Type of CHP system: Gasification

Plant owner:

Biomassekraftwerk Güssing is a limited company & CO limited partnership. The Limited Company is owned by BEGAS 26%, Güssinger Fernwärme 74%; the limited partnership by Mr. Markus Koch 51% and BEGAS 49%.

Commissioned: 2001

Status of plant: Demonstration

Contractor details: CHP: Jenbacher; Gasifier: Austrian Energy & Environment; Generator: AVK Deutschland, Boiler: Bertsch

Power generation: Gas engine

Biomass is gasified in a dual fluidised bed reactor. The producer gas is cooled, cleaned and used in a gas engine. Biomass chips are transported from a daily hopper to a metering bin and fed into the fluidised bed reactor via a rotary valve system and a screw feeder. The fluidised bed gasifier consists of two zones, a gasification zone and a combustion zone. The gasification zone is fluidised with steam which is generated by waste heat of the process to produce a nitrogen free producer gas. The combustion zone is fluidised with air and delivers the heat for the gasification process via the circulating bed material.

The producer gas is cooled and cleaned by a two stage cleaning system. A water cooled heat exchanger reduces the temperature from 850 °C – 900 °C to about 160 °C – 180 °C. The first stage of the cleaning system is a fabric filter to separate the particles and some of the tar from the producer gas. These particles are returned back into combustion zone of the gasifier. In a second stage the gas is liberated from tar by a scrubber. Spent scrubber liquid saturated with tar and condensate is vaporized and introduced into the combustion zone of the gasifier.

The scrubber is used to reduce the temperature of the clean producer gas to about 40 °C which is necessary for the gas engine. The clean gas is finally fed into a gas engine to produce electricity and heat. If the gas engine is not in operation the whole amount of producer gas can be burned in the boiler to produce heat. The flue gas of the gas engine is catalytically oxidised to reduce the CO emissions. The heat of the engine´s flue gas is used to produce district heat.

The sensible heat of the flue gas for the combustion zone is used for preheating of the air, superheating the steam and also to deliver heat to the district heating system. A gas filter separates the particles before the flue gas is released via a stack to the environment.

Main fuel: Wood chips

Wood chips from forestry are used. The wood trunks are tried naturally by storage of about 1-2 years in the forest. Then they are delivered to the CHP plant and chipped there. When the biomass is used, it has a water content of about 25 (to max. 40%). The total consumption of wood chips amounts to about 10,500 t/a. The average heat value is 16,500 MJ/t at a water content of 25%.

Nominal capacities & efficiencies:

Thermal input, biomass & waste: 8 MW

Gross electrical output: 2 MWe

Net electrical output: 1,85 MWe

Electrical efficiency, gross: 25 %

Electrical efficiency, net: 23 %

Overall efficiency, gross: 79 %

How is plant controlled: The plant is controlled according to the amount of gas produced.

Heat backup:

For the case of a breakdown of the gas engine, the gas is burnt in the hot water boiler. The heat is then fed into the district heating network. The hot water boiler is equipped with an oil burner used as ignition for the gas burner. This hot water boiler can also be used for covering the heat demand of the district heating.

Heat usage: Heating only

Energy usage:

Heat is delivered to the district heating system which has a lenght o f more than 20 km. The consumers are mainly private houses (300), public offices, schools, and hopsital (50). Furthermore, there is a growing demand of industrial heat which is needed over the whole year. The heating station itself operates drying chambers which are additional heat consumers. Currently, first experience could be made with cooling using district heat.

DH inlet temperature: 120 °C

DH return temperature: 60°C

Hours of full load that the heat storage can meet: 1400

Fuel storage: The fuel storage has a capacity of 2,500 t

Ash discharge: 1,040 t/a of ash are directly landfilled

Plant description:

In Guessing (AT) a biomass CHP is demonstrated, where a gasifier is coupled to a gas engine to produce electric power and heat. As

gasification technology a steam blown fluidised bed gasifier is used, which produces a nitrogen free gas with a high

calorific value (12 MJ/Nm3) and only a low amount of tar. A cooling and two stage gas cleaning system makes sure that

the gas engine gets a cool and clean gas. In this paper the main results of a two years demonstration program are

described. Until the end of March 2004 about 9700 hours of operation with the gasifier and 7100 hours with the gas

engine could be reached, which demonstrates the smooth functionality of the CHP plant. The favourable characteristics of

the product gas (low nitrogen content, high hydrogen content) allow also other usages of this gas. Research projects

concerning the production of SNG (synthetic natural gas), Fischer-Tropsch Diesel and electricity in a SOFC (solid oxid

fuel cell) have been started

Fuel feeding system: The fuel feeding occurs mechanically.

Gasifier:

The basic idea of the gasifier concept is to divide the fluidized bed into two zones, a gasification zone and a combustion zone. Between these two zones a circulation loop of bed material is created but the gases should remain separated. The circulating bed material acts as heat carrier from the combustion to the gasification zone.

Gas quality:

Main components of the producer gas (dry gas): hydrogen 35-45 Vol-%, carbon monoxide 20-30 Vol-%, carbon dioxide 15-25 Vol-%, methane 8-12 Vol-%, nitrogen 3-5 Vol-%.

The calorific value of the dry producer gas is constant at about 12 MJ/Nm3.

Gas cleaning: The flue gas from the gas engine and the flue gas from the combustion zone are mixed together and released via the stack of the environment.

Engine: Gas engine with an installed capacity of 2 Mwe and a nominal electric efficiency, gross of 25%.

Flue gas cleaning:

The flue gas from the gas engine and the flue gas from the combustion zone are mixed together and released via the stack to the environment. Emissions are below the emission limits which were set by the local authorities.

There are no liquid emissions from the CHP plant. The condensate from the scrubber is evaporated and fed into the combustion zone where the organic matter is combusted.

The only solid residue is the fly ash from the combustion zone. Therefore the carbon content in this fly ash is very low (< 0.5 w-%) and can be handled similar to an ash from biomass combustion. Electricity sale info: The feed in rate in Austria is regulated by law and depends on the type of biomass used and on the size of the plant.

Total capital cost: € 10,000,000

Investment costs of 10 Mio. €, operation costs/year: 10 – 15% of investment costs.

For the next plant 25% reduction of investment cost can be expected due to the experience and learning at the demonstration plant. Furthermore, the operation costs will be reduced essentially. This will be done by aiming at an unmanned operation and a reduction and optimisation of operation means.

Data collected and quality assured by: Austrian Energy Agency.

Contact person: Elvira Lutter