Natural gas reserves are comprised mostly of CH4, N2, CO2

 

Raw natural gas must be purified to meet the quality standards specified by the major pipeline transmission and distribution companies. Those quality standards vary from pipeline to pipeline and are usually a function of a pipeline system's design and the markets that it serves. In general, the standards specify that the natural gas:

  • Be within a specific range of heating value (caloric value). For example, in the United States, it should be about 1035 ± 5% British Thermal Units (BTU) per cubic foot of gas at 1 atmosphere and 60 degrees Fahrenheit (41 Megajoule ± 5% per cubic metre of gas at 1 atmosphere and 15.6 degrees Celsius).

  • Be delivered at or above a specified hydrocarbon dew point temperature (below which some of the hydrocarbons in the gas might condense at pipeline pressure forming liquid slugs that could damage the pipeline).

  • Dew-point adjustment serves the reduction of the concentration of water and heavy hydrocarbons in natural gas to such an extent that no condensation occurs during the ensuing transport in the pipelines

  • Be free of particulate solids and liquid water to prevent erosion, corrosion or other damage to the pipeline.

  • Be dehydrated of water vapor sufficiently to prevent the formation of methane hydrates within the gas processing plant or subsequently within the sales gas transmission pipeline. A typical water content specification in the U.S. is that gas must contain no more than seven pounds of water per million cubic feet (MMCFD) of gas.

  • Contain no more than trace amounts of components such as hydrogen sulphide, carbon dioxide, mercaptans, and nitrogen. The most common specification for hydrogen sulphide content is 0.25 grain H2S per 100 cubic feet of gas, or approximately 4 Parts per million (ppm). Specifications for CO2 typically limit the content to no more than two or three percent.

  • Maintain mercury at less than detectable limits (approximately 0.001 parts per billion (ppb) by volume) primarily to avoid damaging equipment in the gas processing plant or the pipeline transmission system from mercury amalgamation and embrittlement of aluminium and other metals.

 

Species

Symbol

Composition

Methane CH4 70 – 90%
Ethane C2H6 0 – 5%
Propane C3H8 0 – 20%
Butane C4H10 0 – 5%
Carbon Dioxide CO2 0 – 8%
Oxygen

O2

0 – 0.2%
Nitrogen N2 0 – 5%
Hydrogen Sulphide H2S 0 – 5%
Rare Gases Ar, He, Ne  Trace

 

Clean Gas Standards

 Master gas pipeline requirements for gas

   N2 levels need to less than 3% to be fed into grid
   CO2 Levels need to be less than 1% to allow for liquefaction
  Methane harvesting standards for household purposes, for electricity
generation and for transportation fuel.

 


 High quality requirements limit existing technologies

When gas is sour , processes such as Gaseous diffusion, Gas centrifuge  Technology, Vortex tube processes, and Laser Excitation are not economically viable.

 

 

Can process gas reserves previously classified unsuitable for processing

ASP is Cost competitive
ASP is energy neutral and uses gas turbines to fuel  its compressors