OBTAINING BIOETHANOL USED AS BIOFUEL FOR AUTO-VEHICLES USING A SELF PRESSURED BIOREACTOR

Transcription

1 FACULTATEA DE MANAGEMENT AGRICOL OBTAINING BIOETHANOL USED AS BIOFUEL FOR AUTO-VEHICLES USING A SELF PRESSURED BIOREACTOR MARIANA DUMITRU, GEORGE MOISE, MARIUS BIBU, MIRELA STANCIU 1 Lucian Blaga University of Sibiu, Romania mariana_dumitru2001@yahoo.com, georgemoise@yahoo.com, marius.bibu@yahoo.com, mirela_stanciu2008@yahoo.com Abstract: Between the bio-fuels used for autovehicles, bio-ethanol has an important role, due to the advantages it presents, having a good efficiency and a level of emissions released in the environment much lower than the conventional fuels. As bio-ethanol is obtained through the fermentation process of agricultural feedstock, these must be separated and concentrated. This can be obtained in more ways, we propose in this paper using of semi permeable membranes for separation in so-called process membrane distillation or prevaporation. The paper presents some constructive and functional principles of such a bioreactor. Key words: bio-ethanol, biofuels, self pressured bioreactor INTRODUCTION Due to the present situation, when the whole mankind is looking for new sources of energy, one of the best solution is to replace the conventional fuels with some fuels obtained from renewable sources, which are known as bio-fuels. A permanent sourse of energetic material is represented by plants, which contain carbohydrates which store energy. There area many bio-fuels which were tested, but we think that some of the best which can be used are bio-ethanol, bio-diesel, bio-gas, and hydrogen. All of these fuels, except hydrogen, are obtained from plants or other materials used as waste in households and industry. In this paper we will especially reffer to using bio-ethanol as a fuel, considering the advantages that this renewable fuel presents. There are advantages and disadvantages of using bio-fuels instead of classic fuels. Some of the advantages of using bio-fuels that must be considered are the following: They are obtained from renewable staples, one of the most important advantage Burnig of bio-fuels releases less CO 2 than oil, which means less pollution for the environment, so using bio-fuels reduces the environmental pollution They are bio-degradable Using bio-fuels leads to developing of agriculture and has a positive social impact, through the creation of new work places The bio-fuels can be used mixted in certain proportions with clessic fuels, without the need of changing the autovehicles motors The disadvantages of using bio-fuels are: For the moment, the prices of bio-fuels are bigger than the classic fuels The increasing demand of bio-fuels could lead to significant amendments on the food products market 150

2 LUCRĂRI ŞTIINŢIFICE, SERIA I, VOL.XV (1) Some of the plants that are cultivated for bio-fuels are: the corn, sugar beet, palm trees and soya. Some of researches insist that cultivation of these plants, although represents an alternative to oil, will worsen the global warming phenomenon. Bio-ethanol can be synthetically made from oil or through germ conversion of biomass in the fermentation process. In 1995, approx. 93 % from the entire world bioethanol was produced through fermentation and only 7 % through synthetic method. A bigger increase of energetic efficiency can be considered of obtaining bio-ethanol from bio mass, thus promoting its use as efficient renewable fuel and environment friendly. A new technology which allows using bio-ethanol from bio mass as a fuel will also create a large market for the agricultural products. Such a technology could provide a new source of energy, efficient and not polluted, for the small communities in small remote villages. Bio-ethanol is easy to transport and has a low toxicity, which makes it more advantageous from the environment point of view. From all bio mass used for making bio-ethanol, there are 2 types of basic materials: direct fermentable and cellulose and starch based materials. From the first type, the biggest use has sugar beet and different intermediate products of making sugar. In our country, bioethanol is mostly obtained from sugar beet. Considering the agricultural conditions of our country and the Romanian farmers experience, the sugar beet crop can assure the basic material for bio-ethanol, without jeopardizing population food supply. Considering the technologies of obtaining bio-ethanol and other fuels, the technologies of compounds separation from nutritive mediums are the most used and in continuous increasing. In these technologies are used bioreactors. But the most important field of industry in which bioreactors are used is obtaining the alternative fuels. Most known fuel where bioreactors are implemented in production process is ethanol. Bioethanol, the ethanol produced through fermentation process from agricultural feedstock, must be separated from yeast nutritive medium and concentrated. This thing can be done by two processes, using heat to evaporate and separate ethanol from water or by using semi permeable membranes for separation in so-called process membrane distillation or prevaporation. MATERIALS AND METHODS Bioethanol, used as biofuel, can be obtained, for example, using a self pressured membrane bioreactor. This biofuel is obtained using special membranes for separation in the distillation process, Below is presented the construction and operation of this self pressure membrane bioreactor. The installation is composed of membrane bioreactor directly connected to culture medium supply tank (T1) and starter culture supply tank (T2). The main segment of the system is the membrane bioreactor. Operation takes place in a closed system, ensured by valves located on the supply and drain paths, with which it 151

3 FACULTATEA DE MANAGEMENT AGRICOL regulate flows. Yhe installation consists of the bioreactor itself directly coupled to the membrane separation module. In fig.1 is presented the constructing diagram of such a bioreactor. Starter culture membrane bioreactor supply is provided by the T1 buffer tank and the nutrient medium through the buffer tank T2. They are kept at working pressure of the membrane bioreactor with open positions by the valves V2 and V4, respectively closed position, by valves V1 and V3. The circulation of culture, the medium and its brecycle into the system is provided by the pumps P1 and P2, corresponding to T1 and T2 tanks. In turn, buffer tanks, for maintaining the constant pressure in bioreactor, is supplied with material up to maximum level, at atmospheric pressure, by closing valves V2 and V4 and opening valves V1 and V3. As a result, we have two circuits, which supply a buffer tank at atmospheric pressure and the other, constantly feeding the bioreactor on its working pressure. Feeding the bioreactor with starter culture is achieved by a uniform distribution in the vecinity of the sediment layer at the base of the machine. In this way, at the top of the layer 353 will be always deposited yeast with maximum metabolic activity that will cover the full yeast, whose activity decreases as they move towards the drain at the bottom. In figure below is presented block diagram of a bioreactor, configuration with two fermentators separated by a membrane separation module with two membranes on both sides of it. Due to the limitation of useful work pressure of the membrane, the optimum pressure can be maintained by regulating the flow of carbon dioxide evacuated from system using valve V5. Fig.1. Block diagram of membrane bioreactor with two membranes separation module and two fermentators T1, T2- buffer tanks, V1,V2, V3, V4, V5,V6, V7- valves 152

4 LUCRĂRI ŞTIINŢIFICE, SERIA I, VOL.XV (1) Putting in series of plates creates an internal cavity specific for processing segment. In fig.2 is presented the serial arrangement of plates in the supply zone with starter culture and also for generating gas that creates the internal pressure. The versatility of this type of bioreactor is given by the possibility of changing the configuration as needed. Therefore, we have three possibilities of use the device: as membrane bioreactor; as simple bioreactor; as a separation module. In quantitative terms, the capacity of this device may be increased by putting in series a large number of modules. In the case when it is needed the separation of a compound from a process where the production of gas does not take place, there is the possibility to use as driving force the gas produced in one module of this installation, where we have gas producing microorganisms to separate the compound from the existent medium in other module. Of course, the two modules are isolated in terms of culture medium. Fig. 2. Serial arrangement of plates in the supply zone with starter culture: 1-Screw holes in the deck plates; 2-Feed with microorganism culture; 3-Drain dead culture; 4-Distributor of microorganisms. The main material used for construction of these membranes is polycarbonate. We chose this material considering the following reasons: ease of manufacturing, processing costs are low, relatively low material cost, it allows transparency for the process of photosynthesis and it is within required parameters of the pressure characteristic process. RESULTS AND DISCUSSION Bio-ethanol can be used either as additive, or as substitute for gasoline. Ethanol with <1 % content of water can be combined with gasoline in any proportion, until to pure ethanol 100 %. There are the following alternatives of using bio-ethanol to motors with internal burning: Additive for gasoline (ETBE- ethil-tert-buthil-ether), the procedure is simple and not expensive, but now there are not enough production capacities for ETBE 153

5 FACULTATEA DE MANAGEMENT AGRICOL Through adding ethanol in moderate quantities, direct in gasoline or in diesel oil up to %, fuels known as E15 or E25. In this case, there are fears concerning the quality of the obtained fuel Through using mixtures rich in ethanol (E85, E95, 85-95% ethanol of fermentation). It is the most desirable method, these mixtures can replace gasoline or diesel oil through using ethanol direct in the car (this is the case of Brazil) Reffering to consumption, approx. 1,5 l of ethanol replace 1 l of gasoline. The efficient use of alcohols as fuels supposes some constructive and adjusting modifications of motors, both for diminishing some negative influences and for capitalization of favorable properties. Between the main problems which occur at using alcohols as fuels in motors with sparkle ignition can be considered: - the tendency of reducing of the effective power at a constant debit of alcohols, as a result of their smaller thermal power, compared to gasoline ( through ethanol burning results only 66 % from the energy released through gasoline burning) - the decreasing of necessary Oxygen for burning, thus, in whole, the thermal power of the mixture Oxygen air, compared to mixture volume, is a little modified (ethanol needs only 61 % from the air necessary to burn gasoline). As a result, the maintain of unchanged motor power can be assured to a given cylinder capacity, through the correspondent increase of the fuel debit (in the same time, the fuel tank capacity must be increased) - the difficulty of starting the engine to low temperatures, determined by the reduced steam pressure to low temperatures. This disadvantage can be solved through improving spraying (ethanol needs for vaporization 2,6 times heat than gasoline) - the tendency of worsening spraying in the admission system to carburetor motors, determined by the high values of vaporization heat of alcohols, which needs re-projection of the admission system - bad qualities of oiling, determined by the reduced oiliness of alcohols, which concerns directly the rubbing couples, in the first place to the pump level and in the high pressure section of the supplying system - the incompatibility of alcohols with the lubrication oil; corrosion determined by alcohols and also the direct chemical attack of some specific compounds resulted during burning At this stage of research, we built a segment of the system presented above who have two compartments: fermentation module and membrane separation module, both coupled. The tests were conducted using Saccharomyces cerevisiae and Saccharomyces Bayanus) because those reactivity translated in large amounts of CO2 and ethanol produced in short term. For ethanol separation the chosen membrane was Desal DK. The amount of ethanol separated in the first phase of the experiment was insignificant when was used only direct pressure. This thing conducted to increase the concentration of ethanol from culture medium and as result the reactivity of yeasts decreased. 154

6 LUCRĂRI ŞTIINŢIFICE, SERIA I, VOL.XV (1) By applying vacuum to the permeate side of membrane the ethanol production increased enough to establish the equilibrium between low alcohol concentration from medium, CO2 pressure and ethanol removing. This phenomenon manifested because of azeotrope solution of water-ethanol. P.M.B. Fernandes (2005) have found in conditions, which apply hydraulic pressure above 50 MPa yeast cell morphology is affected. Some wild yeast survived at 220 Mpa. As result, part of the CO2 pressure can be converted in vacuum using a pressure to vacuum conversion system (Moise, 2011) to easy conduct the pervaporation process in this type of bioreactors (Wen-Janq Chen et al., 1995). Exceeded CO2 can be store using hydraulic drive system being a possible good alternative to another sources of energy (Dumitru M., 2010). CONCLUSIONS A technology which allows using bio-ethanol from bio mass as a fuel will create a large market for the agricultural products. Such a technology could provide a new source of energy, efficient and not polluted, for the small communities in small remote villages. All the disadvantages presented in the paper can be annulled by small changes made to motor components. From all the aspects presented above, using bio fuels is a tendency in countinous growing all over the world. In what concerns the bioreactor, the main advantage is the use of gas pressure generated by microorganisms to reduce the energy consumption needed for membrane separation. large. This system having multiple possibilities of configurations the applicability is very REFERENCES 1. DUMITRU, MARIANA,2011, Researches on the Advantages for the Environment of Using Bio-Fuels to Vehicles, Bulletin UASVM Agriculture, 68(1)/2011, pag DUMITRU, MARIANA (2010). Researches on the alternative fuels which can be used to motors, The 9 th International Symposion Prospects for the 3-rd Millenium 30 sept.-2 oct. 2010, Bulletin of University of Agricultural Sciences and veterinary Medicine Cluj- Napoca, ISSN , vol.67, pag , Cluj-Napoca 3. MOISE, G., 2011, Modular Self Pressurized Membrane Bioreactor, Bulletin UASVM Animal Science and Biotechnologies, 68(1-2)/2011, pag MOISE, G., Obtaining mechanical force using gas pressure generated by microorganisms in a selfpresurized membrane bioreactor, The 7th International Conference on Integrated Systems for Agri-food Production, nov.10-12, 2011, Nyiregyhaza, Hungary, ISBN ; ISBN , pag