Burner crucible furnace

Crucible furnaces are indirectly heated using fuel-fired burners or electrical resistors. For fuel-fired crucibles, the thermal efficiency is not as high as for other melting furnaces, since it is difficult to make use of the heat of the combustion products. They are relatively inexpensive and since the flames are not in contact with the molten metal, metal losses are low and the melt quality is high, and also alloy changes can be readily carried out. [175, Brown, 1999]... 

Reverberatory furnaces melt metals in batches using a pot-shaped crucible that holds the metal over an electric heater or fuel-free burner. The flux reacts with impurities. 

Preparation and Properties of Sodium Ferrite. Mix 2 g of an iron(III) oxide powder and 20 g of anhydrous sodium carbonate in an iron crucible. Fuse the mixture on the flame of a gas burner or in a muffle furnace at 800-900 °C. Pour out the hot melt onto a glazed tile. When it solidifies, grind pieces of the melt in a mortar and spill the powder into a beaker with water. What settles onto the bottom of the beaker Write the equations of the reactions. What type of oxides does iron(III) oxide belong to Which salts hydrolyze more strongly, iron(II) or iron(III) salts What does this depend on ... 

Moisten the residue with ca 10 ml of acetone, slant the dish at ca 45° angle and ignite. Remove the gas burner, cool the dish, and repeat the above treatment. Heat the crucible on a gas burner or in a muffle furnace until the disappearance of carbonaceous matter, cool in a desiccator and weigh (Ref 1)... 

Substances that will not dissolve in acid can usually be dissolved by a hot, molten inorganic flux (Table 28-6). Finely powdered unknown is mixed with 2 to 20 times its mass of solid flux, and fusion (melting) is carried out in a platinum-gold alloy crucible at 300° to 1 200°C in a furnace or over a burner. The apparatus in Figure 28-9 fuses three samples at once over propane burners with mechanical agitation of the crucibles. When the samples are homoge-... 

Place the uncovered beaker on a hot plate, and heat the contents vigorously until the center of the bottom of the beaker becomes clear. Remove the beaker, and cool to room temperature. Add 5 mL of hydrochloric acid, and heat again until white fumes evolve. After cooling, dilute the solution to approximately 100 mL with water, adjust to pH 6 0.2 with 10% sodium hydroxide, and heat the solution to boiling. Add 15 mL of 10% barium chloride solution, and leave the solution overnight in a fresh beaker in a steam bath at 90° to 95°. Filter through ashless filter paper (Whatman No. 42, or equivalent), and wash the precipitate with 200 mL of warm water. Transfer the paper and precipitate to a tared crucible. Heat the crucible slowly on a Bunsen burner to expel moisture. Place the crucible and contents in a muffle furnace at 850° for 1 h. Let the crucible cool in a desiccator, and then weigh the residue to the nearest 0.0001 g. Calculate the percent of sulfonate sulfur by the formula... 

Allow a crucible that has been subjected to the full flame of a burner or to a muffle furnace to cool momentarily (on a wire gauze or ceramic plate) before transferring it to the desiccator. 

If a precipitate is to be ignited in a porcelain filter crucible, the moisture should be driven off first at a low heat. The ignition may be done in a muffle furnace or by heating with a burner. If a burner is to be used, the filter crucible should be placed in a porcelain or platinum cradble to prevent reducing gases of the flame diffusing through the pores of the filter. 

The use of cokes as fuels, or the heating of crucibles and furnaces with gas or oil-fired burners can cause emissions of combustion products, such as NOx and SO2. Additionally, the use of cokes and the presence of impurities (e g. oil, paint,. . . ) in scrap can cause the production of some products of incomplete combustion or recombination (such as PCDD/F) and dust. 

Fig. 1.15. Crucible or pot furnace. Tangentially fired integral regenerator-burners save fuel, and their alternate firing from positions 180 degrees apart provides even heating around the pot or crucible periphery. (See also fig. 3.20.)...

Total Oxide, RO2. An aliquot of the zirconium hafnium solution that will provide approximately 0.5 g. of the ignited oxide is diluted with water to 100 ml. and treated with ammonium hydroxide to precipitate the mixed hydroxides. The precipitate is filtered on quantitative paper, washed free of sulfate, placed in a weighed crucible, and ignited (900°) to constant weight in a muffle furnace or over a Fisher burner. 

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