Plant types

3 TANKS DIGESTOR

2 TANKS DIGESTOR

1 TANK DIGESTOR

Main features:
The process of anaerobic digestion uses the dejections as such (liquid fraction + solid fraction), with immission of proper biomass even in great quantities that overcome the pumping limit. Usually a plant needs two or more digestors (primary and secondary).
The primary digestor (cylindric type) is equipped with a special mixer with horizontal axis that grants the complete mixin  of the slurry and of the biomass. The primary digestor is constantly feeded with fresh slurry and biomass according to a fixed loading plan and considering the compositions and characteristics of the different compounds, while the digested slurry will go out after a medium HRT in the tank of about 20 - 30 days to be then transferred in the secondary digestor, and then mixed again so to recover the remaining quantity of biogas. The HRT in the second digestor is of 30 - 40 days for a medium HRT up to 60 days.


Who needs it: 

Agricultural and breeding farming that have sufficient biomass availability during the whole year, thanks to which the production of biogas boosts, as well as the electric energy produced, improving at best the performance of the process.

Stages of the process:
To obtain the highest possible production of biogas, it is essential that the slurry are fresh when they arrive at the primary digestor and that the quality of the biomass is complete in its energetic structure. The slurry is conveyed to a collection, equalization, mixing and lifting tank, equipped with mixer and crushing pump that homogenize and transfer the slurry in the primary cylindric digestor. A special hopper equipped with dosing screw feeders for the loading of the biomass, that, through a specific program, let the necessary quantities in the digestor to grant the good operation of the process of digestion. The biogas produced in these anaerobic conditions is collected directly in the upper part of the digestor (or digestors), by a dome gasometric covering that has the form of a spheric cap. Through a pipeline connected with the collection covering of the digestors, the gas is bilance, cooled, dehumidified, filtered and transferred to the cogenerator groups, that produce electric energy and heat through the burning of biogas.
At the end, the slurry coming out from the digestor, now stabilized and deodorized, will be piled in one or more storage
tanks while waiting to use it in agriculture.

SUPER-FLOW PLANT FOR THE DIGESTION OF BIOMASSE

Main features:
This process of anaerobic digestion uses the dejections as such (liquid fraction + solid fraction), and therefore the digestor in these plants is a cylindric type equipped with a propelled mixer, an external timed- recirculation pump and a system of bottom openings, to obtain the movement of the slurry and the up-flow effect and the breaking of the scab. The digestor is constantly feeded with fresh slurry, while the digested slurry will go out after a medium HRT in the tank of about 20/25 days.


Who needs it:
Farming that intend to gain the maximum in terms of energy and money; because, thanks to the solid fraction in the dejections, the production of biogas boosts. It is suitable also for farming with limited or interrupted availability of biomass to add for the digestion with the dejections.
For this plant, too, there are many environmental advantages.


Stages of the process:
To obtain the highest possible production of biogas, it is essential that the slurry are fresh when they reach the digestor; that's why it is necessary to adopt all the most appropriate precautions to help the quickest evacuation of the slurry produced in the farm. The slurry collected is then transferred in a collection, equalization, mixing and lifting tank, equipped with mixer and crushing pump, where a small quantity of biomass can be added in fixed quantities, to enrich with organic matter the slurry for the digestor. The anaerobic digestion of the slurry as such with small quantity of biomasses to grant the pumping, is obtained inside a special digestor through the activity of bacteria that can break the complex molecules forming methane, carbon dioxide, water and hydrogen sulphide. The above mentioned biological activities are influenced by some factors such as: pH, time of permanence of the slurry in the digestor.

The two main factors that affects the whole process are undoubtedly the temperature and the time of permanence of the slurry in the digestor. In particular, the process of anaerobic digestion is helped by keeping the ideal temperature (for thermophilic bacteria 50 - 55°C, for the mesophilic bacteria 35 - 40 °C, for the psycrophilic bacteria 10-25°C). If the proper plant and managing conditions are respected, the energetic yields of the plant will reach excellent results in every season; the biogas produced is collected directly in the upper part of the digestor by a dome gasometric covering that has the form of a spheric cap.

Through a special pipeline connected with the covering of the digestor, the gas produced and recovered is transferred to the cogeneration group, that produces energy and heat throuth the burning of the biogas. Part of the heat produced and dissolved by the engine of the cogenerator is then recycled and used for the maintenance of the temperature in the digestor. At the end, the slurry coming out from the digestor, now stabilized and deodorized, will be piled in one or more storage tanks while waiting to use it in agriculture.

UP-FLOW CILYINDRIC MIXED PLANT

Main features:
This process of anaerobic digestion requires a previous separation using only the liquid fraction of the dejections, therefore it is absolutely free from mixing organs inside the digestor that prefers the channel structure. The effect of separation of the sedimentable solids from the liquid fraction of the slurry, due to a lack of mixing inside the digestor, will cause a positive effect of increase of the retention times of the solid fraction compared to the liquid one. This phenomenon, in fact, allows the quicker moving of the liquid fraction – that contains the matters ready for the digestion - from the digestor, and helps keeping the more complex molecules in the digestor for a longer time, allowing the bacteria to carry out their demolition and make them available for the transformation into biogas. However, the solids will reach the output of the digestor using the matched effect of the rising moves caused by the biogas and the presence of heating coils of the digestors, with the advancement movements caused by the positioning in the initial and final section in the digestor of the pipes for immission and exhaust of the fresh digested slurry.

Who needs it:
Essentially the farming of medium and large dimensions that wants to produce energy to use almost completely for the direct needs and, only in case of a surplus, to give it to a net operator. In addition, those who in general are forced to reduce or are sensitive to the reduction of the impact of their farming activity on the environment.

Stage of the process:
To obtain the highest possible production of biogas, it is essential that the slurry are fresh when they reach the digestor; that's why it is necessary to adopt all the most appropriate precautions to help the quickest evacuation of the slurry produced in the farm. The slurry collected is then transferred in a collection tand and then conveyed, by a special pumping station, to the separation treatment.

The treatment of mechanical separation of the liquid fractions from the coarse solids is always necessary and it is necessary to remove the slurry from the non-biodegradable parts in the time limits fixed for the digestion, as, for example, vegetable remains and hair that tend to reach the surface as an effect of the rising of biogas and to form a scab on the surface of the slurry; being formed by an intricate cellulose material, it fills some usable volume and can cause blocks in the digestor.

The solid fraction separated on top of the digestor can be collected and distributed as fertilizer on the agricultural soils, while the liquid fraction, rich in organic matters, will feed the digestor, usually of rectangular section and with one or more channels. The anaerobic digestion of the liquids is carried out in a special digestor by the activity of bacteria that can break the complex molecules forming methane, carbon dioxide, water and hydrogen sulphide.

The above mentioned biological activities are influenced by some factors such as: pH, time of permanence of the slurry in the digestor. The two main factors that affects the whole process are undoubtedly the temperature and the time of permanence of the slurry in the digestor. In particular, the process of anaerobic digestion is helped by keeping the ideal temperature (for thermophilic bacteria 50 - 55°C, for the mesophilic bacteria 35 - 40 °C, for the psycrophilic bacteria 10-25°C).

When the temperature of the digestion decreases, it is necessary to grant a longer retention time of the slurry in the digestor. Therefore, in psycrophilic conditions, it is convenient to fix a HRT of at least 60 days, while in mesophilic conditions it is possible to grant a HRT of just 18-20 days. If these conditions are respected, the energetic yields of the plant will reach excellent results in every season.

The biogas produced is collected directly in the upper part of the digestor by a gasometric covering with pressure control dome. Through a special pipeline connected with the covering of the digestor, the gas produced and recovered is transferred to the cogeneration group, that produces energy and heat throuth the burning of the biogas. Part of the heat produced and dissolved by the engine of the cogenerator is then recycled and used for the maintenance of the temperature in the digestor. At the end, the slurry coming out from the digestor, now

CHANNEL PLUG-FLOW PLANT

The biogas plants most frequently used and activated can be included in 3 different types, each one with particular features and, therefore, each one with its specific destination for the different farms.


PLANTS:
 


• Channel plant plug-flow type;
• Cylindric plant up-flow type mixed;
• Super-flow type plant for super thick biomasses

HIGHEST FLEXIBILITY
A planning element not to be ignored is the plant's flexibility, intended both as an aptitude for future enlargements and a san opportunity to use for long products that are different from those initially formulated.

WE GRANT THE VALUES AND PLANNED INCOMES
The guarantee for the success of a biogas plant is connected to the professionality of the single competences involved.
Rota Guido team is formed by engineers and technicians in every branch (mechanical, electric, electronic, chemical, environmental and microbiological) and they work for the research, the development and the planning in the technical offices and laboratories in our operating center of Corte de' Frati (CR).
We will be pleased to welcome you and be at your disposal, to fulfil all your special demands.
We will give you advices with competence and professionality and we will study with you the plant that fits your situation.

4 TANKS DIGESTOR

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