Hardware furnaces

Because indirect-heat calciners frequently require close-fitting gas seals, it is customaiy to support aU parts on a selFcontained frame, for sizes up to approximately 2 m in diameter. The furnace can employ elec tric heating elements or oil and/or gas burners as the heat source for the process. The hardware would be zoned down the length of the furnace to match the heat requirements of the process. Process control is normaUy by shell temperature, measured by thermocouples or radiation pyrometers. When a special gas atmosphere must be maintained inside the cyhnder, positive rotaiy gas se s, with one or more pressurized and purged annular chambers, are employed. The diaphragm-type seal ABB Raymond (Bartlett-Snow TM) is suitable for pressures up to 5 cm of water, with no detectable leakage. 

Above temperatures of 900°F, the austenitic stainless steel and other high alloy materials demonstrate inereas-ingly superior creep and stress-rupture properties over the chromium-molybdenum steels. For furnace hangers, tube supports, and other hardware exposed to firebox temperatures, cast alloys of 25 Cr-20 Ni and 25 Cr-12 Ni are frequently used. These materials are also generally needed because of their resistanee to oxidation and other high temperature corrodents. 

Additional sources of the elements are tin slag and scrap. For instance, cassiterite deposits, in Australia, Brazil, Thailand and some other countries, contain a significant amount of tantalum. The bulk of this tantalum is collected in the slag and processed separately. Recycling of various tantalum-bearing scrap is also a veiy important source for tantalum production. These scrap materials include powder surplus from sintering operations, scrap from mill products, rejected and used capacitors, scrapped cutting tools and furnace hardware. 

Electric tube furnaces of appropriate dimensions are available from various manufacturers. A model RO 4/25 by Heraeus GmbH, Hanau, FRG is suitable. However, a very satisfactory furnace can be built by any well equipped laboratory workshop at little cost and effort. The material required consists of thin walled ceramic tubing, 3.5 cm i.d., nichrome resistance wire, heat resistant insulation, and ordinary hardware material. A technical drawing will be provided by the submitters upon request. The temperature of the furnace can be adjusted by an electronic temperature controller using a thermocouple sensor. A 1.5 kW-Variac transformer and any high temperature thermometer would do as well for the budget-minded chemist. 

Referring to the hardware in Figure 5—4, there are much larger facilities required for heavier liquids cracking than for ethane or propane. As you saw in Table 5—1, the yield of ethylene from the heavier feeds is much lower than from ethane. That means that to produce the same amount of ethylene on a daily basis, the gas-oil furnaces have to handle nearly five times as much feed as ethane furnaces. As the design engineer scales up these volumes, he or she has to worry about the size of the cubes necessary to heat up that much feed, the residence times best for each kind of feed, and the best pressure/temper-ature/steam mixture conditions. 

The reaction relies on the brute force of high temperatures and pressures and must be carried out in hardware much like the cracking furnaces described in the ethylene chapter. As always with cracking, undesirable reactions occur, resulting in the formation of CO2 and carbon. The latter is particularly a nuisance because it sets down on the catalyst and deactivates it. 

Numerous industrial solid wastes are disposed of in incinerators that have energy recovery capability. Most of these systems are smaller than MSW incinerators. The compositions of specific industrial wastes are more uniform than those of MSW, but the range of waste categories is so broad that special hardware and furnaces must sometimes be used. Rotary kilns, multihearth furnaces, and fluidized-bed incinerators have been employed for industrial waste incineration systems. 

A furnace which will serve every purpose in making potassium cyanide can be made with one of the five gallon cans, a galvanized bucket and a 20 pound bag of cat litter. You can get the bucket from any hardware store for under five dollars ... 

The tube furnace starts with a section of thinwall iron tubing about 75 cm long and 3 to 3.2 cm in internal diameter. Thinwall iron tubing has a metal thickness of. 024 inch. The outside of the tubing is wrapped with asbestos cloth or asbestos paper to a thickness of about 2 millimeters. Asbestos cloth or paper is available at hardware stores. 

Figure 9.18 is a schematic of BP s commercial demonstration unit39 for their process, which can be seen to have the expected hardware for a process of this type, namely heat exchangers for the feed which is mixed with hydrogen prior to and after the furnace, a downflow trickle bed reactor followed by a separator, coolers, and a stripper system to remove naphtha and diesel and adjust the flash of the product. 

Pyromet . [Carpenter Tech.] Nickel-base alloy for heat shiel(Is, furnace hardware, gas turbine engine ducting, combustion liners, chemi( l plant hardware, seawater applies. 

Before we consider crystal growth in detail, let us examine the hardware needed to obtain a melt. Many of the furnace components available have temperature limitations, and many of the crystals we might wish to grow have high melting points, i.e.- >1600 C. Thus, we may have to choose certciin combinations in order to get a furnace which will adequate for the task at hand. 

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