U.S. patent application number 10/583391 was filed with the patent office on 2009-01-29 for fuel for homogeneous charge compression ignition (hcci) systems and a process for production of said fuel.
Invention is credited to Luis Pablo Dancuart, Delanie Lamprecht, Ian Stradling Myburgh, Carl Louis Viljoen.
Application Number | 20090025279 10/583391 |
Document ID | / |
Family ID | 34704302 |
Filed Date | 2009-01-29 |
United States Patent
Application |
20090025279 |
Kind Code |
A1 |
Lamprecht; Delanie ; et
al. |
January 29, 2009 |
Fuel for homogeneous charge compression ignition (hcci) systems and
a process for production of said fuel
Abstract
The invention provides a HCCI fuel or fuel component, which fuel
includes at least n-paraffins and iso-paraffins having from 7 to 14
carbon atoms, and which fuel has an ignition delay of less than 7
ms, according to ASTM D6890. A process for preparing a HCCI fuel or
fuel component.
Inventors: |
Lamprecht; Delanie;
(Vanderbijlpark, ZA) ; Myburgh; Ian Stradling;
(Vanderbijlpark, ZA) ; Dancuart; Luis Pablo;
(Sasolburg, ZA) ; Viljoen; Carl Louis;
(Vanderbijlpark, ZA) |
Correspondence
Address: |
HAHN AND MOODLEY, LLP
P.O. BOX 52050
MINNEAPOLIS
MN
55402
US
|
Family ID: |
34704302 |
Appl. No.: |
10/583391 |
Filed: |
December 17, 2004 |
PCT Filed: |
December 17, 2004 |
PCT NO: |
PCT/ZA2004/000157 |
371 Date: |
July 15, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60531428 |
Dec 19, 2003 |
|
|
|
Current U.S.
Class: |
44/309 |
Current CPC
Class: |
C10L 1/08 20130101; C10L
10/02 20130101 |
Class at
Publication: |
44/309 |
International
Class: |
C10L 1/18 20060101
C10L001/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2003 |
ZA |
2003/9849 |
Claims
1. A HCCI fuel or fuel component, which fuel includes at least
n-paraffins and iso-paraffins having from 7 to 14 carbon atoms, and
which fuel has an ignition delay of less than 7 ms, according to
ASTM D6890, which fuel has an ASTM D86 distillation range from
90.degree. C. to 270.degree. C.
2. A fuel as claimed in claim 1, which fuel contains less than 1%
wt of aromatic and negligible levels of sulphur.
3. A fuel as claimed in claim 1, which fuel has an ignition delay
of less than 5 ms.
4. A fuel as claimed in claim 1, which fuel has an ignition delay
of between 2 and 5 ms.
5. A fuel as claimed in claim 1, wherein the mass % of the
n-paraffins exceeds that of any other single component in the
fuel.
6. A fuel as claimed in claim 1, wherein the mass % of the
n-paraffins is in excess of 25% by mass of the fuel
7. A fuel as claimed in claim 1, wherein the mass % of the
n-paraffins is in excess of 50% by mass of the fuel.
8. A fuel as claimed in claim 1, wherein the mass % of the
n-paraffins is in excess of 80% by mass of the fuel.
9. A fuel as claimed in claim 1, wherein the mass % of the
n-paraffins is in the order of 95% by mass of the fuel.
10. A fuel as claimed in claim 1, wherein the n-paraffins are
Fischer-Tropsch (FT) reaction derived n-paraffins.
11. A fuel as claimed in claim 1, wherein the iso-paraffins are FT
reaction derived iso-paraffins.
12. A fuel as claimed in claim 1, which fuel includes one or more
of: olefins, lubricity improver, and oxygenates.
13. A fuel as claimed in claim 1, which fuel is substantially free
of heteroatoms such as nitrogen, sulphur and oxygen.
14. A process for preparing a fuel, which process includes blending
HCCI fuel or fuel component as claimed in claim 1, as a blending
component with conventional fuel.
15. A process for preparing a HCCI fuel or fuel component, which
fuel or fuel component includes at least n-paraffins and
iso-paraffins, which fuel has an ignition delay of less than 7 ms,
said process including one or more steps selected from: a)
hydrotreating at least a Condensate fraction of a Fischer-Tropsch
(FT) synthesis reaction product, or a derivative thereof; b)
hydroconverting a Wax fraction of the FT synthesis product or a
derivative thereof; c) fractionating in a single unit or in
separate units, one or more of the hydrotreated Condensate
fractions of step a) and the hydroconverted fraction of step b) to
obtain the desired HCCI fuel or fuel component having from 7 to 14
carbon atoms and which fuel has an ASTM D86 distillation range from
90.degree. C. to 270.degree. C.; and d) optionally, blending two or
more of said components from step c) in a desired ratio to obtain
the desired HCCI fuel.
16. A process as claimed in claim 15, wherein the hydroconversion
is by way of hydrocracking.
17. A process as claimed in claim 15, wherein the blending of step
d) is the blending of FT condensate derivative and hydroconverted
FT wax derivative in a blending ratio of from 1:99 to 99:1 by
volume.
18. A process as claimed in claim 15, wherein the fuel produced by
the process is a fuel as claimed in claim 1.
19. (canceled)
20. (canceled)
21. (canceled)
22. (canceled)
Description
FIELD OF THE INVENTION
[0001] The invention relates to a fuel for Homogeneous Charge
Compression Ignition (HCCI) systems and to a process for producing
such a fuel.
BACKGROUND TO THE INVENTION
[0002] The HCCI engine is a relatively new concept under
development by several institutions and companies. The principle of
HCCI combustion is that a dilute, premixed, homogenous mixture of
fuel and air reacts and burns volumetrically throughout the
cylinder as it is compressed by the piston. Combustion reactions
start when the mixture reaches a sufficiently high temperature to
autoignite. These reactions initiate at multiple locations
simultaneously, proceed very quickly, and there is a complete
absence of localized high-temperature regions or flame-fronts.
[0003] In essence, the HCCI combustion process seeks to combine the
low nitrogen oxides (NOx) exhaust emissions associated with the
gasoline engine, with the high thermal efficiency associated with
the diesel or compression ignition (CI) engine. In theory, HCCI
offers the potential for sootless combustion and very low emissions
of nitrogen oxides (NOx), together with an energy efficiency that
can exceed that of the CI engine.
[0004] Successful implementation of HCCI combustion would therefore
increase the competitiveness of the internal combustion (IC) engine
against emerging technologies such as fuel cells, thereby extending
its lifespan.
[0005] Because HCCI is effectively an evolution of the IC engine,
there are no external barriers to its implementation, and the
gradual adoption of this technology may see it eventually being
implemented in the majority of automotive IC engines, in one form
or another. A 2001 report by the US Department of Energy to the US
Congress speculated that, with successful R&D, passenger car
HCCI engines might be commercialised by 2010.
[0006] Thus a need exists for a fuel for HCCI systems and
engines.
SUMMARY OF THE INVENTION
[0007] According to one aspect of the invention, there is provided
a HCCI fuel, which fuel includes at least n-paraffins and
iso-paraffins, and which fuel has an ignition delay of less than 7
ms. The HCCI fuel may also be used as a fuel component.
[0008] Typically, the fuel contains hydrocarbon species having from
7 to 14 carbon atoms.
[0009] The fuel may be substantially cyclo-paraffins free. Thus,
the fuel may have less than 5 mass %, typically less than 1 mass %
cyclo-paraffins.
[0010] Moreover, it contains less than 1 wt % of aromatic and
negligible levels of sulphur.
[0011] In this specification, the ignition delay is measured using
the ASTM Method D6890 in a constant volume combustion bomb,
Ignition Quality Tester (IQT.TM.)
[0012] The ignition delay of the fuel may be less than 5 ms.
[0013] The ignition delay of the fuel may be between 2 and 5
ms.
[0014] The weight % of the n-paraffins may exceed that of any other
single component in the fuel.
[0015] The n-paraffins may be in excess of 25% by weight of the
fuel
[0016] The n-paraffins may be in excess of 50% by weight of the
fuel.
[0017] The n-paraffins may be in excess of 80% by weight of the
fuel.
[0018] The n-paraffins may be in the order of 95% by weight of the
fuel.
[0019] The n-paraffins may be Fischer-Tropsch (FT) reaction derived
n-paraffins.
[0020] The iso-paraffins may be FT reaction derived
iso-paraffins.
[0021] The fuel may include olefins.
[0022] The HCCI fuel may include oxygenates.
[0023] The HCCI fuel may be substantially sulphur free.
[0024] The HCCI fuel may be substantially oxygenate free.
[0025] The fuel may have an ASTM D86 distillation range from
90.degree. C. to 270.degree. C.
[0026] The fuel may include a lubricity improver or other fuel
additives to make meeting product specifications possible.
[0027] The fuel may be used as blending component with conventional
fuel.
[0028] The invention extends to a process for preparing a HCCI fuel
or fuel component, which fuel or fuel component includes at least
n-paraffins and iso-paraffins, which fuel has an ignition delay of
less than 7 ms, said process including one or more steps selected
from: [0029] a) hydrotreating at least a Condensate fraction of a
Fischer-Tropsch (FT) synthesis reaction product, or a derivative
thereof; [0030] b) hydroconverting a Wax fraction of the FT
synthesis product or a derivative thereof; [0031] c) fractionating
in a single unit or in separate units, one or more of the
hydrotreated Condensate fractions of step a) and the hydroconverted
fraction of step b) to obtain the desired HCCI fuel or fuel
component; and [0032] d) optionally, blending two or more of said
components from step c) in a desired ratio to obtain the desired
HCCI fuel.
[0033] The hydroconversion may be by way of hydrocracking.
[0034] The properties of the fuel made according to the process may
be as disclosed above and elsewhere in the specification.
[0035] The blending of step d) may be the blending of FT condensate
derivative and hydroconverted FT wax derivative from 1:99 to 99:1
by volume
[0036] The table below gives a typical composition of the two
fractions.
TABLE-US-00001 Typical FT product after separation into two
fractions (vol % distilled) FT Condensate FT Wax (<270.degree.
C. fraction) (>270.degree. C. fraction) C.sub.5-160.degree. C.
44 3 160-270.degree. C. 43 4 270-370.degree. C. 13 25
370-500.degree. C. 40 >500.degree. C. 28
[0037] The >160.degree. C. fraction, contains a considerable
amount of hydrocarbon material, which boils higher than the normal
naphtha range. The 160.degree. C. to 270.degree. C. fraction may be
regarded as a light diesel fuel. This means that all material
heavier than 270.degree. C. needs to be converted into lighter
materials by means of a catalytic process often referred to as
hydroprocessing, for example, hydrocracking.
[0038] Catalysts for this step are typically of the bifunctional
type; i.e. they contain sites active for cracking and for
hydrogenation. Catalytic metals active for hydrogenation include
group VIII noble metals, such as platinum or palladium, or a
sulphided Group VIII base metals, e.g. nickel, cobalt, which may or
may not include a sulphided Group VI metal, e.g. molybdenum. The
support for the metals can be any refractory oxide, such as silica,
alumina, titania, zirconia, vanadia and other Group III, IV, V and
VI oxides, alone or in combination with other refractory oxides.
Alternatively, the support can partly or totally consist of
zeolite.
SPECIFIC DESCRIPTION AND EXAMPLES
[0039] The following table summarises the origin and carbon number
ranges for the proposed fuels usable in HCCI engines of this
invention:
TABLE-US-00002 Typical (LTFT) Carbon Number range Class Feedstock
Composition C.sub.7-C.sub.9 C.sub.7-C.sub.14 C.sub.10-C.sub.14 SR
FT FT Condensate Paraffins, X X X olefins and oxygenates HT SR FT
FT Condensate Mostly linear X X X paraffins HX FT FT Wax Mostly
iso- X X X paraffins GTL FT Condensate Fully X X X and Wax
paraffinic Definitions SR FT Straight Run Fischer-Tropsch HT SR FT
Hydrotreated Straight Run Fischer-Tropsch HX FT Hydrocracked
Fischer-Tropsch GTL Hydroconverted Product as expected from a
Fischer-Tropsch Gas-to-Liquid plant
[0040] The fuel might contain hydrocarbon species having from 7 to
14 carbon atoms and has been found to define unique characteristics
with respect to vapour pressure and ignition delay. Moreover, the
criteria also made consideration to the highly paraffinic nature of
the fuel as well as the high linearity of the hydrocarbon
species.
[0041] The C7 to C14 carbon number range has been found to exclude
hydrocarbons like pentane or hexane that have high vapour
pressures. Adequate volatility is important to establish a
homogeneous gaseous charge in the combustion chamber, with enough
cetane character (propensity to auto-ignite) to effect the
homogeneous ignition throughout the whole volume.
[0042] Furthermore, the C7 to C14 carbon number range has been
found to exclude hydrocarbons like n-hexadecane that conventionally
has cetane number of 100. The cetane number of the HCCI fuel must
not be too high and its ignition delay not too short to ensure
controlled in-cylinder combustion.
[0043] The inventors believe that the abovementioned twelve options
cover almost all practical options for FT-based synthetic HCCI
fuels.
[0044] The key quality requirements for these fuels are summarised
in Table 1.
TABLE-US-00003 TABLE 1 Selected Quality Characteristics of
Synthetic FT HCCI Fuels Analytical Desired Range Procedure
Distillation Range 90-270.degree. C. ASTM D86 Density 0.65-0.78
kg/l ASTM D1298 Composition hydrocarbon GC-FID Ignition delay (IQT)
2-7 ms ASTM D6890-03 Cetane Number 25-75 ASTM D613-03a Aromatics
content <1.0% wt ASTM D5186-99 ASTM D6591-00 Sulfur content
<1 ppm wt ASTM D5453 Oxygen content <5000 ppm GC-TCD
[0045] The ignition delay is a good indication of the elevated
pressure, high temperature autoignition characteristics of the fuel
and can be correlated to the distillation range and cetane number
of the fuel, which in turn relate to its chemical composition. The
conditions at which the ignition delay is determined in the
IQT.TM.; at 22.4 bar air pressure and 565.degree. C., are
comparable to the conditions that an HCCI fuel could experience in
an HCCI engine, thus the ignition delay (ID) can be used as an
appropriate yardstick for HCCI fuel ignition quality. The
implications are that fuels with a high propensity for autoignition
under compression will have short ignition delays (.about.2-4 ms),
while fuels with increased resistance against autoignition
(equivalent to high octane spark ignition gasoline) will have
longer ignition delays (.about.7-11 ms).
[0046] Since the resistance against autoignition is no different to
a resistance against oxidation at the specific pressure and
temperature conditions to which the fuel is exposed in an HCCI
engine's combustion chamber, it follows that those sulphur (S) and
nitrogen (N) heteroatoms present in crude oil derived HCCI fuel
will act as oxidation inhibitors, leading to longer ignition delays
and a lower propensity towards autoignition.
[0047] FT fuels are virtually sulphur free, with lower levels of
nitrogen-containing compounds, and the absence of these naturally
occurring anti-oxidants represent a benefit when FT fuels are
applied in HCCI engines. This results in FT fuels outperforming
conventional fuels in terms of their propensity to autoignite under
HCCI conditions.
Process Scheme
[0048] A generic block diagram flow scheme is included as FIG. 1.
The process options for all four classes of HCCI fuels are shown in
a simple format. The following table 2 summarises the basic
processing for these fuels and feeds.
TABLE-US-00004 TABLE 2 Generic Requirement for FT Feedstock
Processing Process Step Process Description Reference Distillation
Atmospheric Distillation (1) Hydrotreatment H.sub.2 saturation of
olefinic double bonds. U.S. Pat. No. H.sub.2 saturation of
oxygen-containing 6,475,375 hydrocarbons with formation of water
Other hydroconversion reactions Hydrocracking Cracking of heavy
molecules (mostly EP 1129155 paraffinic) H.sub.2 saturation of
olefinic double bonds. H.sub.2 saturation of oxygen-containing
hydrocarbons with formation of water Other hydroconversion
reactions (1) There are many references for this unit operation.
For example, refer to P A Schweitzer, Handbook of Separation
Techniques for Chemical Engineers (McGraw-Hill, 1979) or R H Perry
and C H Chilton, Chemical Engineers' Handbook (McGraw-Hill,
5.sup.th Edition, 1973)
[0049] The production of the synthetic HCCI fuel components can be
achieved following at least four process configurations. The
selection of one for a specific plant is an exercise in process
synthesis that demands additional site and market specific
information.
[0050] A first group of HCCI fuels--named SR FT in this
description--can be produced by fractionation of a light synthetic
FT hydrocarbon stream 10 in Distillation unit 1. The operation of
this fractionation unit to the required product specification
results in the group of products 11.
[0051] A second group of HCCI fuels--named SR HT FT in this
description--can be obtained from a light synthetic FT hydrocarbon
stream 10 which is first hydrogenated in hydrogenation unit 2 to
saturate the olefinic double bonds and remove the oxygen from the
oxygenate species. Then the hydrogenated products can be
fractionated in fractionation unit 3 to the required specification,
obtaining the group of products 13.
[0052] A third group of HCCI fuels--named HX FT in this
description--can be obtained from a heavy synthetic FT hydrocarbon
stream 14 which is hydrocracked in hydrocracking unit 4 to result
in lighter saturated hydrocarbon species. Then the hydrocracked
products can be fractionated in fractionation unit 5 to the
required specification, obtaining the group of products 16.
[0053] An alternative to produce a fourth group of HCCI
fuels--named GTL (GTL=gas to liquid) in this description--can be
produced by direct blending of the hydrotreated and hydrocracked
products described above. This can be done in an optimised way by
using a common fractionator unit 6 to the required specification,
obtaining the group of products 18.
[0054] It is also possible to blend the products 11 and 16, either
by sharing a common fractionator or after fractionation to also
obtain synthetic HCCI fuels.
[0055] In all of these process options there is co-production of
non-HCCI hydrocarbon stream, both lighter and heavier than the
designed HCCI synthetic products. The former can be described as a
light naphtha and the latter as a heavy diesel stream. These can be
used in fuel and non-fuel applications.
[0056] All fuels in any of these four groups can be used as blends
components for final HCCI fuels.
Emissions Performance of the Synthetic FT HCCI Fuels
[0057] There is wide acceptance to the fact that the synthetic FT
fuels produce less noxious emissions than conventional fuel. This
point has been brought into the public domain several times--for
example refer to "Processing of Fischer-Tropsch Syncrude and
Benefits of Integrating its Products with Conventional Fuels"
presented at the National Petrochemical & Refiners Association
Annual Meeting held in March 2000 in San Antonio, Tex.--paper
AM-00-51. This document makes reference to both FT naphthas and FT
diesels.
Typical Quality of Synthetic FT HCCI Fuels
[0058] Table 3 contains the typical quality of synthetic FT HCCI
fuels produced as described and conforming to the selected
requirements. Table 4 shows a comparison between HT SR FT fuel and
crude derived fuel.
TABLE-US-00005 TABLE 3 Typical Quality of Synthetic FT HCCI Fuels
SR FT HT SR FT Desired Range C.sub.7-C.sub.9 C.sub.7-C.sub.14
C.sub.10-C.sub.14 C.sub.7-C.sub.9 C.sub.7-C.sub.14
C.sub.10-C.sub.14 Distillation Range 90-270 .degree. C. 103-183
103-251 164-251 90-160 90-254 165-254 Density 0.65-0.78 kg/l 0.67
0.71 0.76 0.71 0.74 0.76 Composition n-paraffins wt % 52.5 63.1
68.4 94.6 94.9 95.1 i-paraffins wt % 0.4 1.6 2.2 5.4 5.1 4.9
Olefins wt % 38.5 26.5 20.5 0 0 0 Oxygenates wt % 8.6 8.8 8.9 0 0 0
Ignition delay 2-7 ms 3.34 2.79 2.60 3.44 2.74 2.54 (IQT .TM.)
Cetane Number 30-70 60 75 83 58 77 86 Aromatics content <1.0% wt
% <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Sulphur content
<1 ppm wt <1 <1 <1 <1 <1 <1 Oxygen content
<5000 ppm (wt) 700 2000 2150 <80 <80 <80 HX GTL Desired
Range C.sub.7-C.sub.9 C.sub.7-C.sub.14 C.sub.10-C.sub.14
C.sub.7-C.sub.9 C.sub.7-C.sub.14 C.sub.10-C.sub.14 Distillation
Range 90-270 .degree. C. 80-163 80-250 135-250 90-163 90-250
155-250 Density 0.65-0.78 kg/l 0.68 0.72 0.74 0.69 0.72 0.75
Composition n-paraffins wt % 46.0 30.7 26.6 57.5 41.0 38.0
i-paraffins wt % 54.0 69.3 73.4 42.5 59.0 62.0 Olefins wt % 0 0 0 0
0 0 Oxygenates wt % 0 0 0 0 0 0 Ignition delay 2-7 ms 4.92 4.06
3.50 4.55 3.34 3.08 (IQT .TM.) Cetane Number 30-70 41 49 57 44 60
66 Aromatics content <1.0% wt % <0.1 <0.1 <0.1 <0.1
<0.1 <0.1 Sulphur content <1 ppm wt <1 <1 <1
<1 <1 <1 Oxygen content <5000 ppm (wt) <80 <80
<80 <80 <80 <80
TABLE-US-00006 TABLE 4 Comparison between equivalent synthetic FT
Fuel for HCCI Fuels and Crude Derived Fuels HT SR FT Crude Derived
Fuels Desired Range C.sub.7-C.sub.9 C.sub.7-C.sub.14
C.sub.10-C.sub.14 C.sub.7-C.sub.9 C.sub.7-C.sub.14
C.sub.10-C.sub.14 Distillation Range 90-270 .degree. C. 90-160
90-254 165-245 80-159 80-257 151-257 Density 0.65-0.78 kg/l 0.71
0.74 0.76 0.7329 0.7715 0.7961 Composition n-paraffins wt % 94.6
94.9 95.1 28.2 23.8 24.7 i-paraffins wt % 5.4 5.1 4.9 32.8 53.0
55.3 Olefins wt % 0 0 0 0.4 0.4 0.5 Oxygenates wt % 0 0 0 0 0 0
Aromatics wt % 0 0 0 10.3 14.2 18 Naphthenes wt % 0 0 0 28.3 8.6
1.5 Ignition delay 2-7 ms 3.44 2.74 2.54 6.17 5.22 4.79 (IQT .TM.)
Cetane Number 30-70 58 77 86 34.1 39.0 42.0 Sulphur content <1
ppm wt <1 <1 <1 50 50 50
[0059] Table 5 below presents an example of the quality
characteristics of blends of the C7-C9 GTL HCCI fuel with an
equivalent Petroleum fraction. The benefits of including synthetic
FT fuel in conventional blends are quite evident.
TABLE-US-00007 TABLE 5 Quality of blends of the C7-C9 GTL HCCI fuel
with an equivalent Petroleum fraction GTL Fuel Content 0% 25% 50%
75% 100% Density kg/l 0.733 0.722 0.711 0.700 0.690 Composition
n-paraffins wt % 28.2 35.4 42.8 50.1 57.5 i-paraffins wt % 32.8
35.1 37.6 40.0 42.5 Olefins wt % 0.4 0.3 0.2 0.1 0.0 Oxygenates wt
% 0.0 0.0 0.0 0.0 0.0 Aromatics wt % 10.3 7.8 5.2 2.6 0.0
Naphthenes wt % 28.3 21.3 14.2 7.1 0.0 Total wt % 100.0 99.9 100.0
99.9 100.0 Ignition delay ms 6.17 5.75 5.22 4.75 4.55 (IQT .TM.)
Cetane Number 34.1 36.0 39.1 41.9 44.0 Sulphur content ppm 50 38 25
13 <1
* * * * *