HORNO MAERZ

Document No. AK685_971.01

Revision 0

Revision Date / saved on 06 January 2014 Author Patrick Ewert Based on template edition 14-1 / MRZTD.DOT

Maerz Ofenbau AG Telefon: +41 44 287 27 27 Richard Wagner-Strasse 28 Telefax: +41 44 201 36 34 CH-8027 Zrich E-Mail: [email protected] Switzerland www.maerz.com

INSTRUCTION MANUAL IM BOOK-1 GENERAL INSTRUCTION & OPERATION

AK685 CALQUIPA S.A.C.

Callalli, Peru

F2S - 300/400 tpd MAERZ finelime kiln (coal / opt.gas)

IM GENERAL INSTRUCTION & OPERATION

AK685_971.01_0 CALQUIPA S.A.C.

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Table of Contents

1 BASIC INFORMATION 9

1.1 About this instruction manual 9

1.2 Terminology 9

1.3 Reference material 9

1.4 Explanation of signs and symbols 10

1.4.1 Signs and symbols used in the manual 10

1.4.2 Safety labels and signs on plant equipment 10

1.5 Liability and warranty 16

1.6 Copyright protection 16

1.7 Transport, Packaging and Storage 17

1.7.1 Safety notes 17

1.7.2 Transport inspection 18

1.7.3 Packaging 18

1.8 Spare parts 19

1.9 Storage 19

1.10 Disassembly 20

1.11 Waste disposal 20

2 SAFETY 21

2.1 General 21

2.2 Responsibility of the plant operator 22

2.3 Intended use 23

2.4 Workers' safety 23

2.5 Personal safety equipment (PSE) 24

2.6 Possible dangers at the plant 25

2.7 Emergency process stop 28

2.7.1 Staff and kiln protection 28

2.7.2 Emergency process stop system 28

2.7.3 Emergency stop switch reset 29

2.8 Operating personnel 30

2.9 Conduct in dangerous situations and in case of accidents 30

2.10 Danger areas 32

2.11 Noisy areas 34



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3 TECHNOLOGICAL PRINCIPLE 37

3.1 Useful literature 37

3.2 Calcination of limestone and dolomite 37

3.2.1 Limestone 37

3.2.2 Formation of limestone 37

3.2.3 Mineralogical composition 37

3.2.4 Impurities 38

3.2.5 Mineral structure and grain size 39

3.2.6 Porosity and density 39

3.2.7 Bulk density and particle size 40

3.2.8 Thermal dissociation of carbonate 40

3.2.9 Mechanical strength and abrasion resistance 41

3.2.10 Data and properties of limestone 42

3.3 Calcination of limestone 43

3.3.1 Thermal decomposition of calcium carbonate 43

3.3.2 Physical-chemical phenomena during calcination 44

3.3.3 Reactivity of quicklime 47

3.3.4 Influence of feed size on retention time 48

3.3.5 Lime to limestone factor 50

3.4 Fuel 51

3.4.1 Definition of calorific values 52

3.4.2 Combustion air volume (vol) 52

3.4.3 Wobbe index 52

3.4.4 Heat flow 53

3.4.5 Fuel data 53

4 DESIGN AND FUNCTIONING (TYPE FS) 55

4.1 Design 56

4.2 Design 58

4.2.1 Parallel-flow firing system 58

4.2.2 Preheating the combustion air 58

4.2.3 Two-shaft kiln 58

4.2.4 Burner lances 59

4.2.5 Reversing devices 59

4.2.6 Charging device 60

4.2.7 Discharge device 61

4.2.8 Hydraulic system 62

4.2.9 Kiln refractory lining 62

4.3 Functional description 63

4.3.1 Special requirements of limestone calcination 63

4.3.2 Process description 63

4.4 Characteristic data 66

4.4.1 Grain size of charged limestone 66

4.4.2 Operating cycles 66



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4.4.3 Heat and mass flow 67

4.4.4 Temperature profile 68

4.5 Kiln control system 69

4.6 Electric switchboard 70

4.6.1 Main components 70

4.6.2 Safety information 73

4.6.3 Additional documents 73

4.7 Local operation panel 74

4.7.1 Main components 74

4.8 Instrumentation 76

4.8.1 General description 76

4.8.2 Arrangement of instruments 76

4.8.3 Wiring diagrams 76

4.8.4 Purpose of the most important measuring instruments 76

5 COMMISSIONING 81

5.1 General information / Definition 81

5.2 Requirements for cold commissioning 82

5.2.1 Consumables 82

5.2.2 Lubricating points 82

5.2.3 Shaft construction 83

5.2.4 Refractory 85

5.2.5 Kiln systems 85

5.2.6 Electrical installations / instrumentation 85

5.2.7 Firing system 86

5.2.8 Waste gas filter 86

5.3 Cold commissioning 87

5.3.1 Suspended cylinder (if existent) 87

5.3.2 Components 87

5.3.3 Software 87

5.3.4 Integration test 87

5.3.5 Charging the kiln with limestone: 88

5.4 Hot commissioning 89

5.4.1 Process adjustments 89

5.5 Conclusion of the commissioning 89



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6 OPERATION 91

6.1 General 91

6.2 Safety 91

6.3 Visualization system 95

6.3.1 Screen layout 96

6.3.2 Color definitions 99

6.3.3 User level 101

6.3.5 Parameter tables 102

6.3.6 Process pictures 105

6.3.7 Alarms 120

6.3.8 Tuning screens 124

6.3.9 Trend messages 125

6.4 Theoretical Basis of Lime Kiln Operation 127

6.4.1 Modes of operation 127

6.4.2 Filling mode 127

6.4.3 Heating mode 128

6.4.4 Production mode charging during reversal time 128

6.4.5 Production mode charging during burning time 129

6.5 Reversal and charging sequences 130

6.5.1 Production mode charging during the reversal time 130

6.5.2 Production mode Charging during burning time 133

6.6 Calculation of the process parameters (sample) 135

6.7 Description of the Operational Procedures 137

6.7.1 Limestone charging 137

6.7.3 Filling the kiln 138

6.7.4 Start-up process 139

6.7.5 Production operation 145

6.8 Preconditions for production operation 147

6.8.1 Basic recommendations 147

6.8.2 Key factors for the lime burning process in the lime kiln 147

6.8.3 Adjustment of the cooling air 147

6.8.4 Setting the Heat Input 148

6.8.5 Adjusting the Air Excess Factor 148

6.8.6 Setting the Fuel Parameters 150

6.8.7 Setting the Reversal Time 150

6.8.8 Setting the Nominal Burn-out Time 150

6.8.9 Setting the discharge tables 151

6.9 Kiln stoppage and restarting 152

6.9.1 Kiln stoppage 152

6.9.2 Restarting 153

6.9.3 Kiln stoppage by an alarm 154

6.9.4 Kiln stoppage in the case of a power cut 155

6.9.5 Emptying the kiln 155



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6.10 Fine Lime Charging 157

6.10.1 Effect on lime quality 157

6.10.2 Distribution system 158

6.10.3 Kiln charging method 158

7 MALFUNCTION 165

7.1 Safety 165

7.2 Steps to be taken in the event of a failure 166

7.3 Alarm systems 167

7.3.1 Failure of machine components 168

7.3.2 Failure of the machine's control system 168

7.4 Restart after failure 169

7.5 Steps for troubleshooting 169

8 MAINTENANCE 175

8.1 In general 175

8.2 Safety 176

8.3 Lubricating instruction 176

8.4 Maintenance schedule 177

8.4.1 Check list 177

8.5 After maintenance 188

9 INDEX 189

IM GENERAL INSTRUCTION & OPERATION Basic information


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1 Basic information

1.1 About this instruction manual

This instruction manual describes the design, start-up, operation, and maintenance of the kiln plant.

Compliance with all safety notes and directives specified is a precondition for safe working with and proper handling of the plant. Furthermore, all specific local accident prevention regulations and general safety rules must be strictly observed.

This instruction manual is an essential part of the product. At least one copy must be kept in the kiln plant control room at all times. It must be accessible to the operating, maintenance, and cleaning personnel.

The illustrations in this manual are meant for better understanding and are not necessarily true to scale. The contents of the manual may vary from the version of the actual plant. For more precise and detailed information, the respective drawings and diagrams must be kept on hand.

In addition, the individual documents and instructions related to the installed components and equipment will apply. Strictly observe the notes contained therein - especially safety notes.

1.2 Terminology

The terms "plant" or "kiln used in this manual refer to the Maerz Parallel Flow Regenerative Shaft Kilns for Limestone and Dolomite.

Some views in this manual, the PI diagrams, as well as other documents and drawings use identifiers and tag numbers to refer to a specific component installed.

The term "operating company" is used to relate to the "plant owner". The term "operator" however is used strictly to refer to the "operating person" to the "kiln attendant".

1.3 Reference material

Unless otherwise specified, the individual components of the kiln plant are purchased from other manufacturers than MAERZ. All components used in the plant have been tested and subjected to risk assessment by the respective manufacturers. The manufacturers of these components have confirmed the compliance of the equipment with applicable European and national regulations.

The declarations of conformity of the manufacturers as well as operating, maintenance, and repair instructions for the various plant components are integral parts of the overall documentation. The directives on safety, setup and installation, operation, preventive maintenance, disassembly and disposal of the components included in the manufacturers' documentation must be strictly observed by all personnel involved.



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1.4 Explanation of signs and symbols

1.4.1 Signs and symbols used in the manual

Important safety and technical notes in this operating manual are marked with symbols. These notes must be adhered to in order to avoid accidents, personal injuries and damage to property.

WARNING

This symbol stands for dangers that can lead to adverse effects on health, injuries, permanent physical damage, or death.

Absolutely adhere to the notes regarding safety at work, and be particularly careful in this respect.

DANGER OF ELECTRIC CURRENT

This symbol draws attention to dangerous situations involving electrical currents. There is the risk of serious injuries or death if the safety notes are not complied with. Any work is to be carried out by qualified electricians only.

CAUTION

This symbol stands for dangers that can lead to adverse effects on health, injuries, or physical damage.

NOTICE

This symbol indicates notes, which if not complied with can lead to damage, malfunctions and/or breakdown of the plant.

INFORMATION

This symbol highlights tips and information to be observed for efficient and trouble-free operation of the plant.

1.4.2 Safety labels and signs on plant equipment

The following table lists all mandatory signs, prohibition, warning, fire, and rescue labels attached to plant equipment.

WARNING

The safety labels below indicate prohibitions, dangers, and directives. Strictly comply with these safety labels. Failure to observe any of them may lead to death, serious injury, or damage to the plant.



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Prohibition labels

Prohibition labels are white and contain a crossed-out black symbol surrounded by a red circle.

Smoking prohibited

Risk of fire caused by combustible or explosive solid, liquid, or gaseous materials.

Do not touch, live housing

Danger caused by electric shock.

Fire, open light, and smoking prohibited

Do not introduce or generate any kind of ignition source, such as:

- open flames and hot gases (e.g. burning candles, matches, welding beads, welding sparks, or gleaming charcoal)

- warm / hot surfaces (e.g. radiators, hot plates, light bulbs, crankcases, exhaust systems)

- frictional heat (e.g. hot bearings)

- mechanically generated sparks (e.g. rock, concrete, metal sparks produced by grinding, abrasive cutting, or hammer strokes)

Fire extinguishing with water prohibited

Water may prove to be unsuitable for extinguishing fires and may further increase the danger caused by fire

Authorized personnel only

Access to the danger area is limited to authorized persons (personnel authorized by the plant operator to enter the danger area).

Do not touch

Containers or parts may become damaged when touched.

Prohibition

Used in combination with another sign specifying the prohibition



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Mandatory signs

Mandatory signs are blue and contain a white symbol.

Wear safety goggles

Wear hearing protection

Wear safety shoes

Wear safety clothing

Wear safety harness

Wear safety hat

Wear breathing mask

Wear safety gloves

Wear face screen

Switch off before beginning work



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Warning signs

Warning signs are yellow and contain a black symbol.

Warning of inflammable materials

Warning of a danger area

Danger of tripping and falling

Warning of gas bottles

Warning of explosive atmosphere

Danger of crushing

Warning of automatic start

Warning of hand injuries

Warning of dangerous voltage

Warning of hot surface

Warning of toxic materials

Warning of chemical burns



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Fire labels

Fire labels are red and contain a white symbol.

Fire hose

Fire fighting equipment

Directional arrow (only to be used in combination with another fire label)

Ladder

Fire alarm box

Fire fighting facility



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Rescue signs

Rescue signs are green and contain a white symbol.

First aid

Stretcher

Eye rinsing facility

Emergency phone

Arrow pointing to first-aid facilities (only to be used in combination with another first aid symbol)

Rescue paths and emergency exits

Emergency path

Emergency path

Emergency exit

Emergency exit

Emergency exit



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1.5 Liability and warranty

All specifications and information used in this instruction manual are provided in consideration of all applicable regulations, the current state of the art, and our long-standing expertise and experience.

For special designs and order-specific configurations or, in the event of technical changes, the actual scope of supply may deviate from the described specifications and provided drawings and sketches. Please contact MAERZ if you have any questions.

INFORMATION

Carefully read this instruction manual before starting any work at or with the plant and, in particular, before first-time operation. MAERZ cannot assume any liability for damage or failures caused by the non-observance of the instructions provided in this instruction manual.

We reserve the right to introduce technical modifications to the product with the intention to improve and further develop the useful properties of the plant.

Components, such as tools that are subject to normal wear and tear during standard operation of the kiln, as well as commodities, such as greases, oils, or detergents, are excluded from the warranty.

The obligations agreed upon in the supply contract, the terms and conditions, as well as the manufacturers terms of delivery, and all legal requirements applicable at the time of conclusion of the contract remain in full effect.

1.6 Copyright protection

The instruction manual is to be treated confidentially. It is exclusively intended for persons working on and with the plant. Leaving the instruction manual to a third party without written approval of the manufacturer is not permitted. Please contact MAERZ in case of any questions.

INFORMATION

The contents, text, drawings, illustrations, and other presentations contained in this manual are protected by copyright and subject to additional commercial property rights. Any misuse is punishable by law.

Copying by use of any type and format even in excerpts as well as the use and/or publication of the contents is not permitted without written approval by MAERZ. Infringements are liable to damage compensation. Additional claims are reserved.



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1.7 Transport, Packaging and Storage

INFORMATION

The installation and initial operation of the kiln must only be performed by employees of the manufacturer or by persons authorized by him to perform such tasks.

However, the installation and further use of the kiln may require that employees of the operator be entrusted with the task of handling packing units. When performing such tasks, make sure to observe the information provided below:

1.7.1 Safety notes

WARNING

Danger of injury!

There is a danger of injury due to falling parts when lifting, swinging, and lowering materials. The machine can be damaged or destroyed by improper transport.

For this reason, basically observe the following safety notes:

Always use appropriate lifting tackle and slinging devices with sufficient carrying capacity.

Only secure the machine on the fastening points provided; do not fasten at projecting machine parts or eyelets of attached components. Make sure the slinging device is secure!

Ropes and belts must be equipped with safety hooks. Do not use torn or worn ropes. Do not lay ropes and belts on sharp edges and corners, do not knot or twist. Pay attention to the centre of gravity of the equipment when fastening the tackle.

Never lift, swing, or lower loads over people.

Always move the equipment with utmost care and attention.

WARNING

Risk of death!

Suspended loads can fall down and lead to severe injuries. Do not stand or pass under suspended loads when transporting with lifting tackle!



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1.7.2 Transport inspection

Check delivered goods immediately on receipt for completeness and transport damage.

Do not accept the delivery or only accept under reserve if there is externally recognizable transport damage. Note the scope of damage on the transport documents/delivery note of the carrier. Start complaints procedure.

Register complaint about hidden deficiencies as soon as they are discovered, as indemnity claims can only be asserted within the applicable time for complaints.

1.7.3 Packaging

INFORMATION

Keep environmental protection in mind!

Packaging materials are valuable raw materials and can continue to be used in many cases, or can be suitably reconditioned and recycled.

If there is no return agreement for packaging, sort materials according to type and size, and route them for further use or recycling.

NOTICE

Always dispose of packaging materials in an environmentally friendly manner and in accordance with the applicable, local disposal guidelines. If necessary, order a recycling company.



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1.8 Spare parts

Use only spare parts authorized by the manufacturer of the relevant equipment.

NOTICE

Wrong or faulty spare parts can lead to damage, malfunctions, or total failure of the plant.

All claims for warranty, service, damage compensation, as well as liability claims against the manufacturer or his representatives, dealers and agents become void when unauthorized spare parts are used.

1.9 Storage

Keep packed goods in this state until installation, and store such items as specified by the externally attached installation and storage information.

Store packing units only under the following conditions:

- Do not keep in the open air.

- Store in dry and dust-free environment.

- Do not subject to aggressive media.

- Protect against direct sunlight.

- Avoid mechanical vibration.

- Storage temperature: 15 to 25C

- Relative humidity: max. 60%

- For longer periods of storage (>3 months), check the general condition of all parts and the packaging at regular intervals. If necessary touch up or renew conservation.

INFORMATION

Refractory magnesite stones may absorb moisture from the surrounding air and chemically react with this moisture. If the stones are stored for more than 3 months, this reaction may cause damage to the magnesite stones, even if the storage information provided above is observed. It is therefore recommended to store impregnated stones only.



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1.10 Disassembly

For disassembly, the plant must be cleaned and dismantled in strict compliance with the applicable industrial safety regulations and accident prevention instructions.

WARNING

Danger of injury!

Stored residual energies, sharp edged components, pointed corners and edges on and inside the plant or on the required tools can cause severe injuries. Any disassembly work on the plant is therefore to be carried out by skilled personnel only.

Before starting disassembly:

- Shut down the plant and secure it against restarting.

- Physically disconnect the complete energy supply from the plant, and properly discharge stored residual energies.

- Dispose of fuels and lubricants as well as residual processing materials in an environmentally acceptable manner.

1.11 Waste disposal

If no agreement concerning retrieval or waste disposal has been made, disassembled components must be passed on for recycling after correct dismantling:

- Metal material residues must be scrapped

- Plastic elements must be forwarded for recycling of plastics

- Other components must be sorted by material properties

NOTICE

Electric scrap, electronic components, lubricants and other auxiliary materials must be treated as hazardous waste and must only be disposed of by specially approved waste disposal companies!

Remove operating materials like greases, oils, preservation agents and detergents from the plant, separate by type, and dispose of in an environmentally responsible manner. In this process, use collection and storage containers that are suitable and approved for the respective operating materials.

Clearly mark containers; provide information about contents, filling level and date, store until final disposal so that improper use is impossible.

IM GENERAL INSTRUCTION & OPERATION Safety


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2 Safety

This section provides an overview of all important safety aspects for optimal protection of personnel against any danger and ensures safe and trouble-free operation of the plant.

In addition, specific notes on safety to avert danger are provided and marked with symbols in the individual chapters.

All pictograms, signs, and labels on the plant are to be strictly observed and kept legible at all times.

2.1 General

The plant has been manufactured according to generally accepted engineering standards applicable at the time of its development, and production and is considered operationally safe. However, the plant may entail dangers, if not used properly or according to its intended purpose by professionally trained personnel. Therefore, any person commissioned to work on or with the plant must have read and understood the Instruction Manual before commencing work. It is recommended that the company operating the plant should request concrete proof that the personnel have taken full knowledge of the instruction manual's contents.

Modifications of any type as well as attachments or changes to the plant without written authorization by Maerz are prohibited.

All safety, warning and operating notes affixed to the plant or any of its components must always be kept legible. Damaged signs or stickers are to be replaced without delay.

Specified settings or ranges of operating parameters must be observed by all means.



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2.2 Responsibility of the plant operator

- Store the instruction manual in the direct vicinity of the kiln and keep it readily available for the erection, operating, maintenance and cleaning personnel at all times.

- Do not operate the lime kiln plant unless it is in proper technical condition and operationally safe.

- Keep safety devices accessible at all times and check proper functioning on a regular basis.

All information regarding safety at work refers to the guidelines issued by the European Union applicable at the time the kiln was manufactured. The plant operator is responsible for ensuring that while the kiln is in operation, the specified work safety regulations comply with the latest updates of all applicable current and future regulations. Outside the territory of the European Union, the plant operator must comply with all work safety laws as well as with all regional laws and regulations applicable at the place of operation.

In addition to the information regarding safety at work specified in this instruction manual, the plant operator must also follow and comply with all regulations regarding general safety, accident prevention, and protection of the environment applicable at the place of operation.

The plant operator and any personnel authorized by him are responsible for the trouble-free operation of the kiln as well as for assigning unambiguous responsibilities with regard to the installation, operation, maintenance and cleaning of the kiln.

The information provided in this instruction manual must be followed in full and without limitation.

The plant operator has the obligation to attach signs limiting access to the kiln to trained and authorized personnel. In accordance with this instruction manual, the plant operator must also attach warning signs or plates at all access points to the kiln, informing of the dangers involved with working at and with the kiln.

The plant operator must provide a sufficient number of fire-fighting equipment inside the kiln area.

The plant operator must equip the personnel working at the kiln with sufficient and suitable first-aid equipment. The personnel must be trained in handling first-aid equipment.

The plant operator must familiarize his personnel with the recommendations provided by the "International Chemical Safety Cards" for handling calcium oxide, fuels, and other dangerous materials, and the personnel must adhere to these recommendations.



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2.3 Intended use

Safety and reliability of the equipment is only guaranteed if it used as intended in accordance with the information provided in the instruction manual.

The intended use of the lime kiln is the production of quicklime in accordance with specifications. The kiln may only be operated with the fuel specified in the chapter Technical Data.

NOTICE

Any use of the system, beyond or different from the intended one, is prohibited and considered not as intended.

Claims of any kind against the manufacturer and/or his authorized representatives resulting from damage caused by use of the kiln not as intended are excluded.

The customer/plant operator is solely liable for any damage caused by a use other than intended.

Intended use also includes correct adherence to erection, operating, maintenance and cleaning instructions.

2.4 Workers' safety

Follow the safety instructions to prevent persons and property from becoming injured or damaged during the operation of the kiln. Failure to observe this information represents a serious risk of injury to the personnel and may cause damage to or the destruction of the kiln, especially if the kiln is operated in an explosive environment.

The manufacturer or his agents shall not be liable for any defects caused by failure to observe these safety instructions.



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2.5 Personal safety equipment (PSE)

Operation, maintenance, troubleshooting/fault elimination/repairs and cleaning work require wearing a personal protective outfit.

The plant operator must make sure that all persons involved in work with or at the kiln have the required protective equipment at their disposal and wear it for work.

Operating persons and expert personnel occupied with work at the kiln are obliged to wear their personal safety equipment before and during work.

In principle, the following items are to be worn when working on or with the plant:

Tight-fitting work clothing

minimal tear strength, no wide sleeves, no rings or other jewellery, etc.

Safety goggles

to protect the eyes against liquids and particles flying about

Face screen

to protect the eyes and the face against flames, sparks, or embers as well as hot particles or emissions

Breathing mask

to protect against inhaling particles or emissions

Safety shoes

to protect against heavy parts being dropped, and slipping on slippery surfaces

Safety gloves

to protect the skin against friction, excoriation, pricking and deeper injuries on the hands and against contact with health affecting substances

Safety helmet

to protect against objects and materials falling down or flying around

Ear defenders

to protect against hearing damage



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2.6 Possible dangers at the plant

The plant has been subjected to risk assessment. The resulting construction and design of the plant correspond to the state of the art. Nonetheless, some risks remain.

The plant works with high pressure hydraulic oil

Any damage to the hydraulic system may result in a strong stream of liquid.

WARNING

Risk of injury

Danger caused by liquids spurting out under high pressure. Wear personal safety equipment when working at the kiln.

The plant works with electrical voltage

DANGER OF ELECTRIC CURRENT

Electrical power can cause severe injuries. There is imminent danger to life and health caused by electrical current if the insulation or individual components are damaged.

- Disconnect the main switch, and secure against switching on again before maintenance, cleaning, or repair work.

- Switch off the power supply before starting work in the electrical system and make sure that the system is dead.

- Do not remove any safety features or do not modify such installations in a way that would affect their function.

The plant works with movable components

WARNING

Risk of injury

Rotating and/or linearly moving components can cause severe injuries. Do not reach with your hands into or touch moving parts during operation. Do not open covers and maintenance flaps.

- Allow components to run out after switching off the plant.

- Before starting cleaning, repair, maintenance, or any other work, wait until all components have stopped, switch off the plant and reliably secure against being switched on again.

- After cleaning, repair, maintenance, or any other work, close and lock all covers, maintenance flaps, etc.



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The plant comprises pneumatic components

WARNING

Risk of injury

Pneumatic energies can cause severe injuries. In case of damage to individual components, operating media can escape under high pressure and cause injuries and material damage.

Therefore:

- Always relieve the system from any pressure before starting work on pneumatic equipment.

- Do not remove or inhibit any safety facilities.

- Do not adjust pressure levels beyond the limits specified in the instruction manual.

The plant has sharp edges and corners

CAUTION

Risk of injury

Sharp-edged housing parts and sharp corners can cause grazes on the skin. Wear protective gloves when working at the plant.

The kiln works with powerful fans

WARNING

Risk of injury

The fast-running impeller installed inside the blower may cause serious injuries such as cutting or severing of body parts. Therefore:

- Do not operate the blowers, unless the impeller cage, protection caps, and maintenance covers are closed.

- Prior to performing any work at the blower, shut down the unit, secure it against re-starting, and keep it closed until all running components have come to a complete stop.

- Do not open the impeller cage, protection caps, and maintenance covers until the impeller has come to a complete stop. Afterwards, secure all moving components against uncontrolled movements by appropriate means such as clamping.



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Operation of the kiln may release highly flammable materials

WARNING

Risk of injury

Highly flammable materials, liquids, and/or gases might catch fire and cause serious injuries.

- Smoking, handling open light, fire, and/or sources of ignition of all kinds in the vicinity of the kiln and within a distance of 5 m or less is strictly prohibited.

- Locate any suspicious materials, liquids and gases, and notify your superior without delay.

- Stop working immediately. Leave the danger zone, until the all-clear is given.

The kiln works with CaO (quicklime)

WARNING

Risk of chemical burns caused by CaO

There is a risk of sustaining chemical burns in places labeled accordingly.

Any person working inside these areas must proceed with great caution when handling caustic materials.

In addition to the danger of damaging one's clothing, there is also the risk of burning one's eyes, skin and possibly one's mucous membranes. Burning ones eyes may cause irreparable visual impairment.

When handling caustic materials, wear personal safety equipment as required by the Chemical Safety Datasheet.

The plant operator must keep available at all times rinsing liquids for cleaning eyes.

When burnt lime is mixed with water it reacts by generating a lot of heat and thus becoming leach.

The kiln works under high pressure

WARNING

Risk of injury

The kiln is operated under pressure. Flames or hot gases may spurt out when any access or inspection doors are opened. The high pressure inside the kiln may cause the kiln doors to fly open with great force.

Do not open the kiln doors until the pressure difference between the inside and the outside of the kiln is zero.



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2.7 Emergency process stop

2.7.1 Staff and kiln protection

To protect the kiln and the staff working at it, the kiln is equipped with an emergency process stop system comprising emergency process stop buttons and safety locks.

The emergency process stop system is a category 1 system with one-channel disconnection. The emergency process stop and safety features of the kiln control system are fully integrated into this emergency system, which is equipped with its own controller.

The operating, cleaning, service and maintenance personnel must be instructed about the location and the functionality of the safety devices on a regular basis. Proof of such instruction must be provided upon request.

2.7.2 Emergency process stop system

The entire emergency process stop system consists of an emergency process stop sequence. This means that as soon as the emergency process stop button has been pushed or the safety lock has been engaged, the entire kiln will immediately be set to a safe operating mode.

The safe operating mode is either achieved by immediately interrupting the power supply to the drives, by shutting down the drives until they have come to a complete stop, or by moving them into a safe position until the power is cut off with a delay.

For kilns with suspended cylinders

NOTICE

The operating process requires the cooling system of the suspended cylinders to continue to run, even if the emergency process stop function has been activated.

Do not turn off the cooling system of the suspended cylinders as otherwise the suspended cylinders, and consequently the kiln, may become heavily damaged.

In the event of a failure of the cooling system of the suspended cylinders, activate the emergency cooling system without delay.

If the operation of the cooling system for the suspended cylinders poses a danger to the kiln operating person, immediately shut down the kiln by pushing the emergency process stop button. However, make sure to manually activate the emergency cooling system directly after shutting down the kiln.



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2.7.3 Emergency stop switch reset

WARNING

Risk of injury

Any uncontrolled re-starting of the kiln may cause serious personal damage.

Prior to re-starting the kiln or any of its components, check whether the cause of the emergency process stop has been eliminated, and make sure that all safety devices have been re-installed and are properly functioning.

After having successfully reset the triggered contact (e.g. by rotating and unlocking the emergency process stop button), proceed by acknowledging the emergency process stop.



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2.8 Operating personnel

The kiln may only be operated and maintained by authorized, qualified and instructed personnel. These personnel must have received special instructions regarding any dangers that may occur.

Instructed personnel have been taught about the tasks entrusted to them and the possible dangers resulting from improper actions, and if necessary, have been instructed practically in this respect. Moreover, the personnel have been informed of the required protective features and protective measures.

Qualified personnel are persons who can assess the work entrusted to them and recognize potential dangers based on their special training, expertise, and experience as well as on their knowledge of appropriate conditions.

If staff members do not have the necessary knowledge, they are to be trained accordingly.

Responsibilities for operation and maintenance must be clearly determined and adhered to so that there is no unclear division of competence with regard to safety.

The kiln may only be operated and maintained by persons who can be expected to carry out their work reliably. This means that any mode of operation that affects the safety of persons, of the environment or the kiln is to be avoided.

Persons who are under the influence of drugs, alcohol, or medication that affects their responsiveness may under no circumstances carry out work on or with the kiln plant.

When selecting personnel, attention must be paid to the regulations protecting young workers in the relevant country regarding the minimum age and, if necessary, to the job-related instructions based on this.

The operating company must ensure fully that only authorized persons work on or with the kiln plant.

All non-authorized persons, such as visitors etc., must at any time be kept at an appropriate safety distance to the kiln and any of its ancillary equipment.

The operating personnel are obliged to immediately report to the plant operator or his representative any safety-relevant incidents in kiln operation.

2.9 Conduct in dangerous situations and in case of accidents

Always be prepared for accidents or fire.

In a dangerous situation or in case of an accident, stop the kiln by immediately activating the EMERGENCY PROCESS STOP SWITCH.

The EMERGENCY PROCESS STOP SWITCH may only be operated in emergency situations and must not be used for normal kiln stops.

Keep first-aid equipment (first-aid kit, eye rinsing bottle, etc.) and fire extinguisher close to hand.

Personnel must be acquainted with the location and handling of safety equipment, accident reporting facilities, first-aid and rescue equipment. This will enable them to avert dangers and provide the best possible help in case of accidents.



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2.10 Danger areas

Fig. 1 Danger areas (typical)



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Item Description

1 Reversal flap (filter / direct chimney)

2 Reversal flap (combustion air / waste gas)

3 Shaft closing flap

4 Thermal radiation and heat on kiln shaft

5 Access doors and inspection openings to kiln

6 Lime belt conveyor

7 Lime vibrating feeder

8 Lime discharge hopper

9 Discharge flap

10 Discharge table

11 Air blast unit (not shown)

12 Poking hole

13 Emergency venting for suspended cylinder cooling system

14 Relief flap combustion air (not shown)

15 Stone distribution flap

16 Rotating bucket

17 Reversible belt conveyor

18 Limestone vibrating feeder

Additional danger areas (not shown)

Hydraulic unit and hydraulic system

Blowers and ventilators

Limestone belt conveyor

Waste gas filter

All stairs and platforms



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2.11 Noisy areas

Fig. 2 Noisy areas (typical)



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Item Description ~LAeq [dBA]

1 Chimney exit 80

2 Reversal flap 70

3 Relief flap combustion air (not shown) 105

4 Relief flap cooling air (not shown) 95

5 Lime vibrating feeder 90

6 Discharge flap and hopper 90

7 Discharge table 85

8 Emergency fan for suspended cylinder 100

9 Air blast unit (not shown) 95

10 Emergency venting suspended cylinder cooling system 100

11 Kiln charging 95

12 Rotating bucket 105

13 Limestone feeder 95

14 Stone hopper 105

Additional noisy areas (not shown)

Description ~LAeq [dBA]

Hydraulic unit 90

Blower house internal 110

Blower house external 75

Transport system for limestone and lime 105

Waste gas filter 85

IM GENERAL INSTRUCTION & OPERATION Technological Principle


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3 Technological Principle

3.1 Useful literature

- Boynton, R.S., "Chemistry and Technology of Lime and Limestone" John Wiley &. Sons, 1980, ISBN 0-471-02771-5.

- Oates, J.A.H., "Lime and Limestone" Wiley-VCH, 1998, ISBN 3-527-29527-5

- European Commission, "Integrated Pollution Prevention and Control (IPPC)" - Reference Document on Best Available Techniques in the Cement and Lime Manufacturing Industries (adopted Dec 2001)

- Schiele, E., Berens L.W., "Kalk Herstellung, Eigenschaften, Verwendung" (in German), Stahleisen m.b.H., 1972, ISBN 3-514-00115-4

3.2 Calcination of limestone and dolomite

3.2.1 Limestone

Limestone is found widely throughout the world and is an essential raw material for many industries.

3.2.2 Formation of limestone

Limestone is one of the most widely distributed sedimentary rocks throughout the world. Commercially used limestone is mainly of organic origin. Deposits were formed by the building-up of fossiliferous marine sediments in oceans consisting of shells and skeletons of plants and animals. Some of these sediments were deposited by natural chemical reaction. Calcium bicarbonate was produced by the extremely slow dissolution of calcium carbonate fossils through the solvent action of carbon dioxide, which was subsequently re-precipitated in carbonate form. Layer by layer of these deposits form massive beds of limestone.

3.2.3 Mineralogical composition

Limestone and dolomite can be composed of the following four minerals, characterized by the following physical data:

Chemical formula

Molecular weight

Specific gravity [g/cm

3]

Hardness

[Mohs Scale]

Crystal system

Calcite CaCO3 100.1 2.71 3.0 rhombohedral

Aragonite CaCO3 100.1 2.94 3.5-4.0 orthorhombic

Dolomite CaMg(CO3)2 92.2 2.84 3.4-4.0 rhombohedral

Magnesite MgCO3 84.3 3.00 5.0-4.5 rhombohedral

Dolomite and calcite play the main role as industrial minerals.

- Pure limestone (calcite and aragonite) is 100% calcium carbonate.

- Pure dolomite contains 54.3% CaCO3 and 45.7% MgCO3 (30.4% CaO, 21.8% MgO, and 47.8% CO2).



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INFORMATION

Limestone and dolomite used for industrial purposes include:

- Pure calcite with 9799% CaCO3

- Pure dolomite with 4043% MgCO3 and 5760% CaCO3

Impurities in these limestone and dolomite rocks are usually between 1 and 3%.

3.2.4 Impurities

Impurities in limestone are classified as homogeneous and heterogeneous.

Silica and alumina

- Homogeneous impurities such as clay, silt, sand, and other forms of silica like quartz are well dispersed throughout the formation.

- Heterogeneous impurities, which are found, for example, as siliceous pieces or nodules of sand, chert or flint are loosely embedded in the limestone.

Iron

- The third major impurity is homogeneously distributed after the limestone has started to form iron carbonate by chemically replacing calcium with iron. This frequently occurs in oolitic limestone.

- It is heterogeneously distributed as iron sulphide or iron oxide in minerals like pyrite, limonite, and hematite.

Phosphorous and sulphur

- They usually occur only in small quantities.

Manganese, copper, titanium

- These and further impurities are virtually negligible and considered as trace elements in the pure stone.



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3.2.5 Mineral structure and grain size

Limestone is crystalline. The grain size (to be distinguished from particle size) increases with the amount of re-crystallization that has occurred during the formation of the deposit.

The crystalline structure varies greatly in density and hardness.

Micro 250 10-6 m (up to about 1000 10-6 m)

The particle shape depends partly on the microstructure of the grain, but also on the crushing characteristics of the crushing machine.

NOTE

Cubic or spherical shapes of limestone particles are usually preferred for lime kilns.

Avoid processing layered or flat limestone particles whenever possible.

3.2.6 Porosity and density

The porosity of limestone particles varies considerably depending on the degree of compaction and structure of the limestone. It is defined as the ratio of the void volume Vv and the total volume Vtot. The void volume Vv comprises both accessible and inaccessible pores. The figure below illustrates different kinds of pores.

Fig. 3 Different kinds of pores (typical)

Item Description

1 solid pore

2 inaccessible pore

3 accessible pore

Density is defined as the ratio of mass m and volume V of a particular particle.

The solid or specific density (D) considers the volume of the pure solid without any void volume.



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The apparent density (Ds) considers the volume of the solid with the inaccessible space.

The apparent porosity (Ps) describes the accessible volume as the difference of that part of the specific density minus the apparent density with the amount of inaccessible space.

1001

D

DP ss

Ps = Apparent porosity [%]

Ds = Apparent density

D = Specific density

Some data regarding apparent porosities and apparent densities of commonly used types of limestone is provided in the table below.

Industrial limestone shows a wide range of apparent porosities (0.1 to 40%) and densities (1.50 to 2.90 g/cm3) caused by the different forming conditions and levels of re-crystallization.

Apparent porosity [%] Apparent density [g/cm3] dried at 110 C

Dense limestone 0.1 to 3.0 up to 2.7

Marble 0.1 to 2.0 2.7 to 2.8

Chalk 15 to >40 1.5 to 2.3

3.2.7 Bulk density and particle size

Bulk density is the mass per unit volume of a solid, including the voids in a bulk sample of the material.

Bulk density depends largely on the apparent density of the limestone, its particle size distribution, and on the particle shape.

Crushed, screened limestone with a size ratio of 2:1 generally has a bulk density of 1.3 to 1.6 g / cm3.

Crushed, unscreened limestone has a bulk density of 1.6 to 1.75 g / cm3.

3.2.8 Thermal dissociation of carbonate

Thermal dissociation is the most important characteristic of limestone.

All carbonate rocks dissociate at high temperatures, forming oxides and CO2 gas.

For example:

CaCO3 + heat = CaO + CO2

The dissociation temperature of commercially attractive limestone ranges between 896 and 910C (at a partial CO2 pressure of 100 kPa).

The dissociation heat of calcium carbonate is about 3180 kJ/kg of CaO at 25C. This value is mainly influenced by the purity of the lime and the impurities affecting the quality of the lime. The dissociation temperature varies considerably with the chemical composition.



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The dissociation temperature may be reduced by several hundred degrees due to higher amounts of impurities, such as SiO2, Al2O3, and Fe2O3 in the limestone. The effect of SiO2 (silica) is shown in the following figure.

Fig. 4 p,t diagram of the CaO-SiO2 system (typical)

Curve Element Temperature range

1 CaCO3 + SiO2 400590 C

2 CaCO3 + 2CaOSiO2 400750 C

3 CaCO3 650890 C

3.2.9 Mechanical strength and abrasion resistance

Pore volume and pore distribution give the limestone a specific structure, which results in different apparent densities. They have a direct influence on the mechanical properties of the limestone.

Mechanical strength and abrasion resistance of the limestone must be sufficiently high to avoid breakage. Breakage of limestone particles during handling or passage through the kiln causes the generation of fine lime and compresses the stone packing in the kiln. The gas flow and heat transfer may thus be adversely affected causing downgrading of the quality of the quicklime (also see Influence of feed size on the retention time in this chapter).

The compressive strength varies from 10 MPa for some types of marl and chalk to 200 MPa for some types of marble.

INFORMATION

The compressive strength of limestone to be burnt in a Maerz lime kiln should generally not be lower than 30 MPa.



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3.2.10 Data and properties of limestone

The following table lists some fundamental data and properties of limestone.

Properties Data

Expansion coefficient 5 x 10-6 K-1 at 20C. Total expansion of limestone during heating up from 20 to 800C is approx. 2-2.5%.

Thermal conductivity Limestone at 130 C

Dolomitic limestone at 123 C

1.6341 W / mK

1.4246 W / mK

Integrated specific heat

CaCO3

at 100C

at 800C

CaO

at 100C

at 800C

[kJ / Kg C]

0.874

1.104

0.786

0.887

[kcal/kg C]

0.209

0.264

0.188

0.212

Strength

Compressive strength:

Shear strength:

Tensile strength:

10 200 MPa

5 20 MPa

2 7 MPa

Chemical properties Limestone and dolomite are unaffected by CO2-free water. Decomposition can only occur at very high temperatures or by reaction with strong acids.



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3.3 Calcination of limestone

Carbonate rocks decompose at high temperatures releasing gaseous CO2 and convert into calcium oxide and/or magnesium oxide. Depending on the process temperature, a range of products from soft-burnt to hard-burnt lime can be produced.

The Maerz lime kiln is designed to primarily produce soft-burnt lime. Therefore, this manual focuses on the production of soft-burnt lime obtained from high-purity limestone.

By appropriately adapting kiln design and operating mode, the Maerz lime kiln is also suitable for burning dolomite.

3.3.1 Thermal decomposition of calcium carbonate

The thermal decomposition of CaCO3 into CaO and CO2 is an endothermic reaction.

CaCO3 + heat = CaO + CO2

It starts at about 810C with surface calcination and is completed at about 900C at a partial CO2 pressure of 100 kPa.

In order to produce 1 kg of CaO, approximately 3180 kJ of energy are required.



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3.3.2 Physical-chemical phenomena during calcination

During heating-up, the limestone passes several stages of physical-chemical and thermo-mechanical phenomena.

The chemical reaction of calcination starts at the surface of the limestone particle and moves into the core with the progress of reaction. Mechanisms of mass and heat transport take place in parallel during this process.

The physical-chemical phenomena may be described, in principle, by the 5 steps represented in the figure below.

Fig. 5 Processes during calcination (typical)

Item Description

1 Heat transfer by convection and radiation from the surrounding area to the surface of the limestone particle.

2 Heat transfer through the already calcined lime zone.

3 The heat is absorbed by the chemical reaction at the lime-limestone interface on the way into the core. The limestone decomposes into lime and CO2.

4 The generated CO2 diffuses from the centre to the surface of the particle.

5 The CO2 is released from the particle surface into the surrounding atmosphere.

The diameter and density of the particles have a strong influence on the speed for these mechanisms.



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With increasing process temperature, the physical properties (especially the volume of the limestone crystals) change through the different stages of calcination. The figure below visualizes these steps by means of a cubical sample.

Fig. 6 Stages of limestone decomposing to lime during calcination (typical)

Item Description

1 When heating up from room temperature to calcining temperature the limestone expands.

2

3 After surface calcination has begun, the pore volume of the surface zone increases while the volume of the sample remains more or less constant.

4 After calcination is completed, the sample has reached the maximum porosity, but the volume of the sample remains unchanged.

5 When temperature and calcining time are further increased, the lime crystals will start to sinter. The pore volume and the sample volume will decrease.

The strong decrease of the pore and sample volume at high temperatures is caused by crystal growth. Fig. 5 below shows different apparent densities of quicklime which was calcined at different temperatures and over periods ranging from about 3 to 30 hours.



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Fig. 7 Apparent density of quicklime varying with temperature and time, produced from dense, high-calcium limestone (typical)

Item Description

1 1400C

2 1300C

3 1200C

4 1200C

5 1000C

In Fig. 6 below, structures of quicklime with different apparent densities are shown in three scanning electron micrographs.

Fig. 8 Scanning electron micrographs of quicklime (typical)

Item Density

1 1.5 g / cm3

2 1.9 g / cm3

3 2.3 g / cm3



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3.3.3 Reactivity of quicklime

The reduction in pore volume notably reduces the specific surface area of the quicklime and causes a strong decrease in reactivity.

Quicklime with many pores has a high affinity to water. The reaction with water is exothermal, causing the release of hydration heat, which may be measured as an indicator for the reactivity of quicklime. Other test methods are mentioned in the following figure. The reference values given in Fig. 7 below only apply to the specific limestone examined and may differ from values applicable to different types of limestone.

Fig. 9 Relationship between reactivity testing methods used for quicklime (typical)

Item Description

1 BS 6463 [C] after 2 min.

2 EN 459-2 t60 [min] - time to reach 60C

3 EN 459-2 tu [min] - time for 80% slaking

4 ASTM C110 [C] - temperature rise after 30 s

5 ASTM C110 [C] - maximum temperature rise

6 ASTM C110 [min] - time to maximum temperature

7 Acid titration [ml] after 3 min.





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Fig. 10 Relationship between reactivity (BS 6463) and apparent density of quicklime (typical)

Due to the influence of the pore volume, the reactivity of quicklime is indirectly proportional to the apparent density.

3.3.4 Influence of feed size on retention time

The size of particles fed to the kiln influences the retention time required for the calcining process.

Fig. 9 below shows that bigger particle sizes need more retention time in the kiln than smaller ones at a given process temperature.

INFORMATION

The figure may be used as a guideline for adjusting the burning time to the particle size of the stone.



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Fig. 11 Calcining times for spheres of dense limestone (typical)

Item Description

1 15 cm

2 12.5 cm

3 10 cm

4 7.5 cm

5 5 cm

6 2.5 cm

The influence of particle size and temperature on the calcining and sintering mechanisms leads to the important issue of heat distribution in the kiln. The distribution of open voids in the limestone package must be optimized to allow for uniform gas flow and efficient heat transfer.

A lime shaft kiln has to be designed in such a way that the heat is evenly distributed over the whole shaft cross-section. Areas with a high ratio of fine particles can cause heat stagnation, which will result in local overheating. The particles in this area will be overheated, which may lead to an inappropriately high apparent density and possibly even to sintering and/or fusion.

The right particle size distribution of the limestone feed, the kiln type, and the kiln operation procedure are closely related, and only an optimized concept will result in optimal quicklime quality.



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Summary

Heat distribution, temperature, and retention time influence the properties of the produced quicklime.

Three categories of particle types may be discharged from the kiln:

- not fully calcined

- just fully calcined

These two categories of particles have a low apparent density and a high reactivity with water.

- different grades of calcining/sintering

In this case, the particles have an increased apparent density and a reduced reactivity with water.

3.3.5 Lime to limestone factor

Calculation based on dry limestone:

AORMgOCaO

ORMgOCaO

COLimestone

Lime

32

32

2 )092.2()785.1(100

100

CO2 [%] Residual CO2 content in burnt lime

CaO [%] CaO content in burnt lime

MgO [%] MgO content in burnt lime

R2O3 [%] Impurities in burnt lime

Calculation based on wet limestone:

100

)-100( moistureA

Limestone

Lime

Moisture [%] Water content of limestone related to dry limestone



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3.4 Fuel

Different heating systems burning solid, liquid or gaseous fuels are available for the lime kiln. Quality and type of fuel have a considerable impact on the quality of the quicklime produced. In limestone calcination, fuel is more than just a heat source. The fuel interacts with the process and the combustion products, which in turn react with the quicklime.

In the kiln, fuels such as coal, lignite, petcoke, light and heavy fuel oils, low calorific fuels, lean gas, natural gas, as well as combinations of these fuels are used. The selection of the right fuel requires experience and the consideration of numerous parameters.

The most important parameters are listed in the following table.

Properties Remarks

Costs Fuel costs represent 40 to 70% of the production cost.

Calorific value The calorific value is linked to the costs of fuel per unit.

Moisture Solid fuels have to be dried to prevent them from sticking together during dosing and transport to the lances.

Sulphur About 70% of the fuel sulphur is absorbed by the quicklime forming calcium sulphate. The sulphur retained in the quicklime may affect the quality of the product.

Particle size The particle size of solid fuels influences combustion time and thus production time.

Volatile components

The combustion properties of solid fuels vary with the amount of volatile components and moisture. Consequently, the calorific value and the shape of the flame may change. Volatile components lead to the release of energy, whereas moisture consumes extra energy for vaporization.

Ash

Ash generally contaminates the lime to some degree with silica, alumina, and iron oxide. This may cause the lime lumps to stick together. The pressure on the lime lumps in the charge may enhance this bridging effect. The mixture of ash, lime dust and/or alkali (sodium and potassium) form low-melting mineral stages at the surface of the limestone particles. High amounts of ash may increase the danger of clogging caused by the effects of sintering (bridging) and the formation of low-melting stages.



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3.4.1 Definition of calorific values

Lower calorific value (LCV)

The lower calorific value is the heat available after complete combustion of 1 kg or 1 m3n of fuel and cooling down of the combustion products to start-up temperature.

The LCV is defined by excluding the latent heat produced by the condensation of water in the waste gas.

Higher calorific value (HHV)

This value is the lower calorific value plus the latent heat produced by the condensation of water in the waste gas. Since the water in the waste gas is usually in the steam phase, the vaporization heat cannot be regained.

Fuel Lower calorific value [LCV] Higher calorific value [HCV]

[MJ/kg] or [MJ/m

3n]

[kcal/kg] or [kcal/ m

3n]

[MJ/kg] or [MJ/m

3n]

[kcal/kg] or [kcal/ m

3n]

Hard coal, anthracite, coke

28 33 6500 8400 28 35.5 6760 8500

Dry wood dust 18 4300 19.3 4600

Fuel oil class S 40.5 9680 43.1 10290

LPG (~30% propane ~70% butane)

92.9 22190 101.2 24181

Natural gas 35.9 8570 39.8 9510

Lean gas 17.9 4275 20.1 4800

3.4.2 Combustion air volume (vol)

The lime kiln burns fuels using combustion air. The required combustion air volume (see tables under 1.3.5) considering any excess or deficiency factor must be entered into the combustion calculation program of the lime kiln.

3.4.3 Wobbe index

For gaseous fuels, e.g. coke oven gas, containing tar or other impurities, the installation of an orifice plate to measure the gas flow is required. In order to compensate for varying gas densities, the Wobbe index is added to the formula used for calculating the heat flow.

Analogously to the calorific value, the Wobbe index is expressed as Ws and Wi.



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The Wobbe index considers the ratio between the calorific value and the relative density of the gas.

AirGas

HW

/

W Wobbe index

H Calorific value

Gas Gas density

Air Air density

3.4.4 Heat flow

The heat flow is calculated as follows:

Heat flow [kJ / h] = gas volume [m3 / h] Wobbe index [kJ / m3]

3.4.5 Fuel data

Solid fuels

Fuel Average composition (% by weight)

Vola-tiles

Lower calorific value

Required combustion air

C H O N H2O S LCV vol

[%] [kcal/kg] [MJ/kg] [m3n/Mcal] [m

3n/MJ]

Wood 50.4 6.2 43.3 0.1 11 0 75 4300 18.02 1.09 0.2603

Lignite (Rheinbraun) 58.5 4.3 21.0 0.7 11 0.35 46 5278 22.1 1.09 0.2606

Bright burning coal 84.0 5.5 8 1.5 11 1.0 35 8100 33.94 1.08 0.258

Hard coal 88.0 5.0 4.5 1.5 11 1.0 25 8350 34.99 1.09 0.2603

Forge coal 90.0 4.5 3.0 1.5 11 1.0 15 8450 35.41 1.09 0.2603

Anthracite 91.5 3.8 2.2 1.5 11 1.0 10 8425 35.30 1.08 0.258

Coke 96.7 0.6 0.6 1.1 11 1.0 0 7870 32.98 1.12 0.2675

Petcoke 89.7 3.6 0.6 0.6 11 5.5 10.7 8240 34.5 1.10 0.2627

Liquid fuels

(Table valid for sulphur contents up to 2.5%)

C/H Number Density Lower calorific value Required combustion air

d LCV vol

[g/cm3] [kcal/kg] [MJ/kg] [m

3n/Mcal] [m

3n/MJ]

Fuel oil L (light) 6.7 0.86 10150 43 1.099 0.2625

Fuel oil S (heavy) 7.8 0.96 9680 40.5 1.103 0.2634

6.5 0.843 10052 42 1.096 0.2618

7 0.889 9906 41.5 1.098 0.2623

7.5 0.935 9760 41 1.102 0.2623

8 0.981 9614 40 1.108 0.2646

8.5 1.026 9468 39.6 1.114 0.2661



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Gaseous fuels

Fuel Lower calorific value Average composition (% by volume) Required combustion air

LCV CO H2 CH4 CnHm CO2 N2 O2 HHC* vol

[kcal/m3n] [MJ/m

3n] [%]

[m3n/

Mcal] [m

3n/MJ]

Carbon monoxide CO

3021 12.64 100 0.79 0.1887

Hydrogen H2 2572 10.76 100 0.93 0.2221

Methane CH4 8556 35.80 100 1.12 0.2675

Ethane C2H6 15370 64.31 100 1.09 0.2603

Propane C3H8 22363 93.57 100 1.07 0.2556

Butane C4H10 29280 122.51 100 1.06 0.2532

Liquefied petroleum gas (LPG) ~30% propane ~70% butane

27366 114.5 100 1.06 0.2532

Russian natural gas

8915 37.30 93.3 4.9 1.1 0.8 1.109 0.2649

Groningen natural gas (NL)

7552 31.6 81.4 3.2 0.8 14.1 1.109 0.2649

Blast furnace gas

750951 3.143.98 2430 12 1921 5657 0.8 0.1911

Coke oven gas

4275 17.9 8.6 51.4 25.9 2.7 8.1 0.3 3.0 1.027 0.2453

HHC* = Heavy Hydrocarbons

IM GENERAL INSTRUCTION & OPERATION Design and Functioning (Type FS)


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4 Design and Functioning (Type FS)

Mandatory reference material

This chapter contains general and typical information. For details, dimensions as well as to determine and locate a specific component, reference to diagrams and drawings is mandatory. The complete reference list is included in the Appendix.

Items required with this chapter

- 010 Steel binding - assembly

- 059 Poking door with measuring point

- 154 Protection tubes for measuring points

- 178 Stone distributor

- 192195 Installation of limit switches

- 500 Hydraulic scheme + 502 list of material

- 510 Firing system: Liquid fuel (if applicable)

- 520 Firing system: Natural gas (if applicable)

- 530 Firing system: Lean gas (if applicable)

- 540 Firing system: Solid fuel (if applicable)

- 550 Compressed air scheme

- 600 PI Diagram

- 603 Configuration control system

- 611 Installation: Electrical equipment

- 612 Installation: Measuring equipment

- 640 Instrument list

- 641 Motor list

- Electrical documentation / Manufactures documentation

- Instruction Manual Book-02, Specific Data & Component Description

Technical data

Important benchmark figures and performance data can also be found in chapter Technical Data at the beginning of this of Book-02.



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4.1 Design

Fig. 12 Overview



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Item Description

1 Reversal flap filter / direct chimney

2 Reversal flap combustion air / waste gas

3 Reversible conveyor belt

4 Rotating bucket

5 Shaft closing flap

6 Lance cooling air duct

7 Combustion air duct

8 Kiln door

9 Discharge hopper

10 Lime vibration feeder

11 Discharge flap

12 Cooling air duct

13 Discharge table

14 Crossover channel

15 Suspended cylinder

16 Ring channel

17 Kiln shaft

18 Burner lances

19 Level indicator

20 Stone distributor

21 Stone distributor - swivel-mounted

22 Limestone vibration feeder

23 Kiln hopper



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4.2 Design

4.2.1 Parallel-flow firing system

The parallel-flow firing system yields ideal burning conditions.

The flame moves in the same direction as the charge, providing the maximum temperature difference at the beginning of calcination in the burning zone.

The flame pattern ensures a minimum temperature at the end of the calcination process in order to protect the smaller particles in the charge from over burning.

4.2.2 Preheating the combustion air

The regenerative preheating of the combustion air provides a thermodynamic advantage. The stone preheating zone acts as a regenerator for preheating the combustion air produced by the excess heat of the waste gas. The limestone itself temporarily stores the heat. This regenerative process is completely insensitive to dust-laden or corroding gases while providing excellent heat transfer characteristics.

Regenerative preheating of combustion air makes the kiln virtually independent of the excess combustion air factor. This considerably simplifies setting the correct length of the flame, as a large volume of excess air produces a shorter flame while a smaller volume of excess air produces a longer flame.

4.2.3 Two-shaft kiln

The regenerative system and the parallel-flow firing system demand a kiln with two shafts (1 and 2). The two shafts alternate their firing and regenerative functions at intervals. The connecting channel between the shafts is located near the bottom end of the burning zone. At this point, the kiln gases flow from the combustion shaft to the regenerative shaft.

Fig. 13 Top view: definition of shaft number

Item Description

1 Kiln shaft

2 Combustion air pipe



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4.2.4 Burner lances

Fuel is fed from a main system through a number of steel lances and is evenly distributed over the cross-section of the burning shaft. The lances enter the shafts at the upper, cooler part of the preheating zone and are freely suspended into the vertically descending charge.

In addition to housing them, the regenerative shaft also flushes air through the lances to cool and protect them from dust.

The amount of fuel entering the lances of the firing shaft is regulated by means of a valve system that ensures even distribution to all lances.

4.2.5 Reversing devices

Periodically switching from the burning to the non-burning shaft (regenerative shaft) requires reversing devices for fuel, combustion air, and waste gas. All reversal processes are controlled automatically.

The reversal processes are steered automatically.

The supply of the combustion air, alternatively the waste gas, is steered by a hydraulic cylinder.

Positions of the reversal flap

Regenerative shaft (secondary shaft) waste gas pipe is open

Burning shaft (primary shaft) combustion air pipe is open

Fig. 14 Combustion air / waste gas reversal (typical)

Item Description

1 Regenerative shaft

2 Burning shaft



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4.2.6 Charging device

The constant and accurate throughput required by a kiln of such great thermal efficiency is provided by the charging and discharging device. With each charging sequence, a scaled quantity of limestone is released into the shaft. This cold stone will absorb the excess heat from the waste gas. The number of charges per hour and the duration of the heating period are adjusted according to the corresponding production parameters. Charging starts with the kiln hopper (1) above the charging platform. From here a vibration feeder (2) serves the limestone onto a reversible conveyor belt (3). The conveyor will now fill one of the rotating buckets (4) alternately. These buckets will charge the kiln shaft, distributing the stone appropriate and evenly via the stone distributor (5). The filling level of the shaft itself is observed and maintained by the signal of the level indicator.

Fig. 15 Charging device (typical)

Item Description Item Description

1 Kiln hopper 4 Rotating bucket

2 Vibration feeder 5 Stone distributor

3 Reversible conveyor belt



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4.2.7 Discharge device

Calcined lime is continuously discharged from the shafts by means of hydraulically operated discharge tables (1). The rate of discharge is automatically controlled by the kiln control system according to the level of stone measured in the preheating zone.

The moving discharge tables (1) are located under the cooling zone of each shaft. The tables feed a hopper, located below and collecting the calcined lime discharged during each burning period. The cooling air enters through this receptacle and flows to the shaft via the lime embankments on the discharge tables. Because of the high pressure inside the kiln, the area is sealed off by airtight, hydraulically operated discharge flaps (2). During each reversing period, the discharge flaps will open to allow the lime to drop into a pressure-free discharge hopper (3) equipped with a vibrating feeder (4) for final discharge.

Fig. 16 Discharge device (typical)

Item Description Item Description

1 Discharge table 3 Discharge hopper

2 Discharge flap 4 Vibrating feeder



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4.2.8 Hydraulic system

Most flaps inside the air supply pipes, the reverse flaps, and the charging and discharging devices are all operated hydraulically. A hydraulic system is provided because it can generate great force by means of small components. It is also safe and requires only minimum servicing.

4.2.9 Kiln refractory lining

The preheating and cooling zones are lined with abrasion-resistant fire bricks. Due to combustion with preheated air and the high cross-section output, the burning zone must be lined with magnesite. After a certain period of time, a thin crust of dust will cover the lining, which considerably contributes to the protection of the brickwork.

Permanent lining consisting of different insulating stones, mats, or plates is arranged behind this chamotte or magnesite lining.



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4.3 Functional description

The Maerz Lime Kiln allows for thermally efficient production of high-quality soft-burnt lime.

To reach a high degree of thermal efficiency, the Maerz Lime Kiln is equipped with special features to provide ideal calcination conditions for the production of quick lime.

A brief summary of the calcination of limestone with regard to necessary kiln features illustrates the requirements the Maerz Lime Kiln has to meet. For details about limestone calcination, please refer to chapter Basic Technological Principles.

4.3.1 Special requirements of limestone calcination

The carbonate in the limestone decomposes under specific thermal and heat flow conditions.

- The decomposition or calcination temperature depends upon the partial pressure of carbon dioxide. In order to enable decomposition of the stone, the necessary dissociation heat must penetrate the surface of the stone through an insulating shell of calcined lime. This requires that the stone surface be preheated. Since an enormous amount of this heat may be transmitted into the stone, the admissible heat flow rate is considerably less towards the end of the calcination process.

- The kiln charge comprises a range of small and large particle sizes.

As smaller particles absorb heat more readily, the admissible heat flow for these particles will drop to the minimum value after a short firing period.

Longer particles require a longer period of heat exposure to complete calcination. As the kiln charge moves towards the end of the calcination zone, the calcination process requires less heat.

4.3.2 Process description

The two key operating principles are:

The stone-laden preheating zone (C) in each shaft acts as a regenerative heat exchanger, while the charge has the function of a heat accumulator. During the first stage, the excess heat produced by the waste gas (8) is transferred to the stone in shaft 2 (3). During the second stage, the heat is transferred from the stone to the combustion air (1). As a result, the combustion air is preheated to about 700C. The net heat consumption of the kiln lies between 3'500 and 3'700 kJ/kg of quick lime.

The calcination of the quick lime is completed at the level of the crossover channel (7) at a moderate temperature of about 1'050 C. This favourably affects the production of highly reactive quick lime, which can, if required, be produced with a low CaCO3 content.

During the burning period, cooling air (5) flows evenly and continuously into the bottom end of the shafts. Prior to reversal, pressure relief flaps vent both combustion air (1) and cooling air (5) to the outside.



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The figure shows the basic operating principle of the PFR Lime Kiln and illustrates the two operating stages. The two shafts are alternately charged with limestone while lime is discharged continuously from the bottom of the shafts.

Fig. 17 Operating principle

Item Description

1 Combustion air

2 Burning shaft

3 Regenerative shaft

4 Burner lance

5 Cooling air

6 Heating gas ring channel

7 Crossover channel

8 Waste gas

A Cooling zone

B Burning zone

C Preheating zone

First stage

During the first stage, fuel is injected through lances (4) into shaft 1 (2) and burns down in this shaft using combustion air (1). The heat is released and partially absorbed by the calcination of limestone. Through the base of each shaft, cooling air (5) is blown upwards to cool the lime. The cooling air (5) in shaft 1, together with the waste gas (8) and the carbon dioxide from calcination, passes through the interconnecting overflow channels into shaft 2 (3) at about 1'000C. In shaft 2 (3), the gases from shaft 1 (2) mix with the cooling air (5) blown upwards from the base of the shaft. These gases heat up the stone in the preheating zone (C) of the regenerative shaft (3).



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Second stage

The second stage will start after 8 to 15 minutes. The fuel and air flow to shaft 1 (2) is stopped, while reversal is initiated. After shaft 1 (2) has been charged with limestone, the same amounts of fuel and combustion air (1) are injected into shaft 2 (3). The waste gas (8), the carbon dioxide produced during calcination, and the cooling air (5) flow upwards through shaft 1 (2) and heat up the charge in the preheating zone (C) of this shaft. Waste gas is vented through the top of shaft 1 (2).

Reversal

During each reversal cycle, the shaft has first to be de-pressurized. Afterwards, the burnt lime is discharged. Finally, the shaft is charged and re-pressurized.

Another possible operating mode is to charge the regenerative shaft while the burning process is still in progress.



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4.4 Characteristic data

4.4.1 Grain size of charged limestone

The Maerz Lime Kiln is designed to process different limestone grain sizes.

Fine lime kiln type

For grain sizes between 15 to 40mm or 40 to 80mm (exceptionally, 10 to 90mm).

Standard lime kiln type

For grain sizes between 30 to 70mm or 60 to 120mm (exceptionally, 25 to 140mm).

INFORMATION

For the exact specifications of this particular lime kiln, refer to chapter Technical Data.

4.4.2 Operating cycles

The duration of one operating cycle per shaft ranges from 8 to 15 minutes at nominal output.

INFORMATION

For the exact specifications of this particular lime kiln, refer to chapter Operation.



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4.4.3 Heat and mass flow

Fig. 18 Heat and mass flow (typical)

The figure above illustrates the heat and mass flow based on 1 kg of quick lime produced inside the Maerz Lime Kiln.

(The limestone used for this example is of average quality).



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4.4.4 Temperature profile

Fig. 19 Typical temperature profile of a Maerz lime kiln as witnessed by a passenger observer.

Item Description

A Material flow

B Gas flow

C Heat input (fuel)

a Preheating zone

b Burning zone

c Cooling zone

1 Air

2 Waste gas

3 Product



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4.5 Kiln control system

The kiln control system comprises the following main components:

- Programmable logic controller PLC with local I/O stations

- Data bus system

- Visualization system

INFORMATION

Detailed information can be found in the documents listed under Mandatory reference material at the beginning of this chapter.

The PLC cabinet is usually housed in the same room as the MCC room above the blower house. To reduce the number and length of cables used, the local I/O stations (ET200S family) have been installed in various positions at the kiln.

The data bus system (Simatic Profibus) connects the PLC with the local I/O stations.

The visualization system is located inside the control room and runs usually on "Siemens WinCC" or the PCS7 software.

INFORMATION

For the operation of the visualization system, see chapter Operation.



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4.6 Electric switchboard

INFORMATION

T

HORNO MAERZ

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