Combustion system and combustion method for reducing generation amount of carbon dioxide and / or nitrous oxide

Abstract

To provide a system and method for reducing GHG(greenhouse gas), such as CO2 and N2O, generated by fuel combustion.SOLUTION: A combustion system and a combustion method that reduces a generation amount of carbon dioxide and / or nitrous oxide, can supply a minimum amount of air required to maintain good combustion, using a method that inputs a signal of a carbon monoxide concentration into a control device and controls a flow rate of supply air so that a carbon monoxide concentration in exhaust gas reaches a set value (for example, 200 ppm or less), where an oxygen-enriched air supply device comprises an oxygen concentration meter a supply air amount measurement device, and a supply air flow rate adjustment device; a fuel supply device comprises a supply fuel measurement device; the control device can control the flow rate of the supply air based on signals from the oxygen concentration meter, the supply air volume measurement device, and the supply fuel measurement device; and an exhaust system comprises a carbon monoxide concentration measurement device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a system and method for reducing greenhouse gases (GHGs), such as carbon dioxide (CO2) and nitrous oxide (N2O), generated by fuel combustion and improving the boiler efficiency of a boiler as calculated by the heat loss method, by increasing the proportion of oxygen (oxygen concentration) in the air supplied to the combustion device and raising the combustion temperature in the combustion chamber of the combustion device. [Background technology]

[0002] As part of efforts to prevent global warming, there is a need to reduce the amount of carbon dioxide and / or nitrous oxide emitted from combustion equipment. Carbon dioxide is produced when carbon (C) contained in fuel reacts with oxygen in the combustion chamber of a combustion equipment. Therefore, in order to reduce the amount of carbon produced, it is necessary to reduce the proportion of carbon contained in the fuel that corresponds to the amount of heat required to function as a combustion equipment. Since the function of a combustion equipment installed in a boiler is to convert water into steam using thermal energy, it is possible to reduce the amount of carbon dioxide and / or nitrous oxide produced by improving the amount of heat used to convert water into steam per unit mass, i.e., boiler efficiency.

[0003] In response to this, by using substances that do not contain carbon as fuel for combustion equipment, such as ammonia (NH3) or hydrogen (H2), or by co-firing these, it is possible to either not emit carbon during combustion or reduce carbon emissions in proportion to the co-firing ratio.However, when ammonia is burned, although no carbon dioxide is emitted, there is a possibility that large amounts of nitrous oxide may be emitted, and therefore, in order to achieve a carbon-neutral society, it is necessary to establish technology to reduce nitrous oxide.

[0004] For example, Patent Document 1 describes a "technique for reducing nitrous oxide by using propane or pulverized coal as fuel for a burner and heating the combustion exhaust gas to 1000°C or higher to decompose and reduce nitrous oxide." Patent Document 2 describes a method for reducing nitrous oxide in combustion exhaust gas by passing the combustion exhaust gas through a porous ceramic filter for dust removal, and then passing the exhaust gas through a catalyst layer made of γ-alumina that is placed in an area where the temperature of the exhaust gas is 550°C or higher during the flow of the filter. Patent Document 3 describes a method for reducing nitrous oxide in combustion exhaust gas, in which the nitrous oxide in the combustion exhaust gas is decomposed into nitrogen using a perovskite-type oxide as a catalyst in a range of 600°C or higher, in order to reduce the amount of nitrous oxide in the exhaust gas, which contains nitrous oxide and is generated from a combustion furnace with a low combustion temperature. Patent Document 4 describes a technology in which "in order to effectively decompose nitrous oxide contained in combustion exhaust gas at low temperatures and reduce the amount of nitrous oxide emissions, the combustion exhaust gas containing nitrous oxide is brought into contact with a sulfuric acid-treated zeolite catalyst to decompose the nitrous oxide into nitrogen and oxygen." However, none of the techniques described in the literature mentions the simultaneous reduction of carbon dioxide and nitrous oxide, which are greenhouse gases. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 3-236510 [Patent Document 2] Japanese Patent Application Publication No. 5-15742 [Patent Document 3] Japanese Patent Application Publication No. 5-269352 [Patent Document 4] Japanese Patent Application Publication No. 5-49866 Summary of the Invention [Problem to be solved by the invention]

[0006] Nitrous oxide is generally not produced in high-temperature (above 1300°C) combustion methods (such as pulverized coal combustion, gas combustion, and oil combustion), but is said to be produced in considerable concentrations in low-temperature (700°C to 900°C) combustion methods. Fuel generally consists of carbon, hydrogen, and sulfur (S), and in order to burn it and obtain thermal energy, it is necessary to mix the fuel with oxygen (O2) and ignite it. Since the atmosphere (air) contains approximately 21 vol.% and 23.2 wt.% oxygen, in order to achieve good combustion, one of two methods is used: premixed combustion, in which fuel and air are mixed beforehand and then ignited and burned, or diffusion combustion, in which fuel and air are supplied separately to the combustion chamber, mixed, ignited, and burned, and then continuously mixed and burned afterwards. In the premixed combustion method, it is easy to mix fuel and air uniformly, making it easy to maintain the temperature inside the combustion chamber above the temperature at which nitrous oxide is generated. However, in the diffusion combustion method, fuel and air are supplied separately and mixed and burned inside the combustion chamber, making it difficult to mix them uniformly throughout the combustion chamber.

[0007] The theoretical air amount A0, which is the amount of air theoretically required to burn fuel, is expressed by the following formula. A0= (22.4 / 0.210){c / 12 + 1 / 4(h - o / 8) +s / 32}[Nm 3 / kg-f] ·····(1) In the above formula, "c", "h", "o", and "s" represent the proportions of carbon, hydrogen, oxygen, and sulfur in the fuel, respectively, and "0.210" represents the proportion of oxygen in the air. The theoretical air volume is the amount of air theoretically required for complete combustion of fuel. In the case of premixed combustion, the amount of air required for fuel combustion is almost the same as the theoretical air volume. However, in the case of diffusion combustion, in which fuel and air are supplied separately and mixed and burned in the combustion chamber, it is difficult to mix them uniformly throughout the combustion chamber. Therefore, if only the theoretical air volume is supplied, there will be areas where there is a shortage of air, and unburned gases such as carbon monoxide (CO) and unburned fuel (HC), as well as soot, will be generated and emitted. To prevent this, it is common to supply more air than the theoretical amount to the combustion device, and the ratio of the amount of air actually supplied to the theoretical amount of air is called the excess air ratio. The excess air ratio m is expressed by the following formula, where A is the amount of air actually supplied. A = mA0 (2) The value of the excess air ratio varies depending on the type of combustion equipment and its operating state, but in equipment equipped with a combustion equipment, when effective combustion is occurring (the combustion state when the effect required of the equipment with respect to the supplied fuel is near its maximum), the excess air ratio will be almost constant. In other words, it can be said that the general value of the excess air ratio is determined by the type of equipment and its combustion state.

[0008] When the amount of combustion air A is heated by the thermal energy Q generated by combustion, the temperature is T, and the mean constant pressure specific heat of the air is cp. The relationship between the two is expressed by the following equation. Q = A x cp x (T-25), (T-25) = Q / (A x cp) From the above equation, if the amount of fuel supplied to the combustion chamber is constant, and the mean constant pressure specific heat of the air, cp, is constant, the temperature of the air in the combustion chamber is determined by the amount of combustion air. The amount of combustion air (the amount of air required to burn fuel) A is expressed as the product of the theoretical air amount A0 and the excess air ratio m, as shown in equation (2). The theoretical air amount A0 is expressed as follows, as shown in equation (1): A0= (22.4 / 0.210){c / 12 + 1 / 4(h - o / 8) +s / 32}[Nm 3 / kg-f] ·····(1) It is shown as follows. In equation (1), it can be seen that when the ratio of components contained in the fuel is constant, the theoretical air amount A0 changes depending on the oxygen concentration. From this, it can be seen that by increasing the oxygen concentration in the combustion air above 21%, the theoretical air volume A0 decreases, and if the excess air ratio m is constant, the combustion air volume A also decreases, and therefore the temperature T when the combustion air is heated increases.

[0009] The function of a boiler's combustion device is to convert water into steam using thermal energy. Specifically, fuel is burned in the combustion chamber to generate high-temperature combustion gases, which are then used to convert water into steam (phase change). During this process, the heat contained in the combustion gases is transferred to the water through a canister installed in the combustion device (thermal conduction). Because the amount of heat transferred is proportional to the temperature difference and time, effective heat transfer is achieved by increasing the temperature of the combustion gases and keeping them in the furnace as long as possible. To achieve this, minimizing the amount of air supplied to the furnace (minimizing the excess air ratio, assuming a constant oxygen concentration in the supplied air) increases the temperature of the combustion gases and extends their time in the furnace. However, insufficient mixing of the fuel and air results in incomplete combustion, which not only reduces boiler efficiency but also potentially generates other air pollutants (e.g., PM).

[0010] Therefore, the present invention aims to provide a device and system that is versatile, applicable to existing combustion equipment, and that reduces CO2 emissions during fuel combustion in a combustion equipment and improves boiler efficiency, and that includes the following elements: 1. By using carbon monoxide (CO) contained in exhaust gas as an indicator of incomplete combustion, it is possible to unambiguously determine the superiority or inferiority of fuel in combustion equipment and all combustion equipment that involves combustion. 2. As a method for improving incomplete combustion, the present invention uses a technology that increases the oxygen concentration of the supply air, making it possible to improve incomplete combustion in combustion equipment and all combustion equipment that involves combustion. 3. The excess air ratio, an evaluation index based on the theoretical amount of air required for fuel combustion, is generally used to determine the cause of incomplete combustion. However, in this invention, because a technology is used to increase the oxygen concentration in the supply air, a new term, "excess oxygen ratio," is defined and used in the analysis. [Means for solving the problem]

[0011] Combustion equipment converts the chemical energy of fuel into thermal energy through a process called combustion, and then uses that thermal energy to generate high-temperature combustion gases. Therefore, it is possible to theoretically consider boiler efficiency using the theories of heat transfer engineering and thermodynamics, which are based on combustion engineering, and to consider practical ways to improve it. The basis of combustion is to generate thermal energy by effectively and efficiently combining (completely combusting) fossil fuels such as petroleum, coal, and LNG, which are primarily composed of C (carbon), H (hydrogen), S (sulfur), and O (oxygen), as well as renewable plant and animal fuels, and NH3·H2, which do not contain C as a component of the material, with O (oxygen) in the air. The basis of combustion equipment is to effectively and efficiently change the phase of water (liquid) to steam (gas) using the thermal energy generated by the combustion of fuel.To do this, we will consider the basics of heat transfer engineering, which is the theory for effectively and efficiently transferring the heat contained in combustion gas to water. The present invention provides a system and method for improving boiler efficiency using the principles of combustion engineering, heat transfer engineering, and thermodynamics, as follows:

[0012] The invention described in claim 1 is a combustion system comprising an oxygen-enriched air supply device equipped with an oxygen concentration meter, a supply air flow rate measuring device and a supply air flow rate adjusting device, a fuel supply device equipped with a supply fuel measuring device, a diffusion combustion type combustion device that mixes fuel and air and burns it, and a control device, in which the supply air flow rate is changed (reduced) to an air excess ratio attributable to the combustion device corresponding to the oxygen concentration based on signals from the oxygen concentration meter, supply air flow rate measuring device and supply fuel measuring device, and the combustion temperature is raised while maintaining good combustion, thereby reducing the amount of carbon dioxide and / or nitrous oxide produced.

[0013] The invention described in claim 2 provides a combustion method for reducing the amount of carbon dioxide and / or nitrous oxide produced in a combustion system comprising an oxygen-enriched air supply device equipped with an oxygen concentration meter, a supply air flow rate measuring device, and a supply air flow rate adjusting device, a fuel supply device equipped with a supply fuel measuring device, a diffusion combustion type combustion device that mixes fuel and air and burns it, and a control device, by changing (reducing) the supply air flow rate to an air excess ratio attributable to the combustion device that corresponds to the oxygen concentration based on signals from the oxygen concentration meter, supply air flow rate measuring device, and supply fuel measuring device, and by using a method to increase the combustion temperature while maintaining good combustion.

[0014] The invention described in claim 3 is a combustion system for reducing the amount of carbon dioxide and / or nitrous oxide produced as described in claim 1, which is capable of supplying the minimum amount of air necessary to maintain good combustion by using a method in which an oxygen-enriched air supply device, a fuel supply device, and a diffusion combustion type combustion device in which fuel is mixed with air and burned, are equipped with a carbon monoxide concentration measuring device in the exhaust system, and a signal of the carbon monoxide concentration is input to a control device and the flow rate of the supplied air is controlled so that the carbon monoxide concentration in the exhaust gas becomes a set value (for example, 200 ppm or less).

[0015] The invention described in claim 4 is a combustion method for reducing the amount of carbon dioxide and / or nitrous oxide produced as described in claim 2, which is capable of supplying the minimum amount of air necessary to maintain good combustion by using a method in which, in an oxygen-enriched air supply device, a fuel supply device, and a diffusion combustion type combustion device in which fuel and air are mixed and burned, a carbon monoxide concentration measuring device is provided in the exhaust system, a carbon monoxide concentration signal is input to a control device, and the flow rate of the supplied air is controlled so that the carbon monoxide concentration in the exhaust gas becomes a set value (for example, 200 ppm or less).

[0016] The invention described in claim 5 is characterized by having a system for improving boiler efficiency calculated by the heat input / output method by using a device for adjusting the flow rate [kg / h] of air supplied to a combustion device in a boiler to reduce the amount of air supplied to the combustion device to a value close to the theoretical oxygen amount, which is defined as the amount of oxygen contained in the supply air relative to the amount of oxygen required for the theoretical complete combustion of the elements that make up the fuel, or to an amount at which the concentration of carbon monoxide (CO) contained in the exhaust gas is 200 ppm or less, thereby increasing the temperature of the supply air heated by the combustion of a unit fuel and reducing the flow velocity of the combustion gas in the furnace (combustion chamber of the combustion device) to increase the amount of heat transferred from the combustion gas to the feedwater, thereby maximizing the value of the effective heat output (amount of heat absorbed by the combustion device).

[0017] In a boiler, the boiler efficiency calculated by the heat input / output method is given by the following formula: Boiler efficiency = effective heat output (amount of heat absorbed by the combustion device) / total heat input (low heat value of fuel oil used + heat added to the fuel and air sides other than the heat value of the fuel) In the above formula, the amount of heat absorbed by the combustion device is the amount of heat energy held by the combustion gas in the furnace (combustion chamber of the combustion device) that is transferred to the water supplied to the combustion device. In a combustion device, the amount of heat transferred between materials is proportional to the heat transfer coefficient, heat transfer area, temperature difference between the materials, and time, and the amount of heat transferred within a material is proportional to the thermal conductivity, heat transfer area, temperature difference between the materials, and time. In a specific combustion device, if the heat transfer coefficient, thermal conductivity, and heat transfer area are considered to be the same, the amount of heat transferred will be proportional to the temperature difference between the materials and time. By reducing the flow rate [kg / h] of air supplied to the combustion device, the temperature of the supplied air heated by the combustion of the unit fuel becomes higher, and the speed at which the combustion gas flows in the furnace (combustion chamber of the combustion device) is reduced, so that the combustion gas remains in the furnace for a longer period of time. As a result, the amount of heat transferred from the combustion gas to the water increases, and the amount of heat absorbed by the combustion device increases.

[0018] The invention described in claim 6 is characterized by using a device that adjusts the flow rate [kg / h] of air supplied to the combustion device to reduce the flow rate to a value close to the theoretical oxygen amount, which is defined as the amount of oxygen contained in the supply air relative to the amount of oxygen required for the theoretical complete combustion of the elements that make up the fuel, or to an amount that reduces the concentration of carbon monoxide (CO) contained in the exhaust gas to 200 ppm or less.This method increases the temperature of the supply air heated by the combustion of a unit fuel, reduces the flow rate of the combustion gas in the furnace (combustion chamber of the combustion device), and increases the amount of heat transferred from the combustion gas to the feedwater, thereby maximizing the value of the effective heat output (amount of heat absorbed by the combustion device) and improving the boiler efficiency calculated by the heat input / output method.

[0019] The amount of heat obtained by burning a unit of fuel [kg] is called the calorific value [kJ / kg], and the low calorific value is used to calculate boiler efficiency. The supply air is heated by the combustion of fuel and its temperature rises, but the smaller the amount, the higher the temperature. When calculating boiler efficiency using the heat input / output method, the amount of heat generated when a unit of fuel is burned is constant, so the smaller the amount of air supplied, the higher the temperature of the combustion gases generated. The air supplied to the combustion device becomes high-temperature combustion gas in the furnace, supplies heat to the water supplied to the combustion device, and then becomes exhaust gas and is discharged from the combustion device.However, the smaller the amount of air supplied, the slower the flow rate within the furnace will be, and the longer the air will remain in the furnace. The amount of heat (effective heat output) transferred from the combustion gases generated by the combustion of fuel to the water supplied to the combustion device increases the higher the combustion gas temperature (the greater the temperature difference between the substances) and the longer the combustion gases remain in the furnace, so it can be said that the less air is supplied, the greater the effective heat output and the better the boiler efficiency. However, if this amount is less than the amount of air required to combust the fuel, heat cannot be generated by combustion of the fuel, so there is a minimum value for the amount of air supplied, and this is called the theoretical air amount.

[0020] The invention described in claim 7 is characterized by having a system for improving boiler efficiency calculated by the heat loss method by reducing the amount of exhaust gas by using a device that adjusts the flow rate [kg / h] of air supplied to the combustion device to a value close to the theoretical oxygen amount, thereby reducing the amount of exhaust gas and slowing down the flow rate of the combustion gas in the furnace (combustion chamber of the combustion device), thereby increasing the amount of heat transferred from the combustion gas to the feedwater and lowering the exhaust gas temperature, thereby minimizing the value of heat loss [kJ / h] calculated as the product of the exhaust gas flow rate [kg / h], exhaust gas temperature [℃] and specific heat [kJ / kg·℃].

[0021] The boiler efficiency calculated by the heat loss method is given by the following formula: Boiler efficiency = [1 - (total heat loss in combustion equipment) / (total heat supplied to combustion equipment)] x 100 [%] In the above formula, the "amount of heat supplied to the combustion device [kJ / h]" is calculated by multiplying the fuel consumption [kg / h] burned in the combustion chamber of the combustion device by the lower heating value of the fuel [kJ / kg]. Because the fuel is injected from a burner installed in the combustor, if the discharge pressure of the fuel injection pump is constant, the amount of heat supplied per unit time is almost constant. In contrast, the heat loss in a combustion device (kJ / h) is mainly calculated as the product of the exhaust gas flow rate (kg / h), the exhaust gas temperature (℃), and the specific heat of the exhaust gas (kJ / (kg·℃)), and the exhaust gas flow rate (kg / h) is approximately equal to the amount of air supplied to the combustion device (kg / h). In order to burn the fuel injected from the burner, oxygen contained in the air supplied to the combustion device is required, but the minimum amount of air required to burn a unit mass of fuel [kg-Fuel] is called the theoretical air amount [kg-Air / kg-Fuel], and when fuel is completely burned under conditions of the theoretical air amount, the oxygen concentration in the exhaust gas will be 0 (zero). From this, it can be seen that in order to minimize the heat loss [kJ / h] in a combustion device, which is calculated mainly as the product of the exhaust gas flow rate [kg / h], exhaust gas temperature [℃], and the specific heat of the exhaust gas [kJ / (kg·℃)], if the specific heat of the exhaust gas is considered to be approximately constant, the amount of air supplied to the combustion device can be brought closer to the theoretical air amount, thereby reducing the exhaust gas flow rate and the value of the heat loss. In addition, by reducing the flow rate [kg / h] of air supplied to the combustion device, the speed at which the combustion gas flows in the furnace (combustion chamber of the combustion device) is reduced, and the amount of heat supplied from the exhaust gas to the feedwater increases (the thermal energy contained in the combustion gas decreases), thereby lowering the exhaust gas temperature. In this way, by reducing the flow rate [kg / h] of air supplied to the combustion device, the amount of exhaust gas is reduced and the exhaust gas temperature is lowered, thereby reducing heat loss and improving boiler efficiency.

[0022] The invention described in claim 8 is characterized in that the amount of exhaust gas is reduced by using a device that adjusts the flow rate [kg / h] of air supplied to the combustion device to a value close to the theoretical oxygen amount, thereby reducing the amount of exhaust gas and lowering the flow rate of the combustion gas in the furnace (combustion chamber of the combustion device) to increase the amount of heat transferred from the combustion gas to the feedwater, thereby lowering the exhaust gas temperature, thereby minimizing the value of heat loss [kJ / h] calculated as the product of the exhaust gas flow rate [kg / h], exhaust gas temperature [℃], and specific heat [kJ / kg·℃], thereby improving the boiler efficiency calculated by the heat loss method.

[0023] In a combustion device, the amount of heat transferred between materials is proportional to the heat transfer coefficient, heat transfer area, temperature difference between the materials, and time, and the amount of heat transferred within a material is proportional to the thermal conductivity, heat transfer area, temperature difference between the materials, and time. In a specific combustion device, if the heat transfer coefficient, thermal conductivity, and heat transfer area are considered to be the same, the amount of heat transferred will be proportional to the temperature difference between the materials and time. By reducing the air flow rate [kg / h] supplied to the combustion device, the speed at which the combustion gas flows in the furnace (combustion chamber of the combustion device) is reduced, and the combustion gas stays in the furnace for a longer period of time, which increases the amount of heat transferred from the combustion gas to the water and reduces the exhaust gas temperature.

[0024] The invention described in claim 9 is characterized in that a device is provided for reducing CO2 emitted from the combustion device by mixing ammonia with fossil fuel as fuel for the combustion device, and improving ammonia combustion by increasing the oxygen concentration of the air supplied to the combustion chamber to 22% or more and increasing the combustion temperature in the combustion chamber.

[0025] Theoretically, by bringing the amount of air supplied per unit of fuel in a combustion device closer to the theoretical air amount, boiler efficiency calculated using the heat input / output method and heat loss method will improve; however, to achieve this, it is necessary to effectively and efficiently mix the injected fuel and supply air inside the furnace, and combine (cause a chemical reaction) the C (carbon) and H (hydrogen), the main components of fuel oil, with the O (oxygen) contained in the supply air to produce CO2 and H2O. The minimum amount of air supplied to a combustion device relative to the fuel injected into the furnace is indicated by the theoretical air volume and the oxygen concentration in the exhaust gas. When the oxygen concentration in the exhaust gas is 0 (zero) when the supplied air volume matches the theoretical air volume, it can be said that the fuel is completely burned. However, when the oxygen concentration in the exhaust gas is 0 (zero) or higher when the supplied air volume matches the theoretical air volume, unburned fuel remains in the exhaust gas in the form of HC (hydrocarbons), CO (carbon monoxide), PM (particulate matter), etc. This is undesirable because releasing these substances into the atmosphere has a negative impact on the environment. Furthermore, the presence of unburned fuel in the exhaust gas means that the amount of heat generated by fuel combustion is reduced, which in turn reduces boiler efficiency. For this reason, the amount of air supplied to the combustion device is increased beyond the theoretical amount to prevent the reduction in heat generated by incomplete combustion and the reduction of environmental pollutants remaining in the exhaust gas. To sum up, (1) Boiler efficiency is improved by bringing the amount of air supplied to the combustion device closer to the theoretical air amount. (2) However, if incomplete combustion occurs in the furnace, the amount of heat supplied to the combustion equipment decreases, resulting in a decrease in boiler efficiency, and unburned components remaining in the exhaust gas have a negative impact on the environment. (3) To prevent this, the amount of air supplied to the combustion device should be greater than the theoretical amount to prevent incomplete combustion in the furnace. This means that... Indicators of the combustion state inside the furnace include oxygen concentration (if this value is high, there is a high possibility that the fuel is completely burned), smoke color (the degree of complete combustion can be evaluated by the color of the smoke being black), and carbon monoxide concentration (if this value is high, there is a high rate of incomplete combustion). Even if the oxygen concentration in the exhaust gas is high, if there is an imbalance in the combustion state inside the furnace, incomplete combustion may be occurring. Evaluation based on the color of the smoke is a simple method when visually inspected, but because there are individual differences, it is necessary to express this numerically, which requires an optical sensor and a converter to convert it into a numerical value. In contrast to these evaluation methods, measuring the carbon monoxide (CO) concentration in the exhaust gas using a carbon monoxide (CO) concentration meter makes it possible to continuously evaluate the combustion state.

[0026] The invention described in claim 10 is characterized in that CO2 emitted from a combustion device is reduced by using a method of mixing ammonia with fossil fuel, and ammonia combustion is improved by using a method of increasing the oxygen concentration of the air supplied to the combustion chamber to 22% or more, thereby increasing the combustion temperature in the combustion chamber. This system improves boiler efficiency, calculated using the heat loss method, by reducing the flow rate [kg / h] of air supplied to the combustion device. It is characterized by using a method in which the quality of the combustion state in the furnace is evaluated by the concentration of carbon monoxide (CO), and the amount of air supplied is adjusted in conjunction with this.

[0027] When evaluating the combustion state in a furnace based on the carbon monoxide (CO) concentration in the exhaust gas, the absolute value of the carbon monoxide (CO) concentration is important in determining whether combustion is good or bad. According to the Ministry of the Environment's "Environmental Standards for Carbon Monoxide," (1) These environmental standards shall apply to any area or place where the general public lives or works on a regular basis. (2) However, this standard does not apply to roadways and other places used exclusively for the driving or parking of automobiles. The limit is set at 10 to 20 ppm (6 ppm as amended in 2022). Combustion equipment is not used in "any area or place where the general public lives and works on a regular basis," and the chimneys through which exhaust gas from combustion equipment is discharged into the atmosphere are generally located above the combustion equipment. Therefore, after being released into the atmosphere, the exhaust gas will diffuse and it is unlikely that the levels will exceed the Ministry of the Environment's "environmental standards for carbon monoxide." The carbon monoxide concentration in exhaust gas emitted from internal combustion engines, which are often used in generators, often indicates a value of 100 to 300 ppm. Therefore, it is thought that the value for evaluating the quality of combustion in a combustion device could be set at, for example, 100 ppm. However, this value must be determined taking into account other evaluation factors such as oxygen concentration, smoke color, and the absolute amount and composition of PM.

[0028] The invention described in claim 11 is a system for improving combustion and efficiency of a combustion device described in claim 1, characterized in that a device is installed to mix water with fuel in order to improve combustion and reduce NOx produced during combustion.

[0029] By mixing water into the fuel, the fuel injected from the fuel injector and the air supplied to the combustion chamber can be mixed effectively and efficiently, which is said to improve combustion. By reducing the amount of air supplied relative to the injected fuel and bringing it closer to the theoretical amount, boiler efficiency can be improved, but generally, combustion deteriorates rapidly when the amount of air supplied falls below a certain value. To prevent this, by installing a device that mixes water with the fuel, it may be possible to maintain good combustion even when the amount of air supplied approaches the theoretical amount in a combustion device operating in a steady state (constant fuel injection amount).

[0030] The invention described in claim 12 is a method for improving combustion and efficiency of the combustion device described in claim 2, characterized in that by using a method of mixing water with fuel, combustion is improved and NOx produced during combustion is reduced.

[0031] The boiling points of fuel oils at atmospheric pressure are approximately 150°C to 350°C for diesel and heavy oil A, and approximately 350°C to 400°C for vegetable fuels. In contrast, the boiling point of water at atmospheric pressure is 100°C. Therefore, by mixing water into fuel oil in a state where the water droplets are finer than the fuel droplets injected from the fuel injection nozzle, the water droplets mixed with the fuel oil evaporate (vaporize) before the fuel oil in a furnace with high temperatures and pressures close to atmospheric pressure, expanding their volume by approximately 1,500 times. This promotes atomization of the fuel oil, increasing its evaporation and combustion rate, and promoting mixing with the surrounding air during expansion, improving combustion. This potentially allows for good combustion even when the air supply volume to the combustion equipment is close to the theoretical air volume, further improving boiler efficiency. [Effects of the Invention]

[0032] By using the present invention, it is possible to improve boiler efficiency calculated by the input / output heat method and the heat loss method, and reduce GHG (greenhouse gas) emissions. [Brief explanation of the drawings]

[0033] [Figure 1] 1 illustrates an example of a basic configuration according to an embodiment of the present invention. [Figure 2] 1 illustrates an example of a basic configuration according to an embodiment of the present invention. [Figure 3] The following is a specific example according to an embodiment of the present invention. [Figure 4] This shows how to improve boiler efficiency as calculated by the heat loss method. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a basic configuration according to an embodiment of the present invention. This system is composed of an oxygen-enriched air supply device equipped with an oxygen concentration meter, a supply air flow rate measuring device, and a supply air flow rate adjusting device, a fuel supply device equipped with a supply fuel measuring device, a combustion device that mixes fuel and air and burns it, and a control device.By using signals from the oxygen concentration meter, supply air flow rate measuring device, and supply fuel measuring device, the supply air flow rate is changed (reduced) to an air excess ratio attributable to the combustion device that corresponds to the oxygen concentration, and by raising the combustion temperature while maintaining good combustion, the amount of carbon dioxide and / or nitrous oxide produced can be reduced.

[0035] In oxygen-enriched air supply devices, fuel supply devices, and combustion devices that mix fuel and air and burn them, by providing a carbon monoxide concentration measuring device in the exhaust system and inputting a carbon monoxide concentration signal into the control device, it becomes possible to supply the minimum amount of air necessary to maintain good combustion by controlling the flow rate of the supplied air so that the carbon monoxide concentration in the exhaust gas becomes a set value (for example, 200 ppm or less).

[0036] FIG. 2 shows an example of a basic configuration according to an embodiment of the present invention. In the figure, water, fuel, and air are supplied to the combustion device, and the fuel injected from the fuel injector reacts with oxygen contained in the supplied air in the furnace (combustion chamber) to generate heat.

[0037] When fuel is completely burned, the carbon (C), hydrogen (H), and sulfur (S) in the fuel react with the oxygen (O) contained in the supplied air to produce CO2, H2O, and SO2, which are exhausted outside the combustion device. During this process, some of the nitrogen (N) contained in the supplied air reacts with the oxygen to produce nitrogen compounds (NOx), most of which are exhausted outside the combustion device. Additionally, any oxygen (O) not consumed during fuel combustion is simply exhausted outside the combustion device. On the other hand, when fuel does not burn completely, in addition to the components that are emitted outside the combustion device when complete combustion occurs, unburned components of the fuel such as hydrocarbons (HC), carbon monoxide (C) and PM are generated and emitted outside the combustion device together with the exhaust gas.

[0038] When evaluating the quality of combustion in a furnace, the content (concentration) of hydrocarbons (HC), carbon monoxide (C), and PM, which are unburned components of fuel generated when fuel is not completely burned, is used, but measuring hydrocarbons (HC) and PM requires advanced measurement technology and expensive measuring equipment. Therefore, in this invention, we decided to evaluate the quality of combustion using the carbon monoxide (C) concentration, which is relatively easy to measure and available with commercially available, reliable, and inexpensive measuring equipment.

[0039] In the diagram, the carbon monoxide (CO) concentration in the exhaust gas is measured by a "CO Meter," and the signal is sent to a "Controller." If the carbon monoxide concentration sent from the "CO Meter" is higher than a preset value, the rotation speed of the "Blower" is increased to increase the amount of air supplied to the combustion device, and if the carbon monoxide concentration is lower than the preset value, the rotation speed of the "Blower" is decreased to reduce the amount of air supplied to the combustion device. This ensures that the minimum amount of air necessary for combustion is always supplied to the combustion device, making it possible to maintain good boiler efficiency.

[0040] In Figure 1, a control device is used that converts the carbon monoxide concentration value measured by the "CO Meter" into a signal and sends it to the "Controller," which then adjusts the rotation speed of the "Blower" based on that value. However, it is also possible to visually check the carbon monoxide concentration value measured by the "CO Meter" and manually adjust the rotation speed of the "Blower" using that value. In this case, more effective operation can be achieved by using a device that issues an alarm or other notification when the carbon monoxide concentration value measured by the "CO Meter" falls above or below a certain range.

[0041] FIG. 3 shows a specific example according to an embodiment of the present invention. In the figure, the amount of air supplied to the combustion device "Air [Nm 3 / h] decreases, the cross-sectional area "A [m 2 By decreasing the flow velocity (V = Air / A [m / h]) of the fluid (air, combustion gas) passing through the furnace, the time that the fluid that has been supplied to the combustion device and turned into high-temperature combustion gas remains in the furnace is extended. This increases the amount of heat transferred from the combustion gas to the feedwater, increasing the effective heat output (amount of heat absorbed by the combustion device) in the heat input / output method, improving boiler efficiency. At the same time, the exhaust gas temperature, which is the temperature at which the combustion gas is discharged from the combustion device, decreases, reducing heat loss in the heat loss method, improving boiler efficiency.

[0042] Figure 4 shows how to improve boiler efficiency as calculated by the heat loss method. In the figure, (1) In the control device of the combustion device, in order to minimize the amount of exhaust gas relative to the fuel injected from the fuel injection device, the CO (carbon monoxide) concentration in the exhaust gas is continuously measured and the amount of air supplied to the combustion device is adjusted so that it is close to a standard value (for example, 200 ppm) (increasing the amount if the CO concentration is high and decreasing it if it is low). (2) By keeping the amount of air supplied to the combustion device to the minimum amount required for fuel combustion, the amount of exhaust gas is reduced. (3) As the amount of air supplied to the combustion device decreases, the temperature of the combustion gas in the furnace increases and the time the combustion gas remains in the furnace of the combustion device increases, increasing the amount of heat transferred from the combustion gas to the water and lowering the exhaust gas temperature. (4) The reduction in the amount of exhaust gas discharged from the combustion device and its temperature improves the boiler efficiency calculated by the heat loss method. [Industrial Applicability]

[0043] By increasing the proportion of oxygen (oxygen concentration) in the air supplied to the combustion device and raising the combustion temperature in the combustion chamber of the combustion device, the present invention makes it possible to reduce greenhouse gases (GHGs) such as carbon dioxide (CO2) and nitrous oxide (N2O) generated by fuel combustion and improve the boiler efficiency of the boiler, as calculated by the heat loss method.

Claims

1. In a combustion system consisting of an oxygen-enriched air supply device equipped with an oxygen concentration meter, a supply air flow rate measuring device, and a supply air flow rate adjusting device, a fuel supply device equipped with a supply fuel measuring device, a combustion device that mixes fuel and air and burns it, and a control device, the flow rate of the supply air is changed (reduced) to an air excess ratio attributable to the combustion device that corresponds to the oxygen concentration based on signals from the oxygen concentration meter, supply air flow rate measuring device, and supply fuel measuring device, and the combustion temperature is raised while maintaining good combustion, thereby reducing the amount of carbon dioxide and / or nitrous oxide produced.

2. In a combustion system consisting of an oxygen-enriched air supply device equipped with an oxygen concentration meter, a supply air flow rate measuring device, and a supply air flow rate adjusting device, a fuel supply device equipped with a supply fuel measuring device, a combustion device that mixes fuel and air and burns it, and a control device, this combustion method reduces the amount of carbon dioxide and / or nitrous oxide produced by using a method in which the supply air flow rate is changed (reduced) to an air excess ratio attributable to the combustion device that corresponds to the oxygen concentration based on signals from the oxygen concentration meter, supply air flow rate measuring device, and supply fuel measuring device, thereby raising the combustion temperature while maintaining good combustion.

3. 10. A combustion system for reducing the amount of carbon dioxide and / or nitrous oxide produced, as described in claim 1, in which an oxygen-enriched air supply device, a fuel supply device, and a combustion device that mixes fuel and air and burns them are provided with a carbon monoxide concentration measuring device in the exhaust system, and a signal of the carbon monoxide concentration is input to a control device, and the flow rate of the supplied air is controlled so that the carbon monoxide concentration in the exhaust gas becomes a set value (for example, 200 ppm or less), thereby making it possible to supply the minimum amount of air necessary to maintain good combustion.

4. A combustion method for reducing the amount of carbon dioxide and / or nitrous oxide produced as described in claim 2, in which an oxygen-enriched air supply device, a fuel supply device, and a combustion device that mixes and burns air are provided with a carbon monoxide concentration measuring device in the exhaust system, and a signal of the carbon monoxide concentration is input to a control device, and the flow rate of the supplied air is controlled so that the carbon monoxide concentration in the exhaust gas becomes a set value (for example, 200 ppm or less), thereby making it possible to supply the minimum amount of air necessary to maintain good combustion.

5. 2. A combustion system for reducing the amount of carbon dioxide and / or nitrous oxide produced as described in claim 1, characterized in that it has a system for improving boiler efficiency calculated by the heat input / output method, by using a device for adjusting the flow rate [kg / h] of air supplied to the combustion device in the boiler to reduce the amount of air supplied to the combustion device to a value close to the theoretical air amount, thereby increasing the temperature of the supply air heated by the combustion of unit fuel and slowing the flow rate of the combustion gas in the furnace (combustion chamber of the combustion device) to increase the amount of heat transferred from the combustion gas to the feedwater, thereby maximizing the value of the effective heat output (the amount of heat absorbed by the combustion device).

6. 3. A combustion method for reducing the amount of carbon dioxide and / or nitrous oxide produced as set forth in claim 2, characterized in that in a boiler, a device for adjusting the flow rate [kg / h] of air supplied to the combustion device is used to reduce the amount of air supplied to the combustion device to a value close to the theoretical air amount, thereby increasing the temperature of the supply air heated by the combustion of a unit fuel and slowing down the flow rate of the combustion gas in the furnace (combustion chamber of the combustion device), thereby increasing the amount of heat transferred from the combustion gas to the feedwater, thereby maximizing the value of effective heat output (amount of heat absorbed by the combustion device) and improving boiler efficiency calculated by the heat input / output method.

7. 2. A combustion system for reducing the amount of carbon dioxide and / or nitrous oxide produced according to claim 1, characterized in that it comprises a system for improving boiler efficiency calculated by the heat loss method by reducing the amount of exhaust gas in a boiler by using a device for adjusting the flow rate [kg / h] of air supplied to the combustion device to a value close to the theoretical air amount, thereby reducing the amount of exhaust gas and slowing down the flow speed of the combustion gas in the furnace (combustion chamber of the combustion device), thereby increasing the amount of heat transferred from the combustion gas to the feedwater and lowering the exhaust gas temperature, thereby minimizing the value of heat loss [kJ / h] calculated as the product of the exhaust gas flow rate [kg / h], the exhaust gas temperature [°C] and the specific heat [kJ / kg・°C].

8. 3. A combustion method for reducing the amount of carbon dioxide and / or nitrous oxide produced according to claim 2, characterized in that in a boiler, a device for adjusting the flow rate [kg / h] of air supplied to the combustion device is used to reduce the amount of air supplied to the combustion device to a value close to the theoretical air amount, thereby reducing the amount of exhaust gas, and at the same time, a method is used to reduce the flow rate of the combustion gas in the furnace (combustion chamber of the combustion device) and increase the amount of heat transferred from the combustion gas to the feedwater, thereby lowering the exhaust gas temperature, thereby minimizing the value of heat loss [kJ / h] calculated as the product of the exhaust gas flow rate [kg / h], exhaust gas temperature [°C] and specific heat [kJ / kg°C], and improving boiler efficiency calculated by the heat loss method.

9. 10. A combustion system for reducing the amount of carbon dioxide and / or nitrous oxide produced, as described in claim 1, characterized in that the system is for improving boiler efficiency calculated by the heat loss method by reducing the flow rate [kg / h] of air supplied to the combustion device in a boiler, and further comprising a device for evaluating the quality of the combustion state in the furnace based on the concentration of carbon monoxide (CO) and a device for adjusting the amount of air supplied.

10. A combustion method for reducing the amount of carbon dioxide and / or nitrous oxide produced, as described in claim 2, characterized in that in a system for improving boiler efficiency calculated by the heat loss method in a boiler by reducing the flow rate [kg / h] of air supplied to the combustion device, the quality of the combustion state in the furnace is evaluated by the concentration of carbon monoxide (CO), and the amount of air supplied is adjusted based on the result.

11. 10. A combustion system for reducing the amount of carbon dioxide and / or nitrous oxide produced, as described in claim 1, for improving boiler efficiency calculated by the heat loss method by reducing the flow rate [kg / h] of air supplied to the combustion device in a boiler, characterized in that it comprises a device for evaluating the quality of the combustion state in the furnace based on the concentration of carbon monoxide (CO), a device for adjusting the amount of air supplied, and a device for mixing water with the fuel.

12. A combustion method for reducing the amount of carbon dioxide and / or nitrous oxide produced, as described in claim 2, characterized in that in a system for improving boiler efficiency calculated by the heat loss method by reducing the flow rate [kg / h] of air supplied to the combustion device in a boiler, the quality of the combustion state in the furnace is evaluated by the concentration of carbon monoxide (CO) and the amount of air supplied is adjusted, and water is mixed with the fuel.

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