The global challenges of pollution emission in cement industry in relation to energy

consumption factor are overwhelming. No doubt it has been established that economic

development has an impact on the environmental pollution and ecological system. With major

constituent of environmental affluence been CO2, the consideration has to be on the type of

manufacturing process, the consumption mix and the additive ratio. This paper focuses on the

cement industry and aims to provide a systematic review of the specific operations, its trend

and its impact on environmental pollution in terms of energy consumption and emissions

evolved

Ayoola, A. A.

Fayomi, G.U.

Fayomi, O. S. I

Mini, S. E.

Covenant University Repository

IOP Conference Series: Earth and Environmental SciencePAPER • OPEN ACCESSPerspectives on environmental CO2 emission and energy factor inCement IndustryTo cite this article: G U Fayomi et al 2019 IOP Conf. Ser.: Earth Environ. Sci. 331 012035 View the article online for updates and enhancements.This content was downloaded from IP address 165.73.192.252 on 24/03/2021 at 12:26Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing LtdInternational Conference on Energy and Sustainable EnvironmentIOP Conf. Series: Earth and Environmental Science 331 (2019) 012035IOP Publishingdoi:10.1088/1755-1315/331/1/0120351		 Perspectives on environmental CO2 emission and energy factor in Cement Industry  G U Fayomi 1, 2, S E Mini1, O S I Fayomi3, 4*, A A Ayoola5   1Strategic Business Services, Covenant University, Ota, Nigeria 2Department of Geography, University of South Africa, Johannesburg, South Africa 3Department of Mechanical Engineering, Covenant University, P.M.B 1023, Ota, Ogun State, Nigeria 4Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, Pretoria, South Africa 5Department of Chemical Engineering, Covenant University, P.M.B 1023, Ota, Ogun State, Nigeria *Corresponding author: ojosundayfayomi3@gmail.com, +2348036886783   Ayodeji.ayoola@covenantuniversity.edu.ng  Abstract. The global challenges of pollution emission in cement industry in relation to energy consumption factor are overwhelming. No doubt it has been established that economic development has an impact on the environmental pollution and ecological system. With major constituent of environmental affluence been CO2, the consideration has to be on the type of manufacturing process, the consumption mix and the additive ratio. This paper focuses on the cement industry and aims to provide a systematic review of the specific operations, its trend and its impact on environmental pollution in terms of energy consumption and emissions evolved.   Keywords: CO2, Pollutions; energy consumption; environmental pollution  1. Introduction Cement is widely regarded as one of the most important building materials available to man, and concrete, which is primarily composed of cement, is classified as one of the most universally utilized materials on earth [1, 2]. The buildings sector is classified as the third largest CO2 emitting institution worldwide [3, 4], with cement production figures stand at between 3.0 - 3.6Gt/year, and it has been estimated that per 1kg of cement produced, 0.5-0.9kg of CO2 emissions are evolved, and this equates to about 3.24 billion tons of CO2/year for 3.6 billion tons of cement produced annually [5] Gartner 2004). Over 90% of the energy required for cement manufacture is obtained from fossil fuels, while the remaining 10% of energy is obtained via electricity, the statistical figure of energy consumption for the cement industry stands at 2% of global primary energy consumption or about 5% of total global industrial energy consumption [1].  Ali et al., 2011 affirmed to this, that the cement industry is one of the highest consumers of fossil fuel energy, it approximately consumes 12-15% of total industrial energy use, with an estimated 1.75±0.1 MJ of energy required to produce 1kg of cement, and China being the largest manufacturer of cement in the world with 57.3% of total world production [4, 6]. In terms of mean energy consumption and CO2 emissions, the cement industry ranks as one of the highest, and this still comes after radical measures were enforced on the industry in the 1970s due to an embargo on oil and gas, that led to innovative solutions and necessitated a need for increased efficiency of production processes, this led to a reduction in consumption of fossil fuel due to the embargo [7].  Having established the fact that industrialization directly influences environmental pollution, the cement industry historically, has affirmed to this trend, and has been observed to generate a high volume of particulate emissions (CO2), particularly in the production of Portland cement clinker, due to the usage of high carbon fuels and emissions from the cement production process [7, 8]. [9], argued that research trends estimates CO2 emissions from the cement industry to stand at 5% of the overall global CO2 emissions due in part to two reasons: the Portland cement make, which is the highest percentage of cement variety in production, having a highly pollution production process, and two, the International Conference on Energy and Sustainable EnvironmentIOP Conf. Series: Earth and Environmental Science 331 (2019) 012035IOP Publishingdoi:10.1088/1755-1315/331/1/0120352		use of outdated industrial equipment (vertical kilns) in some plants, that consume high amounts of energy as well as evolve a high percentage of particulate matter. While it has been established that economic development has an impact on the environmental pollution and ecological damage. This paper focuses and narrows down on the cement industry and aims to provide a systematic review of the specific operations of the cement industry, and its impact on environmental pollution in terms of energy consumption and emissions evolved.   2. Raw Materials Utilized In Cement Industry Pollution in the cement industry in part stems from the raw materials used in the making of Portland cement, ordinary Portland cement (OPC), is the major cement product, and is produced from a mixture of limestone and clay, pyrolysed  in a kiln at temperatures around 1,450°C, and then blended with some additives [2, 8]. According to [12], the average worldwide production figure for clinker stood at 3.6 billion, with worldwide production figures projected to reach over 5 billion by 2030. Typical reactions for the production of clinker include:  3CaCO3 + SiO2 → Ca3SiO5 + 3CO2: with clay (SiO2) CaCO3 + heat → CaO + CO2 As can be seen from the process reaction all clinker production processes evolve CO2, the major constituent of Portland Cement is CaO, and the amount of CaO found is clinker is estimated at 65%, the CO2 emissions produced are estimated at about 0.5-0.9kg per 1kg of clinker produced [10-12] .Therefore a subsequent increase in the amount of clinker produced indirectly leads to an increase in worldwide CO2 pollution as seen in Table 1.  Table 1. Constituents of modern Portland cement clinker [12]   The hydration (mixture) of these clinker compounds with water is what produces cement, in which the constituents undergo a chemical reaction and produce an amorphous solid hydrate. 2CaSiO4 + 5H20 → 3CaO2SiO2 + 4H20 + Ca(OH)2 (Phase 2 cement) 2.1. Pollution in Cement Industry The major industrial pollutant emanating from the manufacture of cement is the evolution of CO2, an estimated 40% of the total CO2 generated from the industry, emanates from fossil fuel burning which is used in the production process, and another 50%, from the raw materials utilized and the manufacturing process, and 10% from indirect emissions by transportation of finished goods [3, 12, 13]. According to [1], for every 1kg of cement produced, 0.9kg of CO2 is evolved, and this equates to the evolution of about 3.24 billion tons of CO2/year for the current projected 3.6 billion produced annually, and these figures don’t take into account the emissions from the quarrying and transportation of raw materials and the transport and delivery of produced cement.  The emission sources at different stages of the product life cycle process are: Constituents of a finished modern Portland cement clinker Tricalcium silicate 50% Ca3SiO5 or 3Ca.SiO2 Dicalcium silicate 25% Ca2SiO4 or 2Ca.SiO2 Tricalcium aluminate 10% Ca3Al2O6 or 3CaO.Al2O3 Tetracalcium aluminoferrite 10% Ca4Al2Fe2O10 or 4CaO.Al2O3.Fe2O3 Gypsium 5% CaSO4.H20 International Conference on Energy and Sustainable EnvironmentIOP Conf. Series: Earth and Environmental Science 331 (2019) 012035IOP Publishingdoi:10.1088/1755-1315/331/1/0120353		• The combustion of fossil fuel in the clinkering process to heat the raw material of limestone (CaCO3), produces CO2 at temperatures exceeding 1450°C. • The calcination process (raw material conversion) in cement production process, also generates a significant amount of CO2. • Indirect emission from transportation and delivery of raw materials and finished goods. • CO2 generated from fossil fuel based electricity generation means, for running plant and equipment [14]. It should however be observed that the amount of CO2 evolved in the manufacturing process also depends on: • The type of manufacturing process adopted i.e. type of kiln used • The type of fuel used (petroleum, natural gas, coal etc.) • The clinker/cement ratio i.e. percentage of additives [14, 15]. Thus these three areas provides a wide scope for improvement and innovation in the production process for the both the management of energy consumption and reduction of CO2 emissions. Figure 1 provides an estimate of CO2 emissions produced at 0.38MJe/kg of electricity/clinker, emission factor of electricity production 0.22kg/MJe, fuel use: 3.35MJ/kg of clinker for dry process and 5.4MJ/kg for wet process.  Table 2. CO2 emissions in kg per 1kg cement produced for dry and wet cement production process for various fuels and clinker/cement ratios [1]    Process emissions Process and fuel-related emissions (CO2) Dry process Wet process Clinker/cement ratio Clinker Coal Fuel oil Natural gas Waste Coal Fuel oil Natural gas Waste 55% 0.28 0.55 0.5 0.47 0.36 0.67 0.59 0.53 0.36 75% 0.38 0.72 0.66 0.61 0.47 0.88 0.77 0.69 0.47 (Portland) 95% 0.49 0.89 0.81 0.75 0.57 1.09 0.95 0.9 0.57  Cement production is largely an energy-dependent process, which begins with: raw materials preparation, fuel preparation and finish grinding. The world cement production has been observed to be increasing from the 1990s and is projected to keep increasing till 2050 as can be seen in the figure below. Cement is observed to be the second most consumed resource after water, as demand increases annually due to infrastructural development in developing and developed nations [15].  Figure 1. Current and estimated global cement production figures [12]. International Conference on Energy and Sustainable EnvironmentIOP Conf. Series: Earth and Environmental Science 331 (2019) 012035IOP Publishingdoi:10.1088/1755-1315/331/1/0120354		 2.2. Historical Review of Cement Industry Statistical estimates show that global trend for cement production, emission rates and energy consumption have been consistently increasing [16] in 1994, an estimated 1.381Gt of cement was produced, accompanied by an estimated 1.126Gt of CO2 emissions. Average primary energy consumption for production was estimated at 4.8MJ/kg of cement, while consuming 6.6EJ of primary energy overall, and evolution of CO2 was estimated at 1126Tg (=1.126Gt) of CO2, these estimates account for ≥5% of the world carbon emission [1]. It should be noted that the amount of energy consumed and quantity of CO2 emitted during these periods came after OPEC enforced an embargo on oil and gas in the 1970s, which forced the cement industry to innovate, become less fuel dependent and more fuel efficient, turning to cokes, coal and other forms of fuels, hinting that prior to this period, the emissions generated and energy consumed were even much higher. The table 3 and 4 presents the primary cement production data and growth rates, production figures have grown from 594Mt in the 1970 to 1453Mt in 1995, at an estimated rate of 3.6%  Table 3.  Cement production data between 1970-1995 for major world regions [1]    Global estimates have predicted the mean carbon emission intensity of CO2 emissions from cement production for this period as 0.81kg of CO2 per kg of cement, with China being the largest emitter of CO2. Table 4 provides the key statistics for carbon emission for cement production as at 1994.               Table 4. Global emission of CO2 from cement production [1] International Conference on Energy and Sustainable EnvironmentIOP Conf. Series: Earth and Environmental Science 331 (2019) 012035IOP Publishingdoi:10.1088/1755-1315/331/1/0120355		   3. Conclusion • As observed from the statistical data, cement production and energy consumption has increased steadily between 1994 and 2010, and this has also characterized an increase in the emission of CO2. • It was observed that the cement industry has been one of the highest energy consuming and CO2 emitting institutions worldwide (rated third worldwide), and while improved techniques and modern technologies have brought about an increase in efficiency of production, reduced energy consumption and reduced CO2 emissions through a variety of techniques. • However, despite the efforts of the industry and government to increase efficiency of production and regulate the emission of CO2 associated with cement production, a rise in CO2 continues particularly as a consequence of increased demand for infrastructural development.  Acknowledgement The author will like to acknowledge the financial support from Covenant University CUCRID toward the publication of this manuscript.  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Perspectives on environmental CO2 emission and energy

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Perspectives on environmental CO2 emission and energy factor in Cement Industry

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