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Filtration in Multiple Phases of Natural Gas Production
While natural gas is generally clean-burning, with significantly lower levels of harmful emissions than other fossil fuels (oil and coal), raw natural gas from the drilling process is far from clean.
After extracting the raw natural gas from drilling, to make it commercially usable, the gas goes through multiple filtration processes to remove impurities and make it safe. Among the contaminants may be ethane, propane, butane, pentanes, water vapor, hydrogen sulfide (H2S), carbon dioxide (CO2), helium (He), nitrogen (N), and other compounds.
There are many steps in natural gas production, and in each phase, filtration of the natural gas is necessary.
Natural Gas Drilling
After a well is drilled, natural gas rises to the surface naturally. The gas coming from the earth is full of contaminants. By filtering with particulate and coalescing filters, solids and liquids, such as sand, dust, and water, are removed. If they weren't these solids would likely damage the compressors. After gas compression, the natural gas goes through another filtration to remove compressor lube oil and then transported to treatment facilities.
Treatment of Natural Gas
At treatment facilities, natural gas is filtered through multiple filtration processes to remove hydrocarbons, water vapor, contaminants, and acid gas. The methane needs to be filtered and treated before transportation, and among the treatment processes are:
Amine Sweetening is the removal of acid gases like hydrogen sulfide (H2S) and carbon dioxide (CO2) by subjecting the natural gas to amines and subsequently removing other trace hydrocarbons before the gas is sent to the stripper.
Desiccant Dehydration is a process where coalescing filters are used to remove unwanted contaminants, and the gas is dried using desiccants like a molecular sieve or silica gel.
Glycol Dehydration is a process where coalescing filters are used to remove liquids and particles, and glycol is used to remove water vapor.
Natural Gas Transmission (Pipeline)
Natural gas is transported through a network of pipelines and at times, even stored. The natural gas goes through a two-stage filtration, then through a compressor station, heated, and filtered again. Some contaminants within pipelines may be CO2, which is created by corrosion damage of the pipe.
Natural gas makes its way to consumers through distributors, such as your local gas company. Methane tends to lose pressure from friction as it flows through pipelines, so compressor stations are necessary to maintain high enough pressure to flow. A standard cleaning practice of pigging the lines may displace solid and liquid contaminants. Therefore, further filtration before and after compressor stations is necessary to remove both particulates and liquids.
Like most natural ingredients, natural gas requires a bit of engineering and tweaking to deliver it to market safely. At every phase of production, methane is filtered multiple times to help assure safety and prevent damage to our pipelines. Without the filtration process, natural gas would not be the "clean fossil fuel" and best nonrenewable energy to bridge us to a sustainable energy future.
Edited from original article dated November 11, 2010.