Evaporation stage

A published analytical procedure [1] for decomposing the sodium salt with ferrous-sulfate/peroxide in nitric acid at pH 2 led to deflagration or explosion dining the evaporation stage when applied to 10 g samples, but not with 5 g samples. Presence of sulfuric acid avoids the problem [2],... 

Open vessel digestion (HF HC104) for ceramics, glass, rocks, and soil These acids should completely dissolve most materials. HF removes the silica (as volatile SiF4), which reduces the total dissolved solid content and therefore reduces interferences, and C104 produces perchlorates, which are soluble (but explosive if dried out). The use of hydrofluoric and perchloric acids therefore has considerable safety risks and requires specialized fume hoods, handling equipment, and safety equipment. The hydrofluoric and perchloric acids are removed by a later evaporation stage unless the analytical instmment and safety considerations have been specially adapted. 

If the cycle is then repeated, during the evaporation stage the sodium chloride is precipitated (and removed ) whilst the concentration of the nitrate re-attains 160 kg/100 kg water. On cooling again, the amount of sodium nitrate which crystallises out is 91.7 kg/100 kg water,... 

The slope, — d(2ri) /d0, of the straight lines which characterize combustion of various compounds as well as the lighter petroleum fractions during the evaporation stage has been termed the evaporation constant —i.e., n2 = rr -o — 0/4 and e = 2M/(tp°ti) (7-11, 4 )- Experimentally determined values of this constant are presented in Table IV. The burning lifetimes of fuel drops initially at the boiling point—i.e., with no preheat period—can be calculated by dividing the square of the initial drop diameter by the evaporation constant. 

Because of the high conversions in the synthesis, the recycle section of the plant is very small. An evaporation stage with vacuum condensation system produces urea melt with the required concentration either for the Stamicarbon fluidized-bed granulation or for prilling. Process water produced in the plant is treated in a desorbtion/hydrolyzer section. This section produces an effluent, which is suitable for use as boiler feedwater. 

Due to high conversions in the synthesis, the recycle section is very small. An evaporation stage with vacuum condensation system produces urea melt with the required concentration either for granulation or for prilling. 

In the reverse osmosis stage of the plant, the water passes through the membranes and is again separated into two streams one with a high salt concentration destined for the brine evaporation stage and the other clarified, which is directed to a tank of clean water mixture, where other streams of the process meet. 

The evolutions of the eomposition residuals during the evaporation stage 4.2.2. Diagnosis results... 

Evaporation Stage Evaporation takes place from a moisture film which establishes on the droplet surface. The droplet surface temperature is kept low and close to the adiabatic saturation temper-... 

During the evaporation stage the atomized spray droplet size distribution may undergo changes as the droplets shrink, expand, collapse, fracture, or agglomerate. 

All the above mentioned evaporators can be equipped with aroma recovery units which for better heat balance can be integrated directly into the evaporator stages. Apple juice evaporators are designed in such a way that the de-aromatised juice can be taken out of the evaporator with approx. 50°C for clarification. The clarified juice is fed back to the next evaporator stage at the same temperature. The evaporation process is not interrupted and the evaporator can operate smoothly and uniformly. 

Vaporizer and condenser pressures Distillation pressures Distillation reflux ratios Evaporator pressures Number of evaporator stages Reactor conversion Recycle flowrates... 

The bottom product of the pre-evaporation stage (Figure 6.7) can eventually be sub] ected to hydrogenation in a trickle bed reactor, to purify the solvent recycle stream by eliminating impurities in the form of formaldehyde and acetaldehyde, reducing them to methanol and ethanol, and also to eliminate traces of unconverted HP. Moreover, traces ofhydroperoxypropanol and hydroxyacetone are converted into 1,2-propanediol. This allows a considerable decrease in catalyst deactivation in the epoxidation reactor and the improvement of product quality [20k]. 

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