ANALYSIS OF THE POSSIBILITIES OF COMBUSTION OF ANIMAL FAT MIXED WITH LIQUID HYDROCARBONS IN BOILERS WITH SMALL FURNACES [305585]

ANALYSIS OF THE POSSIBILITIES OF COMBUSTION OF ANIMAL FAT MIXED WITH LIQUID HYDROCARBONS IN BOILERS WITH SMALL FURNACES

Mihăescu1 L., Lăzăroiu Gh., Pîșă I., Pop E., Negreanu G., Berbece V., [anonimizat], in boilers with small furnaces. [anonimizat], for a good efficiency. The resulting pollutant emissions were also studied.

INTRODUCTION

Combustion of animal fats is a necessity imposed by compliance with environmental requirements. [anonimizat], [anonimizat].

The choice of industrial applicability at a [anonimizat] a small furnace is a consequence of the amount of animal fats resulting from an industrial unit from the tannery industry in Romania.

All the developed research has taken into consideration a [anonimizat] a maximum mixing limit of 30%.

This paper presents the interpretation of a [anonimizat]:

energetic characteristics of fats;

determination of atomizing possibilities;

the choice of a technical-economical combustion technology;

application of the combustion technology as defined in a hot water producing boiler.

The energy characteristics have demonstrated the possibility of spraying animal fats both in a pure state (viscosity at 450C being 1.5 – 2E) and mixed with liquid hydrocarbons. [anonimizat] a value of 35000-35500 kJ/kg.

EXPERIMENTAL TESTS. RESULTS AND DISCUSSIONS

Combustion tests were conducted using a 50 [anonimizat] a mechanical spraying pump burner. The burner includes a [anonimizat] a level of 750C. The installation was completed by a fuel preheater up to a temperature level of 500C.

Figure 1 shows the boiler installation with the annexes relating thereto.

Figure 1. The boiler installation with the related annexes

The burner was equipped with an injector whose spray nozzle diameter was 0.5 mm to achieve as fine droplets as possible. Fuel flow rate during experimental testing was 15 l/h. Flame length Lf at the combustion of sprayed liquid fuels can be determined using relation [5]:

where: u [anonimizat] m/s; t – time, s; A – coefficient characterizing the interaction between the energy characteristics of the fuel and the geometry of the burner.

where: [anonimizat] N/m; -air density, i.e. fuel, kg/m3; -[anonimizat] m2/s, dj, do-diameter of the output section, m.

The burner air duct diameter is 80 mm, the output section being 20 mm ().

For ; ; ; ; results: A = 11.3

[anonimizat] R0 is determined with the relationship [5]:

where: is the fuel density in kg/m3; cc – specific heat of the fuel, ; R0 – [anonimizat], – thermal conductibility, ; -lower heat value of the fuel; – gravimetric concentration of oxygen; -oxygen required for burning the unit of fuel; – enthalpy increase when the particle is vaporized, ; Ts – particle surface temperature, ; Tg – flue gas temperature, .

For the used fuel, represented by a 30% mix of animal fat in light hydrocarbon liquids, the calculations were performed for the following physical sizes:

; ; ; ; ; ; ; ;

Testing the burner yielded a flame length of Lf = 0.45 m. The flow rate determined from the burner aerodynamics has indicated a value of u = 20 m/s at 200C. For a temperature of 900, flow velocity reaches the value of u = 66 m/s. The burning time for these values will become:

for this type of burning, the total combustion particle diameter has resulted in:

Within the experimental tests, the burner shown in Figure 2 was mounted on a 55 kW hot water boiler, whose furnace has the dimensions L = 0.76 m, cross-section radius 0.65 m. Figure 3 shows to maximum burning space inside the furnace.

Figure 2. The burner used and the flame obtained during testing, in a free atmosphere

Figure 3. Maximum burning space inside the furnace

As the flame length during the burner tests in free atmosphere for the animal fat fuel mixed in a proportion of 30% in light liquid hydrocarbons was of 0.45 m, there results full compatibility of the burner with the boiler’s furnace. In addition, it also highlights a possible flame size with a maximum of 0.3 m, which allows less fine spraying, with a maximum particle diameter of up to 100 μm in diameter.

CONCLUSIONS

The tests carried out have shown a good combustion, characterized by the absence of soot particles and by an acceptable content of carbon monoxide for such fuel. For an excess of air of 2.15-2.43, the emission of CO had values within 900-1200 ppm (animal fats mix 10%, 20%, and 30%), and NOx emissions within the limits of 90-152 mg/m3N. As the temperature of the flue gases exhausted at the stack had values of 340-3780C, the efficiency of the boiler was: =70.4-82%.

In conclusion, as a result of this research, we could prove the limitations of using animal fats mixed in a mass proportion of up to 30% for boilers with low thermal powers. The conclusions drawn lead to the hypothesis of the possibility of the successful use of this fuel in high power thermal plants as well.

References

Mihăescu L., Pănoiu N., Totolo Cr. „Arzătoare turbionare”, Ed. Tehnică, București, 1986

Mihăescu, L., „Arzătoare pentru hidrocarburi cu NOx scăzut”, Ed. Printech, București 2004, ISBN 973-718-039-9

E. Pop, L. Mihaescu, Gh. Lazaroiu, I. Pisa, G. Negreanu, „Energetic characteristics of animal fats from tannery for energy production” 4th International Conference on Thermal Equipment Renewable Energy and Rural Development TE-RE-ED 2015, Posada Vidraru 4-6 iunie 2015, Editura Politehnica Press, ISSN 2359-7941, pp 475-478

Nicolici A., Lăzăroiu Gh., Pană C., Negurescu N., Cernat Al., Nuțu C, Mocanu M „On animal fat use at diesel engine”, 5th International Conference on Thermal Equipment, Renewable Energy and Rural Development, TE-RE-RD 2016 Proceeding, ISSN: 2359-7941, ISSN-L:2457-3302, , Golden Sands, 2-4 June 2016, Bulgaria, pp 483- 488

Lemneanu N, Cristea E., Jianu C. Instalatii de ardere cu combustibili lichizi, Editura Tehnica, Bucuresti, 1982.