Torwash® Sewage Sludge Treatment

Transcript

TORWASH® sewage sludge treatment Increased biogas production, highly-efficient dewatering and phosphate recovery A.J. Grootjes, H. Kuipers, J.R. Pels, M.C. Carbo, J. Vogelaar Symposium slibontwatering, Utrecht 14 September 2017 www.ecn.nl Table of Contents • Introduction to TORWASH® • What can TORWASH® do for sewage sludge? – Two process diagrams • Experimental results – dewatering – elemental distribution of elements – digestion of effluent • Process configuration for maximum biogas (methane) and energy yield • Controlling the fate of phosphorus  recovery as fertilizer 2 Waar het mee begon 3 Waar het mee begon • Bestuur ZZL wil minder en droger slib, meer duurzame energie en grondstoffen • 2015 1- 1,5 % droger door procesvoering • 2018 10% minder slib door Ephyra • 2018 -2020 dosering kationen ??? • 2017-2030 groei in Flevoland • ZZL na 2018 34.000 ton slibkoek, circa € 2,5 miljoen, (nu in NL circa 110 miljoen) • Verbetering ontwaterbaarheid minimaal • Er blijft altijd slib over!! 4 “haal eruit wat erin zit, doe datgene weg waar je niets meer mee kan en doe dit zo goedkoop mogelijk” 5 Hoe? “zo goedkoop mogelijk” Kunnen we de hoeveelheid slib niet verder verkleinen? en is er nog een waarde aan toe te kennen? In 2015 mogelijk het antwoord gevonden: TORWASH® ??? 6 ECN acts as a bridge between science and corporate innovation Mission We develop knowledge and technologies that enable a transition to a sustainable energy system Not-for-profit research institute Founded in 1955 5 Commercial licensing deals / year 500 Employees +/-20 patents a year € 80 M annual turnover 7 TORWASH® = Wet torrefaction + Washing • Upgrading of biomass feedstocks that have too much water or too much salt • Under pressure in liquid water 150-250°C  changes in biomass structure that weaken fibres and releases water + ions • Unique concept: – – – – It enables efficient mechanical dewatering It enables removal of salts to a high degree Mild process conditions allow digestion of the effluent ECN patent WO 2013/162355 • Goal: maximum energy in form of 2 fuels – Solid biomass pellets – Biogas from digestion of effluent • Latest development: controlled recovery of phosphorus 8 TORWASH® : A multi-purpose process for green solutions clean solid fuel grass/straw biogas manure reduced transport and disposal costs husks/shells TORWASH® seaweed sewage sludge empty fruit bunches biochar fertilizers hygienic animal bedding densification of semi-finished product 9 Why is TORWASH® unique? Because: • It enables efficient mechanical dewatering • It opens up biomass and thus enables complete removal of salts • Its mild process conditions allow digestion of the effluent to biogas • It doesn’t use additives: – – – – no catalysts no pH control no flocculants no enzymes • ECN patent WO 2013/162355 Why using TORWASH® at a sewage treatment plant? • Dewatering turns wet sludge  fuel – – – – – – Volume reduction = saving disposal costs Solid fuel could be directly suitable for thermal conversion Biogas from effluent locally used in gas engine Less costs for flocculant (polyelectrolyte = PE) Independent plant operation Contributes to objectives Grondstoffen en Energiefabriek PE may even have a negative influence on dewatering • Opportunities – P recovery from effluent – Solid fuel drying and pelleting  flexibility in logistics of sludge – In future, no more incineration, but….. – recovery of resource materials – applications in agriculture, provided that issues with heavy metals can be solved The TORWASH® promise Almere as an example Dry matter Volume [ton] Disposal costs* Centrifuge 8% 56 000 Existing Press 21% 21 000 M€ 1.3 Best Press 24% 19 000 M€ 1.1 THP 30% 15 000 M€ 0.9 TORWASH® 65% 3 100 M€ 0.2 * € 60 per ton “as received” in all cases repeatedly obtained for various raw materials • Amounts of sludge reduced from 21 to 3 kton/year • Potential savings on disposal costs € 1.1 million/year • Additional savings when polyelectrolyte (PE) is no longer needed: € 0.2 million/year TORWASH®  Digestion incinerator >60 wt% dry matter TORWASH® Reactor Press Dewatered cake Liquids Anaerobic Digester Liquid Effluent No Solids Sewage sludge 8-12 wt% dry matter 13 Digestion  TORWASH® >60 wt% dry matter Dewatered cake Press Liquids recycling TORWASH® Reactor 10 wt% dry matter Anaerobic Digester Slurry digested sewage sludge Filter Sewage sludge 8-12 wt% dry matter Liquid Effluent No Solids 14 Visible effect of TORWASH® Sludge from AWZI Almere before and after TORWASH® • Left: untreated sludge • Right: TORWASHed sludge Project TORWASH® of sewage sludge • Experimental programme – – – – – Two kinds of sewage sludge: digested and undigested (Three kinds of manure (cows, pigs, chicken)) Testing in 20L autoclave with sewage sludge “as received” Slurry pressed in Carver Die (2¼ inch) Digestion tests, batch 18-25 days • Highly efficient mechanical dewatering – modern sludge presses reach 21-24% dry matter – manure separator: up to 20% dry matter Undigested sludge Digested sludge Manure Sludge before TORWASH® 8-12% 8-12% 5-20% Press cake after TORWASH® 67% 61% 67% 16 TORWASH® of undigested sludge Distribution of elements 120% fraction to effluent fraction to solids fraction to solids and effluent 100% K and Cl: >90% in effluent 80% nutrients mostly in effluent 60% Si, Al, Ca, Fe to solids 40% 20% 0% Mass Energy Si Al Ca * Mass and Energy in solid product Fe N P K Cl S Cr Cu Pb Zn heavy metals stay in solids  incinerator 17 TORWASH® of digested sludge Distribution of elements 120% fraction to effluent fraction to solids fraction to solids and effluent 100% comparable results, e.g. > 90% Cl in effluent 80% 60% Si, Al, Ca, Fe and heavy metals all in solids 40% nutrients: • 40% K in solids • 95% P in solids 20% 0% Mass Energy Si Al Ca Fe N P K Cl S Ni Cd Cr Cu Pb Zn 18 Fuel Quality – undigested sludge Moisture Ash 550°C Ash 815°C Non-digested sludge – input Non-digested sludge – product Wood chips Coal mixture % 95 33 8 3 % 16 21 2.6 - % 16 20 2.1 12 Non-digested sludge – input Non-digested sludge – product Wood chips Coal mixture C % 42 49 48 72 H % 6.2 6.3 6.5 4.5 N % 6.9 4.1 0.5 1.4 Values are on dry basis, except moisture Volatile Matter Calorific Value (HHV, dry) % MJ/kg Non-digested 69 Sludge (input)19 Non-digested 64 Sludge - Product 22 Wood chips 79 - green 19 Coal mixture 32 24 S % 0.8 0.7 0.04 0.85 Cl mg/kg 2100 260 300 260 Calorific Value (LHV, as received) MJ/kg negative 13 16 22 municipal waste 10 MJ/kg (LHV, wet) TKI-BBEG EnCORE EnCORE (Efficiente Cascadering en Opwerking Rioolslib voor Energie-neutrale bedrijfsvoering) Doel: Het doel is meer biogas en grondstoffen uit zuiveringsslib te produceren t.o.v. een klassieke slibvergister, door adaptatie en optimalisatie van de combinatie van een 'Upflow Anaerobic Sludge Blanket' (UASB) vergister van slib dat middels TORWASH® is voorbehandeld. Activiteiten: • Kleine schaal vergistingstesten • Pilotschaal TORWASH® testen (Almere) • Adaptatietesten effluentvergisting • Kwantificeren fosfaat terugwinning Na EnCORE: opschalen naar volleschaal demo 20 Digestion tests • Batch tests at OPURE – 18-25 days – Filtered effluent after TORWASH® • Measurements – COD measurements before and after – biogas production – methane content  methane production • For TORWASH® assessment purposes, digestibility is defined as the COD conversion 21 Digestion of TORWASH® effluent Undigested vs. digested sewage sludge • Digestion expressed as conversion of COD 100 90 • Green = undigested sludge • Blue = digested sludge COD conversion [%] 80 70 60 • Effluents equally well digestible 50 40 30 20 10 0 Dry matter content After centrifuge, before TORWASH® 8% w/w After TORWASH® and dewatering 61% w/w COD conversion 71% Biogas yield 11.1 Nm3/m3 Methane content 69% v/v Methane yield 7.6 Nm3/m3 Temperature [°C]  22 Methane and energy yield in different configurations • TORWASH® + digestion of only effluent gives the same amounts of biogas as TPH + full classic digestion (= +10% compared to classic digestion) • TORWASH® of digestate after classic digestion: – Digestion of effluent gives extra biogas, solid product easy to dewater Process configuration (starting with undigested sludge) Methane Production [Nm3/kg organic dm] Dry matter content of press cake after dewatering [wt%] Total energy production * [MJ/kg organic dm] Current situation Classic digestion Classic Digestion TORWASH®  with TPH IC(X) digestion 0 0.13 0.14 0.14 0.19 21 – 24 21 – 24 max. 30 > 65 > 60 2.8 6.3 7.0 11.7 12.2 Classic Digestion  TORWASH®  IC(X) digestion * Energy production is sum of thermal values of two fuels, biogas and press cake, based on LHV 23 P-recovery via TORWASH® • Sewage sludge and manure contain large amounts of phosphorus • Solubility of phosphorus changes with TORWASH® chemistry – Temperature is the most important parameter • Fate of P can be controlled in TORWASH® – 95% P in solids is possible – 95% P in effluent is also possible • Effluent from TORWASH® may contain double the amount of P compared to effluent from TPH 24 Summary • Lab tests have been successful for both digested and undigested sludge • Pilot TORWASH® reactor will be tested (EnCORE project) • Main result: Sewage sludge converted into solid fuel and biogas – – – – – Chemical changes enable efficient dewatering and salt removal Digested and undigested sludge: press cake > 60% dry matter Effluent from TORWASH® digestible TORWASH® of digested sludge gives extra biogas Two TORWASH® process configurations that boost energy production • Fate of Phosphorus can be controlled for recovery – Temperature determines fate of P and other elements 25 Back to Almere • Input TORWASH® : non-digested sludge from centrifuge with 8-9% dry matter – Non-digested sludge from centrifuge (8-9% dry matter) – 4500 ton (dry matter) instead of 21000 ton • Output TORWASH® : – – – – – – Press cakes with 65% dry matter content  3100 ton press cake Potentially saving M€ 1.1 in disposal costs per year Combustion at AEB waste incinerator  renewable power and heat Effluent digestible in UASB-type reactor: biogas  more renewable heat and power Effluent after digestion recycled to treatment plant Optional: P-recovery • Extrapolated to The Netherlands…. € 100 million per year less disposal costs Consortium This presentation was made in close cooperation with Water Authority Zuiderzeeland ECN Westerduinweg 3 1755 LE Petten The Netherlands P.O. Box 1 1755 ZG Petten The Netherlands T +31 88 515 49 49 F +31 88 515 44 80 [email protected] www.ecn.nl 27