Pipeline Injection and Custody Transfer

Application Summary

Analysis Point Analyte Typ. Range Suitable Analyzer
Pipeline Injection and Custody Transfer H2S 0-10 PPM OMA-300 Process Analyzer
BTEX 0-40 PPM OMA-300 Process Analyzer

Introduction

Biogas can be generated through a few different processes. The more common production methods come from capturing gas from the natural decomposition in landfills, and through decomposition of biomass collected specifically for use in biogas generation. Landfill gas (LFG) is a useful product of solid waste disposal. Landfills naturally generate CH4 and CO2 as waste decomposes over time. Biogas generation from a biomass feedstock, by contrast, is a dedicated process through which either waste biomass or biomass specifically grown for biogas production is digested to methane. The gas from both sources can be collected and, once it is purified, it can either be used to supplement natural gas, or it can be used as its own alternative fuel source. The purified gas is often referred to as biomethane.

Biomethane is created by upgrading the biogas produced by anerobic digestion of organic material. Biogas has a relatively low heating value as it typically only contains around 50% methane, with the balance being CO2 and other minor components. For the biogas to be sent to the natural gas grid or for it to be used as a natural gas replacement fuel, the methane concentration must be increased. This is typically done through either a sorption technique where the CO2 is scrubbed from the gas, through a membrane separation, or through a cryogenic separation. The upgraded biomethane can be mixed in with natural gas before being odorized and sent to the grid.

The mixed natural gas and biomethane that make up the stream going to the natural gas pipeline must meet local regulations in order to be sent to consumers. These regulations include H2S and BTEX requirements. H2S is an extremely dangerous chemical. Exposure can be lethal at around 500 PPM, and it is explosive at higher concentrations. H2S is also corrosive and can lead to sulfur stress cracking. For these reasons it is a closely monitored contaminant with permissible limits typically around 4 PPM. BTEX compounds all have negative health effects for humans. The level of these compounds is regulated to ensure the gas is safe, and so that BTEX environmental emissions are minimized. It is important that these specifications be met and closely monitored for variations.

The OMA-300 process analyzer continuously measures 0-10 PPM H2S and 0-40 PPM BTEX in the biomethane/natural gas stream being sent to the natural gas distribution network. Monitoring the H2S concentration ensures that the sulfur is being kept at safe concentrations and below local regulatory levels. Monitoring the BTEX concentration ensures that the gas stays within safe bounds, and that the gas will meet regulatory standards. Response time is critical for the biomethane/natural gas stream to ensure the gas being produced meets the regulations for the gird. An online analyzer at this location allows the control room to rapidly adjust upstream processes to react to changing conditions.

System Benefits

  • Continuously measures 0-10 PPM H2S, 0-40 PPM BTEX in the biomethane/natural gas stream.
  • Totally solid-state build with no moving parts — modern design for low maintenance.
  • Fast response time, analyzer updates reading in under 5 seconds

Example Gas Sample Conditioner

0-10 PPM H2S, 0-40 PPM BTEX in the combined biogas stream. Key features for this application include:


  • Stainless steel components/fittings & Viton or Kalrez gaskets for corrosion resistance.
  • Particulate filtration to remove solids that could influence the measurement.
  • Liquid filtration to remove droplets and mists that could influence the measurement.

Further Reading