Siloxanes are among the most technologically troublesome trace compounds present in biogas. As a result of their combustion, hard-to-remove sediments are formed, blocking biogas energy processing devices and reducing the efficiency of biogas plants. The purpose of this study was to help investors and designers to choose the optimal technology for the adsorptive removal of volatile methylsiloxanes (VMSs) from biogas and to identify adsorbents worth further development. This paper critically reviews and discusses the state-of-the-art technologies for the adsorption removal of siloxanes from biogas, indicating potentially beneficial directions in their development and deficiencies in the state of knowledge. The origin of VMSs in biogas, their selected physicochemical properties, technological problems that they can cause and their typical versus limit concentrations in biogases are presented. Both the already implemented methods of adsorptive VMSs removal from landfill and sewage gases and the ones being under development are verified and systematized. The parameters and effectiveness of adsorption processes are discussed, and individual adsorbents are compared. Possible ways of regenerating spent adsorbents are evaluated and prospects for their application are assessed. Finally, zeolite-based adsorbents—which can also be used for biogas desulfurization—and adsorbents based on polymer resins, as being particularly active against VMSs and most amenable to multiple regeneration, are identified.
There were presented technological and ecological aspects of biogas quality evaluation and introduced an overview of the limits of its selected parameters. There were characterized analytical methods for determining the basic composition of biogas, hydrogen sulfide, ammonia, condensation, dust, oils, siloxanes, and aggregated content of sulfur, chlorine and fluorine. The result of comparative analysis and literature studies are proposes of the most adequate to the studies of biogas -analytical methodologies.
Hydrogen sulphide (H2S) and volatile methylsiloxanes (VMSs) are key pollutants from the point of view of the operators of biogas plants. H2S poses corrosive hazards, while VMSs transform into difficult-to-remove deposits, reducing the availability and yield of biogas combustion equipment. This study provides a critical overview and evaluation (so-called SWOT analysis) of implemented and promising methods to reduce the content of the above pollutants in biogas, with particular emphasis on biological techniques. The aim of the analyses was to develop an innovative concept for a hybrid biological method for the combined removal of H2S and VMSs using the same device, i.e., a two-phase biotrickling filter (BTF), in which the organic phase that intensifies the mass transfer of VMSs is in the form of a low-viscosity methyl silicone oil. The finally developed technological schematic diagram includes the basic devices and media streams. The concept is characterized by closed media circuits and comprehensively solves the problem of purifying biogas from sewage sludge. In conclusion, key issues requiring further research are identified.
Abstract. This paper presents a method for estimating the balance of carbon dioxide (CO 2 ) emission and absorption by Polish forest ecosystems. Based on the existing literature, a method for estimating the net absorption of CO 2 and a synthetic index to assess this amount per hectare per year was developed. The calculation was derived using two alternative methodologies. The first is based on estimating the amount of CO 2 sequestered over a trees' life, and the second based on estimating the age-dependent biomass growth of trees. Obtained results indicate that total CO 2 sequestration by Polish forest ecosystems is the equivalent of approximately 25% of Polish anthropogenic carbon emissions and suggest that previous calculations may have been underestimated.Key words: greenhouse effect, forest, carbon dioxide balance WstêpOcieplanie siê ziemskiego klimatu w ostatnim 100-leciu jest faktem. Faktem jest równie¿, ¿e stê¿enie gazów cieplarnianych w atmosferze wzros³o w tym czasie. Spooeród tych gazów, za wzrost temperatury atmosfery odpowiada -ze wzglêdu na swoje stê¿enie i d³ugi czas rozpadu -g³ównie ditlenek wêgla. Wed³ug prognozy IPCC (2008), w zale¿nooeci od przyjêtego scenariusza emisji gazów cieplarnianych, temperatura przyziemnej warstwy atmosfery zwiêkszy siê od 1,1 do 6,4°C, a poziom mórz i oceanów podniesie siê od 0,2 do 0,6 m w tym stuleciu. Skutkiem tego bêdzie m.in. nasilenie ekstremalnych zjawisk klimatycznych, z którym ju¿ dzioe mamy czêoeciowo do czynienia. Potencjalne zagro¿enia, a tak¿e podejmowane i planowane dzia³ania zaradcze zosta³y obszernie przedstawione w licznych publikacjach na ten temat (m.in. Kornatowska, Smogorzewska 2010;Kundzewicz, Juda-Rezler 2010).Niezale¿nie od tego, czy odpowiedzialnym za zmiany klimatu jest cz³owiek, w interesie ludzkooeci le¿y powstrzymanie tej tendencji. OErodkiem do tego celu, oprócz ograniczenia zu¿ycia emisjogennych paliw kopalnych (przy zachowaniu zasad zrównowa¿onego rozwoju) mo¿e byae intensyfikacja zalesieñ. Dotychczasowa polityka UE, polegaj¹ca m.in. na forsowaniu drogich, technologicznych metod redukcji emisji CO 2 (np. Carbon Capture and Storage -CCS), doprowadziae mo¿e -w przypadku krajów takich jak Polska -do silnego zahamowania ich rozwoju. Zbyt ma³y nacisk k³adzie siê na rozwój naturalnych mechanizmów poch³aniania CO 2 . Globalny ubytek powierzchni leoenej jest -obok spalania paliw wêglowodorowych -g³ówn¹ antropogeniczn¹ przyczyn¹ wzrostu stê¿enia CO 2 w atmosferze. Roczna powierzchnia wylesieñ na oewiecie w latach 2001-2010 wynosi³a ok. 13 mln ha, a ubytek netto powierzchni lasów -ok. 5,2 mln ha (FAO 2010). O tym, ¿e zmniejszenie wylesieñ mo¿e znacz¹co ograniczyae globalne ocieplenie, oewiadczy udzia³ emisji ditlenku wêgla powodowanej deforestacj¹ w oewiatowej emisji gazów cieplarnianych, wynosz¹cy ok. 17% (Katere 2010).Pod wzglêdem lesistooeci Polska plasuje siê nieco poni¿ej oeredniej europejskiej i oewiatowej, dysponuj¹c jednak znacznym potencja³em w zakresie jej zwiêksze-nia (udzia³ gleb klasy V i VI stanowi ok. 34% ca³kowitej powierzchni gru...
Basing on long-standing cyclic measurements of sludge-originated biogas composition and considering statistical analysis of their results, a regression model describing time variation of biogas desulfurization using bog iron ore has been developed. The model was verified by theoretical calculations and results from laboratory examinations of the sorbent. It was also used to estimate the depletion time and sorption capacity of the bed and to determine the demand index for bog ore.
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