US1904144A

US1904144A - Apparatus for fractionating liquids

Info

Publication number: US1904144A
Application number: US423367A
Authority: US
Inventors: Paul E Kuhl
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1930-01-25
Filing date: 1930-01-25
Publication date: 1933-04-18
Anticipated expiration: 1950-04-18

Description

April 18, 1933. P. E. Kul-n. 1,904,144

APPARATUS FOR FRACTIONATING LIQUIDS Filed Jan. 25, 1930 INVENTOR ATTORNEY PAUL E. KUHL, F ELIZABETH, NEW JERSEY, ASSIGNOR TO STANDARD OIL DEVELOP- Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE KENT COMPANY, A CORPORATION OF DELAWARE APPABATIIS FOR IRAGTIONATING LIQUIDS Application filed January 25, 1930. Serial No. 423,367:

This invention relates to improvements in fractionating equipment and particularly to means for controlling the side stream leaving the fractionating column.

In the operation of fractionating towers usually several side streams are taken out besides the overhead product and the bottoms. The side streams consist of hot liquid collected on one or several plates of a bubble tower, or in a pan, and are preferably passed through a str pping column before entering the final cooler. In this column the hot oil is brought into contact with a stripping agent, such as for instance superheated steam w ich evaporates the light ends of the hot oil. The stripping agent and the vaporized light ends discharge into the fractionating column.

Control of the amount of distillate taken out from the system of each side stream'is essential since a change in this quantity affects the quality of all the heavier streams including the bottoms. It has been customaryto control the stream withdrawn from the main fractionating column by means of a valve in the hot liquid line between thefractionating and the stripping columns and then maintain the level in the bottom of the stripping column with a liquid. level controller which regulates the discharge from the stripping column. Such a control, however, is very inefiicient because the position of the valve may be changed accidently and the valve opening often becomes obstructed by solid or gummy material carried in the stream. I

The main object of the invention is to provide for the adjustment of a stable refluxin the fractionating column by controlling the quantity of the side streams leaving the system through the stripping columns by means of a commercial rate of flow controller placed after the stripping column and then causing the liquid level control on the stripping column to operate a valve controlling the amount of oil entering from the fractionating tower into the stripping column.

The invention will be fully understood from the following description read in con-' nection with theaccompanying drawing, in

which the figure is a diagrammatic side elevatien partly in section of preferred equipmen In the drawing, the numeral 1 denotes a fractionatiiig column such as for example a bubble tower from which one or several side streams are taken out. 2 is the line for the hot feed entering the tower, 3 for the overhead vapors, 4 for bottoms, 5 for reflux. 6, 6, 6" are the stripping columns, their number being equal to the number of side streams. The further elements are identical on all side streams and 'will be shown only on one of them. 7 is a valved line for the superheated ments of this type, the differential of the pressure at both sides of the orifice plate 15 controls the flow of air which in turn closes the valve 16 through the lead 17 when the differential pressure reaches a certain fixed value. The flow in line 10 may be caused either by gravity or by a pump 18. In the latter case controlled valve 16 in line 10 may be dispensed with and a controlled valve 19 placed in the steam line of the pump 18 as marked by dotted line. A certain portion of the cooled stripped liquid may be returned through line 20 to provide reflux condensate.

Thepump or valve in this line'may again be do not requirefurther description.

By placing the rate of flow controller after the stripping column accordin to the present invention and especially y placing it after the cooler, as in the preferred form of the invention, inaccuracies of the rate of flow controller due to vaporization in the liquid flow to be controlled are avoided and an accurate control of the side streams becomes possible. The amount of open steam ad.- mitted 'to the stripping column can be easily controlled inasmuch as it is satisfactory to regulate the steam valve by hand as long as the pressure of the superheated steam supply is kept constant. If desired a rate of fiow controller may also be inserted in the steam line, or in the case of a' very light side stream closed steam coils may be used in column 6 for stripping.

Instead of returning the stripping agent and the light ends to the fractionating columnby line 9, this line may be connected by a balance line 24 to the vapor line 3 as shown in dotted line. Since the amount of liquid vaporized in the stripping column is small in comparison to the total amount of liquid passing through the same column it is still possible in this 'case to maintain steady reflux conditions in the fractionating column 1 by controlling the amount of side stream removed from the system with a rate of flow controller 12 placed behind the cooler 11.

As an example of fractionation carried out according to this invention, a Colombian lubricating distillate was heated in a pipe still and fractionated into an overhead product consisting of gas oil, a bottoms of fuel oil quality and 3 lubricating cuts taken oif the tower as side streams. Rate of

flow controllers

12, 12, 12 were placed into the side A streams after-the

coolers

11, 11, 11" as shown on the figure and the stripping columns 6 were balanced against the vapor line 3' by means of

lines

24, 24, 24. The greater part of the first side stream was returned as reflux to the same three plates in the fractionatin column, from which it was taken out. imilarly a large amount of gas oil was returned as reflux to the top plate. The principal data of the operation are given in the following:

Table Amount Viscosity Baybolt Gravity sae es ie Gala/hr 8, 7

Reflux (gas oil) Reflux 1st side stream-...-

may be replaced by an receptacle adapted to contain a column 0 the liquid product removed from the system. The stripping of the side stream from the light ends by means of a stripping fluid such as steam is therefore not an essential part of the invention but the two constitute an advantageous combination.

Having thus described my invention and the method of carrying it out, what I claim 15:

1. In a fractionating system, a fractionatin tower, means for taking off liquid pr not from an intermediary portion of the tower, means for stripping said liquid from light ends, a line in connection with said stripping means to remove at least part of the stripped liquid from the system, a, rate of flow control device in said line to regulate the amount of stripped liquid removed from the system, and a liquid level control on the strippin column to regulate the amount of liqui taken out of the fraction-' ating tower.

2. Apparatus according to claim .1 in

which a cooler is provided between the stripping means and the rate of flow control device.

"3. Apparatus according to claim 1 in which the stripping means consists of a column and a line is provided to connect the upper part of the stripping'column to the fractionating column.

4. In a fractionatin system, a fractionatin tower, means or taking ofifliquid pro uct from an intermediary portion of the tower, a container connected with said means and adapted to hold a column of the liquid product, a liquid discharge line connected with the container, a rate of flow control device in said line to re late the amount of li uid removed from" t e system, and a liqui level control on the container to regulate the amount of liquid taken dut of the fractionating tower.

PAUL E.

scribed with specialreference to the case I when the side stream is removed from the fractionating tower through a stripping