Blast furnace slag weak cold granulating device and granulating process thereof

Abstract

The invention belongs to the technical field of blast furnace slag resource utilization, and particularly relates to a blast furnace slag weak cold granulating device and a granulating process thereof. The implementation method comprises the following steps: high-temperature slag from a blast furnace enters the intermediate slag tank through the slag runner and then enters the slag cooling and granulating device from the slag nozzle of the intermediate slag tank, and in the slag cooling and granulating device, the high-temperature slag is in full contact with water mist under the combined action of the granulator and the water mist spray head to be cooled into fine particles with the temperature of about 750 DEG C. 300 DEG C water vapor formed by the slag in the water mist granulation process is discharged from an exhaust passage at the top. And the cooled particle slag is discharged into a slag car below and is transported out. The blast furnace slag weak cold water mist granulation device can efficiently utilize a granulation medium, weak cold granulation is carried out on molten blast furnace slag, meanwhile, waste heat resources contained in the blast furnace slag are reserved to the maximum extent, and the blast furnace slag weak cold water mist granulation device serves as a preposed procedure for further effectively utilizing blast furnace slag waste heat, and the recycling efficiency of the blast furnace slag is improved.

Description

Technical Field

[0001] The invention relates to a blast furnace slag weak cooling granulation device and a granulation process thereof, belonging to the technical field of blast furnace slag resource utilization. Background Art

[0003] At present, the liquid blast furnace slag produced in the iron-making process is generally granulated and cooled by water quenching to produce blast furnace slag suitable for large-scale cement production. During the water quenching process, 7 to 12 tons of slag water with a temperature of about 75°C are produced for every ton of blast furnace slag. Except for some steel enterprises in the north that use a small amount of slag water for heating in winter, a large amount of heat contained in it is lost in vain, causing thermal pollution to the factory and the surrounding environment; the blast furnace slag water is recycled, and the higher the temperature, the more sulfides are discharged during the slag flushing process, and the worse the quality of the blast furnace slag; about 1 ton of new water is consumed for each ton of slag, resulting in waste and pollution of water resources. The current improvement of the water quenching method mainly starts from improving the utilization rate of circulating water and collecting low-temperature waste heat, which cannot fundamentally improve the problems of low thermal utilization rate and large water resource consumption of the water quenching method. Summary of the invention

[0004] 1. Key issues to be addressed

[0005] The purpose of the present invention is to provide a blast furnace slag weakly cooled water mist granulation device in view of the problems in the prior art that the water quenching method cannot recover the residual heat of the slag and the material recovery effect of the dry granulation method is poorly matched, and the technical advantages of the water quenching method and the wind quenching method are combined. Studies have shown that if slag particles with a sufficiently high glass content are to be generated, the blast furnace slag must be quickly cooled to below 800°C. Based on this, in order to take into account the subsequent utilization of the blast furnace slag and the efficiency of waste heat recovery, the molten blast furnace slag is weakly cooled to 750°C, so as not to affect the activity of cement or building materials made from the slag. The device can weakly cold granulate the molten blast furnace slag while retaining the waste heat resources contained in the blast furnace slag to the maximum extent, as a pre-process for further effective utilization of the waste heat of the blast furnace slag.

[0006] 2. Technical solution

[0007] The technical scheme of the present invention is as follows: a blast furnace slag weakly cooled water mist granulation device and control method, which includes an intermediate slag pot, a granulation device, a slag car, and a slag water inlet, wherein the granulation device is provided with an exhaust duct, a water mist nozzle, a water supply device, an air supply device, a water inlet pipe, an air inlet pipe, and an auxiliary granulator. The high-temperature slag from the blast furnace enters the intermediate slag pot through the slag ditch, and then enters the slag cooling granulation device from the slag water inlet of the intermediate slag pot. In the slag cooling granulation device, the high-temperature slag hits the auxiliary granulator and is divided into multiple streams and fully contacts the water mist jet sprayed by the water mist nozzle. Under the action of the water mist jet, it is weakly cold granulated into fine particles with a temperature of about 750°C. The 300°C water vapor formed during the slag granulation process is discharged from the exhaust duct at the top. For the water mist granulation cooling process of the slag, the main function of the water mist is to weakly cold vitrify and solidify the slag, and the function of the air is to break the slag droplets. Therefore, the granulated slag slag making process can be approximately regarded as wind quenching granulation. Therefore, the water flow rate in the water mist sprayed by the water mist nozzle, the slag flow rate flowing out of the slag nozzle and the final granulated slag diameter follow the following mathematical model:

[0008] Heat calculation of water mist granulation process:

[0009] For a constant slag flow rate Q 渣 , the heat released is q 渣 There are the following expressions:

[0010] dq=Q 渣 ·ρ 渣 ·t·C·dT (1)

[0011] Where: t is the slag discharge time, C is the 渣 Specific heat of blast furnace slag, T Blast furnace slag temperature, ρ 渣 Density of blast furnace slag.

[0012] Since the blast furnace slag is cooled from 1380℃ to 750℃, integrating both sides of the equation gives:

[0013]

[0014] q 渣 =630·Q 渣 ·ρ 渣 ·t·C 渣 (2)

[0015] In this case, the density of blast furnace slag can be considered constant, but its specific heat capacity is a variable. Therefore, the correction coefficient λ is introduced to characterize the specific heat capacity of slag. The corrected heat release expression is obtained:

[0016] q 渣 =630λQ 渣 ρ 渣 tC 渣 (3)

[0017] If the water mist is to be completely evaporated into 300℃ water vapor, the heat released by the blast furnace slag must be equal to the heat absorbed by the water mist during evaporation. Taking the initial water temperature as 20℃, we get:

[0018]

[0019] Where: t is the slag discharge time, C is the l Specific heat of liquid water, C g Specific heat capacity of water vapor, T Temperature of water, ΔH vap Heat of evaporation of water, Q 水 Water flow.

[0020] Similarly, the specific heat capacity of water vapor is also a variable. Therefore, a positive coefficient η is introduced to characterize the specific heat capacity of water vapor. The modified heat release expression is obtained by rearranging:

[0021] q 渣 =q 水 =Q 水 ·ρ 水 ·t·(80C l +ΔH vap +200ηC g ) (5)

[0022] Substituting (3) into (5)ρ 水 Take 1g / cm 3 After finishing, we get:

[0023]

[0024] Formula (6) is the relationship between blast furnace slag flow rate and water mist volume.

[0025] Kinetic calculation of air quenching granulation process:

[0026] The Ohnesorg number Oh1 is the ratio of the surface tension at the gas-liquid interface to the viscosity inside the slag droplet, which can express the effect of the viscosity of the slag on crushing:

[0027]

[0028] Where: D1 is the diameter of the molten slag flow,

[0029] When Oh1<0.1, the viscosity of the liquid flow can be ignored relative to the surface tension, and the Oh1 number of air quenching is just in this range. Therefore, the air quenching of molten blast furnace slag only considers the influence of aerodynamic force and slag surface tension, and the Weber number We is used to help solve the air quenching crushing process:

[0030]

[0031] Where: ρ' na Gas density at the collision point between air and slag in wind quenching method, kg / m 3 , μ' na , the speed difference between air and slag at the collision point, u1 is too small and u' is used directly na Representative, m / s.

[0032] Ignoring the effect of slag viscosity, the slag will break when the aerodynamic force exceeds the slag surface tension. The aerodynamic force at the critical breaking point is in equilibrium with the slag surface tension:

[0033]

[0034] Where: C Dl The drag coefficient of the slag drop, C Dl =0.725, D pl Critical crushing and granulation slag droplet size.

[0035] Substituting (8) into (9), we can obtain the dimension of slag droplet breakage, i.e., the critical Weber number:

[0036]

[0037] Based on the spherical droplet assumption, the critical Weber number We, which is used as a reference for slag droplet breakage, is calculated. crit The magnitude is about 11, but the actual aerodynamic force often causes the slag surface to fluctuate and deform first and then break. By introducing the correction factor ζ that characterizes the sphericity of the slag, the modified critical Weber number is obtained:

[0038]

[0039] The particle size of slag crushing is closely related to the wind quenching granulation parameters. The mass ratio of granulation air to slag, the initial slag thickness, and the slag surface tension will all affect the particle size distribution. The particle size of granulated slag is calculated as follows:

[0040]

[0041] Where: k D Empirical coefficient, k D =40~50, k D Take 50; N empirical coefficient, 0.5; kinematic viscosity ratio of molten slag to granulating gas; Liquid-gas ratio, that is, the mass flow rate ratio of blast furnace slag to gas at the collision point.

[0042] Substituting (8) into (12), we can obtain the particle size of granulated slag:

[0043]

[0044] The principle of controlling the water consumption and blast furnace slag particle size of this device is based on expressions (6) and (13).

[0045] The technical solution of the present invention can be further improved:

[0046] Preferably, the water mist nozzles in the granulating device are coaxially arranged in an annular array with the slag nozzles, and the number of the arrays can be selected at will.

[0047] Preferably, the inclination angle and spray range of the water mist nozzle in the granulation device can be adjusted automatically.

[0048] As a preferred embodiment, in order to achieve the best granulation effect, the auxiliary granulator is specially designed. The auxiliary granulator is a hollow cone fixed below the slag nozzle, which is used for preliminary crushing and diversion of blast furnace slag.

[0049] As a preference, only one water mist nozzle is selected as an example in this article. If necessary, the structure of the water mist nozzle can be selected according to actual conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of blast furnace slag granulation device

[0051] Figure 2 Arrangement of water mist nozzles

[0052] Figure 3 The internal structure diagram of the water mist nozzle

[0053] Figure 4 It is the structure of the auxiliary granulator.

[0054] The markings of the components in the accompanying drawings are as follows:

[0055] 1: Slag cooling and granulation device;

[0056] 2: Air supply device;

[0057] 3: Water supply device;

[0058] 4: Water mist nozzle;

[0059] 5: Exhaust duct;

[0060] 6: Intermediate slag tank;

[0061] 7: Slag nozzle;

[0062] 8: Water inlet pipe;

[0063] 9: Air inlet duct;

[0064] 10: Auxiliary granulator;

[0065] 11: Dregs truck. DETAILED DESCRIPTION

[0066] The following is a further description of the specific embodiments of the present invention in conjunction with the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0067] Examples

[0068] The high-temperature slag from the blast furnace enters the intermediate slag pot (6) through the slag ditch, and then enters the slag cooling and granulating device (1) from the slag outlet (7) of the intermediate slag pot (6). In the slag cooling and granulating device (1), the high-temperature slag hits the auxiliary granulator (10) and is divided into multiple streams. The slag is fully contacted with the water mist sprayed by the water mist nozzle (4) and is weakly cold-granulated into fine particles with a temperature of about 750°C. These fine particles are discharged through the slag outlet and enter the slag car (11) set below for transportation to prepare for the next process. Then the slag car (11) returns to its original position and continues to be recycled; the 300°C water vapor formed by the slag during the water mist granulation process is discharged from the exhaust duct (5) at the top of the granulating device (1). For the weak cold granulation of the slag, the water flow in the water mist sprayed by the water mist nozzle, the slag flow out of the slag outlet and the final granulated slag diameter follow the following mathematical model:

[0069]

[0070]

[0071] Formula (1) is the relationship between the blast furnace slag flow rate and the water mist volume calculated from the perspective of heat exchange; Formula (2) is the equivalent formula for the particle size of the granulated slag. The principle of controlling the water consumption and the particle size of the blast furnace slag of this device is based on the formula (1) and (2). 水 Water flow rate, Q 渣 Slag flow rate, C 渣 Specific heat capacity of blast furnace slag, ρ 渣 Density of blast furnace slag, C l Specific heat of liquid water, C g Specific heat capacity of water vapor, ΔH vap Heat of evaporation of water, η water vapor specific heat capacity correction coefficient, λ slag specific heat capacity correction coefficient; D' pl Granulated slag particle size, ρ' na Gas density at the collision point between air and slag in wind quenching method, μ' na The velocity difference between air and slag at the collision point, Kinematic viscosity ratio of molten slag to granulation gas, σ1 slag surface tension, k D Take 50, N take 0.5, Liquid-gas ratio is the mass flow rate ratio of blast furnace slag to gas at the collision point, D1 is the molten slag flow diameter. Formula (1) is the process relationship between blast furnace slag flow and water mist volume calculated from the perspective of heat exchange; Formula (2) is the equivalent formula for the particle size of granulated slag. Preliminary estimates show that this device can consume 1 ton of water and 1200m of air per hour. 3 5 tons of blast furnace slag were treated under the conditions, and the particle size of the blast furnace slag after treatment was about 5mm.

[0072] The present invention uses water mist to cool and granulate high-temperature molten metallurgical slag into 750°C hot slag as a pre-process for further effective utilization of blast furnace slag waste heat. The device can granulate molten blast furnace slag while retaining the waste heat resources contained in the blast furnace slag to the maximum extent, reducing water consumption in the metallurgical slag treatment process.

[0073] In addition, in order to suppress the turbulence in the slag flow process and maintain the stability of the slag discharge from the slag outlet, the connection between the bottom of the intermediate slag pot and the slag outlet adopts a streamlined design; the inner wall of the shell of the slag cooling and granulating device and the surface of the auxiliary granulator have a wear-resistant coating. The inner wall of the shell and the auxiliary granulator will be worn during the discharge of blast furnace slag particles, and both need to be made of wear-resistant materials.

[0074] Figure 2 There are two optional arrangements of water mist nozzles. The Y shape in the figure represents the water mist nozzle. Figure 2 There are 4 water mist nozzles in a circular array on the left. Figure 2 On the right, there are 6 water mist nozzles arranged in a circular array; Figure 4 The auxiliary granulator is an optional structure in this embodiment. The auxiliary granulator shown in the figure is open in four directions. Figure 2 Left Figure 4 The array of water mist nozzles corresponding to the auxiliary granulator shown in FIG. If the auxiliary granulator is selected to have six-direction openings, then Figure 2 The right side shows the array of water mist nozzles corresponding to the auxiliary granulator.

[0075] Figure 3 It is a structure used by water mist nozzles, which is a siphon water mist nozzle. If necessary, the structure of the water mist nozzle can be selected according to actual conditions.

[0076] The above is only an embodiment of the present invention with better effects, and is not intended to limit the scope of the present invention. Any simple deformation or equivalent transformation made by any technician based on the content of the present invention, or directly or indirectly applied in other related technical fields, is included in the scope of the present invention.

Claims

1. A blast furnace slag weak cold granulation device and granulation process thereof, characterized in that: The blast furnace slag weak cooling granulation device comprises a slag cooling granulation unit (1), an intermediate slag pot (6), a water supply device (3), an air supply device (2) and a slag car (11). The slag cooling granulation unit (1) is provided with an exhaust duct (5), a water mist nozzle (4), a water inlet pipe (8), an air inlet pipe (9), a slag water inlet (7) and an auxiliary granulator (10); the water mist nozzle (4) of the slag cooling granulation unit (1) is coaxial with the slag water inlet (7) and forms a circular array with a certain tilt angle; the exhaust duct (5) gradually expands from bottom to top and then gradually contracts from bottom to top; the auxiliary granulator (10) is a hollow cone fixed below the slag water inlet (7) and is used for preliminary crushing and diverting the blast furnace slag; in order to suppress the turbulence in the slag flow process and maintain the stability of the slag discharge from the slag water inlet (7), the connection between the bottom of the intermediate slag pot (6) and the slag water inlet (7) adopts a streamlined design.

2. A blast furnace slag weak cold granulation device and granulation process thereof, characterized in that: The weak cold granulation of blast furnace slag has the following process relationship. The high-temperature slag from the blast furnace enters the intermediate slag pot (6) through the slag groove, and then enters the slag cooling and granulation device (1) from the slag outlet (7) of the intermediate slag pot (6). In the slag cooling and granulation device (1), the high-temperature slag hits the auxiliary granulator (10) and is divided into multiple streams and fully contacts the water mist jet sprayed by the water mist nozzle (4). Under the action of the water mist jet, it is weakly cold granulated into fine particles with a temperature of about 750°C; the 300°C water vapor formed during the slag granulation process is discharged from the exhaust duct at the top; for the water mist granulation cooling process of the slag, the main function of the water mist is to weakly cold vitrify and solidify the slag, and the function of the air is to break up the slag droplets. Therefore, the granulated slag slag making process can be approximately regarded as wind quenching granulation. Therefore, the water flow rate in the water mist sprayed by the water mist nozzle (4), the slag flow rate flowing out of the slag outlet (7) and the final granulated slag diameter follow the following process relationship: Where Q 水 Water flow rate, Q 渣 Slag flow rate, C 渣 Specific heat capacity of blast furnace slag, ρ 渣 Density of blast furnace slag, C l Specific heat of liquid water, C g Specific heat capacity of water vapor, ΔH vap Heat of evaporation of water, η water vapor specific heat capacity correction coefficient, λ slag specific heat capacity correction coefficient; D' pl Granulated slag particle size, ρ' na Gas density at the collision point between air and slag in wind quenching method, μ' na The velocity difference between air and slag at the collision point, Kinematic viscosity ratio of molten slag to granulation gas, σ1 slag surface tension, k D Take 50, N take 0.5, The liquid-gas ratio is the mass flow rate ratio of blast furnace slag to gas at the collision point, and D1 is the molten slag flow diameter. Formula (1) is the process relationship between blast furnace slag flow and water mist flow from the perspective of heat exchange; Formula (2) is the equivalent formula for the particle size of granulated slag.

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