Furnace load

Power Supplies and Controls. Induction heating furnace loads rarely can be connected directiy to the user s electric power distribution system. If the load is to operate at the supply frequency, a transformer is used to provide the proper load voltage as weU as isolation from the supply system. Adjustment of the load voltage can be achieved by means of a tapped transformer or by use of a solid-state switch. The low power factor of an induction load can be corrected by installing a capacitor bank in the primary or secondary circuit. 

Carhon Monoxide Carbon monoxide is a key intermediate in the oxidation of all hydrocarbons. In a well-adjusted combustion system, essentially all the CO is oxidized to CO9 and final emission of CO is veiy low indeed (a few parts per million). However, in systems which have low temperature zones (for example, where a flame impinges on a wall or a furnace load) or which are in poor adjustment (for example, an individual burner fuel-air ratio out of balance in a multiburner... 

A particularly striking recent application was by Deevi and Sikka (1997) they developed an industrial process for casting intermetallics, especially nickel alumi-nides, so designed (by modifying the furnace-loading sequence) that the runaway temperature rise which had made normal casting particularly dangerous was avoided. 

FIGURE 7.16. Hierarchical Task Analysis of the Task of Increasing Furnace Load. 

Because little has been said concerning difficulties arising from derivati-zation of samples to render them suitable for GC analysis, replacement of GC by HPLC for non-volatile or thermally labile compounds is a possibility. However, the demands of reproducible solvent removal for a reliable LC-C-IRMS approach are formidable. Caimi and Brenna [685,686] have developed an instrument based on a moving wire transport system. The analytes are deposited on the wire as they elute from the HPLC column and, after solvent drying at 200 °C, are transported into an 800 °C combustion furnace loaded with CuO, where the resulting C02 is picked up by an He carrier stream and swept via a drying trap into the IRMS. 

Results of the flexibility study are shown in Table III. The furnace loading is limited by the crossover temperature and radiant duty in the case of both ethane and n-butane feeds. In the case of naphtha feed, the constraints were the radiant duty and the tubeskin temperature. The maximum loadings for the ethane, n-butane and naphtha feeds were 4,450, 5,000, 4,625 lb/hr/coil, respectively compared to 4750 lb/hr/coil for the propane feed. 

Keywords tubular furnaces, load balancing control, dynamic simulations. 

The presence of contaminants and oxides in the furnace load, will consume part of the melting energy. Furthermore, the removal of slags necessitates a higher bath temperature to keep the slags in a liquid state. 

Q1. How can furnace loads be heated without scaling (oxidizing) ... 

Trinks and Mawhinney s 5th Edition mentions heating more load per unit of hearth area by alternating short-flame and long-flame burners. Prior to that, one of Professor Trinks countrymen, Dipl. Ing. Otto Lutherer, Chief Engineer of North American Mfg. Co., dreamed of being able to increase the heat flux to a furnace load by alternating luminous and clear flames in furnaces. 

Mr. Lutherer reasoned that the opaque soot particles in luminous flames would increase radiation to furnace loads and refractory crown, and that if clear flames then momentarily replaced them, that would allow the refractory to radiate to the load and dump its accumulated high-thermal-head heat on the load. 

Because ample heat can usually be released at sufficiently high temperatures in industrial furnaces, the next problem to be studied in calculation of furnace capacity should be heat transfer to the furnace load and temperature equalization within the load. With adequate heat release at sufficiently high temperature assured, note the following factors that affect furnace capacity. 

The principal purpose of indirect firing is to protect the furnace load from corrosion, oxidation, carbon and/or hydrogen absorption, or other reactions with the poc. The protection is accomplished by placing a solid barrier wall between the poc and the load, and by pumping an inert atmosphere into the chamber on the side of the wall where the load is located. The barrier wall may be refractory or metal, but it must... 

Preheating furnace loads by using waste heat... 

Fig. 5.17. Schematic piping for diiution air for a recuperator. TSBA = temperature sensor for controi of bieed-off air, TSDA = temperature sensor for control of dilution air. Both elbows at the right function as in fig. 5.21 to prevent radiation between recuperator and the furnace load from damaging either. Both eibows aiso assure good mixing between the furnace poc and dilution air, and both eibows prevent the TSDA from being fooled by seeing hotter or colder surfaces in the furnace or recuperator. If a velocity thermocouple at or near the same location, or a wall-mounted sensor, is found to be reading, say, 50° low, the setpoint should be adjusted 50° lower to protect the recuperator.

Ducting between a recuperator and a furnace must follow the dictates of figures 5.21 and 5.22. The top views of figure 5.21 are concerned about damage to the recuperator the lower two views are concerned about damage to the furnace load. The solutions for both are the same, and apply to most types of recuperators. 

In furnaces loaded with pieees of very different front-to-back dimensions, three or more lengthwise zones are neeessary for uniform heating. In furnaces loaded with pieces having very different thieknesses (vertically), two or more vertical zones should be used to achieve uniform heating. 

The increased mass flow of gas in the passages below the loads becomes a stabilizing factor in holding a near-constant temperature aeross the furnace load s width. 

---