Circular furnace

One and one-half grams of clean sodium are placed in a boat and inserted into a combustion tube mounted in a circular furnace. Bone-dry ammonia is passed through the apparatus which is heated to 850°C and maintained at this... 

In the age of the Hubble Telescope, the mirrors for such giant structures often use as much as 20,000 lb (9,000 kg) of a Pyrex-like glass called borosilicate. Such a vast stretch of material, 7 yd (6.5 m) across, cannot be ground normally. Surface irregularities could too easily develop. The material is melted and whirled in a huge circular furnace until it settles into shape. Afterwards the exterior is polished by a computer-programmed machine, to avoid human error as much as possible. 

In the eleventh and final picture of this series, we see the courtyard of a magnificent palace. The naked alchemist sits chest-deep in a cylindrical bath, which rests upon a circular furnace. The... 

Circular Exhibit 7-3 illustrates a circular furnace that houses tubes mounted vertically or helically in the radiant seaion. These furnaces are generally used for such smaller duties as start-up heaters or reboilers. Inlet and oudei connections are usually located at the top or the bottom of the radiant section, depending on... 

This seaion describes the general arrangement of various types of furnaces and discusses how operatidn and naaintenance affect furnace elevation, how to plan all necessary access, and platform requirements, associated equipment, and stack design. Exhibit 7-14 shows a typical arrangement of a circular furnace. 

Because furnace tubes must be periodically replaced, clear areas are provided directly in line with the tubes. The removal mechanism may be a trolley beam located on the stack of a circular furnace, a crane, or a cherry picker. If only one or two tubes require removal, a tube extraaor, similar to the type used for extracting shell and tube exchanger bundles, may be used. As can be seen in Exhibit 7-l6, radiant... 

EXHIBIT 7-16 Radiant Tube Removal in a Circular Furnace... 

A circular furnace platform layout is shown in Exhibit 7-22. The firing platform, v ich is usually a full 360 circle, can be reached by a variety of stairway configurations and ladders, as illustrated on the lower plan in this exhibit. Each scheme shown may be set to accommodate the layout as required. Stairway variations shown here are ... 

Exhibits 7-33 and 7 34 present simplified piping and instrumentation diagrams for a circular furnace. The furnace has 6-in inlet and outlet lines, with control valves, combination burners, and soot blowers in the... 

The lower level of the circular furnace is shown in Exhibits 7-37 through 7-39. In the radiant seaion, all piping should be grouped together for common sup-... 

The first of these reactions takes place at temperatures of about 150°C, the second reaction proceeds at about 550—660°C. Typical furnaces used to carry out the reaction include cast-iron retorts the Mannheim mechanical furnace, which consists of an enclosed stationary circular muffle having a concave bottom pan and a domed cover and the Laury furnace, which employs a horizontal two-chambered rotating cylinder for the reaction vessel. The most recent design is the Cannon fluid-bed reactor in which the sulfuric acid vapor is injected with the combustion gases into a fluidized bed of salts. The Mannaheim furnace has also been used with potassium chloride as the feed. 

Multiple-Hea.rth Roasters. The circular types consist of a series of hearths arranged vertically in such a way that the ore entering the top is rabbled and dropped down from hearth to hearth, until it is completely oxidized. The hearths are usually stationary and the plows revolve, such as in the Wedge, Herreshoff, Ord, Skinner, and other roasters (21). In other furnaces, the hearths revolve and the rabbles are fixed, eg, the deSpirlet and its modification, the Barrier. 

The circular burner shown in Fig. 27-17 is widely used in horizontally fired furnaces and is capable of firing coal, oil, or gas in capacities as tigh as 174 GJ/h (1.65 X 10 Btii/h). In such burners the air is often swirled to create a zone of reverse flow immediately downstream of the burner centerline, which provides for combustion stability. 

The basic configuration and features of the multiple hearth incinerator are illustrated in Figure 23. This incinerator is the most prevalent incinerator technology for the disposal of sewage sludge in the U.S. due to it s low ash discharge. Sludge cake enters the furnace at the top. The interior of the furnace is composed of a series of circular refractory hearths, which are stacked one on top... 

Typically, modern, vertical boilers are of tubeless design. They contain a suspended, dry-back, two- or four-pass, circular water jacket, of pressure vessel construction, about 5/16th inch (7.94 mm) in thickness. The inner tube of the water jacket is in reality the furnace tube, whereas the outer tube is the boiler shell. 

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