Frequently asked questions

 

 

Gas processing and recycling

Wood gas consists in the use of air as a gasifying agent to a large part of nitrogen and carbon dioxide, while
the calorific value by the content of the combustible gases carbon monoxide (CO), hydrogen (H2) and in small
amounts of methane (CH4) is determined.

 

It is in the normal state already a so-called "Lean gas", ie a gas with a heating value of about 1.2 kilowatt hours
per cubic meter far below the natural gas (about 10 kWh / m³) is.

 

When hot - the temperature of the product gas is located at the outlet of a direct current gasifier at several hundred degrees Celsius - is the energy density, that is the calorific value per unit volume, but again significantly lower.

 

Cooling is therefore not only necessary to the thermal load limits not to exceed an engine, but also to the use of the already lean gas reduced engine power is not further reduced.

 

When recovery in a gas turbine may be dispensed with cooling of the gas, however, these aggregates in the considered power range, so-called micro gas turbines, for Wood gas is not available.

 

 

Gas Processing

While large gasification plants to invest in very expensive purification  such as wet electrostatic precipitators or quenching is concerned, bewith small wood gasification plants for cost reasons often simpler procedures favors.

 

A first cooling stage is usually installed before each cleaning system. There on followed by either a filter system for hot product gases or more cooling stages andafter a cleaning system for cooled gas timber.

 

For small wood gasifiers the gas cleaning normally restricted to theRemoval of dust and tar. The assessment of the technologies can be based on the ratiocarried out by investment and operating costs for gas purity attainable. There inincluded is the evaluation of the long-term operability, the useful life andthe costs for the disposal of the resulting waste materials

 

 

Gas recovery

For the production of electricity and heat from wood gas can in principle Cogeneration (CHP) are used with lean gas engines such as, for example, even when the Find utilization of biogas application. However, wood gas has not only a lower calorific value as biogas (about 1.2 kWh / m³ to about 5 kWh / m³), ​​but is also quite different
composed.

 

Therefore, must not motorized adjustment with the use of wood gas modified operating behavior and increased wear are expected. In principle, must be expected even with a motor adaptation with a decrease of power and efficiency  become.

Apart from the engine and the generator coordinated a CHP still has the associated switchgear and control mechanisms, as well as heat exchanger to heat remove from the exhaust, the engine cooling water and lubricating oil circuit.

 

Ideally this heat can, if necessary with the involvement of a buffer memory, as heating or completely
process heat can be used. Otherwise, the operation of the wood gasification plant must
be restricted in the times of low heat demand, or the CHP needs
have a cooler.