Composite tubes prove corrosion resistant in waste incineration
Methods
Composite tubes prove corrosion resistant in waste incineration
Keywords Composite materials, Corrosion, Sandvik Steel, Tubing
It is reported that composite tubes supplied by Sandvik Steel and installed in a waterwall within the waste incineration process at London Waste Ltd, Edmonton, London have proved over a two year trial period to offer exceptional corrosion resistance.
Used as a replacement for carbon steel tubes, refractory protected carbon steel tubes and as an alternative to overlay welded tubes, the trial shows that Sandvik's composite tubes have the potential for a ten year life. In comparison carbon steel tubes needed to be changed after just 18-24 months, before refractory protection,which is costly to maintain, was installed.
The main cause of tube deterioration in the area of the trial the lower radiation shaft above the furnace has been due to corrosion attack on the tube surfaces from unburnt gases and the resulting reducing atmosphere. Gas temperature in this region is 850-900°C while the water temperature is about 250°C,corresponding to the working pressure of 43 bar.
Sandvik's composite tubes consist of two components metallurgically bonded together in the manufacturing process. By selecting the correct material composition for each component,corrosion resistance and mechanical properties can be optimised. Part of Sandvik's manufacturing process is 100 percent ultrasonic examination to prove the metallurgical bond.
In the application, the outer component is produced from Sandvik Grade Sanicro 28 a stainless steel which has excellent high temperature corrosion properties and, because of its high chromium content, is very resistant to gas corrosion. The inner layer,is produced from Sandvik Grade 4L7 and is a standard carbon steel, boiler tube material designed to carry water.
Based on the positive trial results achieved, Sandvik Sanicro 28/4L7 composite tubing is now being considered for other applications within the waste incineration process at London Waste.
Details from Sandvik Steel UK. Tel: +44 (0)121 504 5100; Fax +44 (0)121 504 5151.
