Flameless combustion of hydrocarbons

Abstract

The invention relates to a flameless combustion method. The flameless combustion method comprises the steps that a combustion area is preheated to be higher than 800 DEG C; maintaining the temperature of the combustion zone at a temperature between 850 DEG C and 1400 DEG C; simultaneously injecting an oxidant and hydrocarbon fuel mixture into the combustion zone, wherein the oxidant and hydrocarbon fuel mixture are injected independently of one another from respective first and second locations; combusting the hydrocarbon fuel mixture without flame; and discharging an exhaust gas wherein the hydrocarbon fuel mixture is combusted without flame by maintaining a furnace oxygen concentration of less than 12% (by volume) of the combustion zone and maintaining an exhaust gas recirculation rate of 0 to 0.5. The present disclosure also relates to a furnace (2) for flameless combustion of a hydrocarbon fuel mixture.

Description

Technical Field

[0001] The present invention relates to a method for flameless combustion of hydrocarbons and is applicable to devices and systems for flame combustion. Background Art

[0002] Hydrocarbons are used as fuel sources globally. These hydrocarbons often originate from natural sources such as oil fields and gas fields. A significant portion of the extracted hydrocarbons are burnt / flared at the extraction source. For example, in 2020, 8 billion cubic feet of hydrocarbons were emitted or flared in Saudi Arabia, which is equivalent to approximately 2% of Saudi Arabia's natural gas production. Hydrocarbons are also often burnt during oil refining, where the burning is used as a safe release of the generated waste and / or excess gas. Excess gas is also burnt during the storage of hydrocarbons in fuel depots (storing chemicals, petroleum products [such as diesel, gasoline, kerosene, heavy marine fuel oil, etc.], biofuels, vegetable oils). During storage, to avoid overpressure accumulation of volatile hydrocarbons in the storage tank, the volatile components are extracted and fed to a flare, where they are burnt. Hydrocarbon combustion also occurs when storage tanks (such as oil depots or LPG tanks) need to be purged before filling with new hydrocarbons.

[0003] Combustion of hydrocarbons by traditional means often occurs with significant formation of nitrogen oxides such as nitric oxide (NO) and nitrogen dioxide (NO2). These nitrogen oxides are often abbreviated as NO x compounds. NO x emissions are involved in the formation of smog, which is formed by the reaction of NO x compounds with other volatile organic compounds (VOCs) in the atmosphere. NO x emissions are also a major source of acid rain. Therefore, from a health and environmental perspective, it is preferable to reduce NO x emissions.

[0004] In addition, the problem of degassing of hydrogen storage tanks in ships / marine vessels is similar to the problem of burning hydrocarbons. Both methods involve releasing harmful gases into the atmosphere, which can cause environmental problems.

[0005] Degassing of hydrocarbon storage tanks involves removing unwanted gases, vapors, volatile substances such as VOCs (volatile organic compounds) from inside the hydrocarbon storage tank. This is often achieved by heating the hydrocarbon storage tank to evaporate the residual liquid hydrocarbons and discharging the evaporated hydrocarbons into the atmosphere. Then, the hydrocarbon storage tank is flushed with a purge gas to displace the unwanted substances, effectively purging the harmful or unwanted vapors in the tank. The unwanted substances / purge gas are often released into the atmosphere through an appropriate ventilation system or ventilation mechanism.

[0006] Flameless combustion is an effective technique that can be used to reduce pollutant emissions (especially NOx emissions) from combustion and degassing.

[0007] During the combustion of hydrocarbons, there are three main NO x compound sources, which are often referred to as: (i) "prompt NO"; (ii) "fuel NO"; and (iii) "thermal NO". "Thermal NO", produced by the "Zeldovich mechanism", is the main source of NO x emissions from the combustion of clean hydrocarbon sources such as natural gas.

[0008] The three main reactions leading to the formation of NO x from thermal NO are as follows (in simplified form):

[0009] (1)

[0010] (2) and

[0011] (3)

[0012] These reactions are only significant at high temperatures (often above 1400 °C). Therefore, an early method of reducing NO x emissions from the combustion of hydrocarbons was to reduce the flame temperature, for example by flame cooling. An alternative approach involves "flame staging", where the reagent is introduced into the primary combustion zone under non-stoichiometric conditions, then the resulting combustion products are cooled, and finally introduced into the secondary combustion zone. Since 1989, "flameless combustion", often referred to as "flameless oxidation" or trademarked as "FLOX", has been studied to reduce NO x formation. This flameless combustion is achieved with a furnace temperature of approximately 1000 °C and by preheating the air to approximately 650 °C before introducing it into the combustion zone. The characteristics of flameless combustion are that no flame is visible and the UV emission is minimal. It has been found that such flames can burn clean fuels, with minimal NO x emissions and a carbon monoxide content of less than 1 ppm in the exhaust, indicating complete combustion of the fuel. EP0463218A1 describes such flameless combustion. Flameless oxidation allows for lower NO x production than combustion staging.

[0013] Since the mid-1990s, the commercial development of flameless combustion systems has grown slowly and is used as a clean fuel in steel mills (as a heat source for silicon steel strip lines, annealing lines, and pickling lines), Stirling engines, and gas turbines.

[0014] Research has determined that the uniform mixing of fuel and air / oxidant in the combustion zone is important for the formation of a stable flameless oxidation zone, as this avoids the formation of "hot spots" in the combustion zone where the temperature exceeds 1425 °C, at which temperature NO xRapid formation. One way to achieve this is by pre - mixing fuel / air or fuel / oxidant streams before introducing the oxidation zone / furnace. While this ensures good mixing and thus more uniform combustion, it often places limitations on: (i) what fuels can be used; (ii) what impurities the fuel can contain; and (iii) what concentration of such fuel can be used to avoid forming mixtures prone to explosion and / or deflagration. For example, (i) if methane is used as the fuel: (ii) the methane fuel can contain only up to 15% (by volume) of hydrogen; and (iii) methane must be diluted in air to below the lower flammability limit (LFL) of 4.4% (by volume).

[0015] Flame - less combustion requires a minimum threshold temperature of approximately 850 °C. Below this temperature, incomplete oxidation occurs. When clean fuel can be reliably supplied at a sufficient rate, the temperature in the combustion zone above the threshold temperature is relatively easy to maintain. However, when fuel is supplied occasionally and for short periods, where the actual fuel supplied to the combustion zone is insufficient, incomplete combustion occurs. For fuels that cannot be continuously and stably supplied at a sufficient rate, that is, fuels that are often sufficiently supplied but occasionally experience short - term shortages of a few seconds, this problem can be partially solved by filling the combustion zone with a porous matrix structure made of a high heat - storage ceramic material. The porous matrix maintains sufficient heat to restart flame - less combustion after a short period without sufficient fuel supply. The disadvantages of such complex structures are that they suffer from rapid fouling of the passages, cannot cope with extended defects in fuel supply, high pressure differences across the matrix, and difficult maintenance. Another disadvantage is that the high heat capacity of the matrix makes it difficult to detect insufficient fuel supply through a temperature drop in the combustion zone. Such systems also employ pre - mixing of fuel and air / oxidant and thus inherit the limitations of such pre - mixing. Summary of the Invention

[0016] An object of the disclosure of the present application is to provide a method, apparatus, and system that allow for flame - less combustion of hydrocarbon fuels: (i) whose composition can vary over time; (ii) which can contain high - volume impurities such as hydrogen; (iii) at a high volume percentage for the combustion zone; and / or (iv) at a rate insufficient to sustain spontaneous flame - less combustion.

[0017] Furthermore, an object of the flame - less combustion method is to achieve efficient and complete combustion over different ranges of combustion gas composition and energy content (lower heating value), while minimizing the formation of NOx.

[0018] Another object of the present invention is to address the environmental challenges associated with the degassing of hydrogen storage tanks for hydrocarbon fuels on ships. The present invention attempts to establish a more sustainable and environmentally friendly ship degassing method, ensuring that harmful emissions are effectively suppressed and mitigated.

[0019] In addition, another object of the present invention is to provide a compact flameless combustion device that is movable (i.e., the ability of the flameless combustion device or system to be easily transported and used in various positions).

[0020] In view of the above discussion, a first aspect of the present disclosure relates to a method of flameless combustion, comprising:

[0021] (i) preheating a combustion zone to a temperature higher than 800 °C;

[0022] (ii) maintaining the temperature of the combustion zone at a temperature between 850 °C and 1400 °C;

[0023] (iii) simultaneously injecting an oxidizer and a hydrocarbon fuel mixture into the combustion zone, wherein the oxidizer and the hydrocarbon fuel mixture are injected independently of each other from respective first and second positions; (iv) flamelessly combusting the hydrocarbon fuel mixture; and

[0024] (v) discharging the exhaust gas,

[0025] wherein the hydrocarbon fuel mixture is flamelessly combusted by maintaining the furnace oxygen concentration in the combustion zone below 12% (by volume) and maintaining an exhaust gas recirculation rate of 0 to 0.5.

[0026] A second aspect of the present disclosure relates to a flameless combustion device adapted to the flameless combustion method of the foregoing aspect, comprising:

[0027] - a furnace including a combustion zone;

[0028] - at least one FLOX burner, the FLOX burner including a first injection port, the first injection port including a first nozzle configured to allow injection of a first hydrocarbon fuel mixture and a second nozzle configured to allow injection of an oxidizer;

[0029] - at least one start-up burner capable of operating under FLOX and flame combustion conditions, the start-up burner including a second injection port, the second injection port including a third nozzle configured to allow injection of a first ancillary / auxiliary fuel and a fourth nozzle configured to allow injection of an oxidizer;

[0030] - means for measuring the combustion temperature;

[0031] - an exhaust gas port (chimney);

[0032] - wherein the first nozzle and the second nozzle are arranged in parallel to allow supply of the first hydrocarbon fuel mixture and the oxidizer to the FLOX burner; and

[0033] - wherein, the third nozzle and the fourth nozzle are arranged in parallel to allow a first ancillary / auxiliary fuel mixture and an oxidizer to be supplied to the start-up burner.

[0034] A third aspect of the present disclosure relates to a method for combusting boil-off gas (BOG) containing hydrocarbons, the method comprising:

[0035] - collecting BOG including at least one hydrocarbon from at least one hydrocarbon storage tank;

[0036] - conveying the collected BOG to a combustion device adapted to perform the method of the first aspect; and

[0037] - combusting the BOG under flameless conditions according to the method (according to any embodiment of the first aspect).

[0038] A fourth aspect of the present disclosure relates to a method for combusting residual gas and / or liquid (RGL) including hydrocarbons, the method comprising:

[0039] - fluidly connecting a hydrocarbon storage tank to a combustion device adapted to perform the method according to any embodiment of the first aspect;

[0040] - conveying a gas containing residual gas and / or liquid from the hydrocarbon storage tank to the combustion device;

[0041] - when the temperature of the combustion zone of the combustion device exceeds 850 °C, combusting the residual gas and / or liquid under flameless conditions according to the method (according to any embodiment of the first aspect);

[0042] - controlling the supply of residual gas and / or liquid to the combustion zone to maintain a temperature above 850 °C so as to maintain flameless combustion in the combustion zone

[0043] - when the maximum supply of residual gas and / or liquid to the combustion zone of the combustion device becomes insufficient to maintain a temperature above 850 °C, supplying auxiliary fuel to the combustion zone of the combustion device and combusting under flameless conditions according to the method (according to any embodiment of the first aspect): (i) the auxiliary fuel; and (ii) both the residual gas and / or liquid.

[0044] A fifth aspect of the present disclosure relates to a system adapted to combust residual gas and / or liquid (RGL), comprising:

[0045] - at least one hydrocarbon storage tank; and

[0046] - a combustion device adapted to perform the method according to any embodiment of the first aspect,

[0047] wherein the (one or more) hydrocarbon storage tanks are connected to the combustion device by means of a connection that allows fluid communication between the hydrocarbon storage tank and the combustion device.

[0048] The sixth aspect of the present disclosure relates to a method for degassing a hydrocarbon storage tank, wherein the method comprises the following steps:

[0049] - Pump out any liquid from the hydrocarbon storage tank until less than 5% (by volume) of the hydrocarbon storage tank is filled with hydrocarbon liquid;

[0050] - Place the hydrocarbon storage tank in liquid communication with an intermediate storage tank;

[0051] - Evaporate the residual hydrocarbon liquid in the hydrocarbon storage tank;

[0052] - Allow the evaporated hydrocarbon to move from the hydrocarbon storage tank to the intermediate storage tank;

[0053] - Optionally condense and / or compress the evaporated hydrocarbon in the intermediate storage tank;

[0054] - Purge the hydrocarbon storage tank with an inert gas;

[0055] - Transport the purge gas from the hydrocarbon storage tank to: (i) a storage tank, and / or (ii) a combustion device adapted to perform the method according to any embodiment of the first aspect;

[0056] - Transport at least some of the purge gas comprising hydrocarbon to the combustion device;

[0057] - When the temperature of the device exceeds 850 °C, burn the gas transported to the device under flameless conditions according to the method (according to any embodiment of the first aspect);

[0058] - When the temperature of the device is below 850 °C, provide an auxiliary fuel as a co-feed to the purge gas comprising hydrocarbon, and burn the auxiliary fuel and the gas transported to the device under flameless conditions according to the method (according to any embodiment of the first aspect).

[0059] The seventh aspect of the present disclosure relates to a system adapted to degas a hydrocarbon storage tank of a ship, comprising:

[0060] - An intermediate storage tank;

[0061] - A combustion device adapted to perform the method according to any aspect of the first aspect;

[0062] - Means for placing the hydrocarbon storage tank of the ship in fluid communication with the intermediate storage tank; and

[0063] - Means for placing the hydrocarbon storage tank of the ship in fluid communication with the combustion device and / or means for placing the intermediate storage tank of the ship in fluid communication with the combustion device. Description of the Drawings

[0064] Figure 1 A schematic layout of a method for burning boil-off gas (BOG) containing hydrocarbons for three connected storage tanks is depicted.

[0065] Figure 2 Depicts the representative exhaust gas rate of multiple connected storage tanks over a year.

[0066] Figure 3 Depicts an apparatus according to a second aspect of the present invention.

[0067] Figure 4 Depicts the volumetric variation of the combustion zone temperature and O2 concentration with respect to the exhaust gas hydrocarbon fuel mixture flow from 50 to 910 kg / hr.

[0068] Figure 5 Depicts the simulated volumetric variation of the combustion zone temperature and O2 concentration under the simulated decline of the hydrocarbon fuel mixture exhaust gas stream and the incoming auxiliary LPG fuel gas.

[0069] Figure 6 Depicts the simulated volumetric variation of the combustion zone temperature and O2 concentration with respect to the waste gas hydrocarbon fuel mixture upon detachment of the hydrocarbon fuel mixture exhaust gas stream and the incoming auxiliary LPG fuel gas.

[0070] Definitions and Abbreviations

[0071] Recirculation rate, K v . Recirculation rate, K v , is defined as follows:

[0072] K v = M E / (M F + M A ),

[0073] where: (i) M E is the mass of the recirculated exhaust gas; (ii) M F is the mass of the hydrocarbon fuel (hydrocarbon fuel mixture); and (iii) M A is the mass of the combustion air. The recirculation rate is used to calculate the recirculation rate of the recirculated exhaust gas in relation to the mass of the hydrocarbon fuel (hydrocarbon fuel mixture) and the combustion air. The recirculated exhaust gas can help control the combustion temperature and dilute the hydrocarbon concentration.

[0074] Detailed Description of the Invention

[0075] The systems, methods, and apparatuses of the present invention are

[0076] The first aspect of the present disclosure relates to a flameless combustion method, comprising:

[0077] (i) preheating the combustion zone to a temperature higher than 800 °C;

[0078] (ii) maintaining the temperature of the combustion zone at a temperature between 850 °C and 1400 °C;

[0079] (iii) Inject an oxidizer and a hydrocarbon fuel mixture into the combustion zone simultaneously, where the oxidizer and the hydrocarbon fuel mixture are injected independently of each other from respective first and second positions;

[0080] (iv) Burn the hydrocarbon fuel mixture flamelessly; and

[0081] (v) Discharge the exhaust gas,

[0082] wherein the hydrocarbon fuel mixture is burned flamelessly by maintaining the furnace oxygen concentration in the combustion zone below 12% (by volume) and maintaining an exhaust gas recirculation rate of 0 to 0.5.

[0083] The above method helps to reduce the combustion temperature and reduce the formation of NOx to a level far below the specified threshold.

[0084] The oxidizer and the hydrocarbon fuel mixture (hydrocarbon fuel) are fed separately into the combustion zone of the furnace interior. No mixing, including recirculated exhaust gas, occurs until the hydrocarbon fuel mixture and the oxidizer are well mixed in the combustion chamber. The terms "hydrocarbon fuel" and "hydrocarbon fuel mixture" are used interchangeably.

[0085] In a preferred embodiment, the method of the first aspect may include a first step: preheating the combustion zone to above 800 °C using an auxiliary fuel (such as natural gas) to ensure optimal combustion conditions and reach a temperature level at which the auto-oxidation of the hydrocarbon fuel will start and establish flameless combustion conditions.

[0086] The flameless combustion method operates under continuous operation, where hydrocarbon oxidation occurs under flameless conditions.

[0087] The method of the first aspect may include an additional step: providing an auxiliary fuel during a situation where the hydrocarbon fuel mixture level rapidly decreases (the hydrocarbon concentration in the existing fuel mixture decreases or the total flow rate of the purge / purging gas with hydrocarbon decreases) or the entire hydrocarbon fuel mixture flow stops, aiming to effectively mitigate temperature fluctuations and ensure stable thermal conditions. The rapid initiation of the auxiliary fuel supply is designed to prevent the combustion process from completely extinguishing due to a sudden reduction in the supply of the hydrocarbon fuel mixture. By providing a short injection of the auxiliary fuel, the combustion temperature can rapidly rise back to the operating level, ensuring a stable and continuous combustion process.

[0088] Furthermore, precise control of the exhaust gas recirculation rate (ranging from 0 to 0.5) is used to effectively dilute the concentration of hydrocarbons in the combustion chamber. When the exhaust gas recirculation rate exceeds 0.5, it results in an increased total gas volume in the system. This in turn increases the level of turbulence, thus requiring the deployment of larger and bulkier flameless combustion equipment, which is not desirable given that one of the objectives of the present invention is to maintain a compact design suitable for mobile (transportable) applications.

[0089] One advantage of this method is that it allows flameless combustion of hydrocarbon fuel mixtures with a very high operating adjustment ratio. Thus, this method is suitable for the flameless combustion of the following hydrocarbon fuel mixtures: (i) varying over time in terms of hydrocarbon composition; (ii) flow rate / mass transfer; and / or (iii) varying over time in terms of individual hydrocarbon concentrations. Changing the hydrocarbon composition, flow rate, and / or hydrocarbon concentration often results in changes in different combustion enthalpies and / or combustion entropies. This advantageously allows the flameless combustion of hydrocarbon fuel mixtures without analyzing the exact hydrocarbon composition and operating concentration, such as evaporative gas.

[0090] Another advantage of this method is that it generates less noise than traditional combustion methods.

[0091] Yet another advantage of this method is that it operates in the combustion chamber at a lower oxygen concentration (below 12%) than known flameless oxidation systems. This advantageously allows significantly higher concentrations of hydrocarbons in the hydrocarbon fuel mixture to be safely burned, in the range of 1.5 to 15% (by volume) of the fuel mixture, without exceeding the lower explosion limit.

[0092] One advantage of simultaneously and separately injecting the oxidizer and the hydrocarbon fuel mixture into the combustion zone, where the oxidizer and the hydrocarbon fuel mixture are injected independently of each other from respective first and second positions, is that it can avoid pre-mixing of the hydrocarbon fuel mixture and the oxidizer before they are introduced into the combustion chamber of the furnace of the flameless combustion device. This advantageously allows significantly higher concentrations of hydrocarbons in the hydrocarbon fuel mixture to be safely burned, in the range of 1.5 to 15% (by volume) of the fuel mixture, without exceeding the lower explosion limit.

[0093] Preferably, this method is one in which the oxidizer is preheated before being injected into the combustion zone. This preheating of the oxidizer advantageously allows a higher operating adjustment ratio to be employed.

[0094] Preferably, this method is one in which the hydrocarbon fuel mixture is preheated before being injected into the combustion zone. This preheating of the hydrocarbon fuel mixture advantageously allows a higher operating adjustment ratio to be employed.

[0095] Preferably, this method is one in which the hydrocarbon fuel mixture is selected from evaporative gas, residual gas or liquid, hydrocarbon storage purge gas, or any combination thereof.

[0096] Preferably, this method is one in which the temperature of the furnace is maintained at a temperature ranging from 850 to 1200 °C by:

[0097] - introducing cooling air with a temperature below 40 °C into the furnace; and / or

[0098] - introducing auxiliary fuel into the furnace.

[0099] One advantage of this preferred embodiment is that the temperature in the combustion zone can be better controlled by adding cold (40 °C) air to the furnace and / or adding auxiliary fuel.

[0100] More preferably, the auxiliary fuel is selected from propane, liquefied petroleum gas (LPG), natural gas (NG), refinery fuel gas, or any combination thereof.

[0101] Preferably, the method is one in which the oxygen concentration in the furnace is maintained at 3% to 12% (by volume), preferably 3% to 10% (by volume). The hydrocarbon fuel mixture (or hydrocarbon fuel) can be blended with the oxidant and the exhaust gas in such a way that the oxygen concentration in the furnace is maintained between 3% (by volume) and 10% (by volume).

[0102] Maintaining the oxygen concentration above 3% (by volume) advantageously minimizes the formation of CO.

[0103] Preferably, the method is one in which the furnace temperature is maintained at a temperature from 800 - 1400 °C, preferably from 850 to 1200 °C, more preferably from 900 - 1100 °C.

[0104] Preferably, the method is one in which the method includes a first step of preheating the combustion zone to above 800 °C using auxiliary fuel.

[0105] Preferably, the auxiliary fuel is selected from methane, ethane, propane, butane, natural gas, any other combustible hydrocarbon, or a combustible gaseous feed (such as H2), or any combination thereof, more preferably selected from methane, ethane, propane, butane, natural gas, any other hydrocarbon, hydrogen, or any combination thereof, and most preferably selected from methane, ethane, propane, butane.

[0106] Preferably, the method is one in which the (preheated) oxidant is introduced into the oxidation zone at a speed of at least 40 m / s, preferably at a speed of at least 50 m / s.

[0107] Preferably, the method is one in which the first hydrocarbon fuel mixture is introduced into the oxidation zone at a speed of at least 40 m / s, preferably at least 50 m / s, more preferably at least 80 m / s.

[0108] High-speed nozzles for the hydrocarbon fuel mixture and the oxidant are used to ensure the immediate mixing of the two combustion components and the recirculation of the exhaust gas (high turbulence conditions) when injected into the combustion chamber, resulting in the complete combustion of the hydrocarbon fuel mixture.

[0109] Preferably, the method is one in which the first hydrocarbon fuel mixture is at 0.8 to 50 megajoules per standard cubic meter (MJ / Nm 3 ), preferably 1.0 to 30 MJ / Nm 3, more preferably 1.5 to 20 MJ / Nm 3 Supplied to the combustion zone.

[0110] Preferably, the method is a method in which the first hydrocarbon fuel mixture is hydrocarbon off-gas.

[0111] Preferably, the method is a method in which if the first hydrocarbon fuel mixture includes hydrogen, the method is designed to effectively process a hydrocarbon fuel mixture containing hydrogen without compromising safety due to the flammability characteristics of hydrogen. Preferably, the hydrocarbon fuel mixture is introduced at a flow rate of at least 50 m / s. This can be measured using a dP measurement on the injector. This advantageously allows minimizing the risk of flare backs.

[0112] A second aspect of the present disclosure relates to a flameless combustion apparatus adapted to the flameless combustion method of the foregoing aspect, comprising:

[0113] - A furnace including a combustion zone;

[0114] - At least one FLOX burner, the FLOX burner including a first injection port, the first injection port including a first nozzle configured to allow injection of a first hydrocarbon fuel mixture, and a second nozzle configured to allow injection of an oxidant;

[0115] - At least one start-up burner capable of operating under FLOX and flame combustion conditions, the start-up burner including a second injection port, the second injection port including a third nozzle configured to allow injection of a first auxiliary fuel, and a fourth nozzle configured to allow injection of an oxidant;

[0116] - Means for measuring the combustion temperature; and

[0117] - An exhaust gas port (chimney);

[0118] - wherein, the first nozzle and the second nozzle are arranged in parallel to allow supply of the first hydrocarbon fuel mixture and the oxidant to the FLOX burner; and

[0119] - wherein, the third nozzle and the fourth nozzle are arranged in parallel to allow supply of the first auxiliary fuel mixture and the oxidant to the start-up burner.

[0120] Preferably, the furnace of the flameless combustion apparatus includes a combustion chamber having a combustion zone. The combustion zone refers to a specific area in the combustion chamber of the furnace where flameless combustion reactions occur.

[0121] The terms "auxiliary" or "ancillary" are used interchangeably herein.

[0122] The apparatus according to the second aspect can advantageously permit the implementation of the method of the first aspect, with all attendant advantages.

[0123] The configuration of the injection ports allows the first hydrocarbon fuel mixture and the first auxiliary fuel to be supplied to separate burners (FLOX burner and start burner) capable of FLOX combustion. This configuration advantageously allows the apparatus to maintain an operating temperature that minimizes NO x emissions, despite the low hydrocarbon concentration in the first hydrocarbon fuel mixture. Thus, this configuration allows the apparatus to have a high turndown ratio. This configuration also advantageously allows the apparatus to maintain an operating temperature that minimizes NO x emissions in the case of a temporary interruption in the supply of the first hydrocarbon fuel mixture.

[0124] The independent injection of the feed components (including the oxidizer and the hydrocarbon fuel mixture) at a minimum gas velocity results in intense mixing at the furnace inlet upon entry into the combustion chamber, and this intense mixing ensures the efficient and uniform oxidation of all available hydrocarbons. The minimum gas velocities at the furnace inlet are important for meeting the mixing requirements because they affect the rate of fuel and air mixing. The minimum gas velocities should be high enough to ensure turbulent conditions at the injection points such that the fuel and air are completely mixed within the combustion chamber. If the gas velocities are too low, the fuel and air will not mix properly and combustion will not be efficient. The term furnace inlet refers to the exact point within the flameless combustion device where the oxidizer and the hydrocarbon fuel mixture collect before entering the combustion chamber. The first injection port is a nozzle configured to allow the injection of the first hydrocarbon fuel mixture, and the second nozzle is configured to allow the injection of the oxidizer. These two nozzles are positioned such that the hydrocarbon fuel mixture and the oxidizer can be closely mixed. In the combustion chamber, a homogeneous oxidation reaction occurs in the gas phase, utilizing the entire volume of the combustion chamber. Non-hydrocarbons are completely oxidized (S, N, etc.).

[0125] A wide range of hydrocarbons can be applied;

[0126] Notably, the combustion chamber of the furnace has a compact design and operates at a reduced oxygen concentration (in the range of 3% to 12% by volume, more preferably in the range of 3 - 10% by volume). Additionally, the reduced oxidizer level also enhances the ability of the flameless combustion device to ensure safety, guard against risks, and maintain optimal operation. Thus, the method and apparatus of the present invention ensure complete hydrocarbon combustion, complete oxidation of pollutant components (S, N, and others), and achieve low NOx (nitrogen oxides) formation.

[0127] The configuration in which the first injection port and the second injection port are arranged in parallel advantageously allows the operation of the device without pre-mixing of the first hydrocarbon fuel mixture before introducing it into the device.

[0128] Preferably, the flameless combustion device can be designed to be movable so that it can be transported from one place to another.

[0129] Preferably, the flameless combustion device is compact because it is designed taking into account transportability, ensuring that it can be efficiently deployed anywhere needed, and the device is also designed to be assembled on a dedicated transport device, where for example the combustion chamber of a furnace can have dimensions of 5 meters in length, 2 meters in height and 2 meters in width.

[0130] Preferably, the flameless combustion device has a plurality of FLOX burner units. This advantageously allows the flameless combustion device to have an even higher turndown ratio.

[0131] Preferably, the flameless combustion device has means for measuring the pressure in the combustion zone.

[0132] Preferably, the flameless combustion device includes means for measuring the O2 concentration in the combustion zone. Such means advantageously allow the flameless combustion device to operate with better combustion control.

[0133] Preferably, the flameless combustion device includes a heat exchanger. More preferably, the heat exchanger is configured to allow heat to be transferred from the exhaust gas to: (i) the hydrocarbon fuel mixture; (ii) the oxidant; (iii) the auxiliary fuel; (iv) generate steam for energy combustion; and / or (v) any combination thereof. This advantageously allows for higher fuel efficiency when the device is operating with a low hydrocarbon concentration in the hydrocarbon fuel mixture. This also advantageously allows for a lower exhaust gas temperature, which may be required for safe operation in areas at risk of hydrocarbon leakage such as LPG tanks or LPG tank transporters.

[0134] Preferably, the flameless combustion device includes a start-up burner. The start-up burner is configured to allow the combustion chamber to reach a temperature of at least 850 °C. More preferably, the flameless combustion device includes a start-up burner using a start-up gas selected from propane, liquefied petroleum gas (LPG), natural gas (NG), refined fuel gas or any combination thereof.

[0135] In a preferred embodiment, the flameless combustion device can be configured to perform the flameless combustion method according to the first aspect.

[0136] The third aspect of the present disclosure relates to a method for combusting boil-off gas (BOG) containing hydrocarbons, the method comprising:

[0137] - collecting BOG containing at least one hydrocarbon from at least one hydrocarbon storage tank;

[0138] - The combustion device to which the collected BOG is delivered, preferably a flameless combustion device, is adapted to carry out the method of the first aspect; and

[0139] - Burn the BOG under flameless conditions according to the method (according to any embodiment of the first aspect).

[0140] In a preferred embodiment, the combustion device for collecting boil-off gas (BOG) according to the third aspect may be a flameless combustion device configured to facilitate and achieve flameless combustion according to the flameless combustion method of the first aspect.

[0141] The fourth aspect of the present disclosure relates to a method for burning residual gas and / or liquid (RGL) containing hydrocarbons, the method comprising:

[0142] - Connecting a hydrocarbon storage tank in fluid communication with a combustion device, preferably a flameless combustion device, adapted to carry out the method according to any embodiment of the first aspect;

[0143] - Delivering the gas containing residual gas and / or liquid from the hydrocarbon storage tank to the combustion device;

[0144] - When the temperature of the combustion zone of the combustion device exceeds 850 °C, burn the residual gas and / or liquid under flameless conditions according to the method (according to any embodiment of the first aspect);

[0145] - Controlling the supply of residual gas and / or liquid to the combustion zone to maintain a temperature above 850 °C in order to maintain flameless combustion in the combustion zone;

[0146] - When the maximum supply of residual gas and / or liquid to the combustion zone of the combustion device becomes insufficient to maintain a temperature above 850 °C, providing auxiliary fuel to the combustion zone of the combustion device and burning under flameless conditions according to the method (according to any embodiment of the first aspect): (i) the auxiliary fuel; and (ii) the residual gas and / or liquid.

[0147] Preferably, the method includes additional steps:

[0148] - Purge the storage tank with an inert gas and deliver the hydrocarbon including the purge gas to the combustion device;

[0149] - When the temperature of the combustion zone of the combustion device exceeds 850 °C, introduce the hydrocarbon including the purge gas into the combustion zone to burn the hydrocarbon in the purge gas under flameless conditions according to the method (according to any embodiment of the first aspect);

[0150] - Controlling the supply of the hydrocarbon including the purge gas to the combustion zone to maintain a temperature above 850 °C in order to maintain flameless combustion in the combustion zone; and

[0151] - When the maximum supply of purge gas to the combustion zone of the combustion device becomes insufficient to maintain a temperature above 850 °C, auxiliary fuel is supplied to the combustion zone of the combustion device and burned under flameless conditions according to the method (according to the first aspect): (i) the auxiliary fuel; and (ii) the hydrocarbons of the purge gas.

[0152] The term RGL (residual gas and / or liquid) refers to a mixture of gas and liquid that remains in the system, container / ship, hydrocarbon storage tank, or process after primary extraction or separation. In the context of hydrocarbons, RGL specifically represents a combination of gas and / or liquid composed of hydrocarbon compounds.

[0153] In a preferred embodiment, the combustion device according to the fourth aspect of the present invention may be the flameless combustion device described according to the second aspect of the present invention, wherein the flameless combustion device is configured to facilitate and implement flameless combustion according to the method of the first aspect.

[0154] Preferably, the method is carried out under the following conditions: if flameless combustion is not possible, the purge gas is passed through the combustion torch.

[0155] Preferably, the purge gas is selected from nitrogen, argon, or a mixture thereof.

[0156] The fifth aspect of the present disclosure relates to a system adapted to combust residual gas and / or liquid (RGL), comprising:

[0157] - at least one hydrocarbon storage tank; and

[0158] - a combustion device, preferably a flameless combustion device, adapted to carry out the method of any embodiment of the first aspect,

[0159] wherein the (one or more) hydrocarbon storage tanks are connected to the combustion device by means of allowing fluid communication between the hydrocarbon storage tank and the combustion device.

[0160] The sixth aspect of the present disclosure relates to a method for degassing a hydrocarbon storage tank within a flameless combustion system according to the eighth aspect of the present invention, wherein the method comprises the following steps:

[0161] - pumping out any liquid from the hydrocarbon storage tank until less than 5% (by volume) of the hydrocarbon storage tank is filled with hydrocarbon liquid;

[0162] - bringing the hydrocarbon storage tank of the container (ship) into fluid communication with an intermediate storage tank;

[0163] - evaporating the residual hydrocarbon liquid in the hydrocarbon storage tank;

[0164] - allowing the evaporated hydrocarbon to move from the hydrocarbon storage tank to the intermediate storage tank;

[0165] - Optionally condense and / or compress the evaporated hydrocarbons in the intermediate storage tank;

[0166] - Deliver at least a major portion of the evaporated, condensed, and / or compressed hydrocarbons from the intermediate storage tank to a flameless combustion device configured to perform the flameless combustion method according to the first aspect of the present invention, and / or facilitate the output of a minor portion of the condensed hydrocarbons,

[0167] - After removing the residual hydrocarbon liquid in the foregoing steps, purge the hydrocarbon storage tank with an inert gas such as nitrogen, argon, or a mixture thereof;

[0168] - Deliver the hydrocarbons including the purge gas from the hydrocarbon storage tank to: (i) the intermediate storage tank, and / or (ii) a flameless combustion device suitable for performing the method according to the first aspect;

[0169] - Deliver at least some of the purge gas including hydrocarbons to the flameless combustion device;

[0170] - When the temperature of the combustion zone of the flameless combustion device exceeds 850 °C, burn the gas delivered to the device under flameless conditions according to the method (according to any embodiment of the first aspect);

[0171] - Control the supply of hydrocarbons including the purge gas to the combustion zone to maintain a temperature above 850 °C in order to maintain flameless combustion in the combustion zone; and

[0172] - When the maximum supply of the purge gas to the combustion zone of the flameless combustion device becomes insufficient to maintain a temperature above 850 °C, provide auxiliary fuel to the combustion zone of the combustion device, and burn under flameless conditions according to the method of the first aspect: (i) the auxiliary fuel; and (ii) the hydrocarbons in the purge gas.

[0173] The above method for degassing can be used for loading / discharging or cleaning hydrocarbon storage tanks in a ship.

[0174] The term "hydrocarbons including the purge gas" refers to a purge gas rich in hydrocarbons, or more specifically to the gas removed from the hydrocarbon storage tank during the degassing process, a mixture including the inert gas used for purging.

[0175] In a preferred embodiment, the combustion device according to the sixth aspect of the present invention can be the flameless combustion device described according to the second aspect of the present invention, wherein the flameless combustion device is configured to facilitate and implement flameless combustion according to the method of the first aspect.

[0176] In a sixth aspect of the present invention, the hydrocarbon storage tank is emptied and any residual hydrocarbon liquid that cannot be extracted is vaporized, for example by heating. The vaporized hydrocarbon liquid is moved to an intermediate storage tank, potentially condensed or compressed and subsequently stored in the intermediate storage tank. The condensed hydrocarbon can be supplied to a flameless combustion device or used for other purposes. During an additional purging step, the hydrocarbon storage tank is purged with an inert gas (i.e., the purge gas). Then, the hydrocarbon-rich purge gas is not simply released into the atmosphere. Instead, it is directed to the intermediate storage tank and / or the flameless combustion device. Thus, the present invention eliminates the need for ventilation, which conventionally releases potentially harmful emissions into the environment.

[0177] In a preferred embodiment, the hydrocarbon storage tank can have a volume of 4000 - 30000 m3 , more preferably 4000 - 10000 m3 liters.

[0178] This aspect of the present invention is particularly advantageous for removing residual hydrocarbons from the purge gas, as it can cope with extreme variations in the hydrocarbon content of the purge gas. Purging a hydrocarbon storage tank with an inert gas typically results in the purge gas initially containing a high hydrocarbon content, mainly highly volatile hydrocarbons. As the purging process continues, the total hydrocarbon content decreases over time and the composition becomes increasingly dominated by less volatile hydrocarbons. This aspect advantageously allows nitrogen to be used as the purge gas without excessive NO x emissions. This aspect also advantageously eliminates the need for real-time analysis of the total hydrocarbon concentration and / or hydrocarbon composition in the purge gas. Preferably, the purge gas is selected from nitrogen, argon, or a mixture thereof, and more preferably, the purge gas is nitrogen.

[0179] Furthermore, the degassing method involves capturing and burning hydrocarbons in a controlled manner. This can significantly reduce the release of volatile organic compounds (VOCs) and other harmful pollutants into the atmosphere.

[0180] A seventh aspect of the present disclosure relates to a system adapted to degas a hydrocarbon storage tank, comprising:

[0181] - an intermediate storage tank;

[0182] - a combustion device, preferably a flameless combustion device, adapted to perform the method according to any aspect of the first aspect;

[0183] - means for fluidly connecting the hydrocarbon storage tank to the intermediate storage tank; and

[0184] - means for fluidly connecting the hydrocarbon storage tank to the combustion device and / or means for fluidly connecting the intermediate storage tank to the combustion device.

[0185] In a preferred embodiment, the combustion device according to the seventh aspect of the present invention may be the flameless combustion device described in the second aspect of the present invention, wherein the flameless combustion device is configured to facilitate and implement flameless combustion according to the method of the first aspect.

[0186] An eighth aspect of the present disclosure relates to a system for flameless combustion, comprising at least one hydrocarbon storage tank and a flameless combustion device according to the second aspect of the present invention, the flameless combustion device comprising:

[0187] A furnace having a combustion chamber and a combustion zone;

[0188] At least one FLOX burner, the FLOX burner comprising a first injection port, the first injection port comprising a first nozzle configured to allow the injection of a first hydrocarbon fuel mixture, and a second nozzle configured to allow the injection of an oxidant;

[0189] At least one start-up burner capable of operating under FLOX and flame combustion conditions, the start-up burner comprising a second injection port, the second injection port comprising a third nozzle configured to allow the injection of a first auxiliary fuel, and a fourth nozzle configured to allow the injection of an oxidant;

[0190] Means for measuring the combustion temperature; and

[0191] An exhaust gas port;

[0192] Wherein the first nozzle and the second nozzle are arranged in parallel to allow the supply of the first hydrocarbon fuel mixture and the oxidant to the FLOX burner; and

[0193] Wherein the third nozzle and the fourth nozzle are arranged in parallel to allow the supply of the first auxiliary fuel and an optional oxidant to the start-up burner,

[0194] Wherein the at least one hydrocarbon storage tank is connected to the flameless combustion device.

[0195] In one embodiment, the second injection port and the furnace of the system for flameless combustion are configured to allow the first auxiliary fuel to perform flameless combustion at an exhaust gas recirculation rate of 0 to 0.5.

[0196] In addition, the flameless combustion device of the flameless combustion system is configured to perform a flameless combustion method according to the flameless combustion method of the first aspect of the present invention.

[0197] Additionally, a system for flameless combustion may include an intermediate storage tank and means for fluidly connecting the hydrocarbon storage tank to the intermediate storage tank. Further, a system for flameless combustion may include means for fluidly connecting the hydrocarbon storage tank to the flameless combustion device and / or means for fluidly connecting the intermediate storage tank to the flameless combustion device.

[0198] The system for flameless combustion can be used for ship degassing, i.e., the process of removing residual hydrocarbon gas from the cargo hold (hydrocarbon storage tank). Thus, in a preferred embodiment, the hydrocarbon storage tank can be located inside the ship.

[0199] Furthermore, the flameless combustion device and / or the system for flameless combustion can be designed to be movable and can be transported from one place to another. The system for flameless combustion can be used on different ships, adapting it to different vessels and locations where ship degassing is required. It is designed with portability in mind, ensuring that it can be efficiently deployed wherever needed.

[0200] In addition, the system for flameless combustion can be used for the flameless combustion of residual gas and / or liquid (RGL).

[0201] Detailed Description of the Figures

[0202] The present disclosure will now be discussed with reference to the preferred exemplary embodiments illustrated in the accompanying drawings.

[0203] Figure 1 A schematic layout of a method for combusting boil-off gas (BOG) containing hydrocarbons is depicted. The term boil-off gas (BOG) refers to the evaporation of liquefied gas (such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), or liquefied ethylene gas (LEG)) due to changes in temperature and pressure. In this example, there are three hydrocarbon storage tanks [T1, T2, and T3]. In the described method, BOG containing at least one hydrocarbon is collected from at least one of the hydrocarbon storage tanks [T1, T2, and / or T3]. This is depicted by arrows [A1, A2, and / or A3]. BOG containing at least one hydrocarbon can be collected simultaneously or sequentially from one, two, or all of the tanks. Optionally, the BOG containing at least one hydrocarbon passes through a [A4] pretreatment device [P1], such as an AC filter, which allows: (i) residual H2S and / or (ii) condensed hydrocarbons to be removed completely or partially from the BOG. The collected BOG containing at least one hydrocarbon is delivered to a combustion device, more preferably a flameless combustion device, adapted to perform the method of the first aspect [C1]. This is depicted by arrow [A5]. The BOG is combusted under flameless conditions according to the method for flameless combustion (according to any embodiment of the first aspect).

[0204] Figure 2Depicts the representative off - gas rates of multiple connected storage tanks over a year. The term "off gas" refers to the gases released as waste or secondary products during various operations. The typical flow pattern is shown for 8800 hours (flow rate on the y - axis, scale 100 m 3 / h, time on the x - axis, scale 1000 hours), with data points corresponding every 4 hours. The average flow is estimated at 145.2 m 3 / h, and the maximum flow rate is estimated at 839 m 3 / h.

[0205] Figure 3 Depicts a non - restrictive example of the arrangement (PFD) of a device according to the second aspect of the present invention. In this non - restrictive example, the furnace (2) of the flameless combustion device includes a combustion chamber, which is a square combustion chamber with a length of 5 m, a height of 2 m, and a width of 2 m. The combustion chamber is designed with a start - up burner, eight high - speed ventilation injectors, and four probes for (cooling) air injection. The probes are devices for introducing (cooler) air into the combustion chamber. Two LPG or propane probes will be installed for the injection of auxiliary fuel.

[0206] Figure 4 Depicts the simulated variations of the combustion zone temperature and O2 concentration (by volume) with the off - gas hydrocarbon fuel mixture flow for unit start - up conditions from 50 to 910 kg / hr.

[0207] The x - axis is time in minutes, from 2 to 29 minutes, scale 4 minutes. The four y - axes read from left to right are as follows:

[0208] 1. Hydrocarbon fuel (hydrocarbon fuel mixture) mass flow ("LCV4", unit kg / h), 0 to 1250 kg / h, scale 250 kg / h;

[0209] 2. Temperature of the combustion zone (°C), 0 to 1500 °C, scale 300 °C;

[0210] 3. Calculated mole fraction O2 (unit %) is 0.0250 - 0.160, scale 0.0250; and

[0211] 4. Auxiliary fuel mass flow (propane, denoted as "Fuel206", unit kg / h) from 0 to 20 kg / h, scale 4 kg / h.

[0212] The lines, from top to bottom when they intersect the y - axis, are as follows:

[0213] a. Temperature, starting value 900 °C;

[0214] b. Auxiliary fuel flow rate, initial value 2.7 kg / h;

[0215] c. Calculated mole fraction of O2, with an initial value of 3.5%; and

[0216] d. Mass flow of hydrocarbon fuel (hydrocarbon fuel mixture), with an initial value of 0.

[0217] In the first shaded region (read from left to right), hydrocarbon fuel (hydrocarbon fuel mixture) starts to be supplied to the combustion zone in the furnace, and the amount of auxiliary fuel supplied for preheating starts to decrease (and becomes zero at about 7 minutes). As the hydrocarbon fuel (hydrocarbon fuel mixture) burns, it supplies sufficient energy to the combustion zone to maintain the temperature above 850 °C required for flameless oxidation (FLOX).

[0218] In the second shaded region (read from left to right), the decline in the supply of hydrocarbon fuel (hydrocarbon fuel mixture) is simulated. This causes the temperature to rapidly drop to about 900 °C and the oxygen concentration to spike to about 12%. To maintain the temperature above 850 °C and the oxygen concentration in the safety zone below 12%, auxiliary fuel is supplied rapidly. The auxiliary fuel burns under FLOX conditions, supplying sufficient energy to the combustion zone to maintain the temperature above 850 °C and consuming sufficient oxygen to maintain the oxygen concentration below 12%.

[0219] In the third shaded region (read from left to right), due to the low mass flow of hydrocarbon fuel supply, the supply of hydrocarbon fuel (hydrocarbon fuel mixture) stops. Accordingly, the supply of auxiliary fuel increases.

[0220] Therefore, before introducing the hydrocarbon fuel mixture, the combustion zone is preheated to a temperature above 800 °C using auxiliary fuel. Once the minimum temperature of 800 °C is reached, the burner switches from the flame mode (start-up mode) to the flox (flameless oxidation) mode, and flameless combustion is established. In the flameless combustion mode, auxiliary fuel is used to maintain the furnace temperature above 800 °C during the time when the level of the hydrocarbon fuel mixture decreases or is zero (completely stopped), maintaining the furnace temperature at a constant level.

[0221] Figure 5 Depicts the simulated changes in the combustion zone temperature and O2 concentration (by volume) under the simulated supply of exhaust gas to the combustion chamber in the furnace.

[0222] The x-axis is time in minutes, from 3575 to 3640 minutes, scaled at 5 minutes. Four y-axes, read from left to right, are as follows:

[0223] 1. Mass flow of hydrocarbon fuel ("LCV4", in kg / h), from 0 to 1260 kg / h, scaled at 252 kg / h;

[0224] 2. Calculated mole fraction of O2 from 0.0250 to 0.160, scaled at 0.0250;

[0225] 3. Auxiliary fuel mass flow (propane, denoted as "Fuel206", in kg / h), from 0 to 20 kg / h, scaled at 4 kg / h; and

[0226] 4. Temperature (°C) in the combustion zone, from 0 to 1500 °C, scaled at 300 °C.

[0227] Lines, from top to bottom when they intersect the y-axis, as follows:

[0228] a. Temperature, starting value of 900 °C;

[0229] b. Auxiliary fuel flow rate, initial value of 3.1 kg / h;

[0230] c. Calculated mole fraction of O2, initial value of 5%; and

[0231] d. Hydrocarbon fuel mass flow, initial value of 0.

[0232] A rapid increase in hydrocarbon fuel supply is simulated (at approximately 3568 minutes), from 0 to 950 kg / h. This represents the value of opening a partially filled hydrocarbon storage tank at ambient temperature. The rapid supply of hydrocarbon fuel (hydrocarbon fuel mixture) causes a rapid increase in the temperature of the combustion zone to 1030 °C, a rapid shut-off of the auxiliary fuel supply, and a rapid increase in the oxygen concentration from approximately 5% to approximately 12%. A rapid stop in the supply of hydrocarbon fuel (hydrocarbon fuel mixture) is simulated (at approximately 3595 minutes, region A), from 950 kg / h to 0. This represents the value of closing a partially filled hydrocarbon storage tank at ambient temperature. The rapid stop in the supply of hydrocarbon fuel (hydrocarbon fuel mixture) causes the temperature in the combustion zone to rapidly decrease from approximately 1000 °C to below 850 °C, and the oxygen concentration to rapidly increase from approximately 12% to approximately 14%. This causes the auxiliary fuel supply to almost instantaneously turn on at approximately 3595 minutes, resulting in the temperature dropping below 850 °C for a very short time of approximately 120 seconds. This is much shorter than similar methods, and this method correspondingly produces much less NOx. Thus, by providing a short burst of auxiliary fuel, the combustion temperature can be rapidly increased to the operating level, ensuring a stable and continuous combustion process.

[0233] Figure 6 : Depicts the simulated variations in the combustion zone temperature and O2 concentration (by volume) relative to the exhaust gas hydrocarbon fuel mixture during the descent and entry of auxiliary fuel (e.g., LPG gas) from the hydrocarbon fuel mixture exhaust gas.

[0234] The x-axis is time in minutes, from 3575 to 3640 minutes, scaled at 5 minutes. There are four y-axes, read from left to right, as follows:

[0235] 1. Temperature: (i) Combustion zone in the furnace (°C); and (ii) Reactor (°C), from 0 to 1455 °C, scaled at 291 °C;

[0236] 2. Calculated mole fraction of O2 from 0.090 to 0.160, scaled at 0.016; and

[0237] 3. Hydrocarbon fuel mass flow (“LCV4”, in kg / h), 0 to 1260 kg / h, scaled at 252 kg / h.

[0238] Lines, from top to bottom when they intersect the y-axis, are as follows:

[0239] a. Temperature of the combustion zone (“Furnace T”);

[0240] b. Calculated mole fraction of O2, with an initial value of approximately 0.128;

[0241] c. Temperature of the reactor (“Reactor T”); and

[0242] d. Hydrocarbon fuel mass flow, with an initial value of 0.

[0243] List of reference numerals

[0244] 1 Flameless combustion device

[0245] 2 Furnace

[0246] 3 Combustion zone

[0247] 4 First injection port

[0248] 5 First nozzle, configured to allow injection of the first hydrocarbon fuel mixture of

[0249] 6 Second injection port

[0250] 7 Device for measuring combustion temperature, such as a thermocouple

[0251] 8 Exhaust gas port

[0252] 9 Fan

[0253] 10 Valve

[0254] 11 Solenoid valve

[0255] 12 Air inlet filter

[0256] 13 Draft for cooling air

[0257] 14 Actuator motor

[0258] 15 Pressure switch

[0259] 16 Filter

[0260] 17 Ball valve

[0261] 18 Solenoid with pressure reducer

[0262] 19 Valve

[0263] 20 First FLOX burner

[0264] 21 Second FLOX burner

[0265] 22 Ignition burner capable of operating under FLOX and flame combustion conditions

[0266] 23 Oxygen sensor

[0267] 24 Fan

[0268] 25 Linear flow control

[0269] 26 Air

[0270] 27 Hydrocarbon fuel (hydrocarbon fuel mixture)

[0271] 28 Exhaust gas

[0272] 29 Auxiliary fuel

[0273] Examples

[0274] The following non - limiting examples illustrate the products and methods according to the present disclosure.

[0275] Example 1 - Process simulation of the method according to the present disclosure

[0276] The device according to Figure 3 is used in the simulation. The simulation is based on the schematic setup of Figure 1 . Using the device according to the second aspect of the present invention, a mixture of exhaust gas and air is used to simulate the performance of the method according to the first aspect of the present invention under the minimum, low, average, and maximum conditions detailed in Table 1.

[0277] The lower calorific values of the minimum and low mixtures are calculated to be 5.5 and 7.7 MJ / Nm 3 respectively. The heat - and mass - balance (H&M balance) of the average case in Table 1 is calculated. It is determined that starting from 6.6 kmol / hr of LCV gas (= air - hydrocarbon exhaust gas mixture from the tank, see Table 1), 12.9 kmol / hr of cold air is required for temperature control and oxygen supply. In practice, the entire furnace operates at 10% v O2, which is a safe oxygen content for any sudden change in hydrocarbon content. The combustion temperature is estimated to be 1000 °C.

[0278] The maximum case has been simulated to obtain the calculated H&M balance. It is determined that for a 26.4 kmol / hr tank waste gas mixture, 110.6 kmol / hr of cold air is required for temperature control and oxygen supply. Also for this case, we estimate the effective combustion temperature to be 1000 °C.

[0279] It is estimated that the method according to the first aspect results in NO x emissions of less than 25 mg / Nm 3 and less than 12 parts per million by volume (ppmv). It is estimated that when the method is carried out, wherein the furnace oxygen concentration is maintained at 3% to 12% (by volume), this results in: (i) NO x emissions of less than 25 mg / Nm 3 and less than 12 ppmv; (ii) CO emissions below 20 mg / Nm 3 and less than 16 ppmv; and (iii) total organic compound emissions of less than 2 mgC / Nm 3 and less than 4 ppmv.

[0280] component minimum low average maximum unit C1 - C2 0.0 0.4 4.7 12.5 kg / hour C3 - C5 0.0 1.0 12.6 86.5 kg / hour total 0.0 1.4 17.3 99 kg / hour air 0.0 14 176 700 kg / hour total flow 0.0 15.4 193.3 799 kg / hour

[0281] Table 1. Tank waste gas - gas flow and composition.

[0282] Example 2 - Dynamic process simulation of the method according to the present disclosure

[0283] Considering the characteristics of the high flow variations for the tank waste gas flow pattern Figure 2 , a series of dynamic simulations are carried out to quantify the system response when the waste gas supply flow changes rapidly.

[0284] The key elements of the corresponding part of the extended process flow diagram (PFD) are as follows:

[0285] 1. The tank waste gas supply system includes a gas booster and flow control. In our simulation, we work based on an initial pressure of 103 kPa (outer tank), to be adjusted to the actual level.

[0286] 2. Auxiliary fuel, i.e., a gas, which can be propane or LPG (optionally, natural gas, NG, can be used), ensures fuel control for the step of preheating the combustion zone to above 800 °C, and supplementary fuel addition in the case of a very lean waste gas composition, and for maintaining the furnace temperature above 800 °C during zero flow.

[0287] 3. The oxidizer is selected from combustion air. The control of the fresh air supply serves to: (i) combustion; (ii) O2 concentration and (iii) temperature control.

[0288] 4. The burner section and combustion chamber in the furnace include a set of 8 hydrocarbon fuel - mixed gas burners ( Figure 3)。Each burner is modeled to have a minimum capacity of 45 kg / hr and a maximum capacity of 140 kg / hr. Additionally, a start-up burner is modeled to preheat the combustion chamber from cold start to above 800 °C or to provide additional heat during flameless combustion to maintain the temperature above 850 °C. For the zero-flow case, two additional propane or LPG probes are modeled. For dynamic simulations, only 8 LCV gas burners are relevant.

[0289] 5. The kinetics of the unit operation are simulated where the inlet gas flow varies continuously from 50 to 910 kg / hr, increases from 50 to 910 kg / hr within 5 minutes, and subsequently the inlet flow suddenly decreases back to 50 kg / hr, dropping to 50 kg / hr within 1 minute.

[0290] 6. In Figure 5 the system response over 10 minutes is plotted. For key parameters such as furnace temperature and O2 concentration in the flue gas, we see the following variations:

[0291] - In the case of a rapid flow increase, the O2 concentration varies between 12.9 %v (initial) and 11.7 %v (lowest point), while the combustion zone temperature varies between 977 °C and 1044 °C, both being under control; and

[0292] - In the case of a sudden drop in the inlet gas flow of the hydrocarbon fuel mixture, we calculate that the combustion zone temperature briefly drops to 902 °C while the oxygen concentration rises to 13 % (by volume) and then drops to 12 % (by volume) during subsequent stabilization. The full kinetics show effective control of the key parameters of the combustion chamber, ensuring complete and stable combustion throughout the entire scan of the hydrocarbon fuel mixture gas inflow from low to high and back to low.

[0293] In a similar simulation over a longer time period (65 minutes), the effect of the combination of zero waste gas flow and the incoming auxiliary fuel gas (LPG in our example) is analyzed. As Figure 6 shown, for the incoming LPG gas, the combustion zone temperature is well controlled within the requirements of the method. In response to a reduction in the air supply for controlling the combustion zone temperature (due to a reduction in flow caused by a lower furnace temperature), the O2 level in the combustion chamber can drop to 5 % (by volume), which is still within the correct window for complete combustion under flameless combustion conditions. Thus, the present method, when optionally including the step of maintaining the temperature of the furnace at 850 to 1200 °C by introducing auxiliary fuel into the furnace, is simulated to advantageously allow flameless combustion that can withstand temporary supply shocks of the hydrocarbon fuel mixture without emitting undesired levels of NO x or CO.

Claims

1. A flameless combustion device (1) for flameless combustion, comprising: - A furnace (2) including a combustion zone (3); - At least one FLOX burner (20), the FLOX burner including a first injection port (4), the first injection port (4) including a first nozzle (5) configured to allow the injection of a first hydrocarbon fuel mixture and a second nozzle configured to allow the injection of an oxidant; - At least one start-up burner (22) capable of operating under FLOX and flame combustion conditions, the start-up burner including a second injection port (6), the second injection port (6) including a third nozzle configured to allow the injection of a first auxiliary fuel and a fourth nozzle configured to allow the injection of an oxidant; - Means (7) for measuring the combustion temperature; and - An exhaust gas port (8); - Wherein, the first nozzle and the second nozzle are arranged in parallel to allow the supply of the first hydrocarbon fuel mixture and the oxidant to the FLOX burner; and - Wherein, the third nozzle and the fourth nozzle are arranged in parallel to allow the supply of the first auxiliary fuel and an optional oxidant to the start-up burner.

2. The flameless combustion device according to claim 1, wherein, The second injection port and the furnace are configured to allow flameless combustion of the first auxiliary fuel at an exhaust gas recirculation rate from 0 to 0.

5.

3. A flameless combustion method in a flameless combustion device according to any one of claims 1-2, comprising: (i) Preheating the combustion zone to a temperature higher than 800 °C; (ii) Maintaining the temperature of the combustion zone at a temperature between 850 °C and 1400 °C; (iii) Simultaneously injecting an oxidant and a hydrocarbon fuel mixture into the combustion zone, wherein the oxidant and the hydrocarbon fuel mixture are injected independently of each other from respective first and second positions; (iv) Flamelessly combusting the hydrocarbon fuel mixture; and (v) Discharging the exhaust gas, wherein, by maintaining the furnace oxygen concentration in the combustion zone below 12% by volume and maintaining an exhaust gas recirculation rate from 0 to 0.5, the hydrocarbon fuel mixture is flamelessly combusted.

4. The method according to claim 3, wherein, The oxidant is preheated before being injected into the combustion zone.

5. The method according to claims 3-4, wherein The hydrocarbon fuel mixture is preheated before being injected into the combustion zone.

6. The method according to any one of the preceding claims, wherein, The hydrocarbon fuel mixture is selected from evaporated gas, residual gas or liquid, hydrocarbon storage purge gas or any combination thereof.

7. The method according to any one of the preceding claims, wherein, The temperature of the furnace is maintained at a temperature from 850 to 1200 °C by: - Introducing air with a temperature lower than 40 °C into the furnace; and / or - Introducing auxiliary fuel into the furnace.

8. The method according to any one of the preceding claims, wherein, The furnace oxygen concentration is maintained at from 3% to 12% by volume, preferably from 3% to 10% by volume.

9. The method according to any one of the preceding claims, wherein, The furnace temperature is maintained at a temperature from 800 - 1400 °C, preferably from 850 to 1200 °C, more preferably from 900 - 1100 °C.

10. The method according to any one of the preceding claims, wherein, The method includes a first step of preheating the combustion zone to a temperature higher than 800 °C using auxiliary fuel.

11. The method according to any one of the preceding claims, wherein, The auxiliary fuel is selected from methane, ethane, propane, butane, natural gas, any other hydrocarbon or combustible gaseous feed or any combination thereof, more preferably selected from methane, ethane, propane, butane, natural gas, any other hydrocarbon, hydrogen or any combination thereof, most preferably selected from methane, ethane, propane, butane.

12. The method according to any one of the preceding claims, wherein, Introduce the (preheated) oxidant into the oxidation zone at a velocity of at least 40 m / s, preferably at least 50 m / s.

13. The method according to any one of the preceding claims, wherein, Introduce the first hydrocarbon fuel mixture into the oxidation zone at a velocity of at least 40 m / s, preferably at least 50 m / s.

14. The method according to any one of the preceding claims, wherein, The first hydrocarbon fuel mixture is provided to the combustion zone at 0.8 to 50 megajoules per standard cubic meter (MJ / Nm3), preferably 1.0 to 30 MJ / Nm3, more preferably 1.5 to 20 MJ / Nm3.

15. The method according to claim 11, wherein The method includes the step of providing auxiliary fuel during a period when the level of the hydrocarbon fuel mixture rapidly decreases or the hydrocarbon fuel mixture completely stops.

16. A method for combusting boil-off gas (BOG) comprising hydrocarbons, the method comprising: - Collect BOG comprising at least one hydrocarbon from at least one hydrocarbon storage tank; - Transport the collected BOG to a combustion device, preferably the flameless combustion device according to claim 1, the combustion device being adapted to perform the method according to any one of claims 3 - 15; and - Burn the BOG under flameless conditions according to the method according to any one of claims 3 - 15.

17. A method for combusting residual gas and / or liquid (RGL) comprising hydrocarbons, the method comprising: - Place the hydrocarbon storage tank in fluid communication with a combustion device, the combustion device preferably being the flameless combustion device according to claim 1, adapted to perform the method according to any one of claims 3 - 15; - Transport the gas comprising residual gas and / or liquid from the hydrocarbon storage tank to the combustion device, preferably a flameless combustion device; - Control the supply of residual gas and / or liquid to the combustion zone to maintain a temperature above 850 °C in order to maintain flameless combustion in the combustion zone, - When the maximum supply of residual gas and / or liquid to the combustion zone of the combustion device becomes insufficient to maintain a temperature above 850 °C, provide auxiliary fuel to the combustion zone of the combustion device and burn under flameless conditions according to any one of claims 3 - 15: (i) the auxiliary fuel; and (ii) both the residual gas and / or liquid.

18. The method according to claim 17, wherein, The method includes the following additional steps: - Purge the hydrocarbon storage tank with an inert gas, the purge gas preferably selected from nitrogen, argon, or mixtures thereof, and transport the hydrocarbon comprising the purge gas to a combustion device, preferably a flameless combustion device; - When the temperature of the combustion zone of the combustion device exceeds 850 °C, introduce the hydrocarbon comprising the purge gas into the combustion zone to burn the hydrocarbon within the purge gas under flameless conditions according to the method according to claims 3 - 15; - Control the supply of the hydrocarbon comprising the purge gas to the combustion zone to maintain a temperature above 850 °C in order to maintain flameless combustion in the combustion zone; and - When the maximum supply of the purge gas to the combustion zone of the combustion device becomes insufficient to maintain a temperature above 850 °C, provide auxiliary fuel to the combustion zone of the combustion device, and burn under flameless conditions according to the method according to claims 3 - 15: (i) the auxiliary fuel; and (ii) both the hydrocarbon of the purge gas.

19. A system for flameless combustion, comprising: At least one hydrocarbon storage tank and a flameless combustion device according to claim 1, the flameless combustion device comprising: A furnace having a combustion chamber and a combustion zone; At least one FLOX burner, the FLOX burner including a first injection port, the first injection port including a first nozzle configured to allow injection of a first hydrocarbon fuel mixture and a second nozzle configured to allow injection of an oxidant; At least one start-up burner capable of operating under FLOX and flame combustion conditions, the start-up burner including a second injection port, the second injection port including a third nozzle configured to allow injection of a first auxiliary fuel and a fourth nozzle configured to allow injection of an oxidant; Means for measuring the combustion temperature; and An exhaust gas port; Wherein the first nozzle and the second nozzle are arranged in parallel to allow the first hydrocarbon fuel mixture and the oxidant to be supplied to the FLOX burner; and Wherein the third nozzle and the fourth nozzle are arranged in parallel to allow the first auxiliary fuel and an optional oxidant to be supplied to the start-up burner, Wherein the at least one hydrocarbon storage tank is connected to the flameless combustion device by means allowing fluid communication between the at least one hydrocarbon storage tank and the flameless combustion device.

20. The system for flameless combustion according to claim 19, wherein, The second injection port and the furnace are configured to allow flameless combustion of the first auxiliary fuel at an exhaust gas recirculation rate from 0 to 0.

5.

21. The system for flameless combustion according to claim 20, further comprising: An intermediate storage tank, means for fluidly connecting the hydrocarbon storage tank to the intermediate storage tank, means for fluidly connecting the hydrocarbon storage tank to the flameless combustion device, and / or means for fluidly connecting the intermediate storage tank to the flameless combustion device.

22. Use of the system for flameless combustion according to claim 21 or the flameless combustion device according to claim 1 for degassing a hydrocarbon storage tank, the hydrocarbon storage tank being part of the system for flameless combustion.

23. Use of the system for flameless combustion according to any one of claims 21-22 for degassing a hydrocarbon storage tank of a ship.

24. A method for degassing a hydrocarbon storage tank within a flameless combustion system according to claims 21-23, wherein, The method comprises the following steps: - Pumping out any liquid from the hydrocarbon storage tank until less than 5% by volume of the hydrocarbon storage tank is filled with hydrocarbon liquid; - Fluidly connecting the hydrocarbon storage tank of the container / ship to the intermediate storage tank; - Evaporating the residual hydrocarbon liquid in the hydrocarbon storage tank; - Allowing the evaporated hydrocarbon to move from the hydrocarbon storage tank to the intermediate storage tank; - Optionally condensing and / or compressing the evaporated hydrocarbon in the intermediate storage tank; - Conveying at least a major part of the evaporated, condensed and / or compressed hydrocarbon from the intermediate storage tank to a flameless combustion device configured to perform the flameless combustion method according to any one of claims 3-15, and / or facilitating the output of a minor part of the condensed hydrocarbon, - After removing the residual hydrocarbon liquid in the foregoing steps, purging the hydrocarbon storage tank with an inert gas such as nitrogen, argon or a mixture thereof; - Conveying the hydrocarbon including the purge gas from the hydrocarbon storage tank to: (i) the intermediate storage tank, and / or (ii) a flameless combustion device adapted to perform the method according to any one of claims 3-15; - Conveying at least some of the purge gas including hydrocarbon to the flameless combustion device; - When the temperature of the combustion zone of the flameless combustion device exceeds 850 °C, the gas supplied to the device is combusted under flameless conditions according to the method described in any one of claims 3-15; - Controlling the supply of hydrocarbons including purge gas to the combustion zone to maintain a temperature above 850 °C in order to maintain flameless combustion in the combustion zone; and - When the maximum supply of purge gas to the combustion zone of the flameless combustion device becomes insufficient to maintain a temperature above 850 °C, auxiliary fuel is supplied to the combustion zone of the combustion device, and the following are combusted under flameless conditions according to the method described in any one of claims 3-15: (i) the auxiliary fuel; and (ii) both the hydrocarbons of the purge gas.

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