Tar from pilot scale co-pyrolysis of biological dairy sludge and - - PowerPoint PPT Presentation

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Tar from pilot scale co-pyrolysis of biological dairy sludge and - - PowerPoint PPT Presentation

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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:

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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

2nd International Conference on Sustainable Energy and Resource Use in Food Chains, ICSEF 2018

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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

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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)

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Wastewater sludge from milk processing

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  • 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
  • rganic material, containing suspended solids, microbial biomass, and

non-biodegradable pollutants such as heavy metals resulting from biological aerobic or anaerobic waste water treatment processes.

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  • 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.
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Current use of dairy sludge - challenges

  • Composting

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  • Anaerobic digestion

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  • Land spreading

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– Nutrient Management Plan approved by EPA – Farmers obtain sludge for free ─ Local oversupply due to high transport costs. ─ Local oversupply can lead to accumulation of certain substances in soil through annual application over many years. ─ Odour and pathogens. ─ Sludge is tested only for NPK content before land application. ─ Irish weather conditions. ─ Milk fat is not easily bio-degraded and causes technological issues6,7.

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  • 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.
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Pyrolysis as a waste treatment - challenges

  • Pathogens removal
  • Reduced volume
  • Pyrolysis of sludge can cover its
  • wn heat demand

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pyrolysis). ─ The potential application of pyrolysis products greatly depends on the presence of various contaminants. ─ Release of contaminants: tar, NH3, HCN, HCl, H2S → gas cleaning is compulsory. ─ Release and fate of heavy metals.

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  • 8. Salman et al., Poster presentation, SMICE 2018, 23-25 May, Rome, Italy.
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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.

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Feedstock – biological diary sludge & spruce wood

  • Dairy sludge rich on macronutrients

N, P, K, Ca, Mg and S.

  • Bulk density:

– Air-dried dairy sludge 550 kg m-3 – Spruce wood chips 197 kg m-3

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  • Fig. 1. (left) air-dried dairy sludge granules; (right) spruce wood chips.

Table 1. Properties of biological dairy sludge, spruce wood chips, and the blend of biological dairy sludge + spruce wood chips (50/50). Proximate analysis (wt. %) Dairy sludge Spruce wood chips (50/50) Moisture (after air drying) 20.0 4.7 10.9 Volatile Matter (d.b.) 59.7 84.1

  • Ash (d.b.)

31.8 0.4 14.7 Fixed Carbon a (d.b.) 17.0 15.5

  • LHV (d.b.) (MJ kg-1)

14.3 17.6 16.4 Ultimate analysis (d.b.) (wt. %) 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.

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Feedstock – biological diary sludge & spruce wood

TGA / DTG in N2 atmosphere

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  • Fig. 2. Thermo-gravimetric analysis showing TGA-percentage and DTG-rate for (left) air dry biological dairy sludge; (right) spruce wood chips.

protein fat hemicellulose cellulose lignin

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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.

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  • Fig. 3. Pilot scale facility consisted of four main sections: feeding system, pyrolysis reactor, gas conditioning section and a gas engine.

Tar sampling

  • Feeding rates in

the range 40.9 - 68.6 kgd.a.f h-1.

  • Pyrolysis

temperatures in the range 700 - 770 °C.

  • 9. Basu, Biomass gasification and pyrolysis: practical design and theory; Academic press, 2010.
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What is tar?

  • Tar is defined as aromatic hydrocarbons in a wide range of molecular size and

polarity properties

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  • Undesirable pyrolysis product causing installation malfunction if upon

condensation.

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  • Fig. 4. Condensed tar from gasification rig at UL.
  • 10. Rabou et al., Energy & Fuels 2009, 23, 6189– 6198.
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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.

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  • Fig. 5. (1) SPA sampling port, (2) taking SPA tar sample, (3) SPA cartridges, (4) tar extraction.
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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).

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  • Fig. 6. GC-MSD chromatograms of pyrolysis tar (left) biological dairy sludge + spruce wood chips, (right) spruce wood chips.

Biological sludge + spruce wood Spruce wood

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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 1H-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 (o/m/p Xylene) 9.067 1,2/1,3/1,4-Dimethylbenzene (o/m/p Xylene) 9.075 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 1H-Indene 15.182 1H-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 9H-Fluorene 29.778 9H-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 / 11H-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 47 Benz[e]acephenanthrylene 52.238 Benz[e]acephenanthrylene 52.235

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Tar from pilot scale pyrolysis - tar quantities

  • The total tar yields from spruce wood pyrolysis are on average 30 % higher than

yields from dairy sludge and spruce wood co-pyrolysis.

  • Total tar yields comprise about 0.5 wt. % of the initial weight of the feedstock.

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Table 3. Total gas chromatography detectable tar from three pyrolysis tests feeding a blend of biological dairy sludge + spruce wood chips and three tests feeding the spruce wood chips solely. Biological dairy sludge + spruce wood chips Spruce wood chips Test nr. gtotal tar Nm-3

dry gas

Pyrolysis tempetarure (°C) gtotal tar Nm-3

dry gas

Pyrolysis tempetarure (°C) 2a 10.01 700 11.18 700 2b 10.67 12.43 3a 7.25 700 12.17 735 3b 7.63 13.31 4a 10.32 770 11.54 740 4b 10.51 13.09

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Tar limits given for downstream applications

  • Acceptable total tar limits in the gas with regard to the requirements of common

downstream applications. Literature data

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  • Tar limits are given for tar groups divided according to the aromatic ring number.

Manufacturer's specification of internal combustion gas engine

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Table 4. Upper limits of biomass gasification tar. Application Tar (mgtotal tar Nm-3) Direct combustion No limit specified Syngas production 0.1 Industrial gas turbines < 5 Internal combustion engine 50-100 Table 5. Upper limits of gasification/pyrolysis tar given by internal combustion gas engine manufacturer. Tar group Tar (g MJ-1) Tar (g Nm-3) Calculated for gas calorific value 14.0 MJ Nm-3 Tar (mg Nm-3) 1 aromatic ring < 1.5 21.0 21000 2 aromatic ring < 0.2 2.8 2800 3 aromatic ring < 0.003 0.04 40 4+ aromatic ring

  • 11. Milne et al., Biomass gasifier’’Tars’’: their nature, formation, and conversion; 1998.
  • 12. Fuel Gas Specifications - Synthesis Gas (Syngas); IC-G-D30–004e ed.; 2016.
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Tar limits given for downstream applications

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Table 4. Upper limits of biomass gasification tar. Application Tar (mgtotal tar Nm-3) Direct combustion No limit specified Syngas production 0.1 Industrial gas turbines < 5 Internal combustion engine 50-100 Table 5. Upper limits of gasification/pyrolysis tar given by internal combustion gas engine manufacturer. Tar group Tar (g MJ-1) Tar (g Nm-3) Calculated for gas calorific value 14.0 MJ Nm-3 Tar (mg Nm-3) 1 aromatic ring < 1.5 21.0 21000 2 aromatic ring < 0.2 2.8 2800 3 aromatic ring < 0.003 0.04 40 4+ aromatic ring Table 6. The yields of tar groups classified according to the number of aromatic rings in the compound. . Biological dairy sludge + spruce wood chips Spruce wood chips Sum (gtar Nm-3

dry gas)

Sum (gtar Nm-3

dry gas)

Test nr. 1 ring 2 ring 3 ring 4+ ring Unknown Total tar 1 ring 2 ring 3 ring 4+ ring Unknown Total tar 2a 5.2 0.9 0.3 0.1 3.5 10.01 3.1 4.6 1.1 0.6 1.8 11.18 2b 4.6 1.2 0.3 0.1 4.4 10.67 3.4 5.1 1.3 0.7 1.9 12.43 3a 4.0 1.0 0.2 0.1 1.9 7.25 7.0 3.2 0.9 0.5 0.6 12.17 3b 4.1 1.3 0.3 0.1 1.9 7.63 7.6 3.6 0.9 0.6 0.6 13.31 4a 5.9 1.8 0.5 0.1 2.7 10.32 6.7 1.6 0.3 0.1 2.8 11.54 4b 6.0 2.0 0.5 0.1 1.9 10.51 8.2 1.7 0.3 0.1 2.8 13.09

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Tar reduction methods

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  • Physical treatments

– Dry: Cyclones, electrostatic precipitators, filters, adsorbents. – Wet: Spray towers (i.e. scrubber), wet electrostatic precipitators.

  • Chemical (i.e. catalytic) treatments

– Heavy metal based catalysts – Alkali metal & earth alkali metal based catalysts – Acid catalysts – Activated carbon catalysts

  • Thermal tar cracking

– At certain temperature for a certain residence time

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  • 13. Anis and Zainal, Renewable and Sustainable Energy Reviews 2011, 15, 2355–2377.
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Conclusions

  • The total gas chromatography detectable tar yields from spruce wood pyrolysis are

found to be on average 30 % higher than yields from dairy sludge and spruce wood chips co-pyrolysis.

  • Main difference in tar composition is a number of nitrogen-containing tar

compounds reflecting high nitrogen content in a dairy sludge feedstock.

  • According to given specification, both tested feedstock produced excessive yields
  • f 3 and 4+ aromatic rings tar calling for tar removal prior to combustion.

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2nd International Conference on Sustainable Energy and Resource Use in Food Chains, ICSEF 2018

“This work was supported by the Irish State through funding from the Technology Centres programme - Grant Number TC/2014/0016”

Thank you for your attention

alenhorvat@hotmail.com