| OCR Text |
Show 5.2 Mo03 removal method 16 When a metal containing M o is heated to high temperatures, the M o on the surface oxidizes, becomes gaseous M o 0 3 and mixes in the exhaust. In the regenerative burner system, this M o 0 3 crystallizes on the low temperature parts of the regenerator element, attaches to the regenerator element, accumulates and may cause blocking of the regenerator element. To solve this problem, w e have made practical, a system equipped with a M o 0 3 removal method (Mo03 cleaning mode) as shown in Fig. 19. The method utilizes the characteristic of Mo03 in which Mo03 sublimates from a solid to gas at approximately 750°C. In concrete terms, this is a simple method in which combustion changeover which is normally made at fixed intervals is suspended temporarily for several to several tens of minutes. By this, the temperature of the burner regenerator element which sucks exhaust continues to rise, the temperature of the low temperature regenerator element part also rises above 750°C, the attached M o 0 3 again sublimates, and is discharged together with the exhaust. However to prevent overheating of the changeover valve and exhaust fan which are positioned down-stream, the damper installed in the air chamber below the regenerator element is opened to let in outside air, to dilute the exhaust and lower temperature to around 300°C. The above operation is conducted once a day for each burner. In an example where a regenerative burner was mounted using alumina balls for the regenerator element in a furnace to process material containing 4 % M o at 1270°C, pressure loss doubled in about 3 months by attachment of M o 0 3 in the past. With the addition of this cleaning mode, it has become possible to completely control the increase of pressure loss. High temperature exhaust gas M o 0 3 deposited part Outside,-^ air Damper opened Changeover valve fixed ] ? • Fig. 24 MoO removal method |
