Increase the Efficiency of Pumping Spa Water From Glauber Salt Spring
Progressing cavity pump conveys healing water with a high brine content
High brine content, sodium sulphate, and chloride levels attack the systems, and the demands on pumps for conveying healing water are high. As a global specialist in complex fluid management, NETZSCH Pumps & Systems has sophisticated solutions for pumping spa water.
Efficient pumping of spa water with high brine content from the depths
The state baths in Saxony originally commissioned a planning company with the investigation and development of brine exclusively for geothermal purposes. After exploration – that is a geophysical investigation of fault zones – enabled a suitable site in the Elster Valley to be found, exploratory drilling and an initial pumping trial were carried out starting in 2007. In the process, at a depth of around 1,200 m, they came across highly mineralized water with a particularly high sodium sulfate and chloride content.
High sodium sulfate and chloride content demand healing water pumps
During the exploratory drilling, those responsible came across highly mineralized water with exceptionally high sodium sulfate and chloride content. Due to the mineral content of the healing water, a special pump was needed to transport the medium gently to the surface. The aim was to cover the water demand of three pools in the thermal brine bath with a capacity of 450 cubic meters of healing water. In addition to the composition of the healing water, the challenge was to find a pump that would efficiently bring the fluid, which is unique in Germany, to the surface from a depth of 1,200 meters in the Elster Valley.
Progressing cavity pump conveys healing water flexibly and efficiently
NETZSCH developed an innovative solution for pumping the spa water based on a downhole system initially designed for pumping in oil fields. Thanks to years of experience in the oil and gas sector, the solution was obvious to the global specialist in complex fluid management. Due to the borehole's small diameter of 95 millimeters, a progressing cavity pump with a drive unit at the surface was chosen. The advantage of this solution for pumping the healing water also lies in its rapid availability and maximum flexibility in the delivery rate and the medium to be pumped. No other pump system can cover such a wide range of delivery rates. For this reason, this pump technology is being used more and more frequently, especially during test phases.
In the end, an NTZ 278 type progressing cavity pump was used. Its body is comparatively slim and can in principle also be operated with a submersible motor within a well bore. However, downhole pump with surface drive system was chosen due to the small diameter of 95 mm. The advantage of this solution is also rapid availability and maximum flexibility in terms of flow rate and the product being conveyed.
No other pumping system can cover such a wide field of flow rates. That is why this pumping technology is used more and more frequently, particularly for test phases.
In order to prevent the possibility of the salt crystallizing during conveyance and grinding the elastomer, the spring water was pumped with a salt content of 22 percent – in other words diluted – and at a temperature of 42 °C during the long-term pumping trial. In addition, the speed of the NTZ 278 was 100-200 rpm, enabling the natural lubricating effect which brine exerts at higher flow velocities to be used and any elastomer abrasion to be avoided.
The NTZ 278 was installed by NETZSCH engineers at the well site in the Elster Valley in 2009, together with the drive head and sucker rod. It was used for more than one year in the context of the long-term pumping trial and, over this period of time, pumped spa water reliably from underground for salt water thermal baths. As the pump only has a small number of wearing parts, it only generates low life cycle costs. Use of a NETZSCH pump with a heating jacket is currently planned to enable the energy efficiency of the system to be further increased: if this is placed around the pump, the brine warms up and can dissolve more salt. In this way, the lubricating effect increases and the service life would be further extended.
Since September 2015, visitors to a 4,500 m² thermal baths environment with a variety of pools where diluted brine is used to enable weightless floating in water, have been benefiting from the data which it was possible to collect in the long-term pumping trial with NETZSCH technology. Thus, there are for instance two pools with a 10 or 6 percent brine content and a salt lake with a brine concentration of 15 percent.