Distribution of ash forming elements during pyrolysis of municipal - PowerPoint PPT Presentation

6 th International Conference on Sustainable Solid Waste Management Distribution of ash forming elements during pyrolysis of municipal wastewater sludge and sludge from milk processing factories Marzena Kwapinska, D. A. Agar, J.J. Leahy

Pyrolysis – an alternative to land spreading of sludge - challenges - The potential application of all pyrolysis • Pathogens removal products greatly depends on the presence of • Reduced volume various contaminants. • Pyrolysis of sludge can fulfil - Release and fate of heavy metals. its own heat demand * (necessary heat for drying - Release of contaminants NH 3 , HCl, HCN, H 2 S – water scrubbing is compulsory and pyrolysis) • Nutrients recovery * Salman C.A, S. Schwede, H. Li, E. Thorin, J. Yan: Integrated concept fpr sludge pyrolysis in waste water treatment plants for biofuel production and nutrients recovery, SMICE 2018

Objectives Investigate the potential of pyrolysis as a conversion technology for sludge • Examine properties of dairy sludge (DS) and sewage sludge (SS) • Pyrolysis of sludge in laboratory reactor in order to measure the amount of pyrolysis products and determine their properties • Investigate distribution of major (Al, Ca, Fe, K, Mg, Na, P, S, Si) and minor (As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se, Ti, V and Zn) ash forming elements between solid and liquid pyrolysis products

Materials Dairy Sludge (DS): Sewage Sludge (SS): - DS-1 biological sludge, 13 % solids - SS-1 biological sludge, dried pellets - 91 % solids - DS-2 biological sludge, 32 % solids - SS-2 biological sludge, dried granules -94 % solids - DS-3-DAF sludge from dissolved air - SS-3 biological sludge, belt press cake -15 % solids floatation, 32 % solids Bench drying at ambient temperature

Properties of dried sludge ash fixed C volatiles 100 100 90 90 Properties DS-1 DS-2 DS-3- SS-1 SS-4 80 80 wt. % DAF 70 70 C 30.0 39.3 43.3 37.3 39.0 60 60 wt. % H 4.6 5.6 6.9 5.5 5.4 50 50 N 5.4 7.7 1.6 5.7 6.8 40 40 S 0.5 0.6 0.1 1.0 0.7 30 30 O 23.2 23.2 11.6 17.9 19.2 20 20 10 10 0 0 DS -1 DS -2 DS-DAF -1 SS -1 SS -2 SS -3  high volatile matter content  low fixed carbon content in DS-DAF-1

Major ash forming elements Dairy Sludge Sewage Sludge SS1 SS2 SS4 DS-1 DS-2 DS-3-DAF 600000 600000 500000 400000 400000 200000 300000 70000 40000 mg/kg of dry sludge mg/kg of dry sludge 35000 60000 30000 50000 25000 40000 20000 30000 15000 20000 10000 5000 10000 0 0 Al Ca Fe K Mg Na P S Si Al Ca Fe K Mg Na P S Si - Si content was the highest among all elements for both sludge types (higher in SS (270-400 g/kg) than in DS (150-300 g/kg)) - Similar content of Na (20 - 30 g/kg), K (3 – 9 g/kg), P (12 - 18 g/kg) and S (1 - 4 g/kg) in all sludge samples - Al and Ca content similar in all SS but significant difference in DS - Fe and Mg content higher in SS than in DS but large differences between samples

Minor ash forming elements Sewage Sludge Dairy Sludge 450 2000 1500 DS-1 DS-2 DS-3-DAF SS1 SS2 SS4 1000 400 450 350 mg/kg of dry sludge 400 mg/kg of dry sludge 300 350 250 300 200 250 200 150 150 100 100 50 50 0 0 As Ba Cd Co Cr Cu Hg Mn Ni Pb Sb Se Ti V Zn As Ba Cd Co Cr Cu Hg Mn Ni Pb Sb Se Ti V Zn - In general content of heavy metals is higher in SS ( Ti, Zn, Cu, Ba and Mn four times higher than in DS also Cr, Pb, Ni and V ) - Similar concentrations of Hg with trace amounts of Se and Sb in all sludge samples - SS samples contained trace amounts of As, Co and Cd

Laboratory scale fixed bed pyrolysis Experimental set-up Temperature 700°C Residence time 10 min quartz tube reactor - mass of char condenser cooler - mass of liquid (oil and aqueous) - mass of gas by difference

Pyrolysis of dried sludge Mass balance Chars – pyrogenic carbonaceous material Properties, DS-3- Solid wt. % db. DS-1 DS- 2 DAF SS-1 SS-2 Sample product, Liquid, Gas, Ash content 75.47 66.32 81.88 69.4 71.21 wt. % wt. % wt. % Volatile matter 4.05 6.77 14.48 3.2 16.02 DS-1 30.5 37.2 32.3 Fixed carbon 20.48 26.91 3.63 27.4 12.77 DS-2 39.7 37.9 22.5 C, db. 20.00 27.48 10.11 11.7 8.56 DS-3-DAF 37.5 14.7 47.8 H, db. 0.40 0.31 0.55 28.68 28.11 SS-1 44.8 25.7 29.5 N, db. 1.98 2.46 0.39 0.09 0.54 40.2 SS-2 - - S, db. 0.36 0.41 0.04 1.94 2.67 SS-4 36.5 33.2 30.3 O, db. 0.55 0.99 7.07 0.41 0.57 - 11 % of N was retained in the char

Pyrolysis char / pyrogenic solids – major elements Dairy Sludge Sewage Sludge SS1 SS2 SS4 DS-1 DS-2 DS-3-DAF 150 150 125 Mass fraction (%) 100 Mass fraction (%) 100 75 50 50 25 0 0 Al Ca Fe K Mg Na P S Si Al Ca Fe K Mg Na P S Si - 50 to 70 % of S was retained in the solids

Pyrolysis char / pyrogenic solids – minor elements Dairy Sludge Sewage Sludge DS-1 DS-2 DS-3-DAF SS1 SS2 SS4 200 200 175 175 150 150 Mass fraction (%) Mass fraction, % 125 125 100 100 75 75 50 50 25 25 0 0 As Ba Cd Co Cr Cu Hg Mn Ni Pb Sb Se Ti V Zn As Ba Cd Co Cr Cu Hg Mn Ni Pb Sb Se Ti V Zn - Cu, Cr, Mn, Ni, Pb, Ti, and Zn , most were retained in the char (pyrogenic solids) of both sludge types - only from 25 to 50% of Cd, Sb and Se was conserved in the char (pyrogenic solids)

Distribution of major and minor elements - between liquid products Sewage Sludge – SS-1 Dairy Sludge – DS-2 - Ca, Mg, Fe, P, Si, Al, Na and K char oil aqueous char oil aquoeous 200 200 predominantly retained in pyrolysis chars (pyrogenic solids) 150 150 Mass % Mass % 100 100 - substantial quantities of Al, K, Na and 50 50 Si and S were detected in pyrolysis oil and in the aqueous fraction. 0 0 Al Ca Fe K Mg Na P S Si Al Ca Fe K Mg Na P S Si 200 200 150 150 - The heavy metals and trace elements As, Ba, Cd, Se, Sb and Pb, Mass % Mass % 100 100 were also detected in the liquid products. 50 50 0 0 As Ba Cd Co Cr Cu Hg Mn Ni Pb Sb Se Ti V Zn As Ba Cd Co Cr Cu Hg Mn Ni Pb Sb Se Ti V Zn

Conclusions  Sewage sludge samples from different plants had similar properties while there were substantial differences in the proximate and ultimate properties between dairy sludge samples.  The concentration of P, K, Na and S was similar in SS and DS.  There were significant differences in concentration of Al, Ca and Fe between samples within the two tested groups.  The heavy metal content was much lower in the DS in particular: Cr, Pb, Ni, V and the content of Ti, Zn, Cu, Ba and Mn was four times lower then that in SS.

Conclusions  Both sludge types produced a significant quantity of pyrolysis solids from 30 to 40 % (DS) and from 36 to 45 % (SS) of the initial residue mass.  Distribution of major elements between pyrolysis products was similar for DS and SS, with Ca, Mg, Fe, P, Si, Al, Na and K predominantly retained in pyrolysis chars (pyrogenic solids).  However, substantial quantities of Al, K, Na and Si were detected in pyrolysis oil and in the aqueous fraction.  50 to 70 % of S was retained in the solids with significant quantity captured in the liquid fraction.  The heavy metals and trace elements were mainly retained in the pyrolysis chars (pyrogenic solids) with the exception of As, Ba, Cd, Se, Sb and Pb, which were also detected in the liquid products.

Thank you for you attention Marzena.Kwapinska@ul.ie “This work was supported by the Irish State through funding from the Technology Centres programme - Grant Number TC/2014/0016” And as a part of OF-PYRO project funded by the Environmental protection agency in Ireland