The following benefits can be obtained from the infrared thermometer at each stage of the steel production process: high-quality products, improved productivity, reduced energy consumption, enhanced personnel safety, reduced downtime, easy data recording, infrared temperature measurement for steel processing and manufacturing. Main applications: continuous casting, hot blast stove, hot rolling, cold rolling, bar / wire rolling intelligent sensor head with digital circuit and two-way communication, remote parameter setting of the sensor head can be carried out in the control room, so that the function is enhanced and the control is more perfect. This is particularly important for metal materials with emissivity changes. To produce high-quality products and improve productivity, accurate temperature measurement is the key in the whole process of steelmaking.

When continuous casting turns molten steel into flat billet, slab or square billet, there may be production reduction or shutdown. Accurate real-time temperature monitoring, coupled with water nozzle and flow regulation, is required to provide appropriate cooling, so as to ensure the metallurgical properties required by the billet and finally obtain high-quality products. Improve productivity and prolong equipment life. The model of the selected sensor head is determined by the production process and the location of the sensor head. If it is installed in a harsh environment and its line of sight is blocked by dust, water mist or steam, the optical fiber dual color sensor head and integrated dual color sensor head are the best choices. If you need a temperature profile from edge to edge of the slab, you can use a line scanner. The type of hot rolling and the number and type of rolling mills in the rolling process vary with the type of products processed.

(1) During the whole production process of steel, continuous temperature measurement and frame adjustment of the descaling machine can ensure product quality and normal use of the production line, and avoid accidental shutdown.

(2) The billet of the rolling mill unit has been continuously cooled before entering the rolling mill. If the production line stops working for a period of time, the billet temperature may be lower than that before restart. This roller must be set to compensate for the corresponding changes in temperature.

The roll can be set manually by the operator, or an infrared thermometer can be installed in front of each rolling mill, and the rolling mill can be set automatically. This ensures that the mill is set correctly. In order to eliminate the influence of steam and dust in the control cooling area on temperature measurement, a two-color thermometer is used to accurately measure temperature even when the energy of the target is blocked by 95%.

(3) During the hot rolling process of the coiler, the normally cooled steel plate is rolled into steel coils by the coiler for transportation to the cold rolling or other equipment. In order to maintain the reasonable cooling of laminar cooling area, accurate temperature measurement is required at the coiler. The temperature at this point is crucial because it determines whether the steel is reasonably cooled before being rolled. Otherwise, unreasonable cooling may change the metallurgical properties of steel and cause scrap.

(4) Because the temperature of the coil box is low at this point and the steel is running at the speed of 75 ~ 100 feet / second, a low-temperature series infrared thermometer with fast response time is needed. Cold rolling is often carried out after finishing rolling and cooling, and the steel coil is transported to another plant for cold rolling or to other plants. Cold rolling makes the steel thinner and smoother. At this time, the steel is rolled at about 94 ℃ or at ambient temperature. The thermometer installed between finishing mills enables the operator to adjust the mill according to the detected temperature changes. Another high-speed processing process of bar / wire rolling is bar / wire rolling. The billets are reheated and sent to be rolled into bars.

After that, the bar is processed into different sizes through a series of intermediate rolling. After finishing rolling, the bar can be made into more than 100 different products. Reheating the billet to a uniform temperature is very important for the whole rolling process, because uneven bar temperature will aging the equipment and increase the maintenance downtime of the equipment. Knowing the product temperature between racks enables the operator to adjust the roll as required. When the product begins to enter the cooling zone, quickly and carefully monitor the cooling temperature to ensure the metallurgical performance of the product. If the cooling control is not good, the product cannot meet the requirements of process indicators, resulting in quality reduction or waste products. In some production processes, such as high-speed rolling and vibration of thin bars or wire products, temperature measurement is very difficult, infrared two-color thermometer can solve this problem. When the target deviates from the field of view or is partially blocked (dust, steam, obstacles, etc.), it can still accurately measure the temperature. The blast furnace hot blast stove provides high-temperature and stable hot air for the blast furnace.

In order to operate safely, it is necessary to monitor the dome temperature of the hot blast stove. At present, thermocouples are mostly used to measure the dome temperature of hot blast furnaces in China. Due to the limitations of the use environment (high temperature, high pressure) and structure of the thermocouple, the temperature fluctuates greatly. Under the influence of many factors such as vibration and installation mode, the service life of thermocouple is short. The measurement accuracy is unstable. Troublesome maintenance and other shortcomings. A special infrared temperature measurement protection device for hot blast stove dome temperature measurement can replace the thermocouple temperature measurement method to avoid many shortcomings caused by this method. The user's use results show that the device is stable, reliable and effective.

Applicable Machine

High air temperature is an important technical feature and development direction of modern blast furnace ironmaking. Increasing air temperature can effectively reduce fuel consumption and improve the efficiency of blast furnace energy utilization. A customer company owns two 5500m³blast furnace, each blast furnace is equipped with four BSK top burning hot stoves with a design air temperature of 1300 ° C.

1.1Problems in hot blast stove system

The hot blast system (hot blast stove body and pipe system) generally has the problem of high-temperature point cracking, and the frequency increases and the degree increases. The design specification of hot air system requires that the temperature of hot air stove body is less than 150 ° C, and the temperature of hot air duct is less than 200 ° C. However, there are many high-temperature points in the hot blast stove body and hot blast pipe, such as 2^# stove. The average detection temperature of the embedded thermocouple (16 points) in the hot blast stove body is 128 ° C, of which the temperature of 5 points is > 150 ° C. Statistics show that the hot blast furnace shell cracked 57 times in 2014, 30 times in 2015 and 58 times in 2016, and the cracking parts are mainly concentrated in 14-16 zones. After the bellows of the hot air system was put into operation, high temperature points (the design temperature is less than 200 ° C) and cracks occurred successively. As shown in Figure 1.

1.2Limitations of manual inspection

The blast furnace hot blast stove (shell and piping) belongs to the ultra-high temperature area (internal hot blast temperature 1400 ° C), and the weak points crack to varying degrees under high temperature, which has great potential safety hazards. The blast furnace hot air system has no prediction or feedback measures and means, and only relies on routine manual inspection every 2h. There are two problems in manual patrol inspection: ① due to the limitation of site and time, there are great limitations and contingencies. The inspection route is affected by the platform, the distribution of high temperature points and the uncertainty of inspection time, so the status of hot blast stove shell cannot be monitored comprehensively and all-weather; ② The cracking of the furnace shell is sudden, and the safety of the inspectors cannot be guaranteed, so there are great potential safety hazards. In order not to affect the normal production and operation of blast furnace hot blast stove, the primary task is to comprehensively, in detail and in real time monitor the unsafe factors of the existing hot blast system, and process the monitoring data information, so as to control the hot blast system within the safe operation range.

2.Development of infrared imaging monitoring system for hot blast stove

2.1Infrared imaging system of hot blast stove

The infrared imaging monitoring system of the hot air system is equipped with 15 temperature monitoring points, including 9 temperature monitoring points of the hot air furnace shell and 6 hot air piping monitoring points. Considering the cost, after site investigation, it is proposed to set five fixed thermal imager temperature measurement points and another mobile temperature measurement point. The monitoring pictures of each infrared thermal imager are transmitted to the monitoring computer in real time through optical fiber. The computer displays the picture online, establishes a database at the same time, automatically analyzes and processes the data of monitoring points, draws the temperature change curve of each region, and gives the temperature change rate of each region and the alarm of abnormal points. As shown in Figure 2.

2.2Principle of infrared imaging system for hot blast stove

According to the principle that the infrared intensity is different under different temperatures of the object, the infrared thermal imager uses the infrared detector and optical imaging objective lens to receive the infrared radiation energy distribution pattern of the measured object and reflect it on the photosensitive element of the infrared detector, so as to obtain the infrared thermal image. This kind of thermal image corresponds to the thermal distribution field on the surface of the object, and the temperature distribution in different areas of the measured object is obtained by conversion. The data measured by the infrared thermal imager is transmitted to the computer system. The computer software integrates, analyzes and processes the data, obtains useful information, and presents it to the operator through a simple and clear interface. Using infrared imaging equipment to complete the test work has the advantages of all-weather and wide coverage. Figure 3 shows the infrared imaging monitoring diagram of hot blast stove.

2.3Development of infrared imaging system for hot blast stove

Main objective: to develop infrared imaging monitoring technology for blast furnace hot air system. Main research contents: ① hardware and network architecture scheme and implementation; ② Program code writing and software system development.

The functions to be realized or satisfied by the infrared imaging technology of the hot air system: ① monitoring function, the monitoring range of the hot air system in the suspicious area, continuous monitoring in time sequence, and reliable trend and high accuracy in the monitoring results of the surface temperature; ② For the alarm function after reaching a certain temperature, according to the design specifications, the hot air duct ＜ 200 ° C, the hot air stove body 150 ° C, according to the degree close to the temperature, carry out warning or alarm, and give the location of the warning area (accuracy 0.5m); ③ For parts or areas that exceed the design specifications, in addition to the above temperature monitoring data, video data information for a period of time can be recorded and played back; ④ The system should have strong compatibility and redevelopment. The research and development of infrared imaging technology is applied to practical production to ensure the safe and stable operation of large blast furnace hot air system.

3.Application of infrared imaging monitoring system for hot blast stove

3.1Architecture of infrared imaging monitoring system for hot blast stove

According to the layout and internal equipment connection of 4 hot blast furnaces of 1^# blast furnace, in order to realize the temperature measurement monitoring coverage of the hot blast furnace shell (14-16 belts) and hot blast pipe system (hot blast branch pipe and hot blast main pipe), five fixed thermal imager temperature measurement points and one mobile temperature measurement point are set after field investigation. As shown in Figure 4, probe 1 is under the viaduct of the blast furnace control room; Probe 2 is on the top platform of blast furnace gas bag dedusting system; Probe 3 is at the east end of the East-West Center Line on the hot blast stove frame; Probe 4 is at the center point of the East-West Center Line on the hot blast stove frame; Probe 5 is at the west end of the East-West Center Line on the hot blast stove frame.

Each point thermal imager is equipped with an automatic rotating PTZ, in which probe 1 and probe 2 are supported PTZ, and probe 3, probe 4 and probe 5 are suspended PTZ. Through the rotation of each PTZ, the thermal imager can realize the regular scanning or fixed-point monitoring of all monitoring target areas. According to the monitoring results of each fixed point, the setting point of the mobile infrared thermal imager sets the mobile infrared thermal imager at a short distance for continuous monitoring when the most dangerous area is blocked by pipes or equipment around and cannot be directly monitored by the fixed probe.

The monitoring picture of infrared thermal imager is transmitted to the monitoring computer in real time through optical fiber. The computer displays each picture online, establishes a database at the same time, automatically analyzes and processes the data of the monitored points, draws the temperature change curve of each area, and gives the alarm of the temperature change rate and abnormal points of each area.

3.2Problems and solutions in the application of infrared imaging monitoring system

(1) The infrared radiation emission characteristic of the material itself is the key to the accurate temperature measurement of the hot blast stove shell by the thermal imager. In the previous hot blast stove test, it was found that the temperature measured by the thermal imager in different areas of the same equipment was different at the same temperature. The reason for analysis is that the emissivity of different surface materials of the equipment is different, and the infrared radiation energy is different. When the temperature of the whole monitoring object is converted with a fixed emissivity, a large error will occur.

Solution: ① investigate the infrared emissivity of different materials (base metal steel plate, weld material, antirust paint, etc.) on the surface of hot blast stove shell; ② The contact surface thermometer is used to measure the surface temperature of representative areas of different materials, and the infrared emissivity of different material areas is determined by comparing with the temperature measurement of infrared thermal imager; ③ The monitoring area of each measuring point is set with different infrared emissivity to obtain the accurate thermal imaging monitoring temperature of the area; ④ Regularly use the contact surface thermometer for local inspection and correction to ensure the long-term accuracy of the temperature measurement results of the infrared thermal imager.

(2) Setting of measuring points of infrared thermal imager. Each blast furnace has 4 hot blast stoves, which are arranged in a staggered rectangle. The on-site investigation found that, except for the relatively open and unobstructed north side, there are many devices around the other three sides, so it is difficult to find a fully covered installation point of the infrared thermal imager. The equipment area for close monitoring is limited. In addition, the internal pipelines and valves of the four hot blast stoves are densely covered, and there is no directional installation point that can cover all the monitoring areas.

Solution: realize full coverage monitoring in all areas by setting multiple measurement points and adopting the method of rotating pan tilt. The scanning frequency of the automatic rotating pan tilt to the monitoring area also fully meets the monitoring requirements. For the partially sheltered area, by comparing the temperature changes in the surrounding monitoring area and directly measuring with the surface thermometer, if it is considered to be a dangerous area, a movable infrared thermal imager is set for online monitoring.

(3) Data analysis and processing. The multi-point infrared thermal imaging thermometer set in the system will generate massive data in real time, and the change of hot blast stove shell state is a relatively slow and continuous process. Therefore, the computer system is required to screen and compare massive data, obtain the required parameters and change process of key parts, and accurately predict the change trend and possible risks.

Solution: according to the monitored hot blast stove shell area, establish the corresponding database. Develop temperature data to ensure the accuracy and representativeness of monitoring data and processing results.

4.Epilogue

The infrared imaging monitoring system of blast furnace hot blast stove is based on the principle that the infrared thermal imager is based on the different intensity of infrared radiation under different temperatures of the object, and uses the infrared detector and optical imaging objective lens to receive the infrared radiation energy distribution pattern of the measured object and reflect it on the optical sensor of the infrared detector, so as to obtain the infrared thermal image, which corresponds to the thermal distribution field on the surface of the object, The temperature distribution in different areas of the measured object is obtained by conversion. The data measured by the infrared thermal imager is transmitted to the computer system. The computer software integrates, analyzes and processes the data, obtains useful information, and presents it to the operator through a simple interface. The infrared imaging monitoring system can monitor and analyze data changes, prevent and alarm the cracking of the hot blast stove shell and hot blast pipe. It is suitable for the hot blast stove system of iron making blast furnace, realize real-time monitoring and data analysis, replace the inspectors in the dangerous area of the hot blast stove, eliminate potential safety hazards, and ensure safe production.

Applicable Machine