Furnace performance temperatures

Wet mixes are usually dried before calcination. Calcination is performed continuously in rotary or tunnel kilns, or batchwise in directly fired drum or box furnaces. The temperature at which the mixed metal oxide pigments are formed can be reduced by adding mineralizing agents [3.75]. In the case of chromium rutile pigments, addition of magnesium compounds [3.81] or lithium compounds [3.80] before calcination improves thermal stability in plastics. 

Figure 8 shows the discharge profile of a cell with different gas flow rates heated to a furnace set temperature of 606°C. A maximum power density of about 0.66 W/cm2 (corresponding to 0.44 V) was obtained at a cell temperature of 744°C using a porous electrolyte. Performance of the cell increased with increasing gas flow rate however, this could usually be attributed to an increase in temperature [4],... 

To perform quenching experiments utilizing a horizontal furnace, the tube-in-tube assembly is modified slightly, as follows the normally evacuated and sealed inner tube-in-tube is inserted into an open-ended closely fitting thick-walled tube. This assembly is placed into another closely fitting tube, which is evacuated and sealed. These runs were successfully carried out for experiments in platinum or in platinum-rhodium wound horizontal furnaces with temperatures beyond 1400 °C. After a predetermined heating period the probes were quenched in either air or water. 

The sample was pulverized using an agate mortar and placed in a cell. The thickness of the sample was adjusted to obtain lelectrically controlled furnace. The temperatures at which measurements were performed were r.t., 40, 80, 120, 160, 200 and 220°C. The spectra obtained are shown in Fig. 3. 

The properties which determine heat transfer through a deposit layer of given thickness are thermal conductivity, emissivity, and absorptivity. These properties vary with deposit temperature, thermal history, and chemical composition. Parametric studies and calculations for existing boilers were carried out to show the sensitivity of overall furnace performance, local temperature, and heat flux distributions to these properties in large p.f. fired furnaces. The property values used cover the range of recent experimental studies. Calculations for actual boilers were carried out with a comprehensive 3-D Monte Carlo type heat transfer model. Some predictions are compared to full-scale boiler measurements. The calculations show that the effective conduction coefficient (k/As)eff of wall deposits strongly influences furnace exit temperatures. 

Clifton Park, New York). The samples were then imaged using a LEO 1530 PEG SEM with Energy Dispersive X-ray Spectroscopy (EDS) capability. TGA analysis was performed with a TGA 2050 thermogravimetric analyzer from TA Instruments. A silica sample of 10 mg was placed in a ceramic pan and the pan positioned in the TGA furnace a temperature ramp at a rate of 10°C/min was used to heat the sample from room temperature to 800°C in an air flow of 100 seem. 

Whether preheated air is desirable to improve furnace performance. The temperature of furnace exit gases can increase considerably. 

The experimental apparatus employed to study the catalytic performance of the samples consists of a flow measuring and control system, the reactor and an on line analytical system. The reactor is a 30 cm long pyrex tube with an expanded 2 cm long section in the middle (8 mm l.D.) in which the catalyst sample is placed. The catalyst powder is held in dace by means of quartz-wool pieces. The furnace temperature is controlled by means of a temperature contrcdler using a K-type thermocouple placed between the reactor and the walls of the furnace. The temperature inside the catalyst bed is measured by means of a K-type thermocouple (0.5 mm O.D.) placed in a 1/16 O.D. ss well which runs through the center of the cell. 

The temperature profile in Run A corresponds to an ordinary sidewall-fired furnace. The temperature profiles in Run B allow establishment of reforming equilibrium at the outlet due to the reduced firing in the bottom. The profile in Rim C simulates maximum heat flux at the very bottom similar to a bottom-fired reformer. It is evident that such changes can only be performed in a pilot plant. 

Although the above calculations are simplistic they can be used to clearly illustrate the impact of key process parameters on furnace performance, such as the CO C02 ratio in exit gas, the Pb content of sinter, the blast rate and the oxygen content of blast air. There are other practical limits on these parameters to maintain practical operating temperatures at various regions in the furnace shaft, and to minimise the formation of accretions and other obstructions. 

Depending on the smelting process used there can be limits to the acceptable proportion of feed represented by such residues. For the sinter plant-blast furnace combination the input of sulfate residues is commonly limited to around 25 per cent of net new feed. The decomposition of lead sulfate is endothermic and can limit the attainment of peak bed temperatures in the sinter plant, affecting the quality of sinter produced, which is critical to blast furnace performance. This is discussed in detail in Chapter 4. Many of the direct smelting processes covered in Chapter 7 are more able to cope with residue feeds, particularly the Kivcet and Kaldo processes. 

Plate (16 mm, or 0.640 In., thick) and bar (13 mm, or 0.5 in., diameter) were solution treated above the transus, water quenched, and aged at temperatures indicated in neutral salt baths or air circulating furnace with temperature control to 10 °C. Yield strengths varied from 65 to 1103 MPa (140 to 160 ksi). Tests were performed on standard Charpy specimens In three-point bending to determine plane-strain fracture toughness. 

The test equipment shown in a schematic drawing in the mefliod consists of a test flask, a furnace, a temperature controller, a syringe, a thermocouple and other auxiliary parts. The measurement is performed in a dark room for optimum visual detection of cool flames. The results are reported as ignition temperature, time lags (delay between sample insertion and material ignition), and reaction threshold temperature (the lowest flask temperature at which nonluminous pre-flame reactions (e.g., temperature rise) oceur). 

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