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 UE AND 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: Techniques for controlling it: 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