What impurities can one expect to find in natural gas produced from a gas field?
Answer:
The most common and serious contaminant is sulfur, usually in the form of hydrogen sulfide (H2S), and to a much lesser extent, sulfur dioxide (SO2), methyl mercaptan (CH4S), carbonyl sulfide (OCS), and carbon disulfide(CS2).
All of these sulfur compounds are corrosive, toxic, and are serious atmospheric pollutants. Hydrogen sulfide will attack most common metals, and also many plastics. The cost of removing sulfur from low quality "sour gas" can easily outweigh the potential profits.
The simplest method of removing sulfur, is to run the gas through a bed of iron filings. However this is not economical for large scale operations, because the iron has to be replaced constantly. It is also not economical for gas that has a moderate to high sulfur content.
Activated carbon (charcoal) can also be used to absorb sulfur. The used carbon is then heated in a closed vessel to liberate the sulfur, and can then be recycled. The excess sulfur gases are captured and converted into solid sulfur, or into sulfuric acid. Another method is to use some type of catalyst to convert hydrogen sulfide into solid sulfur, or some other type of solid compound.
It's possible to liquefy natural gas, and then distill out the various components, but this usually requires too much heat and energy to be worthwhile.
The most common industrial method is to bubble the gas through some type of liquid solvent, usually monoethlamine (MEA), that will dissolve the sulfur compounds, and then to heat or boil the solvent to remove the sulfur. Often, this is a multi-step process, each step removing incrementally smaller concentrations of sulfur. Again, the separated sulfur gases are usually processed into solid sulfur, or into sulfuric acid.
http://www.naturalgas.org/naturalgas/pro...
Nitrogen, CO2, and water vapor are also common, up to about 5-7% respectively, but these gases do not usually pose major problems. MEA solution can also be used to remove carbon dioxide.
One promising new technology, is the use of natural "sulfur eating" bacteria, (which are commonly found in hydrothermal springs and vents.) These bacterial have an insatiable appetite for hydrogen sulfide, converting it into sulfur powder. The problem is creating conditions where they will grow and thrive, and remove sulfur in an economical manner.
http://www.npgas.ca/parent-p2.htm...
Natural gas usually contains small but appreciable amounts of radon gas. This gas is not reactive, and unless combustion products or unburned gas are allowed to accumulate in a closed area, this is not considered a problem.
Probably more than you wanted to know,
~Soylent Yellow
Natural gas contains..
1..Carbon dioxide forms corrosive Carbonic acid with water, If the gas is going to LNG, CO2 will freeze and block the cryogenic equipment. It is removed by washing with an Amine (MEA or DEA) solution. This method is also used to remove: -
2..Hydrogen Sulphide .. Acid, Foul smelling, Toxic gas deadly in low concentrations, forms Sulphurous acid with water, will freeze at cryogenic temperatures. Also causes 'Hydrogen Blistering' in piping due to reaction with iron forming FeS and Hydrogen. (More on this is available).
3..Water and water vapour ..Corrosive, forms the above mentioned acids, easily freezes. Removed by absorption into Di- and Tri- ethylene glycols (DEG & TEG) or by adsorption into Alumina (Aluminium oxide, Silica Gel etc).
4. Solid particles of rust, scale and other debris produced from a well .. cause erosion and blockage in equipment.
5...Nitrogen is also present but is not considered for removal.
...
The answers post by the user, for information only, FunQA.com does not guarantee the right.
More Questions and Answers: