SU42649A1 - Distillation column for petroleum distillates - Google Patents

Description

During deep distillation of hydrocarbon mixtures in tubular plants, i.e., such distillation, when the components in the mixture have a high boiling point, or when a significant percentage of the feedstock is required to be obtained as distillate, it is necessary to heat the latter to high temperature . This need is quite obvious for the distillation of high boiling mixtures, but to a lesser degree, heating to high temperatures is also necessary for the distillation of mixtures containing hydrocarbons with lower boiling points, if such mixtures are required to drive off a significant percentage. This is explained by the fact that liquids need to be overheated in order to give nm sufficient latent heat for evaporation. Heating to too high temperatures is not possible due to decomposition under these conditions. In order to avoid overheating too high, the distillation temperature is reduced by applying a vacuum or water vapor, or both. Cost

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the creation of a vacuum and the consumption of water vapor are the higher, the more the boiling point decreases. Temperature is the most effective means for distillation, i.e., a slight decrease in temperature significantly increases the consumption of water vapor and the creation of a vacuum. Therefore, it is economically more profitable to evaporate at the highest possible heating. The use of high temperature during evaporation is also beneficial in terms of reducing the size of the apparatus.

The evaporation temperature is always lower than the temperature of the raw material in the furnace, since heat is consumed by evaporation and heat is limited by the possibility of decomposition. For that; in order to reduce the decrease in temperature from evaporation, it is necessary to introduce from the outside an additional amount of heat that would compensate for the heat consumption of evaporation.

The introduction of heat into the column is possible with the help of reboilers. In this case, two methods can be used:

1. When the body for heat transfer is the raw material itself.

2. When this body is an extraneous substance (in2, no pair, divinyl, etc.)

The first option is that the heated to the limit, in the sense of safe decomposition, temperature, in the furnace, the raw material goes to coils laid in the column, after which it enters the furnace again and is heated to the same temperature.

In both cases, in addition to a significant heat exchange surface in the column, an additional surface is also required. In addition to the need for large surfaces and significant constructive complications of the column, the use of reboilers is still irrational because the steam reboiler requires a large consumption of steam, sometimes exceeding several times the need for technological needs. Another method of heat transfer, by adding a liquid that is not distilled under the given conditions to the raw material, is unprofitable in terms of heat, and in some cases, due to deterioration of residues. These drawbacks are eliminated if the residue from this distillation is taken as a non-distilled liquid, however, repeated circulation of this residue through the furnace causes its decomposition, and in some cases, when distilled with some kind of reagent (soda ash, caustic soda, lime, etc.) will also cause excessive contamination of the kiln.

In most modern columns of tubular refineries, in addition to an evaporator, there is also a luther part, in which the residue from a single evaporation in an evaporator is stripped by unheated steam. For this purpose, one or more plates are placed in the column, below the raw material input into it from the furnace, along which the remainder is poured; 1t to the bottom of the column into which superheated water vapor is introduced. In this case, countercurrent movement of the steam residue and steam is carried out, which should contribute to a better distillation of the residue, i.e., the removal of lighter fractions from it.

The main disadvantage of the above stripping method is

It is noted that due to the evaporation occurring on each plate, the temperature of the residue decreases as it moves towards the bottom of the column. In other words, just the highest boiling parts of the fractions to be removed must be evaporated at the lowest temperature. The use of reboilers in the lute part of the column, i.e., the use of exchangers for conveying additional heat to the remainder, in most cases, especially for large scale installations, is too complicated.

The device proposed by the authors makes it possible to introduce additional heat that compensates for all or a considerable part of the latent heat of evaporation in the Luther or Evaporation part, so that the whole distillation process can be carried out at higher temperatures.

In the schematic drawing of FIG. Figures 1 and 2 depict a vertical section of the device proposed for the luteral and evaporating parts of the column. Above the entry point of the raw material heated in the furnace (oil, fuel oil, distillates and t, p.) There is a kolizchkova plate 1. Below the entry, the working section of the column is narrowed and one or more plates (or one or more layers of packing , pr zm or other packed material). The wall of the constricted lute part of the column protrudes above the bottom of the column 2, or a special partition, if the bottom is located below the lute part (see Fig. 1 for the first case and Fig. 2 for the second). Some capacity is thus created between this protruding wall and the bottom (or partition), from which there is a discharge line 3 to the pump 4. On top, the constricted part of the column is blocked by a protective cap 5, which prevents the liquid flowing through line 6 to the plate (or top .- s) 7. At the bottom of the lute part there is a supply of 16 superheated steam, as well as a discharge line 8. Pump 4 supply the fluid collected in the vessel between the wall

lute part and bottom (or partition), tubular heater 9 back to the column, or along line 10 to plate I or along line 11 to plate 7. Plate 1 has one or more drainage tubes, but with which liquid can flow from it to the plate 7, etc.

The distillation method is as follows. The raw material heated in the furnace enters through the line 6 into the space between the plate 1 and the shield 5 to is subjected to a single evaporation here. The residue from this evaporation (residue I) is collected on the bottom (or partition) 2, is taken from there by the LINE 3 pump. 4 and pumped them through a separate coil of the same. a tubular furnace where the feedstock is heated, or through an independent tubular furnace. Being heated in the same way to the desired temperature, this residue is returned to the column again. At the same time, further evaporation of the fractions to be separated can be carried out dzoy by: 1) The first option is that residue 1 is introduced along the line and onto plate 7, from here it flows to the plate -13, 14, 15, etc., meeting while raising C1-: izu

steam that is introduced at the bottom of the liter portion of the column. The final residue (residue II) is removed from the bottom of the column through line 8 by gravity or by means of a pump. 2) The second option is that the remainder I returns after additional heating to the plate 1 through line 10. The sum of water vapor and vapors separated in the lower part of the bell passes through this plate. The residue resulting from evaporation on plate 1 flows along one or several lines onto plate 7 and further, for final removal of the light parts, by countercurrent stripping (again at temperatures above normal distillation methods). The final residue is removed in the same way as in the first embodiment.

The subject matter of the invention.

A distillation column for petroleum distillates, characterized in that the working cross section of the column below the distillate inlet is narrowed and the walls of this narrowed part protrude above the bottom of the column in order to form a cavity to contain the residue that is returned to the column.