Componentry, constructive and process solutions of sodium vapour precipitation problem

Sodium vapour trap for periodic operation (SVT) is installed to present of sodium vapour emissions after response of safety valve on tanks with sodium and to provide protection from sodium vapour during planned argon blowing from tanks. It is recommended that SVT be placed directly above tanks with sodium. But the main problem of BN-600 and BN-800 componentry (grouping) is the lack of premises. So, the recommended placement is impossible. The principal scheme of SVT piping BN-800. Argon purification from sodium vapor is carried out by air refrigerating. Refrigerating degree is regulated by control valve on the air delivery pipe to SVT. There is montejus tank in the scheme of SVT piping for liquid sodium drainage that is condensed in SVT. Sodium drainage pipe is combined with argon delivery pipe (line E). There are two main problems with the present construction of SVT based on operation experience of BN-600: 1. The horizontal pipeline 'Ar+Na' before the SVT entrance is a dangerous section of this piping. Electric heating of this pipeline is always 'on'. Inspite of this, sodium vapour condenses before SVT. It means that the pipeline becomes progressively clogged up. 2. Two substances (argon with sodium vapour and liquid sodium) are moving towards each other in one pipeline (line E). This is the most probable place of clogging by sodium, especially branch-pipe in the connection point of line E with SVT. Sodium cruds turn into solid state in the process of argon delivery pipe clogging.In most cases solid scrubs melting temperature exceeds 400-500C depending on chemical composition of crud (for example caustic soda - 1200C). It means that it is almost impossible to heat the pipeline to restore its passability. The only measure in this case is the change of pipe section during BN stop. The first problem can be solved by: - Increasing the diameter (which was DN40 in the project of BN-600, and is DN80 in BN-800); - Increasing the temperature of electric heating; - Minimizing pipeline lengths; The second problem can only be solved by changing SVT design: The principal scheme of SVT piping that is optimal in the lack of premises. Argon delivery pipeline is separated from sodium drainage pipeline. Drainage clogging is less probable in such SVT design