US 2016798 A
Description (OCR text may contain errors)
M. B. cooKE 2,016,798
PROCESS FOR PYROLYTIC DECOMPOSITION OF HYDROCARBONS Oct. 8, 1935.
Filed March l2, 1932 c k R. 0 m w w N m w w m T W A w M LJ GSW Qxv B Patented Oct. 8, 1935 UNITED s'm'rizs PATENT OFFICE PRooEss Fon rYRoLrrro DEooMrosrrloN oF rrrnnooamsoivs My invention relates to a process for the'pyrolytic decomposition of hydrocarbons to form gasoline-like hydrocarbons suitable for using las a motor fuel having high antiknock qualities. The
process' is usually known as a cracking process and relates more particularly tothe cracking of hydrocarbons in the vapor phase by hot gases of combustion.
When fuel is burned with no excessive air, the
10. temperature of combustion is between 3,000 and 4,000 F. These temperatures are too high for efficient cracking and accordingly they must be tempered or brought down to about 1500 F. in order to give an efficient cracking process.
15 In an lapplication of William O. Keeling, Serial No. 586,573, now U. S. Patent 1,991,750, a method of tempering the combustion gases by means of a cooler, inert gas is disclosed.
This application relates to a process in which 20 the combustion gases are tempered in a novel and more eiiicient manner.
When a great volume of gas is introduced into the fractionating tower, many disadvantages result. 'The equipment must be lmade of a larger 25 size. The volume of gas to'be compressed for absorption purposes is so increased that the process becomes expensive. The use of a cool, inert gas to temper the combustion gases represents a direct loss of heat besides increasing the volume 30 of the gases to be handled.
. One object of my invention is to avoid the disadvantages above pointed out.
Another object of my invention `is to provide a. process in which the hot gases of combustion 35 are tempered by means of heat exchange.
A further object 'of `my invention is to employ the gas heat for topping the charging stock, vaporizing the charging stock for conversion into the vapor phase and supplying heat for other 40 purposes such as distilling the rich absorption oil which contains gasoline or the generation or high superheatlng of steam.
Still another object of my invention is to provide a vapor phase cracking process in which hot 45 gases of combustion are used to supply the cracking heat which is iiexible of control and efficient in operation. a
Still another object of my invention is to check the reaction to prevent over-cracking by means 50' oi shock chilling the products of reaction.
Other objects of my invention will appear from the following description: i
'I'he gure shows a diagrammatic view of one embodiment of the process of my invention.
In general, my invention consists in burning fuel and air with surface combustion in a furnace to supply hot gases of combustion substantially devoid of free oxygen. I charge crude oil from storage through suitable heat exchangers through a coil situated within the furnace. The temperature of the hot gases of combustion will be lowered and lose part of their heat in heating the incoming charge during its passage through the topping heating coil. The heated products are discharged into a fractionating tower preferably of the bubble type, whence the vapors are withdrawn overhead, condensed and passed intoy a separator. The gasoline is withdrawn from the separator and passed to storage. A fraction collects in the separator and is reiiuxed into the bubble tower. The reiiux condensate from the bubble tower may be pumped to storage and forms in part the cracking stock which is used in my process. The reux condensate may, if desired, be pumped directly-through suitable heat exchangers into an Vaccumulator tank.' Oil is pumped from the accumulator tank through suitable heat exchangers, through a second coil situated` in my'furnace where the heat necessary to convert a substantial portion ofthe charging -stock into vapors is supplied. The heated charging stock is passed into a fiash evaporator whence the vapors are withdrawn and passed 'to the cracking zone. In the cracking zone the vaporized hydrocarbons encounter the hot gases of combustion which have been tempered to about 1500 F. The hot gasesvof combustion admixing with the vapors bring the mixture to about41050 F. at which temperature lcracking ytakes, place rapidly. 'I'he increasel inlvolume is accommo- 35 dated for by a progressively increasing cross sectional area. After leavingvthe vcracking zone, the products of; the reaction are shock chilled by means of an oil spray. The products, after being chilled, pass into a tar separator. The tar laden quenching oil is ldrawn through a cooler and pumped to storage and may be used for fuel oil. The vapors andgases vare passed through a sectional entrainment condenser and then into a fractionating tower. The condensate fromthe entrainment condenser collects in suitable pockets y and may be passed either into the separator or into a fractionatingtower dependingupon their nature and character. 1 A
The reilux condensate from the fractionating tower is withdrawn and pumped through acooler in order to reduce the temperature thereof to render it suitable as a quenching medium. vAfter `passing through the cooler, it is passed through the sprays in order to be used in the chilling zone. f
' A portion of the reflux condensate of the fracy oil in a gasoline absorption process.
A fat oil drawn from the bottom of the absorber is passed into a steam still to recover a gasoline fraction. The fixed gas is passed into a gas main to supply fuel for the burner of the furnace.
More particularly referring now to the drawing, the crude oil from storage is charged through line I and pumped by pump v2 through heat exchanger 3, Ithrough heat exchanger 4, through topping heating coil 5, where the crude oil being charged is heated. The-heat imparted to the incoming crude lowers the temperature of the combustion gases. The oil leaves the topping heating coil through line 6 and is charged into the fractionatingltower 1. 'This tower is preferably of the bubble type but it is to be understood that any suitable fractlonating column may be employed. The topped oil is withdrawn through line 8 and pumped by pump 9 through heat exchanger 4. If valve I8 be closed, and valve I I be opened, the oil will pass through cooler I2 into storage I3. The cooler I2 is cooled by circulating water or any suitable means. The pump I4 will pump oil from the cracking stock storage tank I3 if valve I5 be open. If valves I5 and II be closed and valve I0 open, the topped crude will pass through line I6 into line I1 to pump I4.
`The vapors from the bubble tower 1 are withdrawn through line I8, through heat exchanger 3 into cooler I9 where they are condensed. 'Ihe condensate passes through line 28 into separator 2l. The gasoline is withdrawn through line 22 and passed to storage. A fraction is withdrawn from the separator throughline 23 by pump 24 and pumped back into the bubble tower 1 as a reflux. The topped crude is pumped by pump I4 through heat exchanger 25, through heat exchanger 26, through heat exchanger 21, whence it passes through'line 28 into the accumulator 29. The charging stock thus preheated is withdrawn through line SI!l by pump 3| and is pumped through line 32, it being understood that valves 33 and 34 are open and valve 35 is closed. The charge passes from line 32 through the tubing 36 of the sectional entrainment condenser 31 and leaves said condenser through line 38 passing through valve 34 into line 39, through theI vaporizing heating coil 40. The products of combustion in the furnace are tempered by losing some of their heat to the charging stock passing through coil 40. The heated charging stock leaves the coil 48 through line 4I and passes into the flash evaporator 42. 'I'he unvaporized oil from the flash evaporator may pass through line 43. through valve44, through line 4 5, into the accumulator 29. Line extends from the accumulator 29 to the flash evaporator 42 and serves as a vapor release line permitting any vapors in the accumulator to escape into the flash evaporator. If desired, valve 44 may be closed and valve 46 may be open so that the unvaporized oil will pass through line 41 into .line 48 through cooler 49, where it is pumped by pump 50 to storage as fuel oil. The vapors from the ila-Sh evaporator will pass through line 5I and be discharged into a mixing zone 52. Valve 5I' controls the vapor flow.
Gas is withdrawn from the gas main 53 through branch line 54 and compressed by compressor 55 into gas supply tank 56, whence gas is withdrawn through line 51 being controlled by valve 58 into the mixing chamber 59' of a surface combustion burner. Compressed air, controlled by valve 6I', also passes into the mixing chamber 59'. The
mixture burns with surface combustion about the refractory granules 62 of the surface combustion burner 63. The hot gases of combustion will pass into the furnace 64 and be tempered by heat exchange with the material passing through coils 40 and 5 respectively and into the mixing zone 52, whence a commingling of the hot products of combustion so temperedy to about 1500 F. will take place with the hydrocarbon vapors coming from the flash evaporator 42. After admixture, the temperature will be about 1050 F. and cracking or pyrolitic decomposition will take place rapidly.
As cracking takes place, the volume of the products will increase and, in order'to prevent the building up of pressure, a progressively increasing cross-sectional volume of the cracking chamber is provided.
Inasmuch as the cracking will take place very rapidly, at the temperature of 1050 F., I resort to shock chilling or cracking chamber of quenching to reduce the temperature of the products of reaction from 1050 to '700 F. l I do this by means of oil sprays 53', 54', 55,`and 56', oil spray 56 being located in the tar separator 51. The temperature of '700 is low enough to prevent any further reaction and high enough to permit the distillate to escape in the vapor state into the fractionating tower. The heavy, tarry fuel oil, however, will accumulate in the bottoms of the separator 51. 'I'his tar laden quenching oil is withdrawn through line 58 which joins with line 41 and permits the fuel oil bottoms to be passed through the cooler 49 to fuel oil storage.
The vapors from the tar separator 51 pass overhead through line 59 into a sectional entrainment condenser 31, whence they will pass in counterflow relation to the incoming charging stock which is passing through tubes 36. The hot vapors will be cooled considerably by the incoming charging stock which in turn will be heated. The condensate is allowed to collect in compartments 60, 6I and 62. The condensate may be withdrawn from the respective compartments and selectively passed into the separator or fractionating tower through lines 63 and 64 respectively. The condensate may be supplied as desired by means of valves 65, 66, 61 and 68, so that all or part of the condensate collected in the sectional entrainment condenser 31 may be passed to either the separator or the fractionating tower as desired and depending upon the nature of the condensate. The vapors and gases leave the sectional entrainment condenser through line 69 and pass into the fractionating tower 10. The reflux condensate from the fractionating tower is withdrawn through line 1I and passed through heat exchanger 21, through line 12, through pump 13, through cooler 14 and through line 15 into line 16, which terminates in a manifold for the quenching sprays. The quenching oil leaves line 15 through valve controlled lines 11, 18, 19, and 80. If desired, a portion of the reflux condensate from the fraction ating tower may be diverted through valve conthe superheated steam will be condensed in cooler- 83 and will form water in the bottom of the separator 85. This water is withdrawn through line 88. The gasoline-like hydrocarbons are withdrawn through line 81 and passed to storage. The gases from' the yseparator will contain a quantity of gas rich in gasoline-like hydrocarbons. Accordingly, I propose to withdraw it,
through line 88 and compress thegas in compressor 89, pass it through cooler 90 into receiver 9|. The cooling and compressing will precipitate further gasoline-like hydrocarbons which are withdrawn through line 92 and pass into line 81 to storage. 'Ihe gases from the receiver are withdrawn through line 93 and passed into the gasoline absorption tower 94 where it is scrubbed by lean oil entering through line 95. The fixed gas is withdrawn through line 96 into gas main 53. The fat oil from the bottom of the absorption tower BI-is withdrawn through line 91 and passed to a steam still for the distillation therefrom of the gasoline-like hydrocarbons.
It will be appreciated that my process has many advantages. I temper the hot products of combustion by means of heat exchange and use the heat obtained by tempering to perform useful steps in my process. 'Ihe thermal efficiency of my process will be exceedingly high. The ilexibility of control is manifest. The temperature of the combustion gases, the temperature of the quenching loil and hence the temperature of reaction may be controlled within close limits. I am enabled by my process to crack hydrocarbon oil in the vapor phase and obtain a gasoline-like hydrocarbon suitable for use 'as a motor fuel and having an exceedingly high antiknock value. I may use a portion of the gas formed in my process for otherv purposes where gaseous fuel maybe needed. It.wi11 be noted that the cracking reaction takes place in the pure vapor phase, it being impossible for any hydrocarbon oil which is not in the vapor form to be present. This insures the absence of the danger of the formation of coke or carbon deposits within my cracking zone. It will be understood, of course, that suitablel lagging is provided throughout the piping and the piece of apparatus used in my process to prevent the loss of heat by radiation.
It will be understood that certain features, subcombinations and operations are of utility and may be employedwithout reference to other features and sub-combinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is, therefore, to be understood that my invention is not tobe limited to the specific details shown and described. s
By this method of cracking hydrocarbons in the vaporphase, in which the hydrocarbons arey combined with the combustion gases, the latter being maintained at selected, controlled temperatures of reaction, a motor fuel having a high octane number and high antikneck value is obtained. The process eliminates parasitic cracking which accompanies conventional cracking y drocarbons to take place to`form gasoline-like methods, in which the hydrocarbons are converted in tubular containers and heatedby external circulation of the combustion gases thereabout. The intimate mixture of the combustion gases with the hydrocarbonfvapor produces a distribution of heat impossible with the conventional tubular cracking processes.
Having Athus described my invention, what I claim is:
l. The process of converting hydrocarbon oil into gasoline-like hydrocarbons of lower molecular weight which includes the steps of generating hot combustion gases, passing the hydrocarbon oil to be cracked in indirect heat exchange with said hot combustion gases to reduce the temperature of the gases and effect a heating of the oil substantially without pyrolytic decomposition,
subjecting the hydrocarbon oil thus heated to a topping operation, passing the topped hydrocarbon oil in indirect heat exchange with said 20 with said tempered products of combustion and permitting a pyrolytic decomposition of said hyhydrocarbons having a lower molecular weight.v
2. The process of converting hydrocarbpn oil into gasoline-like hydrocarbons of lower molecular weight which includes the steps of generating hot combustion gases, passing the hydrocarbon oil to be cracked in indirect heat exchange with said hot combustion gases to reduce the temperature of the gases and effect a heating of the oil substantially without pyrolytic decomposition, subjecting the oil thus heated to a topping operation, passing the topped oil as the hydrocarbons to be cracked in indirect heat exchange with said combustion gases `to lower their temperature,
flashing the oil thus heated into vapors in a vapor- 40 izing stage, directly commingling said vapors with said tempered products'of combustion, permitting a pyrolytic decomposition of said hydrocarbons to take place to form gasoline-like hy` drocarbons having a lower molecular weight, and 45 stopping said reaction by spraying oil into the reacting mixture after the reaction has progressed a desired extent whereby over-cracking is prevented.
3. The processl of into gasoline-like hydrocarbons' of lower molecular weight which includes the steps of generating hot combustion gases, passing the hydrocarbon oil to be cracked in indirect heat exchange with said hot combustion gases to reduce the temperature of the gases and effect a heating of the oil substantially without pyrolytic decomposition, subjecting the oil thus heated to a topping operation, passing the oil as the hydrocarbons to converting hydrocarbon oil 50 be cracked in indirect heat exchange with said combustion gases to lower their temperature, flashing the oil thus heated into vapors in a vaporizing stage, directly commingling said varpors with said tempered products of combustion',
permitting a pyrolitic decomposition of said hydrocarbons to take place to form gasoline-like hydrocarbons having a lower molecular weight, fractionating the 'products of reaction, and withdrawing the reflux condensate from the fractionating stage. l
4. The process of converting hydrocarbon oil into gasoline-like hydrocarbons of lower molecular weight which includes the steps of generating hot combustion gases, passing the hydrocarbon oil in indirect heat exchange with said hot combustion gases to reduce the temperature of the gases and effect a heating of the oii. substantially without pyroiytic decomposition, subjecting the oil thus heated to a. topping operation passing the topped oil as the hydrocarbons to be cracked in indirect heat exchange with said combustion gases to lower the temperature thereofi flashing the oil thus head into vapors in a vaporizing stage, directly commn'gling saidyapors with said 10 tempered products of combustion, permitting apymlyizic decomposition oi' said vapors to take -place'to form gasoline-like hydrocarbons having a lower molecular weight, fractionating the products of the reaction, withdrawing the vapors and gases from the fractionating stage, cooling said vapors and gases, withdrawing-the condensate formed in the cooling stage,l and subjecting the uncondensed gases to gasoline absorption treatfment.
MAURICE B. COOKE.