- Email: [email protected]
Fuel from waste animal fats
Chemical Engineering Journal xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej
Fuel from waste animal fats } Hancsók ⇑ Peter Baladincz, Jeno University of Pannonia, Faculty of Engineering, Institute of Chemical and Process Engineering, MOL Department of Hydrocarbon and Coal Processing, P.O. Box 158, H-8201 Veszprém, Hungary
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
Purification of waste brown grease
from rendering facilities. Feedstock component with practically zero iLUC (indirect land use change) value. Coprocessing of waste lard and gas oil fraction. Gas oil fraction from waste polyolefin cracking. Bioparaffin containing high quality diesel fuel.
Citric acid
Triglyceride containing waste feedstock
i n f o
Article history: Available online xxxx Keywords: Waste lard Brown grease Hydrotreating Biofuels Bio gas oil
Straight run gas oil
Pre-treatment
Contaminants Gas oil fraction from waste polypropylene cracking Bio gas oil containing gas oil fraction (renewable diesel fuel) HDS –hydrodesulphurisation HDN –hydrodenitrogenation HDA –hydrodearomatisation
a r t i c l e
Bleaching earth
HDS/HDN/HDA + OLH/HDO
Isomerization
OLH –Olefin hydrogenation (saturation) HDO - Hydrodeoxygenation
Bio paraffin containing hydrogenated gas oil fraction
a b s t r a c t The hunger of the modern human society for energy is tremendous, which is increasing with the increasing population and with the pursuit of higher standards of living. A significant proportion of this energy demand is made up by the different fuels which ensure mobility. Based on environmental and energetic considerations, a larger proportion of this energy is trying to be covered with renewable energy sources on the whole world. Recently mankind utilised the first generation of biofuels for the transportation sector (bioethanol and biodiesel), but the development has not stopped. Today, the second generation is on the border of utilisation (2nd gen. bioethanol and bio gas oil – mixture of iso and normal paraffins). In this article, we are focusing on the topic of 2nd generation bio derived Diesel fuel, the so-called bio gas oil. We are investigating the possibilities of the utilisation of a new, waste feedstock, namely the brown greases which are the products of rendering facilities, in co-process with high sulphur containing heavy gas oil (1.2% sulphur content). During our experiments we produced bio gas oil containing gas oil fraction via the most favourable process parameters of hydrogenation (T: 330–340 °C, p: 50 bar, LHSV: 1.0 h 1) and isomerisation (T: 340 °C, p: 50 bar, 1.0 h 1) of waste lard containing gas oil stream. We determined that these kinds of waste fatty materials can be appropriate feedstocks for the production of renewable diesel–fuel components. In addition, these materials are cheap, and their iLUC (indirect land use change) value is practically zero. The properties (cetane number: P54, CFPP: 10 to 20 °C, yield: >91%) of the product obtained after the two consecutive process steps met the valid standard for diesel fuel, thus we proved that this kind of waste feedstock can be an option for bio derived engine fuel production. Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction One of the greatest challenges of the modern transportation sector is to ensure the supply for the increasing energy demand ⇑ Corresponding author. Tel.: +36 88 624313; fax: +36 88 624520. E-mail address: [email protected] (J. Hancsók).
of the mobility, while bearing in mind the environmental issues, too [1,2]. Because of energetic and environmental demands mankind has begun to utilise bio derived fuels to replace part of the fossil energy source of the mobility. The steady development of bio derived fuels resulted in a wide range of options, which can be divided into multiple generations on the basis of feedstocks and of technologies [3]. Nowadays, mankind apply the first generation
http://dx.doi.org/10.1016/j.cej.2015.04.003 1385-8947/Ó 2015 Elsevier B.V. All rights reserved.
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
2
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
biofuels in the transportation sector (bioethanol and biodiesel), but the development has not stopped. Today, ones belonging to the second generation are on the border of utilisation (2nd gen. bioethanol and bio gas oil) [3]. 1.1. Bio derived diesel–fuels In case of diesel-engines, the most widely used bio derived fuel is the biodiesel, but due to its disadvantages [4] a product of a new chemical structure, the bio gas oil has been developed and applied in some extent. During the production of the bio gas oil, natural triglyceride (fatty acid) containing feedstock is converted via heterogeneous catalytic hydrogenation mainly to a mixture of iso and normal paraffins [5] (Fig. 1), which are the most important and best quality components of conventional diesel fuels, too [3–4,6–8]. At first, the aim of the triglyceride hydrogenation was to produce a cetane booster additive [9], but later on it became a widely researched area for bio derived diesel fuel production [3–8,10–20]. The production of bio gas oil can be made in itself [9–12] or as a co-process quality improvement process if the triglyceride is mixed with gas oil stream [7,13–16]. Almost without exceptions, the triglyceride feedstocks of these processes are some kind of vegetable oil with low impurity content, so pre-treatment is not necessary or only a slight cleaning is needed before the hydrogenation step. When the feedstock is a so-called waste oil or fat, it
usually means slightly contaminated feedstocks, like used cooking oils [14,15,17]. Nevertheless the commercial price of this kind of feedstocks can be high and in some cases they may have high iLUC (indirect land use change) value as well (Fig. 2) [2]. The solution can be the processing of various triglyceride (fatty acid) containing waste materials.
1.2. Waste feedstocks for bio derived diesel fuel production This type of material is the waste cooking oil, which does not require high degree of purification either, but its large scale collection has not been solved (apart from some experimental systems [16]) yet. However, a relatively high amount of triglyceride and free fatty acid containing fatty materials are formed everywhere in the rendering facilities (Fig. 3), which can be used as feedstock for bio gas oil production [19]. In these plants various fatty materials, meals, fodders are made from the waste of slaughterhouses and carcasses of livestock. A high amount product of these rendering plants is the technical grade brown lard, which should not be used for animal feeding. However, after proper pre-treating this material can be a cheap feedstock for bio gas oil production. The biggest problem with these materials is that their solid contaminant as well as metal and phosphorous contents (Fig. 4) can be considerably high, therefore pre-treatment/cleaning is required, otherwise the high H 2O
H2 O
O
i-C16 n-C16 Isomerization i-C18 n-C18 Propane
O
O
HDO =R1
O
O
R2=
R1
H2
O
O
CO2
R2
H2 O
Triglyceride O (vegetable oil, animal fat, etc.)
R3=
O
Saturated O triglyceride
R3
Monoglycerides Diglycerides Carboxylic-acids Waxes
Decarb o H2
xylatio
Cracking
n
CO
Decarbonylation
n-C15 n-C17 Propane
Lighter paraffins
i-C15 Isomerization i-C17
Fig. 1. Reaction pathway of the bio gas oil production [7]. (R1, R2, R3: carbon chains with C11–C23 carbon number) (examples are for C15 and C17 carbon chains.)
Fig. 2. iLUC values of some typical bio derived diesel fuel compared to conventional diesel gas oil [2].
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
3
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 3. Simplified pathway of livestock to Wheel method.
Citric acid
Triglyceride containing waste feedstock
Bleaching earth
Straight run gas oil
Pre-treatment
Contaminants Gas oil fraction from waste polypropylene cracking Bio gas oil containing gas oil fraction (renewable diesel fuel) HDS –hydrodesulphurisation HDN –hydrodenitrogenation HDA –hydrodearomatisation
HDS/HDN/HDA + OLH/HDO
Isomerization Bio paraffin containing hydrogenated gas oil fraction
OLH –Olefin hydrogenation (saturation) HDO - Hydrodeoxygenation
Fig. 6. Utilised technological solution of the bio gas oil production.
Fig. 4. Typical phospholipid molecule.
2. Experimental concentration of impurities greatly shortens the lifetime of the catalysts. In the course of the food grade vegetable oil production various cleaning processes are used (Fig. 5) [20], but their applicability for this type of material has to be examined in detail. Any of the main processing routes, furthermore any of the individual process steps can be applied for the treatment and purification of triglyceride materials, but there are some things that need attention in the case of this kind of triglyceride base stock. Waste lards from a rendering facility have a high free fatty acid content, and fairly high metal and phosphorous contamination, too, in comparison to the edible or less ‘‘waste’’ fats and oils. According to the literature, the applicability of these kinds of materials (waste lards from rendering facilities) is not really investigated for biofuel production (except for a few publication e.g. [19]), so during our experimental work we investigated that possibility. Thus during our research, the main goal was to produce alternative fuel components via co-processing of waste lards obtained from different rendering facilities and straight run heavy gas oil derived from Russian crude oil.
Physical refining
Degumming
Crude oil/fat of vegetable/animal origin
Alkali refining
Degumming
As stated above, during our experiments, we investigated the hydrogenation and isomerisation of expediently pre-treated waste fatty material of animal origin in co-process with a heavy gas oil fraction (5–30/95–70 ratio of lard/gas oil) on an ‘‘in situ’’ sulphided NiMo/Al2O3 hydrodesulphurization catalyst widely used in refining, and on a Pt/SAPO-11 catalyst developed by us (HU 225912 patent), applying a wide range of process parameters (hydrogenation: 300–380 °C, 20–80 bar, 0.75-1.0–1.5 h 1, 600 Nm3/m3; isomerisation: defined based on previous experiments with bio derived paraffins [22]). At first, co-process hydrogenation of the waste lard containing gas oil fraction was carried out. After separating and analysing the bio gas oil containing intermediate product its gas oil boiling point range fraction was isomerized to improve mainly the cold flow properties in the second step (Fig. 6). Hydrogenation and isomerisation experiments were carried out in a reactor system (Fig. 7) equipped with a tubular reactor of 100 cm3 efficient volume. The applied reactor system contains all the equipment and instruments which are present in a
Deodorization/ Vacuum stripping
Bleaching
Gum
Soapstock
Neutralization
Splitting
FFA
Refined oil/fat of vegatable/animal origin
Bleaching
Deodorization
Fig. 5. Possible cleaning processes in the edible oil/fat industry of vegetable/animal origin.
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
4
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 7. Reactor system utilised during the experiments.
Table 1 The typical fatty acid composition of the applied waste lard feedstock (before pretreatment/purification). Property
Value
Density (50 °C) (g/cm3) Kinematic viscosity (40 °C) (mm2/s) Acid number (mg KOH/g) Free fatty acid content (%) Sulphur content (mg/kg) Nitrogen content (mg/kg) Oxygen content (%) Water content (mg/kg)
0.8928 42.47 16.5 8.3 270 480 11 4400
Contaminants (mg/kg) Ca Mg K Na P Fe
202.6 26.8 107.2 74.2 214.8 29
Fatty acid composition* (%) C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 C18:3 C20:1 C20:2 C22:1
1.24 24.67 3.13 12.61 37.79 16.45 1.28 0.78 0.46 1.56
* The first number represents the number of carbon atoms and the second means the number of double bonds in the molecule.
heterogeneous catalytic hydrogenation plant. The experimental work was carried out in continuous mode, and on catalyst of stable activity. Brown lard made by a Hungarian rendering company as waste stream (Table 1) and a high sulphur containing straight run heavy
Table 2 Properties of the straight run heavy gas oil feedstock. Property
Value
Density (15.6 °C) (g/cm3) Kinematic viscosity (40 °C) (mm2/s) Aromatic content (%) Polyaromatic content (%) CFPP (°C) Sulphur content (mg/kg) Nitrogen content (mg/kg) Flashpoint (°C) Initial boiling point (°C) 10, v/v% (°C) 50, v/v% (°C) 90, v/v% (°C) Final boiling point (°C)
0.8664 6.44 40.4 15.1 8 12,000 250 76 174 278 320 362 378
gas oil fraction (Table 2) obtained from Russian crude were used as feedstocks for the experiments. For the pre-treatment/purification of the waste lard feedstock, we applied acid degumming process using citric acid solution and a bleaching process using activated bleaching earth, bentonite. Waste lard/gas oil fraction mixed in 5–30/95–70 weight percents was used as feedstock. The sulphur content of the gas oil part preserved the sulphide state of the NiMo/Al2O3 catalyst used in the hydrogenation step. The total saturated fatty acid content of the waste lard was 38.5%. During the isomerisation step, we used a Pt/SAPO-11 catalyst, which was developed by us for paraffin hydroisomerisation [21]. The fractionation of the product mixtures was carried out as it can be seen in Fig. 8. In the course of the experiments, the product mixture was separated into gaseous and liquid phase in the separator unit of the experimental equipment. After separating the water from the obtained liquid product mixture, the light hydrocarbons (C5–C9) were separated by distillation up to 180 °C from the organic liquid phase.
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
5
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Product mixtures
Gaseous phase
Water phase
(H2, CO, CO2 , C3 H8, C3H6, C1-C4 Hydrocarbons , H2 S, NH3 )
Liquid organic phase (C5+)
Residue Light hydrocarbons (C5-C10)
Main product fraction (180-360°C)
(triglycerides , diglycerides , monoglycerides , hydrocarbons of higher carbon numbers , carboxylic -acids, esters)
Fig. 8. The method of the product fractionating.
The fraction above the boiling point of 180 °C was separated to gas oil boiling point range main product (C10–C22 hydrocarbons up to the boiling point of 360 °C) and to residual fraction by vacuumdistillation. All product yields are based on the weight of the feedstock. The properties of feedstocks and products were determined according to the specifications given in EN 590:2013 standard for diesel fuel, and with standardised calculation methods. Additionally, the composition of the obtained liquid organic product was determined by high temperature gas chromatography. 3. Results and discussion 3.1. Most important results of the hydrotreating (HDS/HDO) step The yield of the main hydrogenated product fraction slightly decreased with increasing the temperature (Fig. 9). The conversion
of the triglyceride part of the feed was nearly complete even at the mildest reaction parameters, thus with the increasing temperature, partially because of the gaseous products (mainly propane, CO, CO2) and water forming during the triglyceride hydrogenation, and partially because the cracking reactions came to the front, that caused the decreasing yield. In addition, the conversion of the high sulphur content (0.84-1.14%) of the feed to hydrogen sulphide, also clearly reduced the yield. As a function of the pressure it can be seen that with increasing pressure, the yield slightly decreased above 320 °C, also as a result of the hydrocracking reactions. The decrease in LHSV favoured the triglyceride conversion but it increased the hydrocracking activity of the catalyst, too, so the yield decreased with decreasing LHSV (Fig. 10). The yields of the fraction in the gas oil boiling point range (in case of 10% waste lard content 91.7–93.6%) approached well the ⁄ theoretical yields (in case of 10% waste lard content ⁄94.7–95.0%) during the hydrogenation step. The theoretical yield is calculated by accounting only the reactions resulting propane splitting and oxygen and sulphur removal. Fig. 11 displays the yield of the main hydrogenated product in function of the waste lard content of the feedstock. By increasing the waste lard content of the feedstock, the yield of the liquid product decreased because the conversion of triglyceride resulting not only valuable paraffins, but gas products (propane, CO2, CO, CH4) and water, too, decreasing the yield based on the weight of the feedstock. Table 3 and Figs. 12–15 show that the main properties of the product fraction obtained in the hydrogenation step are quite different from the properties of the feedstock (Tables 1 and 2). During
Fig. 9. Yield of the main hydrogenated product as a function of temperature and pressure (10% waste lard content, LHSV: 1.0 h
1
).
Fig. 10. Yield of the main hydrogenated product as a function of temperature and LHSV (10% waste lard content, pressure: 80 bar).
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
6
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 11. Yield of the main hydrogenated product as a function of temperature and waste lard content (LHSV: 1.0 h
1
, pressure: 50 bar.)
Table 3 Properties of the main product fractions after the hydrogenation step. Process parameters Waste lard content of the feedstock
10%
Temperature (°C) Pressure (bar) LHSV (h 1)
360 50 1.0
30% 380 80 0.75
360 50 1.0
380 80 1.0
Properties of the gas oil boiling point range product fractions 3
Density on 15.6 °C (kg/m ) Kinematic viscosity on 40 °C (mm2/s) Sulphur content (mg/kg) Nitrogen content (mg/kg) Total aromatic content (%) Polycyclic aromatic content (%) CFPP (°C) Cetane number
844.0 4.55 38 3 23.1 2.9 8 55
EN 590:2013 838.1 4.50 7 9 17.8 1.8 6 55
the hydrogenation, the triglyceride content is converted mainly to normal paraffins, a part of the aromatic content is saturated, and the sulphur, nitrogen and oxygen content of the feedstock are greatly decreased. Because of the increasing paraffin content, the cetane number of the product fractions is increased as well. The CFPP value of the products was quite high, because the heavy gas oil part of the feed (which has high CFPP value, too) and because of the increasing content of normal paraffins (originating from the triglyceride part). The sulphur content of the gas oil boiling range fraction decreased with the increasing temperature, because of increasing
832.2 4.24 12 2 13.0 2.4 12 60
831.2 4.39 6 2 9.0 1.6 11 62
820–845 2.00–4.50 Maximum 10.0 No restriction No restriction Maximum 8.0 20 (winter) to +5 (summer) Minimum 51
desulphurisation activity of the applied catalyst (Fig. 12). During the experiment with the increase of the temperature and pressure, desulphurisation took place in a considerable extent, but only in case of 80 bar pressure and 380 °C temperature we could achieve the value <10 mg/kg sulphur content in the product. In any other case, the sulphur content of the product was higher than the maximum allowable value of the EN 590:2013 standard. The main cause of this may be the high oxygen heteroatom content of the feedstock originating from the triglyceride part (10% triglyceride in the feedstock means about 1.1% of oxygen content). During the triglyceride hydrogenation, after splitting the propane,
Fig. 12. Sulphur content of the main hydrogenated product as a function of temperature and pressure (10% waste lard content, LHSV: 1.0 h
1
).
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
7
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 13. Total aromatic content of the main hydrogenated product as a function of temperature and pressure (10% waste lard content, LHSV: 1.0 h
Fig. 14. Viscosity of the main hydrogenated product as a function of temperature and pressure (10% waste lard content, LHSV: 1.0 h
Fig. 15. Density of the main hydrogenated product as a function of temperature and pressure (10% waste lard content, LHSV: 1.0 h
the oxygen removal is faster from the linear fatty acid chains (higher reaction rate) than the desulphurisation of cyclic/polycyclic sulphur compounds. The saturation of the aromatic compounds occurred, too, during the hydrogenation step, but for the better efficiency, higher pressures are needed. As it can be seen in Fig. 13, in the case of the lowest applied pressure (20 bar), the aromatic content of the product remained nearly the same as in the feedstock. This was due to the typical aromatic compounds in the feedstock gas oil fraction,
1
1
).
).
1
).
namely the aromatic sulphur containing molecules (like dibenzothiophenes and its derivatives). In the case of these kinds of compounds, the effective desulphurisation and aromatic saturation requires severe process parameters. The aromatic content reaches a minimum about 360 °C and above this temperature value, the aromatic content of the products was higher again because of the thermodynamic inhibition of the exothermic dearomatisation reactions (more aromatic compounds remained in the product).
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
8
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 16. Yield of the isomerised product as a function of temperature and pressure on the basis of the basic feedstock (10% waste lard content, LHSV: 1.0 h
1
).
Fig. 17. CFPP (random samples) and cetane number (average) values of the hydrogenated and isomerised final product.
During the hydrogenation experiments, the kinematic viscosity of the products decreased with increasing temperature and pressure (Fig. 14), due to the triglyceride conversion, the aromatic saturation and cracking reactions. Because of the high viscosity of the feedstock gas oil, the viscosity of the product was above the maximum value prescribed in the standard. Due to the aforementioned reasons the density of the main hydrogenated products was also above the value of the valid standard (Fig. 15). The density of the hydrogenated main products decreased as an effect of the triglyceride conversion and the aromatic saturation, but above 360 °C it correlated with the aromatic content, because of the high density of the aromatic compounds. This correlation to the aromatic content can be observed in the change of the product viscosity, too, (Fig. 14). Because of the high CFPP values and the higher than standard sulphur values, it is necessary to submit the hydrogenated product to an additional process, hydroisomerisation. During this, a part of the n-paraffin content in the product is converted to isoparaffins, which has lower CFPP values, but unfortunately slightly lower cetane numbers as well [21,22]. Furthermore the sulphur content continues to fall at this second ‘‘hydrotreating’’ process. It shall be noted that in order to increase the ratio of alternative source derived components, we performed such experiments also in which the feedstock contained 2–5% gas oil boiling point product fraction of a thermal cracking process (550 °C and 6 bar) with
waste polypropylene feedstock. The obtained hydrotreated intermediate product had the same quality as the previously described products. However the CFPP value of these was 3–5% higher, which was due to the high paraffin and olefin content (84% total) of the feedstock component. At the applied favourable process parameters, the olefin hydrocarbons were practically hydrogenated completely (iodine number of products: <3 gI2/100 g). 3.2. Most important results of the isomerisation Due to the not adequate cold flow properties of the hydrogenated product (straight run heavy gas oil fraction and increased n-paraffin content via the hydrogenation of the triglyceride and fatty acid content) a second, isomerisation step can be necessary, if the produced bio gas oil containing gas oil fraction is utilised in cooler than tropical or Mediterranean climates. During this step, the high n-paraffin content of the intermediate feedstock is converted to isoparaffins, which have lower pour points, but slightly lower cetane number values, too. Isomerisation was carried out on a Pt/SAPO-11 isomerisation catalyst [21]. In the isomerisation step, the product yields varied in the range of 88.1-90.4% on the basis of the triglyceride containing feedstock (Fig. 16). With increasing temperature, especially above 340 °C, the cracking activity of the catalyst steeply increased resulting loss in the yield of the liquid product.
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 17 clearly shows that during the isomerisation step, the cold flow properties (CFPP value in this case) improved, but the cetane number values decreased. However, specifically the improvement in the cold properties is greater than the cetane number reduction, so a good balance between these properties can be set during the isomerisation process. The cetane number of the main product fractions was about 56– 58 after the hydrogenation step (in case of 10% waste lard content), while their CFPP values were about 8 °C. After the isomerisation step, the cetane number was 54, while the CFPP value was between 15 and 20 °C. 4. Conclusions During the hydroconversion of waste animal fat containing (530%) gas oil (sulphur content: 1.2%, polycyclic aromatic content: 15.1%, total aromatic content: 40.4%) over sulphided NiMo/Al2O3 catalyst, the yields of the gas oil boiling point range main product fraction well approached the theoretical yields at the most favourable process parameters (T: 340 °C, p: 50 bar, LHSV: 1.0 h 1). For example, in the case of 10% waste lard containing feedstocks, the yield was between 95.1% and 95.5% while the theoretical yield is 96.7–97.0%. During the experiments, the triglyceride part was fully converted, and the sulphur and nitrogen heteroatom removal and aromatic saturation of the gas oil part also occurred with high conversion. The cetane number of the products obtained in the case of 10% waste lard containing gas oil was 56–58 after the hydrogenation, while their CFPP values were about +8 °C. After the isomerisation step, which served for the improvement of the cold flow properties, the product yields were 91.4-92.4% on the basis of the triglyceride containing feedstock. The cetane number of the final product was 54-55, while the CFPP value between 15 and 20 °C. The sulphur and polycyclic aromatic content of the final products comply with the valid standard EN 590:2013 for diesel gas oils, as well (sulphur content <10 mg/kg; polycyclic aromatic content <8%). During the product analysis it was determined that these kinds of waste fatty materials can be appropriate feedstocks for the production of bio component containing gas oils after proper pretreatment. In addition, these materials are cheap, their iLUC value is practically zero, and as waste materials they count as twofold inside the EU when calculating the ratio of renewable fuels respectively [23]. Acknowledgements This work was supported by the European Union and co-financed by the European Social Fund – Hungary in the frame of the TAMOP-4.1.1.C-12/1/KONV/2012-0017 and TAMOP-4.2.2.A-11/1/ KONV-2012-0071 projects.
9
References [1] BP Plc., BP Statistical Review of World Energy 2014, June, 2014.. [2] J. Adolf, D. Liebig, Biofuels – What Role in the Future Energy Mix?, Shell Dutchland Oil GmbH, Hamburg, 2012 [3] J. Hancsók, M. Krár, Sz. Magyar, L. Boda, A. Holló, D. Kalló, Investigation of the production of high cetane number biogasoil from pre-hydrogenated vegetable oils over Pt/HZSM-22/Al2O3, Microporous Mesoporous Mater. 101 (1–2) (2007) 148–152. [4] G. Knothe, Biodiesel and renewable diesel: a comparison, Prog. Energy Combust. Sci. 36 (2010) 364–373. [5] B. Donnis, R. Gottschlack Egeberg, P. Blom, K. Gron Knudsen, Hydroprocessing of bio-oils and oxygenates to hydrocarbons. Understanding the reaction routes, Top. Catal. 52 (2009) 229–240. [6] S. Kovács, T. Kasza, A. Thernesz, I. Wálhné Horváth, J. Hancsók, Fuel production by hydrotreating of triglycerides on NiMo/Al2O3/F catalyst, Chem. Eng. J. 176– 177 (2011) 237–243. [7] G.W. Huber, P. O’Connor, A. Corma, Processing biomass in conventional oil refineries: production of high quality diesel by hydrotreating vegetable oil in heavy vacuum oil mixtures, Appl. Catal. A: Gen. (2007) 120–129. [8] M. Krár, A. Thernesz, Cs. Tóth, T. Kasza, J. Hancsók, Investigation of catalytic conversion of vegetable oil/gas oil mixtures, in: I. Halász (Ed.), Silica and Silicates in Modern Catalysis, Transworld Research Network, Kerala, India, 2010, pp. 435–455. [9] M. Stumborg, A. Wong, E. Hogan, Hydroprocessed vegetable oils for diesel fuel improvement, Bioresour. Technol. 56 (1996) 13–18. [10] M. Mohammad, T.K. Hari, Z. Yaakob, Y.C. Sharma, K. Sopian, Overview on the production of paraffin based-biofuels via catalytic hydrodeoxygenation, Renew. Sust. Energy Rev. 22 (2013) 121–132. [11] K.S. Kim, S. Brand, H. Lee, Y. Kim, J. Kim, Production of renewable diesel by hydrotreatment of soybean oil: effect of reaction parameters, Chem. Eng. J. 228 (2013) 114–123. [12] D. Kubicka, L. Kaluza, Deoxygenation of vegetable oils over sulfided Ni, Mo and NiMo catalysts, Appl. Catal. A: Gen. 372 (2010) 199–208. [13] A.A. Lappas, S. Bezergianni, I.A. Vasalos, Production of biofuels via coprocessing in conventional refining processes, Catal. Today 145 (2009) 55–62. [14] B.S. Rana, R. Kumar, R. Tiwari, R. Kumar, R.K. Joshi, M.O. Garg, A.K. Sinha, Transportation fuels from co-processing of waste vegetable oil and gas oil mixtures, Biomass Bioenergy 56 (2013) 43–52. [15] S. Bezergianni, A. Dimitriadis, Temperature effect on co-hydroprocessing of heavy gas oil-waste cooking oil mixtures for hybrid diesel production, Fuel 103 (2013) 579–584. [16] S. Bezergianni, Exploring catalytic hydroprocesses for the conversion of lipids in co-processing, in: 46th International Conference on Petroleum Processing, Bratislava, June 7, 2013, CD Proceedings, ISBN 978-80-969792-4-0. [17] M. Toba, Y. Abe, H. Kuramochi, M. Osako, T. Mochizuki, Y. Yoshimura, Hydrodeoxygenation of waste vegetable oil over sulfide catalysts, Catal. Today 164 (2011) 533–537. [18] A.T. Madsen, E.H. Ahmed, C.H. Christensen, R. Fehrmann, A. Riisager, Hydrodeoxygenation of waste fat for diesel production: study on model feed with Pt/alumina catalyst, Fuel 90 (2011) 3433–3438. [19] J. Hancsók, P. Baladincz, T. Kasza, S. Kovács, Cs. Tóth, Z. Varga, Bio gas oil production from waste lard, J. Biomed. Biotechnol. (2011) (Article ID 384184). [20] F.D. Gunstone, L. Harwood, A.J. Dijkstra, The Lipid Handbook, 3rd ed., CRC Press, 2007, p. 1472, ISBN: 978-0849396885. [21] T. Kasza, A. Holló, A. Thernesz, J. Hancsók, Production of bio gas oil from bioparaffins over Pt/SAPO-11, Chem. Eng. Trans. 21 (2010) 1225–1230. [22] T. Kasza, D. Kalló, J. Hancsók, Quality improvement of bio-paraffin mixtures, Fuel 120 (2014) 1–7. [23] Directive 2009/28/EC of the European Parliament and of the Council, Official Journal of the European Union, (2009), L 140/16-61.
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
Contents lists available at ScienceDirect
Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej
Fuel from waste animal fats } Hancsók ⇑ Peter Baladincz, Jeno University of Pannonia, Faculty of Engineering, Institute of Chemical and Process Engineering, MOL Department of Hydrocarbon and Coal Processing, P.O. Box 158, H-8201 Veszprém, Hungary
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
Purification of waste brown grease
from rendering facilities. Feedstock component with practically zero iLUC (indirect land use change) value. Coprocessing of waste lard and gas oil fraction. Gas oil fraction from waste polyolefin cracking. Bioparaffin containing high quality diesel fuel.
Citric acid
Triglyceride containing waste feedstock
i n f o
Article history: Available online xxxx Keywords: Waste lard Brown grease Hydrotreating Biofuels Bio gas oil
Straight run gas oil
Pre-treatment
Contaminants Gas oil fraction from waste polypropylene cracking Bio gas oil containing gas oil fraction (renewable diesel fuel) HDS –hydrodesulphurisation HDN –hydrodenitrogenation HDA –hydrodearomatisation
a r t i c l e
Bleaching earth
HDS/HDN/HDA + OLH/HDO
Isomerization
OLH –Olefin hydrogenation (saturation) HDO - Hydrodeoxygenation
Bio paraffin containing hydrogenated gas oil fraction
a b s t r a c t The hunger of the modern human society for energy is tremendous, which is increasing with the increasing population and with the pursuit of higher standards of living. A significant proportion of this energy demand is made up by the different fuels which ensure mobility. Based on environmental and energetic considerations, a larger proportion of this energy is trying to be covered with renewable energy sources on the whole world. Recently mankind utilised the first generation of biofuels for the transportation sector (bioethanol and biodiesel), but the development has not stopped. Today, the second generation is on the border of utilisation (2nd gen. bioethanol and bio gas oil – mixture of iso and normal paraffins). In this article, we are focusing on the topic of 2nd generation bio derived Diesel fuel, the so-called bio gas oil. We are investigating the possibilities of the utilisation of a new, waste feedstock, namely the brown greases which are the products of rendering facilities, in co-process with high sulphur containing heavy gas oil (1.2% sulphur content). During our experiments we produced bio gas oil containing gas oil fraction via the most favourable process parameters of hydrogenation (T: 330–340 °C, p: 50 bar, LHSV: 1.0 h 1) and isomerisation (T: 340 °C, p: 50 bar, 1.0 h 1) of waste lard containing gas oil stream. We determined that these kinds of waste fatty materials can be appropriate feedstocks for the production of renewable diesel–fuel components. In addition, these materials are cheap, and their iLUC (indirect land use change) value is practically zero. The properties (cetane number: P54, CFPP: 10 to 20 °C, yield: >91%) of the product obtained after the two consecutive process steps met the valid standard for diesel fuel, thus we proved that this kind of waste feedstock can be an option for bio derived engine fuel production. Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction One of the greatest challenges of the modern transportation sector is to ensure the supply for the increasing energy demand ⇑ Corresponding author. Tel.: +36 88 624313; fax: +36 88 624520. E-mail address: [email protected] (J. Hancsók).
of the mobility, while bearing in mind the environmental issues, too [1,2]. Because of energetic and environmental demands mankind has begun to utilise bio derived fuels to replace part of the fossil energy source of the mobility. The steady development of bio derived fuels resulted in a wide range of options, which can be divided into multiple generations on the basis of feedstocks and of technologies [3]. Nowadays, mankind apply the first generation
http://dx.doi.org/10.1016/j.cej.2015.04.003 1385-8947/Ó 2015 Elsevier B.V. All rights reserved.
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
2
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
biofuels in the transportation sector (bioethanol and biodiesel), but the development has not stopped. Today, ones belonging to the second generation are on the border of utilisation (2nd gen. bioethanol and bio gas oil) [3]. 1.1. Bio derived diesel–fuels In case of diesel-engines, the most widely used bio derived fuel is the biodiesel, but due to its disadvantages [4] a product of a new chemical structure, the bio gas oil has been developed and applied in some extent. During the production of the bio gas oil, natural triglyceride (fatty acid) containing feedstock is converted via heterogeneous catalytic hydrogenation mainly to a mixture of iso and normal paraffins [5] (Fig. 1), which are the most important and best quality components of conventional diesel fuels, too [3–4,6–8]. At first, the aim of the triglyceride hydrogenation was to produce a cetane booster additive [9], but later on it became a widely researched area for bio derived diesel fuel production [3–8,10–20]. The production of bio gas oil can be made in itself [9–12] or as a co-process quality improvement process if the triglyceride is mixed with gas oil stream [7,13–16]. Almost without exceptions, the triglyceride feedstocks of these processes are some kind of vegetable oil with low impurity content, so pre-treatment is not necessary or only a slight cleaning is needed before the hydrogenation step. When the feedstock is a so-called waste oil or fat, it
usually means slightly contaminated feedstocks, like used cooking oils [14,15,17]. Nevertheless the commercial price of this kind of feedstocks can be high and in some cases they may have high iLUC (indirect land use change) value as well (Fig. 2) [2]. The solution can be the processing of various triglyceride (fatty acid) containing waste materials.
1.2. Waste feedstocks for bio derived diesel fuel production This type of material is the waste cooking oil, which does not require high degree of purification either, but its large scale collection has not been solved (apart from some experimental systems [16]) yet. However, a relatively high amount of triglyceride and free fatty acid containing fatty materials are formed everywhere in the rendering facilities (Fig. 3), which can be used as feedstock for bio gas oil production [19]. In these plants various fatty materials, meals, fodders are made from the waste of slaughterhouses and carcasses of livestock. A high amount product of these rendering plants is the technical grade brown lard, which should not be used for animal feeding. However, after proper pre-treating this material can be a cheap feedstock for bio gas oil production. The biggest problem with these materials is that their solid contaminant as well as metal and phosphorous contents (Fig. 4) can be considerably high, therefore pre-treatment/cleaning is required, otherwise the high H 2O
H2 O
O
i-C16 n-C16 Isomerization i-C18 n-C18 Propane
O
O
HDO =R1
O
O
R2=
R1
H2
O
O
CO2
R2
H2 O
Triglyceride O (vegetable oil, animal fat, etc.)
R3=
O
Saturated O triglyceride
R3
Monoglycerides Diglycerides Carboxylic-acids Waxes
Decarb o H2
xylatio
Cracking
n
CO
Decarbonylation
n-C15 n-C17 Propane
Lighter paraffins
i-C15 Isomerization i-C17
Fig. 1. Reaction pathway of the bio gas oil production [7]. (R1, R2, R3: carbon chains with C11–C23 carbon number) (examples are for C15 and C17 carbon chains.)
Fig. 2. iLUC values of some typical bio derived diesel fuel compared to conventional diesel gas oil [2].
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
3
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 3. Simplified pathway of livestock to Wheel method.
Citric acid
Triglyceride containing waste feedstock
Bleaching earth
Straight run gas oil
Pre-treatment
Contaminants Gas oil fraction from waste polypropylene cracking Bio gas oil containing gas oil fraction (renewable diesel fuel) HDS –hydrodesulphurisation HDN –hydrodenitrogenation HDA –hydrodearomatisation
HDS/HDN/HDA + OLH/HDO
Isomerization Bio paraffin containing hydrogenated gas oil fraction
OLH –Olefin hydrogenation (saturation) HDO - Hydrodeoxygenation
Fig. 6. Utilised technological solution of the bio gas oil production.
Fig. 4. Typical phospholipid molecule.
2. Experimental concentration of impurities greatly shortens the lifetime of the catalysts. In the course of the food grade vegetable oil production various cleaning processes are used (Fig. 5) [20], but their applicability for this type of material has to be examined in detail. Any of the main processing routes, furthermore any of the individual process steps can be applied for the treatment and purification of triglyceride materials, but there are some things that need attention in the case of this kind of triglyceride base stock. Waste lards from a rendering facility have a high free fatty acid content, and fairly high metal and phosphorous contamination, too, in comparison to the edible or less ‘‘waste’’ fats and oils. According to the literature, the applicability of these kinds of materials (waste lards from rendering facilities) is not really investigated for biofuel production (except for a few publication e.g. [19]), so during our experimental work we investigated that possibility. Thus during our research, the main goal was to produce alternative fuel components via co-processing of waste lards obtained from different rendering facilities and straight run heavy gas oil derived from Russian crude oil.
Physical refining
Degumming
Crude oil/fat of vegetable/animal origin
Alkali refining
Degumming
As stated above, during our experiments, we investigated the hydrogenation and isomerisation of expediently pre-treated waste fatty material of animal origin in co-process with a heavy gas oil fraction (5–30/95–70 ratio of lard/gas oil) on an ‘‘in situ’’ sulphided NiMo/Al2O3 hydrodesulphurization catalyst widely used in refining, and on a Pt/SAPO-11 catalyst developed by us (HU 225912 patent), applying a wide range of process parameters (hydrogenation: 300–380 °C, 20–80 bar, 0.75-1.0–1.5 h 1, 600 Nm3/m3; isomerisation: defined based on previous experiments with bio derived paraffins [22]). At first, co-process hydrogenation of the waste lard containing gas oil fraction was carried out. After separating and analysing the bio gas oil containing intermediate product its gas oil boiling point range fraction was isomerized to improve mainly the cold flow properties in the second step (Fig. 6). Hydrogenation and isomerisation experiments were carried out in a reactor system (Fig. 7) equipped with a tubular reactor of 100 cm3 efficient volume. The applied reactor system contains all the equipment and instruments which are present in a
Deodorization/ Vacuum stripping
Bleaching
Gum
Soapstock
Neutralization
Splitting
FFA
Refined oil/fat of vegatable/animal origin
Bleaching
Deodorization
Fig. 5. Possible cleaning processes in the edible oil/fat industry of vegetable/animal origin.
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
4
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 7. Reactor system utilised during the experiments.
Table 1 The typical fatty acid composition of the applied waste lard feedstock (before pretreatment/purification). Property
Value
Density (50 °C) (g/cm3) Kinematic viscosity (40 °C) (mm2/s) Acid number (mg KOH/g) Free fatty acid content (%) Sulphur content (mg/kg) Nitrogen content (mg/kg) Oxygen content (%) Water content (mg/kg)
0.8928 42.47 16.5 8.3 270 480 11 4400
Contaminants (mg/kg) Ca Mg K Na P Fe
202.6 26.8 107.2 74.2 214.8 29
Fatty acid composition* (%) C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 C18:3 C20:1 C20:2 C22:1
1.24 24.67 3.13 12.61 37.79 16.45 1.28 0.78 0.46 1.56
* The first number represents the number of carbon atoms and the second means the number of double bonds in the molecule.
heterogeneous catalytic hydrogenation plant. The experimental work was carried out in continuous mode, and on catalyst of stable activity. Brown lard made by a Hungarian rendering company as waste stream (Table 1) and a high sulphur containing straight run heavy
Table 2 Properties of the straight run heavy gas oil feedstock. Property
Value
Density (15.6 °C) (g/cm3) Kinematic viscosity (40 °C) (mm2/s) Aromatic content (%) Polyaromatic content (%) CFPP (°C) Sulphur content (mg/kg) Nitrogen content (mg/kg) Flashpoint (°C) Initial boiling point (°C) 10, v/v% (°C) 50, v/v% (°C) 90, v/v% (°C) Final boiling point (°C)
0.8664 6.44 40.4 15.1 8 12,000 250 76 174 278 320 362 378
gas oil fraction (Table 2) obtained from Russian crude were used as feedstocks for the experiments. For the pre-treatment/purification of the waste lard feedstock, we applied acid degumming process using citric acid solution and a bleaching process using activated bleaching earth, bentonite. Waste lard/gas oil fraction mixed in 5–30/95–70 weight percents was used as feedstock. The sulphur content of the gas oil part preserved the sulphide state of the NiMo/Al2O3 catalyst used in the hydrogenation step. The total saturated fatty acid content of the waste lard was 38.5%. During the isomerisation step, we used a Pt/SAPO-11 catalyst, which was developed by us for paraffin hydroisomerisation [21]. The fractionation of the product mixtures was carried out as it can be seen in Fig. 8. In the course of the experiments, the product mixture was separated into gaseous and liquid phase in the separator unit of the experimental equipment. After separating the water from the obtained liquid product mixture, the light hydrocarbons (C5–C9) were separated by distillation up to 180 °C from the organic liquid phase.
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
5
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Product mixtures
Gaseous phase
Water phase
(H2, CO, CO2 , C3 H8, C3H6, C1-C4 Hydrocarbons , H2 S, NH3 )
Liquid organic phase (C5+)
Residue Light hydrocarbons (C5-C10)
Main product fraction (180-360°C)
(triglycerides , diglycerides , monoglycerides , hydrocarbons of higher carbon numbers , carboxylic -acids, esters)
Fig. 8. The method of the product fractionating.
The fraction above the boiling point of 180 °C was separated to gas oil boiling point range main product (C10–C22 hydrocarbons up to the boiling point of 360 °C) and to residual fraction by vacuumdistillation. All product yields are based on the weight of the feedstock. The properties of feedstocks and products were determined according to the specifications given in EN 590:2013 standard for diesel fuel, and with standardised calculation methods. Additionally, the composition of the obtained liquid organic product was determined by high temperature gas chromatography. 3. Results and discussion 3.1. Most important results of the hydrotreating (HDS/HDO) step The yield of the main hydrogenated product fraction slightly decreased with increasing the temperature (Fig. 9). The conversion
of the triglyceride part of the feed was nearly complete even at the mildest reaction parameters, thus with the increasing temperature, partially because of the gaseous products (mainly propane, CO, CO2) and water forming during the triglyceride hydrogenation, and partially because the cracking reactions came to the front, that caused the decreasing yield. In addition, the conversion of the high sulphur content (0.84-1.14%) of the feed to hydrogen sulphide, also clearly reduced the yield. As a function of the pressure it can be seen that with increasing pressure, the yield slightly decreased above 320 °C, also as a result of the hydrocracking reactions. The decrease in LHSV favoured the triglyceride conversion but it increased the hydrocracking activity of the catalyst, too, so the yield decreased with decreasing LHSV (Fig. 10). The yields of the fraction in the gas oil boiling point range (in case of 10% waste lard content 91.7–93.6%) approached well the ⁄ theoretical yields (in case of 10% waste lard content ⁄94.7–95.0%) during the hydrogenation step. The theoretical yield is calculated by accounting only the reactions resulting propane splitting and oxygen and sulphur removal. Fig. 11 displays the yield of the main hydrogenated product in function of the waste lard content of the feedstock. By increasing the waste lard content of the feedstock, the yield of the liquid product decreased because the conversion of triglyceride resulting not only valuable paraffins, but gas products (propane, CO2, CO, CH4) and water, too, decreasing the yield based on the weight of the feedstock. Table 3 and Figs. 12–15 show that the main properties of the product fraction obtained in the hydrogenation step are quite different from the properties of the feedstock (Tables 1 and 2). During
Fig. 9. Yield of the main hydrogenated product as a function of temperature and pressure (10% waste lard content, LHSV: 1.0 h
1
).
Fig. 10. Yield of the main hydrogenated product as a function of temperature and LHSV (10% waste lard content, pressure: 80 bar).
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
6
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 11. Yield of the main hydrogenated product as a function of temperature and waste lard content (LHSV: 1.0 h
1
, pressure: 50 bar.)
Table 3 Properties of the main product fractions after the hydrogenation step. Process parameters Waste lard content of the feedstock
10%
Temperature (°C) Pressure (bar) LHSV (h 1)
360 50 1.0
30% 380 80 0.75
360 50 1.0
380 80 1.0
Properties of the gas oil boiling point range product fractions 3
Density on 15.6 °C (kg/m ) Kinematic viscosity on 40 °C (mm2/s) Sulphur content (mg/kg) Nitrogen content (mg/kg) Total aromatic content (%) Polycyclic aromatic content (%) CFPP (°C) Cetane number
844.0 4.55 38 3 23.1 2.9 8 55
EN 590:2013 838.1 4.50 7 9 17.8 1.8 6 55
the hydrogenation, the triglyceride content is converted mainly to normal paraffins, a part of the aromatic content is saturated, and the sulphur, nitrogen and oxygen content of the feedstock are greatly decreased. Because of the increasing paraffin content, the cetane number of the product fractions is increased as well. The CFPP value of the products was quite high, because the heavy gas oil part of the feed (which has high CFPP value, too) and because of the increasing content of normal paraffins (originating from the triglyceride part). The sulphur content of the gas oil boiling range fraction decreased with the increasing temperature, because of increasing
832.2 4.24 12 2 13.0 2.4 12 60
831.2 4.39 6 2 9.0 1.6 11 62
820–845 2.00–4.50 Maximum 10.0 No restriction No restriction Maximum 8.0 20 (winter) to +5 (summer) Minimum 51
desulphurisation activity of the applied catalyst (Fig. 12). During the experiment with the increase of the temperature and pressure, desulphurisation took place in a considerable extent, but only in case of 80 bar pressure and 380 °C temperature we could achieve the value <10 mg/kg sulphur content in the product. In any other case, the sulphur content of the product was higher than the maximum allowable value of the EN 590:2013 standard. The main cause of this may be the high oxygen heteroatom content of the feedstock originating from the triglyceride part (10% triglyceride in the feedstock means about 1.1% of oxygen content). During the triglyceride hydrogenation, after splitting the propane,
Fig. 12. Sulphur content of the main hydrogenated product as a function of temperature and pressure (10% waste lard content, LHSV: 1.0 h
1
).
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
7
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 13. Total aromatic content of the main hydrogenated product as a function of temperature and pressure (10% waste lard content, LHSV: 1.0 h
Fig. 14. Viscosity of the main hydrogenated product as a function of temperature and pressure (10% waste lard content, LHSV: 1.0 h
Fig. 15. Density of the main hydrogenated product as a function of temperature and pressure (10% waste lard content, LHSV: 1.0 h
the oxygen removal is faster from the linear fatty acid chains (higher reaction rate) than the desulphurisation of cyclic/polycyclic sulphur compounds. The saturation of the aromatic compounds occurred, too, during the hydrogenation step, but for the better efficiency, higher pressures are needed. As it can be seen in Fig. 13, in the case of the lowest applied pressure (20 bar), the aromatic content of the product remained nearly the same as in the feedstock. This was due to the typical aromatic compounds in the feedstock gas oil fraction,
1
1
).
).
1
).
namely the aromatic sulphur containing molecules (like dibenzothiophenes and its derivatives). In the case of these kinds of compounds, the effective desulphurisation and aromatic saturation requires severe process parameters. The aromatic content reaches a minimum about 360 °C and above this temperature value, the aromatic content of the products was higher again because of the thermodynamic inhibition of the exothermic dearomatisation reactions (more aromatic compounds remained in the product).
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
8
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 16. Yield of the isomerised product as a function of temperature and pressure on the basis of the basic feedstock (10% waste lard content, LHSV: 1.0 h
1
).
Fig. 17. CFPP (random samples) and cetane number (average) values of the hydrogenated and isomerised final product.
During the hydrogenation experiments, the kinematic viscosity of the products decreased with increasing temperature and pressure (Fig. 14), due to the triglyceride conversion, the aromatic saturation and cracking reactions. Because of the high viscosity of the feedstock gas oil, the viscosity of the product was above the maximum value prescribed in the standard. Due to the aforementioned reasons the density of the main hydrogenated products was also above the value of the valid standard (Fig. 15). The density of the hydrogenated main products decreased as an effect of the triglyceride conversion and the aromatic saturation, but above 360 °C it correlated with the aromatic content, because of the high density of the aromatic compounds. This correlation to the aromatic content can be observed in the change of the product viscosity, too, (Fig. 14). Because of the high CFPP values and the higher than standard sulphur values, it is necessary to submit the hydrogenated product to an additional process, hydroisomerisation. During this, a part of the n-paraffin content in the product is converted to isoparaffins, which has lower CFPP values, but unfortunately slightly lower cetane numbers as well [21,22]. Furthermore the sulphur content continues to fall at this second ‘‘hydrotreating’’ process. It shall be noted that in order to increase the ratio of alternative source derived components, we performed such experiments also in which the feedstock contained 2–5% gas oil boiling point product fraction of a thermal cracking process (550 °C and 6 bar) with
waste polypropylene feedstock. The obtained hydrotreated intermediate product had the same quality as the previously described products. However the CFPP value of these was 3–5% higher, which was due to the high paraffin and olefin content (84% total) of the feedstock component. At the applied favourable process parameters, the olefin hydrocarbons were practically hydrogenated completely (iodine number of products: <3 gI2/100 g). 3.2. Most important results of the isomerisation Due to the not adequate cold flow properties of the hydrogenated product (straight run heavy gas oil fraction and increased n-paraffin content via the hydrogenation of the triglyceride and fatty acid content) a second, isomerisation step can be necessary, if the produced bio gas oil containing gas oil fraction is utilised in cooler than tropical or Mediterranean climates. During this step, the high n-paraffin content of the intermediate feedstock is converted to isoparaffins, which have lower pour points, but slightly lower cetane number values, too. Isomerisation was carried out on a Pt/SAPO-11 isomerisation catalyst [21]. In the isomerisation step, the product yields varied in the range of 88.1-90.4% on the basis of the triglyceride containing feedstock (Fig. 16). With increasing temperature, especially above 340 °C, the cracking activity of the catalyst steeply increased resulting loss in the yield of the liquid product.
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003
P. Baladincz, J. Hancsók / Chemical Engineering Journal xxx (2015) xxx–xxx
Fig. 17 clearly shows that during the isomerisation step, the cold flow properties (CFPP value in this case) improved, but the cetane number values decreased. However, specifically the improvement in the cold properties is greater than the cetane number reduction, so a good balance between these properties can be set during the isomerisation process. The cetane number of the main product fractions was about 56– 58 after the hydrogenation step (in case of 10% waste lard content), while their CFPP values were about 8 °C. After the isomerisation step, the cetane number was 54, while the CFPP value was between 15 and 20 °C. 4. Conclusions During the hydroconversion of waste animal fat containing (530%) gas oil (sulphur content: 1.2%, polycyclic aromatic content: 15.1%, total aromatic content: 40.4%) over sulphided NiMo/Al2O3 catalyst, the yields of the gas oil boiling point range main product fraction well approached the theoretical yields at the most favourable process parameters (T: 340 °C, p: 50 bar, LHSV: 1.0 h 1). For example, in the case of 10% waste lard containing feedstocks, the yield was between 95.1% and 95.5% while the theoretical yield is 96.7–97.0%. During the experiments, the triglyceride part was fully converted, and the sulphur and nitrogen heteroatom removal and aromatic saturation of the gas oil part also occurred with high conversion. The cetane number of the products obtained in the case of 10% waste lard containing gas oil was 56–58 after the hydrogenation, while their CFPP values were about +8 °C. After the isomerisation step, which served for the improvement of the cold flow properties, the product yields were 91.4-92.4% on the basis of the triglyceride containing feedstock. The cetane number of the final product was 54-55, while the CFPP value between 15 and 20 °C. The sulphur and polycyclic aromatic content of the final products comply with the valid standard EN 590:2013 for diesel gas oils, as well (sulphur content <10 mg/kg; polycyclic aromatic content <8%). During the product analysis it was determined that these kinds of waste fatty materials can be appropriate feedstocks for the production of bio component containing gas oils after proper pretreatment. In addition, these materials are cheap, their iLUC value is practically zero, and as waste materials they count as twofold inside the EU when calculating the ratio of renewable fuels respectively [23]. Acknowledgements This work was supported by the European Union and co-financed by the European Social Fund – Hungary in the frame of the TAMOP-4.1.1.C-12/1/KONV/2012-0017 and TAMOP-4.2.2.A-11/1/ KONV-2012-0071 projects.
9
References [1] BP Plc., BP Statistical Review of World Energy 2014, June, 2014.
Please cite this article in press as: P. Baladincz, J. Hancsók, Fuel from waste animal fats, Chem. Eng. J. (2015), http://dx.doi.org/10.1016/j.cej.2015.04.003