BRPI0622125A2 - oil refining process - Google Patents

Abstract

OIL REFINING PROCESS. The present invention describes a process for heating used lubricating oil (ULO) to dehydrate and / or recover distillable components therefrom. The ULO feed is heated by direct contact heat exchange with a non-pyrolytic molten fluid, molten metal or molten salt, preferably maintained as a continuous phase bath, operating at a temperature above the boiling point of water and below 600 <198> C. The ULO feed is heated and at least partially vaporized at, or above, or by contact with the molten fluid. Hydrocarbons in the lubricant boiling range are recovered as a vapor product. The additive package in the ULO, or decomposition products therefrom, is recovered as a liquid phase.

Description

Report of the Invention Patent for "OIL REFINING PROCESS".

The present invention relates to direct contact heating of normally liquid and similar hydrocarbons, especially those which are thermally unstable or difficult to heat, for example, process motor oil used to recover distillable and non-distillable hydrocarbons.

BACKGROUND OF THE INVENTION

Automotive oils and many industrial lubricating oils are typically formulated from paraffin-based petroleum distilled oils or synthetic-based lubricating oils. Lubricating oils are combined with additives such as soaps, extreme pressure (EP) agents, viscosity index (VI) enhancers, anti-foaming agents, corrosion inhibitors, anti-wear agents, antioxidants and polymeric dispersing agents to produce a motor lubricating oil with viscosity from SAE5 to SAE 60.

After use, this oil is collected from truck and bus fleets, car service stations, municipal motor oil recycling centers and retail stores. There is also a significant volume of oil collected from the industrial sector, for example cutting, stamping and cooling oils, which are collected on a direct basis or are collected from oily water dewatering facilities. This collected oil contains organometallic additives such as zinc dialkylthiophosphate from the original lubricating oil formulation, engine sludge and water. Waste oil may also contain contaminants such as refuse grease, brake fluid, transmission oil, transformer oil, railway lubricant, crude oil, antifreeze agents, dry cleaning fluid, solven. - degreasers such as trichlorethylene, edible fats and oils, mineral acids, soot, earth and refuse of unknown origin.

Recovering waste oil is largely accomplished by small processors, which use various processes tailored to available waste oil, product demands, and site environmental considerations. These processes include at least partial dehydration and coarse filtration. Some more sophisticated processors may perform chemical demetallization or distillation. The presence of organometallic substances in waste oils such as zinc dialkylthiophosphate results in the decomposition of dialkyl dithiophosphate to form a zinc-rich carbonaceous layer and often other metals such as calcium, magnesium and other metals present as additives. these waste oils are difficult, if not impossible, to process. The carbonaceous layer, which contains several metals, forms quickly on heated surfaces and can grow to a thickness of over 1 mm in 24 hours. This layer not only rapidly reduces the heat transfer coefficient of tubular heaters. It also results in substantial or total occlusion of these tubes within a few days.

Successful recovery processes require reducing the content of organometallic substances (or ashes) to a level where hot oil is not embedded in heated surfaces. Such reduction may be accomplished by chemical processes, which include reacting a phosphate cation or sulfate cation with the chemically bonded metal to form metal phosphate or metal sulfate. In US 4,432,865, Norman describes contacting the used motor oil with polyfunctional mineral acid and a polyhydroxy compound to react with undesirable pollutants to form easily removable reaction products. These chemical processes suffer from resulting disposal problems, depending on the metal by-products formed.

The ash content can also be reduced by heating the used lubricating oil to decompose organometallic additives. But indirect heat exchange surfaces cannot be kept above 200-205 ° C for extended periods without extensive fouling and metal deposition of the additives. Used lubricating oils may be heated to an additive decomposition temperature of 205-540 ° C by direct heat exchange by mixing with a heated oil product as described in US 5,447,628, Harrison et al. . But diluting product oil with waste oil requires reprocessing of already processed product oil. The UOP Hy-Lube process described in US 5,244,565 and US 5,302,282, and many other patents, use hot circulating hydrogen as a heating medium to prevent the deposition of organometallic compounds on heated surfaces. .

The problem of fouling of heated surfaces can be improved to some extent by more moderate heating. Some processes, such as the fixed-layer catalytic cracking version, Houdry's process, use a molten salt bath to achieve somewhat moderate controlled heating of vaporized liquid hydrocarbon through the pipes. of catalyst immersed in the salt bath. Molten metal baths have also been used as a convenient means of heating difficult-to-process substances to a control temperature, for example, the flammability of some plastics is tested by placing a plastic bottle in a molten metal bath. The use of a salt bath, or molten metal bath, or a high temperature condensing steam may reduce uneven heating of heat exchange surfaces and thus reduce dT on a metal surface and perhaps delay in-service lubricating oil (ULO) fouling, but additives in the ULO still tend to decompose on the warmer surface, which may be the heat exchanger tubes.

Although not related to ULO heating, there has been use, either commercially or reported in the patent literature, of molten metal for direct contact heating of various substances. The flotation process to produce glass is almost 50 years old. Molten metal, mostly lead, coal or shale heating has been practical in one form or another for almost 100 years. There are patents on the use of molten metal baths for scrap pyrolysis and latex conversion by heating plants above ground in a metal bath to make a superior oily product. Also related in some way, but unlike anything described above, is the HyMelt® process, using a cast iron bath to dissolve feedstock reserves. The temperatures in the HyMelt process are so high that if a liquid hydrocarbon is fed to a HyMNelt reactor, the feed material dissociates almost instantaneously into hydrogen and carbon with the carbon dissolving. in cast iron. This is an excellent process for decoupling a hydrocarbon into elemental constituents, but it is too much to reprocess ULO when all that is needed is sufficient heat to vaporize the components within the boiling range of the lubricant.

JP 59-124,991 in Ex. 1 used a molten metal bath for thermal cracking of ULO, preferably ULO with added water, to form a cracking vapor and a solid carbonaceous residue. The cracked vapors were condensed to form something like pyrolysis naphtha. The solid residue was removed from contact with the molten metal bath by an endless screw conveyor.

Some researchers took the position that metallic surface fouling would occur during ULO processing, and the best way to deal with this was to inject something into the ULO that would clean the metal by scrubbing, ie by injecting an abrasive material.

Solvent extraction with light paraffin solvents such as propane, butane, pentane and mixtures thereof was performed by Interline et al. Details of the Interline Process are presented in US 5,286,380 and US 5,556,548. Although the extraction method seems an excellent solution to the problem of processing ULO, the process can be relatively expensive to operate. Their quarterly report of May 15, 2002 states that "It has become clear that demanding production-based royalties is unfeasible in many situations and countries. Unless and until refined oil produced in a mill can be sold at prices comparable to base lubricating oils, receiving production-based royalties will be difficult.This reality was experienced in Korea, where royalty was extinguished for the first mill, and in England, where royalties were reduced and postponed until the plant would become profitable. " Advancement in ULO processing has occurred with direct ULO contact heating with steam or a non-hydrogenating gas. This method solved the problem of decomposition fouling of the zinc additive of hot metal surfaces by ensuring that the metal surfaces supporting the ULO were always relatively cold. The hottest point was the steam injection point. Decomposing additives had only themselves to condense. This steam and ULO injection process was described in my previous patent, US 6,068,759, Process for Recovering Lube Oil Base from Used Motor Oil, and US 6,447,672, Continuous Plural Stage Heated Vapor Injection. Process for Recovering Lube Oil Base Stocks from Used Motor Oil. Further variations on the subject of ULO steam injection processes are described in US 6,402,937, Pumped Recyele Vapor, and US 6,402,938, Vaporization of Used Motor Oil with Non-hydrogenating Reeyele Vapor.

The "state of the art" of used engine oil processing can be summarized as follows:

Chemical additive and extraction methods can be used to react with zinc additives, or to extract anything except zinc additives. High costs and low reliability have prevented widespread commercial use.

Indirect heating in a heated heater causes rapid encrustation of metal surfaces. The use of more moderate heating, molten metal heating medium or molten salt may minimize but not eliminate fouling on hot metal surfaces.

Direct contact heating with high pressure hydrogen can eliminate fouling, but requires high capital and operating expenses. Direct contact heating with recycled oil helps, but it is necessary to process the ULO twice.

Direct contact thermal cracking with a molten metal bath can be used to crack ULO into lighter cracked products and solid waste, but these methods thermally degrade the lightweight product.

Steam direct contact heating or non-hydrogenating steam works, but it is not the optimal solution.

Direct steam heating, as described in my US patent 6,068,759, was a good solution, but not perfect. When steam is injected, the process can create a water discharge problem and is less thermally efficient because latent steam heat is lost when steam is condensed. When, for example, propane is injected, large volumes of steam are required to produce sufficient heat input and recycle these steam streams.

An even better method for refining ULO and other thermally unstable feeds was desired. The beneficial aspects of ULO heating should be retained by injecting something warm into it but avoiding the problems created by the use of steam or a light hydrocarbon vapor as the heating medium. A means has been found to overcome these deficiencies by using a non-pyrolizing molten fluid as the heating fluid.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method for refining used lubricating oil (ULO) with lubricating oil boiling components and thermally decomposable additives comprising heating said USE by direct contact heat exchange with a non-pyrolyzing molten fluid, selected from the molten metal group and molten salt, at a temperature and for a time sufficient to vaporize at least a portion of said lubricating oil component and remove said vaporized hydrocarbons from the boiling range of lubricant as a vapor product.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a simplified schematic drawing of a preferred embodiment in which waste oil is refined by direct contact heating with a continuous phase of molten metal.

Figure 2 is similar to Figure 1, but differs in that ULO, instead of molten metal, is the continuous phase.

Figure 3 shows one embodiment with a dewatering station upstream of the molten metal heating zone.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In Figure 1, Used Lubricating Oil (ULO) 1 as received flows from a feedstock storage system 10 through line 12 to feed pump 13 into contact container 14 or near at the bottom of it. A molten metal or molten salt heat transfer fluid 15, which is ULO-immiscible and much denser than it, circulates from the bottom of the contact vessel 14 along line 16 to a heater 18 which heats the heat transfer fluid to the desired temperature. Heating can also be accomplished by operating electrical resistors in the heat transfer fluid phase in the contact vessel 14. The heat transfer fluid flows back to the contact vessel along line 20. The heat transfer fluid current Heat through 15 may be by natural convection as shown, or fluid may be pumped through heater 18 by use of a pump not shown. The total liquid level in the contact vessel 14 is maintained by a vertical outlet tube 22 through which all gas, vapor and liquid leave the vessel and flow through line 22 to the separator vessel 26. A The heat transfer fluid ratio establishes its level in the contact vessel 14. When the heat transfer fluid level 15 is relatively high, as shown in Figure 1, the ULO is the predominantly dispersed phase and the transfer fluid. Heat transfer is the predominantly continuous phase. When the heat transfer fluid level is relatively low, as shown in Figure 2, the ULO is the predominantly continuous phase and the heat transfer fluid is the predominantly dispersed phase.

The liquid and vapor entering the waste separator container separate into a liquid stream 28 and a vapor stream 32. The liquid stream 28 flows into the waste storage system 30. A The steam stream 32 flows through a cooling device 34 which may use air as shown in Figures 1 and 2 as cooling fluid or any other cooling means such as water in boiling water, cooling water or some other fluid. The outlet temperature of the cooling device 34 should be low enough to substantially condense all the oil in the feed material 10. Normally, an outlet temperature of less than 65 ° C causes virtually all the feed material be condensed. The condensed stream flows through line 36 into an upper separating container 38, where any water in feed material 10 separates and flows through line 40 into a water storage system 42. Liquid oil in stream 36 flows through line 40 to a water storage system 42. Liquid oil in stream 36 flows through line 44 to a higher oil storage system 46. Any noncondensable gases flow through line 48 to a gas handling system 50. For low noncondensing gas streams and the operating pressure of the upper separating vessel 38, the gas handling system may be a single opening. For larger currents, continuous combustion or some other appropriate gas treatment system may be required. The gas handling system may be a vacuum system so that the contact vessel 14, the waste separator 26 and the upper separator 38 operate at a sub atmospheric pressure.

Figure 3 shows a particularly preferred embodiment of the present invention. ULO feed material 10 runs through line 12 for a loading pump 13 for a partial condenser 50, which heats the ULO by partial condensation of steam from the upper separating vessel 42 to a temperature of about 175-180 ° C. The heated feed material flows through line 14 to a pressure reducing valve 16, and then to a flash container 18. All water and approximately 1% of the hydrocarbons contained in feed material 10 vaporize and flow through the line 22 to a thermal oxidation device 24, or any other appropriate treatment system, where hydrocarbons are converted to carbon dioxide and water and discharged through line 26.

The dried feed material flows through line 20 to feed pump 28, where it enters the bottom of contact container 30, where it contacts heat transfer fluid 31. Heat transfer fluid may be the phase continuous or dispersed as described above. Vertical outlet tube 32 maintains the total liquid level in the contact vessel 14. All gas, vapor and liquid leaving the contact vessel through line 34 to the waste separator vessel 42. Liquid waste flows through from line 44 to a waste storage system 46. Steam flows through line 48 to partial condenser 50, where it is partially condensed by heating the feed material as described above. Partially condensed vapor flows through line 51 to a cooling device 52, where it is cooled to about 65 ° C by heat exchange with a cooling fluid. The resulting condensed stream flows through line 53 to the upper separator 54. Upper liquid flows through line 56 to an upper storage system 58. Any noncondensable gases flow through line 60 to a gas handling system. The gas handling system may include a vacuum system such that the contact vessel 14, the waste separator 26 and the upper separator 38 operate at a sub atmospheric pressure.

DESCRIPTION OF PREFERRED EMBODIMENTS

Any molten fluid may be used that is immiscible with ULO (or other oil) feed material and is reasonably stable in use. Molten metal is preferred in part because such material has such a high thermal conductivity, and there is plenty of operational experience associated with molten metal baths, albeit for other purposes. There are several metal alloys available which are fluid at relatively low temperatures which have ideal properties for use at present. They are non-corrosive. They are highly conductive, allowing models of compact furnaces to heat the metal. The metals are dense and contain a large amount of energy per fluid volume, so the used lubricating oil (ULO) reprocessing plant can be small. They are not volatile, so they contribute to air or water pollution. It has a high surface tension, which means that decomposition products and wastes found in the ULO do not adhere to or remain in the molten metal, allowing extended use of the metal bath. Molten metal also allows for a flexible adaptation method, allowing injection of the metal into the oil or vice versa, although not necessarily with equivalent results. When oil is injected into a molten metal bath, it is easy to increase or decrease the process intensity by changing the depth of the molten metal in the bath or the metal temperature or pressure in the molten metal bath.

Metals that can be used include lead, tin, antimony, mercury, cadmium, sodium, potassium, bismuth, indium, zinc, gallium. Preferably, the metal used melts below about 300-325 ° C or forms an alloy that does. Not all metals give equal results and some have significant safety considerations, for example lead or mercury, but they can be included as part of the molten metal bath if desired.

Any feed material containing a normally liquid, thermally unstable hydrocarbon may be heated using the process of the present invention. Normally liquid hydrocarbons include C5 and heavier hydrocarbons, for example, naphtha boiling ranges through residual fractions, which contain sufficient olefins, diolefins or other compounds to make them difficult to heat in a water heater. Conventional heating. Heavy feed materials, so heavy that they are not liquid at room temperature, for example a grease, wax, petrolatum or any high melting hydrocarbon, may be used as food. Treatment of solids is beyond the scope of the present invention, that is, treatment of coal or oil contaminated dirt is beyond the scope of the present invention.

What is essential to the practice of the present invention is direct contact heat exchange of a liquid feed material with a molten fluid. The liquid must contain hydrocarbons. The feedstock is typically contaminated with unwanted lighter or heavier components that can be removed by heating by either vaporizing a desired feedstock component from a waste fraction or removing a lighter contaminant from a fraction. of desired waste product.

ULO often contains both light and heavy contaminants. Light contaminants include water, naphtha and may include some impurities, such as solvents, introduced during the ULO collection process. Heavy contaminants include the additive package.

When processing ULO, the economic objective is to vaporize as much of the feed material as possible. Generally there are demands on processing "intensity" and% vaporization. It is important to be able to remove the residue fraction from contact with the molten fluid by simply removing it as a liquid. When processing ULO, waste does not run when more than 83 to 85% of the feed material is vaporized. A practical limit is believed to be 80% vaporization of dry oil. Another requirement is to obtain vaporization without undue degradation of the product. Degradation, or thermal cracking, can occur when the upper or bottom fraction is thermally cracked. When the upper fraction is thermally cracked, there is a reduction in value. A rich fraction of potential lubricating oil may be degraded to pyrolysis naphtha by intense cracking of the ULO feed material, as in JP 59-124991. The bottom fraction can also be cracked by thermal cracking, since a residual liquid fraction has more value - and is much easier to remove - than a solid residual fraction. Generally, it is easier to shrink the residual fraction because this material can be left in contact with the molten fluid heating bath for a long time, unlike the vapor fraction which typically has a very long residence time. contact with molten heating fluid.

A surprising aspect of using molten metal to heat ULO and vaporize the lubricating oil boiling range components of it is that deep oil removal from the ULO is easy to achieve. The temperature of the metal at the bottom of a continuous molten metal bath and the oil temperature at the top of the contact vessel, the oil floating on the surface of the molten metal, are very close. I have never found more than 3 ° C different in them, and there is no sign of fouling.

The invention contemplates the use of a range of molten metals or molten salt for high intensity drying and / or the heating process. They include low melting metal alloys. Where simple drying or only a modest amount of thermal processing is desired, the candidate melt fluids may have melting points typically ranging from 60-230 ° C.

It is essential that the heating fluid be immiscible with the ULO and substantially denser.

It is preferable that the interfacial surface tension between the molten metal heat transfer medium or other fluid that is immiscible with the feed material being treated and the liquid feed material is high enough to prevent sticking. molten fluid on the wetted surface. The thermal conductivity of the molten fluid must also be sufficiently high to ensure that the molten fluid remains in a liquid state at least during the process so that the fluid does not solidify to form a solid film or freezing cone at the point. contact with the ULO.

When the thermal conductivity of the fluid is sufficiently high, the fluid conducts heat from the molten bath body to the interfacial contact region between drops or streams of molten heating medium, or drops or streams of molten heating medium. , when the ULO is the continuous phase. The use of cast metal alloys is preferred because of their high interfacial surface tension with decomposition products that may form from the ULO and scrap that can be found there. Metals are also preferred over other immiscible fluids due to their high thermal conductivity. An additional benefit is the high density of the molten metal over the ULO, which favors rapid transit of one fluid through another and plenty of thrust if deflector plates or column lining are used.

Table 1 summarizes some calculated properties for various recommended cast metal eutectic alloy materials when only moderate intensity heating is required. This information on alloys is taken from information reported in US 5,619,806, which is incorporated by reference.

TABLE 1

Properties of Candidate Cast Materials

Melting Temperature ° C

ln / Sn (52/48) 118

Bi / Pb (55/45) 124

Bi / Sn (58/42) 138

Sn / Pb (63/37) 183

Sn / Zn (92/8)

"Tin Film"

Sn / Cu (99/1) 227

The metallic material of the bath may consist of a selected alloy from the group which includes:

i) Ga / ln ii) Bi / In iii) In / Sn iv) Bi / Pb V) Bi / Sn vi) Sn / Pb vii) Sn / Zn viii) Sn / Cu

A spectrum of molten metal temperatures can be used from top to bottom. Based on the float bath process for making sheet glass, tin has ideal properties when a relatively high temperature bath is desired. Tin has a melting point of 232 ° C and a boiling point of 2623 ° C. This means that a variety of temperatures can be obtained in the molten metal bath, ranging from temperatures close to the boiling point of water (when a low-melt alloy such as Wood's metal is used at temperatures above 500 ° C). For ease of initiation, that is, a relatively low melting point, a tin-bismuth alloy is preferred.

EXPERIENCES

The experiments were conducted at a length of about 10 cm from an ID 4 "SCH40 stainless steel tube. The alloy was a bismuth tin eutectic, which is 42% tin and 58% bismuth. The depth of the metal was about 50 cm, with about 30 cm of free space or vapor space above the molten metal.The stainless steel tube was heated by a cylindrical heater, an electric wrap with a thermostat. ULO testing was performed at about 316 ° C of the molten metal layer temperature.The ULO feed material was fed to the bottom of the molten metal bath by means of a 6 mm threaded nozzle to which a length of 3 mm SS pipe was set.The pipe did not extend into the molten metal bath.The process was carried out under vacuum, which is usual for lubrication oil recovery processes. that the pressure was about 3.45-6.89 kPa (0.5-1 psia), but the pressure gauge used was not very accurate at such low pressures.

The first tests were performed on a low ULO concentration sample that had about 10% by weight of water, much more than is present in any car engine. I don't know where all this water came from, but it was there, and it caused considerable processing difficulties, perhaps due to the slow addition of an aqueous phase, which caused the apparatus to vibrate and the metal to spill out. A significant amount of metal was lost due to the unusual water level of the feed material, but the process worked to vaporize ULO lubricating oil components.

The following set of tests was performed after dewatering the ULO1 feed material to essentially remove all water. This series of tests approaches the process course shown in Figure 3, ie dehydration, prior to "distillation" of the ULO in the molten metal bath. The process worked smoothly, without the crashes and drips associated with the initial series of tests. The product on the upper side was a clear, golden liquid that almost looked like honey. There was some odor associated with both the upper and liquid residue, but the liquid residue had less odor than the ULO feed material.

A problem was encountered in initial testing, the freezing of metal near the point of feed injection. This was overcome by adding a heating tape to the stainless steel tube. This would probably not be a problem on commercially sized units, but if so, some form of heating the feed injection medium can be used to overcome it.

Experiments represent the actual work done in a laboratory, but they should not be interpreted as either limiting the process or optimizing it. ULO refiners can operate at even lower temperatures, using a molten metal bath or molten salt bath, merely to remove water and / or "light terminals" that may be present. This gentle use of technology allows a fleet operator to periodically condition motor oil used in vehicles, removing water and crankcase dilution, and refilling the conditioned motor oil to the vehicle, perhaps with some additional additives. Some refineries, especially those without a market for a heavy liquid waste product, may wish to use higher temperatures to maximize the production of distillable hydrocarbons and minimize the production of ULO heavy "residual" liquid. This use would simultaneously improve product recovery and minimize disposal costs.

EXAM

For me, the most surprising result of the experiments was the low temperature difference between the top and bottom of the molten metal bath and the residual liquid oil fraction, all within about 3 ° C. In a conventional refining process using a metal-walled heat exchanger or a metal-tube heated heater, temperature differences at any point on the metal surface are typically 6-30 ° C, with large differences in temperature. temperature between the input and output of the device. As an example, if a heated heater was used to heat and vaporize a ULO feed material, the oil feed temperature at or immediately inside the heater is room temperature, or perhaps 65 ° C if Some heat exchange has been practiced on the ULO feed material. At the heater outlet, the ULO is at the desired process temperature, typically 260-400 ° C, and the oven-side temperature of the pipe is 290-485 ° C, to give sufficient ΔΤ to propel heat through. the pipe walls and into the ULO. Relatively large ATs are required to reduce the surface area of the heat exchange pipe or heater pipe to an allowable amount. Heat transfer is relatively slow across a solid metal surface, thermal energy must pass from the inside of the hot oven by convection and radiation to the outside surface of the heater tube through the metal tube (and this is typically efficient ) through the interface between the inner tube wall and the vapor / liquid layer in close proximity to the tube wall and, if necessary, in the ULO feedload stream. There are many "narrowing points" that slow down the full speed of heat transfer. Part of the problem with a heated heater is that relatively hot metal tube surfaces cause vaporization and fouling, both of which dramatically reduce heat transfer. Vaporization reduces heat transfer because it is approximately an order of size more difficult to heat a gas than a liquid. Fouling reduces heat transfer because a thin but growing layer of carbonaceous deposits acts as an insulator, while creating a relatively porous place to hold hydrocarbon liquids and vapors for a long time, allowing for thermal cracking and further fouling. .

In the process of the invention, especially when practiced with a continuous metal bath phase, the phenomenon that occurs during heating becomes an advantage rather than a disadvantage. ULO1 when injected into the base of the bath is heated almost instantaneously, causing some vaporization and fragmentation of any large ULO droplets that may attempt to form. The ULO vapors produced are much lighter than residual ULO liquid, and are believed to form something like a three-phase bubble, with a vapor top and a liquid oil bottom in a metal wrap. cast. If a large bubble is formed, the light vapor part moves away from the residual ULO liquid, or at least causes some form of vigorous agitation as the large multi-phase bubble rises. If the vapor part moves away, this leaves the residual ULO liquid to form a new bubble, but of liquid, or at least much more liquid than before the vapor phase had moved away, and that denser bubble does not rise so quickly. in the molten metal bath, giving the molten metal more time to heat the ULO.

Radiant heat transfer is also believed to play a significant role, since the lens-shaped oil pool at the bottom of a bubble has a large surface area to volume ratio, a or more orders of size most favorable for the heat transfer that can occur when the ULO passes through a metal pipe 10 - 15 cm in diameter in a heated heater. Radiant heat transfer is considered to play an insignificant role in heat transfer from a hot metal heat exchange surface to oil flowing in or around the surface. In my process, the bubbles are small and "see" sufficiently hot molten metal, so significant radiant heat transfer occurs.

Based on the work done so far, the preferred metal composition is bismuth tin eutectic, which is 42% tin and 58% bismuth. It seems that the optimum conditions for temperature and pressure are around 315 - 330 ° C and 50 to 75 mm Hg of pressure. There are, in fact, an infinite number of temperature and pressure combinations, which will yield the highest yield of 80%. For ULO, the limits on pressure and temperature combinations may range from about 300 ° C to 0.5 mm Hg of pressure at 425 ° C, at a pressure close to atmospheric. Either end can result in an inoperable situation. The fundamental parameter is to vaporize 75 to 80% of the feed material without causing problems that render the process inoperable.

The end use of the products, both the upper lubricating oil fraction and the waste fraction, can have an important influence on operating conditions. When the process is being performed to recover a high quality base material of high quality lubricating oil, relatively low temperatures and somewhat lower product recoveries can be optimal. When the waste product is to be an asphalt thinner, the desire is to conserve as much as possible of the plastic present in the ULO, especially the viscosity modifier, to improve asphalt properties. When the superior product is going to be FCC feed material, a lower quality product can be tolerated so that higher temperatures and higher recovery can be optimal. To minimize low waste production, and this is usually the residual fraction of the ULO, after the lubricating boiling range hydrocarbons have been removed, it may be important to have very high and / or low temperatures to reduce the residual fraction as much as possible.

BATH OF SALT

When a molten salt bath is used, it is important to maintain reducing conditions during processing. Salt baths can be reactive, especially when used in an oxidizing atmosphere. Oxidizing atmospheres, when present during the recovery of lubricating oil, degrade the quality of the recovered lubricating boiling hydrocarbons on the upper side, so that a reducing atmosphere is preferable. When a salt bath is used for simple dehydration of ULO1 or to remove light terminals such as naphtha or other materials, sometimes present as "crankcase dilution", maintaining a reducing atmosphere is not as critical as the temperatures involved they are usually so low that oxidation reactions either do not occur or occur so slowly so as not to cause problems.

Any salts used to date can be used as heat transfer medium. Some common salts used in heat transfer are:

KNO3, KNO2, NaNO3, and NaNO2

Na2CO3, Li2CO3In K2CO3

NaF, ZrF1 LiF1 BeF2

Frequently, salts are combined from eutectics or other low melting mixtures such as Sun Salt; 60% NaNO3 and 40% KNO3, or Hi Tech XL; 48% Ca (NO3) 2, 7% NaNO3 and 45% KNO3. Mixtures of Na2CO3 and K2CO3 have long been used in coal gasification and pyrolysis.

GENERAL CONSIDERATIONS

It is important to use a molten fluid with the "heat range" within what is required for desired process objects. When all that is required is simple dehydration of ULO, and this is usually a first or preliminary treatment rather than the entire process, molten metal is preferred over molten salt, since water in the material The feed agent may react with or dissolve molten salt. For dehydration molten metal which is molten within the temperature range of 80 ° C + is appropriate. When distillation of ULO lubricating oil boiling components is desired, the molten fluid must remain molten at temperatures above 100 ° C to about 600 ° C;

The upper limit on temperature / choice of molten salt or molten metal is usually determined by volatility and process requirements. Molten metals or molten salts having a low vapor pressure at the temperatures used are preferred, so that loss of molten metal due to "dust raising" or for any other reason is less than 1% per day. . The metals or salts chosen should not be corrosive under process conditions and preferably are non-toxic for safety.

The invention allows the drying and / or recovery of base volumes of lubricating oil and / or other used motor oil hydrocarbons. The process and apparatus of the present invention also permit efficient processing of other low value or waste streams, which contain so much water and / or emulsified additives that conventional processing is not feasible.

When used to process ULO1 the present invention allows the separation of valuable additive distillable hydrocarbon metal additive packets in the engine oil with limited decomposition or none of such distillable hydrocarbons. When the ULO residual fraction is intended for use as an asphalt thinner, it may be advantageous to have some or most or all of the additive package intact. Plastic viscosity modifiers used in some lubricating oils can have beneficial effects on asphalt, so it is useful to have a process that gives re-refiners the option of decomposing, or not decomposing, the additive package.

The process and apparatus of the present invention may also be used to heat other thermally unstable or difficult to heat liquids.

Although tests have been performed at relatively low pressure, refineries may wish to operate under a more intensive vacuum to maximize the recovery of lubricating oil components and minimize additive decomposition. Others may wish to operate above a pressure of 1 atm to 100 atm, or minimize steam volume and facilitate the processing of streams with large amounts of water. Higher pressures allow a more compact plant to be built.

The tests were performed using a single molten metal bath, but the invention is not limited to this embodiment. Multiple molten metal baths may be used, more or less as product fractionators using multiple distillation trays, each operating at a slightly different temperature.

Claims (10)

1. Method for refining waste lubricating oil (ULO), with boiling lubricating oil components and thermally decomposable additives, comprising: a. heating said ULO by direct contact heat exchange with a non-pyrolyzing molten fluid selected from the molten metal group and molten salt at a temperature and time sufficient to vaporize at least part of the components of the scope. boiling oil, and b. removing as a vapor product said vaporized hydrocarbons from the lubricant boiling range. The method of claim 1, wherein said molten fluid is maintained as a continuous phase. A method according to claim 2, wherein said molten fluid is disposed as one or more baths and said ULO is injected into, or bubbled therethrough fluid. The method of claim 1, wherein said ULO is maintained as a continuous phase and said molten fluid is poured, sprayed or otherwise passed through said continuous ULO phase. The method of claim 1, wherein said molten fluid is molten metal. The method of claim 1, wherein said molten fluid is maintained at a temperature of 100 to 600 ° C and said contact of said ULO with said molten fluid occurs under vacuum. The method of claim 1, wherein said thermally decomposable additives are recovered as a liquid phase. The method of claim 1, wherein said ULO fluid is dehydrated prior to contact with said molten fluid. The method of claim 1, wherein at least a majority of about 85% LV of said lubricant boiling hydrocarbon in said ULO is recovered as a vapor product. A process according to claim 1, wherein said vapor product is condensed to produce a boiling oil fraction of liquid product lubricant, such as honey.