In modern power generation and petrochemical processes, energy recovery systems play a crucial role in maximizing efficiency and reducing operational costs. Among these systems, hot gas expanders are integral components, particularly in processes like fluid catalytic cracking (FCC) and gas turbines. Their role in converting thermal energy into mechanical energy has a direct impact on performance, longevity, and cost-effectiveness. Explore the importance of hot gas expanders and how Kennametal Stellite™ leverages advanced alloys to improve durability and reduce downtime.
Improving Efficiency and Durability of Hot Gas Expander Blades with Kennametal Stellite™ Alloys
What is a Hot Gas Expander?
A hot gas expander is a mechanical device used to convert thermal energy in high-temperature gases into mechanical energy, which can drive turbines or compressors in power generation and refining processes. These expanders are typically placed in the exhaust stream of a high-temperature system like a gas turbine, FCC unit, or other industrial setups where hot gases are produced as a byproduct of combustion or chemical reactions.
In the FCCprocess, which is a critical operation in petroleum refining, hot gases produced during cracking reactions are captured and expanded by the expander to generate mechanical power. This energy recovery can be used to drive other parts of the refinery, such as compressors and pumps, enhancing the overall efficiency of the process.
Harsh Operating Conditions
Hot gas expanders face extreme operating conditions, particularly high temperatures and corrosive environments. Gases passing through the expander can exceed 1,000°F, subjecting components to prolonged exposure to these elevated temperatures. This can lead to material degradation over time.
Additionally, the gases in these processes contain aggressive elements such as sulfur and chlorine, which can cause corrosion and wear. To address these challenges, the materials used in hot gas expanders must be durable enough to withstand both the heat and the chemically aggressive environment without failing.
Power Plant
Kennametal Stellite’s Role in Hot Gas Expander Technology
Kennametal Stellite serves as a leading global manufacturer of advanced materials and components, providing solutions to the challenges faced by hot gas expanders. Known for its high-performance alloys, Kennametal Stellite offers materials designed to withstand high heat, corrosion, and mechanical stress within harsh environments.
Stellite™ 31: The Ideal Alloy for Hot Gas Expanders
One of the key materials used in hot gas expanders is the Stellite™ 31 alloy—an advanced cobalt-based high-temperature superalloy that offers exceptional resistance to wear, galling, and corrosion. This material is often used in gas turbine engines in areas subject to hot gas erosion. Its properties make it highly suited for hot gas expanders, where high temperatures, corrosive gases, and mechanical stress can otherwise lead to component failure.
Stellite 31 cast microstructure
Stellite™ 31 Used in Expander Components
The blades and vanes of hot gas expanders are the most critical components exposed to wear, as they are subjected to high temperatures and mechanical stresses while rotating and expanding gases. These components require materials like Stellite™ 31, which can maintain structural integrity under heat and pressure over extended periods. Kennametal Stellite blades have demonstrated a service life of 5 to 10 years.
Stellite™ 31 provides the following key properties to hot gas expander components:
- High strength and toughness
- Exceptional creep and fatigue resistance
- Thermal and mechanical shock resistance
Benefits of Using Stellite™ 31
Along with the superior properties mentioned above, using Stellite 31 can include many benefits within your business processes including:
- Extending component/service life
- Reducing maintenance costs
- Lowering downtime
- Performing in severe service environments
Application Processes for Stellite™ 31 on Expander Components
The production of hot gas expander components using Kennametal Stellite alloys involves sophisticated manufacturing techniques, including:
- Investment Casting
- Sand Casting
- Near Net Shape
- Finish Machining
- Hot Isostatic Pressing (HIP)
- Non-Destructive Testing (NDT)
Stellite 31 Nominal Composition (Mass %) and Physical Properties
| Co | Cr | W | C | Ni | Others | Hardness | Density (deposit) | Melting Range |
| Base | 26 | 7.5 | 0.5 | 10.5 | Mo, Fe, Si | 25-35 HRC* | 8.61 g/cm3 0.311 lb/in3 | 1340-1395ºC 2245-2545ºF |
*Hardness dependent on amount of work hardening.
Summary
Hot gas expanders are essential for converting waste heat into mechanical energy in power generation and refining. To withstand the harsh conditions of high temperatures and corrosive gases, advanced materials like Stellite™ 31 are crucial. Kennametal Stellite provides these high-performance alloys, helping extend component life, reduce maintenance, and improve operational efficiency, making industries more sustainable and cost-effective.