Alternative and Renewable Energy - Advanced Materials ...

Spiral 2: 3/28/2011Department of Defense Energy HandbookAlternative and Renewable Energy Options for DoD Facilities and Bases6.2.1.3.2 ProcessingNatural gas harvested from petroleum wells and other sources must be processed and refined toremove many of the unnecessary components and impurities to produce a commercial grade fuel.Alkanes other than methane are removed and collected for other uses.Particulates, such as sand, are removed by scrubbers. In the case of natural gas dissolved in crude oil, itmust be separated using a gravity separator, for example. Some water can be condensed out of thenatural gas during refining, but dissolved water must be removed through absorption or adsorption.Organic contents other than methane, such as ethane, propane, and butane are also extracted andsubsequently separated as byproducts for other uses. Absorption is the method commonly used toextract the heavier organic compounds from the unrefined natural gas, while cryogenic expansion isused to extract compounds, such as ethane, which is close in molecular weight to methane. Separationof the hydrocarbons is then accomplished by fractionation methods.Hydrogen sulfide is removed from unrefined natural gas by an absorption process. Amine compoundscan be used to absorb hydrogen sulfide, thereby extracting it from the natural gas stream. Elementalsulfur can subsequently be recovered for use in other applications.6.2.1.3.3 ApplicationsAs a combustible substance that can provide thermal energy, natural gas is commonly used for heatingand cooking. However, there are several other applications of natural gas, such as fuel for vehicles andas a source of hydrogen for hydrogen production.Natural gas vehicles (NGVs) use compressed natural gas (CNG) or liquid natural gas (LNG). This isbecause if natural gas is used in its unpressurized, gaseous form, a large volume is needed to power avehicle for an acceptable distance. Even with CNG or LNG, NGVs have a more limited range thanvehicles powered on conventional fuels. However, the power output of engines fueled by natural gas iscomparable to those powered by conventional fuels. Natural gas vehicles can be powered by dedicatednatural gas engines or bi-fuel engines, which can run on either natural gas or a conventional fuel. 636.2.1.3.4 DistributionSmall diameter pipelines are typically used to transport unrefined natural gas from the collection pointto the processing plant or storage facility. The US has a network of interstate and intrastate pipelines(see Figure 18) that are used to transport natural gas from processing plants to the point of finaldistribution and consumption. Interstate pipelines are high pressure lines and are kept pressurized bycompressing stations. Metering stations are also placed along the pipeline to monitor the natural gas inthe line.63