Biogastechnik Süd GmbH
Am Schäferhof 2
D 88316 Isny im Allgäu

 

Administration

 
phone+49 (0) 7562 970 85 – 40
e-mailinfo@biogastechnik-sued.de
fax+49 (0) 7562 970 85 – 50
homewww.biogastechnik-sued.de

 

Sales

phone
+49 (0) 7562 970 85 – 555
e-mailvertrieb@biogastechnik-sued.de

 

Service Biogas plants and components

 

phone

+49 (0) 7562 970 85 – 412
e-mailservice@biogastechnik-sued.de

 

Service Digestate evaporator and Biogas - small plants

phone
+49 (0) 7562 970 85 – 512
e-mailserviceGEW@biogastechnik-sued.de
FR DE
bg topillu
digestate evaporator
 

Vapogant Digestate Evaporator

Biogastechnik Süd GmbH

Our system processes the digestate of the biogas plant to produce a usable, concentrated fertiliser with reduced water content.

We remove most of the water from the digestate through vacuum evaporation using waste heat from the CHPS. At the same time, volatile nitrogen is bound so that any emissions during spreading will be minimised, making the nitrogen available as ammonium sulphate solution (ASS).

The goal is to use the available waste heat to thicken or enhance 100 % of the digestates produced in the biogas plant. This is achieved with a very high evaporation rate of 2.5 litres per kilowatt of thermal output. At 500 kW plant capacity, this is equivalent to a volume reduction of about 10,000 m³ per year.

The plant is available in a module size of 400 kW or 500 kW.

This provides the following advantages:

Storage
► The thickened digestate has much less volume and saves up to 70 % of digestate storage capacities.
► Digestate evaporation as an alternative to building additional digestate storages.
► No additional digestate storage problem due to the amended ordinance on facilities for handling substances that are hazardous to water (AwS) and the fertiliser ordinance.

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Transport

► Reduced volume means fewer trips (less impact on roads and population)
► Fewer passes over fields due to concentrated nutrients
► The weather risk is reduced and the impact of spreading increased.
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Nutrient management

► Upgrading the digestate to ammonium sulphate solution (ASS) that can be transported and concentrated fertiliser.
► Less nitrogen loss through ammonia emissions on the field so that less nitrogen has to be purchased.
► Improved nutrient management:

Thanks to the separate nutrient fractions, nutrients can be applied much more selectively and efficiently.
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Heat utilization

► Efficient heat use throughout the year
► CHP bonus guaranteed through efficient fertiliser production
► Integrates easily with existing plants (also for partial heat use)
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Structure

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Process description: Concentration and vapour cleaning


A mechanical separation precedes the digestate evaporation where the digestate passes through a fine-meshed screen (e.g. 0.5 mm) to be separated in a liquid and a solid phase.

The solid matter (solid phase) is put out on a suitable area for intermediate storage and can be used for targeted fertilisation as needed. During the time when no fertiliser is spread, it can be stored on open areas or in bunker silos.

The liquid phase is introduced into the process of digestate evaporation.

Inside the plant, the liquid phase is heated and put under a vacuum. In this step, part of the liquid phase evaporates, thereby thickening and concentrating the digestate. This step is repeated in a second evaporator. Heat recovery allows energy efficient evaporation and multiple use of the heat.

Inside the vapour cleaner, the gas phase that is produced through heat and vacuum is stripped of ammonia by adding sulphuric acid. In this process, ammonia is converted into ammonium sulphate and concentrated.

The ammonium sulphate solution (ASS) can be stored in separate containers.

The vapour produced in this process, which has been stripped of ammonia, is condensed to water (distillate) in heat exchangers and the recovered heat is used. The distillate is transported to storage tanks for intermediate storage. After the distillate has cooled down in the dry or wet cooling tower, it is used as a cooling liquid e.g. in the condenser heat exchangers.

The plant is sealed hermetically, resulting in a low-emission process.

The vacuum required for energy-efficient evaporation is generated by a vacuum pump. This pump is connected at the pressure side of the gas compartment of the biogas plant; thus, residual gases emerging from the digestate are safely returned to the biogas plant.

There they are either metabolised microbially (e.g. H2S that is converted to sulphur) or burnt in the CHPS (CH4).

At the end of the process, the concentrate (the thickened liquid phase of the digestate) exits the process under vacuum. This digestate is now concentrated and contains all nutrients also found in untreated, non-dried digestate – with the exception of ammonia. This highly volatile substance is concentrated in the form of ammonium sulphate solution (ASS).

Subsequently, the ASS is stored in a separate tank and can either be used selectively as a mineral fertiliser or sold.

Evaporation capacity of the plant

The Vapogant digestate evaporator has a modular design. The evaporation capacity is up to 2.5 litres per kW (therm) depending on the flow temperature, temperature difference and dry matter content in the inlet and outlet of the plant.

Closed loop of a biogas plant with Vapogant
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Substrate flow
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Mass balance
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Digestate composition
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1 Digestate from digester
2 Solid material through separation
3 Liquid phase after separation
4 Distillate: The water removed from the digestate for introduction, evaporation or use as process water
5 Liquid phase as concentrate
6 Ammonium sulphate solution (ASS)


Distillate use
Customers may use the vapour-cleaned distillate obtained from the evaporation process as needed:

Using the distillate for operation
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There are different options to use the distillate for operating purposes:  Storing the water to be used as washing water for stables and areas, as thinning water for pesticides and liquid fertilisers, etc.

Evaporation of the distillate through the wet cooling tower
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As a cooling unit is needed to operate the plant, part of the water may also be evaporated continuously through a cooling tower. Additionally, the cooled water is used as a cooling medium.

Indirect and direct distillate introduction
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The water is introduced continuously to a receiving stream, combined with an upstream distillate processing module if necessary, or it can be allowed to drain.


ASS storage and addition to the digestate

The ammonium sulphate produced by the plant can be used further as customers see fit:

Direct addition to the digestate
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The ASS is added directly to the digestate (thickened liquid phase):
Very easy integration into the system while retaining the full nitrogen benefit

Separate storage
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The ASS is stored in separate storage tanks (e.g. 100 m³ horizontal) to be spread subsequently using a sprayer. - Ideal to supply plants with the amount of nitrogen they need.


Sulphuric acid store
Sulphuric acid is added to the process. It binds the ammonia and produces an ammonium sulphate solution (ASS).

There are different ways to store sulphuric acid.
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Control

Fully automated visualized process display of the control system on a 15" multi-touch screen

Technical data

Performance data of the 2-stage plant with up to 400 kW heat consumption
Suction volume: up to 2000 l/h digestate at 40° C*
Dry matter content: max. 6 %
Particle size in digestate: < 0.5 mm
Concentration to DM content: up to 15 % **
Distillate output: approx. 2.5 l/kWh thermal ***
Distillate current: approx. 1000 l/h **
Flow temperature: 86° C
Return temperature: up to 73° C
Heat consumption: up to 400 kW
Dimensions L x W x H in m: 16.5 x 4 x 6.4


    * Digestate from biogas plants fed with agricultural feedstock.
  ** With a dry matter concentration of more than 15 % to maximally possible 25 %, the performance data are lower.
*** The value is reduced accordingly when heat is extracted.


Performance data of the 2-stage plant with up to 500 kW heat consumption
Suction volume: up to 2000 l/h digestate at 40° C*
Dry matter content: max. 6 %
Particle size in digestate: < 0.5 mm
Concentration to DM content: up to 13% **
Distillate output: approx. 2.5 l/kWh thermal ***
Distillate current: approx. 1250 l/h **
Flow temperature: 86° C
Return temperature: up to 73° C
Heat consumption: up to 500 kW
Dimensions L x W x H in m: 16.5 x 4 x 6.4

    * Digestate from biogas plants fed with agricultural feedstock.
  ** With a dry matter concentration of more than 13% to maximally possible 25 %, the performance data are lower.
*** The value is reduced accordingly when heat is extracted.

The performance data of the two plants are based on a constant flow temperature and a maximum ambient air temperature of 27 °C.

Downloads

Deutschlandkarte GRV Referenzkunden DE.jpg
18 003 06 FO Fragebogen Gaerrestverdampfung DE.pdf
101 012 02 BRO DE VVT GRV KD.pdf
101 014 03 BRO VVT GRV EN KD.pdf
101 015 03 BRO VVT GRV FR KD.pdf
101 016 02 BRO VVT GRV CZ KD.pdf
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