FI71841B - ENMETOD FOER TEMPERATURMAETNING AV SMAELT MATERIAL - Google Patents

Description

71 841

Method for measuring the temperature of molten material.

5 Reliable continuous temperature measurement of molten material has so far been an unsolved problem, especially in steelmaking, but also in most other metals and vitreous materials. other applications are described in more detail below.

Modern steelmaking takes place through the following sub-processes 15: sintering or pelletizing of ore; the purpose is to give the Ore suitable reactivity and strength for the blast furnace.

- manufacture of pig iron in a blast furnace; in the process, iron oxide is reduced to a metallic state with carbon and the SiO 2 from the ore and some of the sulfur in the pig iron are removed from the ore.

- production of steel in an oxygen blowing converter; in the process, the silicon and manganese of the pig iron are partially oxidized and the phosphorus as accurately as possible into the slag and the carbon to a concentration which k.o. steel batch is desired. Mixtures may be added.

2 71841 - ladle handling; the method is new and so far only used in a few steel mills. In the treatment, the temperature is equalized by means of a gas purge, and by blowing (injecting) directly into the molten steel, the most reactive alloys are added in powder form.

The oxygen blowing converter (designations; LD converter in low-alloy steels, AOD converter in stainless steel) plays a key role in the manufacturing process because it determines for the most part (in the absence of bucket-treatment) the final properties of the steel, on the one hand, ° C and puts a heavy strain on the refractory lining. Both factors are strongly related to the operating costs of the manufacturing process. The L-D converter is shown in Figure 1. An oxygen balance (9) is used to blow a strong oxygen jet onto the surface of the molten pig iron (3) charged to the converter, which effectively mixes the pig iron and the molten slag (4) on top of it. When oxygen reacts with silicon, manganese and phosphorus, their oxides are formed, which together with the lime charged to the converter form molten slag. Upon combustion of the carbon 20, carbon monoxide is formed, which rises through the slag as bubbles (6) and causes it to foam vigorously. The force of the oxygen jet causes droplets (5) to detach from the surface of the metal melt, which, as they flow through the slag, have excellent conditions for the progress of the reactions intended for the process. Oxidation-25 reactions generate a significant amount of heat and raise the charge temperature more than 1700 degrees already in the early stages of blowing; the temperature rise is then prevented by adding either steel rum or ore to the converter according to an empirically developed program. It is important for the service life of the brick lining 30 that the temperature does not rise too much.

The qualitative goals of the L-D process are the correct composition and temperature of the steel; the process technical objectives are a steady temperature rise and rapid slag formation at the beginning of the blow, to keep the temperature constant at the end of the blow, and to control the behavior of the slag. Matching the composition and temperature of the batch also saves time and cost in subsequent processing steps; the quality of the steel also improves, because the impurities transferred from the slag back to the steel after blowing cannot be completely returned to the kiln in the further blowing. A uniform temperature and the prevention of temperature overshoot extends the service life of the converter liner (2).

At present, the composition and temperature of the converter charge cannot be measured continuously. During the blowing, splashes fly from the converter, as a result of which it is extremely difficult to make the measuring devices mounted on the gas hood (7) on the upper 5 side of the converter work reliably. Microwave noise measurement has so far been used mainly in radio astronomy to measure the temperature of planets and to some extent for remote sensing from an aircraft. Applications of Method 10 to industrial processes are rare. The measurement frequencies used are usually in the range 0.3 ... 15GHz. The method is characterized by the measurement of extremely low noise powers and difficult-to-construct measuring equipment; on the other hand, the method is well suited for remote temperature measurements under process conditions where dust, dirt and gas absorption make the use of an optical pyrometer impossible.

Methods for measuring temperature based on microwave noise are published in patents FI 54656 "Feedback Stabilized Radiometer" and DE2803480 A1 "Verfahren und Anordnung 20 zur Messung der physikisenchen Objekttemperatur mittels Mikro-Wellen", both of which can be used in the present invention.

The application based on the measurement of microwave noise according to US 3446074 uses a microwave antenna separated from 25 objects to be measured by a refractory wall.

The temperature measuring method according to U.S. Pat. No. 3,747,408 uses a measuring tube equipped with a gas blower, but applies an optical pyrometry which, as a measuring device and measuring properties, is completely different from measuring microwave noise.

The temperature measurement method of the present invention is based on measuring radio frequency noise (microwave noise) emitted by a molten charge in proportion directly to its absolute temperature using the tube from which the gas required in the melt treatment process is passed from the measuring object to the measuring device (waveguide). In addition to the principle based on the measurement of microwave noise, the present invention is characterized by the way described in the claim, in which the microwave noise is transmitted from the object to be measured 40 to a measuring device located further away.

71841 The L-D converter uses an oxygen lance (9) as the waveguide. The nozzle part at its lower end is the narrowest opening between the measuring object (1) and the measuring sensor (10) and determines the lower limit frequency of the noise coming from the object to the measuring sensor: half-wavelength corresponding to the lower limit frequency is equal to the largest dimension of the nozzle orifice. Normally the diameter of the opening is 15 ... 35mm and correspondingly requires a measuring device operating at a frequency of at least 10 ... 4.3 GHz.

Noise enters the measuring device from a cavity (1), the oxygen jet of which is produced at the interface between the steel (3) and the slag (4); the gas exits through the slag as bubbles (6) and thus the cavity remains closed to radio frequency noise. Due to the higher emissivity of the slag, the noise is for the most part emitted by the slag and thus mainly describes the temperature of the slag delimiting the cavity.

15 However, the temperature difference between the steel and the slag is small after the initial stage of blowing and allows a fairly accurate determination of the steel temperature. The temperature measurement according to the previous description can also be carried out by using a separate auxiliary lance (8) as the waveguide.

The measurement method can be carried out exactly as described above in the AOD converter used in the stainless steel process, since it differs from the L-D converter mainly in the composition of the gas mixture used for blowing; due to the higher process temperature and more expensive raw materials, the benefit of continuous measurement of temperature 25 is greater compared to the L-D process. As such, the measurement method is also suitable for post-converter bucket handling; the waveguide then acts as a lance used for gas flushing and injection of alloys. In the copper and nickel converter as well as in the 30 blast furnaces, the gas is blown through nozzles mounted on the wall of the process device; these nozzles can be used, or they can be made to function as waveguides with minor modifications and the temperature measurement can thus be carried out through these nozzles. The flame melting furnace used in the production of non-ferrous metals is shown in Figure 2. A powdered concentrate mixture (14), combustion air (15) and fuel used for temperature control (16) are fed to the reaction shaft (13). The reactions in the shaft are heat-generating and the concentrate melts and reacts when it falls in the shaft in about a second. The temperature measurement of the melt (11) 40 accumulating at the bottom of the furnace can be performed by describing the present invention

Claims (3)

5 71841 method using auxiliary lance (12) as a waveguide. In the reaction shaft, the reaction rate is determined by temperature, and its continuous measurement has not been successful by the means currently used. By the method of the present invention, it can be measured using either a separate auxiliary lance (17) or a nozzle (15) as a waveguide, from which air or oxygen-enriched air is blown into the reaction shaft. The claims; A method for measuring the temperature of molten material based on measuring radio frequency electromagnetic noise in processes in which a gas is blown into a molten material or its surface or melted in a gas stream, characterized in that a measuring point (15) is used to transmit radio frequency noise to the measuring sensor (10). a gas-blown pipe extending in the immediate vicinity of the tea (1), which is either a blower pipe (9) belonging to the process equipment or a pipe (8) used for measuring the melt properties complementing the process equipment, that there are 20 refractory pipes between the object to be measured (1) and the open mouth a wall made of material and that the noise measurement is performed at a microwave frequency higher than the lower limit frequency specified by the tube. claim; 25 In the case of electromagnetic radio frequency, the basic method for the temperature of the material is to process the gas biases in the material or to the material or to the material, to the radio frequency, the radio frequency to be used in the process (30) paratet (10) genome and of a gas-fired power plant, in which case a commercial account is used for the purpose of the object, for example, for the purpose of processing a complete set of materials (9) (1) 35 and on the other hand, the overturning of the high-frequency material, and the separation of the high-frequency material from the high frequency of the high frequency of the high-frequency material.