Multi-stream gas analysis in bio-methane upgrading
Biogas is increasingly seen as a more renewable source of natural gas for injection into gas networks for home heating, cooking and fuel.
The gas entering in the network must have a high calorific value, and therefore scrubbed of contaminants such as CO2, O2 and H2S.
The advantages of using the Panametrics thermoparagnetic and thermal conductivity sensors are:
• Continuous measurement of all streams
• The sensors can be calibrated in minutes
• The rugged design means many years of service. Global hazardous area certifications for all devices
Challenge
Oxygen concentration is measured in the gas generated by the decomposition of waste. Methane is a flammable gas, and its flammable limits in air are 5% to 15%.
In order to transport the biogas safely through pipelines it is therefore necessary to ensure that the oxygen content is less than 2%. The hydrogen sulfide must be scrubbed by carbon filters from the gas before entering the networks and needs to be <10 ppm.
Carbon Dioxide is measured as it is separated from the bio-methane and the efficiency of the separation technique needs to be monitored. Finally, the methane purity of the cleaned biogas needs to be measured before entry into the gas grid.
All of the measurements need to take place in hazardous area environments.
The Panametrics XMO2 transmitter utilizes thermoparamagnetic technology to measure the oxygen level and the Panametrics XMTC transmitter utilizes thermal conductivity technology to measure the carbon dioxide and methane. The H2S is measured using fuel cell technology. These are all incorporated into a single sample system solution that regulates the pressure and flowrates of the gas streams ensuring accurate measurement of:
• 0-2% oxygen range in the oxygen/H2S stream
• Methane content in the CO2 off gas
• CO2 impurities in the methane stream
• Methane purity
Oxygen content range: 0-2%
Carbon Dioxide content range: 90-100% against methane background
Methane content range: 90-100% against CO2 background
Hydrogen Sulfide: 0-10ppm
Operating temperature: -5°C (23°F)to 50°C (122°F)
Operating pressure: Regulated to 14.7 psia (101.3 kPa)