Analysis of oxy-fuel combustion as an alternative to combustion with air in metal reheating furnaces

Using oxygen instead of air in a burning process is at present being widely discussed as an option to reduce CO2 emissions. One of the possibilities is to maintain the combustion reaction at the same energy release level as burning with air, which reduces fuel consumption and the emission rates of CO2. A thermal simulation was made for metal reheating furnaces, which operate at a temperature in the range of 1150-1250 degrees C, using natural gas with a 5% excess of oxygen, maintaining fixed values for pressure and combustion temperature. The theoretical results show that it is possible to reduce the consumption of fuel, and this reduction depends on the amount of heat that can be recovered during the air pre-heating process. The analysis was further conducted by considering the 2012 costs of natural gas and oxygen in Brazil. The use of oxygen showed to be economically viable for large furnaces that operate with conventional heat recovering systems (those that provide pre-heated air at temperatures near 400 degrees C). (C) 2014 Elsevier Ltd. All rights reserved.

Induction reheating of A356.2 aluminum alloy and thixocasting as automobile component

The development work for producing an automobile component by thixocasting using A356.2 alloy was introduced. As the first step, the alloy was electromagnetically stirred and solidified to produce a billet with non-dendritic microstructure. The microstructure depended on several process parameters such as stirring intensity, stirring frequency, cooling rate, and melt initial superheat. Through a series of computational studies and controlled experiments, a set of process parameters were identified to produce the best microstructures. Reheating of a billet with non-dendritic microstructure to a semisolid temperature was the next step for thixo-casting of the components. The reheating process was characterized for various reheating cycles using a vertical-type reheating machine. The induction heating cycle was optimized to obtain a near-uniform temperature distribution in radial as well as axial direction of the billet, and the heating was continued until the liquid fraction reached about 50%. These parameters were determined with the help of a computational fluid dynamics (CFD) model of die filling and solidification of the semisolid alloy. The heated billets were subsequently thixo-cast into automobile components using a real-time controlled die casting machine. The results show that the castings are near net shape, free from porosity, good surface finish and have superior mechanical properties compared to those produced by conventional die casting processes using the same alloy.

Burning Low Volatile Fuel in Tangentially Fired Furnaces with Fuel Rich/Lean Burners

Pulverized coal combustion in tangentially fired furnaces with fuel rich/lean burners was investigated for three low volatile coals. The burners were operated under the conditions with varied value N-d, which means the ratio of coal concentration of the fuel rich stream to that of the fuel lean stream. The wall temperature distributions in various positions were measured and analyzed. The carbon content in the char and Nox emission were detected under various conditions. The new burners with fuel rich/lean streams were utilized in a thermal power station to burn low volatile coal. The results show that the N-d value has significant influences on the distributions of temperature and char burnout. There exists an optimal N-d value under which the carbon content in the char and the Nox emission is relatively low. The coal ignition and Nox emission in the utilized power station are improved after retrofitting the burners.

Receipt from G. Lloyd, dealer in hot air furnaces, stoves, ranges, gas fixtures and pumps

Receipt from G. Lloyd, dealer in hot air furnaces, stoves, ranges, gas fixtures and pumps, located on King Street, St. Catharines regarding payment received for burners, dampers and other gas fixtures, Jan. 1, 1875.

Province of Ontario Patent issued to Cyrus Dean of St. Catharines for a machine for effecting more perfect combustion of fuel in the furnaces of locomotives

Province of Ontario Patent issued to Cyrus Dean of St. Catharines for a machine for effecting more perfect combustion of fuel in the furnaces of locomotives. This patent was listed in the Records Office of the Registrar General of Canada in Lib. JE, folio 361. This patent is accompanied by a 36 cm. x 57 cm. detailed sketch and explanation of the machine. [Samuel D. Woodruff was the assignee of Cyrus Dean in a in a patent for a rotary washing machine in November of 1869 according to The Commissioners of Patents' Journal by the Great Britain Patent Office], March 23, 1870.

Numerical simulation of heat and mass transfer in fluidised bed heat treatment furnaces

In this paper, a novel combined theoretical and computational model is developed to simulate the heat and mass transfer between a fluidised bed and a workpiece surface, and within the workpiece by considering the fluidised bed as a medium consisting of a double-particle layer and an even porous layer. The heat and mass-transfer flux from the fluidised bed to the workpiece surface is contributed by dense and bubble phases, respectively. The convective heat and mass transfer is simulated by analysing the gas dynamics in the fluidised bed, while radiative heat transfer is modelled by simulating photon emission in a three-dimensional particle array. The simulation shows that convection is approximately constant, while radiation contributes significantly to the heat transfer. The heat-transfer coefficient on an immersed surface near particles is about 6–10 times that on other areas. The transient heat and mass-transfer coefficient, heat and mass-transfer flux on any surface of the workpiece, transient temperature and carbon distributions at any position of the workpiece during the metal carburising process are studied with the simulation.

Measurement of the mass transfer coefficient at workpiece surfaces in heat treatment furnaces

The mass (e.g. carbon) transfer coefficient at a workpiece surface is an important kinetic factor to control the heat treatment process of the workpiece and to evaluate heat treatment equipment. The coefficient can be calculated from the carbon concentration at the surface of a sample carburized in a carburizing furnace for a given time. Two common measurement methods which use a thin plate and employ a component as samples respectively are evaluated and compared for sensitivity and uncertainty. The comparison shows that the use of a component produces higher measurement precision and also has the advantage in measuring the carbon transfer coefficients at different treated positions. This method is then extended and discussed methodologically. Also two equations are proposed to calculate the carbon transfer coefficient and its uncertainty, respectively. This method is also applied to measure the carbon transfer coefficient in a fluidized bed heat treatment furnace.

Heat and mass transfer in fluidised-bed heat-treatment furnaces

The mechanisms of heat and mass transfers between heat-treatment fluidised beds and immersed workpiece were studied by using computational simulation and experimental validation. A model called Double Particle-layer and Porous Medium was developed to simulate the gas flow and heat transfer between fluidised beds and immersed workpiece.

A method and its optimal parameters for the measurement of mass transfer coefficient in heat treatment furnaces

The mass transfer coefficient is an important kinetic factor to control the thermo-chemical treatment processes of metals and alloys. More importantly, the mass transfer coefficient is different at different surface positions of a metallic part treated, which depends on the dynamic characteristics of the atmosphere close to the treated surface. Understanding the local mass transfer coefficient would be significant to approach the expected physical and mechanical properties of treated surfaces. In this paper, a reverse method was proposed to measure the mass transfer coefficient at component surface and the diffusivity in metal during heat treatment. The methodology of the reverses method and the optimal parame-ters are discussed in some detail. This method was successfully used to determine the car-bon transfer coefficient at the surface of a part in a carburizing furnace and carbon diffusiv-ity from the carbon distribution within the diffusion layer.

Synthesis and characterization of CaBi4Ti4O15 thin films annealed by microwave and conventional furnaces

CaBi4Ti4O15 thin films were deposited by the polymeric precursor method and crystallized in a domestic microwave oven and conventional furnace. The films obtained for microwave energy are well-adhered, homogeneous and with good specularity, when treated at 700 degrees C for 10 min. The microstructure and the structure of the films can be tuned by adjusting the crystallization conditions. When microwave oven is employed, the films presented bigger grains with mean grain size around 80 nm. For comparison, films were also prepared by the conventional furnace at 700 degrees C for 2 h. (C) 2007 Elsevier Masson SAS. All rights reserved.