2/2011
Laboratory pyrolysis study of dried waste water sevage sludge
The article deals with the low-temperature pyrolysis of dried waste water sevage sludge. The performed laboratory experiments suggest that this material is well decomposed at temperatures achievable in the current technological practice (350 - 550 °C). The resulting products are very rich mixture containing an entirely non-toxic, but also toxic substances. The article summarizes the know-how, which were used to launch a pilot unit designed to test this technology in the practice of sevage sludge disposal.
Comparison of methods for estimation of biogas production from phytomass
Identification of microbial communities in biogas
This paper deals with the detection of microbial species in biogas, their influence on corrosion and their potential risk of spreading disease via biogas using molecular techniques. Because the vast majority of microbial species cannot currently be grown in the laboratory, molecular techniques enable a better appreciation of the compositions and variability of microbial communities than traditional bacterial cultures. Biogas samples for molecular methods were collected by filtration through a 0.22 μm nylon membrane filter. Two different sites were chosen: behind an anaerobic digester, and behind an adsorption unit, which is designed for sulphur and siloxane removal. Using methods of molecular biology, we found that raw biogas contains about 8 million bacteria in m3, which is most likely the result of microbial transmission from the anaerobic digestion process. Our results show that Firmicutes and Proteobacteria were the most frequently encountered bacterial phyla. Some bacterial species may contribute to corrosion of pipelines and equipment; others are opportunistic pathogens that can cause toxic reactions. However, most of bacterial species, more than 40% in biogas, are still unknown as well as their influence on digestion process and human health. Further study is needed to better understand the behavior of microorganisms in anaerobic digestion and the prevention of microbial-influenced corrosion and microbial dissemination.
Continuous pyrolysis of carbonaceous materials with model gasification of the solid product
Samples of lignite from Jiří Mine in Sokolov Basin, alone and mixed samples of coal with a 30 % addition of variantly waste tire-rubber, Forsan (ABS) and cellulose were pyrolyzed at a temperature of 900 °C on a laboratory model rotary kiln, with the throughput being 100 gph. The influence of the additive on the composition of the pyrolytic gas was observed. By means of thermal analysis, the rate of gasification of the solid product by steam and carbon dioxide was studied, both at a temperature of 900 °C.
The comparison of selected pollutants emissions from domestic combustion of biomass and lignite
Emissions from domestic heating appliances significantly participate in total environmental pollution. To estimate the influence of current trend of fossil fuel substitution by biomass fuels on pollutant emission is therefore desirable. Emissions of CO, PM, and selected POPs from beech and lignite combustion in Czech common types of hot-water boilers are observed in the paper. Moreover, design of boilers itself is discussed there. From the results can be concluded, that design of boilers play the key role in pollutant emissions levels. Significant influence of fuel was not observed; it was not found also due to similar chlorine content in both fuels.
Laboratory method for evaluation of emissions emitted during drying of wet solid biofuels
This paper deals with emissions from the drying of alternative fuels (barley grains and forest wood) with high moisture content. Laboratory method was used in purpose of identification and quantification of greenhouse gases (CO2, CH4), volatile organic compounds (VOCs) with different physicochemical nature (organic acids, aldehydes, ketones, terpenoid compounds). Drying of two wet model materials was carried out by hot air (75 °C) in a closed circulating gas system with limited internal volume. Used temperature conditions are characteristic for the operation of the belt dryers using low-grade heat energy.