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Straw gasification for co-combustion in large chp plants ('STRAWGAS')

Objective

Objectives and problems to be solved: The project will develop and test gasification of straw in a circulating fluid bed gasifier (CFBG). The gas is intended as supplementary fuel in a modern coal-fired power plant, which also supplies district heat (CHP). The project includes development and test of a straw feeding system, of gas cleaning equipment and of procedures to ensure reuse of the residues. The project is preparation for a demonstration gasifier which will have a thermal input of 100 MWth and use app. 150.000 tons of straw per year. The energy efficiency from straw to electricity will be 40%. The project can lead to demonstration of an efficient and clean method to use straw for power production in a large scale. The method is clean, since the straw-gas is burnt in a boiler with modern flue-gas cleaning equipment. Since straw is a major biomass resource in large parts of Europe, this project will help increase the share of renewable energy in the energy system, and also improve economy and employment in the agricultural sector. Description of work: The work is divided into two phases: the development and demonstration phases. The present project covers only the development phase. It is based on results from completed and ongoing work, which includes experience with large-scale wood gasification, straw gasification and gas cleaning tests in small-scale and in pilot-plant scale (3 MWth) and also tests with a new gas-tight straw feeder. These are new results, which clearly show that the process using the difficult fuel straw is feasible. Further validation is however necessary, before a demonstration plant can be decided. The main risk elements in the demonstration plant are scale-up and long-term availability. The present project is a development phase and consists of two work packages:· Process validation, which includes development and optimisation of straw feeder and gas cleaning system, and gasification tests with loose straw in the pilot plant.· Design study, where the process and the technical solutions for a full-scale plant are selected, and the basis for the final decision to build the demonstration plant is established. Expected Results and Exploitation Plans: The combined results from both the practical and the theoretical part of the project are expected to give a sound basis for the decision to build a 100 MWth gasifier for straw. The milestones that need to be reached are:· Validation of feeding and gas cleaning systems.· Gasification process conditions optimised.· Design study completed and basis for decision to start demonstration project. In case of realisation of the demonstration plant, the experience from the full-scale plant will give a strong know-how basis for the next plants. In Europe more than 100 plants could be established based on a fuel consumption of only 10% of the straw surplus. The technology can also be applied for other fuels such as RDF and biogases.
WP 1: Task 1.1. The new type feeding system for loose straw has been tested and results are in this scale acceptable. Some experiences in the tests will be taken in the considerations, when full-scale plant will be designed;
Tasks 1.2. The results in the gas cleaning testing are acceptable. However some new observations have been detected, which will be taken in the considerations, when full-scale plant will be designed. In the ash treatment a new ash handling system has been developed and tested;
Task 1.3. The gasification tests of loose straw were positive and some important operations and actions were found to be able to run the plant. Test results will be reported in the final technical report.

WP 2: To overcome some of the observed problems the designed gasification plant is now somewhat more complicated than originally estimated. The design is presented in the design study report. The investment cost of this gasification plant having capacity 100 MJ/s straw as fuel has been estimated up to ca. 40 MEUR.
WP 8: The internal report has be made as planned. First a part of this report will be published in a Bioenergy 2001 Conference in Denmark September 26-28.The results of this development work will be published also in the professional magazines. Decision to build the demonstration plant will be delayed due the liberation of the electric power market and the requirement to use biomass as fuel at same time. The straw price is very high in Denmark at the moment (5.6 EUR/GJ) and price for heat in greater Copenhagen area is lower than average in Denmark. This means, that the investment for the gasification plant using 100 MJ/s straw is not profitable.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

FOSTER WHEELER ENERGIA OY
Address
Antintie, 3
48601 Karhula /Kotka
Finland