Cement Raw Meal Research Articles

Feasibility of disposing waste glyphosate neutralization liquor with cement rotary kiln

The waste neutralization liquor generated during the glyphosate production using glycine-dimethylphosphit process is a severe pollution problem due to its high salinity and organic components. The cement rotary kiln was proposed as a zero discharge strategy of disposal. In this work, the waste liquor was calcinated and the mineralogical phases of residue were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The mineralogical phases and the strength of cement clinker were characterized to evaluate the influence to the products. The burnability of cement raw meal added with waste liquor and the calorific value of waste liquor were tested to evaluate the influence to the thermal state of the kiln system. The results showed that after the addition of this liquor, the differences of the main phases and the strength of cement clinker were negligible, the burnability of raw meal was improved; and the calorific value of this liquor was 6140J/g, which made it could be considered as an alternative fuel during the actual production.

Effects of Preparation of Cement Raw Meal with Carbide Slag on the Environment and Equipments

Based on the physical and chemical properties of carbide slag, the contents of heavy metals in effluent came from carbide slag drying process were studied, and then the composition of exhaust gas emitted from the carbide slag drying process and calcinations process of raw materials prepared with carbide slag was detected, in order to know whether there are harmful or corrosive gases released and the effect of the emissions on the environment and related equipments. The results indicate that the exhaust gases emitted from the calcination process of raw meal prepared with carbide slag is mainly composed of CO2 and water vapor, and is free from harmful gases. However, a lot of water in carbide slag during the pre-heat and decomposition process under high temperature would accelerate the corrosion of equipments. Simultaneously, a small number of heavy metal ions contained in the carbide slag can cause environmental pollution and sulfides would be adverse to the cement calcination process resulting in the crust blockage of kiln.

High temperature cement raw meal flowability

The flowability of cement raw meal is investigated at temperatures up to 850°C in a specially designed monoaxial shear tester. Consolidation stresses of 0.94, 1.87 and 2.79kPa are applied. The results show that the flowability is reduced as temperature is increased above 550°C, indicated by increasing unconfined yield strength and reduced flowability factors. Deviation and reproducibility are acceptable for all temperatures except for 850°C where belite formation and possibly calcination sinter the raw meal.

A Hybrid Carbon Capture System of Indirect Calcination and Amine Absorption for a Cement Plant

Here we present the process integration of the indirect calcination process existing in the literature [1] into a cement plant. The indirect calcination process is composed of a circulating fluidized bed combustor and a fluidized bed calciner where hot solid particles are circulated between those reactors for heat transfer. It allows separation of CO2 from limestone calcination in a concentrated form. The process integration proposed in this study minimizes the total thermal energy requirement by using excess energy from high temperature flue gases for cement raw meal preheating as in the conventional cement manufacturing process. It also suggests a new hybrid carbon capture system where an additional CO2 capture unit is combined with the indirect calcination process, since the standalone indirect calcination application can only provide a moderate level of CO2 avoidance. The amine process is added to increase CO2 avoidance rate further. Full process flowsheets have been developed and analyzed using the commercial software UniSim Design R400 from Honeywell. The hybrid system can achieve more than 90% carbon capture rate thanks to the supplementary amine process while the indirect calcination can capture only 56% without the amine process. With the support of a simple and transparent economic analysis, the capture cost involved in the hybrid system was estimated to be higher than that of the indirect calcination only but significantly lower than that of the standalone amine process on a basis of unit CO2 avoided. © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of GHGT.

Production Quality Control of Moderate Heat Portland Cement and Analysis of Application Effect in Roller Compacted Concrete

Moderate Heat Portland Cement is not only frequently-used cement for dam but also one of the largest amount of special cement as a main cementitious materials of concrete in hydraulic structure in China. Due to the high quality requirement and the complicated technology in the construction of dam, a series of measures are adopted to control the production quality of Moderate Heat Portland Cement used in the dam construction. In this paper, the measures of production quality control of the Moderate Heat Portland Cement are introduced, including controlling the raw materials such as the cement raw meal, fuel, clinker and gypsum, managing the discharge from the mill and the entrance test, which ensure that the various targets of physical and mechanical indexes are in accordance with the standard requirement. Moreover, the engineering quality of Roller Compacted Concrete (RCC) for the dam is effectively guaranteed through the lower pot temperature and the less hydration heat. The construction experience is available for the like-kind engineering interiorly.

CO2 Capture by Cement Raw Meal

The cement industry is one of the major sources of CO2 emissions and is likely to contribute to further increases in the near future. The carbonate looping process has the potential to capture CO2 emissions from the cement industry, in which raw meal for cement production could be used as the sorbent. Cyclic experiments were carried out in a TGA apparatus using industrial cement raw meal and synthetic raw meal as sorbents, with limestone as the reference. The results show that the CO2 capture capacities of the cement raw meal and the synthetic raw meal are comparable to those of pure limestone. The CO2 capture capacity of limestone in the raw meal is lower than for pure limestone. The difference in the CO2 capture capacity decreases with an increase in cycle number. The calcination conditions and composition are major factors that influence the CO2 capture capacity of limestone. At 850 °C in N2, the capacity of synthetic raw meal was similar to that of pure limestone, whereas at 950 °C in N2 and in a CO2-rich atmosphere there was a significant difference. The SEM and BET analyses indicate that sintering is the main reason for the lower capture capacity of the limestone in the raw meal. The main components of the raw meal used along with the limestone have different effects on the CO2 capture capacity of the limestone. Al2O3 has the most negative effect, followed by Fe2O3, whereas SiO2 showed no effect. These interactions can be observed as a correlation between the measured surface area and the CO2 capture capacity. The XRD results indicated an increase in crystallite size and the formation of new phases due to the reaction between the main components of the raw meal and the limestone, which also has an effect on the CO2 capture capacity. The formation of dicalcium silicate was also observed by XRD analysis in the calcined synthetic raw meal. The effect of calcination conditions and compositions on the CO2 capture capacity as a function of cycle number is described by a correlation equation. This equation is used to determine the decay constant (k) and residual CO2 capture capacity (Xr). This shows that raw meal could be used as a sorbent for the easy integration of the carbonate looping process into the cement pyro process for reducing CO2 emissions from the cement production process.

The Phase Transformation of Recycling Concrete in Recalcination

In this paper, the artificial aggregates were prepared by limestone and industrial wastes in accordance with the ratio of cement raw meal, to obtain the recycling concrete replacing natural aggregates. Cement clinker could be regenerated by these recycling concrete and the aim of recycling could be realized. After these concrete was cured for 90 days, then was crushed and grinded, the phase transformation of recycling concrete in recalcination would been studied by XRD and so on. The experimental results showed that the composition of the recycling concrete met the demand of clinker modulus and C2S, C3S, C4AF, C3A were well crystallized at 1400 °C. So these recycling concrete could be directly calcined. The calcium hydroxide dehydrated around the temperature of 500°C. The calcium silicate hydrate was dehydrated gradually between the temperature of 400°C and 1000°C. At the same time, C2S crystallized during the temperature range. C4AF and C3A stared to crystallize around the temperature of 1000°C. Due to the composition of these concrete was complex, the lowest eutectic temperature dropped. C3S started to crystallize around the temperature of 1250°C and the best crystallization was achieved at the temperature of 1400°C.

The Depth Analysis of Different Form Sulfur in the Cement Minerals by Three-Step Extraction Method

In order to investigate the different forms of sulfur in the cement, certain amount gypsum were blended into cement raw meal, which was pre-prepared by the cement plant. The above blends were firstly calcined to form cement clinker in a furnace at ~1450oC. Serious chemical solutions, such as, salicylic acid - methanol (SAM), potassium hydroxide - sucrose (KOSH) and acetic acid, were used to select the extractors from laboratory clinker. After the separation of silicate phase, iron aluminate phase, and intermediate phase of minerals, the trace amount minerals phase were enriched. Corresponding analytical methods, such as, XRD, XRF, SEM-EDS, were used to analyze the different sulfur type during the three-step extraction process. As a result, the trace sulfur minerals of cement was identified as three major forms of（KAl(SO4)2）,C4A3S, and（CaSO4）

Incorporation of Cadmium into Clinker during the Co-Processing of Waste with Cement Kiln

The incorporation of cadmium into clinker during the co-processing of waste with cement kiln was investigated. Cadmium contained reagent was added to the cement raw meal to produce clinkers after clinkerization process. XRD analysis and SEM-EDS analysis were employed to indentify the major mineral phase of clinker and the cadmium contained mineral phase. Leaching test, sequential extraction procedures were employed to evaluate the leaching potential of cadmium in clinker. The results show the stabilization rate of cadmium during the clinkerization process is low. The incorporation ratio of cadmium in C2S is 0.32%~1.14%, the incorporation ability of cadmium in C2S is higher than C3S. The major mineral phases of clinker with the incorporation of cadmium were CH, C3S and C2S. The average leaching concentration of cadmium of clinker was 1.4 μg/L, which was higher than the blank samples. BCR Sequential extraction procedures analysis of the clinkers show exchangeable, water and acid-soluble fraction and residual fraction were very small, while the reducible phase of cadmium was up to 95.13%.

Exploration on Feasibility of Preparing Cement Clinker with Artificial Aggregate Concrete

Combining with the utilization of waste, an new idea of using the waste to prepare high-strength artificial aggregates was put forward in this paper. The concrete was also prepared by using these aggregates. The demolished concrete could be recovered and used as cement raw meal to produce new cement clinker. In this study, the feasibility of making cement clinker with this kind of demolished concrete was studied. The concrete aggregates composed of steel slag, blast furnace slag, coal gangue and fly ash were prepared. The concrete was prepared using these aggregates with the water-cement ratio of 0.45, 0.50 and 0.55 respectively. The compressive strength of the concrete in 28 days is 52.8MPa, 46.4.2MPa and 42.6MPa, respectively, higher than that of ordinary concrete. In accordance with the ratio of cement raw meal, the cement clinker is produced by adding appropriate limestone, clay and other correction materials. After hydrated for 3 days, 7 days and 28 days, the cement paste compressive strength is 47.1 MPa, 59.8 MPa, 75.6 MPa, respectively, which reach the requirements of ordinary 42.5 Portland cement.

Analysis and Design Recommendations for the Collapse of a Concrete Silo

Accidents of the cement manufacturers’ reinforced concrete silo structures frequently occurred currently in China, because of quality problems, causing enormous losses. The collapse status of a cement raw meal silo is investigated. Combined with the test results of the location and spacing of silo wall’s reinforcing bars, concrete strength, cracks and defects, the reasons for collapse of silo wall are analyzed and design recommendations for concrete silo structures are made. This can give reference to reinforced concrete silo structure design and construction in the future.

Experimental Study on the Dynamic Process of NO Reduction in a Precalciner

The dynamic processes of NO reduction by coals and char at different O2 concentrations have been investigated under the suspension conditions of a precalciner. The effects of cement raw meal, tempe...

Drying Rates Under Non-isothermal Conditions

The process of drying under non-isothermal conditions has been investigated. Experiments with cement raw meal module with 10–18% moisture content were carried out in a mettler thermoanalyser at 10, 15 and 25°C/min heating rates at an air flow rate of 500 ml/min. Drying rate equations were derived for non-isothermal conditions. It was observed that the drying process occurs in two stages with a transition about the boiling point of water. The activation energy for the drying rate constant for Stages I and II was about 35–55 and 90–135 kJ/mole, respectively. The activation energy values obtained for normal drying condition below boiling point of water, i.e. Stage I, were in very good agreement with the theoretical values. The rate parameters viz., activation energy and frequency factors, follow the kinetic compensation law.

Velocity measurements and flow field characteristic analyses in a turbo air classifier

Turbo air classifier is one of the most widely used powder classification equipment. The rotor cage as a rotary component can create a forced centrifugal field, so it is a key part for turbo air classifier. In order to investigate the effect of structural variations of the rotor cage on flow field characteristics, three dimensional velocity measurements of the annular region in a turbo air classifier equipped with two different rotor cage bottom plates (A and B type) are performed by laser Doppler velocimeter (LDV). It is found that the different bottom plates have different axial and tangential velocity distributions in the annular region. However, the structural variations of the rotor cage have hardly any effect on the radial velocity. Based on the classification principle, the relation between the classification performance and the flow field characteristics is investigated in great detail. The results of the flow field measurements were tested by the classification experiments carried out with cement raw meal and ground calcium carbonate. The results demonstrate that B type bottom plate can realize the production of narrow particle size distributions, so it is more favorable for classification than A type bottom plate. Classification experiment results are in good agreement with the results of the flow field measurements.

Numerical simulation of the gas-solid two-phase flows in a precalciner

The gas-solid two-phase flows of the precalciner were simulated by different multiphase models, such as mixture model, the Eulerian model, including mixture and dispersed, and discrete phase model (DPM). The results of the different multiphase models were analyzed and compared, showing the rationality of the diffusion and mixture of the cement raw meals and coal powder to some extent. Moreover, the results also show the rationality of the given inlets' parameters of actual process of the precalciner.

Use of construction and demolition wastes as raw materials in cement clinker production

The aim of the present paper was to investigate the possibility of utilizing Construction and Demolition (C&D) wastes as substitutes of Portland cement raw meal. The C&D wastes that were so used, were the Recycled Concrete Aggregates (RCA) and the Recycled Masonry Aggregates (RMA) derived from demolished buildings in Attica region, Greece. RCA and RMA samples were selected because of their calcareous and siliceous origin respectively, which conformed the composition of the ordinary Portland cement raw meal. For that reason, six samples of cement raw meals were prepared: one with ordinary raw materials, as a reference sample, and five by mixing the reference sample with RCA and RMA in appropriate proportions. The effect on the reactivity of the generated mixtures, was evaluated on the basis of the free lime content (fCaO) in the mixtures sintered at 1350°C, 1400°C and 1450°C. Test showed that the added recycled aggregates improved the burnability of the cement raw meal without affecting negatively the cement clinker properties. Moreover, the formation of the major components (C 3S, C 2S, C 3A and C 4AF) of the produced clinkers (sintered at 1450°C) was corroborated by X-Ray Diffraction (XRD).

Development and Application of a Cement Raw Meal Controller

The development and implementation of a cement raw meal controller are illustrated. The study has established that the controller parameters shall be adjusted and optimized under the existing field of application. The optimization was performed by the utilization of actual production data and simulation studies. The control action follow-up was carried out using the control chart technique. The application of the controller not only improves the raw meal stability but also facilitates the inquisition on probable deviation sources. By utilizing the controller and the developed simulation, a series of further improvements can be considered.

On-line bulk elemental analysis in the resource industries using neutron-gamma techniques

There is an increasing need in industry, arising from both economic and environmental considerations, to reduce costs and improve product quality through the use of automation. The use of on-line analysis instrumentation provides plant operators with a means for continuous measurement and rapid response. This can result in better control of process efficiency, product quality and resource utilization, all of which produce significant economic and environmental benefits. On-line measurement of bulk elemental composition is important in many industrial applications and is best achieved with highly penetrating neutron-gamma techniques. This paper presents recent work by CSIRO Minerals on the development and implementation of such a technique, NITA (neutron inelastic-scattering and thermal-capture analysis). NITA is distinct from the more common PGNAA (prompt neutron gamma activation analysis) technique in its use of fast neutron sources to generate inelastic scattering reactions, and in its consequent ability to excite gamma-rays from industrially important elements such as carbon and oxygen. The paper will compare the features of NITA and PGNAA analysers and will discuss applications of NITA in industry, including the on-line analysis of composition in pyrometallurgical applications and the on-conveyor belt monitoring of cement raw meal and coal.

Microstructure and properties of hercynite–magnesia–calcium zirconate refractory mixtures

Refractory manufacturers have focused their investigations on the development of chrome-free products that suitably meet the refractory lining requirements of cement rotary kilns. The experimental development of refractory mixtures based on magnesia and calcium zirconate, to which electrofused hercynite was added, was carried out in this work. Formulations, in which various amounts of hercynite were added to study its influence on MgO–CaZrO 3 microstructure and properties, were prepared. Samples were obtained by compacting powders and sintering in an industrial tunnel kiln. The samples were characterized via XRD and SEM. The strength of the refractory was determined at room temperature. Resistance to attack by cement raw meal at 1300 °C was studied. According to the results, formulations with the addition of hercynite show superior cold crushing strength compared to those without the additive, moreover, all compositions showed good chemical resistance to the presence of cement raw meal.

Properties of cement made by partially replacing cement raw materials with municipal solid waste ashes and calcium carbide waste

An investigation on using municipal solid waste incinerator bottom ash (MSWI) and calcium carbide waste (CCW) as a part of the cement raw materials was performed. Cement raw meals were replaced by 5% and 10% of MSWI and CCW to study properties of the laboratory produced MSWI and CCW cements. Chemical composition, setting times, compressive strength and expansion in sulfate solution of the pastes and mortars made of MSWI cements and CCW cements were tested and compared with these made of conventional cement. It was found from the study that the chemical compositions of MSWI cements and CCW cements were similar to that of the control cement. However, SiO 2 content of MSWI cements was higher than that of the control cement, whereas CaO content was lower. Setting times of cement pastes were slightly delayed when MSWI or CCW were used to replace a part of raw meal in cement production. The longer setting times of these cement pastes were observed due to the lower C 3S but higher C 2S content than those in the control cement. Compressive strength of CCW cement mortars was close to that of the control cement. However, compressive strength of the mortars produced from MSWI cements was smaller than that of the control cement mortar, especially when the percentage of MSWI in the raw meal was increased. When compared to the control cement, the performance of MSWI cement and CCW cement in sodium sulfate solution was superior due to the lower C 3S and C 3A.