Combined Heater and Power Generation

Application Summary

Analysis Point Analyte Typ. Range Suitable Analyzer
Biogas in Combined Heater and Power Generation H2S 0-50 PPM  OMA-300 Process Analyzer
CH4 50-100% MicroSpec MCP-200 Infrared Analyzer

Introduction

Biogas production can be generated through a few different processes. The common production methods are capturing gas from the natural decomposition in landfills, and the decomposition of biomass collected specifically for use in biogas generation. Landfill gas (LFG) is a useful product of solid waste disposal. Landfills naturally generate methane 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 process of anerobic digestion can generate H2S when proteins containing sulfur are broken down. 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. Analyzers at AT2 and AT3 monitor the gas to ensure that it is safe for storage. H2S is closely monitored at the inlet to the Combined Heater and Power Generation unit to ensure that the H2S concentration is minimized and will not cause downstream issues in the process.

Methane is measured at the inlet to the Combined Heater and Power Generation (CHP) unit to monitor the heating value of the gas going to the generators. The Heating value plays a large role in how efficiently the turbines work, and how much power can be produced. Smooth operation of a CHP plant relies on a consistent concentration of supplied methane. If the concentration of methane being supplied is not consistent, then it must be compensated for. Measuring the methane here allows the user to monitor and maintain the concentration of the gas, and to make any adjustments to the process if the feed changes.

The OMA-300 process analyzer continuously measures 0-50 PPM H2S in the biogas stream to the CHP plant. Monitoring the H2S concentration ensures that the sulfur is being kept at safe levels, and that it will not exceed levels that could damage the turbines. The MCP-200 continuously measures CH4 in the biogas stream. Monitoring the CH4 concentration ensures that the gas maintains a consistent BTU value. Response time is critical for the CHP plant to keep high levels of sulfur from damaging the turbines, and to maintain a consistent production of power. An online analyzer at this location allows for rapid adjustments to keep the plant functioning at peak performance.

System Benefits

  • Continuously measures 0-50 PPM H2S and 50-100% CH4 in the biogas feed to combined heater and power generation facility.
  • Totally solid-state build with no moving parts — modern design for low maintenance.
  • Fast response time, analyzer updates reading in under 5 seconds.
  • Combined sampling system and controller allows for a cost-effective solution.

Example Gas Sample Conditioner

0-50 PPM H2S and 50-100% CH4 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 entrained liquid that could influence the measurement.
  • Integrated MCP-200 analyzer housed in an explosion-proof enclosure.

Further Reading