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AER-GAS II Informe resumido

Project ID: 518309
Financiado con arreglo a: FP6-SUSTDEV
País: Germany

Final Report Summary - AER-GAS II (Biomass Fluidised Bed Gasification with in situ Hot Gas Cleaning)

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).

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Michael SPECHT, (Head of Department)
Tel.: +49-711-7870-252
Fax: +49-711-7870-200
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