Method for on-line monitoring of sinter mix permeability

Abstract

The application discloses a kind of sintering mixture air permeability on-line monitoring method, belong to sintering field.In the application, the amount of air leakage Q3 is measured by the following method: the grate bar gap below sintering ignition furnace is blocked with sealing material, the gas valve is closed, the air valve is used to exhaust air with fan, the gas flow Q'3 is measured from the branch pipe of air valve, the negative pressure P of ignition furnace is detected ign ; different furnace negative pressure values P ign are obtained by changing the frequency of exhaust fan, and the corresponding Q'3 value is recorded, that is, the relationship between P ign and Q'3 can be obtained, and the amount of air leakage Q3 can be obtained by real-time ignition furnace negative pressure P ign . The application does not need new equipment, greatly increases the stability of the system, and solves the equipment maintenance problem in harsh environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sintering, more particularly to an online monitoring method for the permeability of sintering mixture. BACKGROUND

[0002] Permeability is one of the key physical properties in the sintering process, which affects the temperature distribution of sintering material and the efficiency of fuel combustion. By precisely controlling the permeability, the mechanical strength and chemical uniformity of sintered blocks can be optimized, thereby improving the quality of the final product. Sintering material with good permeability can more effectively transfer heat and oxygen, which helps to fully burn the fuel and speeds up the sintering process, thereby reducing energy consumption and increasing production. Therefore, detecting and controlling the sintering permeability is an important means to improve the efficiency and quality of the sintering process, and has a significant impact on improving the economic benefits and environmental sustainability of the entire production process.

[0003] Generally, the permeability of sintering mixture refers to the amount of gas passing through a unit area and a certain height of sintering material layer per unit time under certain pressure conditions. The most classic calculation method for the permeability of sintering raw material layer is the Voice formula, which is simple to calculate and has strong empirical nature, but due to the problem of inaccurate air flow detection, it is limited in practical application. The typical evaluation methods for the permeability of sintering raw material layer include the Ramsin formula, the Carman formula, the Ergun formula and the Voice formula, among which the Ramsin formula and the Carman formula are suitable for theoretical analysis but not for actual production; the Ergun formula is difficult to measure online due to its complex parameters; the Voice formula is simple to calculate, has strong empirical nature and is the most widely used. However, due to the irregular shape of the air box branch, high temperature, high dust and high shear force, there is currently no online detection means for the flow rate at the air box branch in China, which greatly limits the application of the Voice formula.

[0004] The permeability is generally characterized by offline sintering cup experiments, or by installing other measuring devices on the sintering machine to achieve characterization. For example, the invention patent with publication number CN101672762A designs a comprehensive determination test device for sintering material layer permeability index, which is equipped with a main cup body, a secondary cup body, an air extraction base, an air extractor with a frequency converter, pressure sensors and mass flow sensors, etc. The test method includes loading the sintering material into the cup, gradually increasing the air volume of the air extractor to the set upper limit, during which the material layer permeability index is determined by formula, and the comprehensive permeability index is calculated after the air volume reaches the maximum. This method reduces edge effects, improves the accuracy and flexibility of permeability determination, and automatic data collection enhances the comparability of the results. However, the sintering cup method is an offline detection method that transfers the permeability detection process to laboratory equipment, which is difficult to guide the process adjustment in the field in a timely manner. The invention patent with publication number CN111929222A designs a detection unit including a blower, a main pipe and a branch pipe, one end of the main pipe is in communication with the blower, and the other end of the main pipe is in communication with the two branch pipes. The permeability of the mixed material is continuously measured by using a gas pressure measuring instrument in the detection unit at the head of the sintering machine. The invention patent with publication number CN101349632A realizes accurate measurement of the permeability of the mixed material and efficient control of the sintering process by installing a closed device with a gas space and an exhaust air bellow between the holding furnace and the mixed ore tank of the sintering machine, and arranging a gas detection device in the exhaust air bellow. The invention patent with publication number CN117110164A reduces the invasion of particulate matter and improves the accuracy of flow detection by installing a gas guide pipe above the side wall of the sintering machine bellow, designing a slanting upper section in the gas guide pipe and a bulk material air duct, thereby improving the calculation accuracy of the permeability of the sintering raw material layer. The invention patent with publication number CN107894385A introduces an online detection device for sintering cup material layer permeability, which includes a flow guide mechanism and a suspension mechanism. The flow guide mechanism is responsible for guiding air into the sintering cup and can seal the top of the sintering cup under the action of its own gravity. The suspension mechanism controls the switching of the flow guide mechanism between the detection position and the idle position. This device not only accurately determines the original permeability of the sintering cup material layer, but also monitors the permeability of the entire sintering process online, improving the real-time and accuracy of the detection. The above methods are all by installing other measuring devices on the sintering machine body, and the structure is complex. These devices not only increase the cost, but also have a high failure rate and are difficult to maintain due to the long-term harsh environment of high temperature and high dust.The invention patent with publication number CN 113077848 A provides an online determination and calculation method for the permeability of a sintering material bed. By tracking the gas flow within the sintering machine's ignition furnace, including the usage and air leakage of ignition gas and combustion air, the air volume beneath the sintering material bed is calculated. The Voys algorithm is used to calculate the permeability index, and the results are corrected using multiple sets of offline measured data, thereby improving the reliability and accuracy of the results and optimizing sintering production control. However, this method estimates the air volume in the ignition and holding sections based on an empirical formula for furnace pressure, and furnace pressure is significantly affected by air leakage, which seriously interferes with the calculation results. Summary of the Invention

[0005] 1. Technical problem to be solved by the invention

[0006] In view of the fact that the permeability detection of sintering mixtures in the existing technology is inconvenient to use and its accuracy needs to be improved, the present invention intends to provide an online monitoring method for the permeability of sintering mixtures, which can realize the online measurement and early warning functions of sintering permeability, and provide a reference for the optimization of the sintering process.

[0007] 2. Technical solution

[0008] In order to achieve the above object, the technical solution provided by the present invention is:

[0009] The present invention provides an online monitoring method for the permeability of a sintering mixture. The gas input of the ignition furnace includes the ignition gas volume Q1, the combustion air volume Q2, and the leakage air volume Q3. The leakage air volume Q3 is measured by the following method: using a sealing material to block the gap between the grate bars below the sintering ignition furnace, closing the gas valve, using a fan to extract air from the air valve, measuring the gas flow rate Q3' from the branch pipe of the air valve, and detecting the negative pressure P from the ignition furnace. ign ; By changing the exhaust fan frequency, different furnace negative pressure values ​​P are obtained ign , and record the corresponding Q3′ value to obtain P ign The relationship between the air leakage Q3 and Q3′ is that the air leakage Q3 can be adjusted by the real-time ignition furnace negative pressure P ign Obtain.

[0010] Furthermore, there are straight pipe sections in the ignition gas and air delivery pipelines in the ignition furnace that can be used to detect flow rates, and gas and air flow meters can be used directly to perform online detection of Q1 and Q2.

[0011] Furthermore, P ign The relationship with Q3′ is: P ign is the negative pressure of the ignition furnace, Pa.

[0012] Furthermore, blast furnace gas is used for ignition. After the ignition reaction, the volume of the mixed gas at room temperature and pressure is:

[0013]

[0014] The air volume of the final material layer is Q4=Q' 混 ′=Q′ 混 *T ign *P 大 / T 室 *P ign , m 3 / min;

[0015] In the formula, T ign is the ignition furnace hearth temperature, K; P ign is the ignition furnace hearth negative pressure, Pa; P 大 is the atmospheric pressure, Pa; T 室 is the indoor temperature, K.

[0016] Further, the air permeability of the mixed material layer is calculated as follows:

[0017] S ign is the projection area of the ignition furnace in the material layer, m 2 ; P ign is the ignition furnace hearth negative pressure, Pa; P be is the negative pressure of the air bellow below the ignition furnace, Pa; h is the material layer height, m; and n is a coefficient related to the flow state, which varies with the material particle size.

[0018] Further, P be is the negative pressure of the air bellow below the ignition furnace, and when there are multiple air bellows below, the average value of the negative pressures of the air bellows is used.

[0019] Further, for the calculation of the volume fractions of the coal gas CO and H2 and , a portable flue gas analyzer is used to detect the coal gas composition regularly, and the sampling results are used to represent the values of and in the fixed period.

[0020] Further, the optimal air permeability index range is set, and when the on-line monitored air permeability index exceeds the set range, an alarm is given.

[0021] 3. Beneficial effects

[0022] Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects:

[0023] (1) The online monitoring method of the present application fully considers the periodic variation of the composition of the coal gas, the combustion reaction and volume variation of the coal gas and air in the ignition furnace, and the air leakage amount of the ignition furnace cover, and is based on the combination of mass conservation and experimental measurement, so that the monitoring result is more accurate.

[0024] (2) The online monitoring method of the present application does not need to install new equipment, greatly increases the stability of the system, and solves the equipment maintenance problem in harsh environments.

[0025] (3) The online monitoring method of the present application can realize online monitoring of sintering permeability, timely feedback adjustment of process parameters such as water distribution and distribution of the front-end process, and improve the quality and yield of sinter. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is an ignition furnace air volume analysis schematic diagram in the embodiment;

[0027] Figure 2 It is a P ign and Q'3 linear fitting relationship schematic diagram;

[0028] Figure 3 It is the operation interface of the permeability model developed in the embodiment. DETAILED DESCRIPTION

[0029] In order to further understand the content of the present application, the present application will be described in detail in combination with the drawings.

[0030] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" 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 convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0031] The present application will be further described below in combination with the embodiments.

[0032] EMBODIMENT

[0033] In combination Figures 1-3 with the drawings, the present embodiment provides an improved online monitoring method for sintering mixture permeability, which is improved based on the Voice formula, and uses an indirect calculation method to calculate the ignition air volume of the sintering, so as to realize online monitoring of the permeability without increasing new devices.

[0034] The air permeability belongs to the state parameter, which cannot be directly measured. The commonly used material layer air permeability representation is generally calculated by the Voice formula, and the formula is as follows:

[0035]

[0036] In the formula:

[0037] Pe-material layer air permeability index, J.P.U;

[0038] Q-air volume passing through the material layer, m 3 / min;

[0039] S-exhaust area, m 2 ;

[0040] h-material layer height, m;

[0041] Δp-pressure loss, Pa;

[0042] n-coefficient related to the flow state, which changes with the particle size of the material, generally 0.65 in the sintering point firing process.

[0043] At the ignition cover, the material layer on the trolley is mainly composed of the original mixed material, and the air permeability of the material layer can be regarded as the air permeability of the mixed material, so the corresponding parameters at the ignition cover can be used to calculate the air permeability of the mixed material by using the Voice formula. The Voice formula is simple to calculate, and basically reflects the mutual relationship of the main process parameters in the sintering process, which is the best representation method for online detection of the air permeability of the material layer. However, due to the characteristics of the sintering working condition, the irregular shape of the wind box branch, high temperature, high dust, and high shear force, there is no online detection means for the flow of the wind box branch in China at present, and the air volume Q value in the formula cannot be obtained, so the air permeability representation has been one of the industry problems.

[0044] The sintering ignition section is in a high temperature and high dust working condition, and the detection device is easily damaged and difficult to maintain. In order to represent the ignition air volume in the formula without adding a device, the indirect representation of the ignition air volume is carried out by combining the mass conservation theory analysis and experimental parameter determination. The specific process is as follows:

[0045] The gas balance of the ignition furnace is analyzed, as shown in Figure 1 The gas input of the ignition furnace includes the input ignition gas volume Q1, the combustion air volume Q2, and the leaked air volume Q3. Since there is a long straight pipe section in the conveying pipe of the ignition gas and air, which meets the measurement requirements of the flow, a general sintering machine is equipped with a gas and air flow meter to realize the online detection of Q1 and Q2.

[0046] Because the ignition furnace is under the action of continuous negative pressure, and there is a large gap between the ignition cover and the material layer, the air in the environment is continuously sucked into the ignition furnace under the action of negative pressure, Q3 refers to the amount of air leaked in under normal production conditions, but this flow Q3 cannot be directly measured. Considering that the suction air flow and the negative pressure in the ignition furnace show a significant positive correlation, the corresponding empirical formula can be obtained by experimental method through the gap of the sintering pallet car maintenance. The specific method is to seal the grate gap below the sintering ignition furnace with sealing material, close the gas valve, and use the air valve to extract air from the air valve branch, and measure the gas flow from the ignition furnace detection negative pressure P ign . Because the pallet grate is sealed, other air passages are blocked, so the extracted air flow Q'2 is all from the leaked air Q'3, thereby indirectly obtaining Q'3, which is equal to Q3 value. By changing the frequency of the air extractor, different furnace negative pressure values P ign are obtained, and the corresponding Q'3 values are recorded. Then the linear fitting method is used to obtain the relationship between P ign and Q'3, as shown in Figure 2 .

[0047] The obtained empirical formula is: P ign is the negative pressure of the ignition furnace, Pa.

[0048] Therefore, the amount of air sucked in, i.e. the amount of air leaked in Q3, can be indirectly obtained based on the empirical formula through the real-time ignition furnace negative pressure P ign .

[0049] Under normal ignition conditions, according to the law of conservation of mass, the input gas and the leaked air are mixed in the ignition furnace, and finally all pass through the material layer.

[0050] But the flow of mixed gas is not the simple addition of Q1, Q2 and Q3, the mixed gas will react violently in the ignition furnace, and the volume will expand under the action of high temperature, resulting in a large change in gas flow.

[0051] This embodiment takes blast furnace gas ignition as an example. The composition of blast furnace gas is as follows: there are mainly two combustible gases CO and H2, and the content of CH4 is less, which is ignored. The ignition furnace generally needs to control the best air-fuel ratio to ensure complete combustion of the gas, so the reaction equation is as follows:

[0052]

[0053] 2CO + O2 = 2CO2;

[0054] 2H2 + O2 = 2H2O;

[0055] According to the above reaction formula, assuming that the temperature and pressure remain unchanged before and after the reaction, the volume of the mixed gas after the reaction of CO and O2 will decrease by 0.5V CO ; the volume will decrease by 0.5V after the reaction of H2 and O2 H2 . Thus, the volume of the mixed gas at normal temperature and pressure after the reaction is calculated as:

[0056]

[0057] However, the mixed gas reaction releases a large amount of heat, causing the gas to expand several times before passing through the material layer. According to the ideal gas formula, we can obtain:

[0058] Q4 = Q" 混 = Q' 混 *T ign *P 大 / T 室 *P ign , m 3 / min;

[0059] In the formula, T ign is the ignition furnace hearth temperature, K; P ign is the ignition furnace hearth negative pressure, Pa; P 大 is the atmospheric pressure, Pa; T 室 is the indoor temperature, K.

[0060] After obtaining the air volume of the material layer, the air permeability of the mixed material layer can be calculated by the Voice formula:

[0061]

[0062] After mathematical conversion, we can obtain:

[0063] Where S ign is the projection area of the ignition furnace in the material layer, m 2 ; P be is the negative pressure of the air bellow under the ignition furnace, Pa; in this embodiment, the average negative pressure of the 6 air bellows under the ignition furnace is used instead, i.e. P ign is the negative pressure of the ignition furnace hearth, Pa; h is the height of the material layer, m; n is a coefficient related to the flow state, which varies with the particle size of the material, and is taken as 0.65.

[0064] Most sintering plants are equipped with coal gas and air flow meters, ignition furnace hearth pressure gauges, thermometers and other detection equipment to obtain online values of these parameters in real time. However, the volume fractions of CO and H2 in the coal gas and are unknown variables, so a portable smoke analyzer is used to detect the composition of the coal gas periodically, and the sampling results represent the and The real-time value of Pe can be calculated according to the value of the permeability index and the value of the oxygen content in the flue gas. According to the actual production process, an optimal range of the permeability index can be set, and when the permeability index monitored on-line exceeds the set range, an alarm is given.

[0065] The sintering endpoint control and permeability soft-sensing model developed based on the method is applied in a certain steel plant, and the on-line measurement and early warning of the sintering permeability are realized, which provides a reference for the optimization of the sintering process.

[0066] The above description of the present application and its embodiments is illustrative only, and is not restrictive, and is only one of the embodiments of the present application, and is not limited thereto. Therefore, if a person skilled in the art is inspired by it, without departing from the purpose of the present application, similar structural modes and embodiments can be designed without creativity, and all of them should belong to the protection scope of the present application.

Claims

1. A method for online monitoring of the permeability of sintering mixture, characterized in that: The gas input of the ignition furnace includes the ignition gas volume Q1, the combustion air volume Q2, and the leakage air volume Q3. The leakage air volume Q3 is measured by the following method: Use sealing material to block the gap of the grate bar below the sintering ignition furnace, close the gas valve, use a fan to extract air from the air valve, and measure the gas flow from the branch pipe of the air valve. , detect the negative pressure P from the ignition furnace ign ; Different furnace negative pressure values ​​can be obtained by changing the exhaust fan frequency P ign , and record the corresponding value, you can get P ign and The air leakage Q3 can be controlled by the real-time ignition furnace negative pressure P ign to obtain; Among them, P ign and The relationship is: =62.11+19.17P ign -0.336 ;P ign is the ignition furnace negative pressure, Pa; Using blast furnace gas for ignition, the volume of the mixed gas at room temperature and pressure after the ignition reaction is: ； In the formula and Refers to the volume fraction of gas CO and H2 respectively; The final air volume passing through the material layer is: , m 3 / min; In the formula T ign is the furnace temperature of the ignition furnace, K; P ign is the negative pressure of the ignition furnace, Pa; P 大 is atmospheric pressure, Pa; T 室 is the indoor temperature, K; The air permeability of the mixture layer is calculated as: ; is the projected area of ​​the ignition furnace on the material layer, m 2 ; P ign is the negative pressure of the ignition furnace, Pa; is the negative pressure of the wind box below the ignition furnace, Pa; is the material layer height, m; n It is a coefficient related to the flow state and changes with the particle size of the material.

2. The method for online monitoring of sintering mixture permeability according to claim 1, characterized in that: There are straight pipe sections in the ignition gas and air delivery pipelines in the ignition furnace that can be used to detect flow rates, and gas and air flow meters can be used directly to perform online detection of Q1 and Q2.

3. The method for online monitoring of sintering mixture permeability according to claim 1, characterized in that: It is the negative pressure of the bellows below the ignition furnace. When there are multiple bellows below, the average negative pressure of the bellows is used.

4. The method for online monitoring of sintering mixture permeability according to claim 1, characterized in that: For the volume fraction of CO and H2 in coal gas and The calculation of the gas composition is carried out by using a portable flue gas analyzer to regularly detect the gas composition, and the sampling results are used to represent the gas composition within a fixed period. and value.

5. The method for online monitoring of sintering mixture permeability according to claim 1, characterized in that: Set the optimal air permeability index range. When the online monitored air permeability index exceeds the set range, an alarm will be issued.

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