US2054777A - Treatment of hydrocarbon oil - Google Patents

Description

TREATMENT 01 HYDROCARBON OIL Filed-May s1, 1 1955 INVENTOR JOHN T W120 BMW ATTORNEY Patented Sept. 515, i938 PATENT OFFICE murmur or HYDROOABBON on. John T. Ward, Weltileld, N. 1., alsllnor to line Products Company, Inc., corporation of Delaware .Galo- Newark, N. 1., a

\ Application May 31, 1933, Serial N0 618,618

4Claims.

This invention relates to the art of pyrolytically treating hydrocarbon oils, more particularly crude petroleum oils containing waxy constituents of both pressable and non-pressable. nature, for the recovery of valuable products therefrom. Certain crude oils, for example, of the Pennsylvania and Mid-Continent types contain wax in a form readily recovable by pressing from the distillatefractionin which it is initially recovered and generally known as crystalline wax, as well as wax which is dimcult or impossible to recover by pressing from the somewhat heavier fraction in which it is found. Wax in this latter form is sometimes known as amorphous wax by reason of the difficulty encountered in removing it, although actually itmay be similar to or identical with wax known as crystalline wax except as to crystalline size or structure.

My invention has for an object the provision of a process for the removal of a maximum amount of wax in pressable or crystalline form from a crude petroleum oil containing waxy constitutents and adapted to bring wax which would ordinarily be obtained in non-pressable form into pressable wax. 7

My invention has for further objects such further operative advantages and improvements as may hereinafter be found to obtain.

' wax fraction.

The heavy fraction containing amorphous or non-pressable wax is subjected to moderate cracking conditions in a separate coil provided for that purpose and is delivered to a. separate fractionating stage, the wax fraction previously recovered from the initial fractionation stage preferably being commingled with the stream of cracked products. The separate or secondary fractionation stage is operated in such a manner as to effect the condensation of all constituents up to and including such amorphous or nonpressable wax as may remain after the cracking operation. The condensates are separated into various cuts, including a fraction containing the (CL 19H!) pressable wax, one or more fractions of lighter materials, and a heavier or "slop wax cut, while the residual products are withdrawn as fuel oil.

The slop wax cut containing amorphous or nonpressable wax is preferably recycled in the cracking operation to increase the yield of pressable wax.

My invention thus makes it possible to obtain a maximum yield of pressable wax by avoiding unnecessary cracking of wax initially recoverable in pressable form, while subjecting the initial yield of amorphous or non-pressable wax to an operation which tends to produce wax in pressable form and at the same time reduces to a minimum loss of lubricating oil constituents through pyrolysis.

The action which takes place in the cracking coil may be either an actual conversion of amorphous wax (protoparaflln) to crystalline wax (paroparaflin) or it may be a decomposition and removal of certain viscousoils or other hydrocarbon materials, the presence of which tends to hinder crystallization or separation of the true wax, and I do not limit myself to any particular theory as to the precise nature of the action which takes place, but in any, event theeflect of the cracking in the secondary stage is to increase the yield of pressable wax and to diminish or eliminate the quantity of theyield of wax present in a non-pressable form, irrespective of whether the chemical or physical nature of the wax itself has been altered in the process.

In order that my invention may be clearly set forth and understood, I now describe, with reference to the drawing accompanying and forming a part of this specification, a preferred manner in which my invention may be practiced and carried out. In this drawing, the single figure is a more: or less diagrammatic representation of a flow sheet of a preferred form of my process.

Referring to the figure, a crude-petroleum 011 containing a considerable amount of waxy constituents enters the system through a conduit I in which is located a pump 2 and heat exchangers 3, l, 5 and 6. The oil passesthrough the heat exchangers 3, A, I. and 6 and is then supplied in preheated form" to a convectioncoil I within .a furnace 8. The oil after leaving the convection coil I passes through a radiation coil 9 where it is brought to a suitable distillation temperature, for example, about 700 F. and preferably not over. 750' F. The oil at this temperature then passes through a further convection coil ill and leaves thefurnace 8 through a conduit I2 leading to the lower portion of a fractionating tower I3,

The fractionating tower I3 may be of conventional design and provided with suitable plates or trays I4 and also with an inlet I5 for superheated steam.

By means of reflux delivered to the tower I3 through conduits I8 and I I, the vapors liberated in the lower portion of the tower I3 are fractionally condensed into a plurality of fractions which are removed from the tower I3 through a corresponding plurality of outlets 20 to 25, while the residual products are withdrawn from the bottom of the tower I3 through an outlet 28. Vapors which are not condensed in the tower I3 pass through an overhead vapor line 21, through the heat exchanger 3 where they are partially cooled by indirect contact with the incoming crude oil, to a condenser 28 where they are further cooled to such an extent as to condense out substantially all constituents of a normally liquid character. The condensed products pass through a conduit 29 through a gas separator 30 from which separated gas is withdrawn through a conduit 3i. A portion of the gasoline or other condensate is withdrawn from the separator 38 through an outlet pipe 3I' having a pump 32 which delivers it through the conduit I6 to the upper portion of the tower I3 as reflux, while the remaining portion of the condensate is removed from the separator 38 through an outlet 33.

The various fractions ranging from naphtha to and including gas oil, which are withdrawn from the tower I3 through outlets 28 to 24, are passed to strippers 48 to 44 respectively while the fraction recovered and removed from the tower I3 through the outlet 25 is delivered to a stripper 45. The stripped products from the stripping sections 48 to 44 are withdrawn through outlets 46 to 58 and delivered to coolers 5i to 86, respectively, from which they are withdrawn for storage or for further treatment.

A portion of the oil withdrawn through one of the outlets 28 to 24, for example, refined oil, which is withdrawn from the tower I3 through the conduit 23, is taken off through a conduit 51 and after passing through the heat exchanger 4 where it gives up a portion of its heat to the incoming crude oil, is returned through a conduit 58, a pump 59 and the conduit IT to an intermediate level in the tower I3 as reflux.

The amount and conditions of refluxing are so regulated as to make possible the recovery through the outlet 25 of a fraction containing the greater portion of the pressable or crystalline wax but substantially free from amorphous or non-pressable wax, while the residual oil. removed from the bottom of the tower I3 through the conduit 26 contains substantially all of the amorphous wax as well as a small amount of pressable wax not recovered in the stream leaving the tower I3 through the conduit 25, as well as lubricating oil stock and asphaltic bottoms.

In order to effect the conversion of the amorphous or non-pressable wax in the residual oil leaving the tower I3 through the outlet 26 to pressable or crystalline wax, this hot residual oil is delivered by means of a pump 6i and the conduit 62 to a radiation coil 63 within the furnace 8 where it is brought to conditions of pressure and temperature which are effective to promote a moderate cracking of constitutents of the oil, for example, a temperature of from 800 to 875 F. and a pressure of around 200 pounds per square inch. The oil then passes through a convection coil 84 where it is maintained for a short additional period of time under these cracking conditions of temperature and pressure and then passes through a conduit to an auxiliary fractionating tower 86. To the stream of partially cracked products leaving the coils 83 and 84, I preferably add the wax distillate withdrawn from the tower I3 through the outlet 25, which distillate after passing through the stripper 45 is delivered by a pump 61 through a conduit 88, through the heat exchanger 5 and a preheater 89 to the conduit 88 which serves to carry the stream of cracked products from the coil 64 to the auxiliary fractionating tower 86.

In the lower part of the fractionating tower 88 a separation of the cracked products into volatilized and non-volatilized or residual products takes place, the residual products collecting in the bottom of the tower 66 being withdrawnthrough a conduit II' to be forced by a pump I2 through the heat exchanger 8 and a cooler I3. These residual products are useful as fuel oil.

During the passage of the vapors upward through the tower 68 a fractional condensation is efiected by means of reflux introduced to the upper portion of the tower 68 through the conduit I4. A side stream consisting of heavy wax distillate, which contains substantially all of the pressable wax and is substantially free from nonpressable or amorphous wax, is withdrawn from the tower 66 through an outlet I5 and passes to a stripper I8, the stripped heavy wax distillate being then delivered through a conduit II by means of a pump I8 to a cooler I8. After leaving the cooler I9, the heavy wax distillate is withdrawn and processed in the usual manner for the recovery of wax therefrom.

A lighter fraction which may comprise a gas oil is withdrawn from a higher point in the tower 66 through an outlet 8| leading to a cooler 82, while uncondensed vapors pass through an overheadline 83 and through a condenser 84 to a gas separator 85. Gas removed in the separator 85 is withdrawn through a conduit 88. A portion of the cracked distillate which is recovered in the separator 85 is returned by means of a conduit 81 and pump 88 and the conduit I4 to the top of the tower 68 for use as reflux, while the remaining portion of the cracked distillate is withdrawn from the separator 85 through an outlet 83.

For the purpose of removing a slop wax fraction containing such amorphous or non-pressable wax as is volatilized in the lower portion of the tower 86, I provide a suitable trapout tray 8|, the slop wax fraction being withdrawn through the trap-out tray 9i through a conduit 82 having a pump 93 and delivered through a conduit 84 to mingle with the stream of residual oil from the tower I3 which is about to enter the cracking coils 63 and 64. This recycling of the slop wax fraction is advantageous in that it further assists in bringing the amorphous or non-pressable wax into a crystalline or pressable condition and in reducing or eliminating the amount of nonpressable wax removed from the system, at the same time increasing the yield of pressable wax.

A vapor return conduit 95 is provided for the purpose of returning vapors from the strippers 48 to 45 to the tower I3 and a similar vapor return conduit 96 is provided for the purpose of returning vapors liberated in the stripper 18 to the tower 68.

In the operation of my process the pressures maintained in the towers I3 and 88 are as low as it is possible to maintain them and still accomplish the passage of the vapors therethrough. Thus the pressure on the tower l3 may be up to 50 pounds per square inch at the outlet and possibly as high as 200 pounds per square inch at the inlet, while the pressures in the tower 66 may be of the order of 50 pounds per square inch or less.

The wax distillate removed from the tower l3, which as aforesaid represents a fairly large cut of wax distillate, should ordinarily have a boiling point range of 600 to 750 F. and the outlet temperatures at the bottom of thetower i3 are ordinarily maintained at from 650 to 700 F. On the other hand, the wax distillate removed from the tower 66 through the conduits I5 and I1, due to the increase in the amount of pressable wax and the decrease in the amount of non-pressable wax may have a considerable narrower boiling point range of, for example, from 625 to 700 F.

It will be obvious to those skilled in the art, however, that such temperatures and pressures as have been given hereinabove by way of speciflc example may be considerably varied in accordance with the nature of the crude material treated and the results desired.

My invention is, therefore, not limited to the specific details given hereinabove by way of illustrative example but may variously be embodied within the scope of the claims hereinafter made.

7 I claim:

1. The process of. recovering pressable wax from a crude petroleum oil containing wax constituents in pressable and non-pressable form, which comprises distilling said oil, separating the products of distillation into a fraction containing pressable wax substantially free from non-pressable wax, lighter products and heavy material containing the bulk of the non-pressable wax, subjecting said heavy material to a cracking operation to bring non-pressable wax constituents into pressable form, combining the resultant cracked products with said pressable wax fraction, and separately subjecting the volatilized portion of the mixture to fractional condensationto recover therefrom a pressable wax distillate. i

2. The process of. recovering pressable wax from a crude petroleum oil containing wax constituents in pressable and non-pressable form, which comprises distilling said voil, separating the products of distillation into a fraction containing pressable wax substantially free from non-pressable wax, lighter products and heavy material containing the bulk of the non-pressable wax, subjecting said heavy material to a cracking operation to bring non-pressable wax constituents into pressable form, combining the resultant cracked products with said pressable wax fraction, separately subjecting the volatilized portion of the mixture to fractional condensation to recover therefrom a pressable wax distillate, and a slop wax cut containing non-pressable wax, and commingling said slop wax fraction with said heavy material for further cracking.

3. The process of recovering pressable wax from a crude petroleum oil containing wax constituents in pressable and non-pressable form, which comprises distilling said oil at a temperature of not more than 750 F., separating the products of distillation into a fraction containing pressable wax substantially free from non-pressable wax, lighter products and heavy material containing the bulk of the non-pressable wax, subjecting said heavy material to a cracking operation at a temperature of from 800 to 850 F. to bring nonpressable wax constituents into pressable form, combining the resultant cracked products with said pressable wax fraction, separately subjecting the volatilized portion of the mixture to fractional condensation to recover therefrom a press.-

able wax distillate and a slop wax out containing non-pressable wax, and commingling said slop wax fraction with said heavy material for further cracking.

4.- The process of recovering pressable wax from a crude petroleum oil containing wax constituents in pressable and non-pressable form, which comprises distilling said oil at a temperature of not more than 750 F., separating the products of distillation into a fraction containing pressable wax substantially free from non-pressable wax and having a boiling point range of from 600 to 750 F., lighter products and heavy material containing the bulk of the non-pressable wax, subjecting said heavy material to a cracking operation at a temperature of from 800 to 850 F. to bring non-pressable wax constituents into pressable form, combining the resultant cracked products with said pressable wax fraction, separately subjecting the volatilized portion of. the mixture to fractional condensation to recover therefrom a pressable wax distillate and a slop wax cut containing non-pressable wax, and commingling said slop wax fraction with said heavy material for further cracking.

JOHN T. WARD.

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