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Open access

Alicja Uliasz-Bocheńczyk, Aleksandra Pawluk and Michał Pyzalski

Abstract

When it comes to the production of energy from renewable sources, biomass is the main fuel, burned directly or co-fired with coal, used in the professional power industry. As in the case of coal, the use of biomass in the professional power industry is accompanied by the generation of by-products of the combustion process, primarily in the form of fly ash. These wastes significantly differ from those resulting from coal combustion. Their properties depend primarily on the burned biomass and boiler type. Due to the growing pressure on the use of energy from renewable sources resulting from the Energy Policy of Poland and the requirements imposed by the EU, more and more by-products are produced. Ashes from the co-firing of biomass are relatively well studied, especially when it comes to those resulting from the combustion in conventional boilers. The by-products of biomass combustion are of limited economic use due to their specific characteristics. The ashes resulting from the combustion in fluidized bed boilers are particularly problematic. The paper presents the research results on the basic properties of the three ashes generated from the combustion of biomass in fluidized bed boilers and one ash resulting from the co-firing of biomass with coal in pulverized coal boiler for the same biofuel type. The conducted analysis of the chemical composition has shown a high content of CaO and CaOw, SO3, and K2O and a low content of SiO2 and Al2O3 compared to ash from co-combustion of biomass. The elemental analysis indicates a high content of: P, S, Cl, K, and Ca and lower content of chromium and cobalt in the ashes generated from burning of biomass when compared with the ashes produced as a result of co-combustion. All the tested ashes have similar granulometric composition. Particular attention was paid to the leachability of pollutants, which is one of the most important factors determining the use of waste in mining technologies, using mainly the mixtures of fly ash and solid waste from calcium-based flue gas desulphurization (10 01 82). The pH of leachates from the analyzed ashes is the lowest for the ashes resulting from the co-combustion of biomass. The pH value of leachates was approximately 12 for all of the tested samples. The results have shown a high leachability of potassium and chlorides, which is characteristic for by-products resulting from the combustion of biomass, and a high leachability of sulphates due to the type of used boilers. The phase composition is dominated by calcium and potassium carbonates, quartz, K2SO4, halite, sylvite, CaO, MgO.

Open access

Alicja Uliasz-Bocheńczyk, Aleksandra Pawluk and Michał Pyzalski

Summary

As a result of energy production processes, the power industry is the largest source of CO2 emissions in Poland. Emissions from the energy sector accounted for 52.37% (162 689.57 kt) of the total emissions in 2015, which was estimated at 310.64 million tons of CO2. In recent years, the tightening of regulations on the use of renewable energy sources has resulted in an increased amount of biomass used in the professional energy industry. This is due to the fact that the CO2 emissions from biomass combustion are not included in the total emissions from the combustion of fuels, resulting in the zero- emission factor for biomass. At the same time, according to the hierarchy of waste management methods, recycling is the preferred option for the management of by-products generated during energy production. The fly ashes resulting from the biomass combustion in pulverized boilers (which, due to their chemical composition, can be classified as silicate ash) were subjected to analysis. These ashes can be classified as waste 10 01 17 - fly ash from co-firing other than mentioned in 10 01 16 according to the Regulation of the Minister of the Environment of December 9, 2014 on waste catalogues. The maximum theoretical carbon dioxide binding capacity for the analyzed fly ashes resulting from the co-combustion of biomass is 8.03%. The phase composition analysis of the fly ashes subjected to carbonation process has shown, in addition to the components identified in pure fly ash samples (SiO2, mullite), the presence of calcium carbonate − calcite − the primary product of the carbonation process, as indicated by the results of both X-ray and thermogravimetric analysis.The degree of carbonation has been determined based on the analysis of the results of the phase composition of fly ash resulting from the co-firing of biomass and bituminous coal. The calculated degree of carbonation amounted to 1.51%. The carbonation process is also confirmed by the lowered pH of the water extracts, decreasing from 11.96 for pure ashes to 8.7 for CO2 treated fly ashes. In addition, the carbonation process has reduced the leaching of pollutants, most notably chlorides, sulphates, and potassium.

Open access

Alicja Uliasz-Bocheńczyk, Marek Gawlicki, Eugeniusz Mokrzycki and Michał Pyzalski

Streszczenie

Zaczyny cementowe stosowane w technologiach wiertniczych wykorzystywanych w geologicznym składowa­niu CO2 będą ulegać intensywnej karbonatyzacji. Ditlenek węgla powodujący korozję węglanową lub kwasowo- -węglanową zaczynu cementowego reaguje przede wszystkim z portlandytem Ca(OH)2, stanowiącym obok uwodnionych krzemianów wapnia C-S-H główny produkt reakcji z wodą podstawowych składników cementu, alitu i belitu. Węglan wapnia powstający w wyniku reakcji CO2 z Ca(OH)2 może występować we wszystkich trzech odmianach polimorficznych CaCO3, jako kalcyt, aragonit i vateryt. Potwierdziły to badania próbek pobranych z otworów wykonanych w celu intensyfikacji wydobycia ropy naftowej przy użyciu CO2 (Carem i in. 2006, 2007; Scherer, Huet 2009). Prawdopodobnie jako pierwszy powstaje vateryt, który następnie przechodzi w kalcyt. Aragonit pojawia się zazwyczaj jako faza przejściowa (Kurdowski 2010). W artykule przedstawiono wyniki badań składów fazowych zaczynów cementowych, które mogą być użyte w pracach wiertniczych wyko­nywanych w celu geologicznego składowania CO2. W zaczynach stwierdzono równoczesne występowanie obok siebie różnych odmian polimorficznych węglanu wapnia. Zaczyny pozostające w kontakcie z solanką i ditlenkiem węgla wykazywały oprócz kalcytu, aragonitu i vaterytu, również obecność faz będących produktami korozji chlorkowej zaczynu cementowego.