Operation process improvement method for prolonging service life of rotary kiln

Abstract

The invention relates to the technical field of nonferrous metallurgy production, and discloses an operation process improvement method for prolonging the service life of a rotary kiln, which comprises the following steps: S1, raw material preparation: using a composite material silicon-calcium-iron containing iron ions, silicon and calcium as a main raw material, and controlling the pH value of the raw material within a subacid range; s2, washing and absorbing: enabling the raw materials to sequentially pass through a washing tower and an absorbing tower, removing impurities and ensuring the purity and acid-base balance of the raw materials; s3, filter pressing and thickening: carrying out solid-liquid separation on the purified raw materials through a filter press to obtain solid particles; and the solid particles are further concentrated through a thickener. By forming a stable metal slag protection layer on the surface of the kiln brick, high-temperature abrasion and thermal erosion of the kiln brick are effectively prevented, so that the service life of the kiln brick is remarkably prolonged, silicon-calcium-iron is adopted as main raw materials, and the characteristic of balanced components of the silicon-calcium-iron is utilized, so that furnace charge is calcined in a subacid environment, a good reducing atmosphere is formed, and the volatilization rate of metal is increased.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metallurgical production, and in particular to an improved method for operating a rotary kiln to extend its life. Background Art

[0002] Rotary kiln is a commonly used thermal equipment in metallurgy, chemical industry and building materials industries. It is widely used in the calcination and roasting of cement clinker, limestone, bauxite and other materials. However, in the actual use of rotary kiln, the wear problem of kiln bricks has always troubled manufacturers. The kiln bricks wear quickly, resulting in a short kiln life and the need for frequent maintenance, which not only increases the maintenance cost, but also prolongs the production cycle and reduces production efficiency.

[0003] During the operation of a traditional rotary kiln, the ratio of iron ions to silicon-calcium in the raw materials is unbalanced, which will affect the reducing atmosphere in the kiln, leading to an imbalance in the acid-base balance of the charge, and seriously affecting the kiln mouth bonding and operation control. In addition, the slag loss rate is high and the metal loss is large, further increasing the production cost. In order to improve the operating efficiency of the rotary kiln, extend the kiln life, and reduce the wear of the kiln bricks, an improved operating process method is urgently needed.

[0004] At present, the existing technical solutions mainly improve the kiln brick wear problem by adjusting the raw material ratio, optimizing the furnace temperature control, etc., but these methods have limited effect in practical applications. Especially during the high-temperature calcination process, how to form a stable protective layer on the surface of the kiln brick to effectively prevent the kiln brick from wear and thermal erosion is a key technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides an improved method for the operation process of a rotary kiln to extend the kiln life, which solves the problem that the traditional rotary kiln has a high slag loss rate, large metal loss, and further increases production costs.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for improving the operation process of a rotary kiln to extend the kiln life, comprising the following steps:

[0007] S1. Raw material preparation: Use silicon-calcium-iron, a composite material containing iron ions, silicon and calcium, as the main raw material, and control the pH value of the raw material within a slightly acidic range;

[0008] S2. Washing and absorption: The raw materials are passed through the washing tower and the absorption tower in sequence to remove impurities and ensure the purity and acid-base balance of the raw materials;

[0009] S3. Filtration and thickening: The purified raw material is passed through a filter press for solid-liquid separation to obtain solid particles; the solid particles are then further concentrated through a thickener;

[0010] S4. Sedimentation separation: The concentrated solid raw materials enter the supernatant tank for sedimentation separation to obtain pure raw materials and wastewater, and the wastewater enters the sewage station for treatment;

[0011] S5. Grinding and liquid preparation: The pure raw materials are sent to the ball mill for grinding, and additives are added as needed during the grinding process, and then enter the liquid preparation tank for mixing and liquid preparation to adjust the pH and chemical properties of the raw materials;

[0012] S6. Kiln preheating: Before starting the rotary kiln, preheat the kiln so that the kiln temperature gradually rises to about 800 degrees and maintains it for a certain period of time to stabilize the kiln body;

[0013] S7. Feeding and furnace temperature control: gradually feed the prepared silicon-calcium-iron raw materials into the rotary kiln, adjust the combustion system, control the temperature in the kiln between 1000 and 1200 degrees, and use the automatic control system to monitor and adjust the furnace temperature in real time;

[0014] S8. Formation of a protective layer: Under high temperature conditions, the iron ions in the silicon-calcium-iron form liquid iron on the surface of the kiln bricks, which solidifies through cooling to form a 30 to 40 centimeters metal slag protective layer. Start the cooling system and sprinkle cooling water to quickly condense the liquid iron.

[0015] Preferably, the treatment carried out in the washing tower and the absorption tower includes removing impurities caused by the unbalanced ratio of iron ions and silicon-calcium in the raw materials.

[0016] Preferably, the additive added in the ball mill is lime or silicate to adjust the pH of the raw material.

[0017] Preferably, the cooling system includes a water spray cooling device installed outside the kiln lining, which rapidly reduces the temperature of the kiln lining by spraying cooling water.

[0018] Preferably, the rotary kiln temperature control system is an automatic control system that monitors and adjusts the temperature in the kiln in real time to ensure that it fluctuates stably between 1000 and 1200 degrees.

[0019] Preferably, the wastewater generated during the sedimentation separation process enters a sewage station for treatment to ensure that the wastewater meets discharge standards or is recycled.

[0020] Preferably, the raw material pretreatment step further comprises removing most of the impurities by wet scrubbing.

[0021] Preferably, the concentration process in the thickener is performed by adding a flocculant to improve the settling efficiency of the solid particles.

[0022] Preferably, the grinding time and speed of the ball mill in the grinding step are adjusted according to the initial particle size of the raw materials and the final requirements.

[0023] Preferably, step S8 further includes step S9, which is to gradually lower the temperature before stopping the kiln so that the temperature inside the kiln drops slowly to prevent damage to the kiln bricks due to a sudden drop in temperature. After stopping the kiln, comprehensive equipment inspection and maintenance are carried out to clean and repair the protective layer on the kiln bricks. The cooling process before stopping the kiln is carried out by gradually reducing the fuel supply and controlling the cooling rate through the ventilation system to prevent damage to the kiln bricks due to a sudden drop in temperature.

[0024] The present invention provides a method for improving the operation process of a rotary kiln to extend the kiln life.

[0025] Beneficial effects:

[0026] 1. The present invention forms a stable metal slag protective layer on the surface of kiln bricks, effectively preventing high-temperature wear and thermal erosion of kiln bricks, thereby significantly extending the service life of kiln bricks. Traditional rotary kiln bricks wear quickly and have a short life. By optimizing the raw material ratio and furnace temperature control, the present invention can extend the kiln life to more than 900 days, reducing the need for frequent maintenance and improving the overall operating efficiency of the kiln.

[0027] 2. The present invention uses silicon-calcium-iron as the main raw material, and utilizes its balanced composition to ensure that the charge is calcined in a slightly acidic environment, forming a good reducing atmosphere and increasing the metal volatilization rate. By accurately controlling the temperature in the kiln and the cooling system, the metal recovery rate is further improved, the metal loss in the production process is reduced, and the goal of improving production efficiency and reducing production costs is finally achieved.

[0028] 3. The present invention reduces the slag loss rate and metal loss and reduces production costs by optimizing the operating process and raw material ratio. In particular, in the steps of washing, absorbing, filter pressing, thickening, grinding and liquid preparation, effective wastewater treatment and resource recovery are used to reduce environmental pollution and achieve environmental benefits. By reducing the maintenance frequency and improving production efficiency, the present invention has significant advantages in both economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall steps of the present invention;

[0030] Figure 2 The figure is a schematic diagram of the preparation process of the silicon-calcium-iron raw material in the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example:

[0033] Please see attached Figure 1 -Attached Figure 2 The embodiment of the present invention provides a rotary kiln operation process improvement method for extending the kiln life, comprising the following steps:

[0034] S1. Raw material preparation: Use silicon-calcium-iron, a composite material containing iron ions, silicon and calcium, as the main raw material, control the pH of the raw material within a slightly acidic range (pH value of about 6), and the raw material pretreatment step further includes removing most of the impurities by wet washing. Put the silicon-calcium-iron raw material into the washing equipment, add appropriate amount of clean water and detergent, stir thoroughly for 15 minutes, and ensure that the impurities are thoroughly washed. Then separate the clean silicon-calcium-iron raw material through a filter. The specific operation of wet washing is to place the raw material in a tank containing an acidic solution and use chemical reactions to remove impurities. For example, using hydrochloric acid to wash iron ore, the reaction is as follows:

[0035] Fe2O3+6HCl→2FeCl3+3H2O

[0036] S2. Washing and absorption: The raw materials are passed through the washing tower and absorption tower in turn to remove impurities and ensure the purity and acid-base balance of the raw materials; the treatments carried out in the washing tower and absorption tower include removing impurities caused by the imbalance of iron ions and silicon-calcium ratio in the raw materials. In the washing tower, the raw materials are contacted with the washing liquid and stirred for 10 minutes, and then the raw materials are sent to the absorption tower through a pump and mixed with the absorption liquid for 20 minutes to make the raw materials reach the required purity and acid-base balance. The chemical reactions in the absorption tower are as follows:

[0037] CaCO3+2HCl→CaCl2+H2O+CO2

[0038] Through this step, the calcium ions and silicates in the raw materials are balanced, ensuring the stability of subsequent processing.

[0039] S3. Filtration and thickening: The purified raw materials are passed through a filter press for solid-liquid separation to obtain solid particles; then the solid particles are further concentrated through a thickener. The washed and absorbed raw materials are sent to a filter press, which is started for filtration. After filtering out the solid particles, the solid particles are transferred to a thickener, which is started and flocculants are added to concentrate the solid particles to form a high-concentration solid raw material slurry. The filter press separates the liquid from the solid through high pressure, and the formula is expressed as:

[0040]

[0041] Where P is pressure, F is force, and A is area. The thickening process in the thickener improves the settling efficiency of solid particles by adding flocculants, commonly used flocculants such as polyacrylamide (PAM). The use of flocculants can significantly improve the settling efficiency and shorten the processing time.

[0042] S4. Sedimentation separation: The concentrated solid raw materials are sent to the supernatant tank for sedimentation separation to obtain pure raw materials and wastewater, and the wastewater is sent to the sewage station for treatment; the wastewater generated during the sedimentation separation process is sent to the sewage station for treatment to ensure that the wastewater meets the discharge standards or is recycled.

[0043] During wastewater treatment, lime is used for neutralization:

[0044] Ca(OH)2+H2SO4→CaSO4+2H2O

[0045] Through this step, the acidic components in the wastewater can be effectively removed to ensure that the discharge meets environmental protection standards.

[0046] The concentration process in the thickener improves the sedimentation efficiency of solid particles by adding flocculants. Start the supernatant tank sedimentation system. After sedimentation and separation for 1 hour, collect the supernatant and send it to the sewage station. Start the sewage treatment equipment to treat the wastewater and discharge or reuse it after it meets the discharge standards.

[0047] S5. Grinding and liquid preparation: The pure raw materials are sent to the ball mill for grinding, and additives are added as needed during the grinding process, and then they are sent to the liquid preparation tank for mixing and liquid preparation to adjust the pH and chemical properties of the raw materials; the additives added to the ball mill are lime or silicic acid to adjust the pH of the raw materials. The grinding time and speed of the ball mill in the grinding step are adjusted according to the initial particle size and final requirements of the raw materials. The solid raw materials are sent to the ball mill, and the ball mill is started. The grinding time is set to 2 hours. Lime or silicic acid is added every 30 minutes. After the grinding is completed, the raw materials are sent to the liquid preparation tank, and an appropriate amount of water and mixing agent are added. Stir for 15 minutes to ensure that the raw materials are evenly mixed. The operating formula of the ball mill is:

[0048]

[0049] Where E is energy, d1 and d2 are initial and final particle sizes respectively, and k is a constant. By properly controlling the grinding time and speed, the required fineness and uniformity of the raw materials can be ensured.

[0050] S6. Kiln preheating: Before starting the rotary kiln, preheat the kiln to gradually raise the kiln temperature to about 800 degrees and maintain it for a certain period of time to stabilize the kiln body; start the preheating system and gradually increase the kiln temperature by 100 degrees per hour until it reaches 800 degrees, and maintain this temperature for 2 hours to ensure that the kiln body is evenly heated. After stabilization, proceed to the next step. Heat conduction formula during preheating

[0051] Q=mcΔT

[0052] Where Q is heat, m is mass, c is specific heat capacity, and ΔT is temperature change. By heating slowly, thermal stress in the kiln body can be prevented due to rapid temperature changes, ensuring the stability of the kiln structure.

[0053] S7. Feeding and furnace temperature control: gradually feed the prepared silicon-calcium-iron raw materials into the rotary kiln, adjust the combustion system, control the temperature in the kiln between 1000 and 1200 degrees, and use the automatic control system to monitor and adjust the furnace temperature in real time; the rotary kiln temperature control system is an automatic control system that monitors and adjusts the temperature in the kiln in real time to ensure that it fluctuates stably between 1000 and 1200 degrees. Turn on the automatic feeding system, control the feeding amount at about 5 kilograms per minute, and turn on the combustion system at the same time. Use the automatic control system to monitor the furnace temperature to ensure that the furnace temperature is stable at 1100 degrees, and adjust the fuel supply and air volume to maintain a constant temperature. The combustion system is adjusted by controlling the supply of oxygen and fuel, and the formula is expressed as:

[0054]

[0055] By precisely controlling the ratio of fuel and oxygen, a stable combustion process and uniform temperature can be ensured.

[0056] S8. Formation of protective layer: Under high temperature conditions, the iron ions in silicon calcium iron form liquid iron on the surface of kiln bricks, and form a 30 to 40 cm metal slag protective layer through cooling and solidification. Start the cooling system, sprinkle cooling water to quickly condense the liquid iron. The cooling system includes a water spray cooling device installed on the outside of the kiln skin. The kiln skin temperature drops rapidly through the spraying of cooling water. When the furnace temperature reaches 1100 degrees, the iron ions in silicon calcium iron begin to form liquid iron on the surface of the kiln bricks. Start the cooling system, adjust the water pump flow, ensure that the cooling water is evenly sprinkled on the outside of the kiln skin, so that the liquid iron quickly condenses and forms a stable protective layer.

[0057] The role of cooling water is achieved through the heat conduction formula:

[0058] Q=mcΔT

[0059] Through rapid cooling, a dense protective layer can be formed, which effectively prevents the erosion and wear of kiln bricks by high-temperature gases.

[0060] S9, kiln shutdown and maintenance. Before stopping the kiln, gradually lower the temperature so that the temperature inside the kiln drops slowly to prevent the kiln bricks from being damaged by a sudden drop in temperature. After stopping the kiln, conduct a comprehensive equipment inspection and maintenance, clean and repair the protective layer on the kiln bricks. 48 hours before stopping the kiln, gradually reduce the fuel supply, reduce the temperature by 50 degrees per hour, and control the cooling rate through the ventilation system until the temperature inside the kiln drops to room temperature. After stopping the kiln, conduct a comprehensive equipment inspection, repair the protective layer on the kiln bricks, clean the accumulated dust and impurities, and ensure that the kiln body is in the best condition before the next use. The cooling process before stopping the kiln prevents the kiln bricks from being damaged by a sudden drop in temperature by gradually reducing the fuel supply and controlling the cooling rate through the ventilation system. The heat exchange formula during the cooling process is:

[0061]

[0062] Where h is the thermal conductivity, A is the surface area, T s is the surface temperature, T ∞ is the ambient temperature, L is the thickness. By properly controlling the cooling rate, the kiln bricks can be effectively protected and their service life can be extended.

[0063] Through the above steps, the present invention can not only significantly extend the service life of the rotary kiln, but also improve production efficiency, reduce production costs, and also has obvious advantages in environmental protection.

[0064] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving the operation process of a rotary kiln to extend the kiln life, characterized in that: The following steps are involved: S1. Raw material preparation: Use silicon-calcium-iron, a composite material containing iron ions, silicon and calcium, as the main raw material, and control the pH value of the raw material within a slightly acidic range; S2. Washing and absorption: The raw materials are passed through the washing tower and the absorption tower in sequence to remove impurities and ensure the purity and acid-base balance of the raw materials; S3. Filtration and thickening: The purified raw material is passed through a filter press for solid-liquid separation to obtain solid particles; the solid particles are then further concentrated through a thickener; S4. Sedimentation separation: The concentrated solid raw materials enter the supernatant tank for sedimentation separation to obtain pure raw materials and wastewater, and the wastewater enters the sewage station for treatment; S5. Grinding and liquid preparation: The pure raw materials are sent to the ball mill for grinding, and additives are added as needed during the grinding process, and then enter the liquid preparation tank for mixing and liquid preparation to adjust the pH and chemical properties of the raw materials; S6. Kiln preheating: Before starting the rotary kiln, preheat the kiln so that the kiln temperature gradually rises to about 800 degrees and maintains it for a certain period of time to stabilize the kiln body; S7. Feeding and furnace temperature control: gradually feed the prepared silicon-calcium-iron raw materials into the rotary kiln, adjust the combustion system, control the temperature in the kiln between 1000 and 1200 degrees, and use the automatic control system to monitor and adjust the furnace temperature in real time; S8. Formation of a protective layer: Under high temperature conditions, the iron ions in the silicon-calcium-iron form liquid iron on the surface of the kiln bricks, which solidifies through cooling to form a 30 to 40 centimeters metal slag protective layer. Start the cooling system and sprinkle cooling water to quickly condense the liquid iron.

2. The method for improving the operation process of a rotary kiln to extend the kiln life according to claim 1, characterized in that: The treatment carried out in the washing tower and absorption tower includes removing impurities caused by the unbalanced ratio of iron ions and silicon and calcium in the raw materials.

3. The method for improving the operation process of a rotary kiln to extend the kiln life according to claim 1, characterized in that: The additives added to the ball mill are lime or silicate to adjust the pH of the raw materials.

4. The method for improving the operation process of a rotary kiln to extend the kiln life according to claim 1, characterized in that: The cooling system includes a water spray cooling device installed outside the kiln lining, which rapidly reduces the temperature of the kiln lining by spraying cooling water.

5. The method for improving the operation process of a rotary kiln for extending the kiln life according to claim 1, characterized in that: The rotary kiln temperature control system is an automatic control system that monitors and adjusts the temperature inside the kiln in real time to ensure that it fluctuates stably between 1000 and 1200 degrees.

6. The method for improving the operation process of a rotary kiln to extend the kiln life according to claim 1, characterized in that: The wastewater generated during the sedimentation and separation process enters the sewage station for treatment to ensure that the wastewater meets the discharge standards or is recycled.

7. The method for improving the operation process of a rotary kiln to extend the kiln life according to claim 1, characterized in that: The raw material pretreatment step further includes removing most of the impurities by wet washing.

8. The method for improving the operation process of a rotary kiln to extend the kiln life according to claim 1, characterized in that: The concentration process in the thickener improves the settling efficiency of solid particles by adding flocculants.

9. The method for improving the operation process of a rotary kiln to extend the kiln life according to claim 1, characterized in that: The grinding time and speed of the ball mill in the grinding step are adjusted according to the initial particle size of the raw materials and the final requirements.

10. The method for improving the operation process of a rotary kiln to extend the kiln life according to claim 1, characterized in that: The step S8 also includes step S9, which is to gradually reduce the temperature before stopping the kiln so that the temperature inside the kiln drops slowly to prevent the kiln bricks from being damaged due to a sudden drop in temperature. After stopping the kiln, a comprehensive equipment inspection and maintenance is carried out to clean and repair the protective layer on the kiln bricks. The cooling process before stopping the kiln is carried out by gradually reducing the fuel supply and controlling the cooling rate through the ventilation system to prevent the kiln bricks from being damaged due to a sudden drop in temperature.

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