JOULE JOR3-CT97-0130 Gasification of biomass with oxygen rich air in a reverse-flow, slagging gasifier

Contacts




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Drying/Pretreatment : JOULE/THERMIE Programme : Solid Biofuels : Thermochemical Conversion

	Type of Project	Shared Cost
	Contract No	JOR3-CT97-0130
	EC Contribution	798,595 ECU
	Start Date	27/03/1997
	Duration	36 Months

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

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 MW_e, 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 and 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 Results 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 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 of the project.

Contacts

Coordinator

• Bert van de BELD / BTG Biomass Technology Group BV NETHERLANDS

Participant

• A V BRIDGWATER / Aston University Bio-Energy Research Group / UNITED KINGDOM
• Juan E CARRASCO GARCIA / CIEMAT Instituto de Energias Renovables / SPAIN
• Klaas REINDERS / KARA Energy Systems B.V. NETHERLANDS
• Kema Nederland BV NETHERLANDS