Slags measurements

Can one explain this importance of the slag Measurements of conductance as a function of temperature and of transport number indicate that the slag is an ionic conductor (liquid electrolyte). In the metal-slag interface, one has the classic situation (Fig. 5.81) of a metal (i.e., iron) in contact with an electrolyte (i.e., the molten oxide electrolyte, slag), with all the attendant possibilities of corrosion of the metal. Corrosion of metals is usually a wasteful process, but here the current-balancing partial electrodic reactions that make up a corrosion situation are indeed the very factors that control the equilibrium of various components (e.g., S ) between slag and metal and hence the properties of the metal, which depend greatly on its trace impurities. For example,... 

Temperature values of calcine and slag, measured by laser pyrometer. 

VISCOSITY OF COAL-ASH SLAG. Measurement of viscosity of coal-ash slags provides reliable data that can be used for determining suitability of coals for use in slag-tap-type boilers. 

Compared to natural gas and oil, complete combustion of coal requires higher levels of excess air, about 15% as measured at the furnace outlet at high loads, and this also serves to avoid slagging and foifling of the heat absorption equipment. 

Shear viscosity is a measure of the ahihty of one layer of molecules to move over an adjacent layer. Bulk viscosity will be mentioned in Section V.2. Since viscosity usually refers to shear viscosity, the term will he used in this way unless otherwise stated. Recommended techniques for measuring the viscosity of high-temperature melt are given below. Experimental data are available from the database mentioned in Section 1.2. Data on viscosities of slags (7 single component systems, 35 two-component... 

It is necessary to measure the viscosity under the condition of a small Reynolds number, and experiments with high precision can be expected for viscosities over 0.1 Pa s. This method has also been used to measure the viscosity of slag melts,when the time taken to pull a ball out of the melt with constant force was measured. 

Mills has concluded in his review article on molten slags that (1) most viscosity measurements were subject to experimental imcertainties of 25% (2) in some cases experimental uncertainties could be > 50% and (3) experimental uncertainties as low as 10% could be achieved by careful calibration of viscometers with high and low temperature reference materials. 

In the laser flash method, a melt of interest is placed between two parallel plates. The upper plate is heated stepwise and the thermal diffusiv-ity is measured from the rise in temperature. The specific design for molten materials and especially slags employed by Ohta et al. is based on the differential three-layer technique utihzing a special cell that can be accommodated in the system. A schematic diagram of the principle of the measurement section is shown in Fig. 31. A laser pulse irradiates the upper (platinum) crucible and the temperature response of the surface of the lower platinum crucible is observed, a liquid specimen being sandwiched between the two. 

The sum of measured volumes of these gases represented less than 1 percent of the total gas volume generated. However, the solubility of these gases in the reaction water was not accounted for. Any one of these gases (except methane and carbon monoxide), or a combination of them, could contribute to the observed odor. Furthermore, the reaction of the slag with water may give rise to potential health hazards if workers are exposed to excessive concentrations of these gases. 

Mass balance measurements for 41 elements have been made around the Thomas A. Allen Steam Plant in Memphis, Tenn. For one of the three independent cyclone boilers at the plant, the concentration and flow rates of each element were determined for coal, slag tank effluent, fly ash in the precipitator inlet and outlet (collected isokinetically), and fly ash in the stack gases (collected isokinetically). Measurements by neutron activation analysis, spark source mass spectroscopy (with isotope dilution for some elements), and atomic adsorption spectroscopy yielded an approximate balance (closure to within 30% or less) for many elements. Exceptions were those elements such as mercury, which form volatile compounds. For most elements in the fly ash, the newly installed electrostatic precipitator was extremely efficient. 

As in the case of the slag tank, there was no way to measure quantitatively the precipitator residue flow rate. These residues are slurried with water and flushed continuously into the ash pond. However, for all of the elements except selenium, the precipitator was extremely efficient (>95%) as calculated from the inlet and outlet fly ash concentrations using Equation 6. The reason that selenium fails to be scavenged effectively is not known and certainly warrants investigation. One possibility is that part of the selenium is in a volatile state but is readily adsorbed on particulates trapped by the alundum thimbles. 

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