Clinkering Process Research Articles

The Lukala Cement Plant's Life Cycle Analysis: Towards a More Sustainable Production

This paper presents an in-depth Life Cycle Assessment (LCA) of the Lukala Cement Plant, highlighting the environmental impacts associated with cement production. The cement industry, as one of the largest emitters of CO2, raises major sustainability concerns, particularly due to the deleterious effects on climate and public health. The objectives of this research include not only assessing greenhouse gas emissions but also identifying concrete methods to reduce these impacts. The study reveals that the Lukala Cement Plant emits approximately 579,130 tons of CO₂ per year, mainly from the decarbonation of limestone (67%) and the clinkerization process (33%). These figures far exceed regulatory thresholds, highlighting the urgency of rapid and effective intervention to mitigate these emissions. The LCA identified the most polluting production steps, including extraction, grinding, and clinkerization, paving the way for targeted and strategic improvements. Opportunities for optimization were identified, including the use of less pure limestone, the integration of recycled materials, and the transition to renewable energy sources for the clinkerization process. This research is crucial in the current context of the fight against climate change. As a major contributor to greenhouse gas emissions, the cement industry must imperatively adopt sustainable practices. LCA provides a robust methodology to quantify environmental impacts and identify appropriate solutions. The results of this study can be applied to other cement plants around the world, serving as a model for other carbon-intensive industries. Future research should explore the integration of innovative technologies, such as carbon capture and storage, and the use of alternative materials in cement production. This study highlights the importance of immediate and coordinated action to transform the cement industry into a sustainable sector, ensuring economic profitability while protecting the environment for future generations. Commitment to environmentally responsible production practices is not only desirable but also essential to ensuring a sustainable future.

EFFECT OF ALTERNATIVE RAW MATERIALS OVER CLINCKER QUALITY AND CO2 EMISSIONS

In the cement industry, the actual challenges are the preservation of the raw materials and energy resources, as well as reduction of pollutant emissions. In this context, the cement producers demand studies to reduce of the production costs and atmospheric emissions. One way to achieve these objectives, is to use alternative fuels or by-product raw materials. Any reduction in the required energy has a beneficial influence both on the viability of the cement plant and on the environment. One of the approaches aimed at reducing thermal energy consumption is the partial substitution of traditional raw materials (limestone, clay, gypsum) with other alternative materials, with a melting effect, among which stand out byproducts of the steel industry such as furnace and steel slag. Another way for preservation of energy resources is using alternative fuels instead of traditional fuels like coal, petroleum coke or gas. The clinkering process and clinker quality can be influenced by any additions, in this study was determined these influences.

Optimization of Process Loading Clinker to MV. Star Royal by PT. Varia Usaha Bahari at Maspion Port Gresik

The main focus of this research is to find out the process of loading clinker onto the MV. Star Royal that the activity is running optimally. The factors include in this research loading and unloading equipment, facilities and infrastructure, human resources, weather conditions. This research will identify each of these factors and analyze their impact on the overall clinker loading process. The research method used in the study is a qualitative method involving direct observation in the field, interviews with relevant parties at PT Varia Usaha Bahari, and analysis of data related to the clinker loading process. With a comprehensive approach, this research aims to provide concrete and implementable recommendations to improve the optimization of the clinker loading process at Maspion Gresik Port. The results of this research are expected to make a positive contribution in improving the performance of PT Varia Usaha Bahari in carrying out clinker loading activities on other vessels. With a deeper understanding of the factors that influence the clinker loading process, it is expected that the company can implement a more optimized strategy in the clinker loading process to better achieve their goals in the future.

Effects of Fineness and Morphology of Quartz in Siliceous Limestone on the Calcination Process and Quality of Cement Clinker.

With the increasing depletion of high-quality raw materials, siliceous limestone, sandstone and other hard-to-burn raw materials containing crystalline SiO2 are gradually being used to produce clinker. This study investigates the influence of the quartz content and particle size in siliceous limestone on the calcination process and the resultant quality of cement clinker. Two different siliceous limestones were grinded to different fineness, and calcinated with some other materials. The content of the clinkers was analyzed with the XRD-Rietveld method and the microstructure of the clinkers was observed with laser scanning confocal microscopy (LSCM) and field emission scanning electron microscopy (FESEM). Three key outcomes of this study provide new insights on the use of siliceous limestone in cement production, namely that (i) reducing the fineness values of siliceous limestone from 15% to 0% of residue on a 0.08 mm sieve decreases the quantity of these larger quartz particles, resulting in an increase in C3S content by up to 8% and an increase in 28d compressive strength by up to 4.4 Mpa, which is 62.30 Mpa; (ii) the morphology of quartz-either as chert nodules or single crystals-affects the microstructure of C2S clusters in clinker, finding that chert nodules result in clusters with more intermediate phases, whereas large single crystals lead to denser clusters; (iii) the sufficient fineness values of siliceous limestone SL1 and SL2 are 5% and 7% of residue on a 0.08 mm sieve, respectively, which can produce a clinker with a 28d compressive strength greater than 60 Mpa, indicating that for different kinds of quartz in siliceous limestone, there is an optimum grinding solution that can achieve a balance between clinker quality and energy consumption without having to grind siliceous limestone to very fine grades.

A Review on durability and microstructure of Fly-Ash based geopolymer concrete (FA-GPC)

Concrete, being the fundamental material in the construction industry, relies largely on cement for its structural integrity and performance. However, new researches have emphasized a significant concern—the considerable increase in global greenhouse gas emissions linked to cement manufacturing. This rise in emissions derives mostly from the thermal decomposition of calcium carbonate during the clinkering process, establishing cement as a key contributor to the rising CO2 footprint. This alarming trend demands prompt attention and inventive remedies. This study intends to solve this important environmental issue by studying the transformational potential of Geopolymer Concrete (GPC) as a sustainable alternative. By adding FA, an abundant industrial waste by-product, as a supplementary cementitious material (SCM) in GPC, we have the possibility to dramatically cut carbon emissions by up to 80%.This transition towards sustainable materials not only decreases the load on traditional cement resources but also illustrates how waste materials may be utilized for the sake of the environment. Our analysis comprises factors such as consistency, curing temperature, chloride corrosion resistance, XRD (X-ray Diffraction) and SEM (Scanning Electron Microscopy) investigations. Through these findings, we hope to underline the considerable potential of GPC, particularly when strengthened with FA, as a strong tool for decreasing the carbon footprint within the building sector.

A theoretical model of cross-flow heat transfer for the cooling process in a horizontal moving bed of high-temperature particles

ABSTRACT Besides waste gas and liquid, high-temperature particles are important media of waste heat and their temperature exceeds 1000°C on many occasions. The cross-flow heat transfer is important in this waste heat recovering process, but there are few references reported about the theoretical modeling. Therefore, a theoretical model was developed for the cooling process in a horizontal moving bed of high-temperature particles. The purpose of the study is to estimate the influence of temperature field and flow field on heat transfer and bed resistance in the cross-flow cooling process. Three modes such as conduction, convection and radiation are considered in the model. This model was used to analyze heat transfer in a horizontal moving bed of cement clinker and was verified by comparing some simulative results with the tested and collected data from an actual cement clinker plant in China. The simulative temperature of cement clinker was 200°C as same as that collected in the actual cement clinker plant. In the moving bed, the highest pressure drop occurs at the front top and the strongest heat transfer occurs at the front bottom. In the considered conditions with even distribution of cooling air, the highest pressure drop is 3205.9 Pa/m, the biggest specific heat transfer rate of 1683.1 kW/m3. Thermal radiation plays a minor role in this cooling process with the biggest radiation proportion is only 0.149 at the front top. This mode plays a minor role in this cooling process of the cement clinker, comparing with the thermal convection. With constant flow rate of cooling air, the distribution can regulate the local cooling rate rather than the final temperature of the cement clinker.

Comparative Life Cycle Assessment of Different Portland Cement Types in South Africa

Cement has long been recognized as an energy- and emission-intensive construction material. Cement production has recently experienced significant growth despite its high energy consumption, resource usage, and carbon emissions. This study aims to assess and compare the life cycle assessment (LCA) of traditional Portland cement (CEM I) to those of three blended cement types (CEM II/B-L, CEM II/B-V, and CEM III/A), which assume mature technologies for reducing carbon emissions in South Africa, using LCA in compliance with ISO/TS 14071 and 14072. As its scope, the study employs the “cradle to gate” method, which considers the raw materials, fuel usage, electricity, transportation, and clinkering stages, using 1 kg of cement as the functional unit. The LCA analyses were performed using SimaPro 9.1.1.1 software developed by PRé Consultants, Amersfoort, Netherlands and impact assessments were conducted using the ReCiPe 2016 v1.04 midpoint method in order to compare all 18 impact categories of 1 kg of cement for each cement type. The assessment results show reductions in all impact categories, ranging from 7% in ozone depletion and ionizing radiation (CEM II/B-L) to a 41% reduction in mineral resource scarcity (CEM III/A). The impacts of global warming were reduced by 14% in the case of CEM II/B-L, 29% in the case of CEM II/B-V and 35% in the case of CEM III/A. The clinkering process was identified as the primary cause of atmospheric impacts, while resource depletion impacts were attributed to raw materials, fuels, and electricity processes, and toxicity impacts were primarily caused by raw materials. Alternative materials, like fly ash and ground granulated blast furnace slag (GGBFS), can significantly help to reduce environmental impacts and resource consumption in the cement industry.

Capitalization of tires waste as derived fuel for sustainable cement production

The co-incineration of tires waste is inexpensive; the questions are referring to the influence over clinker quality and gaseous emissions. The use of tires waste as a waste-derived fuel imposes more researches to establish influence over process parameters, technological availability, costs, kiln design for processing different type of fuels, quality and homogeneity of alternative fuels, the caloric value, quality of clinker, gaseous emission, etc. The data was obtained at an industrial scale, during two periods when 11% tires waste replaces coal, with or without raw mill in function. The results were compared with the period when coal was the only fuel used. The principal objective of this paper is to establish the influence, at the industrial scale, of the use of tires waste on: the technological parameters of the clinker kiln as well as on its energy efficiency and stability; the effects of tires waste incineration on clinker process and properties of clinker, SO2, NOx and heavy metals emission. The experimental results presented in the paper demonstrated that the co-incineration of tires wastes in cement plants have the multiple benefits: save raw materials, reduced CO2 emission, thermo-energy recovery of waste with rich energy content, reduces waste disposal, etc.

New Types and Dosages for the Manufacture of Low-Energy Cements from Raw Materials and Industrial Waste under the Principles of the Circular Economy and Low-Carbon Economy.

The cement manufacturing industry is one of the main greenhouse gas emission producers and also consumes a large quantity of raw materials. It is essential to reduce these emissions in order to comply with the Paris Agreement and the principles of the circular economy. The objective of this research was to develop different types of cement clinker blends using industrial waste and innovative design to produce low-energy cement. Several types of waste have been studied as alternative raw materials. Their main characteristics have been analyzed via X-ray fluorescence (XRF), X-ray diffraction (XRD), Attenuated total reflectance Fourier trans-form infrared spectroscopy (ATR-FTIR), thermal analysis (TG-DTG-DSC) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). The results obtained from the experimental work carried out in this research focused on the study of crude blends for low-energy cement created from industrial waste. The effect of the addition of different industrial waste types, as a substitution for raw materials, in the production of low-energy cement with high dicalcium silicate content has been investigated. Thus, the dosage design has been performed using modified Bogue equations and quality indexes (LSF, AM, and SM). The calculations of both the modified Bogue equations and quality indexes necessitate knowledge of the weight percentages of CaO, SiO2, Al2O3, and Fe2O3, determined via XRF. In this theoretical design of the different blends, it has been established that a dicalcium silicate ratio of 60-65 wt % and an LSF of 78-83% as the limit are values common to all of them. The calculation basis for the crude blends has been based on calcined materials. Therefore, the chemical composition was established, following this premise. Thus, it was possible to develop cement clinker blends with compositions of 50 wt % and 100 wt % using industrial wastes. This research has shown that the clinkerization process is one of the main options for the valorization of waste and its consideration for inclusion as a raw material within the circularity of the cement industry's production process. Thus, waste is used as a raw material for the production of a more useful substance, taking into account the fundamental principles of the circular economy.

Environmental Impacts Evaluations of Different Alternative Fuel Substitution Rate Scenarios in Clinker Production

Cement production is an energy-intensive industry that primarily relies on fossil fuels like coal and natural gas to meet energy needs. Extreme usage of fossil fuels leads to depletion of their source and higher greenhouse gas (GHG) emissions such as NOx, SOx, and CO2. Clinker, as the primary material for cement, is a product of the clinkerization process in the kiln system, where the utilization of fossil fuel happens massively. Pre-calciner, as a part of the kiln system, combusts around 60% of the fuel requirement in the kiln system. The calcination reaction occurs within the pre-calciner at 700 - 900 ˚C and produces over 50% of the emissions. Alternative fuels proved the capability to meet the energy demand and mitigate GHG emissions. Previous studies show Aspen Plus is one of the powerful software, able to simulate the calcination and combustion process realistically. The process model in this study uses data from one of the leading cement plants in Yemen. The main aim of this study is to evaluate the environmental impacts of alternative solid fuel mixture (Tires-derived "TDF" and Plastic waste "PW") and coal with various scenarios of substitution rate. It mainly concentrates on the environment, quality, and energy outputs. Based on the simulation results of the investigated model, in the implementation of 100% alternative fuels mixture scenarios, PW increased the moisture percentage, affecting the outlet temperature, While TDF has higher emissions than PW. Likewise, the 50% alternative fuels mixture with various substitution rates of coal has shown satisfactory results with a low amount of coal regarding the emissions percentages.

ადგილობრივი ნედლეულის გარდაქმნის პროცესები კლინკერის წარმოების მბრუნავი ღუმელის სისტემაში რეაქტორ-დეკარბონიზატორის გამოყენების გათვალისწინებით

In cement and clinker production energy consumption reduction, specific emissions reduction and quality stable increase always has been daily challenge which was addressed in many studies. Nowadays, CO2 emissions are under special focus since the gas is a main contributor in global warming and many other environmental topics. Considering existing challenges, the PhD study is addressing following: Revamping from wet process to the new dry line clinker production process Revamping from the old Kavtiskhevi quarry to new Saskhori quarry Raw meal, kiln feed and clinker quality adjustment after changing the type and amount of the fuel Study of clinkerization process based on the modified design Activation of puzzolanic material – Tuff in the clinker cooler Clinker production process change from wet process to dry process was performed the way that clinker quality was at least the same but grindability of the clinker was increased with relatively lower lime saturation factor. Of course by avoiding drying wet slurry and making heat exchange process more efficient due to more dispersive, powderous material the heat consumption was reduced twice and capacity of the kiln line was doubled. The difficulties caused by switching the Kavtishkevi quarry were solved by using Saskhori limestone as a main source and Dedopsitskaro limestone was used as a sweetener, which contains more than 95% calcium carbonate. This substitution took place in such a way that it did not have a negative impact on the quality of the clinker and on the contrary made it more stable and active. After reducing coal and thus ash by 2 times, raw flour chemistry was recalculated so that the quality of clinker was the same or increased. Appropriate recalculation was done at all stages of trials. The clinker process burning with a new method was studied and optimized. As a result of 20 industrial experiments of raw material and fuel distribution, the best mixes were determined, by means of which the quality of clinker increases or remains the same, while the thermal consumption was reduced as was CO2 emissions from fuel and from raw meal. The most important achievement was the thermal activation of Tuff (Zeolite), which was successfully completed not only in the laboratory but also in the industrial experiment. The origin of the innovative idea was that the drying out of physically bound water makes the puzzolanic material much more active due to created pores. The material usage (with clinker) up to 10% in relation to clinker not only preserves but also increases the strength of this mix compared to clinker. The method of activation of existing puzzolanic material has been studied since the ancient Roman period. However, the activation of the puzzolanic additive requires less thermal energy than the clinker, and therefore also emits additional CO2 emissions. Therefore, the puzzolanic material activated by the standard approach reduces emissions, thermal and other costs relatively less, and also requires an investment of at least 10 million and an installation period of at least 6 months. Based on a complete study of the clinker production processes, a section was identified where the temperature ranges from 600°C to 1200°C and we use ambient air to reduce it. This section is a clinker cooler, where clinker heated at temperatures 1200-1300°C is coming out of from the rotary kiln. The clinker is passing a 30-meter cooler and cools down to about 100°C. The temperatures we wanted were 5 to 10 meters from the hot side. 10 meters away from the hot end, a material discharge chute was arranged, where tuff is supplied with transport conveyors and hopper. The production experiment with a dose of 5% was successful, but it is also possible to increase the proportions to 10% in the following trials. Also, the feeding point on the clinker cooler roof can be moved to the hotter side, which will further activate the tuff and allow us to increase its percentage in the clinker. The most important is that this experiment allowed us to produce 100% clinker with 90% emissions and thermal consumption, which is an incredible result globally, especially for CO2 reduction. The project was implemented with minimal costs (200,000 GEL) and, most importantly, does not include the thermal energy obtained with fuel, which almost cancels the operating costs and emissions. This section of the clinker cooler can be studied to use for drying and heating any other cement additive material.

Feasibility Studies for Use of Copper Slag in Clinker Manufacture

This study investigated the feasibility of using copper slag (CS-C) as a raw material in the production of Portland cement (PC). The effect of addition of 0%-3.5% CS-C on the clinkerization process, mineralogy, microstructure, and compressive strength development was studied. The Presence of CS-C in the raw mix resulted in the reduced temperature of clinkerization by about 50 °C. The quality of clinker prepared from the raw mix containing 3% CS-C and burned at 1400 °C was comparable to that of clinker prepared from the raw mix containing no CS-C and burned at 1450 °C. Gradual polymorphic modification of alite phase from rhombohedral to monoclinic upon the addition of CS-C was confirmed by X-ray diffraction (XRD) study. XRD and optical microscopy studies revealed the formation of more alite in the clinker prepared, at 1400 °C, from the raw mix containing 3% CS-C compared with the clinker prepared, at 1450 °C, from the raw mix containing no CS-C. This finding indicated the mineralizing effect of CS-C on clinkerization. Well-developed and large-sized alite grains were observed in the clinker samples prepared using CS-C. Portland clinker, prepared using CS-C as a raw mix component showed better mechanical performance characteristics than the control clinker. These results clearly establish the beneficial role of CS-C as a raw mix component in clinkerization and can replace conventional sources of iron such as laterite.

Carbonation of concretes containing LC³ cements with different supplementary materials

Due to the clinkerization process during the Portland cement production, large amounts of CO2 are emitted, increasing the effects related to climate change (approximately 5-10% of global CO2 emissions come from cement production), consequently, the seek for alternatives to mitigate these high emissions are necessary. The use of supplementary cementitious materials (SCM) to partial replace of Portand clinker/cement has been the subject of different research, including the use of LC3 cements (Limestone Calcined Clay Cements), where up to 50% of Portland clinker can be replaced, however, cement industry has already used othersupplementary cementitious materials with pozzolanic activities in commercial cements. In this sense, this work evaluates the performance of concretes containing LC3 mixtures with the presence of different SCM (silica fume, fly ash, sugarcane bagasse ash and açaí stone ash) regarding durability issues by carbonation. The results showed that all concretes with LC3 presented higher carbonation fronts in relation to the reference concrete, with Portland cement, due to the lower availability of calcium to react with the CO2 that penetrates into the concrete pores, so the adoption of curing procedures and coatings are recommended.

Cement and Clinker Production by Indirect Mechanosynthesis Process

Global cement production has reached 3.9 billion tons. However, the clinkerization process, which is the basis of cement production, is responsible for an approximate annual global CO2 emission of 2 billion tons. As part of CEMBUREAU’s 5C strategy, the European cement industry aims to achieve carbon neutrality throughout the cement-concrete value chain by 2050. This article is a continuation of the previous article on the indirect mechanosynthesis clinkerization process, which combines mechanical activation (high-energy milling) and thermal treatment at lower temperatures (from 900 °C) than those used for conventional clinkerization to produce clinker. With this process, we manufactured cement and clinker from industrial and laboratory raw mixes, which had to be rectified by adding kaolinite in compliance with the different cement indicators (LSF, SM, AM). The cement and clinker produced by indirect mechanosynthesis (15 min of mechanical activation and heat treatment 900 °C or 1200 °C) were characterized. In order to test the hydraulic properties of the cement produced, cement pastes were made. Mechanical and structural studies were carried out (between 70 and 90% of C2S). Mechanical tests revealed for 7 curing days, the values of 3.60 and 7.60 MPa at 900 °C and 1200 °C, respectively, in comparison to commercial cements CEM I and CEM III (23.03 and 19.14 MPa).

Revealing the co-doping effects of fluorine and copper on the formation and hydration of cement clinker

Fluorine in fluorite mineralizer and copper were easily doped together into cement clinker during cement kiln co-disposing wastes bearing Cu, yet that co-doping effects on the formation and hydration of cement clinker get few attention. The findings in this work revealed that the co-doping CaF2 (fluorine source) and CuO (copper source) into cement clinker showed a synergistic effect on the burnability, the immobilization rates of fluorine and copper in clinker phased were promoted. Compared with doping CaF2 into cement clinker, Co-doping CaF2 and CuO further enhanced the formation of alite and brownmillerite, while hindered the formation of tricalcium aluminate, and also triggered the right shift of characteristic diffraction peaks for C3S polymorphisms. It co-doping not only changed the microstructures, but also induced the visible defects on the surfaces of clinker mineral grains. In addition, most of fluorine would likely enter into the alite structure by replacing O2– of silicate phases, while most of copper would possibly enter into the brownmillerite structure by replacing Fe3+. Compared with the hydration process of cement clinker doped with CaF2, Co-doping CaF2 and CuO further accelerated the initial hydration process, obviously prolonged the induction period, but promoted the later hydration of co-doped clinker. Although the mechanisms about co-doping on the hydration process of co-doped clinker need more investigation, the above findings could extend the value-added utilization of wastes bearing Cu to reduce the large CO2 emission and energy/resource consumption in cement industry.

Clinkering design of sulfobelite cements using clay overburden residue from bauxite mining

Sulfobelite (belite-rich calcium sulfoaluminate (BCSA)) cements are promising alternatives to ordinary Portland cement (OPC) due to their lower carbon dioxide generation and lower energy consumption in the clinkering process. Additionally, they are cost effective because of their less-restrictive raw meal composition compared with that of calcium sulfoaluminate (CSA), in which expensive bauxites are used as the alumina source. Diverse mining residues have been proved to be reliable alumina sources for BCSA production, including the clay residues that cover bauxites (Belterra Clay (BTC)) in the Brazilian Amazon region. The clinkering settings of BCSA using a different (less alumina) BTC were examined in this work. The mineralogy of the BCSA clinkers was optimised by a design of experiments and studied using X-ray powder diffraction, scanning electron microscopy and thermal analysis. The raw meal composition, boron doping and firing temperature were investigated to obtain the optimal clinker composition. Hydration of the cement pastes was investigated by calorimetry and the strength development of mortars was tested and compared with that of a commercial OPC. The BCSA mortars produced with gypsum additions developed compressive strength comparable to that that OPC within 28 days. The main hydrated phase was ettringite, with minor amounts of kuzelite, straetlingite and gibbsite.

Comparative life cycle assessment of three 2030 scenarios of the Brazilian cement industry.

The cement industry is intensive in energy and feedstock use. It includes three main phases: raw materials and energy supply, transport, and manufacturing. The sector is known for its considerable environmental impacts. The increase in energy efficiency and the use of non-fossil fuels and raw materials are considered mature technologies in cement industries. We evaluate different environmental impacts of the production of 1 t of cement in four Brazilian scenarios. We compare one business-as-usual reference scenario (case 1) to three alternative 2030 carbon mitigation sectoral plan scenarios (cases 2, 3a, and 3b) that assume mature technologies. We analyze all 18 impact categories within the ReCiPe 2016 Life Cycle Assessment methodology. Results show reductions in 17 impact categories, ranging from no change in ozone depletion (case 2) to 39% reduction in fossil resource scarcity (case 3b). The effects on climate change decreased 14% in case 2 and 33% in cases 3a and 3b. The clinkerization process is the greatest contributor to atmospheric impacts, while raw material consumption to toxicity impacts. In contrast, there is no single main process contributing to resource depletion impacts. The changes in cement production lead to carbon emission reductions above expected levels and to reductions in other environmental impact categories modeled in ReCiPe 2016 method.

Investigation on industrial trial production of multi-phased clinker with crude granular steel slag

Steel slag multi-phased clinker implemented trial production in cement plant for the first time, which provided an effective low carbon strategy for comprehensive utilization of granular steel slag to produce high quality cement clinker. The results show that through optimizing process parameter of cement kiln system, superior qualified clinker was produced stably along with a river of granular steel slag fed in the smoke chamber directly. The grindability of steel slag has been dramatically improved after clinkerization. The content of C3S and C4AF in multi-phased clinker was higher than that of general clinker and thereby improving the mortar strength. Moreover, the multi-phased clinker showed significant improvement on abrasive resistance. The application of steel slag multi-phased sintering technology in a 2500 t/d production line could result in comprehensive utilization of 72368.4t granular steel slag, 67163.3t of CO2 emissions reduction and economic benefits of 15.21 million RMB every year. Multi-phased clinker process is a breakthrough on crude steel slag utilization from the bottlenecks of soundness, grindability and hydration activity of steel slag. The industrial trail of producing higher quality clinker from granular steel slag without grinding and sieving provides a new approach to utilize steel slag directly with extraordinary economic and environmental benefit.

Preparation and Performance of Ternesite-Ye’Elimite Clinker Produced from Steel Slag at Lower Temperature

Ternesite (4CaO·2SiO2·CaSO4)-Ye’elimite (3CaO·3Al2O3·CaSO4) (simplified as TY) cement clinker was successfully prepared from steel slag at 1200°C in this study. XRD, TG/DSC and SEM were used to analyze the mineral composition and hydration products of the TY clinker. The sintering process and hydration mechanism of the TY clinker were investigated. Results show that a large amount of ternesite and ye’elimite have been formed at 1200°C, while ternesite has not been decomposed. Clinker minerals include ternesite, ye’elimite, gypsum and a small amount of iron phase. Iron phase from steel slag can promote the formation of liquid phase with the presence of gypsum at 1200°C and thus lead to the coexistence of ternesite and ye’elimite. The compressive strength of TY cement cured at 28 d is 59.5 MPa, which is higher than that of P. II 42.5 cement. This research provides a sustainable and energy-effective way for the reutilization of steel slag, an otherwise valueless waste.

Use of asbestos cement tile waste (ACW) as mineralizer in the production of Portland cement with low CO2 emission and lower energy consumption

The reuse of solid waste by the cement industry promises a reduction in the amount of raw materials used for the production of clinker (clay and limestone), which may result in lower energy consumption and CO2 emissions. In this context, asbestos-cement tile waste (ACW) represents an alternative to the inputs used in the clinker process because of its similar chemical composition to that of limestone. However, there is a dearth of studies that address the effect of sulfur dioxide (SO3), present in the ACW as mineralizing agent during the clinker process. Thus, this study proposes to evaluate the incorporation of ACW in Portland cement production, with the aim of reducing CO2 emissions and energy consumption. Clinkers were produced without ACW (the reference clinker) and by incorporating different proportions of ACW to replace the mixture of limestone and clay (approximately 24%, 49%, 74%, and 86%) at different temperatures (1300 °C, 1350 °C, 1400 °C, and 1450 °C). The phases formed in the produced clinkers were identified using X-ray diffraction (XRD), followed by an analysis of their physical-mechanical properties. From the results obtained, it was observed that the clinkers produced at 1350 °C and containing 74% ACW represent the ideal proportion for the production of experimental cement, exhibiting compressive strength similar to that of pastes produced with reference cement (without adding ACW), in addition to reducing CO2 emissions by 11.85% and energy consumption by 10.13%.