US2089511A - Gasoline production - Google Patents

Description

ug. l0, 1937. M. H. TUTTLE GASOLINE PRODUCT ION Filed Aug. 7, 1929 xv) amJoou insnzmmm h (MPM Swvemtoz s. om.

Patented Aug. 10, 1937 UNITED STATES PATENT OFFICE GASOLINE PRODUCTION Malcolm H. Tuttle, New Rochelle, N. Y., assignor to The Gyro Process Company, Detroit, Mich., a corporation of' Michigan 4 This invention relates to the production of gasoline by cracking. 1

An object of this invention is an improved process of, and apparatus for, obtaining gasoline from petroleum oil by cracking, wherein cracked vapors are contacted with the high boiling fractions of the charging stock to remove the volatile constituents of such stock, thereby obtaining the maximum yield of gasoline and reducing the charging stock to coke or heavy tar residue.

According to this invention the low boiling constituents of the charging stock are vaporizedtherefrom by contact with vaporized cracked hydrocarbons and gasoline is separated from the vapor mixture thus obtained by fractionation.

The condensed cracked hydrocarbons form recycle stock, which, together with the unvaporized charging stock is heated and high boiling compounds are Vaporized therefrom at an absolute pressure not exceeding 100 pounds per square inch and are subjected to a suiiciently high temperature to promote cracking. 'I'he mixture of recycle stock and unvaporized charging stock is preheated by out of contact heat exchange with the cracked vapor and the cracking reaction is arrested by the cooling of the cracked vapors in ythe heat exchange operation. The cracked vapors are intimately contacted with the unvaporized stock completely to evaporate therefrom the volatile constituents and produce a coke or heavy tar residue and the vapor is then utilized to vaporize the low boiling constituents of the charging stock.

The gasoline obtained in accordance with the invention has high anti-knock value and is Very suitable for use in high compression internal combustion engines. The vaporization of the highest boiling point fractions is effected by causing intimate contact between the liquid stock and the cracked'hydrocarbon vapors so that the sensible heat of the cracked vapor and the latent heat of the highest boiling point hydrocarbon produced by the cracking reaction are utilized for the nal stripping of the volatile constituents of the stock. The major part of the charging stock is vaporized and raised to cracking temperature and the remaining part thereof is evaporated to a coke or heavy tar residue. The higher boiling point hydrocarbons produced as a by-product of the cracking reaction are condensed by contact with the non-vaporized portion of the charging stock to vaporize such fractions. The utilization of heat from the cracked hydrocarbon vapors to eifect the nal vaporization of the cracked stock increases the amount of gasoline produced.

Heretofore, in the operation of vapor phase cracking systems, heat exchange between the cracked vapors and charging stock has been' avoided because of deposition of carbon or coke in the exchanger. Such deposition is due to the condensation of higher boiling point hydrocarbons produced by the cracking` reaction, but heat exchange is possible at temperatures above the condensing temperature of the high boiling point hydrocarbons. Upon lcooling below this temperature, condensation takes place, which is followed by re-vaporization when a slight rise in temperature occurs. The re-vaporization leaves a coke residue which makes heat conservation by heat exchange impracticable below the condensing temperature. I have discovered that the heat of the cracked vapors can be utilized by direct contact of the vapors with the liquid stock for evaporating the latter to a coke or heavy tar residue in which case the products of condensation of the cracked vapor and the residue from the charging stock are deposited together. By the provision of a chamber for receiving this residue, the remainder of the system may be kept free fromcoke and because of the complete vaporization of the charging stock by the cracked vapors, the maximum conversion of charging stock will be obtained.

Other objects, novel features and advantages of this invention will be apparent from the following specication and accompanying drawing, wherein one type of apparatus is disclosed for carrying out the process.

The apparatus disclosed provides for recycling the unconverted hydrocarbons thereby obtaining the maximum yield of gasoline. Charging stock is drawn from the tank l through the pipe 2 by the pump 3 and is delivered through the pipe 4 to the fractionating column 5. The charging stock in descending through the fractionating column is heated by ascending cracked hydrocarbon vapors produced in the manner subsequently to be described and supplied to the column. The cracked hydrocarbon vapor strips the charging stock of the low boiling constituents which it contains and the vaporization of such constituents cools the ascending cracked hydrocarbon vapors, thereby condensing unconverted high boiling point hydrocarbons to produce recycle stock which is mixed with the non-vaporized portion of the charging stock. The vapor mixture thus obtained is fractionated in the column 5 and the vapors produced are conducted from the column by a pipe B through condenser 'l to a gas separator 8 from which the non-condensable gases escape the gasoline ows through the pipe I I to the rundown tank I2, the pipe I| being provided with a valve |3.

5 The mixture of recycle stock and non-vapormd charging stock is conducted from the bottom of the fractionatingcolumn 5 through a pipe I4 to pump I5 by which it is forced through pipe I6, heat exchanger I1 and pipe |8 to the heating element of the tube still I 9 and thence through pipe 20 to an evaporator 2|. In the evaporator 2| a portion of the higher boiling constituents of the stock is vaporized and steam may be supplied through the pipe 22 controlled by the valve 23 to assist such vaporization. 'I'he vapor produced in the evaporating chamber 2| is conducted by pipe 24 to the heating element of a tube still 25 in which the vapors areraised to conversion temperature. From `the conversion still 25, the

cracked vapors are conducted through pipe 26 to the heat exchanger I1 in which the vapors are brought into out of contact heat exchange relation with the liquid stock, thereby pre-heating the same and cooling the vapors to a temperature 25 slightly above the temperature of condensation of the highest boiling point fraction thereof. 'I'he cooled vapors are conducted from the heat exchanger through pipe 21 to a coke chamber 28. A by-pass pipe 29 leads from the pipe 26 to the 30 pipe 21 and provides a path for cracked vapors to pass directly from the converterV 25 to the coke chamber 28. Valves 30 and 30a are provided for controlling theY flow of vapor through the pipes.

'Ihe cracked hydrocarbon vapors ascend '35 through the coke chamber 28 and the unconverted liquid stock in the evaporator 2| is caused to ow counter-current to the vapors, thus eiectv stock and the cracked vapor effects the vaporization of the volatile constituents of the liquid 45 stock, the sensible heat of the cracked vapor and the latent heat of the high boiling point vapors being utilized to effect the nal stripping of the stock. Steam may be supplied to the coke chamber through the pipe 34 controlled by the valve 50 35 to assist in the vaporization inthe chamber. The cooled cracked vapors are conducted through the pipe 36 from the coke chamber to the fractionating column 5 and are caused to flow counter- 4current to the descending charging stock as pre- 55 viously described. The residue left in the coke chamber may be either tar or coke. The nature of the residue depends upon the extent of the vaporization eiected in the coke chamber and this is dependent upon the temperature of the 6.0 cracked hydrocarbon vapors supplied to the coke chamber. The temperature of suchvaporsislower when they are passed through the heat exchanger and under this condition the residue is liquid tar and is conducted from the coke chamber through 65 the pipe 31 to the pump 38 which forces the same through pipe 39, cooler 40 and pipe 4| to the run down tank 42. The temperature of the cracked hydrocarbon vapors conducted directly from the converter still 25 to the coke chamber 28 is sufli- 0 ciently high that the residue in the chamber 28 is evaporated to dryness thereby forming a coke.

The pressure to which the vaporized hydrocarthrough the pipe 8 controlled by the valve I8 and bons are subjected in the cracking operation is determined by regulation of the valves III and I3. The pressure maintained inthe system by the valves I 0 and I3 preferably does not exceed ten pounds per square inch absolute. 'I'he temperature in the fractionating column .may be conl trolled by reiiuxing gasoline from the low down tank I2 through pipe 43, pump 44, pipe l45 and temperature control valve 46 to the top of the ratus from that disclosed may be utilized for car-l rying out the process and modifications may be` made in the process without in any way differing from the spirit of the invention as defined in the appended claims.

I claim:

1. 'I'he method of producing motor fuel from petroleum oil which comprises vaporizing vthe low boiling vcompounds therefrom, heating the remainder to vaporize a portion thereof, subjecting the vapor thus obtained to cracking conditions, passingthe cracked vapor into heat exchange relation with the remainder from the first vaporizing step to pre-heat the same for the second vaporization step, then into counter-current contact with the remainder from the second vaporization step for completely removing therefrom volatile constituents and forming a coke residue and finally into counter-current flow with fresh oil to effect the first vaporization step, fractionating the mixed vapors thus obtained and condensing the fractionated vapor to produce gasoline.

2. In a cracking system, a fractibnator, means to introduce charging stock into said fractionator at an intermediate point, a heater, a vaporizer, means to supply liquid from said fractionator through -said heater to said vaporizer, a second heater, a chamber, means to supply vapor from said vaporizer through said heater to said chamber, means to supply liquid from said vaporizer to said chamber, means to conduct vapor from said chamber to said fractionator, a condenser into which vapors are discharged from said fractionator and means to establish heat exchange relation between the vapor owing from said second heater to said chamber and liquid flowing from said fractionator to said rst heater.

3. In a. cracking system, a fractionator, means to introduce charging stock into said fractionator at an intermediate point, a heater, a vaporizer, means to supply liquid from said fractionator through said heater to said vaporizer, a second heater, a chamber, means to supply vapor from said vaporizer through said heater to said chamber, means to supply liquid from said vaporizer to said chamber, means to conduct vapor from said chamber to said fractionator, a condenser into which vapors are discharged from said frac-A tionator, means to establish heat exchange relation between the vapor owing from said second heater to said chamber and liquid flowing from said fractionator to said rst heater, and a vapor by-pass around said heater.

MALCOLM H.. TU TELE.

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