Optimizing Cement Recipe to Reduce Carbon Footprint: Role of MAPEI Performance Enhancers
Optimizing Cement Recipe to Reduce Carbon Footprint: Role of MAPEI Performance Enhancers
Cement is a crucial building material that is used worldwide. In 2022, approximately 4.1 billion tons of cement were produced globally. However, the production of cement is one of the leading sources of greenhouse gas emissions. The cement industry is responsible for ~ 7% of global anthropogenic CO2 emissions, with the amount of CO2 released depending on differences in the materials used in production, the types of cement kiln used, and the fuels being burned, etc.
The production of cement emits large amounts of carbon dioxide (CO2). For every tonne of Ordinary Portland Cement produced, up to 622 kg of CO2 is emitted. Carbon dioxide emissions per ton of clinker are approximately about 825–890 kg CO2 when a modern clinker kiln technology is considered, and the worldwide average is about 840 kg CO2. The medium-term target on carbon dioxide emission levels should be lower than 400 kg per ton of cement to achieve the net zero emissions target by 2050.
Total global CO2 emissions from the cement sector are more than 2.52 Gt. They are primarily direct CO2 emissions which in turn are primarily from the heated limestone itself (approx. 60%) and combustion of the fuels used in the cement kiln and other plant processes (approx. 40%). Electricity used by the sector contributes further CO2 emissions.
Producing clinker is carbon intensive because of both the combustion of fuels and the decomposition of limestone in the clinker production process. Therefore, emissions will be reduced once the clinker demand is reduced and is substituted with waste materials like blast furnace slag and coal ash, Pozzolana, limestone, etc. In order to achieve Net Zero Emissions by 2050, a sharper focus is needed in two key areas: reducing the clinker-to-cement ratio (including through greater uptake of blended cements) and deploying innovative technologies, such as carbon capture and storage and clinkers made from alternative raw materials.
As per Global Cement and Concrete Association (GCCA), Cutting emissions from cement and concrete production by up to 25% by 2030 is estimated to avoid about 5bn tonnes of CO2. Emissions from the industry would be expected to rise over this period, as the market for both materials is forecast to nearly double from $333bn (￡245bn) in 2020 to about $645bn in 2030.
Key strategies to cut carbon emissions in cement production include improving energy efficiency, switching to lower-carbon fuels, promoting material efficiency (to reduce the clinker-to-cement ratio and total demand), and advancing innovative near-zero emission production routes. The latter two contribute the most to direct emission reductions in the Net Zero Scenario. The following strategies have been listed to achieve the net Zero target by the year 2050 by the GCCA:
1.??????Savings in clinker production
??Thermal efficiency
??Savings from waste fuels (“alternative fuels”)
??Use of decarbonated raw materials
??Use of hydrogen as a fuel
2.??????CO2 sink: recarbonation
??Natural uptake of CO2 in concrete – a carbon sink
3.??????Carbon capture and utilisation/storage
??Carbon capture at cement plants
4.??????Efficiency in Cement & concrete production
??Optimised mix design
??Optimisation of constituents
??Continue to industrialise manufacturing
??Quality control
5.??????Decarbonisation of electricity
??Decarbonisation of electricity used at both cement plants and in concrete production
The above figure explains the actions which can lead to the net zero emissions by the cement industry by 2050. This will serve as a road map to identify the key levers for decarbonisation of the cement industry by working on areas such as recipe optimisation; establishing carbon sinks; optimizing our design and construction techniques, etc.
The global thermal energy intensity of clinker is estimated to have remained relatively flat over the past five years, at 3.4-3.5 GJ/t. majority of this requirement is fulfilled by fossil fuel and only 4% of the total consumption is met by using bioenergy and biomass-based wastes derived fuels.
Reducing the clinker-to-cement ratio, including through greater uptake of blended cements, and deploying innovative technologies, such as carbon capture and storage and clinkers made from alternative raw materials, are crucial to achieving the net zero emissions target. However, the global clinker-to-cement ratio is estimated to have increased at an average of 1.6% per year from 2015 to 2020, reaching an estimated 0.72 in 2020. This rise was the main reason for the increase in direct CO2 intensity of cement production over the period. The clinker-to-cement ratio should fall by 1.0% per year to a global average of 0.65 by 2030 to achieve the net zero scenario, owing to greater use of blended cements and clinker substitutes.????????????
In the long run, clinker replacements made from widely available materials, such as calcinated clay in combination with limestone, will become more important as the decarbonization of other sectors reduces the availability of industrial by-products currently used as alternatives, such as fly ash from coal power plants and ground granulated blast furnace slag from
Mapei in its bid to support global carbon emission reduction, has devised a family of performance enhancer which helps in increasing the early and late strength of the cement to facilitate the increase of cementitious filler materials such as Pozzolana, high-grade limestone, grounded Blast furnace slag, etc in the cement recipe.
As a continuous effort to enhance the customer experience by optimising the product use at the client site, we undertook a challenge to provide a performance enhancer to a client which will enable him to extend the filler addition by >5% against the current cement recipe.
A trial was conducted in a cement plant located in East Africa which is currently using Volcanic pozzolana as a filler material in their cement recipe. It’s an integrated cement plant having their own mine for limestone and producing Clinker. The plant operates with VRM for cement production with an installed capacity of 210 - 220 TPH to grind the cement product and uses hot air sourced from HAG and cooler tertiary air as a heat source.
The objective of the trial was “Cement production and Strength enhancement (2 Days & 28 Days) in order to increase the filler content up to maximum permissible limits in the cement recipe.”
After dedicating sufficient time in the R&D and extensive lab scale trials a product from the MA.P. E/S family (a performance enhancer family specially designed to boost early and late strength in cement) was used to run a plant scale trial in order to achieve the above-mentioned quality target.
The plant is currently producing CEM IV/B type cement with the below-mentioned cement recipe. The Strength target and the chemical analysis of the cement are mentioned below:
Strength Age??????????????????Compressive Strength (MPa)
2 – Days??????????????????????????11.8 MPa
7 – Days??????????????????????????22.9 MPa
28 – Days???????????????????????34.4 MPa
Cement Recipe
Component???????????????????% Composition
Clinker %????????????????????????50.7%
Gypsum %??????????????????????4.3%
Volcanic Pozzolana %????45%
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Cement Chemical Analysis (32.5N)
Oxides?????????????????????????????% Composition
SiO2 %??????????????????????????????35.49
Al2O3 % ????????????????????????????7.3
Fe2O3% ????????????????????????????4.43
CaO %??????????????????????????????42.23
MgO % ????????????????????????????0.86
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A study on the chemical analysis of clinker and volcanic pozzolana was conducted to understand the potential of the clinker in terms of reactivity and to look for possible contamination in the Volcanic pozzolana used for cement manufacturing. The chemical composition of the clinker and volcanic pozzolana is as follows:
Clinker Chemistry
Oxides?????????????????????????????% Composition
SiO2 %????????????????????????????21.25
Al2O3 % ??????????????????????????6.2
Fe2O3 %???????????????????????????3.58
CaO %????????????????????????????65.17
MgO % ??????????????????????????1.4
SO3?????????????????????????????????0.57
K2O?????????????????????????????????0.59
Na2O??????????????????????????????0.25
TiO2????????????????????????????????0.27
Mn2O3???????????????????????????0.09
P2O5???????????????????????????????0.14
Cl????????????????????????????????????0.01
LOI?????????????????????????????????0.48
Volcanic Pozzolana Chemical Analysis
Oxides?????????????????????????????% Composition
SiO2 %??????????????????????????????60.4
Al2O3 % ????????????????????????????13.07
Fe2O3% ????????????????????????????6.45
CaO %??????????????????????????????2.59
MgO % ????????????????????????????1.01
The average results of the trial showing an improvement in the mill grinding efficiency in terms Mill feed, Mill power consumption, Specific mill power consumption, water spray on the grinding table and product fineness.
All these parameters have shown a positive change implying a consistent performance of MA.P. E./S.
Parameter??????????????????????Unit???????????????????Blank????????????????MA.P.E/S???????????% Improvement
Specific Power???????????????kWh/t???????????????18.6???????????????????17.2???????????????????7.5 %
Water Spray??????????????????m3/h.???????????????3.1?????????????????????2.6?????????????????????????????16.13 %??????
The strength results during the trial have shown a tremendous increment in ?2,7 & 28 days. Owing to its rich constituents of MA.P.E./S?product, which worked effectively during the CSH gel formation and make sure that the C3S is available for the early and late cement strength formation within the minimum dosage of 400 g/ton of cement.
During the trial, a 27% increment is observed in the 2 days strength resulting in an increment of 3.2 MPa similarly an increment of 16% & 19% was observed in the 7 & 28 days cement strength resulting in an increase of 3.7 MPa and 6.6 MPa respectively.
Grinding Aid?????????????????????????????????Blank????????????????MA.P. E/S???????????????????????% Increment
Volcanic pozzolana %?????????????????45??????????????????????45?????????
2 Day (MPa)??????????????????????????????????11.8???????????????????15.0????????????????????????????????27.12 %
7 Day (MPa)??????????????????????????????????22.9???????????????????26.6????????????????????????????????16.15 %
28 Day (MPa)????????????????????????????????34.4???????????????????41.0????????????????????????????????19.18 %
The strength increment can be utilised to increase the filler % in the cement recipe by ~ 5% by keeping 28 days strength increment as a reference for substitution.??We can always increase the filler % to equate the difference in strength on 28 days between MA.P. E/S treated cement with blank.
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The cement production plant has achieved significant results in its commitment to reduce its carbon footprint. The plant is producing 3 million metric tons of cement, using 1.52 million metric tons of clinker, which generated 1.28 billion kilograms of CO2. However, by implementing a new cement recipe with a reduced clinker requirement of 1.37 million metric tons, the plant will be able to achieve a 10 % reduction in CO2 production, which is equivalent to 126 million kilograms of CO2 reduction.
Moreover, the plant will be able to achieve a reduction of 1.4 kWh/t in specific power required to grind cement, resulting in a CO2 reduction of 2.39 million kilograms per year. This substantial reduction in CO2 emissions demonstrates the plant's commitment to environmental sustainability and the adoption of responsible production practices.
Further, the usage of Performance Enhancer will contribute 2.01 kg?CO2 eq (Tentative) / kg of cement additive into the atmosphere, but the total contribution from the performance enhancer is less significant due to its reduced volume usage. The adoption of the MA.P.E/S family performance enhancer will result in an impressive saving of 126?million kilograms of CO2, which will be a testament to the plant's dedication to sustainable production practices.
The results clearly demonstrate the effectiveness of the MA.P.E/S performance enhancer in improving the physical properties of the cement produced, while simultaneously reducing the carbon footprint of the production process. The use of the performance enhancer has become a crucial step in the cement production process, and its adoption should be encouraged in all cement production plants.
In conclusion, the study provides evidence that the adoption of sustainable practices in cement production can significantly reduce carbon footprint. The use of the MA.P.E/S performance enhancer showcases the potential of innovative solutions to achieve significant carbon reduction. The study emphasizes the importance of adopting sustainable practices in the cement industry to mitigate the impact of climate change. By continuing to optimize its operations and invest in research and development, the cement production plants can continue to reduce their carbon footprint and contribute to a sustainable future.
References:
1.??????IEA (2022), Cement, IEA, Paris https://www.iea.org/reports/cement, License: CC BY 4.0
2.??????Global cement and concrete association: https://gccassociation.org
5.??????Robbie M. Andrew: Global CO2 emissions from cement productionTop of Form