System and method for recycling oxygen-rich combustion flue gas of bell-type annealing furnace

Abstract

The invention relates to the technical field of flue gas recirculation, in particular to a bell-type annealing furnace oxygen-rich combustion flue gas recycling system and method, and the system comprises a circulating flue gas heating cylinder, an oxygen-rich combustor and a system control valve group; oxygen of the oxygen-rich combustor is mixed with fuel, after the fuel enters the circulating flue gas heating cylinder, the oxygen is mixed with part of the fuel to form root flame, and the unburned fuel and oxygen are completely combusted in the circulating flue gas heating cylinder to form flameless flame; the number of the circulating flue gas heating cylinders is one or more, each circulating flue gas heating cylinder is provided with an oxygen-rich combustor, heat generated by combustion is used for heating flue gas generated by combustion of oxygen and fuel in the circulating flue gas heating cylinders, the heated flue gas is circulated to the bell-type furnace through the high-temperature and high-pressure circulating flue gas fan, and redundant flue gas is recycled in a centralized mode. According to the system, heat is fully utilized through flue gas circulation, heating uniformity and quality are improved, combustion flue gas is high-purity carbon dioxide, and zero emission of the flue gas can be achieved through trapping and recycling.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flue gas recirculation, in particular to a cover type annealing furnace multi-oxygen combustion flue gas recycling system and method. BACKGROUND

[0002] In the steel industry, the cover type annealing furnace is used for annealing treatment of cold-rolled steel strips, which is an important link in the production process, and the energy consumption and heating annealing effect directly affect the production efficiency and cost. The traditional cover type annealing furnace uses fuel and ordinary air to assist combustion, and the following problems exist in the combustion process: in the flue gas discharged during combustion, the concentration of nitrogen oxides is high, the total amount of flue gas discharged is large, and it cannot meet the increasingly stringent atmospheric pollutant ultra-low emission requirements of the local area, and investment in flue gas treatment equipment is required. The fuel and air combustion heat loss is large, and the nitrogen and oxygen in the air react to generate nitrogen oxides in the combustion process, polluting the environment. In order to solve the above problems, respond to the energy double control target and carbon emission double control target, promote the deep reform of energy and industrial system, save the amount of heating fuel and reduce flue gas emission, therefore, the cover type furnace multi-oxygen combustion heating flue gas recycling device and use method are invented. SUMMARY

[0003] The purpose of the present application is to provide a cover type annealing furnace multi-oxygen combustion flue gas recycling system and method, which can solve the above technical problems.

[0004] The present application provides a cover type annealing furnace multi-oxygen combustion flue gas recycling system, which comprises a circulating flue gas heating cylinder, a multi-oxygen combustor and a system control valve group; the oxygen and fuel of the multi-oxygen combustor are mixed, the oxygen and part of the fuel are mixed to form a root flame after the fuel enters the circulating flue gas heating cylinder, and the unburned fuel is completely burned with oxygen in the circulating flue gas heating cylinder to form a flameless flame; the circulating flue gas heating cylinder is provided with one or more, and one multi-oxygen combustor is arranged on each circulating flue gas heating cylinder, the combustion-supporting mode adopts oxygen combustion-supporting, the heat generated by combustion is used for heating the flue gas generated by the combustion of oxygen and fuel in the circulating flue gas heating cylinder, and the heated flue gas is circulated to the cover type furnace by a high-temperature and high-pressure circulating flue gas fan, the excess flue gas is concentrated and recycled, and zero emission of carbon dioxide flue gas is realized.

[0005] Preferably, the multi-oxygen burner comprises a fuel injection lance, an oxygen injection lance, a circulating flue gas injection lance, and an automatic ignition lance; the fuel injection lance is connected to a fuel control unit through a fuel pipe at the inlet end and directly extends into the combustion zone at the outlet end, the oxygen injection lance is arranged around the fuel injection lance, is connected to an oxygen control unit at the inlet end, and surrounds the fuel injection area in the form of a multi-nozzle at the outlet end, the circulating flue gas injection lance is connected to a circulating flue gas control unit through a pipe at the inlet end and is connected to a circulating flue gas heating cylinder at the outlet end, the automatic ignition lance is fixed on a burner brick fixing panel and adopts a tail premix ignition form, fuel and combustion-supporting agent are mixed in the tail and ignited by a spark plug, the combustion gas is injected into the front part of the automatic ignition lance to ignite the main fuel, and the automatic ignition lance is provided with a flame detector.

[0006] Preferably, the system control valve group comprises a fuel control unit, an oxygen control unit, and a circulating flue gas control unit.

[0007] Preferably, the fuel control unit comprises a filter, a manual valve, a pressure transmitter, a gas shut-off valve, a blind valve, a flow meter, and a flow regulating valve connected in sequence, and further comprises an ignition branch and a diffusion branch, the ignition branch branches from the front of the flow regulating valve, and the diffusion branch branches from the rear of the gas shut-off valve.

[0008] Preferably, the oxygen control unit comprises a shut-off valve, a flow regulating valve, a flow meter, a pressure regulating valve, a pressure transmitter, and a thermal resistor connected in sequence.

[0009] Preferably, the circulating flue gas control unit comprises a circulating flue gas fan, a flow regulating valve, a flow meter, a pressure transmitter, and a thermal resistor connected in sequence.

[0010] Preferably, the heat preservation material of the circulating flue gas heating cylinder is refractory fiber.

[0011] The application also provides a multi-oxygen combustion hot flue gas recycling method for a bell-type annealing furnace, which applies the above system and comprises the following steps.

[0012] One or more multi-oxygen combustion circulating flue gas heating devices are arranged on the bell-type furnace, pure oxygen is used as a combustion-supporting agent to burn with fuel, and the flue gas in the furnace that is drawn back by a high-temperature high-pressure circulating flue gas fan is heated;

[0013] The heated flue gas exchanges heat with the materials in the furnace, and the high-temperature flue gas after heat exchange is led back to the circulating flue gas heating device by the circulating fan to be reheated and recycled.

[0014] The high-purity carbon dioxide flue gas generated by multi-oxygen combustion is recycled and reused in addition to recycling.

[0015] Preferably, the multi-oxygen combustion adopts a diffuse flameless combustion mode.

[0016] Preferably, automatic ignition, double flame detection and automatic protection purging are realized by the PLC control system, and the oxygen flow, fuel flow, circulating flue gas flow and temperature are automatically adjusted, the temperature is automatically increased, heated and kept according to the temperature curve, the fuel supply is increased when the temperature is low, and the fuel supply is reduced when the temperature is high.

[0017] Advantages:

[0018] The fuel and oxygen are high-speed sprayed from independent nozzles, the concentration and partial pressure of triatomic gas in the flame and flue gas are greatly improved due to the absence of a large amount of nitrogen in the combustion-supporting agent, in addition, the effective high-temperature zone of the flame is rigid and large in volume, the flue gas is fully stirred and the temperature is uniform, the radiation heat exchange efficiency is improved, and the flue gas emission heat loss is reduced. The cover type furnace multi-oxygen combustion circulating flue gas heating device uses pure oxygen as a combustion-supporting agent to generate a flame with fuel to heat the flue gas in the furnace that is drawn back by a high-temperature and high-pressure circulating flue gas fan in one or more circulating flue gas heating devices. The flue gas heated by multi-oxygen combustion enters the furnace to exchange heat with the material. In this way, only a small amount of fuel is needed to raise the temperature of the circulating flue gas to the temperature required for heat exchange with the material. Both the flue gas heat can be fully utilized, and the heating uniformity and quality can be improved.

[0019] The flue gas generated by the combustion of oxygen and fuel is high-purity carbon dioxide gas, and the heated flue gas is circulated to the cover type furnace by a high-temperature and high-pressure circulating flue gas fan, and the excess flue gas is recycled. Zero carbon dioxide flue gas emission is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0021] Figure 1 It is a schematic diagram of the overall structure of the system of the present application.

[0022] Explanation of reference numerals: 1-circulating flue gas heating cylinder, 2-multi-oxygen burner, 301-fuel control unit, 302-oxygen control unit, 303-circulating flue gas control unit. DETAILED DESCRIPTION

[0023] The technical solutions of the present application will be described clearly and completely below in connection with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0024] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0025] In addition, the terms "first", "second" are only for descriptive purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features referred to. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited. In addition, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] The technical route of the present application is: one or more multi-oxygen combustion circulating flue gas heating devices are arranged on the cover furnace to replace the existing air combustion heating device, and the multi-oxygen combustion heating flue gas is used to replace the existing air combustion direct heating mode of the material, the multi-oxygen combustion circulating flue gas heating device uses pure oxygen as a combustion-supporting agent to heat the flue gas in the furnace through the high-temperature and high-pressure circulating flue gas fan in one or more circulating flue gas heating devices, and the flue gas is heated in one or more circulating flue gas heating devices. After the flue gas is heated by the circulating flue gas heating device, it enters the furnace for heat exchange. The high-temperature flue gas after heat exchange is introduced back to one or more circulating flue gas heating devices by the circulating fan to be reheated for recycling, so that only a small amount of fuel is needed to increase the temperature of the circulating flue gas to the temperature required for heat exchange with the material. The flue gas generated by multi-oxygen combustion is high-purity high-temperature carbon dioxide gas, and the remaining high-purity carbon dioxide flue gas can be recycled and reused in addition to recycling, which truly realizes no flue gas emission, and the specific scheme is shown in the following embodiment 1.

[0027] Embodiment 1

[0028] A multi-oxygen combustion flue gas recycling system of a cover annealing furnace, comprising a circulating flue gas heating cylinder 1, a multi-oxygen burner 2 and a system control valve group; the oxygen and fuel of the multi-oxygen burner are mixed, the fuel enters the circulating flue gas heating cylinder, the oxygen and part of the fuel are mixed to form a root flame, and the unburned fuel is completely burned with the oxygen in the circulating flue gas heating cylinder to form a flameless flame; the circulating flue gas heating cylinder is provided with one or more, and one multi-oxygen burner is arranged on each circulating flue gas heating cylinder, the combustion-supporting mode adopts oxygen combustion-supporting, and the heat generated by combustion is used for heating the flue gas generated by the combustion of oxygen and fuel in the circulating flue gas heating cylinder. The heated flue gas is circulated to the cover furnace by a high-temperature and high-pressure circulating flue gas fan, and the excess flue gas is recycled.

[0029] Multi-oxygen combustion principle:

[0030] Multi-oxygen combustion uses pure oxygen as a combustion-supporting medium to release heat through strong oxidation reaction with fuel. The flue gas generated by combustion is mainly composed of high-purity carbon dioxide gas. Multi-oxygen combustion is considered to be an innovation in the field of combustion, and the energy-saving and emission-reducing effect is remarkable. The technology realizes clean utilization of fuel and achieves the ideal effect of low carbon and no emission.

[0031] The nitrogen in air accounts for about 78%, and oxygen accounts for about 21%. The nitrogen does not contribute to combustion, and a large amount of nitrogen is heated to the material heating temperature, and nitrogen oxide is generated. The heated nitrogen is discharged at high temperature, which not only causes a large amount of heat loss, but also emits a large amount of flue gas and pollutants. The multi-oxygen combustion technology uses pure oxygen for combustion support, avoids the invalid heat absorption and emission of nitrogen in air, produces less flue gas, and improves the radiation heat transfer efficiency and effective utilization rate of fuel after recycling. At the same time, due to the participation of a large amount of nitrogen in air in combustion, the amount of flue gas and nitrogen oxide generated is greatly reduced, and more than 30-50% of fuel is saved while achieving zero emission of carbon dioxide, achieving the dual effects of energy saving and emission reduction.

[0032] The system control valve group comprises a fuel control unit 301, an oxygen control unit 302, and a circulating flue gas control unit 303.

[0033] The fuel control unit comprises a filter, a manual valve, a pressure transmitter, a gas shut-off valve, a blind valve, a flow meter, and a flow regulating valve connected in sequence, and further comprises an ignition branch and a diffusion branch. The ignition branch branches from the front of the flow regulating valve, and the diffusion branch branches from the rear of the gas shut-off valve. Oxygen and fuel of the multi-oxygen burner are mixed. After the fuel enters the circulating flue gas heating cylinder, the oxygen is first mixed with part of the fuel, a root flame is formed during combustion, and the unburned fuel enters the circulating flue gas heating cylinder and reacts violently with the oxygen in the circulating flue gas heating cylinder to completely burn and form a flameless flame. The oxygen amount can be adjusted within a certain range according to the needs of the combustion process.

[0034] The oxygen control unit comprises a shut-off valve, a flow regulating valve, a flow meter, a pressure regulating valve, a pressure transmitter, and a thermal resistance connected in sequence.

[0035] The circulating flue gas control unit comprises a circulating flue gas fan, a flow regulating valve, a flow meter, a pressure transmitter, and a thermal resistance connected in sequence. The cover furnace multi-oxygen combustion circulating flue gas heating device is provided with one or more circulating flue gas heating cylinders, and a multi-oxygen burner is arranged on each circulating flue gas heating cylinder. The combustion support method adopts oxygen combustion support, and the heat generated by the mixed combustion of fuel and oxygen is used to heat the flue gas generated by the combustion of oxygen and fuel in the circulating flue gas heating cylinder. The heated flue gas in each circulating flue gas heating cylinder is circulated to the cover furnace by a high-temperature and high-pressure circulating flue gas fan for recycling, and the excess flue gas is collected and transported through a pipeline and then recycled.

[0036] The multi-oxygen burner comprises a fuel injection lance, an oxygen injection lance, a circulating flue gas injection lance, and an automatic ignition lance; the inlet end of the fuel injection lance is connected to a fuel control unit through a fuel pipeline, and the outlet end directly extends into a combustion area; the oxygen injection lance is arranged around the fuel injection lance, the inlet end is connected to an oxygen control unit, and the outlet end surrounds the fuel injection area in the form of multiple nozzles; the inlet end of the circulating flue gas injection lance is connected to a circulating flue gas control unit through a pipeline, and the outlet end is connected to a circulating flue gas heating cylinder; the automatic ignition lance is fixed on a burner brick fixing panel, adopts a tail premix ignition form, fuel and combustion-supporting agents are mixed in the tail and then ignited through a spark plug, the combustion gas is injected into the front part of the ignition lance to ignite the main fuel, and the automatic ignition lance is provided with a flame detector. Specifically, the burner brick is installed at the center of the circulating flue gas heating cylinder, and the burner brick is provided with a fixing panel, the purpose of the fixing panel is to fix the oxygen lance, the fuel lance, the ignition lance, and the flame detection device. The automatic ignition lance is fixed on the burner brick fixing panel, adopts a tail premix ignition form, fuel and combustion-supporting agents are mixed in the tail and then ignited through a spark plug, the combustion gas is injected into the front part of the ignition lance to ignite the main fuel of the roaster, and the automatic ignition lance is provided with a flame detector to judge whether ignition is successful. The tail premix ignition automatic ignition lance does not have an ignition component at the end, perfectly solves the high failure rate of the existing end ignition ignition lance, and cannot work in a high-temperature zone. The tail premix ignition automatic ignition lance does not need to be provided with a permanent fire, and fuel consumption is reduced.

[0037] The multi-oxygen combustion system of the bell-type furnace adopts automatic ignition, double-flame detection, and automatic protection and purging system in case of flameout, fully ensures combustion safety. The ignition lance and the main fuel lance are each provided with a flame detection system, when the flameout state occurs, the system automatically closes the fuel supply valve and purges and replaces the fuel valve group and the fuel pipeline after the valve group, and ensures combustion safety.

[0038] The multi-oxygen combustion system of the bell-type furnace has the functions of oxygen flow regulation, fuel flow regulation, fuel and oxygen ratio regulation, circulating flue gas flow regulation, temperature regulation, automatic purging, flame detection, fuel gas leakage detection, fault alarm and cutting, and circulating flue gas emission, fully ensures the start, operation, and safe operation of the combustion system.

[0039] The heat preservation material of the circulating flue gas heating cylinder is refractory fiber. The original cover furnace heat preservation adopts rock wool material, in the production process, the flue gas will take part of the rock wool fiber particles into the flue gas heat exchange system, often causing the heat exchange fin to be blocked, which needs to be disassembled and cleaned frequently, which delays production, and the rock wool heat preservation material has relatively poor durability, is easily affected by humidity, temperature and other external environments, and causes performance to decline. In a high temperature environment, rock wool may melt, producing toxic gases, posing a threat to personnel safety. The patent application replaces the cover furnace heat preservation material with refractory fiber, which has excellent high temperature resistance and will not melt or deform for a long time. Refractory fiber has good chemical stability and can be stable for a long time in harsh working conditions. Refractory fiber is an excellent thermal insulation material that can effectively insulate heat and prevent heat transfer, providing good heat preservation and insulation. Using refractory fiber can perfectly solve the drawbacks of using rock wool for heat preservation.

[0040] The application also provides a multi-oxygen combustion hot flue gas recycling method for a cover furnace, which applies the device described above and comprises the following steps:

[0041] One or more multi-oxygen combustion circulating flue gas heating devices are arranged on the cover furnace, pure oxygen is used as a combustion-supporting agent to burn with fuel, and the flue gas in the furnace that is drawn back by a high-temperature and high-pressure circulating flue gas fan is heated;

[0042] The heated flue gas enters the furnace to exchange heat with the materials, and the high-temperature flue gas after heat exchange is led back to the circulating flue gas heating device by a circulating fan to be heated and recycled;

[0043] The high-purity carbon dioxide flue gas generated by multi-oxygen combustion is recycled and reused in addition to recycling.

[0044] The multi-oxygen combustion adopts a diffuse flameless combustion mode.

[0045] The PLC control system realizes automatic ignition, double-flame detection and automatic protection and purging when extinguishing, and automatically adjusts the oxygen flow, fuel flow, circulating flue gas flow and temperature, automatically increases the fuel supply when the temperature is low, and reduces the fuel supply when the temperature is high.

[0046] The PLC control system comprises a Siemens PLC, an intelligent instrument, a temperature measuring thermocouple, a gas flow detection and adjustment system, an oxygen flow adjustment and detection system, a circulating flue gas flow detection and adjustment system, a safety protection and fault alarm system and an air / fuel ratio setting system. The multi-oxygen combustion circulating flue gas heating device adopts a remote / local control mode and can be manually or automatically controlled.

[0047] Control mode: Multi-oxygen combustion cycle flue gas heating device adopts proportional control mode (i.e. flow measurement closed loop control), oxygen and fuel are supplied in precise proportion. Temperature measurement automatically increases according to temperature curve, automatic ignition, flame detection, flameout alarm and automatic cut-off protection are realized by PLC programming.

[0048] The above control unit takes Siemens S7 series PLC + host computer as the main body to form a control system with various unit instruments and valves. The operation of the control process is realized by PLC, and the flow signal and pressure signal are transmitted to PLC by 4-20 mA.

[0049] The main modes of realizing system safety detection and control are flow regulation and pressure detection, and GFT (burner flameout interlock protection system) is provided in the control unit to ensure the safety of the production process. The system can operate in manual or automatic mode. In manual mode, fuel flow, oxygen flow and circulating flue gas volume can be manually adjusted; in automatic mode, flow control adopts proportional-integral-derivative (PID) control. After setting the fuel flow parameters, oxygen automatically tracks the proportional value, and the flow control parameters can be adjusted through the human-machine interface.

[0050] All pressure, flow, valve opening and fire detection signals enter the PLC system for programming and configuration.

[0051] Safety control system

[0052] Combustion safety system. When the multi-oxygen combustion cycle flue gas heating device is working, if the fuel pressure is too low (lower than the set value), the pressure transmitter will send an alarm signal, and the PLC will simultaneously cut off the supply of fuel, oxygen and circulating flue gas. After the fault is eliminated, the equipment is restarted.

[0053] When the oxygen pressure is overpressure or underpressure, the pressure transmitter will send an alarm signal, and the PLC will simultaneously cut off the supply of fuel, oxygen and circulating flue gas. After the fault is eliminated, the equipment is restarted.

[0054] A pressure and temperature sensor is provided on the circulating flue gas heating cylinder. When the pressure and temperature in the circulating flue gas heating cylinder are higher than the system safety set value, the system automatically interlocks and stops, closes the fuel line and oxygen line cut-off valve and starts the automatic purging program.

[0055] Gas leakage safety system. Gas pipeline and valve group are provided with gas leakage alarm system. When gas leakage occurs, the gas leakage alarm will send an alarm signal. After the leakage is eliminated, production can continue.

[0056] Oxygen pipeline adopts stainless steel material. Oxygen pipeline and its accessories are subjected to degreasing treatment, and are strictly designed and manufactured according to the specifications of oxygen pipeline. Low pressure alarm, quick cut-off and anti-static facilities are provided on the pipeline to ensure safe use.

[0057] The technical features of the cover furnace multi-oxygen combustion circulating flue gas heating device are as follows:

[0058] 1. Cover furnace multi-oxygen combustion improves the heat radiation and heat transfer capacity of the flame, and shortens the flue gas heating time

[0059] The flue gas amount of the cover furnace multi-oxygen combustion circulating flue gas heating device is greatly reduced compared to ordinary air combustion, and the back pressure is small. The fuel and oxygen are sprayed at high speed from independent nozzles. Since there is no participation of a large amount of nitrogen in the combustion aid, the concentration and partial pressure of three-atom and multi-atom gases in the flame and flue gas are greatly improved. According to the gas radiation theory, only three-atom and multi-atom gases have strong radiation ability, thereby greatly improving the radiation capacity of the flue gas. In addition, multi-oxygen combustion is a diffuse flameless combustion method, and the effective high-temperature zone of the flame has sufficient rigidity and a large volume. The flue gas is fully stirred and the temperature is uniform, thereby improving the radiation and heat exchange efficiency and reducing the heat loss of flue gas emission.

[0060] 2. High-temperature flue gas recycling greatly saves heating fuel

[0061] The cover furnace multi-oxygen combustion circulating flue gas heating device uses pure oxygen as a combustion aid to heat the flue gas in the furnace that is drawn back by a high-temperature induced draft fan in one or more circulating flue gas heating devices. The flue gas heated by multi-oxygen combustion enters the furnace to exchange heat with the material. The high-temperature flue gas after heat exchange is drawn back to one or more circulating flue gas heating devices by a circulating fan for reheating to be recycled. Thus, only a small amount of fuel is needed to raise the temperature of the circulating flue gas to the required temperature for heat exchange with the material. This can fully utilize the heat of the flue gas and improve the uniformity and quality of heating.

[0062] 3. The cover furnace multi-oxygen combustion circulating flue gas heating device can reduce fuel consumption by about 30-50% compared to air combustion, thereby reducing the fuel cost of equipment operation.

[0063] 4. The flue gas emission of the cover furnace multi-oxygen combustion circulating flue gas heating device is reduced by 100% compared to air combustion, achieving zero emission of carbon dioxide. The dust content is also greatly reduced. Multi-oxygen combustion achieves denitration at the furnace front, and no denitration equipment is needed for subsequent flue gas treatment, thereby saving the investment in flue gas treatment equipment. The flue gas generated by multi-oxygen combustion is high-purity carbon dioxide, which provides great convenience for carbon dioxide capture and reuse.

[0064] 5. The cover furnace multi-oxygen combustion circulating flue gas heating device uses oxygen for combustion, and no nitrogen is involved in the combustion, so no nitrogen oxides are generated. This achieves the dual effects of energy saving and emission reduction.

[0065] 6. The cover furnace multi-oxygen combustion circulating flue gas heating device adopts program control intelligent automatic adjustment of operating parameters. The heating device is provided with a thermocouple temperature detection and adjustment system. The highest heating temperature can be set through the temperature detection instrument. The temperature is automatically raised according to the temperature curve, and automatic heating and automatic heat preservation are realized. When the temperature is low, the fuel supply is automatically increased, and when the temperature is high, the fuel supply is automatically reduced. Automatic ignition, flame detection, flameout alarm and automatic cut-off protection are realized by PLC programming.

[0066] 7. The cover furnace multi-oxygen combustion circulating flue gas heating device greatly reduces energy consumption and realizes zero emission of CO2 greenhouse gas.

[0067] A. In ordinary air combustion, 78% of nitrogen is heated from low temperature to high temperature and is discharged with flue gas, taking away a large amount of heat. The multi-oxygen combustion circulating flue gas heating device uses pure oxygen for combustion support, and the flue gas volume is greatly reduced, and the heat taken away by the flue gas is also greatly reduced. Therefore, the flue gas heat loss can be greatly reduced, and the fuel consumption can be reduced.

[0068] B. The flue gas volume of the multi-oxygen combustion circulating flue gas heating device is greatly reduced compared with ordinary air combustion support, the back pressure is small, the high temperature area of the flame can be widely used, the flue gas residence time is long, the flue gas heat can be fully utilized, the heat loss taken away by the flue gas can be reduced, and the energy consumption can be reduced.

[0069] C. When using ordinary air combustion support, the combustion support air flow is large, the pipe diameter is thick, and the adjustment valve action speed and accuracy are not ideal. When using oxygen combustion support, the flowmeter pipe diameter is greatly reduced, and the oxygen combustion ratio is adjusted sensitively. In addition, the mixing method of the multi-oxygen combustion circulating flue gas heating device is excellent, and only a small amount of oxygen is needed for complete mixing. Therefore, the oxygen and fuel can be accurately matched, and the fuel waste can be reduced.

[0070] D. The flue gas volume of the cover furnace multi-oxygen combustion circulating flue gas heating device is reduced by 100% compared with air combustion support, and zero emission of carbon dioxide is realized.

[0071] 8. The cover furnace multi-oxygen combustion circulating flue gas heating device can use low-calorific value gas as fuel, saving high-calorific value gas

[0072] Increasing the theoretical combustion temperature, especially the theoretical combustion temperature of low-calorific value gas, can use low-calorific value gas for baking fuel. For the same fuel, the theoretical combustion temperature increases with the increase of the oxygen volume ratio in the combustion support air.

[0073] 9. The cover furnace multi-oxygen combustion circulating flue gas heating device has fast temperature rise, can shorten the heating time by 30%-50% compared with ordinary air combustion support, has high thermal efficiency, and improves production efficiency.

[0074] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A cover annealing furnace multi-oxygen combustion flue gas recycling system, characterized in that, The system comprises a circulating flue gas heating cylinder, a multi-oxygen burner and a system control valve group; the multi-oxygen burner is mixed with oxygen and fuel, the fuel enters the circulating flue gas heating cylinder, the oxygen and part of the fuel are mixed to form a root flame, and the unburned fuel is completely burned with oxygen in the circulating flue gas heating cylinder to form a flameless flame; the circulating flue gas heating cylinder is provided with one or more, and each circulating flue gas heating cylinder is provided with a multi-oxygen burner, the combustion-supporting mode adopts oxygen combustion-supporting, the heat generated by combustion is used for heating the flue gas generated by the combustion of oxygen and fuel in the circulating flue gas heating cylinder, and the heated flue gas is circulated to the cover furnace through a high-temperature and high-pressure circulating flue gas fan, and the excess flue gas is recycled.

2. The cover type annealing furnace multi-oxygen combustion flue gas recycling system according to claim 1, characterized in that, The system control valve group comprises a fuel control unit, an oxygen control unit and a circulating flue gas control unit.

3. The cover type annealing furnace multi-oxygen combustion flue gas recycling system according to claim 2, characterized in that, The multi-oxygen burner comprises a fuel injection gun, an oxygen injection gun, a circulating flue gas injection gun and an automatic ignition gun; the inlet end of the fuel injection gun is connected with the fuel control unit through a fuel pipeline, the outlet end directly extends into a combustion area, the oxygen injection gun is arranged around the fuel injection gun, the inlet end is connected with the oxygen control unit, and the outlet end surrounds the fuel injection area in the form of a multi-nozzle, the inlet section of the circulating flue gas injection gun is connected with the circulating flue gas control unit through a pipeline, and the outlet end is connected with the circulating flue gas heating cylinder, the automatic ignition gun is fixed on a burner brick fixing panel, adopts a tail premix ignition form, the fuel and the combustion-supporting agent are mixed in the tail and ignited through a spark plug, the combustion gas is injected into the front part of the ignition gun to ignite the main fuel, and the automatic ignition gun is provided with a flame detector.

4. The cover type annealing furnace multi-oxygen combustion flue gas recycling system according to claim 3, characterized in that, The fuel control unit comprises a filter, a manual valve, a pressure transmitter, a gas shut-off valve, a blind valve, a flow meter and a flow regulating valve which are connected in sequence, and further comprises an ignition branch and a diffusion branch, the ignition branch is branched from the front of the flow regulating valve, and the diffusion branch is branched from the rear of the gas shut-off valve.

5. The cover type annealing furnace multi-oxygen combustion flue gas recycling system according to claim 3, characterized in that, The oxygen control unit comprises a shut-off valve, a flow regulating valve, a flow meter, a pressure regulating valve, a pressure transmitter and a thermal resistance which are connected in sequence.

6. The cover type annealing furnace multi-oxygen combustion flue gas recycling system according to claim 3, characterized in that, The circulating flue gas control unit comprises a circulating flue gas fan, a flow regulating valve, a flow meter, a pressure transmitter and a thermal resistance which are connected in sequence.

7. The cover type annealing furnace multi-oxygen combustion flue gas recycling system according to claim 1, characterized in that, The heat preservation material of the circulating flue gas heating cylinder is refractory fiber.

8. A method for recycling multi-oxygen combustion hot flue gas of a batch annealing furnace, characterized in that, The system is applied to the steps of: One or more multi-oxygen combustion circulating flue gas heating devices are arranged on the cover furnace, pure oxygen is used as a combustion-supporting agent to burn with fuel, and the flue gas in the furnace is heated through a high-temperature and high-pressure circulating flue gas fan; The heated flue gas exchanges heat with the materials in the furnace, 90% of the high-temperature flue gas is introduced into the circulating flue gas heating device through the circulating fan for heating and recycling; The high-purity carbon dioxide flue gas generated by multi-oxygen combustion is recycled.

9. The cover type annealing furnace multi-oxygen combustion hot flue gas recycling method according to claim 8, characterized in that, The multi-oxygen combustion adopts a diffusion flameless combustion mode.

10. The cover type annealing furnace multi-oxygen combustion hot flue gas recycling method according to claim 8, characterized in that, The PLC control system is used for automatic ignition, double-flame detection, automatic protection and blowing in case of extinguishing, automatic adjustment of oxygen flow, fuel flow, circulating flue gas flow and temperature, automatic temperature rising, heating and heat preservation according to a temperature curve, increasing fuel supply when the temperature is low, and reducing fuel supply when the temperature is high.

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