**1. Introduction**

[103] Parnphumeesup, P., S. A. Kerr, Classifying credit buyers according to their attitudes

10.1016/j.enpol.2011.07.026.

54 Sustainable Energy - Recent Studies

towards and involvement in CDM sustainability levels, Energy Policy (2011) doi:

In terms of sustainable energy development in Serbia, as well as in the whole world, there is a growing need for using the alternative energy sources. Alternative energy sources are, in most cases, renewable: biomass, wind power, solar energy, hydro-power and geothermal energy. A need for the utilization of this kind of energy sources is dictated by the market, on one side, as well as by environmental protection, on the other. Prices of fossil fuels grow proportionally to the decreasing of fossil fuel reserves. Since available reserves of fossil fuels in Serbia, especially those of high quality, are relatively limited, this problem becomes even more emphasized [1-3]. On the other hand, it is necessary to harmonize the energy produc‐ tion legislation and practice in Serbia with the directives of the European Union, in the sense of intensifying the utilization of renewable energy sources and thus reducing pollution and greenhouse effect formation.

Biomass is one of key renewable energy sources [4]. This is the reason for the development of cheap thermal devices (boilers and furnaces) burning biomass from agricultural produc‐ tion as quite available and cheap energy source. These devices could be used primarily in villages, small towns and small businesses processing agricultural goods (greenhouses, dai‐ ry farms, slaughterhouses etc.) [5]. The devices could also be used for heating schools, hospi‐ tals, prisons and other institutions.

Annual energy consumption in the Republic of Serbia currently reaches 15 million tons oil equivalent (Mtoe), out of which 7.4 Mtoe represents the net consumption and 3 Mtoe is elec‐ tricity consumption. According to the official date of Ministry of Infrastructure and Energy

© 2012 S. Repić et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 S. Repić et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

of Republic of Serbia [6], Serbia is in dispose of 4.3 Mtoe of renewable energy sources, while biomass is represented with 2.7 Mtoe. 60% out of registered biomass potential are residuals from agricultural production, and the rest is wood biomass. Currently, only a small portion of waste biomass is being used in energy production mostly for heating (not taking into ac‐ count burning in the individual households, in small ovens), for several reasons: low elec‐ tricity price and non-resolved problems in biomass gathering. Also, there is no regulated biomass market, and no developed technologies for its utilization as fuel. Besides, small fi‐ nancial power of potential buyers have to be mentioned, as well as costly commercial credits and total absence of state subsidizing of biomass facilities.

The advantages of large cylindrical bales are moderate presses price, simple and fully mecha‐ nized manipulation, in the case of unwinding a simple and inexpensive device, conveniently storing for own needs on medium farms, the opportunity to work with medium power trac‐ tors etc. The disadvantages of this bundle are: the highest consumption of binder, the lower per‐ formance because of the need to halt the bale tying and ejection from the workspace, the sensitivity of trusses on the quality of the binder, the deformation under the bonding quality,

Development of the Technology for Combustion of Large Bales Using Local Biomass

http://dx.doi.org/10.5772/51095

57

Large square bales have the following advantages: high pressure compression, high per‐ formance, low consumption of binder, best transportability, good storage conditions, the whole mechanization and the lowest price of manipulation, the lowest consumption of bind‐ er etc. The disadvantages are reflected in the following: high initial cost of machinery, re‐ quired a large tractor, requires special means for manipulation, machinery sensitive to the

Furnaces and boilers that would use baled biomass from agricultural production can be a wide power range from 0.1 to 2 MW or more. Baled biomass as a fuel does not require big investments in preparation because balers have nearly every farmer. These are not expen‐ sive and complicated machines and do not require high energy consumption per kg of baled biomass. On the other hand, neither of which would be the biomass used as fuel, not far from the place of origin nor transport is not a major problem. Storage can be a problem, but as there is plenty of farmland damage caused by his occupation is insignificant, and in‐ creased investment costs to build a warehouse to quickly pay the difference in price be‐ tween the liquid or gaseous fuels and biomass. In addition, profit get from the green credits - benefits that are obtained in the case of renewable energy usage are paid this facilities only

In the Laboratory for Thermal Engineering and Energy of the "Vinca" Institute in Belgrade, efforts have been made to develop a clean technology for utilizing baled biomass for energy production. The initial set of analyses carried out in the research investigation conducted fo‐ cused on the combustion of small, 40x50x80 cm straw bales in cigar burners. For the said purpose, an experimental, 75 kWth hot water boiler was designed and constructed [9]. The furnace was built entirely out of an insulating material providing favorable biomass com‐ bustion conditions. Appropriate boiler tests were conducted in order to properly determine required design parameters. Although the boiler assembly examined was a small-scale fa‐ cility intended to be used by individual farm owners and utilized for space heating, it pro‐

Following the initial set of analyses, combustion of rolled, ø180x120 cm straw bales in cigar burners was analyzed in the next investigation phase. In order to assess the combustion quality and obtain data needed for proper design of the straw-fired hot water boiler, a 1

As a result of the specified investigation efforts, a pilot plant capable of burning large, 0.7x1.2x2.0 m straw bales was designed and built [11]. A 1.5 MWth industrial-scale hot wa‐ ter boiler was constructed and installed in the Agricultural Corporation Belgrade, where it

vided a good basis for development of large, industrial scale straw-fired facilities.

MWth demonstration furnace was designed, constructed and tested [10].

lower transportability because the empty space, need more storage space etc.

application of low-quality binders, need of special funds for the disintegration etc.

through the benefits in a very short period of time.

This biomass is a cheap and available fuel, but its utilization is linked to the problems of its collection, preparations for its transportation (cutting, tying into haystacks, baling), trans‐ portation and storage [7]. The best way for utilizing residual agricultural biomass for energy production in industrial or district heating is to be used close to place of its gathering - in large agricultural companies. That is the optimal solution, from energy, as well as economic point of view. Agricultural biomass is usually collected in form of bales, varying in size and shape, so it is most convenient to use it in that form. One of the most efficient ways, recom‐ mended by many institutions worldwide, is the combined heat and power (electricity) pro‐ duction – CHP [8], which use residual biomass as fuel, and have least as possible own power consumption.

Two technologies are currently used for the combustion of biomass bales. The first is based on whole-bale combustion in the combustion chamber, while the second considers combus‐ tion of biomass bales in "cigar" burners. The "cigar" firing technology provides better quali‐ ty of the combustion process, resulting in lower pollutant emissions and increased plant efficiency. This technology was found to be very suitable for straw combustion and was deemed not to be associated with any process limitations.
