During the summer months with very low consumption, excess volumes from the gas fields, which deliver at a preferably uniform rate, can be stored. During high consumption in cold winter months, storage caverns quickly provide large additional amounts of natural gas. The proximity of the storage capacity to the customers is clearly an important prerequisite for high availability.
Growing demand requires enlargement of the storage capacity
The Empelde natural gas store with its three caverns has helped ensure reliability of supply for almost three decades. It is part of the gas management infrastructure in northern Germany and is integrated into the transport network of 'Erdgas Münster Transport' and the distribution grid of the enercity grid company.
To meet the growing demand for storage capacities, Gasspeicher Hannover GmbH (GHG) has been upgrading and expanding the plants in Empelde since 2003. Three caverns are currently in use. Expansion to four caverns is being planned. Approximately 100 million cubic meters of natural gas can be stored per cavern at a depth of 1,300 to 1,700 metres in a salt dome.
Solution mining of a new cavern
Solution mining of a new cavern takes roughly two and a half years, and the filling with natural gas half a year. Deep drilling is done in the first step. In the subsequent solution-mining process fresh water is pumped into the borehole, the salt dissolves and a cavern is created. The generated brine (salt solution) is used to flood a disused potassium mine. The salt solution is transported via a steel pipeline roughly 50 km long. Depending on the solution mining process, the transport rates vary between 250 and 450 cbm/h. To prevent oxygen corrosion in the steel pipeline a 40% sodium hydrogen sulphite solution is added before entry into the pipeline.
The dosing point is located in the connecting line from the brine settling tank to the suction manifold of the brine settling tank to the suction manifold of the brine transport pumps. A sera dosing system CVD2 - 550.1 -C 409.2-75e withdraws the medium from a horizontally installed outdoor cylindrical storage tank with a capacity of 20 cbm.
Magnetic/inductive flow meters record the flow rates of the brine and the oxygen-binding sodium hydrogen sulphite. The regulation of the electronically controlled sera dosing pumps takes place proportionally to the volume. A metering device for the measurement of the free oxygen monitors the proper function of the dosing system. Once the cavern has reached its planned capacity, natural gas is pumped into the cavern and the salt solution is completely displaced from the cavity. The cavern is now available for storage operation.
sera CVD2 wins over adherents thanks to numerous technical and economic benefits
The CVD2 dosing system purchased from sera is already designed for the upcoming expansion of the storage capacities in Empelde. Apart from its technical values and the Profibus connection, it stands as the right choice thanks to its modular design: ease of expansion, the defined interfaces, the variety of optional accessories and its swift availability. This also convinced the customer who with the CVD2 has a technically advanced product at his disposal, combining a maximum of application flexibility and adaptability with the economic advantages of a standardised series product.
sera offers three types of this dosing system under the CVD2 designation. The types differ primarily in the maximum delivery capacity of the pumps used, ranging from up to 60 l/h up to 550 l/h and up to 1,450 l/h per pump.
The basic version of the systems comprises the following components
- 2 x diaphragm pumps (of the same type)
- 4 x two-way ball valves on the pressure side (shut-off and evacuation)
- 2 x diaphragm overflow valves
- Wall mounting pallet from PP
- with integrated drip pan and drainage nozzle
- Pipe assembly on pressure side from PVC-U or PP
- Final connection on suction side: Connecting thread of the diaphragm
- Final connection on pressure side: Outside thread at final shut-off