Technical article Biogas scrubber monitoring

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1 Author: Patrick Rotzler More profit, less hazard Scrubber monitoring for biogas plants Investing in a biogas cleaner makes your biogas plant profitable and an additional monitoring system covers your investment! Scrubbing is the operation that removes unwanted compounds from the biogas before it is used. Usually these compounds will cause several pains in some way. The main culprit to be scrubbed will be Hydrogen Sulphide (H 2 S). Depending on the biomass and the preceding production process the content of H 2 S in the raw biogas is typically between 0.1% and 3.0%, in special cases up to 5.0%. Under combustion H 2 S converts into Sulphuric Acid (H 2 S O 4 ) which will lead to heavy corrosion of engines and auxiliaries. The results are much shorter life time, loss of income during overhauls and break downs as well as expensive repairs and frequent oil shifts. H 2 S scrubbers reduce H 2 S levels to an absolute minimum and are reliable, economical and an essential part of the engine life providing operating stability. Desulphurisation of biogas is absolutely necessary for economical engine operation. The costs of servicing and repairs will increase significantly with uncleaned biogas, and a gas filter can pay for itself in 1-1½ years. We ve had very favorable experiences with BioGasclean s desulphurisation plant, which functions very efficiently and reliably. Thomas Elsenbruch, Biogas Program Manager GE Energy When theory meets practice BioGasclean Bio Scrubber Monitoring with AwiFlex from Endress+Hauser. To decrease the H 2 S content, companies use bio-scrubbers from BioGasclean. BioGasclean s biological H 2 S scrubbers easily meet the mentioned requirements given any flow volume and H 2 S content of raw biogas. The H 2 S is removed in a biological process, no chemicals are required and therefore no chemical waste is being produced. The used sulphur oxidation bacteria need certain living conditions: Seite 1/5

2 - Place to live and multiply (on a packed media inside a closed acid-proof tank) - Sulphur (the H 2 S containing biogas) - Oxygen (supplied by atmospheric air) - Moisture (soft water or gas condensate) - Nutrients (liquid NPK nutrient or digested sludge liquors) - Temperature between C The selected cocktail of bacteria and nutrients oxidizes the H 2 S back to SO 4 and brings the sulfur back to the wastewater where it came from. The wastewater with sulfur is a valuable fertilizer and is normally used for plantations or farmland. Additional injections of atmospheric air feed the bacteria with O 2 and increases the biological scrubber s efficiency. With BioGasclean s technology, the H 2 S content can be reduced from over 3% to less than 0,001%. Furthermore, operating and maintenance costs are approximately 90% lower than the ones of a chemical scrubber system. Scrubber monitoring with Endress+Hauser AwiFlex gives your investment the necessary safety In order to monitor the fuel quality and to control the O 2 content for safety reasons, an additional gas analyzing system is needed like AwiFlex from Endress+Hauser. It is specifically designed for biogas applications and it s already successfully implemented in hundreds of biogas plants worldwide. Configuration and installation are easy for every plant layout and setup. It is individually expandable and doesn t need much maintenance effort. By integrating an industry PC with Linux multi-user/multi-tasking operating system, AwiFlex offers more options than any other conventional analysis system. It is a complete solution adjusted to every customer s needs. AwiFlex actively sucks in biogas with a vacuum pump from one or several measuring points, even over greater distances. When measuring abnormal values AwiFlex stops for safety reasons. The designated levels can be defined by an Endress+Hauser Service Engineer during on-site commissioning or set independently. In the past, hydrogen sulfide monitoring in both inlet and outlet of scrubbers caused problems for standard H 2 S gas sensors. In contrast, AwiFlex H2S sensors are developed especially for conditions with condensing humidity: Between the measuring intervals the sensors are flushed with fresh air which considerably prolongs their life span. Seite 2/5

3 AwiFlex Performance characteristics: - Easy installation, simple calibration & user friendliness - Minimal operating and maintenance requirements - Error messages and alerts/alarms in clear text - Automatic detection of overloads, temporary switch-off of involved measuring channels to preserve the sensors - Practically unlimited storage of measured values and other events - 12 months warranty period (including wearing of the sensors) - No cross-sensitivity of sensors to other gases - Direct measurement of all components, no indirect calculation or gas dilution - One or more measuring points (fermenter, secondary fermentation, desulphurization, CHP) - one system for all analysis applications - Integration into plant-wide systems via Profibus, Ethernet, RS232 & analog outputs - Modular composition and subsequent extension of systems possible - Comfortable remote retrieval of measured values and status information AwiFlex sensor measuring ranges Measuring range Principle of Measurement H 2 S 0-20/-200/-500 ppm Electrochemical H 2 S /-3000/ ppm Electrochemical H /-5000/-20000/ ppm Electrochemical O vol.-% Electrochemical or paramagnetic CH vol.-% Infrared 2-beam, temperature & pressure compensation CO vol.-% Infrared 2-beam, temperature & pressure compensation P mbar pressure compensation of all sensors Seite 3/5

4 SWE, Korat, Thailand Capacity: 4,000m3/h, H 2 S: 3,000 to 100ppm 5.6 Mw power plant GFE, Denmark Capacity: 1,200m 3 /h H 2 S: 3,000 to 10ppm Cogeneration on gas engines SK Power Suratthani, Thailand Capacity: 2,000m3/h, H 2 S: 3,000 to 100ppm 4.2 Mw power plant Endress+Hauser AwiFlex Seite 4/5

5 The Endress+Hauser Group Endress+Hauser is a global leader in measurement instrumentation, services and solutions for industrial process engineering. In 2010, the Group generated with over 8,500 employees worldwide net sales of around 1.3 billion euros. Structure Company-owned sales centers and a network of partners guarantee competent worldwide support. Production centers in eleven countries meet customers needs and requirements quickly and effectively. As a successful family-owned business, Endress+Hauser is set for continued independence and self-reliance in the future. Products Endress+Hauser provides sensors, instruments, systems and services for level, flow, pressure and temperature measurement as well as liquid analysis and data acquisition. The company supports customers with solutions and services in automation engineering, logistics and information technology. Our products set standards in quality and technology. Industries Customers are primarily from the chemical/petrochemical, food & beverage, water/wastewater, life science, oil & gas, power & energy, renewable energies, primaries & metal, pulp & paper and shipbuilding industries. Endress+ Hauser supports its customers to optimize their process engineering procedures while taking into consideration reliability, safety, economic efficiency and environmental protection. History Founded in 1953 by Georg H Endress ( ) and Ludwig Hauser ( ), Endress+Hauser has been solely owned by the Endress family since The company group, headed by Klaus Endress since 1995, has developed from being a specialist in level measurement to a provider of complete solutions for industrial measuring technology and automation, with constant expansion into new territories and markets. For further information, please visit or Contact Patrick Rotzler patrick.r@th.endress.com Marketing Manager Phone Ext.217 Endress+Hauser (Thailand) Ltd. Fax Moo 4, Bangkruai-Jongthanom Road Mahasawat Bangkruai Nonthaburi Thailand Seite 5/5