A secondary converter flue gas assisted cooling method

Abstract

The present application provides a kind of converter secondary flue gas auxiliary cooling method, belong to converter steelmaking secondary dust removal field.This method includes: setting temperature sensor at the outlet of converter flue gas to measure the temperature of converter exhaust flue gas;Several spray guns for cooling are arranged in the inside of the flue gas box on both sides of the converter and in the secondary pipeline connected with the converter and secondary dust collector;Mixing valve is provided on the secondary pipeline;Each spray gun is provided with an electric valve for controlling start and stop;According to the temperature measured by temperature sensor, the start and stop of each spray gun and mixing valve in the pipeline are regulated, and the flue gas in the pipeline is adaptively cooled.The present application has simple structure, is easy to install, does not need to transform workshop, and simply and effectively solves the problem that the pipeline of secondary flue gas cannot be extended in old steel workshop due to difficulty in transformation, resulting in the burning of dust collector bag and the forced stop of production process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary dust removal of converter steelmaking, and particularly relates to a secondary flue gas assisted cooling method for a converter. BACKGROUND

[0002] In the production process, the secondary dust removal equipment of the converter is an environmental protection measure taken to make up for the deficiency of the primary dust removal, and mainly collects the flue gas emitted during the addition of iron, the addition of scrap steel and the tapping operation. Under normal working conditions, the inlet temperature of the dust collector needs to be lower than 120 DEG C, so as to avoid the burning of the bag caused by high-temperature flue gas and the production stop accident.

[0003] According to the relevant requirements of the ultra-low emission treatment of the steel industry, in the converter process, the operation parameters of the secondary dust removal equipment need to be monitored on the same screen with the parameters of the converter smelting equipment, and the data is saved for more than one year. The online monitoring data of the secondary dust removal is uploaded to the provincial environmental protection website for real-time monitoring. Therefore, it is very important to ensure the normal work of the secondary dust removal equipment.

[0004] However, there is uncertainty in the actual smelting process. Too much powder material is added in the steelmaking raw material, and in the process of adding iron, a large area of flame spouting at the furnace mouth is easy to occur, which causes the temperature of the smoke box inlet to be too high, and even the sparks are directly sucked into the dust removal pipeline. In the process of converter smelting, the scrap steel added into the furnace cannot be 100% qualified. In special cases, the converter may appear a large area of slag spouting. The flame and the flue gas are mixed to form high-temperature flue gas. The temperature of the smoke box in front of the furnace can reach 600-800 DEG C. At this time, once the high-temperature flue gas passes through the pipeline to reach the dust collector, a large area of bag burning will occur. The converter will be shut down. (In the steel industry, due to the limitation of the cost of the bag and the filter material, 120-180 DEG C dust removal bag is generally used), once this fault occurs, the function precision of the secondary dust removal equipment will be reduced, the emission will not meet the standard, and the converter process will be shut down for a long time.

[0005] The existing solution is that the secondary dust removal equipment and the converter body have a certain length distance in the general planning, so that the secondary high-temperature flue gas is sucked into the smoke hood and has a natural cooling process through the dust removal pipeline. However, except for the new and relocated steel enterprises, most of the steel enterprises have not considered the problem of secondary dust removal flue gas cooling when they were built, and the distance between the secondary dust removal equipment and the converter cannot reach the effective cooling distance. In the smelting field, water can be used to cool the flue gas, such as patent CN100357458C “Converter flue gas cooling and dust removal method”. However, the cooling method is to participate in the flue gas circulation by using liquid water. Although this method can achieve the cooling effect, sewage will be generated in the cooling process, and the formed sewage needs to be further treated. The sewage treatment system is increased, and the sewage needs to be recovered and purified to meet the discharge standard. The process is complicated, and the liquid water is easy to freeze in the low temperature state, which is not suitable for the low temperature weather in the north in winter.

[0006] Therefore, a method for cleaning and environmentally-friendly cooling of the secondary flue gas of the converter under the condition of not rebuilding the plant is needed.

[0007] Summary of the invention.

[0008] In view of the problem that the secondary flue gas temperature of the converter is too high due to various reasons, a large number of cloth bags are burned and lost, causing production stop accidents, and the industry cannot effectively control the problem, the present application provides a converter secondary flue gas auxiliary cooling method for cooling the secondary flue gas of the converter and ensuring the normal work of the secondary dust removal equipment.

[0009] Therefore, the present application provides the following technical solutions:

[0010] A converter secondary flue gas auxiliary cooling method, a set of temperature sensors are installed on the flue gas pipeline inside the smoke box on both sides of the converter; a set of spray guns are arranged behind the temperature sensors on the flue gas pipeline inside the smoke box on both sides along the flue gas flow direction; a set of temperature sensors are installed on the straight pipe section of the secondary pipeline, and a plurality of spray guns are arranged on the secondary pipeline at intervals along the flue gas flow direction; the spray guns are inserted into the pipeline from the oblique upper side, and the nozzle direction is installed along the flue gas flow direction; each spray gun is provided with an electric valve for controlling start and stop; the distance between the temperature sensor and the spray gun and the interval distance between the spray guns are set according to the flue gas flow rate, the pipeline length and the electric valve action time, and a air mixing valve is arranged on the secondary pipeline; comprising:

[0011] The multiple temperature sensors arranged at the outlet of the converter flue gas are used to measure the temperature of the converter flue gas in real time;

[0012] The temperature measured by the temperature sensor is used to control the opening and closing of the spray guns and the air mixing valve in the pipeline through the electric valve, and the flue gas temperature is always greater than 110 DEG C when the water mist is used for cooling; the spray gun is a double medium mixed spray gun, and the medium includes water and compressed air; the spray nozzle at the front end of the spray gun, the sprayed water mist particles will be instantly gasified into water vapor under high temperature flue gas, and the water vapor with molecular structure can pass through the dust removal cloth bag and be directly discharged with the filtered flue gas, without forming sewage and mud attached to the surface of the cloth bag.

[0013] Further, the diameter of the water mist particles is within 121 microns.

[0014] Further, the spray gun and the medium pipeline are connected by a metal hose.

[0015] Further, the double medium spray gun has six sets, two of which are arranged inside the smoke box on both sides of the converter, and four of which are arranged in the straight pipe section of the secondary pipeline.

[0016] Further, the opening and closing of the spray guns and the air mixing valve in the pipeline are controlled according to the temperature measured by the temperature sensor, including:

[0017] The opening of the air mixing valve and the spray gun is controlled according to the temperature detected by the temperature sensor inside the smoke box on both sides of the converter.

[0018] During the cooling process, the closing of the air mixing valve and the opened spray gun is controlled according to the temperature detected by the temperature sensor on the straight pipe of the intermediate section of the secondary pipeline.

[0019] Further, the opening of the air mixing valve and the spray gun is controlled according to the temperature detected by the temperature sensor inside the smoke box on both sides of the converter,

[0020] Including:

[0021] When the temperature detected by the temperature sensor inside the smoke box on both sides of the converter is 150-250 DEG C, the air mixing valve is opened to reduce the flue gas temperature value, and the inlet temperature of the dust remover is lower than 120 DEG C.

[0022] When the temperature detected by the temperature sensor inside the smoke box on both sides of the converter is 250-350 DEG C, the air mixing valve is opened, and one spray gun near the inlet of the dust remover is opened for cooling.

[0023] When the temperature detected by the temperature sensor inside the smoke box on both sides of the converter is 350-450 DEG C, the air mixing valve is opened, and two spray guns near the inlet of the dust remover are opened for cooling.

[0024] When the temperature detected by the temperature sensor inside the smoke box on both sides of the converter is 450-500 DEG C, the air mixing valve is opened, and four spray guns in the secondary pipeline are opened for cooling.

[0025] When the temperature detected by the temperature sensor inside the smoke box on both sides of the converter is greater than 500 DEG C, open the air mixing valve and all 6 spray guns to reduce the temperature.

[0026] Further, in the cooling process, the closing of the air mixing valve and the spray guns is controlled according to the temperature sensor on the straight pipe of the middle section of the secondary pipeline, comprising:

[0027] When the temperature detected by the temperature sensor on the straight pipe of the middle section of the secondary pipeline is reduced to 250-350 DEG C, 3 spray guns in the secondary pipeline are closed;

[0028] When the temperature detected by the temperature sensor on the straight pipe of the middle section of the secondary pipeline is reduced to 170-250 DEG C, 4 spray guns in the secondary pipeline are closed;

[0029] When the temperature detected by the temperature sensor on the straight pipe of the middle section of the secondary pipeline is reduced to 110-170 DEG C, all spray guns in the secondary pipeline are closed;

[0030] When the temperature detected by the temperature sensor on the straight pipe of the middle section of the secondary pipeline is less than or equal to 110 DEG C, all spray guns and air mixing valves in the secondary pipeline are closed.

[0031] The advantages and positive effects of the present application are:

[0032] The present application realizes the goal of self-discovery of high-temperature flue gas by the device, and the blocking and cooling of the echelon group by interlocking control of the temperature sensor and the spray gun quick valve. The medium of the spray gun of the present application is water and compressed air, which is not only easy to obtain, but also requires low medium pipeline and has safety. Moreover, the heat of the flue gas is taken away by water vapor, meeting the environmental protection and cooling requirements, and the temperature of the secondary flue gas can be controlled below 120 DEG C, which is much lower than the ignition point of the dust cloth bag, effectively preventing the dust cloth bag from being burned due to high temperature of the flue gas. The water droplet size of the spray gun of the present application is less than 121 mu m, and the gasification is 0.0004 mu m, which can pass through the dust cloth bag (gap 4 mu m), and will not form mud attached to the surface of the cloth bag. After cooling, the water vapor is discharged together with the filtered flue gas, without any waste to be treated. It meets the requirements of cooling, not affecting the dust removal effect of the flue gas, and being clean and environmentally friendly. Thus, the economic loss caused by the failure of the dust remover to work normally and the production stoppage is reduced, and the national call for environmental protection is responded. The device of the present application only needs spray guns and temperature sensors, has less equipment, low cost and small installation difficulty, and does not need to be reconstructed. The spray gun of the present application is inserted into the pipeline from the oblique upper side, which is convenient for removing water in the medium pipeline in winter, preventing ice formation in winter, and causing damage to the equipment. The nozzle direction of the spray gun is installed in the direction of the flue gas flow, which can prevent particles in the flue gas from entering the spray gun and causing blockage. The present application enables the secondary dust removal process of the old smelting steel plant that cannot be reconstructed to run smoothly. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0034] Figure 1 The schematic diagram of the secondary flue gas assisted cooling method in the embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the person skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of the present application.

[0036] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units need not be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0037] According to the guidance scheme in section 6.4.6 of "General Technical Specification for Bag Dust Removal Engineering HJ2020-2012", when the flue gas temperature in the pipeline is greater than 350℃, the flue gas should be cooled. Considering the cost and the occurrence rate of the secondary flue gas higher than 350℃, the most effective cooling medium, water, is selected for secondary flue gas cooling in the present application.

[0038] In general awareness, water injection in the converter secondary flue gas pipeline will cause particulate matter to combine with water droplets, and the combination will deposit in the pipeline, even the dust and water mixed into "mud" attached to the bag surface, causing the bag to be blocked and unable to be effectively used. According to data query, water will vaporize above 100 DEG C, and change into water vapor. The essence of water vapor is composed of countless water molecules. The diameter of water molecules is 0.0004 μm. The filter material commonly used in the steel industry has a filtering accuracy of about 5 μm. In theory, water injection in the closed flue gas pipeline above 350 DEG C will be gasified into water vapor in a short time, and change into small molecules, which will not stay in the pipeline, and will not attach to the surface of the dust bag. The above principle analysis shows that, under the condition that the secondary flue gas temperature is as high as a certain limit, water injection in the secondary pipeline for cooling, as an auxiliary means of the mixing valve, is feasible in principle.

[0039] The inventive concept of the present application is that: by spraying water mist into the secondary flue gas pipeline, the high temperature of the secondary flue gas makes the water mist evaporate into water vapor instantly, and carries away part of the heat, assisting the mixing valve to cool the secondary flue gas; through the linkage control of multiple temperature sensors, the flue gas temperature is maintained within a suitable range.

[0040] In order to facilitate understanding, first, the related equipment is described:

[0041] In order to realize the auxiliary cooling of the converter secondary flue gas, three sets of temperature sensors, six sets of double medium spray guns, six sets of electric valves and other parts are arranged in the present application. Specifically, T101, T102 and T103 are three temperature sensors, two sets (T101, T102) are arranged in the inside of the smoke box on both sides of the converter, and one set (T103) is arranged on the straight pipeline in the middle section of the secondary pipeline, about 100 meters away from the converter. V-ZLP1, V-ZLP2, V-ZLP3, V-ZLP4, V-ZLP5 and V-ZLP6 are six sets of double medium spray guns, which are made of stainless steel and have water and compressed air as the internal medium. The single water supply pressure is 0.3-0.4 Mpa, and the flow is 3-5 m 3Low pressure compressed air pressure 0.6Mpa, single spray gun flow 4500Nm3 / h. Spray gun front nozzle, spray particle size D90<121μm. Two sets of spray guns are arranged inside the smoke box on both sides of the converter, and the remaining four sets are arranged in batches at a distance of about 30 meters in the straight pipe section of the dust collector, considering that the filtration air speed of the straight pipe section is higher than that of the vertical section. In this embodiment, the distance between the converter body and the inlet of the secondary dust collector is about 150 meters, and the high-temperature flue gas is drawn by the suction of the fan at a speed of 18 meters per second during production. Before the high-temperature flue gas reaches the inlet of the dust collector, the temperature of the flue gas is reduced to a safe value or below, the double-medium spray gun is arranged in sections, and the temperature sensor is controlled in a step-by-step starting mode. When high-temperature flue gas failure occurs, the spray gun V-ZLP6 at the end of the pipe is started first to spray and cool, avoiding the situation that the high-temperature flue gas has passed through other spray guns and cannot be effectively cooled. If the temperature of the flue gas exceeds a certain range, the spray guns are started from the back to the front to overcome the contradiction between the flue gas flow rate and the cooling.

[0042] As shown in Figure 1 The embodiment of the present application provides a converter secondary flue gas auxiliary cooling method. During production, when T101, T102 detect that the secondary flue gas temperature is 120℃ higher, the following specific steps are executed:

[0043] S1, when T101, T102 detect that the temperature is 150-250℃, open the air mixing valve to reduce the flue gas temperature value, and the dust collector inlet temperature is lower than 120℃;

[0044] S2, when T101, T102 detect that the temperature is 250-350℃, open the air mixing valve and start V-ZLP6 spray gun to cool;

[0045] S3, when T101, T102 detect that the temperature is 350-450℃, open the air mixing valve and start V-ZLP6, V-ZLP5 spray gun to cool;

[0046] S4, when T101, T102 detect that the temperature is 450-500℃, open the air mixing valve and start V-ZLP3, V-ZLP4, V-ZLP5, V-ZLP6 spray gun to cool;

[0047] S5, when T101, T102 detect that the temperature is above 500℃, open the air mixing valve and start all V-ZLP1, V-ZLP2, V-ZLP3, V-ZLP4, V-ZLP5, V-ZLP6 spray guns to cool.

[0048] In the cooling process, in order to avoid the temperature of flue gas being too low, causing the combination of particulate matter and water droplets, the combination depositing in the pipeline, even the dust and water mixing into "mud" adhering to the bag surface, causing the bag to be blocked and unable to be effectively used. The specific steps of adjusting the closing of the spray gun and the air mixing valve by the temperature measured by T103 are as follows:

[0049] S1, when the temperature detected by T103 is 250-350 DEG C, the spray guns V-ZLP5, V-ZLP4 and V-ZLP3 are closed;

[0050] S2, when the temperature detected by T103 is 170-250 DEG C, the spray guns V-ZLP3, V-ZLP4, V-ZLP5 and V-ZLP6 are closed;

[0051] S3, when the temperature detected by T103 is 110-170 DEG C, all the spray guns V-ZLP1, V-ZLP2, V-ZLP3, V-ZLP4, V-ZLP5 and V-ZLP6 are closed;

[0052] S4, when the temperature detected by T103 is less than or equal to 110 DEG C, all the spray guns V-ZLP1, V-ZLP2, V-ZLP3, V-ZLP4, V-ZLP5 and V-ZLP6 and the air mixing valve are closed.

[0053] In order to facilitate understanding, one of the converter secondary flue gas auxiliary cooling methods in the above embodiments is described below with an application example.

[0054] The D furnace blower of the steelmaking plant, the secondary dust removal monitoring system alarm, the computer records show that the temperature of the flue gas tank on both sides of the converter is as high as 583.6 DEG C at T101 measuring point and 643.4 DEG C at T102 measuring point.

[0055] The PLC control system starts the auxiliary cooling system according to the program; the air mixing valve is opened, and all the spray guns V-ZLP1, V-ZLP2, V-ZLP3, V-ZLP4, V-ZLP5 and V-ZLP6 are opened for cooling; during the cooling process, when the temperature measured by T103 is lower than 350 DEG C, the spray guns V-ZLP4, V-ZLP5 and V-ZLP6 are closed; when the temperature measured by T103 is lower than 250 DEG C, the spray gun V-ZLP3 is also closed; when the temperature measured by T103 is lower than 170 DEG C, all the spray guns are closed; when the temperature measured by T103 is lower than 110 DEG C, the air mixing valve is also closed. At this time, the inlet temperature of the dust remover is only 52 DEG C. After cooling by the method of the application, none of the dust remover bags is burned, and the one-time production equipment accident is successfully avoided.

[0056] The C furnace of the steelmaking plant, the secondary dust removal monitoring system alarm, the computer records show that the temperature of the flue gas tank on both sides of the converter is as high as 414 DEG C at T101 measuring point and 365.5 DEG C at T102 measuring point.

[0057] PLC control system according to the program set to start auxiliary cooling system, computer record display, at this time the dust collector inlet temperature is only 62℃. The dust collector bag no burn loss, successfully avoid a production equipment accident.

[0058] Two short-term flue gas temperature is higher than 350℃ case occurs, verify the system is indeed effective. According to the past experience estimate, when the flue gas temperature is higher than 350℃-500℃, the dust collector body mostly dust bag have burn through the possibility. According to the secondary dust removal of 4080 bags in the fourth plant, 180 yuan per bag. Two times of failure directly reduces the loss of about 1500 million yuan. Accident downtime to replace 4080 bags, is expected to take more than 24 hours. Reduce the accident time to create economic benefits of more than 2000 million. The temperature of the converter secondary flue gas is higher than 350℃, which cannot be solved in the industry, is successfully solved; successfully realize the requirement of the flue gas temperature in the national "bag type dust removal engineering general technical specification"; at present, the system is the only successful example for the converter secondary flue gas temperature is too high.

[0059] Finally, it should be noted that: the above examples are used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; 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 method for secondary flue gas assisted cooling of a converter, characterized in that, A temperature sensor is installed on each of the smoke gas pipes in the interior of the two side smoke boxes of the converter; a set of spray guns is arranged behind the temperature sensor on the smoke gas pipe in the interior of the two side smoke boxes along the direction of the flow of the smoke gas; a temperature sensor is installed on the straight pipe section of the secondary pipe, and a plurality of sets of spray guns are arranged on the secondary pipe along the direction of the flow of the smoke gas at intervals; the spray guns are inserted into the pipe from the oblique upper side, and the nozzle direction is installed along the direction of the flow of the smoke gas; each spray gun is provided with an electric valve for controlling start and stop; the distance between the temperature sensor and the spray gun and the interval distance of each spray gun are set according to the flow rate of the smoke gas, the length of the pipe, the action time of the electric valve, and a smoke mixing valve is arranged on the secondary pipe; comprising: Real-time temperature measurement of the converter exhaust smoke gas is performed by using a plurality of temperature sensors arranged at the outlet of the converter smoke gas; The start and stop of each spray gun and the smoke mixing valve in the pipe are controlled by the electric valve according to the temperature measured by the temperature sensor, and the temperature of the smoke gas is always greater than 110 DEG C when the water mist cooling is used; the spray gun is a double-medium mixed spray gun, and the medium includes: water and compressed air; the water mist particles sprayed by the front nozzle of the spray gun will instantaneously gasify under high-temperature smoke gas and change into water vapor, and the molecular structure of the water vapor can pass through the dust cloth bag and be directly discharged with the filtered smoke gas, without forming sewage and mud slurry attached to the surface of the cloth bag; Among them, the double-medium spray gun has 6 sets, 2 sets of which are arranged in the interior of the two side smoke boxes of the converter; 4 sets of which are arranged in the straight pipe section of the secondary pipe; The start and stop of each spray gun and the smoke mixing valve in the pipe are controlled according to the temperature measured by the temperature sensor, comprising: The opening of the smoke mixing valve and the spray gun is controlled according to the temperature detected by the temperature sensor in the interior of the two side smoke boxes of the converter; During the cooling process, the closing of the smoke mixing valve and the opened spray gun is controlled according to the temperature detected by the temperature sensor on the straight pipe of the middle section of the secondary pipe; The opening of the smoke mixing valve and the spray gun is controlled according to the temperature detected by the temperature sensor in the interior of the two side smoke boxes of the converter, comprising: When the temperature detected by the temperature sensor in the interior of the two side smoke boxes of the converter is greater than or equal to 150 DEG C and less than 250 DEG C, the smoke mixing valve is opened to reduce the temperature of the smoke gas, and the inlet temperature of the dust collector is lower than 120 DEG C; When the temperature detected by the temperature sensor in the interior of the two side smoke boxes of the converter is greater than or equal to 250 DEG C and less than 350 DEG C, the smoke mixing valve is opened, and one spray gun close to the inlet of the dust collector is opened for cooling; When the temperature detected by the temperature sensor in the interior of the two side smoke boxes of the converter is greater than or equal to 350 DEG C and less than 450 DEG C, the smoke mixing valve is opened, and two spray guns close to the inlet of the dust collector are opened for cooling; When the temperature detected by the temperature sensor in the interior of the two side smoke boxes of the converter is greater than or equal to 450 DEG C and less than or equal to 500 DEG C, the smoke mixing valve is opened, and four spray guns in the secondary pipe are opened for cooling; When the temperature detected by the temperature sensor in the interior of the two side smoke boxes of the converter is greater than 500 DEG C, the smoke mixing valve is opened, and all six spray guns are opened for cooling.

2. The method according to claim 1, wherein The diameter of the water mist particle is within 121 μm.

3. The method according to claim 1, wherein The spray gun and the medium pipe are connected by a metal hose.

4. The method according to claim 1, wherein During the cooling process, the closing of the smoke mixing valve and the spray gun is controlled according to the temperature detected by the temperature sensor on the straight pipe of the middle section of the secondary pipe, comprising: When the temperature sensor on the straight pipe of the middle section of the secondary pipe detects a temperature decrease to greater than 250℃ and less than or equal to 350℃, 3 spray guns in the secondary pipe are closed; When the temperature sensor on the straight pipe of the middle section of the secondary pipe detects a temperature decrease to greater than 170℃ and less than or equal to 250℃, 4 spray guns in the secondary pipe are closed; When the temperature sensor on the straight pipe of the middle section of the secondary pipe detects a temperature decrease to greater than 110℃ and less than or equal to 170℃, all spray guns in the secondary pipe are closed; When the temperature sensor on the straight pipe of the middle section of the secondary pipe detects a temperature less than or equal to 110℃, all spray guns and air mixing valves in the secondary pipe are closed.

Images