US1941440A - Process of converting hydrocarbon oil - Google Patents

Description

De. 26, 1933. H. D. LOEB 1,941,44'0' PROCESS OF CONVERTING HYDROCARBON OIL Filed Nov. 12, 1930 F/L TEE 46 J Z M N 9% version vessel and Patented Dec. 26, 1933' UNITED STATES PATENT OFFICE A Henry D. Loeb, Port Arthur, Tex.

Application November 12, 1930 Serial No. 495,014

2 Claims.

This invention relates to the process of converting higher boiling hydrocarbon oils into lower boiling hydrocarbon oils and relates more particularly to the cracking of higher boiling hydro- 5 carbon oils in the presence of alkaline materials such as lime or its equivalent, which are beneficial in the cracking reaction.

In the conversion of higher boiling oils into low boiling products, such as gasoline, by heating w the oil to cracking t mperatures, there are formed, in addition to he desired low boiling hydrocarbons, decomposition products that often limit the duration of the process and prevent continuous operation. Thus, large quantities of coke are often liberated and cling to the interior of those parts of the apparatus wherein conversion takes place to the extent that the system must be shut down and cleaned out. Sulphur compounds present in the original oil are decomgo posed to a certain extent to form volatile compounds such as hydrogen sulphide and organic sulphur compounds which are highly corrosive to the metals used in the apparatus. Other corrosive materials, presumably formed during the cracking reaction, particularly organic acids, have been noted in cracked products. All of the above compounds, for the most part undesirable, are mentioned by way of example to show the desirability of introducing certain materials into the oil undergoing cracking in order to inhibit the formation of these compounds or combat the undesirable effects produced by them after they are formed.

Heretofore, various alkaline materials have been introduced into stills employed in the distillation of hydrocarbon oils for the beneficial effect produced during the distillation operation. In the conversion of hydrocarbons at high temperatures, these materials have usually been used in the dry form due to the difficulty of introducing aqueous solutions into conversion apparatus subjected to drastic conditions of temperature and pressure. Thus, lime, magnesium oxide and various other alkaline earth oxides, as well as caustic alkali'es have beenemployed for this purpose. The usual method of introducing these materials into the conversion apparatus has been to inject them into the oil at, or near the point at which cracking occurs. This may be conveniently done by the method disclosed in the application of George W. Gray, filed July 3, 1926, Serial No. 120,272. The method therein described comprises, briefly, heating-to a cracking temperature a stream of oil flowing to a conintroducing a substantially non-aqueous alkaline material into the fresh oil stream before it attains the cracking temperature.- The beneficial results obtained from methods heretofore, will not be discussed but suflice it to say that a substantial elimination of corrosion so has been observed, a distillate of lower sulphur content and sweeter quality has been noted, and various advantages in the character and quantity of coke have been claimed.

While lime and other alkaline materials have 05 been employed in the conversion of oils in the prior art, I am not aware that these materials have been used together with a comminuted solid material. I have discovered that not only all the advantages of the prior use of the alkaline material is obtained and even accentuated, but also many additional advantages are observed by the use of the mixture above suggested. In this way the efliciency of the alkaline material has been substantially increased and while the explanation for this is not fully understood, it may be postulated that certain sulphur compounds are adsorbed or changed to a form more readily reacted upon by the alkali. Reaction products of the alkaline material with constituents of the oil are also adsorbed or coagulated, thereby destroying unfavorable equilibrium conditions between the reacting components and tending to produce cleaner oils. Furthermore,

a finer and more efiicient grade of lime or other alkaline material may be employed and yet fuel oil bottoms having a reduced sediment test are withdrawn from the stills. Also, in case it is desirable to filter the fuel oil, the solid material serves as a filter aid in the subsequent filtra- 00 tion. Other advantages will be apparent from the description of the apparatus and the operation of the process.

My invention may be applied to any known or preferred type of commercial cracking process in which the pressure employed may vary over a wide range, for instance, 100 to 1000 lbs. per sq. in. However, in operating under pressures of the order of 200 lbs. or more, it is believed that the greatest benefit may be derived. The accompanying drawing ill trates the application of the process to an apparatus comprising a heating coil and a series of vertical reaction chambers. This type of apparatus is shown only for purposes of illustration and the process may well be carried out in other types of well known cracking systems.

Referring to the drawing, the reference numeral 1 indicates a furnace in which is mounted the continuous heating coil 3 adapted for the 1 circulation of oil therethrough, which may be raised to a cracking temperature by the heat of the burner 2. .The reaction chambers preferably take the form of a series of vertical conversion vessels 4, 5, 6 and 7, provided with pipes 9 to interconnect the vapor spaces of the vessels. A second series of interconnecting pipes 10 are located immediately below the vapor pipes 9 to maintain a common liquid level in the several vessels. The heating coil 3 is connected by pipe 12 to vessels 4 and 5 to deliver the heated oil to either or both of these vessels by suitable manipulation of valves therein. The vapor space of the last vessel of the series is connected by pipe 13 to the bottom of the dephlegmator 14. The dephlegmator is shown partly in section, and as indicated, may be provided with vertically spaced plates or trays for the fractionation of the vapors. A vapor pipe 15 leads from the top of the dephlegmator 14 to a reflux condenser 16. A pipe 1''! extends from the bottom of the reflux condenser into the top of the dephlegmator to return reflux condensate to the dephlegmator and to distribute the condensate over the trays for a cooling and fractionating medium.

A vapor pipe 18 connects the top of the reflux condenser to a condenser 19 shown diagrammatically, which may be provided with any suitable cooling medium for condensing the vapors. A pipe 20 connects the vapor condenser with a receiver 21, provided with the usual vapor release pipe 22 and liquid draw-ofi line 23.

A pump 24 in communication with a feed line 25 supplies charging stock through pipe 26 to the system. Coils 27 and 28 located in the reflux condenser and the bottom of the dephlegmator respectively, are connected so that by regulation of suitable valves, the cool charging stock may be passed in heat exchange with the volatile products from the conversion vessels to condense the high boiling constituents and preheat the charging stock. A reflux line 29 in which is interposed a pump 30 is used for conducting reflux condensate from the bottom of the dephlegmator through the line 31. The condensate is then mixed with the preheated charging stock in line 26 and the mixture passed to the heating coil. A portion of the reflux condensate from line 31 may be diverted, however, through pipe 32 to the first conversion vessel 1-.

A mixing tank 33 provided with hoppers 34 and 35 is used for mixing the alkaline material and the solid comminuted material with oil to be supplied to the heating coil. The bottom of this tank is connected to the heating coil by a line 36 in which is interposed a pump 37. The line 36 preferably terminates in branches 38, 39 and 40 for introducing the mixture at a plurality of points into the heating coil.

The vessels 4, 5, 6 and 7 are equipped with separate draw-off lines for the withdrawal of residual material from the bottoms thereof through a residue line 41. By the regulation of suitable valves this residue may be passed to storage or otherwise disposed of through the pipe 42. It is preferable, however, that the residue be divertedy through the cooler 43 to a filter 44. This filter is shown diagrammatically and may be any known or preferred type of pressure or suction filter. The solid material-separated in the filter is discharged through line 45 and the clean fuel oil withdrawn from the filter through pipe 46.

In practicing the invention with an apparatus such as that previously described, a charging stock suitable for cracking is drawn from a source neensso in the reflux condenser and the dephlegmator respectively. In this way the cool charging stock is not only preheated, but the vapors are cooled to control the end point of the final condensate and to produce a reflux condensate .in the dephlegmator. This reflux condensate is drawn from the bottom of the dephlegmator by pump 30 and forced through line 31 into the charging stock line 26 or under certain circumstances it may be desirable to divert any or all of the reflux condensate into the first of the vertical reaction vessels 4. The charging stock is subjected to cracking temperatures in the heating coil 3 and the heated oil is then delivered from the cracking coil to either or both of the. vertical reaction chambers 4 and 5.

The liquid oil is maintained at cracking tem-' peratures in the vertical reaction chambers for a period of time suitable for extensive conversion. The liquid level in the reaction chambers is kept constant by means of overflow pipes 10 through which the liquids flow, while vapors generated by the cracking and distillation taking place in all the vessels pass through vapor lines 9. The vapors are delivered to the dephlegmator, where they are fractionated as they pass through the vertically spaced trays in intimate contact with reflux condensate. The heavier constituents of the vapors are condensed and collected in the bottom of the dephlegmator to be recycled through the system While the lighter vapors pass 119 densed in condenser 19 and collected in receiver A mixture comprising oil, alkaline material and a comminuted solid is prepared in tank 33. The alkaline material is conveniently introduced to the tank by means of the hopper 34. The solid 120 comminuted material may likewise be introduced by means of a similar hopper 35. It is important that the mixture be uniform and fluid in order to be injected into the oil undergoing cracking. The preferred procedure, therefore, is to finely pulverize the alkaline material, which may be quick lime or slaked lime. It is desirable also to use a finely comminuted solid material. The finely divided solids are then thoroughly mixed with sufiicient oil, usually about an equal weight, preferably of the same oil which is being charged to the conversion system, to form a paste or suspension of a consistency that can be handled in a pump. This mixture, which is usually only a small percent of the charging stock, is drawn from the bottom of the mixing chamber 33 and forced by the pump 37 under high pressure, at a single or a plurality of points, into the cracking coil.

In the application of the invention to a process and apparatus for the conversion of oil, such as the one described, it is preferable to continuously introduce the suspension from the mixing tank into the apparatus in contact with the oil undergoing conversion. This suspension is designated broadly as a mixture comprising 011, an alkaline material, and a solid comminuted mineral material. The alkaline material is preferably lime, however, various other oxides, hydroxides and 1 carbonates of the alkali and alkaline earth metals are contemplated in the invention. The solid comminuted inorganic material is preferably fullers earth, however, I contemplate the use of any comminuted inorganic material which may serve to increase the efiiciency of the alkaline material and function as a filter aid in subse-' quent filtration of the residual oil. As suitable materials'for this purpose, also may be mentioned natural clays and artificially prepared filtering materials such as silica gel and filter cel.

The introduction of the mixture of the solid comminuted material and the alkaline material into the oil undergoing conversion maybe done in various ways depending on the type of apparatus. With the apparatus and method under discussion, it is preferable to inject the mixture I have shown pump 37 connected to the coil at a plurality of points by branches 38, 39 and 40. By suitable regulation of valves in these branches a certain degree of flexibility is provided in the selection of the point of introduction of the mixture. In this way the mixture can be injected into the oil at or near the point at which decomposition of the oil occurs and evolution of corrosive substances begins.

The solid material is carried with the oil from the cracking coil into the vertical reaction vessels and the coke and other coagulated insoluble materialscollect at the bottom of these reaction chambers. The solids are drawn off from the vessels with the oil residue. since as in the case of the use of lime alone, there is practically no tendency for the solids to adhere to the walls or otherwise collect in the still. It is a well known fact that the oil residue from cracking contains very finely divided carbon-like or coking material which is very diflicult and practically impossible to segregate from the oil even I by filtration.- Lime improves to a certain extent the removal of the coky particles from the oil, yet even in cases where lime is used, there is a certain degree of diificulty in removing all the solid material so as to obtain a finished oil of low ash content.

One of the special features of my process lies in the fact that the oil residue therefrom may be easily filtered and a fuel oil of improved quality obtained. Thus the use of a 'solid adsorbent material or a filter aid material not only tends to coagulate the finely solid materials normally produced in the oil during the cracking reaction, but also precipitates and absorbs in the pores reaction products of the lime with sulphur com,- pounds and other undesirable constituents in the oil. The fuel oil can consequently be readily filtered since the solid materials are coagulated excessive.

in the oil. The residual material from the vertical stills may therefore be drawn off through the line 41 and passed through the cooler 43 to a filter 44. However, if desired, the cooler 43 may be by-passed by suitable regulation of valves and the hot oil passed directly to the filter. The filter 44 is shown diagrammatically and may be any well-known type of pressure or vacuum filter in which the solids are intermittently or continuously discharged through the pipe 45. An improved fuel oil of low sediment and ash content is obtained from the filter through pipe 46.

The quantity and proportion of the alkaline and solid comminuted material required during the conversion of higher boiling oils in accordance with my invention will vary with the type of cracking system and the character of the oil treated. It has been found that by increasing the efiiciency of the alkaline material by means of mixing therewith a solid comminuted material, that the total quantity of solids introduced into the oil undergoing conversion is notnecessarily The quantity of lime, for example, used in cracking coils may be substantially reduced in this way. It has been found in the prior art that quantities of lime from 2 lbs. per bbl. up to 2 percent by weight of the oil charged to the cracking apparatus has been sufiicient to produce the desired results. It may be said that a quantity of the solidcomminuted material such as fullers earth or a filter aid material such as filter eel, in quantities equal to the amount of lime, is usually satisfactory. However, these proportions may be varied within wide limits.

Sometimesthe quantity of solid comminuted material may be reduced substantially below the amount of lime required and at other times the quantity of the solid comminuted material may be substantially. in excess of the alkaline material used. 1

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

l. The process of treating hydrocarbon oil which comprises heating said oil to'a cracking temperature under superatmospheric pressure and mixing with said oil during the cracking thereof a small percentage of finely divided lime and fullers earth, in substantially equal quantities.

2. The process oftreating hydrocarbon oil which comprises heating said oil to a-cracking temperature under superatmospheric pressure, mixing with said oil during the cracking thereof a small percentage of finely divided lime and fullers earth, in substantially equal quantities, separating the cracked products into vapors and a liquid residue containing solid matter, and filtering said residue to remove said solid matter and form a finished ofl of low ash content.

- my D. LQEB;

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