Evaporators Jacketed

The thermos phon circulation rate can be as high as 10 to 15 times the coolant evaporation rate. This, in turn, eliminates any significant temperature difference, and the jacket is maintained under isothermal conditions. In this case, the constant wall temperature assumption is satisfied. During starting of the thermosiphon, the bottom can be 20-30°C hotter, and the start of circulation can be established by observing that the difference between the top and bottom jacket temperature is diminishing. Figure 2.2.5 (Berty 1983) shows the vapor pressure-temperature relationship for three coolants water, tetralin, and Dowtherm A. 

O When scale formation due to flash evaporation is a problem or filtrate temperature must be maintained a vacuum box steam jacketing may be provided. 

Preparation of 18,20-Cyclo-5a-pregnane-3, 20-diol 3-Acetate ° A solution of 5 g of 3j9-hydroxy-5oc-pregnan-20-one 3-acetate in 1000 ml of spectroscopically pure ethanol is irradiated with a 250 Watt Philips Biosol A mercury high pressure lamp No. 10/27 through a cental water cooled pyrex jacket under nitrogen for 4 hr. The solvent is then evaporated under reduced pressure and the residues from 2 such reactions are combined and chromatographed on 300 g of neutral alumina (activity II). 

Figure 7.1 Some agitated hatch crystallizers, a) Simple unhaffied, (h) draft-tube baff led, (c) jacket or coil heat exchange, (d) external heat exchange, and (e) vacuum or evaporation...

A recent development in heat recovery has been the heat tube. This is a sealed metal tube which has been evacuated of air and contains a small quantity of liquid which, for boiler applications, could be water. When heat from the flue gases is applied to one end of the heat pipes the water in the tube boils, turning to steam and absorbing the latent heat of evaporation. The steam travels to the opposite end of the tube which is surrounded by water, where it gives up its latent heat, condenses and returns to the heated end of the tube. Batteries of these tubes can be arranged to form units, usually as a water jacket around a section of a flue. 

Figure 7.1 Flooded evaporators, (a) Shell-and-tube. (b) Jacketted.

Dairy farms have bulk-storage tanks with their own refrigeration plants. These are usually made in the form of a double-skin, insulated tank, having the evaporator coils in the jacket, which also contains water. The refrigeration system runs throughout the 24 hours and... 

Hexanediol (0.5 mol/L), dimethyl fumarate (0.5 mol/L), toluene and Novozyme (33.3 g/L) are introduced in a thermostatted double-jacketted reactor fitted with a short thermostatted distillation column and a nitrogen inlet. The temperature is set at 60°C and a nitrogen flow (0.2 L/min) is bubbled into reaction medium. Methanol and toluene are collected in a flask and die volume of the solution is held constant by addition of toluene. After reaction (15 days) the catalyst is removed by filtration and the solvent is evaporated under reduced... 

Low-pressure steam is used as the heating fluid in the machine jacket. The H20/dioxane vapors are conveyed to the condenser while the stripped FAES is sucked by an extraction pump and sent to the adjustment of AM content or directly to the storage and buffering tank. Starting from FAES containing a maximum of 50 ppm of 1,4-dioxane (on 100% AM), an 80% yield of removal can be achieved by water evaporation that is markedly dependent on the applied vacuum degree. 

The reaction heat is removed by the vacuum evaporation of dilution water. The resulting water vapors allow complete degassing and stripping of any trace of undesired low boiling by products (i.e., 1,4-dioxane for ethoxy sulfates). The product temperature is accurately controlled with the vacuum level kept in the reactor and by the temperature control in the reactor jacket. The automatic control of the different process parameters, i.e., flow rate of reagents, vacuum degree, temperature of thermostatting water, also allows for accurate control of the product concentration. 

Fig. 4.19. Reaction cell 1 - ZnO sensor 2 - evaporator 3 band evaporator 4, 5 - thermocouples 6 — shutter 7, 8 — iron rods sealed into a glass jacket 9 - contact rings...

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