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This study reviews test results for a biomass-fired hot water boiler with a nominal boiler thermal power of 120 kW. In the experiments, prismatic wheat straw bales were used as biomass. The impact of the quantity (220, 290, 360 and 430 m 3 h −1 ) of inlet air fed to the boiler firebox was continuously monitored. This was to examine the influence of the quantity of inlet air and recirculation (0, 16.5 and 33%) of combustion products on the boiler thermal power and boiler energy efficiency. Thus, the following mathematical models and formulas were presented: correlation between boiler thermal power and bale residence time; bale mass loss during the combustion process; correlation between boiler energy efficiency and bale residence time. Mathematical models were obtained by using experimental data and by applying nonlinear regression analysis. Adjustment evaluation of mathematical models with experimental data was performed based on the determination coefficient, t-test and F-test. Increase the amount of air throughout the firebox produced boiler thermal power increase and bale residence time decrease. It was shown that combustion products recirculation of 16.5% partly improved boiler characteristics, while the recirculation of 33% did not, comparing with the case without recirculation.

This research analyzed the degree of utilization of the agricultural biomass for energy purposes (combustion), in order to indicate the reasons that limit its use. The biomass potential was studied by means of the methodology of the biomass potential, whereas the factors suggesting a low degree of biomass utilization were identified by means of factor analysis. The research results reveal that there is an enormous potential of the unused agricultural biomass. This dissertation research significantly contributes to the establishment of a genuine mathematical model based on multiple linear regression. The solution obtained by this analysis, in both a mathematical and a scientific manner, conveys the primary reasons for an insufficient utilization of the biomass for energy purposes. Moreover, the paper suggests the measures to be applied for a more substantial use of this renewable source of energy and presents the expected benefits to be gained.

REZIME U ovom radu su prikazani rezultati pri postizanju toplotnih snaga kod sagorevanja prizmatičnih bala sojine slame u kotlovskom postrojenju nazivne toplotne snage od 120 kW sa ručnim opsluživanjem. Ispitivanja su vršena tako što je promena snage kotla praćena u kontinuiranom radu pri različitim zapreminskim protocima vazduha za sagorevanja od 150, 220, 290, 360 i 430 m 3 h-1 i različitim udelima recilkulisanih dimnih gasova od 0%, 16,5% i 33%. Za određivanje toplotne snage kotla korišćena je direktna metoda. Korelacija između postizanih toplotnih snaga kotla i vremena sagorevanja bala slame je ustanovljena i prikazana empirijskom jednačinom. Opšti zaključci su sledeći: u režimu bez recirkulacije dimnih gasova u vazduh za sagorevanje sojine slame povećanjem protoka ulaznog vazduha za sagorevanje u ložište smanjuje se vreme sagorevanje bala i povećava toplotna snaga kotla. U tom režimu kod protoka vazduha za sagorevanje od 360 m 3 h-1 i 430 m 3 h-1 toplotna snaga kotla je bila veća od nominalno deklarisane snage kotla. U režimu sa ulaznim protokom vazduha za sagorevanje od 290 m 3 h-1 toplotna snaga kotla bila je jednaka nominalnoj snazi od 120 kW. Uvođenjem recilkulisanih dimnih gasova u vazduh za sagorevanje sa udelom od 16,5% povećava se vreme sagorevanja bala slame i smanjuje prosečna toplotna snaga kotla u svim režimima, osim u režimu sa ulaznim protokom vazduha za sagorevanje od 220 m 3 h-1. Ključne reči: kotao, toplotna snaga, sagorevanje sojine slame 1. UVOD Korišćenje biomase kao energenta u Srbiji nije novost. U Vojvodini, se najčešće za produkciju energije koriste balirani biljni ostaci ratarske proizvodnje, kao što su: slama pšenice, ječma i soje ili kukurozovine (Brkić i sar., 2012). Balirana biomasa se u Srbiji uglavnom sagoreva u toplovodnim kotlovima, pri čemu su kao najbrojniji i najrasprostranjeniji posebno interesantni kotlovi toplotnih snaga od 50 do 120 kW sa ravnim nepokretnim rešetkama za sagorevanje (Janić i sar., 2010). Unapređenje konstrukcije i tehnologije rada toplovodnih kotlova sa ravnom nepokretnom rešetkom toplotnih snaga do 120 kW je od suštinske važnosti, pošto je u

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The biomass combustion process is inevitably accompanied by the emission of pollutant gasses. This paper gives a comprehensive analysis of the external variables and combustion products of the biomass plant. The analyzed data were collected from 18 MWt boiler in combined heat and power plant Sremska Mitrovica over a period of four months. The correlations between the recorded data were determined using a unique methodology, which is based on association rule mining. The results of the study can be further used for the reduction of the harmful combustion products, as well as for the optimization of the operation process.

This study reviews test results of the combustion of square soybean straw bales used as fuel in manually fed boiler with nominal thermal power of 120 kW t . The influence of the mass flow rate (180, 265, 350, 435, and 520 kg/h) of inlet air and flue gas re-circulation (0%, 16.5%, and 33%) fed to the boiler furnace was continuously monitored. Direct method was used for determination of the boiler thermal power. Correlation between boiler thermal power and bale residence time has been observed and simple empirical equation has been derived. General conclusions are as follows: the increase of the flow rate of inlet air passing through the boiler furnace results in decrease of the bale residence time and increase of the boiler thermal power. Share of the flue gas re-circulation of 16.5% increases bale residence time and decreases average boiler thermal power in all regimes except in the regime with inlet air flow rate of 265 kg/h. In regime with 0% flue gas re-circulation boiler thermal power was higher than nominal in regimes with 435 and 520 kg/h inlet air flow rates. In regimes having inlet air mass flow rate of 350 kg/h boiler thermal power is equal to the nominal power of 120 kW t . most part, in rural environment [5], i. e. in places with larger space available for biomass storage. There are no accurate data on the number of such boilers used in Serbia due to the fact that, in addition to factory production, a large number of boilers are manufactured by local craftsmen. Based on the general information obtained from the authors' research, it can be assumed that in Serbia there are over 5,000 boilers with over 300 MW t of installed power using biomass as energy-generating product.Although more developed countries use boilers of higher energy efficiency, i. e. the standards of used equipment and exploited biofuel are much more developed, the improvement of construction and manner of operation of hot water boilers with flat fixed grates and thermal power of up to 120 kW t is essential for the more extensive use of biomass for energy generation in the territory of Serbia. Widely used constructions of boilers with flat fixed grate rarely exceed thermal power of 500 kW t , but, regardless of their power and manner of construction, they encounter major problems during operation [6]. Some of the most prominent problems in operation of the said boilers are: significant varying in the intensity of generated thermal power, frequent thermal overload of combustion chamber, sudden cooling of combustion chamber (while inserting new bales of biomass), emission of flue gases with high concentration of uncombusted compounds (CO, H 2 , CH 4 , etc.), which occasionally reach high temperatures (over 650°C), especially in order to obtain as higher as possible thermal power output of the boiler plant. In addition to the above mentioned problems, a specific problem encountered during the operation of boiler plants for agricultural biomass combustion is also ash melting at relatively low temperatures [5], resulting in clogging of prima...

Tema rada je višekriterijumska analiza stanja poljoprivrednih povrtarskih gazdinstava u Vojvodini, na osnovu istraživanja sprovedenog na sedam gazdinstava lociranih u četiri vojvođanske opštine: Futog (tri gazdinstva), Temerin (dva gazdinstva), Čurug (jedno gazdinstvo) i Begeč (jedno gazdinstvo). Cilj rada je da se kroz višekriterijumsku analizu utvrde pretpostavke razvoja poljoprivredne proizvodnje na osnovu analize proizvođača povrća. Povrtarstvo pokazuje stanje poljoprivredne proizvodnje u Srbiji na mikro nivou, te se izvedeni zaključci mogu opšte primeniti na poljoprivrednu proizvodnju. Istraživanje je pokazalo da nijedno gazdinstvo ne obavlja povrtarsku proizvodnju u zatvorenom prostoru, da se navodnjavanje vrši samo površinski na svim gazdinstvima osim dva koja su učestvovala u ispitivanju, da je nivo opremljenosti relativno visok, da se gazdinstva oslanjaju na subvencije države, ali je podrška države kroz savete i druge instuitucije relativno slaba. Sadržaj rada i izvedeni zaključci imaju za cilj da identifikuju ključne oblasti u okviru kojih je potrebno preduzeti neophodne razvojne mere, odnosno da ukažu na najbolju alternativu razvoja.