2 nd International Conference on Sustainable Energy and Resource Use in Food Chains, ICSEF 2018 Tar from pilot scale co-pyrolysis of biological dairy sludge and spruce wood chips Presenter: Alen Horvat alenhorvat@hotmail.com Co-authors: Marzena Kwapinska, James J. Leahy 1
Outline • Background - dairy sludge • Feedstock - biological diary sludge & spruce wood • What is pyrolysis? • What is tar? • SPA - tar sampling • Tar from pilot scale pyrolysis • Tar limits given for downstream applications • Tar reduction methods • Conclusions 2
Motivation for the study • Dairy industry in Ireland – 30 % of Irish agri-food export – 80 % of milk products is exported • Increase of milk production by 50 % by 2020 – increase in primary production will inevitably lead to an increase in generation of processing waste • Dairy Processing Technology Centre (DPTC) – Industry – academic collaborative research and innovation centre (5 universities and 2 research institutes, over 100 employees) 3
Wastewater sludge from milk processing 1,2 • DAF sludge (chemical sludge) mixture of fat, oil, grease and suspended solid particles removed from raw effluent together with some proteins and minerals (P) by Dissolved Air Floatation. • Biological sludge organic material, containing suspended solids, microbial biomass, and non-biodegradable pollutants such as heavy metals resulting from biological aerobic or anaerobic waste water treatment processes. 1. Ryan and Walsh, The Characterisation of Dairy Waste and the Potential of Whey for Industrial Fermentation ; 2016. 2. Pankakoski, et al., A survey of the composition, treatment and disposal of sludge from dairy effluent treatment plants ; 2000. 4
Current use of dairy sludge - challenges • ─ Local oversupply due to high transport costs. Composting 3 ─ Local oversupply can lead to accumulation of certain substances in soil through annual application over • Anaerobic digestion 4 many years. ─ Odour and pathogens. • Land spreading 5 – Nutrient Management Plan approved by EPA ─ Sludge is tested only for NPK content before land application. – Farmers obtain sludge for free ─ Irish weather conditions. ─ Milk fat is not easily bio-degraded and causes technological issues 6,7 . 3. Elvira et al., Bioresource Technology 1998, 63 , 205 – 211. 4. Najafpour et al., Am. Eurasian J. Agric. Environ. Sci 2008, 4 , 251 – 257. 5. Collins et al., Food Safety Implications of Land-spreading Agricultural, Municipal and Industrial Organic Materials on Agricultural Land used for Food Production in Ireland ; 2008. 6. Petruy and Lettinga, Bioresource technology 1997, 61 , 141 – 149. 7. Watkins and Nash, Open Agric J 2010, 4 , 1 – 9. 5
Pyrolysis as a waste treatment - challenges • ─ The potential application of pyrolysis products greatly Pathogens removal depends on the presence of various contaminants. • Reduced volume ─ Release of contaminants: tar , NH 3 , HCN, HCl, H 2 S → gas cleaning is compulsory. • Pyrolysis of sludge can cover its ─ Release and fate of heavy metals. 8 ( heat for drying and own heat demand pyrolysis ). 8. Salman et al., Poster presentation, SMICE 2018, 23-25 May, Rome, Italy. 6
Objectives • Investigate the potential of pyrolysis as a waste treatment and energy recovery technology for dairy sludge. • In the pilot scale pyrolysis reactor two feedstock were tested. – Dairy sludge blended with spruce wood chips (50/50) – Spruce wood chips as a reference feedstock • Detailed tar analysis including the quality and quantity of tar in the raw pyrolysis gas with respect to the tar limits given for downstream applications and tar removal methods. 7
Feedstock – biological diary sludge & spruce wood • Dairy sludge rich on macronutrients Table 1. Properties of biological dairy sludge, spruce wood chips, and the blend of biological dairy sludge + spruce wood chips (50/50). N, P, K, Ca, Mg and S. Proximate analysis (wt. %) Dairy Spruce wood (50/50) sludge chips Moisture (after air drying) 20.0 4.7 10.9 Volatile Matter (d.b.) 59.7 84.1 - • Bulk density: Ash (d.b.) 31.8 0.4 14.7 Fixed Carbon a (d.b.) 17.0 15.5 - – Air-dried dairy sludge 550 kg m -3 LHV (d.b.) (MJ kg -1 ) 14.3 17.6 16.4 Ultimate analysis (d.b.) (wt. %) – Spruce wood chips 197 kg m -3 N 5.8 0.2 3.0 C 35.9 50.7 42.9 H 5.6 6.6 6.1 S 0.8 0.02 0.4 Cl 0.2 0.005 0.1 O a 19.9 41.9 32.7 a Calculated by difference, d.b. − dry basis. Fig. 1. (left) air-dried dairy sludge granules; (right) spruce wood chips. 8
Feedstock – biological diary sludge & spruce wood TGA / DTG in N 2 atmosphere cellulose hemicellulose protein lignin fat Fig. 2. Thermo-gravimetric analysis showing TGA-percentage and DTG-rate for (left) air dry biological dairy sludge; (right) spruce wood chips. 9
What is pyrolysis? • It is an endothermic thermo-chemical process, conducted in an inert atmosphere, carbonaceous material is thermally decomposed into gaseous, liquid and solid products 9 . • Feeding rates in Tar sampling the range 40.9 - 68.6 kg d.a.f h -1 . • Pyrolysis temperatures in the range 700 - 770 ° C. Fig. 3. Pilot scale facility consisted of four main sections: feeding system, pyrolysis reactor, gas conditioning section and a gas engine. 9. Basu, Biomass gasification and pyrolysis: practical design and theory ; Academic press, 2010. 10
What is tar? • Tar is defined as aromatic hydrocarbons in a wide range of molecular size and polarity properties 10 . • Undesirable pyrolysis product causing installation malfunction if upon condensation. Fig. 4. Condensed tar from gasification rig at UL. 10. Rabou et al., Energy & Fuels 2009, 23, 6189 – 6198. 11
Solid Phase Adsorption (SPA) - tar sampling • Tar from the hot pyrolysis gas is condensed and adsorbed onto aminopropylsilane sorbent, followed by solvent extraction and chromatographic analysis. Fig. 5. (1) SPA sampling port, (2) taking SPA tar sample, (3) SPA cartridges, (4) tar extraction. 12
Tar from pilot scale pyrolysis - identification • Main differences in tar composition. (1) a large number of nitrogen-containing tar compounds, (2) larger number of polycyclic aromatic hydrocarbons (PAHs). Biological sludge + spruce wood Spruce wood Fig. 6. GC-MSD chromatograms of pyrolysis tar (left) biological dairy sludge + spruce wood chips, (right) spruce wood chips. 13
Table 2. Identified pyrolysis tar compounds with the chromatographic retention times. Biological dairy sludge + spruce wood chips Spruce wood chips Tar compound Retention time (min) Tar compound Retention time (min) 1 2-Methylpropanenitrile (Isobutyronitrile)* 2.175 / 2 5-Methylcyclopenta-1,3-diene 2.268 / 3 2-Butenenitrile* 2.350 / 4 Benzene 2.928 Benzene 2.978 5 Pyrazine* 4.332 / 6 Pyridine* 4.707 / 7 1 H -Pyrrole* 5.280 / 8 Toluene 5.340 Toluene 5.385 9 2-Methylpyridine* 7.320 / 10 4-Methylpyrimidine* 7.507 / 11 4-Methylpentanenitrile* 8.260 / 12 Ethylbenzene 8.758 Ethylbenzene 8.832 13 1,2/1,3/1,4-Dimethylbenzene 9.067 1,2/1,3/1,4-Dimethylbenzene 9.075 (o/m/p Xylene) (o/m/p Xylene) 14 / Ethynylbenzene 9.543 15 Ethenylbenzene (Styrene) 9.883 Ethenylbenzene (Styrene) 9.888 16 2-Methyl-2-cyclopenten-1-one 10.613 / 17 1-Ethyl-3-methylbenzene (3-Ethyltoluene) 12.445 / 18 Benzenecarbonitrile (Benzonitrile)* 13.333 / 19 1-Ethyl-2-methylbenzene (2-Ethyltoluene) 13.597 / 20 Benzenol (Phenol) 13.857 Benzenol (Phenol) 13.618 21 / 1-Benzofuran 13.675 22 1 H -Indene 15.182 1 H -Indene 15.203 23 2/3/4-Methylphenol (o/m/p Cresol) 16.062 2/3/4-Methylphenol (o/m/p Cresol) 16.168 24 2/3/4-Methylphenol (o/m/p Cresol) 16.795 2/3/4-Methylphenol (o/m/p Cresol) 16.965 25 / 7-Methyl-1-benzofuran 17.127 26 1,2-Dihydronaphthalene 18.650 1,2-Dihydronaphthalene 18.678 27 2,5-Dimethylphenol 18.885 / 28 Naphthalene 19.500 Naphthalene 19.543 29 2-Methylnaphthalene 22.613 2-Methylnaphthalene 22.625 30 1-Methylnaphthalene 23.052 1-Methylnaphthalene 23.068 31 1,1'-Biphenyl 24.895 1,1'-Biphenyl 24.920 32 2-Ethenylnaphthalene 26.138 2-Ethenylnaphthalene 26.167 33 Acenaphthylene 26.583 Acenaphthylene 26.610 34 / Dibenzo[b,d]furan 28.290 35 9 H -Fluorene 29.778 9 H -Fluorene 29.800 36 / 4-Methyldibenzo[b,d]furan 31.103 37 Phenanthrene 34.070 Phenanthrene 34.090 38 Anthracene 34.285 Anthracene 34.333 39 / 4H-Cyclopenta[def]phenanthrene 36.825 40 / 2-Phenylnaphthalene 37.990 41 Fluoranthene 39.550 Fluoranthene 39.550 42 Pyrene 40.468 Pyrene 40.470 43 / 11 H -Benzo[b]fluorene 42.320 44 / Cyclopenta[cd]pyrene 46.133 45 Tetraphene (Benz[a]anthracene) 46.215 Tetraphene (Benz[a]anthracene) 46.270 46 Benzo[k]fluoranthene 52.013 Benzo[k]fluoranthene 52.008 14 47 Benz[e]acephenanthrylene 52.238 Benz[e]acephenanthrylene 52.235
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