Stacks are categorized by their construction material. These include:
• Carbon Steel
• Stainless Steel
Both steel and concrete stacks have been used in Company refineries. Concrete stacks are more durable than steel, while steel stacks are more economical.
However, concrete stacks are rarely used in new construction. Metal temperatures play an important part in selecting material for steel stacks. If temperatures are too low, corrosion may be serious due to condensing acids from sulfur compounds in the flue gas; if temperatures are too high, allowable stresses may be the controlling factor.
The Company’s fired heater Specification HTR-MS-1350 sets minimum steel surface temperatures in Figure 400-6.
To save fuel, flue gas temperatures should be as low as possible without causing corrosion. We ask the furnace supplier to provide an alternative quote for an externally insulated, double wall construction, or other stacks designed to provide a corrosion-free inner wall.
Fiberglass stacks may be considered in services that are corrosive to steel and concrete. If the materials and method of wall construction are known, then an analysis can be made similar to that for a steel stack.
Several unguyed fiberglass stacks are currently in service at the Chevron Ortho Plant in Kennewick, Washington.