Emission x-ray. XES x-ray emission


Equation V-64 is that of a parabola, and electrocapillary curves are indeed approximately parabolic in shape. Because E ax tmd 7 max very nearly the same for certain electrolytes, such as sodium sulfate and sodium carbonate, it is generally assumed that specific adsorption effects are absent, and Emax is taken as a constant (-0.480 V) characteristic of the mercury-water interface. For most other electrolytes there is a shift in the maximum voltage, and is then taken to be Emax 0.480. Some values for the quantities are given in Table V-5 [113]. Much information of this type is due to Gouy [125], although additional results are to be found in most of the other references cited in this section.  [c.199]

Mary G. Enig Enig Associates, Inc.  [c.390]

The heating element of a forced circulation evaporator is usually of the conventional shell-and-tube type, most often single pass and vertical but frequendy multiple pass and horizontal. The heater is usually located fat enough below the Hquor level in the body so that hydrostatic head prevents boiling in the tubes. In crystallizing service it is desirable, but not always possible, to locate the heater far enough below the Hquor level so that boiling does not occur even in a tube which has had its inlet blocked and thus has Hquor in temperature equiHbrium with the heating medium. This avoids complete filling of the tube with cemented soHds which ate most difficult to remove. Tube size and length are chosen to give reasonable (1.5—3-m/s) tube velocities for the circulation rate available and the heating surface needed. In crystallizing service, small (less than 0.03-m) tube diameters are avoided to reduce risk of plugging, and the heaters are preferably vertical single-pass to afford more uniform distribution of dow to all tubes. Vortices in circulating lines and heater-inlet water boxes may result in such nonuniform velocities that there is Httie or no dow at all in some tubes and these quickly became plugged with soHds.  [c.473]

S. J. Pennycook. EMSA Bulletin. 19, 67, 1989. A summary of compositional imaging using a high-angle annular dark-field detector in a field emission STEM instrument published by the Electron Microscopy Society of America, Box EMSA Woods Hole, MA 02543.  [c.174]

When used to separate solid-solid mixtures, the material is ground to a particle size small enough to liberate particles of the chemical species to be recovered. The mixture of solid particles is then dispersed in the flotation medium, which is usually water. Gas bubbles become attached to the solid particles, thereby allowing them to float to the surface of the liquid. The solid partices are collected from the surface by an overflow weir or mechanical scraper. The separation of the solid particles depends on the different species having different surface properties such that one species is preferentially attached to the bubbles. A number of chemicals are added to the flotation medium to meet the various requirements of the flotation process  [c.70]

All that can be done is to make a reasonable initial assessment of the number of stages. Having made a decision for the number of stages, the heat flow through the system is temporarily fixed so that the design can proceed. Generally, the maximum temperature in evaporators is set by product decomposition and fouling. Therefore, the highest-pressure stage is operated at a pressure low enough to be below this maximum temperature. The pressure of the lowest-pressure stage is normally chosen to allow heat rejection to cooling water or air cooling. If decomposition and fouling are not a problem, then the stage pressures should be chosen such that the highest-pressure stage is below steam temperature and the lowest-pressure stage above cooling water or air cooling temperature.  [c.87]

Now cascade any surplus heat down the temperature scale from interval to interval. This is possible because any excess heat available from the hot streams in an interval is hot enough to supply a deficit in the cold streams in the next interval down. Figure 6.18 shows the cascade for the problem. First, assume that no heat is supplied to the first interval from a hot utility (Fig. 6.18a). The first interval has a surplus of 1.5 MW, which is cascaded to the next interval. This second interval has a deficit of 6 MW, which reduces the heat cascaded from this interval to -4.5 MW. In the third interval the process has a surplus of 1 MW, which leaves -3.5 MW to be cascaded to the next interval, and so on.  [c.178]

Overall, the accuracy of the capital cost targets is more than good enough for the purposes for which they are used  [c.233]

Flash point. The flash point of a liquid is the lowest temperature at which it gives off enough vapor to form an ignitable mixture with air. The flash point generally increases with increasing pressure.  [c.256]

Reactors. Perhaps the worst safety problem that can occur with reactors occurs when an exothermic reaction generates heat at a faster rate than the cooling can remove it. Such runaway reactions are usually caused by coolant failure, perhaps for a temporary period, or reduced cooling capacity due to perhaps a pump failure in the cooling water circuit. The runaway happens because the rate of reaction, and hence the rate of heat generation, increases exponentially with temperature, whereas the rate of cooling increases only linearly with temperature. Once heat generation exceeds available cooling capacity, the rate of temperature rise becomes progressively faster." If the energy release is large enough, liquids will vaporize, and overpressurization of the reactor follows.  [c.262]

Reaction rates often may be improved by using more extreme operating conditions. More extreme conditions may reduce inventory appreciably. However, more extreme conditions bring their own problems, as we shall discuss later. A very small reactor operating at a high temperature and pressure may be inherently safer than one operating at less extreme conditions because it contains a much lower inventory. A large reactor operating close to atmospheric temperature and pressure may be safe for different reasons. Leaks are less likely, and if they do happen, the leak will be small because of the low pressure. Also, little vapor is produced from the leaking liquid because of the low temperature. A compromise solution employing moderate pressure and temperature and medium inventory may combine the worst features of the extremes. The compromise solution may be such that the inventory is large enough for a serious explosion or serious toxic release if a leak occurs, the pressure will ensure that the leak is large, and the high temperature results in the evaporation of a large proportion of the leaking liquid.  [c.263]

In this accident, the steam was isolated from the reactor containing the unfinished batch and the agitator was switched ofiF. The steam used to heat the reactor was the exhaust from a steam turbine at 190 C but which rose to about 300°C when the plant was shutdown. The reactor walls below the liquid level fell to the same temperature as the liquid, around 160°C. The reactor walls above the liquid level remained hotter because of the high-temperature steam at shutdown (but now isolated). Heat then passed by conduction and radiation from the walls to the top layer of the stagnant liquid, which became hot enough for a runaway reaction to start (see Fig. 9.3). Once started in the upper layer, the reaction then propagated throughout the reactor. If the steam had been cooler, say, 180 C, the runaway could not have occurred.  [c.264]

Relief systems are expensive and introduce considerable environmental problems. Sometimes it is possibly to dispense with relief valves and all that comes after them by using stronger vessels, strong enough to withstand the highest pressures that can be reached. For example, if the vessel can withstand the pump delivery pressure, then a relief valve for overpressurization by the pump may not be needed. However, there may still be a need for a small relief device to guard against overpressurization in the event of a fire. It may be possible to avoid the need for a relief valve on a distillation column  [c.265]

At first sight, it might seem that making vessels strong enough to withstand the possible overpressurization would be an expensive option. However, we must not lose sight of the fact that we are not simply comparing one vessel with a thick wall versus one vessel with a thin wall protected by a relief valve. Material discharged through the relief valve might need to be partially contained, in which case the comparison might be between Fig. 9.4a and ft.  [c.266]

Similarly, instead of installing vacuum relief valves the vessels can be made strong enough to withstand vacuum. In addition, if the vessel contains flammable gas or vapor, vacuum relief valves will often need to admit nitrogen to avoid flammable mixtures. A stronger vessel often may be safer and cheaper.  [c.266]

Install enough intermediate storage to allow reworking of off-specification material.  [c.290]

Knowing where waste is going is the key to reducing it. When reducing waste from process operations, a steady-state mass balance is not usually comprehensive enough. A balance that takes into account start-up, shutdown, and product changeovers is required.  [c.296]

Allowing enough intermediate storage to rework ofT-specification material.  [c.297]

Evaporation processes usually separate a single component (typically water) from a nonvolatile material. As such, it is good enough in most cases to assume that the vaporization and condensation processes take place at constant temperatures.  [c.355]

Ain pollution, as defined by textbooks published in the 1970s and 1980s, is any atmospheric condition in which substances are present in concentrations high enough above thein normal ambient levels to produce a measurable effect on humans, animals, vegetation, or materials. This definition is deficient, however, because it does not include the so-called greenhouse or o2one-depleting gases which have the potential to alter the global climate and hence the global ecosystem. (The effects of these gases on humans, animals, vegetation, or materials have not been, and may never be, observed.) Therefore, in an attempt to be more comprehensive, the following definition is offered air pollution is the presence of any substance in the atmosphere at a concentration high enough to produce an objectionable effect on humans, animals, vegetation, or materials, or to significantly alter the natural balance of any ecosystem. Substances can be soHds, Hquids, or gases, and can be produced by anthropogenic activities or natural sources. In this article only nonbiological material is considered and the discussion of airborne radioactive contaminants is limited to radon [10043-92-2] (see Helium group, gases), which is discussed in the context of indoor air pollution.  [c.366]

In the classical method for the quantitative analysis of tungsten in ore concentrates, the ore is digested with acid, the tungsten is complexed with cinchonine, purified, ignited, and weighed. More commonly, x-ray spectrometry is used and its accuracy is enhanced by using tantalum as an internal standard. Plasma spectroscopy determines concentrations as low as 0.1 ppm in solutions and 10 ppm in soHds. Measurement by atomic absorption is a very rapid method, but not accurate enough for assay-grade analyses. The thiocyanate—tungsten color complex is specific for tungsten and used for colorometric analyses for concentrations in the 0.1—1% range. However, it is not accurate enough for assaying concentrates.  [c.284]

Special experimental procedures are necessary for samples that have a strong texture, or preferred crystallite orientation. If the texture is very strong it might happen that no crystalline planes are aligned relative to the incident beam to satisfy the Bragg condition and no diffraction peaks from the surface layer are observed. The best procedure then is to try a d-2d scan, because a very strong texture will render the diffraction peak from the preferentially oriented planes intense enough to be detected, even from rather thin films. This might fail if the film is too thin or if the preferred orientation is associated with an unallowed diffraction peak. An example of the latter would be the preferred 111 orientation of a bcc metal such as iron or chromium, although the 222 peak should appear if the diffractometer can run to a high enough 2 6 angle in the 6-26 geometry. If the preferred orientation cannot be determined in the 6-26 geometry the only procedure left is to use different incident angles to try to find an asymmetric geometry where the Bragg condition is satisfied for some set of planes. If the surface crystalline structure is not known, this must be found by trial and error. If the probable crystalline structure is known then it is not difficult to calculate the appropriate angle of incidence for different sets of planes under the assumption of a particular preferred orientation. Weak texture in a surface layer will manifest itself in different peak intensity ratios than those of a randomly oriented material. Such samples can prove to be the most difficult with regard to identification of the direction of preferred orientation, especially if the film is too thin for detection at high angles of incidence. It is possible [4.141], assuming a certain direction and spread of orientations, to calculate how the relative peak intensities will be modified at different glancing angles, although this is not always straightforward.  [c.216]

Holland, C. D., Gallun, S. E. and Lockett, M. J., Modeling Azeotropic and Extractive Distillations, Chem. Engg., 88 185, March 23, 1981.  [c.93]

Porter, K. E., and Momoh, S. O., Finding the Optimum Sequence of Distillation Columns—An Equation to Replace the Rules of Thumb (Heuristics), Chem. Engg. J., 46 97, 1991.  [c.157]

Gas turbine integration. Figure 6.34 shows a simple gas turbine matched against a process. The machine is essentially a rotary compressor mounted on the same shaft as a turbine. Air enters the compressor, where it is compressed before entering a combustion chamber. Here the combustion of fuel increases its temperature. The mixture of air and combustion gases is expanded in the turbine. The input of energy to the combustion chamber allows enough shaftwork to be developed in the turbine to both drive the compressor and provide useful work. The expanded gas may be discharged to the atmosphere directly or may first be used to preheat the air to the  [c.196]

FIgura 7.1 Two alternative graphs. (Reprinted from Linnhoff, Mason, and Wardle, Understanding Heat Exchan r Networks Computers Ckem. Engg., 3 295, 1979 with permission from Elsevier Science, Ltd.)  [c.214]

FIgur 7.4 If film transfer coefficients difier significantly, then nonvertical h t transfer is necessary to achieve the minimum area. (Reprinted from Linnhoff and Ahmad, Cost Optimum Heat Exchanger Networks I. Minimum Energy and Capital Using Simple Models for Capital Cost," Computers Chem. Engg., 7 729, 1990 with permission from Elsevier Science, Ltd.)  [c.218]

Figure 7.9 The Xp parameter avoids steep slopes on the Fp curves, whereas minimum Fp does not. (Reprinted from Ahmad, Linnhoff, and Smith, Cost Optimum Heat Exchanger Networks II. Targets and Design for Detailed Capital Cost Models, Computers Chem, Engg., 7 751, 1990 with permission from Elsevier Science, Ltd.) Figure 7.9 The Xp parameter avoids steep slopes on the Fp curves, whereas minimum Fp does not. (Reprinted from Ahmad, Linnhoff, and Smith, Cost Optimum Heat Exchanger Networks II. Targets and Design for Detailed Capital Cost Models, Computers Chem, Engg., 7 751, 1990 with permission from Elsevier Science, Ltd.)
Figure 10.5 The direct chlorination step of the vinyl chloride process using a liquid phase reactor. (From McNaughton, Chem. Engg., December 12, 1983, pp. 54-58 reproduced by permission.) Figure 10.5 The direct chlorination step of the vinyl chloride process using a liquid phase reactor. (From McNaughton, Chem. Engg., December 12, 1983, pp. 54-58 reproduced by permission.)
Rgure 10.6 The direct chlorination step of the vinyl chloride process using a boiling reactor eliminates the washing and neutralization steps and the resulting effluents. (From McNaughton, Chem. Engg., December 12, 1983, pp. 54-58 reproduced by permission.)  [c.286]

McNaughton, K. J., Ethylene Dichloride Process, Chem. Engg., 12 54, 1983.  [c.298]

It is not only the stream number that creates the need to split streams at the pinch. Sometimes the CP inequality criteria [Eqs. (16.1) and (16.2)] CEmnot be met at the pinch without a stream split. Consider the above-pinch part of a problem in Fig. 16.13a. The number of hot streams is less than the number of cold, and hence Eq. (16.3) is satisfied. However, the CP inequality also must be satisfied, i.e., Eq. (16.1). Neither of the two cold streams has a large enough CP. The hot stream can be made smaller by splitting it into two parallel branches (Fig. 16.136).  [c.376]

Lang, H. J., Cost Relationships in Preliminary Cost Estimation, Chem. Engg., 54 117, 1947.  [c.426]

Guthrie, K. M., Data and Techniques for Preliminary Capital Cost Estimating, Chem. Engg., 76 114, 1969.  [c.426]

Hall, R. S., Matley, J., and McNaughton, K. J., Current Costs of Process Equipment, Chem. Engg., 89 80, 1982.  [c.426]

HaU, R. S., Vatavuk, W. M., and Matley, J., Estimating Process Equipment Costs, Chem. Engg., 95 66, 1988.  [c.426]


See pages that mention the term Emission x-ray. XES x-ray emission : [c.78]    [c.89]    [c.310]    [c.696]    [c.184]    [c.1092]    [c.33]    [c.69]    [c.88]    [c.93]    [c.157]    [c.266]    [c.298]    [c.377]    [c.383]   
Physical chemistry of surfaces (0) -- [ c.0 ]