Strong Acid System - Acid Cooling - PTFE Tank Coils
June 22, 2003

Introduction

PTFE tank coils were first introduced by Dupont in 1965.   All surfaces exposed to the acid are made of PTFE/Teflon.  The PTFE tubes are 2.54 mm (0.10") in diameter with a wall thickness of 0.254 mm (0.01").   Tube bundles can be designed with several thousands of tubes.  Tube lengths can range from 3350 mm (11 ft) to 7010 mm (23 ft) long.

An installation of tank coils was done in 1973 in a 600 ton per day sulphuric acid plant in Lancashire, UK.  The tank coils were used to replaced cast iron coolers which were the cause of extensive maintenance and downtime.  The installation consisted of eight (8) tank coils in the intermediate absorber system and three (3) in the final absorber system.  Each tank coil measured 5180 mm (17 ft) long with 3100 tubes in each bundle giving 116.6 m² (1255 ft²) of surface area.

The tank coils are installed in a rectangular tank.   Acid enters at a temperature of 100°C (212°F) and leaves at a temperature of 72.2°C (162°F).  Cooling water enters the tubes at 22.8°C (77°F) and exits at 40°C (104°F).  Acid is bypass around the tank to control acid temperature.   Cooling water flow is maintained constant.

The water side pressure is higher than the acid side so any leaks result in water entering the acid.  The small diameter tubes result in relatively small amounts of water entering the acid.

The operating status of the plant is unknown.