Objectives and problems to be solved:
The successful implementation of biomass and waste gasification for power production depends on the availability of low-cost, simple, reliable and high performance gas cleaning systems. Present solutions for gas cleaning do not fulfil these conditions. Hence, the project concentrates on improving gas-cleaning systems. The study has several objectives:
1. Develop and improve nickel-activated filter substrates and screen the performance.
2. Determine the stability of the catalytic filter in extended time test with real biomass gasification gas and scale-up the preparation technique.
3. Determine the performance of nickel monolith catalyst, catalytic filter and fluid bed dolomite catalyst combined to fluidised bed gratifier.
4. Determine long-term stability of a nickel monolith catalyst in real gasification gas, characterise the catalyst and develop and test in pilot-scale an optimised complete gas cleaning train. Description of work: The work in this project is concentrated on the development of the catalytic filter, long-term testing and demonstration of the monolith catalyst. In short, two novel catalytic tar decomposition processes will be studied. Additional important work is performed to optimise the operation of catalytic gas cleaning process based on these techniques. A techno-economical evaluation of both systems will be performed as well. The first process deals with a monolith catalyst which will be subjected to long-term tests, and its technical feasibility will be demonstrated in full-scale. Previous stages are followed by construction of a second-generation monolith reactor in pilot-scale and testing it after a novel fixed bed gasification process. Monolith catalyst long-term testing is carried out in a slipstream unit connected to a full-scale fixed bed gratifier, with dust containing gasification gas at very long test run. The second process aims at developing a catalytic filter which includes testing and optimisation of catalyst formulations with simulated and real gases. Long-term stability of this optimal formulation is then tested and finally preparation procedures for large-scale candle filters are developed. Process deals with further developing and testing a catalytic filter which simultaneously removes particles. Comparison and evaluation of catalytic gas cleaning processes, as well as optimisation of the catalytic gas cleaning processes, are needed. Finally, a study about the economical feasibility of catalytic gas cleaning based on monolith and catalytic filter for small-scale gasification processes is carried out. Expected Results and Exploitation Plans: The systems developed in this project would make biomass gasification much more attractive for local energy generation to a large number of users. On the whole, the project will result a catalyst formulation and deposition method for the catalytic filter and a method for manufacturing large-scale catalytic candle filters. Long-term testing of monolith catalyst gives an outlook of its performance. The monolith catalyst process will also be demonstrated in pilot-scale. The objective concerning the gas cleaning system as a low-cost, simple, reliable and high performance should be achieved. Long-term test runs, evaluation of the catalytic gas cleaning processes and the operational limits of a catalytic gas cleaning system will show the results and improvements in reliability and performance for power production-based gas cleaning systems.
The development of the catalytic filter included testing and optimization of catalyst formulations with simulated and real gases. A novel modified nickel-activated alumina filter substrates were developed, prepared and screened. Improvement in resistance to deactivation by sulphur compounds in biomass gasification was one of the main objectives and achievements of the work. Valuable information about catalyst improvement techniques was obtained. The catalytic filter was also tested with real gases and promising results were achieved. Preparation procedures for large-scale candle filters were also developed. The gas reformer studies included long-term testing of the nickel catalyst and demonstration of the monolith catalyst-based gas cleaning system in pilot scale. Additional important work was performed to optimize the operation of catalytic gas cleaning process based on these techniques. The long-term testing was performed with a slipstream apparatus that was connected to a CFB gasifier. Total test length was 2267 h.
Main conclusions of the long-term test were
1) The nickel monolith catalyst activity remained at high level during the test. Slight activity decrease was observed during the first 1000 h on stream. After this the catalyst activity with respect to tar and ammonia decomposition remained constant until the end of the test
2) It is probable that the catalyst will remain active for longer periods of time
3) Tar conversion after the test was 92 % and ammonia conversion 70 % at the 900 °C operation temperature
4) Fouling or clogging of the monolith by carbon did not occur.
The technical feasibility of the monolith based concept was demonstrated by performing pilot-scale test run with a process consisting of a NOVEL fixed bed gasifier, a catalytic reformer followed by a filter and gas scrubber/cooler. Gas produced had very low tar (< 100 mg/m3n), ammonia (< 50 ppm) and particulate (< 5 mg/m3n) contents and it can be considered suitable for use in modern turbo charged engines. Optimised operation conditions were found for the nickel monolith and the effects of the main process variables were studied. These included temperature, gas residence time, partitioning of the air feeding, gas H2O/C* ratio and gas superficial velocity. This work included also screening of limiting operation conditions as well as studies on the effects of process starting and shutting down procedures. The technical and economical data of the NOVEL gasifier gives a promising base for the promotion of the plant. The rather interesting aspects are the reduced size of the plant, the continuous operational system and the capability of gasifying various types of biomass, without endangering the performance of the gas engine. With these characteristics the diffusion of the technology might be successful, especially in the European present market conditions.
Funding SchemeCSC - Cost-sharing contracts