Vapor capping

The environment for the water treatment can be in the presence of liquid water, steam, or humidified air as long as it contains more than 2% by weight of water. One approach is to heat aqueous slurry of the polymer slurry capping. Another technique is to treat the polymer with steam or humidified heated air vapor capping). In the slurry capping technique, the polymer is mixed with sufficient water to form slurry under sufficient pressure to keep the water in liquid form at the reaction temperatures (ca. 200°C). Salt or base is dissolved in the aqueous phase. The inorganic compound is blended with the polymer in the solid phase, which is heated to the reaction temperature. The moisture, usually carried by air and sometimes in the form of steam, is passed over and through the polymer. 

FIGURE 39.5 Gottingen minipig SM cutaneous injiiry 24 h after 30-120 min vapor cap exposures. 

Logan et al (1999) determined the cutaneous uptake of C-sulfur mustard from saturated vapor by the hairless guinea pig using vapor caps adhered to the dorsal skin. The skin was exposed to the saturated vapor at... 

Three principal vapor—Hquid contacting devices are used in current crossflow plate design the sieve plate, the valve plate, and the bubble cap plate. These devices provide the needed intimate contacting of vapor and Hquid, requisite to maximizing transfer of mass across the interfacial boundary. 

Figure 14-25 or Eq. (14-92) may be used for sieve plates, valve plates, or bubble-cap plates. The value of the flooding vapor velocity must be considered as approximate, and prudent designs call for approaches to flooding of 75 to 85 percent. The value of the capacity parameter (ordinate term in Fig. 14-25) may be used to calculate the maximum allowable vapor velocity through the net area of the plate ... 

Plate Layouts Cross-flow plates, whether bubble-cap, sieve, or valve, are similar in layout (Fig. 14-28). Possible zones on each plate are Active vapor-dispersion Peripheral stiffening and support Disengaging Distributing Downcomer... 

The peripheral stiffening zone (tray ring) is generally 25 to 50 mm (1 to 2 in) wide and occupies 2 to 5 percent of the cross section, the fraction decreasing with increase in plate diameter. Peripheiy waste (Fig. 14-28) occurs primarily with bubble-cap trays and results from the inabihty to fit the cap layout to the circular form of the plate. Valves and perforations can be located close to the wall and little dead area results. Typical values of the fraction of the total cross-sectional area available for vapor dispersion and contact with the liquid for cross-flow plates with a chord weir equal to 75 percent of the column diameter are given in Table 14-6. 

The plate thickness of bubble-cap and sieve plates is generally estabhshed by mechanical design factors and has little effect on pressure drop. For a sieve plate, however, the plate is an integral component of the vapor-dispersion system, and its thickness is important. 

Regarding a historical perspective on carbon nanotubes, very small diameter (less than 10 nm) carbon filaments were observed in the 1970 s through synthesis of vapor grown carbon fibers prepared by the decomposition of benzene at 1100°C in the presence of Fe catalyst particles of 10 nm diameter [11, 12]. However, no detailed systematic studies of such very thin filaments were reported in these early years, and it was not until lijima s observation of carbon nanotubes by high resolution transmission electron microscopy (HRTEM) that the carbon nanotube field was seriously launched. A direct stimulus to the systematic study of carbon filaments of very small diameters came from the discovery of fullerenes by Kroto, Smalley, and coworkers [1], The realization that the terminations of the carbon nanotubes were fullerene-like caps or hemispheres explained why the smallest diameter carbon nanotube observed would be the same as the diameter of the Ceo molecule, though theoretical predictions suggest that nanotubes arc more stable than fullerenes of the same radius [13]. The lijima observation heralded the entry of many scientists into the field of carbon nanotubes, stimulated especially by the un-... 

Fuel system components involved in the refueling process include the fuel tank, filler pipe, filler cap, vapor control valve, liquid-vapor discriminator (LVD) valve, and the carbon canister [27,28]. During vehicle refueling, which is monitored during the integrated refueling test as outlined in Fig. 1, the following operations occur in the evaporative emission control system ... 

In valve trays, perforations are covered by liftable caps. Vapor flows lifts the caps, thus self creating a flow area for the passage of vapor. The lifting cap directs the vapor to flow horizontally into the liquid, thus providing better mixing than is possible in sieve trays. 

Health Hazards Information - Recommended Personal Protective Equipment Dust mask, gloves, safety glasses, dust cap Symptoms Following Exposure Inhalation of dust may cause respiratoiy irritation. Compound is non-toxic when ingested. Prolonged contact with eyes or skin may cause irritation General Treatment for Exposure INHALATION move to fresh air. EYES flush with water get medical attention if irritation persists. SKIN flush with water Toxicity by Inhalation (Threshold limit Value) Data not available Short-Term Inhalation Limits Data not available Toxicity by Ingestion Data not available Late Toxicity Data not available Vapor (Gas) Irritant Characteristics Data not available liquid or Solid Irritant Characteristics Data not available Odor Threshold Odorless. 

The vapors from a fluid catalyst unit carry a small amount of fine catalyst particles which might clog the narrow clearances of a conventional bubble cap plate. 

At low vapor rates, valve trays will weep. Bubble cap trays cannot weep (unless they are damaged). For this reason, it is generally assumed that bubble cap trays have nearly an infinite turndown ratio. This is true in absorption processes (e.g., glycol dehydration), in which it is more important to contact the vapor with liquid than the liquid with vapor. However, this is not true of distillation processes (e.g., stabilization), in which it is more important to contact the liquid with the vapor. 

As vapor rates decrease, the tray activity also decreases. There eventually comes a point at which some of the active devices (valves or bubble caps) become inactive. Liquid passing these inactive devices gets very little contact with vapor. At very low vapor rates, the vapor activity will concentrate only in certain sections of the tray (or, in the limit, one bubble cap or one valve). At this point, it is possible that liquid may flow across the entire active area without ever contacting a significant amount ot vapor. This will result in very low tray efficiencies for a distillation process. Nothing can be done with a bubble cap tray to compensate for this. 

Fnr stripping service, as in a glycol or amine contactor (see Chapt 7 a bubble cap trays are the most common. In recent years, there has b growing movement toward crimped sheet structured packing. Improved vapor and liquid distributor design in conjunction with struc-... 

When he was about to replace the cap on the end of the filler pipe, a spark jumped from the cap to the pipe, and a flame appeared on the end of the pipe. It was soon extinguished. The flame could not travel back into the gasoline tank. The mixture of vapor and air in the tank was too rich to explode. 

Figure 4-64A. Adjustable floating" caps for vapor flow. By permission, Koch Engineering Co., Inc.

Data from bubble cap and perforated tray columns for the Murphree vapor plate efficiencies are correlated [86] ... 

Vapor rises up through risers or up-takes into bubble cap, out through slots as bubbles into surrounding liquid on tray. Bubbling action effects contact. Liquid flows over caps, outlet weir and downcomer to tray below. Figures 8-63-67, 79, and 81. 

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