Rotary Kiln Research Articles

Potential of Biomass Utilization in Rotary Kiln of Nickel Processing Plant

Global energy-related CO2 emissions rose by 1.4% in 2017 and reached a historic high of 32.5 Gigatonnes (Gt). One of the biggest contributors to CO2 emission is coal combustion that emits 96.1 kg CO2 for each GJ energy production. Top consumers of coal in the world are the iron-steel industry (28.5%) and the non-metallic minerals (21.4%). Rotary kiln is one of the most energy consuming equipment in nickel pyro-metallurgy processing plant. The specific energy consumption for calcine production is determined to be 2.26 GJ/ton calcine. In the rotary kiln, coal is used as fuel and a reducing agent. Charcoal from palm kernel shell has similar characteristics with coal and very suitable to substitute coal. Charcoal from PKS has many advantages compared to other biomass: high fixed carbon content, high heating value, and low ash content. Charcoal from palm kernel shell can be used as fuel and a reducing agent. Potential 9.9% reduction of CO2 emission can be achieved by using 20% PKS charcoal as fuel and 5% PKS charcoal as a reducing agent with minimum impact on the current operation.

Study of integrated treatment of used bleaching earth cake from lubricant oil recycling process

“Used Bleaching Earth Cake (UBEC)” is the bleaching earth which has been used and filter pressed from the lubricant oil recycling industry. Comprehensive treatment required to treat UBEC as hazardous waste. This research tested the physical and chemical characteristics of UBEC to acknowledge its potential as engine fuel, and then UBEC was combusted in rotary kiln as refuse derived fuel (RDF). The bottom ash from the combustion process was used as fine aggregate replacement in concrete K350 production, compressive strength and Toxicity Characteristic Leaching Procedure (TCLP) was analyzed. UBEC consists of bleaching earth material (Monmorillonite 53.3% and Klinoptilolith 40%), oil residue, and impurities (heavy metals, carbon residue, etc.). Its calorific value ranges from 3000 to 5000 calories and meet the standards for being used as RDF. The average compressive strength result by replacing fine aggregate with 0%, 5%, 10%, 15% and 20% of its ashes were 31.88 MPa, 34.15 MPa, 38.45 MPa, 37.66 MPa, and 36.69 MPa, respectively. The highest compressive strength was at 10% of replacement. TCLP results still meet the standard. Overall, UBEC can be use as RDF and its bottom ash can be safely use as replacement for fine aggregates in concrete K350 production.

Options for processing of aspen wood to carbon materials

.Thermochemical processing of aspen wood to produce carbon materials is of interest considering that it allows increasing the cost of its products several times and enhancing the sustainability of forest complex enterprises.Currently, the enterprises are confined to the manufacture of charcoal, although it is possible to produce other carbon materials, such as charcoal briquettes, activated carbon and oxidized coal.While processing aspen wood, it is feasible to arrange manufacturing charcoal briquettes. Increased mechanical strength and high bulk density of briquettes raises the range of economically viable transportation of manufactured products, i.e. logistics is being improved.To obtain stable quality activated carbon from aspen coal, water vapor activation is the least environmentally hazardous. For such activation implementation, we recommend using a rotary kiln equipped with a Z - shaped insert. For reasons of environmental safety, the oxidation of activated carbon is preferably carried out using hot, humid air. In this case, unlike liquid-phase oxidation, no wastewater is formed.

Development and Evaluation of Mathematical Model based Region of Interest for Rotary kiln Burning Zone Temperature in Cement Industry by Digital Image Processing

Industrial processes particularly cement manufacturing unit consumes about 7% of total fuel used in the industry and hence there are strenuous efforts to reduce the fuels and lower the production costs by applying Optimal Control Algorithms. In order to achieve these parameters in the Rotary Kiln Plant, we need to continuously monitor the temperatures of the burning zone inside the rotary kiln at Regions of Interest (ROI) in real-time. In this image processing setup a thermal camera samples the temperatures inside the kiln at a rate of 5 frames per 2 seconds. The images which are highly sensitive to red and green wavelengths provide sufficient resolution to differentiate between various burning temperatures. The present burning zone temperature measurement obtained from the radiation pyrometer is not reliable on the one hand and indicates temperature information about particular point in the burning zone on the other hand. This is inadequate for optimizing the operation the kiln where a kiln furnace camera has been already installed at the plant for watching the burning status the inside the kiln. Software will be developed to determine the temperature T, for the video captured from the camera. Presently real time video from the camera is displayed in a computer monitor at kiln control room. We will tap the video signal from the setup and the calculate the burning zone temperature at the Region of Interest utilizing real time Image Processing Technologies. The temperature signal so estimated will be validated using the radiation pyrometer signal obtained from the field. The graphical tool developed in MATLAB automatically converts the receiving color images to temperature measure by proposed algorithms and also interactively analyzes the temperatures in a neat graphical user interface, in less than 2 seconds duration. ROI can be selected by a movable and re-sizable window which acts like a probe on the kiln temperatures at this instant, then displays the summary statistics of the temperatures. The tool is extended to provide a real-time graph of average temperature in the ROI over a long time when the probe is fixed at a particular region. However, the developed temperature tool and the point burning zone temperature measured by a proposed mathematical model as like thermocouple in the plant. The results are carried out by MATLAB software and benefits will be quantified in terms of enhancement in the Production efficiency, Energy efficiency, Pollution Control and clean environment.

ADSORPTION OF BENZENE, ACETONE AND CARBON TETRACHLORIDE VAPORS ON MICROPOROUS CARBON ADSORBENT FAS-3

In this paper, the study of the adsorption of organic matter vapors (benzene, carbon tetrachloride, acetone) on the microporous carbon adsorbent FAS-3 in the region of pressures from 0.1 PA to 0.1 MPa and temperatures from 293 to 313 K was conducted, which showed sufficiently high adsorption characteristics of the used adsorbent in comparison with traditional absorbers. Microporous carbon adsorbent FAS-3 is quite new and still not fully understood. The purpose of this study was to determine the parameters of the adsorbent FAS-3, as well as the study of the processes of vapor adsorption of various organic substances on it. The microporous carbon adsorbent FAS-3, obtained on the basis of furfural, was used in the work. Obtaining spherical granules of the adsorbent FAS-3 was carried out in the result of liquid molding of a copolymer of furfural and epoxy resin on the basis of a fundamentally new process of combining the stages of blending monomer, molding the mixture in spherical product of the cured pellets. The activation of spherical grains of FAS-3 was carried out in a rotary kiln by a mixture of water vapor and carbon dioxide at a temperature of 850-900°C to burning that was consistent with the development of porosity in the adsorbent. The equilibrium values of vapor adsorption of substances on FAS-3 were measured on the gravimetric vacuum unit developed in the Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences. Regeneration of the adsorbent was carried out for 6 h at a temperature of 623 K to a pressure of 0.1 Pa. The maximum absolute measurement error was ± 0.01 mmol / g with 95% confidence. Measurement of vapor pressure of organic substances within 0.13 Pa-0.13 MPa was carried out by absolute pressure gauges M10, M1000, developed and manufactured in the Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences. The pressure measurement error by the manometer M10 in the range of 0.13 to 1330 Pa was ±0.066 Pa, and the manometer M1000 in the range from 13 Pa to 130 kPa was ±4.0 Pa.

Combustion Evaluation of Renewable Fuels for Iron-Ore Pellet Induration

Induration (or sintering) of iron-ore pellets requires high temperature (∼1300 °C), which today is generated by burning fuel oil in the firing zone of the straight-grate plant (SG) or coal in the rotary kiln of grate-kiln (GK) plants. In this study, ∼150 kWth combustion experiments were used to investigate the opportunity of totally replacing fuel oil with H2 or pyrolysis oil and replacing coal with wood pellets or black pellets powder. For SG plants, the fuel oil can probably be replaced with either H2 or pyrolysis oil without any major concerns, except for slightly or much higher NOx emissions in the case of pyrolysis oil and H2, respectively. For GK induration machines, it is probably challenging to replace coal entirely with biomass since the temperature profile will be different, and there is a risk for increased ash related operational problems. For both SG and GK plants, the slightly lower O2 concentration in the flue gas observed during biomass combustion (pyrolysis oil, wood pellets, and black pellets) may, however, be negative for the induration process, and this needs to be clarified in future research.

Alternative for the Use of Sewage Sludge in Romania

In Romania, for more than 50% of the amount of sewage sludge, the life cycle ends with the most unfavorable stage of the waste management hierarchy or storage. This study indicates the feasibility of using sewage sludge as an alternative fuel in clinker rotary kilns by presenting theoretical information and personal research data.

Scaling of Pulverized-Fuel Jet Flames That Apply Large Amounts of Excess Air—Implications for NOx Formation

Measures to reduce nitrogen oxides (NOx) formation in industrial combustion processes often require up-scaling through pilot-scale facilities prior to being implemented in commercial scale, and scaling is therefore an important aspect of achieving lower NOx emissions. The current paper is a combined experimental and modelling study that aims to expand the understanding of constant velocity scaling for industrial jet flames applying high amounts of excess air. These types of flames are found in e.g., rotary kilns for production of iron ore pellets. The results show that, even if the combustion settings, velocity, and temperature profiles are correctly scaled, the concentration of oxygen experienced by the fuel during char combustion will scale differently. As the NO formation from the char combustion is important in these flames, the differences induced by the scaling has important impacts on the efficiencies of the applied primary measures. Increasing the rate of char combustion (to increase the Damköhler number), by using, for example, smaller-sized particles, in the pilot-scale is recommended to improve scaling.

Deposits in Gas-fired Rotary Kiln for Limonite Magnetization-Reduction Roasting: Characteristics and Formation Mechanism

The formation mechanism of deposits in commercial gas-fired magnetization-reduction roasting rotary kiln was studied. The deposits ring adhered on the kiln wall based on the bonding of low melting point eutectic liquid phase, and the deposit adhered on the air duct head by impact deposition. The chemical composition and microstructure of the deposits sampled at different locations varied slightly. Besides a small amount of quartz and limonite, main phases in the deposits are fayalite, glass phase and magnetite. The formation of the deposits can be attributed to the derivation of low melting point eutectic of fine limonite and coal ash, and the solid state reaction between them. Coal ash, originated from the reduction coal, combining together with fine limonite particles, results in the accumulation of deposits on the kiln wall and air duct. Fayalite, the binder phase, was a key factor for deposit formation. The residual carbon in limonite may cause an over-reduction of limonite and produce FeO. Amid the roasting process, SiO2, originated from limonite and coal ash, may combine with FeO and reduce the liquefaction temperature, therewith liquid phase generates at high temperature zone, which can significantly promote the growth of deposits.

A lab-scale rotary kiln for thermal treatment of particulate materials under high concentrated solar radiation: Experimental assessment and transient numerical modeling

Rotary kilns are worldwide used for industrial processes that involve thermal treatments of particulate materials. However, a great amount of fossil fuels is employed in such processes. As alternative, solar rotary kilns are considered for this application due to their versatility and potential to substitute traditional fossil-fuel driven devices. In order to boost the development of this technology, efforts have to be focused on the control of the particle temperature during the treatment. In this context, a lab-scale rotary kiln was built and tested using a 7-kWe high-flux solar simulator at University of Antofagasta. It was conceived to treat particulate materials of different nature and it is able to reach temperatures higher than 800 °C under different operation strategies. Silicon carbide was selected for initial tests because it is inert, endures high temperatures (up to 1600 °C) and it has been proposed as thermal storage vector in several researches on concentrated solar power. In a first stage, the empty kiln was preheated up to about 800 °C, reaching a steady state in less than three hours and with a power of approximately 370 W entering the kiln cavity. Afterwards, 43 g of silicon carbide were introduced in the furnace and the system was heated again up to a second steady state above 800 °C. In this stage, particles showed a fast increment of their temperature and exceeded 700 °C in less than three minutes after loading. A one-dimensional transient numerical model was also developed to perform the thermal analysis of the kiln and the estimation of both the particle temperature and the system efficiency. Numerical results showed good agreement with experimental data and thermal losses could be quantified in detail. Therefore, the model was also used to predict the thermal behavior of a solar rotary kiln working in batch mode.

Air gasification of digestate and its co-gasification with residual biomass in a pilot scale rotary kiln

In this study energy recovery of digestate from a biogas plant was investigated via air gasification. Gasification tests were executed in a pilot scale rotary kiln plant having a nominal biomass feeding rate of about 20 kg/h. The equivalence ratio was varied from 0.22 to 0.39 with the goal to approach the autothermal condition. Tests were carried out for 5 h in steady state condition. Syngas composition, char and gas yields were measured. To improve the cold gas efficiency of the process, a mixture of digestate and almond shells (60:40 wt%) was gasified. Autothermal condition was reached with the mixture using equivalence ratio of 0.30 where the corresponding cold gas efficiency achieved the maximum value of 55%. The raw gas had a lower heating value of 4–5 MJ/Nm3. To evaluate possible improvements in the produced gas properties, in this work the effect of steam injection was also investigated.

Waste gas treatment technology against dust in vortex apparatuses with closed water circulation

This article covers the development results and manufacturing application of high technology of water scrubbing for waste gases against dust for environmental management of finely broken stone of limestone wastes burning in rotary kilns. The followings are obtained under production conditions firstly: current sanitary standards for gas cleaning, comprehensive utilization of trapped slurry and closed water circulation.

Application of Improved Fuzzy-Smith Controller in the Control System of Cement Rotary Kiln

Rotary cement kiln is a large time delay and inertia component. It is a typical problem in industrial process control, so advanced control methods should be adopted. This paper designs an improved Fuzzy-Smith controller. It combines Fuzzy with improved Smith predictor control method. Smith predictor algorithm compensates for the time delay and Fuzzy control is used to enhance the robustness of the system. The simulation results show that the improved Fuzzy-Smith controller owns stronger robustness and much better control quality. And it is an appropriate and simple control method for the system with pure lag.

Technology for cleaning off-gases from dust in vortex devices with closed water circulation

AnnotationThe results of the development and implementation in the production of highly efficient technology of wet cleaning of waste gases from dust to solve environmental problems of the processes of burning waste of small limestone in rotary kilns. For the first time in industrial conditions is reached: modern sanitary standards of cleaning gases, full utilization of collected slurry and closed-loop water circulation.

Identification of Cement Rotary Kiln in Noisy Condition using Takagi-Sugeno Neuro-fuzzy System

Cement rotary kiln is the main part of cement production process that have always attracted many researchers’ attention. But this complex nonlinear system has not been modeled efficiently which can make an appropriate performance specially in noisy condition. In this paper Takagi-Sugeno neuro-fuzzy system (TSNFS) is used for identification of cement rotary kiln, and gradient descent (GD) algorithm is applied for tuning the parameters of antecedent and consequent parts of fuzzy rules. In addition, the optimal inputs of the system are selected by genetic algorithm (GA) to achieve less complexity in fuzzy system. The data related to Saveh White Cement (SWC) factory is used in simulations. The Results demonstrate that the proposed identifier has a better performance in comparison with neural and fuzzy models have presented earlier for the same data. Furthermore, in this paper TSNFS is evaluated in noisy condition which had not been worked out before in related researches. Simulations show that this model has a proper performance in different noisy condition.

Effect of Hercynite Spinel on the Technological Properties of MCZ Products Used for Lining Cement Rotary Kilns

Magnesia-calcium zirconate (MCZ) composite products have been tested in the transition zones of cement kilns. Such products are of interest because they are environmentally safe and demonstrate high resistance when exposed to cement clinker at elevated temperatures. Such modifiers as hercynite spinel FeO·Al2O3 (FA) can be added in small quantities to MCZ products to enhance elasticity, improve their ability to form a protective coating on the lining surface, and create a reinforced structure. In this study, various FA amounts (2, 4, and 6 wt.%) were added to the MCZ-clinker made from magnesite and ZrO2 (9.8 wt.%). Next, the material densification parameters, cold compressive strength (CCS), severity of exposure to cement clinker components (CCC), and other technical characteristics of the products made from this material were studied. The maximum product strength was obtained upon introduction of 2 wt.% of FA additive, however, further increase in FA quantity was prevented by an excessive number of micro-cracks and glass-phase formation. The penetration depth of the cement clinker components into the MCZ-FA products decreased with an increase in the FA additive content. In other words, the penetration depth was lower at higher FA quantities. In addition, the behavior of the protective coating and thermal shock resistance of the products improved considerably upon increasing the FA content to 6 wt.%. The products with different FA content can be used for lining the cement rotary kiln zones, in which different protective coating formation conditions are observed.

Densification of coal fines and mildly torrefied biomass into composite fuel using different organic binders

Coal processing industries generate millions of tons of fines (<3 mm) during mining operation and are often considered as wastes. These wastes have enormous potential in serving as energy and metallurgical operation feedstock. One avenue for its use is densification into briquettes or pelletizes. Various briquetting techniques have been adopted in the past few decades; however, the main issues upfront in commercializing these techniques are significant binder cost and poor mechanical integrity. Therefore, the present study concentrates on utilizing commonly available organic binder along with pretreated biomass in developing coal fine briquettes. Briquettes were produced after initial pretreatment of the raw materials under a load of 2 tons. Briquettes were cured in an inert environment and eventually characterized for its main litmus requirements (physical properties). It was observed that pitch-molasses bonded briquettes have better physical properties leading to good mechanical integrity than briquettes produced from individual binder. The proximate, ultimate and calorific value analyses of the briquettes do not deteriorate but mildly improved compared to the raw coal fines. With a density of 1.18–1.32 g/cm3, drop to fracture that is greater than 100 (times/2 m), impact resistance index well above 6000, water resistance index of 99% and cold crushing strength of 9 MPa, pitch-molasses bonded briquettes clearly surpassed recommended physical properties benchmarked for briquettes of industrial and domestic end use. The physical properties of the briquettes favorably meet requirements as feedstock for rotary kiln direct reduced iron and COREX iron-making processes as well as fuel for thermal operations.

Döner Fırına Etki Eden Yüklerin Analizi ve Hidrolik Dizayn

Rotary kilns are the equipment for which crystallization and mixing is carried out with the help of high temperature. In this study, evaluation of replacing the electric motor which was used for moving the pinion gear with a hydraulic motor were carried out. The force and torque value exerts on the gear that provides the rotation of the rotary kiln was calculated analytically. As a result of the calculation, it was concluded that the pinion gear is exposed to 21,208 kN and the torque value is 6097,3 N.mm. By these values, detailed calculations of the hydraulic motor, pump, electric motor, minimum pipe diameter and reservoir capacity which constitute the rest of the system were performed. According to the calculations made, the final system was created by selecting the components to be used in the system.&amp;nbsp;

Influence of heating and cooling rate on the stress state of the brick lining in a rotary kiln using finite element simulations

Rotary kilns for iron-ore pellets production are highly dependent on a well-functioned refractory brick lining. To improve the long-term capability of the lining, in-situ observations of the bricks' performance are desired, however, the harsh environment inside the rotary kiln makes it difficult or nearly impossible to study the lining during operation. By using numerical simulations as a tool, some of the problems encountered by the brick lining can be studied without limitation of the extreme conditions.In this work, stress state of the lining was studied under the influence of different heating and cooling rates, and different brick compaction cases. A finite element model was created for conducting the numerical simulations. The numerical model was calibrated for transient heat transfer. Temperature dependent material properties of the bricks and casing were used as input. The heating and cooling was controlled by temperature prescription on the boundary of the brick lining, while brick lining compaction by defining relative position of the bricks in axial and radial directions.The conducted numerical simulations showed that considerable tensile stress may appear in a large area of the brick during initial heating stage. The large tensile area corresponds well with the typical circumferential cracks experienced by the bricks. It was demonstrated that the compressive stresses counteract the development of tensile stresses. However, the compressive stresses may become very large in the initial stage of heating. The positive effect of lower heating rate was considerable on the tensile stresses, while influence on the compressive stresses was almost unnoticed. The hypothetical cooling rates showed that very high tensile stresses may occur on the surface of the bricks, potentially leading to surface spalling. Furthermore, it was demonstrated that axial compaction is highly important on the stress development in the lining, which, may not always be followed in practice. As a general conclusion, it is recommended to always achieve a tight compaction of the brick lining and to take measures for lowering the heating and cooling rates.The conducted work exemplifies behaviour of the brick lining for realistic heat transfer and material properties. The insight into the behaviour gives possibilities to make adjustments and directed investments for lowering risk of brick lining failure.

A column study of persulfate chemical oxidative regeneration of toluene gas saturated activated carbon

Soil vapor extraction (SVE) is a remediation technology for removing volatile organic contaminants (e.g., toluene) from the subsurface. Charcoal activated carbon (AC) adsorption is a commonly applied method of containing the chemical vapors exhausted as SVE offgas. This study aimed to investigate the potential for the thermal activated persulfate (TAP) process to regenerate toluene gas saturated AC. The experimental AC adsorption column setup consisted of AC and wet TAP regeneration units. When influent toluene gas saturated the AC and achieved breakthrough from the adsorption column, regeneration of the saturated AC was achieved by flushing with 50 or 100 mM persulfate solution at 50 or 80 °C. The TAP regenerated AC retained >90% of its adsorption efficiency when regenerated with 100 mM sodium persulfate (SPS) solution flushed at 50 and 80 °C. The removal of sorbed toluene during the TAP process relied on mass transfer (i.e., sorbed toluene dissolved into the SPS solution). The flushed toluene was rapidly destroyed in the SPS solution by oxidative degradation. These results suggested that, sufficient oxidation of toluene occurs with thermal assistance at a Δ[SPS]/AC dosage of approximately >50 (g/g) at 50 °C or above. These parameters successfully regenerated AC saturated toluene in the TAP process. An economic evaluation based on the amount of SPS and electricity required indicated that, the cost is far less than conventional rotary kiln and microwave heat AC regenerations. This TAP oxidative AC regeneration could be a cost effective alternative to other types of carbon bed regeneration, and will likely provide cost benefit when used to treat toluene offgas from on-site SVE, because it both removes toluene from the AC, and destroys it in the regeneration solution.