How to Clean Boiler Scale in Textile Mills?

Boiler scale is a hard, heat-insulating deposit on boiler pipes and heat exchangers. It forms when dissolved minerals in water precipitate during heating. In textile mills, steam is crucial for dyeing, drying, and treating cloth. Boiler scale can greatly impact efficiency and safety.

The main components of scale include minerals like calcium, magnesium, iron, aluminum, and silicon dioxide. These minerals form insoluble precipitates at high temperatures, sticking to the boiler's heating surface. Common types include calcium carbonate, calcium sulfate, magnesium hydroxide, and silicate compounds.

These scales have low thermal conductivity. For example, calcium sulfate's conductivity is only 1 ~ 2 kcal/m h c, compared to steel's 15 kcal/m h c. Even a thin layer of scale can cause a 20%~25% loss in heat conduction efficiency. This means more fuel is needed to produce steam, increasing costs and carbon emissions.

Scale also causes local overheating, metal fatigue, and can lead to boiler tube bursting. This poses a serious safety risk. Understanding boiler scale's formation and harm is crucial for textile mills to keep equipment running efficiently and safely.

Causes of Boiler Scale

Many factors contribute to boiler scale formation. Knowing the root cause is key to prevention and treatment. Common causes include water quality issues, operational factors, and inadequate maintenance.

1. Water quality problems

Water quality is the main cause of boiler scaling. Poorly treated feed water with high hardness ions and impurities easily forms scale. For instance, calcium and magnesium ions combine with carbonate and sulfate ions to create insoluble precipitates like calcium carbonate and calcium sulfate. These adhere to the heating surface, forming scale.

High silicon content in water can also lead to hard silicate scale. Iron and aluminum ions in water or pipelines can form oxide or hydroxide deposits at high temperatures, worsening scale formation. Therefore, effective softening, deoxygenation, and desilication of raw water are essential to prevent scaling issues.

2. Operational factors

Irregular boiler operation can significantly speed up scale formation. Frequent replenishment of cold water without softening treatment introduces hardness substances, leading to rapid scale accumulation. Improper water level control can cause local overheating, speeding up mineral precipitation and scale formation.

Operating the boiler under overload increases temperature, accelerating scale precipitation. Timely boiler blowdown is also crucial to prevent concentrated boiler water and reduce scaling risk. Standardized operation is vital to prevent boiler scaling.

3. Insufficient maintenance

Not keeping up with regular maintenance can lead to a lot of boiler scale buildup. If you don't check the water quality often, you won't catch changes in time. This makes it hard to treat the water properly, making scaling worse.

Not cleaning the boiler when needed can also cause problems. Scale gets thicker and sticks better, making it harder to clean. Without the right tools, like automatic dosing devices, water quality can get out of balance. This causes more scale to form.

Ignoring maintenance of equipment like softeners and deaerators can also lead to issues. Hard water can get into the boiler, making scaling even worse. So, having a good maintenance plan is key to keeping boilers running well for a long time.

Influence of Boiler Scale

Boiler scale is a big problem. It can make equipment less efficient, cause it to fail, and increase costs. It's important to pay attention to it.

1. Reduced efficiency

Scale doesn't conduct heat well. For example, calcium sulfate has a low thermal conductivity compared to steel. Even a thin layer of scale can reduce efficiency by 20%–25%.

This means boilers have to burn more fuel to produce the same amount of steam. This increases energy use and costs, affecting business efficiency.

2. Equipment damage

Scale doesn't just affect heat transfer. It also damages equipment mechanically. Scale can cause overheating, leading to metal fatigue and even failure.

It can also cause stress, speeding up equipment aging. This shortens the boiler's life and increases maintenance needs.

3. Economic and environmental impact

Boiler scaling wastes energy, raising fuel costs and carbon emissions. This hurts business finances and environmental goals. It also leads to more maintenance and part replacements, adding to costs.

Long-term scaling can force early boiler replacement, leading to big expenses. This is a financial burden for businesses.

Method of Cleaning Boiler Scale

1. Mechanical descaling

Mechanical descaling uses tools to remove scale from the boiler. Tools like wire brushes and high-pressure water guns are common. It's good for small-scale cleaning and regular maintenance.

It's safe and doesn't use chemicals. But, it's not effective for thick or stubborn scale, and it's hard work.

2. Chemical descaling

Chemical descaling is a good way to remove stubborn scale. It uses chemicals to break down the scale. There are two main types: alkaline boiling descaling and pickling descaling.

Alkaline boiling descaling works well for new boilers or early scale. It uses agents like NaOH to soften the scale. This makes cleaning easier later on.

Pickling descaling is for more serious scale. It uses acids like hydrochloric acid to dissolve hard substances. This is the most effective way to remove scale.

3. Standard operation steps of chemical descaling

To clean safely and effectively, follow these steps:

Chemical supervision:Experts should watch over the whole process. They make sure the right amount of chemicals is used safely.

Put in pickling solution:First, mix the pickling agent with water. Then slowly add it to the boiler to avoid damage. After cleaning, use caustic soda to neutralize any acid left.

Flushing boiler:Use clean water to rinse the boiler several times. This ensures no leftover liquid is left inside.

Open manholes and handholes:After rinsing, open the manholes and handholes. Remove any loose scale by hand. Check if the heating surface is clean.

Check the cleaning effect:Check if the cleaning was successful by looking, feeling, or testing. If there's still scale, you need to clean again.

Close the hole cover and prepare for passivation:Once clean, seal the manholes and handholes again. Then add passivating agents to protect the metal from corrosion.

Final inspection:After passivation, do a final check before starting the boiler again. Make sure there's no leftover medicine or scale.

Preventive Measure

Preventing scale is better than removing it. Removing scale is expensive and risky. So, it's important to prevent it from forming in the first place.

1. Water treatment system: the first line of defense against scale.

Water quality is key to preventing scale. A good water treatment system is essential.

Softening treatment: Remove calcium and magnesium ions to stop calcium carbonate and sulfate from forming.

Deoxygenation equipment: Get rid of dissolved oxygen to prevent corrosion and scale.

Desilication device: In areas with lots of silicon, special equipment is needed to prevent silicate scale.

Dosing system: Add chemicals like corrosion inhibitors to keep water stable and prevent scaling and corrosion.

A good water treatment system is crucial for preventing scale.

2. Regular monitoring: dynamic control of water quality changes.

Even with great equipment, you need to keep an eye on the water system. Use scientific monitoring to stay on top of changes.

Detection of inlet water and boiler water: regularly check for hardness, pH value, conductivity, oxygen content, and silicon content in both inlet and boiler water.

Real-time recording: keep water quality monitoring files up to date. This helps in judging if the water treatment system is working right by comparing data.

Alarm mechanism: set up an alarm system to alert managers when standards are exceeded. This ensures quick adjustments or pollution discharge measures.

Laboratory inspection: send samples to labs for detailed water quality analysis. This boosts monitoring accuracy.

Monitoring is key to preventing boiler scale. It helps managers predict and quickly respond to problems.

3. Maintenance plan: establish a long-term and effective operation mechanism.

Preventing scale is ongoing, not a one-time task. A good maintenance plan ensures continuous, effective prevention.

Periodic blowdown: blow down the boiler bottom and surface at set intervals. This controls water concentration and prevents salt precipitation.

Cleaning cycle setting: set annual or semi-annual cycles for thorough cleaning. This prevents scale buildup.

Equipment maintenance: regularly check and maintain water treatment equipment. This ensures they operate correctly.

Personnel training: enhance operators' knowledge and skills in boiler water quality management. This prevents scale due to operational mistakes.

Emergency plan: create emergency treatment plans for sudden water quality issues or equipment failures. This reduces losses.

A solid maintenance management system normalizes and institutionalizes anti-scaling efforts. It effectively extends boiler life.

Conclusion

Boiler scale significantly affects boiler efficiency and equipment life. It's mainly due to water quality issues, improper operation, and insufficient maintenance. Scale reduction is crucial to maintain efficiency and prevent damage.

EPCB boiler offers efficient, stable, and easy-to-maintain steam solutions for the textile industry. Its boiler design prioritizes scale protection and cleaning. It works with professional water treatment and intelligent control systems to reduce energy and maintenance costs.