cement milling products

cement finish milling (part 1: introduction & history)

cement finish milling (part 1: introduction & history)

Cement is manufactured by heating a mixture of ground limestone and other minerals containing silica, alumina, and iron up to around 1450 C in a rotary kiln. At this temperature, the oxides of these minerals chemically transform into calcium silicate, calcium aluminate, and calcium aluminoferrite crystals. This intermediate product forms nodules, called clinker, which is then cooled and finely ground with gypsum (added for set-time control), limestone, supplementary cementitious materials, and specialised grinding aids which improve mill energy consumption and performance to produce cement.

The finish mill system in cement manufacturing is the second to last major stage in the process, where the feed material is reduced in size from as large as several centimeters in diameter, down to less than 100 microns (typically less than 10% retained on 45 microns). This is accomplished by grinding with the use of either ball mills or vertical roller mills, sometimes in combination with a roll press.

This operation typically consumes somewhere between 30 to 50 kWh per tonne of cement produced, and is the single largest point of consumption of electrical power in the process. Although concrete is the most sustainable building material available [1], with over 4 billion tonnes of cement produced and consumed world-wide, optimisation of the grinding process can provide significant reductions in energy consumption and environmental impacts.

As concrete became the preferred building material, it became readily apparent that in order to meet the increasing demand, improvements in grinding technologies and operational efficiencies were required.

Early hydraulic cements were relatively soft and readily ground by the technology of the day using millstones. The emergence of portland cements in the late 1840's presented a challenge however, due to the hardness of the clinker, resulting in a coarse cement product (with up to over 20% over 100 microns). This resulting cement was slow to hydrate and prone to issues with expansion due to large free-lime crystals. It wasnt until improved quality of steels were developed and the introduction of the ball mill in the late 19th century that grinding technology improved, allowing for a four-fold increase in compressive strengths during the 20th century [2] where finer grinding was needed to improve concrete performance and meet construction schedule demands.

Although ball mills were first introduced in the 1860s, the main progress was made during the 1870s to 1900s in Germany, where its growing cement and chemical industries increased the demand for finer grinding [3]. The first tumbling mill to gain reasonable acceptance was designed by the Sachsenberg brothers and Bruckner and built by Gruson's Workshop in 1885, which was subsequently acquired by the Krupp Company.

The mill consisted of a drum lined with stepped steel plate with 60-100 mm steel balls. Fines were discharged from the mill through apertures in the plates, with coarse material in the discharge screened and reintroduced through slits between the plates.

The initial product on the early mills was particularly coarse, due to large aperture sizes necessary to prevent blockages, which led to a modification to discharge product through an end trunnion in the early 1900s to improve performance up to a couple tonnes per hour. Around this same time, F.L. Smidth and Co. was rapidly growing through contracts to build cement plants and acquired the rights to a tube mill from a French inventor, selling it worldwide after redesigning it.

A modern ball mill is a horizontal cylinder thats partially filled with high-chrome martensitic steel balls that rotates on its axis imparting a tumbling and cascading action to the balls. Material is fed through the mill inlet and initially crushed by impact forces and then ground finer by attrition (chipping and abrasion) forces between the balls.

An early approach to grinding was the use of a short tumbling mill to break the large clinker down to the size of grit and then a long tube mill to grind the grit down to powder. The next development involved the combination of those two stages into one piece of equipment, known as the multi-compartment mill, in Germany.

Modern ball mills are usually divided into two chambers, separated by an intermediate diaphragm, allowing the use of different sized grinding media to focus the crushing action in the first chamber, and attrition in the second. The ball mill shell is protected by carefully designed wear-resistant liners which promote lifting action to the ball charge in the first chamber, and cascading action in the second. Liners in the second chamber are sometimes designed to classify the balls so that the larger balls tend toward the central partition and smaller balls tend toward the outlet.

Balls diameters are typically 50-80 mm in the first chamber and 15-40 mm in the second chamber, where the ball charge design must be optimised based on the inlet material size, material hardness, and the desired size reduction. The ball charge typically occupies around 30%-36% of the volume of the mill, depending on the mill motor power and desired energy consumption and production rates. Air is pulled through the mill by an induction fan to control material throughput and temperature.

To solve the issue of large particulate in the discharge, the industry looked to closed-circuit operation with an air classifier to collect the fine particles as one product and recycle the larger particles back to the mill. As early as 1885, Mumford and Moodie secured a patent for an air separator being used in the flour industry.

This type of circuit started a trend which became common practice in the 1920s after Sturtevant developed an air classifier for the tobacco industry. Its adoption, which became commonplace by the 1950's, led not only to improved cement performance, but increases to production and energy efficiency by as much as 25% due to reductions in over-grinding. Development of the separator has continued from the so-called first generation to the current third generation of high-efficiency separators.

The first generation separators are very similar to the Mumford-Moodie design with one motor driving a distribution plate, the main fan, and an auxiliary fan. The second generation incorporated an external fan and external cyclones but gained only marginal improvement in classification efficiency. The modern generation of high efficiency separators, led by the development of the O-Sepa by Onoda Cement Co. in Japan in the 1970s, has an external fan which draws significantly more air through a rotating cage, increasing the ratio of air to material and the size of the open area in the classification zone to greatly increase efficiency.

Around this same time in the late 1970's and early 1980's, Professor Schonert developed and patented the key requirements for size reduction of many particles by compression of the particle bed using high pressure grinding rolls, first licensed to Polysius. The incorporation of this as a pre-crushing stage to ball mills with high efficiency separators led to circuits that were even more efficient and versatile. The roller press consists of a pair of rollers set 0.25 to 1.25 apart rotating against each other, through which the feed is introduced and compressed at up to 300 MPa. The material emerges as a cake of highly fractured particles and can reduce energy consumption of a ball mill by 20 to 40%.

Another major development was in 1906 by Grueber with the initial stages of what would become the vertical roller mill for grinding coal in Germany. In 1927 the first Loesche mill was patented which featured a rotating grinding track that used centrifugal force to push the grinding stock outwards from the center of the mill under high pressure roller wheels and into the airstream of the internal air classifier. This mill was adapted in the late 1930s for grinding raw mix and cement. However, it wasnt until the 1960s where rapid development in optimisation and up-sizing led to its increasing popularity in cement production, and not until the early 2000s that it began to become popular for cement grinding, due to higher grinding capacities and around 25% lower power consumption compared to the ball mill.

One of the most significant developments for the cement industry dates back to 1931, when an attempt was made to mix carbon black in concrete to make a darker middle lane on U.S. Route 1, in Avon for passing. Initially, the carbon black did not disperse well and rose to the surface giving the concrete a mottled appearance. Dewey & Almy (acquired by W.R. Grace in 1954 and later leading to GCP Applied Technologies) developed and produced a product called TDA (Tuckers Dispersing Agent) which helped the dispersion of carbon black and led to better workability and strength.

TDA was then tried in cement finish mills where it was found to improve mill operability with higher throughput and better product fineness, strength, and flowability, due to the dry dispersion of cement powder. The initial commercial versions of TDA were based on modified lignosulphonates and this began the modern grinding aid industry as well as leading to the development of water reducing admixtures. By the early 1960s amine acetates and acetic acid were also being used in grinding aids, and then glycols in the late 1960s and early 1970s. The 1990's saw the introduction of performance enhancing grinding aids which are continuing development to optimise particular mill circuits and product performances.

One of the biggest challenges faced in the grinding industries was matching an appropriate mill and motor to the required feed rate, product size, and material grindability. This led to Allis-Chalmers Company establishing a research laboratory in 1930 where Fred Bond further developed the theory of comminution by introducing Bonds Work Index in 1952 (to be continued)

products for cement and mining i flsmidth

products for cement and mining i flsmidth

FLSmidth provides sustainable productivity to the global mining and cement industries. We deliver market-leading engineering, equipment and service solutions that enable our customers to improve performance, drive down costs and reduce environmental impact. Our operations span the globe and we are close to 10,200 employees, present in more than 60 countries. In 2020, FLSmidth generated revenue of DKK 16.4 billion. MissionZero is our sustainability ambition towards zero emissions in mining and cement by 2030.

cement mill - all industrial manufacturers - videos

cement mill - all industrial manufacturers - videos

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... plastic products and scraps. Optional tangential rotor housing for efficient size reduction of hollow body blow moulding products. Universal, straight, staggered, guillotine or clamping vedge type rotor ...

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... from 30% to 65% compared to ball mill, from 10% to 20% compared to vertical mill The best product quality with lower clinker ratio Zero water consumption No need of grinding aid for blended cements ...

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DESCRIPTION The Cylinder mill, commonly known as the Roller Press works by crushing the material between two cylinders kept under pressure by a hydraulic system (2 to 10 T/linear cm). This mill uses ...

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cement - cemex

cement - cemex

Cement is a fine powder, obtained from the calcination at 1,450C of a mix of limestone, clay, and iron ore. The product of the calcination process is clinkerthe main ingredient of cementthat is finely ground with gypsum and other chemical additives to produce cement.

Cement is the most widely used construction material worldwide. It provides beneficial as well as desirable properties, such as compressive strength (construction material with highest strength per unit cost), durability, and aesthetics to a variety of construction applications.

Our Gray Ordinary Portland Cement is a high-quality, cost-effective building materialmainly composed of clinkerthat meets all applicable chemical and physical requirements and is widely used in all construction segments: residential, commercial, industrial, and public infrastructure.

CEMEX is one of the world's largest producers of White Portland Cement. We manufacture this type of cement with limestone, low iron content kaolin clay, and gypsum. Customers use our White Portland Cement in architectural works requiring great brightness and artistic finishes, to create mosaics and artificial granite, and for sculptural casts and other applications where white prevails.

Masonry or mortar is a Portland cement that we mix with finely ground inert matter (limestone). Our customers use this type of cement for multiple purposes, including concrete blocks, templates, road surfaces, finishes, and brick work.

Our oil-well cement is a specially designed variety of hydraulic cement produced with gray Portland clinker. It usually forges slowly and is manageable at high temperatures and pressures. Produced in classes from A to H and J, our oil-well cement is applicable for different depth, chemical aggression, or pressure levels.

Blended hydraulic cements are produced by intergrinding or blending Portland cement and supplementary cementitious materials or SCM such as ground granulated blast furnace slag, fly ash, silica fume, calcined clay, hydrated lime, and other pozzolans. The use of blended cements in ready-mix concrete reduces mixing water and bleeding, improves workability and finishing, inhibits sulfate attack and the alkali-aggregate reaction, and reduces the heat of hydration.

CEMEX offers an array of blended cements which have a lower CO2footprint resulting from their lower clinker content due to the addition of supplementary cementitious materials. The use of blended cements reinforces our strong dedication to sustainable practices and furthers our objective of offering an increasing range of more sustainable products.

This takes places in vertical steel mill, which grinds the material through the pressure exerted by three conical rollers. Which roll over a turning milling table. Horizontal mills, inside which the material is pulverized by means of steel balls, are also used in this phase.

Calcination is the core portion of the process, in which huge rotary kilns come into play. Inside, at 1400 degrees C, the raw material is transformed into clinker: small, dark gray nodules 3-4 centimeters in diameter.

The cement is then housed in storage silos, from where it is hydraulically or mechanically extracted and transported to facilities where it will be packaged in sacks or supplied in bulk. In either case, it can be shipped by rail car, freighter truck or ship.

We're here to answer any questions or concerns you might have. We also appreciate any feedback you'd like to give. It's only through close relationships and an ongoing dialogue with our customers that we're able to better serve your needs.

all about cement | lafarge - cement, concrete and aggregates

all about cement | lafarge - cement, concrete and aggregates

Although cement is one of the oldest building materials around, its production process is a mix of traditional chemistry and hi-tech equipment to make the cement used in homes, hospitals and schools around the world From theraw materialquarry to the delivery of the end product, follow every step in the cement manufacturing process

The raw materials needed to produce cement (calcium carbonate, silica, alumina and iron ore) are generally extracted from limestone rock, chalk, shale or clay. These raw materials arewonfrom the quarry either by extraction or throughblasting. These naturally occuringminerals are then crushed through a milling process. At thisstage,additionalminerals areadded to ensure the correct chemical composition to make cement is in place. These minerals can be obtained fromwaste or by-products of other industries, suchas paper ash. Aftermilling, the raw meal (as it is known) istransported to the plant where it is stored.

Grinding produces a fine powder, known as raw meal, which is preheated and then sent to the kiln. The kiln is at the heart of the manufacturing process. Once inside the kiln, the raw mealis heated to around 1,500C -it is of a similartemperature tomolten lava. At this temperature, chemical reactions take place to form cement clinker, containing hydraulic calcium silicates.

In order to heat the materials to this very high temperature, a2,000C flame is required, which can be produced through the use of fossil and waste-derived fuels. The kiln itself isangled by 3to the horizontal to allow the material to pass through it, over a period of between 20-30 minutes.

A small amount of gypsum (3-5%) is added to the clinker to regulate how the cement will set, the mixture is then very finely ground. During this phase, different mineral materials, called additions', may be added alongside the gypsum. Used in varying proportions, these additions, which are of natural or industrial origin, give the cement specific properties such as reduced permeability, greater resistance to sulfates and aggressive environments, improved workability, or higher-quality finishes.

Cement manufacturing does have an impact on the surrounding environment so Lafarge is committed to reconciling industrial imperatives with the preservation of ecosystems. Becoming more sustainable is a commitment of Lafarge in all of its operations.

Use of alternative fuels is part of the broader framework of industrial ecology. Lafarge Group started to substitute some wastes and by-products for fossil fuels or raw materials, particularly in Western Europe and North America, at the end of the 1970s.

Alternative fuels are now used by 78 plants around the world, representing 15% of the energy mix. Lafarge has therefore increased its use of non-fossil fuels by more than 30% in three years. The Group has the ambition for alternative fuels to exceed 50% of its energy mix by the end of 2020.

Industrial ecology proposes a new organization of the industrial system, minimizing materials lost in the consumption and production processes. In cement plants, industrial ecology can be reflected in two ways:

- use of cement additives as raw materials as a partial substitute for clinker. This may involve by-products such as slag from the steel industry or fly-ash from coal-fired power stations.

This development is a strategic part of the sustainable development program of the Group to improve the plants performance as providing a service to community and contributing to the protection of the environment. The Group is convinced that sustained economic growth cannot occur without social progress, environmental protection and respect for local communities.

Lafarge Industrial Ecology(LIE) is a "Waste Management" specialized subsidiary of Lafarge Group that takes advantage of the unique opportunities of the cement industry to use waste in an environmentally safe and responsible manner.

LIE is backed by the experience of Lafarge operating in 64 countries.Out of 8,5 million Tons of waste recovered by the Lafarge Group in 2012, more than 800 000 T were shredded solid waste coming from Municipal, Industrial and Commercial wastes.Indeed, the cement plant process operates at a very high temperature compared to boilers or incinerators and is therefore able to combust difficult to burn fuels with no increase in emissions compared to fossil fuels.Adding value to waste by using it as alternative fuel or materials, makesit possible to:

Lafarge has been operating since 2008 in Iraq; it is the largest non-oil & gas investor in Iraq having 3 cement plants (8 MT capacity), 22 RMX plants and 1 aggregate quarry. In the frame of creating economic and social value for the country, Lafarge aims to take the lead in terms of sustainable development based on society, economy and environment.

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