Severe deposits removed using multi-step programme
60,000 tonnes of refined nickel and 5,600 tonnes of refined cobalt are processed at this African plant every year. A Vertical, Helicoid, Naphtha Evaporator containing a single 70 loop x 600m diameter steel coil, measuring 130m long and 38mm internal diameter had become blocked / fouled. Deposit thickness was expected to be no more than 2mm of very hard hydrocarbon coke which had increased back pressure dramatically from 1 bar to 7bar putting a critical strain on the process with the only option being a costly replacement!
The Challenge
- To decoke the coil by removing the fouling so as not to damage the carbon steel tube which would cause a key way for future build up to form more quickly.
- After arriving on site and opening the coil, the coke deposit was measured at 10 mm thick.
Solution
- A bespoke range of Micro-darTT projectiles were developed to decoke this small diameter tube.
- The coil was inspected using a Micro-camera Dart.
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Tube Tech Comment
Scott Donson, Technical Sales Manager: “Despite adverse seasonal cyclones our team decoked this Naphtha Evaporator Coil back to bare metal using a unique range of projectiles within time allocated and on budget.