Design of retention systems
In most cases, the substance flows that escape when a safety valve or bursting disc responds may not simply be blown into the environment, especially if the flows contain explosive, toxic or potentially environmentally hazardous media.
It is therefore necessary to provide for containment and/or to properly treat the substance flows in order to minimize and clean them, so that the potential hazards are reduced to an extent that they may be discharged into the environment.
Many plants contain a collection system in which the liquid phase can be collected, with either a freely vented collection tank or a collection tank secured to a lower pressure. It is important here for the collection tank to be placed lower if possible than the equipment from which the blow-off lines leading into the tank originate. If a liquid-carrying line is laid on an incline it may fill up and, due to the geodetic difference in height, hydrostatic pressure is created which, in bursting disc blow-off lines, acts as additional pressure on the safeguarded equipment. In the case of safety valve blow-off lines, this hydrostatic pressure may even cause the safety valve to close prematurely and result in a higher set pressure when reopening, but in any case it may hinder stable operation of the safety valve.
For cases where a two-phase flow may occur across a bursting disc or safety valve, a separator capable of separating the phases should be used. The simplest form of separator is the gravity separator, but large volumes are required for effective separation. For larger volume flows, a cyclone separator with a tangential inlet can be used, in which the phases are separated by gravity and centrifugal force. The individual phases can then be fed separately to a further treatment, e.g., a scrubber system, an emergency flare, a collection tank, or a SAFEBAG®.
The gas phase may be condensed, absorbed or neutralized beforehand, e.g., condensed in a suitable fluid in a direct condenser with a perforated gasifier. During the design process, attention must be paid to the volume, the number and size of the holes, the minimum overlap, and the developing back pressure. When using jet nozzles for direct condensation, smaller volumes and lower liquid quantities may be sufficient.
Our experienced experts will be happy to support you in the concept development, design and optimization of a retention system tailored to the needs of the specific operation. We will gladly calculate the necessary collection volume as well as the optimum dimensions of a cyclone or a perforated gasifier for your specific case.