AD Europe ( February 2011) Cleaning & Pre-Treatment of Biowaste - A Chance with Wet Digestion. Stephan Schulte, Torsten Rahn, Harry Wiljan

Transcription

1 AD Europe 2011 ( February 2011) Cleaning & Pre-Treatment of Biowaste - A Chance with Wet Digestion Stephan Schulte, Torsten Rahn, Harry Wiljan 1

2 Importance of an effective pretreatment Overview BTA Hydromechanical Pretreatment Anaerobic digestion Dewatered digestate & Composting References Outlook 2

3 Introduction Requirements on biowaste methanization plants: High process flexibility (fluctuating waste composition and amounts) High process stability and reliability Maximal biogas production Production of quality digestate for further composting The key lays in an high-efficient removal of contaminants before the anaerobic digestion 3

4 Introduction BTA is just refurbishing the 3 rd anaerobic digestion plant (Replacement of the exsiting pre-treatment by the BTA Hydromechanical Pretreatment References Verona Barcelona Ecoparc I Burgos Others in discussion These examples underline the importance of a flexible, robust and efficient pre-treatment system for the removal of contaminants 4

5 BTA Process Main process steps in an AD Plant according to the BTA Process 5

6 BTA Process - Possible Input Materials Municipal Solid Waste Food Waste Biowaste Commercial Waste 6

7 BTA Hydromechanical Pre-treatment Main objectives Disintegration of biodegradable waste to enhance the subsequent digestion process Removal of non-biodegradable contaminants bigger than 10 mm as a heavy fraction and a light fraction Efficient removal of the grit fraction (sand, little stones, glass splinters) smaller than 10 mm 7

8 BTA Hydromechanical Pre-Treatment The removal of impurities in the BTA Hydromechanical Pre-treatment occurs in two steps: 1) removal of coarse impurities > 10 mm in the BTA Waste Pulper (right side) and 2) removal of the grit fraction (< 10 mm) in the BTA Grit Removal System (left side) 8

9 BTA Waste Pulper Heavy Fraction Heavy fraction Stones Glass Metals Bones Batteries etc. 9

10 BTA Waste Pulper Light Fraction Light fraction Plastics Foils Wood 10 10

11 Organic Suspension BTA Waste Pulper - Suspension Dissolved Organics Defibered Organics Sand, Glass Splitters etc. ( Grit ) Foreign Material < 2% Particles < 10 mm 6-12 % TS Approximately 90% of the digesteable organics go into the digester 11 11

12 BTA Grit Removal System (GRS) Importance: Grit is rated one of the main reasons for technical and procedural problems in waste digestion plants, as for example: High abrasion in subsequent components (e.g. pumps) Clogging of pipes Sedimentation in digester tank 12 12

13 BTA Grit Removal System In the BTA Grit Removal System the grit fraction (sand, splitters of glass, mushrooms, etc.) is efficiently removed in an active process on the basis of centrifugal forces 13 13

14 Clean organic suspension Characteristics Dry matter content: 6 12% Homogeneous suspension Easy handling at anaerobic digestion Almost free of contaminants Already at this stage the impurities have been removed in a degree to meet, in most cases, the requirements for physical characteristics of the compost 14 14

15 BTA Suspension Buffer Suspension Buffer Link between pre-treatment & anaerobic digestion Reception of additional low-impurity (sludge, fat etc.) Constant feeding of digester peaks) waste (handling of Further homogenization before the anaerobic digestion Patented Process for - low-emission storage - no organic (biogas) loss 15 15

16 Digester Digester One-step digestion Mesophilic conditions (36 38 C) Mixing system with gas lances External heat exchanger 16 16

17 Anaerobic Digestion Mixing System Mixing in the digesters and the suspension buffer is accomplished by a gas (air) mixing system with gas lances Buoyancy and Convection high efficiency Computer simulation Advantages: no movable parts in the digester gas lances are flushable from outside no torques or leverage 17 17

18 Sanitation Sanitation The sanitation can be achieved either in the posterior composting stage or by heating up the organic suspension to (70 C, 1 hour) before entering the digester. The concept considers three tanks to allow a constant feeding of the digesters: First to heat up to 70 C Second to ensure exposure time of 1 hour Third to discharge 18 18

19 Gas Treatment and Valorisation Gas treatment and valorisation External biological desulphurization (optional) Gas storage (optional) Gas cooling Combied Heat and Power Production (CHPs) Biogas upgrading (up to natural gas quality) Emergency gas flare 19 19

20 Dewatering of Digestate The digested material is dewatered either in centrifuges or in screw presses obtaining two phases: dewatered solids with approx. 30% TS content centrate with approx. 1,5 3% TS content 20 20

21 Process Water Management Process water types Process water 1: recirculated to BTA Waste Pulper Process water 2 (after microfiltration) for rinsing purposes after reduction of solids load Process water 3 (optional - after WWTP) for rinsing purposes of the solid-liquid-separation and flocculants preparation Minimised consumption of fresh water Minimised production of excess water Micro Strainer 21 21

22 Process Water Management Effluent Treatment Biological treatment plant BOD/COD degradation Denitrification / Nitrification Sedimentation Process Water 3 Discharge into sewer 22 22

23 Composting Post-composting in boxes Post-composting in piles In both stages a forced aeration is foreseen, controlled in function of oxygen content and temperature 23 23

24 Dewatered digestate Thanks to the efficient removal of impurities in the BTA Hydromechanical Pretreatment the dewatered digestate is an ideal substrate for the further composting to produce quality compost, almost free of contaminants and homogeneous

25 Composting Rottegrad Mülh Rottegrad Gärrest, entw. Beginn 2.Wo 3.Wo 4.Wo 50,0 45,0 40,0 35,0 30,0 25,0 20,0 15,0 10,0 5,0 0,0 Maximaltemperatur [ C] Rottegrad Maximaltemperatur Tests executed with the digestate from the AD plans in Mülheim and Kirchstockach have shown that with a simple windrow composting with controlled air system it is possible to achieve the Rottegrad V quality within only 3-4 weeks. 25

26 Digestate in Dufferin Toronto (Canada) Start-up: 2002 Input: Throughput: Source Segregated Organics (with up to 15% of plastics) ton/year (design) ton/year (2009) 26 26

27 Digestate in Dufferin Toronto (Canada) 27 27

28 Digestate in Kirchstockach (Germany) Start-up: 1997 Input: Throughput: Biowaste (with up to 30% of green waste) ton/year (design) ton/year (2009) Samples frequently taken indicate that requirements to physical contaminants acc. PAS100 or the Community ecolabel to soil improvers (2006/799/EC) are met 28 28

29 Digestate in Ieper (Belgium) Start-up: 2003 Input: Throughput: Biowaste, commercial waste ton/year (design) Samples frequently taken indicate that requirements to physical contaminants acc. PAS100 or the Community eco-label to soil improvers (2006/799/EC) are met 29 29

30 Digestate Digestate characteristics Dry matter content % Homogeneous material Rottegrad 3 Physical contaminants 1) : In tendency it can be said that requirements regarding the physical contaminants are met in the AD plants for biowaste that have a hydromechanical pre-treatment from BTA. 1) In the final product (with mesh size 2 mm), the content of glass, metal and plastic shall be lower than 0,5 % as measured in terms of dry weight

31 Current Projects I Granollers (Spain) Maresme (Spain) Burgos (Spain) Itzig (Luxembourg) ton/year ton/year ton/year ton/year FORM Pre-treated MSW Pre-treated MSW Biowaste, food waste Start-up Assembly Assembly Start-up Partners: Partners: SUFI & Hera SUFI, Veolia Propiete, BKW, PROINOSA, Tau- Ingeniería, SURIS S.L Partners: CESPA, Jovilma Partners: Bakona s.a.r.l 31 31

32 Current Projects II Castelleone (Italy) Suldouro (Portugal) Valorlis (Portugal) Reliance Street (UK) Bredbury Parkway (UK) ton/year ton/year ton/year ton/year ton/year Biowaste, manure, maize silage In operation Partners: Biotec Sistemi s.r.l. Biowaste, municipal solid waste Start-up Partners: EFACEC, Monte Adriano Biowaste, municipal solid waste Start-up Partners: EFACEC, Monte Adriano Pretreated municipal solid waste Start-up Partners: ENPURE Ltd. (BTA licensee for UK and Ireland) Pretreated municipal solid waste Assembly Partners: ENPURE Ltd. (BTA licensee for UK and Ireland) 32 32

33 Selected References Baden-Baden (Germany) EcoParc I (Spain) Pulawy (Poland) Villacidro (Italy) ton/year ton/year ton/year ton/year Biowaste FORM; Pre-treated municipal solid waste Municipal solid waste Municipal solid waste, sewage sludge Start-up 1993 Start-up 2008 Start-up 2001 Start-up

34 Contact : Biotec Sistemi S.r.l. Via Privata Galla, Serra Riccò - Genova Italy Tel: Fax: biotec@biotecsistemi.it