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Improved technologies for the gasification of energy crops

Objective


The project work was intended to provide data that would increase opportunities for fuel flexibility in state-of-the-art fluidised bed gasification concepts. Reduced operational costs following improved process conditions and refined system designs are expected to promote current technology by offering increased availability and independence through a broadening of the fuel palette. A promising market is anticipated in the area of small to intermediate scale heat and power generation. Although the development has reached far towards fuel flexibility, still there are a number of factors that need to be looked into further. The project has touched upon a few of these where the knowledge and experience will be utilised on an individual basis. The results from the project is not of the kind that immediately is suited for commercialisation. The results may be exploited in a further strengthening of existing technology for near term commercialisation in Europe.

In the ITEC Technical Annex Objectives it was stated that the project shall investigate how to efficiently and cost-effective utilise energy crops in heat and power production based on fluidised bed gasification. The project work has been characterised by a close collaboration between utilities and more pronounced research organisation (universities and R&D companies). This mixture makes a reasonable foundation for the stated objectives to succeed, i.e. to finding solutions, which are both technically and economically viable.
In approaching the specific aims of the project, a combination of applied research and techno-economic case studies is vital. The industrial bearing on the project work has throughout the work been of great importance and support and it is believed that the final result was heavily depending on the extent of industrial participation. Clear directives has been given on to what thematic should be focused on and hereby cut a path clear for increased commercial utilisation of energy crops.
It is of common apprehension among the project partners that the work performed has shed much light on the defluidisation aspect with high alkali fuels. The selected fuels have been thoroughly investigated in terms of thermodynamic performance and defluidisation tendencies together with a number of bed materials. The ash composition has shown to be the outermost important parameter, the other fuel constituents being very similar in types and amounts.
The interactions with bed materials have likewise been comprehensively studied both experimentally and in thermodynamic global equilibrium calculations. A few "rule-of-thumbs" have been accomplished which has formed the basis for a "manual" for the gasification of energy crop fuel.
The ambitions with the manual was set high and it is a common feeling in the consortium that we may not have reached all the way but significantly far towards operational guide-lines for energy crop utilisation. Experimental facts have been produced but it may be wise to acknowledge that both fuel specific and technology specific reasons contribute to the sintering tendencies. Since the system tends to be both sensitive and complex chemically, technical aspects such as reactor design/geometry, fuel/gas distribution and flow rates all contribute to the encountered difficulties with high alkali biofuels. The project work might have cast some light on the problematic. The challenge remains, however, to determine which one of the fuel specific/technology specific reasons is dominating at certain conditions. It was however concluded that although the design parameters probably have important roles whether or not agglomeration occurs or not in the bed, it is daunting from the consortium's point of view to give direct recommendations. A few remarks were pointed out in this respect. Nevertheless, estimations on the commercial side were made involving feasible commercial concepts for the Northern and the Southern part of Europe. Concepts were decided upon and presented with reasonable cost figures. The final conclusion for Northern Europe is that presently it seems very difficult to get biomass gasification plants of this based on energy crops economically interesting in the medium size range. The alternative seems to be to build either larger plants, with higher efficiencies and lower specific investment, or small distributed plant (less than 1 MW electricity). In the latter case the transmission cost is avoided and therefore a higher production cost might be acceptable. It is not very likely that large plants (above 50 MW electricity) based on energy crops will be built in the Northern Europe in the nearest future, at least not of economical reasons. An option might then be the concept studied by PPC in this project for the Southern region of Europe, to incorporate a biomass gasifier to an existing pulverized coal boiler or natural gas boiler.
Project objectives
The overall objective is to investigate how to utilise energy crops efficiently and cost-effectively in heat and power production based on fluidised bed gasification. This specifically implies finding solutions that minimise associated operational problems and to stipulate recommendations for commercial utilisation in existing gasifier concepts. The specific aims are to investigate a number of potential energy crop fuels concerning their handling and characteristic performance in fluidised bed gasification to study interactions in the fluidised bed between the selected fuels and cheap bulk bed-materials reflecting agglomeration, partial sintering and defluidisation to test promising combinations of fuel and bed-material mixtures in bench-scale gasifiers revealing gasification regimes, i.e., temperature, pressure and feed rates that may be more adequate for energy crops
to assemble a manual with operational conditions for optimal commercial utilisation of energy corps as gasifier fuel for heat and power production.
Technical approach
The actual project work is divided into four interdependent tasks. Task 1 will study characteristic performance of selected energy crops and bed materials both separately and in combination. International standard characterisation methods (ASTM) including SEM surface analysis will be dominating tools in this part of the investigation.
Based on the results from Task 1 an experimental bench scale investigation will be carried out involving three different fluidised bed gasifiers ranging from 5 - 50 kg/h feed (ds).
In a third task the experimental results will be assessed for commercial implementation where two process designs will be presented; one for the Southern European market and one for the Northern/mid European region. A final task will condense the project results to clear-cut guidelines in a manual for commercial use of energy crop fuels in fluidised bed gasification.
Expected achievements and exploitation
The project work will focus on several restraining factors for an efficient and cost-effective commercial utilisation of energy crops. Firstly, the industrially targeted characterisation and testing of highly potential energy crop fuels and bed materials are anticipated to result in knowledge to drastically increase fuel flexibility in existing fluidised bed gasification concepts.
Secondly, successful experimental results will provide operational ways to avoid critical bed defluidisation through intelligent combinations of bed materials mixtures and process parameters. This will generically further strengthen the technology based on fluidised bed biomass gasification. Thirdly, reduced operational costs following improved process conditions and refined system designs are expected to promote current technology to gain ground by offering increased availability and independence through a broadening of the fuel palette. A promising market is anticipated in the area of small to intermediate scale heat and power generation.
The results from the project work will be exploited through a further strengthening of existing technology for near term commercialisation in Europe where one of the project partners is on the threshold of a market introduction.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

TPS TERMISKA PROCESSER AB
Address
Studsvik
611 82 Nyköping
Sweden

Participants (6)

AABO AKADEMI UNIVERSITY
Finland
Address
14-18B,lemminkäinengatan 14-18 B
20500 Turku / Abo
AGRICULTURAL UNIVERSITY OF ATHENS
Greece
Address
75,Iera Odos 75
11855 Athens
Centre for Renewable Energy Sources
Greece
Address
Km 19Th,marathonos Avenue
19009 Pikermi Attiki
Kungliga Tekniska Högskolan
Sweden
Address
42,Tenikringen
100 44 Stockholm
Public Power Corporation of Greece
Greece
Address
10,Navarinou Street
10680 Athens
Vattenfall Utveckling AB
Sweden
Address
99,Jaemtlandsgatan
162 87 Stockholm