Better biogas plant substrate mixing during fermentation is great news for a biogas operator. The importance of “creating a stir” in the fermentation tanks of fully mixed bio-reactors for better biogas yields, and improved process stability, is becoming better understood by many AD plant clients around the globe, as more Anaerobic Digestion Plants are being built and the biogas industry matures.
A scan of world news on this subject revealed that biogas operators, and researchers, from China to Malta are investing in biogas reactor mixing equipment.
In the first news release we have here, the Landia GasMix system has been installed as a research tool. This has been done in order to discover achievable “best practise” biogas production data, for feedstocks consisting mainly of rice straw and liquid pig manure.
In the second a new completely mixed biogas reactor will have a biogas recirculating gas sparge system installed centrally in the top of the circular fermentation tank, to provide good mixing. And, in the third another proprietary mixing system is installed for process improvement purposes.
In our final release, it is clear that water treatment companies are also retrofitting enhanced mixing systems, and in this case the system (with other optimizations included) is said to be 3 times quicker to achieve the required biogas output, than a standard plant, as a result.
Now let's get started. Read the following to understand why good reactor tank mixing is so important:
One of China's key comprehensive educational institutions has installed Landia’s GasMix digester mixing system to test various feedstocks and ascertain the best methods for optimising the AD process.
Located in the ancient capital of six dynasties in eastern China, the University of Nanjing’s Bioenergy Research Institute has so far been experimenting with feedstocks consisting mainly of rice straw and liquid pig manure that is mixed and pumped to the digester.
The 300m³ digester at the pilot plant benefits significantly from the fact that the Landia GasMix is externally mounted. This makes routine servicing much easier than trying to gain access to traditional propeller mixer systems that are located inside the digester. This disadvantaged design always creates significant downtime, as well as health and safety issues because of having to empty the digester.
Mr. Zhang Yabing, Manager of the biogas plant at Nanjing’s Bioenergy Research Institute, commented:
“Not only is the entire mixing system of the Landia GasMix mounted outside the digester, the power consumption is also low and the cutting system of the chopper pump cuts straw into smaller particles”.
He continued: “As an added bonus, it has also turned out that biogas production is much higher than expected”.
An 18.5 kW Landia GasMix is installed at the university’s biogas plant, but because it only requires only a short operation time to mix the whole digester, approximately 20% – it is very energy efficient. Compared to the increased biogas production, GasMix can be considered an ‘energy neutral’ mixing system – one that truly mixes the entire contents of the tank for optimum efficiency.
“The digestion tanks are equipped with state-of-the-art mixing technology which uses part of the biogas extracted from the tanks and compresses it to high pressures by means of water-cooled industrial gas compressors. The compressed biogas in turn flows through a series of pipes (lances) installed within the tank to agitate the waste-water slurry thereby preventing any sediment formation within the tank.”
“The robust MULTIMix system guarantees continuous utilisation and homogenisation of the substrates, and stable plant operation.”
“the Omnivore retrofit demonstrates how wastewater treatment plants (WWTP) can increase digester loading and biogas production using existing infrastructure. David Schneider, vice president of business development with Anaergia, said the retrofit includes the company’s high solid hydraulic mixing system and the proprietary recuperative thickening system. The system’s purpose is to create capacity in the existing digester tank. In fact, a traditional digester must have three times the volume of an Omnivore digester to produce the same amount of biogas, according to the company.
We hope that you agree that the evidence we have provided in this article shows that biogas plant substrate mixing during fermentation is creating a “stir”, or at least a lot of action from AD Plant Operators!