Less time is typically spent on the oxygen measurement, even though it is often just as important. There are several issues with the presence of oxygen in natural gas:
- Natural gas is sold for its heating value, contaminants detract from this
- Transportation cost for pushing contaminants in a pipeline is wasted energy
- Oxygen reacts to form acids, resulting in corrosion and maintenance costs
- Oxygen degrades amines and mercaptans.
There is a short list of sources of oxygen entering natural gas in pipeline applications. Air leaks into the system during operation through equipment seals such a compressors and vacuum pumps. Ambient air enters during maintenance and down time. Since vapor pressure of oxygen in ambient air is far greater than in the natural gas, oxygen will leak in even at pipeline pressures.
Pipeline operators are looking to sell the natural gas. Tariff limits restrict the levels of contaminants. Each country imposes their own regulatory limits for the oxygen that can be in the natural gas. In North America, the limits are typically lower than 0.25%. We anticipate that these limits will continue to go down, as operators attempt to limit the costs associated with oxygen and as measurements become more reliable.
There are several technologies available for measuring oxygen in natural gas. Panametrics offers several of these. The technology that has the greatest opportunity for successful measurement is the one with the smallest sensor! Galvanic fuel cell technology is commonly used in the industry. Simple sensor replacement makes maintenance easy. Sensors are available for ppm and percent level applications. The low initial purchase price and the low cost of replacement sensors makes this ideal for most operators.
Panametrics offers this technology in the form of a tiny transmitter with display. The oxy.IQ is offered for use in Class 1 Division 1 and Division 2 configurations. The small form factor makes it ideal for combining this in a sample system with the companion moisture measurement, whether this is a tunable diode laser analyzer or with an aluminum oxide.
As with any measurement, the proper sample system design will ensure a reliable and low-maintenance measurement. Ensure that you share all attributes of the application using an application data sheet. Feel free to give the oxygen and moisture measurement experts at Panametrics a call, should you need to make this critical measurement.
