Sustainable approach in cement industry

Sustainable approach in the cement industryCement industry and environment:

Global news is often reported about climate change, but what is the reason for this?Is it the industrial revolution that caused a boom experienced by individuals and societies in all areas of life? Scientific research has answered this question and confirmed that the industrial sector - including the cement industry - is primarily responsible for about a third of global carbon dioxide emissions. As we know, cement is an indispensable material in various construction and engineering works, in addition to the fact that its production and consumption are closely linked to the development, urban and industrial expansion, and infrastructure we are experiencing now, and thus to global economic activity.

Cement and energy industry:

If scientific research is the main driver of the events we are experiencing now, it has placed in the reader’s hands a lot of information about various industries, including the cement industry. The basic chemistry of the cement manufacturing process revolves around the decomposition of calcium carbonate (CaCO3) at about 900 degrees Celsius to produce calcium oxide (CaO) and lime and the release of carbon dioxide (CO2). This process is known as “calcination,” and the production unit is known as “calcinizer.”Then the process of forming the main compounds begins inside the furnace, through the reaction of calcium oxide at a high temperature (usually 1400-1500 degrees Celsius) with silica, alumina, and ferrous oxide. To form silicates, aluminates, and calcium iron, the resulting mixture is called “clinker,” which is then ground with gypsum and other additives. For cement production.We conclude from the above that reaching our achievements in the field of building and construction includes injustice to the environment; This is because the cement industry requires reaching very high temperatures, and they must be maintained throughout operating times. Therefore, the cement industryis considered one of the largest energy-consuming industries. Fuel is used to increase the temperature to the required levels. In order to speed up chemical reactions.

Cement industry and global warming:

Although the cement industry is one of the largest major industries that contribute to greenhouse gas emissions, approximately 4.4 billion metric tons of cement are currently produced worldwide, which results in about 9% of carbon dioxide emissions. In the future, researchers in this industry expect that the quantities of cement production will continue to increase steadily, which in turn will add more carbon dioxide emissions to the atmosphere, but it is not the only one responsible for carbon dioxide emissions. Greenhouse Gases (GHGs), and many industries share this; Such as iron, steel and other industries.

Cement industry and sustainability:

Research is scouring all over the world in search of how to achieve the application of sustainable environmental practices in the various major cement industry activities, which have already received great interest from scientists and researchers in this field, but the fact cannot be overlooked that the basic stages that make up the cement manufacturing process are considered to a large extent unsustainable, in addition to being among the most energy-consuming industries and generating environmental pollutants.In recent decades,The Portland cement industry has undergone further research and development by many research bodies and centers. It has also become subject to some local laws and regulations that set limits on its emissions and regulate the process of disposing of the resulting waste. Because it is the most important factor in infrastructure development and the main consumer of energy and natural resources.Fortunately,The cement industry can be the nucleus of the move towards achieving environmental sustainability, by adopting some new technologies in the field of energy efficiency and alternatives to traditional fuels to reduce the carbon footprint, in addition to proper management of the waste resulting from this industry, converting them into products or reusing them again in the various stages of manufacturing processes, and reducing the use of new raw materials. Therefore, all of the above is considered the cornerstone on which the manufacturing of green concrete, or what is called “sustainable concrete,” will be based.

Cement and fuel industry:

But how is this achieved? This question can be answered by researching the priorities of large industries such as the cement industry, which the scientific community has confirmed spares no effort in trying to conserve energy by reducing dependence on traditional fuels and resorting to finding alternatives to them, such as using some types of waste as fuel and alternative materials in the cement manufacturing process. The advantage of this option lies in achieving two basic goals, which are: reducing dependence on fossil fuels; Such as: coal, natural gas, and oil on the one hand, in addition to proper waste management on the other hand.The use of alternative fuels is the most environmentally sustainable solution.Examples include fuels derived from rejected waste (RDF), agricultural waste, rubber waste, plastics, etc., in addition to liquid wastes such as chemical wastes, oils and greases...etc. All of these options are considered energy-rich materials that can be used to replace coal or gas. In the cement manufacturing process.Reliance on the use of alternative fuelshas given way to cement manufacturers; To preserve non-renewable resources and reduce waste disposal requirements, it also enabled them to reduce carbon dioxide emissions by 0.1 to 0.5 kg/kg of cement produced, compared to production techniques currently used using fossil fuels, but the main obstacle in using this technology is that it cannot be relied upon 100% as an energy source, as most current manufacturing lines can use alternative fuels by A maximum of 40%, and research is currently focusing on raising this percentage, and it is not considered a suitable option in the white cement industry. Because color brightness is affected by the indicated fuel alternatives.

Blended cement is a living model for achieving sustainability:

Reducing the percentage of clinker used in cement production is a key focus for reducing carbon dioxide emissions. Therefore, it is not surprising that research is directed at finding out how to replace certain percentages of “clinker” in the cement mixture. As we mentioned before, the production of “clinker” is the most energy-consuming step in the cement manufacturing process, in addition to causing large emissions of carbon dioxide. This trend also represents an attractive economic option for cement manufacturers. Because calcined materials are expensive compared to alternatives.Mixed cement is a living example of this; Where a percentage of the “clinker” is replaced by complementary by-products (SCMs) resulting from other industries. Such as: coal fly ash (residue from power plants), blast furnace slag (residue from the iron industry), or other pozzolanic materials (such as volcanic materials), etc. These byproducts are then mixed with ground clinker to produce a homogeneous mixture.Because the practical application is based on live examples, science proves the extent of the possibility and suitability of its application on the ground, and when the total carbon dioxide emissions were calculated for each ton of Portland cement that resulted, it was found to be approximately 970 kg, while only 70 kg of carbon dioxide was produced per ton of granulated blast furnace slag.It should be noted herethat although it is possible to use these clinker alternatives in percentages that may exceed 33%, this may come with some properties that are not required in the final product, which requires sufficient research before determining the type and percentage of the complementary material used.

A new type of sustainable cement:

We also have another example: clay cement “calcined” with limestone, or Limestone Calcined Clay Cement, also known as “LC3”.This type of cement is a new breakthrough provided by scientific research in the field of environmental sustainability. It is a new type of cement based on a mixture of limestone and calcined clay. This mixture can reduce carbon dioxide emissions by up to 40%, and it can be manufactured using low-quality limestone and clay available in abundant quantities, in addition to being a cost-effective option. The advantage of this new mixture lies in “LC3”.  In that it requires smaller amounts of clinker to produce cement, amounting to 50%, which consequently means significantly reducing the use of fuel, and thus reducing various emissions, most notably carbon dioxide. This innovative type of cement is also characterized by having mechanical properties similar to traditional cement, which makes it a sustainable, environmentally friendly option.

Cement industry and sustainable technologies:

After presenting the previous examples, it became clear to us that the field of environmental sustainability has added a lot to the cement industry, and this is evident from the use of various technological techniques that will develop this industry, but in a way that preserves environmental resources for future generations. Therefore, it must be noted here that scientific research has been able to replace a percentage of “clinker” with complementary secondary materials, in addition to the possibility of using nanoscale calcium carbonate as a complementary material also for the production of mixed cement. It can counterbalance the undesirable properties that may result from the use of SCMs; This allows for an increase in the replacement rate of cement used, and also opens the way for the use of nanotechnology in the cement industry, which means producing a new generation of sustainable and environmentally friendly building materials.What is striking here is the possibility of producing nanoscale calcium carbonate using carbon dioxide gas emitted from the cement manufacturing process itself; In order to achieve the principle of recycling waste, this is done by capturing carbon dioxide from the flue gas coming out of the “clinker” production unit (calciner and kiln), and then passing the captured carbon dioxide after purifying it through the manufacturing unit. Nanoscale calcium carbonate deposits are produced through the process of chemical synthesis.The source of calcium for this process can be industrial waste (including steel slag and cement kiln dust),by adding nanoscale calcium carbonate (in the required amount) to the “clinker”. The mixture is ground in addition to the raw limestone; To produce blended Portland cement, excess nanocalcium carbonate can also be sold to some other industries, thus generating new economic revenue for cement plants.This technology is unique not only in reducing the amount of fuel used,and thus reducing carbon dioxide emissions, but also by converting this gas into an input into the production process. In order to achieve the principle of green circular economy.The scientific research also praised its uniqueness in producing nanoscale calcium carbonate using carbon dioxide captured from cement factory chimneys, replacing “Portland clinker” by approximately 2% by weight. Resulting in a reduction in CO2 emissions from 0.96 kg equivalent/kg cement to 0.3 kg equivalent/kg cement, representing a reduction of approximately 70%.

Cement industry and recycling:

The process of getting rid of side lane dirtrepresents a time and material burden without achieving any benefit, despite the tireless efforts made by cement factories to reuse it, which has attracted the attention of many researchers to find alternatives to using this dirt instead of getting rid of it.But what is bypass dirt?Bypass dirt is a by-product generated during the Portland cement production process. When raw materials are heated in the kiln, dust particles (dust) are created that are carried by the exhaust gases into the upper end of the kiln. The use of side lane dirt as the main raw material (45%-50%) along with silica and sandstone to make dark green glass with high durability is one of the most important innovations presented by the field of environmental sustainability. This is due to the high content of calcium oxide (CaO), which can be used to produce containers for chemicals. It is also possible to produce what is known as “ceramic glass”, if it is made after processing operations on the previous product. Ceramic glass has very high strength and looks like marble.Beneficial uses of bypass dirt include using it as a fill material in highway construction and maintenance, and it can also be used in brick making; For use in industrial construction, as it was found that the bricks containing the dirt of the side passages have acceptable properties and a much lower cost than other types of bricks.

Cement industry between reality and hopes:

In conclusion, it is worth noting that demand for concrete and cement is expected to grow around the world along with the need to rationalize energy use and reduce carbon dioxide emissions. Over the past few decades, cement manufacturers have increased their adoption of some environmentally sustainable technologies and innovations that have already brought about a gradual change to advance this sustainable industry. However, this may not be enough to move forward!Therefore; We must praise scientific research and its role in achieving environmental sustainability goals in the industrial sector, especially the cement industry. Because it is one of the leading industries not only in the development and prosperity of our human civilization, but also in promoting sustainability in some other sectors. In pursuit of green buildings and sustainable infrastructure.