Liquid pool

Operation m the Simple Mode if there is no concentration gradient within the liquid pool and if there is no coalescence within the rising foam, then the operation shown by the sohd hnes of Fig. 22-42 is truly in the simple mode, i.e., a single theoretical stage of separation. Equations (22-45) and (22-46) will then apply to the steady-flow operation. 

A small amount of collector (surfactant) or other appropriate additive in the liquid may greatly increase adsorption (Shah and Lemlich, op. cit.). Column performance can also be improved by skimming the surface of the liquid pool or, when possible, by removing adsorbed solute in even a tenuous foam overflow. Alternatively, an immiscible liquid can be floated on top. Then the concentration gradient in the tall pool of main hquid, plus the trapping action of the immiscible layer above it, will yield a combination of bubble fractionation and solvent sublation. 

In the horizontal condenser, it is necessary to prevent cooled condensate from forming liquid pools and impeding the flow of vapors. 

CASRAM predicts discharge fractions, flash-entrainment quantities, and liquid pool evaporation rates used as input to the model s dispersion algorithm to estimate chemical hazard population exposure zones. The output of CASRAM is a deterministic estimate of the hazard zone (to estimate an associated population health risk value) or the probability distributions of hazard-zones (which is used to estimate an associated distribution population health risk). 

This is a subroutine that calculates an evaporation rate from a pool of spilled liquid in presence of wind (ORG-40), or in still air (TP-10). It was developed by the U.S. Array for downwind hazard prediction following release from smoke munitions and chemical agents. The code calculates the evaporation rate of a liquid pool, given the physical stale variables, wind speed, and diameter of pool. ORG-40 and TP-10 models are coded as a Fortran 77 subroutine, EVAP4.FOR, in D2PC. The user s manual is Whiiacre (1987). 

Tatem, P. et al., 1982, Liquid Pool Fires in a Complete Enclosure, 1982, Tecf --- —... 

Combustion behavior differed in some respects between continuous and instantaneous spills, and also between LNG and refrigerated liquid propane. For continuous spills, a short period of premixed burning occurred immediately after ignition. This was characterized by a weakly luminous flame, and was followed by combustion of the fuel-rich portions of the plume, which burned with a rather low, bright yellow flame. Hame height increased markedly as soon as the fire burned back to the liquid pool at the spill point, and assumed the tilted, cylindrical shape that is characteristic of a pool fire. 

Experiments by Schmidli et al. (1990) were focused on the distribution of mass on rupture of a vessel containing a superheated liquid below its superheat-temperature limit. Flasks (50-ml and 100-mI capacity) were partially filled with butane or propane. Typically, when predetermined conditions were reached, the flask was broken with a hammer. Expansion of the unignited cloud was measured by introduction of a smoke curtain and use of a high speed video camera. Large droplets were visible, but a portion of the fuel formed a liquid pool beneath the flask. Figure 6.5 shows that, as superheat was increased, the portion of fuel that... 

Liquid Pool Flames. Liquid fuel or flammable spills often lead to fires involving a flame at the surface of the liquid. This type of diffusion flame moves across the surface of the liquid driven by evaporation of the fuel through heat transfer ahead of the flame. If the liquid pool or spill is formed at ambient conditions sufficient to vaporize enough fuel to form a flammable air/fuel mixture, then a flame can propagate through the mixture above the spill as a premixed flame. 

Other seemingly solid fuel flames such as those from the burning of plastics are actually more like liquid pool flames because the plastic melts and vola-tizes ahead of the advancing flame front. 

The combustion of liquids is a fertile area for further study. Kowledge of the combustion science of individual droplets as well as groups of droplets helps improve performance of devices that rely on spray burning, particularly diesel engines. Understanding of the science of liquid pool fires potentially effects safety during spills. 

Unless the liquid pool is purposely lengthened vertically in order to give additional separation via bubble fractionation, it is usually taken to represent one theoretical stage. A bubbler submergence of 30 cm or so is usually ample for a solute with a molecular weight that does not exceed several hundred. 

Pool fire A fire where the fuel is in the form of a liquid pool at the base of the fire. 

Note The factor of 2 in items a, b, and c above is to account for the aerosol formation and entrainment in the flashing release. Also, when determining the material in the cloud resulting from a two-phase or flashing release, consideration should be given to the contribution to the cloud from liquid pool evaporation. 

Deflagration involves combustion of a material, usually in presence of air. In a normal liquid pool fire, combustion in an open situation will normally proceed... 

T is the temperature of the liquid pool (degree), as is the thermal diffusivity of the soil (area/time), and t is the time after spill (time). 

Flash point temperatures are determined using an open-cup apparatus, shown in Figure 6-3. The liquid to be tested is placed in the open cup. The liquid temperature is measured with a thermometer while a Bunsen burner is used to heat the liquid. A small flame is established on the end of a movable wand. During heating, the wand is slowly moved back and forth over the open liquid pool. Eventually a temperature is reached at which the liquid is volatile enough to produce a flammable vapor, and a momentary flashing flame occurs. The temperature at which this first occurs is called the flash point temperature. Note that at the flash point temperature only a momentary flame occurs a higher temperature, called the fire point temperature, is required to produce a continuous flame. 

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