Carboxylic acid combustion method

Abstract

To provide a carboxylic acid combustion method of vaporizing an aqueous solution of a carboxylic acid to make it easily mixable with main liquid fuel to enhance combustibility thereof so that the release of fume and mist resulting from incomplete combustion is eliminated.SOLUTION: An aqueous solution of a carboxylic acid prepared by dissolving a carboxylic acid such as formic acid and acetic acid in water, is evaporated (vaporized) by a vaporizer 3 to obtain vapor containing a carboxylic acid, and the vapor containing a carboxylic acid is mixed with liquid fuel such as heavy oil together with air and is combusted using combustion means such as a burner 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for burning carboxylic acids. [Background technology]

[0002] In 2020, Japan declared its goal of becoming carbon neutral by 2050. CO2 reduction technologies are advancing in an innovative way, with the goal of using CO2 as a carbon source to produce fuels and chemicals, thereby reducing CO2 emissions from conventional fossil-derived hydrocarbons. Among these, formic acid can be synthesized efficiently from CO2 and H2, so it can be considered a clean raw material that uses CO2. Currently, there are an increasing number of methods for synthesizing formic acid from CO2, and some of them are shown below.

[0003] The first method uses a synthetic catalyst of CO2 and H2 to generate formic acid. The second method is artificial photosynthesis, in which light is applied to CO2 in water, generating formic acid and O2 through the action of a photocatalyst. A third method involves exposing methane in water to chlorine dioxide and light, which produces formic acid and methanol due to the oxidizing effect of the chlorine dioxide. A third method involves replacing methane with ethane to produce acetic acid and ethanol.

[0004] Technologies for producing carboxylic acids such as formic acid and acetic acid from CO2 and fossil-derived hydrocarbons are attracting attention. The reason is that carboxylic acids such as formic acid and acetic acid are the main raw materials for various chemicals and fuels. Carboxylic acids can be used to synthesize conventional fuels, and in the case of formic acid, they can be decomposed to produce H2 fuel.

[0005] Carboxylic acids are liquids, chemically stable, and safe, with no regulations depending on the concentration. In other words, synthesizing carboxylic acids, transporting and storing them as carboxylic acids, and burning them as fuel has become an advantageous option from the standpoints of the environment, economy, and safety. For example, in the above method, formic acid and acetic acid are synthesized in water and, because they are water-soluble, may be extracted as an aqueous solution. The fuel here is assumed to be fuel for boilers, gas turbines, heaters, etc. However, when an aqueous carboxylic acid solution is used as fuel, it is difficult for it to spontaneously combust.

[0006] Although not for fuel use, Patent Document 1 below proposes a technology to increase the combustibility of anthracite, which has low combustibility and is not generally used as boiler fuel, by using alcohol or carboxylic acid, thereby burning it with low NOx. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-214618 Summary of the Invention [Problem to be solved by the invention]

[0008] Aqueous carboxylic acid solutions in a liquid state have a low calorific value per unit mass, making it difficult to burn (spontaneous combustion) using a liquid spray burner. Furthermore, fumes and mist generated during incomplete combustion are harmful to the human body and are corrosive to metal materials.

[0009] The present invention aims to provide a method for burning carboxylic acids in which an aqueous carboxylic acid solution is vaporized to facilitate mixing with a main liquid fuel, thereby increasing combustibility and eliminating the emission of fumes and mist due to incomplete combustion. [Means for solving the problem]

[0010] The method for burning carboxylic acids of the present invention is characterized in that an aqueous carboxylic acid solution is vaporized (steamed) to form a carboxylic acid-containing vapor, and the carboxylic acid-containing vapor is mixed with air and a liquid fuel and combusted by a combustion means such as a burner.

[0011] In the above method, the carboxylic acid-containing vapor can be mixed with air and supplied as secondary or tertiary air to a combustion means such as a burner.

[0012] Furthermore, the method for burning carboxylic acid of the present invention is characterized in that an aqueous carboxylic acid solution is vaporized to form a carboxylic acid-containing vapor, and the carboxylic acid-containing vapor is supplied together with air to a reactor equipped with a heating means such as a heater and a catalyst, whereby catalytic combustion is carried out.

[0013] In these methods, the carboxylic acid that can be used includes formic acid, acetic acid, propionic acid, butyric acid, acrylic acid, and the like.

[0014] The carboxylic acids described above are often converted into aqueous solutions during production or storage, and can be used as they are. Of course, the aqueous solution may also be prepared by dissolving the carboxylic acid in water. [Effects of the Invention]

[0015] In the method for burning carboxylic acids of the present invention, carboxylic acid-containing vapor is mixed and sprayed (or pre-mixed) with a liquid fuel as an atomizing medium, thereby achieving complete combustion and preventing the release of carboxylic acids into exhaust gas. The method of the present invention vaporizes the liquid carboxylic acid, making it easier to mix with liquid fuel and increasing its combustibility, thereby eliminating the emission of mist and fumes due to incomplete combustion. When the carboxylic acid-containing steam is mixed with air and supplied as secondary or tertiary air, it further contributes to improving combustibility and reducing the main fuel. When a formic acid aqueous solution is used as an example of a carboxylic acid aqueous solution, the formic acid itself, even in any amount, improves the combustibility of the liquid fuel, while also contributing to lowering NOx and reducing the main fuel. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is an explanatory diagram showing an example of the schematic configuration of an apparatus to which the carboxylic acid combustion method of the present invention is applied. [Figure 2] FIG. 2 is an explanatory diagram showing another example of the schematic configuration of an apparatus to which the carboxylic acid combustion method of the present invention is applied. [Figure 3] FIG. 3 is an explanatory diagram showing yet another example of the schematic configuration of an apparatus to which the carboxylic acid combustion method of the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments and can be modified as appropriate. 1 to 3 show a schematic configuration of an apparatus to which the carboxylic acid combustion method of the present invention is applied.

[0018] In this embodiment, formic acid is used as an example of a carboxylic acid. Among carboxylic acids, formic acid is a common substance, but it has particularly low flammability and is not suitable for combustion in a burner, so it is treated as a representative example here. The characteristics of formic acid are as follows. It is easily soluble and is available in aqueous solutions of any concentration. In the case of 100%, higher heating value = 5540kJ / kg, lower heating value = 4288kJ / kg In the case of a 75% aqueous solution, the lower heating value is approximately 2500 kJ / kg If it is less than 78%, it is not subject to the Fire Service Act, and if it is less than 90%, it is not subject to the Poisonous and Deleterious Substances Control Act. In addition, formic acid has a boiling point of 100.8°C, making it difficult to concentrate by distillation. Furthermore, formic acid has a low pH, which corrodes and deteriorates metal parts and sealing materials. The reaction formula common to the first and second embodiments is: HCOOH + 1 / 2O → CO + H

[0019] In the first embodiment, a high-pressure airflow internal mixing burner or a high-pressure airflow external mixing burner is used for flame-mixed combustion. In Figures 1 and 2, a high-pressure airflow internal mixing burner is used as an example. The device shown in Figure 1 uses a formic acid solution as an atomizing medium, as an example of a carboxylic acid solution. The formic acid solution is pressurized, heated and vaporized, and used as a fuel atomizing medium in a steam-type atomizing burner, where it is mixed with fuel and burned. While the amount of formic acid itself is arbitrary, it improves the combustibility of liquid fuel, while also contributing to lower NOx and reducing the main fuel (an effect of several percent relative to the boiler evaporation volume is expected). The main fuel may be heavy oil, kerosene, alcohol, or the like.

[0020] Referring to Fig. 1, an aqueous formic acid solution stored in a storage tank 1 is supplied to a vaporizer 3 by a pump 2. The pump 2 can be controlled by an inverter (not shown). The formic acid solution is heated by a heater (not shown) in vaporizer 3, and converted into formic acid vapor, which is then supplied to burner 4. The heater is heated by combustion exhaust heat or, if insufficient, by external energy. 5 is a control valve. Control valve 6 between vaporizer 3 and burner 4 can control the supply amount and vapor state (to prevent liquefaction). Formic acid steam is supplied to the outer side 7 of the double pipe of the burner 4, and is supplied to the mixing chamber 9 at the tip while preheating the main liquid fuel (heavy oil, etc.) supplied to the inner side 8 of the double pipe. In the supply section, formic acid vapor and liquid fuel are mixed and atomized and supplied to the nozzle 10. The mixed mist is sprayed from a nozzle 10 and combusted. 11 is an igniter.

[0021] In the system shown in Figure 2, a formic acid solution, an example of a carboxylic acid solution, is mixed with burner combustion air. When using the formic acid solution as an atomizing medium, it is pressurized, heated, and vaporized. It is then used as a fuel atomizing medium in a steam-type atomizing burner, where it is mixed with fuel and burned. Formic acid itself, regardless of the amount used, improves the combustibility of liquid fuel while also contributing to low NOx emissions and reduced main fuel consumption. The formic acid solution is heated and vaporized, mixed with air supplied by a blower, and supplied to the burner. It is used as a fuel atomizing medium in an air-type atomizing burner. It can also be supplied as secondary or tertiary air, contributing to improved combustibility and reduced main fuel consumption. The effects of Figure 1 can be enhanced by adding vaporized formic acid vapor using a separate pressure pump to the above fuel atomizing medium (an estimated 5-20% effect on the boiler's heat output).

[0022] 2, the formic acid aqueous solution stored in a storage tank 1 is supplied to a vaporizer mixer 13 by a pump 12. The pump 12 can be controlled by an inverter (not shown). Air is supplied to the vaporizer mixer 13 by an air blower 14. During pre-purge and post-purge, air is supplied to the burner 4 through a bypass line 15. 16 is a control valve. In the vaporizing mixer 13, the formic acid solution is heated by a heater (not shown) to produce formic acid vapor. The heater heats the solution by combustion exhaust heat or, if insufficient, by external energy. In the vaporizing mixer 13, air and formic acid vapor are mixed and supplied as diluted formic acid air to the burner 4 (primary air), secondary air, and tertiary air. 1, the heated formic acid solution is pressurized and vaporized by a pump 17, mixed with dilute formic acid air, and supplied as formic acid air to the burner 4 (primary air). The supply amount can be controlled by an inverter (not shown) of the pump 17 and a control valve 18. Formic acid air is supplied to the outer 7 of the double pipe of the burner 4, and is supplied to the mixing chamber 9 at the tip while preheating the main liquid fuel (heavy oil, etc.) supplied to the inner 8 of the double pipe. In the supply section, formic acid air and liquid fuel are mixed and atomized and supplied to the nozzle 10. The mixed mist is sprayed from a nozzle 10 and combusted. 11 is an igniter.

[0023] The second embodiment is for catalytic combustion. In the device shown in Figure 3, a formic acid solution is used as an example of a carboxylic acid solution through catalytic combustion. The formic acid solution can be heated (heated) using combustion exhaust heat, external energy, or direct recirculation of exhaust gas. It may also be used as a burner (flameless combustion) to assist the combustion of conventional fuels. The catalytic combustion effect results in ultra-low NOx exhaust gas and eliminates the emission of formic acid mist and fumes due to incomplete combustion. The formic acid system uses acid-corrosion-resistant materials to prevent corrosion and deterioration. As the catalyst, platinum, palladium, or the like supported on alumina, zeolite, or the like can be used.

[0024] Referring to FIG. 3, the formic acid solution stored in storage tank 19 is supplied to vaporizer 21 by pump 20. Pump 20 can be controlled by an inverter (not shown). In vaporizer 21, the formic acid solution is sprayed, heated, and vaporized into formic acid vapor, which is then mixed with air and supplied to reactor 22 filled with a catalyst. Vaporizer 21 is equipped with heater 23. Heater 23 is heated by combustion exhaust heat or, if insufficient, by external energy. It is also possible to heat the mixture by directly mixing it with combustion exhaust gas. In the reactor 22, the mixture of formic acid steam and air is catalytically combusted to produce high-temperature exhaust gas, which is supplied to a heat recovery section 25 of a boiler 24 (for example, a latent heat recovery boiler). [Explanation of symbols]

[0025] 1, 19 Storage tank 2, 12, 17, 20 pumps 3, 21 Vaporizer 4 Burner 5, 6, 16, 18 Control valves 7 Double pipe outside 8 Inside the double pipe 9 Mixing chamber 10 nozzles 11 Igniter 13 Vaporizer mixer 14 Air blower 15 Bypass Line 22 Reactor 23 Heater 24 Boiler 25 Heat recovery section

Claims

1. A method for burning carboxylic acids, comprising vaporizing an aqueous carboxylic acid solution to form carboxylic acid-containing vapor, mixing the carboxylic acid-containing vapor with air and liquid fuel and burning the mixture in a combustion means, and mixing the carboxylic acid-containing vapor with air to supply as secondary air and tertiary air to the combustion means.

2. A method for burning a carboxylic acid, comprising dissolving a carboxylic acid in water to prepare an aqueous carboxylic acid solution, vaporizing the aqueous carboxylic acid solution to prepare a carboxylic acid-containing vapor, and supplying the carboxylic acid-containing vapor together with air to a reactor equipped with a heating means and a catalyst to carry out catalytic combustion.

3. 3. The method for burning a carboxylic acid according to claim 1, wherein the carboxylic acid is at least one selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid and acrylic acid.

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