Vapor generation system

Derivatization and Measurement by Liquid Chromatography Systems Apart from classical applications with liquid chromatography (LC)-ICP-MS (see above) two new applications have been reported. A vapor generation system and LC combined with ICP-MS were used to determine Hg species in extracts of biological tissues. The efficiency of the mobile phase, a mixture of L-cysteine and 2-mer-captoethanol, was evaluated for the LC separation of three Hg-species (Hg2+, Me-Hg, and ethyl-Hg). The LoDs (see Table 22.2) and repeatability of the... 

Vapor Generation Vapor generation systems are based on the principle of maximizing the surface area of the liquid, and the temperature (within the limits of chemical stability) and airflow across the surface of the liquid as a means of increasing efficiency. 

Fig. 7.7. Vapor generation system comprising three legs (1) humidified air, (2) dry air, and (3) vapor from delta tube or similar type evaporator...

Fig. 12.12 Scheme of a cold vapor generation system for mercury (redrawn from [17]). 

A chemical vapor generation system consists of the vapor source and volume dilution through a mixing device. The controlled vapor from the vapor source is introduced into the dilution flow and mixing device to achieve the desired concentration. The process is very simple. Precise control of various flow blends and understanding pertinent basic physical chemical laws determine the suitabihty of a given dissemination technique. 

This SOP involves the operation of a multipurpose chemical vapor generation system for generating controlled toxic vapor concentrations over a wide range, in an approved hood or agent test chamber. This vapor generation system is primarily used for testing detection and alarm systems. 

Ong, K.Y., Multi-purpose chemical agent vapor generation system, ERDEC-TR-424, U.S. Army Edgewood Research, Development and Engineering Center (ERDEC), Aberdeen Proving Ground, Maryland, July 1997. 

Ong, K.Y., Controlled multi-purpose chemical agent vapor generator system, U.S. Patent no. 

Heat Pumps. A heat pump is a refrigeration system that raises heat to a useful level. The most common appHcation is the vapor recompression system for evaporation (qv) (Fig. 14). Its appHcation hinges primarily on low cost power relative to the alternative heating media. If electricity price per unit energy is less than 1.5 times the cost of the heating medium, it merits a close look. This tends to occur when electricity is generated from a cheaper fuel (coal) or when hydroelectric power is available. 

Chlorine dioxide decomposition occurrences in the generator system ate less explosive when operating under reduced pressure with water vapor... 

The generation of au pollutants, ineluding VOC s, from automotive vehieles was identified to eome from two prineipal sourees vehiele exhaust emissions, and fuel system evaporative emissions [4], Evaporative emissions are defmed as the automotive fuel vapors generated and released from the vehiele s fuel system due to the interactions of the speeific fuel in use, the fuel system characteristics, and environmental factors. The sources of the evaporative emissions are discussed below and, as presented m the remainder of this chapter, control of these evaporative emissions are the focus of the application of activated carbon technology in automotive systems. 

A key parameter in the generation of fuel vapor is the temperature level reached in the fuel tank during vehicle operation. As the temperature approaches the top of the fuel distillation curve, a sizable increase in vapor generation will occur, which severely impacts the amount of HC vapor that the carbon canister system must handle. Limiting the temperature increase in the fuel tank is an important parameter affecting the ability of the evaporative emission system to maintam allowable emission Levels. 

The example vehicle has been run through the test sequence using a two liter carbon canister and a 150 BV purge level. Fig. 22 presents the results for both a return and retum-less fuel system used in the vehicle. As shown, the fuel vapor temperature and the amount of fuel vapor generated are both lower for the retum-less system. This reduces the amount of HC adsorption required in the carbon canister, and it also reduces the amount of HC emissions in the test sequence, fhe return fuel system used with the stated purge volume and canister size emits an unacceptable level of HC during one of the diurnal sequences (2.12 grams), while the retum-less system emission values are well below the acceptable level. 

The reduced adsorption capacity at ORVR vapor generation rates requires increased efficiency in the canister design, in order to limit the effect on cost and performance of the evaporative control system. 

Abnormal Process Heat Input - The required capacity is the maximum vapor generation rate at PR valve relieving conditions, including any noncondensibles produced from overheating, less the normal condensation or vapor outflow rate. In every case, one should consider the potential behavior of a system and each of its components. For example, the fuel or heating medium control valve or the mbe heat transfer may be the limiting consideration. Consistent with the practice... 

Abnormal Heat Input From Reboiler - Reboilers are designed with a specified heat input. When they are new or recently cleaned, additional heat input above the normal design can occur. In the event of temperature control failure, vapor generation may exceed the process system s ability to condense or otherwise absorb the buildup of pressure, which may include noncondensibles due to overheating. 

A survey within the Fine Chemieal Manufaeturing Organization of ICI has shown that gassy reaetion systems predominate due to established proeesses sueh as nitrations, diazotizations, sulphonations, and many other types of reaetions [22]. Very few vapor pressure systems have been identified that also generate permanent gas (i.e., hybrid type). 

Vapor pressure system A vapor pressure system is one in whieh the pressure generated by the runaway reaetion is solely due to the inereasing vapor pressure of the reaetants, produets, and/or solvents as the temperature rises. 

Tran TN, Wambsganss MW, France DM (1996) Small circular and rectangular channel boiling with two refrigerants. Int J Multiphase Flow 22 485-498 Unal HC (1975) Determination of the initial point of net vapor generation in flow boiling system. Int J Heat Mass Transfer 18 1095-1099... 

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