Calcine storage

The calcined product from the WCF is spherical and granular in nature and readily transported pneumatically to the calcine storage bins (100 yds distant) where it will be safe and readily retrievable. 

A calcine storage silo to store calcine with capacity for 6,500 tonne will be constructed, along with wet and pneumatic transport systems from the silos to the leaching plant for the calcine. 

Larese, C., Lopez Granados, M., Mariscal, R. et al. (2005) The effect of calcination temperature on the oxygen storage and release properties of Ce02 and Ce—Zr—O metal oxides modified by phosphorus incorporation, Appl. Catal. B Environ., 59, 13. 

CaC03 is then heated by secondary fuel combustion in the calciner. CaO is regenerated and C02 is released for storage according to the reaction in Equation (8). The calciner temperature can reach 900°C, depending on the C02 partial pressure. 

The CSIRO Division of Mineral Products, Port Melbourne, Victoria, Australia, is conducting research to develop a process to recover fluoride and aluminum from spent pot lining ash with concurrent production of an environmentally safe residue that is suitable for disposal. The proposed method involves initial calcination which thermally decomposes the cyanide in the spent pot lining. Successful completion of this research would reduce the amount of hazardous wastes that contain potentially harmful leachable cyanides that can enter the groundwater during open air storage. 

According to the vendor, PET is over 50% more cost effective than alternative treatment and storage technologies for low-level calcine waste (D20637B, p. 4). 

Figure 17. Weak acid recovery plant used by Sachtleben Chemie (based on know-how of Bayer AG) a) Heat exchanger b) Evaporator c) Injection condenser d) Stirred salt maturing vessels e) Filter press f) Bunker for pyrites g) Coal silo h) Bunker i) Mixing screw unit j) Covered store for mixed filter cake k) Calcination furnace 1) Waste-heat boiler m) Cyclone n) Electrostatic precipitator o) Stirred tank p) Storage tank q) Pump r) Cooler...

The solidification of waste takes place in two steps, a calcining step and an incorporation of the calcined material into borosilicate glass. Calcining can be done in various ways but primarily involves the removal of volatile products like water or NO3" and conversion of all species in the HLW to solid stable oxides. The oxides are then mixed with SiC>2, B2O3, and the like to make a borosilicate glass, which is then prepared for geologic storage (Fig. 16.13). 

An important point is to use metal hydroxides instead of metal oxides as adsorbents of S04. Since solid supcracids lose supcracidity by absorbing moisture and carbon monoxide [12], calcination in Pyrex glass tubes and storage in scaled tubes are recommended. 

Figure 21.13 TEM of commercial MgO smoke following calcination after prolonged storage in air. (Reproduced from [44] with permission).

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