ANDRITZ SEPARATION Thermal Treatment of Sludge

Transcription

1 ANDRITZ SEPARATION Thermal Treatment of Sludge

2 Sludge drying according to EU guidelines Principles: (in the order given below) Applicable to SEWAGE SLUDGE? Avoid waste Not possible Use waste materially As fertilizer or soil conditioner Use waste thermally If material use is not possible Residual waste to landfill e.g. ashes from thermal use* * After extraction of organic matter depending of landfill type < 5% (< 1%) 2

3 Why sludge drying? For example a town with population equivalent (approx kg DS/day) m 3 sludge/day 130 m 3 /day 50 m 3 /day DS = 3% DS = 25% DS = 92% Total Volume Reduction achievable: 95 % 3

4 From Waste to Product from Waste Dewatered Sludge to Product Dried Granulate by Sludge Drying 20-35% DS Sticky Caloric heating value < 4 MJ/kg biologically active (digestion processes) > 90% DS free flowing Caloric heating value 8-11 MJ/kg (digested) > 12 MJ/kg (non-digested ) pathogen free biologically stable 4

5 Principle of different drying technologies Convective Drying The sludge is directly dried by the flue gas or hot air and the humidity is discharged. Contact Drying Heat is transported via a lateral surface to the sludge. The humidity evaporates and is discharged. flue gas or hot air water vapour gas and water vapour air water vapour water vapour flue gas or hot air gas and water vapour heating medium 5

6 Different drying technologies Contact dryer Convective dryer Fluid Bed Dryer (FDS) Belt Dryer (BDS) 6 Paddle Dryer (GPD) Drum Dryer (DDS)

7 Sludge preparation in drum and belt dryers Back-mixing of dried material in drum and belt dryers Short distance for water transport (diffusion) wet layer Homogeniously dried product Thin sludge layer around the dry core of back mixed material Drying Process dry dry core DS content after drying: 88 % Final product particle size: 0-15 mm (can be influenced by additional equipment) 7

8 Direct sludge feed without back mixing Fluid Bed Dryer Paddle Dryer Belt dryer noodles Method sludge feeding with spiked roller in the fluid bed intensive mixing by two paddle shafts Sludge is pressed through a die and forms spaghetti-like Final product Properties of the product >90% DS particle size: 0-4 mm - Full dried: >85% DS particle size: 0-10 mm 85 90% DS Rod shaped with dust - Partial dried: 35 85%DS Diameter: 5 8 mm Granulation: 0,5 4 mm 8

9 Energy supply to thermal dryer Directly heated Natural gas / Biogas / Diesel DRYER COMBUSTION CHAMBER Indirectly heated Recovery of energy Hot Water / Low Pressure Steam / Flue Gases DRYER HEAT EXCHANGER 9

10 Selection criteria temperature of energy source Drum Dryer Paddle Dryer Fluid Bed Dryer Belt Dryer Heat source Heat carrier Water evaporation capacity in one line Natural gas, bio gas, LPG Flue gas >350 C Directly heated by Flue gas C Natural gas, Bio gas, Heating steam < 11bar, Flue gases >160 C Indirectly heated by Steam < 20 bar, Thermal oil C Natural gas, Bio gas, Heating steam < 5bar, Flue gases >160 C Indirectly heated by Steam 6 40 bar Thermal oil C Natural gas, Bio gas, Heating steam,flue gases Hot water Directly or indirectly heated Drying air < 130 C kg/h kg/h kg/h kg/h Sludge preparation Backmixing Direct Feeding Direct Feeding Back-mixing or extruder Partial Drying (< 88%DS) no yes 70-88% DS no no Preferred Application High capacity, Perfect product properties, e.g. Fertilizer Compact design, Wide range of dry substance = partial and full dried product possible Fully automated process with nearly dust-free product, high flexibility in terms of different sludge properties Suitable using of waste energy with low temperatures ( C) 10

11 Energy sources for belt dryers BDS with backmixing Direct heated with natural gas biogas flue gases BDC Direct heated with - Indirectly heated low temperature steam hot water (T > 95 C) thermal oil Indirectly heated low temperature steam hot water (T > 95 C) thermal oil For BDS also a combination of direct and indirect heating is possible, f.e. use waste heat (hot water) and add only the missing energy with f.e. natural gas 11

12 Properties of final product of belt dryers BDS with back mixing system BDC - Extruder ( Spaghetti press ) bulk density 500 kg/m 3 dry substance >90%DS ( class A product ), biological activities are stopped bulk density 280 kg/m 3 dry substance >90%DS ( class A product ), biological activities are stopped 12

13 Use of low temperature energy sources in belt dryer project issued: SE/ KT Date Rev 1 Biogas to Engine approx kw Fumes Gas from engine 480,0 C kg/h Sludge to Dryer t/a kg/h 20,0 C 30,0% DS Fumes to stack Product granulate 120,0 C 19,37 t/d kg/h 80,0% DS Fresh Air 807 kg/h approx. 25 C 80% DS heat recovery fumes approx. 303 kw Backmixing emergency air cooling 60,0% DS Cooling Air Fan Cooling return 80 kw Fresh Air after Cooler 70,0 C kg/h electrical output engine approx. 500 kw Cooling cycle approx. 282 kw Cooling forward 85,0 C kg/h Circulation gas temperature < 120 C Fresh Air preheating 72 kw Recycle Air preheat. 152 kw heat recovery Cooling Cycle other utilization approx. 282 kw Natural Gas to Burner Heat Duty Burner kj/nm3 904 kw 87 Nm3/h 904 kw kg/h Water Evaporation 80,0% DS Offgas kg/h Recycle m3/h m3/h 38,0 C Summary Water Evaporation kg/h Heat-Recovery Gas Engine 223 kw Circulation Heat from Gas burner 904 kw Fan Cooling Water Thermal duty Heat-Recovery 19,8% kg/h Thermal duty Burner 80,2% 20,0 C Offgas Fan Condensate+CW kg/h 43,0 C 13

14 Use of low temperature energy sources in belt dryer Belt dryer without use of waste heat DS content after dewatering: 25 % DS content after drying: 90 % (dewatered) Sludge per year: t Belt dryer with use of waste heat DS content after dewatering: 25 % DS content after drying: 90 % (dewatered) Sludge per year: t Primary energy source: Natural gas Primary energy source: Natural gas Waste energy: Engine cooling 90 C Product (@90 % DS): kg/hr Product (@90 % DS): kg/hr Hourly natural gas consumption: 199,1 kg/hr Hourly natural gas consumption: 178,5 kg/hr Savings: 154,5 t natural gas per anno (assuming hrs. of operation) 14

15 Final use of dried sludge Recycling Thermal Application Agriculture - pathogen free - Recycling of minerals - long-term fertilizer Incineration in Cement kilns Substitution of fuel and minerals = residue free process Composting - improvement of the soil - accelerated vegetation of eroded soil ( street works, slopes ) Incineration in coal fired power stations Substitution of fuel Landfilling Garbage incineration plants 15

16 Sludge Drying Summary of main advantages - Significant reduction of the weight, therefore lower costs in disposal and transport - Significant reduction of the volume - Increase of the heating value valuable fuel made from waste! - Odour poor end product - Simple storage possible - Multiple disposal- / recycling possibilities of end product Class A according to US EPA Regulations Chapter 5 16

17 Disclaimer Peter Rottenmanner Sales Manager Sludge SEPARATION ANDRITZ AG Stattegger Strasse Graz, Austria Phone: +43 (316) , Fax: +43 (316) 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. 17