Clinker Dust Research Articles

DESIGN OF RICE HUSK ROTARY DRYER USING WASTE HEAT ELECTROSTATIC PRECIPITATOR OF THE CEMENT INDUSTRY

ESP or electrostatic precipitator is a device used to capture particulate matter, such as dust, in exhaust gases using electrostatic principles. In the cement industry, ESP is commonly placed after the clinker cooler to clean the exhaust air from the cooling process, ensuring it is free from clinker dust. The clinker cooler is a device that cools down the clinker using air, reducing its temperature from an initial temperature of around 1450°C to approximately 100°C - 120°C. The exhaust air from the clinker cooler is then passed through the ESP at temperatures ranging from around 237°C to 311°C. Based on the temperature data, the exhaust air from the ESP has the potential for heat reuse for other processes, including as a heat source for drying rice husk, which is a common alternative fuel used in the cement industry and typically has a moisture content of around 25%-37%. The results of this design indicate that the exhaust heat from the ESP, with an input temperature of 275°C, is capable of drying rice straw pellets from a moisture content of 25% to 14.73% using a designed rotary dryer with a capacity of 21.6 t/h, a length of 41.58 m, and a diameter of 2.92 m. It is constructed using ASTM 283 C material with a thickness of 8.76 mm and is insulated with a 15.6 mm thick layer of aluminum foil.

Cement production efficiency improving

The paper considers the issues of increasing the efficiency and environmental safety of cement production by using clinker dust in slurry preparation and replacing a certain part of clinker with mineral additives having pozzolanic activity. On the basis of research work carried out at the production site of the Baherden cement plant (Turkmenistan), the suitability of a Venturi scrubber to capture the dust generated in wet clinker kilns of cement plants has been established. The technological scheme for the use of the sludge generated in the scrubber in the preparation of clinker was developed. Based on the results of analyses of the main indicators of cement prepared with the addition of sludge the possibility of using the collected dust in the production of cement has been established. The optimal solution for three interrelated problems, such as increasing the efficiency of cement production, reducing the amount of harmful gases emitted into the atmosphere, and rational use of natural resources, is to reduce the specific consumption of clinker by compensating a certain part of it with mineral additives with pozzolanic activity.

Cement Bypass Dust as an Ecological Binder Substitute in Autoclaved Silica-Lime Products.

The cement industry is one of the most developed industries in the world. However, it consumes excessive amounts of natural resources and can negatively impact the environment through its by-products: carbon dioxide (CO2), cement clinker dust (CKD) and cement bypass dust (CBPD). The amount of dust generated in the cement clinker production process depends largely on the technology used. It typically ranges from 0 to 25% by weight of the clinker, and a single cement plant is capable of producing 1000 tons of CBPD per day. Despite practical applications in many areas, such as soil stabilisation, concrete mix production, chemical processing or ceramic and brick production, the dust is still stored in heaps. This poses an environmental challenge, so new ways of managing it are being sought. Due to the significant content of free lime (>30%) in CBPD, this paper uses cement bypass dust as a binder replacement in autoclaved silica−lime products. Indeed, the basic composition of silicate bricks includes 92% sand, 8% lime and water. The investigation shows that it is possible to completely replace the binder with CBPD dust in the autoclaved products. The obtained results showed that all properties of produced bricks were satisfactory. The study concluded that many benefits could be achieved by using cement bypass dust in the production of bricks, including economic bricks for building, reducing the dependency on natural resources, reducing pollution and reducing negative impacts on the environment.

Recycling of Cement Industry Waste for Alkali-Activated Materials Production.

The cement industry is recognized as an environmental nuisance, and so there is a need to not only minimizes the consumption of cement, but also to completely recycle the waste of the cement industry. This paper’s originality lies in the fact that, for the first time, a comprehensive study of the structure formation of alkali-activated materials (AAM) based on aspiration dust and clinker dust has been carried out. The tasks for achieving this goal were to characterize cement production waste as a new binder and comprehensively research the microstructure, fresh, physical, and mechanical properties of alkali-activated material based on a cement-free binder. Grains of cement production waste are represented by coarse volumetric particles with pronounced cleavage, and a clear presence of minerals is observed. The mineral composition of cement production waste is characterized by calcium silicates, which guarantee good binding properties. The results of the X-ray diffraction analysis of the samples (based on the alkaline-activated cement-free binder using clinker dust and aspiration dust) confirmed the presence of calcite, quartz, feldspar close to albite, micas, and zeolites. The obtained products of the chemical interaction of the binder components confirm the effectiveness of the newly developed AAM. As a result of comparing several binders, it was found that the binder based on aspiration dust with Na2SiO3 and Na2SiF6 was the most effective, since, for specimens based on it, a density of 1.8 g/cm3, maximum compressive strength of 50.7 MPa, flexural strength of 5.6 MPa, minimum setting time (starting at 24 min and ending at 36 min), and water absorption of 12.8 wt. % were obtained. The research results will be of interest to specialists in the construction industry since the proposed recipes for eco-friendly, alkali-activated materials are an alternative to expensive and energy-intensive Portland cement, and they provide for the creation of strong and durable concrete and reinforced concrete composites.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ДОБАВКИ АКТИВНОГО КРЕМНЕЗЕМА НА СВОЙСТВА ВЯЖУЩИХ ЩЕЛОЧНОЙ АКТИВАЦИИ

The world experience of implementation and the uniqueness of building alkaline composites prove the prospects and relevance of the development of clinker-free technology. The development of formulations of alkaline activation binders based on fine powders of aluminosilicate nature will allow obtaining new effective and high-quality products. The paper investigates the effect of active microsilica on the kinetics of strength gain, changes in density and pore space of cement stone, formulation and technological factors and hardening conditions. The chemical transformations of active silica under alkaline conditions, leading to changes in the pH value, have been substantiated. By electron microscopy, the foundations of the formation of the structure of a cement stone on a binding bond "aspiration dust (60%) - clinker dust (40%) - microsilica - Na2SiO3" amorphous substance, calcium sulfoaluminates, calcium hydroaluminates are developed. According to authors, the research results are important for the construction industry, since the proposed formulations of clinker-free cements can replace expensive and energy-intensive Portland cement, making it possible to create strong and durable concrete and reinforced concrete structures

Thermal Behavior of Ceramic Bodies Based on Estonian Clay from the Arumetsa Deposit with Oil Shale Ash and Clinker Dust Additives

The thermal behavior of green clay samples from the Arumetsa and Füzérradvány deposits (Hungary) and the influence of two new types of Estonian oil shale (OS) ashes and cement bypass dust (clinker dust) additives on it were the objectives of this study. Thermal and thermo-dilatometric analysis methods were applied using a Setaram Setsys 1750 thermoanalyzer coupled with a Pfeiffer Omnistar spectrometer and a Setaram Setsys 1750 CS Evolution dilatometer. The kinetic parameters were calculated based on the differential isoconversional method of Friedman. The results of the thermal analysis of clays and blends indicated the emission of physically bound water at 200–250 °C. At temperatures from 200–250 °C to 550–600 °C the release of water is caused by oxidation of organic matter and dehydroxylation of different clay minerals like illite, illite-smectite, mica and kaolin. From blends, in addition, also from the decomposition of portlandite. The emission of CO2 at these temperatures was a result of the oxidation of organic matter contained in the clays. In the temperature range from 550–600 °C to 800–900 °C, the mass loss was caused by ongoing dehydroxylation processes in clay minerals but was mainly due to the decomposition of the carbonates contained in the OS ashes and clinker dust. These processes were accompanied by contraction and expansion of the ceramic bodies with the corresponding changes in the SSA and porosity values of the samples. Therefore, the decomposition of the clays took place in one step which blends in two steps. At first, dehydroxylation of the clay minerals occurs, followed by decomposition of the carbonates. The value of the conversion-dependent activation energy E along the reaction progress α varied for the Arumetsa and illitic clay between 75–182 and 9–206 kJ mol−1, respectively. For the blends based on Arumetsa and illitic clay, the activation energy of the first step varied between 14–193 and 5–205 kJ mol−1, and for the second step, it was between 15–390 and 135–235 kJ mol−1, respectively, indicating the complex mechanism of the processes.

Prospects for the use of waste cement industry in the production of clinker-free concrete

The production of Portland cement clinker is accompanied by huge dust release and the accumulation of huge amounts of aspiration and clinker dust in the dust collection system. The rational use of this high-quality corrected fine-dispersed resource is an urgent task not only in technological, but also in ecological terms. Aspiration dust cannot be returned to the technological cycle. It is taken out of the cement plant, disrupting the ecological situation of valuable agricultural land and mountainous landscape. Taking into account the fact that it can be used in its natural form, without an additional mechanical intervention, this will expand the material and raw material base for the production of alkaline cements. This paper presents the results of studies of the particle size distribution of particles in samples of dispersed material and the determination of the shape and size of cement dust particles. The reactivity of the investigated powders of technogenic nature has been proved. These characteristics of cement dust electrostatic indicate feasibility of these powders dispersed as component binders ligaments alkaline activation.

NORM-related industrial activities in Estonia – Establishing national NORM inventory

There is incomplete information available concerning NORM-related (naturally occurring radioactive material) industries in Estonia. In order to fill the gap in this knowledge, a nationwide study was carried out between 2015 and 2017 to determine and radiologically characterize potential NORM-related industries. The study included compiling available literature and studies as well as on-site measurements (external dose rate and radon) and samplings in multiple industries, which had been determined to be potential NORM creators. The results from this study concluded that there are 3 industries in Estonia where the activity concentrations of naturally occurring radionuclides can reach an increased level which may require further regulatory control. Radionuclide exemption values were clearly exceeded in the filter materials of drinking water treatment plants that use water from Cambrian-Vendian aquifer. 226Ra and 228Ra values in filter materials reached over 40 kBq kg−1. Additionally, the gross radionuclide activity concentrations of 238U and 232Th in waste from a rare metal production industry reached up to 191 kBq kg−1. Clinker dust from the cement industry showed elevated concentrations of 210Pb, rising to over 2 kBq kg−1 in fine clinker dust. The creation of a national NORM inventory can be the basis for establishing a national NORM strategy for the management of NORM residues. This work provides a thorough overview of the radiological parameters of the potential NORM-related industries, describes the radionuclides that have elevated concentrations, provides estimations on their yearly creation amounts and produces input for determining possible NORM management options.

РАЗРАБОТКА СПЕЦИАЛЬНЫХ РЕЦЕПТУР ВЯЖУЩИХ КОМПОЗИЦИЙ С УЛУЧШЕННЫМИ СВОЙСТВАМИ

the ecological safety of earthly civilization suffers from the accumulation of huge volumes of industrial waste, the natural resource potential is decreasing, therefore, special attention is paid to the development of less costly and low energy-intensive technologies for obtaining new building materials, the implementation of which does not require high-temperature and expensive technological processing, and will allow the use of secondary and substandard raw materials.
 The work presents the results of the development of special formulations of binder compositions of alkaline activation based on cement production wastes in the form of aspiration and clinker dust from electrostatic precipitators of rotary kilns and waste from the metallurgical industry - ferrosilicon additives in the form of active silica, which will allow obtaining new building materials with improved properties.
 The paper investigates the properties of an alkaline cement paste and cement stone, reveals issues related to the theoretical foundations of the formation of the structure and strength of an artificial stone based on an alkaline activator. The research results, in our opinion, are certainly of practical importance for the construction industry, as the proposed formulations of clinker-free cements can partially replace expensive and energy-intensive Portland cement, making it possible to create strong and durable concrete and reinforced concrete structures

A novel application of waste cement clinker dust in the extraction of potash from mica scraps

The prospect of using cement clinker dust (CKD) as an additive in recovering potash values from an Indian mica scrap sample, containing 7.64% potash, is explored. It is found that the clinker dust, mostly treated as solid waste in the cement industry, can act as the calcium source in the chloridizing roasting of mica. The experiments have been carried out as per the central composite design. Factors such as the dosage of mica, clinker dust, NaCl along with roasting parameters such as temperature and time have been optimized. At a roasting temperature of 950 °C, time of 40 min, and the dosages of clinker dust and NaCl to the tune of 70–75% of the mica weight, the process is found to recover 99% of the potash values. With lowered process conditions such as a temperature of 900 °C and time of 10 min, it is possible to recover 89% of the potash values with clinker dust and NaCl each at a dosage of 50% of the weight of mica. Characterization studies like X-ray diffraction and field-emission scanning electron microscopy coupled with energy dispersive spectroscopy have been carried out to identify the different phases of the feed and processed products, and thereby propose the reaction sequence.

Usage of dual-channel radiation thermometers in dusty environment

The article presents the simulation results of noncontact temperature measurements uncertainty (in the measurement range of 350…750 °C), which were performed using dual-channel radiation thermometers through a cloud of clinker dust in the cases of different dust concentrations. It is shown that the use of dual-channel spectral ratio radiation thermometers is more efficient compared to single-channel measuring instruments. According to the simulation study the best results in terms of the uncertainty level of dual-channel radiation thermometer were obtained by the using in its design the couple of a wide-band and a narrow-band measuring sensors. It is proven that in order to cover the entire temperature range of 350…750°C with an acceptable level of uncertainty, it is advisable to utilize the dual-channel radiation thermometer in the combined single-channel and dual-channel mode of operation.

Influence of waste products from electricity and cement industries on the thermal behaviour of Estonian clay from Kunda deposit

The influence of two different oil shale ashes formed, respectively, at pulverized firing and at circulated fluidized bed combustion of Estonian oil shale (OS) at electricity production, and clinker dust (CD) formed at cement production on the thermal behaviour of Estonian clay from Kunda deposit, and, for comparison, on the illitic clay from Fuzerradvany (Hungary) was studied. Composition of clay with 40% of previously fired at 1050 °C clay (grog) was used as a basement one. In the blends studied the fired clay was partly or totally replaced with OS ash or CD additives. Experiments were carried out under non-isothermal condition up to 1050 °C using a Setaram Setsys 1750 thermoanalyzer coupled with Pfeiffer Omnistar Spectrometer at the heating rates of 1.25, 2.5, 5 and 10 °C min−1 in an oxidizing atmosphere containing 79% of Ar and 21% of O2. The differential isoconversional method of Friedman was applied to calculate the kinetic parameters. Depending on the origin of the additive the thermal behaviour of blends following the two-step route differentiated remarkably from the same characteristics of clays. The value of activation energy along the reaction progress varied for illitic clay and its blends with OS ash and CD additives more than based on Kunda clay, but, contrary, the average activation energy values for blends based on Kunda clay are, as a rule, bigger than based on illitic clay.

NORM-related industrial activities in Estonia – Establishing national NORM inventory

Abstract There is incomplete information available concerning NORM-related (naturally occurring radioactive material) industries in Estonia. In order to fill the gap in this knowledge, a nationwide study was carried out between 2015 and 2017 to determine and radiologically characterize potential NORM-related industries. The study included compiling available literature and studies as well as on-site measurements (external dose rate and radon) and samplings in multiple industries, which had been determined to be potential NORM creators. The results from this study concluded that there are 3 industries in Estonia where the activity concentrations of naturally occurring radionuclides can reach an increased level which may require further regulatory control. Radionuclide exemption values were clearly exceeded in the filter materials of drinking water treatment plants that use water from Cambrian-Vendian aquifer. 226Ra and 228Ra values in filter materials reached over 40 kBq kg−1. Additionally, the gross radionuclide activity concentrations of 238U and 232Th in waste from a rare metal production industry reached up to 191 kBq kg−1. Clinker dust from the cement industry showed elevated concentrations of 210Pb, rising to over 2 kBq kg−1 in fine clinker dust. The creation of a national NORM inventory can be the basis for establishing a national NORM strategy for the management of NORM residues. This work provides a thorough overview of the radiological parameters of the potential NORM-related industries, describes the radionuclides that have elevated concentrations, provides estimations on their yearly creation amounts and produces input for determining possible NORM management options.

Properties of blastfurnace cements (CEM III/A, B, C) based on Portland cement clinker, blastfurnace slag and cement kiln dusts

This study has examined the effectiveness of characteristically different cement kiln dusts (CKDs) as a partial replacement for the ground granulated blastfurnace slag (GGBFS) in the development and production of three types of blastfurnace cements (CEM III/A, B, C) according to the standard EN 197-1.27 CEM III cement blends, 9 blends per type of cement, i.e., CEM III/A, CEM III/B and CEM III/C, were prepared in the laboratory mill from industrial starting materials (Portland cement clinker, gypsum, GGBFS, CKDs). The addition of gypsum as the setting regulator was fixed at 4 mass % in all blends studied. The content of both CKDs (cement clinker dust and cement filter dust) as slag replacements was 4 mass % in all CKD blends studied. The ordinary Portland cement (OPC) type CEM I 42.5N was used as the control cement. The results have shown that the chemical composition and chemical and physical properties of prepared CEM III/A, B, C cement blends meet the EN 197-1 requirements. Strength development in these cement blends is obviously related to the Portland cement clinker-to-GGBFS ratio. When compared to OPC, the blastfurnace cement developed lower compressive strength at early ages, but equal or higher at later ages in more cases, i.e., all 9 CEM III/A and 7 CEM III/B cement blends meet, while no CEM III/C cement blend meets the EN 197-1 requirements for standard compressive strength Class 42.5N. From the perspective of strength, the presence of the cement clinker dust is more effective than that of the cement filter dust due to their different chemical and mineralogical compositions.

Short-Term Influence of Clinker Dust and Wood Ash on Macronutrients and Growth in Norway Spruce (Picea abies) and Scots Pine (Pinus sylvestris) Seedlings

The effects of clinker dust and wood ash on Norway spruce and Scots pine seedlings were compared in buried pots. Clinker dust (0.5 kg m−2) and wood ash (0.5 kg m−2) were applied to the surface of a nutrient-poor mineral soil. In the second year, the increase in soil pH by the dust and ash were larger than in the first year. Both alkaline treatments caused a large increase in the needle potassium (K) concentration. An excess of soil K relative to magnesium (Mg) was observed by decreased Mg concentration in needles shortly after treatment. However, Mg concentration in needles stayed in the sufficiency range. Current results confirmed earlier findings that despite a positive effect on base cation nutrition, wood ash has a low potential for increasing the biomass of forest stands on mineral soils due to the N limitation in these soils.

Inhibition of Acid Mine Drainage from a Pyrite-rich Mining Waste Using Industrial By-products: Role of Neo-formed Phases

In the present study, the potential use of the industrial waste residues, such as coal fly ash and clinker dust, was evaluated in inhibiting acid mine drainage generation from pyrite-rich wastes using non-saturated column experiments. Two columns (B and C) were filled with a mixture of industrial residues over pyrite-quartz sand (PS), while one column (A) used as the control was solely filled with PS. Artificial irrigation was maintained in each column by pouring Milli-Q water (pH 6.5). The leachate chemistry and the precipitation of neo-formed phases in the columns were examined. Based on the pH and concentration of SO4 2− in the effluent collected over a period of time, it can be inferred that pyrite dissolution was dominant in column A. In columns B and C, the addition of industrial waste produced a near neutral to alkaline leachate. At this pH, Fe released from pyrite oxidation was immediately depleted by precipitating into Fe-oxyhydroxide phases that likely coated the pyrite grains (termed as microencapsulation) which inhibited oxidation. This was supported from the scanning electron microscope observation and the geochemical modeling results. In addition, the precipitation of other neo-formed phases such as calcium carbonate and gypsum, along with the pozzolanic reactions of industrial wastes, possibly increased the cementation of fly ash particles leading to the development of a compact material, which prevented further oxidation by restricting infiltration and oxygen contact to the pyrite surface. This occurred best in column B; thus, it produced better quality of leachates than column C, though at the end both columns showed a significantly decreased concentration of Fe (up to 99.9 %) and other metals such as Cu, Cr, Pb, Zn, and Mn (lower values than the WHO permissible limits of drinking water) compared to control.

Fresh and Hardened Properties of Self- Compacted Concrete at Different Curing Regimes(eng)

The aim of this study is to compare the properties of three self-compacted concrete (SCC) mixes, with normal concrete mix. For the SCC mixes, the cement was replaced partially with either limestone dust or clinker waste dust. Compressive strength, tensile splitting, and flexural strength tests were conducted at ages of 3, 7, 14, 28, and 56 days to trace the strength development. Modulus of elasticity tests were conducted at 28-days. The test results showed that mixes containing lime-stone dust have better fresh properties than the other SCC mix. The compressive strength test results showed that the mix containing clinker waste powder give higher compressive strength. and mix containing eight percent limestone give higher tensile splitting strength and flexural strength than the mix has ten percent of limestone give for all curing regimes. The results showed that the modulus of elasticity is relatively lower than that for normal concrete and the voids volume in normal concrete is greater than that of SCC. Keywords: Clinker dust, Compressive strength, Concrete, Fresh properties, Lime-stone

Pozzolanic-based materials for stabilization/solidification of contaminated sludge with hazardous heavy metal: case study

ABSTRACT In this study, the efficiency of metals immobilization in sludge using pozzolanic materials fly ash and cement clinker dust (CCD) was investigated. Also, estimation of the optimum binder to waste ratio was determined. Different leaching tests such as the standard European (EN) 12457-2 leaching tests; the toxicity characteristic leaching procedure; and the multiple extraction procedure test were used to evaluate the efficiency of metals stabilization in sludge matrix, and they showed that the availability of metals leaching (Cd, Cu, Cr, Pb, Ni, Zn) from the stabilized sludge were lower than the permissible limit set by National and International regulations for hazardous waste management. Examination of the solidified sample for its compressive strength after curing for 28 days yielded a value of 1.55 and 4.57 MPa for fly ash, and CCD which indicates that the treated sludge was well solidified and safe to be used in a wide variety of applications, for instance as a raw material for pavement blocks.

Short-term responses of soil chemistry, needle macronutrients and tree growth to clinker dust and fertiliser in a stand of Scots pine

Waste management of clinker dust by spreading it on forest soil was studied in a 25-year-old Scots pine stand on acidic sandy soil. Clinker dust (0.5 kg m⁻²), fertiliser (N, P, K, Mg, 0.05 kg m⁻²; N 190 kg ha⁻¹) and untreated soil were applied on 120-m² plots in four replicates. The fertiliser was included to confirm the nutrient limitation in the stand. Clinker dust increased the soil pH by 1.2 units relative to the pH of 4.6 in the untreated soil by the second year. Soil K and Mg concentrations were larger in the dust and fertiliser treatments. Nutrient diagnostics indicated that needles of untreated trees were deficient in N and K. Fertiliser treatment indicated that the growth of trees was limited by N, since the fertiliser tended to increase needle K, N, N/P, needle dry mass and diameters of stem and shoots. By an auxiliary dataset, no effects of the dust and fertiliser on possible excess of the micronutrient Mn were observed. Clinker dust increased needle K concentration, but due to the N limitation, there was no increase in the growth of stems, branches, shoots and needles. It was concluded that in plots of 120 m² application of clinker dust at a rate of 0.5 kg m⁻² was safe for the 21-year-old Scots pine stand in this trial on an acid nutrient-poor sandy soil during 4 years after the treatment.

Influence of cement clinker dust on carbohydrates in needles of Scots pine shortly after the application

Clinker dust could be used as an amendment of forest soils to improve the nutrition of trees. Soil pH, needle carbohydrates (glucose, fructose, sucrose, starch), and chlorophyll fluorescence (Genty parameter) were measured about two months after the application of 0.5 kg clinker dust m -2 and in a reference treatment with a slow release N, P, K, Mg fertilizer in a Scots pine plantation. The spatial variation of the soil pH values between the sampling locations and soil layers was not increased by the clinker dust treatment although small-scale heterogeneity in the distribution pattern of dust was observed. The photosynthetic parameters were measured by chlorophyll fluorescence and were not affected by treatments. Dust and fertilizer reduced significantly the concentration of hexoses (glucose + fructose) in 1-year-old needles.