Co-firing of coal and biomass
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Polityka Energetyczna – Energy Policy Journal 2003;6(Zeszyt specjalny 2):297–307
"Strategy of renewable energy development" approved by the Parliament of the RP on 23rd August 2001 assumes increasing share of energy from RES in the fuel-energy balance of the country to 7.5% in 2010 and to 14% in 2020. The implementation of this assumption depends both on intensification of implementation of biomass use in the power industry and on stability of its supply, what is determined by the demand for a homogeneous, stable and qualified quality biomass. Intensification of biomass implementation will depend also on appropriate preparation to such a project in power engineering installations. Three groups of technical solutions may basically be distinguished in the field of practically used power technologies of biomass utilisation: - direct biomass combustion (baled straw, woodchips, granulated sewage sludge, briquetted sawdust); - co-firing of coal with biomass, where traditional boilers are used, to which coal and biomass are introduced as pre-blended or separately; - thermal utilisation of biomass connected with its pyrolysis and gasification directed towards production of heat or production of heat and electricity. Direct combustion and gasification or pyrolysis require using installations with designs that ensure efficient power conversion of fuel of high, nearly twice higher as compared with coal, volatile matter content. However, co-firing of shredded biomass in a blend with coal may be efficiently carried out in existing installations, both in stoker-fired, fluidised-bed and pulverised-fuel boilers. The achievement of intended effect of co-firing technology implementation in industrial conditions is determined both by the preparation of power installation together with modification of coal and biomass batching and also by working out a method of stable quality biomass preparation for energy objectives, both in respect of physical (moisture content) and chemical (volatile matter, calorific value) properties. These conditions depend on the type of boiler installations. The optimisation of biomass share depending on the type of coal-fire boiler, the preparation method of qualitatively stable coal-biomass fuel blend and also the operational adaptation of existing technological systems to the properties of the obtained blend are integral and crucial from the point of view of co-firing processes development. This paper presents the experience gained during pilot tests of woodchips co-firing with coal, obtained both from energy crops of quickly growing Salix and from waste wood from forestry, in stoker-fired, pulverised-fuel and fluidised-bed boilers. The addition of biomass to coal was shown, apart from CO2, SO2 and NOx emission reduction resulting from additive amount of added biomass, to cause the effect of synergism in respect of CO, TOCs, including PAHs and VOCs emission. Moreover, when firing fuel blends a reduced amount of combustible parts in the ash (slag) is observed, what results in increasing energy efficiency of chemical energy contained in the fuel conversion and hence in specific economic effects in the form of reduced coal consumption.
Współspalanie biomasy z węglem
biomasa, węgiel kamienny, współspalanie, odnawialne źródła energii, zanieczyszczenia
Odnawialne źródła energii (OZE) stają się istotnym składnikiem bilansów energetycznych państw europejskich i będą odgrywać zasadniczą rolę w działaniach na rzecz redukcji emisji gazów cieplarnianych, poprawy bezpieczeństwa energetycznego i wspierania rozwoju społeczno-gospodarczego. W Polsce w efekcie przyjęcia proekologicznych dokumentów politycznych i rozwiązań prawnych, energetyka odnawialna może wejść w okres dynamicznego rozwoju. Jednym z rozwiązań technologicznych nie wymagających znaczących nakładów finansowych wdrażania OZE, mogących przynieść natychmiastowy efekt ekologiczny, energetyczny i ekonomiczny jest współspalanie węgla i biomasy w kotłach energetycznych. Przedstawiono wybrane doświadczenia przemysłowe technologii współspalania biomasy z węglem, korzyści i bariery jej wdrażania.