Renewable energy use (biomass)

BUCO heat exchange plates for fermenter heating directly in the biomass as a use of regenerative energies

In order to ensure an optimal fermentation process and thus achieve the highest possible gas yield, the temperature level in particular should be kept as constant as possible. These processes take place in thermally insulated, heated fermenters. To heat the fermentation substrate and to keep the temperature level constant, the fermenter is equipped with a heating device. The main focus is on the integrated heating devices and wall mounting. Our BUCO heat exchange plates are attached to the fermenter wall via brackets. All parts are made of stainless steel. They are therefore resistant to corrosion and ageing and have a very good thermal conductivity and better heat transfer values than plastic, which has a positive effect on the dimensioning of the heat exchanger surface.

The importance of renewable energy sources such as solar, wind and geothermal energy is increasing due to the current situation. In Germany, around 60 % of total consumption is currently made up of oil and natural gas, and only 40 % of Germany‘s energy needs can be met from domestic sources. Biogas is a frequently discussed topic due to technical developments. Environmental and climate compatibility as well as social acceptance make this energy source a component worth promoting to secure the energy supply. According to conservative estimates, about 5.5 % of natural gas consumption in Germany could be covered by biogas. Biochemical conversion processes such as biogas production are based on fermentation processes. One of the most important process variables that influence process stability and biogas production is the fermentation temperature, which influences the rate of anaerobic degradation. Within the fermentation spectrum, a distinction is made between three temperature ranges in which the corresponding bacterial strains thrive.

  • below 25 °C (psychrophilic strains)
  • 30 °C to 45 °C (mesophilic strains)
  • above 50 °C (thermophilic strains)

Most agricultural biogas plants are operated in the mesophilic temperature range. Fermentation and release of biogas do not occur uniformly. Rather, gas generation depends on the biological activity of the microorganisms involved and the digestibility of the initial substrates. In order to ensure an optimal fermentation process and thus achieve the highest possible gas yield, the temperature level in particular should be kept as constant as possible. These processes take place in thermally insulated, heated fermenters. To heat the fermentation substrate and to keep the temperature level constant, the fermenter is equipped with a heating device. The following can be ascertained from the experience gained in the industry: A distinction is made between integrated heating equipment and wall mounting, on which the main focus is.

This is usually done with plastic pipes. Although these are inexpensive, they lengthen and have to be laid much closer together. This reduces the number of passages and leads more quickly to deposits of substrate with the disadvantage of poorer mixing and reduced thermal conductivity. Oxygen diffuses through all plastic pipes and gets into the heating water. This undesirable fact leads to silting of the heating water and thus to a constant deterioration of the energy exchange. Thus, more and more energy is needed to achieve the desired heating effect. In order to compensate for the heat loss, the flow temperatures are usually increased, but this results in faster evaporation of the stabilisers in the plastic and thus faster embrittlement. Oxygen diffusion, on the other hand, increases even more as the plastic pipes become brittle. This fact can also lead to corrosion of metallic heating pipes and boilers, as these are not protected against corrosion. Heating devices integrated into the tank wall have not proved successful with concrete, as this can lead to spalling of the building material.

In some cases, underfloor heating systems are also concreted into the tank floors. However, their effectiveness is limited, as sinking layers have a heat-insulating effect and the heat output of the underfloor heating is severely restricted.

Our solution

BUCO Heat exchange plates are attached to the fermenter wall via brackets. Heat exchange plates mounted on the tank wall (see picture).

Conclusion

All parts are made of stainless steel. They are therefore resistant to corrosion and ageing, and have very good thermal conductivity and better heat transfer values than plastic. which has a positive effect on the dimensioning of the heat exchanger surface. There is no oxygen diffusion and no entry of hydrocarbons or ammonia into the heating system. Lower pressure losses allow the use of smaller and thus cheaper pumps. Incrustations, clumping and blockages due to long- and short-fibre substrate, which cause insulating behaviour, are avoided.

We have always assimilated engineering science and thermodynamics optimally in the various manufacturing processes.

Thermodynamicists,mechanical engineers and welding engineers define the dimensioning, design and construction of customised heat exchanger panels and systems in materials ranging from mild and austenitic steels through to titanium, and ensure successful distribution of their work worldwide.

In doing so they fall back on production engineering expertise and calculations developed in the course of the past hundred years that are still being continuously optimised in an ongoing process.

In the perception of our customers, the Buco product stands for:

Technical and process-oriented consulting
Thermodynamic efficiency
Quality and longevity