Technological breakthrough of vertical semi submersible long axis turbine pump in the field of new energy (geothermal/photothermal)

New Energy Sector (Geothermal/Thermal): Breakthrough in Pump Technology for High Temperature and Special Corrosion Environments

With the global energy structure shifting towards low-carbon, geothermal energy and solar thermal power generation, as stable and dispatchable clean energy sources, are entering a period of rapid development. However, its core equipment - pumps used for transporting high-temperature geothermal water or molten salt - faces unprecedented technological challenges: medium temperatures can reach up to 120 ℃~550 ℃, and often contain high concentrations of sulfides, chloride ions, dissolved oxygen, and solid particles, far exceeding the design limits of traditional industrial pumps. The vertical semi submersible long shaft turbine pump, with its structural advantages and material innovation, has become a key technology to break through these "high-temperature corrosion" bottlenecks.
In the field of geothermal power generation, geothermal water is usually extracted from depths of 1500-3000 meters underground, with temperatures ranging from 120 ℃ to 180 ℃, and contains high concentrations of hydrogen sulfide (H ₂ S), chloride ions (Cl ⁻), carbon dioxide (CO ₂), and silicates. H ₂ S forms a strong reducing acidic environment at high temperatures, causing severe sulfide stress corrosion cracking (SSCC) in ordinary stainless steel; Cl ⁻ causes pitting and crevice corrosion; Silicates are prone to precipitate and form hard scale at high temperatures, which can block flow channels. Traditional pumps have a very short lifespan under such operating conditions. The breakthrough of the vertical semi submersible long shaft turbine pump in this scenario is reflected in the collaborative innovation of high-temperature guide bearings and corrosion-resistant overcurrent components. Its core is to use titanium alloy TC4 as the main material for the impeller, pump casing, and shaft. The TiO ₂ oxide film formed by titanium in high-temperature water environment has excellent thermal stability and self-healing ability, and exhibits excellent corrosion resistance to H ₂ S, Cl ⁻, and CO ₂. Its corrosion rate in geothermal water at 180 ℃ is less than 0.02mm/a. To address the lubrication challenges of bearings at high temperatures, the guide bearing system has abandoned traditional water lubrication and adopted self-lubricating bearings made of graphite+silicon carbide (SiC) composite materials. Graphite can maintain good lubricity at high temperatures, while SiC provides high hardness and wear resistance. The combination of the two can operate stably in a high-temperature environment of 180 ℃ for a long time without external cooling water. In a geothermal power station project in Xizang, China, the vertical semi submersible long shaft turbine pump with TC4 material pump body+graphite/SiC guide bearing was successfully used to extract media from 170 ℃ geothermal water wells, which has been running continuously for more than 18 months. The 316L vertical semi submersible long shaft turbine pump used in the same period was scrapped due to corrosion perforation within 6 months. In addition, to cope with geothermal water with high sediment content (>300g/m ³), the pump body is designed with a patented sand throwing ring structure, which uses centrifugal force to throw more than 90% of solid particles away from the bearing area, effectively protecting key friction pairs.
In the field of solar thermal power generation (CSP), the challenges are even more severe. Molten salt (usually 60% sodium nitrate+40% potassium nitrate) is used as a thermal storage medium, with a working temperature of up to 550 ℃. It has strong oxidizing and corrosive properties at high temperatures and is prone to crystallization during temperature fluctuations. The pump for transporting molten salt needs to operate continuously under extreme conditions of high temperature, high oxidation, and easy crystallization at 550 ℃. The application of vertical semi submersible long shaft turbine pumps in this field is the pinnacle of materials science and engineering design. The core breakthrough lies in high-temperature alloys and special structures. The overcurrent components of the vertical semi submersible long shaft turbine pump are made of titanium alloy TC4 or nickel based high-temperature alloys (such as Inconel 625), which can maintain high strength and oxidation resistance at 550 ℃. The guide bearing system adopts a fully ceramic (SiC or silicon nitride) closed bearing box and is equipped with an inert gas (such as argon) blowing system to prevent oxidation caused by contact between molten salt vapor and oxygen. In a 50MW solar thermal power plant project in Gonghe, Qinghai, China, a vertical semi submersible long shaft turbine pump design was adopted to solve the high-temperature sealing problem of the molten salt pump. The pump body length reached 20 meters, and the impeller and shaft were cast as a whole with TC4 titanium alloy. The guide bearing was made of silicon carbide ceramic and equipped with a double end mechanical seal. High purity nitrogen gas was used as the isolation gas, with a pressure 0.3 MPa higher than the molten salt pressure, to ensure that the molten salt did not leak out. The pump unit has been running continuously for over 8000 hours at 550 ℃ without any leakage or bearing failure, providing a key guarantee for the stable operation of the molten salt thermal storage system. In addition, to address the risk of molten salt crystallization, the pump body is designed with an electric heat tracing insulation jacket to maintain the pump body temperature above the solidification point of molten salt (220 ℃) during shutdown, preventing crystal blockage.
new energy sector
 
medium characteristics
 
Recommended materials
 
key technology
 
Application Cases
 
Geothermal power generation
 
120-180 ℃ geothermal water, containing H ₂ S, Cl ⁻, SiO ₂
 
Titanium alloy TC4
 
Graphite/SiC self-lubricating guide bearing, sand throwing ring structure
 
Xizang geothermal power station, 170 ℃ geothermal water, continuous operation for 18 months
 
Thermal power generation (molten salt)
 
550 ℃ molten salt (NaNO ∝/KNO ∝), strong oxidation, easy crystallization
 
Titanium alloy TC4/Inconel 625
 
Ceramic bearings+inert gas blowing, double end face sealing+nitrogen blocking sealing, electric heat tracing insulation
 
Qinghai Gonghe 50MW solar thermal power station, 550 ℃ molten salt, operating for 8000 hours
 
Biomass pyrolysis oil
 
200-300 ℃, containing tar and acidic substances
 
316L stainless steel+PFA lining
 
High temperature magnetic drive, no shaft seal design
 
A certain biomass power plant transports pyrolysis oil, saving 40% of maintenance costs annually
 
These cases demonstrate that the application of vertical semi submersible long shaft turbine pumps in the field of new energy has moved from traditional "corrosion resistance" to a comprehensive technological breakthrough of "high temperature resistance+crystallization resistance+zero leakage". Its "dry motor+deep liquid" structure provides an irreplaceable safety platform for the transportation of high-temperature and high-risk media. With the large-scale development of geothermal and thermal projects, the vertical semi submersible long axis turbine pump is upgrading from an "industrial equipment" to a core component of "energy infrastructure", and its technological evolution will continue to promote the efficient and safe utilization of clean energy.