Guide for the manufacture of lime in vertical mixed-feed type kiln, Part 1: From lime-stone
1990 Edition

Overview of Scope (Clause 3.1):

• Definitions align with IS 6508:1988, which provides terminology for building lime.
• The standard covers specifications, testing protocols, and quality assurance for lime products.

Important References (Clause 2.1):

• Terminology to be used as per IS 6508:1988.
• Particulate emissions measurement methods as specified in IS 11255 Part 1:1985.

Quality Control & Product Identification:

• Continuous inspection and testing ensure compliance with BIS norms.
• Application of the Standard Mark is governed by the BIS Act, 1986.

Lime Sorting Process (Clause 5.9):

• Lime after extraction is cooled on floors then manually divided into categories:
  • Properly burnt (well-burnt) lime
  • Excessively burnt (overburnt) lime
  • Insufficiently burnt (unburnt) lime

Additional Remarks:

• Users should refer to the latest BIS amendments.
• Detailed testing and emission assessment methods are provided in relevant IS codes.

flowchart TD
    RawLime[Raw Lime] --> Cooling[Cooling on Floor]
    Cooling --> Sorting{Sorting}
    Sorting --> WellBurnt[Well-burnt Lime]
    Sorting --> OverBurnt[Overburnt Lime]
    Sorting --> Unburnt[Unburnt Lime]

Primary and Related Standards:

• IS 6508:1988 — Glossary defining terms related to building lime (critical for Clause 3.1).
• IS 11255 (Part 1):1985 — Methods for measuring particulate emissions from fixed sources.

Sorting Instructions (Clause 5.9):

• Lime is spread to cool and then manually separated into well burnt, over burnt, and unburnt.

BIS Licensing and Marking:

• Products carrying the Standard Mark adhere to BIS surveillance and quality checks.
• License management and amendments are handled by BIS headquarters in Manak Bhavan, New Delhi.
• Indian Standards undergo periodic revisions; always consult the latest edition.

Contact Points:

• BIS Headquarters: Manak Bhavan, New Delhi
• Regional Offices: Kolkata, Chandigarh, Chennai, Mumbai, etc.

This compilation ensures comprehensive adherence to IS 1861 Part 1 requirements through applicable standards and BIS directives.

Definition Sources (Clause 3.1):

• IS 1861 Part 1 adopts definitions as outlined in IS 6508:1988, which provides a glossary for lime-related terms.

Highlights:

• Standardized terms include quicklime, hydrated lime, burnt lime, overburnt lime, among others.
• Ensures consistent interpretation of terminology across lime production and testing disciplines.
• IS 1861 Part 1 does not provide direct definitions but refers to IS 6508 for clarity.

Additional References:

• Emission measurement techniques correspond to IS 11255 (Part 1).
• Sorting and quality control procedures are explained in Clause 5.9.

flowchart LR
    IS1861[IS 1861 Part 1] --> Definitions[Definitions]
    Definitions --> IS6508[Refer to IS 6508:1988]
    Definitions --> EmissionMethods[Refer to IS 11255 (Part 1)]
    Definitions --> Sorting[Sorting & Quality Control - Clause 5.9]

Core Clauses:

• Clause 3.1: Terminology references IS 6508:1988.
• Clause 4.1: Chemical makeup of limestone and proximate fuel analysis are vital for producing quality lime.
• Clause 2.1: Relevant standards include IS 6508:1988 and IS 11255 (Part 1):1985.
• Clause 5.9: Lime sorting involves cooling on floors followed by manual separation into well burnt, over burnt, and unburnt categories.

Critical Data for Quality Control:

Chemical Composition Example:

flowchart TD
    Limestone[Raw Limestone] --> ChemAnalysis[Chemical Composition Analysis]
    FuelSample[Fuel Sample] --> ProxAnalysis[Proximate Analysis]
    ChemAnalysis & ProxAnalysis --> Calcination[Calcination Process]
    Calcination --> DrawnLime[Drawn Lime]
    DrawnLime --> Cooling[Cooling & Sorting]
    Cooling --> QualityCheck{Lime Quality}
    QualityCheck --> WellBurnt[Well Burnt]
    QualityCheck --> OverBurnt[Over Burnt]
    QualityCheck --> Unburnt[Unburnt]

Key Manufacturing Aspects:

1. Analysis of Raw Materials (Clause 4.1):

• Determine chemical content of limestone.
• Conduct proximate analysis of fuel.
• These analyses ensure production of lime with required properties.

2. Lime Sorting Post-Calcination (Clause 5.9):

• After extraction, lime is cooled spread on floors.
• Manual sorting divides lime into:
  • Well burnt (usable)
  • Over burnt (excessively heated, less reactive)
  • Unburnt (insufficiently heated)

Notes:

• Terminology per IS 6508:1988 applies.
• Quality assurance is monitored by BIS.
• Use of the Standard Mark indicates compliance.
• The standard is subject to periodic review for updating.

flowchart TD
    MaterialsAnalysis[Limestone & Fuel Analysis] --> Kiln[Calcination in Kiln]
    Kiln --> DrawnLime[Drawn Lime]
    DrawnLime --> Cooling[Cooling & Spreading]
    Cooling --> Sorting{Sorting}
    Sorting --> WellBurnt[Well-burnt Lime]
    Sorting --> OverBurnt[Overburnt Lime]
    Sorting --> Unburnt[Unburnt Lime]

Guidelines for Limestone Preparation (Clause 5.1):

• Ideal limestone particle size ranges from 40 to 100 mm.

Fuel Size Considerations (Clause 5.2.1):

• Coal or coke particle size should be approximately half the limestone size.
• For limestone sized 40-100 mm, fuel size should be between 20-50 mm.

Fuel Mixing Ratios (Clause 5.4.1):

• Fuel percentage depends on heat demand and fuel calorific value.
• Typical coal usage ranges from 12% to 16% by limestone mass.

Fuel Percentage Calculation Formula:

[ \text{Fuel %} = \left(\frac{\text{Heat required for calcination}}{\text{Calorific value of fuel}}\right) \times 100 ]

flowchart LR
    Limestone[40-100 mm Limestone] --> Mix[Mix with Fuel]
    Mix --> FuelSize[Fuel Size 20-50 mm]
    Mix --> Proportions[Mix Ratio by Fuel Type]
    Proportions --> SteamCoal[Steam Coal 12-16%]
    Proportions --> SoftCoke[Soft Coke 12%]
    Proportions --> Firewood[Firewood 16-20%]

Fuel Sizing and Conditioning (Clauses 5.2 & 5.2.1):

• Coal and coke must be crushed and graded appropriately.
• Maximum fuel particle size should be half the maximum limestone size.
• Minimum fuel size should be half the minimum limestone size.
• In hot weather, moistening fuel helps reduce dust and improves handling.

Fuel Proportions (Clause 5.4.1):

Fuel Mass Calculation:

[ \text{Mass of Fuel} = \text{Mass of Limestone} \times \left(\frac{\text{Fuel %}}{100}\right) ]

Notes:

• The fuel-to-limestone ratio depends on heat requirements and fuel calorific value.
• Chemical and proximate analysis of inputs ensures consistent lime quality.

flowchart LR
    LimestoneSize --> FuelPreparation[Reduce & Grade Fuel Size]
    FuelPreparation --> MaxSize[Max Fuel Size = 1/2 Max Limestone]
    FuelPreparation --> MinSize[Min Fuel Size = 1/2 Min Limestone]
    FuelCalc[Calculate Fuel Mass] --> KilnCharge[Charge Kiln]
    FuelCalc -->|Mass Limestone x Fuel %| KilnCharge

Reserve Materials Management (Clause 5.3):

• Adequate reserves of sized limestone and fuel must be maintained onsite to avoid production interruptions.

Storage Sizing Considerations:

• Reserve volume depends on daily consumption and desired backup duration.
• Formula:

[ V = Q \times D ] Where:

• V = reserve volume
• Q = daily consumption
• D = number of reserve days

Particle Size and Storage Conditions:

• Limestone size generally ranges from 10 to 40 mm as per IS 6508:1988.
• Fuel size must suit efficient combustion.
• Reserves commonly cover 3 to 7 days of operation.
• Storage areas should be dry, ventilated, and segregated to prevent contamination.

flowchart LR
    Supply[Raw Material Supply] --> Storage[Reserve Storage]
    Storage --> LimestoneStorage[Limestone]
    Storage --> FuelStorage[Fuel]
    LimestoneStorage & FuelStorage --> KilnCharge[Charging to Kiln]
    KilnCharge --> LimeDischarge[Discharging Lime]

Fuel Proportioning for Charging (Clause 5.4):

• Fuel percentage is based on calcination heat requirements and fuel calorific value.
• Typical fuel ratios by mass of limestone:

Additional Preparation Notes (Clause 5.2):

• Coal and coke must be crushed and graded prior to charging.
• Fuel may be moistened during hot weather to reduce dust.

Heat Balance Formula:

[ \text{Mass of Fuel} = \frac{\text{Heat Required for Calcination}}{\text{Fuel Calorific Value}} ]

Where heat required is a function of limestone quantity and calcination energy.

flowchart LR
    Mix[Limestone and Fuel Mix] --> Charge[Charging into Kiln]
    Charge --> Calcination[Calcination Process]
    Calcination --> Discharge[Discharging Calcined Lime]

Temperature Monitoring Points (Clause 5.5):

• Calcination zone temperature
• Drawn lime temperature
• Exhaust gas temperature

Calcination Zone Temperature Ranges (Clause 5.5.1):

• Temperature is measured using thermocouples inserted via poke holes.
• Flame color provides a rough indication of temperature:

Exhaust Gas Temperature and Composition (Clause 5.5.3):

• Exhaust gas temperature should ideally be near 100°C to maximize thermal efficiency.
• Gas composition for efficient combustion:
  • Carbon dioxide (CO₂): 25-40%
  • Carbon monoxide (CO): ≤ 0.5%
  • Oxygen (O₂): ≤ 3%
• Approximately 10% excess air is necessary; excessive air reduces efficiency.

graph LR
    CalcZoneTemp[Calcination Zone Temp] --> FlameColor[Flame Color]
    FlameColor -->|Bright red| Temp1000[1000°C]
    FlameColor -->|Bright orange| Temp1200[1200°C]
    ExhaustTemp[Exhaust Gas Temp ~100°C] --> GasComp[Gas Composition]
    GasComp --> CO2[CO₂ 25-40%]
    GasComp --> CO[CO ≤ 0.5%]
    GasComp --> O2[O₂ ≤ 3%]

Visual Indicators During Kiln Operation (Clause 5.6):

• Presence of dense black smoke indicates incomplete combustion.
• Flames visible at the kiln top signify inefficient fuel use and wastage.
• A light haze with minimal smoke and controlled air flow indicates satisfactory combustion.
• A clear kiln top suggests excessive air supply, which reduces efficiency.

Temperature and Gas Monitoring (Clause 5.5 & 5.7):

• Temperature is measured at calcination zone, drawn lime, and exhaust gases (ideally ≤ 100°C).
• Exhaust gas composition is checked for CO, CO₂, and O₂ levels per IS 11255 (Part 1).

Gas Composition Indicators:

flowchart LR
    KilnOperation[Kiln Operation] --> VisualCheck[Visual Observation]
    VisualCheck -->|Black Smoke| IncompleteCombustion[Incomplete Combustion]
    VisualCheck -->|Flame at Top| Wasteful[Fuel Wastage]
    VisualCheck -->|Light Haze| Satisfactory[Good Operation]
    VisualCheck -->|Clear Top| ExcessAir[Too Much Air]

    KilnOperation --> TempMonitoring[Temperature Monitoring]
    TempMonitoring --> CalcZoneTemp[Calcination Zone Temp]
    TempMonitoring --> DrawnLimeTemp[Drawn Lime Temp]
    TempMonitoring --> ExhaustTemp[Exhaust Gas Temp ≤ 100°C]

    KilnOperation --> GasAnalysis[Exhaust Gas Composition]
    GasAnalysis --> CO[CO ≤ 0.5%]
    GasAnalysis --> CO2[CO₂ 25-40%]
    GasAnalysis --> O2[O₂ ≤ 3%]

Monitoring and Adjustments (Clause 5.7):

• Analyze exhaust gases for CO, CO₂, O₂, and suspended particulates to optimize combustion.
• Adjustments include air supply regulation, limestone-fuel ratio, and feed rate.

Temperature Checks (Clause 5.5):

• Measure temperatures at the calcination zone, drawn lime, and exhaust gas.
• Aim for exhaust gas temperature around 100°C for best thermal efficiency.

Gas Composition Criteria:

Fuel and Feed Estimation:

• Use mass-volume conversion factors instead of weighing to estimate feed and fuel quantities.

Excess Air Calculation Formula:

[ \text{Excess Air (5)} = \frac{\text{Measured Oxygen}}{\text{Theoretical Oxygen}} \times 100 ]

flowchart LR
    FeedFuel[Feed and Fuel Input] --> Kiln[Kiln Operation]
    Kiln --> CalcZoneTemp[Calcination Zone Temp]
    Kiln --> DrawnLimeTemp[Drawn Lime Temp]
    Kiln --> ExhaustGas[Exhaust Gas Temp & Composition]
    ExhaustGas --> GasAnalysis[Gas Analyzer (CO, CO₂, O₂)]
    GasAnalysis --> Adjustments[Adjust Air Supply, Fuel Ratio, Feed Rate]

Raw Material and Fuel Requirements (Clause 4.1):

• Accurate chemical composition of limestone and proximate fuel analysis are fundamental.

Temperature Control (Clause 5.5.2):

• Temperature of drawn lime should not exceed 100°C to preserve quality.

Quality Characteristics (Clause 5.8):

• Lime must exhibit proper slaking properties.
• It should perform effectively in mortar and concrete applications.
• Achieved through precise calcination temperature, suitable fuel selection, and controlled kiln operation.

flowchart LR
    RawMaterials[Analysis of Limestone & Fuel] --> Calcination[Calcination Process]
    Calcination --> TempControl[Temperature ≤ 100°C]
    TempControl --> LimeDrawn[Drawing Lime]
    LimeDrawn --> Slaking[Slaking & Testing]
    Slaking --> Use[Application in Mortar & Concrete]

Sorting Method (Clause 5.9):

• Freshly drawn lime is spread on floors for cooling.
• Manual sorting classifies lime into:
  • Well burnt (ideal quality)
  • Over burnt (excessively burnt, low reactivity)
  • Unburnt (insufficient combustion, ineffective)

Purpose:

• Ensures only well burnt lime proceeds for construction use, maintaining consistent quality.

Sorting Characteristics:

• Well burnt lime: White to light grey, porous, reacts readily with water.
• Over burnt lime: Dark grey or black, dense, poor slaking.
• Unburnt lime: Hard lumps, no reaction with water.

flowchart LR
    DrawnLime[Drawn Lime Spread on Floor] --> Cooling[Cooling Stage]
    Cooling --> Sorting[Manual Hand Picking]
    Sorting --> WellBurnt[Well-Burnt Lime (Accepted)]
    Sorting --> OverBurnt[Overburnt Lime (Rejected)]
    Sorting --> Unburnt[Unburnt Lime (Rejected)]

Fuel Proportions for Charging (Clause 5.4.1):

• Fuel percentages depend on fuel type and required heat.
• Typical proportions:

Fuel Preparation (Clauses 5.2 & 5.2.1):

• Fuel is graded in size.
• Size limits:
  • Max fuel size = half of max limestone size.
  • Min fuel size = half of min limestone size.
• Moistening fuel in warm weather aids handling.

Chemical and Proximate Analysis (Clause 4.1):

• Both limestone chemistry and fuel proximate analysis are important for quality lime.

Fuel Mass Calculation Formula:

[ m_{fuel} = \left(\frac{\text{Fuel %}}{100}\right) \times m_{limestone} ]

flowchart LR
    Limestone[Graded Limestone] --> KilnCharging[Kiln Charging]
    Fuel[Graded and Conditioned Fuel] --> KilnCharging
    KilnCharging --> Calcination[Calcination Process]
    Calcination --> QualityLime[Quality Lime Production]