Sirvi Autor "Ivanova, T." järgi
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Kirje Effect of different compositions on anaerobic co-digestion of cattle manure and agro-industrial by-products(2018) Meiramkulova, K.; Bayanov, A.; Ivanova, T.; Havrland, B.; Kára, J.; Hanzlíková, I.The present research is dedicated to the study of anaerobic co-digestion process of different biomass materials. Anaerobic co-digestion of digested sludge, grass silage, haylage and cattle manure was evaluated in mesophilic tank reactors in the lab-scale experiment. Twelve laboratory scale tank reactors (1.5 L) were used during the incubation period of 45 days. First triplet of reactors was fed with pure digested sludge and the other three with different mixtures having the volumetric ratios of 30/35/25/10, 40/30/20/10 and 50/25/15/10 for digested sludge/corn silage/grass haylage/cattle manure. Methane production was analyzed for all labscale reactors individually. The resulting specific methane production of above-mentioned batches was 336.34, 238.1 and 233.23 LSTP[CH4] kg-1 [TVS], respectively. Other results such as cumulative biogas and methane yield, volumetric biogas and methane yield, volumetric biogas and methane yield per day were also assessed. These results had the highest meaning when complex substrate had no more than 30% of inoculum.Kirje Evaluation of dried compost for energy use via co-combustion with wood(2018) Malaťák, J.; Bradna, J.; Velebil, J.; Gendek, A.; Ivanova, T.There is still a question of utilization of compost of unsatisfactory quality. This article deals with energy utilization of untreated compost. The energy utilization of raw compost as a fuel is not directly possible without further processing. Separation might be necessary due to large amount of mineral content (soils and other inert substances). This article is focused on the analysis of the basic fuel characteristics of compost. Proximate and elemental analyses were performed and stoichiometric combusti on was calculated. Finally, the sample was co - burned with wood biomass in a fixed grate combustion device and the gaseous emissions were determined in dependence on the amount of combustion air supplied. The emissions were expressed in graphs against exces s air coefficient and flue gas temperature. Elemental analysis of the compost sample shows high percentage of ash up to 61.70% wt. on dry basis causing low average calorific value of 8.51 MJ kg - 1 on dry basis. For combustion tests, the heating value was in creased by addition of wood chips to reach an average calorific value of the mixture to 13.4 MJ kg - 1 . The determined stoichiometric parameters can help in optimization of diffusion controlled combustion of composts or similar materials. In combustion of th e mixture of compost and wood biomass an optimum of emission parameters was found not exceeding the emission limits. Measured emission concentrations show the possibility of optimizing the combustion processes and temperatures while lowering CO emissions v ia the regulation of combustion air.Kirje Influence of raw material properties on the quality of solid biofuel and energy consumption in briquetting process(2017) Muntean, A.; Ivanova, T.; Hutla, P.; Havrland, B.The present paper is related to a pressing process research of raw materials with different density in order to investigate impact of biomass density on a formation of monolithic structure and the briquette’s strength. Another focus of the study is an influence of raw materials particles’ size on agglomeration process and quality of final product. Different biomass materials like two varieties of miscanthus, industrial hemp and apple wood were selected for experimental purposes of this research. Mechanical durability which represents one the main indicator of briquettes’ mechanical quality (strength) was determined. The research was conducted using hydraulic piston briquetting press. For assessment of briquetting efficiency during the whole process energy consumption was measured. One of the most important factors that can affect briquetting process is the temperature of pressing chamber which was registered as well. The main goal of the research was practical study of possibilities for increasing production efficiency and quality of briquettes on hydraulic piston briquetting press with respect to optimization of particles’ size of raw materials and use of raw materials the most appropriate density.Kirje Particle size and shape characterization of feedstock material for biofuel production(2019) Chaloupková, V.; Ivanova, T.; Krepl, V.Particle size and shape are key factors influencing the properties of particulate and agglomerated materials, and having an impact on a quality as well as utilization of a final product. In case of plant biomass particle morphology is greatly irregular. Large errors at most determinations of biomass particle sizes are caused by simplification on a single parameter of size, assuming particle sphericity or circularity. Thus, the aim of a present research was to determine the particle size in a complex way. Pine sawdust as an experimental material and typical biofuel feedstock was ground by a hammer mill to a fraction size of 12 mm. The dimensional features of such ground sawdust particles were identified for all particles individually via photo-optical analysis, a method based on a digital image processing that is sensitive to irregular particles’ shapes. The particles were described mainly by variables of length, max width, equivalent diameter, max and min feret diameter, sphericity, roundness, circularity together with length/width ratio and aspect ratio. Data were analysed by descriptive statistics, i.e. by arithmetic means, medians, minimum and maximum values, variance and standard deviation. The obtained results may contribute to a better knowledge of material properties needed for designing an optimal technology for the production of quality biofuels.Kirje Particle size distribution analysis of pine sawdust: comparison of traditional oscillating screen method and photo-optical analysis(2018) Chaloupková, V.; Ivanova, T.; Muntean, A.Particle size and particle size distribution (PSD) are crucial parameters which affect properties of particulate and agglomerated materials, and have an impact on a quality and utilization of a final product. The aim of this paper was to determine PSD as well as to assess dimensional features of pine sawdust fractions via mechanical sieve analysis and photo-optical analysis. The first one is a traditional and standard method taking into account only one parameter of particle shape and the second one is a modern method based on a digital image processing that considers also irregular shapes of biomass particles. Pine sawdust was grinded into three fractions: 4, 8 and 12 mm and analysed using two mentioned methods. A horizontal vibrating sieve shaker comprising 11 sieves and a bottom pan was used, and the obtained data of retained particles on each sieve were evaluated. For comparison, a computerized photo-optical particle analyser was applied with max Feret’s diameter as a measurement algorithm for a particle length, and PSD was analyzed by grouping the particles according to their distinct lengths adjusted to the sieves’ sizes used in the screening method. Moreover, additional results in dimensions and parameters of PSD were obtained and evaluated through the photo-optical method. Pine sawdust particles can be described as non-uniform, mainly prolonged, finer particles dominated in all fraction samples. The study showed differences in the results, inaccuracy and other drawbacks of the conventional sieving method such as clogging and falling-through phenomena as well as the limitations of the machine vision. Strong sides of both methods were discussed, too. Overall, the results contributed to a better knowledge of the material properties and different methods of PSD analysis.Kirje Research on solid biofuels from cotton waste biomass – alternative for Tajikistan’s energy sector development(2017) Akhmedov, S.; Ivanova, T.; Krepl, V.; Muntean, A.An increasing awareness of the negative environmental cost associated with the combustion of fossil fuels and concerns over the geopolitical instability of the main oil producing regions is driving the development of renewable energy sources and biofuels. Use of solid biofuels made of different types of biomass became perspective alternative to conventional fuels in many countries. Such positive indicators as low cost of the final product that meets the quality of standards, not capital intensive production, possibility of producing briquettes/pellets from almost any agricultural waste or combination of raw materials are undoubted advantages of biomass based fuels. The main challenges for Tajikistan’s energy sector, which is depended on energy imports, are: to increase energy supply through better exploitation of hydropower and other renewable energy sources such as wind, solar and primary biofuels. Within the agricultural sector of Tajikistan, which is highly agrarian country, cotton accounts for 60% of agricultural output. According to the Ministry of Agriculture of Tajikistan 199,400 hectares of lands have been allocated to cotton cultivation in the year of 2014. Plenty of unused cotton residual biomass could be effectively utilized for winter heating in rural areas. The main focus of the research was to investigate and assess physical, chemical and mechanical properties of pellets and briquettes produced form cotton waste biomass.Kirje Using of high-speed mills for biomass disintegration(2019) Karráa, G.; Ivanova, T.; Kolarikova, M.; Hutla, P.; Krepl, V.The need for mechanical disintegration of biomass is very current topic with regard to the requirements of an agrarian sector, beside the importance of a material’s moisture content reduction to be used in further applications. The drawbacks of commonly applied devices are the limited use of moist biomass and high energy consumption for disintegration. In collaboration with LAVARIS company, there were tested two high-speed mills LAV 400/1R with single rotor (used for a first milling) and LAV 300/2R with double rotors (used for a second milling), which were primarily designed for crushing of concrete, rubber and construction waste. The goal of the new technical solution was a disintegration of biomass on example of pine sawdust and miscanthus together with examination of simultaneous drying in order to achieve a desired fraction (particle size) and moisture content of biomass material. Experimental tests on highspeed mills have shown the following results: in case of pine sawdust about 98% of output particle size after passing through the first and second milling was smaller than 1.5 mm, and smaller than 1 mm for miscanthus (sieve analysis method was used for determination), i.e. significant reduction was achieved comparing to initial particle size. Moisture content of the materials after disintegration (first and second) decreased from 37.08% to 8.55% for pine sawdust and from 24.43% to 7.19% for miscanthus. Based on the results, it can be concluded that the mechanical disintegration of biomass by high-speed mills has a great potential to become an effective part of raw materials’ pre-treatment technology, not only in agriculture, but also in production of different types of biofuels.