Youtube Linkedin Facebook Tiktok Twitter
  • Email
  • Tel
  • whatsapp
Search
Close this search box.
Tiktok Twitter Youtube Linkedin
The Darko logo showcases a bold design, representing quality and innovation.
Search
Home > 2024 > November

CONATCT

MORE+
  • Tel: +86-15370455293 +86 15365564889
  • Email: sales@darko-tech.com
  • 24-hour hotline: +86 15370455293 +86 15365564889 ( WhatsApp )
The Importance and Optimization of Powder Silos

Powder silos are crucial facilities in industrial enterprises. They are responsible for the homogenization, storage, and balancing of production materials. These silos come in different materials, capacities, and structures to meet various needs. However, many companies face issues like low storage capacity, poor homogenization, and difficulties in discharging materials. These problems often disrupt normal production.

 

Many enterprises have tried to innovate their technology, but results have been limited. The main issue lies in the design philosophy. Here are some of my thoughts on optimizing powder silos:

There is a pressure reducing cone on the upper part of the discharge port in the powder storage.

1. Design of the Discharge Cone

Many powder silos have a discharge cone above the outlet. Its purpose is to reduce the pressure of the material inside the silo, allowing for a smooth flow. However, the reality is often different. Without running the aeration discharge system, materials rarely flow out. When the system is on, excessive pressure can make control difficult.

 

I suggest removing the discharge cone and installing a high-efficiency flow valve at the outlet. This valve can monitor material pressure in real time. When pressure is too high or the material level rises, the valve closes quickly. When pressure decreases or the level falls, the valve opens. This system works like an ABS brake system in cars, controlling material flow effectively.

2. Effectiveness of Air Homogenization

Clients often ask how air homogenization equipment achieves material homogenization. In fact, the silo itself has a homogenization function. When materials enter the silo and exit, this process is self-homogenizing. The main role of homogenization equipment is to ensure normal discharge, not to mix materials forcefully. Using fans for gas mixing can harm the strength and efficiency of the silo.

 

The true purpose of air homogenization equipment is to ensure steady discharge of materials. This allows the silo's self-homogenization function to work correctly. However, after long-term use, equipment may fail due to improper operation or material characteristics. When this happens, maintenance and cleaning of the silo become necessary.

3. Optimizing Discharge Equipment

Discharge equipment includes gates, feed devices, metering devices, and conveying equipment. Using the gate and level control system mentioned earlier allows for even material discharge. I recommend using air slide conveyors as the discharge method. This design is popular due to its low investment and operating costs, good sealing, and flexible layout.

 

However, air slide conveyors have some drawbacks. They may struggle to handle hard clumps or wet materials. Therefore, I suggest using air chain conveyors. These devices combine chain conveyors with air slide conveyors. They can effectively manage clumps and moisture while lowering the height of the silo base.

 

According to well-known design firms, using air chain conveyors can save significant construction costs. Their operating costs remain relatively low. More design firms are now adopting air chain conveyors to replace traditional belt conveyors, improving powder transport efficiency and reliability.

 

Conclusion

The design and optimization of powder silos are key to enhancing industrial production efficiency. With proper design and advanced equipment, companies can improve silo functionality and achieve efficient homogenization and stable discharge of materials.

If you have any questions about silo design or related equipment, feel free to contact us. We are Darko, and we are here to provide you with professional support and solutions!

MORE+
Unlocking Efficiency with Air Slide Conveyors

Reversible conveyors primarily address the need to transport materials in both forward and reverse directions. They are widely used for short-distance transport. However, when the transport distance is longer, technical limitations reduce their applications. In 2022, Company C proposed using a reversible air slide conveyor with a capacity of 300t/h and a distance of 70 meters for the storage of mineral powder. Although Darko has some experience with short-distance reversible air slide conveyors, this is our first attempt at such a large capacity and distance with multiple discharge points. Therefore, Darko focused on the following technical issues:

Several large metal boxes are stacked together to demonstrate the structure and function of the air slide conveyor

1. Drive System Design

First, we determined that the drive should be at one end of the conveyor. This design avoids the need for two drives at both ends, simplifying operation. When one end is driving, the other end remains inactive. This setup reduces the risk of mechanical accidents and ensures smooth production.

Next, we considered placing the drive in the middle. However, we found that this would complicate the structure and increase stress on the chain, reducing its lifespan. Therefore, we decided to place the drive at one end for simplicity.

2. Chain Tensioning

Once we chose the one-end drive, chain tensioning became critical. The long transport distance requires effective tensioning. We opted for a rear tensioning system, which includes weight tensioning and screw tensioning. After evaluation, we selected a simple rear tensioning method to minimize wear and extend the lifespan of the chain and components.

3. Chain Transition Handling

After deciding on the drive and tensioning methods, we focused on handling chain transitions. Poor transition handling can lead to chain jams and affect normal operation. In reversible operation, we need to manage tensioning for both the upper and lower chains. Thus, we added a transition structure between the drive sprocket and the lower chain to ensure smooth operation.

4. Intermediate Discharge Design

The reversible air slide conveyor is installed at the top of the storage facility, primarily for material entry. Therefore, it must accommodate multiple discharge points. To prevent blockages, we installed discharge openings in the middle and ensured that the opening below the drive sprocket is always open. This design helps manage different types of materials and prevents mixing, which can affect product quality. We implemented high-pressure air blowing at the intermediate discharge points to solve this issue effectively.

Conclusion

Through the design optimization of the reversible air slide conveyor, Darko meets high capacity and long distance transport needs while ensuring stable operation and efficient material entry. We are committed to providing high-quality solutions to enhance production efficiency. For more information, please feel free to contact us.

MORE+
Brief analysis of air leakage in raw meal vertical mills

Raw material vertical mills are key grinding equipment in cement production. Their operational stability directly impacts production efficiency and product quality. However, many enterprises often face air leakage issues in the vertical mill system. This not only increases energy consumption but may also lead to equipment failures, affecting the continuity and reliability of production lines. This article analyzes the causes of air leakage in raw material vertical mills and proposes corresponding solutions.

I. Impact of Air Leakage in Vertical Mills

1.Increased Energy Consumption: Air leakage in the vertical mill system causes heat loss. The internal temperature of the mill decreases. To maintain the required temperature, additional hot air supply is necessary, leading to increased energy consumption.


2.Decreased Output: Air leakage results in the loss of some materials. This reduction in material inside the mill lowers the load, which subsequently decreases production output.


3.Equipment Failures: Prolonged air leakage accelerates the wear of internal components, especially seals and pipes. This shortens equipment lifespan and increases maintenance costs.


4.Decline in Product Quality: Air leakage affects the grinding efficiency of materials, leading to either overly fine or coarse products, which compromises product quality.

 

II. Causes of Air Leakage in Vertical Mills

1.Aging or Damaged Seals: Seals, such as roller seals and feeder seals, can age or break after long-term operation, causing air leakage.


2.Loose Pipe Connections: If the ventilation pipes between the vertical mill and the dust collector are installed loosely or improperly connected, air leakage may occur.


3.Unreasonable Design of Locking Feeders: Traditional locking feeders, such as segmented wheels with blades, may cause air leakage if their gaps are too large or too small.


4.Inefficient Roller Seal Structure: The current roller seal design is simple and has poor sealing effectiveness. This is especially true for lower seals, where space is limited, making it difficult to ensure effective sealing.

 

5.Defective Slag Discharge Design: The direct chute from the slag discharge port to the belt conveyor is a major leakage point. The single flap valve used in the original design can easily become jammed by large materials, causing the mill to stop.

 

III. Solutions for Air Leakage in Vertical Mills

1.Replace Aging Seals: Regularly check and replace aging or damaged seals to ensure effective sealing.

 

2.Strengthen Pipe Connections: Conduct a thorough inspection of the ventilation pipes to ensure connections are secure and tight, and reinforce any loose connections.

 

3.Optimize Locking Feeder Design: Implement a material seal at the mill head. Adjust the gaps in the segmented wheels to avoid excessive or insufficient spacing that leads to air leakage.

 

4.Improve Roller Seal Structure: Change the roller seal to a circular silicone wave seal. This design offers better elasticity and sealing effectiveness, effectively reducing air leakage.

 

5.Redesign the Slag Discharge Port: Modify the discharge port to a non-powered flap locking valve. This design combines a valve body with a material curtain, using system negative pressure to create a sealed structure, effectively addressing the air leakage issue.

 

Two combined scenes of a vertical roller mill, showcasing its operational setup and components in a cement production environment.

IV. Case Study

In a cement enterprise with a 4500 t/d clinker production line, the raw material system is equipped with a TRM53.4 raw material vertical mill. Due to severe air leakage, the oxygen content at the kiln tail reached 10.3%, and the electrical consumption for the raw material process was 16.5 kWh/t. The electrical consumption for the circulating fan was as high as 8.6 kWh/t, and the output temperature was low, only 45–55°C.

This severely limited the energy-saving needs of the raw material mill. After addressing the air leakage and improving fan efficiency, the enterprise implemented measures such as replacing the locking feeder, upgrading the roller seals, and redesigning the discharge port.

As a result, air leakage significantly decreased, electrical consumption dropped by 3.8 kWh/t, the output temperature increased, and hourly production improved. After these upgrades, the enterprise saved approximately 2.58 million yuan in energy costs annually, achieving significant economic benefits.

 

V. Conclusion

Air leakage in raw material vertical mills is a complex and critical issue. Enterprises should address this from multiple angles, including design, installation, and maintenance. By optimizing equipment design, enhancing maintenance, and improving sealing effectiveness, companies can effectively reduce air leakage, increase the operational stability of vertical mills, and enhance production efficiency. If you have any questions about improving equipment performance, please feel free to contact us. Darko is here to provide you with professional solutions and support.

MORE+
Dust Collector Bag Replacement Guide

In industrial production, the lifespan and replacement frequency of dust collector bags are crucial for efficient operation. First, you must understand when to replace these bags. Next, you need to know how to choose the right filter material. This knowledge can significantly improve dust collection efficiency. Additionally, it can help reduce operating costs.

Dust Collector Bag Replacement Cycle

The theoretical replacement cycle for dust collector bags is about 4-5 years. However, due to working conditions, many bags often last shorter than expected. Extreme environments can cause wear or damage, leading to more frequent replacements. Sometimes, incorrectly chosen bags may need replacement in less than six months.

 

Reasons for Frequent Replacement

Choosing the Right Bag for the Working Condition: Different materials suit different environments. For example, polyester bags can only work in temperatures below 120°C. Using them in high-temperature situations drastically shortens their lifespan.
Quality of the Bags: Generally, high-quality dust collector bags last longer than lower-quality ones. Therefore, when selecting bags, consider both price and quality.
Operating Time and Dust Concentration: The operating time and dust concentration in the gas directly affect bag lifespan. For instance, a collector running 8 hours a day has a different replacement cycle than one running 24 hours. Higher dust concentrations also lead to more frequent replacements.

 

Replacement Recommendations

  • In harsh conditions or when running over 8 hours daily, bags may need replacement within 2 years or even sooner.
  • In milder environments, bags in collectors running 8 hours a day may last about 2-3 years before needing replacement.
High-efficiency dust collector filter bag designed for industrial applications, ensuring optimal dust capture and air quality.

Key Points for Selecting Filter Materials

Different industries have varying needs for dust collector bags, making the choice of filter material important. Here are key points for selecting filter materials for several industries:

1.Steel Plant Blast Furnace Gas Purification

  • Characteristics: High dust output, complex composition, small particles, strong adhesion.
  • Recommended Material: Synthetic fiber materials that withstand temperatures above 200°C, such as aramid, P84, and PTFE.

2.Cement Plant Kiln Tail Dust Collection

  • Characteristics: High gas temperature (around 350°C), high dust concentration, high humidity.
  • Recommended Material: Glass fiber cloth with PTFE coating or P84 and Nomex needle felt.

3.Coal-Fired Power Plant Boiler Dust Collection

  • Characteristics: High-temperature gas with SO₂, NOₓ, and high dust concentration.
  • Recommended Material: PPS and P84 needle felt, resistant to acid and oxidation.

4.Chemical Carbon Black Production

  • Characteristics: High temperatures and corrosive gas with fine particles.
  • Recommended Material: Glass fiber needle felt or Nomex needle felt, durable and resistant to high temperatures.

5.Waste Incineration (Municipal Solid Waste)

  • Characteristics: Severe smoke pollution, high moisture content, strong corrosiveness.
  • Recommended Material: Glass fiber cloth with PTFE coating or PTFE needle felt, suitable for high temperatures and corrosion.

 

Conclusion

The replacement cycle of dust collector bags and the selection of filter materials greatly affect dust collection efficiency and equipment performance. First, understand the characteristics of different working conditions. Then, choose the right bags and materials. This approach helps you extend the lifespan of the bags and improve production efficiency. If you have any questions during the selection or replacement process, contact us. We are here to provide professional advice and support.

MORE+
Optimizing Bucket Elevator Discharge Chutes

In 2022, a cement plant initiated a project to renovate its bucket elevator discharge chutes. They entrusted Nantong Darko Building Materials Machinery Co., Ltd. with the entire process, from production to equipment installation and operation. Darko quickly dispatched technicians to the site for an on-the-spot evaluation. They identified several key issues with the discharge chutes.

Main Issues

1.Insufficient Wear Resistance: The discharge chutes used wear-resistant manganese steel plates, which had poor durability. This led to multiple wear-through points and material leakage. The worn manganese steel plates became uneven, causing material to stick.

 

2.Unreasonable Structural Design: The angle in the middle of the discharge chutes was too steep, failing to effectively cushion the material. As a result, the lower part of the chute experienced severe wear.

 

3.Uneven Design of the Sloped Chute: The design of the sloped section was uneven. Material concentrated on one side, while the other side showed little wear. This uneven force distribution caused severe wear on the side in contact with the material and led to material accumulation.

 

Solutions

To address these issues, Darko's technicians proposed practical solutions:

1.Optimize Overall Structure: They adjusted the angle in the middle of the discharge chutes to reduce the impact force of the material. This modification effectively slows down and cushions the material.


2.Redesign the Sloped Chute: They changed the lower sloped section from an irregular rhomboid shape to a parallelogram. This design distributes the impact force more evenly across the bottom and sides, extending the equipment's lifespan.

 

3.Replace Wear Materials: They substituted wear-resistant ceramic liners for the manganese steel plates. The ceramic liners offer superior wear and corrosion resistance, and their smooth surface reduces material buildup.

Vertical bucket elevator system for lifting bulk materials, highlighting the conveyor mechanism and bucket arrangement

Simulation Testing and Expected Results

Darko's technicians conducted simulation tests using the new solutions. They expect to increase the lifespan of the bucket elevator discharge chutes by 3 to 5 times, improve work efficiency by 3% to 12%, and reduce the likelihood of material blockage by 20% to 30%.

These design optimizations will significantly enhance the performance of the discharge chutes. They will ensure the cement plant's production efficiency and the long-term stability of the equipment. If you are facing similar issues, feel free to contact us. We are ready to provide you with professional solutions.

MORE+
Effective Dust Control with Stainless Steel Collectors

The stainless steel bag dust collector is an advanced type of bag dust collector, distinguished from traditional iron models by its unique material. Thanks to its excellent corrosion resistance and oxidation resistance, this dust collector performs exceptionally well in many industrial applications. This article explores the working principle, features, and customization considerations of stainless steel bag dust collectors to help you choose the right dust control solution.

 

Working Principle of Stainless Steel Bag Dust Collector

The working process of the stainless steel bag dust collector is simple and efficient. Dust-laden air first enters the hopper or filter bag chamber through the inlet. The air passes through the filter bags, where it is purified before entering the clean air chamber. The clean air then exits through the exhaust port via a fan. As dust accumulates on the filter bag surface, the resistance of the equipment increases. To ensure that the resistance does not exceed 1200Pa, regular dust cleaning is necessary.

The cleaning process is automatically controlled by a PLC program. The controller periodically activates the pulse valve, releasing compressed air (0.5-0.7Mpa) through the blowing pipe. This action draws in several times more surrounding air, causing the filter bags to expand rapidly. The reverse airflow helps dislodge the dust from the bags, achieving effective cleaning.

Reasons to Choose a Stainless Steel Bag Dust Collector

1. Corrosion and Oxidation Resistance

Stainless steel bag dust collectors are primarily made from 304 and 316 stainless steel plates. These materials ensure stability and durability when handling corrosive gases. In contrast, traditional iron dust collectors cannot meet these demanding application needs.

2. Longer Lifespan

Due to the superior properties of stainless steel, these dust collectors have a significantly longer lifespan than traditional models. This feature reduces the frequency of replacements and maintenance costs.

3. Aesthetic Appeal

The appearance of stainless steel is more attractive, making it suitable for industrial environments where aesthetics matter.

 

The Stainless Steel Bag Dust Collector is placed in an open area, effectively removing dust particles from the air to ensure a cleaner workspace.

Considerations for Customizing a Stainless Steel Bag Dust Collector

When customizing a stainless steel bag dust collector, companies should consider the following aspects:

1. Size and Capacity

Choose the appropriate model and specifications based on the actual conditions of the production site. If space is limited, opt for a compact unit. If dust concentration is high, select a larger capacity collector to ensure effective dust removal.

2. Filter Material

Select filter materials based on the size, chemical properties, and temperature of the dust particles. Common materials include polyester fiber, fiberglass, and PPS.

3. Number of Bags

The number of bags should correspond to the dust concentration and air flow rate at the production site. More bags typically result in better dust removal efficiency.

4. Auxiliary Equipment Configuration

Consider configuring cleaning systems and control systems based on actual needs. A cleaning system can effectively remove dust from the bags, ensuring long-term stable operation. An automated control system can enhance efficiency.

Maintenance and Care

To ensure the long-term stable operation of the stainless steel bag dust collector, companies should pay attention to the following points:

Ensure that the materials and manufacturing processes meet relevant standards for stability and durability.
Design the layout based on the production site conditions to ensure effective and safe operation.
Conduct regular maintenance and replace damaged parts and bags promptly.

Conclusion

The stainless steel bag dust collector is an essential piece of equipment in modern industry due to its efficiency and reliability. With proper customization, companies can obtain dust control solutions that meet their specific needs. Darko can provide you with flexible and efficient dust control equipment to improve the cleanliness of your production environment and protect employee health. If you have any needs or questions, please feel free to contact us. We are dedicated to providing you with professional service and support.

MORE+
What is a Butterfly Valve?

Butterfly valves play a crucial role in controlling the flow of various fluids, including air, water, steam, corrosive substances, slurries, oils, liquid metals, and radioactive materials. Specifically, these valves primarily function as shut-off and throttling devices in piping systems. Notably, a butterfly valve features a disc-shaped plate that rotates around its axis within the valve body, which allows for precise opening and closing of the flow.

Structural Characteristics of Butterfly Valves

Butterfly valves have several notable features:

 

1.Simple Structure: Designed with simplicity in mind, butterfly valves are compact, lightweight, and material-efficient. Furthermore, their small installation size enables quick operation with a 90° rotation, requiring minimal torque. As a result, this design makes them ideal for effective fluid flow control and reliable sealing.

 

2.Efficient Fluid Handling: In addition, these valves handle slurries effectively while minimizing liquid accumulation at the pipeline entrance. Moreover, they excel in sealing at low pressures and provide excellent throttling performance.

 

3.Streamlined Design: Therefore, the aerodynamic shape of the disc reduces fluid resistance, making butterfly valves an energy-efficient choice for fluid control.

 

4.Robust Stem Structure: The through-stem design enhances mechanical properties and corrosion resistance. Furthermore, the stem rotates during operation, preventing any vertical movement that could damage the packing seal. In addition, the stem securely attaches to the disc, ensuring it remains intact in case of failure.

 

5.Versatile Connection Options: Butterfly valves can be connected via flanged, wafer, butt-welded, or lugged connections. Moreover, they can be actuated manually or using various mechanisms, including worm gear, electric, pneumatic, hydraulic, or electro-hydraulic systems, which allows for remote control and automation.

 

Classification of Butterfly Valves

Butterfly valves can be classified based on their actuation methods:

1.Electric Butterfly Valves: Electric Butterfly Valves use electric power as the driving force, enabling remote and automated control via electrical signals. They are suitable for applications requiring precise control and long-distance operation. However, their complexity demands regular maintenance of the motor and associated components, and their response time is relatively slow.

2.Pneumatic Butterfly Valves: Utilizing compressed air as the power source, pneumatic butterfly valves respond quickly to control signals. They are best suited for applications where high precision is not critical. Their simpler structure requires minimal maintenance, mainly focusing on the condition of the air supply.

3.Hydraulic Butterfly Valves: These valves operate using hydraulic oil as the power source, converting hydraulic signals into mechanical force to open or close the valve. They thrive in environments with high temperatures, pressures, and corrosive substances, making them perfect for chemical, metallurgy, and petroleum industries.

4.Manual Butterfly Valves: Manual butterfly valves are operated by hand, allowing users to directly control the opening and closing of the disc.

A set of three pneumatic butterfly valves featuring red and blue handles, showcasing their distinct operational controls.

Conclusion

Butterfly valves are efficient solutions for fluid control in various applications. Their simple design, effective sealing, and diverse actuation methods make them indispensable in many industries. As a leading brand, Darko is committed to providing high-quality butterfly valve products to meet various customer needs. By understanding the features and classifications of butterfly valves, you can select the right valve for your specific requirements. If you have any questions or need assistance, please feel free to contact us!

MORE+
Vertical Mill Maintenance: Rollers and Liners Replacement

The vertical mill serves as a key piece of equipment in cement production. Its operational status directly impacts both the yield and quality of cement products. Rollers and liners are core wear components in the vertical mill. Over time, they experience wear, leading to decreased grinding efficiency, increased energy consumption, and fluctuations in product quality. Therefore, regularly replacing rollers and liners is essential for ensuring smooth operation and enhancing production efficiency. This plan outlines the detailed process for replacing rollers and liners in cement plant vertical mills. It includes key considerations and safety measures to ensure a successful replacement operation.

Two combined scenes of a vertical roller mill, showcasing its operational setup and components in a cement production environment.

I. Project Preparation

1.Material Preparation: First, assess the vertical mill model and its wear condition. Then, procure rollers, liners, and fasteners that meet specification requirements. Also, prepare necessary tools such as lifting equipment, wrenches, and welding tools.

 

2.Downtime Planning: Next, coordinate with the production planning department. Determine the best downtime window to minimize production disruptions. Inform relevant departments to prepare for emergency responses during the downtime.

 

3.Personnel Training: Conduct safety training for all personnel involved in the replacement operation. Ensure everyone is familiar with operating procedures and emergency response measures.

 

4.Site Setup: Clear the area around the vertical mill to provide ample workspace. Set up safety warning signs and isolate non-working areas.

 

II. Replacement Steps

1.Shutdown and Lockout: First, follow the operating procedures to shut down the mill. Disconnect the power supply. Hang a "Do Not Energize" sign. Use locks or mechanical devices to prevent accidental restarts.

 

2.Dismantling Old Components:

  • Use specialized tools to remove the fastening bolts or weld points at both ends of the rollers.
  • Carefully loosen the roller securing device. Use lifting equipment to remove each roller and place them in a designated area.
  • Clean residual materials from the grinding chamber. Inspect and remove old liners, noting their installation positions for reinstallation.

 

3.Inspection and Preparation:

  • Inspect the new rollers and liners for any damage, cracks, or defects.
  • Clean the installation surfaces to remove oil, rust, and other contaminants.

 

4.Installing New Components:

  • Install new liners in their original positions or optimized layouts. Ensure they are flat and securely fastened.
  • Use lifting equipment to install each new roller. Adjust their positions for optimal grinding conditions.
  • Tighten the bolts or weld points at both ends of the rollers to secure the fit.

 

5.Debugging and Inspection:

  • After installation, perform initial debugging. Check for proper installation and any looseness or abnormal noises.
  • Gradually start the vertical mill. Conduct a no-load trial run. Observe its operation and make adjustments to achieve the best working state.

 

III. Safety Considerations

1.Personal Protective Equipment: Personnel must wear appropriate safety gear, including hard hats, safety glasses, dust masks, and protective clothing.

 

2.Safety During Elevated Work: When performing work at heights, secure safety harnesses. Install fall protection nets or safety barriers.

 

3.Electrical Safety: Verify that the power supply is disconnected. Hang warning signs to prevent accidental operation.

 

4.Lifting Safety: During lifting operations, strictly follow lifting procedures. Ensure equipment stability to prevent dropped loads.

 

5.Emergency Response Measures: Develop an emergency response plan. Familiarize staff with evacuation routes and first aid measures. Ensure swift action during emergencies.

 

IV. Conclusion

Replacing the rollers and liners in a cement plant’s vertical mill is complex yet crucial. This task requires careful preparation and strict adherence to safety. This plan outlines project preparation, replacement steps, and safety considerations. It ensures the replacement process is efficient, safe, and smooth. Ultimately, it supports the stable operation of the cement production line.

If you have any needs or questions regarding cement machinery and equipment, please feel free to contact Darko. We are committed to providing professional products and solutions to support the efficient operation of your production line.

MORE+
Cement Kiln Preheater: Opportunities and Challenges

The cement production process continually seeks innovation and optimization. The introduction of a 7-stage cement kiln preheater raises important questions. What does this change mean? What opportunities and challenges will it bring to cement enterprises?

I. Advantages of the 7-Stage Cement Kiln Preheater

(A) Significant Energy Savings

The 7-stage cement kiln preheater increases the overall height from about 105 meters in a 5-stage system to 135 meters. This height increase leads to improved energy efficiency. The first-stage outlet temperature in a 5-stage preheater typically ranges from 310-330°C. In contrast, a 7-stage preheater can lower this temperature to 180-200°C. This adjustment reduces standard coal consumption from 98-102 kg to below 90 kg. For cement companies with high coal costs, this represents a valuable cost-saving measure. Additionally, using less coal lowers carbon emissions, helping companies meet future environmental standards.

(B) Improved Separation Efficiency

The 7-stage cement kiln preheater also shows better separation efficiency compared to the 6-stage system. In a 5-stage cyclone preheater, the first-stage separation efficiency is around 92%, reaching only 95% at best. This inefficiency leads to significant raw material loss. In contrast, the 6-stage system has a specific material consumption of about 1.55 to 1.58. The 7-stage preheater can improve this to a consumption of 1.49 to 1.52. Higher separation efficiency reduces energy consumption and boosts overall production efficiency.

(C) Support for Alternative Fuel Combustion and Ultra-Low Emissions

  • Optimized Alternative Fuel Combustion: The additional stage in the preheater allows for better combustion of alternative fuels. This improvement ensures that these fuels burn more completely, maximizing energy use. It also lessens the impact on SCR and baghouse equipment, extending their lifespan.

  • Enhanced Ultra-Low Emission Efficiency: The high collection efficiency of the 7-stage preheater positively affects SCR systems. Stable and low-dust concentration flue gas enters the SCR system, improving catalyst efficiency. This helps cement companies achieve and maintain ultra-low emission targets, complying with stricter environmental regulations.

(D) Advantages of Low Pressure Drop Design (New Production Lines)

New production lines using 6-stage or 7-stage cement kiln preheaters benefit from a low pressure drop design. The redesigned pre-decomposition system minimizes resistance. Each stage's pressure drop can be controlled at 600-800 Pa. When the production line reaches its designed feed rate, the first-stage outlet pressure drop stays below 5500 Pa. Even with a 20% overproduction, the pressure drop can remain below 6500 Pa. Lower pressure drops reduce energy consumption of high-temperature fans and lower long-term operating costs.

(E) Benefits from the Elimination of the Humidification Tower

The lower outlet temperature of the 7-stage preheater allows for the removal of the humidification tower. This change simplifies the process and eliminates the need for water spraying operations. When the preheating boiler is not running, operators can manage the dust collector's temperature effectively. This reduction in equipment decreases corrosion risks and improves system reliability.

Two pictures from a cement plant showing the working scene of a cement kiln preheater.

II. Challenges of the 7-Stage Cement Kiln Preheater

(A) Increased Construction Costs and Difficulty

Upgrading from a 5-stage to a 7-stage preheater raises investment costs. The higher frame and equipment heights complicate installation. This complexity requires more resources for equipment hoisting and precise installation, leading to longer project timelines and increased financial pressure.

(B) Impact on Raw Material Drying

The lower first-stage temperature means the kiln tail preheating boiler has an inlet temperature of about 200°C and an outlet temperature as low as 120°C. If raw materials have high moisture content, the mill may struggle to achieve production targets. To meet drying needs, companies may need to increase the load on high-temperature fans, raising energy consumption and affecting production stability.

(C) Reduced Waste Heat Power Generation

The lower kiln tail flue gas temperature leads to a decrease in waste heat power generation. The temperature drops from 35-40°C in a 5-stage system to 22-24°C per ton of clinker in a 7-stage system. While the 7-stage preheater brings energy savings, the reduced waste heat power generation means lower returns on energy recovery. Companies must optimize their energy management strategies to find new energy sources.

(D) Challenges in Controlling Flue Gas Temperature

To meet environmental requirements, bag dust collection is used at the kiln head and tail. If the waste heat boiler cannot run simultaneously, the maximum daily output of a 6-stage kiln system can reach only 60-70% of its designed capacity. Even with adjustments like small drafts or thicker layers, flue gas temperatures may exceed limits, risking damage to bag filters and increasing maintenance costs.

(E) High Costs for Upgrading Old Production Lines

Existing cement kilns face high retrofitting costs. Each stage of an old production line typically experiences a pressure drop of about 1200 Pa. Upgrading to a 7-stage preheater requires modifications to achieve low pressure drop design. If companies add a stage without upgrading the dust collector, system resistance will increase, causing operational costs to soar.

III. Conclusion and Outlook

In summary, the 7-stage cement kiln preheater offers significant advantages in reducing energy consumption, enhancing separation efficiency, supporting alternative fuel applications, and achieving ultra-low emissions. However, it also presents challenges, including high construction costs and impacts on raw material drying and waste heat power generation.

 

For new production lines, adopting the low pressure drop design of 6-stage or 7-stage preheaters is wise. This choice allows companies to benefit from technological advancements while avoiding complications and cost increases. For existing production line enterprises considering an upgrade, a thorough assessment of production conditions, energy costs, environmental requirements, and budgets is essential for informed decisions.

 

As the cement industry advances and faces stricter environmental requirements, the 7-stage preheater is likely to achieve further breakthroughs.

 

At Darko, we are dedicated to providing innovative solutions tailored to your needs. If you have questions or require assistance with our products, please contact us. We can offer customized solutions to support your transition to more efficient and sustainable operations. Let’s work together to lead the cement industry into a greener, smarter, and more efficient future.

MORE+
Low Energy Consumption Cement Grinding System Upgrade Plan

System Problems

China Huaxing has a combined open-circuit grinding system composed of a roller press, a dispersion classifier, and a cement ball mill:

  • Roller Press: HFCG160-140, diameter Φ1600 mm, width Φ1400 mm, rotating speed 18.75 r/min, design capacity 670–780 t/h.
  • Dispersion Classifier: Model SF650/160, design capacity 700–850 t/h.
  • Ball Mill: Φ4.2 m × 13 m two-bin mill, rotating speed 15.8 r/min, design capacity 150 t/h.

Main Issues Encountered

  • Metal Impurities: Introduced by material and equipment wear, causing frequent vibrations in the roller press and leading to spalling of the roller surfaces. The accumulation of metal impurities creates a buffering effect on the grinding, resulting in accelerated wear and deteriorating efficiency.

  • Low Efficiency of the Dispersion Classifier: Rapid wear and difficulty in grade control make it challenging to regulate the fineness of entering material. High moisture content can lead to clogging of sieve plates, preventing normal production.

  • Clogging Issues: Coarse fineness of entering material clogs the discharge grate's gaps, causing poor ventilation, material return at the mill head, environmental contamination, and reduced production capacity.

Retrofitting Program

1. Installation of Iron Removers and Metal Separators

  1. Increase iron removal testing for raw materials upon delivery. Install iron removers at each raw material feeding point, lowering the height between the iron remover and the material surface to enhance the iron removal effect.

  2. Install a metal separator to detect any metal not removed by the iron remover. Detected metal will be separated using a vibrating screen at the conveyor belt head for manual retrieval.

  3. Install a pipeline iron remover at the coarse powder discharge chute of the V-type classifier to ensure continuous removal of iron slag from the system.If you require any further information, please contact us.

2.Retrofitting of Roller Press & Breaking Classifier

2.1 Upgrading the Dispersing Classifier to a Two-Stage Small V-Type Powder Classifier

The original dispersion classifier has the following deficiencies:

 

  1. Low Classification Efficiency: Approximately 22%, resulting in coarse fineness. Sieve residue reaches 55% with particles up to 8 mm.
  2. High Maintenance Costs: The mechanical classification leads to increased costs.
  3. Poor Material Adaptability: Reduced classification ability with high moisture content and inadequate handling of material changes.

 

The system has been upgraded to a two-stage small V-type classifier. The material pressed by the roller press is conveyed to the first-stage classifier. Qualified material is sent to the ball mill, while return material enters the second-stage classifier for further sorting.

 

Advantages of this System:

 

  • Low energy consumption (total installed power of 200 kW)
  • Low investment
  • High classification efficiency (87%)

 

2.2 Upgrade of Material Stabilization and Pressure Stabilization for the Roller Press

The HFCG160-140 roller press has the following issues:

  1. Manual feeding device adjustment lacks central control.
  2. Poor performance with a low fine powder content (about 15%) and low working current.
  3. Constant pressure control system does not auto-adjust roller gap based on material feed conditions.

 

To solve the above defects, Darko upgraded the roller press system through a number of new technologies. The upgrade plan includes:

  • Modification of Feeding Device: A new multi-directional feeding device ensures stable roller operation.
  • Addition of a Roller Gap Adjustment Device: Introduces a constant pressure and roller gap control system, minimizing variations.
  • Replacement of Hydraulic System: Upgraded to include damping and stroke adjustment valves for improved stability and performance.

 

3.Modification of Ball Mills

Transforming the Feeding Device: The new device incorporates a five-blade spiral feeder and a deceleration buffer plate to enhance grinding efficiency.
Lightweight and Transformation of Lining Plates: New lighter lining plates improve ball-carrying capacity and reduce power consumption.
Using Anti-Clogging Grates: Modifications to sieve holes increase material passage capacity and prevent over-grinding.

 

4.Upgrade of the Dust Collector Ash Return Discharge Point

The specific surface area of the ash returned from the dust collector is between 365 and 410 m²/kg. The discharge point of the original dust collector has been changed to directly channel the ash into the ball mill, reducing the load and amount of material entering the mill.

 

MORE+
The Importance of Vertical Roller Mills in Cement Production

Vertical roller mills (VRMs) have become essential equipment in the cement industry. They are widely used for drying and grinding processes. These machines grind cement raw materials, coal, clinker, and other industrial materials, such as steel slag and ceramics.

 

Two combined scenes of a vertical roller mill, showcasing its operational setup and components in a cement production environment.

The Significance of Vertical Roller Mills

Vertical roller mills offer unique advantages in their operation, grinding mechanisms, mechanical structures, and process performance. As a result, they attract more attention in the global cement industry. With the introduction of kiln outside decomposition technology, many countries now use VRMs to grind cement raw materials and clinker. Here are the key advantages of vertical roller mills compared to traditional cement ball mills:

1. High Energy Efficiency

Vertical roller mills reduce energy consumption significantly. They typically use 20% to 30% less energy than ball mills. This efficiency makes them a more sustainable choice for cement production.

 

2. Compact Footprint

Vertical roller mills require less floor space. Their compact layout integrates the classifier within the mill, eliminating the need for separate classifiers and elevators. This design can reduce building area by 30% for the same production capacity.

 

3. Strong Drying Capacity

Vertical roller mills effectively dry materials with a moisture content of 12% to 15%. They achieve this by using hot gas for material transport. This capability allows producers to eliminate the need for a separate drying system and further optimize production processes.

 

4. Long Lifespan of Wear Parts

The design of vertical roller mills minimizes direct metal contact. This reduces wear and increases operational rates. As a result, the lifespan of critical wear components extends, lowering maintenance costs.

 

5. Large Feed Size

Vertical roller mills handle larger feed sizes, typically between 80 to 120 mm. Some large-scale mills can accommodate up to 200 mm. This feature enhances crushing capacity and simplifies the overall process compared to ball mills, which usually require smaller feed sizes.

 

6. Lower Noise Levels

Vertical roller mills operate at noise levels about 10 dB lower than ball mills. This reduction improves the working environment. Additionally, they make it easier to monitor and control product fineness and composition. Maintenance is also simpler.

 

Layout Options

Vertical roller mills usually offer two layout options based on the positioning of the humidification tower and dust collector: a three-fan system and a dual-fan system. They use a cyclone dust collector for product collection, which reduces the system's negative pressure and the volume of gas passing through the dust collector. The exhaust gas can directly enter the dust collector, which may be an electrostatic precipitator or a bag filter. This setup reduces the number of equipment units and simplifies the overall layout.

 

Common Issues

Wear of Grinding Rollers

During operation, the grinding rollers and wear plates face various forces, such as roller pressure and material friction. When wear increases the gaps in the fit, it can lead to severe impacts, causing cracks or breakage. This damage affects equipment performance. Traditional repair methods often fail and take too much time. Therefore, many developed countries, including the U.S. and Europe, use high-performance composite materials for on-site repairs. This approach effectively extends equipment lifespan, improves productivity, and minimizes downtime.

 

Bearing Chamber Wear

The assembly of bearings in vertical roller mills is strict. Typically, operators cool the bearings to low temperatures for precise assembly. If gaps appear between the bearings and their chambers, it can cause overheating and even seizure. Traditional repair methods, such as welding and coating, risk damaging the bearing material due to thermal stress. High polymer composite materials, like those from our brand Darko, offer the necessary strength and flexibility. They absorb external impacts effectively, preventing further wear from gap enlargement.

 

Conclusion

Vertical roller mills play a crucial role in modern cement production. Their efficiency, energy savings, and compact design make them increasingly popular. If you have any questions or needs regarding vertical roller mills, please feel free to contact us. Our team at Darko is here to help you with advanced solutions for your cement production challenges.

MORE+
Key Considerations for Star Discharge Valve Selection

The star discharge valve is an unloading device designed for discharge points that operate under negative pressure. It conveys materials using a rotating rotor. This design provides a sealing effect that prevents air from being drawn in during pneumatic conveying, ensuring normal discharge.

 

Features of Star Discharge Valve

  • Compact Structure and Attractive Design: The design is user-friendly and convenient.

 

  • Smooth Operation and Low Noise: It operates quietly, enhancing user comfort.

 

  • Superior High-Temperature and Lubrication Performance: The bearings and gearboxes are positioned away from the housing, improving performance under high temperatures.

 

  • Custom Design: We can create designs tailored to your specific requirements.

 

  • Lubrication Maintenance: Each valve is filled with special lubricants before leaving the factory. Regular checks for lubrication are recommended.

 

Star discharge valves are commonly used in pneumatic conveying systems. They supply materials uniformly and continuously to the conveying pipe. This ensures stability for gases and solids within the pneumatic transport system. Additionally, they isolate pressure in the valve's upper and lower sections, achieving a locking effect. Therefore, the star discharge valve is essential for pneumatic conveying systems.

 

Star ash discharge valve in operation, illustrating the mechanism of controlled ash discharge in a power plant setting

Applications of Star Discharge Valve

Star discharge valves serve as unloading devices in material collection systems, particularly for silos. They rank among the most advanced unloading devices available today. These valves are commonly used in dust removal systems and are especially suitable for dust and small particle materials. Industries such as environmental protection, metallurgy, chemicals, food, cement, road construction, and drying equipment favor star discharge valves for various projects.

 

 

Selection Guide for Star Discharge Valves

Choosing the right star discharge valve involves several key steps:

 

1. Define the Usage Location

Determine if the valve will be used indoors or outdoors. This choice influences protective measures.

 

2. Determine the Purpose of Use

Clarify if the valve will discharge materials in a metered, full-volume, or air-locking manner. This helps select the appropriate model.

 

3. Specify the Material Flow Rate

Understand the valve's hourly flow rate. Specify whether the discharge is metered or variable to select the right capacity.

 

4. Define the Conveying Method

Classify the type of conveying: pneumatic or gravity flow. Clarifying this helps in selecting the correct valve.

 

5. Understand the Conveyed Material

Know the material characteristics and the pressure difference between the inlet and outlet flanges of the blower. This knowledge aids in determining the valve's material and structure.

 

6. Analyze Material Properties

Consider properties like material name, particle size, true density, bulk density, temperature, repose angle, moisture content, and viscosity. These factors will influence the valve's selection and configuration.

 

7. Consider Special Requirements

If you need an acceleration chamber or exhaust chamber, specify the models required. Also, consider the manufacturer of the reducer motor and the protection level.

 

8. Material Selection

Different materials have specific requirements. For example, food processing and pharmaceutical industries often require stainless steel star discharge valves due to their corrosion resistance and durability at high temperatures.

 

9. Safety Performance

Ensure safety and ease of operation by selecting reliable brands and models known for stability.

 

By following these steps, you can effectively choose a star discharge valve that meets your needs, ensuring stable operation and high performance in your production process.

 

 

Conclusion

In summary, selecting the right star discharge valve is crucial for efficient operation in your material handling systems. If you seek high-quality valves, Darko offers a range of reliable options tailored to your needs. For any inquiries or to discuss your specific requirements, please contact us. We are here to help!

MORE+

November 2024

Take a break and read all about it

Do You Want To Boost Your Business?

drop us a line and keep in touch

Contact Us
Darko logo

Nantong Darko Building Materials Machinery, a leading manufacturer and supplier in China, specializes in R&D, design, manufacturing, and installation of solutions for desulfurization, denitrification, dust removal, and environmental protection projects, as well as slag micro powder and powder grinding production lines.

Products

Spare Parts

Cases

News

Contact Info

  • Address: No. 218, Xisu Road, Huji Street, Haian High-tech Zone (formerly Haian Town)
  • +86 15370455293
  • +86 15365564889
  • sales@darko-tech.com
Linkedin Facebook Youtube Tiktok Twitter
en_USEN_US
en_USEN_US ru_RURU fr_FRFR pt_AOPT arAR es_ESES jaJA