function of clincer in cement production line

shaft kiln, vertical shaft kiln, vertical kiln | cement kiln manufacturer

shaft kiln, vertical shaft kiln, vertical kiln | cement kiln manufacturer

Shaft kiln, also known as vertical kiln, vertical shaft kiln, is a vertical and fixed clinker firing equipment. The raw meal ball with coal is fed into cement kiln from the kiln crown, and raw meal ball moves from top to bottom, air move from bottom to top. In fact, the physical and chemical changes of shaft kiln are similar to that of cement rotary kiln.

As for the types of shaft kiln, there is ordinary shaft kiln and machinery shaft kiln. The ordinary shaft kiln adopts manual feeding, manual discharging or mechanical feeding and manual discharging. The machinery shaft kiln adopts mechanical feeding and discharging.

AGICO Cement offers shaft kiln for cement plant, as a proffetional cement plant manufacturer from china, we are always specilized in vertical shaft kiln, cement rotary kiln, and other cement equipment, with rich experience, strong production capacity, excellent quality, and one stop service, ourshaft kiln has been exported to many vsk cement plant around the world.

preheater in cement plant, cyclone preheater, cement preheater | suspension preheater

preheater in cement plant, cyclone preheater, cement preheater | suspension preheater

The cyclone preheater, also called cement preheater,suspension preheater, is a kind of preheater in cement plant. As the core equipment of dry method cement production line, cyclone preheater use suspension preheating to preheat and partly decompose the cementraw mix, shorten the length of rotary kiln, fully mix raw mix and hot air in the kiln, increase heat exchange rate, which promote the efficiency of rotary kiln plant and reduce the energy consumption.

The cyclone preheater can take full advantage of heat in the cement rotary kiln, reduce the heat consumption of clinker production, and reduce the room occupied. To meet ideal effect, AGICO Cement design preheater in the cement plant according to different regions and scale of production.

The cyclone preheater use the high-temperature airflow accumulated in the kiln and adopts multi-stage circulating suspension preheating method to make the raw material powder and the hot air flow fully exchange, complete the suspension preheating and partial raw material decomposition, and prepare for the clinker production.

As we all know that cement rotary kiln is used to calcine raw meal into clinker. The temperature of the cement rotary kiln produced during the calcination is lower than that of other cement kiln. If the material is to be decomposed during the calcination, the temperature must reach the melting point of the material itself. Due to the rotary kiln cannot produce too high temperature in the production. In order to solve this problem, technicians have found that the materials used for clinker production can be put into the preheater firstly, when the temperature reaches the production requirement, it is discharged from the preheater into the rotary kiln for calcination. So the preheater is not possible in the production of rotary kiln.

cyclone preheater design for 5500 ton cement production line

cyclone preheater design for 5500 ton cement production line

Cyclone preheater is one of the core equipment in the new dry cement production process, which is responsible for many functions such as gas-solid dispersion, material heating, gas-solid separation, material transportation and some physical and chemical reactions.

The world's first cyclone preheater kiln was put into production by Humboldt in 1951. After more than 40 years of development, Humboldt introduced a new and improved cyclone preheater in the early 1990s. JY, XJ, ZG, SD, YN and other cement production lines have been used in China for this new type of preheater, and the overall application is fine. All cement production lines basically meet or exceed the design targets, among which JY 5500T /d cement production line exceeds more than a quarter of the designed output. A comprehensive and systematic study and analysis of the key equipment of these production lines with ideal overall performance can improve the level of new dry cement production technology in China from a high starting point, which is beneficial to promote the progress of the industry. For this reason, we have carried on the system comprehensive test and the determination research to the top cyclone preheater tube of the new dry method cement production line of JY cement plant.

The basic function of cyclone preheater is gas-solid separation, and the separation effect is determined by the cyclone structure and the distribution of gas 3-dimensional flow field. In this article, a test system is used to measure the 3-dimensional flow field of gas in the preheater cyclone tube. Meanwhile, the resistance loss of the cyclone tube and the separation characteristics of the cyclone tube are measured in no-load condition. On this basis, the comprehensive analysis and review of the cyclone preheater are made by comparing the actual test data of the cement plant.

The basic characteristics of JY 5500T/D top cyclone preheater tube in structure are the adoption of 4-core gradual spiral shell structure, the top center area is convex, the inner cylinder is long, The ratio of the inner cylinder diameter and the diameter of the cylinder segment is a little more than 1:2.

11 planes are divided along the axial direction of the cyclone cylinder, and each plane is set with holes in four directions along the flow direction: A,B,C and D. Each hole measures the 3-dimensional velocity and pressure of the gas at 4-7 measuring points. The flow field measurement is carried out in the 2 self-modeling area to increase the reliability of the measurement.

In the figure, positive axial wind speed represents axial upward flow, and negative axial flow represents axial downward flow. It can be seen from the axial velocity distribution diagram that the area with relatively high axial velocity is basically located in the area near the inner cylinder and the inner cylinder wall, and is located in this area.

The airflow velocity in outer space is relatively stable. This indicates that the airflow moves downward spiral along the cylinder wall after entering the cyclone cylinder from the inlet, and then turns back upward and moves in an axial direction at the lower part of the cylinder, resulting in certain backmixing, but generally showing a relatively good movement trend. Down the wall of the airflow velocity is helpful for the cone part downward discharge, to reduce the secondary dust float in the sky, thus improving the separation efficiency, but this cyclone tube cone area has a wide range of air flow is upward mobility, is bad for the material of successful eduction down, in the high wind speed or material concentration is greater cause secondary float in the sky.

The tangential movement of the airflow provides the centrifugal force of the material particles. The higher the tangential velocity at the outlet of the cyclone tube is, the greater the force of the material particles will be. From this figure, the new Humboldt cyclone preheater can provide sufficient tangential velocity to improve its separation efficiency. However, the tangential wind speed is large, and the coil and suction are also large when the wind flows from the cone, which may cause the secondary flying, which is also unfavorable for gas-solid separation.

FIG. 5 shows the measurement results of separation efficiency. It can be seen that the separation efficiency of the cyclone tube (JY) is the highest at the inlet wind speed of 17.4m/s, reaching about 95%. However, with the increase of inlet wind speed, the separation efficiency decreases gradually. When the cross-section wind speed of the cylinder is about 3.5-3.6m/s, the separation efficiency decreases to 93.8%, and then if the wind speed is further increased, the separation efficiency will rapidly decline (FIG. 4).

This indicates that the new type of Humboldt cyclone has a good gas-solid separation capability under the condition of low wind speed (the cross-section wind speed of the cylinder is about 3.2m/s or lower), but the separation efficiency is not stable and fluctuates greatly with the change of operating parameters. This is consistent with the analysis result of gas 3-dimensional flow field measurement.

In recent years, with the improvement of large-scale cloth bag dust collecting technology in China, the long bag dust collector technology used in rotary kiln tail gas treatment of cement rotary kiln with dry process method is increasing da...

Cyclone preheater is one of the core equipment in the new dry cement production process, which is responsible for many functions such as gas-solid dispersion, material heating, gas-solid separation, material transportation and some physical...

portland cement clinker

portland cement clinker

Portland cement clinker is a dark grey nodular material made by heating ground limestone and clay at a temperature of about 1400 C - 1500 C. The nodules are ground up to a fine powder to produce cement, with a small amount of gypsum added to control the setting properties.

In the above image of a whole nodule in polished section, the nodule has a high alite content and so most of it consists of alite (light gray). Some clusters of belite are visible (arrowed). Aluminate and ferrite phases are present but not visible at this relatively low magnification.

Nodules range in size from 1mm to 25mm or more and are composed mainly of calcium silicates, typically 70%-80%. The strength of concrete is mainly due to the reaction of these calcium silicates with water.Portland cement clinker contains four principal minerals:

In the polished section image above, brown crystals are alite, blue crystals are belite, bright interstitial material is mainly ferrite, with small dark inclusions of aluminate. Gray regions are the epoxy resin used to make the specimen. NB: Alite is not actually brown and belite is not actually blue - they appear brown and blue here because the polished section has been etched with hydrofluoric acid to show the crystals more clearly.

Articles like this one can provide a lot of useful material. However, reading an article or two is perhaps not the best way to get a clear picture of a complex process like cement production. To get a more complete and integrated understanding of how cement is made, do have a look at the Understanding Cement book or ebook. This easy-to-read and concise book also contains much more detail on concrete chemistry and deleterious processes in concrete compared with the website.

Almost everyone interested in cement is also concerned to at least some degree with concrete strength. This ebook describes ten cement-related characteristics of concrete that can potentially cause strengths to be lower than expected. Get the ebook FREE when you sign up to CEMBYTES, our Understanding Cement Newsletter - just click on the ebook image above.

what is the purpose of adding gypsum in cement? - civil engineering portal biggest civil engineering information sharing website

what is the purpose of adding gypsum in cement? - civil engineering portal biggest civil engineering information sharing website

Gypsum is a mineral and is hydrated calcium sulfate in chemical form. Gypsum plays a very important role in controlling the rate of hardening of the cement. During the cement manufacturing process, upon the cooling of clinker, a small amount of gypsum is introduced during the final grinding process.

Gypsum is added to control the setting of cement. If not added, the cement will set immediately after mixing of water leaving no time for concrete placing. Advertisements This question is taken from book named A Closer Look at Prevailing Civil Engineering Practice What, Why and How by Vincent T. H. CHU.

clinker production - an overview | sciencedirect topics

clinker production - an overview | sciencedirect topics

Energy demand in clinker production has been significantly reduced over the last few decades. The theoretical minimum primary energy consumption (heat) for the chemical and mineralogical reactions is approximately 1.61.85 GJ/t (Klein and Hoening, 2006). However, there are technical reasons why this will not be reached, for example unavoidable conductive heat loss through kiln/calciner surfaces. A critical review on energy use and savings in the cement industries can be found in Madlool et al. (2011). The main reason is that a significant decrease in specific power consumption can only be achieved through major retrofits, which need high investment cost with low payback potentials and strengthened environmental requirements which can increase power consumption (e.g., dust emissions limits require more power for dust separation regardless of the technology applied). As a consequence, the best available technique (BAT) levels for new plants and major upgrades are 2,9003,300MJ/t clinker, based on dry process kilns with multistage preheaters and precalciners (European Commission, 2010).

As the change in cement kiln size is difficult, waste heat recovery may play an important role. Currently, a large quantity of low temperature waste heat (below 350C), approximately 30% of the total heat consumption of the system, is still not recovered and could be a promising low investment cost solution (Jintao et al., 2009).

At the optimum calcium sulfate level, the early hydration products of the C3A form ettringite which deposits as a fine-grained material on the clinker surface. This hydration product does not bridge the water-filled gaps between particles of clinker, and the paste becomes only slightly stiffer due to initial hydration during the early period.74 Two cements produced from the same clinker to two different specific surface areas, show very different levels of water demands and setting times.

It is argued that the quantity of sulfate in solution should be adjusted to the level of activity of C3A in order to optimise fluidity: if there is too little sulfate present, then, in addition to ettringite, platy crystals of calcium aluminate hydrate or calcium monosulfoaluminate hydrate are formed. If there is too much sulfate, then secondary gypsum is formed during early hydration of the hemihydrate present. Both additional hydration products result in reduced fluidity and increased water demand and may lead to premature setting.

The solubility behaviour of the sulfate agent depends on the form in which it is present in the cement.79 Gypsum dissolves relatively slowly; hemihydrate and soluble anhydrite dissolve much faster, and in much greater quantities. Natural anhydrite dissolves substantially more slowly. The high temperatures and relatively long residence time in the ball mill ground product produce almost complete dehydration of the gypsum. A high sulfate concentration at the start of hydration can therefore be obtained easily. Different conditions prevail in the high-pressure grinding rolls: the temperature is much lower and the residence time is much shorter. Consequently, dehydration of the gypsum is much reduced and, if a fast dissolution of sulfate is required, hemihydrate must be added before grinding.

In addition to the form of the sulfate, the fineness of grinding and the distribution of the sulfate will affect the water demand. The optimum percentages of calcium sulfate hemihydrate required in a hemihydrate anhydrite mixture are much higher for the more finely ground cement. A sufficiently homogeneous distribution can only be achieved by sufficiently high fineness of grinding. With ball mill grinding, the sulfate becomes concentrated in the finest fraction, and is distributed homogeneously throughout the cement. On the other hand, when grinding by high-pressure rolls, the sulfate agent is often not sufficiently finely ground and an adequately homogeneous distribution in the cement is not always achieved.

The fluidity of cement mortars and the water demand of fresh concretes reach optimum levels at intermediate additions of gypsum.80 It has been deduced81 that the activity of C3A is influenced by the stressing of crystal lattices that accompanies fine grinding. This conclusion was drawn from a series of tests in which Portland cement was ground either conventionally in a ball mill or in high-pressure grinding rolls. The water demand of the ball milled cement was 27 per cent and of the high-pressure ground cement was 32.5 per cent, at the same specific surface area (350 m2/kg). It was argued that a significant increase in C3A activity had occurred; however, the observed differences in water demand were shown to be the result of differences in the rates of interaction between the calcium sulfate agent present and the C3A in the two systems.82

In addition to the particle size distribution of the cement, a further factor affecting the water demand is the extent of the gypsum dehydration.70 In roller mills, the grinding temperature remains low and as a consequence most of the gypsum remains as gypsum, and results in a higher water demand. The uneven distribution of gypsum produced by the roller mill would also result in local setting and again cause increased water demand. A relationship has been found between the mill outlet temperature and the water demand, such that the water demand for normal consistency fell from 30.5 to 29 per cent as the mill outlet temperature increased from 90 to 130C.

Alkalis affect the reactivity of the C3 A present in a cement: the higher the K2O bound in the crystal lattice, the greater the reactivity and the greater the concentration of rapidly soluble sulfate required to control the setting and fluidity reduction.83 If the same quantity of potassium is added as sulfate, there is no increase in activity. In contrast to K2O, the absorption of Na2O into the lattice reduces the activity of the C3A,83 while neither alkali present as sulfate affects the rate of hydration of the aluminate or the water demand.

Investigations of the effect of alkali additions on the rheological properties of cement pastes84 has shown that the plastic viscosity values were unaffected, but the yield stress values were much higher for high-alkali cements than for low-alkali cements.

The presence of alkali sulfates in clinker can also affect the bleeding of cement pastes. Bleeding is the development of a layer of water at the top surface as a result of the sedimentation of the cement particles. Both the bleeding rate and bleeding capacity of cement pastes decreased with increased amounts of water-soluble alkalis.85

The surface area and the particle size distribution have a major effect on strength, setting time and more particularly on water demand.78,86 For equal specific surface area, cements with a narrower particle size distribution have a higher proportion of fine particles, and thus an increasing proportion of fine particles is completely hydrated and a higher strength is obtained. The increased water demand with narrowing particle size range largely arises from the need to fill the voids between cement particles with water, in order to make the paste fluid, and a narrower particle size range inevitably leads to an increase in void content and consequently an increased water demand.

The amount of cement and clinker production is increasing worldwide. The production and clinker capacity of countries in 2015 and 2016 are summarized in Table1 [9]. China is the leader on both cement production and clinker production, accounting for more than 50% of total production. Top two countries, China and India, make up about two-thirds of total cement production in the world. Turkey ranks the fourth and produces 1.83% of the cement in the world. According to the Turkish Cement Manufacturers' Association, 72 cement factories were operating in the Turkish cement sector, including 54 integrated plants and 18 grinding and packaging plants [10].

Among these companies, Akansa is the greatest cement producer in Turkey, with sales of more than 1.4 billion Turkish lira (TL), according to the Top 500 Industrial Enterprises report [11] of the Istanbul Chamber of Industry. In this study, we will focus on the cement production process of Akansa. Akansa is a joint venture of Sabanc Holding and HeidelbergCement, and is the leader in cement production in Turkey. It is responsible for 10% of the total production of Portland cement and 12.5% of clinker production in Turkey [12]. The process of the company is illustrated in Fig.1. It starts with crushers that feed raw material storage. The raw materials are fed to raw mills that feed the raw material silos. Finally, the raw materials are conveyed to kilns where they are transformed into clinkers. The clinkers are processed in cement mills and then stored in the cement silo.

Currently Akansa derives its production plan conventionally and does not take into account changes in electricity prices. In other words, Akansa generates its production plan by assuming that electricity prices are constant. As a result, most of their production process is conducted during the day unless there is a need for overproduction. However, prices are not constant and there is a significant difference between hourly price levels. Hence, there is a potential for improvement in the cost of the electricity consumed. This potential can be used by shifting working hours from the day to the night shift. However, shifting working time to night has a cost. First, workers and engineers must work at night and the wages paid for the night shift is higher than those for the day shift. Second, the raw materials and finished products have to be shipped at night, which is costlier. Therefore, the cost of shifting the production process to night should be justified by savings in the consumption of electricity at night. If the benefit is high enough, the management can be convinced to execute the production plan that employs the electricity prices. To determine the savings of this plan, one must compare its energy consumption with the current conventional approach. In this study, our aim was to find an upper bound for this savings potential to see whether the benefits of executing the plan exceeded the cost of executing it.

The incorporation of calcium chloride in the raw material mixture for Portland clinker production by utilising molten salt technology, has enabled the temperature of clinker formation to be reduced by 400C500C. This clinker contains alinite, a structural variant of alite (tricalcium silicate) incorporating chloride ions.256,291,292 The quantitative content by weight of the mineral phases present in alinite clinker varies within the following limits: alinite 60%80%, belite (-dicalcium silicate) 10%30%, calcium chloroaluminate (Ca6A107Cl) 5%10%, dicalcium ferrite 2%10%. Weak CaCl bonds are developed which result in alinite clinker being softer than alite and requiring less energy for grinding. Gypsum addition is reported293 to intensify strength development rather than principally functioning as a regulator of set.

Alinite has also been produced by clinkering steel plant wastes such as fly ash from an in-house power generating plant, limestone fines, mill scale and magnesite dust with calcium chloride as a sintering aid at 1150C.294 The optimum calcium chloride addition to the raw mix was found to be 7%8% by weight. These cements have been found to be relatively insensitive to the various impurities in the raw mix and can tolerate higher levels of MgO than Portland cements. This low-temperature clinkering route offers scope for the conversion of industrial wastes into hydraulically setting cements. Alinite cement is compatible with Portland cement and additions of 20% by weight of fly ash can be satisfactorily accommodated. Alinite is stable in impure systems with different elements, but is unstable in the pure system CaOSiO2Al2O3CaCl2. Typical alinite clinker contains alinite (65%), belite (20%), mayenite (C11A7CaCl2; 10%) and C4AF (5%).295 Alinite was ascribed the formulation Ca21Mg[Si0.75A10.25O4]8O4C12. The presence of magnesia appears to be essential for alinite formation.296 Jasmundite [Ca22(SiO4)8O4S2], which has S2 instead of Cl ions in the crystal lattice, is poorly hydraulic.297 Later work showed alinite not to have a fixed composition and to be best represented as Ca10Mg1(x/2)x/2 [(SiO4)3+x(A1O4)3+x(AlO4)1xO2Cl] where 0.35

Calcium silicate sulfate chloride [Ca4(SiO4)(SO4)Cl2], a derivative of alinite having an orthorhombic structure,300 is formed at only ca. 600C800C. It has appreciable hydraulic activity,301 greater than that of belite. Compressive strengths of 25MPa at 28days have been found.301

The hot farine exiting from the abgas which is a rotten gas that appeared in clinker production in the rotary kiln system. Ventilation at point 5 passes through the cooling tower to transfer excess heat into the cooling flow, as illustrated in Fig.1. Under the steady-state and steady-flow conditions, the mass, energy, entropy, and exergy balance equations can be defined as for the cooling tower:

Cement manufacturing has several opportunities for WHR, specifically in the process step where the clinker material is produced. For clinker production, a mixture of clay, limestone, and sand is heated to temperatures near 1500C. The kiln and clinker cooler have hot exhaust streams where waste heat could be recovered.

The kiln exhaust stream, when no WHR is used, is at about 450C. The heat from this exhaust stream is currently recovered by using it for preheating and power generation with steam cycles. Organic Rankine cycle (ORC) and the Kalina cycle have been considered for use in power production.

The clinker cooler exhaust is at a temperature near 200C and is typically used for preheating the kiln or other parts of the clinker production process. The ORC and Kalina cycles have also been considered for use to recover the waste heat from the clinker cooler. The sCO2 cycle could also be considered for both waste heat streams.

Oxy-fuel combustion capture systems are restricted to processes that generate CO2 in combustion processes, such as fossil-fuel power plants, clinker production in cement plants, and the iron and steel industry. As the name suggests, fuels are burned in the presence of pure oxygen rather than air to produce flue gas with higher CO2 concentrations and free from nitrogen-derived pollutants (Cullar-Franca and Azapagic, 2015). However, oxygen is expensive and the environmental impacts associated with its production are high because of the energy intensive air-separation processes (Azapagic etal., 2004). Three oxygen separation technologies are used currently in oxy-fuel combustion capture systems:

Where it is not appropriate to use blastfurnace slag as a cementitious material, the composition and origin of slag provides a potential raw material for clinker production. Most raw materials for cement manufacture are quarried and prepared for firing in the cement kiln at a cost. In addition, most sources of CaO for cement making are found as carbonate and when calcining calcium carbonate the producer is increasingly becoming subject to penalties for releasing CO2 to the atmosphere. Blastfurnace slag contains CaO from limestone or dolomite which has already been calcined and therefore the clinker producer will not be liable to penalties for CO2 release from the limestone. Blastfurnace slag typically contains about 40% CaO, together with other oxides needed for cement clinker manufacture which have already been heat treated and therefore will require less energy to convert to clinker. An additional advantage is that the melting point of blastfurnace slag is about 1200C which means that it is easily distributed through the feed within the liquid phase in the rotary kiln.

The fundamental requirement for clinker manufacture is a source of lime (CaO) and sources of silica, alumina and iron oxide. In almost all cases the lime comes primarily from limestone. Limestone is a sedimentary rock composed of the hard parts of once living organisms.

If raw material limestone has a LSF of more than about 200 it should not be difficult to devise a recipe with LSF, SM and AM suitable for clinker production. If LSF in limestone is lower than about 200 it becomes harder to find suitable non-calcareous components. Limestone is rarely pure calcium carbonate; deposits often incorporate siliciclastic components, such as silt from rivers or even volcanic ash. Limestone may also contain compounds of zinc, lead and fluorine, for example. Contaminants in limestone and other raw meal components may have a significant impact on clinker quality, kiln operation and emission to atmosphere. Of special relevance to quality and kiln operation are:

MgO: Dolomite CaMg(CO3)2 in limestone may arise from the original depositional environment or from diagenesis, the process of change to the sediment since deposition. It may be dispersed very unevenly within a limestone deposit. The ratio of MgO to CaO in dolomite is about 70% by weight. The European Standard EN 197 stipulates that The magnesium content (MgO) shall not exceed 5.0% by mass in cement. The US ASTM C150-07 allows 6% MgO. Only a small proportion of dolomite in the raw materials recipe would be required to breach these limits.

Chlorides: Limestone, especially porous limestone found near the sea, may be contaminated with sodium chloride (NaCl). Chloride is commonly found in alternative fuels, such as domestic-refuse-derived fuels. Chloride in cement is limited by most national cement standards and a kiln bypass may be required to remove chloride from the kiln system.

Fluorides: Limestone altered by mineralising solutions may contain a suite of minerals including fluorine as fluorite, CaF2. The presence of fluoride acts as mineraliser. It also decreases the viscosity of the liquid phase in the sintering section of the kiln and if present in sufficient quantity may result in what should be nodular clinker becoming more like lava, resulting in serious damage to the clinker cooler.

Alkalis, compounds of Na and K: The alkalis are found both in the clay (or shale) and the calcareous components of the recipe, but at higher levels in the clay or shale. If alkali levels in clinker are higher than required, selective use of low alkali clay or shale may overcome the problem. Increasing SM by addition of quartz sand also reduces clinker alkalis by reducing the proportion of clay or shale in the recipe. If those options are not available, non-alkali chloride can be added to the kiln system and alkali removed as potassium chloride (KCl) in bypass dust. For example with increased use of alternative fuels containing PVC (polyvinyl chloride), Na2Oequiv in clinker can be reduced by between 0.05% and 0.1%.

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