Kiln For Production Research Articles

Model-based optimization of the operation of the coke calcining kiln

A mathematical model was recently developed to simulate the calcination process of regular petroleum coke suitable for aluminum industry applications. The model is made of 14 ordinary differential equations describing energy and mass conservation in the gas and in the coke bed, and complemented by correlations and algebraic equations. It calculates temperature and concentration profiles in the kiln, and also yields other information important to kiln operation, such as calcined coke recovery factor and coke loss through the generation of dust. In this paper it is demonstrated that the model is an efficient tool for the optimization of kiln operation. The model is used to study the effect of key control variables upon kiln operation and productivity. Further, it is shown that higher kiln productivity may be obtained with optimized kiln control and without loss of satisfactory kiln operating condition.

The Use of Carbon Monoxide and Other Gases for Process Control

The application of the analysis of trace gas emissions downstream of the process dust filters in a precalciner kiln as the means of controlling the air-fuel ratio is described. This application eliminated the need for a high-temperature probe in the kiln as the kiln excess-air requirement is determined and controlled based on carbon monoxide, nitrogen oxide, and sulfur dioxide concentrations downstream of the bypass dust filter. Control of the excess air in the precalciner is also based on the carbon monoxide concentration downstream of the preheater dust collector. Control by carbon monoxide has shown considerable advantages over the traditional technique of control based on oxygen analysis. These advantages include: 1) simplification of sampling, 2) increased kiln productivity and efficiency, 3) better operator response to analyzer information, 4) precise combustion control showing promise for reducing nitrogen-oxide emissions, and 5) control of clinker quality.

Improving the firing of plates for steel-teeming ladle slide gates

The mathematical simulation of heat exchange during firing of refractories in tunnel kilns made it possible to develop technical measures to increase the productivity of the two-tunnel kilns by 33% and the annual production of the MKTsP-82 plates was 1500 tons. The improved firing conditions for plates in the tunnel kilns are characterized by an average rate of movement of the charge of 0.30 m/h and an interval between pushes of the cars of 20 min. During use of the improved firing method the operation of the basic production zones of the kiln was corrected. The increase obtained in tunnel kiln productivity and the reduction in specific fuel consumption was the result of this study of acceleration of the firing operation and economy in energy resources.

Behaviour of uranium during phosphate ore calcination

AbstractDuring industrial calcination of phosphate rock, uranium is mobilised with changes both in location and oxidation state. Fission track micromapping of uranium under the microscope has been employed to study the precise distribution of uranium within the samples. Oxidation state ratios of U(IV) to U(VI) were determined by chemical separation followed by delayed neutron activation. The calcination process was studied both in the laboratory and in a full‐scale production kiln of the Oron plant (Israel). The phosphate ore contains about 100 parts of 10−‐6 of uranium, and U(IV) comprises 35–40% of the total U present. The uranium which was not extractable in weak acids, was evenly distributed in the apatite rock components. The study revealed that the following changes occur during the calcination process: (a) carbonate‐fluorapatite loses CO2, and recrystallises to fluorapatite. The recrystallisation process intensifies with increasing temperature, (b) Around 600°C all the uranium is oxidised to the hexavalent state, (c) Migration of uranium in the apatite fragments initiates at 800°C. On increase of temperature to around 900°C, it forms uranium‐rich phases in which it reaches 1–2 %. The uranium‐rich phases exhibit different solubilities in dilute acids, in some cases enabling its preferential leaching from the rock. Other U‐rich phases are extremely insoluble (possibly fluorite, Ca‐silicates) even in phosphoric acid, lowering extraction efficiency. Extraction yields can be improved by addition of salts (e.g. Na2CO3) which prevent the formation of insoluble U‐rich phases.

The Effect of Oxygen upon the Rotary Kiln's Production and Fuel Efficiency: Theory and Practice

For some thirty years rotary kiln operators have been looking at the possibility of employing tonnage oxygen-high-purity oxygen produced from air separation plants-to improve kiln performance. Experience has shown that because of differences in kilns, such as size, thermodynamic characteristics, and feed material, the response varies from one kiln to another. A mathematical model has now been developed which can, within reasonable limits, predict the effect of tonnage oxygen on any given kiln. Use of the model technique affords the kiln operator the opportunity to evaluate the benefits of oxygen enrichment for his particular operation.

Conversion of Existing Cement Kilns to Flash Calciners

Contemporary cement kilns equipped with a suspension preheater provide for efficient operation with the lowest specific heat consumption. The incorporation of a flash calciner reduces the fuel requirement of the rotary kiln, thereby improving refractory life and reducing nitrogen-oxide emissions. The benefits of suspension preheat and flash calcination can be achieved in existing wet or dry process plants. Such modifications can increase kiln production while reducing the specific heat consumption. Several existing long wet and long dry kilns and suspension preheater kiln systems have been modified to flash calciner configurations.