Temperature Carbonization Furnace

In the LT furnace, tars are evolved and unless efficiently removed, can deposit tar on the fiber and form tar needles. A tar shield fitted above the fiber band at the inlet end of the furnace can be beneficial. Correct balancing of the furnace can be achieved by adjusting the body flow of N2 at the furnace inlet end to a level where smoke is not forced out from the outlet end and, yet, when looking down into the furnace muffle, the atmosphere is not entirely clear, with some wisps of swirling smoke visible. 

Fiber is underoxidized (oxidized density must be kept above 1.36gcm ) 

Ingress of air (requires checking with a smoke pencil e.g. Draeger) 

Deposition of tar (efficient extraction must be maintained, ensuring that the incinerator is routinely rodded out) 

Tension is too high (tow tension needs checking with a meter, as also shrinkage). 

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Schwel-ofen, m. low-temperature carbonizing furnace, -raum, m. carbonizing space or chamber, -retorte, /. retort for low-temperature distillation, -teer, m. tar from low-temperature carbonization, -teerol, n. carbonization tar oil, esp. from lignite. 

Pinishes are applied to the PAN fiber to improve handling and include silicones (modified polysiloxanes) [132] and trimethylol propane-ethylene oxide adduct [133-135]. These finishes are burned off in the latter stages of stabilization, or in the initial stages of the low temperature carbonization furnace and the breakdown products should be volatile to permit removal. At one time, it was common practice to use adventitious sizes applied prior to the stabilization stage to protect the cosmetics of the oxidized fiber during oxidation. These sizes should preferably break down into gaseous components at about 200° C and typical sizes are the ammonium salt of polystyrene maleic anhydride copolymer, ethyl acrylate, ethyl acrylate/methyl methacrylate and polyacrylic acid. 

Low Temperature Carbonization. The Lurgi Sptlgas process was developed to carbonize brown coal at relatively low temperatures to produce tars and oils (Fig. 5). A shaft furnace internally heated by process-derived fuel gas (Spblgas) is used. The product can range from a friable coke breeze to hard lump coal depending on the quality of the briquettes used in the feed. The briquettes, made in normal extmsion presses, break down into smaller sizes during carbonization. 

Most of the coke produced in the United States today comes from the high-temperature carbonization of coal. The coke is used pnmarily by the metallurgical industries as a fuel and in the rendering of iron from iron ore m the blast furnace... 

Having established the feasibility of niobium metal production by the carbothermic reduction of niobium pentoxide under temperature and pressure conditions readily attainable in the laboratory and in industry, the principles of efficient process execution may now be examined. In a high-temperature vacuum furnace operation, the quantity of gas that is to be pumped off can influence the choice of the vacuum process. When the reduction of niobium pentoxide with either carbon or niobium carbide is attempted according to the following overall equations ... 

Campbell and Ottaway [672] have described a simple and rapid method for the determination of cadmium and zinc in seawater, using atomic absorption spectrometry with carbon furnace atomisation. Samples, diluted 1 + 1 with deionised water, are injected into the carbon furnace and atomised in an HGA-72 furnace atomiser under gas-stop conditions. A low atomisation temperature... 

Samples are oven dried at 100°C after which they are weighed in order to measure water content. TC and TS are measured by introducing dried samples to the Carbon Sulfur (CS) automatic analyzer (Eltra CS-800) instrument. Subsequently, 2g of each sample is introduced in preweighed high temperature porcelain crucibles and is introduced to a high temperature muffle furnace for the removal of carbonates at 900C. Samples are then introduced to the CS automatic analyzer for measurement of organic residual carbon. 

Coke. Metallurgical coke is obtained by high-temperature carbonization of coal. It is a poorly graphitized form of carbon it is mainly used in blast furnace for steel manufacture (see Iron, 5.10). 

One issue that has already been mentioned is the amount of sulfur in the ash that is due to a high amount of carbonates (calcite, CaC03), or pyrite (FeS2), or both, in the coal. Sulfur retained as sulfates may be both unduly high and nonuniform between duplicate samples. The reasons vary from inconsistencies in the furnace temperature and furnace ventilation that have an influence on sulfur trioxide retention in the ash. Consequently, sulfur in ash as determined in the laboratory cannot be assumed to be equivalent to sulfur present in the mineral matter in coal or to the retention of sulfur in ash produced under the conditions of commercial utilization. 

Cementation process. This process, now little used, consists of heating wrought iron or low-carbon steel in powdered charcoal or leather dust for 6 to 11 days in a closed boxlike furnace at 650 to 700°C. At these temperatures, carbon diffuses slowly into the surface of the steel, thus producing a thin coat of high-carbon steel over a core of low-carbon steel. This is essentially a case-hardening procedure, and steel produced in this manner is used largely in the manufacture of tools. 

This procedure involves the pyrolysis of gas molecules with high content in carbon at elevated temperatures in the presence of catalyst [10, 25]. There are two basic protocols, in one of them, called supported growth process (the most used), the catalyst is prepared and deposited on a support medium, which is inserted into a flow apparatus (a tube at atmospheric pressure in a temperature controlled furnace) and exposed to elevated temperatures, usually 500-1100 °C for a given time. In the other protocol, called floating-catalyst growth, the catalyst and the... 

In processes carried out at low temperatures where either iron tubes or chromel and nichrome tubes may be employed, experiments should be performed to determine the relative value of these tubes in life in hours per dollar of cost. There are practically no data available in this regard. In heat-treating furnaces and carbonizing furnaces, chromel A is often used. Chromel C and nichrome last many months in lead baths. Chromel and nichrome do not volatilize so readily as iron. Base-metal couples are thus better protected by these tubes than when iron or steel is employed. Chromel contains practically no iron. Chromel and nichrome have a rather high iron content. 

Indirect heating through a refractory vail, as in the Destrugas process, is very slov. It takes about 20 hours to heat a slovly descending layer of refuse up to the desired temperature of 950 - 1050°C. This results in a lov capacity per unit reactor volume. Even inductive heating of steel balls, admixed to the refuse, as in early WSL-experiments, does not sufficiently accelerate the heating process. Better results are obtained by forced circulation of pyrolysis gas, as in the Lambiotte vood carbonization furnace and in the WSL cross-flov reactor. 

The electrolysis is performed either m a platinum or an alumina cell, this being placed in a temperature-controlled furnace. Electrodes are usually either gold or platinum beads or plates soldered to the lead wires. A carbon anode can also be used ... 

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