ES2574652T3 - Use of combinations of diesel fuel from gas to liquids and derived from crude oil - Google Patents

Abstract

Use of gas-to-liquids (GTL) diesel fuel that has a density at 15ºC below 0.78 kg/l, a sulfur content of less than 1 mg/kg, polyaromatic compounds below 0.1% by mass and a cetane number above 65, as a blending component for at least one crude oil derived diesel fuel to reduce NOx and soot emissions from the resulting diesel fuel composition, characterized in that the crude oil derived diesel fuel has a density at 15ºC below 0.85 kg/l, a sulfur content of less than 10 mg/kg, a content of polyaromatic compounds below 5% by mass and a cetane number of from 51 to 60, with which the NOx and soot emissions of the resulting diesel fuel composition, when burned in an engine, are reduced non-linearly to a greater degree than would be expected when considering the blend ratio of GTL diesel to diesel. to diesel fuel l derived from crude oil.

Description

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DESCRIPTION

Use of combinations of diesel fuel from gas to liquids and crude oil derivative Field of the invention

The invention relates to the use of diesel fuel from gas to liquids (GTL) as a combination component for at least one diesel fuel derived from crude oil to reduce NOx and hollin emissions from the resulting diesel composition.

Background of the invention

Synthetic fuels such as GTL diesel fuel (from gas to liquids) have seen a significant increase in interest in recent years. They are considered to be extremely clean fuels, with negligible amounts of sulfur and aromatic compounds, and have no odor and have a cetane number> 70. The GTL diesel fuel used in the examples in this patent specification was manufactured by the process Sasol Slurry Phase Distillate (Sasol SPD ™), which consists of three process steps, as schematically depicted in Figure 1.

In the first stage, an autothermal reforming process is used to convert natural gas into synthetic gas, a mixture of CO and H2. In a second stage, the synthesis gas is converted into a so-called synthesis oil containing predominantly paraffinic hydrocarbons, by means of a Fischer-Tropsch process. This synthetic crude is mainly in the form of waxes and distillates, which are further refined in a third stage of product improvement by means of gentle hydroprocessing, in order to produce products that meet the specifications of commercial fuel, such as fuel diesel and kerosene.

GB 2387175 A discloses a possible reduction in the emission of hollin from a diesel fuel by oxidizing the fuel to a certain point and then mixing it with certain organic compounds containing oxygen. It does not address the problem of NOx reduction.

WO 03/087273 A1 discloses a method of increasing the cetane index of a diesel product based on a petroleum derived diesel by adding a diesel derived from Fischer-Tropsch having a cetane index greater than the of oil derived from oil. NOx reduction is not mentioned.

WO 01/83848 A discloses a method for achieving emission levels of cracked materials that are equivalent to or greater than those of base fuels while containing higher levels of aromatic and polyaromatic compounds, where the base fuels are base fuels derived from conventional oil.

Summary of the invention

The invention provides the use of a gas-to-liquid diesel fuel (GTL), GTL diesel having a density at 15 ° C below 0.78 kg / l, a sulfur content of less than 1 mg / kg, compounds polyaromatics below 0.1% by mass and a cetane index above 65, as a combination component for at least one diesel fuel derived from crude oil to reduce NOx and hollin emissions from the resulting diesel fuel composition, characterized in that diesel fuel derived from crude oil has a density at 15 ° C below 0.85 kg / l, a sulfur content of less than 10 mg / kg, a content of polyaromatic compounds below 5% by mass and a cetane index of from 51 to 60 whereby the NOx and hollin emissions of the resulting diesel fuel composition, when burned in an engine, are reduced non-linearly to a greater degree than would be expected when the combination reason of the GTL diesel with respect to diesel fuel derived from crude oil.

The resulting diesel fuel composition may have less than 10 mg / kg of sulfur.

The resulting diesel fuel composition may have less than 5% by mass of polycyclic aromatic compound.

Diesel fuel derived from crude oil can be a fuel that complies with the EN590 standard specification.

The range of GTL diesel volumetric ratio: derived from crude oil can be from 1: 9 to 9: 1.

The range of GTL diesel volumetric ratio: derived from crude oil can be from 1: 5 to 5: 1.

The molar ratio of H: C of the resulting diesel fuel composition can be from 1.85: 1 to 2.05: 1.

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The molar ratio of H: C of the resulting diesel fuel composition can be from 1.9: 1 to 2.00: 1.

The resulting diesel fuel composition may have a distillation temperature of 10% according to ASTM D86 from 180 ° C to 220 ° C.

GB 2387175 A discloses a possible reduction in the emission of hollin from a diesel fuel by oxidizing the fuel to a certain point and then mixing it with certain organic compounds containing oxygen (see summary and page 25, lines 22 to 25). Diesel fuels can be derived from various sources including petroleum or Fischer-Tropsch synthesis.

WO 03/087273 A1 discloses a method for increasing the cetane number of a diesel product based on a diesel oil derived from the addition of a Fischer-Tropsch derived diesel oil having a cetane number greater than the of oil derived from oil. The amount of Fischer-Tropsch derivative diesel added to reach a target cetane index is less than the amount that would be added if the increase in the combination cetane index was linear.

The distillation temperature of 10% according to the ASTM D86 standard of the resulting diesel fuel composition can be from 200 ° C to 215 ° C.

The resulting diesel fuel composition may have a flash point between 60 ° C and 80 ° C, usually from 65 ° C to 78 ° C.

The resulting diesel fuel composition may have a density at 15 ° C of from 0.77 kg / l to 0.84 kg / l.

The resulting diesel fuel composition may have a density at 15 ° C of from about 0.8 kg / l to about 0.82 kg / l.

The resulting diesel fuel composition may have a lower calorific value of from 42,500 kJ / kg to 43,800 kJ / kg, usually from 43,100 kJ / kg to 43,600 kJ / kg, usually from 43,200 kJ / kg to 43,500 kJ / kg.

The use of diesel fuel from gas to liquids as a combination component for a diesel fuel composition that, when burned in an engine, has reduced NOx and hollin emissions, produces a composition comprising both diesel fuel derived from crude oil that meets with the specification of the European standard EN590 for sulfur-free diesel fuel (called EU diesel) as gas-to-liquid diesel fuel (GTL), in which the ratio of volumetric combination of diesel fuel derived from crude oil with respect to Gas-to-liquid diesel can range between 1:99 and 99: 1 and the composition can have a molar ratio of H: C between 1.8: 1 and 2.1: 1.

Reductions in both NOx and hollin emissions are obtained that are greater than indicated by the reason for combining GTL diesel in diesel fuel derived from crude oil.

Therefore, more than 70% of the reduction in both NOx and hollin emissions that can be obtained with pure GTL diesel fuel, can be obtained with a GTL diesel ratio: derived from crude oil of 1: 1.

More than 40% of the reduction in both NOx and hollin emissions that can be obtained with pure GTL diesel can be obtained with a GTL diesel ratio: derived from crude oil of 1: 4.

However, in some embodiments, the reduction in NOx emissions may be less than the reduction in hollin emissions, and vice versa.

In some embodiments, the reduction in NOx may be minimal, however, NOx will be reduced by the use of GTL diesel according to the invention.

The properties of the composition and the reasons for the combination of the components are as described above for the composition.

Examples involved in the invention

The effect of combinations of GTL diesel fuel on exhaust emissions and engine performance has been studied. EU diesel fuel was used as the reference fuel, the base material for the combinations being also. Table 1 shows the properties of the test fuels used in the investigation.

 Table 1 Pro

 fuel ceilings investigated in this study

 Property

 GTL units 100% GTL diesel fuel UE50 EU combination: GTL at 50:50 UE80 EU combination: GTL at 80:20 EU European sulfur-free diesel fuel 2005

 15HC density

 kg / l 0.768 0.802 0.821 0.836

 Density at 20 ° C

 kg / l 0.765 0.798 0.817 0.832

 Cetane index

   71 62 58 54

 Total sulfur

 mg / kg <1 4 6 7

 Distillation IBP according to D86

 ° C 169 157 174 193

 5%

 ° C 180 193 204 214

 10%

 ° C 187 201 212 221

 twenty%

 ° C 200 215 225 233

 30%

 ° C 219 231 240 248

 40%

 ° C 235 248 256 264

 fifty%

 ° C 251 264 270 277

 60%

 ° C 267 277 282 287

 70%

 ° C 283 291 294 299

 80%

 ° C 297 305 307 313

 90%

 ° C 312 322 324 332

 95%

 ° C 321 337 339 354

 FBP

 ° C 329 346 350 360

 Flashpoint

 ° C 59 66 76 82

 Kinematic viscosity at 40 ° C

 mm2 / s 1.97 2.54 2.79 2.95

 CFPP

 ° C -19 -18 -17 -17

 Cloud point

 ° C -18 -17 -15 -14

 Total aromatic compounds *

 % m / m 0.1 13.5 21.5 26.8

 Bi and polycyclic aromatic compounds *

 % m / m 0.0 2.3 3.7 4.6

 Hydrogen content *

 % m / m 15.0 14.3 13.8 13.5

 Reason H / C (molar) *

 - 2.10 1.98 1.91 1.86

 Lower calorific value *

 MJ / kg 43.8 43.5 43.2 43.1 43.1

 HFRR wear scar diameter

 pm 370 <400 <400 394

 * Values for combinations calculated according to the combination reason

Dynamometer tests were carried out with a Mercedes Benz ™ E220 CDI vehicle, using the European New Driving Cycle (NEDC) emission test and without any change with respect to the calibration of the engine at basic level 5 of UE3 emission or hardware the motor. The vehicle was tested with its conventional calibration without any adaptation, with EU diesel, the 1: 1 combination and for pure GTL fuel. Table 2 shows the relevant data of the test vehicle.

Table 2 Engine and test vehicle data

 Vehicle Designation

 Mercedes E 220 CDI Limousine

 Model Year

 2003

 Transmission

 6-speed manual gearbox

 Mass of the raw vehicle

 2,145 kg

 Engine designation

 MB OM646, UE3 emission level

 Displacement, configuration

 2.2 l, 4 cylinders in line, 4 valves per cylinder

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 Compression reason

 18: 1

 Fuel management

 Fuel injection by common duct (maximum pressure 1,600 bar)

 Air administration

 Turbocharged (VNT), with intermediate refrigerator

 Emission control

 EGR refrigerated, input swirl control, underground oxidation catalysts and closed coupling

 Nominal torque

 340 Nm at 2,000 rev / min

 Rated power

 110 kW at 4,200 rev / min

The results of the unadjusted vehicle emission tests for EU diesel, EU50 and GTL diesel fuel are shown in Figure 2. The average results for the test series are presented as percentages in relation to the EU diesel reference fuel. FC indicates the volumetric fuel consumption.

It was observed for pure GTL diesel fuel, an unexpectedly high reduction of> 90% for CO and HC emissions.

The CO and HC reductions for the 50% combination are approximately proportional to the ratio of combination. NOx emissions were slightly reduced, with the 50% combination showing again approximately half of the reduction in pure GTL diesel fuel. The same applies to HC + NOx data.

PM emissions were reduced by up to 30% with GTL diesel. Surprisingly, a strong nonlinear characteristic was evident with the 50% combination (UE50), which showed a reduction of approximately 22%.

The potential for further emission reductions with test fuels and including the optimization of a limited number of software parameters in the engine control unit (ECU) of the engine was then investigated. For this purpose, an engine mounted on a test bench was used. Stationary test series were carried out at five characteristic operating points for the NEDC emission test cycle. The software parameters investigated were the exhaust gas recirculation rate (EGR), the start of the pilot injection (SOPI) and the start of the main injection (SOMI). Table 3 shows the five operating points.

 Table 3 Stationary state engine test points chosen for refle

 ar the characteristics of NEDC

 Engine test point

 Motor speed (rev / min) bmep (bar) Power (kW) Description

 one

 1,000 0 0 Pseudo at rest

 2

 1,600 3.3 9 Characteristic operating points for the NEDC emission test

 3

 2,000 2 7

 4

 2,000 5 18

 5

 2800 4 20

Figure 3 shows two examples of results obtained from the work of the steady state test bench. The figure represents representative data for the effect of GTL diesel fuel and its combinations on the NOx-hollin exchange characteristic at two operating points, specifically at 1,600 rev / min and 3.3 bar bmep (average effective brake pressure), and 2,000 rev / min and 5 bar bmep. In this case, the EGR rate was varied, while SOPI and SOMI were kept constant and equal to the reference values. Hollin emission levels were calculated from the exhaust smoke levels determined by FSN measurements (filter smoke index).

It is clear that GTL diesel has a significant reduction in both hollin and NOx emissions for all the EGR rates tested. Hollin emission increases for decreasing NOx values following the expected pattern, and allows a wide variety of possible alternative software calibrations. Surprisingly, the strong nonlinear behavior of the UE50 combination is evident again (this fuel has almost the same benefits as pure GTL diesel fuel).

An experiment design method (DOE) was used to numerically optimize the three software parameters simultaneously. The DOE predictions were verified by real experiments and an example of the results of the simultaneous optimization of the three calibration parameters at each of the engine operating points is shown in Figure 4. In this case, the optimization has been carried out to minimize NOx emissions with GTL diesel fuel. Reductions of between 30% and 75% were obtained, without compromising the other emissions, when compared to EU diesel.

Data measured at the five stationary test points were used to predict emissions throughout the NEDC test cycle. Empirical factors were used to take into account the differences between the

Transient and steady state engine operation. All the results of the selected operating points have been standardized and combined in a universal graph, shown in Figure 5, to mimic the behavior in an NEDC test with an optimized calibration for each fuel. A surprisingly large reduction in hollin and NOx seems to be possible for GTL diesel fuel and combinations UE50 5 and UE80. These reductions are possible without hardware changes with respect to the engine.

The pure GTL would allow a simultaneous hollin and NOx reduction of at least 35% compared to the EU diesel calibration. A 45% NOx reduction seems possible for a constant engine hollin emission. Due to the non-linear response with the GTL combinations, reductions in hollin and NOx that are greater than expected when considering the combination ratio could be obtained with fuels 10 UE80 and UE50. Figure 6 graphically depicts this nonlinear response.

A 50% GTL combination would recover approximately 85% of the hollin / NOx benefits of pure GTL, while a 20% GTL combination would recover approximately 48% of the benefit. It should be noted that the results shown to date have been provided only by a simple and economical adaptation of the software. Additional improvements are expected if additional hardware changes are taken into account, for example in the injection system and / or the combustion chamber design.

Claims (5)

1. Use of diesel fuel from gas to liquids (GTL) having a density at 152C below 0.78 kg / l, a sulfur content of less than 1 mg / kg, polyaromatic compounds below 0.1% en masse and an index of 5 cetane above 65, as a combination component for at least one diesel fuel derived from crude oil to reduce NOx and hollin emissions from the resulting diesel fuel composition, characterized in that the diesel fuel derived from crude oil has a density at 15 ° C below 0.85 kg / l, a sulfur content of less than 10 mg / kg, a content of polyaromatic compounds below 5% by mass and a cetane number of from 51 to 60, with which NOx and hollin emissions of the resulting diesel fuel composition 10, when burned in an engine, are reduced non-linearly to a greater degree than would be expected when considering the reason for combining GTL diesel with respect to to diesel fuel derived from crude oil. 2. Use according to claim 1, wherein a ratio of GTL diesel derived from crude oil of 1: 1 is used, 15 being the reductions in emissions of both NOx and hollin for said reason greater than 70% of the reduction obtained with a 100% GTL diesel fuel. 3. Use according to claim 1, wherein a ratio of GTL diesel: derived from crude oil of 1: 4 is used, the reductions in both NOx and hollin emissions for said reason being greater than 40% of the 20 reduction obtained with a 100% GTL diesel fuel. 4. Use according to claim 1, wherein the ratio of GTL diesel to crude oil derivative is from 99: 1 to 1:99 and the composition of diesel fuel produced has a molar ratio of H: C of between 1.8: 1 and 2.1: 1. 25 5. Use according to claim 4, wherein the molar ratio of H: C is from 1.9: 1 to 2.00: 1.