Furnace, electric, construction

Furnaces with Two Separate Chambers. The metallic raw material, which can be in large pieces, is fed into the first chamber where it melts. This is connected to the second, electrically heated chamber where distillation takes place in the absence of air. The first version of this type of furnace was constructed by Lundevall [2.78]. 

For the areas that do have sufficiently low-cost electric power, the furnaces are constructed with conventional bottoms hut with superstructure only adequate lor initial heat-up. They depend on a blanket of hatch floating on the surface of ihe glass to retain the heat within the tank that is provided by the submerged electrodes. Fresh batch is added to the blanket at a rate equal to the rate of melted glass withdrawn. 

Electric-Arc Furnace. The electric-arc furnace is by far the most popular electric steelmaking furnace. The carbon arc was discovered by Sir Humphry Davy in 1800, but it had no practical application in steelmaking until Sir William Siemens of open-hearth fame constructed, operated, and patented furnaces operating on both direct- and indirect-arc principles in 1878. At that early date, the availability of electric power was limited and very expensive. Furthermore, carbon electrodes of the quality to carry sufficient current for steel melting had not been developed (see Furnaces, electric). 

One of the first precise vacuum or inert-atmosphere instruments was designed and constructed by Whitehead and Breger (37). The furnace was constructed from an alundum core, 9 in. in length by 2 in. ID, wound with Chromel A resistance wire. The core was shielded by four sheet-nickel cylinders, mounted on three posts, and the entire assembly was placed inside a 12 x 24-in. Pyrex bell jar. All electrical connections were made through the bottom of the bell jar mounting base. The sample block was made in the dimensions shown from Type 446 or 309 stainless steel. The furnace heating rate was controlled by a Leeds and Northrup Micromax controller the differential temperatures were recorded on a Beckman Photocell recorder. 

The complete assembly for carrying out the catalytic decomposition of acids into ketones is shown in Fig. Ill, 72, 1. The main part of the apparatus consists of a device for dropping the acid at constant rate into a combustion tube containing the catalyst (manganous oxide deposited upon pumice) and heated electrically to about 350° the reaction products are condensed by a double surface condenser and coUected in a flask (which may be cooled in ice, if necessary) a glass bubbler at the end of the apparatus indicates the rate of decomposition (evolution of carbon dioxide). The furnace may be a commercial cylindrical furnace, about 70 cm. in length, but it is excellent practice, and certainly very much cheaper, to construct it from simple materials. 

Co, by weight, is an extremely powerful magnet that offers a B-H (max) almost twice that of Alnico V. Platinum resistance wires are used for constructing high-temperature electric furnaces. 

Fig. 13. (a) Convection currents around electrically heated furnace tube (b) furnace construction to minimise convection (78). 

Phosphate Fertilizer Industry Granular Triple Superphosphate Storage Facilities Goal Preparation Plants Ferroalloy Production Facilities Steel Plants Electric Arc Furnaces Constructed after October 21, 1974, and on or before August 17,1983... 

Steel Plants Electric Arc Furnaces and Argon-Oxygen Decarhurization Vessels Constructed after August 7, 1983 Kraft Pulp Mills Glass Manufacturing Plants Grain Elevators... 

The design eost will be a function of the incinerator cost plus installation which is normally in the range of 4 to7%. This cost should be doubled to include engineering services during project construction. It should be noted that with the electric furnace, the power needed to start up results in a large connected load. In areas of the country where there are high demand charges for electric power, this system can be economically impractical. 

The principal applications of the outstanding stability of platinum and its alloys at high temperatures lie in their use as materials of construction for equipment to handle molten glass and as electrical resistance windings for high-temperature furnaces. 

The impure iron is made into steel by burning out most of the carbon, sulfur, and phosphorus. Today there are three common furnace types for making steel—the open-hearth furnace (85% of U.S. production), the electric arc furnace (10%), and the Bessemer converter (5%). These furnaces differ in construction but the chemistry is basically similar. 

Muffle furnaces. An electrically heated furnace of muffle form should be available in every well-equipped laboratory. The maximum temperature should be about 1200 °C. If possible, a thermocouple and indicating pyrometer should be provided otherwise the ammeter in the circuit should be calibrated, and a chart constructed showing ammeter and corresponding temperature readings. Gas-heated muffle furnaces are marketed these may give temperatures up to about 1200 °C. 

In addition, Lavoisier and his colleagues introduced programmatically into the chemical laboratory apparatus other than the furnace, the crucible, and the retort, describing and illustrating the new instruments construction and their use in texts like Lavoisier s Traite elementaire de chimie. Lavoisier employed not only the balance and the thermometer but pneumatic apparatus, the electrical machine, the burning lens, and the calorimeter. 80 As the instruments of the chemical laboratory proliferated, so, too, did the problems chemists dreamed of posing and resolving. 

Its high melting point also makes it useful for metal electrodes in glassmaking furnaces. Molybdenum s high resistance to electricity makes it useful in high-temperature filament wires and in the construction of parts for missiles, spacecrafts, and nuclear power generators. 

Platinum metal and its alloys have numerous applications. As a precious metal it is used extensively in jewelry. Other important applications include construction of laboratory crucibles and high temperature electric furnaces in instruments as thermocouple elements as wire for electrical contacts as electrodes in dentistry in cigarette lighters and for coating missile and jet engine parts. 

Light flicker due to arc furnaces requires extra mention. Arc furnaces, commonly found in many industrial towns, typically use scrap metal as the starting point. An arc is struck in the metal by applying voltage to the batch from a specially constructed furnace transformer. The heat due to the arc melts the scrap metal, which is drawn out from the furnace to produce raw material for a variety of industrial facilities. Arc furnaces impose large electrical power requirements on the electrical system. 

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