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Gasification of biomass with oxygen rich air in a reverse-flow, slagging gasifier

Objective



PROJECT OBJECTIVES

The main objective of the project is to develop an innovative, reverse flow molten slag fixed bed gasifier concept for combined heat and power generation in a capacity range of 0.5-2.5 Mwe, and with improved thermal efficiency (5 - 10 %) compared to conventional fixed bed gasifiers. The reactor enables handling of relatively wet (up to 40 % mcdb) and ash-rich biomass fuels. The gasifier will produce a gas with a caloric value of at least 6 MJ/Nm3. Specific objectives are:

Development and testing of a low-cost device for enriching the oxygen content in air (air enrichment unit). An improvement of the energy efficiency of at least 0.1% per 1% point O2 enrichment is expected. The optimum oxygen content (30 - 60%) to be used in the gasifier depends on an economic and technical analysis of the whole process.

Development and testing of a novel and compact reverse-flow, molten slag, fixed bed gasifier with integrated heat exchange and tar removal system, for operation on oxygen-rich-air. A lab-scale unit (2 kg/hr) and a mini-plant (20 kg/hr) will be constructed and operated

Assessment of cost-effective technologies, both existing and under development, for utilisation of process heat from the reverse-flow slagging gasifier for drying biomass feedstock.

TECHNICAL APPROACH

In practice, several methods exist for increasing the oxygen content in air. Within this project pressure/vacuum swing adsorption and membrane separation will be studied in detail for application in biomass gasification systems. Final selection of the technology will be based on both an economic and a technical analysis. The selected technology will be built and tested on a pilot-scale.

The design of the reverse-flow gasifier will start with a literature study of slagging gasifiers. Concerning the design and operation of reverse flow reactors a lot of experience is available, and partly based on previous and running EC-projects (AIR2-CT93-1436 & JOR3-CT95-0053) for the removal of tar from producer gas in a reverse flow reactor. A small laboratory scale slagging gasifier will be designed and constructed which provide the required information for the pilot-plant installation. A pilot-plant with a capacity up to 20 kg of biomass per hour will be built, and subsequently connected with the selected air enrichment unit.


EXPECTED ACHIEVEMENTS AND EXPLOITATION

The novel, enriched-air blown fixed bed gasifier is operated in the molten slag mode. Due to extensive heat integration -which results from the reverse flow principle- this gasifier produces a tar-free, intermediate calorific gas of a low temperature. The main advantages of the proposed system are:
The gasifier will be operated with oxygen enriched air, which will cause higher reaction temperatures and enable operation in a slagging mode. This results in complete utilisation of the carbon. (no carbon remains in the ash).
Due to the use of oxygen enriched air, the fuel gas will have a higher heating value. This will lead to an increased mixture heating value of the gas/air mixture that is to be fed to the internal combustion engine and therefore enables the use of smaller (and cheaper) engines;
The reverse flow principle will lead to improved heat integration; a larger part of the biomass energy content is converted into chemical energy yielding a higher "biomass-to-electricity" efficiency.
The gasifier will have improved thermal and volumetric efficiency.
The different partners will either directly (through the manufacture of equipment or through implementation/exploitation of integrated energy systems) or indirectly (through exploitation of knowledge and experience) commercialise the results from the project.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

BIOMASS TECHNOLOGY GROUP BV
Address
5,Drienerlolaan 5
7522 NB Enschede
Netherlands

Participants (4)

Aston University
United Kingdom
Address
Aston Triangle
B4 7ET Birmingham
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
Spain
Address
22,
04200 Tabernas
KEMA NEDERLAND BV
Netherlands
Address
Utrechtseweg 310
9035 Arnhem
Kara Engineering Almelo BV
Netherlands
Address
27,Plesmanweg
7602 PD Almelo