AD Operators Wrong to Run Pumps Into the Ground – say Landia
Landia, the Danish based water treatment equipment manufacturer which also provides a full installation and maintenance service on their products, (and will also be at the UK AD & Biogas Exhibition and Conference on July 2 & 3 2014, (Stand B001)), has spoken out about mixing problems.
Landia has seen very many anaerobic digestion plants in recent times, and they are apparently witnessing the presence of an increasing amount of improperly shredded food waste. That material is adding to the inevitable additional contaminants in domestic-green-bin-waste already present, and is causing problems for many AD Plant operators in inefficient digestion and lost biogas production.
They feel strongly that that only the very toughest pumping and mixing equipment, which has been designed for the purpose, can meet the industry’s demands (their GasMix product being their offering).
“Mass-produced, bog-standard propeller mixers don’t last very long at all in AD environments”, says Landia’s Paul Davies. “We now see some operators just running their [competitor’s] pumps into the ground because it’s actually cheaper to replace them completely than get at them to carry out maintenance. This can be the case for any type of mixing system that doesn’t allow you to carry out a service from outside the tank. Externally-mounted units have huge operational and safety benefits. Everything is at ground level, so there’s no working at heights. Nothing is in the gas-zoned area, so there’s no need for breathing apparatus. To maintain equipment such as submersible mixers, there’s no option other than to climb up, peel back the lid of the digester and purge the tank, which is extremely costly and time-consuming”.
“Small submersible mixers [provided by other suppliers] will often be running flat out, lasting two years or much less – compared to a chopper pump that can last 25 years. You’d think energy savings would be at least part of most AD operators’ decision making, but that’s not always so. Three 30kW pumps doesn’t automatically mean 90kW hours because they might only need to run for a maximum of fifteen minutes per hour”.
Davies also pointed out that the rising quantity of acidic food waste, which is now very often being being included as feedstock, can be corrosive to lower initial cost cast iron equipment, and that food waste that contains plastics from packaging can also cause problems without the right processing, or sufficiently strong pumps and mixers to handle it.
“Over-shredding of plastics will make particles too small to be screened out”, he says, “But under-shredding can create a floating mattress of plastic in the digester, which will see gas production reduce and then eventually have to stop so that someone has to go in manually and remove it all. AD downtime isn’t something you want. Lost revenue can amount to thousands of pounds per day – and a problem with fulfilling your contract to the energy provider”.
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Landia GasMix Units are:
- Purpose designed for AD Plants
- Provided with in-built shredding/macerating capability
- Manufactured in corrosion free materials
- Do not need to be run continuously – bringing far longer equipment life-times and reduced servicing intervals
- Proven over many years use in AD plants and related process applications
- Energy efficient
- Externally mounted, simple and safe to maintain, without requiring plant downtime.