Showing papers on "Rotary kiln published in 2017"

Thermal treatment of waste from the meat industry in high scale rotary kiln

Abstract: Recently there has been an increase in consumption of meat, especially poultry. This results in an increase in the quantity of waste, including waste feathers. Waste from the meat industry are hazardous, which must be disposed of in accordance with the law. Wastes from the meat industry normally consist of valuable elements such as phosphorus, calcium, potassium, magnesium (macronutrients), and iron, copper, zinc, manganese (micronutrients), which after suitable processing can be used for the purposes of fertilization. The paper presents the results of thermal treatment of feathers with meat and bone meal and feathers with poultry litter in a high scale rotary kiln. Mixtures of wastes were incinerated in temperature range from 600 to 900 °C for about 20–25 min. The resulting ashes were characterized by a high content of phosphorus (4–17%), calcium (17–30%) and potassium (0.6–3.6%). The study revealed that the selection of process parameters allows for obtaining ash with controlled and desired composition of macro and micronutrients, moreover, it is safe in terms of sanitary.

Factors Affecting the Upgrading of a Nickeliferous Limonitic Laterite Ore by Reduction Roasting, Thermal Growth and Magnetic Separation

Abstract: There is considerable interest in the development of new processes to extract the nickel from the oxidic nickeliferous laterite deposits, as the global nickel sulphide resources are rapidly becoming more difficult to access. In comparison to sulphide ores, where the nickel-containing mineral can be readily concentrated by flotation, nickel laterites are not amenable to significant upgrading, due to their complex mineralogy. In this paper, firstly, a brief overview of the conventional techniques used to process the nickeliferous limonitic laterites is given, as well as a review of current research in the area. Secondly, a thermodynamic model is developed to simulate the roasting process and to aid in the selection of process parameters to maximize the nickel recovery and grade and also to minimize the magnetite content of the concentrate. Thirdly, a two-stage process involving reduction roasting and thermal growth in either a tube furnace or a rotary kiln furnace, followed by magnetic separation, was investigated. Thermogravimetric, differential thermal and mineral liberation analyses techniques were utilized to further understand the process. Finally, the nickel grades and recovery results were compared to those available in the literature.

Dechlorination of zinc oxide dust derived from zinc leaching residue by microwave roasting in a rotary kiln

Abstract: The dechlorination efficiency of zinc oxide dust using microwave roasting was investigated capitalizing on the different microwave absorbing capacities of the compounds such as chlorine, lead, and zinc oxide. The associated dechlorination reactions were discussed in detail and the effect of all the influencing parameters such as the air flow rate, steam flow rate, the roasting temperature, roasting duration, and the mixing rate were assessed to identify the optimal conditions. The results indicated that a near 93% dechlorination of zinc oxide dust could be achieved, which would satisfy the requirements of the wet smelting electrolysis process. The optimal process parameters were identified to be an air flow of 300 L/h, a steam flow of 8 mL/min, a stirring speed of 60 rpm, a roasting temperature of 650 oC, and a roasting duration of 60 min. Water vapor has an enhanced effect on dechlorination by microwave roasting.

Improved waste heat recovery through surface of kiln using phase change material

Abstract: The heat losses that occur from the surface of the rotary kilns during calcination process are a major source of waste heat in cement production industry. In order to recover this heat, a multi-shell heat exchanger that forms an annular duct over the high temperature zone of the kiln is used. The phase change material (PCM) paraffin wax with a melting point of 68°C is filled in between the gap of the two concentric annular steel shells which are thermally insulated from the outside. In order to draw a comparison and to establish that phase change material improves the waste heat recovery, the heat exchanger model made up of mild steel, which extracts waste heat from a kiln, is experimentally investigated with and without the tertiary shell that contains the phase change material. The outer surface of the heat exchanger is insulated by glass wool, and to facilitate the passage of air between the shells for heat transfer, a variable speed centrifugal fan (for variable flow rate) is installed. The results show that the waste heat recovery rate is increased by 3% to 8% (depending on different air-flow rate) with the use of phase change material. This implies that phase change materials such as paraffin wax can be used in heat exchangers to obtain an improved waste heat recovery rate.

Heat convection and radiation in flighted rotary kilns: A minimal model

Abstract: We propose a minimal model aiming to describe heat transfer between particles (i.e. grains) and gases in a model of flighted rotary kilns. It considers a channel in which a convective gas interacts with a granular suspension and a granular bed. Despite its simplicity it captures the main experimental findings in the case of dilute suspension of heavy grains typical of what can be observed in many industrial rotary kilns. Energy balance between each phase takes into account the main heat transfer mechanisms between the transverse granular motion and the convective gas. In the absence of radiation heat transfer, the model predicts exponential variations of the temperatures characterized by a length which depends on the granular and gas heat flow rates as well as on the exchange areas. When radiation is taken into account, the model can be solved numerically. For this case, the temperature variations can be fitted by stretched exponentials whose parameters are found to be independent of the studied phases. Finally, an efficiency criterion is proposed to optimize the length of the system.

Radiative Heat Transfer Conditions in a Rotary Kiln Test Furnace Using Coal, Biomass, and Cofiring Burners

Abstract: This work studies the radiative heat transfer in a 580 kW(th) pilot scale test furnace that resembles a full-scale rotary kiln for iron ore pellet production. The aim is to quantify the radiative heat transfer in coal and cofiring flames and also to study the possibility to model the radiative heat transfer for such combustion conditions. Three combustion cases of coal and cofiring are studied, and an evaluation is made using a detailed radiation model. The test furnace is cylindrical and refractory lined but does not rotate and no iron ore pellet bed material is included. In-flame measurements of temperature, gas composition, particle concentration, radiative intensity, and radiative heat flux are conducted for the different fuels and fuel combinations. Overall, the differences in measured radiative intensities and heat fluxes among the three studied fuel cases are minor, which implies that introduction of renewable fuels by cofiring in a full-scale rotary kiln should be feasible with respect to heat transfer conditions. In the model, the furnace is treated as an axisymmetric and infinitely long cylinder, and gas properties are calculated with a statistical narrow-band model, while particle properties are calculated using Mie theory. The modeling results show reasonable to good predictivity compared to the measured intensity data. This indicates that the experimental data is of good quality but also indicates the potential use of the model in full-scale rotary kiln calculations in future work.

Simulated Feedback Mechanism-Based Rotary Kiln Burning State Cognition Intelligence Method

Abstract: Burning state directly determines the clinker quality index in the rotary kiln sintering process. A simulated feedback mechanism-based rotary kiln burning state cognition intelligence method and a calculating model are explored for the purpose of imitating the human cognition process with repeated comparison and inference. The flame image feature space is optimized progressively using the evaluation of uncertain cognition results with different values of cognition demand to realize the simulated feedback cognition mode from global to local. First, the simulated feedback mechanism-based rotary kiln burning state cognition intelligence method with the coupling operation of the training layer and cognition decision layer is proposed, and the framework of the model is described. Second, the evaluation index system of uncertain cognition results based on the bag of words model, latent semantic analysis method, and entropy theory is constructed. Third, the simulated feedback mechanism based on the evaluation of uncertain cognitive results is established, and a concrete calculation model is given. Fourth, the simulated feedback mechanism-based rotary kiln burning state cognition intelligence system is designed, and the relevant cognition intelligence algorithm is provided. Finally, a simulation experiment is carried out with the collected burning zone flame image of a rotary kiln. An average recognition accuracy of 92.32% is achieved with a minor standard deviation in accuracy. The experimental results show that our method is effective and outperforms other open-loop recognition methods with the global configuration feature of flame image.

Method for treating high-zinc iron-containing slime through utilizing rotary kiln

Abstract: The invention relates to a method for treating high-zinc iron-containing slime through utilizing a rotary kiln. The method comprises the steps that blast furnace gas ash and converter OG mud are mixed and pelletized; wet pellets are dried and preheated, and a drying and preheating heat source is hot air generated by high-temperature flue gas of the rotary kiln after passing through a high-low temperature composite air heat exchanger; a pea coal spray gun, a carbon residue spray gun and an ore grain spray gun are arranged at a kiln head of the rotary kiln, and high-volatile matter coal, residual carbon and high-grade iron ore are sprayed into the kiln; the dried pellets are fed into the rotary kiln, and high-temperature metallized pellets are obtained after the dried pellets are subjected to direct reduction and high-temperature solidification in the rotary kiln; after being cooled to the normal temperature, materials like the metallized pellets and excess carbon residue are subjected to magnetic separation, and metallized pellets are obtained; and large-particle dust is removed from the high-temperature flue gas of the rotary kiln, the high-temperature flue gas enters the high-low temperature composite air heat exchanger to be cooled, the cooled flue gas enters a bag-type dust collector, and zinc oxide powder is recycled. According to the method, the high-zinc iron-containing slime generated by iron and steel enterprises is efficiently utilized, and environmental pollution caused by stacking of the high-zinc iron-containing slime is solved.

One-dimensional steady-state thermal model for rotary kilns used in the manufacture of cement

Abstract: Rotary kilns are used extensively in the cement industry to convert raw meal into cement clinker. In order to optimise the operation of cement kilns, computationally efficient thermal models are required. In this work, the development of a one-dimensional thermal model for kilns is explored. To simplify the model, the kiln is assumed to be well mixed in the transverse direction. A simultaneous mass and energy balance is solved based on a steady-state approximation. Existing semi-empirical models for heat transfer in the kiln are implemented and critically evaluated. The resulting one-dimensional model is capable of predicting axial temperature profiles in the rotary kiln which agree well with the available experimental data found in the literature. The model presented here extends from previous published models by considering a full enthalpy balance for the gas in the kiln. This allows the model to be used in a fully predictive manner, taking into account the temperature-dependent thermodynamic, t...

Sludge roller external heat drying and circulating fluidized bed incineration integration and tail gas cleanup device

Abstract: The invention discloses a sludge roller external heat drying and circulating fluidized bed incineration integration and tail gas cleanup device, and belongs to the technical field of sludge incineration treatment. The problem existing in an existing sludge drying and incineration technology is solved. The device comprises a circulating fluidized bed, a drying system and a tail gas cleanup system. The drying system comprises a rotary kiln roller, a fan and a condenser. The rotary kiln roller is inserted into a tail flue of the circulating fluidized bed in a penetrating mode. After water vapor and bed smell generated in the sludge drying process are condensed and water is removed, the water vapor and bed smell are supplied to a hearth of the circulating fluidized bed to be combusted for deodorization; two air preheaters are arranged inside the tail flue and connected with a primary tuyere and a secondary tuyere arranged in the hearth of the circulating fluidized bed respectively. The tail gas cleanup system comprises an activated carbon injection device, a cloth bag dust remover and a wet desulphurization system which are sequentially arranged behind the air preheaters. A gas conveying pipe is arranged between the cloth bag dust remover and the wet desulphurization system to be connected with the primary tuyere. The device is used for sludge drying and incineration.

System and method for preparing building 3D printing material by using municipal waste and industrial solid waste

Abstract: The present invention discloses a system and a method for preparing a building 3D printing material by using municipal waste and industrial solid waste. The system comprises a homogenization pool, a wet powder mill, a filter press, a rotary kiln, a powder mill and a hot water storage tank. According to the method, wet sludge produced from an urban sewage treatment plant is directly mixed with mineralized garbage, red mud, desulfuration gypsum, carbide slag and industrial water to form a mixed solution without dewatering, a dry weight ratio of the wet sludge to the mineralized garbage to the red mud to the desulfuration gypsum to the carbide slag in the mixed solution is 5-10:5-10:15-30:10-20:30-60, the solid-liquid ratio in the mixed solution is maintained at 1:3-1:4, the mixed solution is sequentially subjected to wet milling, homogenization treatment and alkali removing, the homogenization treatment temperature is 60-70 DEG C, the homogenized material is subjected to mechanical pressure filtration dehydration, and the filtered material is subjected to high temperature calcination to obtain the building 3D printing material precursor.

Internet and Fuzzy Based Control System for Rotary Kiln in Cement Manufacturing Plant

Abstract: This paper develops an Internet-based fuzzy control system for an industrial process plant to ensure the remote and fuzzy control in cement factories in Algeria. The remote process consists of control, diagnosing alarms occurs, maintaining and synchronizing different regulation loops. Fuzzy control of the kiln ensures that the system be operational at all times, with minimal downtime. Internet technology ensures remote control. The system reduces downtimes and can guided by operators in the main control room or via Internet.