Frequently asked questions

 

 

Biomass Gasifiers: How do they basically work?

For the central part of the gasification plant, in which the wood calorific value in a product gas is transferred, come
some fundamentally different types in question.

In the power range under consideration here currently no significance is the group of so-called moving bed method
including inpatient and the circulating fluidized bed count.

 

Of the technical complexity of these types of systems basically so high that the specific investment costs with lower power, would be disproportionate.

In fluidized bed gasifiers biomass is introduced into a layer of sand or a similar "bed material" which is maintained by the injection of the gasifying agent to the base in suspension.

 

When circulating Fluidized bed is discharged from the reactor by the resulting flow of bed material upwards,
separated from the product gas and recycled to the gasifier, while the stationary fluidized bed of the influx of gasifying agent just sufficient to maintain the fluidized bed in suspension.

The relevant consideration for the power range type group are the so-called fixed bed process is where the gasification of biomass within a mostly stationary, cylindrical container takes place in "established" zones, which supplied the through chips sequentially.

 

The cylindrical gasifier vessel is made of steel, with a protective layer against the effects of the inside
temperature and gas components is provided.

 

The enclosure can be used as double jacket be carried out. Through the gap the air can be guided for the gasifier and thereby be preheated.
The two main types are of the countercurrent gasifier and the direct current whose Names from the leadership of the gas stream relative to the direction of Fuel feed derived.

 

Countercurrent gasifier

In a fixed bed gasifier, which operates according to the counterflow principle, moves as in  can be seen the air / gas flow in the direction of the fuel opposite.

Usually this means that the fuel from the top, where the gasifier , while the air from the bottom and fed to the product gas is withdrawn above.

This means that wood gas, pyrolysis zone has to happen and there significant amounts of long-chain hydrocarbons, often with the collective term "tar" described, pulls with him.

 

The removal of tars in the product gas for use a CHP is necessary, not only represents a major technical challenge,
but is given the tar amount in a gas countercurrent gasifier also a notable reduction in the efficiency of the system, as far as these residues can not be recycled back into the plant.

 

Due to these problems be counter-flow gasifier despite potential advantages in terms of feedstock insensitivity
and the internal heat utilization rarely offered.

 

 

 

Our DC gasifier

In direct current gasifier is air / gas flow and fuel move in principle in the same direction. Usually the air is supplied in a constricted oxidation zone .

 

The narrowing has the goal despite a possible lateral feed the entire gasifier cross section uniformly to supply air and for a homogeneous fuel distribution to ensure in this zone.

A direct current gasifier can generate significantly tarfree wood gas as a countercurrent gasifier.
However, the theoretically possible low tar yields may in practice
often not be achieved. This is mainly because that wood is a natural product of inhomogeneous
is, which also still exists in large uneven and moist form.

 

To small wood chips may hamper the even distribution of air too large chips may jam and with so-called "bridging" the movement stop of the material through the system, or at least create areas where the
Gases flow preferable and thus hinder a uniform implementation.

 

If the material locally too damp, can at these points by relatively low temperatures remain large amounts of tars. In practice, this means that even with optimal reactor design and process management product gas also from a direct current gasifier can only be used in an engine.