ACC plant visit report

8/12/2019 ACC plant visit report

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ABOUT

INTRODUCTION TO COMPANY

ACCLIMITED (Former Associate Cement Company Limited) isIndiasforemostmanufacturer ofPortland cement and concrete for generalconstruction and special applications.ACCsoperations are spread throughout the countrywith14modern cement factories,19 Readymixconcrete plants, 19 salesoffices,and several zonaloffices. It has aworkforceofabout9000persons and acountry-wide distributionnetwork ofover9,000 dealers.ACCs annualturnoverisRS.7000 cores and annual rated capacity of 24 million tones.ACC Limitedis a part ofWorld-wideHOLCIM Group.ACCs research and developmentfacilityhasauniquetrack recordofinnovativeresearch, product development andspecialized consultancyservices.Since itsinception in 1936, the company hasbeen atrend setter and importantbenchmarkfor thecement industry irrespect of itsproduction,marketingandpersonnelmanagementprocesses. Itscommitment toenvironmentfriendliness,its highethical standards in business dealings and itson-goingefforts incommunity welfare programs havewon it acclaim as a responsiblecorporatecitizen.ACC has made significant contributions to thenationbuildingprocessbywayofquality

products servicesandsharing its expertise.

In the70 years of its existence, ACC has been a pioneer in the manufacture of cement andconcrete and a trendsetter in many areas of cement and concrete technologyincludingimprovement in raw materialutilization, process improvement, energy conservation anddevelopment of high performance concretesACCs brand name is synonymous with cement

and enjoys a highlevel of equity in the Indian market. It is the only cement company 2009thatfigures in the list of Consumer Super Brands of India.

The companies various businesses are supported by a powerful, in-house research andtechnology backup facility the only one of itskind in the Indian cement industry.This ensures

not just consistency inproduct quality but also continuous improvements inproduct,processes,and application areas.

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ACC has rich experience in mining, being the largest user of limestone, and it is also one of theprincipal users of coal. As the largest cement producer in India, it is one of the biggestcustomers ofthe Indian Railways, and the foremost user of the road transport networkservices for inward and outward movement of materials andproducts.

ACC is among the first companies in India to include commitment toenvironmental protectionas one of its corporate objectives, long before pollution control laws came into existenceThecompany installed pollution control equipment and high efficiencysophisticated electrostaticprecipitators for cement kilns, raw mills, coal mills, power plants and coolers as far back as1966. Every factory has state-of-the air pollution control equipment and devices.

HISTORY & PROFILE OF ACCACC was formed in 1936 when ten existing cement companies came together under oneumbrella in a historic merger the countrys Firstnotable merger at a time when the termmergers and acquisitions wasnot even coined.The history of ACC spans a wide canvas

beginningwiththe lonely struggle of its pioneer F E Din Shaw and other Indianentrepreneurslike him who founded the Indian cement industry. Theirefforts to face competition for survivalin a small but aggressivemarket mingled with the stirring of a countrys nationalist pride

thattouched all walks of life including trade, commerce and business.The first success camein a move towards cooperation .In the countrysyoung cement industry and culminated in thehistoric merger of tencompanies to form a cement giant. These companies belonged toFourprominent business groups Tatas, Khataus, Killick Nixon and F EDin Shaw groups. ACCwas formally established on August 1, 1936.Sadly,F E Din Shaw,the man recognized as thefounder of ACC, diedin January 1936.Just months before his dream could be realized.ACCstands out as the most unique and successful merger in Indianbusiness history, in which thedistinct identities of the constituentcompanies were melded into a new cohesive organizationone thathas survived and retained its position of leadership in industry. In asense, theformation of ACC represents a quest for the synergy ofgood business practices, valuesandshared objectives. The use of theplural in ACCs full name, The Associated CementCompaniesLimited, itself indicates the companys origins from a merger. Many years later,

some stockbrokers in the countrys leading stockexchanges still refer to this company simply asThe Merger2009The ACC Board comprises of 13 persons. These include executive,non-executive, and objectives and broad policies of the Company -consistent with the primaryobjective of enhancing long-termshareholder value.The Board meets once a month. Two othersmall groups of directors -comprising Shareholders/Investors Grievance Committee andAuditCommittee of the Board of Directors - also meet once a month onmatters pertaining tothefinance and share disciplines. During the lastdecade, there has been a streamlining of the

senior managementstructure that is more responsive to the needs of the Companiesprimebusiness. A Managing Committee - comprising, in addition to theManaging Director andthe two executive directors, the presidentsrepresenting multifarious disciplines: finance,production, marketing,research and consultancy, engineering and human resourcesmeetsonce a week. Besides these bodies, there are senior executives and other regionalmanagers based at the Companys corporate office andat its marketing offices andmanufacturing units who contribute to thedevelopment and operation of the variousfunctions.While thesegroups form the core management team that frames andguidescorporate policy, ACC is proud of its manpower strength of about9,000 people, whocomprise experts in various disciplines assisted bya dedicated workforce of skilledpersons.Quite a number of themhave logged many years of service with the organization. They

comefrom all parts of the country and belong to a variety of ethnic, culturaland religiousbackgrounds. Because of such a cosmopolitan make-up, ACC can rightly be said to embrace

within its fold a family that formsa mini-India.


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PLANT AND PROCESS LAYOUT


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INTRODUCTION TO PROJECT

The importance of maintenance functions for maintenance management in commonly industrieshas growing rapidly. A lot of researches and publications in the field maintenance decision modelshave been published to improve the effectiveness of maintenance process. Productionsystemshave changed tremendously in recent years. Attention has shifted fromeconomy of scale toeconomy of scope. Todays market conditions are characterized by more emphasis on variety,

delivery performance, and quality. Product life cycles are shrinking. To respond to these newstringent requirements, manufacturers are turning to high-tech equipment such as flexiblemanufacturing systems. They are also adopting new material control methodologies such as the

just-in-time philosophy which calls for production systems working without inventory at all. Set-upand adjustment times are also reduced to a minimum. All these factors are shifting the focus tomaintenance, since unplanned unavailability of machines will result in serious problems. This newreality explains the renewed interest in maintenance and the increased attention it is receivingfrom management. Unfortunately, in many organizations maintenance productivity is very low.However, the maintenance function can no longer be neglected. In order to meet todays

challenges; companies must constantly strive for excellence in maintenance through seriouscomprehensive maintenance improvement program.

In order to measure the effectiveness of any maintenance system, we need to measure itsproductivity and identify the areas where improvements can be made. Audits are used to assessthe current status of the maintenance system so that appropriate improvement program can beformulated.Auditing a maintenance system uses the following steps:(1) A survey carried out usinga well-designed questionnaire. The questions areaimed at comparing the current practices withwhat they should be.(2) Analysis of the data gathered in step 1.(3) Formulation of improvementprogram based on the analysis of the previous step.

The importance of Maintenance in Cement Industries:The importance of maintenance increases when the grade of automation and mechanizationincreases .In cement manufacturing the equipment at the beginning was not so complicated forthe technical point of view and more people were t required to keep the cement production linesin operation. The maintenance activity in the cement industry couldnt influence the productivityso much. It was important to keep equipment running but the maintenance department couldnt

contribute much to productivity because the quality and quantity of cement was to large extentdecided by the skill of the workers and his capacity to work fast .In connection with technicaldevelopment the importance of maintenance was increased as high productivity and quality canbe achieved by mean of well developed and organized maintenance. Maintenance must becontrolled in a way that the equipment is stopped for maintenance in a planned stoppageschedule. it Is not acceptable if equipment stops unplanned .to achieve the right productivity andquality of product ,it is important to procure the right equipment from the very beginning.Maintenance does not start when equipment s delivered and installed, if it starts at an early stage

in the projects and the procurement work.

There are many reasons why maintenance is becoming increasingly important In developingcountries like India .maintenance problems are rising for e.g. in the ACC Cement plant bargarh ,half of the production lines have been operating on average for more then 25 years and most ofthem are fully automatically controlled .Due to the increase in automation, any breakdown willhave as serious impact on production and measures to minimize and reduce breakdowns becomea must. Therefore the main aims of the maintenance activities in cement plants are to preservethe equipment and installation. in order to achieve that all maintenance activities should beperformed and executed to high standard through accurate planning and scheduling for allresources. The main step in doing so is auditing of the existing maintenance system.


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CEMENT CLINKER

Portland cement clinker is the essential ingredient of Portland cement. Portland cement is

obtained by grinding clinker with only minor amounts of a few other minerals, so its

composition does not depart far from that of clinker. Other cements (i.e. non-Portland

cements, for example pozzolanic cements, blast furnace slag cements, limestone cements and

masonry cements) contain larger amounts of other minerals and have a much wider

composition range. Although the other potential ingredients may be cheap natural materials,

clinker is made in an energy-intensive chemical process - in a kiln - and its production is the

main concern of this website. Between one and two billion tons a year of clinker are made

world-wide, and the details of its formation are therefore of great economic significance,

since no viable alternative ingredients for making cement-like materials currently exist.

Unlike many other thermal products (e.g. aluminium, pig-iron), clinker is a fairly complex

mixture of different minerals, and so its production depends on a multi-dimensional control

of raw materials and a multi-staged heat treatment. It has been likened to a "man-made

igneous rock", and an understanding of its structure and chemistry requires the application of

many principles of geochemistry.Clinker produced by early

static kilns was in the form of large pumice-like lumps.

Rotary kilnclinker on the other hand, because of the rolling action of the kiln, emerges asfairly regular roughly spherical hard nodules of diameter typically 5-50 mm, together with a

certain amount of dust abraded from the nodule surfaces.

Clinker minerals react with water to produce the hydrates that are responsible for cements

setting and strength-giving properties. Reaction with water occurs only at the surface of the

clinker particle, and so only proceeds rapidly if the clinker is finely ground to produce a large

reaction surface. Un-ground clinker, when exposed to humid air, is hydrated only very

gradually, and clinker can be kept in a dry place for several months without appreciable

deterioration. It can also be transported from one plant to another in ordinary bulk ships and

vehicles, and is traded internationally.

TYPE OF CEMENTS MANUFACTURED BY ACC

ACC manufactures the following types of cement, in addition to which, it provides Bulk

Cement and Ready Mix Concrete.

Ordinary Portland Cements

43 Grade Cement (OPC 43 Grade)ACC Cement is the most commonly used cement in all

constructions including plain and reinforced cement concrete, brick and stone masonry,

floorsand plastering. It is also used in the finishing of all types of buildings, bridges, culverts,roads, water retaining structures, etc.

Portland Cement Clinkerconsist essential of 4 minerals:

alite

belite

tricalcium aluminate

tetracalcium aluminoferrite
http://www.cementkilns.co.uk/early_kilns.htmlhttp://www.cementkilns.co.uk/early_kilns.htmlhttp://www.cementkilns.co.uk/early_kilns.htmlhttp://www.cementkilns.co.uk/rotary_kilns.htmlhttp://www.cementkilns.co.uk/rotary_kilns.htmlhttp://www.cementkilns.co.uk/ckr_phase.html#alitehttp://www.cementkilns.co.uk/ckr_phase.html#alitehttp://www.cementkilns.co.uk/ckr_phase.html#belitehttp://www.cementkilns.co.uk/ckr_phase.html#belitehttp://www.cementkilns.co.uk/ckr_phase.html#c3ahttp://www.cementkilns.co.uk/ckr_phase.html#c3ahttp://www.cementkilns.co.uk/ckr_phase.html#c4afhttp://www.cementkilns.co.uk/ckr_phase.html#c4afhttp://www.cementkilns.co.uk/ckr_phase.html#c4afhttp://www.cementkilns.co.uk/ckr_phase.html#c3ahttp://www.cementkilns.co.uk/ckr_phase.html#belitehttp://www.cementkilns.co.uk/ckr_phase.html#alitehttp://www.cementkilns.co.uk/rotary_kilns.htmlhttp://www.cementkilns.co.uk/early_kilns.htmlhttp://www.cementkilns.co.uk/early_kilns.html


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What is more, it surpasses BIS Specifications (IS 8112-1989 for 43 grade OPC) on

compressive strength levels.

53 Grade Cement

This is an Ordinary Portland Cement which surpasses the requirements of IS: 12269-53

Grade. It is produced from high quality clinker ground with high purity gypsum. ACC 53Grade OPC provides high strength and durability to structures because of its optimum

particle size distribution, superior crystalline structure and balanced phase composition.

Blended Cements

Fly-ash based Portland Pozzolana Cement

This is a special blended cement, produced by inter-grinding higher strength Ordinary

Portland Cement clinker with high quality processed fly ash - based on norms set by the

company's R&D division. This unique, value-added product has hydraulic binding properties

not found in ordinary cements.

What is special about ACC Fly-ash based PPC?

ACC Fly-ash based PPC is made by inter grinding high strength clinker with specially

processed fly ash. This imparts a greater degree of fineness to ACC Fly-ash based PPC

cement, improved workability properties while mixing, and makes concrete more corrosion

resistant and impermeable. All of this makes for better long-term strength and improved

corrosion resistance and therefore, greater life for your constructions. ACC Fly-ash based

PPC is an eco-friendly cement

What are the advantages of using ACC Fly-ash based PPC ?

In concrete made from ordinary cements, moisture reacts with calcium hydroxide in

concrete to form calcium bicarbonate, which leaches out of the concrete, leaving pores that

reduce its strength. ACC Fly-ash based PPC has ingredients which react with calcium

hydroxide to form CSH gel, to provide additional strength, which actually makes the

concrete grow in strength over the years. It also produces less heat of hydration and offers

greater resistance to the attack of aggressive waters than normal Portland cement.

Can ACC Fly-ash based PPC be used for all jobs in construction?

ACC Fly-ash based PPC easily replaces OPC and provides additional advantages for

practically all types of construction applications - commercial, residential, bungalows,

complexes, foundation, columns, beams, slabs and RCC jobs. It is especially recommended

for mass concreting work, and where soil conditions and the prevailing environment take

heavy toll of constructions made with ordinary cements.

How does ACC Fly-ash based PPC stand up to corrosive environments?

Due to its inherent characteristics, ACC Fly-ash based PPC makes very corrosion resistantconcrete that is superior to concrete made with OPC. It is more impermeable to oxygen, CO2,


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chlorides, etc. Leaching of alkalis is reduced and the alkaline environment around steel ismaintained.

Portland Slag Cement

This is a slag-based blended cement that imparts strength and durability to all structures. It

is manufactured by blending and inter-grinding OPC clinker and granulated slag in suitable

proportions as per our norms of consistent quality. PSC has many superior performance

characteristics which give it certain extra advantages when compared to Ordinary Portland

Cement

What is special about ACC PSC?

Compared to OPC, ACC PSC imparts some important additional advantages

Reduction in free lime leaching.

Ultimate higher strength.

Improved workability, reduced bleeding as well as segregation and corrosion. Denser, less permeable concrete, and mortar.

Better resistance to sulphates, chlorides, and CO2 and alkali-aggregates reaction.

Less heat, reduced plasticity and drying shrinkage.

Increased static modulus of elasticity.

Increased serviceability with less deflection of members and micro cracks and

reduced cost of construction and maintenance.

All these factors make for a strong, durable, and longer lasting construction. ACC PSC

benefits the structure, protects the environment by reducing CO2 emissions and helps

conserve energy. Which is why it is often referred to as an eco-friendly cement.

The Federation International de la Precontrainte (FIP) Guide to Good Practice for "concrete

constructions in hot weather," states that if concrete is likely to be exposed to an

environment of sulphate-bearing water or soil, it is preferable to use a proven type of

blended cement containing ground granulated blastfurnace slag. Concrete made with ACC

PSC has a higher density than concrete made with OPC, and hence it improves the durability

of concrete structures.

It can, therefore, be used for all purposes where OPC or PPC is used.


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DIFFERENT UNITS OF KILN SECTION

1.KILN INPUT UNITS :

1.1 Blending and Storage Silo

Normally there are various sources of limestone, each with different qualities, which are added with

various additives to get the required composition of raw mix. As there are various sources of raw

materials, it becomes necessary to blend and homogenize these different materials efficiently to

counteract fluctuation in the chemical composition of the raw meal. The variations in the

composition of kiln feed have very adverse impacts on the efficiency of the kiln. It results in

undesired coating and ring formation inside the kiln. In order to blend and homogenize the raw

materials properly, continuous blending silos are used.

1.2Preheater

The most important activity in cement manufacturing is clinkering (or burning) of raw material.

Clinkering takes place in the kiln and the preheater system. Preheater systems offer heat transfer

from the hot kiln gases.

1.3 Coal Mill Building

The coal mill building houses the mill for grinding lumpy coals. This fine ground coal is used for

burning in the kiln.The mills used for coal grinding and drying are either trumbling mills (tube mills)

or roller mills.

1.4 Bag House

The term bag house is applied to large filters containing a number of tubular bags mounted in a

usually rectangular casing. The dust laden air is drawn through them by suction. The bag house is

used to remove dusty particles from discharge of different equipment such as cement mill, coal milland kiln. In a bag house system discharge gas containing dusty particles is passed through a series of

bags made of strong fabrics.

2. ROTARY CLINKER KILN

A kiln is the heart of any cement plant. It is basically a long cylindrical-shaped pipe, and rotates ina

horizontal position. Its internal surface is lined by refractory bricks. Limestone and additives

arecalcined in this. The output of the kiln is called clinker.

3.KILN OUTPUT UNITS:

3.1 Cooler

The clinker coming out of the kiln is hot. It is cooled in a set-up called a cooler. In the cooler, cold air

is blown to effect heat exchange between hot clinker and cold air.

3.2 Gas Conditioning Tower and ESP

The conditioning tower is used to reduce the temperature and to increase the moisture level of the

dusty exhaust gas from the kiln, before it is passed through the bag house and ESPs. It is called a

conditioning tower because it conditions the hot gas, thus making it more suitable for the ESP and

bag house to extract dust from it.

The Electrostatic Precipitators are used in cement plants particularly for removal of dust from theexit gases of cement kilns and from the exhaust air discharged by dryers, combined grinding and


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drying plants, finishing mills and raw mills through water injection. Through ESPs, the dust-laden gas

is made to flow through a chamber usually horizontally, during which it passes through one or more

high voltage electric fields formed by alternate discharge electrodes and plate type collecting

electrodes. By the action of electric field, the dust particles, which have become electrically charged

by negative gas ions which are formed at the discharge electrodes and attach themselves to the

particles, fly to the collecting electrodes and are deposited there. The dust is dislodged from these

electrodes by rapping and thus falls into the receiving hopper at the base of the precipitator casing.

3.3Deep Bucket Conveyor

The deep bucket conveyor is essentially an equipment to lift material vertically.

3.4 Clinker/Gypsum Storage

The output of the kiln is stored before it is fed to the cement mill for conversion to cement. This

storage is called clinker storage, if it is used for clinker storage purpose. If the storage space is used

for gypsum storage, it is called gypsum storage.

The storage may be of silo type or covered stacker reclaimer type or simply a gantry type. Silo typeclinker storage has the advantage that there is no dust pollution and spillage of clinker.

sameadvantage can be achieved through stacker reclaimer type as well. However, there is a little bit

of dust generated. Gantry type is not used in modern cement plants because of its environmental

unfriendly nature.


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CEMENT KILN

Cement kilnsare used for the pyroprocessing(Pyroprocessingis a process in whichmaterialsare subjected to high temperatures (typically over 800C) in order to bring about a chemicalor physical change) stage of manufacture ofPortland andother types of hydraulic cement, in which calcium

carbonate reacts with silica-bearing minerals to form amixture of calcium silicates. Over a billion tonnes ofcement are made per year, andcement kilns are the heartof this production process: their capacity usually definethe capacity of the cement plant. As the main energy-consuming and greenhouse-gasemitting stage of cementmanufacture, improvement of kiln efficiency has been thecentral concern of cement manufacturing technology.

KILN HISTORYPortland cement clinker was first made (in 1825) in a modified form of the traditional static

lime kiln.The basic, egg-cup shaped lime kiln was provided with a conical or beehive shapedextension to increase draught and thus obtain the higher temperature needed to makecement clinker. For nearly half a century, this design, and minor modifications, remained theonly method of manufacture. The kiln was restricted in size by the strength of the chunks ofrawmix: if the charge in the kiln collapsed under its own weight, the kiln would beextinguished. For this reason, beehive kilns never made more than 30 tons of clinker perbatch. A batch took one week to turn around: a day to fill the kiln, three days to burn off,two days to cool, and a day to unload. Thus, a kiln would produce about 1500 tons per year.A kiln is basically an industrial oven, and although the term is generic, several quitedistinctive designs have been used over the years.Although perhaps more normallyassociated with pottery making, both Bottle and their very close relatives Beehive kilns,

were also the central feature of anycementworks. Early designs tended to be updraft kilns,which were often built as a straight sided cone into which the flame was introduced at, orbelow, floor level. Reaching heights of up to 70 ft, the dome or bottle shape of the kiln,known as the hovel, would be quite a prominent landmark. As well as protecting the inner

kiln or crown, the opening at the top of the hovel also acted as a flue, to remove the smoke

and exhaust gases that were produced during the production process. There was a three tofour foot gap between the outer wall of the hovel and inner shell of the crown. Due to thefact that the 1-foot-thick (0.30 m) crown wall would expand and contract during firing,it wasstrengthened with a number of iron bands, known as bonts. These were set twelve inches

apart and ran right around the circular oven. The development of downdraft kilns in theearly 20th Century proved to bemuch more fuel efficient and were designed to force theheated air to circulate more around the kiln. The design incorporated a gentle curve at the

'shoulders' of the kiln, which served to reflect the rising heat from the fire at the bottom ofthe kiln, back down again over the material. The smoke and exhaust was then sucked outthrough holes at the bottom of the kiln via a flue,whichwasconnected to anearby chimney.The chimney would also serve a number of neighbouring kilns as well. The kiln would befired for several days to achieve the high temperatures required to producecement clinker,and although the above methods were successful, the problem with any batch kiln was thatit was intermittent and once the product had been produced, the fire had to beextinguished and the contents allowed to cool. This not only wasted a lot of the heat, butalso added to the expense of the finished product.In order to save money on fuel, a kiln was required that could run almost continuously,whilst the raw material was somehow fed through it. It was this scenario that lead to the

development of the Chamber kiln in the late 1850s. This particular kiln comprised anumber of individual chambers, which were arranged so that the hot flue gases from onechamber, were drawn off and used to pre-heat the material in the following chambers,
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before they were drawn up the chimney. Once the first chamber had been filled with rawmaterial, coal was added through the roof holes of the chamber and was then set alight. Atthe same time, the second chamber was being filled with raw material. The airflow from thefirst chamber was then adjusted, using a number of dampers, to funnel the hot air throughto the second chamber to pre-heat the material. More coal was then poured into thesecond chamber and ignited, as the third chamber was being filled and so on. This processcontinued along the length of the kiln, so that by the time the last chamber had been fired,

the first chamber had already been cleared and re-filled with more raw material so that theprocess could start again. Although such chamber kilns were still being installed as late as1900, the development of the rotary kiln was already starting to have a major impact. Therotary kiln was a major advancement for the industry as it provided the continuousproduction of a much more uniform product in larger quantities.Around 1885, experiments began on design of continuous kilns. One design was the shaftkiln, similar in design to a blast furnace. Rawmix in the form of lumps and fuel werecontinuously added at the top, and clinker was continually withdrawn at the bottom. Airwas blown through under pressure from the base to combust the fuel. The shaft kiln had abrief period of use before it was eclipsed by the rotary kiln, but it had a limited renaissancefrom 1970 onward in China and elsewhere, when it was used for small-scale, low-tech plants

in rural areas away from transport routes. Several thousand such kilns were constructed inChina. A typical shaft kiln produces 100-200 tones per day.From 1885, trials began on the development of the rotary kiln,which today accounts formore than 95% of world production

THE WET PROCESS AND THE DRY PROCESS KILN

From the earliest times, two different methods of rawmix preparation were used: themineral components were either dry-ground to form a flour-like powder, or were wet-ground with added water to produce a fineslurrywith the consistency of paint, and with a

typical water content of 4045%.The wet process suffered the obvious disadvantage that, when the slurry was introducedinto the kiln, a large amount of extra fuel was used in evaporating the water. Furthermore, alarger kiln was needed for a given clinker output, because much of the kiln's length was usedup for the drying process. On the other hand, the wet process had a number of advantages.Wet grinding of hard minerals is usually much more efficient than dry grinding. When slurryis dried in the kiln, it forms a granular crumble that is ideal for subsequent heating in thekiln. In the dry process, it is very difficult to keep the fine powder rawmix in the kiln,because the fast-flowing combustion gases tend to blow it back out again. It became apractice to spray water into dry kilns in order to "damp down" the dry mix, and thus, formany years there was little difference in efficiency between the two processes, and the

overwhelming majority of kilns used the wet process. By 1950, a typical large, wet processkiln, fitted with drying-zone heat exchangers was 3.3 x 120 m in size, made 680tones perday, and used about 0.250.30 tones of coal fuel for every tonne of clinker produced. Beforethe energy crisis of the 1970s put an end to new wet-process installations, kilns as large as5.8 x 225 m in size were making 3000 tones per day.An interesting footnote on the wet process history is that some manufacturers have in factmade very old wet process facilities profitable through the use of waste fuels. Plants thatburn waste fuels enjoy a negative fuel cost (they are paid by industries needing to dispose ofmaterials that have energy content and can be safely disposed of in the cement kiln thanksto its high temperatures and longer retention times). As a result the inefficiency of the wetprocess is an advantageto the manufacturer.By locating waste burning operations at olderwet process locations, higher fuel consumption actually equatesto higher profits for themanufacturealthough it produces correspondingly greater emission of CO2. Manufacturerswho think such emissions should be reduced are abandoning the use of wet process.
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THE ROTARY KILN

General layout of a rotary kiln

The rotary kiln consists of a tube made from steel plate, and lined withfirebrick.The tubeslopes slightly (14) and slowly rotates on its axis at between 30 and 250 revolutions per

hour. Raw mix is fed in at the upper end, and the rotation of the kiln causes it gradually to

move downhill to the other end of the kiln. At the other end fuel, in the form of gas, oil,or

pulverized solid fuel, is blown in through the "burner pipe", producing a large concentric

flame in the lower part of the kiln tube. As material moves under the flame, it reaches its

peak temperature, before dropping out of the kiln tube into the cooler. Air is drawn first

through the cooler and then through the kiln for combustion of the fuel. In the cooler the air

is heated by the cooling clinker, so that it may be 400 to 800 C before it enters the kiln, thus

causing intense and rapid combustion of the fuel.

The earliest successful rotary kilns were developed inPennsylvania around 1890, and were

about 1.5 m in diameter and 15 m in length. Such a kiln made about 20 tons of clinker per

day. The fuel, initially, was oil, which was readily available in Pennsylvania at the time. It was

particularly easy to get a good flame with this fuel. Within the next 10 years, the technique

of firing by blowing in pulverized coal was developed, allowing theuse of the cheapest

available fuel. By 1905, the largest kilns were 2.7 x 60 m in size, and made 190 tons per day.

At that date, after only 15 years of development, rotary kilns accounted for half of world

production. Since then, the capacity of kilns has increased steadily, and the largest kilns

today produce around 10,000 tons per day.

In contrast to static kilns, the material passes through quickly: it takes from 3 hours (in

some old wet process kilns) to as little as 10 minutes (in short precalciner kilns). Rotary kilns

run 24 hours a day, and are typically stopped only for a few days once or twice a year for

essential maintenance. One of the main maintenance works on rotary kilns is tyre and roller

surface machining and grindingworks which can be done while the kiln works in full

operation at speeds up to 3,5 rpm. This is an important discipline, because heating up and

cooling down are long, wasteful and damaging processes. Uninterrupted runs as long as 18

months have been achieved.

Kiln Shell
http://en.wikipedia.org/wiki/Firebrickhttp://en.wikipedia.org/wiki/Petroleumhttp://en.wikipedia.org/wiki/Pennsylvaniahttp://en.wikipedia.org/wiki/Pennsylvaniahttp://en.wikipedia.org/wiki/Petroleumhttp://en.wikipedia.org/wiki/Firebrick


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13

This is made from rolledmild steelplate, usually between 15 and 30 mm thick, welded to

form a cylinder which may be up to 230 m in length and up to 6 m in diameter. This will be

usually situated on an east/west axis to preventeddy currents.

Upper limits on diameter are set by the tendency of the shell to deform under its own

weight to an oval cross section, with consequent flexure during rotation. Length is not

necessarily limited, but it becomes difficult to cope with changes in length on heating andcooling (typically around 0.1 to 0.5% of the length) if the kiln is very long.this is cylindrical.

Refractory Lining

The purpose of the refractory lining is to insulate the steel shell from the high temperatures

inside the kiln, and to protect it from the corrosive properties of the process material. It may

consist of refractory bricks or cast refractory concrete, or may be absent in zones of the kiln

that are below around 250C. The refractory selected depends upon the temperature inside

the kiln and the chemical nature of the material being processed. In some processes, such as

cement, the refractory life is prolonged by maintaining a coating of the processed materialon the refractory surface. The thickness of the lining is generally in the range 80 to 300 mm.

A typical refractory will be capable of maintaining a temperature drop of 1000C or more

between its hot and cold faces. The shell temperature needs to be maintained below

around 350C in order to protect the steel from damage, and continuous infraredscanners

are used to give early warning of "hot-spots" indicative of refractory failure.

Tyres and Rollers

Tyres, sometimes called riding rings, usually consist of a single annular steel casting,

machined to a smooth cylindrical surface, which attach loosely to the kiln shell through a

variety of "chair" arrangements. These require some ingenuity of design, since the tyre must

fit the shell snugly, but also allow thermal movement. The tyre rides on pairs of steel rollers,

also machined to a smooth cylindrical surface, and set about half a kiln-diameter apart. The

rollers must support the kiln, and allow rotation that is as nearly frictionless as possible. A

well-engineered kiln, when the power is cut off, will swing pendulum-like many times before

coming to rest. The mass of a typical 6 x 60 m kiln, including refractories and feed, is around

1100 tons, and would be carried on three tyres and sets of rollers, spaced along the length

of the kiln. The longest kilns may have 8 sets of

rollers, while very short kilns may have only two.

Kilns usually rotate at 0.5 to 2 rpm, but sometimes

as fast as 5 rpm. The Kilns of most modern cement

plants are running at 4 to 5 rpm. The bearings of the

rollers must be capable of withstanding the large

static and live loads involved, and must be carefully

protected from the heat of the kiln and the ingress

of dust. In addition to support rollers, there are

usually upper and lower "retaining (or thrust)

rollers" bearing against the side of tires, that

prevent the kiln from slipping off the support rollers.

Friction between tire and rollers causes concave, convex or conical wear on both surfaces oftire and rollers. This wear deforms the cylindrical shape of these units and causes vibration,
http://en.wikipedia.org/wiki/Mild_steelhttp://en.wikipedia.org/wiki/Mild_steelhttp://en.wikipedia.org/wiki/Mild_steelhttp://en.wikipedia.org/wiki/Eddy_currentshttp://en.wikipedia.org/wiki/Eddy_currentshttp://en.wikipedia.org/wiki/Eddy_currentshttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Eddy_currentshttp://en.wikipedia.org/wiki/Mild_steel


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15

the temperatures required to do this are not high,this requires significant time and energy.

In the wet process, the dehydration zone would require up to half the length of the kiln,

while the dry process requires a somewhat shorter distance.

Calcination zone (450C 900C): The term calcination refers to the process of

decomposing a solid material so that one of its constituents is driven off as a gas. At about

600C the bound water is driven out of the clays, and by 900C the calcium carbonate isdecomposed, releasing carbon dioxide. By the end of the calcination zone, the mix consists

of oxides of the four main elements which are ready to undergo further reaction into

cement minerals. Because calcination does not involve melting, the mix is still a free-

flowing powder at this point.

Solid-state reaction zone (900 - 1300C): This zone slightly overlaps, and is sometimes

included with, the calcination zone. As the temperature continues to increase above ~

900C there is still no melting, but solid-state reactions begin to occur. CaO and reactive

silica combine to form small crystals of C2S (dicalcium silicate), one of the four main cement

minerals. In addition, intermediate calcium aluminates and calcium ferrite compounds

form. These play an important role in the clinkering process as fluxing agents, in that they

melt at a relatively low temperature of ~ 1300C, allowing a significant increase in the rate

of reaction. Without these fluxing agents, the formation of the calcium silicate cement

minerals would be slow and difficult. In fact, the formation of fluxing agents is the primary

reason that portland (calcium silicate) cements contain aluminum and iron at all. The final

aluminum- and iron-containing cement minerals (C3A and C4AF) in a portland cement

contribute little to the final properties. As the mix passes through solid-state reaction zone

it becomes sticky due to the tendency for adjacent particles to fuse together.

Clinkering zone (1300C 1550C): This is the hottest zone where the formation of the

most important cement mineral, C3S (alite), occurs. The zone begins as soon as the

intermediate calcium aluminate and ferrite phases melt. The presence of the melt phase

causes the mix to agglomerate into relatively large nodules about the size of marbles

onsisting of many small solid particles bound together by a thin layer of liquid.

Inside the liquid phase, C3S forms by reaction between C2S crystals and CaO. Crystals of

solid C3S grow within the liquid, while crystals of belite formed earlier decrease in number

but grow in size. The clinkering process is complete when all of silica is in the C3S and C2S

crystals and the amount of free lime (CaO) is reduced to a minimal level (


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KILN OPERATION TARGET

1.Highest clinker production of about 2800-3000 TPD with Good quality clinker

And Stable kiln operation

2.Oxygen level as low as possible

Gas and fuel oil1.0 to 1.5%

Coal and coke around2.0% (depending on the variations in fuel mixture)3.Kiln exit temperature as low as possible

Flame as short as possible (with respect of the burning zone refractory)

Keep burning zone short in front of the kiln

4.Secondary air temperature as high as possible but stable

Temperature not above liquid phase temperature in front of kiln to protect refractory and

coating

Run with an under grate pressure as high as possible

Compatible with the cooler fans static pressure capacity

5.Primary air as low as possible

As combustion air to replace by hot air from cooler as much as possible6.Clinker Temperature

Not to exceed 230oF (110oC) as it could promote quality problems (false set) during the

grinding process

KILN MAINTENANCE:

VARIABLES WHICH THE OPERATOR CANNOT CONTROL

Quality and characteristics of the raw materials

Quality of the fuel used as a example: heat value, ash content, volatile matter and moisture

level

Dust quality and quantity returned to the kilnAccuracy of the feeders

Chain system design

Accuracy and good response of all control loops and sensors of the kiln system

For these variables that he cannot control, the operator should be kept informed of any

changes done and should make sure that those variables are kept inside an acceptable

range to maintain a good kiln stabilization.

VARIABLES WHICH THE OPERATOR CAN CONTROL

Material feed to the kiln

Fuel feed to the kilnSpeed rotation of the kiln

Temperature profile along the kiln

Draft at the feed end of the kiln

Supply of combustion air

Retention time of the material in the kiln

Temperature of the combustion air

Flame shape

Observation of instruments, and correct reaction to their readings

Observation of the kiln burning zone, and correct reaction to this evaluation

However, some restrictions are sometimes given on the utilization of those variables andmay vary from plant to plant due to local conditions and are usually the following:

Set point on the maximum speed of the kiln


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Set point on the maximum feed rate to the kiln

Automatic loop set point for oxygen level and ID fan speed.

Settings on the burner pipe and its position

Primary air settings and fuel tip velocity

Set point on cooler fans flow

Set point for the under grate pressure and the clinker bed depth in the cooler

MONITORING OF A ROTARY KILN

The advantages of daily monitoring of critical items and components on a rotary kiln can

lead to substantial costs savings. The items that should be monitored on a daily basis and

corrected with immediate detection of a fault are the following:

Shell temperaturesprovides an indication of the condition of the refractory lining and

slag/ash ring build up inside the rotary kiln. By monitoring the kiln shell, this will create an

early warning system for refractory wear and possible damage to the refractory inside therotary kiln. The wear on the refractory inside the rotary kiln can create hot spots on the

kiln shell. This will create enormous damage to the rotary kiln itself and leads to distortion

of the kiln shell. The monitoring of shell temperatures will give the client an early warning

system regarding slag / ash build up inside the rotary kiln. The build-up of slag / ash is

dangerous for the safe operation of a rotary kiln, it will create a back pressure affect

within the rotary kiln and damage to inlet seals and other mechanical items will occur. It

also has an effect on the production of the rotary kiln by retarding the steady flow of

material down the length of the rotary kiln. To remove the slag build-up inside the kiln is a

costly and very dangerous exercise; it could also lead to premature shutdown of a rotary

kiln.

Girth gear and pinion condition if gear rooting is occurring this will result in an

increase in the amperage of the rotary kiln, which in turn will result in an increase in

electricity consumption and related operating cost. Mechanical failure and or excessive

damage to drive mesh will also occur. The girth gear and pinion is the unit that turns the

rotary kiln. This section with the support rollers is critical to the life of the kiln. Therefore theproper maintenance is critical at this point.

During shutdown phase the following should be inspected and corrective action taken (all

settings to be done to accommodate the hot state of the rotary kiln) to minimise any

breakdowns during the running phase of the rotary kiln;

Rooting of girth gear and pinion

Pitting/chipping of girth gear and pinion

Correct mesh alignment of girth gear and pinion

Rotary kiln main drive gearboxes to be inspected and drive gears to be checked

Alignment of drive couplings


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If any deviation from recommended practice is noted, these should be corrected before kiln

start up.

During normal running of the rotary kiln the following must be inspected on a daily basis;

Correct lubrication of girth gear and pinion

Girth Gear/Pinion lubrication pump. Ensure that the pump is working

Lubrication spray nozzles Meshing of pinion and girth Gear

Rooting of girth gear and pinion.

Support roller monitoring for possible bearing failure - the collapse of a rotary

kiln support roller bearing could cause immense damage to inlet seals and girth and pinion

gears, which will result in loss of production.The collapse of a support roller bearing can

cause immense damage to a rotary kiln. The girth gear will settle into the pinion gear and

chipping, pitting and burring to the teeth of the gears will occur. The amperage of the main

drive motors will increase and the cost of electricity will become very costly. It is

recommended that the following parameters should be monitored on a weekly basis:

Bearing temperature

Correct lubrication

Grease spillage

Plummer block seals

Rotary kiln inlet and discharge seals if not monitored correctly and the seal isdamaged, excess air will enter the rotary kiln which will result in excessive fuel being

required to correct the air-fuel mixture to fire the rotary kiln. If not corrected this will leadto excessive costs and unburned fuel creating a pollution problem. There is furthermore

possible damage to the electrostatic precipitators.

Main drive gearboxesif not checked daily and faults identified for immediate plannedcorrection, could lead to downtime, resulting in a major financial loss of the operating

company.

KILN OPERATION PRIORITIES1. Protection of the personnel working in and around the kiln system is a basic safety rulethat must be strictly followed at all times.

2. Protection of the equipment:.

Around the kiln, the safety of the equipment is mainly related to overheating problems and

could be:

a) Back-end of kiln : Do not exceed 840oF (450oC) at precipitator inlet

b) Feed: Do not exceed 10 minutes without feed as the feed end temperature would go

high.

c) Chain inlet temperature: Do not exceed metallurgical maximum temperature of chain

system. (usually approximately 1900oF or 1038oC)d) Burning zone: Do not over-heat; keep the raw load near end of flame.

Set a maximum amps level on kiln motor.


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e) Cooler :Avoid overloaded cooler grates, cut kiln speed down to protect the cooler grates.

Avoid high exhaust gas temperature; could damage dust filter system.

Avoid high clinker temperature; could damage the clinker evacuation circuit.

3. Quality:.

To produce a well-burned clinker with good free-lime at the desired liter-weight

4. Stability:.

Continuous operation should always have priority over maximum production.Stable kiln operation is the key to long refractory life, high fuel efficiency and uniform

quality clinker.

5. Optimization:.

Strive for optimum production level at the lowest possible cost.

TYPICAL KILN PROBLEMSList of most frequent factors at work when kiln operation is unsatisfactory

1) High leakage, pre-heater only into feed end seal (more than 5%)

2) Faulty suspension results in high pre-heater outlet temperatures, thus reduces capacity

(bleed air)3) Poor operating practices (burning techniques)

4) Reducing conditions in kiln

5) Reducing conditions in burning zone due to flame impingement with load

6) Lack of momentum at burner tip leads to long, lazy flame

7) High primary air, (30%+) due to direct firing of coal, (critical in dry process kiln)

8) High level of volatile elements in raw feed particularly chlorine

9) Systematically hot burning

10) Inadequate chain system

11) Poor cooler heat recovery due to cooler fan design

12) Poor cooler heat recovery due to excessive air flows, insufficient pressure in under gratecompartments

13) Chemically variable raw mix C3S, more than 10 points over a shift

14) Variable slurry moisture (more than 3 points)

15) Variable addition of hi-alkali or hi-volatile dust from precipitator (over a period of more

than one-half hour)

16) Erratic feed rate

17) Erratic fuel rate (wet coal)

18) High leakage into hood seal (more than 10% of combustion air)

19) Inadequate or obsolete design of equipment or facilities

20) High leakage into pre-heater and down-comer duct

21) Flame erosion on lining could create premature brick failure

22) Kiln misalignment, excessive tire clearances and other factors of shell deflection

23) Bricking techniques lead to rings not tight enough

24) Low slurry moisture

25) High slurry moisture

List of Typical Kiln Operating Problems

1) Heat consumption higher than normal

Long dry: Higher than 3.4 MBtu/ton

Long wet: Higher than 5.2 MBtu/ton


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Keep watching the shell temperature trend

Maintain normal burning zone temperature

Change kiln feed chemistry to obtain an easier burning mix

B) For large red spot located under or near a kiln tire or in areas were no coating is formed

SHUT DOWN KILN IMMEDIATELY

Warning: Under no circumstances should a water spray be used on the red spot, as this

could result in severe kiln shell damage.Possible Measures to Prevent Re-occurrence

Make sure flame configuration and characteristics are not causing localized coating erosion

or continuous and excessive overheating

Employ proper refractory installation methods

Minimize frequency of kiln shutdowns and upsets

Minimize frequency of clinker type changes over

Avoid hard burning mixes (i.e. ensure sufficient percentage of liquid content in mix to

promote coating formation)

RAW, UNBURNED FEED IN CLINKER COOLERIndicators:

On rush of raw feed into and beyond burning zone

Black feed position advanced more than way under the flame

Black-out in burning zone

Red grates in cooler

Rapid rise in cooler grate and clinker discharge temperatures

Cooler drag-chain amperage increases rapidly

Possible Effects and Danger

Thermal damage to cooler grates and grate drive mechanism

Fire on clinker conveyor belts

Excessive high temperatures in coal mill air circuit

Warning: Watch for incomplete combustion when visibility in burning zone is severely

restricted.

Actions to Take

First and foremost, do not wait until raw feed is in the cooler; act when the first signs of

impending problems are visible in the burning zone.

Immediately reduce kiln speed to minimum (or turn on auxiliary drive)

Reduce fuel and ID fan speed in accordance with standard slowdown procedures to protect

the kiln back end temperature

Reduce cooler grate drive speed (switch to manual control) to allow material in cooler more

time for cooling

Adjust cooler air flow rates to obtain maximum cooling without the hood pressure going

positive

Advise all unauthorized personnel to stay clear of the firing floor, cooler and coal mill area

Preventive Measures to Avoid Re-occurrence

Accelerate frequency of visual observations of burning zone for early detection of

impending cooler upsets

Evaluate kiln output rates vs. capabilities and kiln operating stability


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Maintain close vigilance over combustion, back-end and flow conditions during kiln starts,

shutdowns and upsets

BLACK SMOKE EMMISION FROM KILN STACK

Indicators

Combustibles in exit gases

Oxygen in exit gas too lowFlame extinguished for poor ignition conditions

Burning zone temperature too low

Excessive fuel rates and/or insufficient kiln draft

Possible Actions

Immediately de-energize electrostatic precipitator

Immediately reduce fuel flow rate (do not shut off)

Increase ID fan speed to obtain:

a) Zero combustible in exit gas

b) Oxygen between 0.2 and a maximum of 0.5% in exit gasAfter black smoke has cleared, maintain the low oxygen/zero combustibles for at least 10

minutes before restoring kiln variables to normal

Preventive Measures

Improve control over flame and firing conditions

Make frequent, vigilant observation of fuel flow rates, gas analysis, flame and kiln draft

conditions during kiln starts and upsets

DISTORTED FLAME SHAPE

Indicators

Irregular and unusual flame shape

Fragmented flame where part of flame impinges on lining near kiln discharge area

Possible Effects and Dangers

Inspect burner pipe for damage or plugged circuit

If flame is erratic and severely impinges upon lining near the kiln discharge area:

Shutdown kiln immediately!

If flame is only slightly distorted; adjust burner position and primary air flow

Check shell temperature on kiln scanner

Schedule a burner pipe repairs for next kiln shutdown

Preventive Measures

Frequent visual inspection when looking inside the kiln

Regular inspection and maintenance of burner pipe during each prolonged kiln shutdown

Improve protection (castable, air cooling) for burner pipe

Maintain primary air flow for at least 2 hours after a kiln has been shutdown or pull back the

burner pipe immediately when kiln is being shutdown

LOSS OF SECTION OF REFRACTORY LINING

IndicatorsLoose bricks in clinker bed of burning zone


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Delineated (linear instead of round) red spot on kiln shell

Rapid rise in kiln shell temperature


Thermal damage and distortion of kiln shell and tire

Further collapse of large sections of linings (especially in alumina brick sections)

Possible Actions

Immediately shutdown the kiln

Preventive Measures

Employ proper refractory installation methods and procedures

Make annual checks of kiln alignment and shell ovality

Have refractory manufacturer provide uniform shapes and proper expansion allowance

for each type of brick

Avoid excessive turning when kiln is cold during shutdowns

COOLER DRIVES OR CLINKER BELT STOPPED

Indicators

Cooler overloaded

Large chunks of coating in cooler

High under grate pressure

High cooler drive amps prior to drive stop

Clinker transfer chutes plugged


Thermal damage to cooler components

Possible Actions

Immediately reduce kiln speed to minimum and attempt to restart clinker belt and/or cooler

drive

If drives cannot be restarted within 5 minutes, shutdown the kiln

Note: After kiln has been shutdown, consider possibility of turning the kiln in less frequent

intervals to prevent further overloading of cooler. (Kiln still had to be rotated periodically

nevertheless)

Preventive Measures

Know at what amperage the cooler drive is likely to fail and provide alarm for overload

Adjust kiln parameters (namely kiln speed) before cooler can become overloaded at the

times when heavier feed load is observed in the burning zone

RED CLINKER AT COOLER DISCHARGE

Indicators

High drag chain amps

Sudden drop in under grate pressure (grate out)

Excessively high under grate pressure (cooler overloaded)Cooler drive amps and clinker bed depth too high


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Cooler loaded with coating and ring fragments

Snowman formation at cooler inlet


Thermal damage to cooler components

Thermal damage to clinker transport equipment

Possible Actions

Immediately make a visual check of the cooler to determine reason for red-clinker discharge

If cooler grate out, shutdown kiln

If cooler overloaded, reduce kiln speed to minimum and reduce cooler grate drive speed to

allow more time for cooling

Increase air flow into cooler

Activate water spray at cooler discharge and reroute clinker to prevent damage to conveyor

belts

Preventive Measuresa) On frequent grate failures

Investigate for possible faulty grate installation methods by maintenance department

Investigate quality of grates and bolts used

b) On frequent one-sided loading of cooler bed

Investigate possible cooler design changes

Investigate possibilities for elimination of stalagmite (snowmen) formation at cooler inlet

c) On frequent overloading of cooler due to upsets

Slow down kiln speed before raw feed enters cooler or cooler can become overloaded

(make your corrective moves before things get out of control)

RAPID RAISE OF TEMPERATURE IN COAL SYSTEM


Explosion

Thermal damage to coal system

Possible Actions

Warning: Do not open any door in the system that could provide the oxygen for an

explosion or a more serious fire.

Inject inert gas (CO2) into coal mill inlet

Flood coal mill with kiln feed or excessive coal

Warn all personnel to stay clear of system

Stop or reduce air flow to coal mill to minimum

Preventive Measures for Re-occurrence

Provide coal mill inlet with magnetic device to extract metal fragments from coal feeder belt

Keep paper, rags, etc. out of coal storage pile

Do not feed coal mill with coal that has undergone spontaneous ignition (smothering) while

in storage

Keep coal mill de-tramp chute clear

Provide coal mill system with automatic fire-extinguishing devicesDo not operate coal mill above predetermined safe temperature for any given type of coal


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POWER FAILURE


Warping of kiln shell

Thermal damage to burner pipe, instrumentation and equipment at kiln discharge area

On coal-fired kilns, settlement of ground coal in coal system that could lead to a fire and/orexplosion

Possible Actions

Immediately start auxiliary power generator and primary air fan (coal mill fan on direct fired

kilns)

Retract burner pipe and protect TV monitor in kiln hood

Start turn on kiln not later than 10 minutes after the power failure

If available, close feed-end damper manually to prevent hot gases from escaping from kiln

by natural draft

Power Failure Main Procedures

Start generator or auxiliary drive

If it is raining, carry out turn as described previously

Close kiln back-end, ID fan damper, or precipitator inlet damper if power failure is of long

duration

Keep primary air fan running to cool down the burner pipe (and pre-calciner burners) or pull

the burners out of the kiln

Try to restore power as soon as possible

The following should be connected on the auxiliary power system:

Emergency light in control room

Emergency light in kiln platform

Telephone system for outside calls

Radio system inside the plant

ID fan louvers and precipitator inlet damper

Kiln auxiliary drive

Primary air fan

Recirculation pump for the industrial water system (water cooling system)

Instructions should be given to all members of the shift for specific responsibilities during a

power failure as example:

Operator A:

Carry out safety procedures on kiln system

Start the auxiliary power system

Close kiln back end (if on auxiliary system)

Rotate the kiln

If it is raining continuously, rotate kiln as soon as possible

Protection of burner pipe (pull out of kiln

Call the power company

Operator B:

Get to main power breaker and try to reset itGo to kiln back-end and close ID fan louvers (if they are not connected on the auxiliary drive)


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If the auxiliary drive control is not remote, make kiln rotation in local

A CHAIN FIRE

Indicators

Rapid, sudden rise in intermediate and exit gas temperatures

By visual observation


Melt-down and loss of chains

Damage to kiln shell in chain system area

On wet process kilns; steam explosion

Thermal damage to kiln back-end equipment

Possible Actions

Warning: Under no circumstances should water be added at the feed end.

Immediately reduce fuel rate to minimum (but dont shut fuel off completely)At the same time, reduce ID fan speed to obtain zero combustibles and less than 0.3%

oxygen

Increase kiln speed and feed rate to maximum until the back end temperature is under

control

On wet process kilns, clear all personnel from firing floor

Preventive Measures

Avoid operating the kiln for more than 10 minutes when there is feed shortage

Establish and enforce maximum permissible operating limits for intermediate and/or exit

gas temperatures

HEAVY RAIN OR THUNDERSTORMS


On kilns that are exposed to elements;

Loss of coating and collapse of refractory lining

Thermal damage and warping of kiln shell

Possibility of power failure

Possible Actions

If storm occurs shortly after a kiln shutdown;

Jack (turn) kiln more frequently or continuously on auxiliary drive

Start auxiliary power generator in preparation for a possible power failure

SUDDEN, HIGH POSITIVE HOOD PRESSURE

Possible Reasons

ID fan failure

Large ring or build-up broken loose inside kiln

Instrumentation failure of cooler air flow, cooler stack damper, or ID fan control

Steam explosion on wet-process kilns


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All personnel on firing floor is in danger

Thermal damage to equipment on firing floor and hood

Danger of backfire in coal system

Possible Actions

Immediately clear all personnel from firing floorImmediately reduce fuel rate to minimum and increase ID fan speed

Reduce cooler air flow rates into under grate compartments

Open cooler excess air damper manually

OVERHEATED KILN BEARINGS

(Procedure needs to be approved by your Maintenance Department)

Slow down kiln speed near minimum 20 rph. Do not stop the kiln (bearing will seize)

Open reset door on top of bearing and pour in sulfur until noise stops

You can add also powdered graphite to the bearing lubricating oil

The sulfur must be poured on the shaft and not on the bearing casingKeep a bag of sulfur near the control room location

Call the Maintenance Supervisor

Check if the oil heating is on or not, and stop it if it is in operation (breaker location must be

known to all)

Check if the water or glycol circulation is okay. If there is no circulation, open the water

valve very slowly

If you cannot reach the Maintenance Supervisor, call for an Oiler and a Maintenance man

Install a water hose to get cold water in the bearing (not a close circuit loop)

Drain the oil and add new oil until the new oil has reached its normal temperature (below

120oF/50oC you should have a temperature gauge showing the oil temperature on each

bearing)

Temperature sometimes requires from 6 to 12 hours to reach 120oF/50oC

Type of oil to use for the bearings to be confirmed by your maintenance department

KILN HAZARDOUS CONDITIONS

Shooting Rings with Gun

Do not allow any employees other than the gun crew on the firing hood during ring shooting

Do not tamper with the ammunition

Keep all live ammunition locked up and away from the firing floor when not in use

Permit only experienced and trained persons to operate the kiln gun

Use ear muffs when firing gun

Cotton stuffed in the ear is not adequate

Clean gun at frequent intervals and do not attempt to fire an apparent defective gun

If kiln has no chain section, keep all persons away from the kiln back end and rope this area

off before shooting

Clinker, Fuel Oil and Coal Dust Spills

Clean up spills immediately

Provide adequate clean-up cans and facilities for easy removal of spills

Initiate repair action when spills are caused by leaks that can be repaired

Gas, Fuel Oil, Coal and Steam Leaks in Fuel SystemReport any gas odor on the firing floor immediately to the shift supervisor


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Provide for periodic inspection of fuel and steam lines and system to detect leaks and other

defects as a preventive measure against major breaks in the system

Burner Hood, Porthole and Cooler Doors

Do not allow anyone to look into the burning zone while the kiln is on operation unless

approved safety equipment for viewing is used

Use proper protective clothing when working near open burner hood and cooler doorswhile the kiln is in operation

Instruct all persons to stay clear of the portholes whenever the hood pressure is temporarily

on the positive side

Relining the Kiln with Refractory Bricks and Materials

Use protective screen when working under loose refractory and coating, if no alternate

procedure is possible

Any employee working inside the kiln should have positive means, such as locking out the

kiln drive with his own lock, to assure that the kiln cannot be started while he is inside

Have proper posture and steady footing when lifting bricks or scaling coatingDo not work underneath the burner hood bridge while material is being hauled in and out of

the kiln

Do not test run cooler fans when workmen are inside the kiln

Do not run ID fan when workmen are at kiln rear or in chain section

Working Near or on Dust Collecting Equipment

Wear extra protective clothing to guard against burns from hot dust

Wash skin thoroughly with clear water after contact with alkaline dust

Have a second workman as safety man standing by whenever working under or in bins or

hoppers containing material

Do not allow workmen to work inside hopper without being properly secured on safety lines

and belts

When working on plugged flue hangers, be constantly on guard against potential dust

flushes and cave in of overhanging materials

Backfire and explosion During Kiln Light-up

Open either one cooler or burner hood door before lighting fire in kiln

Secure proper draft in kiln before fire is lighted (very important)

Do not allow unauthorized person to stand near the burner hood during light-up

Stay clear of burner hood ports when igniting the fuel

Avoid excessive fuel flow on initial light-up of flame

Start the primary air fan before opening the fuel valve

When firing coal, make sure that no coal dust spills are present on firing floor, around coal

feeder, or in the primary air pipe

Setting any Kiln Machinery into Motion During Start-up

Make sure all persons are clear of kiln equipment before each unit started

Sound horn to signal startup

Inspect all circuit breakers before the startup to make sure that all safety tags and locks

have been removedMake sure all machine guards are in place before any equipment is started


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Relining the Kiln with Refractory Bricks

Construct a proper bridge across the burner hood from firing floor to kiln nose

Inspect coating and remove loose overhangs before passing underneath.

KILN CYCLING

This is an unstable condition when the load in the kiln decreases, causing the temperatureof the burning zone to rise and forcing the operator to reduce the fuel rate.

Then, the burning zone starts to cool off in turn forcing the operator to increase the fuel

rate. In severe cases, the temperature continue

to drop, even though the fuel rate is at maximum and it become necessary to reduce the

kiln speed to slow down the entry of the feed into the burning zone. Once a kiln gets into an

upset such as this, the cycle will repeat.

Kiln cycling could be related to the following reasons;

Variations in kiln feed: physical or chemical,

Variations in dust re-introduction to kiln,

Variations in the water spray control system in kiln inlet (if any),Materials hold up in the chain system (for wet process kilns),

Poor chain system design (for wet process kilns),

Variations in hood pressure control

Poor cooler settings and control which promote secondary air temperature variations,

Operating the kiln above its production capacity,

Variations in the quality and the quantity of the fuel supply to the kiln,

Bad operating practices, especially over reacting with the kiln speed and

Volatile recirculation inside the kiln system especially chlorine

So all the above reasons should be investigated in order to find the cause of the cyclingproblem and corrected.

HOW TO BREAK A CYCLE IN A KILN

Reduce feed/speed ratio by approximately 10% in order to change the material load in the

kiln (also mainly to change the material load in the chain system).

Increase the fuel flow rate by 5% above the normal setting of the current production level.

Keep the oxygen level above 2% and try to control the back end temperature variations as

much as possible by using fuel rate and ID fan variations.

Let the kiln amps vary and do not attempt to chase them by varying the kiln speed. Just try

to control them if they get above or below the critical range by varying the fuel flow rate.

If the kiln speed need to be varied than it should be done with very small variations, in order

to avoid upsetting the material in the kiln.

If the kiln speed needs to be increased to go back to normal production level, then it should

be carried out more slowly than normal.

As you get to normal production level, fuel settings should be held above normal before

returning to normal operation settings.


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LOOKING INSIDE A KILN

Viewing the kiln interiorThis may sound somewhat elementary, but we should never forget that we are looking intoan extremely luminous source. Although filtering glasses are used, the light source is sostrong that focusing the eyes into it for too long a time could cause partial blindness. Oneshould look no longer than one minute at a time into the fire. If longer viewing is required,look a side for few seconds occasionally to rest the eyes. Looking steadily too long at theflame results in the eye losing its ability to see details, hence the need for a short rest everyminute or so.The question of what type of colored filter glass to use must be left to the operators.Burning with a natural gas flame usually makes necessary a darker colored than oil firewould require, because of the greater luminosity of the flame. As a rule, one should alwaysuse a glass that enables him to see under and behind the flame. Once a certain glass hasbeen chosen, the operators should stay with this glass at all times in order to properly judgethe burning zone conditions. How frequently should one look into the burning zone? There

is no set answer to this question. Experienced operators sometimes become over-confidentand think that it would be perfectly safe to leave the kiln alone for periods in excess of 30minutes. This action however, is against good burning practice. The secret of every goodoperator is his ability to recognize a change in kiln condition at the time a change takesplace and not later. For this reason, a good operator will never leave a kiln too long a timeunchecked. When things are going smoothly, the kiln should be checked every half hour,with more frequent checks if adjustments are being made. There is no such thing asoperating a kiln by the instrument alone, as the instruments do not show, for exampleheavier and lighter loads entering the burning zone until it is almost too late to make thenecessary adjustment.

Appearance of burning zoneGood or bad visibilityBright white or dark red colorGood appearance is an orange-yellow colorThe gas stream should be calm without great turbulence

Appearance of coatingCoating should begin approximately diameter of kiln size from the nose ringColor of coating tells a great deal about the condition in burning zone as coating acts as heatstorage in burning zoneOverall thickness of coating should be between 9 and 12 inches and is dependent of thetype of raw mixCheck for ring formation near lower or upper section of the kilnIf the surface of the coating appears smooth, then the burning zone in this area is hotIf the coating appears lumpy then the burning zone is okayA bare spot without coating could be due to flame erosion, thick brick or high flametemperature in this location

Appearance of the coating falling off from the top of the kiln shell:Large pieces: normalFine noodles dripping: too hotThe location where the coating pieces are falling from the top of the kiln wall, above the endof the flame is generally where the raw load is. So whenever the raw load cannot be seen in

the bottom and behind the flame of the kiln, try to look at the top.


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Appearance of material loadIs clinker balling or fine?Is material sticky?Is material heavy or light?Is material movement fast or slow?

Is material climbing low or high in the wall? (material should climb up +/- to the 10 oclockposition in normal operation)Appearance of material before falling in the cooler, fine or nodular

Upper burning zone sectionAre rings building up or not?Is coating formation seem normal?Try to evaluate the length of the coating (50 to 100 feet from burning zone to far up)

Raw feed locationLook behind the flame at the bottom of the kilnNormal position is approximately diameter distance under the flameNever allow raw feed to come way under the flame as kiln speed will have to be reducedto control it (kiln low speed)An advancing or receding dark feed is the earliest indication of a burning zone that iswarming up or cooling down. So that is why it is important for the kiln operation to be ableto see this load. Every effort should be done during normal operation to keep this load insight.

Flame appearanceShould always be evaluated during stable kiln conditionLong (100 ft) or short (30 ft)Hard or lazy

Bushy or narrowBright or darkWhite or orange yellowEroding the coating or the brick wallAiming high, low or in the centerEroding the material loadIf fuel is burning in suspension or in the material loadPosition of the ignition point when coal or coke is usedThe flame temperature should be as hot as possible as long as it does not create problemswith the coating and the kiln refractory. Whenever a change is made on the flame shape, aclose monitoring of the shell temperature should be done.

Coal flamesCoal normally burns with longer flame than oilA coal flame normally starts at 3 to 5 feet from the burner tipCoal fineness to be about 85% passing 200 meshKeep the coal system air flow at about 70 ft/sec to avoid coal deposit inside pipe, whilekeeping primary air to minimum (direct system and burner design)On direct firing system, coal fan damper setting should be set at minimum value and thefuel rate changes made only by making changes with the coal feeder system in order tokeep the flame shape short and as constant as possible.

Burner pipe appearance

Is the tip of the blast pipe in good condition?Is the burner cast-able in good condition?


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Is the burner pipe aimed correctly?How is the pipe location relative to the nose ring?Are snowmen building up on top of burner pipe?Whenever a bad condition deflecting the flame is observe, a quick evaluation should bedone to evaluate if the kiln can continue its operation or if it needs to be shut down to fixthe burner pipe.

Nose ring appearance-able or the refractory on the top of the nose ring if okay

Secondary airCalm or upsetDusty if the clinker is fineClear if clinker is ballingFoggy and white if temperature is hot

The secondary air temperature has a major influence on the flame and its shape.

Primary airShould be as low as possible to obtain satisfactory heat recuperation from coolerHas an important influence on the shape of the flame (bushy or narrow)Pressure should be as constant as possibleWhen good settings of the flame have been found, the primary air settings should not bechanged in normal operation unless a high temperature condition in the kiln refractory hasraised and required to change the flame.

When the kiln is downLook for ball or ring formation at upper section of burning zone

Evaluate length of coating if okay, too long means we burned the kiln too far upLoad level inside kiln if even and normalAppearance on load during kiln jacking (sticky or normal)Look at the sealing efficiency of the kiln back end (no suction or gases movement inside ofkiln should be observed).When kiln is shutdown, the gases should be bottled inside of the kiln as fast as possible byclosing the kiln back end damper or its equivalent and by adjusting the hood pressure setpoint, slightly positive.The procedure need to be done to avoid heat loss from the kiln to insure a slow cooling ofthe refractory and avoid thermal shocks on the bricks.


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DECLARATION

I ,SWAET PRAKASH BHOI ,do here by to Declare that ,the project report on

ADVANCEMENT IN OPERATION & MAINTENANCE OF CEMENTKILN, is submitted by me is original to the best of my knowledge & brief .Ithas been prepared by me with my own idea and creativity under directsupervision of my project guide.

Any resemblance to earlier project or research work is purely co-incident.

Place:Bargarh cement works , BargarhDate:


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Documents

ACC plant visit report