Vacuum Distillation
Virtually all natural gas contains some amount of nitrogen which lowers the BTU value of the gas but is no particular problem. However, in some reservoirs gas has been discovered to contain larger amounts of nitrogen than can be tolerated due to contractual considerations on BTU content. In these cases, the operator has three options:
• Blend the gas with richer gas to maintain overall BTU value;
• Accept a reduced price or less secure market;
• Remove the nitrogen to meet sales specifications.
Options 1 and 2 are reasonable approaches to the problem but are very location specific. When a nitrogen rejection unit (NRU) is selected as a process option for a gas stream, it is often combined with natural gas liquids unit (NGL) recovery in an integrated plant design. A block flow diagram of a combined NGL/NRU facility is shown in Figure 1. The overall objective of this facility is to produce a nitrogen vent stream, specification sales gas stream, and a specification NGL product.
NoDoC Cost model presents various nitrogen rejection methods, technologies and design basis.
• Blend the gas with richer gas to maintain overall BTU value;
• Accept a reduced price or less secure market;
• Remove the nitrogen to meet sales specifications.
Options 1 and 2 are reasonable approaches to the problem but are very location specific. When a nitrogen rejection unit (NRU) is selected as a process option for a gas stream, it is often combined with natural gas liquids unit (NGL) recovery in an integrated plant design. A block flow diagram of a combined NGL/NRU facility is shown in Figure 1. The overall objective of this facility is to produce a nitrogen vent stream, specification sales gas stream, and a specification NGL product.
NoDoC Cost model presents various nitrogen rejection methods, technologies and design basis.
