Cement Clinker Production Research Articles

Municipal incinerated bottom ash use as a cement component in concrete

The characteristics of municipal incinerated bottom ash (MIBA) and its potential use as a cementitious component in concrete applications are examined through an analysis and evaluation of global experimental data. As raw feed in cement clinker production, MIBA can be incorporated at minor contents without compromising performance. To avoid damaging hydrogen gas expansive reactions arising due to the metallic aluminium in the ash, treatment of MIBA is required for use as cement components in cement, mortar and concrete. As such, thermal and chemical treatments, as well as tailored slow and wet grinding treatments, have been effective in improving performance. The hydrogen gas expansion associated with MIBA can beneficially contribute towards the lightweight properties required for aerated concrete, with the ash serving as an alternative to aerating agents and also contributing to strength development. Initial work on controlled low-strength materials has highlighted MIBA as a potential cement replacement material that can meet the low-strength requirements.

Sulfates in Completely Recyclable Concrete and the effect of CaSO4 on the clinker mineralogy

To increase the recycling potential of concrete, Completely Recyclable Concrete (CRC) has been developed to be used as a raw material for cement clinker production. Sulfates may penetrate CRC structures in time and their presence could affect the clinkering process of the eventually obtained CRC rubble. Therefore, the effect of CaSO4 additions on the final CRC clinker mineralogy has been investigated using XRD/Rietveld and SEM/EDX. An increasing sulfate content was found to stimulate the formation of sulfates that incorporate CaO, i.e. calcium langbeinite and anhydrite. Moreover, belite tends to be stabilized at the expense of alite with more SO3 present.

THE DEVELOPMENT OF THE REFRACTORY MATERIALS FOR THE ROTARY CEMENT KILN'S SINTERING ZONE

The development of the refractory materials for the hightemperature zone of the rotary kilns used in the cement industry which is the second-largest refractory materials consumer was represented in the article. The history of the refractory materials using in this high-temperature zone of rotary kilns was traced from the alumina-silicate materials down to the purposely designed periclase-based materials which are used at the present time. The advantages and drawbacks of these materials application are regarded. The basic facts are given on the cement clinker production in order to take into account the possible chemical reactions between the raw batch mixture inside the kiln and the refractory materials components. Ill. 10. Ref. 56. Tab. 1.

Effects of limestone petrography and calcite microstructure on OPC clinker raw meals burnability

Limestone represents the main raw material for ordinary Portland cement clinker production. In this study eight natural limestones from different geological environments were chosen to prepare raw meals for clinker manufacturing, aiming to define a parameter controlling the burnability. First, limestones were characterized by X-Ray Fluorescence, X-Ray Powder Diffraction and Optical Microscopy to assess their suitability for clinker production and their petrographic features. The average domains size and the microstrain of calcite were also determined by X-Ray Powder Diffraction line profile analysis. Then, each limestone was admixed with clay minerals to achieve the adequate chemical composition for clinker production. Raw meals were thermally threated at seven different temperatures, from 1000 to 1450 °C, to evaluate their behaviour on heating by ex situ X-Ray Powder Diffraction and to observe the final clinker morphology by Scanning Electron Microscopy. Results indicate the calcite microstrain is a reliable parameter to predict the burnability of the raw meals, in terms of calcium silicates growth and lime consumption. In particular, mixtures prepared starting from high-strained calcite exhibit a better burnability. Later, when the melt appears this correlation vanishes; however differences in the early burnability still reflect on the final clinker composition and texture.

Numerical Simulation of an Improved Structure for High-Resistance Grate Plates

Abstract In a typical cement plant, the cement clinker production consumes 80% of the total energy used in cement production. The grate plate is the main sector of the grate cooler, and its structure can be modified to receive electric power while cooling the clinker. In this paper, Ansys Fluent was used to simulate the flow field of an existing high-resistance grate plate. The structure of the existing high-resistance grate plate was improved based on the velocity and pressure fields. Results showed an improvement in the performance of the modified high-resistance grate plate–greater velocity and lower pressure drop were observed. When the pressure drop decreased by 51.58%, 2.84% of the total energy consumption could be saved. These results, to some extent, guided the rational design of high-resistance grate plates, and played an indirect role in energy conservation as well.

Production of belite calcium sulfoaluminate cement using sulfur as a fuel and as a source of clinker sulfur trioxide: pilot kiln trial

A pilot-scale trial was undertaken in a 7·4 m kiln to demonstrate the production of belite calcium sulfoaluminate cement clinker using sulfur as a raw feed. The sulfur was introduced in its elemental form as fuel to the burner, thus partially offsetting fuel costs while providing sulfur trioxide which is incorporated in the clinker. The study demonstrates that sulfur trioxide is readily sequestered into cement clinker in a standard rotary kiln; however, some scrubbing of the exit gas may still be required. As the products of scrubbing (anhydrite or gypsum) are usually required to optimise the cement formulation, the recovered sulfur product can find an immediate use in the final cement product. This trial demonstrates the successful production of targeted belite calcium sulfoaluminate clinkers at scale using sulfur as both a fuel and sulfur trioxide source.

Wide-scale utilization of MSWI fly ashes in cement production and its impact on average heavy metal contents in cements: The case of Austria

A number of studies present the utilization of fly ashes from municipal solid waste incineration (MSWI) in cement production as a recycling alternative to landfilling. While there is a lot of research on the impact of MSWI fly ashes utilization in cement production on the quality of concrete or the leaching of heavy metals, only a few studies have determined the resulting heavy metal content in cements caused by this MSWI fly ashes utilization. Making use of the case of Austria, this study (1) determines the total content of selected heavy metals in cements currently produced in the country, (2) designs a scenario and calculates the resulting heavy metal contents in cements assuming that all MSWI fly ashes from Austrian grate incinerators were used as secondary raw materials for Portland cement clinker production and (3) evaluates the legal recyclability of demolished concretes produced from MSWI fly ash amended cements based on their total heavy metal contents.To do so, data from literature and statistics are combined in a material flow analysis model to calculate the average total contents of heavy metals in cements and in the resulting concretes according to the above scenario. The resulting heavy metal contents are then compared (i) to their respective limit values for cements as defined in a new technical guideline in Austria (BMLFUW, 2016), and (ii) to their respective limit values for recycling materials from demolished concrete.Results show that MSWI fly ashes utilization increases the raw material input in cement production by only +0.9%, but the total contents of Cd by +310%, and Hg, Pb, and Zn by +70% to +170%. However these and other heavy metal contents are still below their respective limit values for Austrian cements. The same legal conformity counts for recycling material derived from concretes produced from the MSWI fly ash cements. However, if the MSWI fly ash ratio in all raw materials used for cement production were increased from 0.9% to 22%, which is suggested by some studies, the limit values for cements as defined by the BMLFUW (2016) will be exceeded. Furthermore, the concrete produced from this cement will not be recyclable anymore due to its high total heavy metal contents. This and the comparatively high contribution of MSWI fly ashes to total heavy metal contents in cements indicate their relatively low resource potential if compared to other secondary raw materials in the cement industry.

Silico-aluminous bottom ash valorisation in cement clinker production: Synthesis, characterization and hydration properties

The utilization of Silico-Aluminous Bottom Ash (SABA), derived from bituminous coal combustion in power plants, was investigated as a raw material in the kiln feed for the production of ordinary Portland cement clinker. Three different raw meals were studied, containing natural raw materials with 0, 3 and 6wt% of SABA. The raw mixes reactivity was assessed in terms of unreacted lime content, following sintering at 1200, 1350, 1400 and 1450°C. Clinkers produced at 1450°C, were characterized through means of chemical analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterized clinkers were used to produce cement specimens by co-grinding with suitable amount of gypsum. Accordingly, cement quality was evaluated by determining setting times, standard consistency, expansibility and compressive strength at 2, 7 and 28days. XRD and TG/DTG analysis were used for the hydration study evolution after 28days of curing. SABA presents a promising alternative in waste valorisation practice, as it can readily be used in the raw kiln feed as a partial replacement of ordinary raw materials.

Eco innovation strategies for promoting cleaner cement manufacturing

Carbon dioxide (CO2) emissions in cement plants are generated by the decarbonation of raw materials and fuel combustion in the cement kiln during the cement clinker production process and account for 8% of global emissions. This paper presents a mixed integer linear programming (MILP) by considering various mitigation measures, such as co-processing of fuels, kiln improvements and carbon capture and storage (CCS) yields, that can have substantial benefits. The benefits include cleaner cement production with minimum production costs, while satisfying the quality standard, carbon reduction target, and fuels substitution rate. The developed model is applied to a case study in order to demonstrate the applicability of the model. For the base case, the optimal cost for clinker production is USD 90.21/t clinker while CO2 emissions generated from both calcination of raw materials and fuels combustion is 531.68 kg CO2/t clinker and 325.00 kg CO2/t clinker. It was found that the highest possible CO2 emissions reduction that can be achieved by a combination of co-processing, kiln improvements and CCS technology is 79%, with an increment cost of USD 136.46/t clinker.

Modeling the dynamic mechanism between cement CO2 emissions and clinker quality to realize low-carbon cement

To devise low-carbon cement clinker product, in-depth knowledge about the variation mechanism of cement clinker CO2 emissions is the prerequisite. The determinants of cement clinker CO2 emissions in Chinese cement industry have been inquired by several researches recently. However, the impacts and abatement effect of clinker quality on cement clinker CO2 emissions have not been identified yet. In technological sense, there lacks an integrated quantitative model that can elucidate the dynamic mechanism between cement clinker CO2 emissions and clinker quality. To fill this gap, this paper devises a CO2 emission accounting framework integrated with optimization model to explore the dynamic mechanism between cement clinker CO2 emissions and clinker quality. Based on survey data of 2 typical cement clinker production lines in China, the accounting framework is validated with measured data. Through numerical simulation within this framework, a set of sensitivity analysis is conducted. The results indicate that if the target KH (lime saturation ratio) of both production lines climb from −5% to +5%, the process CO2 emission factor will give rise to an increase of about 16.4 and 14.8kgCO2/t clinker, respectively. With the same variation, the fuel CO2 emission factors of two production lines will gain 17.2 and 13.7kgCO2/t clinker, respectively. Obviously, controlled decrease of clinker quality can reduce CO2 emission of clinker manufacturing. The results of sensitivity analysis are robust and highlight the remarkable role of clinker quality in both process and fuel emissions. Besides, the integrated framework can provide in-depth investigation into the dynamic mechanism between CO2 emissions and the other determinants. Using this framework, cement plants or industry can develop optimal clinker quality standards on a quantitative basis to achieve low-carbon clinker.

국내 비의도적 주요 배출원의 지역별 수은 대기 배출량 산정 및 미래 활동도 변화와 최적가용기술 적용 시 배출량 추이

Abstract This study discusses the present status of mercury emission and distribution from major anthropogenic sources in Korea and the future trend of mercury emission by activity changes and application of BATs. Atmospheric mercury emission from major anthropogenic sources based on Annex D of Minamata convention was estimated to around 4.89 tonne in 2012. Emission ratios of cement clinker production, coal-fired power plant, waste incineration and non-ferrous metal smelting were 68.68%, 24.75%, 6.29% and 0.28%, respectively. High mercury emission regions were characterized by the presence of cement clinker production facilities and coal-fired power plants. Prediction of future activities was carried out by linear regression of the previous year data. The (total) mercury emission was estimated to decrease up to 48% Under the scenario of BATs to be applied and the change of future activities. Emissions from coal-fired powerplants and cement clinkers were expected to decrease significantly.

Kinetic Monte Carlo Approach To Study Carbonate Dissolution

Reactive properties of carbonate minerals and rocks attract a significant attention with regard to modern environmental and industrial problems, including geologic carbon sequestration, toxic waste utilization, cement clinker production, and the fate of carbonate shell-bearing organisms in acidifying oceans. Despite the ultimate importance of the problem, the number of studies connecting atomistic-scale models to experimental observations is limited. In this work we employ the Kinetic Monte Carlo (KMC) approach to model carbonate dissolution at the nanometer–micron scale range and to access quantitative relationships between the variety of surface reactive sites and experimentally observed spatiotemporal rate variance. The presented KMC model adequately reproduces experimentally observed dissolution patterns and rates. We examine mechanistic and quantitative relationships between site reactivity, atomic step velocity, etch pit evolution dynamics, and macroscopic dissolution rates. The analysis of reactive...

Use of waste derived fuels in cement industry: a review

Purpose – Cement production has advanced greatly in the last few decades. The traditional fuels used in traditional kilns include coal, oil, petroleum coke, and natural gas. Energy costs and environmental concerns have encouraged cement companies worldwide to evaluate to what extent conventional fuels can be replaced by waste materials, such as waste oils, mixtures of non-recycled plastics and paper, used tires, biomass wastes, and even wastewater sludge. The paper aims to discuss these issues. Design/methodology/approach – The work is based on literature review. Findings – The clinker firing process is well suited for various alternative fuels (AF); the goal is to optimize process control and alternative fuel consumption while maintaining clinker product quality. The potential is enormous since the global cement industry produces about 3.5 billion tons that consume nearly 350 million tons of coal-equivalent fossil and AF. This study has shown that several cement plants have replaced part of the fossil fuel used by AF, such waste recovered fuels. Many years of industrial experience have shown that the use of wastes as AF by cement plants is both ecologically and economically justified. Originality/value – The substitution of fossil fuels by AF in the production of cement clinker is of great importance both for cement producers and for society because it conserves fossil fuel reserves and, in the case of biogenic wastes, reduces greenhouse gas emissions. In addition, the use of AF can help to reduce the costs of cement production.

Mercury transformation and speciation in flue gases from anthropogenic emission sources: a critical review

Abstract. Mercury transformation mechanisms and speciation profiles are reviewed for mercury formed in and released from flue gases of coal-fired boilers, non-ferrous metal smelters, cement plants, iron and steel plants, waste incinerators, biomass burning and so on. Mercury in coal, ores, and other raw materials is released to flue gases in the form of Hg0 during combustion or smelting in boilers, kilns or furnaces. Decreasing temperature from over 800 °C to below 300 °C in flue gases leaving boilers, kilns or furnaces promotes homogeneous and heterogeneous oxidation of Hg0 to gaseous divalent mercury (Hg2+), with a portion of Hg2+ adsorbed onto fly ash to form particulate-bound mercury (Hgp). Halogen is the primary oxidizer for Hg0 in flue gases, and active components (e.g., TiO2, Fe2O3, etc.) on fly ash promote heterogeneous oxidation and adsorption processes. In addition to mercury removal, mercury transformation also occurs when passing through air pollution control devices (APCDs), affecting the mercury speciation in flue gases. In coal-fired power plants, selective catalytic reduction (SCR) system promotes mercury oxidation by 34–85 %, electrostatic precipitator (ESP) and fabric filter (FF) remove over 99 % of Hgp, and wet flue gas desulfurization system (WFGD) captures 60–95 % of Hg2+. In non-ferrous metal smelters, most Hg0 is converted to Hg2+ and removed in acid plants (APs). For cement clinker production, mercury cycling and operational conditions promote heterogeneous mercury oxidation and adsorption. The mercury speciation profiles in flue gases emitted to the atmosphere are determined by transformation mechanisms and mercury removal efficiencies by various APCDs. For all the sectors reviewed in this study, Hgp accounts for less than 5 % in flue gases. In China, mercury emission has a higher Hg0 fraction (66–82 % of total mercury) in flue gases from coal combustion, in contrast to a greater Hg2+ fraction (29–90 %) from non-ferrous metal smelting, cement and iron and/or steel production. The higher Hg2+ fractions shown here than previous estimates may imply stronger local environmental impacts than previously thought, caused by mercury emissions in East Asia. Future research should focus on determining mercury speciation in flue gases from iron and steel plants, waste incineration and biomass burning, and on elucidating the mechanisms of mercury oxidation and adsorption in flue gases.

Characterization of kiln feed limestone by dynamic heating rate thermogravimetry

Quicklime is a product rich in calcium oxide produced in industrial kilns. The process involves thermal decomposition of minerals with high content of calcium carbonate. The kiln feed properties vary with the geological formation from where the mineral is quarried or mined. Characterization of feed properties is necessary to achieve an optimized kiln production. In this work the decomposition of four different types of calcite ore was investigated by comparing conventional constant heating rate and dynamic heating rate thermogravimetric methods.The conclusion of this work is that the conventional method always “overshoots” the calcination temperature when continuously heating during calcination compared to the dynamic rate method that resembles the kiln by holding temperatures constant during the calcination event. This justifies the used of the dynamic rate method. By a correct experimental parameter setup the dynamic rate method can be adapted for individual kilns and feed fractions, giving new additional value to the kiln operator and increasing the high value use of limestone deposits. This new method to characterize calcination properties of kiln feed materials can be utilized in normal kiln operations and when developing new mixes of different quality limestone. The results show differences when comparing the methods and different materials even though CaCO3 is present only as calcite. In addition, the dynamic rate method is faster than the conventional method. Besides quicklime production the method can also be applied in other industries calcining limestone, such as cement clinker production.

Utilization of Iron Ore Tailings as Raw Material for Portland Cement Clinker Production

The cement industry has for some time been seeking alternative raw material for the Portland cement clinker production. The aim of this research was to investigate the possibility of utilizing iron ore tailings (IOT) to replace clay as alumina-silicate raw material for the production of Portland cement clinker. For this purpose, two kinds of clinkers were prepared: one was prepared by IOT; the other was prepared by clay as a reference. The reactivity and burnability of raw meal, mineralogical composition and physical properties of clinker, and hydration characteristic of cement were studied by burnability analysis, differential thermal analysis, X-ray diffraction, and hydration analysis. The results showed that the raw meal containing IOT had higher reactivity and burnability than the raw meal containing clay, and the use of IOT did not affect the formation of characteristic mineralogical phases of Portland cement clinker. Furthermore, the physical and mechanical performance of two cement clinkers were similar. In addition, the use of IOT was found to improve the grindability of clinker and lower the hydration heat of Portland cement. These findings suggest that IOT can replace the clay as alumina-silicate raw material for the preparation of Portland cement clinker.

Development of technology of portland cement using gas condensate sludge recycling waste

The paper deals with the topical issue of increasing the energy efficiency of manufacturing construction materials, such as Portland cement, applying organic-mineral additives. Using gas industry waste - gas sludge as the organic-mineral additive is proposed. Gas sludge due to its chemical composition accelerates the rate of chemical reactions during firing the raw mix of Portland cement clinker, thereby saving energy. Energy saving is associated with a decrease in temperature of the relevant physicochemical reactions during the Portland cement clinker firing. The paper contains the analysis of theoretical and practical aspects of the problem, proposes solutions to improve the energy efficiency of Portland cement clinker production by applying the organic-mineral additive, in particular gas sludge, which lowers the temperature of chemical reactions, and also considers the features of chemical reactions in the process of Portland cement clinker firing using the gas sludge waste in the raw mix.

Influence of magnesia in the infiltration of magnesia-spinel refractory bricks by different clinkers

In cement production, which involves the production of cement clinker in rotary kilns, the main refractories used are magnesia-spinel bricks. These bricks may suffer infiltration by the clinker liquid phase, resulting in the corrosion of the spinel and the formation of low refractoriness mineralogical phases, such as the Q phase (C 20 A 13 M 3 S 3 ), which compromises refractory performance. Thus, the aim of this work is to correlate the infiltration resistance of magnesia-spinel bricks made from different grades of magnesia by clinker collected in three different cement plants (A, B and C). The purity of magnesia, besides its physical properties, strongly influences the proper ties and the infiltration resistance of magnesia-spinel bricks; as such the use of high grade magnesia is essential for producing high performance refractories.

Effect of Selected Alternative Fuels and Raw Materials on the Cement Clinker Quality

Abstract The article deals with the study of the effects of alternative fuels and raw materials on the cement clinker quality. The clinker quality was expressed by the content of two principal minerals alite C3S and belite C2S. The additions of alternative fuels ashes and raw materials, in principle, always increased the belite content and conversely reduced the amount of alite. The alternative fuels with high ash content were used such as the meat-bone meal, sewage sludge from sewage treatment plants and paper sludge and the used alternative raw materials were metallurgical slags - granulated blastfurnace slag, air cooled blastfurnace slag and demetallized steel slag, fluidized bed combustion fly ash and waste glass. Meat-bone meal, sewage sludge from sewage treatment plants and paper sludge were evaluated as moderately suitable alternative fuels which can be added in the amounts of 2.8 wt. % addition of meat-bone meals ash, 3.64 wt. % addition of sewage sludge ash and 3.8 wt. % addition of paper sludge ash to the cement raw mixture. Demetallised steel slag is suitable for production of special sulphate resistant cement clinker for CEM I –SR cement with addition up to 5 wt. %. Granulated blastfurnace slag is a suitable alternative raw material with addition 4 wt. %. Air cooled blastfurnace slag is a suitable alternative raw material with addition 4.2 wt. %. Waste glass is not very appropriate alternative raw material with addition only 1.16 wt. %. Fluidized bed combustion fly ash appears not to be equally appropriate alternative raw material for cement clinker burning with less potential utilization in the cement industry and with addition 3.41 wt. %, which forms undesired anhydrite CaSO4 in the cement clinker.

GLOBAL WARMING AND CONSTRUCTION ASPECTS

The manufacture of cements with several main constituents is of particular importance with regard to reducing climatically relevant CO2 emissions in the cement industry. This ecological aspect is not the only argument in favor of Portland composite cements. They are also viable alternatives to Portland cement from the technical point of view. Substitution of ordinary Portland cement (CEM I) by Portland composite cements (CEM II) and (CEM III), which clearly possess different chemical and mineralogical compositions, results in changes of their reaction behavior with additives like superplasticizers. A common admixture to CEM I in that sense is limestone (industrial CaCO3). Its interaction with polycarboxylates is ignored and its inertness is taken for granted. This study provides a systematic approach in order to better understand the interaction of these polymeric superplasticizers with CaCO3 by adsorption and zeta potential measurements. The results give some fundamental understanding in how far the cement industry can reduce the production of cement clinker by replacing it with limestone as admixture and consequently the CO2-emission is reduced, which is of high political and environmental interest.