Magnesium melt treatment

There are four main metal treatment (or refining) operations carried out in magnesium melting processes. These are as follows ... 

After treatment with water to dissolve out the magnesium salts, and after evaporation of the ether which generally is used as solvent, sticky resinous polymers are left. Their rather low melting point (about 100°) suggests that the phenylene-silicon chains are rather short, and probably they are terminated by methyl groups or by phenyl groups derived from the hydrolysis of structures like Si—CeH4MgBr. 

Magnesium oxide particles in the 2- to 7-p.m median particle size range deposit in the convection pass preferentially, while finer sized particles are not deposited and tend to get carried into the back end of the boiler. When an MgO of 2-p.m median particle size is fed into the fuel at treatment rates of 0.5-1.0 parts by weight Mg to 1.0 part V in the oil, the quantity of MgO deposited on the superheater tubes is 2-3 times that of the V and Na. This treatment rate results in a high Mg V ratio, which is needed to raise the ash-melting point and reduce tube deposits. 

Castrillejo et al. studied the solubility of magnesium oxide in the molten CaCl2-NaCl equimolar mixture at 575 °C [178]. The solubility product index was found to be pPMg0 = 5.3 0.1, on the molality scale. Nevertheless, the information presented in Ref. [178] makes it possible to obtain additional data on the behaviour of MgO in the studied melt. To realize this let us consider Fig. 3.7.18. The first two points in the potentiometric curve can be established, on the basis of the treatment method in Part 6, to belong to the unsaturated... 

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