Feature Pumps The mixer of choice for biogas plants


Denmark has ambitious targets of becoming independent of fossil fuels by 2050, and biogas production will play a crucial role. One company leading the way in biogas plants is ComBigaS, whose new demonstration plant is using pumping and mixing equipment from Landia. Michelle Lea visited the plant to find out more


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ver the last three years ComBigaS has been developing a biogas project in the Ringkøbing-Skjern municipality of Denmark. The demonstrational biogas plant is now working at full capacity, exactly as planned, with the help of pumping and mixing equip- ment from Landia.


Biogas is a renewable energy source that is enjoying a surge in popularity throughout Europe. Countries like Denmark see it as a way of helping them become independent of fossil fuels, and reusing waste from agriculture, that would otherwise have to be treated and disposed of responsibly. Also, the organic waste is more effectively utilised after it has been degassed. Kent Skaanning, CEO at ComBigaS, described the design concept behind the demonstration unit: “Due to its countryside location, the plant is designed to take up as little space as possible, and is compact and symmetri- cal.” In order to transport the waste and biogas via pipeline, it makes sense to have more smaller plants, rather than one larger plant that may be located a fair distance from the farms where the waste is sourced.


Odour control also needed to be taken into consideration during the design stage. Skaanning said: “Biogas smells awful, but that’s only a problem if you get the smell in your nose!” To ensure the plants are completely odourless, all


ures of biogas, said Paul Davies from Landia. But, when you have some sixteen pallets (400kg per pallet) of tomato leaves to dispose of every day, then utilising the heat and electricity from them makes perfect sense, This compares to what used to be a disposal cost of around £100,000 pa, not to mention sending two and half thousand tonnes of waste pa to landfill. With Landia’s help, the tomato producer, has been developing an innovative AD system. This may be an R&D site, but methane is already being extracted and reused to produce considerable amounts of electricity and heat for the site’s green- houses. The company is also close to producing an enzyme-rich fertilizer that works well on grass, as well as an eco-fuel. The masses of thick tomato leaves first have to be fed into a hopper, from where they are chopped by a macerator. Up to 40% dry matter, the leaves have a very thick consistency, so pre-treatment is vital. At this stage, a stainless steel 5.5 kW MPTKR chopper pump from Landia is utilised to break down the organic plant material in a reception tank. “Getting the leaves into the system in a way that you can get them to do what you want them to do has been the biggest challenge,” said Davies. “Our customer has wanted to try and understand what happens at the plant at different phases and times. This isn’t a typical sludge-like digestate you find at most anaerobic digestion systems, where in some cases there seems to be a very non-scientific, ‘chuck everything in’ approach...” After being physically reduced by the macerator, tomato leaf plant matter is transferred to a buffer tank, where it is heated and also agitated by a 3kW DG Landia pump to enhance the enzyme-breakdown process. Careful fine tuning has gradually reduced this retention time from 14 days to just seven. Solids in the green liquid are further reduced in digesters by small (just 0.75kW) Landia transfer pumps, one in each of the four tanks in the batch loading system. Davies concluded: “We’ve tried to understand the aims of our customer as quickly as possible, which has resulted in our chopper pumps becoming a key part of optimising the process.”


I Process & Control JULY/AUGUST 2013


Landia’s GasMix system ensures there are no mechanical parts in the tank


means the biomass is completely safe once it has been degassed.


Annual intake of manure and waste materials is currently 27,700 metric tons, which is used to produce 2.5mil- lion cubic metres of biogas (equivalent to 1.6 million litres of oil). The pro- duced biogas is distributed via pipeline to the district heating plant in the near- est city. From here, electricity and heat is supplied to the households and industries in the local area.


tanks, pipe connections and containers are enclosed, preventing leaks. The raw material for the plant, pig and cattle manure, is transported via underground pipes from three local farms. The plant itself consists of two reactors, two storage tanks, one for manure and one for plant material, and a storage tank for the biogas. An anaero- bic gasification process takes place to produce the biogas.


The plant is powered by a ther- mophilic process, whereby temperature in the reactor is set at approximately 52˚C. After a certain amount of time in the reactor at this temperature, all the bacteria in the waste is killed, which


The ComBigaS demonstration unit shows how:


•80% of manure can be converted to biogas


• energy can be allocated locally or nationally


•manure and bio- gas is transported via pipelines and not the road network


•jobs in rural areas can be created •local ownership of the biogas plants is ensured


Pumps help produce ‘carbon neutral’ tomatoes


n a separate biogas application, this time in the UK, Landia products are proving their value in dealing with a somewhat alternative feedstock. Tomato leaves definitely wouldn’t be your feedstock of choice for trying to generate headline fig-


Landia has a long history of success- ful involvement in biogas applications, one of the reasons it was chosen to supply pumping and mixing technology to this plant. For example, the com- pany’s submersible agitators have many different uses, such as stirring sandy slurry or manure mixed with organic residues like straw, corn or grass, and to carry out the mixing and size reduction of dry matter particles before they are fed into the digester.


Dry installed pumps are used for pumping/transferring manure between tanks. Pump and piping blockages are avoided thanks to a cutting system that is separated from the pump casing and impeller. This ensures all chopping and pulverising of dry matter is completed before it enters the pump housing. And crucial to the successful opera- tion of the plant is Landia’s GasMix system, which mixes the media in the biogas reactor tanks. The stirring effect in the media is both horizontal and ver- tical, optimising the homogenisation of the anaerobic digester contents. GasMix also has many other advan- tages, including; no rotating equipment inside the tank; easy service and main- tenance can be completed outside the tank, eliminating the need to empty the tank and preventing the loss of gas pro- duction during maintenance; powerful mixing and effective size reduction achieved by a chopper pump, top gas/sludge ejector nozzles, and a bottom mixing nozzle; and a 3-dimen- sional mixing pattern which reduces the formation of scum layers. The demonstration plant has been running full scale for almost a year with positive results. The next step is for the concept to be implemented throughout the rest of the municipality, and even- tually throughout the rest of Denmark.


Landia T: 01948 661200


www.landiaworld.com 17 Enter 218


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