Nitrogen Removal From Low Quality Natural Gas

Natural gas provides more than one-fifth of all the primary energy used in the United States. It is especially important in the residential sector, where it supplies nearly half of all the energy consumed in U.S. homes. However, significant quantities of natural gas cannot be produced economically because its quality is too low to enter the pipeline transportation system without some type of processing, other than dehydration, to remove the undesired gas fraction. Such low-quality natural gas (LQNG) contains significant concentration or quantities of gas other than methane. These non- hydrocarbons are predominantly nitrogen, carbon dioxide, and hydrogen sulfide, but may also include other gaseous components. The nitrogen concentrations usually exceeds 4%. Nitrogen rejection is presently an expensive operation which can present uneconomic scenarios in the potential development of natural gas fields containing high nitrogen concentrations. The most reliable and widely used process for nitrogen rejection from natural gas consists of liquefying the feed stream using temperatures in the order of - 300{degrees}F and separating the nitrogen via fractionation. In order to reduce the gas temperature to this level, the gas is compressed, cooled by mullet-stream heat exchangers, and expanded to low pressure. Significant energy for compression and expensive materials of construction are required. Water and carbon dioxide concentrations must be reduced to levels required to prevent freezing. SRI`s proposed research involves screening new nitrogen selective absorbents and developing a more cost effective nitrogen removal process from natural gas using those compounds. The long-term objective of this project is to determine the technical and economical feasibility of a N{sub 2}2 removal concept based on complexation of molecular N{sub 2} with novel complexing agents. Successful development of a selective, reversible, and stable reagent with an appropriate combination of capacity and N{sub 2} absorption/desorption characteristics will allow selective separation of N{sub 2} from LQNG.