Walls, furnace

Refractory organics Refractory-wall furnaces Refrasil Refrigerant... 

These furnaces may operate batchwise or continuous. In the batch, intermittent, or periodic types, the content is heated at the desired temperature for the stipulated time and then removed. In the continuous type, the charge moves at a predeterrnined rate through one or more heating 2ones to emerge in most cases at the end opposite the point of entry. Figures 9 and 10 are representative examples of typical, industrial refractory-wall furnaces. 

Chemical Vapor Deposition- Deposition of silicon oxide films is accomplished by CVD equipment. Either plasma CVD or ozone oxidation is used. Blanket tungsten films are also deposited by CVD equipment to create contact and via plugs. Polysilicon and silicon nitride films are deposited in hot-wall furnaces. TiN diffusion barrier films are deposited by either sputtering or CVD, the latter giving superior step coverage. 

The FPL vertical wall furnace used in our study was described in some detail by Brenden and Chamberlain (6). This furnace is normally used to evaluate the fire endurance of wall assemblies. The basic guidelines for the furnace test method are given in the ASTM E-119 standard (5). The method was designed to evaluate the ability of a structure to withstand a standard fire exposure that simulates a fully developed fire. The furnace is gas fired, and its temperature is controlled to follow a standard time-temperature curve. A load may be applied to the assembly. The failure criterion can be taken as time at burnthrough, structural failure, or a specified temperature rise on the unexposed side of the wall—whichever comes first. The construction of the furnace is not specified in the ASTM E-119 standard. 

Refractory raw materials, 21 483-491 composition of, 21 484 87t Refractory sales, U.S., 21 507t Refractory-wall furnaces, 12 328, 330 Refrigerant-absorbent combinations, 21 525... 

Tests at900°C. The long period or equilibrium apparent leak rates of both the mullite and zircon double-walled furnace units are of the order of the limit of error of the author s measuring method, i.e., 1.7 to 3.4 X 10-9 l.-mm. of mercury per second, or 2 to 4 X 10-9 cc. at N.T.P. per second. These values were observed after 15 to 24 hours of pumping and after exposure to a dry gas atmosphere with the zirconium specimen removed. Control experiments were made without the furnace tube present. 

In many modern top-fired reformers the heat flux calculated for the inner tube wall surface is around 60 000 W/m2, although in some designs it cam be as high as 75 000 W/m2. The maximum heat flux may be 1.4 to 2 times higher. In side-fired and terraced-wall furnaces, where the mean fluxes are generally in the range of 60 000-85 000 W/m2, the difference between mean and maximum flux is much smaller, as shown in Figure 37 [444],... 

The terraced-wall type, developed by Foster Wheeler may be regarded as an intermediate between the side-fired and bottom-fired tubes. The reformer has inclined walls with several terraces on which upward firing burners are installed. This unique burner positioning makes it possible to adjust the heat flux in each zone. Figure 41 is a schematic drawing of the Foster Wheeler terraced-wall furnace [426],... 

At this time, 1977-1978, it appears that the current best boiler-furnace design in use for large, high pressure units is the completely water-tube-walled furnace and radiant section, studded and coated with thin plastic refractory in the intense burning zone, followed by one or more long, open, vertical radiation passes preceding a convention-type superheater and boiler-convection passes and economizer. 

The development of the modern water-tube wall furnace/boiler was in part due to the need for proper air pollution control of incinerators. Flue gases can be cooled with massive air dilution, water spray or boiler. Energy recovery in boilers is the preferred cooling method if a reasonable market can be assured or anticipated. The almost universally accepted method for particulate removal is the electrostatic precipitator. Scrubbers alone have usually failed to meet the particulate standards. 

Figure 1.8 gives a simplified representation of the steam reforming section for natural gas, using a terrace wall furnace equipped with peripheral facilities (desulfurization, waste heat boilers, steam drum eta). 

Diagram c in Fig. 114 gives the metal skin temperatures of the vertical tubes for a terrace wall furnace, as well as the temperatures reached by the wa s and supports. The top part of the figure shows the suspension of the coils by hangers, rod and counterweight Heating is provided in this case by combination burners running both on gas and fad oil atomized with steam, in the form of a line burner for the gas. and a tunnel burner for the fuel. 

Parylene is a unique CVD deposited insulating pol3uner, first discovered in 1947 [52]. The material is supplied as a metastable dimer first described by [53]. The dimer is sublimed under vacuum and flows into a hot wall furnace where it is cracked into a pair of direactive monomer units. These then flow by diffusion into the deposition chamber, which is near or below room temperature, and condense into a high molecular weight polymer. The polymer is fully reacted without the need for any post-processing. 

The hottest gas within a furnace (or any enclosed chamber) rises to the top, creating a higher pressure at the furnace s higher elevations and a lower pressure at the furnace s lower elevations. (This is stack effect within the furnace.) The zero gauge-pressure plane or neutral pressure plane is the locus of points where the pressure inside the furnace is the same as the atmospheric pressure outside the furnace at the same elevation. The neutral or zero plane is the boundary between + and — pressures within the furnace. If there are leaks through the furnace walls, furnace gases will leak outward from the space above the neutral plane and air will leak inward to the space below the neutral plane. (See fig. 6.13.)... 

The inside wall furnace temperature is 982.2°C, and the outside of the tube is 537.8°C. What is the rate of heat transfer ... 

The Foster Wheeler reformer furnace is a Terrace-Wall furnace. The unique feature of this side-fired design is the burner location (Fig. 27 and 28). The burners are directed at the walls of the furnace, which radiate heat to the tubes. As with the top-fired reformer, the process gas enters the top and passes to the bottom. Unlike many top-fired furnaces, the terrace-walled furnace tubes have... 

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