Furnaces design differences

The various designs differ in the extent to which heat exchange is used, in the plan of the pipe-stiU furnace, in the distillation pressure, and in whether recycle of pitch or base tar is involved. 

MDSC, developed by TA instruments (New Castle, Detroit, U.S.A.), is based on the conventional heat flux DSC furnace design. The temperature programs differ... 

In order to maintain the furnace running in a safe, stable, and high-efficiency state it is necessary to control the outlet temperatures of the multiple passes to be the same. Traditional control methods usually have difficulties in controlling these temperatures, and some advanced control methods are too complex for a convenient use. In this paper, a control technique is proposed to distribute the inlet flowrates so that the outlet temperatures are as identical as possible. The principle of the proposed method is firstly explained and demonstrated, then the system analysis, the controller design, and the simulation experiments are presented, and finally the results of application to an industrial refinery furnace are reported. This technique has the following advantages it does not need complicated design procedures, the controller structure is simple, it is easy to apply and it can be extended to furnaces with different number of passes. 

As previously mentioned, secondary smelting operations include many variations of furnace design, operating conditions, and type of feed. Some of these differences include the following. 

Experiments using different probes were conducted in Air Products combustion laboratory furnace shown in Figure 7.58 [46]. The furnace design has been described... 

Pyrolysis and atomization curves of manganese are shown in Fig. 2. The pyrolysis curve was obtained using 2300°C as the atomization temperature. The selected pyrolysis temperature for Mn in THFA is about 1600°C. Using this pyrolysis temperature, the optimum atomization temperature corresponds to 2100°C. These pyrolysis and atomization temperatures do not correspond to the THGA suggested temperatures [21], as the furnace design is different and the rate of the vaporization process is also different. Some loss on manganese is observed above 2100 C, due to the volatility of the atomic species at hi temperature. 

Fuel-fired (combustion type) furnaces are most widely used, but electrically heated furnaces are used where they offer advantages that cannot always be measured in terms of fuel cost. In fuel-fired furnaces, the nature of the fuel may make a difference in the furnace design, but that is not much of a problem with modem indusfrial furnaces and combustion equipment. Additional bases for classification may relate to the place where combustion begins and the means for directing the products of combustion. 

A13. A security factor of 1.3 is suggested, applied to the maximum burner firing rate and with flue gas exit temperatures 200°F (111°C) above the furnace running temperature at maximum rates. Some furnace designers may be irritated by these specifications, but they are needed to recover a furnace s normal temperature profile quickly. These specifications are more necessary for a mill with many delays to provide the versatility needed. It is important to be aware of different goals—furnace designers want to build an inexpensive furnace so that they can get the order, but operators want versatility to be able to heat and roll as many tons as possible. 

Spalling or thermal shock damage of fireclay refractories has always been a concern of furnace designers and operators. It is not always obvious which brand of fireclay brick will exhibit the best spalling resistance from physical property data alone. Three different brands of fireclay brick are given with their physical properties and spalling loss in laboratory tests in Table 6. 

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