The planned 100 MW site is part of a program of renewable energy, driven by the increasing demand for sustainable energy sources in China and around the world.
Molten salts have been used in the nuclear industry for almost 70 years and Sulzer has been involved in the design and manufacture of the pumps that transfer the high-temperature fluids around the cooling circuits.
Molten salt is pumped to solar collectors (tower or parabolic mirror fields) where its temperature increases from around 300 °C to up to 600 °C. The high-temperature salt is then stored in a tank and transferred to a heat exchanger where the thermal energy is used to create steam that will generate power using a turbine/generator. This circuit acts as a thermal battery, which enables solar plants to deliver power round-the-clock in good solar conditions.
The 100 MW CSP Tower project is said to be the first of its type to use Sulzer pumps for both the hot and the cold circuits. The three cold molten salt pumps will be fitted with 2.6 MW motors and will extend 18 meters below the base plate into the cold molten salt tank. These will be matched with two hot pumps, with all the pumps being manufactured in Sulzer’s Suzhou plant.
The most significant challenge in this project was the increased operating pressure required in the molten salt circuits. Sites with smaller outputs normally operate at around 50 bar, but this project needed a 100 bar supply pressure from the pumps.
Each pump is built to order, and this project had to be engineered to account for the increased pressure and the slightly larger power requirement. Compared to the more common, lower pressure pumps, there are several crucial points, such as the throttle bushing and bush bearing design, that need to be assessed, properly engineered and tested before the manufacturing process can begin.
In this case, the end-user wanted to achieve certain objectives in the delivery of this project. They wanted international brands to supply the key equipment, which ideally would be manufactured in China and cost-effective compared to the competition.
Sulzer was able to meet all these objectives. The engineering of the bare-shaft pump will be completed in Europe and the manufacturing will be a close collaboration between the facilities in Belgium and China. In addition, the company will offer a comprehensive support package for the products that will be delivered via its local service centre. By selecting Sulzer for both the hot and cold pumps, the end user can also streamline its spare parts inventory.
As part of the contract, Sulzer’s local engineers will be on hand to support the installation and commissioning of the equipment. Due to their length, the pumps will be assembled on site before installation in the storage tanks.