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.

The goal of this work was to evaluate the potential of reduced application rates in apple trees as well as the potential of selective spray applications by using sensor-based tree detection techniques in Serbian fruit production. Their economical and biological effect was evaluated based on the quality and efficiency of the crop protection and technoeconomic analysis. Results showed that during suitable weather conditions and with properly adjusted sprayer settings, a reduced application rate of 381 L ha -1 gave same quality of crop protection as a medium application rate of 759 L ha -1 . A two-year efficiency trial on Venturia inaequalis and Podosphaera leucitricha infecting apple also showed that there was no significant difference in crop protection results for different types of orchard application techniques and application rates. The techno-economic analysis showed that selective application should be introduced in practice in areas > 3 ha given that the cost of their introduction pays off after 2-3 seasons. Every subsequent season would give a clear economic profit. Besides the economic benefits, selective application technique also has a significant positive ecological effect due to reduction of spray losses and the amount of plant protection products used.

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

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...

REZIME U svetu je opšti trend korišćenja drvne biomase u svrhu dobijanja energije. U težnji da se drvna biomasa pripremi u formi pogodnoj za automatski rad termoenergetskih postrojenja razvijena je tehnologija pripremanja drvne biomase u formi sečke. Cilj ovog rada je da se analiziraju fizičko-hemijske karakteristike sečke od drveta, tehnologija njene proizvodnje, transporta, skladištenja i korišćenja (lanac snabdevanja), kao i da se prikaže kalkulacija njene tržišne vrednosti. U postojećoj tehnologiji u pripremi sečke od drveta postoje adekvatna rešenja za sve činioce u tkz. gorivom lancu (seče, pripreme, transporta, sušenja, skladištenja i doziranja). Ukupna cena sečke od sečke sa svim logističkim troškovima iznosi 10,81 din/kg, što sa usvojenom vrednošću evra od 123 din/evru iznosi 87,89 evra/t. Sa obzirom da se radi o drvnom materijalu niske vlažnosti, zadovoljavajuće toplotne moći i forme pogodne za mehanizovan, tj. automatski rad termoenergetskog postrojenja navedena cena sečke je sa tržišnog aspekta konkurentna i isplativa za korišćenje u svrhu dobijanja energije.