Q. Define FLARE AND VRU SYSTEM?
VRU, HP and LP Flare systems are used to collect normal and emergency releases from the process and recycle or dispose of them in a safe manner.
The HP Flare system is responsible for collecting and disposing of process streams resulting from manual vents, emergency reliefs or upset conditions from diverse equipment throughout the facility.
Fluid from the flare header enters into the HP Flare Knockout Drum, where liquid and vapour are separated. The vapour flows to the HP Flare Stack where the HC gas is combusted into CO2 and H2O. The liquid from HP Flare KO Drum is sent to the Slop Tanks. Both the HP flare header into the drum and the line from the drum to the stack are sloped downwards towards the drum to prevent condensed liquid from accumulating in the flare header or entering the flare stack.
The VRU system is provided for all recoverable tank vapours and low pressure process vapours. Usually this includes vapours from the closed HC Drain Vessels, Evaporator Package, Surge Tank, Skim Tank, De-Oiled Water Tank, IGF Package, Desand Tank, Slop Tank, Dilbit Tank, Off-Spec Tank, Diluent Tank and Slop Treater Package (if any). The VRU Package increases the pressure of recovered vapours in order to mix them with the other vapours feeding the Mixed Fuel Gas Separator. (The description may be different in various SAGD plants). The VRU package may contain a VRU Suction Cooler, Scrubber, Scrubber Pumps, VRU Compressors, Compressor Cooler and Discharge Separator.
The vapour from VRU header flows to the cooler to cool down the vapour and collecting condensed liquids prior to compression. The liquid is pumped out to Slop Tank and vapour is sent to the compressor. The discharge gas flows to the Discharge Cooler and Separator (three phase) and the overhead gas is routed to the FG system and HC liquids are sent to Slop Tank.
The LP Flare Header collects gas from process sources that cannot withstand backpressure in excess of 3.45 kPag. Normally these vapours are recovered by the VRU but should the VRU System shut down or lack sufficient capacity for any reason, excess vapours are collected in the LP Flare header and sent to the LP KO Drum, where liquid and vapour are separated. Vapours flows to LP Flare Stack and liquids are removed from the LP KO Drum and sent to the Surge Tank or Slop Tank.