Sugar Mill Evaporator Cleaning: Preventing Scale and Improving Efficiency

Sugar mill evaporators represent critical capital equipment—and scale buildup represents the primary threat to their efficiency and lifespan. Calcium oxalate, silica, and organic fouling reduce heat transfer, increase energy consumption, and ultimately force costly shutdowns. This guide covers sugar mill evaporator cleaning chemicals and protocols that maximize efficiency while protecting equipment investment.

Understanding Evaporator Scale in Sugar Processing

Scale Formation Chemistry

Sugar juice evaporation concentrates not only sucrose but also non-sugar components:

| Scale Type | Primary Component | Formation Mechanism | Location |
|————|——————-|———————|———-|
| Calcium oxalate | CaC₂O₄ | Oxalic acid + calcium at temperature | Early effects, tubes |
| Calcium sulfate | CaSO₄ | Low solubility at concentration | All effects |
| Silica | SiO₂ | Colloidal silica precipitation | Later effects |
| Organic fouling | Proteins, waxes, gums | Heat denaturation | Flash vessels, tubes |

Scale Impact on Operations

| Metric | Clean Evaporator | Scaled Evaporator | Performance Loss |
|——–|——————|——————-|——————|
| Heat transfer coefficient | 100% | 40-60% | 40-60% |
| Steam consumption | Baseline | +30-50% | Significant |
| Throughput capacity | Rated | -20-40% | Bottleneck |
| Energy cost | Baseline | +25-40% | Major expense |

Economic perspective: A 1mm scale layer on evaporator tubes increases steam consumption by approximately 10-15%. Heavy scaling can increase energy costs by ₹10-25 lakhs annually for a medium-sized mill.

Cleaning Chemistry for Sugar Evaporators

Alkaline Cleaning

Purpose: Remove organic deposits (proteins, waxes, gums)

Chemistry: Sodium hydroxide (caustic soda) + surfactants + chelators

| Parameter | Standard | Heavy Organic Load |
|———–|———-|——————-|
| Concentration | 2-3% NaOH | 3-5% NaOH |
| Temperature | 85-95°C | 90-100°C |
| Contact time | 4-6 hours | 6-8 hours |
| Circulation | Continuous | Continuous |

Clissal MillClean Caustic: Enhanced caustic formulation with organic penetrants for sugar mill applications.

Acid Cleaning

Purpose: Dissolve mineral scale (calcium salts, some silica)

Chemistry options:

| Acid Type | Target Scale | Advantages | Considerations |
|———–|————–|————|—————-|
| Hydrochloric | Calcium carbonate, oxalate | Fast acting, economical | Corrosive, fume hazard |
| Sulfamic | Calcium carbonate | Safer handling, solid form | Less effective on oxalate |
| Phosphoric | General mineral | Good on oxalate, passivating | May leave residue |
| Organic blend | Mixed scale | Safer, biodegradable | Lower strength |
| EDTA-based | Calcium oxalate | Specific chelation | Higher cost |

Clissal MillClean Acid: Blended acid formulation optimized for sugar scale—effective on calcium oxalate with corrosion inhibition.

Specialty Treatment for Difficult Scale

Calcium oxalate (most challenging):

• Standard acids dissolve slowly
• EDTA chelation most effective
• May require extended soak time
• Prevention better than cure

Silica scale:

• Acid-resistant
• Requires alkaline treatment or HF-based specialty products
• Mechanical assistance often needed
• Prevention through juice treatment

Standard Cleaning Protocol

Pre-Cleaning Assessment

1. Drain evaporator completely
2. Inspect accessible areas for scale severity
3. Sample scale for analysis if unusual
4. Plan chemical sequence based on findings

Alkaline Phase

Purpose: Remove organic deposits, prepare surface for acid

Clissal MillClean Caustic Application:

| Step | Duration | Temperature | Circulation |
|——|———-|————-|————-|
| Fill with water | As needed | 50-60°C | Static |
| Add chemical | 15-30 min | 60°C | Agitation |
| Heat to target | 30-45 min | To 90°C | Circulation |
| Hold at temperature | 4-6 hours | 90-95°C | Continuous |
| Drain | Complete | – | – |
| Rinse | 30-60 min | 60-80°C | Through |

Acid Phase

Purpose: Dissolve mineral scale

Clissal MillClean Acid Application:

| Step | Duration | Temperature | Circulation |
|——|———-|————-|————-|
| Fill with water | As needed | 40-50°C | Static |
| Add chemical | 15-30 min | 50°C | Agitation |
| Heat to target | 30-45 min | To 70°C | Circulation |
| Hold at temperature | 4-8 hours | 65-75°C | Continuous |
| Monitor pH | Hourly | – | – |
| Drain | Complete | – | – |
| Rinse | 60-90 min | Clean water | Until neutral |

Post-Cleaning Verification

• Visual inspection of accessible areas
• Clean water rinse pH verification (neutral)
• Heat transfer test on restart
• Document results for trend analysis

Clissal Sugar Mill Product Range

Product Specifications and Dilutions

| Product | Application | Dilution | Temperature | Contact Time | pH Range |
|———|————-|———-|————-|————–|———-|
| MillClean Caustic | Organic removal | 2-5% w/w | 85-95°C | 4-8 hours | 12.5-13.5 |
| MillClean Acid | Mineral scale | 3-8% v/v | 65-75°C | 4-8 hours | 0.5-2.0 |
| MillClean Oxalate Breaker | Calcium oxalate | 5-10% v/v | 70-80°C | 6-12 hours | 7-9 |
| MillClean Silica Control | Silica prevention | 50-100 ppm | Process temp | Continuous | – |
| MillClean Antiscalant | Scale prevention | 20-50 ppm | Process temp | Continuous | – |

Application Guidelines

MillClean Caustic:

• Add to warm water (never add water to concentrate)
• Ensure complete circulation before heating
• Monitor foam—reduce if excessive
• Compatible with stainless steel, mild steel
• Rinse completely before acid phase

MillClean Acid:

• Never mix with caustic or sodium hypochlorite
• Add slowly with agitation
• Monitor pH—add additional if exhausted (pH rises)
• Inhibited formulation protects mild steel for limited exposure
• Neutralize before discharge

MillClean Oxalate Breaker:

• EDTA-based chelating formulation
• Effective at neutral pH
• For heavy calcium oxalate deposits
• May be used alone or after standard acid
• Longer contact time yields better results

Consumption Estimates

| Equipment Type | Volume (m³) | Caustic (kg/clean) | Acid (L/clean) | Cleans/Season |
|—————|————-|——————-|—————-|————–|
| Quadruple effect evaporator | 200-400 | 500-1500 | 2000-5000 | 3-5 |
| Quintuple effect evaporator | 300-600 | 800-2500 | 3000-8000 | 3-5 |
| Vacuum pans | 50-150 | 100-400 | 500-1500 | 4-8 |
| Heaters | 20-80 | 50-200 | 200-800 | 4-8 |

Prevention Strategies

In-Process Antiscalant Treatment

Prevention is more economical than cleaning:

Clissal MillClean Antiscalant:

• Dosing: 20-50 ppm in juice
• Application point: Before first evaporator effect
• Mechanism: Crystal modification—prevents scale adhesion
• Monitoring: Visual inspection during season

Benefits:

• Extended run times between cleanings
• Reduced scale severity when cleaning required
• Lower chemical consumption overall
• Better heat transfer maintained

Juice Treatment Optimization

Liming and clarification:

• Proper liming reduces oxalate-forming compounds
• Effective clarification removes scale precursors
• pH control prevents equipment conditions favoring precipitation

Sulfitation (where used):

• Proper sulfur dosing reduces coloring compounds
• Reduces organic fouling tendency

Seasonal Planning

Pre-Season Preparation

1. Inspect evaporators (cold, dry)
2. Document scale carryover from previous season
3. Plan chemical inventory for season
4. Test cleaning chemical on sample scale (if unusual)
5. Verify CIP systems functional

In-Season Monitoring

1. Track heat transfer coefficients
2. Monitor pressure drop across evaporators
3. Visual inspection during brief stops
4. Schedule cleaning when efficiency drops 20-30%

Post-Season Cleaning

Most thorough cleaning opportunity:

1. Full chemical cleaning sequence
2. Mechanical cleaning for stubborn areas
3. Inspection for corrosion or damage
4. Protective treatment for off-season storage

Troubleshooting Common Issues

Problem: Scale Returns Rapidly After Cleaning

Causes:

• Inadequate cleaning (scale base left on surface)
• Process conditions promoting scale
• Water chemistry changes
• Antiscalant program not optimized

Solutions:

• Extend contact time on next clean
• Add mechanical action (hydroblasting) for severe cases
• Analyze juice and water for changes
• Adjust antiscalant dosing

Problem: Corrosion After Acid Cleaning

Causes:

• Acid concentration too high
• Temperature too high
• Contact time too long
• Inadequate inhibition
• Mixing incompatible chemicals

Solutions:

• Follow concentration guidelines strictly
• Control temperature (max 75°C)
• Monitor and drain when complete
• Use inhibited acid products (Clissal MillClean Acid)
• Never mix acid with other chemicals

Problem: Silica Scale Not Removed

Causes:

• Silica requires different chemistry
• Wrong approach (acid doesn’t work on silica)

Solutions:

• Alkaline treatment specifically for silica
• Extended caustic soak
• Specialty silica solvents (consult Clissal technical team)
• Mechanical removal for heavy deposits

Safety Considerations

Chemical Handling

| Product | Primary Hazard | PPE Required | First Aid |
|———|—————|————–|———–|
| MillClean Caustic | Corrosive (alkali burns) | Goggles, gloves, apron | Flush with water |
| MillClean Acid | Corrosive (acid burns) | Full face, gloves, apron | Flush with water |
| MillClean Oxalate Breaker | Mild irritant | Gloves, safety glasses | Standard |

Environmental Compliance

• Neutralize acid waste before discharge
• Caustic waste may require pH adjustment
• Document all discharges per permit
• Consider on-site neutralization tank

Economic Analysis

Cleaning Cost Example (Quadruple Effect, 300m³)

| Cost Element | Per Cleaning | Annual (4 cleans) |
|————–|————–|——————-|
| MillClean Caustic (1000 kg) | ₹65,000 | ₹2,60,000 |
| MillClean Acid (3500 L) | ₹1,40,000 | ₹5,60,000 |
| Water | ₹15,000 | ₹60,000 |
| Steam/energy | ₹25,000 | ₹1,00,000 |
| Labor (36 hours) | ₹18,000 | ₹72,000 |
| Total | ₹2,63,000 | ₹10,52,000 |

Scaling Cost (If Not Cleaned Properly)

| Impact | Annual Cost |
|——–|————-|
| Increased steam consumption (+30%) | ₹8-15 lakhs |
| Reduced throughput (bottleneck) | ₹5-20 lakhs (opportunity) |
| Extended outage for mechanical cleaning | ₹3-8 lakhs |
| Equipment degradation | Long-term capital impact |

ROI on proper cleaning program: Clear economic benefit vs. poor or deferred cleaning.

Conclusion: Investment Protection Through Proper Cleaning

Sugar mill evaporators represent tens of crores in capital investment—and scale is the primary threat to their efficient operation. Proper chemical cleaning, executed with the right products and protocols, protects this investment while minimizing operating costs.

Clissal MillClean products are formulated specifically for sugar industry scale challenges, with the safety features and technical support that mill operations require. Our ultra-concentrate format reduces handling and storage burden during the critical crushing season.

Preparing for your next season or mid-season cleaning? Contact Clissal for scale analysis, product recommendations, and protocol optimization.

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About Clissal: A brand of Jaivin Surfactants, Clissal serves sugar mills across Maharashtra, Karnataka, and UP with specialized cleaning chemistry. Our sugar industry team understands the operating pressures and seasonal demands of mill operations.