Iodide refining metal zirconium metal as the main reaction, the relevant parameters and their influence to 7 shown in Figure 1, Table 1.
Table 1 Transfer coefficient of impurities in iodine refining zirconium
element | Al | C | Cr | Fe | Hf | N 2 | Ni | Si | Ti |
Transfer coefficient | 0.64~0.73 | 0.02~0.11 | 0.02 | 0.23~0.325 | 1 | 0.003～0.075 | 0.006 | 0.12 | 1 |
The vapor pressure (kPa) equation for zirconium iodide ZrI 4 (Ï=4.36/m 3 ) is:
(548～645K)
(646～678K)
Dissociation reaction Z rI4 ( g ) = Zr + 4I ( g ) equilibrium constant K = (p I ) 4 / p ZrI4 is:
(1273～1583K)
Fig.1 Relationship between partial pressure of various substances in Zr-I 2 system and temperature and total pressure
( )
a-P total = 10Pa; b-P total = 10 - 3 Pa; c-P total = 0.1MPa
Figure 2 Relationship between decomposition rate and pressure of iodine at different temperatures
1-600 ° C; 2-800 ° C; 3-1000 ° C; 4-1200 ° C; 5-1400 ° C
Fig. 3 Variation of partial pressure of zirconium iodide (1,3) and iodine (2,4) with total pressure
1,2-1327 ° C; 3,4-1427 ° C
Figure 4 The logarithm of the equilibrium constant versus temperature
Figure 5 shows the vapor pressure and hot wire temperature of zirconium iodide when starting low zirconium iodide
Figure 6 Relationship between production rate and temperature of crystal strips
(Use a container with a diameter of 30.5cm, a single-needle type hot wire with a length of 160cm, and a constant temperature of 285°C)
Figure 7 Relationship between the growth rate of zirconium and the solid phase (crude zirconium) temperature (the temperature on the curve is the hot wire temperature)
The process conditions for iodinated metal zirconium are shown in Table 2.
Table 2 Metal zirconium iodide refining process conditions
Deposition size | 0.61 in diameter, 1.76 in length, 0.55 diameter molybdenum spacer | Inner diameter 0.229, length 0.610, sponge zirconium cover diameter 0.178 | ||
Hot wire starting size / mm | A diameter of 2.4, a length of 15000, a total of 6 pieces, each of which is bent into an equal length hair needle type wire ring | Diameter 2.54 total length 2030 | Diameter 2 | |
Charge | 136kgZr 2.5 to 3.5 kg I 2 | 9.07 kgZr 0.25 kgI 2 | 1kg zirconium with 50g iodine | 1kg zirconium with 50g iodine |
Coarse zirconium temperature / °C | 350 | 340 | 250~300 | 300 |
Hot wire temperature / °C | 1300 | 1300～1400 | ||
Vacuum before iodine sublimation / kPa | 1.33×10 - 6 | 1.33×10 - 6 | ||
Hot wire voltage / V | 65~245 | 33.0 (beginning) 14.6 (final) | ||
Hot wire current / A | 1600 | 75.0 (beginning) 800 (final) | ||
End of hot wire diameter / mm | 25~30 | |||
Reaction time / h | Stop reaction when power is less than 75kW | 32 | 30~40 | 30~40 |
Crystalline zirconium weight / kg | 53 | 2.8 | ||
Deposition rate / kg · h - 1 | 0.4 | |||
Crystalline zirconium typical analysis /% | Al=0.003 C=0.01 Ca<0.005 Cr=0.003 Cu=0.0005 Fe=0.02 H=0.002 Hf=0.004 Mg<0.001 Mn<0.001 Mo<0.001 N=0.001 Ni=0.003 O=0.02 Pb<0.001 Si=0.003 Sn<0.001 Ti=0.001 | Al=0.003 C=0.01 Ca<0.005 Cr=0.003 Cu<0.005 Fe=0.02 H=0.001 Hf=0.001 Mg<0.001 Mn<0.001 Mo<0.001 N=0.001 Ni=0.001 O=0.001 Pb<0.001 Si=0.003 Sn<0.001 Ti=0.001 |
Schematic diagram of ZrI4 thermal dissociation purification zirconium equipment is shown in Fig. 8.
Figure 8 ZrI4 thermal dissociation purification zirconium equipment
1-porous molybdenum screen; 2-crude zirconium; 3-electrode; 4-purified zirconium wire; 5--iodine bottle
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