Catalytic Effect of Some Oxides on Calcination of Sodium Nitrate
- PDF / 828,017 Bytes
- 5 Pages / 414.72 x 648 pts Page_size
- 72 Downloads / 214 Views
CATALYTIC EFFECT OF SOME OXIDES ON CALCINATION OF SODIUM NITRATE
A. N. Sembira and M. M. Perez Dept. of Chemical Engineering, Nuclear Research Center Negev,
Ben-Gurion University of The Negev. P.0.Box 9001,Beer-Sheva,Israel.
ABSTRACT The calcination process used for sodium nitrate could be the most important part of the liquid-waste calcination process used in high-level-waste (HLW) disposal. A French process that involves conversion of the solution of nitrate fission products into a solid mixture of oxides and undecomposed nitrates. These products are then mixed with a glass-making mixture (called a fritIin an induction melting pot. In 1984, Utake et.al. , suggested the use of the Sol-Gel technique to decrease the calcination temperature of NaNO0• In this work, we used the thermal-analysis t~chnique to study the catalytic effect of some glass network formers like Si02 , B2 0 and of some network modifiers like Al 0 Fe 2 0 , MgO, TiO 2 ' ZnO. The-b~st effect was achieved by adding 20% diaio~aceous3earth (Kieselguhr) and 20g B 0 In that case, the calcination temperature onset decreased from 780 C ?o 3 565°C. The advantages of this process are as follows: 1. The proposed additives (Kieselguhr and B 20) are glass network formers that have to be added anyway in the next piocess step. 2. In the proposed process, no sodium is added, and the only process change suggested is that the glass formers (or part of them) should added at the calcination step, rather than at the glass-melting step. 3. The proposed modification is easily achieved and is expected to improve the homogenization of the final product. INTRODUCTION The partial denitration of sodium nitrate, as well as the partial or total denitration of the other nitrates, is the first step of the French vitrification process. This denitration is achieved by feeding the active liquid waste into a rotating furname The maximum temperature inside this 0 equipment is in the range of 600 C''. The liquid is evaporated and the solid is calcinated and trar erred to the next step in the process. In 1984, Uetake et.al. suggested the Sol-Gel process, to make nuclear radioactive glass at low temperature. For nuclear wastes that contain sodium as the main component (such as the waste in the Savannah River Plant) the suggested Sol-Gel process is not useful, because the additional sodium as sodium silicate will concentrate in the final product and will increase the leaching rate of the glass. The purpose of this research is to suggest an alternative process that will reduce the thermal decomposition temperature without adding sodium to, the final product and without changing the unit operation of the process.
EXPERIMENTAL The thermal-analysis experiments were performed using a Perkin-Elmer DTA1700 that operated in diffrential scanning 5alorimetry (DSC) mode. The solid dried powder was mixed in original 100mm platinum Perkin-Elmer
Mat. Res. Soc. Symp. Proc. Vol. 294. ©1993 Materials Research Society
104
liner. The sample weights were 15-20 mg, and the same weight of aluminum oxid
Data Loading...
