Note: Descriptions are shown in the official language in which they were submitted.
~s~
DESCRIPTION OF THE INVENTION
2 Used oils, especiall~ used lubricating oils
3 which are normally discarded or burned as waste, are
4 reclaimed for reuse by a re-refining procedure com-
prising the steps of~
6 (a) heat soaking the used oil;
7 (b) stripping the heat soaked oil under
8 conditions and employing procedures sufficient to
g remove the low boiling conversion products from the
heat soaker, so as to reduce the Total Acid Number
11 (TAN), Toluene Insolubles (T.I~) and halides content of
12 the oil;
13 (c) distilling the heat soaked, stripped
14 used oil to produce a distillate and a residue;
(d~ passing the distillate through a guard
16 bed of activated material;
17 (e) hydrotreating the guard bed treated
18 distillate to produce a refined oil product suitable
19 for use as lube oil base stock.
Alternatively, the rerefining process can be
21 practiced effectively even when the stripping step (b)
22 recited above i5 omitted. In such a case a greater
23 burden is imposed on the guard bed/ but the overall
24 process still produces a rerefined oil which closely
matches virgin base oils in physical properties and
26 chemical composition.
a~5~ z~
-- 2 --
1 If the used oil to be rerefined contains a
2 quantity of water and/or fuel fraction which the prac-
3 ti~;oner considers sufficiently large to affect the
4 heat soaking operations (by requiring higher pressures
than desirable) the used oil may be subjected to a
6 dewatering/defueling step prior to being heat soaked.
7 BACKGROUND OF THE INVENTION
~. ~
8 Used oils, particularly those used as lubri-
g cating oils, are normally considered waste once they
have been used for their intended purpose, (e.g.,
11 crankcase oils etc.) as lubricants and are normally
12 either discarded or burned, either disposal method
13 having deleterious environmental ramifications asso-
14 ciated therewith.
Consequently, as an alternative, methods for
16 reclaiming the used oil molecules have been developed
17 to reduce the environmental hazard associated with
18 either disposal or burning of the oil, and to conserve
19 valuable oil molecules which can be refined into base
stock having a quality equivalent to virgin base
21 stocks. Acid~clay treating is of diminishing appli-
22 cability due to the complexity of the additives
23 employed in modern lubr;cating oils, as well as in
24 light of the sludge disposal problem associated with
acid/clay treatment.
26 The Phillips (PROP) process combines
27 chemical demetallization with clay/hydrotreating as
28 finishing steps. Used oil is mixed with an aqueous
29 solution of, for example, diammonium phosphate which
reacts with metal contaminants to form metallic phos-
31 phates which separate from both water and oil due to
32 low solubility, The demetallized oil, after filtration
~f~ 2
1 using a filter aid and heating, is con~acted with a
2 guard bed of clay and hydrotreated over a catalyst, for
3 example Ni/Mo and stripped. (See USP 4,151,072).
4 The chief disadvantage of the PROP tech-
nology is the disposal of the large amount of solid
6 wastes associated with the ilter cake and spent clay7
7 In addition, a large amount of waste water, origînated
8 from the chemical solution, is generated by this tech-
g nology.
Vacuum distillation followed by hydrotreat-
11 ing has been proposed in the litera~ure for used oil
12 rerefiningr The process is characterized by pollution-
13 free operation without incurring sludge and oily-clay
14 wastes. However, the drawback of this process is that
contaminants in the distillate, originated from lube
16 additives and/or degraded oil, cannot be removed to a
17 low enough level during the distillation step. As a
18 result, hydrotreater fouling becomes a serious problem.
19 Dewatering/defueling extraction/distilla-
tion/clay contacting and/or hydrofinishing has also
21 been suggested ~See USP 3,919,076, USP 4,073,719 and
22 USP 4,073,720. In these processes, various kinds of
23 extraction solvent are used, e.g., propane or a mixture
24 of alcohol and ketonel to reduce coking and fouling
precursors in the dewatered/defueled used oil prior to
26 the vacuum distillation. The resulting distillate is
27 further upgraded by clay contacting and/or hydrofinish-
28 ing. The chief disadvantage of this approach is the
29 complexity of the solvent recovery systems which
require high energy consumption, and generate waste
31 chemicals via lealcage from the unit and waste/solvent
32 separations.
~2~S~Z
1 In addition to the above-mentioned waste oil
2 re-refining technologies, distillation of used oil in a
3 thin-film or wiped film evaporator (TFE or WFE) to
4 recover lube dis~illate is also known in the art.
"Recent Technology Development in Evaporation
6 Re-Refinery of Waste Oil" r Bishop and Arlidge;
7 "Thin-Film Distillation as a Tool in Re-Refining Used
8 Oil" Pauley; both of these articles in Third Inter-
g national Conference on Waste Oil Recovery and Reuse,
1978. However, the distillate has to be further pro-
11 cessed in order to make an end-product equivalent to
12 the virgin basestock in quality performance. Heat
13 soaking is also known in the industry as a method for
14 breaking up additive molecules and precipitating
~5 polymers. (See USP 4,033,859). Predistilling a used oil
16 preferably by steam stripping said oil, within the
17 temperature range of between 480F and 650F (about
18 249-345C) for at least 4 hours to remove NOX, light
19 oil components and residual water from the stock prior
to distilling the oil in a thin-film evaporator as
21 described in USP 4,101,414.
22 DESCRIPTION OF THE FIGURES
23 Figure 1 is a schematic of the processing
24 step sequence of the present invention.
Figure 2 is a schematic of the processing
26 step sequence of the present invention including the
27 stripping of the heat soaked oil. For the sake of
28 simplicityt the pumps, heaterst piping, etc. which
29 would be employed in the process, and whose location
and mode of operation would be within the scope of the
31 ability of those skilled in the art, have been omitted,
32 as have the subsequent down stream processing steps
~z~c~
1 which would be or could be practiced o~ the various
2 effluent streamsA
3 In Figure 1 used oil would be fed via line 1
4 to an optional dewatering/defueling uni~ (2) operating
under appropriate conditions (to be recited in detail
6 below)~ Dewatering~defueling can be omitted if the
7 water/fuel concentration in the used oil is determined
8 to be low enough so as not to be detrimental to the
9 overall process, e.g., when the used oil is a trans-
former oil already of low water and fuel fraction
11 content; however, in most instances, used lube oils of
12 the crankcase oil type, will require a
13 dewatering/defueling step. This dewatering/defueling
14 unit can be a single unit or a number of units, each
one designed to handle a separate aspect of the
16 dewatering and defuelingO Water and fuel overheads are
17 carried off via lines (3) and 14). The
18 dewatering/defueling operation may be preceded by a
19 filter unit (OPT-2) to remove any grit, solids, metal
filings, etc. which may be present in the used oil. The
21 dewatered/defueled used oil is passed via line (5) to
22 a heat soaker (6) and thence via line (7) to a dis-
23 tillation unit (8) which will not coke up under the
24 conditions employed (explained in detail below).
Residue from unit (8) is removed via line (8~). The
26 distillate from this unit is sent via line (9) to a
27 guard bed (10) wherein the sludge and halide content is
28 reduced. Optionally, a second heat soaker (lO(A)) may
29 precede the guard bed. Effluent from the guard bed (10)
is sent via line (11) to a hydrotreater unit (12)
31 wherein the oil is processed to produce an oil product
32 stream (13) which is equivalent to a virgin oil and can
33 be employed as a base oil for the production of oil
34 products such as lube oil, transformer oil, refriger-
ator oil, turbine oil, white oil, etc.
~C~5~2
-- 6 --
1 In Figure 2 used oil would be fed via line 1
2 to an optional dewatering/defueling unit (2) operating
3 under appropriate conditions (to be recited in detail
4 later). Dewatering/defueling can be omitted if the
water/fuel concentration in the used oil is determined
6 to be low enough so as to be not detrimental to the
7 overall process, (e.g., when the used oil is a trans-
8 former oil already of low water and fuel fraction
g content); however, in most instances, using used lube
oil of the crankcase oil type, dewateriny/defueling
11 will be needed. This dewatering/defueling unit (2) can
12 be a single unit or a number of units each one designed
13 to handle a separate aspect of the dewatering and
14 defueling. Water and fuel overheads are carried off via
lines (3) and (4). The dewatering/defueling unit (2)
16 may be preceded by a filter unit (OPT-2) to remove any
17 grit, solids, metal filings, etc. which may be present
18 in the used oil. The dewatered/defueled used oil from
19 unit (2) is passed via line (5) to a heat soaker ~6)
and thence via line (7) to the light ends stripper
21 tower (8) wherein the i-10, preferably i-5, most
22 preferably i-3 wt.% fraction of the used oil is removed
23 via line (9). Although the heat soaking ~6) and light
24 ends stripper tower (8) are represented by two separate
units it is entirely within the scope of this invention
26 that a single integrated unit can be used to accomplish
27 both the heat soaking and light ends removal. The
28 effluent from this step is sent via line (10) to a
29 distillation unit (11) which will not coke up under the
conditions employed (explained in detail below).
31 Residue from unit (11) is recovered via line (ll(a)).
32 The distillate from the unit is sent via line (12) to a
33 guard bed (13) wherein the sludge and halides content
34 is reduced. Optionally, a second heat soaker (13(a))
may precede the guard bed. Effluent from the guard bed
~iLZ~5~LZ
~ 7 --
1 (13) is sent via line ~14) to a hydrodreating unit 15
2 wherein the oil is processed to produce an oil product
3 stream (16) which is equivalent to a virgin oil and can
4 be employed as a base oil for the production of oil
product such as lube oil, transformer oil, refrigerator
6 oil, turbine oil, white oil, etc. Each processing step
7 in the above-identified sequence is treated in depth
8 helow.
g THE PRESENT INVENTION
.
A used oil re-refining process has been dis-
11 covered which produces a re-refined oil which is com-
12 parable to virgin and can be processed into lube,
13 transformer, refrigerator, white oil or other
14 speciality oil. The process is not marked by the
operational or environmental drawbacks of prior used
16 oil reprocessing procedures.
17 The re-refining process of the present
18 invention comprises:
19 (a) heat soaking the used oil;
(b) stripping the heat soaked oil at atmo-
21 spheric or reduced pressure to remove the low boiling
22 conversion products;
23 (c) distilling the heat soaked, stripped
24 oil;
(d) passing the distilled oil through a
26 guard bed of activated material;
27 (e) hydrotreating the guard bed treated
28 oil.
~2~5~;~
1 If necessary the used oil can be dewatered/defueled
2 prior to the heat soaking step.
3 Alternatively, the rerefining process can be
4 practiced effectively even when the stripping step (b)
recited above is omittedO In such a case a greater
6 burden is imposed on the guard bed, but the overall
7 process s~ill produces a rerefined oil which closely
8 matches virgin base oils in physical properties and
9 chemical composition.
USED OIL FEEDSTOCKS
11 Basically, any used oil which in the past
12 has been recovered for burning or for reclamation or
13 has been discarded after use can be the subject feed-
14 stream for the present invention. The used oil stream
which will be rè-refined is predominantly a lube oil
16 (e.g. crankcase oil, etc) but may contain minor quan-
17 tities of other specialty oils, transformer oil, white
18 oil, refrigerator oil, etc. and mixtures thereof, but
19 is preferably used lube oils. The used oils subjected
to the rerefining procedure of the present invention
21 are preferably relatively free of PCB's for envion-
22 mental reasons. Representative of feedstreams which can
23 be employed are the two streams A and B below (Table 1)
24 which are recovered Canadian lubricating oil (motor
oil) and are offered merely as illustrations and not by
26 way of limitation. The compositional slate is reported
27 for a target l0 grade lube oil. The compositional slate
28 will, of course9 be different if the target product is
29 other than a 10 grade lube oil, for example a 5 or 30
grade oil.
5~LZ
g
1 TABLE 1
2PROPERTIES OF USED OIL FEEDSTOCKS
3 Feedstock A Feedstock B
4 June 1980
API 25.0 25.7
6 Density, kg/dm3 @ 15C 0.9037 0.8996
7 Viscosity, cSt @ 40C - 50.4
8 Composition
g Water (LV~) 5 12
Fuels (LV%) 12 15
11 10-grade distillate (LV%) 68 57
12 Residue 15 16
13 Sulphur, Wt.% 0.49 0 39
14 Nitrogen, wppm n.a. 550
Halogen (Cl/Br), ppm 770/n.a. 2500/340
16 PCB, ppm <0.1 0.4
17 Metals ppm
,
18 PB 2921 2221
19 Zn 1229 1025
Ca 13~6 1010
21 Mg 295 166
22 P 1125 980
23 DEWATERING AND DEFUELING T~E USED OIL
24 Removal of water, fuel fraction light
hydrocarbons and light vacuum gas oil from used oils is
26 a procedure well known in the industry. Typically, such
27 dewatering and defueling is performed by atmospheric
28 and/or vacuum distillation, although other procedures
29 such as settling, decantation or passage through
molecular sieves or treatment with drying agents or
~;~Q$5~Z
-- 10 --
1 selective absorbents or extractants can also be
2 employed. However, for economical and environmental
3 reasons, distillation, be it atmospheric and/or vacuum,
4 is preferred. As an option and depending on the quality
of the used oil being processed, the used oil feed
6 stream can be passed through a filter or other
7 separation means to reduce the level of entrained
8 solids (i.e., dirt, metal filings, sand, etc.) which
g may be present in the oil prior to the dewatering-
defueling step so as to reduce the potential for damage
11 to processing equipment and therefore eventually
12 produce a higher quality re-refined basestock oil.
13 In performing such atmospheric and/or vacuum
14 distillation dewatering and defueling of used oils
standard state of-the-art procedures, techniques and
16 operating conditions may be employe~. ~s is readily
17 apparant this dewatering/defueling step will be prac-
18 ticed only when necessary, i.e., only when the used oil
19 to be rerefined, possesses water or light hydrocarbon
or light vacuum gas oil fraction which the practitioner
21 is desirous of removing. In some instances the water
22 content and/or fuel fraction content of the used oil
23 can already be low enough so that this step can be
2~ omitted (when the used oil is, e.g., a transformer
oil). This step will, therefor, be most usually prac-
26 ticed. Typical dewatering/defueling process parameters
27 are distillation temperature, (in the range of 80C to
28 300C) distillation pressure, (in the range of 0.5 kPa
29 to atmospheric) reflux ratio (from 0.5/1 to 5/1) and
unit throughput presently employed in industry.
31 Dewatering is practiced under conditions, and to the
32 extent necessary to remove as much of the water
33 present, if any, as possible from the used oil,
34 preferably about 90~, more preferably about 95%, most
preferably about 100% of the water present in the used
5~2
1 oil stream being processed~ During defueling the amount
2 Of "fuel fraction" removed, if any, from the used oil
3 and the combination of condi~ions employed are set by
4 the final characteristics~ i~e., the grade of the lube
oil distillate which is desired to be recovered after
6 the subsequent distillation step (covered in detail
7 below). For example, a larger fuel fraction, i.e., a
8 high fuel concentration, can be tolerated in the oil
9 when the target is a light oil distillate Conversely,
if a heavier grade oil is sought a lower concentration
11 of fuel can be tolerated. The exLent and severity of
12 the defueling step is left to the discretion of the
13 practitioner to be set in response to the oil charac-
14 teristics (gradel target of the product to be
recovered. In short, the topping severity, i.e.,
16 atmospheric equivalent tempera~ure (AET) is regulated
17 by the volatility target i.e., the grade of the lube
18 oil to be recovered. In addition to~ or as an altern-
19 ative to conventional distilla~ion in standard distil-
lation towers, thin ilm evaporators (TFE), or wiped
21 film evaporators (WFE~ may be employed. These pieces of
22 equipment, TFE or WFE, have been patented by many
23 inventorsO Their principles of operation and typical
24 operating conditions are described in detail in "Recent
Technology Development in Evaporative Re-Refining of
26 Waste Oil" by J. Bishop and D. Arlidge and in
27 "Thin-Film Distillation as a Tool in Re-Refining Used
28 Oil" by J. F. Pauley, both articles appearing in Third
29 International Conference on Waste Oil Recovery and
Reuse, 1978. See also USP 4,073,719, USP 3,348,600 and
31 USP 4,160,692 inc~p~ b~ b~_~f~4~
32 As an example, dewatering and defueling of a
33 typical Canadian used oil by a batch distillation
34 (atmospheric followed by vacuum) is presented in Table
2. In this example, a 390C atmospheric equivalent
~LZ~5~
- ~2 -
1 temperature (AET) is required to meet an SAE 10-grade
2 oil volatility target. It is, of course, clear that
3 different temperature (AET~ will be required when
4 different grades of oil are the target products,
TABLE 2
6 DEWATERING/DEFUELING OF USED OIL(l) BY BATCH DISTILLATION
7 Dewatering Defueling(2)
8 Distillation Temperature
g (Vapour), oC 100 228
10 Distillation Pressure~ kPa 101 0.887
(atmospheric)
11 Atmospheric Equivalent
12 Temperature, oC 100 390
13 Yield Range on Raw
14 (Whole) Used Oil
15 LV% (Material Removed) i-5 5-17
16 (1) Feedstock A in Table 1
17 (2) The dewatered oil was used as the feed for
18 defueling operation.
19 Table 3 shows the results obtained on
dewatering/defueling of a Canadian used oil feedstock B
21 (Table 1) using a continuous pilot atmospheric and
22 vacuum (A&V) distillation unit. In many instances
23 vacuum distillation alone will be adequate~
$ 5 12
- 13 -
1 TABLE 3
2DEWATERING/DEFUELING OF USED OIL (1)
3BY CONTINUOUS A&V DISTILLATION
4 ~ Defueling
5 Throughput, m3/d 2~2 1.1
6 Temperature~ C ~bottom)250 270
7 Pressure, kPaatmospheric 3.3
8 Reflux Ratio No 3/1
g Yield of Overhead13.8 12.4
(Wt.% on Feed)
11 ~1) Feestock B in Table 1
12 (2) It contained 83 wt.% water, 17 wt.% fuels.
13 Dewatering and defueling of the used oil
14 feedstock A using Luwa TFE and Pfaudler WFE are
presented in Table 4. In both TFE and WFE
16 distillations, water and fuel streams were obtained as
17 overheads in a single pass operation.
18 TABLE 4
19 DEWATERING/DEFUELING OF RAW USED OIL (13
20 Equipment Lu~a TFE Pfaudler WFE
21 Throughput (feed), kg/m2-hr 344-402 180-288
22 Distillation Temperature
23 (hot oil), C 276 264
24 Distillation Pressure, kPa 1.33-2.0 ~2) 4
25 Overhead Yield on Feed, LV% 17.0 1609
26 (1) Feedstock A in Table 1
27 (2) Pressure measured at the exit of an external con-
28 denser
?5~2
:L4 -
1 HEAT SOAKING-OPTIONAL STRIPPING AND
2 TFE OR WFE/DISTILLATION
3 It has been discovered that for the
4 successful practice of the instant used oil re-refining
process scheme, dewatering and defueling is best
6 followed by a heat soaking step. Further, this heat
7 soaking is best conducted at a temperature range of
8 from about 250C to 340C, preferably 280C to 320C,
g most preferably 300C to 320C for a time sufficient to
maximize halide (chloride), phosphorus and sludge
11 precursor removal, such times typically being in the
12 range of from about 15~120 minutes, preferably about 3D
13 to 120 minutes.
14 The heat soaked dewatered/defueled oil is
then optionally treated so as to reduce Total Acid
16 Number (TAN), toluene insolubles (T.I.) and halides
17 content of the oil prior to its being distilled. This
18 treatment may take any of the commonly practiced forms
19 for the removal of materials contributing to TAN, T.I.
and for the removal of halides from oil. Preferably,
21 however, the treatmen~ practiced involves stripping the
22 oil so as to remove the relatively low boiling com-
23 ponents produced after the heat soaking step. This
24 stripping may be conducted under atmospheric pressure
or vacuum. A stripping gas may also be used. Stripping
26 conditions used should be such that the about i-10 wt.%
27 fraction preferably the i-5 wtr% fraction, most pre-
28 ferably the i-3 wt.% fraction of low boiling point
29 conversion product materials generated during ~he heat
soaking step is removed.
31 The stripped material is then subjected to a
32 coke formation resistant distillation step. The dis-
33 tillation is conducted in a manner such that coking in
~ZQ~5~2
- 15 -
1 the unit employed is kept to a minimum under the con-
2 ditions of residence time, temperature and pressure
3 selected to give a distillate having the desired end
4 pointO Distillate end point at this step is set by
determining whether a light, medium or heavy grade oil
6 is the final material desired upon completion of the
7 overall process. Selection of distillate end point as
8 well as the distillation conditions employed are Ieft
9 to the practitioner to set in response to the final
product requirements and the particular distillation
11 apparatus employed in light of the prior recited con-
12 straint that coke formation be kept to a minimum. This
13 distillation step is preferably carried out in a coke
14 formation resistant unit such as the cyclonic distil-
lation tower for waste oil re-refining described in
16 U. S. Patent No. 4,140,212, or in a thin film
17 evaporator (TFE) or a wiped film evapora~or (WFE) due
18 to their higher efficiencies.
19 The key advantage of the preferred TFE (or
WFE) distillation is its ability to fract;onate
21 unstable material under high temperature/short resi-
22 dence time conditions with minimal degradation or
23 coking. Thus, a unit such as this is ideally suited and
24 preferred for distillation of used lube oil~
Although the majority of foreign materials
26 in the dewatered/defueled used oil, i.e., additives~
27 ash, sludge and wear metals, go to the bo~toms during
28 the distillation step, a certain amount of the lube
29 additives (original or decomposed) having a boiling
range similar to that of the lube distillate tends to
31 distil over along with the distillate. In addition, a
32 small fraction of these materials which boils outside
33 of the distillate boiling range may get entrained in
34 the distillate during the distillation stage. As a
~2~5~Z
- 16 -
1 result of these effects, the distillate is contaminated
2 with a high concentration of phosphorus (50-300 ppm3
3 and sludge precursors. The latter tend to form a sludge
4 (1,000~3,000 ppm) during high temperature processing
(i.e., hydrotreating). Because of the presence of these
6 materials, process problems such as hydrotreater
7 catalyst deactivation and reactor plugging are
8 encountered when contaminated distillate is hydro-
g treated over conventional catalystsO These phosphorus
compounds and æludge precursors are identified as the
11 major causes of catalyst deactivation and bed plugging~
12 respectively. These deficiencies associated with the
13 processing sequence comprised of dewatering, defueling,
14 distillation and hydrotreating can be overcome by heat
soaking and stripping the dewatered/defueled used oil
16 prior to distillation. Heat soaking causes the majority
17 of the phosphorus compounds and sludge precursors to
18 form high boiling point materials which essentially all
19 go with the residue during the distillation step. This
is possible because the dispersant and antifoulant
21 materials in the original lube additive package keep
22 the sludge suspended in the oil which, in turn,
23 prevents equipment fouling. The optional stripping step
24 removes low boiling point conversion products from the
heat soaker which conversion products are themselves
26 converted into sludge during the distillation step.
27The beneficial effects of heat soaking prior
28to distillation on distillate quality, in terms of
29phosphorus and sludge contents, is shown in Table 5.
30Dewatered/defueled used oil from a Luwa TFE (Table 3)
31was continuously heat soaked in a pilot plant set-up at
32atmospheric pressure, at two temperatures (280C and
33320C) and three residence times (1/~, 1 and 2 hours)
34 to define the optimum heat-soaking conditions. The
tests were carried out with a 0.95 cm I.D. stainless
~L2a~s~
- 17 -
1 steel tube coil (located in a high temperature sand
2 bath) in a once-through mode. No pressure drop across
3 the heat soaking coil was observed after about 369
4 hours of smooth operation at 320C. Distillations of
used oils, both raw and heat soaked, were carried out
6 with a lab size Pope WFE (1,100 cm2 evaporation area)
7 to define the effect of heat soaking on distillate
8 quality. Results indicated that relative to the non
g heat soaked distillate (base case), the distillate
derived from the heat~soaked oil (320C, 1/2 hour resi-
11 dence time) threw down about 75% less sludge and con-
12 tained only 3-8 ppm of phosphorus (versus 240 ppm for
13 the base case). Phosphorus removal increased with
14 increasing heat soaking temperature. At 320C, the
distillate quality in terms of phosphorus and sludge
16 lay-down improved slightly with increasing residence
17 time.
` ~2~5~2
-- 18 --
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-- 19 - .
1 The advantages of heat soaking prior to WFE
2 distillation were further demonstrated in a Pfaudler
3 WFE (Table 6). The Pfaudler WFE with its internal de-
4 entrainment device produced a much better quality dis-
tillate from the (pilot plant) heat soaked used oil
6 than the lab Pope WFE. A comparison of Tables 5 and 6
7 indicates that at comparable phosphorus levels~ the
8 Pfaudler distillate had a significantly lower sludge
g content. However, it must still be noted that either
piece of equipment, after the heat soaking of the
11 dewatered/defueled used oil, gave a distillate product
12 of significantly reduced phosphorus and sludge content
13 when compared with the non-heat soaked material and
1~ that the heat soaked material from either unit is fully
acceptable for use in the present process.
16 TABLE 6
17EFFECT OF PILOT HEAT SOAKING PRIOR TO
18PFAUDLER WFE DISTILLATION ON DISTILLATE QUALITY
19Dewatered/Defueled Used Oils (1)
.
20 Heat Soaking NO ~2) YES (3)
21 Temperatur~, C - 320
22 Residence Time, Hr. - 0.5
23 WFE Distillation
.
24 Temperature, C 278 . 288
25 Pressure, kPa 0.19 0.28
26 Phosphorus, ppm 337 3
27 Sludge, ppm @ 310C 2860 113
28 (1) Derived from feedstock A in Table 1~
29 (2) This feed was dewatered/defueled in the Pfaudler
WFE (See Table 4).
31 (3) This feed was dewatered/defueled in a batch dis-
32tillation unit (See Table 2 for conditions).
s~
- 20 -
1 Another example illustrating the benefits of
2 high temperature heat soaking prior to WFE distilla~ion
3 is shown in Table 7. A large scale pilot plant heat
4 soaking ~0,62 m3/D) oE A&V dewatered/defueled oil (from
Table 3) was carried out over a wide temperature range
6 using a heating coil in connection with a heat soaker.
7 After heat soaking, the oil was pumped to the WFE where
8 it was fractionated into a lube distillate and a
g residue. Results obtained on the lab (Pope) WFE dis-
tillation of heat soaker feed (non-heat soaked) are
11 also shown in the same table for comparison purposes.
12 As shown in Table 7 r distillate phosphorus content
13 decreased with increasing heat soaking temperature. A
14 low heat soaking temperature ~i~e. <280C) resulted in
high phosphorus content in the WFE distillate which
16 would give a high rate of catalyst deactivation in the
17 downstream Hydrotreating operation, ~n the other hand,
18 too high a heat soaking temperature (340C or above)
19 resulted in a complete decomposition of dispersant type
additives (they boil at 340C with decomposition). As a
21 result, sludge suspended in oil (about 2 vol.%) started
22 to settle. A non-agitated horizontal heat soaker, while
23 it did function, eventually plugged with settled sludge
24 due to areas of liquid stagnation. This potential
operating problem can be effectively avoided by the use
26 of a preferred vertical heat soaker or a horizontal
27 unit augmented with agitationO In addition, excess
28 amount of light-ends was formed and on-spec viscosity
29 distillate (29-31 cSt @ 40C) could not be produced as
heat soaking temperature exceeded 340C~ From this it
31 is seen that the optimum heat soaking temperature is
32 between about 300C-320C.
5~2
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- 22 -
1 Some inspections of the residue made from
2 th~ Pfaudler WFE using heat-soaked used oil feed is
3 given in Table 8. A study indicated that this residue
4 could be disposed of by blending (until about 8 LV% of
the blend is residue) with 85/100 penetration paving
6 asphalt without adversely affecting the asphalt product
7 quality ~Table 9). From this it is seen that the pro-
8 cess of the present invention does not have the serious
g hazardous waste disposal/environmental problem asso-
ciated with it as do typical clay/acid used oil
11 refining techniques.
12 TABLE 8
13 INSPECTIONS OF WFE ~EAT SOAKED) RESIDUE ~1)
14 Penetration @ 25C, dmm >400
15 Flash point tCOC), C 278
15 Viscosity @ 100C, cS~ 127
17 135C, cSt 48
18 Solubility in Trichloroethylene, Wt.~ 98.55
19 Acid No., mg RO~/g 3.8
Metals,_ppm
21 Pb 9000
22 Mg 1100
23 Ca 4700
24 Zn 4100
P 3544
26 Ba 256
27 ~1) Derived from feedstock A in Table 1
5~2
- :23 -
1TABL~ 9
2QUALITY OF ASPHALT/USED OIL RESIDUE BLEND tl)
3Target
5Blend Min. Max,
6 85/100 Penetration Asphalt (Vol %) 91.6
7 Used ~il Residue (Vol %) 8.4
8 Penetration ~ 25C, dmm 166 150 200
g Viscosity @ 135C, cSt 254 200
Flash tCOC)~ C 312 260
11 Ductility @ 40C, cm >50 10
12 Solubility in Trichloroethylene, 99.5 99.5
13 wt.%
14 Acid No. mg KOH/g 0.5 0.8
Thin-film Oven Test
.
16 Change in Weight, % +0.03 1.3
17 Retained Penetration @ 25C 62.7 42
1~ Ductility @ 25C, cm >150 100
-
19 (1) See Table 8
Light Ends Removal
21 The amount of contaminants such as residual
22 sludge tor toluene insolubles) and halides which are
23 present in the distillate produced in the distillation
24 step (explained in detail above) can be reduced even
more by removing, prior to the distillation step, the
26 low boiling point conversion products formed during the
27 heat soaking ~previously described) of the
28 dewatered/defueled used oil. This removal of the low
29 boiling point conversion products can be accomplished
by any procedure known to remove such material but
31 preferably by strippîng either under atmospheric
5~2
- 24 -
1 cond;tions or under reduc,ed pressure. Steam or other
2 conventional stripping streams such as helium,
3 nitrogen, hydrogen, light hydrocarbon gases or flue
4 gases, etc., can be used as the stripping gas for light
ends removal. The about i-10 etc. wt.% fraction
6 preferably the i-5 wt.% fraction most preferably the
7 i-3 wt.% fraction of the heat soaked dewatered/defueled
8 used oil is removed by this stripping step prior to
9 distillation. This light end removal procedure may be
practiced either integrated into the heat soaking step
11 or as a separate, subsequent procedural step. Light
12 ends stripping conditions of temperature ranging from
13 150C to 320C, pressure ranging from 0.2 kPa to
14 atomspheric, and/or stripping stream ranging from 0.5
kmol/m3 to 5 kmol/m3 can be used.
16 Data in Table 9-A show that by removing the
17 about i-3 wt. % fraction of a laboratory ~batch) heat
18 soaked dewatered/defueled Canadian used oil, the
19 toluene insoluables content of the WFE (laboratory unit
designed by Pope Scientific) distillate was reduced to
21 about 100 ppm, Total Acid Number (TAN), toluene
22 insolubles ~TI) and ha~ides were also significantly
23 reduced. While mild topping slightly increased the
24 distillate viscosity, the distillate volatility (by
GCD) was significantly improved (decreased) by removing
26 the about i-3 wt. % of the heat soaked oil.
~2~5 ~
- 25 -
1 TABLE 9-A
2BATCH HEAT-SOAKING DEWATERED/DEFUELED
Heat Soaking
5 Conditions (2) Dewate ed/defueled Used Oil (1)
6 Temperature, C 304 311 330
7 Residence Time (hrs)
8 Pressure, kPa Atmospheric 63 68
g Light-ends Treatment RefluxedRemovedRemoved
Light-Ends
11 Wt.% Removed - 3 3
12 TAN, mg KOH/g - 7.1 11.5
13 WFE (Lab) Distillate (3)
14 Toluene Insolubles, ppm 328 103 91
TAN, mgKOH/g 0.60 0.38 0~32
16 Chloride/Bromine, ppm 110/7771jS8 60/37
17 Viscosity~ cSt @ 40C 31.2931.88
18 Volatility, % off @ 368C 9~5 5,5
19 (1) Produced in Luwa TFE (See Table 4) (Feed stock A)
(2) 1 hour on temperature with N2 agitation ~batch
21 operation)
22 (3) Feed to WFE is heat-soaked, dewatered/defueled
23 used oil, with or without light end removal.
24 The beneficial effect of heat soaking with
light-ends removal (i-3 wt.%) was further demonstrated
26 in a continuous pilot heat soaker connected in series
27 with a packed stripping unit. The oil from the heat
28 soaker passed through the stripper countercurrently to
a flow of nitrogen stripping gas. Heat soaked oils,
with and without light-ends removal, were subsequently
~ 26 -
1 fractionated in the lab using the Pope WFE to produce
2 10-grade distillate. Some inspections of the resulting
3 distillates are shown in Table 9-B.
4TABLE 9-B
5CONTINUOUS HEAT SOAKING DEWATERED/DEFUELED
6USED OIL WITH LIGHT-ENDS REMOVAL
= _
7 Heat Soaking
8 Conditions (2) Dewatered/defueled Used Oil (1)
9 Temperature, C --------------320-------------
Pressure ~ -----Atmospheric-----~---
11 Residence Time, hr --------------1~2-------~-----
12 Light-Ends Treatment Unstripped Stripped(3)
13 Wt. % Removed - i-3
14 WFE Distillate
Toluene Insolubles, ppm 312 127
16 TAN, mgKOH/g 0~82 0.39
17 Phosphorus, ppm 7 5
.
18 (1) Produced in Luwa TFE (See Table 4) (Feed stock ~).
19 (2) Carried out in a 0.95 cm I~D. stainless steel
coiled tubing.
21 (3) Stripping gas (N2) to oil ratio = 2.2 kmol/m3;
22 pressure = 0.3 kPa, average stripping temperatu~e
23 = 160C.
24 Results indicate that heat soaking with
25 lightends removal reduced the contaminant level in the
26 subsequent distillate. This is in agreement with
27 results obtained from the batch operation (Table 9-A).
- 27 -
1 Dewatered/defuelled Canadian used oil, prior
2 to and after pilot plant heat soaking (unstripped see
3 Table 9-B), was fractionated into 1 LV% cuts up to 10
4 LV% under reduced pressure to evaluate the effect of
heat soaking on front-ends composition. Results in
6 Table 9-C for the first three cuts indicate that heat
7 soaking significantly increased the halides content,
8 the bromine number, and the acid number of the front-
9 ends, but the increases decreased with increasing cut
point.
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1 These data are in agreement with the results
2 given in Tables 9-A and 9-B which show that the WFE
3 distillate derived from feed from which light-ends were
removed had lower halide content and lower acid number
than the distillate obtained from the unstripped feed.
6 The preferred i-3 wt.~ fraction is about all that need
7 be removed and still show any improvement in the dis-
tillate quality and not significantly adversely affect
g the light distillate yield. It should be mentioned that
the reduction of the halide content in the distillate
11 should benefit the downstream hydrotreating operation -
12 problems associated with corrosion and plugging due to
13 formation of compounds such as hydrogen halides and
14 ammonium halides can be minimized. The high acid and
bromine numbers of the heat-soaked front-ends suggest
16 that polymeric additives are decomposing into monomers
17 or larger fractions during the high temperature heat
18 soaking. It is believed that these highly acidic and
19 olefinic monomers, etc. form toluene insolubles during
the distillation via some mechanism and eventually end
2~ up in the distillate. Removing these low boiling
22 materials prior to distillation should minimize this
23 effect.
24 Steam is preferred as the stripping gas
because it is better than nitrogen, light hydrocarbon
26 gases, etc. for preventing lay-down of ammonium halides
27 on the top section of the heat soaker and in the vent
28 lines (which would cause plugging of the vent line).
29 The ammonium halides are formed as a result of additive
decomposition during the heat soaking.
31 The severity of the defueling operation can
32 be monitored by a flash point measured on the
33 dewatered/defueled product. The Elash point was set to
34 take into account the v;scosity cut out across the heat
~L2l~$S~
- 30
l soaking (and stripping) steps, and thus to ensur0 that
2 the distillate (in the example WFE) is within the
3 viscosity specification range of the target oil
4 product.
Consequently, stripping may be conducted
6 under a wide variety of conditions of pressure and
7 temperature and stripping atmospheres, the only
8 requirement being that the conditions employed be such
9 that a sufficient fraction of low boiling point con-
version products from the heat soaker be removed,
11 preferably the i~3 wt.% fraction.
12 The benefits ~o be derived from the practice
13 of the reduction in TAN, TI and halide content of the
14 oil, preferably by the employment of a stripping pro-
cedure which removes the preferably about i-3 wto%
16 fraction of low boiling point conversion products from
17 the heat soaker treated used oil, is seen by reference
18 to the following process seguences which form part of
19 the present application, but which sequences were
practiced on oils which had not had its TAN or halide
21 content reduced in accordance with the present inven-
22 tion i.e., were not light ends stripped. From this data
23 it is seen that although a used oil re-refining process
24 which does not include a TAN, TI and halide reduction
step (i.e., removal of the preferred i-3 wt.% fraction
26 of low boiling point conversion products from the heat
27 soaker treated oil) is a viable and extremely valuable
28 process yielding a quality product, the process is
29 marked by a number of operational drawbacks, i.e.
sludge formation (related to the presence of TI and a
31 high TAN) in the distillation units (defueling over-
32 head), WFE vacuum system and alumina bed/hydrotreater,
33 and generation of ammonium chloride etc., in the heat
34 soaker overheads vent lines and in the hydrotreater.
~2~ 5~;~
- 31 -
1 The proce~s of the present invention, therefore
2 includes a step, the express purpose of which is the
3 reduction in TAN, TI and halides by the removal of the
4 low boiling point conversion products from the heat
soaker, preferably the i-3 wt.% fraction preferably by
6 stripping.
7 HYDROTREATER GUARD BED
8 Distillate coming from the distillation step
g but without light ends stripping was subjected to
passage through a guard bed of material suitable for
11 removing various contaminants from the distillate.
12 These contaminants include halides, trace phosphorus,
13 and residual sludge remaining in the distillate after
14 distillation.
lS Various adsorbents, (Fullerls earth,
16 charcoal, lime and activated alumina) were evaluated
17 for removing contaminants from the distillate. In
18 general, solid adsorbents capable of removing phos-
19 phorus, halides and residual sludge from the distil-
late, having high surface area (such as those used in
21 the prior art in clay treating or which are typically
22 used in guard beds in front of hydrotreaters) can be
23 used for this purpose. (See e.g., USP 4,151,072, USP
24 3,919,076, USP 4,073,719, and USP 4,073,720) Results
shown in Table 10 indicate that the most effective
26 adsorbent for the guard bed is activa~ed alumina and
27 for this reason a guard bed of activated alumina is
28 preferred. However, while activated alumina is pre-
29 ferred, it must be noted that all the materials tested
demonstrated some ability to remove phosphorus and
31 halides from the distillate.
5~Z
- ~2 -
1 T E l
2 BATCH GUARD BED TREATING OF USED OIL DISTILLATE (1) (2)
3 Fuller's Activated
4 Feed Earth Charcoal Lime ~lumina
Phosphorus, 100 6 18 30
6 ppm
7 Halogens, ppm 110 12 35 59 9
8 Surface Area, - 98 3474.5 245
9 ~3/g
(13 Norske Esso 130N TFE distillate (not stripped)~
11 (2) Batch treating conditions: 250C, 1 h,
12 oil/adsorbent weight ratio 4~1, using nitrogen as
13 blanket.
14 ~oth continuous flow and static batch bed
contacting can be used. However, the former is pre-
16 ferred since it can be integrated with the downstream
17 hydrotreating operation. Operating conditions for the
18 guard bed which can be employed include a pressure
19 ranging from about atmospheric to about 5 MPa, (700
psi), temperature ranging from about 180 to about
21 340C preferably about 280-320C, LHSV ranging from
22 about 0.5 to about 2 v/v/hr preferably about .5-1.0
23 v/v/hr. Any inert gas can be used. However, the use of
2~ hydrogen as treat gas is preferred because of the pre-
ferred integration with the downstream hydrotreater.
26 The use of hydrogen could prevent coke formation in the
27 guard bed, preferably the alumina guard bed.
28 Some sludge was observed at the top of the29 bed. The amount of sludge formed could have been
reduced by light ends strippingl The removal of halides
31 (chlorides, bromides~ by light ends stripping would
32 augment the capacity of the guard bed, especially the
33 alumina guard bed.
~Z~5~Z
- 33 -
1 The use of activated alumina i5 preferred
2 since, in addition to adsorbing residual sludge from
3 the distillate, the alumina can also remove residual
4 phosphorus as well as high concentrations of halides
(chlorides and bromides)O It is desirable to remove the
6 halides prior to hydrotreating to avoid the formation
7 of corrosive compounds such as hydrogen chloride and
8 hydrogen bromide in the hydrotreater reactor. Removal
g of halides prior to hydrotreating would also minimize
ammonium halide deposits in the hydrotreater exit line.
11 The effectiveness of activated alumina for removing
12 phosphorus and halides from a used oil distillate,
13 i.e., Norske Esso 130N distillate (77 ppm phosphorus,
14 90 ppm halogens) was further studied in the pilot
plant~ This sample of Norske Esso 130N distillate had
16 been vacuum distilled and filtered. Adsorption was
17 carried out by passing the distillate mixed with
18 hydrogen in a continuous flow over a fixed bed of acti-
19 vated alumina at ~rom 180 to 320C, 3.4 MPa H2, 1.0
LHSV and 1.5 kmol/m3 gas rate. The results shown in
21 T3ble 11 indicate that both the phosphorus and halide
22 contents of the alumina treated oil decreased with in-
23 creasing temperature. At 320C, the product phosphorus
24 and the halogen content was 1 ppm and 17 ppm, respec-
tively.
l fl;dQ~ , 2
- 34
1TABLE 11
2ALUMINA TREATING USED OIL DISTILLATE
3(PILOT PLANT RESULTS)
4Luwa TFE Distillate (1)
5Temperature, C (2) Feed 180 280 300 320
6 Phosphorus, ppm 77 55 6 3
7 Halogens, ppm 90 80 60 30 17
8 (1) Norske Esso 130N TFE distillate, vacuum frac-
g tionated (i-95% blend) and filtered with 3 micron
filter (not heat soaked, not stripped)~ This
11 pretreatment reduced the phosphorus and halogen
12 levels of the feed to the reported levels before
13 guard bed treatmen~.
14 (2) Other conditions: 3.4 MPa H2, 1.0 L~SV, 1.5
kmol/m3 gas rate.
16 The effectiveness of alumina treating a heat
17 soaked WFE distillate was also studied in the pilot
18 plant. Results shown in Table 12 indicate that once
19 again the major changes across alumina treating are
removal of phosphorus, halogens and trace metals from
21 the WFE distillate.
~2~S~;~
- 35 -
1 TABLE 12
2 ALUMINA TREATING WFE (HEAT SOAKED) DISTILLATE
3 Conditions Feed(l)
4 LHSV - 1.0
Gas Rate, kmol/m - 7.5
6 Temperature, C - 320
7 Pressure, MPa H2 ~ 3.5
8 Inspections
.
g Density kg/dm3 @ 15C 0.8703 0.8703
Viscosity, cSt @ 40C 3~.46 30.71
11 Viscosity, cST @ 100C5.17 5020
12 VI 98 98
13 Total Nitxogen, wppm150 160
14 Basic Nitrogen, wppm 36 41
Sulfur, Wt% 0.25 0.23
16 Color, ASTM D8 D8
17 Phosphorus, wppm 20 <3
18 Halogens, wppm 140 61
19 Metals, ppm
Pb 12 <1
21 Si 11 <1
22 Ca 7 <2
23 Zn 5 2
24 (1) Derived from used oil feedstock B. Results of
~5 dewatering/defueling and heat soaking/WFE dis-
26 tilling of this feed are shown in Table 3 and 7,
27 respectively.
~z~s~
- 36 -
HYDROTREATING
2 The final processing step is hydrotreating
3 the alumina treated oil over a conventional hydro-
4 treating catalyst to produce the finished re~-refined
base oil. The conditions used are quite similar to
6 those used in conventional raffinate hydrotreating,
7 i.e., about 260-400C preferably about 260-320C, about
8 3-11 MPa, preferably about 3-5 MPa hydrogen pressure,
g about 0.5-4 LHSV, preferably about 0~5-2.0 LHSV and
about 1.5-15 k mol/m3, preferably about 1.5-5.0 k
11 mol/m3 gas rate. Suitable catalysts for this hydrotr-
12 eating are the elemental metals and the oxygen or
13 sulfur-containing compounds of metals of the sixth and
1~ eighth groups of the Periodic Table of the Element,
preferably the metals and the oxides and sulfides of
16 these metals and mixtures thereof. Preference is given
17 to a catalyst which contains both a metal of the sixth
18 group or a compound of this metal and a metal of the
19 eighth group of the Periodic Table or a compound of
this metal. They can be supported on a carrier, such as
21 silica, bauxi~e, clay or alumina. Preference is given
22 to a carrier consisting, at least substantially, of
23 alumina. Preferred catalysts include Co~Mo on alumina,
24 Ni/Mo on alumina wherein the cobalt, nickel and
~5 molybdenum are in the elemental, oxide or sulfide form,
26 preferably the sulfide form.
27 As a result of the improvements on the
28 hydrotreater feedstock quality as a result of the
29 practice of the previously recited steps which are part
of the present invention, (i.e., phosphorus, sludge and
31 halide removal), smooth hydrotreater operations and
32 good quality base oils are secured. While operating on
33 the clean distillate resulting from the previously
34 identified process sequence, (but omitting light ends
~2~3~5~
- 37 -
1 stripping) about 1,500 hours of continuous pilot plant
2 hydrotreating were logged with no noticeable catalyst
3 (Ni/Mo) deac~ivation.
4 Base oils were made for quality evaluation
(base oil target in the example was a 10-grade oil) by
6 hydrotreating oils prepared by the above processing
7 steps (i.e., the feed for each step was the product
8 obtained from the proceding step in sequence) except
g that the oil which was hydrotreated in this example had
not been subjected to the stripping step. The oil was
11 hydrotreated over Ni/Mo catalyst (Co/Mo catalyst can
12 also be used) at the conditions shown in Table 12.
13 Inspections of a virgin SAE 10-grade oil made from
14 Western Canadian crude are also shown in the same table
for comparison purposes. Results indicated that the
16 re-refined (280-300C)oils derived from a Canadian
17 waste oil closely matched the virgin base oil in
18 physical properties and chemical compositions.
~Z,~$5~
- 38 -
1 TABLE 13
2 HYDROFINING ALUMINA TREATED OIL
3 Conditions Fe~d---1 0~ 10 ~A~de
5 Sas Rate, kmol/m3 -----7.5-----
6 Temperature, C 290 284
7 Pressure, MPa ~2 3.5 5.6
8 Inspections
g Density, kg/dm3 0.8703 0.8682 0.8682 0.8741
@ 15C
11 Viscosity, cST 30.71 29.46 29.55 29.50
12 ~ 40C
13 Viscosity, cST 5.20 5.09 5~10 4.97
14 @ 1~0C
VI 98 99 99 90
1~ Total Nitrogen, 160 43 47
17 wppm
18 Basic Nitrogen, 41 23 24
19 wppm
Sulphur, Wt% 0.23 0.09 0.10 0.07-OolO
21 Colour, ASTM D8 <1.0 <1.0 <1.0
22 Halogens, ppm 61 <2 <2
23 Phosphorus, ppm <3 <1 <1
24 TAN, mgKOH/g - 0.02 0.01 0.02 typ
25 Aromatics, Wt~ - 14.7 1408
26 Saturates, wt% ~ 83.3 83.2 80 min
27 Polars, Wt~ - 1.7 1.8
28 G.C. Distillation (D2387)
29 IBP 307 308
30 5% 359 359
31 10~ 371 372
32 Volatility ~ off 268C 8 8.5 10 max
33 (1) Derived from used oil feedstock B (Table 1).
34 Results on dewatering/defueling, heat soaking/WFE
distillation and alumina treating are shown in
36 Table 3, 7 and 12, respectively.
37 The beneficial effects of feed treatment in
38 accordance with the present invention on hydrotreating
39 operation is shown in the following examples. Untreated
TFE distillate (phosphorus ~ 77 ppm), which had not
41 been heat soaked or alumina treated, was hydrotreated
42 with conventional catalysts (Ni/Mo or Co/Mo) at 290C
43 to 330C, 3.4 to 4~8 MPa pressure. The catalyst was
44 quickly deactivated (the product color dropped from 0.5
to 2.0 ASTM, product sulfur increased from 0~2 to 0.6
~2,~5~;2
- 39 -
1 wt.% within 180 hours of operation). Alumina guard bed
2 treating is effective for removing phosphorus and
3 halide compounds from the TFE (or WFE) distillate (see
4 Tables 11 and 12). However, when the feed had not been
first subjected to a heat soaking step the adsorbent
6 bed plugged after about 200 hours of operation due to
7 the presence of excess amount of sludge precursors in
8 the non-heat soaked TFE (or WFE) distillate. Heat
9 soaking prior to TFE or WFE distillation significantly
reduces both phosphorus and sludge precursors in the
11 TFE (or WFE) distillate (see Tables 5, 6 and 7). From
12 this it can be seen that each of the reci~ed steps is
13 necessary for the successful practice of the present
14 invention.
As an optional step, the distillate coming
16 from the distillation unit (TFE or WFE for example~ may
17 be subjected to a second heat soaking and settling
18 prior to being fed to the guard bed and subsequently
19 into the hydrotreater. This step should be practiced in
the event the sludge content cf the distillate is high
21 (see, for example, the sludge content of the material
22 obtained in Table 5). This optional second heat
23 soaking/settling should be considered if the sludge
24 con~ent (toluene insolubles) of the distillate is
greater than about 100 to 300 ppm~
26 Heat soaking (e.g., at preferably 320C, 1/2
27 hour) prior to WFE distillation precipitated the
28 majority of the phosphorus compounds and sludge pre-
29 cursors, but the distillate could still contain about
150-403 ppm of residual sludge at about 310Co This
31 sludge material is comprised of about 100-300 ppm of
32 toluene insolubles (as measured at room temperature)
33 which are usually present in the freshly made distil-
34 late, and about 50-100 ppm of sludge that can form at
i3L2
-- ~10 --
1 the high temperature of 300-320C (from the sludge
2 precursors). This sludge material, especially the
3 toluene insolubles, should be removed from the dis-
4 tillate prior to adsorbent treating in order to avoid
plugging of the guard reactor bed.
6 By allowing the distillate to stand for a
7 period of time (48-72 hours) at a moderate temperature
8 (125-150C~ under quiescent conditions, these parti
g culates tend to settle out of the oil. Results shown in
Table 14 indicated that the settling rate of toluene
11 insolubles was enhanced with increasing temperature.
12 After standing at 150C for 72 hours the distillate
13 toluene insolubles dropped from an initial value of
14 about 200 ppm to about 15 ppm. The sludge from the
sludge precursors was also reduced from about 300 ppm
16 to less than lS0 ppm, which is at the ].ower limit of
17 accurate measurement by the sludge test.
18TABLE 14
19EFFECT OF POST-HEAT SOAKING/SETTLING
20ON TOLUENE INSOLUBLES IN WFE DISTILLATE
21Toluene Insolubles,_ppm (1)
22 Post-Heat Soaking 0 24 40 72 120
.3 tResidence Time Hrs~)
24 Temperature, C (Fresh Distillate)
.
25 25 230 112 110 - 100
26 150 298 92 ~4 15 7
27 (1) Distillate was made from pre-heat soaked oil (at
28 320C, 1/2 hour residence time) and subsequently
29 distilled using the lab Pope WFE. The distillate
was allowed to settle for different time periods
31 at 25C and 150C.
