Application Spotlight: Chemical Manufacturing – Chlorine Gas

APPLICATION:
A bayonet-style heat exchanger is used by this customer to heat and vaporize dry liquid Chlorine, to supply multiple reactors at various flow rates with Chlorine gas, at 54°C (130°F) and 180 psig. Pure liquid Chlorine is fed to the vaporizer from a pressurized railcar. The heat source was low pressure steam. The existing system did not control the liquid level in the vaporizer, and the flow of the liquid CL2, and the vaporizer’s liquid level was limited by equilibrium.

TRICOR PRODUCT SUPPLIED:
TCM-28K Hastelloy Coriolis Mass Flow Meter with Integral Transmitter

CHALLENGE:
Chlorine has a high coefficient of thermal expansion. Process upsets or momentary shutdowns sometimes resulted in excessive liquid levels, which rapidly led to undesired pressure excursions. There were also cases of low liquid levels, which led to superheating of the gas. This problem is compounded by the over-sized tube bundle in the vaporizer.

SOLUTION:
Since a very small amount of liquid CL2 can lead to serious swings in level, and therefore over-pressure excursions, a highly accurate and repeatable flow meter was required. The customer chose the TRICOR TCM-28K Hastelloy C-22 flow meter. The C-22 alloy features excellent corrosion resistance to Chlorine, and has proven to be superior to C276 for these applications.

RESULT:
The new system uses re-circulating hot water as a heat source, rather than steam, and the CL2 liquid level is now controlled via a cascade master and a mass flow control loop.