US1978562A - Treatment of hydrocarbon oils - Google Patents

Description

Oct. 30, 1934. H, P. BENNER TREATMENT OF HYDROCARBONV OILS Filed Feb. 6, 1931 Patented Oct. 30, 1934 1,978,562 TREATMENT F HYDROCARBON OILS' Harry Pr Benner,` Chicago,A Ill., assigner #o Universal Oil Products Company, Chicago, Ill., 1 a corporation of South Dakota Application February 6, 1931, Serial No. 513,899

2 Claims.

This invention relates to the treatment of hydrocarbon oils and refers more'particularly to the conversion of high boiling hydrocarbon oil mixtures to produce substantial yields. of hydrocar- 5 bons of lower boiling point range.

More specifically, the invention has reference to improvements in processes for the treatment of heavy hydrocarbon oils under heat and pressure, methods and means being disclosed which enable hydrocarbon conversion processes to be conducted continuously over longer periods of time than those possible when the improvements disclosed are not utilized.

One of the principal diiliculties encountered in attempts to operate cracking processes continuously, particularly under intensive or lrelatively severe conditions, is the deposition of coke in various parts of the system. The question of operating eiciently when maximum amounts o1 coke are produced is one of major importance because of the fact that by this method of operation the yield of gasoline fractions and their anti-knock value are both increased. It is customary to provide as a portion of the equipment in which cracking occurs vessels of relatively large dimension through which the products undergoing conversion may travel at a relatively slow rate and find time therein sufficient for the .continuance oi reactions initiated in preceding elements of the system. When the conversion zone proper consists of a 'tubular heating element, succeeded by an enlarged vaporizing or reaction chamber, it is possible and feasible to operate under such conditions of flow so that substantially all of the heavy residual products, either in the liquid or solid statemay`be deposited within the enlarged zone, the velocity of flow of the oil during its passage through the heating element being sufcient to prevent adherence of 40 such heavy residual products to the walls of the tubes of the heating element. In this type of equipment, the continuity of the process is limited by the time necessary to ll the reaction chamber with coke, at which point shut-down is necessary in order to remove the deposit from such chamber. To obviate this dilnculty, as well as extend the time period between shutdowns, it has been proposed to use reaction chambers in parallel or multiple arrangement, so that the products from the tubular heating element may be diverted into empty chambers uponthe lling with coke of those in use. While this proposition is sound in theory, it has been found diincult or impractical in application in most instances, due to the extremely large size of the vessels employed and the hazards involved when a stream of highly heated .hydrocarbon products at a conversion temperature and pressure is introduced into a reaction chamber maintained under a substantially lower temperature and pressure than said stream and containing varying amounts of air which has entered a chamber during a clean-out period.

The present invention has reference to improvements in preparing reaction chambers, and the like, for the reception of diverted streams of hydrocarbon liquids undergoing cracking reactions, in the operation of which the most efficient use is made of quantities of heat ordinarily considered as losses incident to the operation of the process. y

In one specific embodiment, the invention comprises heating hydrocarbon oils to a conversion temperature, passing the heated products into any one of a plurality of interconnected enlarged vaporizing or reaction zones substantially lled with oil, discharging substantially all of said oil from said reaction zones under` the expansive action of the gases produced from the heated products undergoing conversion, diverting a portion of the discharged oil to charging oil storage and a portion to associated interconnected reaction zones, continuing the introduction of heater products into the rst of said reaction zones until the same are substantially lled with coke, passing the vapors evolved during such reaction period to fractionators wherein separation of vapors of desired boiling point range may be had, cooling, condensing and collecting said vapors, subjecting the insuniciently converted reflux condensates to further heating and conversion, recycling gases produced in the system for preheating and introduction into said reaction zones to assist in raising the temperature and pressure to be maintained therein, passing a gas containing carbon dioxide, such as hot waste combustion gases through interconnected reaction zones to raise the temperature thereof, and diverting the stream of heated products to said reaction zones, brought to substantially conversion conditions of temperature and pressure.

Other and further objects and advantages oi the invention will become apparent from the following description and accompanying diagrammatic drawing illustrating a side-elevational view of one form of apparatus in which the invention may be carried out.

Referring to the drawing, raw oil charging stock may be taken from a storage tank A through line l, controlled by valve 2, by pump 3 and discharged into line 6, controlled by valve 7, said latter line having a branch line 4, controlled by valve 5 and a branch line 34, controlled by valve 35. Branch line 4 leads to a fractionator 8 which may be employed to fractionate cracked vapors produced in the system, and wherein the portion of raw charging oil introduced thereto effects heat exchange with the products undergoing fractionation therein and assists in their dephlegmation. The stripped and preheated portions of the raw oil, mixed with heavy reflux condensates, may be discharged from said fractionator through line 9,'

controlled by valve 10 and be returned to line 6, through which the combined feed may pass through valve 7 and pump 11, interposed in said line 6, to a heating element 12, disposed in a suitable furnace 13. Heat necessary for conversion reactions may be imparted to the oil stream during its passage through heating element 12, the heated products discharging from said heating element through header line 14, controlled by valve 15. Associated with said header line 14 may be suitable branch lines 16, 16 and 16", controlled by valves 17, 17 and 17", leading to reaction chambers B, C, and D, respectively, which may typify any arrangement in parallel of such chambers. The temperatures employed at the exit of the heating element may be of the order of about 800 to 1000 F., more or less, and the pressures employed in said reaction chambers may be of a substantial superatmospheric order to as high as 500 pounds per square inch, or higher. Reaction chambers B, C, and D may be provided with suitable lines 18, 18 and 18", controlled by valves 19, 19', and 19", respectively, through which vapors may pass from said chambers to a vapor header line 20, controlled by valve 21, leading to said fractionator 8.

Reaction chambers B, C, and D may be filled with oil at the commencement of an operation of the process through oil being passed from line 6 to branch line 34, as previously described, said latter line being provided with branch lines 36, 36' and 36", controlled by valves 37, 37 and 3'7", respectively, leading to the respective chambers B, C, and D. Liquids from said reaction chambers B, C, and D may be returned to storage tank A through lines 38, 38 and 38, respectively; said line 38 being controlled by valves 39 and 40; line 38' being controlled by valves 39 and 40'; and line 38" being'controlled by valves 39" and 40". Liquids introduced into said lines 38, 38 and 33" from chambers B, C, and D respectively, may pass to return header line 44, controlled by valve 45, which may lead to said storage tank A. In order that any desired portion of the oil originally contained Within said reaction chambers may be transferred from one to another or to all of the remainder of said chambers, a suitable header line 41, controlled by valves 42 and 43 may be provided to communicate with said lines 38, 38 and 38 through which liquid may pass to and from the chambers D, C, and D, respectively.

Provision may-be made for heating reaction chambers B, C, and D prior to their employment as receptacles for the heated oil discharged from heating element 1,2, by introducing hot gases, such as combustion gases, waste nue gases or the like, taken from furnace 13 through a line 58, controlled by valve by a. suitable blower 63, which, inl turn, passes said gases into header line 53 through a line 53, controlled by valve 54'. Header line 53 may be provided `: nth branch lines 5l, 51 and 51, controlied by valves 52, 52' and 52, respectively, said linee. communicating 4ln tiran, respectively, 36, 36 and 36 j, leadret/atea ing to the lotver end of each of said chambers B, C, and D. In this manner, recirculated hot gases from furnace 13 may be passed into said reaction chambers, introduced into each, or any of them, at the bottom thereof and passing therethrough to the top Whenever it is desired to effect the preheating of said chambers prior to their employment in the system as coke collectors. Hot gases may also be introduced into the upper end of each of said chambers B, C, and D through lines 61, 61 and 61", controlled by valves 62, 62 and 62", respectively, each of said lines leading from header line 53 and communicating with vapor inlet lines 16, 16 and 16, respectively. Reaction chambers B, C and D may be provided with removable bottom manheads 32, 32 and 32, and removable upper manheads 33, 33 and 33, respectively, through which ready access may be had to each of said chambers for removal of carbon or coke deposits, the upper manheads being removed to permit the escape of heating gases when it is not desirable to retain such gases in the system.

Vapors of approximate gasoline boiling point range from fractionator 8 may pass through line 22, controlled by valve 23, to a condenser 24 to effect their cooling and partial liquefaction, the cooled products passing from said condenser through line 25, controlled by valve 26 to a receiver 27. Fixed gases may be released from said receiver through a line 28, controlled by valve 29, and passed to storage or elsewhere if they are not essential for the maintenance of suitable pressure upon the preceding elements of the system, While liquid hydrocarbon mixtures of approximate motor fuel boiling point range may be Withdrawn from said receiver through a line 30, controlled by valve 3l.

Any desired portion or all of the gases passed from said receiver through line 28 may be taken from said line through branch line 46, controlled by valve 47, leading to a pump 48, and may be discharged from said pump through line 49, controlled by valve 50 into a gas heating coil or economizer 57 which may preferably be disposed so as to receive heat from Waste gases issuing from furnace 13. After passing through said heating coil 57, the reheated gases may pass into header line 53, controlled by valve 54, from which they may be passed into reaction chambers B, C, and D through lines 51, 51 and 51", as previously described in connection with the recirculation of flue gases.

As an example of one operation of the process in a unit substantially similar to that illustrated, the following may be given: To expel all air from the equipment, pumps 3 and 1l may be employed to fill heating element 12, reaction chamber B and fractionator 8 with cold charging oil. With pump 3 shut down, pump 11 may initiate circulation from fractionator 8 through lines 9 and 6 to reaction chamber B through heating element 12 and lines le and 16. At the same time, the fires are lighted in furnace 13 and the circulating oil is gradually brought to conversion conditions of temperature and pressure. As conversion proceeds, gases are generated which are retained in sufficient amount to maintain desired pressure and initial liquid is Withdrawn from reaction' chamber D at a rate suicient to prevent excessive pressure rises ancl excessive temperatures of,

vapors entering fractionator 8 from line 20.' The highly heated vapors entering iifactienator B from line 16 contact with the surface ci? thc oil in chainber B and graduallyr heat the mass in dorm it:

llt)

A somewhat lower.

ward direction, being themselves correspondingly cooled. 'Ihe first portions of the oil mass withdrawn from reaction chamber B are returned to storage tank A through lines 38 and 44, since these are but slightly superheated. When the temperature of the oil discharged reaches an optimum point, however, the stream of oil is diverted through lines 41 and 38 to reaction chamber C, the transfer continuing until substantially all of the remaining liquid oil body has been elTected. Chamber B is now in condition to receive coke resulting from the conversion reactions taking place, and fills with coke at a rate depending on the type of charging stock used and the temperature and pressure conditions employed. To prepare reaction chamber C for the reception of the stream of heated products from heating element l2, flue gases are first used to displace the air, this being passed throughthe chamber from bottom to top, preferably before the admission of heated oil from reaction chamber B, the waste gases being discharged through the upper manhead of said chamber. At such times as it is certain that the major portion of the air has been displaced, admission of flue gases may continue above the oil body until the temperature reaches a point approximating that employed at the exit of the heating element, although this may usually be Reaction chamber C may now be at the approximate temperature of conversion desired. To raise its pressure to the desired conversion pressure, fixed gases from the system may be pumped through economizer 57 and enter re'- action chamber C through lines 51', 61 and 16 y until the pressure is substantially that obtaining within reaction chamber B. At such time as proper tests indicate that reaction chamber B is full of coke, the stream of heated oil is diverted therefrom and introduced into reaction chamber C by the gradual opening of valve 17 in ,line 16. When valve 17 is completely open, valve ,17 in line 16 entering chamber B is closed, and chamber C is then in condition to act as a carbon accumulator, the vaporspassing through vapor header 20, as previously described. Reaction chamber B may now be steamed out and cooled and the coke removed by any suitable mechanical means, such as by pulling a suspended cab-le or by the use of rotary equipment, and again placed in condition to act as a coke accumulator. In case the time needed for cleaning reaction chamber B is greater than that required to fill chamber C withy coke, any other interconnected chamber, such as chamber D, may be prepared to receive the heated oil stream in substantially the same manner as that described for chamber C.

The foregoing description will indicate in a general way an operation which may be employed within the scope of the invention to enable substantially continuous cracking operation with the production of coke, but since it is obvious other types of equipment and varying modes of operation may be employed, it is not intended that such description is to be taken as limiting the broad scope of the invention. For example, while the chambers have been shown in vertical position, they may take any other desired form, and while the bringing of freshly cleaned reaction chambers to suitable conversion temperatures and pressures has been described step-wise, such steps may be taken in varying order or conducted simultaneously, as the invention contemplates any order of use of the various steps.

To exemplify the results obtainable by an operation Within the scope of the invention, and to indicate the advantages accruing, the following may be cited: It may be found when cracking a 24 gravity mid-continent residuum to produce substantially only gasoline hydrocarbons, gas and coke, that when but one reaction chamber is employed it will be completely filled with coke in approximately 40 hours, necessitating shut-down for clean-out, and interrupting the continuity of the process. By utilizing several reaction chambers and the process of thel present invention, such operation may be prolonged to approximately 150 hours before shut-down is necessitated due to the necessity for cleaning the tubes of the heating element. Since it has been found that approximately 8 hours are required to clean carbon from the chamber, the percentage of shut-down time when but one reaction chamber is employed will be 162/3;% When chambers are used to permit an extension of the running time to 150 hours, the shut-down period will be substantially reduced to approximately 5%.

I claim as my invention:-

1. In the art of cracking hydrocarbon oils wherein the oil is continuously passed in a restricted stream through a heating coil disposed in a furnace and heated therein to cracking temperature by indirect heat exchange with combustion gases, and such heated oil separated into vapors and residue in an enlarged chamber; the method which comprises continuing the introduction of heated oil into said chamber until a substantial body. of carbonaceous residue has accumulated therein, simultaneously raising a second enlarged chamber to elevated temperature by passing therethrough spent combustion gases from said furnace, lthen diverting the oil being heated-in the coil from the first-mentioned chamber to said second chamber, and continuing the separation of the heated oil into vapors and carbonaceous residue in the second chamber.

2. In the art of cracking hydrocarbon oils wherein the oil is continuously passed in a restricted stream through a heating coil disposed in a furnace and heated therein to cracking temperature by indirect heat exchange with combustion gases, and such heated oil separated into vapors and residue in an enlarged chamber; the method which comprisescontinuing the introduction of heated oil into said chamber until a substantial body of carbonaceous residue has accumulated therein, simultaneously raising athereto incondensible gases formed in the cracking process, then diverting the oil being heated in the coil from the first-mentioned chamber to said second chamber, and continuing the separa- 4tion of the heated oil into vapors and carbonaceous residue in the second chamber.

HARRY P. BENNER.

Images