Flashing entrainment

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). 

Low temperature 500-700 Relatively higher tar yield (20-35 wt.) compared to gas (5-15 wt. %). COED (fluid bed) Occidental flash (entrained flow) pyrolysis. 

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical Hquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of Hquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quaHty transportation fuels, and to study Hquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

Entrainment losses by flashing are frequently encountered in an evaporator. If the feed is above the boiling point and is introduced above or only a short distance below the liquid level, entrainment losses may be excessive. This can occur in a snort-tube-type evaporator if the feed is introduced at only one point below the lower tube... 

The amount of material released to the atmosphere will be further reduced because liquid entrainment from the two-phase flashing jet resulting from a leak will be reduced or eliminated. 

Flashing of vapour eontaining entrained mist may oeeur on venting equipment or vessels eontaining volatile liquids. This may ereate a toxie or flammable hazard depending on the ehemieal with steam the risk is of sealding. Rupture of equipment ean produee a similar effeet. 

The heated oil is flashed into the VPS flash zone where vapor and liquid separate. Split between distillate and bottoms depends on flash zone temperature and pressure. Separation of vapor and liquid in the flash zone is incomplete, since some lower boiliug sidestream components are present in the liquid while bottoms components are entrained in the vapor. The liquid from the flash zone is steam stripped in the bottom section of the VPS to remove the lower boiling components. 

To obtain a low flash zone pressure, the number of plates in the upper section of the vacuum pipe still is reduced to the minimum necessary to provide adequate heat transfer for condensing the distillate with the pumparound streams. A section of plates is included just above the flash zone. Here the vapors rising from the flash zone are contacted with reflux from the product drawoff plate. This part of the tower, called the wash section, serves to remove droplets of pitch entrained in the flash zone and also provides a moderate amount of fractionation. The flash zone operates at an absolute pressure of 60-90 mm Hg. 

Design a flash drum to separate liquid ethylene entrainment for the following conditions ... 

Carryover refers to the entrainment of BW (and the contaminating solids contained in the water) into the steam. Contamination of steam from entrained water may lead to deposits in superheaters, on turbine valves, and in steam traps, valves, and flash vessels. 

The FCC process is used worldwide in more than 300 installations, of which about 175 are in North America and 70 in Europe. Figure 9.10 shows the principle of an FCC unit. The preheated heavy feed (flash distillate and residue) is injected at the bottom of the riser reactor and mixed with the catalyst, which comes from the regeneration section. Table 9.5 gives a typical product distribution for the FCC process. Cracking occurs in the entrained-flow riser reactor, where hydrocarbons and catalyst have a typical residence time of a few seconds only. This, however, is long enough for the catalyst to become entirely covered by coke. While the products leave the reactor at the top, the catalyst flows into the regeneration section, where the coke is burned off in air at 1000 K. 

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. 

Small droplets of liquid also form in a jet of flashing vapor. These aerosol droplets are readily entrained by the wind and transported away from the release site. The assumption that the quantity of droplets formed is equal to the amount of material flashed is frequently made.18... 

The front jet produces a countercurrent shear environment which entrains reactants and pumps them radially inward toward the flame as depicted in the sketch of Fig. 17.3a. Since the reactants are premixed, the flame sheet must reside at a position where the flame speed (determined by the reactant equivalence ratio and the local turbulence intensity) matches the radial inward velocity of reactants. Since the radial velocity must be zero at the cylinder axis and wall, a maximum must exist (as indicated in Fig. 17.36). As long as the flow rates are maintained at high enough rates, this maximum is greater than the local flame speed and the flame remains confined. If the flame speed exceeds the maximum radial velocity anywhere along the axis of the cylinder, the flame changes modes and flashes out to the cylinder wall. 

The flashed refrigerant vapors are de-entrained by a section of York mesh located near the top of the generator and flow to a Stokes, Model H-149, Microvac compressor. 

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