Evaporator control method for reducing nitrogen oxides by adjusting combustion air through real-time detection of exhaust gas components

Abstract

A method for controlling an evaporator for reducing nitrogen oxide by adjusting combustion air through real-time detection of exhaust gas components, the evaporator comprising: a burner unit (10) configured to generate combustion air by receiving fuel from a fuel supply pipe (11); a combustion air supply pipe (20) configured to supply outside air required for combustion of a fuel to the burner unit (10) through a blower (21); an evaporator unit (30) in which heat exchange is performed by the combustion air combusted by the burner unit (10); a discharge vent (40) configured to carry and guide the combustion air to be discharged from the evaporator unit (30);an exhaust gas recirculation (FGR) duct (60) having one end connected to communicate with a flow path of the discharge vent (40) and the other end connected to communicate with a rear end of the blower (21) such that exhaust gases discharged through the discharge vent (40) are collected and mixed with outside air to be supplied to the combustion air supply pipe (20); a first detection sensor unit (70) provided on the flow path of the discharge vent (40) for detecting a concentration of NOx and a concentration of oxygen in the exhaust gases in real time to generate exhaust gas sensing data; a second detection sensor unit (71) provided on a flow path of the combustion air supply pipe (20) for detecting a concentration of NOx and a concentration of oxygen in outside air introduced in real time to generate inflow gas sensing data;and a control unit (80) configured to receive the exhaust gas values ​​measured in real time and the inflow gas values ​​measured in real time from the first detection sensor unit (70), controlling the opening degrees of the first control valve (90) and the second control valve (91), and storing setting values ​​of the opening degrees of the first control valve (90) and the second control valve (91) according to a corresponding load value when concentrations of NOx and oxygen measured by the first detection sensor unit (70) and the second detection sensor unit (71) are less than or equal to target concentrations of NOx and oxygen, wherein the control unit (80) is configured to perform control to resume the first setting process (S100) when a subsequent step load value is transmitted from the load detector (92) in the first setting process (S100) or the second setting process (S200), or both processes;and perform the control to repeatedly perform the second adjustment process (S200) when the subsequent stage is not present to accommodate a change in combustion under the same load.;

Description

[0001] The present invention relates to an evaporator control method for reducing nitrogen oxides (hereinafter referred to as NOx) by adjusting combustion air through real-time detection of exhaust gas components, and more particularly to an evaporator control method for reducing nitrogen oxides by adjusting combustion air through real-time detection of exhaust gas components, in which a first detection sensor unit for detecting the concentrations of oxygen and NOx in the exhaust gas discharged through an exhaust gas vent and a second detection sensor unit for detecting the concentrations of oxygen and NOx in mixed gases containing exhaust gases discharged through an exhaust gas recirculation (hereinafter referred to as FGR) line and outside air (i.e., ambient air) introduced such that reduction of NOx and complete combustion are achieved through accurate real-time control,and when preset opening degrees of a first control valve and a second control valve become inappropriate due to long-term use of an evaporator and a sudden change in a load value, and the preset opening degrees are sensed as inappropriate in real time, so that the settings of the opening degrees of the first and second control valves are controlled again.,

[0002] The use of fossil fuel is increasing due to the rapid advance of industrialization and has led to air pollution and the worsening of global warming.

[0003] One of the main causes of air pollution is attributed to sulfur oxides (SOx) and nitrogen oxides (NOx), which are present in the exhaust gases of engines, vehicles, hot water and steam generating devices, thermoelectric power plants, and factories. Recently, attention to environmental protection has increased, and emission regulations regarding sulfur oxide (SOx) and nitrogen oxide (NOx) have been implemented in every country. In the exhaust gases emitted by industrial facilities such as factories, office buildings, and households, NOx particles accelerate global warming and cause environmental degradation. They have been identified as the main cause of the generation of particulate matter (hereinafter referred to as PM 2.5), which has recently been considered a growing social issue. Therefore, countermeasures are definitely needed.In Korea, emissions are regulated by the Clean Air Conservation Act and the Environmental Policy Framework Act.

[0004] The present Clean Air Conservation Act specifies all pollutants in Annex 1 of the Implementing Regulations and allows for the legal control of air pollutants through pollutant emission standards in Annex 8 of the Implementing Regulations.

[0005] Nitrogen oxide, which is to be reduced by the present invention, is an air pollutant that may be emitted to a level of less than 60 ppm according to the law (gaseous fuel, less than 10 tons of vaporization per hour for a vaporizer constructed on or after January 1, 2015).

[0006] Nitrogen oxide can be referred to as NOx. Eight types of NOx such as N 2 E, NE, N 2 O 3 , NO 2 , N 2 O 4 , N 2 O 5 , NO 3 , and N 2 O6 are known. However, in connection with pollutants, NOx is often used to describe NO and NO 2 to be referred to jointly.

[0007] When fuel burns, the first substance produced from combustion is typically NO. NO is converted into NO in the air. 2 oxidized. NOx in the air becomes harmful in itself and causes photochemical smog by being dispersed by sunlight.

[0008] In order to meet the emission control standards for nitrogen oxide, which is one of the air pollutants mainly generated in the combustion of an evaporator, various devices for industrial evaporators and the like are used to treat exhaust gases.

[0009] However, in most cases, the goal is to reduce nitrogen oxides, requiring the provision of a separate reduction device or an exhaust gas sensor unit for the reduction to regularly calculate the relevant data and control the oxygen concentration based on the data. Thus, one limitation is the ability to directly respond to a NOx concentration value that changes in real time.

[0010] With regard to the prior art known, for example, from the publication KR 10 0 173 398 B1, for removing the limitations described above when a combustion device is used for combustion with little air, as is clear from the Fig. 7, the concentrations of carbon monoxide and hydrocarbon are detected as voltages by a sensor 3 and transmitted to a microcomputer 6. In addition, the concentration of oxygen and the temperature of flue gases are simultaneously measured as voltages by oxygen, nitrogen oxide, and temperature sensors and transmitted to the microcomputer 6 for comparison and calculation. A carbon monoxide- and hydrocarbon-rich state due to low-air combustion is determined from a comparison with a reference output voltage of optimal combustion, and until the resultant value reaches a reference voltage, an opening angle of a fan 8 or a damper 7 and an opening time of an injector of an evaporator are adjusted so that the air-fuel ratio is optimized.Namely, in the prior art, the concentration of oxygen and the temperature of the exhaust gases are measured as voltages by the oxygen, nitrogen oxide and temperature sensors and are compared with reference values ​​set in the microcomputer to be calculated, and then the opening angle of the fan or damper and the opening time of the injector of the evaporator are adjusted so that the air-fuel ratio is optimized.

[0011] According to the prior art, an opening degree of a recirculation valve 9 is controlled until output voltages of the oxygen and nitrogen oxide sensors become equal to reference voltages to suppress the discharge of the nitrogen oxide component. In this case, the history of information regarding the opening degree of the recirculation valve that has already been operated is stored as data for each load value of the evaporator. When the current load capacity of the evaporator has a load value that matches one of the preset load values, information regarding the opening degree of the recirculation valve corresponding to the load value is supplied to control the opening degree of the recirculation valve, thus achieving faster and more effective control.When the information regarding the recirculation valve opening degree is used according to the preset value, but the target NOx or oxygen concentration is not obtained, the recirculation valve opening degree is reset. In this case, resetting the recirculation valve opening degree based on the previously stored recirculation valve opening degree according to the load value ensures faster control. Such fast control is achieved because the amount of "trial and error" in controlling the recirculation valve opening degree is reduced.

[0012] However, in the prior art, the opening degree of the recirculation valve 9 is controlled until the output voltages of the oxygen and nitrogen oxide sensors are equal to the reference voltages, so that the discharge of a nitrogen oxide component is suppressed. In this case, the control of the opening degree of the recirculation valve must be performed through a predetermined number of repetitions of trial and error until the output voltages of the oxygen and nitrogen oxide sensors are equal to the reference voltages, and the existing control information is not utilized, thus resulting in ineffectiveness.

[0013] In addition, since the recirculation valve 9 used in the prior art is a valve that merely adjusts the amount of outside air supplied by the blower without allowing recirculated air to be introduced therethrough, the amount of exhaust gases cannot be controlled by the exhaust gas analysis, and thus accurate control is not performed.

[0014] Finally, the semiconductor gas sensor 3 described in the prior art is remarkably flawed due to limitations in the manufacturing process and a significant change in performance with aging. In other words, a component with an absolutely accurate standard value, such as a fixed resistor, can represent its accuracy in a numerical value, whereas a semiconductor gas sensor 3 used for exhaust gases with a wide range of value change cannot ensure its accuracy.

[0015] The publication US 2017 / 0 307 215 A1 discloses the acquisition of real-time measured exhaust gas values ​​by a detection sensor unit. This describes the actuation of the FGR valve based on signals from a NOx and O2 sensor module. The NOx and O2 values ​​are the values ​​of an exhaust gas.

[0016] From the document DE 199 05 166 A1, an oxygen content control of supply air is known in order to suppress excessive smoke development.

[0017] The present invention is directed to providing a technology in which a first detection sensor unit and a second detection sensor unit are respectively provided for detecting, in real time, concentrations of oxygen and NOx in mixed gases introduced into the burner and concentrations of oxygen and NOx in exhaust gases discharged after combustion using zirconium electrolyte measuring devices, and to providing a control unit that controls an opening degree of an exhaust gas recirculation (FGR) line and an opening degree of an outside air inflow pipe by sensing data from the first and second detection sensor units in real time, thereby enabling accurate control for reducing NOx and achieving complete combustion through instantaneous feedback.

[0018] The present invention is directed to providing a technology in which, when preset opening degrees of a first control valve and a second control valve become inappropriate due to use of the evaporator for a long time and a sudden change in a load value, the preset opening degree is sensed as inappropriate in real time so that the settings of the opening degrees of the first and second control valves are controlled again.

[0019] According to one aspect of the present invention, a method is provided for controlling an evaporator for reducing nitrogen oxide by adjusting combustion air through real-time detection of exhaust gas components, the evaporator having: a burner unit (10) configured to generate combustion air by receiving fuel from a fuel supply pipe (11); a combustion air supply pipe (20) configured to supply outside air required for fuel combustion to the burner unit (10) through a blower (21); an evaporator unit (30) in which heat exchange is performed by the combustion air combusted by the burner unit (10); a discharge vent (40) configured to direct and supply the combustion air to be discharged from the evaporator unit; an exhaust gas recirculation (FGR) pipe (60) having one end connected,to be connected to a flow path of the discharge vent (40), and having the other end connected to be connected to a rear end of the blower (21), such that exhaust gases discharged through the discharge vent (40) are collected and mixed with outside air to be supplied to the combustion air supply pipe (20); a first detection sensor unit (70) using zirconium electrolyte measuring devices and provided on the flow path of the discharge vent (40) to sense a concentration of NOx and a concentration of oxygen in the exhaust gases in real time to generate exhaust gas sensing data; a second detection sensor unit (71) using zirconium electrolyte measuring devices and provided on a flow path of the combustion air supply pipe (20) to sense a concentration of NOx and a concentration of oxygen in the outside air in real time,to generate inflow gas sensing data; and a control unit (80) configured to receive the real-time measured exhaust gas values ​​and the real-time measured inflow gas values ​​from the first detection sensor unit (70) and the second detection sensor unit (71), respectively, and to perform real-time control on an opening of a first control valve (90) that controls an amount of outside air introduced by the blower (21) and an opening of the second control valve (91) that controls an amount of exhaust gas collected from the FGR line (60); and a load detector (92) configured to detect a load capacity of the evaporator by checking at least one of a temperature and a pressure of a fluid in the cooking unit (30), having the method: a first setting process (S100),to control a fuel damper (12) and a number of revolutions of a blower motor (22) and to drive the evaporator according to the load value received from the load detector (92) in a state in which the second control valve (91) is closed and the first control valve (90) is open, wherein concentrations of NOx and oxygen are measured by the first detection sensor unit (70), a relationship between sensing data concerning the concentrations of NOx and oxygen received by the first detection sensor unit (70) and thus concentrations of NOx and oxygen are determined by the control unit (80), and the opening degree of the fuel damper (12) or the number of revolutions of the blower motor (22) or both are controlled when at least one of the measured concentrations of NOx and oxygen exceeds a corresponding one of the target concentrations of NOx and oxygen, and a load value,when the measured concentrations of NOx and oxygen are less than or equal to the target concentrations of NOx and oxygen, and the opening degree of the fuel damper (12) and the number of revolutions of the blower motor (22) are stored according to the load value; and a second setting process (S200) to drive the evaporator according to a load value after the first setting process, wherein the opening degrees of the first control valve (90) and the second control valve (91) are controlled, and setting values ​​of the opening degrees of the first control valve (90) and the second control valve (91) are stored according to a corresponding load value when the concentrations of NOx and oxygen measured by the first detection sensor unit (70) and the second detection sensor unit (71) are less than or equal to the target concentration of NOx and oxygen, wherein the control unit (80) is configured to perform a control,to control the first adjustment process (S100) when a subsequent step load value is transmitted from the load detector in the first adjustment process (S100) or the second adjustment process (S200) or both processes; and to perform the control to repeatedly perform the second adjustment process (S200) when the subsequent step load value is not present in order to accommodate a change in combustion under the same load.

[0020] The control unit (80) can store the opening degree of the fuel damper (12), the number of revolutions of the blower motor (22), and the opening degrees of the first and second control valves (90 and 91) for each load value in a storage unit (81), and operates the evaporator with the corresponding load value according to the values ​​stored in the storage unit (81), wherein, when a concentration of NOx or oxygen detected by the first detection sensor unit (70) and the second detection sensor unit (71) exceeds a target concentration of NOx or oxygen during driving of the evaporator, the opening degrees of the first and second control valves (90 and 91) are reset, and the reset opening degrees of the first and second control valves (90 and 91) are stored in the storage unit (81) together with the corresponding load value.

[0021] The control unit (80) may be configured, when the subsequent step load value is transmitted from the load detector (92): to set control values ​​of the opening degree of the fuel damper (12) and the number of revolutions of the blower motor (22) according to the corresponding load value pre-stored in the storage unit (81) as initial values ​​in the first setting process (S100), and to set control values ​​of the opening degrees of the first and second control valves (90 and 91) according to the corresponding load value pre-stored in the memory (81) as initial values ​​in the second setting process (S200). BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above-described other objects, features and advantages of the present invention will become more apparent to those skilled in the art by describing exemplary embodiments thereof in detail with reference to the accompanying drawings, in which: The Fig. 1 is a perspective view showing an evaporator for reducing nitrogen oxide according to an embodiment of the present invention; The Fig. 2 is a conceptual diagram schematically showing a configuration of the evaporator for reducing nitrogen oxide according to the embodiment of the present invention; The Fig. 3 is a flowchart showing a control operation of the evaporator for reducing nitrogen oxide according to the embodiment of the present invention; The Fig. 4 is a flowchart particularly showing a first setting process (an air-fuel ratio control) resulting from the Fig. 3 is evident; The Fig. 5 is a flowchart particularly showing a second setting process (an exhaust gas recirculation (FGR) system control) resulting from the Fig. 3 is evident; The Fig. 6 is a graph showing variations in the concentrations of NOx and oxygen at each load with a real-time FGR according to the present invention; and The Fig. 7 is a conceptual sketch representing the state of the art.

[0023] In the following, advantages and objects to be achieved by the present invention will become clear with reference to the descriptions of the following detailed embodiments when considered in conjunction with the accompanying drawings.

[0024] Terms used herein are used to aid in explaining and understanding the embodiments and are not intended to limit the scope and spirit of the present invention. It should be understood that single forms include multiple forms unless the context clearly dictates otherwise. The terms "comprises," "comprising," "has," and / or "having," when used herein, denote the presence of designated features, integers, stages, acts, elements, components, and / or groups thereof, and do not preclude the presence or addition of one or more other features, integers, stages, acts, elements, components, and / or groups thereof.

[0025] In the description, details of redundant descriptions and related known functions or constructions are omitted to avoid obscuring the subject matter of the present invention.

[0026] The Fig. 1 is a perspective view illustrating an evaporator for reducing nitrogen oxide according to an embodiment of the present invention, and Fig. 2 is a conceptual diagram schematically showing a configuration of the evaporator for reducing nitrogen oxide according to the embodiment of the present invention.

[0027] With reference to the Fig. 1 and Fig. 2, an evaporator 100 includes a burner unit 10 configured to generate combustion air by receiving fuel from a fuel supply pipe 11, a combustion air supply pipe 20 configured to supply outside air required for fuel combustion to the burner unit 10 through a blower 21, an evaporator unit 30 in which heat exchange is performed by combustion air combusted by the burner unit 10, a discharge flue 40 configured to carry and guide the combustion air to be discharged from the evaporator unit 30, an exhaust gas recirculation (FGR) pipe 60 having one end connected to communicate with a flow path of the discharge flue 40 and the other end connected to a rear end of the blower 21 such that exhaust gases collected by the discharge flue 40 are collected and mixed with outside air.to be supplied to the combustion air supply pipe 20, a first detection sensor unit 70 provided on the flow path of the discharge vent 40 for sensing a concentration of NOx or a concentration of oxygen in the exhaust gas, or both, in real time to generate exhaust gas sensing data, a second detection sensor unit 71 provided on a flow path of the combustion air supply pipe 20 for sensing a concentration of NOx or a concentration of oxygen in the introduced outside air, or both, in real time to generate inflow gas sensing data, a control unit 80 configured to receive the exhaust gas values ​​measured in real time and the inflow gas values ​​measured in real time from the first detection sensor unit 70 and the second detection sensor unit 71, respectively, and to perform real-time control on an opening of a first control valve 90,that controls the amount of outside air introduced by the blower 21, and an opening of a second control valve 91 that controls the amount of exhaust gas collected from the FGR line 60, and an air preheating unit 50 installed to be connected to the flow paths of the exhaust vent 40 and the combustion air supply pipe 20 to receive heat from exhaust gases discharged through the discharge vent 40 and transfer the received heat to air introduced from the combustion air supply pipe 20 such that the air is preheated.

[0028] The burner unit 10 is provided to generate a first combustion air by generating a flame using a separate spark generating device through a fuel introduced from the fuel supply pipe 11 and air introduced from the combustion air supply pipe 20.

[0029] The combustion air generated by the burner unit 10 transfers heat to a heat exchange medium such as water present in the evaporator unit 30 while moving along a combustion air transport path formed in the evaporator unit 30.

[0030] Accordingly, the combustion air that has completed the heat exchange is guided to be discharged to the outside through the discharge vent 40. The air preheating unit 50 is provided at the discharge vent 40 to preheat the air introduced into the burner unit 10.

[0031] The air preheating unit 50 is connected to the flow paths of the discharge flue 40 and the combustion air supply pipe 20 to receive heat of the exhaust gases discharged through the discharge flue 40 and transfer the received heat to air introduced from the combustion air supply pipe 20 such that the air is preheated.

[0032] Namely, when the transferred air of the discharge flue 40, while being discharged through the preheating unit 50, transfers heat energy thereof to a plurality of heating tubes of the air preheating unit 50 such that the plurality of heating tubes are heated, and the heating tubes are connected to a path of the combustion air supply pipe 20 leading to the burner unit 10 such that air passing through the path is heated by the heat exchange.

[0033] Since the exhaust gases, which are considered as waste heat, are heat exchanged, the waste heat is collected, and since the gases discharged at high temperature are cooled, various shortages as such caused by high temperature exhaust gases are removed.

[0034] In addition, on a transport path of the discharge vent 40, the FGR line 60 is formed to induce collection of waste heat of the exhaust gases discharged at a rear end portion of the air shaping unit 50 and to reburn exhaust gases containing NOx generated by the combustion to reduce the concentration of NOx in the exhaust gases.

[0035] The FGR duct 60 is configured such that one end of the FGR duct 60 is connected to a rear end of the air preheating unit 50 on the flow path of the discharge vent 40, and the other end of the FGR duct 60 is connected to a rear end side of the blower 21 such that exhaust gas discharged through the discharge vent 40 is collected after being heat-exchanged by the air preheating unit 50, and the collected exhaust gases are mixed with outside air introduced by the blower 21 and preheated by the air preheating unit 50.

[0036] As such, the air transferred from the combustion air supply pipe 20 to the burner unit 10 is provided as mixed gases in which exhaust gases introduced from the FGR pipe 60 are mixed with the outside air introduced from the blower 21, and the mixed gases are preheated by passing through the air preheating unit 50 and then transferred to the burner unit 10 as described above.

[0037] A transmission force of the exhaust gases transported through the FGR line 60 is generated by the blower 21. A circulation force of the blower 21 is also used to introduce outside air while exhaust gases are transmitted from the FGR line 60.

[0038] Meanwhile, the detection sensor unit 70 is provided on the flow path of the discharge vent 40 to sense a concentration of NOx or a concentration of oxygen in the exhaust gas, or both, in real time to generate exhaust gas sensing data, and in one implementation, the first detection sensor unit 70 may be formed on the rear end side of the air preheating unit 50 on the flow path of the discharge vent 40.

[0039] The second detection sensor unit 71 may be provided on the flow path of the combustion air supply pipe 20 to sense a concentration of NOx or a concentration of oxygen in the introduced outside air, or both, in real time to generate inflow gas sensing data, and in one implementation, the second detection sensor unit 71 may be installed on a flow path in which air introduced from the FGR duct 60 to the rear end side of the blower 21 is mixed with the outside air introduced to a front end side of the blower 21, and then the mixed air is moved on the flow path of the combustion air supply pipe 20 to the unit 50.

[0040] Sensors of the first detection sensor unit 70 and the second detection unit 71 are implemented as sensors using the zirconium electrolyte measuring devices, which are widely used for accurate real-time measurement of NOx and have ensured accuracy and durability such that accurate real-time measurement is obtained.

[0041] In addition, the control unit 80 is configured to acquire real-time measured exhaust gas values ​​and real-time measured inflow gas values ​​from the first detection sensor unit 70 and the second detection sensor unit 71, respectively, and analyze the received real-time measured exhaust gas values ​​and real-time measured inflow gas values ​​to perform real-time control of an opening of the first control valve 90 that controls the amount of outside air introduced by the blower 21 and an opening of a second control valve 91 that controls the amount of exhaust gas collected from the FGR line 60.

[0042] The control unit 80 can control the amount of inflow of outside air not only by controlling the first control valve 90 but also by controlling the number of revolutions of the blower motor 22 in the blower 21.

[0043] Namely, when the number of revolutions of the fan motor 22 is changed, the amount of inflow of the outside air is changed even with the same opening degree of the first control valve 90. This is a method of controlling the amount of inflow by controlling the inflow speed of the introduced outside air.

[0044] In addition, the control unit 80 is configured to control a fuel damper 12 for determining the amount of fuel supply of the fuel supply pipe 11 that supplies the burner unit 10 with fuel, and to receive a real-time load value from the load detector 92 for sensing a load capacity of the evaporator by checking at least one of a temperature and a pressure of a fluid in the evaporator unit 30.

[0045] The load value refers to the current load capacity of the evaporator. Upon receiving a load value, the control unit 80 extracts the opening degree of the fuel damper 10 and the number of revolutions of the blower motor 22 for each load, which are pre-stored in the storage unit 81, to check the target oxygen and NOx concentrations (S100).

[0046] Then, the control unit 80 extracts information regarding the opening degree corresponding to the current load value of the evaporator between information regarding the opening degree of the first control valve 90 and information regarding the opening degree of the second control valve 91 in the same load capacity to check the target values ​​of the target concentrations of oxygen and NOx by the second detection sensor unit 71 (S200).

[0047] In addition, the opening control of the control unit 80 is performed by the extracted pre-stored information regarding the opening degree, and the multi-stage control system 100 according to the present invention is characterized by a configuration in which the control unit 80 controls the opening based on the pre-stored opening degree, and then obtains sensing data from the first detection sensor unit 70 and the second detection sensor unit 71 again to determine a need for readjustment of the opening degree in real time.

[0048] In other words, the pre-stored opening degree set for each load is information regarding an opening degree suitable for a previous environment and various environmental factors (e.g., long usage time of the evaporator or a sudden change in load capacity). The opening degree information suitable for the previous environment may not always be suitable for the target concentrations of NOx or oxygen in exhaust gases.Due to the environmental characteristics of use in which all environmental factors are not always set equally, the pre-stored opening degree information is mainly applied, the concentration of NOx or oxygen in the exhaust gases is identified immediately after the first application, and when the identified concentration is larger than a target concentration of NOx or oxygen, the opening degree information of the first control valve 90 and the second control valve 91 is adjusted again.

[0049] In addition, the opening degree information calculated as appropriate in the readjustment process is newly stored in the storage unit 81, and when the same load value is measured later, the openings of the first and second control valves 90 and 91 are controlled according to the corresponding opening degree information.

[0050] In contrast, the prior art described above controls the opening degree of the recirculation valve 9 until output voltages of the oxygen and nitrogen oxide sensors become equal to reference voltages in order to suppress output of the nitrogen oxide compound, as can be seen from the Fig. 7. In this case, the history of the information regarding the opening degree of the recirculation valve that has already been operated is stored as data for each load value of the evaporator. When the current load capacity of the evaporator has a load value that matches any of the pre-stored load values, the information regarding the opening degree of the recirculation valve corresponding to the load value is applied to the control of the opening degree of the recirculation valve, and thus faster and more effective control can be achieved. If the information regarding the opening degree of the recirculation valve according to the pre-stored load value is used but the target concentration of NOx or oxygen is not obtained, the opening degree of the recirculation valve is reset.In this case, if the opening degree of the circulation valve is reset from the pre-stored opening degree of the recirculation valve according to the load value, faster control can be achieved. Such fast control can be achieved because the amount of trial and error in controlling the opening degree of the recirculation valve is reduced.

[0051] Different from the prior art, the present invention stores the opening degree of the control valve that satisfies target concentrations of NOx and oxygen according to the load capacity of the evaporator that have already been controlled as data in the control unit, and performs control from a pre-stored load value that matches the next load capacity of the evaporator and on the basis of an opening degree of the control valve corresponding to the load value, and thus more effective control can be achieved.

[0052] In addition, when the pre-stored opening degree of the control valve according to the load value of the evaporator is applied, but the target concentrations of NOx and oxygen are not satisfied, the opening degree of the control valve is reset, and when the target concentrations of NOx and oxygen are satisfied by the reset opening degree, the opening degree according to the load value is stored as data, and thus sufficient data according to different environments is generated, and the control performance can be improved.In addition, while the prior art has only controlling the inflow of air by only the recirculation valve, which only controls the amount of outside air supplied by the blower, the present invention has controlling the amount of exhaust gas by analyzing the exhaust gas in addition to controlling the inflow of outside air of the blower, and thus, accurate control can be achieved.

[0053] In addition, the present technology does not employ a semiconductor gas sensor having a large error as used in the prior art, but employs a sensor using zirconium electrolyte measuring devices, which ensures accurate real-time measurement and lifetime and accuracy, and thus accurate measurement can be obtained.

[0054] In addition, with reference to the Fig. 3 and Fig. 5 In the control process for satisfying the initial target concentrations of NOx and oxygen, the control unit 80 separately performs the first adjustment process and the second adjustment process by obtaining the first adjustment process by controlling the number of revolutions of the blower motor 22 of the blower 21 and controlling the fuel damper 12 to determine the amount of fuel supplied from the fuel supply pipe to the burner unit 10.

[0055] In this case, a first setting process (S100) is obtained by receiving load values ​​in a state where the second control valve 91 is closed and the first control valve 90 is opened, generating control values ​​of an opening degree of the fuel damper 12 and the number of revolutions of the blower motor 22 in which the concentration of NOx and the concentration of oxygen detected by the first detection sensor unit 70 are less than or equal to target concentrations of NOx and oxygen for each of the load values, and previously storing the generated control values ​​in the storage unit 81.

[0056] A second adjustment process (S200) is performed after using the first adjustment process (S100). The second adjustment process (S200) is obtained by adjusting the opening degree of the fuel damper 12 and the rotational speed of the blower motor 22 to be equal to the control values ​​stored for each load value, adjusting the opening degrees of the first control valve 90 and the second control valve 91 to generate opening degrees of the first control valve 90 and the second control valve 91 in which the concentrations of NOx and oxygen detected by the first and second detection sensor units 70 and 71 are less than or equal to the target concentrations of NOx and oxygen, and further storing the generated opening degrees of the first and second control valves 90 and 91 in the storage unit 81.

[0057] Accordingly, the opening degrees of the first control valve 90 and the second control valve 91 are controlled according to the load value received from the load detector 92 during the operation of the evaporator.

[0058] The Fig. 3 is a flowchart showing a control operation of the evaporator for reducing nitrogen oxide according to the embodiment of the present invention, Fig. 4 is a flowchart particularly showing a first setting process (an air-fuel ratio control) resulting from the Fig. 3 is evident, and the Fig. Fig. 5 is a flowchart particularly showing a second setting process (an FGR system control) resulting from the Fig. 3 is evident.

[0059] Referring to the drawings, a process for controlling the evaporator 100 for reducing nitrogen oxides according to the embodiment of the present invention includes the first setting process (S100) and the second setting process (S200) as described above.

[0060] The first adjustment process (S100) is a process to control an air-fuel ratio, and starts the adjustment with the second control valve 91 closed and the first control valve 90 opened (S110), receives load values ​​from the load detector 92, and performs control on the fuel damper 12 and the rotational speed of the blower motor 22 according to the load values ​​by stages (for example, five to ten load values).

[0061] First, the evaporator is operated according to a first load value (S120), and the concentrations of oxygen and NOx are measured by the first detection sensor unit 70 (S130).

[0062] Accordingly, the control unit 80 determines whether the sensed data received from the first detection sensor unit 70 is less than or equal to the target NOx and oxygen concentrations (S140). For example, if the target NOx concentration is 40 ppm or less and the target oxygen concentration is 3.5% or less, the number of times for sensing the data values ​​sensed thereby is four in total.

[0063] In the first case, the concentration of NOx exceeds 40 ppm and the concentration of oxygen is 3.5% or less, in the second case, the concentration of NOx exceeds 40 ppm and the concentration of oxygen is 3.5% or less, in the third case, the concentration of NOx is 40 ppm or less and the concentration of oxygen is 3.5% or less, and in the fourth case, the concentration of NOx is 40 ppm or less and the concentration of oxygen is 3.5%.

[0064] Since the first case is a case where the concentration of oxygen satisfies the target concentration while the concentration of NOx is larger than the target concentration, which occurs when the supply amount of the fuel is high, the control unit 80 reduces the opening degree of the fuel damper 12 from the previous opening degree (S141).

[0065] The control unit 80 receives sensing data of the exhaust gases discharged with the reduced opening degree of the fuel damper 12 from the first detection sensor unit 70, and again determines whether the concentration of NOx is 40 ppm or less (S141'), and when the concentration of NOx still exceeds 40 ppm, the control unit 80 further reduces the present opening degree reduced from the previous opening degree to a predetermined value, and continuously performs the determination regarding the concentration of NOx by the sensing data of the detection sensor unit 70.

[0066] Due to the occurrence of an opening degree in which at a certain time the concentration of NOx becomes 40 ppm or less and the concentration of oxygen becomes 3.5% or less, the following operation is carried out.

[0067] In addition, the second case is a case where both the oxygen concentration and the NOx concentration exceed the target concentrations, and in this case, the rotational speed of the blower motor 22 and the opening degree of the fuel damper 12 are reduced by a predetermined amount (S142), and checking is performed by the sensed data of the first detection sensor unit 70 as in the first case (S142').

[0068] It should be clearly understood that when both the oxygen concentration and the NOx concentration continuously exceed the target concentrations, both the number of revolutions of the blower motor 22 and the opening degree of the fuel damper 12 are gradually reduced by a predetermined value, and when it is detected that one of the oxygen concentration and the NOx concentration has a concentration equal to or less than the target concentration, one of the rotational speed of the blower motor 22 and the opening degree of the fuel damper 12 corresponding to the corresponding one of the oxygen concentration and the NOx concentration that still exceeds the target concentration is adjusted again.

[0069] As such, when the concentration of NOx and the concentration of oxygen reach 40 ppm or less and 3.5% or less, respectively, at a certain time, as in the first case described above, the subsequent operation is performed.

[0070] The third case is a case where both the NOx concentration and the oxygen concentration are less than or equal to the target concentrations, and thus the subsequent process is performed immediately. The fourth case is a case where the oxygen concentration exceeds the target concentration and the NOx concentration is less than or equal to the target concentration, the amount of outside air inflow is reduced by a predetermined value by the rotational speed of the blower motor 22 (S143), and the checking is performed by the sensing data of the first detection sensor unit 70 (S143').

[0071] When the sensing data of the first detection sensor unit 70 is checked to have concentrations of oxygen and NOx less than or equal to the target oxygen concentration and the target NOx concentration for each of the four cases, the corresponding opening degree of the fuel damper 12 as well as the corresponding rotational speed of the blower motor 22 are stored in a first storage unit (not shown) of the storage unit 81 (S150).

[0072] In this case, it should be understood that the opening degree stored in the first storage unit (not shown) is stored together with the current load value detected by the load detector of the evaporator unit 30.

[0073] Then, the control unit 80 determines whether a subsequent stage load value exists (S160), and if the subsequent stage load value exists, it operates the evaporator with the subsequent stage load value (S170), and performs the process S130 and the subsequent processes as described above, and if the subsequent stage load value does not exist, it ends the first setting process (S100) and the second setting process (S200).

[0074] Meanwhile, the second setting process (S200) is an FGR system control in which the evaporator is operated with the opening degree of the fuel damper 12 and the rotational speed of the blower motor 22 set in the first setting process according to the first load value (S210), with the second control valve 91 opened by a certain amount (S220).

[0075] Accordingly, the sensing data regarding the concentrations of NOx and oxygen measured by the first detection sensor unit 70 and the second detection sensor unit 71 are transmitted to the control unit 80 (S230), and the control unit 80 performs adjustment to match the target concentrations of NOx and oxygen by controlling the opening degrees of the control valve 90 and the second control valve 91 according to the received sensing data (S240).

[0076] Accordingly, the control unit 80 determines whether the sensed data after adjustment is less than or equal to the target concentrations of oxygen, and when the target concentrations are satisfied, the setting values ​​of the opening degrees of the first control valve 90 and the second control valve 91 according to the load value are stored in the storage unit 80 (S250).

[0077] Then, the control unit 80 determines whether a subsequent-stage load value exists (S260). If the subsequent-stage load value exists, it does not perform the second setting process (S200), but resumes the first setting process S130 and sets the control values ​​of the opening degree of the fuel damper 12 and the rotational speed of the blower motor 22 according to the subsequent-stage load value. In this case, the control values ​​of the first fuel damper 12 and the blower motor 22 according to the subsequent-stage load value have the opening degree of the fuel damper 12 and the rotational speed of the blower motor 22 of the corresponding load value prestored in the memory 81 as initial values.

[0078] Conversely, if a subsequent-stage load value is not present, the evaporator is operated according to the corresponding load value, and the above-described processes S230 to S250 are performed. In this case, processes S230 to S250 are repeatedly performed until it is determined in process S260 that the subsequent-stage load value is established. This is because, even under the same load, if the evaporator is operated continuously or for a long time, a change in combustion may occur, causing a change in the exhaust gas components, namely, a change in the NOx concentration and / or the oxygen concentration.Accordingly, the control unit 80 performs the control such that the second setting process, namely, the processes S230 to S250, are repeatedly performed to sense the change in the concentration of NOx and / or the concentration of oxygen in the same load in real time so that the target concentrations of NOx and oxygen are satisfied.

[0079] The opening degree of the fuel damper 12, the speed of the blower motor 22 and the opening degrees of the first and second control valves 90 and 91 are stored in the storage unit 81 for each load value.

[0080] The stored values ​​are generated as data, and when the evaporator is to be operated with a load value of the preceding stage, they are inputted as initial setting values ​​of the opening degree of the fuel damper and the speed of the blower motor in the first setting process and are inputted as initial setting values ​​of the opening degrees of the first and second control valves in the second setting process, and thus the control performance of the evaporator can be improved.

[0081] The Fig. 6 is a graph showing variations in the concentrations of NOx and oxygen for each load with a real-time FGR according to the present invention.

[0082] A section of operation S100 of the Fig. 6 represents the first adjustment process, namely the air-fuel ratio driving of the evaporator, a portion of the process S200 represents the second adjustment process, namely the FGR driving portion, and the subsequent portion represents a stable driving process after the first and second processes.

[0083] The diagram at the top section in the Fig. 6 shows the variation of NOx concentration for each load, and the graph in the lower section shows the variation of oxygen concentration for each load.

[0084] First, it can be seen that the concentration of the first NOx for each load gradually decreases in the process S100 and suddenly increases in the process S200, and stably approaches the target concentration after the FGR.

[0085] Next, it can be seen that the oxygen concentration for each load has a distribution that is stable at a larger load but unstable at a smaller load, but after the FGR approaches the target concentrations for all loads.

[0086] In process S100, the NOx concentration reduction rate is low during air-fuel ratio operation in which the opening degree of the fuel damper and the speed of the blower motor are controlled. However, if the opening degrees of the first and second control valves are precisely controlled according to the combustion change at the same load for each load, as in process S200, the NOx concentration quickly approaches the target concentration. Therefore, the evaporator control method by real-time FGR according to the present invention can improve the NOx concentration reduction efficiency.

[0087] As is clear from the above, instantaneous control data is collected by analyzing sensing data of the first and second detection sensor units, and thus accurate control for the target concentrations of NOx and oxygen can be easily performed.

[0088] In addition, the control unit analyzes the sensing data and controls the opening of the FGR line and the opening of the outside air inlet pipe in real time through the control valves, enabling more precise control to reduce NOx and ensure complete combustion of the evaporator.

[0089] In addition, when the preset opening degrees of the first and second control valves become inappropriate due to the long use of the evaporator or a sudden change in the load value, the preset opening degrees are sensed as inappropriate in real time, so that the setting of the opening degrees of the first and second control valves are re-controlled, and thus always maintain the target concentrations of NOx and oxygen in response to a regular occurrence of an environment in which the set values ​​become inappropriate.

[0090] Although the embodiment of the present invention has been described with reference to the accompanying drawings for illustrative purposes, it should be appreciated by those skilled in the art that various modifications, equivalents and other embodiments are possible without departing from the scope and spirit of the present invention.

[0091] Therefore, the scope of the present invention is defined by the appended claims of the present invention. List of reference symbols 10 burner unit 20 Combustion air supply pipe 30 evaporator unit 40 tax deduction 50 Air preheating unit 60 Exhaust gas recirculation (FGR) line 70 first detection sensor unit 71 second detection sensor unit 80 Control unit 90 first control valve 91 second control valve 100 vaporizers

Claims

[1] A method for controlling an evaporator for reducing nitrogen oxide by adjusting combustion air through real-time detection of exhaust gas components, the evaporator comprising: a burner unit (10) configured to generate combustion air by receiving fuel from a fuel supply pipe (11); a combustion air supply pipe (20) configured to supply outside air required for combustion of fuel to the burner unit (10) through a blower (21); an evaporator unit (30) in which heat exchange is performed by the combustion air combusted by the burner unit (10); a discharge vent (40) configured to carry and guide the combustion air to be discharged from the evaporator unit (30); an exhaust gas recirculation (FGR) duct (60) having one end connected to communicate with a flow path of the discharge vent (40) and the other end connected,to be connected to a rear end of the blower (21) such that exhaust gases discharged through the discharge vent (40) are collected and mixed with outside air to be supplied to the combustion air supply pipe (20); a first detection sensor unit (70) provided on the flow path of the discharge vent (40) for detecting a concentration of NOx and a concentration of oxygen in the exhaust gases in real time to generate exhaust gas sensing data; a second detection sensor unit (71) provided on a flow path of the combustion air supply pipe (20) for sensing a concentration of NOx and a concentration of oxygen in outside air introduced in real time to generate inflow gas sensing data; and a control unit (80) configuredreceiving the exhaust gas values ​​measured in real time and the inflow gas values ​​measured in real time from the first detection sensor unit (70) and the second detection sensor unit (71), respectively, and performing real-time control on an opening of a first control valve (90) that controls an amount of outside air introduced by the blower (21) and an opening of a second control valve (91) that controls an amount of exhaust gas collected from the FGR line (60); and a load detector (92) configured to detect a load capacity of the evaporator by checking at least one of a temperature and a pressure of a fluid in the evaporator unit (30), the method comprising: a first setting operation (S100) of controlling a fuel damper (12) and a rotational speed of a blower motor (22), and operating the evaporator according to a load value received from the load detector (92) in a statein which the second control valve (91) is closed and the first control valve (90) is opened, wherein concentrations of NOx and oxygen are measured by the first detection sensor unit (70), a relationship between measurement data concerning the concentrations of NOx and oxygen received by the first detection sensor unit (70) and target concentrations of NOx and oxygen is determined by the control unit (80), and an opening degree of the fuel damper (12) or the speed of the blower motor (22) or both are controlled when at least one of the measured concentrations of NOx and oxygen exceeds a corresponding one of the target concentrations of NOx and oxygen, and a load value,when the measured concentrations of NOx and oxygen are less than or equal to the target concentrations of NOx and oxygen, and the opening degree of the fuel damper (12) and the speed of the blower motor (22) are stored according to the load value; and a second setting process (S200) to operate the evaporator according to a load value after the first setting process (S100), wherein the opening degrees of the first control valve (90) and the second control valve (91) are controlled, and setting values ​​of the opening degrees of the first control valve (90) and the second control valve (91) are stored according to a corresponding load value when concentrations of NOx and oxygen measured by the first detection sensor unit (70) and the second detection sensor unit (71) are less than or equal to target concentrations of NOx and oxygen, wherein the control unit (80) is configured to perform a control,to resume the first adjustment process (S100) when a subsequent step load value is transmitted from the load detector (92) in the first adjustment process (S100) or the second adjustment process (S200), or both; and to perform the control to repeatedly perform the second adjustment process (S200) when the subsequent step is not present in order to accommodate a change in combustion under the same load. [2] The method according to claim 1, wherein the control unit (80) stores the opening degree of the fuel damper (12), the rotational speed of the blower motor (22), and the opening degrees of the first and second control valves (90 and 91) for each load value in a storage unit (81), and operates the evaporator with the corresponding load value according to the values ​​stored in the storage unit (81), and when a concentration of NOx or oxygen detected by the first detection sensor unit (70) and the second detection sensor unit (71) exceeds a target concentration of NOx or oxygen during operation of the evaporator, the opening degrees of the first and second control valves (90 and 91) are reset, and the reset opening degrees of the first and second control valves (90 and 91) are stored in the storage unit (81) together with the corresponding load value. [3] The method according to claim 2, wherein, with reference to the values ​​stored in the storage unit (81) for each load value, the control unit (80) is configured, when the subsequent step load value is transmitted from the load detector (92), to set control values ​​of the opening degree of the fuel damper (12) and the rotational speed of the blower motor (22) according to the corresponding load value pre-stored in the storage unit (81) as an initial value in the first setting process (S100); and to set control values ​​of the opening degrees of the first and second control valves (90 and 91) according to the corresponding load value pre-stored in the memory (81) as an initial value in the second setting process (S200).

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