BUDAPEST UNIVERSITY OF TECHNOLOGY AND ECONOMICS
BIODIESEL TECHNOLOGY WITH PHASE TRANSFER AVOIDED MASS TRANSFER
FÁZISTRANSZFERT KIKÜSZÖBÖLŐ BIODÍZEL TECHNOLÓGIA FEJLESZTÉSE
AUTHOR: DR. ANDRÁS KOVÁCS SUPERVISOR: PROF. JENŐ FEKETE
FACULTY OF CHEMICAL AND BIOENGINEERING, DEPARTMENT OF CHEMICAL AND ENVIRONMENTAL PROCESS ENGINEERING
December, 2011
INTRODUCTION
Biodiesel has been the most matured clean burning renewable energy based alternative automotive fuel. By definition biodiesel consists of a mixture of alkyl esters of C14 -‐ C24 fatty acids. Since most generally the alcohol constituent is methanol, biodiesel ids generally referred as FAME, fatty acid methyl ester. It’s short history of production technologies has been broadened from the basic trans-esterification of refined food grade oils to conversion of various refuse oil bearing wastes. The chemistry of production is being based on the following sequence of chemical reactions:
The so called hydrodiesel, produced by complete hydrogenation of unsaturated and heteroatomic links and isomerization of the alkane products, has not been the scope of the present work. In this thesis I have addressed specific aspects of producing standard quality biodiesel by the use of an apolar solvent. This technique makes the production technology more efficient, improves the reliability of product quality, reduces the carbon footprint by cutting the specific consumption of energy and auxiliaries.
MOTIVATIONS, STATE OF THE ART
An industrial system is sustainable and ecological if the resources and assets of the system are not misused. The trend in biodiesel technology development shows that first generation plants (the feedstock is food quality oil) has been upgraded to second and higher generation plants for success in the market. High fatty acid content refuse stocks, such as used cooking oil and grease, yellow and brown grease constitute the feedstock to convert into standard quality fuel in these plants. It has been an objective of the present work to study and recommend techniques for retrofitting first generation plants to higher rank plants. A concise analysis of ecological principles related to biodiesel processing is being presented in the theoretical section.
For a complete, sound scientific knowledge based support and picture of the state of the art of biodiesel technology the following aspects have been revisited: feedstock pool varieties, agro-industrial perspectives, unit operations involved, colloid chemistry, catalysis, commercial technologies and state of the byproducts. Unit operations have been analyzed as potential sources for losses in production. This “detective” approach collects ideas and concepts for development objectives that lead to improving the overall yield and quality of the products.
EXPERIMENTAL
Description of standards, specifications, test methods and experimental techniques is compiled to include specific procedures and routines employed.
Feedstock matters: it has been acknowledged that the most valuable asset of biodiesel processing is the feedstock, therefore extremely important operations of seed preparation and oil extraction are revisited. Seeds are biological colloid systems. The selected process technology must respond to specific needs as determined by the species and conditions of cultivation.
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TG+CH3OH⇐⇒FAME+DG DG+CH3OH⇐⇒FAME+MG MG+CH3OH⇐⇒FAME+G FFA+CH3OH⇐⇒FAME+H2O
Methanolysis of triglecerides Methanolysis of diglycerides Methanolysis of monoglycerides Esterification of fatty acids
• Sunflower species have been the predominantly cultivated oilseed in Hungary, husk-kernel ratio, oil contents distribution between husk and kernel are those features that must he considered for optimal oil extraction conditions.
• Distillers corn oil is a byproduct of automotive ethanol production. This is a high FFA, high wax content feedstock. It has been studied because of ample interest in USA.
• Yellow grease has saved the biodiesel industry in EU. Colloid chemical structure of these feedstocks becomes more complex in the order of the above presentation.
• Algae oil. It is to anticipate that I see weak chances for algae oil to become a biodiesel feedstock commodity. High content of omega 3 constituents has much higher value potential than combustion. A perspective area of research will be the separation of omega 3 essential fatty acids and converting the rest of the processing into biodiesel.
The core mechanism of the biodiesel technology developed consists in altering the phase behavior of components in the sequential system of the chemical reactions. It has been known that vegetable oil, the substrate of biodiesel synthesis, does not dissolve in the reagent methanol. Neither methanol is dissolved in refined vegetable oil. Since the reagent and the substrate form two distinct immiscible phases intensive mixing is needed to bring reaction partners, including the catalyst methoxy into intimate contact. It has therefore been the general practice to use intensive mixing and high excess of reagent. These promote trans-‐esterification conversion to equilibrium within a period of about 30
minutes, at 55°C and K-‐methoxy catalyst.
The intensive mixing does not only promote the forward (methanolysis), but the reverse (hydrolysis) reactions alike.
I proposed the use of an apolar solvent to avoid phase transfer related transport and phase separation difficulties in
synthesis and refining steps in biodiesel processing. The idea was born in technique of acid number test of lubricating oils. A related recommendation was invented by Boocock by the use a polar solvent for the same sake, to eliminate the mass transfer resistance. I opted for the use of an apolar solvent. By considering reasons considering basic chemical engineering principles:
• The feedstock and the biodiesel are predominantly apolar. Less apolar solvent dissolves more feedstock than do a polar solvent.
• The use of a polar solvent incurs the use of high excess of reagent. The rate of methanol used in polar solvent system exceeds the extent of 16 times to stochiometry,
• The polar solvent dissolves the byproduct glycerol and maintains the conversion in both directions. The difference between polar solvent and no solvent systems consists in faster kinetics to equilibrium.
• The apolar solvent rejects the byproduct glycerol, full conversion can theoretically can be achieved in a single reaction step.
• To separate the byproduct to promote the reaction from partial to full conversion the polar solvent must be separated between two reaction sequences. Separation of the solvent by distillation is highly energy demanding operation.
My goal was to perform trans-‐esterification to full conversion in a single operational contact. Phase behavior experience affirmed that the apolar solvent brings the substrate and reagent into a single phase and rejects the glycerol into a distinct phase as the reaction progresses. Expelling water into the glycerol phase protects the catalyst.
PHASE TRANSFER FEATURES
RESULTS
• PHASE BEHAVIOR TESTS:
1. Without addition of apolar solvent the system forms a homogeneous liquid phase, the possibility of intimate contact of reaction partners allow fast and efficient reaction. Lack of the solvent prevents the intimate contact.
2. Addition (formation) of glycerol turns the system into a duo-sol solvent extraction refining system. In such the apolar solvent (hexane) dissolves the biodiesel feedstock components and rejects the polar ones into the selective polar solvent (glycerol) phase.
3. This duo-sol type feedstock refining lowers the gum and other components that if present make biodiesel processing difficult to perform.
4. Colloid chemistry principles control the phase behavior. Salting effect cannot be disclosed if the catalyst is acidic. Hexane as a solvent had clean effect of avoiding emulsion formation and contributes to breaking temporary emulsion structures.
5. Hexane is necessary to bring vegetable oil and methanol into a single phase.
Despite earlier myths vegetable oil does not dissolve methanol. Intensive mixing can solubilize some methanol in oil. This
solubilized (encapsulated) form of the methanol can initiate trans-‐esterification reactions under optimal conditions. Even in this case phase transfer cannot be avoided. The catalyst is preferably staying dissolved in the polar phase. For catalytic activity at least 0.5%
catalyst must be present in the “reaction phase” and this is only possible to meet in dispersions in two phase systems.
• ESTERIFICATION:
Esterification proved to be a cornerstone operation in biodiesel processing of higher ranked generation process technologies. More than 370 individual esterification reactions have been performed in batch and continuous setups. Modes of operations included esterification under atmospheric and pressure conditions, with partial or total reflux, in loop reactor and in co- and counter current mode of contact. It revealed from the experiments that the proposed phase transfer avoidance in trans-esterification was a relatively easy task compared to stubborn pattern of colloid chemically controlled esterification. In esterification with sulfuric acid the catalyst forms a distinct disperse phase with part of the reagent. Properties of the disperse phase are altered by polar components. The more I progressed with research of the technology the more questions raised, mainly because of the use of difficult to process feedstocks. Some of these questions have not been addressed before and some have been simply ignored. While esterification of oleic acid was an easy to execute exercise, yellow grease and distillers corn oil presented unexpected difficulties and outcomes. In this series I had to answer some never asked before questions:
• Is degumming a necessary upstream operation to esterification?
• Can the reaction be influenced by the use of a promoter?
• Can the high reagent excess of 60-120 to stochiometry reduced to much lower level?
READILY AVAILABLE REAGENT
In conventional biodiesel units, the scope of chemical conversion is limited to trans- esterification of triglycerides. Majority of technology vendors specifies low FFA and P-‐content. Accordingly degumming is necessary to promote this core reaction. Similar to industrial refining for food grade edible oil, super degumming technique (neutralization to separate acids and hydrolysis with phosphorous acid to convert phosphatides into water soluble molecules) results in 5% loss in final yield for every
% of FFA separated. In the case of processing high FFA feedstocks with esterification as a first conversion step it appears to common chemical engineering sense to perform a degumming. The high dosage of reagent seems to be reasoned to weaken the colloid chemical interferences, influences.
It has been shown that:
• Esterification with sulfuric acid catalyst does also degum the esterified stream.
Sulfuric acid has been proved to be equally efficient to phosphoric acid in degumming.
Ion exchange resins are more favorable, although operational costs are higher.
• Conversion and kinetics can be promoted by means of adding adsorbent. Fuller earth type adsorbents and 3A molecular sieves have been found to be equally beneficial.
• The excess of reagent to stochiometry can be reduced by 5-10 times with reference to industrial practice. For such
reduction the esterification must be carried out at higher pressure. This allows the raise of temperature above 100 °C and makes possible the intimate contact of reaction partners in counter current mode of operation. Significant reduction in excess of methanol contributes to reduction of distillation duty for reagent recycle.
Contrary to phase transfer avoidance in trans-esterification the mechanism in esterification reaction follows an interfacial pattern in presence of sulfuric acid catalyst. For
progress in esterification conversion there is no need to bring either of the reaction partner into the phase of the other partner via phase transfer mechanism. The reaction takes place at the interface, for such there must be an easy renewal of interface, for the reactions at the interface. I had to yield in concluding that esterification of FFA with sulfuric acid catalyst could not have been performed in phase transfer avoided mode of operation. The case was different with ion exchange resin catalyst. In such system the phase transfer avoidance could have been
profited. The reagent and substrate formed a single phase, diffused onto the active site of the resin and the reaction took place at the active site, such as is the case of heterogeneous catalyis. By the reduced viscosity both the starting materials and the reaction products could more easily diffuse to and from the surface from and into the bulk than in the case of absence of the suitable solvent.
By intensive mixing the number of
intimate contact events can be increased at TRANS-ESTERIFICATION KINETICS SETTLING RATES
enlarged surface area and under intensified product transport from the interface toward to bulk. Dilution of the apolar phase is beneficial for renewal of the interface from the apolar side, while high excess of reagent promotes the same mass transfer in the polar phase. According to this observation the rate limiting factor in esterification is a function of the rate of renewal of the interface for intimate contact of the reagent, catalyst and substrate.
• NEUTRALIZATION:
Neutralization of the esterified stream is a unit operation with decisive influence on the downstream operations. If the esterification conversion is not adequate the remaining free fatty acids convert into soap and soap initiates emulsification and the emulsion can foul the column of neutralization and the column of trans-esterification.
• TRANS-ESTERIFICATION:
Trans-esterification in phase transfer avoided conditions can be conducted to close to full conversion within minutes either in batch or in counter current operation. The specific benefit of performing the trans-esterification under such conditions is the better yield of the better quality biodiesel due to less dissolution of the biodiesel in the polar G- phase. The higher kinetic rates are observed both in reaction kinetic and in phase settling rates. The success of shifting the reaction of trans-‐esterification toward completion is supported by the very fast separation of the byproduct. This separation is in fact a rejection from the reaction-‐main product phase into the byproduct phase. This rejection has been visalized in an all-‐glass made loop reactor experimental apparatus, in which the drop of glycerol were dropping down in the loop and collected at the bottom of that. This visualized and practically counter-‐current settling made me to think about designing the counter-‐current apparatus and to work techniques that makes possible retrofitting conventional, low in efficiency biodiesel production systems.
Recommended technology variants are presented for fully continuous, counter current technique and for retrofitting conventional, first generation plants into second generation according to research recommendations of the present thesis.
• BYPRODUCT:
G-phase related works revealed that low in efficiency biodiesel production systems dissolve significant amount of main product and this content turns the G-phase system into a Pickering emulsion system, in which an ionic core is surrounded by a multiple emulsion structure. The encapsulated oil content constitute a major difficulty in producing higher grade glycerol. After this emulsion being broken the technology of producing higher grade glycerol follows the sequence of conversion of not reacted glycerides and FFA in a sulphuric acid catalyzed (trans-)esterification, separation of the solid components by centrifuge and decanting the apolar (oil)
phase above the polar (glycerol) phase. The salt can refined by washing with MeOH and dried. The glycerol can be treated with selective adsorbent and the such refined product’s quality is good for animal forage.
G-PHASE STRUCTURE
• INVESTMENT IN PRODUCTION PLANTS:
By revisiting principles and applying the recommendations of the thesis conventional biodiesel production units can be converted to “second generation”
technologies by revisiting the scientific basis of esterification and trans-‐
esterification and redesigning the unit to optimize these reactions. Existing assets can be reused to improve capacity and efficiency of the unit, thus lowering costs of conversion and increasing the profit generation potential of the assets, especially if operated in symbiotically connected industrial units.
The most important findings of the research: The feedstock of biodiesel processing can be as different as many production variables can pertain. Based on the findings that the most valuable asset of any FAME production consists in the feedstock special attention must be paid to selection of the kind of the seed and to strictly adhering to recommended technology conditions. Production of biodiesel at small and medium scale units are at best incorporated into an (agro)-industrial ecological system. Algae feedstocks do not seem to be explored in the near future, mainly because of cost and properties. The most beneficial feature of algae oil can be explored in the field of healthy food, because of high content in polyunsaturated fatty acids and phosphorous.
RETROFIT AN EXISTING FIRST GENERATION PLANT
RETROFIT AN EXISTING FIRST GENERATION BIODIESEL PLANT
FLOW SCHEME OF THE PILOT PLANT DESIGNED TO DEMONSTRATE THE FINDINGS IN CONTINUOUS COUNTER CURRENT OPERATION
THESES:
The most important findings of the research will follow in this section. Before listing achievements with significance to progress in science of biodiesel processing some technical and technological conclusions will also be presented as recommendations to practice.
Feedstocks of biodiesel processing can be as different as many production variables can pertain. Based on the findings that the most valuable asset of any FAME production consists in the feedstock special attention must be paid to selection of the kind of the seed and to strictly adhering to recommended technology conditions. Production of biodiesel at small and medium scale units are at best incorporated into an (agro)- industrial ecological system. Algae feedstocks do not seem to be explored in the near future, mainly because of cost and properties. The most beneficial feature of algae oil can be explored in the field of healthy food, because of high content in polyunsaturated fatty acids and phosphorous.
1. BY THE USE OF SUITABLE APOLAR SOLVENT PHASE TRANSFER RESISTANCE IN TRANS-ESTERIFICATION CAN BE AVOIDED
The aim of my research when conceived was to find a conversion technique by which the rate of reaction of trans-esterification can be increased. My results showed that by avoiding interfacial resistance to mass transfer this can be achieved.
I have demonstrated through liquid-liquid equilibrium tests that there is a beneficial range of addition of apolar solvent to form a single liquid phase by reaction partners. By such removal of the interfacial resistance the rate of trans-esterification reaction could have been significantly improved. The outcome of avoiding phase transfer resistance complete conversion was achieved in 5 minutes, in comparison to 30-60 minutes times on stream for reaching the equilibrium conversion if the solvent was not present.
Avoidance of phase transfer resistance can be done with polar solvents too.
2. BY THE USE OF SUITABLE APOLAR SOLVENT THE REVERSIBLE TRANS-
ESTERIFICATION REACTION CAN BE SHIFTED TOWARD COMPLETE CONVERSION: Another aim of the research was to shift the reversible trans-esterification toward methanolysis on the expense of the reverse glycerolysis reaction. In practice of biodiesel production complete conversion can only be approached if the byproduct is separated in a unit operation after the reaction reached the equilibrium condition. By the use of polar solvents separation is only possible if the solvent is separated in a distinct unit operation to submit the mixture for settling or centrifuging. In operational practice this equilibrium condition is at about 80% conversion, while the standard requires a conversion of at least 96.5%. A common weak point of processes consists in the need to separate the byproduct as a condition for a second step of trans-esterification conversion. The separation can be very long lasting procedure if it is done in gravity settler or can be expensive because of the high energy demand to separate the byproduct by the use of a centrifuge.
I have demonstrated, that the byproduct can be instantaneously rejected from the reaction mixture to shift the conversion toward completion in a single contact event without including an intermittent operation for separation of the byproduct (and another if the solvent is polar). The proposed techniques were demonstrated both in batch and continuous counter current setups.
The mechanism is based on the engineered condition by the addition of the selected apolar solvent to reinstall an interfacial barrier against the return of the byproduct into the reaction phase. The reinstalled interfacial resistance efficiently bars the reverse
glycerolysis reaction of FAME. By such mechanism becomes possible to shift the reversible reaction toward the desired direction. This shift cannot be done by lack of solvent or by the use of a polar solvent. With lack of solvent a desperse condition must be maintained by high input of energy, with the polar the byproduct stays dissolved in the homogeneous reaction mixture.
3. BY THE USE OF APOLAR SOLVENT THE RATE AND SELECTIVITY OF SEPARATION OF MAIN AND BYPRODUCTS CAN BE IMPROVED:
Most common drawback of operational production systems is associated with either lengthy or energy consuming separation of the main and byproducts after reaction steps of transesterification. It has also been subject of concern that the byproduct phase dissolves relatively high amount (10-20%) of main product. My aim was to search for technique to shorten the time and specific energy consumption of this operation with significant improvement of separation selectivity between the by and main products.
I have demonstrated that if the suitable apolar solvent was added at proper rate the rejection of the glycerol has been almost instantaneous and complete. This finding made possible to execute the reaction contact and the phase separation in a single contact device. This contact device is preferably a counter current reactor-extractor. For existing systems modification of reactors to a loop reactor configuration can be a practice for performing the same operations.
In addition to faster splitting of the fuel and glycerol phases the selectivity of selectivity of this operation can be significantly increased to reduce the loss of product into the polar byproduct. The amount main product in the G phase could have been reduced to 0.5-1%.
4. ESTERIFICATION AND TRANS-ESTERIFICATION PROVIDES SOLVENT REFINING FEATURES
In carrying out the experiments of esterification and trans-esterification in solvent assisted mode the solvent refining feature explained to me that mainly because of the selectivity of phase separation the process is a chemical reaction associated solvent refining process. To prove this I demonstrated by addition of glycerol that it forms a polar extractant to selectively extract gum and phosphorous components into the polar phase. Because of kinetic characteristics this can be accomplished in counter current mode of operation too. I have also demonstrated that these improvements in selectivity and kinetics of separation are controlled by colloid chemical characteristics of the system.
Because of the selective refining action of the newly formed polar phase pre- treatment of the feedstock must not be as strict as the requirement for first generation biodiesel plants to remove gum components. In those systems these polar compounds, if not separated selectively and efficiently can initiate the formation of dispersed liquid system, that is a major reason for slow and difficult separation of main and byproduct phases. The industrial relevance and significance of this is to reduce the loss of valuable feedstock in conventional degumming operation. This efficient degumming along with esterification can save significant amount of triglycerides for the synthesis. It has been reported that every percent of polar constituent to be removed can contribute to a loss of up to 5% of the feedstock. The developed technology makes possible to improve the use of resources.
5. ESTERIFICATION OF FREE FATTY ACID CONSTITUENTS FOLLOWS AN INTERFACIAL REACTION PATTERN
There is no unique description of the mechanism of ester formation in biodiesel processing technologies. Some scientists reported that the reaction takes place in the
reaction phase into which the reagent is dissolved, some are claiming that the reaction takes place at the interface of the dispersed globules.
In trans-esterification assisted by a solvent the reaction mechanism is clearly following a homogeneous pattern. In esterification with sulphuric acid catalyst, the reagent is being distributed between the continuous fuel-reagent phase and the disperse sulfuric acid-reagent liquid phase. Accordingly both reaction mechanisms are possible at a time. There must be reactive contact locus at the interface where the reaction can occur. The mechanism of esterification must be of mixed type: partly in homogeneous phase and partly at the interface, I would call this course of reaction interfacial type. The kinetic rate measurements indicate this intermediary position, faster than in conventional systems, but much slower than in homogeneous systems. The rate limiting is being dependent on interface renewal. At the interface the polar head of the free fatty acids orients toward the polar phase, while the hydrocarbon chain stays in the apolar oil phase.
As the FAME leaves the interface a next FFA can substitute the gap at the interface.
High reagent:substrate rates and high solvent:reagent rates are beneficial because of contributing to promotion of diffusion and by such the renewal of the interface. Interface renewal is similarly important in trans-esterification for efficient extraction of polar constituents into the reaction generated polar phase.
By the use of ion exchange resin the reaction is interfacial similar to heterogeneous catalytic chemistry.
6. COLLOID CHEMISTRY AS IMPORTANT CONTROL MECHANISM IN TECHNOLOGIES BIODIESEL PROCESSING
The process of products separation has shown clearly features of colloid chemical principles basis. Beside of this evident colloid chemistry feature of interface renewal there were other findings in my research related to colloid chemistry
• I clearly demonstrated that the more complex the colloid structure of the feedstock was the more difficult and more severe treatment conditions had to be employed. Processing of food grade oils proved to be a simple task, especially if the selected apolar solvent was exploited. With more difficult to process feedstocks, such as distillers grain with dissolved solids and yellow grease or algae the limiting factor was the complex dispersion of the feedstock with encapsulated oily compounds.
• Refining the byproduct G-phase made possible to demonstrate that the main limiting action is based on colloid chemical principles. According to the model proposed there is a multiple, solid particles stabilized emulsion structure (so called Pickering type emulsions) that encapsulates solid and oil components. This structure acted against complete conversion into biodiesel, leaving the oily components encapsulated. Release of the encapsulated compounds must have been done by taking into considerations colloid chemical limitations. Small and medium size companies can profit of these findings by processing G-phase of conventional technology employing units.
DEVELOPMENTS WITH RELEVANCE TO INDUSTRIAL REALIZATIONS: BY THE USE OF APOLAR SOLVENT
• THE OVERALL SPECIFIC ENERGY DEMAND CAN BE REDUCED,
• PROCESSING FOOTPRINT OF A UNIT CAN BE REDUCED,
• OBSOLETE PLANTS CAN BE MODERNIZED
I have been looking for a technique to reduce the overall specific energy demand of biodiesel processing. The most important contribution to reduction of specific energy demand is associated with less energy consumed for intensive mixing. It has been
proved that the specific energy demand of maintaining the disperse state for the promotion of contact of reaction mixture components surpasses the energy needed for pumping. I calculated that the additional amount of energy needed for solvent and reagent recycle is significantly lower (by 20-40%) than the specific energy consumption in cases of reference.
• TECHNOLOGY DEVELOPED
These findings made possible to develop two variants of the apolar solvent assisted biodiesel processing.
A truly continuous operation realized with counter current reaction extraction and distillation columns as the main contact devices. The truly continuous operation makes possible to profit of heat exchangers for rational energy management. Footprint of the operational units and amount of inventory under operational conditions can be reduced accordingly. These features make the system more environmentally respectful, more safe than those mixer-settler based technologies in which the time on stream to product is more than 3 times longer than in the proposed system.
I have recommended a system for retrofit of conventional unites to more efficient, more ecological systems. This can be done switching from mixer-settler operation to loop reactor system by the use of suitable apolar solvent.
Future works are planned in the pilot plant of the truly continuous biodiesel processing and in industrial scale demonstration of retrofitting.
Future works are ongoing to explore other type of feedstocks that are high in essential fatty acids, such as algae and fish oil.
ARTICLES AND COMMUNICATIONS RELATED TO THE SUBJECT OF THE THESIS:
KOVÁCS A.: Megújuló alternatív üzemanyagok (Renewable alternative fuels), Energia Központ, Phare, EU FP5 kiadvány
KOVÁCS A.: Alternatív üzemanyagok (Renewable fuels), Hatékony Energia, 4. 2-‐3, 27-‐28, 1999,
KOVÁCS A., Haas, L: Új Biodízel technológia (New biodiesel technology) MKE, VEN, Veszprém, p 352-‐356, 2002
KOVÁCS A., Haas, L, Majoros, I: Research and application examples for clean technologies, Intl. Conf. on 21ST Century Environmental Technologies, June 13 and 14, Budapest, 2002
KOVÁCS A., Haas: Biodiesel technology, a step closer to hydrocarbon processing practice, Interfaces02, Budapest, Szept. 19-‐20, 2002
KOVÁCS A., Haas: Affordable biodiesel technology, Bioenergy, Proc. P. 172, 2002, Sept. 22-‐26, 2002, Boise, Idaho
KOVÁCS A.: Efficient and affordable biodiesel technology with reserves to improve operational technologies, 4th European Motor BioFuels Forum, 24 -‐ 26 Nov., 2003 Berlin
KOVÁCS A. Industrial Ecology, how do I approach on the basis of energy related disciplines, Industrial Ecology in favor of business and environment, 2. Dec., 2003, Budapest
KOVÁCS A., Haas, L: Jobbított biodízelel technológia kőolajipari tudományos alapokon (Improved biodiesel technology on the ground of petroleum refinery science), Magyar Kémikusok Lapja, 59.6-‐7, 220-‐225, 2004
KOVÁCS A.: Industrial ecology in environmnetal project conception building and implementation, Industrial Ecology Conference of Visegrád Countries, June 2004, Budapest
KOVÁCS A., Haas: Aspects of biodiesel development in regional renewable energy strategies, Energy Forum Debrecen, 2004, Sept. 17
KOVÁCS A., Haas, L: Improved biodiesel technology on the ground of petroleum refining experiences, Olaj Szappan, Kozmetika, vol 54., No, 1, 2005
KOVÁCS A., Haas, L: Feasibilty and technical features of use and production of biodiesel fuels, Olaj Szappan, Kozmetika, vol 54., No, 2, 2005
KOVÁCS A.:Biodiesel perspectives in production and use, Interfaces’05, Sopron, Sept 15-‐17, 2005
KOVÁCS A.: Industrial Ecology Interfaces’05, Sopron, Sept 15-‐17
KOVÁCS A.: Affordable and efficient technology and operational circumstances for biodiesel production, Debrecen, Energexpo and Conference, 2006
Kovács, A., Haas, L: Chemical Engineering Means of Improving Efficiency in Biodiesel Production Technologies, Eastern Biofuels Conference and Expo, II, Budapest, 2006, May-‐June
KOVÁCS A., Czinkota: An essay on environmental and rural development in production and use of alternative fuels from the viewpoint of a chemical engineer, Celje, Slovenia, invited lecture, 2007
KOVÁCS A.: Feedstocks and operational aspects of ecologically engineered biodiesel technologies, WIREC2008, Washington, 2007
KOVÁCS A.: Agro-‐industrial-‐ecology approach to renewable energy resources, BioEnergia, vol2.No.5,7-‐10, 2007
KOVÁCS A.: Are renewable energy based fuel also sustainable? Interfaces08, Sopron, 2008 Tolner, Ződi, KOVÁCS A., Kertész: Biodízelgyártás melléktermékeként keletkező glicerin hatása a talaj ásványi nitrogéntartalmára. (The effect of glycerine, a by-‐product of biodiesel
production, on the mineral nitrogen content of soil.) Zöldenergia, földhő és napenergia hasznosítása a hőtermelésben Konferencia, Gyöngyös, 2010.05.20. Konferenciakiadvány 110-‐114. ISBN:
978-‐963-‐9941-‐12-‐0
KOVÁCS A., Czinkota, Tolner L: Agroökológiai alapú megújuló́ energiatermelési rendszer.
(Agro-‐ecology renewable energy generation system.) Zöldenergia, földhő és napenergia hasznosítása a hőtermelésben Konferencia, Gyöngyös, 2010.05.20. 113-‐114, ISBN:
978-‐963-‐9941-‐12-‐0
KOVÁCS A., Tolner, Czinkota,Tóth: Biodízel technológia hulladék alapanyagokból. (Biodiesel production technologies on refuse basis.) Zöldenergia, földhő és napenergia hasznosítása a hőtermelésben Konferencia, Gyöngyös, 2010.05.20. Konferenciakiadvány 106-‐112. ISBN:
978-‐963-‐9941-‐12-‐0
Tolner, KOVÁCS A., Kovács, Vágó, Czinkota: Ellentmondások a biodízelgyártás melléktermék mezőgazdasági hasznosíthatóságában. (Contradictions in agricultural Utilization of biodiesel byproduct.) Zöldenergia, földhő és napenergia hasznosítása a hőtermelésben Konferencia, Gyöngyös, 2010.05.20. Konferenciakiadvány 154-‐158. ISBN: 978-‐963-‐9941-‐12-‐0
KOVÁCS A., , Czinkota, Kovács, Tolner: Biodízel melléktermék alkalmazása a talajvédelemben.
(biodiesel byproducts in soil chemistry) Erdei Ferenc VI. Tudományos Konferencia, 2011.
augusztus 25., Kecskemét
KOVÁCS A., , Czinkota, Nagy, Issa I, Tolner: Use of biodiesel byproduct in agriculture. 6th ISMOM, International Symposium of Interactions of Soil Minerals with Organic Components and Microorganisms , 26th June-‐1st July 2011, Montpellier, France
Szele, Gombos, KOVÁCS A., , Ember: Feeding Purified Glycerol from Biodiesel to CBA/CA Mice:
Effects on Gadd45a and Nfkb1 Expressions. In Vivo 2010, 24 (3): 303-‐308 (impact factor: 1.143) Szele, Gombos, KOVÁCS A., Ember: Effects of Purified Glycerol from Biodiesel on Cyp1a1 and Cyp2e1 Expressions in CBA/CA Mice. In Vivo 2011, 25 (2): 237-‐240 (impact factor: 1.143)
Szendi, Gerencsér, KOVÁCS A., Varga: Biodízel előállításakor képződött glicerin fázis melléktermék vizsgálata in vivo genotoxikológiai tesztekben. (Testing bydiesel byproduct glecerol phase in in vivo tests) Magyar Epidemiológia 2011; 8(1):21-‐26.
KOVÁCS A.: The potential to boost capacity and efficiency in small to medium sized biodiesel
production systems, Journal of Industrial Ecology, Volume 16, Issue 1, pages 153–162, February 2012 (impact factor: 2.446)
KOVÁCS A.: Aspects of refining biodiesel byproduct glycerin, Petroleum & Coal 53 (1) 91-‐97, 2011, (impact factor: 0.5)
KOVÁCS A., Czinkota, Tóth: Improving Acid Number Testing of Biodiesel Feedstock and Product, Journal of the American Oil Chemists' Society, 2012, Volume 89, Number 3, Pages 409-‐417 (impact factor: 1.587)
Kovács, Zsédey, KOVÁCS A., Vitág, Schmidt: Apparent digestible and metabolizable energy content of glycerol in feed of growing pigs, Livestock Science, Volume 142, Issue 1 , Pages 229-‐234, December 2011 (impact factor:1.295)
KOVÁCS A.: Manipulation of colloid chemistry improves the efficiency and profitability of biodiesel production, poster presentation, International Biomass conference and expo, , 16-‐20, April 2012, Denver, Co., USA
KOVÁCS A., Ball, C.: Modification of colloid chemistry to improve biodiesel production, European Biodiesel 2012, 13-‐14 June in Krakow, Poland
KOVÁCS A., Ball, C.:: Use of colloid chemistry to improve to improve biodiesel production, Periodica Polytechnica, Chemical Engineering, in press (impact factor: 0.2)
PATENTS
KOVÁCS A. et others: P014786, Jobbított biodízelel technológia növényi olaj átészterezésével, 2001
KOVÁCS A. et others.: PCT/HU02/00114 Improvement in or rellating to a method for transesterifying vegetable oils, 2002
KOVÁCS A., Sinoros Szabó: Alternatív szilárd tüzelőanyag (Alternative solid fuel), 2009 KOVÁCS A. Transesterification of vegetable oils, 2009 UK 5633001: PCT/GB2009/000246, WO/2009/095668
BOOK
KOVÁCS A.: Principles and practice of biodiesel production technologies and product evaluation, (Hungarian) 2003, KUKK K+F, ISBN963 00 9789 3, Budapest,
