Patent Application
20190309232
The present invention relates to a mixture of liquid fuels for boiler or diesel engine, comprising specific compounds which reduce particle and nitrogen oxide emissions from boilers and diesel engines during their operation.
From the perspective of fighting greenhouse gases, diesel engines are effective engines because, at equivalent power, they emit about 20% less greenhouse gases than gasoline engines. Just the same they are increasingly criticized because of certain emissions harmful to people, in particular particle and nitrogen oxide emissions. In some major urban centers, even some entire regions, air pollution from these emissions constitutes a major problem.
In many countries, particle and nitrogen oxide emissions from diesel engines are regulated. This is notably the case in Europe where the limits set by regulations are increasingly strict (Euro6 standards currently). This is also the case in other major countries, in particular the United States, but with very low limits in some states such as those set by the California Air Resources Board.
Particles are subject to two categories of measurements:
Particle sizes are varied. Generally, four categories of small particles are recognized: PM10 with a diameter under 10 μm, PM2.5 with a diameter under 2.5 μm, ultrafine particles with a diameter under 0.1 μm and nanoparticles characterized by a diameter under 50 nm.
Most particles emitted from diesel engines have a diameter under 1 μm. They therefore represent a mixture of fine or ultrafine particles and nanoparticles. The smallest are considered the most dangerous for humans.
For 30 years diesel engines have made remarkable progress through the improvement of the quality of fuels (reduction of sulfur content), of the combustion process (optimization of injection systems) and in the methods for exhaust gas treatment (e.g. exhaust gas recirculation, catalytic oxidation systems and particle filters). Despite a reduction of particle emissions from new engines of order 98% over some 30 years, the problem of particles is seen as sufficiently serious that some urban centers have reached the point that they want to ban diesel vehicles in the city. This is due in particular to the fact that diesel vehicles are kept for many years (8 to 10 years for personal vehicles and often over 15 years for trucks and buses).
In addition to emission reduction measures on new vehicles and the promotion of alternative energies (e.g. electric vehicles or natural gas vehicles), it would be very useful to find solutions for existing diesel engine vehicles.
The same problems with particle and nitrogen oxide emission are encountered with liquid fuels for boilers, in particular with old boilers for which the contribution to particle and nitrogen oxides pollution is also very significant.
The goal of the present invention is to address these problems and in particular to provide a simple, effective and economical solution for reduction of emissions from diesel engines and liquid fuel boilers.
For that purpose the invention proposes to incorporate in the diesel engine fuel or the boiler fuel one or more specific esters and one or more specific alkanes together, in addition to those which could already be present in the fuel.
Before the 1990s, biofuels for diesel engines did not exist whereas ethanol had been used in gasoline for a long time, in particular in Brazil and the United States.
Starting around 1992, the use of biodiesel, which is a methyl (or ethyl) ester of vegetable oil, started to be developed in France, and then in Europe and in the world. Today, various types of esters are used depending on the origin of the fats which are transesterified by an alcohol: vegetable oils, animal fats or recovered fryer oils. It involves esters of fatty acids where the length of the chain is primarily included between 16 and 18 carbon atoms. These products are generally incorporated in ordinary diesel fuel at a level below 8% or else they are used at 20% or 30% or, as an exception, pure in captive transport fleets. But the improvements that can be achieved in the area of particle reduction with such mixtures are limited (reduction of the order of half the rate of incorporation of esters). Further, these esters tend to increase the nitrogen oxides. They are subject to the European standard EN14214 and to similar standards, elsewhere in the world, and the rate of incorporation in ordinary diesel fuel is generally limited to 8% by volume, in particular for this reason.
Other biofuels, in particular alkanes from biomass, are starting to be developed, whether they are vegetable oils or hydrotreated animal fats (treated with hydrogen to eliminate oxygen atoms) which also have 16 to 18 carbon atoms or else BTL (Biomass to Liquid) type products from biomass gasification followed by Fischer-Tropsch synthesis. Other solutions were developed, still experimentally, such as hydrotreated oils from pyrolysis and alkanes which can be obtained by anaerobic fermentation of biomass followed by Kolbe electrolysis (patent application WO 2014/170603).
These hydrocarbons are interesting because in general they have a high cetane number which supports a reduction of NOx emissions. However the effect on particles remains limited.
Further, the addition of various oxygenated compounds (e.g. alcohols or esters) to fuels has been proposed for several years—for goals that were not reduction of particle emissions, but the improvement of other functions (e.g. improvement of cold resistance, lubricating power, impact on agriculture, impact on greenhouse effect, etc.), for example:
Tests have also been done on the use of aldehydes in diesel fuel (Reducing the Emission of Particles from a Diesel Engine by Adding an Oxygenate to the Fuel Environmental Science and Technology 39(16):6260-5⋅September 2005) with an objective of reducing emitted particles, but the emissions of acetaldehyde, which is also thought to be dangerous, were greatly increased.
Nonetheless, none of these solutions led to a satisfactory solution with which to reduce particle emissions and nitrogen oxide emissions during operation of boilers and diesel engines.
The present invention specifically targets the incorporation in diesel fuels or liquid fuels for boilers chosen among diesel fuel and home heating oil:
Where the ester(s) with a chain length included between 8 and 14 carbon atoms incorporated in the fuel represented between 1% and 80% by volume of said mixture and where the alkane(s) with a chain length included between 8 and 14 carbon atoms incorporated in the fuel represent between 1% and 80% by volume of said mixture.
In the meaning of the invention, biosourced is understood to mean products coming from biomass, meaning agricultural or forest plants or organic waste.
It should be noted that biosourced esters and alkanes can be distinguished from esters and alkanes of petroleum origin present in a mixture because of dating based on mass spectrometer measurement of the proportion of the C14 isotope relative to all the carbon in the molecule. Fossil products have a smaller C14 concentration than products resulting from more recent photosynthesis.
While the esters are going to lower the particle emissions, it is important according to the invention to add alkanes with chain lengths included between 8 and 14 carbon atoms in addition to those which could already be present in the fuel, because an increase of the nitrogen oxide emission can be avoided that way.
The mixture according to the invention is a liquid mixture which has a variable composition. Advantageously, particle and nitrogen oxide emissions during operation of boilers and diesel engines can be reduced with such a mixture without the worsening of other emissions (e.g. nitrogen monoxide, CO, unburned hydrocarbons, HC, etc.). Also, with the invention the mixture can be made such that it meets all the specifications for liquid fuels, in particular, those which are the most difficult to meet, specifically: the flashpoint must be above 55° C. and the calculated cetane number which must be over 46. Further, the properties of the diesel engine fuel or liquid fuel for boilers—such as for example cold resistance, viscosity, etc.—can be retained with the mixture according to the invention.
The esters and/or alkanes used can in particular be biosourced, meaning be biofuels coming from agricultural or forest biomass or form organic waste, which also has an advantage for combatting the greenhouse gas effect.
The invention therefore aims for a mixture intended to supply a boiler or diesel engine, comprising:
Where the incorporated ester(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture, preferably between 5 and 50%, and where the incorporated alkane(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture, preferably between 5 and 50%.
The incorporated ester(s) with chain length included between 8 and 14 carbon atoms present in the mixture can be chosen among any ester with this size. It can preferably involve ethyl hexanoate (C8), butyl butyrate (C8), butyl valerate (C9), butyl hexanoate (C12) and/or butyl caprylate (C14). Preferably, it does not involve esters of higher fatty alcohols, meaning alcohols obtained from vegetable oil fatty acids that were reduced for example by hydrogenation and that are combined with a short acid such as formic acid or acetic acid.
The incorporated alkane(s) with chain length included between 8 and 14 carbon atoms present in the mixture can be chosen among the alkanes with this size (branched or unbranched). It can preferably involve decane, dodecane and tetradecane.
According to the invention, by specifically selecting esters with a chain length included between 8 and 14 carbon atoms, it will advantageously be possible to continue meeting all current specifications for diesel engine fuel and boiler fuel, including at an incorporation level between 1 and 8%, except for the maximum level of esters because the esters produced that way are not the methyl esters of fatty acids meeting the standard EN14214. Thus, according to a variant, the invention targets the mixture such as previously described in which the ester(s) with chain length included between 8 and 14 carbon atoms represent between 1% and 8% of the volume of said mixture. This mixture can be dispensed as an ordinary fuel in all distribution pumps.
Further, the esters used according to the invention can also be used at higher levels. Thus, according to another variant, the invention targets the mixture such as previously described in which the incorporated ester(s) with chain length included between 8 and 14 carbon atoms represent between 8% and 80% of the volume of said mixture, which will be distributed either as an ordinary fuel if it is approved for that use, or as a fuel for captive transport fleets.
Preferably, the ester(s) with chain length included between 8 and 14 carbon atoms present in the mixture are esters of biosourced origin obtained from volatile fatty acids coming from anaerobic biomass fermentation and esterification by an alcohol.
Likewise, a mixture is preferred in which the incorporated alkane(s) with chain length included between 8 and 14 carbon atoms present in the mixture are alkanes obtained by Kolbe electrolysis of volatile fatty acids coming from anaerobic fermentation of the biomass such as described in the application WO2014/170603 or from the biomass by gasification and Fischer-Tropsch synthesis.
The mixture according to the invention, in addition to the fuel, esters and alkanes of specific chain length, could contain at least one additional additive for improving the cetane number and/or increasing the reduction of particle emissions and/or reducing nitrogen oxide emissions by the boiler or diesel engine during operation thereof. It can involve for example tetranitromethane.
Other additives can be added to improve other functionalities of the mixture like cold resistance, viscosity, etc.
The mixture according to the invention can be obtained by other conventional techniques of the person skilled in the art. Preferably, it is obtained by a simple mixing of the constituents in a single tank or the mixing of two fluids in a single pipe. In most countries, such a mixing would have to be done under the control of the Customs Department.
The invention specifically targets a process for production of a mixture according to the invention such as previously described, which consists of incorporating in at least one liquid boiler fuel or diesel engine fuel chosen among diesel fuel or domestic fuel oil:
In a way that the incorporated ester(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture and where the incorporated alkane(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture.
Preferably, the mixing is done at a temperature included between 10 and 50° C. in a stirred tank or in a device where the various components are mixed by crossflow mixing.
Surprisingly and advantageously, with the mixture according to the invention, which incorporates specific esters and alkanes in diesel engine fuels or in boiler fuels, a very significant reduction of particle emissions is possible without a worsening of other emissions in particular nitrogen oxides and other emissions such as CO, HC, etc. The level of reduction of the particles by mass and count is of order twice the rate of incorporation (30% to 40% for 20% incorporation; 60% to 80% for 40% incorporation; and 80% to 90% for 50% incorporation), which constitutes a considerable advantage for reducing particle emissions in cities. Since there is a parallel reduction for particle mass and count, this process does not enhance smaller particles which are more dangerous.
The invention therefore specifically targets the use for supplying a boiler or diesel engine with a mixture comprising:
The incorporated ester(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture and where the incorporated alkane(s) with a chain length included between 8 and 14 carbon atoms represent between 1% and 80% by volume of said mixture.
In particular, the invention targets the use of the mixture in a boiler or diesel engine for reducing the particle emissions and/or reducing the nitrogen oxide emissions during operation thereof. Advantageously, the cetane number of the fuel can also be improved with the invention.
The mixture according to the invention can be used in any liquid fuel boiler and in any diesel engine, in particular in a fixed diesel engine or diesel engine installed in transportation vehicles or boats or worksite heavy equipment or agricultural equipment or small domestic equipment such as lawnmowers or rototillers.
In addition to the mixture according to the invention, at least one additive can be added in the boiler and/or the engine, where the additive is capable of improving the cetane number and/or improving the reduction of particle emissions and/or reducing the nitrogen oxide emissions by the boiler or the diesel engine during operation thereof, and/or at least one additive capable of improving other functions of the mixture like cold resistance, viscosity, etc.
The invention is now illustrated by examples of mixtures according to the invention and emission test results on an engine test bench showing their effectiveness.
The composition of the various mixtures tested is described in the table (examples 1 to 5 with various load rates which represent the number of RPMs of the engine compared to the nominal number of revolutions). These mixtures are obtained by simple mixing of components in jugs with manual agitation.
The measurements are done at the exhaust of a Renault brand car engine by a Horiba 9100 (CO, CO2, O2, HC and NOx) and PPS PEGASOR particle analyzer.
The results obtained are shown in the following table:
These results show that the alkanes do not have a significant favorable impact on the particle emissions, whereas the esters and alkanes together are unexpectedly able to very significantly reduce particles more or less proportionally to the ester level (drop of particles of order twice the level of incorporated esters) at the same time as a significant drop of NOx. In this respect, example 5 is very persuasive.
The other parameters (CO, HC) are not degraded. There is even a substantial drop of the CO. By adjusting the levels of esters and alkanes, it is thus possible to optimize emissions from diesel engines.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1655403 | Jun 2016 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/064432 | 6/13/2017 | WO | 00 |
