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CEMENT INDUSTRY. GRUPO 5 PILAR DELICADO HERRERAS REBECA DIEZ MORALES CRISTINA MARTÍN SERRANO. GENERAL INFORMATION ABOUT CEMENT INDUSTRY. Cement is a basic material for building and civil engineering construction.

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CEMENT INDUSTRY

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CEMENT INDUSTRY

GRUPO 5

PILAR DELICADO HERRERAS

REBECA DIEZ MORALES

CRISTINA MARTÍN SERRANO


GENERAL INFORMATION ABOUT CEMENT INDUSTRY

  • Cement is a basic material for building and civil engineering construction.

  • Cement is a finely ground, non-metallic, inorganic powder when mixed with water forms a paste that sets and hardens.

  • World cement production has grown steadily since the early 1950s, withincreased production in developing countries, particularly in Asia.


CEMENT PRODUCTION IN THE UEAND THE WORLD

  • Producers in the European Union have increased cement output per man/year from 1700 tonnes in 1970 to 3500 in 1991.

  • As a result of the introduction of larger scale production units.

  • The number of people employed in the cement industry in the European Union is now less than 60000.


EMISSIONS

The emissions from cement plants which cause greatest concern are:

  • Nitrogen oxides (NOx)

  • Sulphur dioxide (SO2)

  • Dust

  • Carbon oxides (CO, CO2)

  • Volatile organic compounds

  • Polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs)

  • Metals and their compounds


APPLIED PROCESSES AND TECHNIQUES

  • It begins with the decomposition of calcium carbonate (CaCO3) at about 900°C to leave calcium oxide (CaO, lime) and liberate gaseous carbon dioxide (CO2).

CALCINATION


MAIN PROCESS ROUTES FOR THE MANUFACTURE OF CEMENT

  • There are four main process routes:

    1) Dry process: raw materials are ground and dried to raw meal in the form of a flowable powder.

    2) Semi-wet process: the slurry is first dewatered in filter presses.


MAIN PROCESS ROUTES FOR THE MANUFACTURE OF CEMENT

3) Semi-dry process: dry raw meal is pelletised with water and fed into a grate preheater before the kiln or to a long kiln equipped with crosses.

4) Wet process, the raw materials (often with high moisture content) are ground in water to form a pumpable slurry.


SUB-PROCESSES

  • Winning of raw materials

  • Raw materials storage and preparation

  • Fuels storage and preparation

  • Clinker burning

  • Cement grinding and storage

  • Packing and dispatch


TECHNIQUES TO CONSIDER THE DETERMINATION OF BAT

  • Consumption of raw materials

    • Reduce the total consumption of raw materials.

  • Use of energy

    • To optimise the input of energy.

  • Process selection

    • The selected process will affect the releases of all pollutants, and will also have a significant effect on the energy use.

  • General techniques

    • Optimisation of the clinker burning process is usually done to reduce the heat consumption, to improve the clinker quality and to increase the lifetime of the equipment

    • Reduction of emissions, such as NOx, SO2 and dust, are secondary effects of this optimisation.


TECHNIQUES TO CONSIDER THE DETERMINATION OF BAT

  • Careful selection and control of substances entering the kiln can reduce emissions.

  • Specific techniques

    • Control NOx emissions

    • Control SO2 emissions

    • Control dust emissions

    • Control other emissions to air


  • DUST EMISSIONS

    • Main point sources:

      • Kiln systems

      • Clinker coolers

      • Cement mills

    • Techniques for controlling it:

      • Electrostatic precipitators

      • Fabric filters

      • Fugitive dust abatement


    ELECTROSTATIC PRECIPITATORS

    • Generate an electrostatic field.

    • The particles become negatively charged and migrate towards positively charged collection plates.

    • The collection plates are vibrated periodically, dislodging the material so that it falls.

      CONDITIONS

    • High temperatures (up to approximately 400ºC).

    • High humidity.


    ELECTROSTATIC PRECIPITATORS

    • Efficiency is affected by:

      • Flue gas flow rate

      • Strength of the electric field

      • Particulate loading rate

      • SO2 concentration

      • Moisture content

      • Shape and area of the electrodes


    ELECTROSTATIC PRECIPITATORS

    • Electronics precipitators can reduce levels down to 5-15 mg/m3 as monthly average.

    • Besides dust, the EP also removes substances that adsorb to the dust particles, such as dioxins and metals if present.

    • EPs are not installed if emissions at startups and shut downs are very high.


    FABRIC FILTERS

    • Fabric membrane which is permeable to gas but which will retain the dust.

    • As the dust cake thickens, the gas pressure drop across the filter increases Periodic cleaning

    • The use of modern fabric filters can reduce dust emissions to below 5 mg/m3.

    • Also removes substances that adsorb to the dust particles, such as dioxins and metals.


    FUGITIVE DUST ABATEMENT

    • Fugitive emission sources mainly arise from storage and handling of substances and from vehicle traffic at the manufacturing site.

    • Some techniques for fugitive dust abatement are:

      • Open pile wind protection

      • Water spray and chemical dust suppressors

      • Paving, road wetting and housekeeping

      • Mobile and stationary vacuum cleaning

      • Ventilation and collection in fabric filters

      • Closed storage with automatic handling system


    COMPARISON


    BEST AVAILABLE TECHNIQUES FOR THE CEMENT INDUSTRY

    • The BAT for the production of cement clinker is considered to be a dry process kiln with multi-stage preheating and precalcination.

    • Process control optimisation.

    • The use of modern, gravimetric solid fuel feed systems.

    • Preheating and precalcination to the extent possible, considering the existing kiln system configuration.

    • The use of modern clinker coolers.


    BEST AVAILABLE TECHNIQUES FOR THE CEMENT INDUSTRY

    • Heat recovery from waste gas.

    • Power management systems.

    • Grinding equipment and other electricity based equipment with high energy efficiency.

    • Careful selection and control of substances entering the kiln can reduce emissions.


    BAT FOR REDUCING DUST EMISSIONS

    • The combination of the above described general primary measures and:

      • Minimisation/prevention of dust emissions from fugitive sources.

      • Efficient removal of particulate matter from point sources by application of:

        - Electrostatic precipitators with fast measuring and control equipment to minimise thenumber of CO trips.

        - Fabric filters with multiple compartments and ‘burst bag detectors’.

    • The BAT emission level associated with these techniques is 20-30 mg dust/m3 on a daily average basis.


    EMERGING TECHNIQUES IN THE CEMENT INDUSTRY

    • Fluidised bed cement manufacturing technology

    • Staged combustion combined with SNCR


    FLUIDISED BED CEMENT MANUFACTURING TECHNOLOGY

    • Consists of a suspension preheater (SP), a spouted bed granulating kiln (SBK), a fluidised bed sintering kiln (FBK), a fluidised bed quenching cooler (FBK) and a packed bed cooler.

    • SP: conventional 4-stage cyclone preheater.

    • Granulating kiln: granulating the raw meal into granules of about 1,5-2,5 mm diameter at a 1300ºC.


    FLUIDISED BED CEMENT MANUFACTURING TECHNOLOGY

    • The sintering of the granules is completed at a 1400ºC.

    • The fluidised bed quenching cooler quickly cools the cement clinker from 1400 to 1000ºC.

    • The cement clinker is cooled down to about 100ºC in the packed bed cooler.


    Configuration of the 20 tonnes clinker/day fluidised bed cement kiln system:


    FLUIDISED BED CEMENT MANUFACTURING TECHNOLOGY

    • The final target of the technical development of the fluidised bed cement kiln system are:

      • Reduction of heat use by 10-12%.

      • Reduction of CO2 emission by 10-12%.

      • A NOx emission level of 380 mg/m3 or less (converted to 10% O2).

      • To maintain the current SOx emission level.

      • Reduction of construction cost by 30%.

      • Reduction of installation area by 30%.


    STAGED COMBUSTION COMBINED WITH SNCR

    • In theory, a combination of staged combustion and SNCR could be comparable to SCR in performance, that is NOx emission levels of 100-200 mg/m3.

    • This combination is considered very promising by suppliers but is not yet proven.


    CEMENT INDUSTRY

    GRUPO 5

    PILAR DELICADO HERRERAS

    REBECA DIEZ MORALES

    CRISTINA MARTÍN SERRANO


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