Innovation: Biomass Fluidised Bed Gasification With In Situ Hot Gas Cleaning

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fisheries, scientific research, resources of the sea, energy saving, biomass, social aspects, technology transfer, environmental protection, energy conversion, gaseous processing, renewable sources of energy, policies, fossil fuels, waste management, energy storage, industrial manufacture, transport, other energy topics, heat transfer, meteorology, energy transport, innovation
The project aim is a low-cost gasification process with integrated in-situ gas cleaning for the conversion of biomass into a product gas with high hydrogen concentration, high heating value and low tar/alkali/sulphur concentration in one process step for s ubsequent power production. The proposed process uses in-situ CO2 capture (AER, Absorption Enhanced Reforming). It is more efficient than conventional gasification due to (i) the in-situ integration of the reaction heat of CO2 absorption and water-gas shif t reaction heat (both exothermic) into the gasification and (ii) the internal reforming of primary and secondary tars, which cuts off the formation of higher tars. Thus, the chemical energy of tars remains in the product gas. The product gas after dust rem oval can directly be used in a gas engine for electricity generation. Due to the low operation temperature (up to 700°C) and due to CaO-containing bed materials, the proposed process allows the use of problematic feedstocks such
as biomass with high minera l and high moisture content, e.g. straw, sewage sludge, etc., leading to an increased market potential for biomass gasification processes. Screening/development of absorbent materials with high attrition stability and tar cracking properties will be carrie d out. Analysis of tar formation/decomposition process will be studied in a lab-scale fixed bed reactor and a 100 kWth circulating fluidised bed reactor (continuous mode). With the acquired data, the 8 MWth biomass plant at Guessing, Austria, will be opera ted with absorbent bed material in order to prove the feasibility of a scale-up and to assess the economical aspects of the process. In order to point out the market potential, the cost reduction of the AER technology will be quantified in comparison with the conventional gasification power plant. Expected results will be: (i) a broad knowledge of the proposed process and (ii) a low-cost technology for biomass gasification with subsequent power
production.

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The project work concentrated on the development and demonstration of a new, efficient, and low-cost steam gasification process for clean conversion of solid biomass. By in situ gas cleaning / conditioning, a product gas with a high H2 content (> 70 vol%), high heating value and low tar/alkali/sulphur concentration is generated. Due to the high product gas quality, it is suitable for various applications like Combined heat and power (CHP) generation, Substitute natural gas (SNG), hydrogen or synthesis gas production. Besides the delivery of an improved catalytic CO2 sorbent bed material, the project aimed to open-up new biomass potentials like humid and mineral-rich resources. The over-all goal was the operation of the 8 MWth power plant at Güssing in Absorption enhanced reforming (AER) mode:
- transfer of AER process in commercial scale;
- development and delivery of CO2 sorbent bed material with catalytic activity;
- suitability of woody biomass with high humidity;
- suitability of mineral-rich biomass resources.

The main characteristic of the AER process for the efficient and low-cost conversion of biomass is a CaO-containing bed material, a CO2 sorbent. It circulates between two fluidised bed reactors, takes up CO2 in the reaction zone of a steam gasifier and releases CO2 in the combustor. As a result of the in situ CO2 removal, the reaction equilibriums are shifted towards hydrogen production and the tar concentration is reduced. Since the CO2 absorption is a highly exothermic reaction, the released heat is integrated directly into the endothermic gasification / reforming process.

The most important advantages of the AER process are the following:
- product gas with high hydrogen content (up to 80 vol%);
- low COx content;
- low tar content (< 500 mg/m³) by in situ hot gas cleaning;
- in situ heat supply for endothermic biomass conversion.

The work that was performed during the project was divided into five work packages (WPs):
1) WP 1: CO2 sorbent development, characterisation, delivery
2) WP 2: Analysis of tar formation / decomposition process
3) WP 3: Multi feedstock and gas quality assessment
4) WP 4: Experimental run with the 8 MW plant in Güssing
5) WP 5: Economic, technical and market analysis of the 8 MWth plant with AER process.

The main achievements of the project are summarised below:
- proof of scale-up by adaptation of the existing power plant at Güssing (8 MWth biomass gasifier) to the AER technology / proof of scale up of AER gasification by operating the commercial power plant in Güssing in AER mode;
- fundamental knowledge of the process for future design of AER gasifcation plants;
- proof of power generation from H2-rich AER product gas by adaptation of the existing gas engine at Güssing;
- production of a raw product gas from biomass with high quality: low tar (< 1 g/Nm3), low sulphur (< 50ppm H2S), and alkali content, increased H2 concentration (up-to 75 vol%), and high calorific value (14-15 MJ/Nm3);
- availability of CO2 sorbent with high mechanical and chemical cycle stability as well as catalytic activity to enhance homogeneous conversion reactions in the gasifier, especially tar removal. Promising materials were identified by screening method with focus on mechanical stability, CO2 capacity, and catalytic activity toward phenol steam reforming. Calcite sorbents appear to be more active than olivine in primary tar reforming;
- development of thermal pre-treatment method to improve the mechanical stability of lime without destroying the CO2 reactivity. Industrial production for tests in Güssing;
- feasibility of new methods to improve CO2 sorbents (coating, agglomeration, etc.) applicable in industrial scale;
- availability of low cost bed material (lime) for fluidised bed applications: eight different limestone-based bed materials were successfully used in AER DFB gasification;
- a comprehensive tar investigation was conducted under continuous AER conditions in DFB mode. The influences of different process parameters were recognised and the best process conditions are identified;
- a commercially available tar catalyst was tested under AER conditions in batch mode;
- proof of the multi-fuel compatibility of the technology by using different fuels, in particular straw and wood, the latter with various moisture;
- a comprehensive experimental and theoretical alkali and sulphur investigation was conducted under AER conditions;
- proof of economical and energetic advantages of the innovative technology.

In this project, the AER process was successfully transferred into commercial scale by operating the gasifier at Güssing in AER mode. Thus, it is possible to operate the gasifier in both operation modes, standard (at temperatures above 800 degrees Celsius) and AER (at temperatures below 800 degrees Celsius, which enables in situ CO2 absorption). This minimises the risk for an investor with view to market launch. Even though the biomass conversion in the Güssing gasifier was not as high as during standard gasification, the cold gas efficiency was in the same range.

Regarding the costs of the gasification plant for CHP generation, the investment of an AER gasifier might be higher because the gasification reactor must be larger compared to the Güssing gasifier (due to smaller reaction rates because of lower temperatures). On the other hand, the operation costs are reduced, because the CaO based bed material is available at lower costs. In addition, low-cost biomass resources can be used as fuel in mixtures with wood. Economic advantages concerning investment are expected for poly-generation plants, because downstream gas conditioning (e.g. for SNG production) will not be necessary in case of AER gasification, simplifying the over-all process.

The AER technology has the potential to improve the gasification technology realised at Güssing because of the following important advantages:
- high quality product gas, suitable for various applications;
- in situ hot gas cleaning and conditioning, simplifying the over-all process for polygeneration;
- multi-fuel compatibility (alternative feedstock besides wood; no competition to food and heating sector).

Collaboration sought: N/A

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This innovation is the result of the project

Title: Biomass Fluidised Bed Gasification With In Situ Hot Gas Cleaning

Acronym: 
AER-GAS II

Runtime: 
01.01.2006 to 30.06.2009

Status: 
completed project

Organisations and people involved in this eco-innovation.

Please click on an entry to view all contact details.

ZENTRUM FUER SONNENENERGIE- UND WASSERSTOFF-FORSCHUNG, BADEN-WUERTEMBERG

(Germany)

Role in project: Project Coordination

Contact person: Dr. SPECHT Michael

Website: http://www.zsw-bw.de

Phone: +49-711-7870-252

Contact

BIOMASSE - KRAFTWERK GUESSING GMBH UND CO. KG

(Austria)

Contact person: Mr. KOCH Reinhard

Phone: +43-3322901085031

Contact

FOUNDATION FOR RESEARCH AND TECHNOLOGY HELLAS

(Greece)

Contact person: Dr. IOANNIDES Theophilos

Website: http://www.iceht.forth.gr

Phone: +30-2610965264

Contact

GE JENBACHER GMBH & CO OHG

(Austria)

Contact person: Dr. HERDIN Günther

Website: http://www.gejenbacher.com

Phone: +43-5244-6002161

Contact

INSTITUTT FOR ENERGITEKNIKK

(Norway)

Contact person: Ms. ERIKSEN Dag Oistein

Website: http://www.ife.no

Phone: +47-63806312

Contact

PAUL SCHERRER INSTITUT

(Switzerland)

Contact person: Dr. STUCKI Samuel

Website: http://www.psi.ch

Phone: +41-56-3104154

Contact

TECHNISCHE UNIVERSITAET WIEN

(Austria)

Contact person: Prof. HOFBAUER Hermann

Website: http://www.tuwien.ac.at

Phone: +43-15880115999

Contact

UNIVERSITAET STUTTGART

(Germany)

Contact person: Dr. BERGER Roland

Website: http://www.uni-stuttgart.de

Phone: +49711-685-3492

Contact

UNIVERSITY OF CYPRUS

(Cyprus)

Contact person: Prof. EFSTATHIOU Angelos

Website: http://www.ucy.ac.cy

Phone: +357-22892776

Contact