A Rotary kiln is a pyroprocessing device used to raise materials to a high temperature (calcination) in a continuous process. Materials produced using rotary kilns include: Cement. Lime.
Rotary kilns have become the backbone of many industrial processes, with new applications being developed all the time. This presentation gives an overview of what types of processes rotary kilns are used for, as well as how both direct-fired and indirect-fired rotary kilns work.
The Indian cement industry today stands at
260 MTPA capacity, with greater growth prospects
and promising future ahead. Cement industry has
been an excellent example of a fast growing sector
showing consistent and steady reduction in its
energy consumption. This has largely been
possible by steady and continuous improvement
across all equipments in cement manufacturing
process.
Rotary kilns have become the backbone of many industrial processes, with new applications being developed all the time. This presentation gives an overview of what types of processes rotary kilns are used for, as well as how both direct-fired and indirect-fired rotary kilns work.
The Indian cement industry today stands at
260 MTPA capacity, with greater growth prospects
and promising future ahead. Cement industry has
been an excellent example of a fast growing sector
showing consistent and steady reduction in its
energy consumption. This has largely been
possible by steady and continuous improvement
across all equipments in cement manufacturing
process.
ENERGY MODELING OF THE PYROPROCESSING OF CLINKER IN A ROTARY CEMENT KILNISA Interchange
This paper highlights the efforts taken by the author in developing an Energy Model for the pyro-processing of Clinker production in a dry-process rotary cement kiln. In this paper this Energy Model is applied to a state of the art cement plant in a Far East Asian country. However this Energy Model is also applicable to all the modern dry process cement kilns. This model is based on actual field input data and site observations.
Rotary kiln design is a complex process, with a variety of factors and material characteristics influencing the sizing and design. This presentation gives an overview of the sizing and design process, including the many factors that will need to be considered during the design stage.
Crushing of coal and calculation of size reduction efficiency.Utsav Kant
Mineral/Coal Processing is the subsequent step after mining of Mineral/Coal. The first step of Mineral Processing is the Crushing of minerals. This presentation is about crushing of coal and how to calculate the crushing efficiency of coal from processing point of view.
Crushing efficiency has been defined in the literature from the power consumption point of view. But while operating a process plant, it is more important that the crushing efficiency is defined in terms of the requirement of subsequent process. The Process plant has been designed for coal size - 13 mm ( 80 % passing). The 610 mm dia cyclones are inefficient at sizes less than 3 mm. Hence a study has been made from the plant data to arrive at the crushing efficiency of crushers.
Design and analysis of ball mill inlet chute for roller press circuit in ceme...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Cement industry : grinding process of ball millPankaj Verma
this is the presrntation which i made when i was in traning in ultratech cement hirmi , i got project on studying the process and operations of grinding process of ball mill in the cement industry , after the clincker formation.
Vertical Roller Mill Gearbox Reduction Ratio CalculationsSyed Fahad Ahmed
This document presents the calculations for finding out the Gear Ratio of a 3 stage (Bevel-Helical-Planetary) gearbox for Vertical Roller Mill (VRM-3700) of a Cement plant. The capacity of this VRM is 260tons/hour and is used limestone grinding.
ENERGY MODELING OF THE PYROPROCESSING OF CLINKER IN A ROTARY CEMENT KILNISA Interchange
This paper highlights the efforts taken by the author in developing an Energy Model for the pyro-processing of Clinker production in a dry-process rotary cement kiln. In this paper this Energy Model is applied to a state of the art cement plant in a Far East Asian country. However this Energy Model is also applicable to all the modern dry process cement kilns. This model is based on actual field input data and site observations.
Rotary kiln design is a complex process, with a variety of factors and material characteristics influencing the sizing and design. This presentation gives an overview of the sizing and design process, including the many factors that will need to be considered during the design stage.
Crushing of coal and calculation of size reduction efficiency.Utsav Kant
Mineral/Coal Processing is the subsequent step after mining of Mineral/Coal. The first step of Mineral Processing is the Crushing of minerals. This presentation is about crushing of coal and how to calculate the crushing efficiency of coal from processing point of view.
Crushing efficiency has been defined in the literature from the power consumption point of view. But while operating a process plant, it is more important that the crushing efficiency is defined in terms of the requirement of subsequent process. The Process plant has been designed for coal size - 13 mm ( 80 % passing). The 610 mm dia cyclones are inefficient at sizes less than 3 mm. Hence a study has been made from the plant data to arrive at the crushing efficiency of crushers.
Design and analysis of ball mill inlet chute for roller press circuit in ceme...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Cement industry : grinding process of ball millPankaj Verma
this is the presrntation which i made when i was in traning in ultratech cement hirmi , i got project on studying the process and operations of grinding process of ball mill in the cement industry , after the clincker formation.
Vertical Roller Mill Gearbox Reduction Ratio CalculationsSyed Fahad Ahmed
This document presents the calculations for finding out the Gear Ratio of a 3 stage (Bevel-Helical-Planetary) gearbox for Vertical Roller Mill (VRM-3700) of a Cement plant. The capacity of this VRM is 260tons/hour and is used limestone grinding.
Rotary kilns are diverse thermal processing machines. This presentation looks at the many options available to customize a rotary kiln to promote improved processing efficiency. This includes, rotary kiln dams, bed disturbers, flights, and more.
Today, lime has many end uses, such as: steel manufacturing, plaster, mortar, and asphalt. We’re not talking about the food, but instead the product that originally began as a sedimentary rock.
Computation of Theoretical Heat of Formation in a Kiln Using Fortran LanguageIOSR Journals
Abstract: The evolution of the early rotary kiln for cement industries and innovation made by man is to ease
cement processing. The rotary Kiln in which cement is burnt at 13000C to 15500C is a long cylinder rotating on
its axis and inclined so that the materials fed in at the upper end travel slowly to the lower end.
The approach adopted is by evolving a mathematical model of the system. Simulation of the process was carried
out using FORTRAN language to compute theoretical heat of formation. The exact value of theoretical heat of
formation was found to be 435.583000.
The aim is to produce a good quality clinker at the optimum fuel consumption and thermal efficiency.
The computer model is in a FORTRAN language. The simulation provides very encouraging result, which
showed trends that enabled the deduction of optimum system parameters.
Significance: This paper investigated the behavior of the kiln through computer simulations, for comparing
the performance of different constitutions under similar operations and conditions. The paper highlighted how a
good quality clinker can be produced at optimum fuel consumption and thermal efficiency.
While rotary kilns are often engineered around the characteristics of the material to be processed, the base of a rotary kiln can be somewhat standard. This presentation looks at the construction and components of both indirect-fired and direct-fired rotary kilns.
Carbon Capture and Storage in the Cement IndustryAntea Group
Heidelberg Cement presented on carbon capture and storage/ utilization as part of the recent Antea Group-sponsored EHS&S workshop for the chemical industry at the Brightlands Chemelot campus in the Netherlands.
Cement refers to the commodities that are produced by burning mixtures of limestone and other
minerals or additives at high temperature in a rotary kiln, followed by cooling, finish mixing, and
grinding. This is the manner in which the vast majority of commercially-important cementations
materials are produced in the United States. Cements are used to chemically bind different
materials together. The most commonly produced cement type is "Portland" cement, though
other standard cement types are also produced on a limited basis.
Cement plants produced 99.8 million metric tons of cement. Worldwide production accounted
for about 2.5 billion metric tons. As with most large manufacturing industries, by-product
materials are generated. These industrial by-product and waste materials must be managed
responsibly to insure a clean and safe environment.
Steel mills, also known as steelworks, are industrial factories that specialize in the production of steel. They typically smelt down iron and carbon, mixing the two together in a specific ratio to create steel.
Innovative engineering design in circulating fluid bed technologyIgor Sidorenko
Sneyd, S., Sidorenko, I., Orth, A., & Laumann, M.-D. (2007) Innovative engineering design in circulating fluid bed technology. Paper presented at CHEMECA conference, Melbourne.
chemical industries cement industry rotary Kiln.2023.pdfDimaJawhar
Abstract:
The assignment describes the cement industry's processes. Cement is a fundamental
building and civil engineering material.
the stages of getting Portland cement is Crushing and grinding the raw materials,
combining the components in precise proportions, burning the prepared mix in a kiln,
grinding the burnt result, known as "clinker," a percentage of gypsum (to limit the
period of set of the cement).
Under high temperatures, a rotary kiln is a physically huge process unit used in cement
manufacturing where limestone is degraded into calcium oxide, which forms the base
of cement clinker particles.
Also, the Location of the control parameters and variables is discussed.
Industry of Cement: Rotary Kiln
4
Introduction:
the cement industry is directly tied to the economy of the construction, In 1995, the
European Union produced 172 million tonnes of cement, accounting for nearly 12% of
global output. (European Commission, 2001)
After mining, grinding, and homogenization of raw materials, the first phase in cement
production is the calcination of calcium carbonate, followed by high-temperature
burning of the resultant calcium oxide with silica, alumina, and ferrous oxide to
generate clinker. To make cement, the clinker is crushed or milled with gypsum and
other ingredients. (European Commission,2001)
It is worth noting that cement is one of the most essential building materials in the
world. It is mostly utilized in the production of concrete. Concrete is made up of inert
mineral aggregates like sand, gravel, broken stones, and cement. Cement consumption
and manufacturing are inextricably linked to the construction industry, and
consequently to overall economic activity. Cement is one of the most developed
products in the world, owing to its importance as a construction material and the
geographical availability of the key raw materials, namely limestone. The extensive
development is also attributed to the low cost and high density of cement. Because of
the comparatively high prices, ground transportation is reduced. Export commerce
(excluding plants grown across borders) is often restricted in comparison to global
output. (N. Martin, m. D. Levine, et al,1995)
Referred to Figure 1 process flow diagram of the cement industry is explained There
are four stages in the manufacture of Portland cement:
• crushing and grinding the raw materials
• blending the materials in the correct proportions
• burning the prepared mix in a kiln
• grinding the burned product, known as “clinker,”
• percent of gypsum (to control the time of set of the cement).
The three manufacturing techniques are known as the wet, dry, and semidry processes,
and are so named because the raw materials are ground wet and fed to the kiln as a
Industry of Cement: Rotary Kiln
5
slurry, ground dry and supplied as a dry powder, or ground dry and subsequently
moistened to form nodules that are fed to the kiln. (Thomas o. Mason 2023)
Figure 1: The cement-making process, from raw material
A 45 days observational training program that gave exposure to the industrial environment and included visit to various plants like RHMP, Coke Oven, Steel Making Units, Blast Furnace which was a learning experience pertaining to the functioning of all the mentioned units.
PRODUCTION OF METHYL TERTIARY BUTYL ETHER (MTBE)Aree Salah
this project submitted in partial fulfilment of the requirements for the degree of bachelor in science in Chemical engineering at Koya University.
The main purpose of our project is to describe and design the production of MTBE, and using it as an additive to gasoline in order to increase its quality.
We work at this plant to produce 112,200tons / year (112,200,000 kg/y) of methyl tertiary butyl ether (MTBE)
Gas hydrate
To prepare natural gas for sale, its undesirable components (water, H2S and CO2) must be removed. Most natural gas contains substantial amounts of water vapor due to the presence of connate water in the reservoir rock. At reservoir pressure and temperature, gas is saturated with water vapor
The probe type is determined by the measurement task. The selection of the most suitable temperature sensor is made according to the following criteria:
- Measurement range
- Accuracy
- Measurement site design
- Reaction time
- Durability.
The objective of this experiment is to calculate the rate of the heat transfer log mean temperature difference, and the overall heat transfer coefficient in case of Counter flow
The objective of this experiment is to calculate the rate of the heat transfer log mean temperature difference, and the overall heat transfer coefficient in case of Counter flow
To demonstrate the effect of cross sectional area on the heat rate.
To measure the temperature distribution for unsteady state conduction of heat through the uniform plane wall and the wall of the thick cylinder.
The experiment demonstrates heat conduction in radial conduction models It
allows us to obtain experimentally the coefficient of thermal conductivity of some unknown materials and in this way, to understand the factors and parameters that affect the rates of heat transfer.
To understand the use of the Fourier Rate Equation in determining the rate of heat flow for of energy through the wall of a cylinder (radial energy flow).
To use the equation to determine the constant of proportionality (the thermal conductivity, k) of the disk material.
To observe unsteady conduction of heat
The aim of this experiment is to measurement linear thermal along z direction conductivity and to investigate and verify Fourier’s Law for linear heat conduction along z direction and we proved that K is inversely proportional with ΔT, and we have many errors in our experiment that made the result not clear.
To assess the performance of the vapor compression cycle as a refrigerator and as a heat pump and its dependence on various parameters. To learn how to use the equipment to measure temperatures at various test points and the flow rates for liquids and gases.
The aim of this experiment is to find the dynamic pressure in a moving fluid using piezometer and pitot tube. By calculating its static pressure and its total
Pressure.
The maximum flame height in millimeters at which kerosene will burn without smoking, tested under standard conditions; used as a measure of the burning cleanliness of jet fuel and kerosene.
The objective of this lab is to measure and study density and specific gravity of different liquids by using hydrometer. This gives information how light or heavy a crude oil is.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
1. 1
Koya University
Faculty of Engineering
Chemical Engineering Department
Chemical Industry
Rotary kiln
Preparation By:
Aree Salah
Alan mawlud
2. 2
List of content:
Abstract………………………………..……………………..3
The history of the rotary kiln...…………………………..….4
The history of cement industry …………………..……….5-6
Introduction ………………………………………...……..7-8
Rotary Kiln Processes …………………..…………………...9
Wet and Dry Processes………....................................10-11-12
The clinker cooler..................................................................13
Thermal profile and kiln subdivisions ……..……....14-15-16
Discussion..…………………………………........17-18-19-20
References………………………………………………......21
3. 3
ABSTRACT:
This work presents the simulation of a rotary kiln used to produce cement
clinker. The effort uses an original approach to kiln operation modeling. Thus,
the moving cement clinker is accurately simulated, including exothermal
reactions into the clicker and advanced heat transfer correlations. The
simulation includes the normal operation of a cement kiln, using coal in an air-
fired configuration. The results show the flame characteristics, fluid flow,
clinker and refractory characteristics. Two types of coal are employed, one with
medium-volatile and one with low-volatile content, with significant differences
noted in the kiln operation.A specific goal of this effort is to study the impact of
oxygen enrichment on the kiln operation. For this purpose, oxygen is lanced into
the kiln at a location between the load and the main burner, and the impact of
oxygen enrichment on the kiln operation is assessed. Different oxygen injection
schemes are also studied. Thus, varying the angle of the oxygen lance enables to
handle various problems as reducing conditions, overheating in the burning
zone or refractory wall. It is concluded that oxygen has a beneficial role in the
fuel combustion characteristics, and its impact on refractory temperature and
the clinker is negligible, in conditions of increased productivity and overall
efficiency.The paper presents the impact of dust insufflation into the kiln, such
as reduced temperature profile, resulting in a less stable combustion process.
The work shows the beneficial influence of oxygen enrichment on kiln operation
in the presence of dust, leading to an increase in the amount of dust capable of
being insufflated into the kiln.The paper presents the impact of dust insufflation
into the kiln, such as reduced temperature profile, resulting in a less stable
combustion process. The work shows the beneficial influence of oxygen
enrichment on kiln operation in the presence of dust, leading to an increase in
the amount of dust capable of being insufflated into the kiln.
4. 4
The history of the rotary kiln:
About 1900, various metallurgists were experimenting with the rotary kiln for
nodulizing flue-dust, fine iron ores, etc. Edison conducted experiments, for
example, on the fine concentrates obtained from his magnetic separators. Within
a few years plants were established for this purpose. The rotary kiln also
furnished a simple means of utilizing the soft clayey ores, such as that of the
Mayari field in Cuba. Practically all of the schemes tried for placing this ore in
satisfactory condition for the blast furnace were unsatisfactory until the rotary
kiln was tried. The plant in Cuba consisted of twelve kilns 30 m long and 3 m in
diameter and producing 1500 - 2000 tonnes per day. In 1914 application of the
rotary kiln for the partial roasting of copper sulfide concentrates containing
appreciable amounts of pyrite, to decrease the sulfur content before charging to
the reverberatory furnace was conducted in USA. The kiln was 2 - 2.5 m
diameter and 5 - 8 m long laid horizontally and operated batch-wise. In later
design the inclined kiln was used; the charge was introduced at the burner side
with provision of introducing secondary air through a pipe in the center of the
kiln (Fig. 8). At present, rotary kilns are used for drying ores and the production
of alumina by the dihydroxylation of Al(OH)3, reduction of iron oxide by the
Krupp–Renn process, in the TiO2 pigment manufacture, and other processes
(Fig. 9).
5. 5
The history of cement industry:
In 1885 a continuous reactor was needed to replace the shaft furnace which was
operated batch-wise. The shaft furnace was used for making cement clinker and
was borrowed from the limestone calcination industry, which was usually
known as lime kiln. Since the process was operated batch-wise, at the end of
heating the charge, the kiln was allowed to cool and the product raked out.
Naturally, this was a wasteful process due to the consumption of large amounts
of fuel. The rotary kiln was adopted by cement manufacturer in 1824 as soon as
Joseph Aspdin (1788-1855), the brick-layer and mason in Leeds, England
discovered what he called Portland cement1. Although Portland cement had
been gaining in popularity in Europe since 1850, it was not manufactured in the
US until the 1870s. The first plant to start production was that of David O.
Saylor at Coplay, Pennsylvania in 1871. In 1885, an English engineer, Frederick
Ransome, patented a slightly titled horizontal kiln which could be rotated so that
material moved gradually from one end to the other. Because this new type of
kiln had much greater capacity and was heated more thoroughly and uniformly,
it rapidly displaced the older type. In 1880, about 42 000 barrels of Portland
cement were produced in the United States; a decade later, the amount had
increased to 335 000 barrels. One factor in this tremendous increase was the
development of the rotary kiln.
6. 6
In 1888, Fredrik Lوssِe Smidth (1850–1899) (Fig.
4), Danish engineer and industrialist in
Copenhagen, in association with two other Danish
engineers, Alexander
Foss and Paul Larsen, delivered the first cement
plant to a manufacturer in Sweden. In 1898, he was
the first to introduce the rotary kiln in the cement
industry and
became later one of the major suppliers of rotary
kilns worldwide. Thomas A. Edison (1847-1931)
(Figs 5 and 6 ), the American inventor, was a
pioneer in the further development of the rotary kiln in his Edison Portland
Cement Works in New Village, New Jersey where he introduced the first long
kilns used in the industry 46 m long in contrast to the customary 18 to 24 m. In
1902, together with José Francisco de Navarro (1823–1909) (Fig. 7) founded the
Universal Atlas Portland Cement Company whose largest plant was in
Northampton, PA and won the enormous contract for supplying cement for the
Panama Canal. By 1904, Navarro became the largest cement manufacturer in the
world, producing 8 million barrels per year. Today, some kilns are more than
150 m long. The increased production of cement due to the use of efficient
rotary kilns has a parallel improvement in crushing and grinding equipment.
7. 7
Introduction:
Rotary kiln is a machine whose working temperature can reach the
temperature to calcine superfine kaolin. At present the rotary kiln
technology in our country is mature and advanced, which represents the
development direction of calcination technology of superfine kaolin. This
calcinations technology has low energy consumption and high output,
and after dehydration and decarburization and whitening, the products
have stable performance and can be used in such industrial fields as
paper making and coating.
The cement rotary kiln produced by Hongxing Machinery has simple and
solid structure, stable operation, convenient and reliable control of the
production process, fewer quick-wear parts, high quality of final products
and high running rate, so that it is the equipment for cement plants to
calcine high quality cement and it is also widely used in metallurgy,
chemistry and construction industry. In addition, Hongxing Machinery is
able to provide customers with highly efficient vertical-cylinder preheater
and five-star cyclone preheater.
8. 8
According to the types of materials to be processed, rotary kiln can be
divided into cement kiln, metallurgical chemical kiln and limestone rotary
kiln. Rotary cement kiln is mainly used for calcining cement clinker and it
can be divided into two types, namely dry type production cement kiln
and wet type production cement kiln. Metallurgical chemistry kiln is
mainly used for the magnetizing roasting of the lean iron ore and the
oxidizing roasting of the chromium and josephinite in the steel works in
the metallurgical industry, for the roasting of high alumina bauxite ore in
the refractory plant, for the roasting of clinker and aluminium hydroxide in
the aluminium manufacturing plant and for the roasting of chrome ore in
the chemical plant. Limestone kiln is mainly used for roasting active lime
and lightly calcined dolomite used in the steel works and ferroalloy
works.
The cement equipments with various types produced by Hongxing
Machinery including rotary cement kiln and rotary kiln have reasonable
price and high quality, and we can design the product manufacturing
scheme according to your specific needs. If you want to learn more
about cement equipments, feel free to contact Hongxing Machinery, and
we will serve you with heart and soul.
9. 9
Rotary Kiln Processes:
With the arrival of rotary kilns, cement manufacturing processes became
sharply defined according to the form in which the raw materials are fed to the
kiln. Raw materials were either ground with addition of water, to form a slurry
containing typically 30-45% water, or they were ground dry, to form a powder
or "raw meal".
1. In the Wet Process, the kiln system is fed with liquid slurry, the water
then being evaporated in the kiln.
2. In the Semi-Wet Process, raw material is prepared as a slurry, but a
substantial proportion (50-80%) of the water is mechanically removed,
usually by filtration, and the resulting "filter cake" is fed to the kiln
system.
3. In the Dry Process, the kiln system is fed with dry raw meal powder.
4. In the Semi-Dry Process, a limited amount of water (10-15%) is added to
dry raw meal so that it can be nodulised, and the damp nodules are fed
to the kiln system.
10. 10
Wet and Dry Processes:
With the arrival of rotary kilns, cement manufacturing processes became sharply
defined as wet process or dry process.
1. In the Wet Process, the kiln system is fed with a rawmix in the form of a
liquid slurry, typically containing 30-50% of water by mass.
2. In the Dry Process, the kiln system is fed with a rawmix in the form of a
dry powder.
The process selected depends to a certain extent upon the nature of the available
raw materials.
At the start of the twentieth century, both the American and the British
industries were highly concentrated geographically. The British industry was
concentrated in the Thames and Medway estuaries, and the epicentre of the
American industry was the Lehigh and Delaware valleys in eastern Pennsylvania
and north-west New Jersey. The Cambrian argillaceous limestones of the
Jacksonburg Formation in that area are hard rock, most readily processed by dry
grinding. This fact provided a further impetus to the development of rotary kilns,
since for shaft kilns, a powdered rawmix must be briquetted in a more-or-less
expensive pressing process, whereas untreated powder can easily be fed to a
rotary kiln. It is for this reason that all the original American rotary kilns used
the dry process. The wet process gradually developed, initially in more remote
wet raw material regions such as the marl belt of central Michigan. Later, the
wet process came to be used in Pennsylvania mainly because of the ease of wet
blending, but the majority of kilns continued to use the dry process throughout
the twentieth century.
In Britain the situation was quite different. In the Thames and Medway areas,
dry process raw material preparation was practically impossible. The wet chalk
(typically 40% water by volume) can't be ground to a powder until it has been
dried, but the un-ground chalk can't easily be dried because its spongy texture
tenaciously retains water. On the other hand, wet-grinding it with water is
trivially easy. Where chalk marl was available in the southern part of the
Medway valley, a dry process developed using brick-making techniques,
allowing shaft kilns to be used in the period 1900-1928, but this was a marginal
technology because of the poor homogeneity of the brick “pug”. So with the
arrival of rotary kilns, wet process was initially the universal choice.
11. 11
Wet Process: Dry Process:
In the parallel wet and dry processes in America, the dry process was marginally
more energy-efficient, but the differential was small due to the lack of good heat
exchange in the kiln – a dry kiln simply produced hotter exhaust gas. The early
short kilns (length : diameter ratio 12:1 or less) were troublesome on wet
process because the hot and over-fuelled conditions of operation necessary to
complete all burning stages in a short length led to high dust loss and emissions
of black smoke. It was early appreciated by the more scientific practitioners that,
at least in theory, the dry process ought to be more efficient. It is characteristic
that the first British dry process rotary kilns were installed by A. C.
Davis at Norman (1904), and Davis promoted the system with an evangelism
that flew in the face of the objective facts. Having started in the industry by
constructing Saxon (1901) with Schneider kilns fed with dry-ground and
briquetted Chalk Marl, his business strategy was to run flat out, selling at or
below cost price, and generally spreading alarm and despondency among the
“old fashioned” manufacturers by suggesting that his costs were half of theirs,
which they may indeed have been. With the arrival of rotary kilns, he naturally
continued the same behaviour, by publicising his use of dry process as an
economy that others could not match. To drive home the point, he installed no
less than five kilns at Norman – a larger installation than at any of the other
independent companies at this stage.
12. 12
The Norman installation was described in great detail in an article in The
Engineer. The kilns were 60 ft long, and of low LD ratio: only 9.61:1. They
were supplied byFellner & Ziegler who also supplied APCM. Whereas the marl
at Saxon was dried in a coal-fired Smidth drier, at Norman, it was dried in rotary
driers heated by the kiln exhaust gases. The article includes a lengthy
description of the raw meal mixer. This was a complex mechanical device with
action equivalent (in theory) to a blending silo operating in “overflow” mode. In
the light of later experience, it would in all probability have spent much of its
time blocked solid, and therefore allowing run-of-mill meal to go straight to the
kiln feed silo. The design makes it clear that rawmix blending was already
understood to be the major stumbling-block in the dry process, and that the
technical challenge was at this stage a long way from being solved. The
perceived success of the Norman kilns was sufficient to persuade several other
plants to embark on rotary kilns using the dry process, but as kilns developed,
the vast majority were wet process.
13. 13
The clinker cooler:
There are various types of cooler - we will consider only one, the 'grate cooler'.
Grate cooler: the hot clinker falls out of the kiln and moves along the cooler,
towards the foreground of the image.
The purpose of a cooler is, obviously, to cool the clinker. This is important for a
several reasons:
From an engineering viewpoint, cooling is necessary to prevent damage
to clinker handling equipment such as conveyors.
From both a process and chemical viewpoint,
it is beneficial to minimise clinker
temperature as it enters the cement mill. The
milling process generates heat and excessive
mill temperatures are undesirable. It is
clearly helpful, therefore, if the clinker is cool
as it enters the mill.
From an environmental and a cost viewpoint,
the cooler reduces energy consumption by
extracting heat from the clinker, enabling it
to be used to heat the raw materials.
From a cement performance viewpoint, faster
cooling of the clinker enhances silicate
reactivity.
The cooled clinker is then conveyed either to the clinker store or directly to the
clinker mill. The clinker store is usually capable of holding several weeks'
supply of clinker, so that deliveries to customers can be maintained when the
kiln is not operating.
14. 14
Thermal profile and kiln subdivisions:
The rotary kiln thermal profile varies throughout its length, depending on the
temperature and chemical reactions involved during the process (see in Table
1).
The rotary kiln can be subdivided into several zones or regions that are exposed
not only to thermal and chemical wear but also to mechanical stresses. The
influence of one or several of these factors, to minor or greater proportion
determines the refractory lining type required for each zone:
• Decarbonation zone: from 300ºC to 1000°C (+)
This stage can occur either inside of the old wet process rotary kilns or in the
preheater tower of modern units consisting of two steps: Firstly, between 300°C
and 650°C where the raw meal heating occurs, accompanied by a dehydration
reaction; Secondly, between 650°C and 1000°C, when the limestone
decarbonation takes place generating CO2 and CaO.
The first step is characterized by the following aspects:
• Presence of raw meal (there are no new mineral phases development);
• Erosion (due to raw meal flow at high velocities);
• low temperature;
• Evaporation and dehydration (of water) chemically bonded to the raw
material.
In this zone it is very important that the refractory products have the capability
to protect the rotary kiln drive (good insulation degree) and good resistance to
impacts of anomalous build-ups. Bricks with less than 45% Al2O3 content are
suitable. Besides that, when alkaline salts are present, a vitreous glassy layer
can develop with the alkali on the brick surface, preventing its propagation or
later infiltration.
In the second stage of these reactions, the development of new mineralogical
phases occurs:
- Formation of CaO and CO2;
- Formation of CA, C12A7 and C2S;
- Temperature variation;
- Alkali attack.
Usually, the use of bricks with a 70% Al2O3 content is recommended, which
offers a high mechanical resistance, low porosity, and low thermal conductivity.
15. 15
However, the risk of eutectic reactions formations on the Al2O3-CaO- SiO2 ,
system and alkali resistance is a limiting factor.
• Upper transition zone: from 1000ºC to 1238°C (+)
It is the most unstable and difficult area for refractory specification. Although
the temperature range varies from 1000°C to 1338°C, incidences of thermal
overloads are frequent. This fact is linked on the flame shape, to the fuel type
and to the design of the kiln main burner. Therefore, it is in this area where
coating starts to develop as soon as first drops of liquid phase appear. Coating
becomes very unstable if the operational conditions present high variability.
Table 1
• Sintering zone: from 1338ºC to 1450°C (+)
In this area a full development of coating at 1450ºC(+) is expected. The
presence of some liquid phase facilitates the dissolution of C2S in the same what
promotes the reaction that generates C3S. The highest temperature in the kiln is
reached at this area. Usually it should be around 1450ºC for ordinary Portland
Cements. Liquid phase is also around 25% at 1450ºC. If process is under
control, coating will be stable and able to protect the lining during the whole
campaign. However, if there is a big variability at ram meal control parameters
or uneven fuels types shifting, coating will be unstable and refractories
submitted to an enormous thermo-chemical wear. The refractory products must
resist high temperatures, infiltration of molten liquid calcium silicates, and/or
alkaline sulfates, and be able to hold a stable coating.
Usually at this kiln zone it is possible to find:
• Presence of incipient liquid phase from 18 to 32%, free lime and C2S;
• Development of C3S by the reaction of CaO and C2S.
• Clinker liquid phase infiltration and coating formation;
16. 16
• Chemical attacks by alkaline sulfates;
• High operational temperature.
• Lower transition zone from: 1400ºC to 1200°C (+)
This area usually operates between 1400°C and 1200°C. Around 1200ºC begins
the crystallization of the clinker the mineral phases, but not. Although the liquid
phase can still be present, it is a stage of low chemical activity, considering that
most of C3S has already been formed with a remaining amount of free lime
around 1%. Nevertheless, it is a zone submitted to temperature variations since
it is right under the influence of the secondary air temperature coming from the
cooler.
This area is characterized by the following aspects:
• Presence of the clinker liquid phase;
• Chemical attacks by alkaline sulfates;
• Frequent temperature variations when flame impinges over the brick;
• Continuous thermal shock;
• Redox atmosphere when using alternative fuels with poorly designed burner;
• Mechanical stress imposed by the tire station and kiln shell ovality.
In order to support the temperature variations under mechanical stress, this part
of the process requires the use of basic bricks with high structural flexibility,
low permeability to gas, high hot modules of rupture and abrasion resistance.
• Pre-cooling zone from: 1200ºC to 1000°C (+)
Originally, many kilns have been designed to promote the end of freezing and
crystallization of the just developed clinker phases. However, nowadays, the
existence of this zone into the kiln depends of the clinker cooler type and the
secondary air temperature entering into the kiln. With old grate coolers it was
around 700ºC, and for the modern high efficiency ones from 1150°C to 1100°C.
In this zone at that temperature range, there is high abrasion (clinker nodules),
accentuated discharge erosion (by the clinker dust carried by secondary and
tertiary airs) and mechanic stresses (nose ring plates and retention ring for
refractory products).
The main characteristics of this kiln zone are:
• High abrasion / erosion;
• Frequent thermal shocks;
• High mechanical stresses (compression/traction).
In most of the modern furnaces equipped with high efficiency coolers, this zone
is not inside the rotary kiln but in the first cooling compartment.
17. 17
Discussion:
Question-1: What is the maximum continuous shell temperature a kiln stands
without permanent damage to the shell?
Answer-1: The maximum recommended kiln shell temperature varies by plant,
by country and by kiln manufacturer, despite the fact that most kiln shells are
made of low alloy carbon steel. Age of the kiln shell, distance between the tires,
and structure of the shell are some important points should be considered before
deciding what the maximum allowable temperature for a kiln is. Let us explain
these points briefly:
1. Age and condition of the kiln shell: Old kilns shells have been exposed to
creep for a long time and are more prone to develop fatigue cracks than newer
shells.
2. Distance between tires: The longer the shell span, the less it will resist high
temperatures without sagging. Therefore, longer spans have more tendencies to
develop permanent deformation than shorter spans.
3. Kiln shell structure: Kiln shells are made with structural rolled steel plate,
such as A.S.T.M. A36. The tensile strength of this type of steel at room
temperature is 50,000 to 80,000 psi. As stated before shell strength is measured
at a room temperature. Figure-1 is showing how shell strength drops
considerably as its temperature is raised. It is interesting to notice that there is a
gain in strength between room temperature and 200 °C, followed by a sharp
loss in strength as the temperature goes up. At 430 °C the ultimate strength of
the steel drops from 75,000 psi to 50,000 psi (a hefty 33%) loss. Some
investigators report a 50% strength loss for the same temperature range.
Figure-1: Kiln shell strength as temperature raise.
18. 18
Question-2: What is the maximum red spot temperature on the shell force kiln to
stop?
Answer-2: The short answer is 550ºC if the spot is permanent and persistent.
This is a short answer, but when we talk about red spot, damaging of shell, long
kiln stoppage, and losing millions of Riyals or Dollars; this answer cannot be 3
acceptable. A number of factors are absolutely necessary to be considered in any
red spot before taking the decision of kiln stoppage:
1. Proximity of the red spot to the tires or gear: Red spots near tires and bull
gears require immediate action. These spots almost invariably force the kiln
down. Shutdown procedure must start immediately to avoid damaging the kiln
shell.
2. Extension of the red spot: The longer the circumferential extension of the red
spot, the greater the risk of shell permanent deformation or collapse. If there is
any persistent red spot covering more than 10% of the kiln circumference
(figure-4); Kiln should stop immediately.
3. Kiln alignment conditions: Misaligned kilns induce localized stresses along
the kiln length. If the red spot coincides with an area of stress concentration, the
shell sometimes elongates or twists beyond recovery.
4. Whether the red spot is exposed or under roof: If the kiln shell is directly
exposed to the elements and a heavy rainstorm hits the red spot, the shell may
develop cracks under sudden quenching. Sometimes the brick results severely
crushed in the red spot area.
5. The presence of shell cracks in the vicinity of the spot: The presence of cracks
in the vicinity of the hot spot calls for an immediate kiln shutdown to avoid shell
splitting.
Figure-4: Circumference red spot
19. 19
Question-3: Every year cement industry loses millions of dollars in unexpected
kiln shutdowns caused by rings build-up inside the kiln. What are the reasons
behind formation such type of build-up?
Answer-3: Kiln Build up (figure-11) or ring formation mechanism can be
divided depend on formation chemistry or formation location as the following:
a). Rings with regard to formation chemistry:
1. Sulphur Rings: Sulphur-induced rings are formed when the molal sulfur to
alkali ratio in the system is more than 1.2. In such cases, there is a considerable
amount of free SO3 circulating in the kiln. At a certain concentration level in the
kiln gas, sulfation of the free lime occurs with anhydrite formation (CaSO4). If
the kiln is burning under slightly reducing conditions, more volatile and lower
melting sulfur salts may form, therefore increasing the severity of the problem.
The salts, in molten state, coat the traveling clinker dust, forcing it to stick to the
kiln wall in the form of rings. Sometimes the chemical analysis of such rings
does not indicate high sulfur concentrations, proving that even a small amount
of free sulfur is sufficient to cause rings.
2. Spurrite Rings: Carbonate or spurrite rings are formed through CO2
desorption into the freshly formed free lime, or even through belite
recarbonation. These rings are hard, layered, and exhibit the same chemistry as
regular clinker. Spurrite is a form of carbonated belite. When the carbonate in
the spurrite is replaced with sulfur the new mineral is called sulfated spurrite.
Spurrite rings form whenever the partial pressure of CO2 above the bed of
material is high enough to invert the calcining reaction.
3. Alkali Rings: The third type of ring occurs whenever the sulfur-to-alkali
molal ratio is less than 0.83, usually in kilns with heavy chlorine loads. In such
cases, low-melting potassium salts provide the binder for clinker dust travelling
up the kiln. Through a "freeze-and-thaw" mechanism, these rings can assume
massive proportions. Alkali rings are far less common than other types because
sulfur and carbonates usually are in excess relative to potassium.
Figure-11: Kiln build-up
20. 20
b). Rings with regard to formation location:
1. Intermediate Rings: Intermediate rings are dense, hard and seldom fall off
during kiln operation. They are elongated, being some 10-15 meters long and
extending from 7 to 11 kiln diameters from the outlet. This ring is clinker-like in
colour indicating it being composed of well burnt material. They have a layered
structure, according the curvature of the kiln shell. Their chemical
composition is very similar to that of clinker. No increase in concentration of
S03 or alkalis takes place, and often the ring shows lower volatile element
values than for clinker. The alite of the inner layers may decompose into belite
and secondary free CaO, resulting from cooling down of the inner layers to a
temperature lower than the stability temperature of the alite (1260°C). The
mechanism of bonding is the freezing of the alumino-ferrite melt. The smallest
clinker particles of 150-450 mm are carried back by the gas stream, fall down
and are deposited on the kiln refractory lining, in a zone where temperatures of
below 1250°C exist. The clinker dust particles freeze in place, and because the
kiln charge is still fine, it does not possess sufficient abrasive action to remove
the growing ring.
2. Sinter Rings: These rings occur in the burning zone inlet, some 4-5 diameters
from the kiln outlet. They are greyish-black in colour, hard and formed by small
clinker nodules and clinker dust. Because of the presence of large pores and
voids, no layered structure is formed. Their chemical composition is that of the
clinker with no concentration of volatile elements. The alite of the inner layers
may decompose into belite and secondary free CaO. The bonding is created by
the freezing of the clinker liquid phase. This
phenomenon occurs especially in the burning zone inlet, where the liquid phase
is just starting to form, at approximately 1250°C. Due to the rotation of the kiln,
the material freezes with each kiln rotation and deposit of clinker particles
having less than 1 mm diameter may reach a large thickness.
3. Coal Ash Rings: In kilns fired with a high ash content coal, rings can form at
7-8.5 diameters from the kiln outlet. They are dense, with a layered structure
and sometimes glassy in appearance and built up from particles some 150-250
mm in size. They are rather less dense and have larger pores and voids than
intermediate rings. Their chemical and mineralogical composition is very
similar to that of clinker. As the ring grows up and the temperature of the inner
layers falls down the alite may decompose into belite and secondary free lime.
The bonding mechanism is the freezing of molten coal ash particles and perhaps
to a slight extent, the freezing of the clinker liquid phase. The molten coal ash
droplets adhere to the kiln refractory lining in a zone where the temperature is
high enough so that they are still partially sticky. When this layer passes under
the kiln charge, one ach kiln rotation, a portion of the still very fine kiln charge
adheres to it.
21. 21
References:
1-
Rotary Kilns: Transport Phenomena and Transport Processes
2-
http://www.cementkilns.co.uk/rotary_kilns.html
3-
http://www.dgengineering.de/Rotary-Kiln-Plants.html
4-
http://www.rotarykilnanddryer.com/index.html?aspxerrorpath=/
5-
http://www.a-cequipment.com/products/rotary-kilns
6-
http://combustion.fivesgroup.com/products/burners/rotary-kiln-precalciner-
burners.html
7-
http://www.merriam-webster.com/dictionary/rotary%20kiln
8-
http://www.khd.com/rotary-kilns.html