postulated that bubble collapse may well have generated sufficient pressure to commence propagation of the pre-existing crack, which then continued, either by direct conversion of the bubble energy, or by the rapid conversion of potential to kinetic energy in the water column. The presence of gas in the lute vessel implies the possibility of a head of... 

Figure 9-77 illustrates the required valve switching for this technique. In the first step (Fig. 9-77A), the injection loop (5 mL) is filled with the solvent sample. Sample delivery is carried out with a simple isocratic pump at a flow rate of 1.5 mL/min for seven minutes out of a reservoir with a small head pressure, so that the loop is rinsed several times with sample. After loading the loop, the sample is transferred with ultra-high purity water to the concentrator column, in which the anions or cations are retained (Fig. 9-77B). The remaining solvent is rinsed off with ultra-high purity water (flow rate 1.7 mL/min rinse time 10 minutes). Afterwards, the concentrator column is put inline with the analytical separator column. The pre-concentrated ions are then eluted from the concentrator column in opposite directions and separated on the analytical separator...

Equation (lO) is written in terms of fluid head. Each term has units of length. (The equation could be written so that each term has units of pressure by multiplying each term by p. ) Fluid head is a way of expressing pressure as an equivalent static pressure of a stationary body of fluid. For exanple, one atmosphere of pressure is equivalent to about 34 feet of water, because the pressure difference between the top and bottom of a column of 34 feet of water is one atmosphere. Equation 18.8. with each term defined as fluid head, is... 

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