Cooling distillation tower with reflux

Figure 3.13. Crude oil vacuum tower. Pumparound reflux is provided at three lower positions as well as at the top, with the object of optimizing the diameter of the tower. Cooling of the side streams is part of the heat recovery system of the entire crude oil distillation plant. The cooling water and the steam for stripping and to the vacuum ejector are on hand control.

A distillation column is a series of stills placed one on top of another. As vaporization occurs, the lighter components of the mixture move up the tower and are distributed on the various trays. The lightest component goes out the top of the column in a vapor state and is passed over the cooling coils of a shell-and-tube condenser. As the hot vapor comes into contact with the coils, it condenses and is collected in the overhead accumulator. Part of this product is sent to storage the rest is returned to the tower as reflux. 

Distillation is conducted at the excess pressure of 0.5-0.55 MPa. From pressure container 1 the mixture is constantly fed into heater 2, from where at 50-60 °C it is sent to the feeding plate of rectification tower 3. In the tower, methylchlorosilanes and methylchloride are separated. Methylchlo-rosilanes from tank 4 are collected into collector 10. The temperature in the tank is maintained within 145-155 °C with vapour (1 MPa) fed into the tank jacket. Methylchloride is condensed in refluxer 5, which is cooled with Freon (-50 °C) from there part of methylchloride is returned into tower 3, and the rest through cooler 6 is collected into receptacle 8. The uncondensed methylchloride from refluxer 5 and cooler 6 is sent into condenser 7, and from there is poured into receptacle 8 and collector 9. The... 

The unreacted dimethyldichlorosilane with hydrogen chloride is distilled when the temperature in the higher part of the tower is 70-72 °C. Dimethyldichlorosilane vapours condense in refluxer 8, which is cooled with water. The condensate flows into the separation box, from where the most part is returned to reflux the tower, and the rest is sent through rotameter into the chlorinator, where it is mixed with the 2% initiator solution for repeated chlorination. After refluxer 8, hydrogen chloride enters the backflow igurit condenser (not shown in the diagram), where it is purified from the impurity of dimethyldichlorosilane, and is sent for water absorption. 

Fraction I, which mainly consists of dimethyldichlorosilane, is distilled at atmospheric pressure when the temperature at the top of the tower is below 72 °C. The vapours from the higher part of tower 9 condense in water-cooled refluxer 10. The condensate is sent into the separation box, from where part of it is returned to reflux the tower, and the rest is collected in receptacle 11. From the receptacle dimethyldichlorosilane with a density not exceeding 1.08 g/cm3 can be used to prepare the initiator solution. 

The vapours of the products formed by the boiling liquid in tank 14 rise through tower 15. After the tower the vapours saturated with low-boiling products enter the built-in condenser. Part of the condensate from the top of the tower is sent back through vapour-heated (1 MPa) heater 16 to reflux the tower the other part is collected in receptacle 17. The rectification takes place under atmospheric pressure. It allows to separate two fractions HMDS (80-100 °C), concentrated PMS-lb (100-153 °C) and concentrated PMS-l,5b (153-194 °C). After the distillation the tank residue is cooled and loaded off into collector 18. 

Reactor 27 is loaded through a hatch with a catalyst (1% solution of H2PtCl6 in tetrahydrofiiran) in the quantity of 0.45% of the reactive mixture. The mixture is heated to 130-145 °C and held for 40-60 hours. At this time toluene and volatile products are distilled. Toluene rises up tower 26, is cooled and partially sent back to reflux the tower the main amount is sent into collector 31 to be used in later synthesis. During the holding, the appearance of oligomer I is checked every 3-4 hours (it should be transparent). When the holding is over, the mixture is cooled in the reactor to 80-90 °C and neutralised with monoethanolamine. After the neutralisation, oligomer I is sampled. 

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