Spray characteristics, combustion performance and palm oil emissions

Subscriber access provided by UNIV OF LOUISIANA

Biofuels and Biomass

Spray characteristics, combustion performance and palm oil emissions in a low-pressure auxiliary air fluid pulverization burner Julio San-José, María Ascensión Sanz-Tejedor, and Yolanda Arroyo Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b01828 • Publication Date (Web): 09 Oct 2018 Downloaded from http://pubs.acs.org on October 10, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Spray characteristics, combustion performance and palm oil emissions in a low-pressure auxiliary air fluid pulverization burner J. San José,*† M.A. Sanz-Tejedor,‡ and Y. Arroyo*‡ †Department

of Energy Engineering and Fluid Mechanics, School of Industrial

Engineering, University of Valladolid, Paseo del Cauce 59, 47011 Valladolid, Spain ‡Department

of Organic Chemistry, ITAP, School of Industrial Engineering, University of

Valladolid, Paseo del Cauce 59, 47011 Valladolid, Spain KEYWORDS: Palm oil, fatty acid composition, atomization, combustion, burner

ABSTRACT: This work presents the experimental results from refined palm vegetable oil atomization and combustion processes in a low-pressure auxiliary air fluid pulverization burner. The physicochemical properties that define palm vegetable oil as a fuel (density, kinematic viscosity, heating value and elemental analysis) were first determined. The fatty acid composition was then established by proton high-resolution nuclear magnetic resonance spectroscopy. A description was provided of a procedure based on direct photographic imaging in order to determine the macroscopic properties that define the atomization spray, spray tip penetration and spray cone angle. The influence of varying the fuel and secondary air flows in the atomization and combustion processes was also studied. 1 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 38

The polluting emissions and combustion efficiencies in the different test conditions and how these vary depending on the atomization parameters was then evaluated. In general, admissible combustion efficiencies were obtained, with CO and NOx emissions below permitted levels. Most of the experiments carried out showed that the lower the spray cone angle the greater the combustion efficiency.

INTRODUCTION Dwindling fossil fuel resources, increased energy consumption at a global scale1 and the growing concern for the environment have led the scientific community to seek alternative fuels to those derived from oil. In this regard, direct use of vegetable oils (VOs) in industrial boilers and for domestic heating is an attractive alternative, given their environmental benefits and ability to use autochthonous resources in countries that lack fossil fuel resources. Such is the case in Spain, where total primary energy consumption in 2016 came to 135,000 ktep, with a level of self-sufficiency of only 26.9%.2 From an environmental perspective, reducing nitrogen oxide and sulphur oxide (NOx and SOx), responsible for acid rain and damaging health, is of vital importance. In this regard, the lack of sulfur and nitrogen in VOs minimizes the risk of these contaminating gases forming, although NOx production depends mainly on the temperature reached during combustion. The main restriction to be taken into account in the combustion of VOs in conventional boilers concerns its high viscosity and low volatility when compared to heating oil, possibly leading to incomplete combustion and carbon deposits in the combustion chamber. One of the most widely used strategies to reduce the viscosity of VOs is their chemical transformation into biodiesel. To achieve this, a transesterification reaction of the VO with 2 ACS Paragon Plus Environment

Page 3 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

methanol, in a basic medium, was performed so as to give the corresponding fatty acid methyl esters (FAME). The combustion of both pure biodiesel3-10 and its mixtures with diesel fuel11-16 in conventional boilers has been widely studied, and the results were compared with derivatives of oil such as extra light heating oil and diesel fuel. It was generally found, that biodiesel is a suitable fuel for domestic and industrial boilers as regards combustion effectiveness and low CO emissions. With regard to NOx levels, published data show that these depend on the quality of atomization and boiler operating conditions.4,5 As a result, depending on experimental conditions, lower 4,6,11,13, equal 9,10,14,16

or higher3,5,7,8,15 emissions than those using oil derivatives were obtained.

Nevertheless, the main limitation of biodiesel lies in the long reaction times required to prepare it and its subsequent purification. Its commercial viability thus remains very much open to question.17 Moreover, during the process large amounts of glycerol (1kg per 10 kg of biodiesel), a sub-product of little added value, are generated.18 In this regard, Ghorbani et al.3 have studied the operating costs of an experimental boiler (70 kw) fed with petrodiesel, SyO, soybean oil methyl ester (SOME) and two mixtures of petrodiesel and SOME. Using SOME the total costs (fuel of price and price of pollutant gases) are higher than those of petrodiesel and make its use not economically viable even though it is considered renewable. Another alternative for reducing the viscosity of VOs involves mixing them with lower viscosity oil derivatives.19-25 Jaafar et al.19 analyzed the effect of various mixtures of palm oil (PlO)-diesel fuel using an industrial oil burner with and without secondary air. Their results showed a reduction in CO and NOx emissions as the percentage of PlO in the mixture increases, with the lowest emissions being obtained for mixtures with 25% PlO. 3 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 38

20

Jiru et al. have shown that degummed soya oil (SyO)-fuel oil blends (20% SyO) were suitable for use in commercial burners without the need to make any changes. Combustion of mixtures of cotton oil (CtO) and fuel oil in a domestic burner were studied by Daho et 21

al. Results showed that CO, NOx and CO2 emissions were similar for all mixtures when 20 bar pressure injection is used. San José et al. performed combustion of VO-diesel oil blends (sunflower oil,22,23 SfO, SyO24,25 and rapeseed oil,26 RpO) as well as animal fatdiesel oil blends27 in a conventional diesel facility equipped with a mechanical pulverization burner and showed that the high viscosity of VOs limited the use of blends containing up to 40% of VO. Combustion efficiencies up to 85% and low NOx emissions (15-52.8 ppm) were obtained under 10 to 14 bar pressure injection. As regards direct use of VOs in standard burners, several authors have shown that these could be an appealing alternative for use as domestic fuels or at an industrial scale if the necessary adjustments are made to the burner.28-36 In this sense, Vaitilingom and Daho, respectively, studied the performance of RpO28 and CtO,29 both refined, in modified fuel oil burners. In both cases, by preheating the oil (T ≥ 125 °C) and applying high injection pressures (≥ 28 bar) they found no fundamental differences between both VOs and fuel oil in terms of CO (≤13 ppm) and NOx emissions (78-88 ppm). Combustion efficiencies were also the same (around 93%). Use of a multi-fueled burner in the combustion of crude, semirefined CtO and diesel oil was also studied.30 The authors found that preheating the CtO to 60 °C resulted in the lowest CO emissions in all the experiments (86 ppm). Oprea et al.31 studied combustion of raw SyO pre-heated (70-80 °C) in a 2MW pilot boiler, and CO (≈ 250 mg·m-3) and NOx (≈ 145 mg·m-3) emissions similar to those of diesel oil were obtained. Józsa et al. studied the flame emission spectrum,32 and analysis of combustion 4 ACS Paragon Plus Environment

Page 5 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

gases of raw RpO combustion in a lean premixed pre-vaporized burner,33 comparing the results to those obtained with diesel fuel. For an atomizing pressure above 1.6 bar, stable RpO combustion was achieved although high CO and NOx emissions were reached. San José et al.34 analyzed the technology of several commercial burners in order to choose the most appropriate for burning liquid fuels in a kinematic viscosity range of 50 to 118 mm2·s1

such as VOs, and showed that the use of a low-pressure auxiliary air fluid pulverization

burner provided a perfect mixture of air and VO in the compressor and good pulverization in the injector. This burner operated using an injection pressure of about 1·105 Pa and required no VO preheating before introduction into the combustion chamber. Using this kind of burner, they studied the combustion of different types of VOs, raw and refined, with different fatty acid profiles and NOx emissions lower than 46 ppm were obtained.35,36 They also found that CO emissions decreased and that combustion efficiency increased as the degree of unsaturation (DU) of VOs rose.36 This work explores the atomization and combustion processes of refined PlO in a lowpressure auxiliary air fluid pulverization burner. Using a direct photographic image technique, the macroscopic parameters characterizing the atomization spray (spray tip penetration and spray cone angle) were studied. In both studies, three fuel emulsion flows and three secondary air flows were analyzed. In addition, the influence of atomization parameters on combustion efficiency and emissions were also studied. 2. MATERIALS AND METHODS 2.1. Materials. The PlO used in this study is commercially available and was chosen for use as a bioliquid since it is the VO that gives the largest quantity of oil per hectare of 5 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 38

cultivated area (about 3.7 tons).37 The physicochemical properties and elemental composition of the PlO were determined at the Castilla and León Regional Laboratory, an accredited laboratory for fuel analysis (Table 1). An understanding of these properties is necessary since they all have a direct effect on the combustion process: the density and kinematic viscosity determine the atomization process, the heating value affects the combustion efficiency of the bioliquid, and the elemental analysis helps to determine the stoichiometry of the combustion and establish the excess air required for it. It is also important to know the fatty acid profile, FA, and degree of unsaturation, DU, of PlO, since the latter influences combustion efficiency and flue gas emissions.36 It is interesting to underscore that because PlO is not a normalized fuel, the percentage of fatty acids varies from one sample to another, this causes changes in their physical properties, so that the combustion results may change compared to those previously published. As regards its FA, it was determined using proton nuclear magnetic resonance, 1H NMR. Spectra were acquired in a Varian (54 Premium Shielded) spectrometer (500 MHz) equipped with a cold probe, at 298 K, in high resolution conditions (number of scans, eight; spectral width 3.9 kHz; 25 s relaxation delay and 90º pulse) so as to ensure quantitative analysis of the oil’s composition. Six identical samples with a concentration of 20 mg PlO in 0.6 ml of CDCl3 were prepared and the percentage of FA with its corresponding standard deviation was calculated. Figure 1 shows the integrated H NMR spectrum of PlO from one of the samples analyzed. Integration values (Ai) are indicated under each signal of the spectrum. To determine the FA of the PlO, the equations (1)-(4) previously reported by us36 have been used.

6 ACS Paragon Plus Environment

Page 7 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

𝐿𝑖𝑛𝑜𝑙𝑒𝑛𝑖𝑐 (% 𝐿𝑛) = 𝐿𝑖𝑛𝑜𝑙𝑒𝑖𝑐 (% 𝐿) =

𝐴𝐺 6

𝐴𝐵

(1)

9

―2·(% 𝐿𝑛)

𝐴𝐸

(2)

𝑂𝑙𝑒𝑖𝑐 (% 𝑂) = 12 ―(% 𝐿𝑛 + % 𝐿)

(3)

𝑆𝑎𝑡𝑢𝑟𝑎𝑡𝑒𝑑 𝐹𝐴 (% 𝑆) = 100 ― [(% 𝐿𝑛 + % 𝐿 + % 𝑂]

(4)

In these equations, the area of signals B (methyl hydrogens of the Ln), H (hydrogens of the glycerol skeleton, G (bis-allylic hydrogens) and E (allylic hydrogens) were considered (see Figure 1). 2.2. Experimental Atomization Technique The quality of atomization plays a key role in a fuel’s characteristic combustion and flue gas emissions. During the atomization process a liquid mass breaks down into much smaller size drops than the initial mass. In the burner used in this study (AR-CO, model BR 5), atomization was performed by injecting an emulsion of PlO in air through a pulverization nozzle, concentric to which the secondary air was introduced. The PlO in air emulsion was continuously injected, such that the process to be studied was steady. This is different from diesel engine injection systems, which occurs in much smaller successive injections. The most relevant macroscopic characteristics of the atomized spray were: break-up length (S), spray cone angle (α) and spray tip penetration. Figure 2 shows a diagram of the macrostructure of the spray. In our study, the break-up length, S, could be considered practically zero because the fuel was atomized as soon as it came out of the nozzle. The spray tip penetration length is the maximum distance covered by the spray from the nozzle tip up to the edge of the spray.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 38

The spray cone angle is the maximum angle between two tangent lines drawn from the tip of the nozzle to the limits of the spray. The opening of the spray cone angle is the result of the rapid rotation that the injector subjects the fuel to, so that the spray in its advance progresses in spiral form. As a result, the speed has a tangential component and another axial component at the outlet orifice. The relation between the tangential and the axial speed defines the value of the angle (α) through the expression, tag () = Vt/Va. The spray cone angle is extremely important in the fuel and air mixing process, since the greater the angle, the greater the amount of air that will interact with the atomized liquid, thereby achieving a more effective mix. Correlations were developed, which allow spray tip penetration38-41 and spray cone angle39 to be determined theoretically depending on the fuel’s physical properties. In this case, analysis of the atomization process could not be modelled using the previously referenced expressions since this is an emulsion of PlO in air, which modifies the properties of the original fuel. As a result, an experimental technique based on analyzing direct photographic imaging was used in this work. The method used consisted of photographing the atomization spray with a fast video camera under direct illumination from a light. The macroscopic characteristics of the spray were then obtained from the photographs taken, using image analysis software. The test bed used is shown in Figure 3. The camera used to capture the images of the atomized spray was a Nikon-D3100 single lens digital reflex equipped with an AF-S DX NIKKOR 18-55mm f/3.5-5.6G VR lens. This device is able to capture sharp images of dynamic movements such as the atomized spray of the fuels studied. A tripod, to fix and stabilize the camera in the various tests carried out, was used. 8 ACS Paragon Plus Environment

Page 9 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

In the burner, the fuel flow was mixed with the primary air through a rotary vane compressor, forming a PlO in air emulsion that was injected into the atomization chamber. A 1,000 W projector was used to light up the chamber. In order to absorb the incident light not reflected by the drops, the camera was coated black. The emulsion was pulverized through an injector, around which there was another air inlet (secondary air), supplied by a separate fan that could be adjusted to control the amount of air entering the combustion chamber. The secondary air spread out concentrically around the injector with components of axial and radial speed components that favored atomization of the emulsion and its subsequent combustion. Figure 4 shows a diagram of the injector with its dimensions and details of the burner nozzle. In this work, PlO atomization was carried out by modifying two of the burner parameters; the fuel flow rate and the secondary air ratio, following an orthogonal design. The three PlO flow rates evaluated were 4.1 kg·h-1, 6.1 kg·h-1 and 7.3 kg·h-1, corresponding to positions C1, C3 and C6 of the burner. Air flow rates were adjusted by a fun dumper setting which controls the amount of air entering the combustion chamber. Values were 29.90 kg·h-1, 41·10 kg·h-1 and 45.11 kg·h-1, corresponding to min, mid and max positions. Nine different conditions were studied. Spray images under each condition were taken six times. 2.2.1. Method for obtaining the images. Image capture commenced by placing the tripod perpendicular to the atomization chamber, 1m away, focusing the camera lens on a point F of f/3.8. The burner was then prepared to work in atomization state: the automatic ignition system was switched off so that it did not cause a spark and only the pulverization process took place. The burner then 9 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 38

started with PlO pre-heated to 40ºC. The initial burner operation parameters were established (fuel and air flow rates) and the facility was run for about two minutes until steady state was reached. At this point, the images of the atomized spray were taken. The camera was programmed to take ten consecutive photographs with an exposure time of 1/40s and an image resolution adjusted to a size of 4608 x 3072 pixels. After recording the images in the initial operating conditions, the operating parameters of the set-up were changed and images were taken for each of the scheduled tests. Once the programmed tests were completed, the burner was fed with diesel fuel to clean the pipes and the session was concluded. In all the experiments carried out, the fuel injection pressure was kept constant at 1x105 Pa, and the atomization chamber was kept at atmospheric pressure and 22 ºC. Figure 5 shows the flowchart of the technique for obtaining the images. 2.2.2. Image processing Based on the images taken in each test, a procedure was established to determine the values of the macroscopic parameters that define the atomization spray. A brief description was given below of the steps involved, and an example of the image processing procedure is shown in Figure 6. Image capture: an exposure time of 40 seconds was used for each of the conditions tested. Negative of the image: the color of the photograph was inverted in order to distinguish the spray from its immediate surroundings more clearly.


Page 11 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Establishing the limits of the spray: a color intensity limit value was established in order to highlight the spray outline. For this purpose, brightness percentages (-20%) and contrast (70%) were applied. Penetration length (L): following the axis of the burner, a line was traced from the nozzle tip where the contrast of the color is below 90%. Radial distance measures: equidistant lines were traced perpendicular to the line of penetration and the radial distances were calculated in each axial position. Tangent lines: two tangent lines were traced to the radial distances from the nozzle tip. Determining the spray cone angle (α): it was calculated by the cosine of the angle formed by the axial distance at L/2 and the tangent line at this point. 2.3. Combustion equipment and procedure An actual image of the facility used in the PlO combustion studied is shown in Figure 7. The facility was comprised of several elements: a low-pressure auxiliary air fluid pulverization burner manufactured by AR-CO (model BR 5); a fuel feed system that allowed fuels to be preheated and changed without the need to stop the burner; a combustion chamber, connected to a chimney, and equipped with a flap valve, which allowed the back-pressure inside to be adjusted. A blower located to one side was used to control the combustion chamber. The facility also contained: the TESTO 350XL gas analyzer equipped with five electrochemical probes to measure the percentages of O2 and CO2 as well as the amounts of CO, SOx and unburnt hydrocarbons (CxHy) in ppm; an electrolytic probe, which indicated the ppm of NOx, and two probes to measure fume 11 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 38

temperature and combustion air temperature. These were located in an opening of the chimney at the boiler exit and at the burner entry point, respectively. The TESTO gas analyzer provided an accurate description of the combustion processes carried out.35,36 The method used in the combustion tests was similar to that described earlier for the atomization process, bearing in mind that in this case the burner worked with the automatic ignition system on switch. In sum, the following stages were carried out: tuning the facility, adjusting the conditions for each of the nine tests performed, test reading using the gas analyzer, duct cleaning and burner shut off. Based on the data obtained when analyzing the combustion (Table 4), combustion efficiency (η) compared to the lower heating value (LHV) of the fuel was calculated. Calculations were expressed per unit of mass. The procedure described by ASHRAE42 shown in expressions (5) and (6) was used:

𝐶𝑜𝑚𝑏𝑢𝑠𝑡𝑖𝑜𝑛 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦, % = 100

𝑖𝑛 𝑓𝑙𝑢𝑒 𝑔𝑎𝑠𝑒𝑠 (𝐿𝐻𝑉 ― 𝐻𝑒𝑎𝑡 𝑙𝑜𝑠𝑠 ) 𝐿𝐻𝑉

(5)

Heat loss depends on the flow of flue gases and the temperature at which it leaves the chimney. It represents sensible heat in the dry flue gases with respect to the input air temperature of combustion. Calculations were made in line with expression (6): 𝐻𝑒𝑎𝑡 𝑙𝑜𝑠𝑠 𝑖𝑛 𝑓𝑙𝑢𝑒 𝑔𝑎𝑠𝑒𝑠 = 𝑚𝑔·𝐶𝑝𝑔·(𝑡𝑔 ― 𝑡𝑎)

(6)

in which mg is the mass of dry flue gases required for combustion with excess air per kilogram of fuel, (kg·kg-1fuel). The mg value was determined depending on the elemental composition by mass of the fuel,36 and of the percentage of oxygen in the flue gases (Tables


Page 13 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

1 and Table 4, respectively). Cpg is the specific heat of the flue gases, at constant pressure, for flue gas temperature ((kJ·(kg·ºCflue)-1). This was calculated in accordance with regulation UNE 9205:1987,43 based on the specific heat of each component in the flue gases, multiplied by its percent by mass. tg is the flue gases temperature at the exit of the heating device (ºC) and ta is the input temperature of combustion air (ºC). 4. RESULTS AND DISCUSSION 4.1. Fatty acid profile of PlO The proportions calculated of each FA in the PlO studied are shown in Table 2. As can be seen, the saturated fatty acids were the main components, with a percentage of 59.2% (mainly palmitic acid). As regards unsaturated fatty acids, 32.4% of oleic and 8.4% of linoleic were found. In the H NMR spectrum of PlO, the signal characteristic of methyl group corresponding to linolenic acid (δ = 0.99-0.94 ppm) was not detected (Figure 1). This means that the percentage of Ln is less than 0.5%. Due to the high proportion of saturated fatty acids, the PlO was in solid state, at 25 oC, as can be observed in Table 2. 4.2. Atomization results The mean values of the spray tip penetration length (L) and spray cone angle (α) obtained for PlO combustion are shown in Table 3. The mean value of each characteristic was shown to an accuracy of ± 5%. An analysis of the measurements taken revealed that when the burner operates in C1 fuel flow conditions, the spray cone angle decreases as the amount of secondary air increases. However, the penetration length hardly changed (43,4-45,2 cm) when varying the air flow 13 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 38

rate. A more noticeable trend was observed for both spray characteristics when combustions were performed at C3 and C6 fuel flows. In this case, the spray cone angle increased with the rise in air flow. The penetration length decreased when increasing the air flow, except for test C6/Amax, which displays unusual behavior. With the exception of minimum flow conditions (C1), it can be seen how as the air flow and fuel flow increased, the value of  also rose. This behavior might be explained bearing in mind that in these conditions the tangential speed increased, leading to greater spray cone and lower tip penetration. 4.2. Combustion results The results provided by the TESTO analyzer and calculated values of mg and η in the different conditions studied are shown in Table 4. The mean value of each variable was shown to an accuracy of ± 5%. As regards the analysis of the combustion results, this work was focused on the gases regulated by directive 2010/75/EU44 (CO, CO2, NOx, SO2 and CxHy), because of their negative environmental impact. In this study, the contribution of CO2 emissions (4.911.8%) to global warming could be deemed virtually insignificant since PlO is a renewable resource. SO2 emissions were virtually insignificant because vegetable oils contain no sulfur in their composition. In all the tests carried out, NOx emissions ranged between 26.5 and 46 ppm, values considerably lower than the maximum allowed by the EU (150 ppm). This highlights the fact that the low-pressure auxiliary air fluid pulverization burner contributes


Page 15 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

efficiently to reducing this kind of emission. This is due to the fact that because this type of burner mixes the fuel with air, the injected fuel has a lower flame temperature than it would have if it were unmixed. As a result, very high temperatures are not reached at the flame front (< 1500 ºC), thereby avoiding the formation of NOx.45 As regards CO and CxHy emissions, a similar trend emerged. They increased as fuel flow increased and air flow decreased, as shown in Figure 8. This result may be explained because of the reduced availability of oxygen in the central areas of the spray, which hinders oil combustion, leading to an increase in both emissions. In virtually all the conditions studied (except C6/min), these emissions were seen to be below legally established limits44. The variations in combustion efficiency with fuel flow at three input air flows are shown in Figure 9. As can be seen, combustion efficiency improved as fuel flow increased and air flow decreased. This result was consistent bearing in mind that according to the expressions (5) and (6) used to calculate η, by reducing the air flow and increasing the fuel flow, the specific flow of flue gases decreases (mg, table 4), in such a way that heat losses in flue gases are reduced. The other term that has a strong impact on combustion efficiency is the temperature of flue gases (tg), which increases with fuel flow. However, this increase is lower than the decrease of the specific flow of flue gases. Consequently, in the final result, η increases. A comparison between atomization characteristics (Table 3) and combustion results (Figure 8) showed that the lowest CO and CxHy emissions were obtained when L was


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 38

small and α was large. Large penetration lengths might lead to flame separation that favor the presence of unburnt fuel, and small cone angles are indicative of bad pulverization. As regards spray cone angle values and comparing them to combustion efficiency, in C3 and C6 fuel conditions it could be seen how combustion efficiency increased as  decreased (Figure 10). This result differs to what was seen in the references.46 In our case, this might be due to the fact that the greatest angle did not correspond to a better atomization but to a greater inertia of oil drops. This would favor spray expansion in its radial direction, given that the spray cone angle normally increases as fuel flow increases. Combustion efficiency and CO and CxHy emissions displayed the same trend: they increased when: i) air flow decreased, and ii) fuel flow increased. Combustion results allow us to establish that combustions with the lowest emissions occurred when the burner was regulated to obtain a spray with: i) large spray cone angle (α), and ii) small spray tip penetration length (L). Flame adjustment affects the spray mix, which has a direct impact on emissions and combustion efficiency. 5. CONCLUSIONS This study shows that the emulsion boiler used is suitable for achieving good PlO atomization. Correctly adjusting the fuel flow and air flow parameters provided energy and environmentally efficient combustions. At the macroscopic level, the PlO spray displayed a rhombic shape.


Page 17 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

In seven of the nine conditions studied, it can be seen how the greater the spray cone angle, the less the spray tip penetration length. In this work, it can be seen how atomizations that lead to the lowest emissions are those which occur with small penetration lengths (< 44.3 cm) and large cone angles (>27.1 º). Mean combustion efficiency were admissible (73.1%) and there were significant variations when varying boiler operating conditions. Combustion efficiency, CO and CxHy emissions evolved in a similar manner and were seen to improve as fuel flow in the burner increased and air flow decreased. As a result, a compromise must be reached wherein emissions were as low as possible when coupled with maximum combustion efficiency. Fuel flow conditions C3 and C6, when operating with an air flowrate in mid position, would seem to be the most appropriate. REFERENCES (1) BP Statistical Review of World Energy 2017. http://www.bp.com. Consulted on May 10, 2018. (2) La Energía en España, 2016. Ministry of Energy, Tourism and Digital Agenda. www.minetad.gob.es. (3) Bazooyar, B.; Shariati, A.; Hashemabadi, S. H. Economy of a utility boiler power plant fueled with vegetable oil, biodiesel, petrodiesel and their prevalent blends. Sustain. Production and Consumption 2015, 3, 1-7.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 38

(4) Bazooyar, B.; Shariati, A.; Hashemabadi, S. H. Characterization and Reduction of NO during the Combustion of Biodiesel in a Semi-industrial Boiler. Energy Fuels 2015, 29, 6804−6814. (5) Bazooyar, B.; Ebrahimzadeh, E.; Jomekian, A.; Shariati. A. NOx Formation of Biodiesel in Utility Power Plant Boilers. Part A: Influence of Fuel Characteristics. Energy Fuels 2014, 28, 3778−3792. (6) Pereira, C.; Wang, G.; Costa. M. Combustion of biodiesel in a large-scale laboratory furnace. Energy 2014, 74, 950-955. (7) Kermes, V.; Belohradsky. P. Biodiesel (EN 14213) heating oil substitution potential for petroleum based light heating oil in a 1 MW stationary combustion facility. Biomass Bioenergy 2013, 49, 10-21. (8) Bazooyar, B.; Ghorbani, A.; Shariati. A. Combustion performance and emissions of petrodiesel and biodiesels based on various vegetable oils in a semi industrial boiler. Fuel 2011, 90, 3078–3092. (9) Macor, A.; Pavanello. P. Performance and emissions of biodiesel in a boiler for residential heating. Energy 2009, 34, 2025–2032. (10) Tashtoush, G.; Al-Widyan, M. I.; Al-Shyoukh. A. O. Combustion performance and emissions of ethyl ester of a waste vegetable oil in a water-cooled furnace. Appl. Therm. Eng. 2003, 23, 285–293.


Page 19 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

(11) Ghorbani, A.; Bazooyar, B. Optimization of the combustion of SOME (soybean oil methyl ester), B5, B10, B20 and petrodiesel in a semi industrial boiler. Energy 2012, 44, 217-227. (12) González-González, J.F.; Alkassir, A.; San José, J.; González, J.; Gómez-Landero, A. Study of combustion process of biodiesel/gasoil mixture in a domestic heating boiler of 26.7 kW. Biomass Bioenergy 2014, 60, 178-188. (13) Ghorbani, A.; Bazooyar, B.; Shariati, A.; Jokar, S.M.; Ajami, H.; Naderi, A. A comparative study of combustion performance and emission of biodiesel blends and diesel in an experimental boiler. Appl. Energy 2011, 88, 4725-4732. (14) San José, J. ; Al-Kassir, A.; López-Sastre, J.A.; Gañán, J. Analysis of biodiesel combustion in a boiler with pressure operated mechanical pulverisation burner. Fuel Process. Technol. 2011, 92, 271-277. (15) Ng, H. K.; Gan. S. Combustion performance and exhaust emissions from the nonpressurised combustion of palm oil biodiesel blends. Appl. Therm. Eng. 2010, 30, 2476-2484. (16) Lee, S. W.; Herage, T.; Young. B. Emission reduction potential from the combustion of soy methyl ester fuel blended with petroleum distillate fuel. Fuel 2004, 83, 1607–1613. (17) Mata, S. Ch.; Idroasa, M.Y.; Hamida, M.F.; Zainala, Z.A. Performance and emissions of straight vegetable oils and its blends as a fuel in diesel engine: A review. Renewable and Sustainable Energy Reviews 2018, 82, 808–823. 19 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 38

(18) Zhang M.; Wu H. Effect of major impurities in crude glycerol on solubility and properties of glycerol/methanol/bio-oil blends. Fuel 2015, 159, 118–127. (19) Jaafar, M. N. M.; Eldrainy, Y. A.; Ali, M. F. M.; Omar, W. Z. W; Hizam, M. F. A. M. Combustion Performance Evaluation of Air Staging of Palm Oil Blends. Environ. Sci. Technol. 2012, 46, 2445−2450. (20) Jiru, T. E.; Kaufman, B. G.; Ileleji, K. E.; Ess, D. R.; Gibson, H. G.; Maier. D. E. Testing the performance and compatibility of degummed soybean heating oil blends for use in residential furnaces. Fuel 2010, 89, 105–113. (21) Daho, T.; Vaitilingom, G.; Sanogo, O. Optimization of the combustion of blends of domestic fuel oil and cottonseed oil in a non-modified domestic boiler. Fuel 2009, 88, 1261-1268. (22) López-Sastre, J. A.; San José-Alonso, J. F.; Romero-Ávila, C.; López E. J.; Rodríguez, C. A study of decrease in fossil CO2 emissions of energy generation by using vegetable oils as combustible. Build. Environ. 2003, 38, 129-133. (23) López-Sastre, J. A.; San José-Alonso, J. F.; Romero-Ávila, C.; López E. J.; Izquierdo-Iglesias, C. Using mixtures of diesel and sunflower oil as fuel for heating purposes in Castilla y León. Energy 2005, 30, 573-582. (24) San José-Alonso, J. F.; López-Sastre, J. A.; Rodríguez-Duque, E.; López, E. J.; Romero-Ávila, C. Combustion of Soya Oil and Diesel Oil Mixtures for Use in Thermal Energy Production. Energy Fuels 2008, 22, 3513–3516.


Page 21 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

(25) San José, J.; López-Sastre, J.A.; Romero-Ávila, C.; López, E. A note on the combustion of blends of diesel and soya, sunflower and rapeseed vegetable oils in a light boiler. Biomass Bioenergy 2008, 32, 880-886. (26) San José, J.; López-Sastre, J.A.; Romero-Ávila, C.; López, E. Combustion of rapeseed oil and diesel oil mixtures for use in the production of heat energy. Fuel Process. Technol. 2006, 87, 97-102. (27) San José-Alonso, J. F.; Gobernado-Arribas, I.; Alonso-Miñambre, S. Study of combustion in residential oil burning equipment of animal by-products and derived products not intended for human consumption. Int. J. Energy Environ. Eng. 2013, 4, 1-13. (28) Vaitilingom, G.; Perilhon, Ch.; Liennard, A.; Gandon, M. Development of rape seed oil burners for drying and heating. Industrial Crops Products 1998, 7, 273-279. (29) Daho, T.; Vaitilingom, G.; Sanogo, O.; Ouiminga, S.K.; Zongo, A.S. Piriou, B.; Koulidiati, J. Combustion of vegetable oils under optimized conditions of atomization and granulometry in a modified fuel oil burner. Fuel 2014, 118, 329-334. (30) Holt, G.A.; Hooker, J.D. Gaseous emissions from burning diesel, crude and prime bleachable summer yellow cottonseed oil in a burner for drying seed, cotton. Bioresour. Technol. 2004, 92, 261-267. (31) Oprea, I.; Pîşă, I.; Mihăescu, L.; Prisecaru, T.; Lăzăroiu, G.; Negrean, G. Research on the combustion of crude vegetable oils for energetic purposes. Environ. Eng. Manag. J. 2009, 8, 475-482. 21 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 38

(32) Józsa, V.; Kun-Balog. A. Spectroscopic analysis of crude rapeseed oil ﬂame. Fuel Process. Technol. 2015, 139, 61–66. (33) Józsa, V.; Kun-Balog. A. Stability and emission analysis of crude rapeseed oil combustion. Fuel Process. Technol. 2017, 156, 204-210. (34) San José, J.; Romero-Ávila, C.; San José, L.M.; Al-Kassir, A. Characterizing biofuels and selecting the most appropriate burner for their combustion. Fuel Process Technol. 2012, 103, 39-44. (35) San José, J.; Sanz-Tejedor, M.A.; Arroyo, Y. Effect of fatty acid composition in vegetable oils on combustion processes in an emulsion burner. Fuel Process. Technol. 2015, 130, 20-30. (36) Sanz-Tejedor, M. A.; Arroyo, Y.; San José, J. Influence of Degree of Unsaturation on Combustion Efficiency and Flue Gas Emissions of Burning Five Refined Vegetable Oils in an Emulsion Burner. Energy Fuels 2016, 30, 7357−7366. (37) Mosarof, M.H.; Kalam, M.A.; Masjuki, H.H.; Ashraful, A.M.; Rashed, M.M.; Imdadul, H.K.; Monirul, I.M. Implementation of palm biodiesel based on economic aspects, performance, emission, and wear characteristics. Energy Conversion and Management 2015, 105, 617–629. (38) Reitz, R. D.; Bracco, F.V. Mechanism of atomization of a liquid jet. Phys. Fluids 1982, 25, 1730-1742.


Page 23 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

(39) Hiroyasu, H.; Kadota, T.; Arai, M. Supplementary comments: Fuel spray characterization in diesel engines. In Combustion modelling in reciprocating engines. Mattavi, J.N. and Amann, C.A. (Eds.), Plenum press, 1980, pp. 369-408. (40) Dent, J.C., A basis for the comparison of various experimental methods for studying spray penetration, SAE paper 710571, (1971). http://doi.org/10.4271/710571. (41) Jawad, B.; Gulari, E.; Henein, N. A. Characteristics of intermittent fuel sprays. Combust. Flame 1992, 88, 384-396. (42) In ASHRAE Handbook Fundamentals. Atlanta GA ed. 2013, chapter 28. (43) UNE 9205:1987 Boilers. Guidance for determination of the combustion data. Madrid 1987. (44) Directive 2010/75/EU of the European Parllament and the Council of 24 November 2010 on industrial emissions (integrated prevention and control). (45) Rørtveit, G. J.; Zepter, K.; Skreiberg, Ø.; Fossum, M.; Hustad, J. E. A comparison of low-NOx burners for combustion of methane and hydrogen mixtures. Proc. Combust. Inst. 2002, 29, 2243-2250. (46) Agarwal, A.K; Chaudhury, V.H. Spray Characteristics of biodiesel/blends in a high pressure constant volume spray chamber. Exp. Therm. Fluid Sci. 2012, 42, 212-218.


Energy & Fuels

PALM VEGETABLE OIL

C A 492.13

50.35

E

G

2.80

2.75 f1 (ppm)

2.70

2.10

2.08

2.06

2.04

2.02 2.00 f1 (ppm)

1.98

1.96

1.94

F B E

H

JI

D

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5 f1 (ppm)

3.0

2.5

2.0

1.5

910.44

5185.37

731.24

492.13

567.33

50.35

222.18

200.00

G

397.74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 38

1.0

0.5

0.0

Figure 1. Spectrum of 1H RMN of a sample of PlO (500 MHz, 8 scans, 90 degrees, 25 s relaxation time, CDCl3). The letters indicate the various types of signals present in vegetable oil. Integration values (Ai) are indicated under each signal.


Page 25 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 2. Macroscopic parameters of the atomized spray.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 38

Figure 3. Diagram of the test bed for image capturing


Page 27 of 38

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Figure 4. Diagram of the injector showing its dimensions (in mm) and detail of the burner nozzle. 1: 26 27 28Diffusor plate; 2: Pressure-atomizing nozzle with tangential slots in the distributor (Steinen, 0.7 USgal·h 29 301); 3: Electrodes; 4: Emulsion pipe; 5: Air combustion pipe. 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 27 59 ACS Paragon Plus Environment 60

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 38

Figure 5. Block diagram of the method for obtaining images


Page 29 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Image capture

Negative of the image

Establishing the limits of the jet

Penetration length

Radial distance measurements

Drawing tangent lines

Determining the cone angle

Figure 6. Example of the image processing procedure.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 38

Figure 7. Photograph of the experimental facility. 1: Burner; 2: Valve system; 3: Oil tank; 4: Diesel fuel tank; 5: Combustion chamber; 6: Refrigeration air; 7: Fume analyzer. (a) Secondary air adjustment; (b) Fuel flow adjustment.


Page 31 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 8. Variation of combustion efficiency, CO and CxHy emissions in the different burner operating conditions


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 38

Figure 9. Variation of combustion efficiency in the different burner operating conditions.


Page 33 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 10. Variation of combustion efficiency, in %, and spray cone angle, in degrees, with fuel flow and secondary air of the PlO.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 38

Table 1. Elemental analysis and physical characteristics of PlO Unit

PlO

Standard

C (%)

% (m·m-1)

76.2

ASTM5291

H (%)

% (m·m-1)

11.7

ASTM5291

N (%)

% (m·m-1)

0.06

ASTM5291

S (%)

% (m·m-1)

< 0.02

ASTM1552

Oa (%)

% (m·m-1)

12.0

-

Ash (%)

% (m·m-1)

0.007

EN 6245

Density at 15 ºC

kg·m-3

913.9b

-

Density at 35 ºC

kg·m-3

900.7

ISO 12185

Density at 60 ºC

kg·m-3

884.2

ISO 12185

Kinematic viscosity at 40 ºC

mm2·s-1

43.95

ISO 3104

8.69

ISO 3104

Kinematic viscosity at 100 ºC mm2·s-1 H.H.V.

kJ·kg-1

38,830

ASTM 240

L.H.V.

kJ·kg-1

36,350

ASTM 240

a

Estimated by difference. b Estimated by extrapolation


Page 35 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table 2. Proportions, obtained by 1H RMN spectroscopy, of the different FAs in PlO (% in moles, and standard deviation for the six individual samples analyzed)

PlO (25 °C)

PlO (40 °C)

FA

% ± SD

Linolenic (%)

< 0.5

Linoleic (%)

8.4 ± 0.1

Oleic (%)

32.4 ± 0.5

Saturated (%)

59.2 ± 0.5

DUa

49.1

a It

measures the average of carbon−carbon double bonds per triglyceride molecule and was determined as: [% oleic acid + (% linoleic acid)·2 + (% linolenic acid)·3]


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 38

Table 3. Variation of spray tip penetration length and spray cone angle with the fuel flow and secondary air flow. Fuel flow emulsion (kg·h-1) C1 (4.1)

C3 (6.1)

C6 (7.3)

Air flow (kg·h-1) (min: 29.90; mid: 41.10; max: 45.11) min

mid

max

min

mid

max

min

mid

max

Spray tip penetration length (cm) 44.3

45.2

43.4

47.7

43.3

43.1

46.7

44.8

47.1

27.7

28.4

33.1

Spray cone angle (o) 28.5

27.3

23.9

25.3

26.5

27.1


Page 37 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Table 4. Variations of gas emissions, mg and η with fuel flow and secondary air flow for PlO.

Fuel flow emulsion C1

Gas emissionsa

C3

C6

Air flow min

mid

max

min

mid

max

min

mid

max

Measured values O2, % Vol

16.23

16.54

16.70

12.75

12.62

13.52

10.43

11.54

12.03

CO, ppm

169.00

130.67

164.67

273.00

213.33

203.33

438.00

227.50

179.00

NOx, ppm

26.50

29.33

29.00

26.50

42.00

45.67

28.00

41.00

45.00

CxHy, ppm

115.00

163.33

160.00

240.00

213.33

190.00

350.00

215.00

190.00

SO2, ppm

0.00

0.33

0.33

0.00

0.00

00.00

00.00

0.00

0.00

31.61

29.73

29.70

28.60

30.63

30.57

30.45

30.90

25.60

286.15

292.10

290.40

417.00

450.73

435.17

485.05

482.80

475.40

ta,

oCb

tg, oCc

Calculated values CO2, kg·kg-1

0.054

0.051

0.049

0.093

0.094

0.084

0.118

0.106

0.101

Cpgd, kJ·(kg·ºC)-1

1.009

1.010

1.010

1.007

1.009

1.010

1.014

1.013

1.010

37.78

40.35

41.83

22.17

21.84

24.37

17.47

19.44

20.45

73.12

70.41

69.53

75.94

74.37

72.45

77.81

75.45

68.58

mg,

kg·kg-1

η, % a The

EU emissions limits for each monitored gas are stablished under Directive 2010/75/EU44. b Temperature of combustion air. c Temperature of flue gases at heating device exit. d Standard UNE 920543.


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 38

Corresponding Author *Tel.: +34983184420. E-mail: [email protected] (Y.A.). *Tel.: +34983423685. E-mail: [email protected] (J.S.J.). NOTES The authors declare no competing financial interest.

ACKNOWLEDGMENTS The financial support for this work provided by the University of Valladolid (Spain) is gratefully acknowledged.


Spray characteristics, combustion performance and palm oil emissions

Recommend Documents