What is the purpose of a vapor recovery unit (VRU) in a natural gas processing plant?

The purpose of a vapor recovery unit (VRU) in a natural gas processing plant is to capture and recover valuable hydrocarbon vapors that would otherwise be vented to the atmosphere, reducing air emissions and increasing overall plant efficiency. Natural gas processing plants generate hydrocarbon vapors from various sources, such as storage tanks, compressor seals, and process vents. These vapors contain valuable hydrocarbons, such as methane, ethane, propane, and butane, which can be recovered and sold. Venting these vapors directly to the atmosphere not only results in economic losses but also contributes to air pollution and greenhouse gas emissions. A VRU uses a compression and cooling process to condense these vapors into a liquid, which can then be returned to the process stream for further processing or sale. The VRU typically consists of a compressor, a cooler, and a separator. The compressor increases the pressure of the vapors, which increases their dew point temperature. The cooler then cools the compressed vapors, causing them to condense into a liquid. The separator separates the liquid from any remaining vapors, which are then recycled back to the compressor. By recovering these valuable hydrocarbon vapors, a VRU helps to improve the economic performance of the plant, reduce air emissions, and comply with environmental regulations. The size and configuration of the VRU are typically tailored to the specific sources and characteristics of the vapors being recovered.