dry process of cement manufacturing

dry process of cement manufacturing\dry process of cement\agico

Dry process cement kiln is a kind of rotary kiln which is mainly used in calcining cement clinker. The cement clinker made by the dry process has better quality and stability. It can bring more economical and social benefits in production.

Dry process method means manufacturing raw materials into raw materials powder, whose water content is generally less than 1%. So, the dry process can `reduces heat loss needed by heating and autoclaving water. But the dry process has its own flaw that is the bad fluidity of materials grain in a kiln. It will cause an uneven mix.

The wet process method is manufacturing raw materials slurry with 32%-40% water content. Wet process methods advantage is that its good fluidity of raw materials slurry makes more even mixed materials and produces high-quality clinker. But it requires more heat consumption, so it is environment-friendly.

New dry process cement production keeps new dry process cement production technology as the core. It adopts new materials, pre-homogenization technology and energy-saving milling technology and device. New dry process cement production uses all fronts computer distribute control system to achieve automation, efficiency, good quality, low energy consumption and environment-friendly.

The key symbol of new dry process cement production technology is that it adopts a new dry process cement kiln(general name for suspended pre-warm machine and predecomposition kiln). New dry process cement production kiln is the upgrading kiln type for old dry process cement kiln(also called dry hollow kiln). New dry process cement production technology is superior to shaft kiln, dry hollow kiln, vertical Bohr kiln and wet process cement production in thermal efficiency, parts and materials consumption like refractory bricks, enlargement, and quality of clinker.

New dry process cement production technology developments in the 1950s. So far, developed countries like Japan and German adopt a new dry process cement production device, which takes suspended pre-warm and pre-decomposition as the core, more than 95%. Chinese first new dry cement production kiln goes into operation in the year of 1976. The development stages of new dry process cement production: The first stage, the 1950s-1970s, newborn and development stage of suspended pre-warm; The second stage, the beginning of the 1970s, newborn and development stage of pre-decomposition.

Dry process cement production kiln is the typical kiln type during the end of the 18th century and the beginning of the 19th century. It is a big step for haft kiln. Because of its less than 1% water content dust raw materials, it reduces the most needed heat for evaporating water. So, it needs less time than wet process cement production. But old dry hollow kiln doesnt have a waste heat utilization device, the temperature of the kiln tail is normally 700-950 degrees centigrade. Some factories may see the scenery of the blazing chimney, which is a serious waste of thermal energy. The thermal energy consumption of dry hollow kiln per kg can reach up to 1713-1828kcal. And it produces lots of dust; pollutes severely; produces production with bad raw material homogenization, terrible quality, and less quantity. Considering the above characters, it is not hard for us to imagine that dry hollow kiln is replaced by wet process cement production kiln for a while. At the beginning of the 1930s, vertical Bohr kiln appeared. It installed great heater in the tail, heating raw materials balls with 12%-14% water content, which takes good advantage of waste heat. The temperature of the kiln tail drops to 100 degree centigrade-150 degree centigrade from 700-degree centigrade.

While the thermal energy consumption widely dropped, the yield and quality sharply increased. In the 1950s, cyclone preheater kiln came out, which made well use of waste heat in kiln tail. Especially, when the beginning years of the 1970s, a new kiln production line with kiln decomposition furnace pushed the dry process to a new stage.

cement manufacturing process - civil engineering

The raw cement ingredients needed for cement production are limestone (calcium), sand and clay (silicon, aluminum, iron), shale, fly ash, mill scale and bauxite. The ore rocks are quarried and crushed to smaller pieces of about 6 inches. Secondary crushers or hammer mills then reduce them to even smaller size of 3 inches. After that, the ingredients are prepared for pyroprocessing.

The crushed raw ingredients are made ready for the cement making process in the kiln by combining them with additives and grinding them to ensure a fine homogenous mixture. The composition of cement is proportioned here depending on the desired properties of the cement. Generally, limestone is 80% and remaining 20% is the clay. In the cement plant, the raw mix is dried (moisture content reduced to less than 1%); heavy wheel type rollers and rotating tables blend the raw mix and then the roller crushes it to a fine powder to be stored in silos and fed to the kiln.

A pre-heating chamber consists of a series of cyclones that utilizes the hot gases produced from the kiln in order to reduce energy consumption and make the cement making process more environment-friendly. The raw materials are passed through here and turned into oxides to be burned in the kiln.

The kiln phase is the principal stage of the cement production process. Here, clinker is produced from the raw mix through a series of chemical reactions between calcium and silicon dioxide compounds. Though the process is complex, the events of the clinker production can be written in the following sequence:

The kiln is angled by 3 degrees to the horizontal to allow the material to pass through it, over a period of 20 to 30 minutes. By the time the raw-mix reaches the lower part of the kiln, clinker forms and comes out of the kiln in marble-sized nodules.

After exiting the kiln, the clinker is rapidly cooled down from 2000C to 100C-200C by passing air over it. At this stage, different additives are combined with the clinker to be ground in order to produce the final product, cement. Gypsum, added to and ground with clinker, regulates the setting time and gives the most important property of cement, compressive strength. It also prevents agglomeration and coating of the powder at the surface of balls and mill wall. Some organic substances, such as Triethanolamine (used at 0.1 wt.%), are added as grinding aids to avoid powder agglomeration. Other additives sometimes used are ethylene glycol, oleic acid and dodecyl-benzene sulphonate.

The heat produced by the clinker is circulated back to the kiln to save energy. The last stage of making cement is the final grinding process. In the cement plant, there are rotating drums fitted with steel balls. Clinker, after being cooled, is transferred to these rotating drums and ground into such a fine powder that each pound of it contains 150 billion grains. This powder is the final product, cement.

Cement is conveyed from grinding mills to silos (large storage tanks) where it is packed in 20-40 kg bags. Most of the product is shipped in bulk quantities by trucks, trains or ships, and only a small amount is packed for customers who need small quantities.

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cement manufacturing process: what is cement made of

These are sedimentary, calcium carbonate rocks (CaC03). Most commonly they contain a small amount of magnesium carbonate also.Besides, usual impurities in limestones are those of iron oxides, silica, and alkalies.

The raw materials (limestone and clay) are subjected to such processes as, crushing, drying, grinding, proportioning, and blending or mixing before they are fed to the kilns for calcination or burning process.

The drying stage is typical of the Dry Process. Drying of crushed materials is essential and is achieved by heating these materials (separately) at temperatures sufficiently high to drive out uncombined water.

Each raw material is thus reduced to a required degree of fineness and is stored separately in suitable storage tanks called SILOS or bins where from it can be drawn out conveniently in requisite quantities.

The blended materials are now ready for feeding into the burning kilns. From this stage onwards, there is practically no major difference between the dry and wet processes, except in the design of the rotary kiln.

(c) Compound Formation: Lime and magnesia as formed above are combined in the next stage with silica, alumina and ferric oxide to form the basic compounds of cement, namely, the tri-calcium and di-calcium silicates, tri-calcium aluminates and tetra-calcium-alunino ferrite.

what is portland cement process of manufacturing,dry and wet

Portland cement is an extreme ground material having adhesive and cohesive properties, which provide a binding medium for discrete ingredients. It is hydraulic cement made by finely pulverizing the clinker produced by calcining to incipient fusion a mixture of argillaceous and calcareous materials. Cement undergoes a chemical reaction with water and sets and hardens when in contact with air or underwater.

Portland cement is a general term uses to describe hydraulic cement. The typical raw materials used for making cement are limestone (CaCo3), sand (Sio2), state clay (Sio2, Al2O3 or Fe2O3) and iron oxide (Fe2O3). Thus, the chemical components of cement are calcium (Ca), silicon (Si), aluminum (Al) and iron (Fe).

The raw materials required for the manufacture of Portland cement are calcareous materials, such as limestone or chalk and argillaceous materials, such as shale or clay. The process of manufacture of cement consists of grinding the raw materials, mixing them and then burning them in a kiln at a temperature of about 1300oC to 1500oC at, which temperature, the material sinters and partially fused to form nodular shaped clinker. The clinker cool sinters and partially fuses to form a nodular shaped clinker. The clinker cool and ground to a fine powder with the addition of about 2 to 3% of gypsum. The product formed by using this procedure is Portland cement.

Portland cement is two processes, known as wet or dry processes depending upon whether the mixing and grinding of materials done in wet or dry conditions. A wet process was popular in the early years because of the possibility of more accurate control in the mixing of raw materials. The nowadays dry process is much popular because the dry process required less fuel than the wet process because in a wet process the slurry contains 35 to 50 percent water.

In the wet process, limestone is first crushed to smaller fragments. Then, it takes to ball or tube mill where it mixes with clay and finely ground. Then, water adds to it to make a slurry. It pumps to slurry tanks, where it keep in an agitated condition by means of rotating arm or by compressed air from the bottom to prevent settling of limestone and of the flexible chain, loses moisture and becomes flakes.

These flakes drop reaction takes place and 20 to 30% of materials get the fuse. Lime, silica, and alumina get recombine The fused mass turns into to nodular form called clinker. The clinker drops into the rotary cooler where it cool under controlled conditions. The cool clinker is then ground in a ball mill with the addition of 2 to 3% of gypsum.

In this process, the raw materials dried and ground to a fine powder by grinding mill. The dry powder is then further blende and corrected for its right composition and mixed by means of compressed air. The blended powder then store in the storage silos from where. It is the pass to the granulator comprising an inclined rotating drum or dish.

A quantity of water about 12 percent by weight then add to make the blended powder into nodules. These nodules are then dry by preheater and then enter to the rotary kiln from the upper end. These nodules drop to lower end where it subject to the temperature about 1500oc Chemical reaction takes place and 20 to 30% material get the fuse. Lime silica and alumina get recombine. The fused mass turns into a nodular form called clinker.

The clinker drops into the rotary cooler, where it is cool under control conditions. The cool clinker is then ground in a ball mill with the addition of 2 to 3% of gypsum. In the ball mill, particles crush to a fine powder and filled into bags.

The equipment used in the dry process in comparatively smaller. This process is economical than the wet process. The total consumption of coal in the dry process is only about 100 kg, as compared to the requirement of about 350 kg, for producing a tonne of cement in the wet process.

manufacturing of cement by dry and wet process

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The process, by which cement is manufactured, depends upon the technique adopted in the mixing of raw materials. Therefore, on the basis of mixing the raw materials, the processes may be classified as:-

(i) Drying Zones: In the wet process, the drying zone is comparatively larger than the dry process. It is because the raw material in slurry form is directly fed into the kiln which has more amount of water. As shown in the figure it is the upper portion of the kiln. In this zone, water is evaporated at a temperature of 100-400C.

(iii) Burning Zone:- The modules enter this zone where temperatures are kept about 1400-1500 C. The modules are converted into dark greenish balls and the product obtained in the kiln, known as clinker, is of varying size 5 to 20 mm. The clinkers are very hot when coming out of this zone.

Also, the gypsum is added during grinding about 2-4%. The gypsum acts as a retarder and so allows the cement to mix with sand or aggregate and to be placed in position. i.e. it increases the initial setting time of cement.

Burning and Grinding: These operations are the same as for the wet process. Except for the mixing of raw materials. In the dry process, the raw materials mixed, fined, and then fed into kiln whereas, in the wet process, the raw materials are crushed separately and then directly mixed in correct proportion in the presence of water to make a fine thin paste known as Slurry.

dry process of cement manufacturing - dry cement | agico

Environmental protection and low consumption have become the standard requirement for cement manufacturing. With the development of the construction industry, the cement production process is also constantly improving. The new dry-process cement production line technology was developed in the 1950s, so far, the new dry process cement equipment rate of Japan, Germany, and other developed countries have accounted for 95%. This cement production process regards the suspension preheating and pre decomposition as the core, and has the advantages of small pollution and a high degree of automation. At present, its application scope in cement production is becoming wider and wider. The success of the new dry process of cement manufacturing cannot be separated from a series of cement production equipment with a high degree of automation. They determine the quality and output of cement, which is very important in the cement plant.

AGICO is a cement plant supplier with rich experience in China. We are specialized in cement plant and cement equipment. Based on our advanced technology and attentive service, our cement equipment has been exported to many countries. For your convenience, we will provide a full guide of the dry process cement manufacturing plant.

The new dry-process of cement manufacturing technology makes good use of the limestone resources discarded in the traditional mining method and applies the pre decomposition technology, suspension preheating technology, and multi-channel burner to reuse the recycled and low-quality fuels. Besides, it effectively reduces the emission of NO2 and other exhaust gases of the system.

The application of new type conveying equipment and multi-functional grinding system in this cement manufacturing process effectively save energy consumption. Meanwhile, the pre decomposition and suspension preheating technology help to improve the calcination efficiency of traditional cement kiln, and continuously reduce the energy consumption required for clinker calcination. At present, the heat consumption of clinker calcination can be reduced to 3000kJ/kg.

Because the new dry-process of cement manufacturing technology has higher requirements for production equipment, transportation, geology, and raw materials, as well as higher consumption of refractory materials, its construction cycle and early investment will be higher than traditional production technology.

Due to the use of high automation equipment in the new dry-process cement production process, the operation of the whole cement production line is consistent and stable, and each link is closely coordinated to ensure the high quality and high output of cement production.

When limestone, clay, and other materials are mined, they will be first broken up in a crushing mill and then transported by a belt type conveyor to the pre-homogenized yard. After batching, these raw materials will be sent to the grinding mill for drying and grinding until they reach the qualified fineness, and finally put into the raw material silo for storage. In this process, we mainly need the hammer crusher, cement ball mill, belt type conveyor, vibrating feeder, etc.

After preheating and pre-decomposing in the cyclone preheater, the raw meal will enter the cement kiln to complete the clinker calcination. In the preheater, we use the suspension preheating technology and pre decomposition technology to replace partial roles of cement kiln, which transfers the accumulation state heating into suspension heating. It increases the heat transfer rate and reduces thermal consumption. After that, the raw meal will be completely calcinated into cement clinker in the cement kiln by high-temperature heating.

Cement kiln: the dry method cement kiln manufactured by AGICO has the characteristic of stable performance, low energy consumption, high yield, and easy operation. We equip our cement kiln with a high metering accuracy plunger pump, flow control valve, and high-quality sealing device to ensure a continuous and steady running.

Cement grinding is the final step in cement manufacturing and it is also a process that consumes a lot of power. Its main purpose is to grind the cement clinker into suitable particle size, form a certain particle size distribution, increase its hydration area, accelerate the hydration speed, and meet the requirements of cement paste setting and hardening. During grinding, we usually add gelatin, gypsum, and other auxiliary materials to enhance or adjust the performance of cement.

Cement ball mill: the cement ball mill grinding system produced by AGICO merges drying, grinding, classifying into a single. It can both grind the raw material and finished cement product in the cement plant, has the advantages of strong adaptability to materials, continuous production, large crushing ratio, easy to adjust the speed, etc.

AGICO is a cement plant and cement equipment manufacturer in China. We offer cement production line, stone crushing plant, cement grinding unit, and other EPC turnkey projects. Besides, we also supply cement equipment such as cement ball mill, cement vertical mill, cement kiln, etc.

Why you choose us? Firstly, we have rich export experience. Every year, we will carry out the construction, commissioning, and operation training of cement turnkey projects overseas. Secondly, our quotation is reasonable. Because we have an independent equipment processing plant, our sales price is the factory price. Finally, we offer attentive service. Our customization service and all-around after-sales service will make every customer have their satisfied cement equipment here.

AGICO Group is an integrative enterprise group. It is a Chinese company that specialized in manufacturing and exporting cement plants and cement equipment, providing the turnkey project from project design, equipment installation and equipment commissioning to equipment maintenance.

cement manufacturing process - civil engineering blog

The entire manufacturing process in a modern plant is now controlled through a microprocessor based programmable logic control system to maintain uniform quality of cement and a high rate of production. The entire operation of the plant is controlled centrally in a single control room and the plant employs minimum of manpower.

The modern plants have also taken adequate care to prevent the environmental pollution and dust nuisance to its surrounding areas. The cement mills have electro-static precipitators (ESP) installed to check the dust emissions. The bag filters and glass bag houses are located at various locations to prevent dust emission and to ensure healthy and hazard-free atmosphere.

The raw materials such as limestone or chalk and shale or clay may be mixed either in dry condition or in wet condition. The process is accordingly known as the dry process or the wet process of mixing.

In this process, the raw materials are first reduced in size of about 25mm in crushers. A current of dry air is then passed over these dried materials. These materials are then pulverized into fine powder in ball mills and tube mills. All these operations are done separately for each raw material and they are stored in hoppers. They are then mixed in correct proportions and made ready for the feed of rotary kiln. This finely ground powder of raw materials is known as the raw mix and it is stored in storage tank.

In modern technology of dry process, the coal brought from the coal fields is pulverized in vertical coal mill and it is stored in silo. It is pumped with required quantity of air through the burners. The preheated raw materials roll down the kiln and get heated in such an extent that the carbon dioxide is driven off with combustion gases. The material is then heated to temperature of nearly 1400C to 1500C when it gets fused together. The fused product is known as the clinkers or raw cement.

The size of clinkers varies from 3mm to 20mm and they are very hot when they come out of burning zone of kiln. The clinker temperature at the outlet of kiln is nearly 1000C. A rotary kiln of small size is provided to cool down the hot clinkers. It is laid in opposite direction and the cooled clinkers having temperature at about 95C are collected in containers of suitable sizes.

The gypsum controls the initial setting time of cement. If gypsum is not added, the cement would set as soon as water is added. The gypsum acts as a retarder and it delays the setting action of cement. It thus permits cement to be mixed with the aggregates and to be placed in position.

The grinding if clinkers in modern plants is carried out in the cement mill which contains chromium steel balls of various sizes. These balls roll within the mill and grind the mixture which is collected in a hopper and taken in the bucket elevator for storage in silos.

The cement from silos is fed to the packer machines. Most of the modern plants have electric packing plant having provision to account for the weights of empty bags of different types and to ensure a 50kg net weight of cement bag within 200g limit. Each bag of cement contains 50kg or 500N or about 0.035m3 of cement. These bags are automatically discharged from the packer to the conveyor belts to different loading area. They are carefully stored in a dry place.