**4.2. Experimental investigation in boiler furnace**

(Table 4). Results of proximate analyze of soybean straw was used as input data for calcula‐ tions. In the case of combustion of soybean straw, with a total moisture content of Wt = 68%, the theoretical calculation shows that the combustion temperature is not possible to achieve satisfactory gas temperature for a real excess air to be used in the process of bales burning. The theoretical combustion temperature of soybean straw for excess air of 2.80 would be

C. In the case of combustion of the same composition biomass, but reduced the moisture content of Wt = 15%, the calculation shows that it is possible to achieve significantly higher gas temperature for a real excess air. In this case, the theoretical combustion temperature

combustion temperature of soybean straw, which in real terms of furnace can not be ach‐ ieved so that the actual combustion temperature significantly lower. This is caused by the

burning soya straw with high moisture content in the flue gases products is a large amount

**Wt = 15%**

α =1,60 1379 801 α=1,90 1217 728 α=2,20 1089 667 α=2,50 987 616 α=2,80 903 572 α=2,95 866 552 α=3,10 833 534

Also was made a bale straw moisture test on the basis of statistical data on the amount of rains on the territory of Belgrade in September, October and November. In September fell

means that the total per bale could fall about 386 kg of water, taking into account data from October and November. If we accept that the initial bale moisture was 10% and the average weight of bales after baling was about 200 kg by the calculation is to the point that one rain bales after October and November had a moisture content of ≈ 70%, which agreed quite well with the obtained moisture analysis of samples. So the increase of moisture in the bales stor‐

Information about the theoretical combustion temperature (Table 4) confirmed the facts of bales combustion impossibility from the upper row of the crowd with such high moisture con‐ tent in it. On the other hand, the vast majority of straw samples from bales, which were in the middle of the crowd (except than bale no. 2), has a moisture content ranging from 11.83 to

fact that the combustion of CO to CO2 achieves at the minimum temperature of 680o

of CO which is due to low temperatures (below 680o

**Excess air Moisture content**

**Table 4.** Theoretical (adiabatic) combustion temperature of soybean straw (<sup>o</sup>C)

3.9 kg rain/m2 of soil, in October 98.8 kg rain/m2

ed in groups is a consequence of atmospheric rains.

C for the excess air of 2.80. Note that this is mathematical calculated theoretical

C. When

. This

C) can not be transformed into CO2.

, while in November fell 62 kg rain/ m2

**Moisture content Wt = 68%**

572o

was 903o

72 Sustainable Energy - Recent Studies

Cigarette baled biomass combustion is a relatively new and unexplored technology. For this reason a complex Computation Fluid Dynamics (CFD) simulation of the combustion process at a specific procedure may be of importance for further investigation of the process of ciga‐ rette combustion. Numerical simulations process of this type of facility involves modeling the transfer of momentum, heat and substances during combustion of biomass bales, which composition is a porous medium [24, 27]. To form a mathematical model of thermo physical parameters except combustion in a porous medium, it is necessary knowledge inputs as thresholds model.

This paper describes experimental studies performed on mentioned boiler in order to deter‐ mine the necessary model input parameters. When performing experiments measured the all parameters necessary to determine the global kinetics of the combustion process, the composition and temperature of flue gases at the outlet section of the space being modeled, and estimates the amount of fuel which is unburnt and which post combustion performed in a fluidized bed of its own ashes. In order to compare with the model made the determina‐ tion or measurement of the temperature profile in soybean bale on its way from entering the combustion chamber to the combustion zone.

Experimental investigation on the demonstration boiler implies the measurements of the fol‐ lowing input parameters [28]:


Schematic of the experimental tests is shown in Figure 21. Measurement of mass flow of air at inlet cross sections was done indirectly through the measurement of velocity in the chan‐ nels using Pitot-Prandtl's probe. Temperature of the flue gas exiting the fluidized bed of its own ashes, and the temperature at the outlet cross section were measured continuously by thermocouples type K. During experiments the acquisition of measurement data using cor‐ responding instrument was performed.

Also, were carried out experimental studies to determine the temperature profile in the cen‐ tral plane of soya straw bales, which participates in the combustion process. For this experi‐ ment, four thermocouples were placed in the central plane of height, according to the scheme at Figure 21. The experiment was performed in a stationary regime of the furnace operation and the temperature measured in function of the position of thermocouples. The appearance of soya straw bales with thermocouples placed in the median plane, just before entering the bale feeding system is shown in Figure 22. Experiments were performed at the maximum capacity of the furnace of 1.57 MW. Proximate and ultimate analysis of combust‐

**Ultimate analysis Proximate analysis**

W

45.2 7.0 0.5 47.3 11.35 60.73 20.91 7.049 13.981

Experimental tests were carried out at a temperature in the furnace between 850-900o

which is the optimum temperature for combustion of soybean straw. This temperature is high enough for complete combustion of straw, and safe from the point of ash melting. The stationary measurement regime remain several hours, but here will be presents the results of measurements for 1 h. It is enough to perform the necessary conclusions about the quality of combustion and comparisons with the proposed model. Data whose values are not

[%] Vol. [%]

Cfix [%]

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

A [%]

Hd [MJ/kg]

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

75

C,

ed soybean straw is provided in Table 5.

N [%]

**Table 5.** Ultimate and proximate analysis of soy straw used in tests

changed during the experiment are shown in Table 6.

**Figure 22.** Thermocouples on the bale in feeding system

**4.3. Results of the experimental investigation**

O [%]

H [%]

C [%]

**Figure 21.** Measurements scheme at demonstrating hot water boiler furnace

Bales feeding were done discontinuous so that the cycle of 1 min the number of seconds the ball travels to the furnace and the rest to 1 min ball is at rest. Therefore, it is done recording the relative position of the bale in relation to entering the combustion chamber and time, which is based on data received on its secondary mass flow *m*˙ *fu* . Composition of dry flue gas at the exit cross section was measured using a gas analyzer. Based on the measured air flow at the entrance to the ash layer *m*˙ *fu* and the temperature difference Tm3 between inlet and outlet flue gases it is possible to determine the degree of conversion of coke residue, based on the energy balance between the energy of combustion of carbon, which falls on the fluidized bed and the enthalpy difference above the entrance of air and flue gas exit from the fluidized bed.

Also, were carried out experimental studies to determine the temperature profile in the cen‐ tral plane of soya straw bales, which participates in the combustion process. For this experi‐ ment, four thermocouples were placed in the central plane of height, according to the scheme at Figure 21. The experiment was performed in a stationary regime of the furnace operation and the temperature measured in function of the position of thermocouples. The appearance of soya straw bales with thermocouples placed in the median plane, just before entering the bale feeding system is shown in Figure 22. Experiments were performed at the maximum capacity of the furnace of 1.57 MW. Proximate and ultimate analysis of combust‐ ed soybean straw is provided in Table 5.


**Table 5.** Ultimate and proximate analysis of soy straw used in tests
