Bertrams vacuum process seals in sodium sulphide evaporation
15 Jan 2000
Sodium sulphide is one of the more hazardous substances regularly used by the process industries. Corrosive to skin and many metals, and producing hydrogen sulphide vapours, the salt is necassary for the production of leather, paper, glass, viscose and in the mining industry.
Production processes make a dilute Na2S solution but it is usually used as a solid. The conventional concentration process uses a direct-fired open evaporator vessel, which poses huge safety problems.
A new process, developed by Swiss process technology specialist Bertrams, removes the evaporation process into a closed-loop system. As the system works under vacuum, the evaporation uses less energy, is more efficient and produces less emissions.
The process concentrates the solution from 62 per cent to 30 per cent in a single-stage forced circulation evaporator. The hot (90 degrees C) solution flows from the evaporator into a water-cooled flaker, where it crystallises on the inner surface of a rotating drum. A hardened steel blade, designed to minimise dust, scrapes this off into flakes.
Bertrams has installed the plant at German firm Industriechemikalian Schwefelnatrium at its complex in Bitterfeld in eastern Germany.
