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ndProceedings of ECOS 2009                                           22 International Conference on Efficiency, Cost, Opti...
fact they have technical means to produce electricity, diesel fuel must be provided. To fill the generators sets, the fuel...
ndProceedings of ECOS 2009                                          22 International Conference on Efficiency, Cost, Optim...
were installed, controlled by solenoid valves to set which fuel should be injected for that experiment. The pre-heating of...
ndProceedings of ECOS 2009                                         22 International Conference on Efficiency, Cost, Optimi...
SVO−1 (T1, T3 and T5) and SVO−2 (T1, T4 and T6) necessary to sustain a given load. For that, diesel fuel wasreplaced by st...
ndProceedings of ECOS 2009                                         22 International Conference on Efficiency, Cost, Optimi...
10.02                  0.07           8.2            9.2           94            0.13           1299             11.77    ...
ndProceedings of ECOS 2009                                         22 International Conference on Efficiency, Cost, Optimi...
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Small Scale Electricity Generation From Simultaneous Burning Of Straight Vegetable Oil


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Small Scale Electricity Generation From Simultaneous Burning Of Straight Vegetable Oil

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Small Scale Electricity Generation From Simultaneous Burning Of Straight Vegetable Oil

  1. 1. ndProceedings of ECOS 2009 22 International Conference on Efficiency, Cost, OptimizationCopyright © 2009 by ABCM Simulation and Environmental Impact of Energy Systems August 31 – September 3, 2009, Foz do Iguaçu, Paraná, Brazil SMALL SCALE ELECTRICITY GENERATION FROM SIMULTANEOUS BURNING OF STRAIGHT VEGETABLE OIL AND SYNGAS IN COMPRESSION IGNITION ENGINEAlexandre Caires Rodrigues, alexandrecaires@gmail.comPedro Amaral Rodrigues, pedrorodrix@gmail.comJoão Nildo de Souza Vianna, vianna@unb.brCarlos Alberto Gurgel Veras, gurgel@unb.brUniversidade de Brasília, Departamento de Engenharia Mecânica, Campus Universitário Darcy Ribeiro, Asa Norte, Brasília DF –70910-900Abstract. In Brazil, electrification of isolated communities, per se, is a necessary action but still insufficient to promotesocial development of the local people. Two large regions in the country show a concerning low Human DevelopmentIndex (HDI); in the northeast (HDI < 0.50) and in the Brazilian Rain Forest (HDI < 0.60). These regions, however,may produce large amount of vegetable oil, from palm and nut trees encountered in different species well adapted tothe respective biomes. This work presents a technological solution, simple of operating, thermodynamically efficient,with a high degree of sustainability and, furthermore, based entirely in renewable fuels for distributed electricitygeneration. Besides the production of electricity the proposed system may help establish the means for a profitableeconomic activity, considering both regions are potentially great producers of plant oils. The endocarp obtained afterextraction of the oil filled a gasification unit while straight plant oil was burnt simultaneously along with synthesis gasin a diesel generator set. In this work, two combinations of biofuels were tested in a 12.5 kW unit, Orbignya sp. andAcrocomia aculeata. In all the cases pure vegetable oil was injected into the engine while the respective endocarp wasgasified in a stratified downdraft system. Experimental results have shown the feasibility of such technology for smallscale electricity generation. Compared to the case when 100% of straight plant oil was employed, for a given power,the addition of biogas allowed up to 80% oil substitution. Specific consumption rate of the derived biomass was ofabout 1.2 kg/kWh. A decrease in emissions of NOx was oberved in dual-mode operation compared to diesel while COand UHC emissions were higher for the renewable fuels. Smoke emissions were of comparable levels for fossil dieseland staright vegetable oil combined with synthesis gas, observed, mainly, in the transient phase in response ofincreased load.Keywords: biomass gasification, straight vegetable oil, electricity generation, downdraft gasifier, diesel engines1. INTRODUCTION The economic development of isolated communities in Brazil will enhance only if electrification, from thecentralized grid is provided or it is locally produced. Toman and Jemelkova (2002) pointed that, economic developmentinvolves a number of other steps in addition to those associated with energy, including the evolution of education andlabor markets, financial institutions to support capital investment, modernization of agriculture, and provision ofinfrastructure for water, sanitation, and communications. In their paper, the authors presented a brief conceptualdiscussion seeking to identify how increased availability of energy services might be a key for stimulating economicdevelopment along different stages of the process itself. One of the conclusions they presented, after detaching the waysin which energy might exert a significant influence on the development process, was that the influence would beespecially important at lower levels of development. For the Brazilian government, the supply of electricity is now a state obligation to all the citizens. Some specificprograms were set in order to guarantee a minimum of electricity for isolated communities as well was to rural areassurrounding the cities. The program is better known as “Luz para Todos” (, meaning “Light toEveryone”. The original target was to bring electricity to more than 10 million people, in the time span of five years,starting from 2003. The cost of the whole program was estimated as 4.5 billion American dollars. The effort started byextending the centralized grid to less remote areas, to the point in which the cost was not prohibitive, and by on sitegeneration in more scattered areas. As the project was executed, many other remote villages without electrification wereidentified making the effort even more challenging. As a consequence, the deadline for reaching the initial figures of theprogram had been postponed to 2010. A great deal of inhabitants living in the Brazilian Rain Forest and in the northeast part of the country have aconcerning Human Development Index (HDI< 0.6), partly explained by the lack of electrification. A portion of theseremote areas in Brazil are generally powered by small diesel generators sets. The widespread usage of such units showsthat this technological system is the straightforward and preferred mode of electricity production, mainly because of theinherent reliability, high efficiency and a relative low cost of acquisition and maintenance of diesel engines. Despite the
  2. 2. fact they have technical means to produce electricity, diesel fuel must be provided. To fill the generators sets, the fuelhas to be transported from large vendors to those communities, roughly increasing the price two to three fold. The availability of biomass in most part of the country, especially in the Rain Forest, may turn gasification of therenewable resources an important option in bringing cheaper and reliable electricity to those communities. Thesynthesis gas could be premixed with air and burnt in a compression ignition engine. Biomass gasification in small units is a proven technology. Typical drawbacks of the entire process, like tarseparation, cooling and filtration of the synthesis gas are now dealt with some degree of success, and by more frequentintervention to the engine and the gasification system. Technical requirements for such units are far less restrictive thanthose claimed by larger systems. Dasappa et al. (2004) reported the existence of over 30 gasification units operating inIndia and abroad accumulating more than 80,000 hours of experience. The gasifiers are of downdraft type with all theauxiliary system for gas clean-up, ash handling, water treatment, and so on. They claimed the system to be reliable forvillage electrification. The mechanical power, from standard engines, was obtained either from dual fuelling (diesel andgas) or gas alone operation. The authors claimed that for small biomass gasification plants, a downdraft reactor wouldgive more chance of success in designing the system for low tar content. In dual fuelling operation, many gaseous fuels burn simultaneously with diesel, such as hydrogen (Gopal, et al.,1982), biomass-charcoal synthesis gas (Batthacharya et al., 2001), biogas ( Henham and Makkar, 1998), ethanol(Noguchi and Sakata, 1996), to mention a few. More recently Singh at al. (2006) tested the performance of dieselengine in dual mode operation with a blend of refined rice bran oil (RRBO) and fossil diesel (FD) along with producergas from a wood gasifier. Stable operation was reported up to the point in which the blend contained 25% of diesel fueland 75% vegetable oil (RRBO). Performance and emissions characteristics of diesel engines fueled by vegetable oils were also investigated byYoshimoto et al. (2001). The engines tested had two combustion chamber configurations, bowl in piston and toroidal.The base fuel, in part of the experiments, was rape-seed oil blended with several kinds of alcohol. One importantconclusion drawn from the work was that, the addition of alcohol to the vegetable oil realized good stable combustion. Based on these renewable resources (biomass and vegetable oil) we present, in this work, experimental results of anew technological concept for rural electrification based on diesel engines and biomass gasification. We were able tocarry out stable operation of a diesel generator set with straight (pure) vegetable oil burning simultaneously withsynthesis gas produced by gasification of endocarps. In a sense, this paper can be thought as one extension of the workof Singh et al. (2006), by firstly considering we were able to use 100% pure vegetable oil as the pilot flame (dual fueloperation), and secondly because the feedstock of the gasifier was the endocarp of the plant from which the oil itselfwas extracted. Two combinations of bio-fuels were tested in a 12.5 kW unit, Orbignya sp. (babaçu) and Acrocomiaaculeata (macaúba). In both cases straight vegetable oil (SVO−1 and SVO−2) was injected into the engine while therespective endocarp of the plant was gasified in a stratified downdraft reactor producing what here is referred assynthesis gas (SG−1 and SG−2). Index 1 for SVO and SG refers to Orbignya sp. and 2 for Acrocomia acuelata.2. RENEWABLE FUELS As a tropical country, Brazil has plenty of renewable sources suitable for producing electricity. Distributedgeneration may be provided by photovoltaic cells, small hydropower plants, direct burning of biomass in steam cycles,burning of pure vegetable oil and biodiesel in small diesel engines as well as through biomass gasification and furtherburning of the synthesis gas. In another paper, it is discussed the productive chain of Orbignya sp. (babaçu) andAcrocomia aculeata (macaúba) for small scale power generation (Xavier et al., 2009). Out of uncountable possibilities,the paper addresses these two species as an instance of what could be a technical proposition towards a sustainableelectrification of remote communities, and mostly to help establish foundations towards local economic development. The extraction and further processing of plant oils require energy. Human effort and animal power have beentraditionally employed on those communities to execute many of the daily tasks while pursuing some sort of incoming.Manpower has also to be invested in subsistence activities like in crops growing, oil and food gathering (fruits andnuts), hunting, fishing and so on. An intermediate stage of economic development would be reached if electrificationtakes place followed by some sort of mechanization. As an example, some medicinal and cosmetic oils are pre-processed and sold as a raw material for large enterprises. Mechanization of the process would free residents to beinvolved in other activities while still generating incoming. More importantly, knowing that the oil is only a smallportion of the extracted biomass one should seek means to bring value for the byproducts of the productive chain. Forinstance, the endocarp of the plants contains, in most cases, the largest portion of the biomass and could easily beexploited as a feedstock for a gasification reactor. Table 1 shows the share of the biomass and oil from the fruits underinvestigation. It can be seen that the endocarp is the second largest (29%) component in the fruit for macaúba, and thelargest (58%) for babaçu. Both feedstocks are excellent candidates for biomass gasification, on account of their highcharcoal yield after carbonization in temperature above 300° C (Silva and Brito, 1986). The authors reported carbonyields of the order of 38 and 44%, respectively after carbonization of the endocarp of babaçu, which are higher thanthat give after carbonization of eucalyptus wood, under the same conditions. Depending on the amount of oil extracted,
  3. 3. ndProceedings of ECOS 2009 22 International Conference on Efficiency, Cost, OptimizationCopyright © 2009 by ABCM Simulation and Environmental Impact of Energy Systems August 31 – September 3, 2009, Foz do Iguaçu, Paraná, Brazilexcess of biomass (endocarp), which is not used as a feedstock for the gasification unit, can be carbonized, used forcooking or commercialized to generate further incoming. Table 1. Amount of biomass in different parts of the fruits, for the species considered in this work. Component - percentage macaúba babaçú Exocarp 39.6 11.0 Mesocarp 24.1 23.0 Endocarp 29.0 59.0 Nut 7.3 7.0 Total 100% 100% Oil content in nut 58.0% 66.75% The press cake (byproduct) after oil extraction is generally used for animal nutrition. The extraction of the oil fromthe plant is accomplished, generally, by mechanical pressing. Oil quality may differ whether obtained after the first orsecond press. If so, the second press oil could be used as a fuel for the diesel engine, along with the synthesis gas in anelectric generator set. The higher quality oil, from the first extraction, is suitable for commercialization, for medicinaland cosmetic purposes. Figure 1 shows the endocarps and oils investigated in this work. The glass container in thepicture of one liter capacity and may serve as a reference scale for the biomass particles. A large bulk of material, dealing with vegetable oils as a substitute for diesel fuels, has been published. The idea isnot new and goes back to 1900 when Rudolf Diesel presented his engine at the Paris Exposition( running with vegetable oil. As regard to technological aspects, thefossil fuel alternative dictated the main improvements on the engine, up to date. As a consequence, there are someobstacles that should be addressed before straight vegetable oils could be used without modifications into the engines. Radu and Mircea (1997) conducted experiments to determine how the injection equipment behaves when sunfloweroils were used in diesel engines as well as how power indexes alter with such fuels. They concluded, among otherthings, that power indexes were reduced, especially with pure oils. Reduction in engine noise was also observedbecause of the decrease of the mean rate of injection. Altin et al. (2000) investigated engine performance and emissions of different vegetable oils and their methyl esters.They concluded, from the performance viewpoint, that the fuels were a promising alternative to feed diesel engines,though vegetable oils still have problems associated to fuel atomization and heavy particulate emissions. Orbignya sp. (babaçu) Acrocomia aculeata (macaúba) Figure 1. Endocarps (for gasification) and straight vegetable oils (for injection as pilot flame).3. MATERIALS AND METHODS The investigation was conducted in a test bench comprised of a small biomass gasification unit and a dieselgenerator set. Biomass gasification was realized in a special designed stratified downdraft reactor, linked to the dieselelectricity generator set (12.5 kW, maximum output). Figure 2 shows, schematically, the gasification unit, the dieselgenerator set and the auxiliary equipment for data acquisition. The system includes a reactor (1), followed by a particleseparator (cyclone - 2), a gas cooling device (3) and a filter (4) filled also with biomass particles. Two butterfly valves(carburetor) were responsible for preparing the stoichiometric combustible mixture (synthesis gas and air) that feeds acompression ignition engine. Because diesel and straight vegetable oils are currently used in the engine, two fuel lines
  4. 4. were installed, controlled by solenoid valves to set which fuel should be injected for that experiment. The pre-heating ofthe vegetable oil, as needed for viscosity correction, was obtained by electric trace heaters, 80 W each, positioned alongthe fuel line between the diesel pump and the fuel injectors. The capacity of the trace heaters allowed the vegetable oilto be heated from just over 65° up to about 120° C, depending on power demand. Lower injection temperatures wereassociated with higher power demands, because of larger fuel flow rates for a constant heat supply. This heating systemallowed the unit to be started with pure vegetable oil without relying in diesel fuel for cold start. Figure 2. Test apparatus - gasification unit, diesel generator set, resistance bank and instrumentation. The generator set was assembled by Heimer Brazil Ltd; model GEHK-18 (220 V, 60 Hz). The rotational speed was1800 rpm with maximum power delivered of 12.5 kW. Because of constant speed operation, tests were conductedvarying the load, by way of an electric resistance bank with five 2.0 kW and one 1.0 kW water immersion heaters.These heaters were set on and off by electrical switches, depending on the requested load. Supplied energy wasconsumed while evaporating water of the resistance bank. Nominal engine power output was penalized, because testswere conducted at about 1200 m altitude (city of Brasília – Brazil). In our investigation we used a direct injection diesel engine (Kirloskar - India), naturally aspirated, with thefollowing features: • two cylinders; • bore/stroke= (100 mm)/(200 mm); • total displacement = 1884 cm3; • compression ratio = 17; • maximum output = 16.9 kW @ 1800 rpm; The gasification system was comprised of an open top downdraft reactor and a gas cleaning system. The gasifierwas designed to operate in the range of about 300 kg/h/m2 specific gasification rate when coupled to the 1884 cm3(1800 rpm) engine. At this rate, the gasifier most certainly operated outside of the optimum envelope. The reason wasthat the engine maximum power was rated at 16.9 kW, while the generator set was for 12.5 kW. If maximum powerfrom the engine and the generator matched, specific gasification rates would approach an optimum, if considering thefigures presented by Jain and Goss (2000). They performed a large number of tests in a downdraft reactor fed by ricehusk, realizing good performance, for different configurations (diameter of the reactor), at equivalence ratio around 0.4and specific gasification rate of about 192.5 kg/h/m2. Following the reactor, a cyclone was installed for particle capture. Producer gas was cooled by a specially designedheat exchanger, were gas flowed inside the tubes and water outside. While cooling the gas, the superheated steamcondensed retaining most of the tar along the process. This mixture (condensed water and tar) accumulated in a tankpositioned at the lower part of the heat exchanger, for further extraction. After operating the gasifier for a couple ofhours the condensed mixture was sent to a laboratory for composition analysis. Concentration of oils and greasedissolved was estimated as 21 mg/liter, showing very low tar content in gas. Dissolved solids were estimated as 8.5mg/liter, also showing a good particle separation, both by the cyclone and by the steam condensation process. In anycase, the gas was further cooled and cleaned by an organic filter, before the carburetor system. A couple of runs were conducted. Here, we present just the results of two large sets of experiments, the firstgasifying the endocarp of Orbignya sp. (babaçu), injecting the extracted oil, from the nuts of the same plant, into the
  5. 5. ndProceedings of ECOS 2009 22 International Conference on Efficiency, Cost, OptimizationCopyright © 2009 by ABCM Simulation and Environmental Impact of Energy Systems August 31 – September 3, 2009, Foz do Iguaçu, Paraná, Brazilengine. The other experiment was conducted by using the endocarp of Acrocomia aculeata (macaúba) as the biomassfeedstock of the gasifier and the respective oil, now extracted from the pulp, into the engine. Water content in thebiomass feedstock was near 11% in a dry basis, for both endocarps. A gas analyzer system, made by Napro-Brazil, was employed to monitor gas emissions, such as O2, CO2, NOx,UHC and lubricant oil temperature. Smoke emission was measured by a Wager opacity meter, model… The amount offuel injected was monitored, real time, by means of an electric scale (balance) whose signal was sent to a computerapplication, via a RS232 port, based on LabVIEW platform. The applied load was registered by a three phaseelectronic kWh meter installed to track the amount of energy delivered, by the generator, to the resistance bank afterevery 90 seconds sampling rate. The system was linked to the computer via a RS232 port and specific protocols. Data acquisition started only after both, the engine and the gasification unit, have reached stable operation. In thetest plan, incremental load was of 1 kW (nominal) up 10 kW. At every load we measured the transient smoke emissions,as the engine automatically recovers rotational speed and the other performance parameters when engine operation wasconsidered stable. Gas sampling was taken two to three minutes having passed load selection, as to make sure purgingwas completed.4. RESULTS AND DISCUSSION Six series of tests were executed: T1. Fossil diesel, at different loads, maximum fuel injection rate allowed; T2. Fossil fuel and synthesis gas, at different loads, maximum fuel injection allowed. T3. SVO−1 (Orbignya sp.), at different loads, maximum fuel injection rate allowed; T4. SVO−2 (Acrocomia acuelata), at different loads, maximum fuel injection rate allowed; T5. SVO−1 + SG−1, at different loads, maximum fuel injection rate reduced; T6. SVO−2 + SG−2, at different loads, maximum fuel injection rate reduced. As a reference case, we executed tests T1 and T2, in which, fossil diesel was the injected, sole and with synthesisgas, produced after gasification of wood ships (pinus). Test T2 was conducted without altering the maximum injectionrate of the diesel pump. Lower diesel injecting rates are expected (T2) considering the addition of chemical energythrough the air-syngas mixture fed to the engine. Adjusts on the fuel injection rate is automatically executed by theengine’s governor to compensate the additional input of energy. Figure 3 shows the results for this verification. As it can be seen, there is a considerable reduction in the fuelinjected as the engine admits a mixture of air and synthesis gas (dual fuel operation) instead of sole air. For the appliedload, pure diesel operation, the consumption varies from 0.45 up to about 1.1 g/s, while in dual-mode the range isrestricted from 0.3 to 0.65 g/s, the remaining power been given by the synthesis gas. Oil substitution was from about 45to 65% with higher levels observed at lower loads. Dual-mode operation, allowing maximum fuel injection rates, gavethe original engine power rating. While trying to decrease the amount of fuel injected a derating of the engine poweroutput was observed because of the lower heating value of the synthesis combined to the vegetable oil, also with aheating value lower than diesel. Figure 3. Diesel consumption rates in sole and dual-mode operation. We combined the remaining tests in two groups, aiming to investigate the performance of straight vegetable oil,solely, and along with synthesis gas in dual-mode operation. In these tests we inferred the amount of fossil diesel,
  6. 6. SVO−1 (T1, T3 and T5) and SVO−2 (T1, T4 and T6) necessary to sustain a given load. For that, diesel fuel wasreplaced by straight vegetable oil and the wood ships, in the gasifier, by the endocarps from both palm trees. Tests T3and T4 were also carried out as reference cases to derive what levels of oil substitution would be reached in dual-modeoperation, after adding synthesis gas (SG−1 and SG−2) to the intake air. At this point, still no alteration in the fuelinjection system has been made, such as maximum rates and timing. Only when putting into practice tests T5 and T6,the fuel pumping system was adjusted so the maximum rate of fuel injection (straight vegetable oil) should be no higherthan 0.4 g/s. Figure 4 presents the results for SVO−1 as the sole fuel, following test T3 plan, and SVO−1with simultaneousburning of synthesis gas, obtained by gasification of the endocarp of the respective fruit (SG−1) as planned in test T5.Besides the consumption of straight vegetable oil, for both operating modes, the consumption of fossil diesel is alsoshown to help the comparison. The oil temperature range, before injection, was estimated from 91 to 111 °C. Highertemperatures were associated with lower injection rates, because of dual-mode operation. On account of the lower heating value (36305 kJ/kg), the consumption of SVO−1, compared to that of diesel (43559kJ/kg), is everywhere higher for the same power output. The difference seems to be larger as power increases. With theaddition of synthesis gas (SG−1) and reduced fuel injection rate (< 0.40 g/s) it was possible to recover power output toloads lower than 10 kW. In the range of 8 and 9 kW the SVO−1 substitution was of the order of 73%. By simplyallowing the engine to receive synthesis gas, at an assigned load, a decrease in straight vegetable oil injection rate wasrealized. This adjusting took place on account of the added chemical energy, contained in the synthesis gas. Theengine’s governor automatically reduces the amount of oil injected to maintain the rotational speed of the electricgenerator. Higher power outputs could not be obtained because fuel injection was limited to 0.4 g/s. Figure 4: Straight vegetable oil (Orbignya sp.) consumption rate, in sole and dual-mode operation. Figure 5 presents the results for SVO−2 as the sole fuel, following test T4 plan, and SVO−2 with simultaneousburning of synthesis gas, obtained by gasification of the endocarp of the respective fruit (SG−2) as planned in test T6. Acurve showing the consumption of fossil diesel was also included to help comparison. For this oil the injectiontemperature range was 91 to 119 °C. The lower heating value of SVO−1 (37577 kJ/kg) opposed to that of diesel also explains the higher fuelconsumption for the renewable oil for any given power output. In like manner, it was observed here an increase inrelative consumption as power increased. By adding synthesis gas (SG−2) to the intake air, with maximum fuelinjection rate reduced it was possible to recover power output to loads lower than 9 kW. At the maximum load applied,about 9 kW, the straight vegetable (type 2) substitution was of the order of 69%. In a previous investigation, using a different gasifier (downdraft with open top) with larger diameter we could reachbetter figures regarding vegetable oil substitution. With a gasifier with improved specific gasification rate the oilsubstitution was of the order of 80% and the maximum power output was 10.9 kW with fuel pumping system limited to0.40 g/s. The engine derating was less than that with the smaller diameter gasifier. From Fig. 4 and 5 we can see that at almost engine full load (~12 kW) the consumption of vegetable oil was about1.35 g/s. By limiting the injection rate to 0.40 g/s (30% of the reference case) when synthesis gas was burntsimultaneously with vegetable oil, less fuel has to be atomized, thus reducing vegetable oil spray penetration. Becauseof that, the most common engine failure is because of deposits on pistons as well as cylinder walls. Injecting 30% lessfuel would probably extended the time engine breakdown would take place. Premixed flame propagation into the enginewould help in lowering carbon deposits, further extending the time period until engine failure. Considering the villages
  7. 7. ndProceedings of ECOS 2009 22 International Conference on Efficiency, Cost, OptimizationCopyright © 2009 by ABCM Simulation and Environmental Impact of Energy Systems August 31 – September 3, 2009, Foz do Iguaçu, Paraná, Brazilusually operate the generator set only a few hours per day, the dual mode operation would (SVO + SG), at least, enlargethe time period between overhauls to a point that it could be considered economically practicable. In Brazil, it is acommon to make use of ethanol in internal combustion engines (gasoline and diesel) with the objective ofdecarburization. This technique allows decarburization without disassembling the engine by burning the alcohol.Ethanol can be purchased virtually in any gas station over the country. It is possible to run the engine in dual-fueloperation, using fumigated ethanol along with fossil diesel, after some cumulative hours on straight vegetable oil andsynthesis gas operation as an alternative means to clean the combustion chamber. Long-run engine testing would showthe extent and nature of the damages to the combustion chamber. Figure 5: Straight vegetable oil (macaúba) consumption rate, in sole and dual-mode operation. Lüft and collaborators (2007) analyzed the spray propagation of pure vegetable oil in an unfired operation pressurechamber. The authors presented a series of pictures, taken by a CCD camera, showing the penetration of the vegetableoil compared to diesel fuel. In general, vegetable oil sprays were constricted and extended in contrast with diesel sprayswhich were outspread and shorter, due to good atomization. At higher temperatures, the pattern of the spray ofvegetable oil was improved (better atomization). Rape seed oil at 70 °C showed an almost similar spray pattern as dieselat 35 °C. Preheating, nonetheless, will not solve all the differences in burning vegetable oil compared to diesel,adjustments to the nozzle geometry are still necessary in order to get failure-free operation of the engine with therenewable fuel. Based on the work of Lüft et al. (2007) we believe that the reduced injection of vegetable oil, in dual-mode operation, would solve, partly, problems related to incomplete combustion and carbonization in the combustionchamber. As regarded to emissions, the use of vegetable oil (type 1 and 2) in dual-mode operation increased the concentrationof CO and CO2, at any power output and HC at lower loads (up to 6 kW). The concentration of HC (unburnedhydrocarbons) at higher loads increased with diesel, compared to both SVO in dual-mode operation. NOx emissions aregreatly reduced when using SVO and synthesis gas compared to fossil diesel, at any given load. Smoke emissions were also measured for tests T1, T5 and T6. Opacity of SVO-1 in dual-mode operation was lowercompared to diesel at any given load. On the contrast, SVO-2 in dual mode operation presented opacity higher than thefossil fuel. By using SVO along with SG, most of the smoke measured was identified in the transient phase, while theengine was responding to the additional load. At stable operation, opacity was always lower than 1%, at any givenpower, in tests T5 and T6. Table 2 shows the emissions and opacity for diesel operation, following test T1 plan. Table 3 summarizes theemissions and opacity obtained for test T5 and Tab. 4 the same parameters for test T6. Table 2. Amount of biomass in different parts of the fruits, for the species considered in this work. DIESEL     EMISSIONS POWER OUTPUT [kW]     CO [%]  CO2 [%]  02 [%]  HC [ppm]  COc [%]  NOx [ppm]  1.97     0.09  3.7  15.5  74  0.36  254  3.91     0.07  4.6  14.2  74  0.22  447  5.87     0.05  5.6  12.9  79  0.13  674  8.33     0.05  5.6  12.9  79  0.13  674 
  8. 8. 10.02     0.07  8.2  9.2  94  0.13  1299  11.77     0.20  9.5  7.4  91  0.31  1378  Table 3. Amount of biomass in different parts of the fruits, for the species considered in this work. SVO‐1+SG‐1     EMISSIONS POWER OUTPUT [kW]     CO [%]  CO2 [%]  02 [%]  HC [ppm]  COc [%]  NOx [ppm]  1.97     1.02  6.0  13.2  123  2.18  58  3.84     0.97  10.8  7.8  102  1.24  43  5.79     0.56  12.5  6.5  117  0.64  89  8.29     0.39  14.1  4.9  81  0.40  144  9.31     0.47  14.4  4.5  73  0.47  206  Table 4. Amount of biomass in different parts of the fruits, for the species considered in this work. SVO‐2+SG‐2     EMISSIONS POWER OUTPUT [Kw]     CO [%]  CO2 [%]  02 [%]  HC [ppm]  COc [%]  NOx [ppm]  1.99     1.25  7.9  11.5  139  2.05  48  3.92     1.07  7.9  11.3  104  1.79  104  5.81     0.81  12.0  7.2  95  0.95  69  7.72     0.86  12.9  5.8  75  0.94  138  8.84     1.30  13.8  7.2  63  1.29  15 CONCLUSIONS The main conclusions of this work can be summarized as follows: • Gasification of endocarps of Orbignya sp. (babaçu) and Acrocomia aculeata (macaúba) in a open top downdraft gasifier was accomplished; • Straight vegetable oil obtained from Orbignya sp. (babaçu) and Acrocomia aculeata (macaúba) could be used in a compression ignition engine without penalizing rated power; • It was possible to operate the engine, in a stable manner, in dual-mode operation of SVO and synthesis gas, with reduced fuel injection up to 80% oil substitution; • NOx emissions were greatly reduced while operating the engine with SVO and SG, from both palm species, compared to diesel at any load; • CO emissions were higher for SVO and SG, compared to fossil diesel. The proposed technological arrangement may be an alternative mean to burn, in a long term, straight vegetable oilin compression ignition engines because the injected amount of fuel was less than 30% of that if no syngas is used.ACKNOWLEDGEMENTS The authors would like to acknowledge the support from CNPq, FAPDF and the Ministry of Mines and Energy inthis research.REFERENCESRadu, R. and Mircea, Z., 1997, “The Use of Sunflower Oil in Diesel Engines”, SAE Technical Paper Series 972979.Yoshimoto, Y., Onodera, M. and Tamaki, H., 2001, “Performance and Emissions Characteristics of Diesel Engines Fueled by Vegetable Oils”, SAE Technical Papers Series 2001-01-1807/4227.Babu, A.K. and Devaradjane, 2003, “Vegetable Oils and Their Derivatives as Fuels for CI Engines: An Overview”, SAE Technical Paper Series 2003-01-0767.Lüft, M., Bernhardt, S., Velji, A., and Spicher, U., 2007,”Optimization of Injection of Pure Rape Seed Oil in Modern Diesel Engines with Direct Injection”, DAE Technical Paper 2007-01-2031.
  9. 9. ndProceedings of ECOS 2009 22 International Conference on Efficiency, Cost, OptimizationCopyright © 2009 by ABCM Simulation and Environmental Impact of Energy Systems August 31 – September 3, 2009, Foz do Iguaçu, Paraná, BrazilDasappa, S., Paul, P.J., Mukunda, H.S., Rajan, N.K.S., Sridhar G. and Sridhar, H.V., 2004, “Biomass Gasification Technology – a Route to Meet Energy Needs”, Current Science Vol. 87, No. 7, 10 October 2004Jainn, A.K., Goss, J.R., 1999, “Determination of Reactor Scaling Factors for Throatless RiceHusk Gasifier”, Biomass and Bioenergy 18 (2000) 249-256Singh, R.N., Singh, S.P., Pathak, B.S., 2005, “Investigetion on Operation of CI Engine Using Producer Gas and Rice Bran Oil Mixed Fuel Mode”, Renewable Energy 32 (2007) 1565-1580Gopal, G., Srinivaska Rao, P., Gopalakrishnan, K.V. and Murthy, B.S., 1981, “Use of Hydrigen in Dual-Fuel Engines”, Hidrogen Energy, Vol. 7, No. 3, pp. 267-272, 1982Bhattacharya, S.C., San Shwe Hla, Hoang-Luang Phan, 2000, “A Study on a Multi-Stage Hybrid Gasifer-Engine System”, Biomass and Bioenergy 21 (2001) 445-460Henham, A. and Makkar, M.K., 1998, “Combustion of Simulated Biogas in a Dual-Fuel Deisel Engine”, Energy Conversion Management Vol. 39, No. 16-18, pp. 2001-2009, 1998Silva, J.C., Barrichelo, L.E.G. and Brito, J.O., 1986, “Endocarpos de Babaçu e de Macaúba Comparados a Madeira de Eucalyptus Grandis para Produção de Carvão Vegetal”, IPEF, No. 34, pp. 31-34, 1986Altin, R., Çetimkaya, S. and Yücesu, H.S., 1999, “The Potential of Using Vegetable Oil Fuels as Fuel for Diesel Engines”, Energy Conversion Management 42 (2001) 529-538.Xavier, E.A., Neitzke, G., Silva, D.C.B., Vale, A.T., and Veras, C.A.G., 2009, “Analysis of the Productive Chain of Orbignya sp. and Acrocomia aculeata for Electricity Generation and Sustainable Development of Isolated Communities”, submitted to ECOS 2009.RESPONSIBILITY NOTICE The authors are the only responsible for the printed material included in this paper.