Performance of diesel engine using an emulsion of ...

STROJNÍCKY ČASOPIS, 56, 2005, č. 3

137

Performance of diesel engine using an emulsion of biodiesel-conventional diesel fuel 1

2

3

TALAL YUSAF , SULAIMAN AL-ZUHAIR , MUSHTAK AL-ATABI *

The use of biodiesels, from palm oil (PO), as additive to conventional diesel fuel (CDF) was investigated. In this work, the effects of adding the biodiesel on fuel consumption rate and the concentration of CO in effluent gaseous emission were quantified. The tests were done on a four-stroke diesel engine operating in speed range of 1000 to 2000 rpm with a load range of 0.0 to 5.0 kW. It was found that by using CDF-biodiesel emulsion (vol. 50 %/50 %) a considerable reduction in fuel consumption and CO concentration was achieved when compared to pure CDF. The saving in the rate fuel consumption was in the range of 0.17 to 0.55 g · sec−1 and percentage reduction of CO concentration in effluent gas was in the range of 11.3 to 32.5 % for the tested engine speeds and loads. The findings of this study strengthen the suggestion of using biodiesel as an additive to CDF. K e y w o r d s : biodiesel, methyl esterification, diesel engine, effluent gas emissions

1. Introduction Biodiesel is defined as monoalkyl fatty acid ester (preferentially methyl and ethyl esters) and represents a promising alternative fuel for use in compression-ignition (diesel) engines. In many countries, considerable interest has been focused on the possibility of using vegetable oils as starting material for biodiesel production. The advantages of this product are its low toxicity, high biodegradation and that it comes from renewable resources [1, 2]. In addition, methyl esters derived from vegetable oil (biodiesel) have good potential as an alternative to conventional diesel fuel (CDF) as they have comparable cetane number, energy 1

College of Engineering, University of Tenaga Nasional, Km 7 Jalan Kajang-Puchong, 43009 Kajang, Selangor, Malaysia 2 Department of Chemical Engineering, University of Nottingham Malaysia Campus, 50450 Kuala Lumpur, Malaysia 3 School of Engineering, Taylor’s College, No. 1, Jalan SS15/8, 47500 Subang Jaya, Selangor, Malaysia * corresponding author, e-mail: [email protected]

138


content and viscosity [2–6]. Several vegetable oils have been evaluated as diesel fuel substituents, including soybean oil [4], sunflower oil [1], and rape oil [7]. In addition, waste (spent) vegetable oils have also been reported as raw material for biodiesel production [2, 8]. Conventional production of biodiesel is by transesterification of triglycerides into smaller, straight chain molecules of methyl esters, using an alkali or acid as a catalyst [1, 2, 4]. Transesterification is a common and well-established chemical reaction in which linear monohydroxyl alcohol reacts with vegetable oil. The alcohol may be butanol, methanol or ethanol. The products of the process are alcohol esters of the fatty acids of the vegetable oil with glycerine as by-product [2, 7]. It has been widely reported that biodiesel performed well in diesel engines and even surpassed the CDF in several aspects of engine operation including thermal efficiency [9]. Using conventional diesel fuel (CDF) has many drawbacks, which include, in addition to being extracted from non-renewable source, high pollutant gaseous emission. This study examines the effect of using a biodiesel-CDF emulsion (vol. 50 %/50 %) on the rate of fuel consumption and the concentration of CO in the effluent gas. The biodiesel used was prepared from palm oil by transesterification to produce methyl esters of the fatty acids. 2. Materials and method 2.1 M a t e r i a l s Conventional diesel fuel (CDF) was obtained from local fuel stations and used as a benchmark for comparison purposes. Refined, bleached and deodorized palm oil (PO) used in this study was obtained from Lam Soon (M) Berhad, Malaysia. Analytical grade methanol and NaOH were obtained from Sigma Chemicals Co., Germany. 2.2 P r e p a r a t i o n o f b i o d i e s e l A solution of NaOH and methanol (CH3 OH) is mixed using magnetic stirrer, which was set at constant speed throughout the experiment. The alcohol/NaOH mixture is then charged into a closed reaction vessel (1L flask). The reactor was immersed in a constant temperature water bath equipped with a temperature controller (Techne-Tempette TE 8D, Melsungen, Germany), that was capable of maintaining the temperature within ±0.2 ◦C. Agitation was provided using magnetic stirrer. The reactor was filled with 500 g (PO) and heated to the desired temperature of 55 ◦C to speed the reaction. 1% NaOH and methanol/oil ratio of 6 : 1 was used since it is reported to be the optimum ratio for transesterification [3]. The system from here on is totally closed to the atmosphere to prevent the loss of alcohol. The reactor contents are mixed for 60 minutes and then left to settle,


139

in a separation funnel, for another eight hours. In this time, two layers separate, the less dense methyl esters float to the top and the denser glycerine settles in the bottom. The methyl ester layer is separated and is used in the diesel engine tests. 2.3 E n g i n e u s e d The study was carried out using a four stroke compressed ignition engine (F4L 913, Klockner-Humboldt-Deutz (KHD)AG, Germany). The engine was connected to an electric generator (32 kW) using four rubber belts and tested at 1000, 1500 and 2000 rpm. The electrical output of the generator was connected through a control panel to electrical kettles to provide load on the generator. Three load levels were examined, namely, light (no load), medium (2.5 kW) and high (5 kW) operating conditions. The gas effluents from the combustion chamber were passed through a gas analyser (Eerco 3000, Germany) capable of measuring the concentration of CO in the effluent gas. 3. Results and discussion The rate of fuel consumption at different electrical loads and engine speeds was measured for the engine using CDF and CDF-biodiesel emulsion, separately. The data collected were recorded after the engine was idling for about 15 minutes. Figures 1 to 3 show the fuel consumption flow rate for different electrical loads at engine speeds of 1000, 1500 and 2000 rpm, respectively. As predicted the fuel consumption increases as the engine speed and/or the electrical load increases for both engine fuels used, namely CDF and CDF-biodiesel emulsion. However, it is noticed that the rate of fuel consumption is considerably reduced by using the Fig. 1. Comparison between consumption CDF-biodiesel emulsion instead of CDF rate of CDF and Biodiesel-CDF for different electrical loads at 1000 rpm. for the range of engine speeds and electrical loads tested. The saving in the rate fuel consumption was found to be in the range of 0.17 to 0.55 g · sec−1 for the range of engine speeds and electrical loads used. The concentration of the toxic component of the effluent gas, CO, at different electrical loads and engine speeds was measured for the engine using CDF and CDF-biodiesel emulsion, separately. Figures 4 to 6 show the concentrations of CO in

140


Fig. 2. Comparison between consumption rate of CDF and biodiesel-CDF for different electrical loads at 1500 rpm.

Fig. 3. Comparison between consumption rate of CDF and biodiesel-CDF for different electrical loads at 2000 rpm.

Fig. 4. Comparison between CO concentration if the effluent gas of the engine using CDF and biodiesel-CDF for different engine speeds at 0.0 kW load.


the effluent gas at different engine speeds for electrical loads of 0.0, 2.5 and 5.0 kW, respectively. The figures show that, generally, the concentration of CO increases as the engine speed and/or electric load increase. This is explained by realizing that as the engine speed and/or electric load increase, more fuel is utilized by the engine, and this results in an increase in the levels of incomplete combustion. However, it can be seen that the concentration of CO in the effluent gases is always less



141

Fig. 7. Percentage reduction of CO concentration in effluent gas at different engine speeds and electrical loads.

when the CDF is replaced with CDF-biodiesel emulsion. Figure 7 shows that the percentage reduction in CO concentration reduces as the electrical load and/or the engine speed increases. This indicates that the CDF-biodiesel emulsion is superior to CDF at low electrical loads and engine speeds, with respect to CO emission. However, this advantage reduces as the electrical loads and engine speeds increase.

4. Conclusion Biodiesel was prepared from palm oil and tested as an additive to conventional diesel fuel. A four-stroke diesel engine operating at a speed range of 1000 to 2000 rpm under different loadings was used to compare the fuel consumption rate and the CO concentration in effluent gas by using CDF and CDF-biodiesel emulsion. When compared to pure CDF, CDF-biodiesel emulsion (vol. 50 %/50 %) shows a considerable reduction in fuel consumption. CO concentration was recorded for engine speeds and electrical loads in the ranges of 1000 to 2000 rpm and of 0.0 to 5.0 kW, respectively. The saving in the rate fuel consumption was in the range of 0.17 to 0.55 g · sec−1 and percentage reduction of CO concentration in effluent gas was in the range of 11.3 to 32.5 % in the range of engine speeds and electrical loads used. The findings of this study strengthen the suggestion of using biodiesel as an additive to CDF.

142


REFERENCES [1] SOUMANOU, M.—BORNSCHEUER, U.: Improvement in Lipase-Catalysed Synthesis of Fatty Acid Methyl Esters from Sunflower Oil. Enz. Microb. Technol, 33, 2003, p. 97. [2] AL-WIDYAN, M.—AL-ZHYOUKH, A.: Experimental Evaluation of the Transesterification of Waste Palm Oil into Biodiesel. Bioresource Technol., 85, 2002, p. 253. [3] DARNOKO, D.—CHERYAN, M.: Kinetics of Palm Oil Transesterification in a Batch Reactor. JAOCS, 77, 2000, p. 1263. [4] NOUREDDINI, H.—ZAHN, D.: Kinetics of Transesterification of Soybean Oil. JAOCS, 74, 1997, p. 1457. [5] ALLEN, C.—WATTS, K.: Comparison Analysis of the Atomisation Characteristics of Fifteen Biodiesel Fuel Types. Trans. ASAE, 43, 2000, p. 207. [6] GOERING, C.—SCHROCK, M.—KAUFMAN, K.—HANNA, M.—MARELY, F.: Evaluation of Vegetable Oil Fuels in Engines. ASAE paper No. 871586, 1987. [7] KORUS, R.—HOFFMAN, D.—BAM, N.—PETERSON, C.—DROWN, D.: Transesterification Process to Manufacture Methyl Ester of Rape Oil: In: Proc. of 1st Biomass Conference of the Americas. Burlington, VT 1993, p. 815. [8] MITTELBACH, M.—TRITTHAT, P.: Emissions Tests Using Methyl Esters of Used Frying Oil. JAOCS, 65, 1988, p. 1185. [9] WAGNER, L.—CLARK, S.—SCHROCK, M.: Effects of Soybean Oil Esters on the Performance, Lubricating Oil and Wear of Diesel Engines. ASAE paper No. 841385, 1984. Received: 20.7.2004 Revised: 10.12.2004