Method for determining an amount of at least one chemical compound

Abstract

The invention relates to a method for determining a value of a quantity relating to an amount of at least one chemical compound emitted by a combustion engine, the method comprising: - determining (100) an initial value of a quantity relating to an amount of hydrocarbons introduced into the combustion engine (1) and deducing therefrom an initial value of a quantity relating to an amount of carbon atoms introduced into the engine; - determining (400) the concentrations of a plurality of carbon-containing chemical compounds expected in the exhaust gases; - deducing (500), from the previously determined initial value of the quantity relating to the amount of hydrocarbons introduced into the combustion engine and from the concentrations of the plurality of carbon-containing chemical compounds, a final value of a quantity relating to an amount of carbon dioxide emitted into the exhaust gases, and deducing therefrom the value of the quantity relating to the amount of the compound. The invention also relates to an associated system.

Description

Method for determining the quantity of at least one chemical compound

[0001] The invention relates to the field of methods for determining the quantity of a chemical compound emitted by a heat engine.

[0002] It finds a particularly advantageous application for determining the quantity of a chemical compound emitted by a ship's heat engine. Technological background

[0003] In recent years, various reasons have motivated the need to measure emissions of gases and other components produced by ship propulsion in order to control and restrict them.

[0004] The overall objective is to reduce the exposure of marine and coastal ecosystems, marine and port operators, passengers and coastal populations to polluting emissions from ship engines into the atmosphere.

[0005] One of the tools of this strategy is to assign a rating to each ship based on the calculation of a carbon dioxide emission intensity index (CO2(CII)) (see resolution MEPC.352(78)). The calculation of this index is itself based on the assessment of the quantity, by mass, of greenhouse gases (GHGs) emitted by the ship.

[0006] The counting requirements for the calculation of the CII currently only concern carbon dioxide CO2 but will be extended to other GHGs, for example CH4 and N2O.

[0007] In the prior art, it is known to perform a direct measurement of such a quantity, for example for carbon dioxide (CO2): the mass of CO2 emitted is obtained by multiplying the total mass flow rate of the exhaust gases by the concentration of CO2 in those exhaust gases. It is also known to perform a calculation whereby the mass of CO2 emitted is obtained by multiplying the fuel mass flow rate by a predetermined factor depending on the fuel used.

[0008] The state-of-the-art method based on direct measurement offers low accuracy and reliability because volumetric or mass flow rates of exhaust gases are difficult to measure. There is no reliable mass flow meter solution for gases circulating at atmospheric pressure, high temperature, and with very low pressure drop. Volumetric flow meters for this type of application do exist (ultrasonic, Pitot tube, vortex, etc.), but they represent a high cost in terms of supply, installation, and maintenance. Furthermore, measuring volumetric flow rate would require conversion to mass flow rate, which would reduce the accuracy of the result.

[0009] The calculation-based method provides satisfactory results for counting carbon dioxide, which is predictive: when a hydrocarbon molecule burns, it almost always produces CO2. The method allows for a rapid assessment of CO2 mass flow rates, and therefore of cumulative masses over time, simply from a mass flow rate measurement of the fuel in question, or even from a change in the fuel used over time, while eliminating the need for (i) a concentration measurement, and (ii) a measurement of emission flow rate.

[0010] However, other carbon-based chemical compounds emitted by the engine, such as methane (CH4), are gases resulting from the naturally imperfect operation of an engine. Their quantities therefore cannot be calculated deterministically. The method does not allow for the evaluation of unburned fuel and thus does not allow for the assessment of engine CH4 or N2O emissions.

[0011] Furthermore, the predetermined factor used in the calculation-based method is determined based on the family of fuel used and is not precisely adapted to the fuel used, resulting in inaccuracy.

[0012] Future maritime transport regulations plan to use empirical formulas developed from engine tests on test benches at deliberately restrictive operating conditions. It is highly likely that these formulas will produce inflated results and therefore be detrimental to ship owners.

[0013] One idea behind the invention is to provide accurate and reliable results for determining the amount of a carbonaceous chemical compound emitted in the exhaust gases of a heat engine.

[0014] According to one embodiment, the invention provides a method for determining the value of a quantity relating to a quantity of at least one chemical compound, said chemical compound being emitted by a heat engine fueled at least partially by hydrocarbons, comprising the following steps: - determining an initial value of a quantity relating to a quantity of hydrocarbons introduced into the heat engine and deducing therefrom an initial value of a quantity relating to a quantity of carbon atoms introduced into the engine, - determining the concentrations of a plurality of expected carbon-based chemical compounds in the exhaust gases, - deducing, from said initial value of the quantity relating to the quantity of hydrocarbons introduced into the heat engine determined previously and from the concentrations of said plurality of expected carbon-based chemical compounds measured in the exhaust gases,a final value of a quantity relating to the amount of carbon dioxide released in the exhaust gases and deduce from this the said value of said quantity relating to the amount of the chemical compound emitted in the exhaust gases.

[0015] Thanks to these characteristics, it is possible to determine the quantity of the chemical compound emitted accurately and reliably. No exhaust gas flow measurement is required.

[0016] According to one embodiment, - the quantity relating to the amount of at least one chemical compound is a mass flow rate of the chemical compound or a mass, - the quantity relating to the amount of hydrocarbons introduced into the heat engine is a mass flow rate or a mass, - the quantity relating to the amount of carbon atoms introduced into the engine is a molar flow rate or a number of moles, - the quantity relating to the amount of carbon dioxide released in the exhaust gases is a molar flow rate or a number of moles.

[0017] According to one embodiment, - the quantity relating to the amount of at least one chemical compound is a mass, - the quantity relating to the amount of hydrocarbons introduced into the heat engine is a mass flow rate, - the quantity relating to the amount of carbon atoms introduced into the engine is a molar flow rate, - the quantity relating to the amount of carbon dioxide released in the exhaust gases is a molar flow rate, a value of a mass flow rate of the chemical compound is determined and the mass of the chemical compound emitted in the exhaust gases is deduced from this value by integrating the mass flow rate determined during this time.

[0018] According to one embodiment, for a given composition of hydrocarbons supplying the heat engine, a value of a quantity characteristic of the hydrocarbon composition is determined depending on a reference ratio between a number of carbon atoms and a number of hydrogen atoms characteristic of this hydrocarbon composition, and this value of the characteristic quantity is taken into account to determine the initial value of the quantity relating to the amount of carbon atoms introduced into the heat engine.

[0019] According to one embodiment, the engine is powered by two fuels of different compositions, each having a reference ratio, and said characteristic quantity depends on the reference ratios of the two fuels.

[0020] According to another embodiment, said characteristic quantity is equal to the inverse of the sum of the molar mass of carbon and the ratio between the molar mass of hydrogen and the reference ratio.

[0021] According to one embodiment, said characteristic quantity is equal to a conversion factor between the consumption of hydrocarbons of the heat engine and the emission of carbon dioxide by this heat engine.

[0022] According to one embodiment, said characteristic quantity is equal to the reference ratio.

[0023] According to one embodiment, the final value of the quantity relating to the amount of carbon dioxide released in the exhaust gases is deduced from the initial value of the quantity relating to the amount of carbon atoms introduced into the heat engine and from each ratio between the concentration of each expected carbon chemical compound in the exhaust gases and the concentration of carbon dioxide in these exhaust gases.

[0024] According to one embodiment, the expected carbonaceous chemical compounds comprise at least carbon dioxide and carbon monoxide, and the chemical compound is chosen from one of the following chemical compounds: carbon dioxide, methane, carbon monoxide, nitrous oxide, nitrogen oxides, sulfur oxides.

[0025] According to one embodiment, the concentrations of at least some of the expected carbonaceous chemical compounds in the exhaust gases are measured using a gas analysis device by gas spectrometry.

[0026] According to one embodiment, at least one exhaust gas sample is taken from said internal combustion engine, this sample is cooled and / or the water vapor is removed from this sample before it passes through the gas analysis device.

[0027] According to one embodiment, the value of the quantity relating to the amount of the chemical compound emitted in the exhaust gases is deduced from the final value of the quantity relating to the amount of carbon dioxide released in the exhaust gases and from the ratios between the concentration of each expected carbonaceous chemical compound in the exhaust gases and the concentration of carbon dioxide in these exhaust gases.

[0028] According to one embodiment, the invention also provides a system for determining the value of a quantity relative to a quantity of at least one chemical compound, said chemical compound being emitted by a heat engine fueled at least partially by hydrocarbons, comprising a computer unit including one or more processors programmed to implement the following steps: - determine an initial value of a quantity relative to a quantity of hydrocarbons introduced into the heat engine and deduce therefrom an initial value of a quantity relative to a quantity of carbon atoms introduced into the engine, - determine the concentrations of a plurality of expected carbon-based chemical compounds in the exhaust gases, including carbon dioxide, - calculate,Based on the aforementioned initial value of the quantity relating to the amount of hydrocarbons introduced into the internal combustion engine, determined previously, and the concentrations of the aforementioned plurality of carbonaceous chemical compounds in the exhaust gases, a final value of a quantity relating to the amount of carbon dioxide released in the exhaust gases is to be determined, and from this, the aforementioned value of the quantity relating to the amount of the chemical compound emitted in the exhaust gases is to be deduced.

[0029] According to one embodiment, this determination system further comprises a gas analysis device by gas phase spectrometry.

[0030] According to one embodiment, the system further includes a fuel analysis device.

[0031] According to one embodiment, the invention further relates to a ship equipped with a system as described above. Brief description of the figures

[0032] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings.

[0033] The diagram schematically represents the steps of a method for determining the quantity of at least one chemical compound, said chemical compound being emitted by a heat engine fueled at least partially by hydrocarbons.

[0034] The diagram schematically represents a system for determining such a quantity, adapted to implement the method of the.

[0035] We have schematically represented on the steps of a method for determining a value of a quantity relating to a quantity of at least one chemical compound emitted by a heat engine fueled at least partially with hydrocarbons.

[0036] Lare represents schematically a system 20 implementing this method in a transport vehicle equipped with three internal combustion engines 1.

[0037] Each internal combustion engine 1 typically receives air and fuel 2 as intake components. The fuel 2 may include, for example, a primary fuel and a secondary fuel called a "pilot fuel," used to initiate combustion. The primary fuel and / or the pilot fuel may contain hydrocarbons. Exhaust gases 3 are expelled from the engine 1.

[0038] In particular, the fuel may consist of: either only a main fuel of the liquid hydrocarbon type, or a main fuel other than hydrocarbons for example methanol, ethanol or ammonia and a pilot fuel of the liquid hydrocarbon type, or only a main fuel of the gaseous hydrocarbon type.

[0039] The transport vehicle is, for example, a ship, in particular a methane tanker or a ship using Liquefied Natural Gas as fuel.

[0040] The system 20 for determining a value of a quantity relating to a quantity of at least one chemical compound emitted by a heat engine fueled at least partially by hydrocarbons includes in particular a computer unit 11 comprising one or more processors programmed to implement the method described below and one or more memories.

[0041] Using the method described below, it is possible to evaluate the quantity emitted of a chemical compound, based on the following data: – a measured value of the overall fuel flow rate, – a measured value of the concentrations of the expected carbonaceous chemical compounds in the exhaust gases and of the chemical compound emitted in the exhaust gases.

[0042] The chemical compound whose quantity is determined by the method according to the invention includes, for example, one of the following carbonaceous chemical compounds: carbon dioxide CO2, methane CH4, carbon monoxide CO.

[0043] In the following description, we consider in particular the case where we determine the quantity of carbon dioxide, carbon monoxide and methane emitted by the heat engine.

[0044] It may also include another non-carbon chemical compound such as nitrous oxide N2O or nitrogen oxides NOx or sulfur oxides SOx.

[0045] In this case, the concentration of this non-carbon chemical compound in the exhaust gases is further determined, as will be described in detail below.

[0046] The proposed method consists of considering that all the carbon atoms C entering the heat engine are supplied by the fuel, and that these C atoms are either transformed (by oxidation) into CO2 and CO, or are unburned, giving for example CH4, and expelled in the exhaust gases.

[0047] In what follows, we consider the quantity of carbon atoms supplied by the air introduced into the internal combustion engine to be negligible compared to the quantity of carbon atoms contained in the fuel. Indeed, the air admitted into the engine as combustion air contains only ~0.042% CO2 by volume. which will not react during combustion.

[0048] It is therefore assumed that all the carbon atoms introduced into the engine and then transformed into CO2 / CO or released as unburned matter come from the fuel alone.

[0049] Carbon fuels, known and used in industry and particularly in the maritime sector, consist almost exclusively of hydrocarbons containing chemical compounds of the C-alkane type. n H 2n+2 , alkenes C n H 2n and all types of cyclic and acyclic unsaturated hydrocarbon compounds, all being chains consisting exclusively of hydrogen and carbon atoms. These compounds contribute a number of carbon atoms n C and a number of hydrogen atoms n H to the internal combustion engine. We will also describe below the case of methanol and ethanol, which also contain carbon atoms.

[0050] In the case of liquid fuels (Fuel Oil ISO8217), the non-carbon chemical compounds of the fuel are: - sulfur compounds, which can amount to up to ~5% by mass for residual fuels such as Heavy Fuel Oil (HFO), - heavy metals, - dissolved gases, - various particles and solid residues.

[0051] For the last three types, the fractions are negligible. However, the method can take into account the mass fraction of sulfur contained in the fuel in question.

[0052] In the case of gaseous fuels such as liquefied natural gas or liquefied petroleum gas (LNG, LPG), the non-carbon chemical compounds of the fuel are: - nitrogen compounds dissolved up to ~1.5% by mass maximum, - other gases dissolved in negligible quantity.

[0053] The process according to the invention comprises the following steps: - an initial value of a quantity relating to the quantity of hydrocarbons introduced into the heat engine 1 is determined, and an initial value of a quantity relating to a quantity of carbon atoms introduced into the engine is deduced from this, - the concentrations of the expected carbonaceous chemical compounds in the exhaust gases 3 are determined, - a final value of a quantity relating to a quantity of carbon dioxide released in the exhaust gases 3 is deduced from said initial value of the quantity relating to the quantity of hydrocarbons introduced into the heat engine 1 determined previously and from the concentrations of the expected carbonaceous chemical compounds in the exhaust gases 3, and said value of said quantity relating to the quantity of the chemical compound emitted in the exhaust gases 3 is deduced from this.

[0054] Here, a "quantity relative to a quantity" is understood to mean a quantity that represents that quantity. A quantity relative to a quantity can generally be one of the following: a mass flow rate, a mass, a volumetric flow rate, a volume, a molar flow rate, a number of moles.

[0055] In particular, here, - the quantity relating to the amount of at least one chemical compound is a mass quantity, for example a mass flow rate or a mass, - the quantity relating to the amount of hydrocarbons introduced into the heat engine is a mass quantity, for example a mass flow rate or a mass v, - the quantity relating to the amount of carbon atoms introduced into the engine is a molar quantity, for example a molar flow rate or a number of moles, - the quantity relating to the amount of carbon dioxide released in the exhaust gases 3 is a molar quantity, for example a molar flow rate or a number of moles.

[0056] The mass of a chemical compound introduced into or emitted by the engine over a given time period can be obtained from the mass flow rate by integrating it over that time period. It can be obtained from the volumetric flow rate by integrating it over the same time period and multiplying the result by the density of the chemical compound. It can be obtained from the volume by multiplying it by the density of the chemical compound. It can be obtained from the molar flow rate by integrating it over the same time period and multiplying the result by the molar mass of the chemical compound. It can be obtained from the number of moles by multiplying it by the molar mass of the chemical compound.

[0057] The number of moles of a chemical compound introduced into the engine or emitted by the engine during a fixed time period can be obtained from the molar flow rate by integrating it over that time period.

[0058] According to a preliminary step, the mass flow rate of hydrocarbons introduced into the internal combustion engine by the fuel is determined (block 100 of the).

[0059] This determination can be made on the basis of a measurement or on the basis of an estimate or a precise calculation.

[0060] To this end, the system 20 includes at least one sensor 7 located in the fuel supply circuit of at least one internal combustion engine 1. This is, for example, a mass or volumetric flow meter measuring the mass or volume of fuel entering the internal combustion engine 1 per unit of time. As shown by an arrow in the figure, the data measured by the sensor 7 is transmitted to the computer unit 11. The mass flow rate can be deduced from the volumetric flow rate by multiplying the latter by the density of the hydrocarbons.

[0061] In the case where the vehicle in question has several internal combustion engines 1, a flow meter is preferably provided on the supply circuit path of each internal combustion engine 1 or a single flow meter measuring the supply of all the internal combustion engines together.

[0062] As mentioned above, the total mass flow of fuel measured includes a non-carbon portion.

[0063] The mass flow rate of hydrocarbons in the fuel is deduced by subtracting from the total mass flow rate of fuel measured the mass flow rate of non-carbon fuel, namely the mass flow rate of fuel consisting of sulfur or nitrogen chemical compounds, i.e. 5% of the total mass flow rate for liquid fuel and 1.5% of the total mass flow rate for gaseous fuel.

[0064] In other words, the hydrocarbon mass flow rate of the fuel is equal to 95% of the total mass flow rate for a liquid fuel type fuel and 98.5% of the total mass flow rate of the fuel for a gaseous fuel type fuel.

[0065] It is possible to consider any other method of determination, for example the reception of this information by the computer unit 11 or its determination from tabulated or estimated fuel hydrocarbon consumption data.

[0066] For this determination, all carbonaceous chemical compounds entering the engine are taken into account, in particular the hydrocarbons of the main fuel alone if no pilot fuel is used, the hydrocarbons of the main fuel and pilot fuel introduced into the heat engine if pilot fuel is used or the hydrocarbons of the pilot fuel alone if the main fuel does not contain hydrocarbons.

[0067] We will see in the following detailed examples in which the engine is powered solely by a primary fuel or by a primary fuel and a secondary fuel.

[0068] According to another preliminary step, a value of a quantity characteristic of the composition of these hydrocarbons is further determined for a given composition of the hydrocarbons powering the heat engine 1, depending on a reference ratio R C / H between a number of carbon atoms and a number of hydrogen atoms characteristic of this hydrocarbon composition (block 200 of the), i.e. R C / H = number of C / number of H = (mass % of C / mass % of H) * 1 / 11.915.

[0069]

[0070] The value of this quantity is calculated by the computer unit 11 or retrieved by it from a database. It can also be received by it using means of communication.

[0071] Computer unit 11 can be programmed to determine the reference ratio based on fuel composition data. This can be a predetermined reference ratio for a generic fuel type or a ratio determined based on the precise measured composition of the fuel used. In particular, the hydrocarbon composition can be determined to establish the reference ratio R C / H .

[0072] The hydrocarbon composition of the fuel can be measured by taking a sample from the fuel supply circuit of each internal combustion engine 1. For this purpose, as shown in the figure, the system can include a fuel sampling device 8 from the supply circuit of the internal combustion engines 1, a conditioning device 9 and an analysis device 10, for example by gas phase spectrometry.

[0073] The conditioning system includes, for example, a condenser, which is a system that produces cold and allows the water vapor to condense. This system cools the (initially hot) gases to a temperature acceptable for the analyzer (for example, no more than 40°C).

[0074] Computer unit 11 receives the analysis results from the analysis device and determines the reference report on this basis.

[0075] In the case where the fuel is almost exclusively composed of the same molecule, for example methanol, the reference ratio is calculated based on the C and H composition of this molecule.

[0076] In the case of fuel composed of a known and limited mixture of molecules, for example in the case of LNG, the concentrations of these molecules can vary from one tank refill to another and also over time during a journey. The concentrations of these molecules are then measured by the fuel analysis device 10 and used to determine the reference ratio.

[0077] In other cases, particularly when the fuel is composed of a mixture of molecules that is unknown and limited, the reference ratio cannot be easily calculated; it is measured upstream and provided by the supplier. Tabulated values ​​from the literature can be used.

[0078] The reference report is, for example, stored in the memory of computer unit 11.

[0079] We first describe here the case where each internal combustion engine of the vehicle is powered by a single fuel: the main fuel, without the addition of pilot fuel.

[0080] According to a first embodiment, the quantity is denoted α fuel and is equal to the inverse of the sum of the molar masses of carbon M C and the ratio between the molar mass of hydrogen and the reference ratio R C / H , according to the formula:

[0081]

[0082] According to a second embodiment, this quantity is equal to a conversion factor C F between the hydrocarbon consumption of the internal combustion engine 1 and the emission of carbon dioxide CO2 by this internal combustion engine 1.

[0083] This conversion factor is determined, for example, according to the type of fuel used. Its values ​​are standardized and listed in resolution MEPC.364(79), "2022 guidelines on the method of calculation of the attained energy efficiency design index for newships", paragraph 2.2.1.

[0084] The corresponding table is reproduced below:

[0085] Fuel type Conversion factor C F Diesel / Gasoline (e.g., ISO 8217 grade DMX to DMB) 3.206 Light Fuel (e.g., ISO 8217 grade RMA to RMD) 3.151 Heavy Fuel (e.g., ISO 8217 grade RME to RMK) 3.114 Liquefied Propane Gas (LPG, propane) 3.000 Liquefied Butane Gas (LPG, butane) 3.030 Liquefied Natural Gas (LNG) 2.750 Methanol (MeOH) 1.375 Ethanol (EtOH) 1.913

[0086] This magnitude C F is an approximation of the product of the characteristic quantity α fuel defined above and the molar mass of carbon dioxide.

[0087] In one step of said method (block 300 of the), a molar flow rate of carbon atoms introduced into the engine (n) is determined. C_fuel ) by the main fuel.

[0088] For this purpose, the value of the characteristic quantity α is taken into account. fuel , C F defined above and the mass flow rate of hydrocarbons introduced into the heat engine by the main fuel determined previously.

[0089] This step is performed by calculation by computer unit 11 of system 20.

[0090] According to the first embodiment in which the characteristic quantity α fuel is determined, we obtain the initial value of the molar flow rate of carbon atoms n C_fuel introduced into the heat engine by the following formula, by multiplying the initial value of the mass flow rate of hydrocarbons m C Hx _fuel introduced by the value of the characteristic quantity α fuel:

[0091]

[0092] Indeed, we have: m CHx_fuel = m C_fuel + m H_fuel with m C_fuel and m H_fuel the mass flow rate of carbon and the mass flow rate of hydrogen introduced into the engine.

[0093] That is: m CHx_fuel = n C_fue l * M c + n H_fuel * M H with n C_fuel and n H_fuel the molar flow rate of carbon and hydrogen introduced into the engine and M c = 12.011 g / mol and M H = 1.008 g / mol.

[0094] That is: m CHx_fuel = n C_fuel * M c + (n C_fuel / R C / H ) * M H .

[0095] And finally: n C_fuel = m CHx_fuel * αfuel.

[0096] According to the second embodiment in which the characteristic quantity C F is determined, we obtain the initial value of the molar flow rate of carbon atoms n C_fuelintroduced into the internal combustion engine by the main fuel using the following formula, by multiplying the initial value of the hydrocarbon mass flow rate m C Hx _fuel introduced by the value of the characteristic quantity C F and by dividing this product by the molar mass of carbon dioxide CO2.

[0097]

[0098] As presented in the assumptions stated above, the proportion of carbon atoms supplied by the air is negligible, and it is therefore assumed that all the carbon atoms contained in the exhaust gases come entirely from the hydrocarbons of the main fuel, i.e., n C_ exh = n C_fuel + n C_ air = nC_fuel, avec nC_exhle débit molaire de carbone dans les gaz d’échappement, nC_fuelle débit molaire de carbone dans le carburant introduit dans le moteur et nC_airle débit molaire de carbone dans l’air introduit dans le moteur.

[0099] According to another step of the method (block 400 of the), the concentrations of the expected carbonaceous chemical compounds in the exhaust gases are determined.

[0100] The carbonaceous part of exhaust gases consists mainly of CO2, but also potentially of CO, unburned CH4 and other unburned hydrocarbons.

[0101] Unburned hydrocarbons other than CH4 are not considered toxic pollutants or greenhouse gases and are present in negligible quantities. They are not taken into account in the following.

[0102] In other words, we determine that the concentration of unburned hydrocarbons other than methane is equal to zero for the remainder.

[0103] Therefore, we will have: n C_fuel = n C_exh = nCO2_exh+ nCO_exh+ nCH4_exh.

[0104] We measure at least some of the concentrations of the expected carbon-based chemical compounds. Preferably, we measure the concentrations of all the expected carbon-based chemical compounds.

[0105] The expected carbon-based chemical compounds include carbon dioxide and carbon monoxide and possibly methane.

[0106] If we know that the fuel cannot emit CH4, we only measure the concentrations of carbon dioxide (CO2) and carbon monoxide (CO). For fuel containing Liquefied Natural Gas, methane emissions are expected, and we also measure the methane concentration in the exhaust gases.

[0107] The system 20 includes an exhaust gas sampling device 4, and an analysis device 6 for the exhaust gases sampled, for example by gas phase spectrometry.

[0108] In order to cool and remove water vapor from the exhaust gases before they pass into the analysis device 6, the system 20 further includes a conditioning device 5 arranged in the path of the exhaust gases sampled by the sampling device 4, as described in more detail below.

[0109] In the case where the vehicle equipped with system 20 includes several internal combustion engines 1, system 20 may include one analysis device per engine or a single analysis device for which samples are taken successively from the exhaust duct of one engine and then another, for example according to variations in engine operating speed, or simultaneously from all the exhaust ducts of the engines.

[0110] This allows us to measure the concentration in the exhaust gases of each expected carbonaceous chemical compound in the exhaust gases: for example, the concentrations of carbon dioxide, carbon monoxide and methane.

[0111] It is also possible to measure, using the same technique, the concentration of at least one non-carbon chemical compound, such as nitrous oxide N2O, nitrogen oxides NOx and sulfur oxides SOx.

[0112] The concentration of said carbonaceous or non-carbonaceous chemical compound in the exhaust gases is measured, for example, using a gas analysis device by gas spectrometry.

[0113] For this purpose, at least one exhaust gas sample 3 is taken from said internal combustion engine 1.

[0114] With a remote infrared gas spectrometry analysis device, the actual concentrations of exhaust gas chemical compounds 3 in the exhaust duct cannot be directly measured.

[0115] The exhaust gas sample taken from the exhaust pipes must be conditioned before introduction into the analysis device 6: the sample taken is cooled and the water vapor is removed from this sample by passing through the conditioning device 5 before its analysis by gas phase spectrometry by the infrared spectrometer.

[0116] In the case where the vehicle in question has several internal combustion engines, it is preferable to take a sample of the exhaust gases from each internal combustion engine and to determine the quantity of the carbonaceous and, possibly, non-carbonaceous chemical compound emitted by all the internal combustion engines.

[0117] According to the ideal gas law, the volume concentrations of gases are equal to the molar concentrations of each of the gases constituting a mixture of ideal gases.

[0118] Under the pressure and temperature conditions of the gases entering the gas analysis device 6, the ideal gas law can be considered valid and can be applied.

[0119] Therefore, we can consider that the molar concentrations of the exhaust gases 3 entering the analysis device 6 are equal to the volumetric concentrations measured by the analysis device.

[0120] The analysis device 6 thus provides the molar concentrations xi_analyser of carbonaceous chemical compounds and the molar concentrations xj_analyser of non-carbonaceous chemical compounds of the analyzed exhaust gases .

[0121] As represented by an arrow on the, the analysis results of device 6 are transmitted to the computer unit 11. This unit thus receives measurement data of the concentration of expected carbonaceous chemical compounds in the exhaust gases.

[0122] According to another step of the method (block 500 of the), the initial value of the hydrocarbon mass flow rate m is deduced C Hx _fuel introduced into the previously determined internal combustion engine and the expected concentrations of carbonaceous chemical compounds in the exhaust gases, x i _analyser measured in exhaust gases, a final value of the molar flow rate of carbon dioxide n CO2_exhreleased in the exhaust gases.

[0123] This determination is made taking into account that all the carbon C present in the fuel ends up in the exhaust gases mostly as CO2, and in smaller quantities as CO and CH4.

[0124] This step is performed by calculation using computer unit 11.

[0125] More precisely, we deduce the initial value of the molar flow rate of carbon atoms n C_fuel introduced into the heat engine from the initial value of the mass flow rate of hydrocarbons introduced into the engine taking into account the characteristic quantity of the composition of the hydrocarbons, as described above.

[0126] Then, we deduce the final value of the molar flow rate of carbon dioxide n CO2_exh released in the exhaust gases based on the initial value of the molar flow rate of carbon atoms n C_fuelintroduced into the heat engine and the sum of the ratios between the concentration of each carbonaceous chemical compound x i _ analyser measured in the exhaust gases by the analysis device, including carbon dioxide, and the carbon dioxide concentration xCO2_analyzed measured in these exhaust gases, for example according to the formula:

[0127]

[0128] Indeed, for two chemical compounds i and y: n i = x i * n total and n y = x y * n total , and therefore, n i = x i / x y .

[0129] More specifically, here we deduce the final value of the molar flow rate of carbon dioxide n CO2_exh released in the exhaust gases based on the initial value of the molar flow rate of carbon atoms n C_fuelintroduced into the internal combustion engine and the sum of the ratios between the concentration of each other expected carbon-based chemical compound in the exhaust gases and the concentration of carbon dioxide xCO2_analyzed in these exhaust gases. For example, here the concentrations of carbon dioxide, carbon monoxide, and methane are determined using the formula:

[0130]

[0131] Indeed, we have the following relationship:

[0132] Where x CO 2 _exh denotes the concentration of CO2 in the exhaust gases sampled,x CO_exh denotes the concentration of CO in the exhaust gases sampled,x C H4 _exh denotes the concentration of CH4 in the exhaust gases sampled,n CO2_exh denotes the molar flow rate of CO2 emitted in the exhaust gases 3.

[0133] Either :

[0134]

[0135] And :

[0136]

[0137] As explained above, the exhaust gas sample taken from the exhaust pipes is dried before introduction into the analysis device 6.

[0138] The sample is therefore altered and the concentrations measured by the analysis device are therefore different from the actual concentrations in the exhaust pipes.

[0139] However, drying the sample only reduces the amount of moisture in the sample taken.

[0140] For all compounds i and y that are not affected by drying, the quantities are conserved and there is equality between the number of moles of chemical compound i or y in the sample taken (n i_sample , n y_sample ) and in the analyzed sample, that is, with n t total_sample the total number of moles of the sample taken and n t otal_ analyserthe total number of moles in the analyzed sample:

[0141] n i_sample = ni_analyser= xi_sample* ntotal_sample= xi_analyser* ntotal_analyser,

[0142] n y_sample = n y _ analyser = x y_sample * n t otal_ sample = xy_analyze* n t otal_ analyser .

[0143] And: x i_sample / x y_sample = xi_analyze / xy_analyzer .

[0144] Finally, we consider that the concentrations in the exhaust gases are the same as in the sample taken, therefore x i_exh / xy_exh= xi_analyser / xy_analyser.

[0145] Since the calculation method uses concentration ratios, it is then possible to use the concentration measurements from the gas analysis device without correcting the values ​​obtained.

[0146] According to another step of the method (block 600), the mass flow rate of the chemical compound emitted in the exhaust gases is determined. This step is performed by calculation using computer unit 11.

[0147] To determine the mass flow rate value of each carbonaceous chemical compound m i _ exh emitted in the exhaust gases, a final value for the molar flow rate of each carbonaceous chemical compound n is deduced. i_exh released in the exhaust gases, the final value of the mass flow rate of carbon dioxide released in the exhaust gases, and the ratio between the concentration of said carbonaceous chemical compound x i_analysermesurée dans les gaz d’échappement et la concentration de dioxyde de carbone xCO2_analyserdans ces gaz d’échappement.

[0148] On an i_exh = n CO2_exh . xi_analyser / xCO2_analyser.

[0149] This final value of the molar flow rate of the carbon-based chemical compound is then multiplied by the molar mass of the carbon-based chemical compound. Finally, the mass flow rate of each carbon-based chemical compound can be obtained using the formula: m i _ exh = n i _exh * Mi= Mi* nCO2_exh* xi_analyser / xCO2_analyser.

[0150] The mass flow rate of carbon dioxide emitted is determined directly by multiplying the molar flow rate of carbon dioxide by the molar mass of carbon dioxide.

[0151] We have the following formula: m CO2_exh = n CO2_exh *M CO2 .

[0152] For all non-carbon chemical compounds of the type nitrous oxide N2O, nitrogen oxide or sulfur oxide whose concentration in the exhaust gases is determined by the analysis device 6, the same formula applies and on an j_exh = n CO2_exh * x j _analyser / xCO2_analyzer .

[0153] In other words, the same steps are performed for a non-carbon chemical compound. A final value for the molar flow rate of each non-carbon chemical compound, n, is determined. j_exh released in the exhaust gases, the final value of the mass flow rate of carbon dioxide released in the exhaust gases, and the ratio between the concentration of said non-carbonaceous chemical compound x j_analysermesurée dans les gaz d’échappement et la concentration de dioxyde de carbone xCO2_analyserdans ces gaz d’échappement.

[0154] In practice, this is how it works:

[0155] m CO2_exh = n CO2_exh * M CO2 , with M CO2 = 44.01 g / mol,

[0156] m CH4_exh = n CO2_exh * M CH4 *x CH4_analyser / xCO2_analyser, avec MCH4= 16,04 g / mol,

[0157] m N2O_exh = n CO2_exh * M N2O * xN2O_analyze / xCO2_analyze, with M N2O= 44, 01 g / mol.

[0158] Once one or more values ​​of the mass flow rate of the chemical compound sought have been determined over a given period, the said value of the mass of the chemical compound emitted in the exhaust gases during this period is deduced by integrating the value(s) of the mass flow rate determined over this period.

[0159] When the main fuel is ammonia and the pilot fuel is hydrocarbons, the method described above is applied taking into account only the quantity of pilot fuel used, consisting of hydrocarbons.

[0160] In the case of internal combustion engines requiring the additional injection of pilot fuel composed of hydrocarbons in addition to the main fuel, the number of carbon atoms supplied by this pilot fuel is taken into account.

[0161] The reference ratio of the pilot fuel may differ from the reference ratio of the main fuel. In this case, a pilot fuel with a reference ratio R is considered. C / H_pilot The primary fuel has the reference ratio R C / H as described previously.

[0162] We will consider the parameter e m which corresponds to the mass proportion of hydrocarbons in the pilot fuel and hydrocarbons in the main fuel such that the mass flow rates of pilot fuel m CHx_pilot and main m CHx_fuel check:

[0163] m CHx_pilot = e m * m CH x _fuel .

[0164] We then have the molar flow rate of carbon atoms supplied by the pilot fuel as a function of the mass flow rate of hydrocarbons in the pilot fuel, which is written with a relationship similar to that established for the main fuel:

[0165] nC_pilot = m CHx_pilot * α pilot

[0166] with

[0167]

[0168] The total molar flow rate of carbon atoms n C_tot Therefore, what is introduced into the internal combustion engine(s) is:

[0169] n C_tot = n C_fuel+nC_pilot.

[0170] Let n C_tot = mCHx_fuel* αfuel+mCHx_pilot* αpilot= mCHx_fuel* αfuel+em*mCHx_fuel* αpilot.

[0171] We can then define an equivalent alpha relating to the main fuel:

[0172] n C_tot = mCHx_fuel* (αfuel+em* αpilot) = mCHx_fuel* αequi.

[0173] with α equi = α fuel + e m * α pilot .

[0174] The method is then similar to that described previously for the case where only one main fuel is used. The same formulas are used, replacing n C_fuel by n C_tot .

[0175] We then have: n CO2_exh = n C_tot / (1 + x CO_analyser / xCO2_analyser+ xCH4_analyser / xCO2_analyser).

[0176] In the case where the internal combustion engine is fueled by methanol CH3-OH or ethanol C2H5-OH, the use of these fuels will only produce CO2 and no CH4 or N2O.

[0177] The established formulas and the method described above can nevertheless be applied. For methanol, we then have:

[0178] m CHx_fuel = n C_f ue l * (M C + 4* M H +M O ) = n C_f ue l * M CH3-OH and α fuel = 1 / M CH3-OH

[0179] M CH3-OH =32.04 g / mol and α fuel = 0.03121.

[0180] For ethanol:

[0181] m CHx_fuel = n C_f ue l * (2*M C + 6* M H +M O ) = n C_f ue l * M C 2H5 -OH and α fuel = 2 / M C 2H5 -OH

[0182] M C 2H5-OH =46.068 g / mol and α fuel = 0.04341.

[0183] In the case of using a sulfur-containing fuel, such as liquid hydrocarbon fuels, the mass of sulfur compounds is subtracted from the total mass of the fuel as described above.

[0184] In the case of residual heavy fuels containing too high a sulfur content, regulations require the implementation of a scrubber, an engine exhaust fume cleaning system (EGCS).

[0185] The main action of scrubbers is to reduce SOx (SO2 and SO3 in particular), that is to say to limit the quantity of these molecules released in the exhaust gases.

[0186] During the combustion of a sulfur-containing fuel, sulfur atoms (S) are primarily transformed into sulfur oxides (SOx), mainly SO2, with SO3 representing less than 4% of the SOx. The remaining fraction of sulfur atoms contributes to the formation of various soot particles. The mass fraction of these soot particles is negligible.

[0187] Sulfur does not affect the formation of CO2 and CO in liquid hydrocarbon fuels. The action of a scrubber, regardless of its removal rate, does not influence the determination method presented above. The method described below can therefore be used with or without a scrubber.

[0188] Therefore, provided that the mass of sulfur to be subtracted from the mass of fuel for the calculation of the hydrocarbon mass share has been correctly quantified, it is not necessary to take into account the action of the scrubber and its effectiveness.

[0189] In the case of liquefied natural gas (LNG) used as fuel, it has already been explained above that the mass of dissolved nitrogen (whatever its quantity) must be subtracted from the total mass of fuel supplied to the engines.

[0190] The fuel supply for the thermal engines of an LNG-powered vessel is a mixture of naturally evaporated gas and vaporized LNG, which means that the nitrogen content and corresponding mass flow rate are not predetermined and vary according to operating conditions and operator demand. These values ​​are therefore measured.

[0191] The LNG from Arzew, for example, is one of the most loaded with dissolved nitrogen, containing 0.71% molar percentage, or ~1.23% by mass.

[0192] It is estimated that naturally evaporated LNG contains ~15.54% dissolved nitrogen by molar percentage, or ~24.3% by mass.

[0193] Therefore, if only natural boil-off gas is consumed, the corresponding CO2 calculation based on the total fuel flow in the internal combustion engine would be overestimated by 24.3%. Subtracting the amount of sulfur compounds is thus an important correction to improve the accuracy of determining the amount of CO2 emitted.

[0194] The following table gives the typically determined reference ratios and the quantities α fuel corresponding for different types of fuel.

[0195] Fuel type Designation Main characteristics Reference ratio R C / H Magnitude α fuelMarine Fuel MGO Fuel #2, Bunker A 0.53-0.56 0.0718-0.0724 MDO Fuel #3: 10% Fuel #6 max + 90% Fuel #2 0.52-0.56 0.0716-0.0724 NFSO Fuel #5, Bunker B: 75-80% Fuel #6 + 20-25% Fuel #2 0.48 0.0710 IFO 180, IFO 380 90% Fuel #6 + 10% Fuel #2 0.57-0.64 0.0726-0.0736 HFO, RFO Fuel #6, Bunker C Liquefied Petroleum Gas Propane C3 100% 0.40.0688 Butane C4 i / n 100% 0.3750.0680 Propane / Butane Mixture C3 / C4 50 / 50% 0.3900.0685 Pure Ethane C2 100% 0.33330.06651 Cargo Ethane 0.33370.06653 Liquefied Natural Gas (LNG) Pure Methane CH4 100% 0.2500.0623 Alaska C1 99.7% 0.2500.0623 Brunei C1 90.2% 0.2680.0634 Libya C1 82.57% 0.2750.0638

[0196] System 20 is used, for example, on ships, including LNG carriers or ships using Liquefied Natural Gas as fuel.

[0197] Some of the elements of computer unit 11 can be implemented in various forms, either individually or in a distributed manner, using hardware and / or software components. Usable hardware components include ASICs (Automatic System Integrated Circuits), FPGAs (Field Programmable Gate Arrays), and microprocessors. Software components can be written in various interpreted or compiled programming languages, such as C, C++, Java, Python, SQL, or VHDL. This list is not exhaustive.

[0198] Using the method and system described above, the quantity of chemical compounds released in the exhaust gases of an engine at least partially fueled by hydrocarbons can be determined quickly and accurately.

[0199] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0200] The use of the verb "comporter", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0201] In claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Method for determining a value of a quantity relating to a quantity of at least one chemical compound, said chemical compound being emitted by a heat engine (1) fueled at least partially by hydrocarbons, comprising the following steps: - determining (100) an initial value of a quantity relating to a quantity of hydrocarbons introduced into the heat engine (1) and deducing therefrom an initial value of a quantity relating to a quantity of carbon atoms introduced into the engine, - determining (400) the concentrations of a plurality of carbonaceous chemical compounds expected in the exhaust gases (3), - deducing (500) from said initial value of the quantity relating to the quantity of hydrocarbons introduced into the heat engine (1) determined previously and from the concentrations of said plurality of carbonaceous chemical compounds expected in the exhaust gases (3),a final value of a quantity relating to a quantity of carbon dioxide released in the exhaust gases (3) and deduce therefrom (600) said value of said quantity relating to the quantity of the chemical compound emitted in the exhaust gases (3)., Method of determination according to claim 1, wherein: - the quantity relating to the amount of at least one chemical compound is a mass flow rate of the chemical compound or a mass, - the quantity relating to the amount of hydrocarbons introduced into the heat engine is a mass flow rate or a mass, - the quantity relating to the amount of carbon atoms introduced into the engine is a molar flow rate or a number of moles, - the quantity relating to the amount of carbon dioxide released in the exhaust gases (3) is a molar flow rate or a number of moles. A method according to one of claims 1 and 2, wherein: - the quantity relating to the amount of at least one chemical compound is a mass, - the quantity relating to the amount of hydrocarbons introduced into the heat engine is a mass flow rate, - the quantity relating to the amount of carbon atoms introduced into the engine is a molar flow rate, - the quantity relating to the amount of carbon dioxide released in the exhaust gases (3) is a molar flow rate, and a value of a mass flow rate of the chemical compound is determined and said value of the mass of the chemical compound emitted in the exhaust gases (3) is deduced from it by integrating the mass flow rate determined during this time. Method according to any one of claims 1 to 3, furthermore, for a given composition of hydrocarbons supplying the heat engine (1), a value of a quantity characteristic of this composition is determined, this characteristic quantity depending on a reference ratio between a number of carbon atoms and a number of hydrogen atoms characteristic of this hydrocarbon composition, and this value of the characteristic quantity is taken into account to deduce the initial value of the quantity relating to the quantity of carbon atoms introduced into the heat engine (1). Method according to claim 4, wherein said characteristic quantity is equal to the inverse of the sum of the molar mass of carbon and the ratio between the molar mass of hydrogen and the reference ratio. Method according to claim 4, wherein said characteristic quantity is equal to a conversion factor between the hydrocarbon consumption of the heat engine (1) and the carbon dioxide emission by this heat engine (1). Method according to any one of claims 4 to 6, wherein the heat engine is supplied with two fuels of different compositions, each having a reference ratio, and said characteristic quantity depends on the reference ratios of the two fuels. Method according to any one of claims 1 to 7, wherein the final value of the quantity relating to the amount of carbon dioxide released in the exhaust gases is deduced (500) from the initial value of the quantity relating to the amount of carbon atoms introduced into the heat engine (1) and from each ratio between the concentration of each expected carbon chemical compound in the exhaust gases (3) and the concentration of carbon dioxide in these exhaust gases (3). Method according to any one of claims 1 to 8, wherein the expected carbonaceous chemical compounds comprise at least carbon dioxide and carbon monoxide and the chemical compound is selected from one of the following carbonaceous chemical compounds: carbon dioxide, methane, carbon monoxide, nitrous oxide, nitrogen oxides, sulfur oxides. Method according to any one of claims 1 to 9, wherein the concentrations of expected carbonaceous chemical compounds in exhaust gases (3) are measured using a gas analysis device (6) by gas spectrometry. Method according to claim 10, wherein at least one exhaust gas sample (3) is taken from said heat engine (1), this sample is cooled and / or the water vapor is removed from this sample before it passes through the gas analysis device. A method according to any one of claims 1 to 11, wherein the value of the quantity relating to the amount of the chemical compound emitted in the exhaust gases is deduced from the final value of the quantity relating to the amount of carbon dioxide released in the exhaust gases and from the ratios between the concentration of each expected carbonaceous chemical compound in the exhaust gases and the concentration of carbon dioxide in these exhaust gases. System (20) for determining a value of a quantity relating to a quantity of at least one chemical compound, said chemical compound being emitted by a heat engine (1) fueled at least partially by hydrocarbons, comprising a computer unit (11) comprising one or more processors programmed to carry out the following steps: - determine (100) an initial value of a quantity relating to a quantity of hydrocarbons introduced into the heat engine (1) and deduce therefrom an initial value of a quantity relating to a quantity of carbon atoms introduced into the engine, - determine (400) the concentrations of a plurality of expected carbon-based chemical compounds in the exhaust gases (3), - calculate (500),on the basis of the said initial value of the quantity relating to the amount of hydrocarbons introduced into the heat engine (1) determined previously and the concentrations of said plurality of carbonaceous chemical compounds expected in the exhaust gases, a final value of a quantity relating to an amount of carbon dioxide released in the exhaust gases (3) and deduce therefrom (600) said value of said quantity relating to the amount of the chemical compound emitted in the exhaust gases. System (20) for determining according to claim 13, further comprising a device for analyzing (6) exhaust gases by gas phase spectrometry. System (20) for determining according to any one of claims 13 and 14, further comprising a fuel analysis device (10). Ship equipped with a system according to one of claims 13 to 15.

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