Neutralization pressure

Spray dryers may operate under positive, negative, or neutral pressures. In general, pressure drop in a complete system will range from 15 to 50 cm of water, depending on duct size and separation equipment employed. 

Zone, pressure A zone within a building or a process that is held at a given positive, negative, or neutral pressure in order to contain process contaminants. 

T1 = temperature of indoor air, °R = temperature of outdoor air, °R H = height from the center of the lower opening to the Neutral Pressure Level (NPL), ft... 

Polyethylene-based membranes are manufactured for use in hazardous waste landfills, lagoons, and similar applications. Two of these products have been tested to determine their effectiveness as barriers against radon diffusion. (In most cases, diffusive flow is considered of little or no significance as a mechanism of radon entry compared with convective flow). A 20-mil high-density polyethylene tested 99.9% effective in blocking radon diffusion under neutral pressure conditions. A 30-mil low-density polyethylene tested 98% effective in blocking radon diffusion under neutral pressure conditions. 

Tightened building shell to minimize the amount of air needed to pressurize the basement and to lower the neutral pressure plane. 

Exiting gaseous HC1 is checked for unreacted Cl2 (Figure 6 5) before neutralization [pressure variations between neutralization tank (Figure 6 6) and active carbon filter (Figure 6 9) are balanced in an intermediate buffer system (Figure 6 8)]. 

S. Lisgo OSM-EIRENE Modeling of Neutral Pressures in the Alcator C-Mod Divertor, J. Nucl. Mater. (2004), to appear... 

Ions prcxluced in the center of the trap (usually by electron impact) are constrained by the magnetic field and applied potentials on the trapping plates to follow orbits within the cell and only slowly diffuse toward the walls. During the time the ions are trapped, they may have maiy collisions with neutral molecules in the trap, and these collisions can lead to thermalization of the ions and may result in chemical reactions. At a neutral pressure of 10 torr, the approximate pseudo first-order rate constant for ion-molecule collisions is 30 s. The ionic products of ionization and subsequent reactions in the cell can be detected at aiy time mass spectrometrically application of a broad range of radio frequencies and detection of resonance at cyclotron frequencies corresponding to m/z values of the ions present. Techniques are available that allow isolation of one or more m/z value in the ion population by ejection of all other ions, and this allows the reactions of a particular ion to be followed directly. Fourier transform methods, intrcxluced by Marshall and... 

The hottest gas within a furnace (or any enclosed chamber) rises to the top, creating a higher pressure at the furnace s higher elevations and a lower pressure at the furnace s lower elevations. (This is stack effect within the furnace.) The zero gauge-pressure plane or neutral pressure plane is the locus of points where the pressure inside the furnace is the same as the atmospheric pressure outside the furnace at the same elevation. The neutral or zero plane is the boundary between + and — pressures within the furnace. If there are leaks through the furnace walls, furnace gases will leak outward from the space above the neutral plane and air will leak inward to the space below the neutral plane. (See fig. 6.13.)... 

In most industrial heat-processing furnaces, it is desirable to have the entire furnace chamber at a positive pressure with an automatic furnace control system having a setpoint of 0.02 in. wc (0.5 mm) at the elevation of the lowest part of the load(s) or better yet, at an elevation just below the lowest leak. To keep out tramp air inleakage, raise the furnace pressure enough to drive the neutral pressure plane below the furnace bottom, in a liquid bath furnace, below the liquid surface level. 

Fig. 6.13. Effects of furnace temperature and input on the level of the neutral pressure plane elevation shown on six sectional elevation views of a furnace with no furnace pressure control. If there were any gas flow in the furnace, the neutral pressure plane would be more like a wrinkled sheet than a plane. The top three show the effect of temperature with no change in input. The bottom three show the effect of input rate with no change in furnace temperature.

The elevation of the pressure-sensing tap does not necessarily have to be at the elevation desired for the neutral pressure plane. The most desirable height for the zero pressure plane may be at a point that turns out to be bad for good measurement, for example, below the hearth, at a level where scale might plug the pressure tap, or in a place where liquid metal may splash into the tap. In such cases, a very workable solution is to locate the sensor tap at a convenient higher position and then adjust the controller s setpoint in accordance with the correction for the rise in pressure for the chosen higher elevation from table 6.2. (See example 6.2.)... 

The next choice would be to locate the tap in the wall opposite the burners, but equally spaced between the burner centerlines and elevated 2 feet above the hearth. The setpoint of the furnace pressure control will have to be biased to correct for the difference in elevation between the pressure tap and the desired level of the neutral pressure plane (at the hearth). Interpolating from table 6.2, the setpoint bias should be 0.0118 in. X 2 feet of elevation = 0.0236, or say 0.025 or 0.03 in. wc to allow for expected wear on the car seals. 

Q4. Is the neutral pressure plane (or zero pressure plane ) really a plane ... 

N or N2 = nitrogen = an inert gas, comprising about 80% of air and a large part of poc, unless using oxygen enrichment, net heating value = nhv = lower heating value, Ihv. See Ihv. neutral pressure plane = zero pressure plane = balanced pressure line (invisible), or level at which the pressure inside a furnace is exactly equal to the pressure outside the furnace at the same elevation. Usually not really a plane, but an invisible surface rumpled by burner jet and draft effects. See sec. 6.6.1. nm /h = normal cubic meters per hour, a unit of volumetric flow rate, equal to 37.9 scfh. nm is standardized at 0 C, 760 mm Hg, dry air or gas. A standard ft is defined at 60 F, 30 Hg, saturated air or gas. normal air = European near-equivalent of U.S. standard air , see also). 

The efficiency of a soil in supporting a structure is influenced by the effective or intergranular pressure, that is, the pressure between the particles of the soil that develops resistance to applied load. Because the moisture in the pores offers no resistance to shear, it is neutral and therefore pore water pressure also has been referred to as neutral pressure. Since the pore water or neutral pressure plus the effective pressure equals the total pressure, reduction in pore water pressure increases the effective pressure. Reduction of the pore water pressure by drainage consequently affords better conditions for carrying a proposed structure. 

When there is a difference between inside and outside temperatures, there is some point between the top and bottom openings where the internal and external pressures are equal. This location is the neutral pressure plane. An overpressure from a fire inside a building will move the neutral pressure plane downward. If the temperature outside a building is less than inside, a vent opening can move the neutral pressure plane upward. 

The location of the neutral pressure plane can influence the distribution and buildup of smoke in a tall building. However, the movement of heat and smoke in tall buildings is not fully understood. It is difficult to model. If air enters at the bottom near a fire, the fire can become more intense, adding smoke. External winds can change the patterns of movement. On a hot summer day, often the external air temperature is higher than the air-conditioned interior air. This reduces or eliminates the stack effect. 

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