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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.

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.

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Low Energy Consumption Cement Grinding System Upgrade Plan

11/15

2024

11/15/2024

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

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.
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.
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:

Low Classification Efficiency: Approximately 22%, resulting in coarse fineness. Sieve residue reaches 55% with particles up to 8 mm.
High Maintenance Costs: The mechanical classification leads to increased costs.
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:

Manual feeding device adjustment lacks central control.
Poor performance with a low fine powder content (about 15%) and low working current.
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.

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The Importance of Vertical Roller Mills in Cement Production

11/15

2024

11/15/2024

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.

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.

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Key Considerations for Star Discharge Valve Selection

11/13

2024

11/13/2024

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.

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!

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Extend Your Dust Filter Bag Life

11/11

2024

11/11/2024

High-temperature dust filter bags play a crucial role in industrial dust collection systems. Their lifespan directly affects both operational efficiency and maintenance costs. Therefore, extending the lifespan of these bags is a key focus for many customers. This article outlines several strategies to help you achieve this goal.

Choose the Right Material

Selecting the appropriate material is vital. When choosing high-temperature dust filter bags, consider your specific working conditions. For flue gases that are hot, humid, and corrosive, opt for materials like fluoropolymer or P84. These materials resist high temperatures and corrosion. For general industrial dust, polyester needle felt bags work well.

Assess Operating Conditions

1. Nature of Flue Gas

The composition of flue gas significantly impacts bag durability. If the gas contains high levels of acidic or corrosive substances, it will weaken the bags. Industries like chemical and metallurgy often face this issue, leading to shorter bag lifespans.

2. Temperature

High temperatures can cause severe damage to filter bags. Each material has a specific temperature limit. If you exceed this limit, the bags will age quickly and fail. Therefore, monitor temperatures closely to protect your investment.

3. Characteristics of Dust

The properties of dust also matter. Sharp or hard particles can wear down the bags. Additionally, sticky dust can accumulate, blocking airflow and increasing resistance. This buildup can lead to premature damage.

Proper Installation and Use

Correct installation and usage are essential for maximizing bag life. Follow the manufacturer’s instructions carefully. Here are some key tips:

Ensure Proper Fit: During installation, make sure the bags fit the flower plate holes precisely. This prevents wear and air leaks.

Conduct Regular Inspections: Frequently check the equipment’s operation. Look for any signs of wear or clogging. Cleaning the bags regularly helps maintain airflow.

Control Flue Gas Temperature: Keep a close eye on gas temperatures. Avoid excessive heat, which can harm the bags.

Choose the Right Filtration Velocity: Select a suitable filtration speed. High speeds can cause unnecessary wear on the bags.

Additional Tips to Extend Bag Lifespan

Avoid Mixing Bags: Do not mix old and new bags. Different wear patterns can disrupt system performance.

Monitor for Aging: Regularly check for signs of aging. High temperatures and exposure to corrosive substances can degrade the bags. Replace any that show significant wear.

Adjust Tightness: Ensure bags are neither too loose nor too tight. Loose bags can collect dust, while tight ones may tear.

Clean and Replace Bags: When replacing bags, use compressed air to blow out dust. Check for holes and repair if needed. If bags are heavily soiled, rinse them with water and let them dry before using them again.

Address Clogging Promptly: Clogging increases resistance, indicated by pressure gauge readings. To fix clogs, consider these steps:
- Temporarily increase cleaning frequency to remove blockages.
- Replace some or all bags as needed.
- Adjust installation or operating conditions to prevent future issues.

Types of Dust Filter Bags

Dust filter bags come in various designs. You can find pulse-jet, shaking, and reverse-jet types. They also vary in shape, including round, flat, and envelope styles. Different designs cater to specific applications, allowing for flexibility based on your needs.

Conclusion

Extending the lifespan of high-temperature dust filter bags is essential for improving the efficiency of dust collection systems and reducing costs. By choosing the right materials, assessing operating conditions, ensuring proper installation, and conducting regular maintenance, you can significantly enhance the longevity of these bags. Use these strategies to protect your investment and maintain effective dust control in your operations.

At Darko, we specialize in high-quality dust filter solutions tailored to your industrial needs. For more information or to discuss your specific requirements, contact us today! Our team is ready to assist you in optimizing your dust collection systems and enhancing performance.

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Common Roller Press Faults and Their Solutions

11/08

2024

11/08/2024

In cement production, the roller press is a key piece of equipment, and its operational stability directly affects production efficiency and product quality. Below are specific cases and experience sharing regarding fault handling from T Company, J Company, and S Company. If you encounter similar issues during equipment operation, feel free to contact us at Darko. As a professional manufacturer and supplier of cement equipment, we are dedicated to providing you with high-quality equipment and services.

Cement Plant A Abnormal Situation Description

Fault Phenomenon

Cement Plant A uses a vertical feeding pipe between the roller press and the weighing silo. However, this pipe is too short. As a result, the roller press experiences low working pressure and poor extrusion capability. Consequently, the feed material has high screening residue and low fine powder content. This situation leads to low system yield and high grinding energy consumption.

System Configuration

Roller Press: 120-50 roller press (material throughput 165t/h, main motor power 250kW, current 21A×2)
Dispersing and Classifying Machine: 550/120 (processing capacity 140—175t/h, motor power 45kW+30kW)
Tube Mill: Φ3.2×13m three-chamber open circuit tube mill (main motor power 1600kW, grinding media loading 127t)
Dust Collection Fan: Comprises an open circuit combined grinding system

Results

The system produces P.O42.5 grade cement with a finished specific surface area of at least 380±10m²/kg. It achieves a yield of 65t/h while consuming 35kWh/t of energy. However, the R80μm residue of the feed material reaches 78.7%, resulting in only 21.3% of the material being fine powder. This leads to a high content of coarse particles in the finished cement.

Technical Diagnosis Analysis

The vertical feeding pipe height between the roller press and the weighing silo is less than 1.2m, causing low material pressure in the pipe, requiring frequent adjustment of the rod valve. The weighing silo frequently experiences segregation or material collapse, and there is significant dust in the production area. The working pressure of the roller press is only 6.0—6.5MPa, which directly affects the extrusion effect of the material.

Technical Measures and Effects

During the annual overhaul, the height of the elevator and weighing silo was increased, raising the vertical feeding pipe height to 2.5m. The side plates of the roller press were repaired by overlay welding to reduce leakage. Maintaining the weighing silo's material level at 60%—70% eliminated segregation and material collapse. The working pressure of the roller press was adjusted to 7.2—7.5MPa, and the R80μm residue of the feed material was reduced to 49.8% (with the fine powder content reaching 50.2%). The system yield increased to 79t/h, and grinding energy consumption decreased to 26.4kWh/t. Annually, this modification can save 4.8 million kWh of electricity, resulting in an economic benefit of over 2.8 million RMB.

Cement Plant B Abnormal Situation Description

Fault Phenomenon

At Cement Plant B,operators face unstable feeding control to the roller press. This instability results in poor working capability. Consequently, the main motor produces insufficient output. As a result, the feed material contains low fine powder content. Ultimately, this situation leads to low yield and high grinding energy consumption.

Grinding System Configuration

Roller Press: 170-100 roller press (material throughput 620t/h, main motor power 900kW)
Classifier: Vx8820
Tube Mill: φ4.2×13m double-chamber tube mill (main motor power 3550kW)
Dust Collection Fan: Comprises a double closed-circuit combined grinding system

Results

The system produces P.O42.5 grade cement at a yield of 165t/h (finished fineness R45μm residue 9.0±1.0%), with grinding energy consumption reaching 44kWh/t.

Technical Diagnosis Analysis

The unstable feeding to the roller press results in poor extrusion capability and insufficient motor output, with the operating current only at 42%—45%. The specific surface area of the feed material is around 160m²/kg.

Technical Measures and Effects

A patent technology from a technology company, the "Lever-type Dual Feeding Device for Roller Press," was adopted to stabilize feeding control, increasing the main motor output to 72%—78%. Internal structural improvements ensured a higher content of finished material in the output. Ultimately, the system yield for P.O42.5 grade cement reached 210t/h, and grinding energy consumption decreased to 38.1kWh/t, achieving a 13.41% energy saving. After optimizing system power, production efficiency was significantly improved.

Cement Plant C Abnormal Situation Description

Fault Phenomenon

At Cement Plant C, both fly ash and desulfurized gypsum with small particle sizes enter the weighing silo together. The high moisture content of the desulfurized gypsum causes severe material adhesion on the silo walls, impacting the output of the roller press and the overall system yield.

Grinding System Configuration

Roller Press: 120-50 roller press (material throughput 165t/h, main motor power 250kW)
Dispersing and Classifying Machine: 550/120
Tube Mill: Φ3.2×13m three-chamber tube mill (main motor power 1600kW)
Dust Collection Fan: Comprises an open circuit combined grinding system

Results

The system produces P.O42.5 grade cement at a yield of 65t/h (finished specific surface area ≥ 360±10m²/kg), with grinding energy consumption of 33kWh/t. The R80μm residue of the feed material is more than 65% (with <80μm fine powder content around 35%).

Technical Diagnosis Analysis

The powdery materials affect the extrusion capability of the roller press, leading to low operating current. The weighing silo experiences severe material adhesion due to high moisture content, affecting the flow of material in the feeding pipe.

Technical Measures and Effects

Fly ash and desulfurized gypsum were switched to separate metering before direct feeding into the tube mill, and the adhesion on the walls of the weighing silo was cleaned to create stable material pressure. The roller press achieved over-saturated feeding, improving extrusion performance. The R80μm residue of the feed material was reduced to 55% (with <80μm fine powder content reaching 45%). The P.O42.5 cement yield increased to 75t/h, a rise of 15.38%; grinding energy consumption decreased to 30kWh/t, achieving a 9.1% energy saving.

Conclusion

The stable operation of the roller press is crucial for cement production. We can achieve this by monitoring equipment status and optimizing operational processes. Additionally, conducting regular maintenance helps us reduce faults effectively. This, in turn, improves production efficiency and enhances product quality. If you encounter any issues with cement equipment, please contact us. Darko, as a professional manufacturer and supplier of cement equipment, is committed to providing quality equipment and solutions. Together, we can drive progress in the industry.

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How Can We Effectively Prevent Dust Explosions?

11/07

2024

11/07/2024

Preventing dust explosions requires a multi-faceted approach. Dust explosions happen when dust concentrations reach a certain level, mix with air, and encounter an ignition source. Fine dust particles create a flammable mixture in the air. When ignited, they release a large amount of energy, leading to an explosion. Therefore, controlling dust concentration and cleaning promptly are crucial to preventing explosions.

Here are some key preventive measures:

Control Dust Concentration

Ensure Equipment Sealing: Make sure that all equipment, containers, and conveying systems are well-sealed to minimize dust leakage.

Improve Ventilation and Dust Removal: Install effective ventilation and dust removal systems. This will enhance dust extraction and reduce dust levels in the workshop. Darko's dust collectors provide high filtration efficiency and reliability to help companies manage dust effectively.

Manage Dust Accumulation and Cleaning: Keep the floors, walls, and ceilings of the workshop smooth and free of protrusions to make cleaning easier. Use explosion-proof vacuum cleaners for regular cleaning. Additionally, spray water to dampen dust when possible. Increasing air humidity to over 65% helps dust settle and absorbs heat from dust oxidation, which reduces static electricity risks.

Control Ignition Sources

Choose Equipment Wisely: When maintaining dust-laden equipment, it is essential to use tools that do not create sparks from impact or friction. Additionally, ensure that all electrical equipment meets explosion-proof standards. Furthermore, avoid installing machinery that generates static electricity or sparks, and implement static grounding measures to enhance safety.

Manage Open Flames: Designate areas with combustible dust as no-fire zones. Moreover, control the use of open flames strictly. Before welding in these areas, ensure that all materials are cleared from the equipment. Additionally, take steps to prevent slag from falling into machines or onto materials.

Install Spark Detection and Extinguishing Systems: In suitable workshops, it is important to install spark detection and fire extinguishing systems. Specifically, these systems can detect sparks in dust removal ducts or powder conveying pipes. In addition, they use water mist to extinguish sparks quickly and effectively.

Control Oxygen Content

In some cases, fill the grinder with inert gases like nitrogen or carbon dioxide. This lowers the oxygen content in the system and helps prevent dust explosions.

Implement Additional Measures

Handle Materials Properly: Screen, de-stone, and remove metals from crushed materials to prevent sparks from impurities entering the crusher.

Control Temperature: Ensure that the surface temperature of heating devices and high-temperature pipes does not exceed the ignition temperature of the dust cloud.

Conduct Regular Inspections and Maintenance: Regularly check electrical equipment to prevent aging or short circuits that can create ignition sources.

Provide Personnel Training: Strengthen safety education for staff. Increase their awareness of dust explosion hazards and teach them basic emergency response skills.

Develop an Emergency Plan

Create an emergency plan for dust explosions. This plan should include steps for emergency evacuation, initial fire-fighting, and personnel rescue. It ensures a timely and effective response in the event of a dust explosion.

By implementing these measures, companies can significantly lower the risk of dust explosions while protecting their personnel and property. At Darko, we are committed to providing efficient dust management solutions. Our products help companies effectively control dust and maintain safe operations. If your company has any questions about dust collection systems, please don’t hesitate to reach out to us.

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A Green Future for Pharma: The Importanc of Cartridge Dust Collectors

11/05

2024

11/05/2024

In today’s rapidly advancing technological landscape, the pharmaceutical industry encounters unique challenges and opportunities. People demand better health and expect higher quality drugs. Additionally, stricter environmental regulations require the industry to prioritize environmental protection during production. Therefore, cartridge dust collectors have emerged as essential green guardians in this sector. Their efficiency and eco-friendliness make them crucial for meeting industry needs.

Basic Principles and Features of Cartridge Dust Collectors

A cartridge dust collector is an advanced dust removal device. It works by filtering dust particles from the air through cartridges. This process purifies the air. The main features include:

High Dust Removal Efficiency: These collectors use advanced filtering materials. They efficiently capture fine dust particles from the air, ensuring a clean production environment.
Energy Saving and Eco-Friendliness: Cartridge dust collectors consume low energy during operation. They can also recover some dust resources for reuse, aligning with modern environmental ideals.
Easy Maintenance: Their well-designed structure makes them easy to disassemble and clean. This feature reduces maintenance costs and enhances reliability and lifespan.

Applications of Cartridge Dust Collector in the Pharmaceutical Industry

Cartridge dust collectors are widely used in the pharmaceutical industry. They cover various processes, such as active pharmaceutical ingredient (API) production, solid dosage form production, and liquid dosage form production. Here are some specific examples:

API Production: This process generates a large amount of dust and harmful gases. Cartridge dust collectors capture these pollutants effectively. They prevent harm to the production environment and protect employee health. Additionally, they recover valuable dust resources, improving raw material utilization.
Solid Dosage Form Production: In the production of solid dosage forms like tablets and capsules, cartridge dust collectors are installed on production lines. They effectively capture generated dust, ensuring a clean production environment and maintaining product quality.
Liquid Dosage Form Production: Although liquid dosage forms produce less dust, some operations, like mixing and filling, may still generate small amounts. Cartridge dust collectors play a crucial role in maintaining cleanliness and ensuring employee health in these processes.

Development Trends and Challenges of Cartridge Dust Collector in the Pharmaceutical Industry

As the pharmaceutical industry evolves, cartridge dust collectors will display several trends:

Intelligent Development: With advancements in IoT and big data, these collectors will become smarter. They will use remote monitoring and data analysis to improve operational efficiency and reliability.
Increased Efficiency and Energy Savings: Future cartridge dust collectors will focus more on efficiency and energy savings. They will use advanced filtering materials and optimize their designs to reduce energy consumption and operational costs.
Environmental Protection and Resource Recovery: These collectors will emphasize environmental protection and resource recovery. They will recycle dust resources, helping conserve resources and protect the environment.

However, the application of cartridge dust collectors also faces challenges. The diversity of dust characteristics and the complexity of production environments require continuous research and development. We must improve technologies to meet the industry’s evolving needs.

Importance of Cartridge Dust Collector in the Pharmaceutical Industry

The use of cartridge dust collectors improves the cleanliness of the production environment and enhances product quality. They also promote sustainable development in the pharmaceutical industry. Their significance includes:

Protecting Employee Health: By capturing dust and harmful gases, these collectors prevent health hazards for employees. They create a safe and healthy working environment.
Improving Product Quality: By ensuring cleanliness in the production environment, cartridge dust collectors enhance product quality and stability. This support is crucial for the industry's development.
Promoting Environmental Protection: Through dust recovery and reuse, these collectors contribute to resource conservation and environmental protection. They play an important role in the sustainable development of the pharmaceutical industry.

Conclusion

Cartridge dust collectors serve as green guardians in the pharmaceutical industry. They provide essential support for development. Their efficiency and environmental benefits are crucial. In the future, as technology advances and awareness of environmental issues increases, these collectors will play an even larger role in the industry. Darko is committed to advancing and innovating cartridge dust collector technology. We aim to contribute to the sustainable development of the pharmaceutical sector. If you have any questions about our dust collectors or services, please feel free to contact us. We look forward to working with you.

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A Comprehensive Comparison of Offline and On-line Pulse Jet Baghouse Filters

11/04

2024

11/04/2024

Air pollution control technology plays a crucial role in modern industrial production. As environmental regulations become stricter, industries increasingly rely on dust collection devices. Pulse bag dust collectors have emerged as a preferred solution for dust removal because they perform efficiently.Among these, Off-line Pulse Jet Baghouse Filters stand out as an effective option.

These dust collectors fall into two categories: online and offline. By understanding the features and applications of both types, businesses can optimize their dust removal systems for better design and effectiveness.

Off-line Pulse Jet Baghouse Filters

Working Principle

The offline pulse bag dust collector features a chambered design. When cleaning is needed, control valves close the airflow to a specific chamber, stopping the filtration process. Subsequently, a pulse blowing device cleans the inactive chamber, using the powerful back pressure of compressed air to quickly remove dust from the filter bag's surface, allowing it to fall into the hopper. Once cleaning is complete, the chamber resumes filtration, and the others follow suit. This method ensures that some chambers remain operational, maintaining continuous dust removal.

Structural Characteristics

The off-line pulse jet baghouse filter mainly consists of the following parts:

Inlet
Filter bags
Cage
Flower plate
Hopper
Pulse cleaning device (including pulse valves, blowing pipes, air tanks, etc.)
Control system
Outlet

Its chambered structure gives each chamber independent control valves and pulse cleaning devices. This design enables each chamber to clean independently. Furthermore,offline pulse bag dust collectors usually have a larger hopper. This hopper collects and stores the dust that has been removed. It also includes baffles to prevent secondary dust emissions.

Application Fields

Off-line pulse jet baghouse filters are common in heavy industries like steel, cement, power, and chemicals. They are especially effective at handling large air volumes, high dust concentrations, and sticky dust. For example, in the steel industry, these collectors can tackle high gas volumes and dust concentrations in sintering machine tail dust removal systems.

Advantages and Disadvantages

Advantages

High Cleaning Efficiency: The offline cleaning method ensures complete removal of dust from the filter bags, maintaining filtration efficiency and prolonging service life.
Strong Adaptability: The chambered design allows stable operation in high dust concentration and humidity environments.
Continuous Operation: While some chambers are being cleaned, others continue filtering, ensuring system continuity.
Low Energy Consumption: The efficient cleaning process reduces operational resistance, minimizing energy use and maintenance costs.

Disadvantages

Complex Structure: The chambered design and numerous valves increase the complexity and manufacturing cost of the equipment.
Large Footprint: Compared to online dust collectors, offline pulse bag dust collectors require more installation space.
High Initial Investment: The complex structure and multiple components lead to higher initial investment costs.
Complex Maintenance: The chambered structure and numerous components make maintenance and repairs relatively complicated.

On-line Pulse Jet Baghouse Filters

Working Principle

The online pulse bag dust collector cleans while it filters. It uses high-pressure airflow to spray the surface of the filter bags. This airflow creates vibrations and impacts that dislodge dust into the hopper. The cleaning process does not require downtime. As a result, it ensures continuous gas flow and effective dust removal.

Structural Characteristics

The on-line pulse jet baghouse filter primarily consists of the following components:

Inlet
Filter bags
Cage
Flower plate
Hopper
Pulse cleaning device
Control system
Outlet

All filter bags install in one or a few chambers. This design simplifies the overall structure and reduces the number of valves and mechanical parts. As a result, it lowers complexity and costs. Additionally, on-line pulse jet baghouse filters usually have a smaller footprint. This feature makes them suitable for industrial sites with limited space.

Application Fields

On-line pulse jet baghouse filters are common in many industrial sectors. They work especially well with medium concentrations and ordinary dust. For example, in the building materials industry, such as in brick and tile production and lime kiln dust removal, these collectors efficiently remove dust generated during processes. This ensures that emissions meet environmental standards.

Advantages and Disadvantages

Advantages

Simple Structure: The design is straightforward, without complex chamber structures or valve control systems.
Low Cost: Manufacturing and maintenance costs are relatively low, making it suitable for budget-constrained scenarios.
Convenient Operation: Cleaning operations do not require downtime, simplifying the operational process.
Small Footprint: The compact design is ideal for environments with space constraints.

Disadvantages

Limited Cleaning Effectiveness: The online cleaning method may not completely remove dust from the filter bags’ surface.
Not Suitable for Sticky Dust: For highly sticky or humid dust, the online cleaning method may lead to filter bag clogging, affecting efficiency.
High Operational Resistance: Prolonged operation may increase system resistance, impacting dust removal efficiency.
Frequent Maintenance: Although structurally simple, more frequent cleaning operations may lead to increased wear on filter bags and other components, raising maintenance costs.

Differences Between Off-line and On-line Pulse Jet Baghouse Filters

Differences in Working Principles

Offline pulse bag dust collectors stop filtration by cutting off airflow to one or more chambers using control valves. This allows for cleaning before they resume filtration. In contrast, on-line pulse jet baghouse filters clean while all chambers are filtering. This design ensures continuous gas flow.

Differences in Structural Characteristics

Off-line pulse jet baghouse filters have a chambered design with independent control valves. This design leads to a complex structure and a larger size. On the other hand, on-line pulse jet baghouse filters have a simpler design. Their compact size makes them suitable for applications with limited space.

Differences in Application Fields

Off-line pulse jet baghouse filters work well in complex conditions with high dust concentration and humidity. In contrast, on-line pulse jet baghouse filters are better for medium dust concentrations and ordinary dust handling.

If you wish to achieve efficient air filtration in dust handling processes, Darko can provide you with the best solution. Our professional team will assist you in selecting the most suitable dust collection equipment based on your specific needs. Feel free to contact us anytime!

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Maximizing Efficiency with Roots Blowers

11/01

2024

11/01/2024

In the cement industry, selecting the appropriate blower, such as Roots blowers, is crucial for production efficiency. Recently, Darko gained valuable experience while working with clients that we would like to share.

Wide range of uses of Roots Blowers

A Roots blower operates as a positive displacement rotary blower, utilizing two rotor-shaped blades to compress and transport gas through relative motion within a cylinder. This design features a simple structure, which facilitates easy manufacturing. Consequently, it is well-suited for gas conveying and pressurization in low-pressure applications. Additionally, it can effectively function as a vacuum pump.

Roots blowers are widely used in various fields due to their stable performance. They find applications in wastewater treatment, water supply, pharmaceutical and chemical industries, flue gas, dust handling, and aquaculture. Furthermore, they are involved in cement transport and desulfurization and dust removal industries, serving essential functions such as gas conveying, pressurization, and ventilation.

Background

Not long ago, a northern cement plant ordered our composite mixer and requested to pair it with a vortex blower. Previously, our composite mixers and air-chain conveyors were typically equipped with Roots blowers, so we were not very familiar with the technical parameters and performance of the vortex blower.

At the same time, a southern cement company reported that when using our FUK800×60 meter air-chain conveyor, the throughput reached 410-420 t/h, but dust began to spill, failing to meet the designed capacity of 650 t/h. This prompted us to quickly visit the site to resolve the issue.

On-Site Investigation and Analysis

Technical Parameter Review

Our technical team arrived at the site. We reviewed the installation and technical parameters of the equipment. We found that all agreed-upon indicators were met. However, the blower in use was not the Roots blower we provided. Instead, it was a vortex blower purchased by the client.

Testing Issues

During the testing process, the throughput remained stuck between 410-420 t/h, accompanied by dusting issues. After careful observation, technicians noticed that opening a viewing port about ten meters from the discharge increased the material level, allowing throughput to rise to 500 t/h. However, dusting issues reappeared under full load, creating concern.

Response Strategy

Blower Replacement

We learned that another nearby company could meet their design requirements with a different blower. Therefore, we decided to take a dual approach:

Replace the blower with a Roots model that closely matched the technical parameters.
Continue to explore the performance of the vortex blower.

Adjusting Variable Frequency Motor Settings

We adjusted the vortex blower. We discovered it used a variable frequency motor. The technical parameters showed that pressure and airflow varied at 50HZ and 60HZ. Therefore, we decided to increase the motor frequency to 60HZ for testing. This change allowed the throughput to easily exceed 500 t/h. Eventually, it reached 680 t/h during adjustments.

Blower Comparison Analysis

Roots Blower vs. Vortex Blower

Through this experience, we conducted a comparative analysis of the two blowers:

Roots Blower: Offers stable pressure and airflow, with a power rating of 15 kW, making it suitable for applications with high pressure requirements.
Vortex Blower: Pressure and airflow vary with different frequencies, with a power rating of around 20 kW. It can be used in various applications but may not be as stable as Roots blowers in certain conditions.

Conclusion and Recommendations

Based on our practical experience, the Roots blower shows better technical performance and energy efficiency. This makes it a better fit for Darko's composite mixers and air-chain conveyors. The vortex blower can serve as a replacement in some situations. However, the Roots blower is preferable when high pressure stability is needed.

If you have any questions about blower selection or would like to learn more about our products, please feel free to contact us at Darko. Together, we can explore ways to improve production efficiency in the cement industry!

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Bucket Elevators: Key to Modern Transport

10/31

2024

10/31/2024

What is a bucket elevator？

Bucket elevators are popular vertical conveying devices. They primarily elevate powdered, granular, and small block materials. These elevators have high conveying efficiency, a compact structure, and a small footprint. They can lift materials to heights of 40 to 100 meters while remaining reliable. This reliability makes them essential in various industries, such as power generation, cement, metallurgy, machinery, chemicals, light industry, and agriculture.

Moreover, bucket elevators are widely used in the cement industry. Their small footprint, simple structure, large capacity, high lifting height, and low energy consumption contribute to their popularity. They are critical at different stages, including raw material storage, transportation, grinding systems, clinker feeding, cement grinding, and packaging. In modern large-scale cement production lines, bucket elevators are vital components in key positions.

Nantong Darko’s Expertise

Nantong Darko has ten years of experience in machinery manufacturing. We use advanced design principles to create our products. We also select high-quality steel and components. Additionally, we strictly control manufacturing precision to ensure reliable operation of our bucket elevators. Our product range includes NE type, TD type, TH/HL type, and dewatering scooping bucket elevators.

Classification of Bucket Elevators

1. By Layout

Vertical: The most common layout for conveying materials straight up.
Inclined: Suitable for scenarios requiring material elevation at a certain angle.

2. By Discharge Method

Centrifugal: Utilizes centrifugal force for discharge, suitable for conveying small, free-flowing materials, such as dry powders.
Gravitational: Relies on the weight of the material for discharge, suitable for large, heavy, and abrasive materials like ores and stones.
Mixed: Combines characteristics of both centrifugal and gravitational discharge methods, offering a wider application range.

3. By Feeding Method

Scoop: The bucket scoops material from the bottom; commonly used for conveying loose powders, granules, and small blocks.
Injection: Material is directly injected into the bucket, suitable for large and abrasive materials.

4. By Bucket Structure

Shallow Bucket: Wider and shallower bucket suitable for conveying damp, easily clumping, and poorly flowing materials.
Deep Bucket: Narrower and deeper bucket ideal for dry, loose, and easily spilled materials.
Triangular Bucket: With slanted walls, typically used for conveying large items.

5. By Traction Component

Belt: Low cost, light weight, and smooth operation, but with lower strength, not suitable for high-temperature or abrasive materials.
Steel Chain: High strength and wear resistance, suitable for high-temperature, heavy load, and abrasive materials.

Structure of Bucket Elevators

Bucket: Used for loading and elevating materials.
Traction Component: Such as belts or chains, which drive the movement of the buckets.
Drive Device: Provides power, typically including motors and reducers.
Upper and Lower Drums (or Sprockets): Change the direction of motion of the traction component.
Casing: Forms a closed transport channel to prevent material spillage and dust escape.
Tensioning Device: Adjusts the tension of the traction component to ensure normal operation.

Working Principle of Bucket Elevators

Bucket elevators scoop material from the storage area below with the buckets and elevate it to the top as the traction component (such as a conveyor belt or chain) moves. At the top, the bucket flips over and dumps the material into the receiving chute.

In belt-driven bucket elevators, the drive belt is typically made of rubber and installed on the drive drums and redirecting drums. Chain-driven bucket elevators usually have two parallel drive chains, with a pair of driving sprockets on either the top or bottom, and a pair of redirecting sprockets on the opposite side. To reduce dust escape, bucket elevators are typically equipped with a casing.

Precautions for Using Bucket Elevators

Strictly follow the principle of “no-load start, empty stop.” Ensure there is no material load before starting, and only feed materials once the machine is running smoothly. Empty the machine before stopping to avoid overload during the next start.
Feed uniformly to ensure unobstructed discharge. If a blockage is found, immediately stop feeding and address the issue.
Keep the bucket belt centered in the casing. If it drifts or becomes too loose, adjust it promptly using the tensioning device.
Prevent large foreign objects from entering the casing to avoid damaging the buckets. A metal grid can be installed at the feed inlet to block fibrous impurities like straw and rope.
Regularly check the tension of the bucket belt and the connection between buckets and the belt. If any looseness, detachment, misalignment, or damage is found, repair or replace it promptly to avoid more severe failures.
In case of sudden shutdown, first clear any accumulated materials in the casing before restarting to prevent excessive load during startup.

Understanding the classification, structure, principles, and precautions of bucket elevators is crucial. This knowledge ensures safe, efficient, and stable operation. If you have questions or need assistance, please contact us. Over the past ten years, Darko has introduced many innovations in vertical conveying technology. We have achieved significant progress in high-performance bucket elevators. Our experience and pioneering spirit have made us industry leaders in the design and manufacture of these elevators.

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Efficient Roller Press Solutions

10/26

2024

10/26/2024

What is a roller press used for?

The roller press, also known as a squeeze mill, roller mill, or double roller machine.A roller press is a grinding device used in industrial applications, particularly in cement production. It consists of two counter-rotating rollers that compress and grind the material. This process significantly reduces the particle size of the material, making it an efficient alternative to traditional grinding methods.

The roller press has high grinding efficiency, low energy consumption, and high output, making it widely used in the cement industry. However, during operation, various issues arise due to factors such as design, usage, and external conditions. These problems lead to poor working conditions, inadequate feed control, and hydraulic system failures, all of which negatively affect the performance of the roller press. To address these challenges, we analyze the root causes and implement improvements across multiple aspects, including design and usage. As a result, we optimize the modification process, enhance efficiency, and achieve better operational results.

I.Role of the Roller Press in Cement Plants

In cement plants, operators use the roller press to grind clinker and other raw materials into fine powder. Typically, they employ it alongside other grinding systems, such as ball mills, to enhance overall efficiency and reduce energy consumption. Furthermore, the roller press's capacity to manage high pressure and produce fine products makes it an essential component of modern cement production.

II.Differences Between Roller Press and Ball Mill

The primary difference between a roller press and a ball mill lies in their grinding mechanisms. A roller press compresses the material between two rollers under high pressure, resulting in lower energy consumption and higher efficiency. In contrast, a ball mill relies on the impact and friction of balls to grind the material, which typically consumes more energy. Therefore, roller presses usually perform better in terms of energy efficiency and product fineness.

III.Skew Issues in Roller Presses

Skew refers to the misalignment between the rollers of the roller press and may arise from mechanical wear or improper installation. This misalignment can lead to uneven pressure distribution, which ultimately reduces grinding efficiency. Therefore, regular maintenance and proper alignment are crucial for minimizing skew and ensuring the optimal performance of the roller press.

IV.Analysis of Issues with Roller Presses

1. Fine Powder Content at the Outlet

The fine powder content at the outlet of the roller press, also known as first-pass yield, directly reflects the effectiveness of the pressing process. However, many companies overlook this critical aspect. Testing samples from various enterprises revealed that the German BHS roller press achieved an outlet fineness of 33% on a 0.9mm sieve and 64% on a 0.08mm sieve (with 36% below 0.08mm). In contrast, many of these machines do not reach similar results.

2. Working Pressure

The pressing force is the most fundamental parameter determining the effectiveness of the roller press. To calculate the total force (in kN) of the roller press, we use the formula:

where:

n= number of hydraulic cylinders
S= effective area of the hydraulic cylinder (m²)
$P_{r}$ = hydraulic system pressure (MPa)

Moreover, the average roller pressure $P_{c p (in kN/m²) is given by:}$

$P_{c p =2F/}$ D⋅B⋅sinα

Here:

$D$ = diameter of the grinding roller (m)
$B$ = effective width of the grinding roller (m)
= pressure angle, also known as the bite angle (°)

Projected Pressure Calculation

In addition, the projected pressure PT (in kN/m²) is calculated using:

$P_{T} =F/ B \cdot D$

Impact of Maximum Roller Pressure on Pressing Efficiency

In practice, the maximum roller pressure significantly affects the pressing effect. Specifically, when the line connecting the centers of the two rollers is set at 0 degrees, the pressure angle starts at 8.3 degrees and ends at -1.6 degrees. Notably, the maximum peak pressure occurs at 1.5 degrees, slightly exceeding twice the average pressure.

Moreover, the hydraulic system of the roller press plays a crucial role, as it provides the dynamic roller pressure necessary to compress the material. This system consists of various components, including the oil station, hydraulic cylinders, nitrogen bags, solenoid valves, overflow valves, pressure gauges, oil lines, and control cabinet. If the configuration lacks damping adjustment valves and stroke adjustment valves, it cannot achieve optimal pressing results. Therefore, in some cases, adding small nitrogen bags may prevent the displayed pressure from accurately reflecting actual pressure changes.

Nitrogen Bag Configuration and Pressure Management

The size of the nitrogen bags and the piping must be calculated based on the size of the hydraulic cylinders. Furthermore, using pipes that are too small will increase resistance. In a parallel setup, when one large and one small nitrogen bag are used, the small bag activates first, followed by the large bag. As a result, this process repeatedly suppresses the opening of the roller gap, which operates in a cycle of retracting, retracting, and advancing, ultimately resulting in low pressing efficiency.

Moreover, the pressures of the nitrogen bags are set at 8, 10, and 12 MPa, meaning that only one nitrogen bag operates within a specific range while the other two become ineffective. Although this theory of differential pressure was initially proposed by German engineers, it failed to achieve the expected results due to significant variations in material properties. Consequently, the Germans did not pursue this approach further.

In general, it is advisable to set the nitrogen bag pressure at 60-80% of the system’s minimum pressure. This approach ensures that when the system operates at its lowest working pressure, a certain level of safety is maintained between the nitrogen bags and the on-off valve. However, the system’s operational state must be monitored on-site to determine its effectiveness. If the oil temperature is too high or too low, it indicates that the system is not in good working condition, which severely impacts pressing efficiency.

3. Roller Speed

The roller speed of the roller press can be expressed in two ways: one is the circumferential linear speed V of the rollers, and the other is the rotational speed of the rollers. The circumferential linear speed is related to output, power consumption, and operational stability. Generally, higher roller speeds lead to increased output; however, excessively high speeds can cause greater relative sliding between the rollers and the material, resulting in poor engagement and increased wear on the roller surfaces, which negatively impacts the output of the roller press.

Currently, the typical roller speed ranges from 1.0 to 1.75 m/s, with some experts suggesting that it should not exceed 1.5 m/s. The linear speed of the rollers usually falls between 1.0 and 1.7 m/s, with most operating around 1.5 to 1.7 m/s, and some even reaching 2.0 to 2.2 m/s. It is crucial to prioritize the squeezing effect when selecting the speed; this effect should be based on actual sampling. If the speed is too high, the pressing time shortens, leading to increased vibrations in the equipment. The significant variations in force become difficult to control, resulting in excessive power consumption without achieving the desired pressing effect.

4. Operating Gap and Material Properties

The operation of the roller gap is influenced by various factors, including the properties of the material (such as hardness, particle size, and moisture content), the form of the roller surface, the speed, the pressure, and the pressure control method. There are two ways to control the hydraulic cylinder pressure: constant pressure control and constant gap control. However, regardless of the method used, both are fundamentally flawed from a hydraulic perspective because pressure and gap continuously fluctuate.

The pressure gauge has a response time of 200 milliseconds, which complicates the control of the oil pump's pressure adjustments. This, in turn, affects the hydraulic cylinder pressure and subsequently the roller gap. As a result, there are two main issues: first, there is a lag in response; second, excessive pressure differentials occur. These factors hinder the stable operation of the roller press and negatively impact pressing efficiency.

5. Feeding Device

Currently, most roller presses use a feeding device that directs material straight from the hopper into the roller gap, pulling the material between the two rollers. This process is commonly referred to as the "pull-in angle" of the roller press. However, controlling the flow from two directions is not feasible, as the adjustment range is limited, making it difficult to achieve precise and stable control. Additionally, the other two directions cannot be adjusted at all. As a result, issues such as material segregation and roller misalignment frequently occur, leading to unmanageable conditions.

V.Roller Press System Modification Plan

1. Replacement of Feeding Device

Replace the roller press feeding device with a new type of four-direction feeding system (patented technology) to control the material feed. This system allows for adjustment and control from two directions, enabling reasonable control of material flow. The other two directions can be adjusted to correct the lateral gap deviation between the rollers, reducing the impact of the material on the roller press and facilitating the formation of a stable material bed. This approach eliminates issues such as material segregation and roller misalignment, and it operates at a low hopper position, making it easier to adjust and control.

2. Upgrading the Hydraulic System

We replaced the hydraulic system of the roller press, including components such as the oil station, overflow valve, pressure gauge, accumulator (nitrogen bag), and valve assembly. Additionally, we incorporated damping adjustment valves and stroke adjustment valves (patented technology) to make the hydraulic system flexible, rigid, and controllable.

During the research and development process, we conducted extensive field tests using a specialized high-precision pressure measurement device (1000 Hz) to collect and analyze data. We employed dedicated simulation software and complex mathematical models to successfully develop a dual-channel adjustable damping anti-vibration regulation mechanism, achieving a reasonable balance of rigidity and flexibility in the hydraulic system.

3. Implementing PLC Control

We replaced the roller press hydraulic PLC and implemented four-directional control of the feeding device, utilizing a constant power control method for easier centralized operation. We configured the system with Siemens SIMATIC S7-1200, integrating Siemens SINAMICS drive products and SIMATIC human-machine interface products. The CPU comes standard with an Ethernet interface that supports various industrial Ethernet communication protocols, including PROFINET, TCP, UDP, and Modbus TCP.

Our company developed this technology through mathematical modeling, gathering extensive field data during the research and development process. We employed specialized simulation software and complex mathematical models, which have been validated through practical application.

VI.Case Studies

1. Chao Lake Hengxin Cement Co., Ltd.

Since the modification in August 2020, production efficiency has increased from 200 tons/hour to 290 tons/hour, with energy consumption controlled at 22 kWh/ton of cement.

2. Hainan Huaren Cement

In June 2022, the roller press was upgraded, increasing hourly output from 150-160 tons to 180-200 tons, with energy consumption reduced to about 23 kWh/ton.

3. Guizhou Southwest

Through the upgrade, output has risen to 180-190 tons/hour, and energy consumption decreased from 32 kWh/ton to 25 kWh/ton.

4. Jiangxi Sanqing Cement Co., Ltd.

After the modification, the output increased to 270-280 tons/hour, with stable operation and nitrogen bag temperatures maintained at 40-60°C.

VII.Benefits of Roller Press Technology Upgrade and Modification

The stability of the roller press has improved, with virtually no side leakage. There are three methods for adjusting roller skew: first, four-directional feed adjustment; second, hydraulic system adjustments; and third, separate pressure adjustments for left and right. Control is stable, with minimal occurrences of material collapse and roller skew.

The hydraulic system of the roller press is flexibly adjustable and controllable. The fluctuation of the roller gap has changed from slow retraction and fast advance to fast retraction and slow advance, increasing pressing efficiency. The fine powder content at the roller press outlet has increased by 3-7%, the specific surface area of the input material has improved, and hourly output has increased by 10-20%.

A constant power control method is used, with operational power maintained at 85±5% of the rated power. The efficiency of the roller press has two requirements: first, high operational power; second, high first-pass yield. By improving the efficiency of the roller press and reducing mill power consumption, the overall energy consumption has been lowered by 2-5 kWh/ton.

If you have needs regarding the modification and upgrading of roller press systems, please feel free to contact us at Darko. We will provide you with professional solutions and support.

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CONATCT

I. Advantages of the 7-Stage Cement Kiln Preheater

(A) Significant Energy Savings

(B) Improved Separation Efficiency

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

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

(E) Benefits from the Elimination of the Humidification Tower

II. Challenges of the 7-Stage Cement Kiln Preheater

(A) Increased Construction Costs and Difficulty

(B) Impact on Raw Material Drying

(C) Reduced Waste Heat Power Generation

(D) Challenges in Controlling Flue Gas Temperature

(E) High Costs for Upgrading Old Production Lines

III. Conclusion and Outlook

System Problems

Main Issues Encountered

Retrofitting Program

1. Installation of Iron Removers and Metal Separators

2.Retrofitting of Roller Press & Breaking Classifier

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

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

3.Modification of Ball Mills

4.Upgrade of the Dust Collector Ash Return Discharge Point

The Significance of Vertical Roller Mills

1. High Energy Efficiency

2. Compact Footprint

3. Strong Drying Capacity

4. Long Lifespan of Wear Parts

5. Large Feed Size

6. Lower Noise Levels

Layout Options

Common Issues

Wear of Grinding Rollers

Bearing Chamber Wear

Conclusion

Features of Star Discharge Valve

Applications of Star Discharge Valve

Selection Guide for Star Discharge Valves

1. Define the Usage Location

2. Determine the Purpose of Use

3. Specify the Material Flow Rate

4. Define the Conveying Method

5. Understand the Conveyed Material

6. Analyze Material Properties

7. Consider Special Requirements

8. Material Selection

9. Safety Performance

Conclusion

Choose the Right Material

Assess Operating Conditions

1. Nature of Flue Gas

2. Temperature

3. Characteristics of Dust

Proper Installation and Use

Additional Tips to Extend Bag Lifespan

Types of Dust Filter Bags

Conclusion

Cement Plant A Abnormal Situation Description

Fault Phenomenon

System Configuration

Results

Technical Diagnosis Analysis

Technical Measures and Effects

Cement Plant B Abnormal Situation Description

Fault Phenomenon

Grinding System Configuration

Results

Technical Diagnosis Analysis

Technical Measures and Effects

Cement Plant C Abnormal Situation Description

Fault Phenomenon

Grinding System Configuration

Results

Technical Diagnosis Analysis

Technical Measures and Effects

Conclusion

Control Dust Concentration

Control Ignition Sources

Control Oxygen Content

Implement Additional Measures