Vapor jacket

A vapor jacket was first used to control the column temperature (1). It kept the column at the constant temperature of a condensing vapor (at the boiling point of an appropriate liquid). This technique was quickly abandoned because it was cumbersome to use and was limited to liquids that boiled up to about 150 -180°C. 

A suitable vapor-jacketed fractionating column may well be used in place of this arrangement. 

The column Is surrounded by a vapor Jacket through which passes trichloroethylene vapor to maintain the temp, at about 67 0. The elution Is performed by passing amm. citrate (buffered with citric acid to pH 3.5— total citric acid cone. 0.25 M) through the column at a rate of 1 drop ( 0.030 cm3) about every 2 min and the drops are collected separately. 

Gel Fractions. Weighed samples were placed in 300 mesh stainless steel baskets and extracted I6 hours in a vapor-jacketed Soxhlet extractor with p-xylene. The insoluble fraction was dried in a vacuum oven with a nitrogen bleed at 80 C overnight and the gel content determined from the initial and final welgpits. 

It is not always possible to elevate the liquid level fed to the extrusion head mandrel and escape high hydrostatic pressure (see Fig. 2.5e) lest the hose should rupture. To avoid this, the Cl is applied on the hose wall during rotation [98]. The liquid vortex formed this way promotes the required level of the liquid on the mandrel near the hose surface, making use of a minimum amount of Cl and changing the rotation velocity of the hose. The dynamic interaction of the hose and the Cl intensifies its diffusion into the polymer material, breaks the vapor jacket at the inhibitor-hose interface and facilitates the uniform distribution of Cl pressure, minimizing the probability of hose rupture. 

When the desired quantity of crude product has collected in the receiver, the latter is cut off or sealed off from the train and the product fractionated at reduced pressure with the use of a suitable column. A satisfactory arrangement consists of a flask sealed to a 22-in. Podbielniak type of column, made of 8-mm. pyrex tubing containing a glass spiral. The column is heated either by means of a vapor jacket, the temperature of which is controlled by refluxing... 

P). Otherwise the baffles should be located iaside the cod helix. A conventional jacket consists of a vessel outside the main vessel with a gap for the flow of heat-transfer fluid. Half-pipe jackets are usefld for high pressures up to 4 MPa (600 psi). They are better for Hquid than for vapor service fluids and can be easdy 2oned. Dimple jackets are suitable for larger vessels and process conditions up to 2 MPa (300 psi) and 370°C. Internal cods can be either hehcal or baffle cods (Fig. 34). 

Batch distillation (see Fig. 3) typically is used for small amounts of solvent wastes that are concentrated and consist of very volatile components that are easily separated from the nonvolatile fraction. Batch distillation is amenable to small quantities of spent solvents which allows these wastes to be recovered onsite. With batch distillation, the waste is placed in the unit and volatile components are vaporized by applying heat through a steam jacket or boiler. The vapor stream is collected overhead, cooled, and condensed. As the waste s more volatile, high vapor pressure components are driven off, the boiling point temperature of the remaining material increases. Less volatile components begin to vaporize and once their concentration in the overhead vapors becomes excessive, the batch process is terrninated. Alternatively, the process can be terrninated when the boiling point temperature reaches a certain level. The residual materials that are not vaporized are called still bottoms. 

Metafile arsenic can be obtained by the direct smelting of the minerals arsenopyrite or loeUingite. The arsenic vapor is sublimed when these minerals are heated to about 650—700°C in the absence of air. The metal can also be prepared commercially by the reduction of arsenic trioxide with charcoal. The oxide and charcoal are mixed and placed into a horizontal steel retort jacketed with fire-brick which is then gas-fired. The reduced arsenic vapor is collected in a water-cooled condenser (5). In a process used by Bofiden Aktiebolag (6), the steel retort, heated to 700—800°C in an electric furnace, is equipped with a demountable air-cooled condenser. The off-gases are cleaned in a sembber system. The yield of metallic arsenic from the reduction of arsenic trioxide with carbon and carbon monoxide has been studied (7) and a process has been patented describing the gaseous reduction of arsenic trioxide to metal (8). 

Liquid carbon dioxide is used as a source of power in certain appHcations. The vapor pressure of Hquid carbon dioxide (7290 kPa or 72 atm at 294 K) maybe used for operating remote signaling devices, spray painting, and gas-operated firearms. Carbon dioxide in small cylinders is also used for inflating life rafts and jackets. 

Exothermicity. The catalytic reactions are often exothermic bond-forming reactions of small molecules that give larger molecules. Consequendy, the reactors are designed for efficient heat removal. They may be jacketed or contain coils for heat-transfer media, or the heat of reaction may be used to vaporize the products and aid in the downstream separation by distillation. 

Corrosion under insulation is also a concern, particularly in refrigeration systems. The specification of the insulation system needs to include painting, vapor barriers, and external metal jackets (16). 

A basic stirred tank design is shown in Fig. 23-30. Height to diameter ratio is H/D = 2 to 3. Heat transfer may be provided through a jacket or internal coils. Baffles prevent movement of the mass as a whole. A draft tube enhances vertical circulation. The vapor space is about 20 percent of the total volume. A hollow shaft and impeller increase gas circulation (as in Fig. 23-31). A splasher can be attached to the shaft at the hquid surface to improve entrainment of gas. A variety of impellers is in use. The pitched propeller moves the liquid axially, the flat blade moves it radially, and inclined blades move it both axially and radially. The anchor and some other designs are suited to viscous hquids. 

Batch distillation equipment can range from a free-standing column with a reboiler, condenser, receiver, and vacuum system, to the use of a jacketed reactor with a condenser. Distillation often involves the generation of combustible vapors in the process equipment. This necessitates the containment of the vapor within the equipment, and the exclusion of air from the equipment, to prevent the formation of combustible mixtures that could lead to fire or explosion. 

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. 

Recirculation of non-boiling liquids can be achieved by bubbling inert gas through the liquid in the reactor jacket. This is less practical for fluids with significant vapor pressure, because the jacket still must be under pressure, and a large condenser must be installed to condense the liquid from the vapor-saturated gas at the jacket temperature. It is more useful with molten metals and salts. For the design details of the reactor tube s inside, the same considerations apply as for a thermosiphon-controlled reactor. 

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