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To finish the items, the process is run for approximately 20 hours at 200 V with a starting current of 300 A (60 kW) for a furnace approximately 9 meters long by 35 cm in width and 45 cm in depth, and the resistance drops as the carbon heats due to a negative temperature coefficient, causing the current to increase. [2] Cool down takes weeks.
Diagram of a Castner lengthwise graphitization furnace. a - Mixture of Coke and Sand, b - Bricks, c - Carbon Electrodes, d - Refractory Material, e - Rods to Graphitize, f - Granulated Coke File usage
Graphitization generally occurs at high temperatures (up to 3,000 °C (5,430 °F)), and can be accelerated by catalysts such as iron or nickel. [ 2 ] When carbonaceous material is exposed to high temperatures for an extended period of time, the carbon atoms begin to rearrange and form layered crystal planes.
Graphite blocks are also used in parts of blast furnace linings [51] where the high thermal conductivity of the graphite is critical to ensuring adequate cooling of the bottom and hearth of the furnace. [52] High-purity monolithics are often used as a continuous furnace lining instead of carbon-magnesite bricks.
This is because carbon must diffuse out of the graphite until it has reached the equilibrium concentration dictated by the temperature and the phase diagram. This step may be done in many types of furnaces, in a high-temperature salt bath, or via direct flame or induction heating. Numerous patents describe specific methods and variations.
For potable water, portland cement is used; for sewage it is common to use sulfate resisting or high alumina cement. Cement mortar linings have been found to dramatically reduce internal corrosion. A DIPRA survey has demonstrated that the Hazen-Williams factor of cement lining remains between 130 and 151 with only slight reduction with age.
GFAA spectrometry instruments have the following basic features: 1. a source of light (lamp) that emits resonance line radiation; 2. an atomization chamber (graphite tube) in which the sample is vaporized; 3. a monochromator for selecting only one of the characteristic wavelengths (visible or ultraviolet) of the element of interest; 4. a detector, generally a photomultiplier tube (light ...
The stationary plate is up to 6 m (20 ft) in diameter. Rotating rabble arms constantly turn over the mixture and move the intermediate product to a lower plate. The kiln portion of the furnace is constructed with bricks that have high resistance to direct flame, temperature, and acid. The other parts of the furnace are heat and acid resistant.