ANAEROBIC BIOGAS PLANTS
- low cost, easy and fast construction;
- cost-effective operation and maintenance;
- effective synthesis of biogas, high product yield;
- clean drains after the reactor;
- exclusive capture system and concentration of stable nitrogen form;
- effective energy saving system;
- payback period is half, in comparison with decisions of competitors.
Stephen Dvorak, designed DVO’s patented digester in 1999, and built the first of this unique new design in 2001. DVO has since installed over 120 digesters at 90 sites in 18 states within the USA (more in other countries). About 10 additional are under construction. Industrial and agricultural DVO digesters collectively produce over 80MW of renewable power.
Spectrum-Product PE is the exclusive representative of DVO Inc. in Ukraine – the leader of the biogas industry in the USA, based on anaerobic digestion of bio-waste.
We are engaged in adapting DVO technology in Ukraine, its promotion and implementation in the production of biogas, environmental protection among Ukrainian companies with available organic waste.
DVO has extensive experience in digesting bio-waste to convert it into biogas (electricity) and fertilizer.
The patented DVO system is a two-stage process of digestion of bio-waste, occurs in one biogas reactor with the production of three products: biogas, which can be used to generate electricity and heat, refueling vehicles and agricultural machinery; solid organic waste – high-quality fertilizers to improve soil fertility; liquid organic waste – they do not emit an odor and can be used as fertilizer for growing crops, as well as for irrigation of agricultural land
Plug-flow-digester operates on the principle of continuous and uniform feed of raw materials to the digester. The digester works with raw materials up to 90% moisture – wet digestion. Continuous mixing and maintaining a temperature of 38 ° C gives the best degree of digestion, allowing bacteria to process more raw materials and produce more biogas, thereby increasing plant productivity. The mixing of raw material is carried out with the help of biogas extracted. Biogas is fed into a biomass layer in the digester under pressure. Under the influence of biogas bubbles moving upwards, a spiraling movement of material in the digester is created, supporting it in a suspended state, which prevents the raw material from settling and stratification. This technology does not apply biomass mixing in the digester with mechanical mixers, which significantly reduces energy consumption and saves electricity.
Overview of the anaerobic digester.
The waste is fed daily to a biogas plant and loaded into the receiving tank. After preparation by dilution, mixing, crushing (if necessary), the effluents goes into the first charmber of the digester which calls – acidic. In this chamber, the mass is homogenized and heated to a temperature of 38 ° C. Capacity of the acid chamber is calculated for 1,5 days of stay. The acid chamber operates in a continuous Plug-flow and passes into the methanogenesis chamber.
In the acid chamber, the hydrolysis process takes place, aerobic bacteria rebuild high molecular organic substances (protein, carbohydrates, fats, cellulose) into low molecular compounds such as sugar, amino acids, fatty acids and water.
In the methanogenesis chamber, the oxidation phase takes place – pH is reduced, and acid-forming bacteria are involved in the cleavage. Individual molecules penetrate into bacteria cells, where they continue to decompose. In this process, the anaerobic bacteria partly participate in the process, they consume the remains of oxygen and thus create the anaerobic conditions necessary for methane bacteria. After that, the decay process takes place – the acid-forming bacterium from organic acids creates the starting products for the formation of methane (acetic acid, formic acid).
The decomposition of organic matter into separate constituents and conversion to methane can only take place in a humid environment, because bacteria can process substances only in a dissolved form.
The digester is a gas-tight, fully sealed tank from acid-resistant reinforced concrete of rectangular shape. To cover the reactor hollow ceiling panels are used, the top of the structure is thermally insulated with a polyurethane foam layer of the insulator by spraying.
Diverting organics from landfills – Goshen, IN
Under the continuous feeding of biomass into the digester, natural movement occurs in it from the inlet to the outlet by hydraulic displacement. Thus, there are no moving parts in the digester itself, that makes the entire system very reliable.
The preheated substrate is constantly mixed. In the digester, mixing takes place with the help of extracted biogas. Biogas is fed into the biomass layer in the digester under pressure. Under the action of biogas bubbles moving upwards, a spiral movement of raw materials is created in the digester, supporting it in a suspended state, which prevents the substrate from settling and disintegrating. Inside the digester, a temperature fixed for microorganisms is maintained – 38.3 ° C (mesophilic digestion process). The average time the hydraulic substrate is located inside the digester- about 20 days. At the output we have two products: biogas and bio-fertilizers (solid and liquid substrate).
The biogas pressure is 0.02 bar. In order to prevent the rise in pressure, the digester is equipped with a relief valve, which activates when the pressure rises and releases biogas into the atmosphere by burning it through a torch.
The biogas plant is equipped with emergency flare units in case the engine / engines (cogenerators) do not work, but biogas needs to be spent. The gas system includes a blower (compressor), a steam trap, a desulphalizator, and etc.
From the digester through the pipeline there is a continuous supply of biogas to the cogenerators. They generate heat and electricity. Heating of the raw material in the receiving chamber (pit) and the maintenance of the temperature in the digester takes place through the pipes, using the hot water recirculation system. The required water temperature, to support the digestion process, is determined by a sensor system that controls the mixing units of the heating system, that is, only the required temperature of the coolant is fed through the pipeline to the necessary digester zone.
Anaerobic Digestion: Beyond Waste Management
Fermented mass from the digester enters the tank, which is equipped in the digester, and then is fed to the screw press separators by pumps. If it is necessary to reuse water for technological purposes, then biogas plant is equipped with devices for additional cleaning of the liquid. All technological processes are controlled by the automation system. For management, only one person is enough, for 2 hours a day. The digester control is fully automated.
Water and solid inclusions after the bio-gas digester do not have an objectionable odor and can be used: solid inclusion – as a litter and fertilizer to improve soil fertility; water – for irrigation of agricultural crops