**2. Research path**

In the process of production of different crop residues that occur in some species exceed three times the amount of crops produced. These residues can be baled and still used. Today in Serbia the producers of baled biomass are mainly farmers who receive biomass in baled form as by-products of primary production. In practice there are two basic types of bales: small square bales (0,40x0,50x0,80 m) and large cylindrical bales (ø1,80x1,20 m) or rectangu‐ lar shape (0,80-1,20x0,70x1,50-2,50 m).

Advantages and disadvantages of specific types of bales are the following [9]. Small conven‐ tional bales have many advantages: low cost of presses, binders moderate prices, the need for a smaller tractor, good storage, a favorable agreement on means of transport, simple dis‐ integration and chopping by means of lower prices, the possibility of firing the entire bales and others. Deficiencies are inevitable manual operation, by hand using auxiliary storage means, a relatively high usage of the binder, the lower reliability than other presses etc.

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

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

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

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

In the process of production of different crop residues that occur in some species exceed three times the amount of crops produced. These residues can be baled and still used. Today in Serbia the producers of baled biomass are mainly farmers who receive biomass in baled form as by-products of primary production. In practice there are two basic types of bales: small square bales (0,40x0,50x0,80 m) and large cylindrical bales (ø1,80x1,20 m) or rectangu‐

Advantages and disadvantages of specific types of bales are the following [9]. Small conven‐ tional bales have many advantages: low cost of presses, binders moderate prices, the need for a smaller tractor, good storage, a favorable agreement on means of transport, simple dis‐ integration and chopping by means of lower prices, the possibility of firing the entire bales and others. Deficiencies are inevitable manual operation, by hand using auxiliary storage means, a relatively high usage of the binder, the lower reliability than other presses etc.

and total absence of state subsidizing of biomass facilities.

deemed not to be associated with any process limitations.

power consumption.

56 Sustainable Energy - Recent Studies

**2. Research path**

lar shape (0,80-1,20x0,70x1,50-2,50 m).

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

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 through the benefits in a very short period of time.

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

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

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 was used for heating 1 ha of vegetable greenhouses belonging to the agricultural complex mentioned. The boiler house was built in the immediate vicinity of the greenhouse complex.

collectors (20, 21, and 22). A mobile tube for ash removal (23) has been placed inside the fur‐ nace, as well as a tube for pneumatic transport of ash (24). The boiler has a revision opening

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

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

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(25) for manual ash removal.

**Figure 1.** Scheme of the small agricultural biomass bale combustion boiler

**Figure 2.** Heat accumulator and bale storage and feeding system
