Circulation Heater Acts As Duct Heater To Raise Chemical Gas To Correct Process Temperature

Problem:

A chemical process was to heat 1211 lbs/hour (510 kg/hour) of air to produce an outlet temperature of 1056°F (570°C) and pressure of 1.8 psig (0.26 kPa) from an ambient inlet temperature of 100°F (35°C) at standard atmospheric pressure. The process could only withstand a maximum allowable pressure drop of 1.5 psi (0.22 kPa) across the heating element bundles.
These specifications made by the customer for an 8-inch (20 cm) flange heater having a maximum sheath temperature of 1300°F (705°C) and a maximum allowable watt density of 3.5 and 8 W/in2 (0.5 to 1.2 W/cm2).

Solution:

The high outlet temperature necessitated using three heaters in series. The first of which was a 60 kilowatt heater of 8 inch (20 cm)flange construction with 24 elements and a designed watt density of 8 W/in² (1.2 W/cm²).

This was connected to a second 8 inch flange heater rated for 40 kW at 8 W/in² (1.2 W/cm²), also a 24 element construction.

This was then connected with the last 8 inch (20 cm) flange heater rated for 20 kilowatt, constructed with 24 elements rated at 3 W/in² (0.46 W/cm²).

Each heater having an immersed length of 122.5 inch (3.1 m) and a 6 inch (15 cm) stand-off housing to reduce the temperature inside the terminal housing for lengthening the service life of the jumpers and lead wires.

The reason that Watlow was the successful bidder on this project was due to the initial ground work and follow-up effort put forth by the local representative.

Other applications on this project were a flanged gas chlorination heater and a flanged gas regeneration heater.

Value Added:

Ability to provide application expertise.