Dewpoint meter

Dewpoints can be measured manually with simple dewpoint apparatus but the use of an in-line dewpoint meter guarantees continuous monitoring of the moisture levels in air. The recommended instrument for in-line measurements is the Shaw hygrometer type HD. 

A dewpoint meter for process air, with a recorded signal, should always be fitted as standard in sulphonation plants. Regular manual checks are essential (see 5.2.2.). 

An alternative to sulphur burning and subsequent SO2 conversion to SO3 is the use of stabilised liquid SO3. The use of stabilised liquid SO3 is restricted by the proximity of a supplier. This chemical should be transported and handled with great care. A simplified flowsheet is presented in figure 14. The stabilised liquid SO3 is transferred by a membrane metering pump from the day tank through a filter and into the vaporiser. The gaseous SO3 thus obtain is filtered to remove any remaining mist and then mixed with dried process air (dewpoint -60 C) to the required SO3 level. 

---