Treatment of organic waste digestates A practical case study

Transcription

1 Treatment of organic waste digestates A practical case study

2 Definition of organic waste and digestates Organic waste is anything that comes from plants or animals that is biodegradable. Thus, it is, either liquid or solid, a good substrate for biogas generation by anaerobic digestion / fermentation (AD). Digestates are the leftovers after digestion / fermentation. ORGANIC WASTE and Agricultural Feedstocks Non-agricultural feedstock Manure (excrements of animals, liquid and solid) Biodegradable Waste (Green waste) Energy crops (Maize,corn,..) Agricultural waste material (harvest residues, straw, grass clippings,..) Industrial organic waste material such as expired food / beverages, slaughterhouse waste, 2

3 Characteristics of digestates Can vary according to input material and operating conditions Low dry matter (typically 1-8% DS) High water content Inorganic nutrients (Ammonium-N and P) May contain potentially toxic elements (f.e heavy metals) Classed as a waste or non-waste Odorous compounds in digestates (hydrogen sulfide, ammonia, amines, volatile organic acids, reduced sulfur compounds) 3

4 Overview of a typical AD plant with dewatering & drying 1 Organic waste (or inputs) 2 Anaerobic digestion (liquid path) 3 Biogas treatment Energy culture or agricultural or organic waste 5 Digestate dewatering / drying (Increased C methane and improved quality) Direct injec<on into natural gas grid Digestate Biogas storage Gas engine Biogas distribu<on Generator Electricity Liquid manure Anaerobic digester / fermenter Heat recovery (digester hea<ng) Hot water produc<on for public distribu<on Agro- food waste Collec<ng basin 4 Heat or electricity distribution 4

5 Dewatering and drying technologies in SE portfolio Screw press Belt dryer Gravity belt thickener Paddle dryer Belt filter press Drum dryer Centrifuge 5

6 Case study: Fertiker designed by FERTIGAZ Place: Brittany (PLOUEDERN 29) Developed in partnership with ADEME, Brittany region, CG 29, Agence de l eau Loire Bretagne Investment 3.7 million 6.8 tonnes of dry matter arriving daily Plant capacity: 400 KW FERTIGAZ 6

7 Feedstock Digestate dewatering on site (currently) Food industry waste WWTP sludge Liquid pig manure (used to dilute matter prior to transfer to digester) Fatty waste (1/3) FERTIGAZ 7

8 Process overview Centrate From D 3 L Pig manure SCREENING Homogeniza<on / Collec<on Tank Farm with about 1500 pigs BIOLOGICAL REACTOR BIOLOGICAL REACTOR Waste recep<on area pigs VACUUM FILTER VACUUM FILTER LAGOON Fat material recep<on Sieve coarse fat material Fat waste storage tank ( T regula<on = 23 C ) Macerator Food industry waste Recep<on, currently SOJA WASTE Storage blending Tank ( Soja waste, pig manure, fat waste ) Digester 1 High efficient Heat recovery Gasmotor / Generator Digester 2 Cake from Centrifuge, Screen and Vacuum filter Drying of Compost. Part of Heat coming from Co - genera<on ; 8

9 Dewatering ANDRITZ D3L centrifuge for dewatering Operational constraints: water used for polymer preparation should be minimized / polymer consumption should also be minimized. Acceptable centrate quality 1.6% maximum FERTIGAZ (Centrate rejected in the bioreactor for the dewatering of liquid pig manure) 9

10 Dewatering of digestate In-/Output results Commissioning (Oct 2011) May 2013 Waste quality - Soja waste - Fatty waste - Pig manure - Waste from food industries - Municipal sludge - Fatty waste - Pig manure SCREENING VACUUM FILTER Throughput [m³/h] 6 6,3 Concentration of total dry solids [% DS] 4,1 5,4 Throughput [kg DS/h] VM/SM [%] 58% < 60 % Centrate [%) 2,5-2,7 <1,5 < 1,1 <1,0 Cake dryness [%] [+-2] Suspended solid extraction yield [%] Operation 70 % 90 % 95 % >95% without polymer with polymer with polymer with polymer Polymer [kg/tdm] Yield on P[%] 85 Yield on K [%] 25 Yield on N [%] Note: FeCl3 injection (2.5 %FeCl3/DM) in parallel permits a capture rate for phosporous > 90%. (May 2013 test)

11 Digestion plant Leonberg, Germany Processing organic waste - Overview Biowaste collected in households and transported to digestion / fermentation plant Produced electricity is fed to local grid Produced biogas is desulfurized and collected in a gas holder. Gas is converted in 3 block heat and power plants into electric power and heat. Heat is partly used for digester heating and partly as heat source for belt dryer Bio / Organic waste t/a Input biowaste t/a Output digestates t/a Digestates to Dryer Output dryer t/a t/a Mixing with undried digestates to composting Weighing of biowaste, finally discharged to receiption hall; Chain scraper conveys waste to cross-flow chipper If required, 1 combustion chamber is operated with biogas for heat provision for belt dryer, additionally Heating oil possible as well Fresh waste is mixed with digestion Residues (1:6) and pumped into digester 1/7 of digestates are fed to Andritz belt dryer Plant Exhaust air cleaned by biofilter Compost available for people to improve Soil quality f.e in garden 11 After chipping / size reduction waste is homogenized in a screen drum Screened Waste is transported via Magnetic separator to mixing unit Digestates dried to 60% DS are delivered to composting plant to Kirchheim or Landkreis Böblingen

12 Organic waste treatment in Leonberg Upgraded pre-treatment Anaerobic Digestion (AD) Input / Output Pre-treatment is essential for methane yield and throughput as well as quality of dried digestate 12

13 Organic waste treatment in Leonberg Original pre-treatment The plant was designed to process 30,000 t per year and to produce 1.5 MWe energy The problem with pre-treatment: Incoming organic waste contained a significant portion of inorganic materials, not adequate broken down by the shredder Second granulation stage and screen too-high portion of inorganic material Multiple runs through granulation stages chopped the inorganic material into small pieces Negative impact on gas yield - plant s two block-type thermal power stations could not convert the inorganics Maintenance activities increased as the extraneous material found its way through the process 13

14 Organic waste treatment in Leonberg Upgraded pre-treatment Bio-QZ (Querstromzerspaner) Dismantling of waste individual components remain intact No cutting tools, just rotating chains Benefits: Increase of the surface of the material Increase of methane yield by 10,5% Increase of throughput to 20 t/hr Before the upgrade, 181 t of foreign materials were separated out each year. Today, the number is around 660 t/a 14

15 Drying of Organic Waste (Leonberg, Germany) Plant: Leonberg, Germany Plant type: 1 x BDS Feed: Digested organic Heat source: waste Biogas & Waste heat from CHP Product IN: % MC Product OUT: % MC Evaporation: l/h H 2 O max. capacity Utilization: Start-up: 2003 Composting 15

16 Digestion plant Leonberg, Germany Processing organic waste Drying of digestates Digestates kg/h; 26% DS kg/h; 26% DS kg/h; 80% DS kg/h; 26% DS kg/h; 50% DS Biogas/ Heating oil Waste heat as Hot water from Combined heat & Power generation And fuel cell Burner Furnace Heat exchanger kg/h Water evaporation Circulation Air fan Belt dryer Potable water Final effluent Saturator 570 kg/h; 80% DS kg/h; 38% DS Exhaust air fan Waste water m³/a to Biofilter 16

17 Digestion plant Leonberg, Germany Processing organic waste Drying Benefits No dust and odor emission to environment Optimum conditions for partial or complete integration/recovery of exhaust heat as flue gas, steam, hot water, etc., from gas motors, waste incineration plants or other processes High thermal efficiency due to optimum air circulation and exhaust air recirculation Minimum condensate discharge/back charge Significant reduction of weight and volume Increasing of heating value (LHV) Reduction of biological activity Increasing of capacities on existing biogas plants 17

18 Summary Proper pre-treatment essential for efficient digestate treatment Dewatering increases solids concentration and reduces transport volume Further Volume reduction by Drying resulting in high quality digestate Heat recovery for drying within digestion plant easily adaptable Efficient kill of pathogens by applying drying Increase of heating value 18

19 Thanks for your attention! Dr. Doris Thamer SEPARATION Application Manager Biomass & Organic Waste ANDRITZ AG Stattegger Strasse Graz, Austria Phone: +43 (316) , Fax: +43 (316) Legal disclaimer All data, information, statements, photographs, and graphic illustrations contained in this presentation are without any obligation to the publisher and raise no liabilities to ANDRITZ AG or any affiliated companies, nor shall the contents in this presentation form part of any sales contracts, which may be concluded between ANDRITZ GROUP companies and purchasers of equipment and/or systems referred to herein. ANDRITZ AG All rights reserved. No part of this copyrighted work may be reproduced, modified or distributed in any form or by any means, or stored in any database or retrieval system, without the prior written permission of ANDRITZ AG or its affiliates. Any such unauthorized use for any purpose is a violation of the relevant copyright laws. 19