A rotary kiln speed control method and control system for producing sintered lime

Abstract

The present invention discloses a rotary kiln speed control method and control system for producing sintered lime, which belongs to the technical field of limestone powder production and steelmaking. The method is characterized by comprising: S1, obtaining basic parameters: kiln length L, repose angle α of limestone particles, m , the residence time T of the solid material in the rotary kiln, the repose angle P of the rotary kiln and the inner diameter D of the rotary kiln; S2, calculate the rotation speed n of the rotary kiln according to the following formula; n = K*L*α m 0.5 / (T*P*D); where K is the influence coefficient. The present invention can adjust the rotary kiln speed according to the limestone particles entering the kiln, thereby controlling the residence time and firing qualified lime products.

Description

Technical Field

[0001] The invention belongs to the technical field of limestone powder production and steelmaking, and in particular relates to a rotary kiln speed control method and control system for producing sintered lime. Background Art

[0002] The types of metallurgical lime used in the steel industry can be broadly divided into sintered lime for ironmaking and pelletizing, and activated metallurgical lime for steelmaking and slag formation. In blast furnace ironmaking, low-melting-point sintered lime flux is added to separate slag from iron. Furthermore, the addition of flux creates a slag with a certain basicity, effectively purifying pig iron containing harmful impurities and improving its quality.

[0003] The current production of steelmaking lime faces a series of problems:

[0004] First, sintered lime is currently produced in vertical kilns, with the feed limestone typically having a particle size of 60-80 mm. However, limestone within this particle size range typically costs 70-80 RMB per ton. With the continuous depletion of limestone resources, the price of larger-sized limestone is expected to rise.

[0005] Second, limestone mining produces a large number of particles smaller than 3mm. This particle size range is difficult to effectively utilize, and its market price approaches zero. Meanwhile, sintered lime requires a particle size of less than 3mm. Therefore, if limestone particles smaller than 3mm could be directly utilized, not only would the crushing of large lumps of lime be unnecessary, but the production cost of sintered lime could also be significantly reduced due to the raw material cost.

[0006] Third, whether in the process of burning lime in a vertical kiln or a rotary kiln, due to the large particle size of the limestone particles, it is inevitable that the limestone surface will be overburned due to the long high temperature time, and the interior of the limestone particles will be deficient due to the short high temperature time. It is impossible to ensure that limestone particles of different particle sizes are in a reasonable high temperature section for a reasonable residence time, and the final lime product has low lime activity.

[0007] Fourth, if the existing vertical kiln is used to burn small-sized particles, the production cannot be sustained because the overly fine limestone particles have too much resistance in the vertical kiln; if the existing rotary kiln + vertical preheater is used to burn, the overly fine limestone particles have too much resistance in the vertical preheater, and production cannot be sustained.

[0008] Fifth, in the existing rotary kiln + vertical preheater limestone burning process, since the 60-80mm limestone is heated unevenly, adjusting the kiln speed is not a good way to regulate production. Summary of the Invention

[0009] The present invention aims to overcome the shortcomings of the prior art and provides a rotary kiln speed control method and control system for producing sintered lime. The rotary kiln speed is adjusted according to the limestone particles entering the kiln, thereby controlling the residence time and firing qualified lime products.

[0010] A first object of the present invention is to provide a method for controlling the rotation speed of a rotary kiln for producing sintered lime, comprising:

[0011] S1. Obtain basic parameters: kiln length L, angle of repose α of limestone particles m , the residence time T of the solid material in the rotary kiln, the repose angle P of the rotary kiln and the inner diameter D of the rotary kiln;

[0012] S2. Calculate the rotation speed n of the rotary kiln according to the following formula;

[0013] n=K*L*α m 0.5 / (T*P*D); where:

[0014] K is the influence coefficient.

[0015] Preferably, K=0.0295.

[0016] Preferably, the residence time T of the solid material in the rotary kiln is determined by first classifying the same batch of limestone particles according to different particle sizes to obtain particles with a maximum particle size of a and particles with a minimum particle size of b, and then putting the batch of limestone particles into the rotary kiln. The time from preheating to complete decomposition of the particles with a maximum particle size of a in the same batch of limestone particles is T. 1a , The time from preheating to overburning is T 2a The time from preheating to decomposition of particles with a minimum particle size of b is T 1b , The time from preheating to overburning is T 2b , must satisfy T 1a ≤T 2b The residence time T of limestone raw materials with a specific particle size range in the rotary kiln is less than the time T from preheating to overburning of the particles with the smallest particle size b in the same batch of limestone particles. 2b , the time from preheating to complete decomposition of the particles with the largest particle size a in the same batch of limestone particles is T 1a .

[0017] A second object of the present invention is to provide a rotary kiln speed control system for producing sintered lime, comprising:

[0018] Basic parameter acquisition module, used to obtain the following basic parameters: kiln length L, repose angle α of limestone particles m , the residence time T of the solid material in the rotary kiln, the repose angle P of the rotary kiln and the inner diameter D of the rotary kiln;

[0019] Calculation module: Calculate the rotation speed n of the rotary kiln according to the following formula;

[0020] n=K*L*α m 0.5 / (T*P*D); where:

[0021] K is the influence coefficient.

[0022] Preferably, K = 0.0295

[0023] Preferably, the residence time T of the solid material in the rotary kiln is determined by first classifying the same batch of limestone particles according to different particle sizes to obtain particles with a maximum particle size of a and particles with a minimum particle size of b, and then putting the batch of limestone particles into the rotary kiln. The time from preheating to complete decomposition of the particles with a maximum particle size of a in the same batch of limestone particles is T. 1a , The time from preheating to overburning is T 2a The time from preheating to decomposition of particles with a minimum particle size of b is T 1b , The time from preheating to overburning is T 2b , must satisfy T 1a ≤T 2b The residence time T of limestone raw materials with a specific particle size range in the rotary kiln is less than the time T from preheating to overburning of the particles with the smallest particle size b in the same batch of limestone particles. 2b , the time from preheating to complete decomposition of the particles with the largest particle size a in the same batch of limestone particles is T 1a .

[0024] A third object of the present invention is to provide an information data processing terminal, characterized in that it is used to implement the above-mentioned rotary kiln speed control method for producing sintered lime.

[0025] A fourth object of the present invention is to provide a computer-readable storage medium comprising instructions, which, when executed on a computer, enables the computer to execute the above-mentioned method for controlling the rotation speed of a rotary kiln for producing sintered lime.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The present invention can use limestones of different particle sizes, unlike vertical kilns and rotary kilns which have high requirements on limestone particle size, thus reducing raw material costs and improving the utilization rate of limestone mines.

[0028] 2) The present invention can utilize a wide range of limestones, with the smallest limestone particles being less than 3 mm, and can directly produce high-quality limestone products from originally almost useless ores. The largest limestone resources can also be utilized, which are 60-80 mm in size.

[0029] 3) The lime fired in the present invention has a uniform decomposition rate and high lime activity, and large particles of raw materials will not be over-burned on the surface or under-burned on the inside.

[0030] 4) The present invention can adjust the rotary kiln speed according to the limestone particles entering the kiln, thereby controlling the residence time and firing qualified lime products. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] A method for controlling the rotation speed of a rotary kiln for producing sintered lime, comprising:

[0033] Rotary kiln speed n (r / min), kiln length L (m), limestone particle repose angle α m (°), the residence time of solid materials in the rotary kiln T (min), the repose angle P (°) of the rotary kiln, and the inner diameter D (m) of the rotary kiln, there is the following relationship:

[0034] n=K*L*α m 0.5 / (T*P*D)

[0035] Furthermore, K is the angle of repose α of limestone according to different kiln length L (m) m (°), the repose angle P (°) of the rotary kiln, a coefficient affected by the inner diameter D (m) of the rotary kiln, the default value can be set to 0.0295;

[0036] A method for controlling the speed of a rotary kiln for producing sintered lime is provided. The limestone particles are classified according to different particle sizes and then rotated in a rotary kiln. The time from preheating to complete decomposition of the particles with the largest particle size a in the same batch of limestone particles is T. 1a , the burning time is T 2a The time from preheating to decomposition of particles with a minimum particle size of b is T 1b , the burning time is T 2b , must satisfy T 1a ≤T 2b ;

[0037] The residence time T of limestone raw materials with a specific particle size range in the rotary kiln is less than the time T from preheating to overburning of the particles with the smallest particle size b in the same batch of limestone particles. 2b , the time from preheating to complete decomposition of the particles with the largest particle size a in the same batch of limestone particles is T 1a ;

[0038] T of limestone raw materials in a specific particle size range 1a 、T 1b 、T 2a 、T 2b Obtained from experimental tests;

[0039] T of the same batch 2a -T 1a 、T 1b -T 2b The smaller the difference, the higher the quality of the lime.

[0040] Technical principle:

[0041] First, limestone particle size has a significant impact on the decomposition of calcium carbonate. Zhang Baosheng, in "Thermogravimetric Experimental Study on the Effect of Particle Size on the Decomposition Kinetics of Limestone" (Proceedings of the CSEE, Vol. 30, No. 2, p. 50), found that the activation energy increases first and then decreases with increasing particle size, reaching a maximum at particle sizes between 100 and 180 μm. Wang Liyou, in "High-Temperature Decomposition Kinetics of Large-Particle Limestone" (Journal of Chongqing University, Vol. 43, No. 8, p. 32), proposed that limestone particles with particle sizes of 8-25 mm and 8-12 mm can decompose approximately 200 seconds faster than those with particle sizes of 20-25 mm. Chen Hai, in "Study on the Calcination Characteristics of Small and Medium-Particle Limestone" (Master's thesis, Chongqing University, 2013), showed that limestone particles of 5-10 mm take longer to reach a high level of activity than smaller particles. Therefore, directly calcining limestone particles regardless of particle size, or even large-particle limestone, does not produce lime with a high decomposition rate.

[0042] Second, Chen Hai, in "Research on the Calcination Characteristics of Small and Medium-sized Limestone Particles" (Master's thesis, Chongqing University, 2013), also pointed out that after the product activity reaches its optimal level, increasing the calcination time further increases the sintering of limestone with a particle size of 5 to 10 mm compared to smaller particles. Therefore, calcining limestone particles regardless of particle size, or directly calcining large-sized limestone, is more likely to cause limestone sintering and reduce lime quality.

[0043] The present invention first classifies limestone particles of different particle size ranges, and controls the residence time between the overburning time of the smallest particles in the same batch of limestone particles and the time from preheating to complete decomposition of the largest particles in the same batch of limestone particles, thereby ensuring that all limestone particles in the same batch are completely decomposed and not overburned, thereby improving the quality of lime.

[0044] Implementation method:

[0045] The sintered lime plant of a Liaoning steel mill originally used 60-80mm limestone to produce sintered lime. This limestone cost 70-80 yuan per ton. Since approximately 2 tons of limestone are required to produce 1 ton of lime, the raw material cost per ton of lime is 140-160 yuan per ton. The combined underburn and overburn rates of the lime product fluctuated between 10-20%.

[0046] After adopting the rotary kiln and the scheme of the present invention, 0.5-3 mm limestone is used for production, and the purchase price of the limestone particles is about 10 yuan per ton.

[0047] Laboratory analysis shows that the time from entering the kiln to complete decomposition of 0.5mm particles is 15 minutes, the time from entering the kiln to overburning of 0.5mm particles is 30 minutes, the time from entering the kiln to complete decomposition of 1.5mm particles is 25 minutes, the time from entering the kiln to overburning of 1.5mm particles is 50 minutes, the time from entering the kiln to complete decomposition of 3mm particles is 35 minutes, and the time from entering the kiln to overburning of 1.5mm particles is 70 minutes.

[0048] Since the time from entering the kiln to complete decomposition of 3mm particles is 35 minutes, which is larger than the time from entering the kiln to over-burning of 0.5mm particles, which is 30 minutes, they are divided into two ranges of 0.5-1.5mm and 1.5-3mm for production respectively.

[0049] T in the range of 0.5-1.5mm 0.5-1.5 Take 27.5min, 1.5-3mm range of T 1.5-3 Take 40 minutes.

[0050] The kiln length of our factory is 40m, and the angle of repose of limestone particles is α m =40°, T 0.5-1.5 =27.5min, T 1.5-3 =40min, the rest angle P of the rotary kiln = 2°, the inner diameter D of the rotary kiln = 3.8m, and K is 0.0295.

[0051] n=K*L*α m 0.5 / (T*P*D)

[0052] n 0.5-1.5 =0.0295*40*40 0.5 / (27.5*2*3.8)=2.26r / min

[0053] n 1.5-3 =0.0295*40*40 0.5 / (40*2*3.8)=1.55r / min

[0054] In future production, the K value can be continuously revised based on actual production data.

[0055] Based on this, the rotary kiln speed is controlled for production, and limestone with a diameter less than 3 mm is used for production. The raw material cost of one ton of lime is reduced to about 20 yuan / ton, and the sum of the under-burning rate and over-burning rate of the lime product is less than 3%.

[0056] A rotary kiln speed control system for producing sintered lime, comprising:

[0057] Basic parameter acquisition module, used to obtain the following basic parameters: kiln length L, repose angle α of limestone particles m , the residence time T of the solid material in the rotary kiln, the repose angle P of the rotary kiln and the inner diameter D of the rotary kiln;

[0058] Calculation module: Calculate the rotation speed n of the rotary kiln according to the following formula;

[0059] n=K*L*α m 0.5 / (T*P*D); where:

[0060] K is the influence coefficient;

[0061] α m The angle of repose is the minimum angle between the inclined plane and the horizontal surface when the inclined plane causes the object placed on it to be in a critical state of sliding down the inclined plane (that is, as the inclination angle increases, the object on the inclined plane will slide more easily; when the object reaches the state where it starts to slide, the angle of the critical state is called the angle of repose).

[0062] α m It is obtained by testing each batch of limestone particles.

[0063] An information data processing terminal is used to implement the above-mentioned rotary kiln speed control method for producing sintered lime.

[0064] A computer-readable storage medium includes instructions, which, when executed on a computer, enable the computer to execute the above-mentioned method for controlling the rotation speed of a rotary kiln for producing sintered lime.

[0065] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented in whole or in part in the form of a computer program product, the computer program product includes one or more computer instructions. When the computer program instructions are loaded or executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL) or wireless (e.g., infrared, wireless, microwave, etc.)) method. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that includes one or more available media integrated. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)).

[0066] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A method for controlling the rotation speed of a rotary kiln for producing sintered lime, characterized in that: include: S1. Obtain basic parameters: kiln length L, angle of repose α of limestone particles m , the residence time T of the solid material in the rotary kiln, the repose angle P of the rotary kiln and the inner diameter D of the rotary kiln; S2. Calculate the rotation speed n of the rotary kiln according to the following formula; ;in: K is the influence coefficient; The method for determining the residence time T of solid materials in the rotary kiln is as follows: first, the same batch of limestone particles are classified according to different particle sizes to obtain particles with a maximum particle size of a and particles with a minimum particle size of b. Then, the batch of limestone particles is put into the rotary kiln. The time from preheating to complete decomposition of the particles with a maximum particle size of a in the same batch of limestone particles is T. 1a , The time from preheating to overburning is T 2a The time from preheating to decomposition of particles with a minimum particle size of b is T 1b , The time from preheating to overburning is T 2b , must satisfy T 1a ≤T 2b The residence time T of limestone raw materials with a particle size range in the rotary kiln is less than the time T from preheating to overburning of the particles with the smallest particle size b in the same batch of limestone particles. 2b , the time from preheating to complete decomposition of the particles with the largest particle size a in the same batch of limestone particles is T 1a .

2. The rotary kiln speed control method for producing sintered lime according to claim 1, wherein: K=0.0295。 3. A rotary kiln speed control system for producing sintered lime, characterized in that: include: Basic parameter acquisition module, used to obtain the following basic parameters: kiln length L, repose angle α of limestone particles m , the residence time T of the solid material in the rotary kiln, the repose angle P of the rotary kiln and the inner diameter D of the rotary kiln; Calculation module: Calculate the rotation speed n of the rotary kiln according to the following formula; ;in: K is the influence coefficient; The method for determining the residence time T of solid materials in the rotary kiln is as follows: first, the same batch of limestone particles are classified according to different particle sizes to obtain particles with a maximum particle size of a and particles with a minimum particle size of b. Then, the batch of limestone particles is put into the rotary kiln. The time from preheating to complete decomposition of the particles with a maximum particle size of a in the same batch of limestone particles is T. 1a , The time from preheating to overburning is T 2a The time from preheating to decomposition of particles with a minimum particle size of b is T 1b , The time from preheating to overburning is T 2b , must satisfy T 1a ≤T 2b The residence time T of limestone raw materials with a particle size range in the rotary kiln is less than the time T from preheating to overburning of the particles with the smallest particle size b in the same batch of limestone particles. 2b , the time from preheating to complete decomposition of the particles with the largest particle size a in the same batch of limestone particles is T 1a .

4. The rotary kiln speed control system for producing sintered lime according to claim 3, characterized in that: K=0.0295。 5. An information data processing terminal, characterized in that: A rotary kiln speed control method for producing sintered lime used to implement any one of claims 1 to 2.

6. A computer-readable storage medium comprising instructions, which, when executed on a computer, causes the computer to execute the method for controlling the rotation speed of a rotary kiln for producing sintered lime according to any one of claims 1 to 2.