Design and Operation of a Mobile Biodiesel Production Unit

Transcription

1 Design and Operation of a Mobile Biodiesel Production Unit Leandro S. Oliveira 1, Alex N. Brasil 1, Diego L. Nunes 2 1 Departamento de Engenharia Mecânica/UFMG, Av. Antônio Carlos 6627, , Belo Horizonte, MG, Brazil. 2 Programa de Pós-Graduação em Ciência de Alimentos/UFMG, Av. Antônio Carlos 6627, , Belo Horizonte, MG, Brazil. Abstract The Brazilian National Program for Production and Use of Biodiesel (PNPB) was launched in 2004 by the Brazilian Government with the objective of guaranteeing an economically viable production of biodiesel, while favoring social inclusion and regional development. Thus, great emphasis was put on small scale production of vegetable oils with attractive fiscal incentives for underdeveloped regions of Brazil. However, no fiscal incentives were planned for the manufacturing of biodiesel production units and their construction and operation are usually costly and out of reach for small-scale producers. Thus, it was the aim of this work to design and construct a mobile biodiesel production unit and verify its feasibility in providing a service to small-scale oil producers in which the oil is processed into biodiesel and the producers costs are only those related to the processing of the oil. In other words, the mobile unit travels from one oil producing farm to another processing the oil into biodiesel which is kept by the oil producers for their own use. The constructed unit is fully operational and has a production capacity of a 100 Liters of biodiesel per hour. The unit was mounted on a truck and it is comprised of a stirred reactor, a decanter and a distillation unit for biodiesel purification. Keywords: biodiesel; mobile production. 1. Introduction Biodiesel production and commercial use in Brazil has greatly expanded in the last couple of years due to the Brazilian Government policy that established a mandatory use of 2% biodiesel in fossil diesel (B2) fuels throughout the country since 2008 [1]. In the last decade, the technologies for producing biodiesel have greatly improved and several different processes are now currently available at different scales [2-4]. However, for small scale production facilities, the preferred technology is still batch transesterification systems [5-7] mostly involving alkali-catalyzed processes. The benefits of installing and operating small-scale biodiesel production units are: (i) low capital investments, (ii) reduction in use of fossil fuels by replacement with local renewable energy sources (e.g., the heat requirements can be supplied by combustion of biomass residues), (iii) electricity needs can be supplied by a generator that runs on biodiesel, and (iv) unit can be operated by inexperienced users not relying on the availability of highly qualified technicians. The scenario originally considered in the development of the Brazilian Government policy for biofuels was focused on fiscal incentives for small scale oilseed producers, thus, favoring small scale oil extraction plants scattered in remote

2 locations of the less developed regions of Brazil (mostly North and Northeast Regions of the country). However, no fiscal incentives were established for the manufacturing of small-scale biodiesel production units and their construction, and operation costs, although usually lower than the industrial scale ones, are out of reach for small scale oilseed producers and cooperatives. In view of the aforementioned, it was the aim of this work to design/construct a mobile biodiesel production unit and verify its feasibility in providing a service to small-scale oil producers in which the oil is processed into biodiesel and the producers costs are only those related to the processing of the oil. 2. Design Specifications The mobile biodiesel production unit was built and commissioned at Biominas, a transportation company located in Itauna, Brazil. A drawing of the unit layout is shown in Fig. 1 and a process flowsheet as related to the mobile unit described is depicted in Fig. 2. The biodiesel production rig is comprised of two storage tanks (T01 and T02) for the reagents (oil and a mixture of ethanol and sodium methoxide, respectively) during transportation of the unit; one 18 kw power generator (E01), working with a Diesel engine running on biodiesel; a screw-press for oil extraction (E02); a press filter (E03) for the removal of suspended solids in the oil; two control panels (E04 and E05); four tanks, made of stainless steel, for storage and feed of vegetable oil (T03) and of waste frying oil (T04), for storage of ethanol (T05), and for storage of purified biodiesel (T06); two 180 liter-capacity reactors (T07 and T08) for the transesterification reactions, equipped with mechanical stirrers and heating coils (A01 and A02, respectively) that allows for temperatures up to 80 o C in the reacting media reactor T07 is made of acrylic to allow for complete visualization of the reaction for educational purposes; two settler tanks (T09 and T10) for the phase separation (fatty acid ethyl ester and glycerin) tank T09 is also made of acrylic; a storage tank for glycerin (T12) with a heating coil that allows for temperatures up to 100 o C; an evaporation column (T13) equipped with a heating unit (A04) for the removal of the alcohol from the ester phase; a heat exchanger (E06) operated in countercurrent mode; a holding tank for process water (T14) and a storage tank for fresh process water (T15) equipped with a heating unit (A05); a water washing column (T16) for the removal of impurities from the alcohol-free biodiesel phase; an evaporation column (T17) equipped with a heating unit (A06), that allows for temperatures up to 100 o C, and a vacuum pump (B08) (100 mmhg) for the final purification of the biodiesel phase. A small lab facility (LB) was built in the rear end of the rig, where the quality of the biodiesel produced can be quickly evaluated employing analytical techniques such as near infrared spectroscopy. Since the mobile unit was also commissioned for educational purposes, it has a training room (ES) at the rear end, in between the processing unit and the lab, where a 34 TV was setup for instructional presentations and videos. Safety features include an emergency exit and a fire extinguisher placed at the back end. 3. Process description The first step in the process is the extraction of the vegetable oil using the expeller (E02), generating a solid residue (press-cake). After extraction, the oil is filtered (E03) and, if necessary, its ph is adjusted so it can be safely pumped to either the storage tank (T01) or directly to one of the reactors (T07 or T08). The reactors work in parallel, but their confi-

3 guration allows for them to be run in series in cases when there is a need for the oil to be purified before being subjected to a transesterification reaction. After the oil is pumped (B01) to the reactor and is heated to the desired temperature, the mixture of alcohol and catalyst is pumped (B02) into the reactor where the reaction is carried on under stirring for about 1 h or 1.5 h depending on the conditions established for the reaction to occur. After completion of the reaction, the mixture is transferred to the settler (either T09, T10 or T11) by gravity action so that phase separation can occur by gravity settling in a period that usually range from 0.5 to 1 h. Upon separation, the ester phase is moved to the evaporation column (T13) where the excess alcohol is removed by evaporation (A03); and the glycerin phase is moved to the storage tank (T12) where, upon heating, the alcohol in that phase is also removed by evaporation. The evaporated alcohol (from both T13 and T12) is condensed in the heat exchanger (E06) where it flows counter-currently to the cold fluid, which is comprised of a mixture of water and glycerin recovered in T12 after cooling. The condensed alcohol is returned to the storage tank T05. After evaporation of the residual alcohol, the ester phase still contains a fraction of glycerin that must be removed to comply with purity specifications established by the Brazilian Biodiesel Standards. Thus, the ester phase is transferred to the water washing column (T16) where water is sprayed over the surface of the ester phase, extracting the glycerin as its tiny drops move down the lighter organic phase. The water with the extracted glycerin settles down at the bottom of the column where it is removed and transferred to tanks T18 and T19. The biodiesel phase, with a bit of water incorporated in it, is transferred to the distillation column (T17), where the water and residual alcohol are removed as vent gases. The purified biodiesel is then transferred to the fuel storage tank T06. Research studies are currently being carried on to evaluate the feasibility of applying the water used in the washing of the ester phase (with a small amount of glycerin and other impurities) for irrigation and fertilization purposes in oilseed plantations. 4. Experimental Results Although the unit has been operated several times for demonstration and educational purposes, only two tests were conducted to verify the quality of the biodiesel produced in the mobile unit. The first test was carried out with refined soybean oil and ethanol in a molar ratio of 1:6, and sodium methoxide (1 % w/w, based on the mass of oil) as the alkali catalyst. The biodiesel produced was analyzed by HPLC following the methodology presented by Holcapek et al. [8]. The ester conversion was determined to be 97% and, after purification, the ester content was 99.4%, asserting the functionality of the unit. The second test was carried out with waste frying oil and the reaction conditions were the same as those used for the refined oil. The ester conversion was determined to be ~ 90% and the purified ester was 98.7% pure. 5. Preliminary economic feasibility Capital cost investment (processing equipment and accessories) is one of the most critical steps in economic feasibility studies. Regarding the constructed mobile unit, the capital cost investment can be divided into: (i) cost of the rig where the processing unit was assembled onto; (ii) cost of the processing equipment; (iii) cost of accessories and ancillaries; and (iv) cost of the built-in lab facility. The cost of the processing equipment, considering a 100 L/h capacity, was esti-

4 mated to be of 40 to 45 thousand US dollars. The cost of the accessories and ancillary equipment was estimated in the range of 20 to 25 thousand dollars and the cost of the rig, assembled with flooring and walls, was in the range of 30 to 32 thousand dollars. The cost of the lab facility was ten thousand dollars and the total investment cost sums up to US$112, Conclusions A mobile biodiesel production unit was designed, constructed and successfully operated. Tests were carried out to evaluate the performance of the unit using both refined and waste frying soybean oil. The ester conversions in both tests were considered satisfactory (higher than 90%) and the purification steps presented a commendable performance, leading to purities higher than 98% for both oils. The technical feasibility of a mobile biodiesel production unit was demonstrated and a preliminary economic analysis showed encouraging prospects for the production, commercialization and operation of such units. 7. References [1] G.P.A.G. Pousa, A.L.F. Santos and P.A.Z. Suarez, History and policy of biodiesel in Brazil, Energy Policy, 35, , [2] L.C. Meher, D.V. Sagar and S.N. Naik, Technical aspects of biodiesel production by transesterification a review, Renewable and Sustainable Energy Reviews, 10, , [3] Y.C. Sharma, B. Singh, S.N. Upadhyay, Advancements in development and characterization of biodiesel: A review, Fuel, 87, , [4] S.A. Basha, K.R. Gopal and S. Jebaraj, A review on biodiesel production, combustion, emissions and performance, Renewable and Sustainable Energy Reviews, 13, , [5] M. Bender, Economic feasibility review for community-scale farmer cooperatives for biodiesel, Bioresource Technology, 70, 81-87, [6] B. Amigun, F. Müller-Langer and H. von Blottnitz, Predicting the costs of biodiesel production in Africa: learning from Germany, Energy for Sustainable Development, 13, 5-21, [7] I. Sarantopoulos, F. Che, T. Tsoutsos, V. Bakirtzoglou, W. Azangue, D. Bienvenue and F.M. Ndipen, An evaluation of a small-scale biodiesel production technology: Case study of Mango o village, Center province, Cameroon, Physics and Chemistry of the Earth, 34, 55 58, [8] Holcapek, M., Jandera, P., Fischer, J. and Prokes, B. Analytical monitoring of the production of biodiesel by high performance liquid chromatography with various detection methods, Journal of Chromatography A, 858, 13 31, Acknowledgements The authors acknowledge financial support from the following Brazilian Government Agencies: CAPES, CNPq and FAPEMIG.

5 Fig. 1: Mobile biodiesel production unit. Fig. 2: Biodiesel production process flowsheet.