Closed Vapor Systems

In this case, the pressure increase is due to the vapor pressure of volatile compounds. Often the solvent can be considered as the volatile compound, so its vapor pressure can be obtained from a Clausius-Clapeyron equation  

For complex systems it may be obtained from a phase diagram P =f(x). 

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An interesting and novel use of a soHd desiccant, the reduction of cold condensate corrosion in automotive exhaust systems, illustrates a hybrid closed—open system. Internal corrosion occurs in mufflers when the water vapor in the exhaust condenses after the engine is turned off and the muffler cools. Carbon dioxide dissolves in the condensate to form an acidic soup. In an essentially closed static drying step, an acid- and heat-resistant desiccant located in the muffler adsorbs water vapor from the exhaust gas as it cools to prevent formation of corrosive acidic condensate. When the engine is restarted, the system becomes open, and the desiccant is regenerated by the hot exhaust gas to be ready for the next cooldown step (19). 

Usually, the closed liquid drain header is run as a separate line to the drum and provided with a high level cut-off valve with local manual reset. In some cases the closed drain system is segregated into a number of subheaders, as described earlier. Hydrocarbon liquids may be bypassed around the drum through a connection from the closed drain header directly to the pumpout pump suction, provided that the liquid can be routed to a safe disposal location, considering its vapor pressure and temperature. Emergency liquid pulldown connections, if provided, are routed to the blowdown drum via the closed drain header. 

In a typical closed-loop system, liquid from the separator is cooled in a heat exchanger then recirculated. Any excess liquid added by mist and vapor flows out through a level-control valve. ... 

SWEC offers a reactor quench system rather than a closed cyclone system. Their typical RTD is an external, rough-cut cyclone (see Figure 9-7). The vapors from the rough-cut cyclone enter the reactor vessel. 

A CVD reaction can occur in one of two basic systems the closed reactor or the open reactor (also known as close or open tube). The closed-reactor system, also known as chemical transport, was the first typetobeusedforthe purification of metals. It is a hybrid process which combines vapor-phase transfer with solid-state diffusion. As the name implies, the chemicals are loaded in a container which is then tightly closed. A temperature differential is then applied which provides the driving force for the reaction. 

Figure 234 is showing a closed sorption system using water vapor as adsorptive. The heat has to be transferred to and from the adsorbent by an heat exchanger. This holds also for the condenser/evaporator. Heat has to be transported to the adsorber and at the same time the heat of condensation has to be distracted from the condenser in order to keep up the water vapor flow... 

Integrated vapor extraction and steam vacuum stripping can simultaneously treat groundwater and soil contaminated with VOCs. The system developed by AWD Technologies consists of two basic processes a vacuum stripping tower that uses low-pressure steam to treat contaminated ground-water and a soil gas vapor extraction/reinjection process to treat contaminated soil. The two processes form a closed-loop system that provides simultaneous in situ remediation of contaminated groundwater and soil with no air emission. 

Tank farms storage flammable liquids The tanks are inerted with a closed vapor recovery system, so the penalty here is zero. 

In some cases a closed drainage system can be used which drains process components directly into the oily water sewer. This has the advantage of avoiding releases of vapors in any instance, but assurance must be obtained that back pressure from one drainage location will not backfeed liquids into another drain point when two valves are open simultaneously or other drainage valves can contain any backpressure on them from other drainage sources. 

All waste hydrocarbon gases (vents, relief valves, and blowdowns) should be routed to a flare or returned to the process through a closed header system. Release of vapors to atmosphere may produce a vapor cloud, and even through the release may be remote from the facility it may drift or the effects of ignition (i.e., blast overpressure) of the cloud will be felt at the facility. 

The source of these compounds is varied. The butanes are found naturally in crude oils and natural gas. They, plus the olefins, are products of various refinery processes and of olefins plants. They are separated by fractionation, except for butadiene and isobutylene, which are sometimes recovered by extractive distillation. They all vaporize at room temperature, so they are handled in closed, pressurized systems.. 

A vapor pressure of 4.5><10 mm Hg at 20 °C has been reported (DCMA 1989). Prior to OSHA 1974 regulations, benzidine and 3,3 -dichlorobenzidine were manufactured in open systems that permitted atmospheric releases of suspended particles at the work site (Shriner et al. 1978), but no historical data were located specifically for 3,3 -dichlorobenzidine emissions (atmospheric or in water). The absence of data may be attributed to analytical methods used at that time that could not distinguish benzidine from its derivatives or many other aromatic amines (Shriner et al. 1978). Under OSHA regulations adopted in 1974, only closed manufacturing systems are permitted, and atmospheric emissions are presumably reduced because of this regulation. 

On the night of the accident, operators heard a screeching noise from the relief valve on one of the tanks. Unfortunately, the closed blowdown system had been taken out of service for maintenance. It was later established that while operators were on their shift change or on a break, someone disconnected a pressure gauge from the cover plate on one of the tanks and attached a water hose. A quantity of water estimated between 450 and 900 kg entered the tank and caused a severe upset and release of MIC vapor. With no means of notifying the public and evacuating the community, thousands were exposed to the vapor cloud, resulting in the deaths and injuries. 

FIGURE 11-1 Schematic diagram of a closed anesthesia system. [/] Vaporizer for volatile liquid anesthetics. [2] Compressed gas source. [3] Inhalation unidirectional valve. [4] Mask. [5] Unidirectional exhalation valve. [6] Rebreathing bag. [73 Carbon dioxide absorption chamber. 

In the process, a residuum is desulfurized and the nonvolatile fraction from the hydrodesulfurizer is charged to the residuum fluid catalytic cracking unit. The reaction system is an external vertical riser terminating in a closed cyclone system. Dispersion steam in amounts higher than that used for gas oils is used to assist in the vaporization of any volatile constituents of heavy feedstocks. 

Closed tempered system vapor pressure in a closed system. 

In most binary liquid-vapor systems, Raoult s law is a good approximation for a component only when its mole fraction is close to unity. Large deviations from this law are com-... 

Since the QRLPP has a fairly high electron temperature, the normal equilibrium between the Cs2 molecules and the Cs atoms is affected in the QRLPP. This means that the bound Cs2 (singlet) density is decreased while the unbound Cs2 (triplets) density is increased due to the QRLPP. We have indeed observed that the transient destruction of molecular state by the pulsed QRLPP can be measured by positioning the cw probe beam close to or in coincidence with the pulsed laser beam. The transient absorption signals observed in the probe beam, with long transient time constants (for example, on the order of 1 msec) provide a new method to study diffusion dynamics in a vapor system (33). 

To summarize this section, use of acid vapor-phase digestion and attack of some organic and inorganic matrices is a convenient and useful method of sample preparation. Closed pressure systems are the technique of choice to avoid loss of elements by volatilization while still maintaining extremely low values for the blank (by application of isopiestic distillation of the reagents and technical grade acids). 

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