Cement is a fine substance that creates a paste when mixed with water and hardens over time. Sintering a range of basic materials produces it. The majority of the substance in the mixture is made up of metallic element carbonates in the form of sedimentary rock and different alumina, silicates in the form of clay or sedimentary rock. During the sintering process, a chemical reaction occurs, resulting in nodules known as clinkers.
As cement manufacturers continue their quest for alternative fuels, many of us are curious as to what types of fuel will be used in the future, method of combustion Figure (1)
Introduction: The cement industry plays a crucial part in a country's quick ascent and growth because cement is a basic demand of all construction operations. Homes, dams, bridges, industrial building, and highways are just a few of the places where cement is employed. As a result, cement is a key component in a wide range of construction projects.
There are four stages in the manufacture of portland cement: (1) crushing and grinding the raw materials, (2) blending the materials in the correct proportions, (3) burning the prepared mix in a kiln, and (4) grinding the burned product, known as “clinker,” together with some 5 percent of gypsum (to control the time of set of the cement). The three processes of manufacture are known as the wet, dry, and semidry processes and are so termed when the raw materials are ground wet and fed to the kiln as a slurry, ground dry and fed as a dry powder, or ground dry and then moistened to form nodules that are fed to the kiln.
Cement manufacturing is a complex process that begins with mining and then grinding raw materials that include limestone and clay, to a fine powder, called raw meal, which is then heated to a sintering temperature as high as 1450 °C in a cement kiln. In this process, the chemical bonds of the raw materials are broken down and then they are recombined into new compounds. The result is called clinker, which are rounded nodules between 1mm and 25mm across. The clinker is ground to a fine powder in a cement mill and mixed with gypsum to create cement.
Clinkerconstruction.quality
type of processes or activities used in cement industry:
The powdered cement is then mixed with water and aggregates to form concrete that is used in depends on raw material composition, which has to be closely monitored to ensure the quality of the cement. Excess free lime, for example, results in undesirable effects such as volume expansion, increased setting time or reduced strength. Several laboratory and online systems can be employed to ensure process control in each step of the cement manufacturing process, including clinker formation.
Figure (2) Common waste stream
The cement industry is one of the main industries necessary for sustainable development. It can be considered the backbone for development. The main pollution source generated from cement industry is the solid waste called cement by-pass dust, which is collected from the bottom of the dust filter. It represents a major pollution problem in Egypt where around 2.4 million tons per ofyearcement dust is diffused into the atmosphere causing air pollution problems because of its size (1- 10 microns) and alkalinity (pH 11.5). Cement by-pass dust is naturally alkaline with a high pH value and represents a major pollution problem. The safe disposal of cement dust costs a lot of money and still pollutes the environment Because of the high alkalinity of the cement by-pass dust, it can be used in the treatment of the municipal sewage sludge, which is considered another environmental problem in developing countries since it contains parasites such as ASCARIS and heavy metals from industrial waste in the Mixingcity.the hazardous waste of cement by-pass dust with the environmentally unsafe sewage sludge will produce a good quality fertilizer. Cement by-pass dust will enhance the fermentation process of the organic waste and kill all microbes and parasites .
The cement industry is the third largest user of coal after the steel and power industries and it consumes more than 5% of total coal produced in India . With so much energy being expended, there is a comparable high potential for energy savings: 2.5 to 3 EJ per year may be saved (28–33% of all energy consumed in this sector) by various means, including waste energy recovery. Such savings in primary energy would have corresponding reductions in greenhouse gas emissions, particularly CO2. Electricity is one of the main energy inputs; worldwide, the electricity intensity of cement production is about 91 kWh per tonne of cement. An international goal has been established to reduce this to 87 kWh/t by 2030 . figure (4) Figure (3)
Additionally, cement producers who create numerous types of pollutants should be properly handled in order to reduce pollution.
Energy Consumption: According to the Inventory of Carbon and Energy at the University of Bath in the United Kingdom, one ton (0.9 metric tons) of portland cement requires 4 million Btu. According to the US Department of Energy, portland cement manufacture accounts for around 0.33 % of yearly energy consumption in the US, which is roughly identical to the energy contained in 13 million tons (12 mmt) of coal.
The cement industry is the third-largest polluter, releasing more than 500,000 tons of sulfur dioxide, nitrogen oxide, and carbon monoxide each year.
Source: Cradle-to-gate measurements of embodied energy taken from University of Bath Inventory of Carbon and Energy (ICE), Version 1.6a, 2008. Figure (4)
Minimizing waste, Pollution prevention & control
Pollution Prevention and Control: The cement industry is concentrating on lowering particle emissions into the atmosphere by reducing the mass load released from stacks and other sources to less than 0.2 kilograms of dust per metric ton (kg/t) of clinker using dust recovery systems.
Carbon emissions: Manufacturing portland cement contributes around 5% of global anthropogenic CO2 emissions and roughly 2% of total CO2 emissions in the United States. Cement manufacture is one of the main CO2 emitters in the building industry. Some of the CO2 produced in the cement industry comes from the use of coal and other carbon-intensive fuels as a heat source in kilns that can run nonstop for over a year. However, Portland cement is unusual in that calcining limestone, which generates CO2 during the chemical process, accounts for nearly half of its carbon emissions. In 2008, the calcination process alone emitted roughly 45 million tons (41 mmt) of CO2. The EPA's report, "Quantifying Greenhouse Gas Emissions from Key Industrial Sectors in the United States," claims that energy-intensive iron and steel manufacturing emits more CO2 than cement production (114 vs 83 mmt, respectively), However, only about half of that steel is utilized in building, compared to 95% of cement, resulting in construction-related emissions of around 57 mmt for iron and steel and 79 mmt for cement.
The content of volatile or reactive sulfur in raw materials and fuels is the primary source of sulfur dioxide (SO2) emissions in cement manufacture, SO2 emissions are best controlled by using low sulfur fuels and raw materials, SO2 emissions is not a serious issue as the “S”
The cement kiln's high-temperature combustion process produces nitrogen oxide (NOX) emissions, NOx emissions are kept to a minimum thanks to effective kiln design, low-NOx burners, and the right amount of surplus air. Typical NOx emissions of clinker are 1.5 kg/t, nitrogen oxide emissions can be reduced further, to 0.5 kg/t of clinker, by afterburning in a reducing atmosphere, and the energy of the gases can be recovered in a preheater.
- The Competent Agency and the concerned and public agencies shall cooperate and coordinate efforts to develop and implement a national plan to monitor, follow up to prevent vessels from dumping or discharging any harmful pollutants, or chemical, toxic, hazardous, or radioactive wastes in the Kingdom’s territorial waters or exclusive economic zone.
- To employ the best available technologies and means and take the necessary precautions to avoid contamination of the surface, ground, and coastal waters; and control and minimize pollution in accordance with the approved environmental criteria.
- Anyone commencing production, service, or other activities must take necessary precautions to achieve: Prevent direct or indirect contamination of the surface, ground, and coastal waters that may be caused by solid or liquid residues.
- Any harmful pollutants, poisonous, hazardous, or radioactive wastes are prohibited to be disposed of or discharged by vessels or alike in the territorial waters or the free economic -zone.Prevent direct or indirect contamination of the surface, ground, and coastal waters that may be caused by solid or liquid residues.
- Remove all forms of contamination of the surface, ground, or coastal waters resulting from the said activities and bear all the costs of the prevention, control, and minimization of contamination, remediation of the contaminated environment, and compensating the affected parties.
The presidency of meteorology and environment set general regulations and rules for implementation for waste streams which is:
- Prevent the discharge, in any quantity, of any type of solid or liquid wastes, substance, element, organic or inorganic compound that may be classified as hazardous into the surface, ground, or coastal waters.
- Hazardous, poisonous, or radioactive waste are prohibited to enter the Kingdom of Saudi Arabia including its territorial waters and free economic zone.
compounds in flue gases react with Lime in cement and get a trapped in cement, The lime content of raw materials can be used to control sulfur oxides, Alkaline dust removed from the kiln gases is normally disposed of as solid waste. When solid wastes such as pulverized fly ash are used with feedstock, appropriate steps are taken to avoid environmental problems from contaminants or trace elements
pg. 8 Requirements for certification to engage in water treatment can be summarized as below:
• Identify the location of the purification station for the industrial, sanitary networks or the treatment of polluted water sites or groundwater treatment sites, indicating their proximity to the coastline, water bodies, or valleys, and submit an environmental impact assessment study on the project.
- In cooperation and coordination with the concerned agencies, the Competent Agency shall apply the regulations, instructions, agreements, and conventions relating to compensation for environmental damages caused by the dumping or discharging of any harmful pollutants or chemical, toxic, hazardous, or radioactive materials in the Kingdom’s territorial waters or exclusive economic zone and charge agencies and persons responsible for contamination for all costs and losses resulting from monitoring, treatment, and control operations as well as costs of the rehabilitation of the contaminated environment.
- Pretreatment guidelines and standards apply to all facilities and modifications covered by the environmental standards which discharge to a central industrial or municipal wastewater treatment facility.
The adequacy and area of the mixing zone shall be determined on a case-by-case basis by the Presidency.
- If the toxic, chemical, hazardous, or radioactive wastes brought into the Kingdom or its territorial waters or exclusive economic zone should cause any environmental, health, or alike, the violator shall be required to remove the violation and bear all the costs arising from its adverse impacts.
- In cases of environmental pollution caused by sources outside Saudi Arabian boundaries and territorial waters, the Competent Agency shall receive contamination reports through regional and international organizations, programs, and agencies. The Competent Agency shall implement the national contingency plans for the abatement of pollution as well as carry out the necessary air, land, and marine monitoring and observation and follow-up and take necessary actions.
- Each direct discharge shall be adequately dispersed and mixed with the receiving waters. A mixing zone shall be designed to minimize adverse effects on the designated beneficial uses.
- Wastewaters of different characteristics shall be segregated to the maximum extent possible. Sanitary wastes may be sent to a central treatment facility without pretreatment. Contaminated wastewaters other than sanitary waste shall be treated on-site to meet applicable pretreatment requirements.
• Describe the methods for transporting wastewater to the site (drainage systems, water tankers, etc.). • Detail the technologies used in the treatment and the method of post-treatment drainage. • Describe the degree of treatment (primary, secondary, tertiary) of the discharged industrial wastewater. • Identify the intended use of the water discharged after treatment. pg. 9 References: 1- https://www.britannica.com/ (Britannica) 2- https://www.thermofisher.com/ (thermofisher) 3- U.S. Environmental Protection 6-for-the-cement-clean-5-environmental-impacts-4-initiativehttps://www.epa.gov/enforcement/cement-manufacturing-enforcement-AgencyBuildinggreenhttps://www.buildinggreen.com/feature/reducing-cement-and-concretePollutionsolutiononline(https://www.pollutionsolutions-online.com/news/air-up/16/ctp-chemisch-thermische/air-pollution-control-and-odour-removal-industry/16181)research:( General Environmental Regulations And Rules for Implementation) (28 Rajab 1422 H (15 October 2001)) cement-industry)7-%20Environmental%20Reghttps://elaw.org/system/files/attachments/publicresource/saudiarabia.Generalulations.pdfsciencedirect(https://www.sciencedirect.com/topics/earth-and-planetary-sciences/