Cement kiln
**Cement Kiln Overview and History**:
– Cement kilns crucial for producing over a billion tonnes of cement annually.
– Process involves grinding raw materials, heating in kiln, and grinding clinker.
– Key components of Portland cement formed during the process.
– Portland cement clinker first produced in 1825.
– Traditional kilns had limitations in size and production capacity.
– Rotary kilns dominate global cement production.
– Rotary kiln is a steel tube lined with firebrick that slowly rotates.
– Rawmix fed in at the upper end and moves downhill as the kiln rotates.
– Rotary kilns have evolved in size and efficiency over time.
– Continuous kiln designs like shaft kiln and rotary kiln improved efficiency.
– The rotary kiln developed in the late 19th century revolutionized cement production.
**Kiln Processes and Equipment**:
– Wet and dry processes for preparing raw materials.
– Preheaters like grate preheaters and gas-suspension preheaters.
– Ancillary equipment includes cooler, fuel mills, fans, and exhaust gas cleaning equipment.
– Cooler types include rotary coolers, satellite coolers, and grate coolers.
– Fuel mills categories: direct firing and indirect firing.
– Fans important for moving gases in the kiln system.
– Gas cleaning methods like electrostatic precipitators and bag-filters.
**Kiln Control and Emissions**:
– Online X-ray diffraction for free calcium oxide measurement.
– Kiln operation objective: produce clinker meeting environmental standards.
– Key controls: feed rate, kiln speed, fuel injection rate, exhaust fan speed.
– Emissions measured by continuous (dust, NOx, SOx) and discontinuous methods.
– Dust emissions majorly from raw material processing, fuel preparation, clinker burning.
– Legal limits for particulate emissions reduced to 30mg/m³ today.
**Environmental Impact and Emissions Reduction**:
– CO₂ main gas emitted during clinker burning process.
– Dust emissions reduced significantly over the years.
– Nitrogen oxides formed in high-temperature clinker burning process.
– Reduction measures aim to optimize plant operation.
– Sulfur dioxide input via raw materials and fuels.
**Other Emissions and Control Measures**:
– Combustion and Selective Non-Catalytic NO Reduction.
– Carbon monoxide and total carbon emissions.
– Dioxins and furans, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons.
– Rotary kilns destroy organic compounds effectively.
– Emission behavior and control measures for various pollutants.https://en.wikipedia.org/wiki/Cement_kiln