CEMENT INDUSTRY

1. CEMENT INDUSTRY GRUPO 5 PILAR DELICADO HERRERAS REBECA DIEZ MORALES CRISTINA MARTÍN SERRANO

2. 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.

3. 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.

4. 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

5. 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

6. 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.

7. 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.

8. SUB-PROCESSES • Winning of raw materials • Raw materials storage and preparation • Fuels storage and preparation • Clinker burning • Cement grinding and storage • Packing and dispatch

9. 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.

10. 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

11. DUST EMISSIONS • Main point sources: • Kiln systems • Clinker coolers • Cement mills • Techniques for controlling it: • Electrostatic precipitators • Fabric filters • Fugitive dust abatement

12. 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.

13. 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

14. 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.

15. 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.

16. 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

17. COMPARISON

18. 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.

19. 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.

20. 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.

21. EMERGING TECHNIQUES IN THE CEMENT INDUSTRY • Fluidised bed cement manufacturing technology • Staged combustion combined with SNCR

22. 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.

23. 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.

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

25. 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%.

26. 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.

27. CEMENT INDUSTRY GRUPO 5 PILAR DELICADO HERRERAS REBECA DIEZ MORALES CRISTINA MARTÍN SERRANO