Portland Cement Manufacturing Technology

Contents

Introduction

Analytical Overview

Process Part

Characteristics of manufactured products

Description of raw materials

Calculation of crude mixture composition

Process diagram selection, justification and description

Operating mode of the enterprise

Calculation of plant capacity by clinker and cement

Material Balance

Selection and calculation of main process equipment

Calculation of consumable silos and warehouses of raw materials, clinker, additives, cement

Calculation of power demand

Determination of the number of employees

Control of raw materials, process and finished products

Project safety and environmental friendliness

Technical and economic indicators

Conclusion

List of sources used

Summary

The explanatory note contains 47 pages, including 14 tables, 18 sources.

This course project outlines the basis for the design of Portland cement and slag Portland cement enterprises using a dry production method. The design capacity of the plant is 1.6 million cement per year.

1. Analytical Overview

Currently, the issue of fuel economy is becoming more and more urgent. Portland cement clinker firing is a highly energy intensive production. Fuel consumption for production of 1 ton of clinker by wet method is - 200 kg of conventional fuel by dry method - 130 kg of conventional fuel

At first glance, the solution to the issue can be reduced to the rejection of the wet method of production and all plants can be transferred to the dry method. But for the sake of the dry method, we must not forget the quality of the clinker produced. The good quality of the clinker depends on many factors and primarily on the quality and type of raw material, i.e. on its chemical and mineralogical composition. It is known that the best clinkers and cements based on them are obtained from solid raw materials, i.e. from limestone of medium and fine grain structure. But the reserves of high-quality limestone for cement production are very limited, while in Russia there are huge reserves of soft high-quality carbonate raw materials - these are fine chalks with a good chemical composition and high reactivity.

The quality of the clinker is ensured not only by the fineness of the grinding of the mixture, but also by its homogenization. When producing raw flour using limestone, there are no special difficulties with homogenization.

When evaluating the processing of dry raw mixtures, most researchers state that a finely ground raw mixture guarantees its better homogenization and, as a result, reliable operation of furnaces and the production of high-quality clinker. However, it is noted on dry mixtures using limestone that agglomeration of material particles occurs during storage of the raw material mixture and in cyclone heat exchangers. This phenomenon served as the basis for the proposal to use coarse ground flour.

At CJSC NIC GiprocementNauka, an experiment was conducted to study the dependence of the distribution of chalk agglomerates in raw materials mixtures on mixing conditions. For this purpose, 3 raw mixtures from the same raw materials were prepared (chalk deposits from the Voronezh region, loam and pyrite fumes). The components were pre-ground under the same conditions and three feedstock mixtures were made from them. The first mixture was stirred on rolls for 2 hours, the second mixture was stirred under the same conditions for 4 hours, the third mixture after stirring on rolls for 2 hours was mixed with ethyl alcohol, which modulates the wet milling process. [4]

In the cement industry, grinding plants with increased productivity are increasingly used, capable of processing raw materials of heterogeneous composition and delivering finished products of high tone with reduced energy consumption. The new vertical mill MVR of Gebv. Preiffev AG for grinding cement raw materials, clinker or cement additives with installed capacity of up to 12,000 kW fully meets these requirements of the customer.

The capacity of such a mill reaches more than 400 t/h Portland cement or blended Blake cements of 3000 cm2/g, or about 250 t/h granular blast furnace slag of Blake 5000 cm2/g. The MVR mill has a modular design of the mill drive MultiDrive, consisting of separate identical drive units.

If one of the drive modules fails, it can be released from gear engagement, and the mill will continue to operate at a lower capacity. These mills use 5 versions of modules and 3 versions of the drive unit, which makes it easier to solve the problem of spare parts, primarily for replacing components with long delivery times. [5]

As a result of the issues of sludge pumping under consideration, the solution of production problems with the help of a sludge pump millMAX was presented.

Krebs millMAX is a new strong metal pump with a set of hydraulic components. In order to provide high quality pumping, the impeller in the pump millMAX is moved in the direction of the rear lining liner until a minimum clearance is obtained, and not forward as is done in other slurry pumps. The resulting clearance on the suction side is eliminated by means of a protective ring, the position of which is adjusted when the pump is operating from the outside and with the help of pressure screws. This adjustable protective ring, along with the special designed shape of the cutting rib, is one of the main features of the design of the pump millMAX.

A patented gap control system without stopping the pump unit improves economic performance compared to conventional durable metal pumps and rubber lining. Thanks to this:

increased wear resistance;

reduced water consumption power;

reduced downtime;

reduced maintenance and repair costs. [6]

The problem of product quality is becoming more and more significant for suppliers of domestic cement grades and dry construction mixtures. The quality of the final product is not least due to the degree of grinding of the clinker and the grain composition of the cements. Therefore, any laboratory is always equipped with granulometric devices.

Screening machines RetschAS 200 control have proved to be excellent in many cement plants. In addition to amplitude (vibration height), sieve acceleration can be set, which does not depend on the frequency of the power supply, so such machines guarantee tremendous results around the world. All sizing parameters - time, interval, vibration amplitude - are set and displayed in digital form. The device can be connected to a computer and controlled by a special program. At the end of sifting, the sieve is placed on the scale, and the mass and cell size data are stored in the computer and the percentage of the rest on the sieve is calculated automatically. Based on the results calculated by the computer, a scattering curve and a table of values are built.

The new air jet screening machine AS 200 je + was specially designed to measure fine fractions. The device is used with sieves with cell sizes from 10 μm or more. The screening procedure does not create additional effects on the material and does not require additional accessories. The average sifting time is 2-3 minutes.

HORIBA LA950V2 dry dispersing unit is used to determine dry powder parameters. The range of variable particle sizes is from 0.1 to 3000 μm. The system has a wide range of capabilities. Agglomerates can be broken down with compressed air by selecting one of 3 power levels, thereby selecting the best conditions for each sample. If it is necessary to measure the size of the adhered agglomerates, samples can be introduced without prior dispersion. Setting the speed of the automatic sample feeder allows you to measure even 10 mg. samples. It is also possible to easily measure a large amount of sample on the same system.

Laser diffraction becomes the preferred method for particle size analysis as a more accurate and rapid method of analysis. LAovergo and LA300 instruments - can be used for research and routine quality control measurements. [7]

To date, the possibility of using citrogypsum for the production of gypsum-known expansion additives has been established. When adding lime and citrogypsum-based additives to cement, expansion is slower than when adding an expansion additive based on modified quicklime. An optimal method of producing expandable cements is the mechanical displacement of the expandable additive based on modified lime and Portland cement.

The results of the tests showed that cement with 10% expansion additive of cement weight has the best characteristics.

Thus, it has been experimentally proved that instead of natural gypsum, gypsum-containing citric acid-citrogypsum wastes can be used to obtain gypsum-known expanded additives. [8]

FLSmidth introduced the world's first girder refrigerator in 1997, and today this company sets a new standard in Cross Bar technology. The new girder refrigerator is quickly and easily installed, ensuring maximum reliability with minimal maintenance. Its modular elements have completely new sizes and structure, which allows both the installation of new refrigerators and the modernization. The refrigerator has high thermal efficiency, low energy consumption and low construction, installation and operation costs.

It has 5 main design features:

separate mechanism of clinker transportation and cooling;

sealed grate system;

self-adjusting mechanical air flow controllers;

modular concept;

horizontal structure with optimized transportation method. [9]

As a result of laboratory and industrial studies, it is shown that when using reducing slag, it is possible to reduce the chromate content of the clinker during its firing. Among various fuels (fuel oil, natural gas, coal), coal has been found to be most suitable for producing clinker with reduced chromate content. At the same time, the oxygen content in the furnace atmosphere can be controlled, as well as the degree of clinker sulfatization. [10]

Cement production refers to materials and energy-intensive industries. Every year in Russia, about 10 million tons of conventional fuel are spent on firing Portland cement clinker. Therefore, one of the leading trends in the development of the cement industry is the desire to reduce energy costs. During the work, the main regularities of the effect of additives of various compounds for producing clinker at a temperature of 1200 ° C. Additives such as CaF2, AeF3, HgF2 et al., had no significant effect on the absorption of calcium oxide and the formation of alite at a temperature of 1150 C. The best results were obtained by introducing 2% LiF into the raw material mixture, which is used in subsequent studies, while significantly accelerating the formation of tricalcium silicate. [11]

Cement milling is the last production cycle in which there is a chance to change the quality of cement taking into account the requirements of consumers and current standards. Grinding intensifiers are typically dispensed in small amounts, 0.020.05% by weight, to the mill feeder or directly to the mill.

Sika offers the latest technologies in the field of grinding intensifiers and the unique Sika Grind-800 technology using polymers of modified polycarboxylicates to increase productivity and compared to traditional amino and glyco-containing additives. [12]

Common (fossil) fuels used in the European cement industry are mainly coal (humate and coal), fuel oil (a product obtained from the purification of crude oil) and untreated oil ("bunker C"). Natural gas is rarely used because of its high cost.

"Alternative" fuels - inorganic fuels produced from industrial waste - are widely used today instead of traditional fossil fuels.

Fuel preparation - that is, grinding, drying, grinding, and homogenization - is usually done on site. This requires coal mills, bunkers and solid fuel storage facilities, liquid fuel tanks and appropriate transport and feed systems to the furnaces.

Fuel consumption is highly dependent on the main process used in sintering cement clinker. [13]

Process Part

2.2 Description of raw materials

The raw materials for the production of Portland cement clinker are natural carbonate and clay rocks, as well as industrial waste from other industries (blast furnace slags, fuel ashes, TPP slags, etc.)

For the production of Portland cement, various types of carbonate rocks can be used: limestone, chalk, lime tuff, limestone paint, marl limestone, marl, etc. Calcium dioxide in limestones is represented by calcite mineral. Calcite has a hardness of 3. Limestone - sedimentary rocks. By origin, organogenic limestones are distinguished - the products of the activity of microorganisms, chemical ones - obtained by precipitation from solutions and debris - the products of reprecipitation of destroyed calcareous rocks. Limestone contains impurity minerals - alumosilicate minerals of clays, impurities of quartz, chalcedon, opal, iron oxide, pyrite (FeS2), gypsum, phosphorite (apatite), barite (BaSO4). Limestone is usually contaminated with magnesium carbonate, which forms a double salt with calcium carbonate - dolomite. Impurities in limestones are in the form of independent compounds, and limestone is a mechanical mixture of minerals (except MgCO3). With a clay mineral content of up to 30%, limestone is called clay, with a content of more than 30% - marl.

From clay breeds use usually clay, loam, clay slate, marlaceous clay, the loess, lessovidny loam. The clay is based on aqueous aluminosilicate minerals in the form of thin particles (< 2 μm), and monomineral and polymineral clays are found. Clay substance is mainly hydroaluminosilicates m Al2O3 * n SiO2 * p H2O, where the values ​ ​ of coefficients for oxides for individual clay minerals are different. The crystal lattice of hydroaluminosilicates may also include K, Na, Mg, Ca, Fe.

Clay minerals include kaolinite - a layered mineral of the composition Al2O3·2SiO2·2H2O, in clays it is present in the form of particles with a size of 0.30.4 microns; montmorillonite is a layered mineral of the composition Al2O3·2SiO2·2H2O, in which up to 5% Fe2O3, 4 - 9% MgO, up to 3.5% CaO is in solid solution. Bentonite clays consist of very thin particles (~ 2· 109 m) of montmorillonite. Hydroslides are minerals close in composition and structure to montmorillonites, however, the latter include alkaline ions, the content of which can reach 4-10%. Argillites are solid rocks, the product of dehydration, pressing and recrystallization of clays. Shale is a rock, a product of recrystallization of clays. Loess is an earthy rock composed of mica, kaolinite, feldspar, calcite, quartz. Loam - clays containing a significant amount of quartz (up to 40%).

Clay rocks contain acid oxides SiO2, Al2O3 and Fe2O3, necessary for the production of Portland cement, in limestones there is a main oxide of CaO. The main sign of the suitability of clay for the production of Portland cement is the values ​ ​ of its silicate and alumina modules, which determine the value of these modules in Portland cement, since the carbonate component of the raw material mixture usually contains few clay impurities.

Gypsum is introduced into composition of Portland cement for regulation of setting time. It slows down the start of setting and increases the strength of cement stone in an early time. The amount of gypsum in the cement is normalized by SO3 content. In conventional cements, it should be at least 1.0 and not more than 3.5%, and in high-strength and fast-hardening cements - at least 1.5 and not more than 4.0%.

With a particularly favorable chemical composition of raw materials, the Portland cement mixture of the desired composition can be prepared from only two components - carbonate and clay. But in most cases, it is almost impossible to obtain a given raw material mixture from two components, so corrective additives containing a significant amount of one of the oxides missing in the raw material mixture are used. As an iron-containing additive, pyrite burns from sulfuric acid plants are usually used, less often - dust from blast furnaces. The content of oxides in corrective additives should be,%: for ferrous Fe2O3 - at least 40; for silica SiO2 - not less than 70; for alumina Al2O3 - not less than 30.

Blast furnace and electrothermophosphoric slags, fuel slags and ashes, nepheline (belite) sludge, gypsum-containing wastes found the most widespread use of the cement industry. The use of slags in cement plants helps solve the problem of providing them with raw materials for a depreciation period. Nepheline (belite) sludge is a waste of the complex processing of apatite - nepheline rocks into alumina, soda, potash. Since the sludge has undergone partial heat treatment, it consists mainly of two-calcium silicate - a mineral included in the Portland cement clinker and capable of hydraulic hardening. Granular slags and nepheline sludge are similar in composition to Portland cement raw materials, therefore they can be used not only as active mineral additives, but also as components of Portland cement raw materials. Since these materials have already undergone heat treatment, do not contain CaCO3 and include a number of minerals similar in composition to the minerals of cement clinker, firing the charge with the presence of nepheline sludge and slag in their composition requires less fuel consumption. For example, when using nepheline sludge, the productivity of rotary furnaces increases by about 25%, the specific fuel consumption for firing clinker, electricity and grinding bodies is reduced (by about 20%). But ground slags and nepheline sludge cause thickening of raw cement sludge. Increased alkali content in nepheline sludge can reduce cement quality.

The designed enterprise produces PP with the content of raw materials: clinker - 95%, gypsum - 5%.

And also SPC with the content of raw materials: gypsum - 5%, slag - 40%, clinker - 55%.

5 Conclusion

In this course project, a company was designed to produce Portland cement and slag Portland cement. The company is designed according to the dry production method, which is most advantageous in terms of technical and economic indicators (compared to enterprises according to the wet production method). There is a production line, using a rotating furnace SMTs26: 4.5x80 m, the fuel is gas. The capacity of the enterprise is 1264176.57 million tons/year, the number of workers at the plant is 221 people.

For further efficient operation of the plant, it is necessary to apply new technologies of the construction industry that improve the quality of raw materials; improved design of main process equipment to increase efficiency.