Fractionating columns partial condenser

When low boiling ingredients such as ethylene glycol are used, a special provision in the form of a partial condenser is needed to return them to the reactor. Otherwise, not only is the balance of the reactants upset and the raw material cost of the resin increased, but also they become part of the pollutant in the waste water and incur additional water treatment costs. Usually, a vertical reflux condenser or a packed column is used as the partial condenser, which is installed between the reactor and the overhead total condenser, as shown in Figure 3. The temperature in the partial condenser is monitored and maintained to effect a fractionation between water, which is to pass through, and the glycol or other materials, which are to be condensed and returned to the reactor. If the fractionation is poor, and water vapor is also condensed and returned, the reaction is retarded and there is a loss of productivity. As the reaction proceeds toward completion, water evolution slows down, and most of the glycol has combined into the resin stmcture. The temperature in the partial condenser may then be raised to faciUtate the removal of water vapor. 

Unstabilized gasoline and light gases pass up through the main column and leave as vapor. The overhead vapor is cooled and partially condensed in the fractionator overhead condensers. The stream flows to an overhead receiver, typically operating at <15 psig (<1 bar). Hydrocarbon vapor, hydrocarbon liquid, and water are separated in the drum. 

A 250-cc. round-bottomed flask is fitted with a thermometer reaching nearly to the bottom (Note 1) and a 3- or 4-bulb fractionating column without a side arm, at the upper end of which is attached a partial condenser (Fig. 3) (Note 2). The side arm (A) of the latter carries a no° thermometer and is connected to a condenser set for downward distillation. The inside container (B) of the partial condenser is filled halfway with toluene, a chip of porous plate is added, and the top is attached to a reflux condenser. 

Fig. 37. Fractionating column with partial condenser (D) (dephlegmator).

The chlorine stream is interrupted, and the reaction mixture is allowed to stand for a short time, then it is poured into a separatory funnel and washed thoroughly with hydrochloric acid, soda solution, and water. If part of the mixture has not already precipitated as a white crystalline solid, the mixture is transferred to a beaker until part of it solidifies, then it is filtered, cooled to about 10°, and centrifuged. About 95 grams of practically pure m-nitrochlorobenzene is obtained. The filtrate and the liquid from the centrifuge are combined and subjected to hractional distillation in vacuo. For this purpose, a column should be used which is about 80 cm. in length and provided with a partial condenser. Approximately the following fractions are collected ... 

The volatile diene dimerizes readily and is prepared as required by depolymerization of technical dicyclopentadiene (Enjay, high purity, Matheson, purity 85% b.p. 170°, sp. gr. 0.98). The depolymerization is done by heating the dimer carefully under a fractionating column by heating the dimer under a partial condenser containing methylene chloride or by adding the dimer at a suitable rate to mineral oil maintained at 240-270°. ... 

It is required to separate the benzene-toluene mixture of Example 6.1 into a benzene-rich distillate with 0.80 mole fraction benzene and a toluene-rich bottoms with 0.05 mole fraction benzene. The separation is to be made using a distillation column with 15 theoretical stages that include a partial condenser and a partial reboiler. Calculate the reflux ratio required to achieve the specified separation and determine the optimum feed location. What effect would lowering the number of stages to ten have on the reflux ratio and the optimum feed location ... 

A column with partial condenser and reboiler is to be used for the separation of benzene (1) from toluene (2), giving a distillate with 0.95 mole fraction benzene and a bottoms product with 0.10 mole fraction benzene. The column will operate at 105 kPa pressure and a reflux ratio of 4. The feed, at 55°C and a flow rate of 100 kmol/h containing 45 mol% benzene and 55 mol% toluene, enters the column at the fifth theoretical stage from the top. The estimated average relative volatility (benzene relative to toluene) is assumed constant, and estimated at 2.41. Based on the column conditions and thermodynamic properties, the predicted q-value is 1.2. It is required to determine the number of theoretical stages below the feed to complete the separation. 

The reaction is carried out in a 500-cc. round-bottomed flask, heated by an oil bath, and fitted with a fractionating column, preferably of the type described on page 342. The column should be at least 20 cm. long and filled with glass rings it should be insulated and equipped with a partial condenser cooled by a stream of air. 

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