U.S. patent application number 13/304964 was filed with the patent office on 2012-05-31 for asphalt oxidation process using liquid jet ejection.
This patent application is currently assigned to EXXONMOBIL RESEARCH AND ENGINEERING COMPANY. Invention is credited to Keith Kaluna Aldous.
Application Number | 20120132565 13/304964 |
Document ID | / |
Family ID | 46125904 |
Filed Date | 2012-05-31 |
United States Patent
Application |
20120132565 |
Kind Code |
A1 |
Aldous; Keith Kaluna |
May 31, 2012 |
ASPHALT OXIDATION PROCESS USING LIQUID JET EJECTION
Abstract
Provided is a process for increasing the softening temperature
of asphalts by use of liquid jet ejector technology, which is used
as both an air compressor and an air/oil mixer. The liquid jet
ejector motive fluid is hot asphalt and the entrained vapor is
air.
Inventors: |
Aldous; Keith Kaluna;
(Winchester, VA) |
Assignee: |
EXXONMOBIL RESEARCH AND ENGINEERING
COMPANY
Annandale
NJ
|
Family ID: |
46125904 |
Appl. No.: |
13/304964 |
Filed: |
November 28, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61417747 |
Nov 29, 2010 |
|
|
|
Current U.S.
Class: |
208/22 ;
208/44 |
Current CPC
Class: |
C08L 95/00 20130101;
B01F 5/0413 20130101; C10C 3/04 20130101 |
Class at
Publication: |
208/22 ;
208/44 |
International
Class: |
C10C 3/04 20060101
C10C003/04 |
Claims
1. A process for increasing the softening point of asphalt
comprising the following steps: providing a liquid jet ejector
comprising a motive inlet, a motive nozzle, a suction port, a main
ejector body, a venturi throat and diffuser, and a discharge
connection; conducting a preheated asphalt feed including fresh
asphalt and recycled oxidized asphalt, at a temperature from
125.degree. C. to 300.degree. C., as the motive liquid into the
motive inlet of the liquid jet ejector; drawing atmospheric air or
compressed air into the suction port of the liquid jet ejector;
mixing the preheated asphalt within the main ejector body with the
air from the suction port of the liquid jet ejector to form a
mixture; conducting the mixture to a heated and pressurized
oxidizer vessel; collecting an off-gas from the overhead of said
oxidizer vessel and an oxidized asphalt product stream from the
bottoms of said oxidizer vessel, wherein said oxidized asphalt
product stream has softening temperature greater than the preheated
asphalt feed; and recycling a portion of the oxidized asphalt
product stream back to the liquid jet ejector to form the recycled
oxidized asphalt.
2. The process of claim 1 wherein the oxidizer vessel is operated
at a temperature from 150.degree. C. to 300.degree. C. with the
proviso that it be at least 10.degree. C. greater than the
temperature of the preheated asphalt feed being conducted to said
motive inlet of the liquid jet ejector.
3. The process of claim 2 wherein the oxidizer vessel is operated
at a temperature from 200.degree. C. to 270.degree. C.
4. The process of claim 1 wherein the recycled oxidized asphalt
feed rate is at least 5 times greater than that of the fresh
asphalt feed rate.
5. The process of claim 4 wherein the recycled oxidized asphalt
feed rate is at least 20 times greater than that of the fresh
asphalt feed rate.
6. The process of claim 1 wherein the oxidizer vessel is operated
at a pressure of from 0 to 10 barg.
7. The process of claim 6 wherein the oxidizer vessel is operated
at a to pressure of from 0 to 5 barg.
8. The process of claim 1 wherein the air feed rate is at least a
stoichiometric amount based on the preheated asphalt feed rate.
9. The process of claim 1 further including the step of injecting
steam from a steam generator to the oxidizer vessel.
10. The process of claim 9 wherein the injecting steam to the
oxidizer vessel is above or below the liquid mixture in the
oxidizer vessel.
11. The process of claim 1 wherein the air is compressed.
12. The process of claim 1 wherein the air is atmospheric.
13. Oxidized asphalt produced by the process of claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a non-provisional application that claims priority
to U.S. Provisional Application No. 61/417,747 filed on Nov. 29,
2010, herein incorporated by reference in its entirety.
FIELD
[0002] The present disclosure provides a process for increasing the
softening temperature of asphalts by use of liquid jet ejector
technology, which is used as both air compressor and air/oil mixer.
The liquid jet ejector motive fluid is hot asphalt and the
entrained vapor is air.
BACKGROUND
[0003] Asphalt is one of the world's oldest engineering materials,
having been used since the beginning of civilization. Asphalt is a
strong, versatile and chemical-resistant binding material that
adapts itself to a variety of uses. For example, asphalt is used to
bind crushed stone and gravel into firm tough surfaces for roads,
streets, and airport runways. Asphalt, also known as pitch, can be
obtained from either natural deposits, or as a by-product of the
petroleum industry. Natural asphalts were extensively used until
the early 1900s. The discovery of refining asphalt from crude
petroleum and the increasing popularity of the automobile served to
greatly expand the asphalt industry. Modern petroleum asphalt has
the same durable qualities as naturally occurring asphalt, with the
added advantage of being refined to a uniform condition
substantially free of organic and mineral impurities.
[0004] Most of the petroleum asphalt produced today is used for
road surfacing. Asphalt is also used for expansion joints and
patches on concrete roads, as well as for airport runways, tennis
courts, playgrounds, and floors in buildings. Another major use of
asphalt is in asphalt shingles and roll-roofing which is typically
comprised of felt saturated with asphalt. The asphalt helps to
preserve and waterproof the roofing material. Other applications
for asphalt include waterproofing tunnels, bridges, dams and
reservoirs, rust-proofing and sound proofing metal pipes and
automotive under-bodies; and sound-proofing walls and ceilings.
[0005] The raw material used in modern asphalt manufacturing is
petroleum, which is naturally occurring liquid bitumen. Asphalt is
a natural constituent of petroleum, and there are crude oils that
are almost entirely asphalt. The crude petroleum is separated into
its various fractions through a distillation process. After
separation, these fractions are further refined into other products
such as asphalt, paraffin, gasoline, naphtha, lubricating oil,
kerosene and diesel oil. Since asphalt is the base or heavy
constituent of crude petroleum, it does not evaporate or boil off
during the distillation process. Asphalt is essentially the heavy
residue of the oil refining process.
[0006] If asphalt is to be used for a purpose other than paving,
such as roofing, pipe coating, or as an under sealant or
water-proofing material, the asphalt is usually oxidized, typically
by air blowing. Oxidation produces an asphalt material that softens
at a higher temperature than non-oxidized asphalts. Oxidation is
conventionally done by air blowing at the refinery, at an asphalt
processing plant, or at a roofing material plant. Air blowing
modifies the asphalt by an oxidation process that involves the
blowing of air through the asphalt, either on a batch or continuous
basis, with a short residue time at a temperature from 175.degree.
C. to 300.degree. C.
[0007] While processes for oxidizing asphalt have been commercial
for many years, there still remains a need in the art for ever more
cost effective processes for modifying the physical properties of
asphalt by oxidation.
SUMMARY
[0008] In accordance with the present disclosure there is provided
a process for increasing the softening point of asphalt including
the following steps: providing a liquid jet ejector comprising a
motive inlet, a motive nozzle, a suction port, a main ejector body,
a venturi throat and diffuser, and a discharge connection;
conducting a preheated asphalt feed including fresh asphalt and
recycled oxidized asphalt, at a temperature from 125.degree. C. to
300.degree. C., as the motive liquid into the motive inlet of the
liquid jet ejector, drawing air into the suction port of the liquid
jet ejector; mixing the preheated asphalt within the main ejector
body with the air from the suction port of the liquid jet ejector
to form a mixture, conducting the mixture to a heated and
pressurized oxidizer vessel; collecting an off-gas from the
overhead of said oxidizer vessel and an oxidized asphalt product
stream from the bottoms of said oxidizer vessel, wherein said
oxidized asphalt product stream has softening temperature greater
than the preheated asphalt feed; and recycling a portion of the
oxidized asphalt product stream plus fresh asphalt back to the
liquid jet ejector to form the preheated asphalt feed.
BRIEF DESCRIPTION OF THE FIGURES
[0009] To assist those of ordinary skill in the relevant art in
making and using the subject matter hereof, reference is made to
the appended drawings, wherein:
[0010] FIG. 1 hereof is a process flow scheme of a conventional
asphalt oxidation process (Prior art process).
[0011] FIG. 2 hereof is a process flow scheme of the inventive
asphalt oxidation process of the present disclosure.
[0012] FIG. 3 hereof is a graph of oxidized asphalt penetration
versus softening point for asphalt produced via the prior art
process and the inventive process disclosed herein.
DETAILED DESCRIPTION
[0013] All numerical values within the detailed description and the
claims herein are modified by "about" or "approximately" the
indicated value, and take into account experimental error and
variations that would be expected by a person having ordinary skill
in the art.
[0014] The instant disclosure is suitable for increasing the
softening temperature of any type of asphalt, both naturally
occurring and asphalts that result is from the distillation of
crude oil. Although it is typically desired to increase the
softening temperature of asphalt for uses other than paving, it may
be desirable to also increase the softening temperature for
asphalts for some paving applications. When the asphalt is to be
used for applications such as roofing, pipe coating, or as an under
sealant or water-proofing material, it is highly desirable to
increase its softening temperature. Such uses typically require the
asphalt to have a softening temperature higher than asphalt used
for paving roads. The softening temperature is typically increased
by oxidizing the asphalt. The softening temperature of asphalts is
increased conventionally by an oxidation process that involves the
blowing of air through the asphalt, either on a batch or a
continuous basis, with the asphalt at a temperature from
175.degree. C. to 300.degree. C.
[0015] Conventional air blowing usually involves preheating the
asphalt, after which it is introduced into a blowing, or oxidizer
column just below the normal liquid level. Air is blown through the
asphalt by means of an air distributor located at the bottom of the
column. The air serves not only as the reactant, but also serves to
agitate and mix the asphalt, thereby increasing the surface area
and rate of reaction. Oxygen is consumed by the asphalt as the air
ascends through the material. Steam and water are typically sprayed
into the vapor space above the asphalt level, the former to
suppress foaming and dilute the oxygen content of waste gases and
the later cools the vapors to prevent after-burning. The "blown"
product flows from the bottom of the blowing column via an external
draw-off line and is pumped through heat exchangers to achieve the
desired product temperature and to provide an economical means of
preheating the incoming asphalt feed. The penetration and softening
point of the blown asphalt are affected by such things as: the
viscosity of the feedstock, the temperature in the blowing column,
the origin of the crude oil used to manufacture the feedstock, the
liquid residence time within the oxidizer, and the air-to-feed
ratio.
[0016] The blowing process dehydrogenates the asphalt, resulting in
oxidation and polycondensation, increasing the overall molecular
size of the asphaltenes already present in the feed and forming
additional asphaltenes from the maltene phase. Because the reaction
is exothermic, close temperature control of the process is
required, which is typically achieved by regulating the
air-to-asphalt ratio in the blowing column.
[0017] To produce penetration grade asphalt suitable for certain
road construction applications, asphalt manufactured from select
crudes requires only a limited amount of air blowing. This process
is termed semi-blowing, or air rectification. Used judiciously,
semi-blowing can be applied to asphalt to reduce the temperature
susceptibility of the asphalt, for example, increasing its
penetration index. The penetration index is a measure of the way
the binder's (asphalt) consistency (penetration value) changes with
temperature. It can be calculated from the penetration at two
different temperatures, or from the penetration at one temperature
and the softening point.
[0018] Fully blown or oxidized asphalts are conventionally produced
by vigorous air-blowing of short residue or short residue blended
with a heavy distillate. Short residue is the residue left after
vacuum distillation. The position of the blowing curve is primarily
dependent on the viscosity of the feed; i.e., the softer the feed
the higher the curve. The severity of blowing depends on the
temperature in the column, the air to feed ratio, and the liquid
residence time. Thus, by controlling the viscosity of the feed and
the conditions in the column, all the blown grades of asphalts can
be manufactured.
[0019] Oxidized asphalts are used almost entirely for industrial
applications, e.g. roofing, flooring mastics, pipe coatings,
paints, etc., and are specified and designated by both softening
point and penetration tests, e.g. 85/40 is an oxidized grade
asphalt with a softening point of 85.degree. C. plus or minus
5.degree. C. and a penetration of 40 dmm plus or minus 5 dmm.
[0020] The aim of the oxidation process is the formation of
asphaltenes in which the following three phenomena can be
identified: [0021] Reactions during which the size of the molecules
increases. The formation of esters is particularly important and
not only account for at least 60% of the oxygen in oxidized
asphalt, but also link two different molecules and thus contribute
to the formation of a material having a higher molecular weight.
This mechanism results in an increase in the asphaltene content and
a change in the colloid-chemical constitution and rheological
properties of the asphalt, [0022] Reactions during which the size
of the molecule is unchanged. For example, the formation of cyclic
hydrocarbons by means of dehydrogenation with H.sub.2O as a side
product. [0023] Reactions during which the size of the molecule
decreases. For example, separation of side branches from molecules
with blown distillate produced as a side product.
[0024] This disclosure can be better understood with reference to
the Figures hereof. FIG. 1 hereof is a process flow scheme of a
conventional asphalt oxidation process (prior art process). An
asphalt feed is passed via line 10 through heat exchanger 1 where
it is preheated to a temperature from 125.degree. C. to 300.degree.
C., then to oxidizer vessel 2. Air, via line 12, is also introduced
to oxidizer vessel 2 by first compressing it by use compressor 3
then passing it through knockout drum 4 to remove any condensed
water or other liquids via line 13. The air flows upward through a
distributor 15 and countercurrent to down-flowing asphalt. The air
is not only the reactant, but also serves to agitate and mix the
asphalt, thereby increasing the surface area and rate of reaction.
Oxygen is consumed by the asphalt as the air ascends through the
down flowing asphalt. Steam or water can be sprayed (not shown)
into the vapor space above the asphalt to suppress foaming and to
dilute the oxygen content of waste gases that are removed via line
14 and conducted to knockout drum 5 to remove any condensed or
entrained liquids via line 17. The oxidizer vessel 2 is typically
operated at low pressures of 0 to 2 barg. The low pressure off-gas,
which is primarily comprised of nitrogen and water vapor, is often
conducted via line 16 to an incinerator 8 where it is burned before
being discharged to the atmosphere. The oxidized asphalt product
stream is then conducted via line 18 and pumped via pump 6 through
heat exchanger 1 wherein it is used to preheat the asphalt feed
being conducted to oxidizer vessel 2. The hot asphalt product
stream is then conducted via line 20 to steam generator 7 where it
is cooled prior to going to storage. While such a conventional
process has been commercially successful, there is still much room
for improvement.
[0025] The practice of the instant disclosure for oxidizing
asphalts presents a substantial improvement over conventional air
blowing techniques. For example, the use of liquid jet ejector
technology of the present disclosure eliminates the need for an air
compressor; improves the air/oil mixing compared to that of a
conventional oxidizer vessel, thus reducing excess air requirements
and reducing the size of the off-gas piping; reduces the excess
oxygen in the off-gas allowing it to go to the fuel gas system,
thus eliminating the need for an incinerator; and reduces the
reaction time, thus reducing the size requirement of the oxidizer
vessel.
[0026] Liquid jet ejectors have not been used to oxidize asphalts
to increase their softening temperatures. Liquid jet ejectors are
comprised of the following components: a body having an inlet for
introducing the motive liquid, a converging nozzle that converts
the motive liquid into a high velocity jet stream, a port (suction
inlet) on the body for the entraining in of a second liquid or gas,
a diffuser (or venturi), and an outlet wherein the mixed liquid
stream is discharged.
[0027] In a liquid jet ejector, a motive liquid under high pressure
flows through converging nozzles into the mixing chamber and at
some distance behind the nozzles forms high-velocity and
high-dispersed liquid jets, which mix with entrained gas, speeding
up the gas and producing a supersonic liquid-gas flow inside the
mixing chamber. Kinetic energy of the liquid jet is transferred to
the entrained gas in the mixing chamber producing vacuum at the
suction inlet. Hypersonic liquid-gas flow enters the throat, where
it is decelerated by the compression shocks. Thus, the low pressure
zone in the mixing chamber is isolated from the high pressure zones
located downstream.
[0028] FIG. 2 hereof is a process flow scheme of the process of the
present disclosure for oxidizing asphalts. An asphalt feed via line
100 is preheated in heat exchanger 60 and combined with a portion
of the oxidized asphalt product from oxidizer vessel 20 via line
110 and pumped via pump 50 via line 120 to the liquid jet ejector
30 motive inlet and mixed with an effective amount of air via line
130 to liquid jet ejector 30 suction inlet via knockout drum 70.
Any liquid collected from knockout drum 70 is drained via line 170.
The amount of oxidized asphalt product recycled from the oxidizer
will be at least 5 times, preferably at least 10 times, and more
preferably at least 20 times that of the volume of incoming asphalt
feed. By effective amount of air we mean at least a stoichiometric
amount, but not so much that it will cause undesirable results from
either a reaction or a process point of view. The stoichiometric
amount of air will be determined by the amount of oxidizable
components in the particular asphalt feed. It is preferred that a
stoichiometric amount of air be used.
[0029] Any suitable liquid jet ejector can be used in the practice
of the present disclosure. Liquid jet ejectors are typically
comprised of a motive inlet, a motive nozzle, a suction port, a
main body, a venturi throat and diffuser, and a discharge
connection, wherein the hot asphalt, at a temperature from
125.degree. C. to 300.degree. C., is conducted as the motive liquid
into said motive inlet and wherein air is drawn into the suction
port and mixed with the asphalt within the ejector body. The air
drawn into the suction port of the liquid jet ejector may be either
atmospheric air or compressed air. The pressurized air/asphalt
mixture is then conducted via line 140 to oxidizer/separation
vessel 20. The pressure of the mixture exiting the liquid jet
ejector will be in excess of the pressure at which the oxidizer is
operated and will be further adjusted to allow for the resulting
off gas from the oxidizer to be introduced into the fuel gas system
of the refinery. The oxidizer vessel 20 is operated at pressures
from 0 to 10+ barg, preferably from 0 to 5 barg and more preferably
from 0 to 2 barg. The temperature of the oxidizer vessel will be
from 150.degree. C. to 300.degree. C., preferably from 200.degree.
C. to 270.degree. C., and more preferably from 250.degree. C. to
270.degree. C. It is preferred that the temperature within the
oxidizer will be at least 10.degree. C. higher, preferably
20.degree. C., and more preferably 30.degree. C. higher than the
incoming asphalt feed temperature. Off-gas is collected overhead
via line 150 and passed through a knockout drum 70 where liquids
are drained off via line 170 for further processing and the vapor
because of its pressure and low oxygen content can be routed into
the refinery fuel gas system via line 180. The oxidized product is
conducted via line 190 through pump 80, heat exchanger 60 and steam
generator 40. An effective amount of steam can be conducted (not
shown) to the vapor space 22 above or below the asphalt level 24 in
the oxidizer 20 to dilute the oxygen content of the off gas,
primarily for safety purposes. By effective amount of steam is
meant at least that amount needed to dilute the oxygen content of
the resulting off gas to a predetermined value. The oxidized
product stream is then routed to product storage via line 190 while
a portion of it is recycled via line 110 to line 120 where it is
mixed with fresh feed, which functions to provide the necessary
motive fluid for the liquid jet ejector.
[0030] The following are examples of the present disclosure and are
not to be construed as limiting.
Examples
[0031] A batch pilot process was constructed to test the
feasibility of the use of a liquid jet ejector to entrain the
necessary air and mix the air/oil sufficiently for the asphalt
oxidation reaction to occur. The results for two experimental runs
for the inventive process are shown in Table 1 below.
TABLE-US-00001 TABLE 1 Liquid Jet Ejector Batch Pilot Air Blower
Pilot Run #1 temperature deg C. 251 257 252 252 249 pressure kpag
28 28 21 103 103 cumulative air liters/kg 0 24 62 93 100 mixer rpm
none none none none none offgas oxygen vol. % 1.5% 1.4% penetration
at 25 C. dmm 194 129 43 38 softening point deg C. 38.0 42.2 55.2
57.6 Pilot Run #2 temperature deg C. 189 199 202 202 231 244 249
pressure kpag 28 28 34 28 28 28 28 cumulative air liters/kg 0 9 18
36 55 64 73 mixer rpm none none none none none none none offgas
oxygen vol % 17.5% 18.0% 18.2% 15.0% 11.7% 10.4% penetration at 25
C. dmm 173 151 130 107 91 softening point deg C. 38.8 39.8 41.3
43.3 44.8
[0032] it should be noted that the liquid distributor within the
oxidizer vessel was removed for Pilot Run #2 resulting in
significantly higher offgas oxygen content. However, at the end of
Pilot Run #1, there was very low offgas oxygen content, which
signifies an approach to stoichiometric air. In addition, it was
discovered that the asphalt product softening points are greater
than the feed softening points.
[0033] By comparison, the same feed was run three times on a
conventional prior art batch pilot unit and the comparative results
achieved are shown in Table 2 below.
TABLE-US-00002 TABLE 2 Conventional Stirred Batch Pilot Air Blower
Pilot Run #1 temperature deg C. 250 250 250 pressure kpag 0 0 0
cumulative air liters/kg 0 50 100 mixer rpm 1750 1750 1750 offgas
oxygen vol % 5.7% 8.1% 9.5% penetration at 25 C. dmm 167 67 34
softening point deg C. 39.1 48.7 59.3 Pilot Run #2 temperature deg
C. 200 200 200 200 200 200 pressure kpag 0 0 0 0 0 0 cumulative air
liters/kg 0 50 100 150 200 250 mixer rpm 1750 1750 1750 1750 1750
1750 offgas oxygen vol % 10.8% 15.1% 15.5% 16.1% 16.3% 16.3%
penetration at 25 C. dmm 167 91 57 41 30 24 softening point deg C.
39.1 44.4 49.6 55.0 60.2 66.0 Pilot Run #3 temperature deg C. 250
250 250 250 250 250 pressure kpag 0 0 0 0 0 0 cumulative air
liters/kg 0 50 150 250 350 650 mixer rpm 0 0 0 0 0 0 offgas oxygen
vol % 10.5% 19.4% 19.4% 19.4% 19.5% 19.5% penetration at 25 C. dmm
167 98 62 softening point deg C. 39.1 44.7 49.1
[0034] As can be seen, the liquid jet ejector pilot process
performed as well as or better than the conventional counterpart.
It should be noted that the conventional pilot unit could not
achieve the low offgas oxygen content at similar conditions as the
liquid jet ejector pilot process signifying the improved efficiency
of the liquid jet ejector air blower versus the conventional air
blower.
[0035] Oxidized asphalt product penetration versus softening point
for product produced from the inventive and prior art processes are
compared graphically in FIG. 3. The results indicate no differences
between the prior art process and the inventive process with regard
to these properties.
[0036] Applicants have attempted to disclose all embodiments and
applications of the disclosed subject matter that could be
reasonably foreseen. However, there may be unforeseeable,
insubstantial modifications that remain as equivalents. While the
present disclosure has been described in conjunction with specific,
exemplary embodiments thereof, it is evident that many alterations,
modifications, and variations will be apparent to those skilled in
the art in light of the foregoing description without departing
from the spirit or scope of the present disclosure. Accordingly,
the present disclosure is intended to embrace all such alterations,
modifications, and variations of the above detailed
description.
[0037] All patents, test procedures, and other documents cited
herein, including priority documents, are fully incorporated by
reference to the extent such disclosure is not inconsistent with
this disclosure and for all jurisdictions in which such
incorporation is permitted.
[0038] When numerical lower limits and numerical upper limits are
listed herein, ranges from any lower limit to any upper limit are
contemplated.
* * * * *