The environmental performance of an alternative fry-drying process for sewage sludge: A life cycle assessment study

Transcription

1 The environmental performance of an alternative fry-drying process for sewage sludge: A life cycle assessment study By : PhD student Carlos-Alberto PEREGRINA-CAMBERO Principal Advisor: Prof Didier LECOMTE Associate Advisor: Prof Victor RUDOLPH Assoc Prof Patricia ARLABOSSE 4th Australian Life Cycle Assessment Conference Sydney, Australia 24 February 2005

2 Presentation Outline Context of the study Life cycle assessment of fry-drying Question and answers 1/15

3 Context of the study

4 Thermal drying of sewage sludge Waste water Wastewater Treatment Plant Clean water Thickened Sewage sludge <5% dry matter Mechanical Dewatering Mechanically dewatered Sewage sludge up to 20% dry matter THERMAL DISPOSAL THERMAL DRYING LAND SPREAD DISPOSAL Thermal Dried Sewage sludge >90% dry matter 2/15

5 Thermal drying of sewage sludge Current sludge thermal drying process direct indirect mixte High energy consumption Plastic phase of the sludge Dry matter content Wet phase Plastic phase Granulated phase 70-75% 45 50% Drying time 3/15

6 Thermal drying of sewage sludge Introducing Fry-drying of sewage sludge direct (Image: Saguy, 1998) Frying is a multi-function operation, which dries, impregnates and transforms chemically 4/15

7 Technical issues Mechanically dewatered sewage sludge Fry-drying operation Water evaporation Recycled cooking oils (RCO) Feed position Oil impregnation Immersion position 5/15

8 Technical issues Main advantages of fry-drying of sewage sludge Rapid and complete drying Simple process train Two ways to increase the calorific value Co-disposal of RCO and sewage sludge Main disadvantages of fry-drying of sewage sludge Availability of frying oils Disposal of fry-dried sludge is limited to incineration Uncertain environmental impacts 6/15

9 Life cycle assessment of fry-drying

10 LCA Case study Stage 1 Goal and scope definition Goal: Compare the environmental performance of two case studies for the incineration and final disposal of 1 ton of a mechanically dewatered sewage sludge (18% dry matter) Boundaries of the assessment: Case study 1: Conventional indirect dryer (Lassus and Toupart, 1999) Case study 2: Fry-dryer (Experimental device) 7/15

11 LCA Case study Stage 1 Goal and scope definition Assumptions: -Autothermal dried sludge has a lower calorific value (LCV) = 9 MJ/kg -Combustion of sludge is complete and no additional fossil fuel is required Impact categories Considered : -Abiotic depletion of resources, MJ; -Climate change, CO 2 eq; GWP at a time horizon of 100 years -Acidification SO 2 eq and -Eutrophication, (PO 4 eq Not relevants :Ozone depletion, land use and soil quality Externalities:Ecotoxicity and Human health effects 8/15

12 Stage 2 Energy consumption: During the drying, Thermal energy = ( M Cp T ) + ( Lv M ) Net heat load = RCO Sensible ds heat = ds Net 1 heat η load LCA Case study Factor = 0.9 MJ/ton kg (Polusen and Hansen, 2003) Distances from the incinerator to the combustor and then to the land filling 10 and 15 km respectively 9/15 ew ( M Cp T ) io M ew : determined from the initial and final moisture content Final moisture content is determined from the correlation: LCV vs moisture content (Niessen, 1995) During the transport, Inventory analysis RCO 2

13 LCA Case study Stage 2 Inventory analysis Analysis of emissions: During the drying, Analysis of condensed gas P, N and COD Analysis of non condensed gas VOC s, NOx and SOx During the combustion, Ultimate Analysis of organic matter and then calculate the stochiometric proportions of the oxidized gases: SO 2, CO 2, NO 2 Technical consideration: HCl is released during the combustion of the fry-dried sludge During the transportation, Factor kg CO 2 /MJ (Polusen and Hansen, 2003) 10/15

14 LCA Case study Stage 2 Inventory analysis Experimental device (Pollutant emission during fry-drying) Flask Thermal oil heater Condenser Vacuum pump Jacketed cylindrical reaction vessel Sealed gas-bag 11/15

15 LCA Case study Stage 2 Inventory analysis Inventory Results Result Case 1(Indirect dryer) Case 2(Fry-dryer) Drying characteristics Energy consumption CO 2 emissions during fuel consumption the drying the incineration Initial dm content 0.18 kg dm/kg sludge 0.18 kg dm/kg sludge Final dm content 0.61 kg dm/kg sludge kg dm/kg sludge Calorific Value 9.00 MJ/kg 9.00 MJ/kg M dewatered sludge 1000 kg 1000 kg M dried sludge 295 kg kg Mass reduction 3.4 fold 2.2 fold Dryer 2272 (±134) MJ 1958(±145) MJ Transport D-C 3(±0.5) MJ 4(±1) MJ Transport C-L 0.8(±0.1) MJ 0.8(±0.1) MJ Dryer (±2000) g CO (±8600) g CO 2 Transport D-C 249(±42) g CO 2 332(±83) g CO 2 Transport C-L 66(±17) g CO 2 66(±17) g CO 2 CH (±62) g CO 2 365(±40) g CO 2 P 0.4 (± 0.2) g (PO 4 <0.2g(PO 4 N 9.6 (± 0.6) g (PO (± 0.03) g (PO 4 COD 3.5 (± 0.2) g (PO (± 6.8) g (PO 4 CO (±29600) g CO (±53200) g CO 2 NO (±3600) g SO (±5000) g SO 2 SO 2 HCl - 7 (±7) g SO 2 12/15

16 LCA Case study Stage 2 Inventory analysis Inventory Results Result Case 1(Indirect dryer) Case 2(Fry-dryer) Drying characteristics Energy consumption CO 2 emissions during fuel consumption the drying the incineration Initial dm content 0.18 kg dm/kg sludge 0.18 kg dm/kg sludge Final dm content 0.61 kg dm/kg sludge kg dm/kg sludge Calorific Value 9.00 MJ/kg 9.00 MJ/kg M dewatered sludge 1000 kg 1000 kg M dried sludge 295 kg kg Mass reduction 3.4 fold 2.2 fold Dryer 2272 (±134) MJ 1958(±145) MJ Transport D-C 3(±0.5) MJ 4(±1) MJ Transport C-L 0.8(±0.1) MJ 0.8(±0.1) MJ Dryer (±2000) g CO (±8600) g CO 2 Transport D-C 249(±42) g CO 2 332(±83) g CO 2 Transport C-L 66(±17) g CO 2 66(±17) g CO 2 CH (±62) g CO 2 365(±40) g CO 2 P 0.4 (± 0.2) g (PO 4 <0.2g(PO 4 N 9.6 (± 0.6) g (PO (± 0.03) g (PO 4 COD 3.5 (± 0.2) g (PO (± 6.8) g (PO 4 CO (±29600) g CO (±53200) g CO 2 NO (±3600) g SO (±5000) g SO 2 SO 2 HCl - 7 (±7) g SO 2 12/15

17 LCA Case study Stage 2 Inventory analysis Inventory Results Result Case 1(Indirect dryer) Case 2(Fry-dryer) Drying characteristics Energy consumption CO 2 emissions during fuel consumption the drying the incineration Initial dm content 0.18 kg dm/kg sludge 0.18 kg dm/kg sludge Final dm content 0.61 kg dm/kg sludge kg dm/kg sludge Calorific Value 9.00 MJ/kg 9.00 MJ/kg M dewatered sludge 1000 kg 1000 kg M dried sludge 295 kg kg Mass reduction 3.4 fold 2.2 fold Dryer 2272 (±134) MJ 1958(±145) MJ Transport D-C 3(±0.5) MJ 4(±1) MJ Transport C-L 0.8(±0.1) MJ 0.8(±0.1) MJ Dryer (±2000) g CO (±8600) g CO 2 Transport D-C 249(±42) g CO 2 332(±83) g CO 2 Transport C-L 66(±17) g CO 2 66(±17) g CO 2 CH (±62) g CO 2 365(±40) g CO 2 P 0.4 (± 0.2) g (PO 4 <0.2g(PO 4 N 9.6 (± 0.6) g (PO (± 0.03) g (PO 4 COD 3.5 (± 0.2) g (PO (± 6.8) g (PO 4 CO (±29600) g CO (±53200) g CO 2 NO (±3600) g SO (±5000) g SO 2 SO 2 HCl - 7 (±7) g SO 2 12/15

18 LCA Case study Stage 2 Inventory analysis Inventory Results Result Case 1(Indirect dryer) Case 2(Fry-dryer) Drying characteristics Energy consumption CO 2 emissions during fuel consumption the drying the incineration Initial dm content 0.18 kg dm/kg sludge 0.18 kg dm/kg sludge Final dm content 0.61 kg dm/kg sludge kg dm/kg sludge Calorific Value 9.00 MJ/kg 9.00 MJ/kg M dewatered sludge 1000 kg 1000 kg M dried sludge 295 kg kg Mass reduction 3.4 fold 2.2 fold Dryer 2272 (±134) MJ 1958(±145) MJ Transport D-C 3(±0.5) MJ 4(±1) MJ Transport C-L 0.8(±0.1) MJ 0.8(±0.1) MJ Dryer (±2000) g CO (±8600) g CO 2 Transport D-C 249(±42) g CO 2 332(±83) g CO 2 Transport C-L 66(±17) g CO 2 66(±17) g CO 2 CH (±62) g CO 2 365(±40) g CO 2 P 0.4 (± 0.2) g (PO 4 <0.2g(PO 4 N 9.6 (± 0.6) g (PO (± 0.03) g (PO 4 COD 3.5 (± 0.2) g (PO (± 6.8) g (PO 4 CO (±29600) g CO (±53200) g CO 2 NO (±3600) g SO (±5000) g SO 2 SO 2 HCl - 7 (±7) g SO 2 12/15

19 LCA Case study Stage 2 Inventory analysis Inventory Results Results Case 1(Indirect dryer) Case 2(Fry-dryer) Drying characteristics Energy consumption CO 2 emissions during fuel consumption the drying the incineration Initial dm content 0.18 kg dm/kg sludge 0.18 kg dm/kg sludge Final dm content 0.61 kg dm/kg sludge kg dm/kg sludge Calorific Value 9.00 MJ/kg 9.00 MJ/kg M dewatered sludge 1000 kg 1000 kg M dried sludge 295 kg kg Mass reduction 3.4 fold 2.2 fold Dryer 2272 (±134) MJ 1958(±145) MJ Transport D-C 3(±0.5) MJ 4(±1) MJ Transport C-L 0.8(±0.1) MJ 0.8(±0.1) MJ Dryer (±2000) g CO (±8600) g CO 2 Transport D-C 249(±42) g CO 2 332(±83) g CO 2 Transport C-L 66(±17) g CO 2 66(±17) g CO 2 CH (±62) g CO 2 365(±40) g CO 2 P 0.4 (± 0.2) g (PO 4 <0.2g(PO 4 N 9.6 (± 0.6) g (PO (± 0.03) g (PO 4 COD 3.5 (± 0.2) g (PO (± 6.8) g (PO 4 CO (±29600) g CO (±53200) g CO 2 NO (±3600) g SO (±5000) g SO 2 SO 2 HCl - 7 (±7) g SO 2 12/15

20 LCA Case study Stage 2 Inventory analysis Inventory Results Results Case 1(Indirect dryer) Case 2(Fry-dryer) Drying characteristics Energy consumption CO 2 emissions during fuel consumption the drying the incineration Initial dm content 0.18 kg dm/kg sludge 0.18 kg dm/kg sludge Final dm content 0.61 kg dm/kg sludge kg dm/kg sludge Calorific Value 9.00 MJ/kg 9.00 MJ/kg M dewatered sludge 1000 kg 1000 kg M dried sludge 295 kg kg Mass reduction 3.4 fold 2.2 fold Dryer 2272 (±134) MJ 1958(±145) MJ Transport D-C 3(±0.5) MJ 4(±1) MJ Transport C-L 0.8(±0.1) MJ 0.8(±0.1) MJ Dryer (±2000) g CO (±8600) g CO 2 Transport D-C 249(±42) g CO 2 332(±83) g CO 2 Transport C-L 66(±17) g CO 2 66(±17) g CO 2 CH (±62) g CO 2 365(±40) g CO 2 P 0.4 (± 0.2) g (PO 4 <0.2g(PO 4 N 9.6 (± 0.6) g (PO (± 0.03) g (PO 4 COD 3.5 (± 0.2) g (PO (± 6.8) g (PO 4 CO (±29600) g CO (±53200) g CO 2 NO (±3600) g SO (±5000) g SO 2 SO 2 HCl - 7 (±7) g SO 2 12/15

21 LCA Case study Stage 2 Inventory analysis Inventory Results Results Case 1(Indirect dryer) Case 2(Fry-dryer) Drying characteristics Energy consumption CO 2 emissions during fuel consumption the drying the incineration Initial dm content 0.18 kg dm/kg sludge 0.18 kg dm/kg sludge Final dm content 0.61 kg dm/kg sludge kg dm/kg sludge Calorific Value 9.00 MJ/kg 9.00 MJ/kg M dewatered sludge 1000 kg 1000 kg M dried sludge 295 kg kg Mass reduction 3.4 fold 2.2 fold Dryer 2272 (±134) MJ 1958(±145) MJ Transport D-C 3(±0.5) MJ 4(±1) MJ Transport C-L 0.8(±0.1) MJ 0.8(±0.1) MJ Dryer (±2000) g CO (±8600) g CO 2 Transport D-C 249(±42) g CO 2 332(±83) g CO 2 Transport C-L 66(±17) g CO 2 66(±17) g CO 2 CH (±62) g CO 2 365(±40) g CO 2 P 0.4 (± 0.2) g (PO 4 <0.2g(PO 4 N 9.6 (± 0.6) g (PO (± 0.03) g (PO 4 COD 3.5 (± 0.2) g (PO (± 6.8) g (PO 4 CO (±29600) g CO (±53200) g CO 2 NO (±3600) g SO (±5000) g SO 2 SO 2 HCl - 7 (±7) g SO 2 12/15

22 LCA Case study Stage 2 Inventory analysis Inventory Results Results Case 1(Indirect dryer) Case 2(Fry-dryer) Drying characteristics Energy consumption CO 2 emissions during fuel consumption the drying the incineration Initial dm content 0.18 kg dm/kg sludge 0.18 kg dm/kg sludge Final dm content 0.61 kg dm/kg sludge kg dm/kg sludge Calorific Value 9.00 MJ/kg 9.00 MJ/kg M dewatered sludge 1000 kg 1000 kg M dried sludge 295 kg kg Mass reduction 3.4 fold 2.2 fold Dryer 2272 (±134) MJ 1958(±145) MJ Transport D-C 3(±0.5) MJ 4(±1) MJ Transport C-L 0.8(±0.1) MJ 0.8(±0.1) MJ Dryer (±2000) g CO (±8600) g CO 2 Transport D-C 249(±42) g CO 2 332(±83) g CO 2 Transport C-L 66(±17) g CO 2 66(±17) g CO 2 CH (±62) g CO 2 365(±40) g CO 2 P 0.4 (± 0.2) g (PO 4 <0.2g(PO 4 N 9.6 (± 0.6) g (PO (± 0.03) g (PO 4 COD 3.5 (± 0.2) g (PO (± 6.8) g (PO 4 CO (±29600) g CO (±53200) g CO 2 NO (±3600) g SO (±5000) g SO 2 SO 2 HCl - 7 (±7) g SO 2 12/15

23 LCA Case study Stage 3 Impact assessment Normalized impact categories 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 Abiotic depletion of resources Climatic change Eutrophication Acidification Case 1 (Indirect dryer) Case 2 (Fry-dryer) 13/15

24 LCA Case study Stage 4 LCA interpretation Study conclusions directed to the abiotic depletion of resources and climatic change categories The most important environmental issue of fry-drying is in the abiotic depletion of resources Examination in perspective of climate change impact results (RCO co-disposal) Chlorine content of RCO could be a major concern and requires further analysis 14/15

25 Presentation summary

26 Presentation Summary Conclusions New research on thermal drying of sewage sludge proposes an innovating fry-drying technique Fry-drying principle avoids the plastic zone difficulties, which are presented in most conventional dryers Because of the oil impregnation, final fry-dried sludge has a calorific value, which supports its application as fuel and facilites the codisposal of RCO and sludge by incineration LCA has been applied in the first stages of the design of a new drying process for sludge integrated in the co-disposal of sewage sludge and RCO Among the selected impact categories, fry-drying has shown a good performance in abiotic depletion of resources and also in climate change if we consider the co-disposal of RCO 15/15

27 Questions & Answers 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 Abiotic depletion of resources Climatic change Eutrophication Acidification

28 Acknowledgments Principal Advisor: Associate Advisor: Prof Didier LECOMTE Prof Victor RUDOLPH Assoc Prof Patricia ARLABOSSE