240 likes | 371 Views
Energetic aspects of urban waste treatments Claire Lecointe, Charlotte Barbut. 2 nd AWAST Workshop November 28-30 th , 2001, Rennes. SUMMARY. Introduction Thermal treatments Incineration Thermolysis Biological treatments Methanisation Landfill Composting Exergy Conclusion.
E N D
Energetic aspectsof urban waste treatmentsClaire Lecointe, Charlotte Barbut 2nd AWAST Workshop November 28-30th, 2001, Rennes
SUMMARY Introduction • Thermal treatments • Incineration • Thermolysis • Biological treatments • Methanisation • Landfill • Composting • Exergy Conclusion
Introduction • waste treatments => energy production (steam or gas) • steam or gas => electricity or heat • gas => fuel for buses or injection in natural gas networks • but different outputs • and how to compare ?
Smokes treatment Dust removal Smokes cleaning Ventilator Heat recovery (boiler) hs+ he = hcg Steam Combustion C (T’ ; P1) alternator hc turbine Waste delivery Electricity W LHV Slags treatment Steam Q (T ; P2) Selfconsumption Selfconsumption Electricity sold Steam sold Incineration thermal treatment with oxygen (even air excess) ; 900 to 1000°C
Outputs Rough estimates • combustion output : hc = C / LHVwaste • electric output : he = W / LHVwaste • heat output : hs = Q / LHVwaste • co-generation output : hcg = he + hs => 75 to 90% => 4 to 10% with counter-pressure => 60 to 70%
Smokes treatment 90 MJe/t Heat recovery Dust removal Smokes cleaning Ventilator 4 MJe/t 50 MJe/t 36 MJe/t Steam/electricity conversion 80% consumption Steam Combustion 78 MJe/t Waste delivery 5 MJe/t Electricity Steam 191 MJe/t Slags treatment 2,7 MJe/t Selfconsumption Selfconsumption Electricity sold Steam sold Electricity consumption : Strasbourg 2MWe 211 MJe/t
Pyrolysis gas (H2, CO2, CO, CH4…) Waste Drying Heating Pyrolysis Ash cooling Residues (liquid, solid) Thermolysis thermal treatment without oxygen ; 400 to 600°C or 600 to 1000°C
Development stage No industrial installation in France => no data => Do we keep this process in the project ?
heating biogas CH4, CO2 electricity Energy recovery fuel injection in natural gas network CO2, H2O solid residues compost Maturation Waste delivery Reactor Press heating solid residues pressing juice sludge water excess Centrifugation Methanisation biological treatment without oxygen ; 35°C or 55°C
heating biogas electricity Energy recovery fuel Deposing and compaction Waste delivery injection in natural gas network leachate Landfill natural biological decomposition
Methanisation : biogas 1663 to 2862 MJLHV/t methanised waste Results for landfill
Farm building : 0,54 MJe Heating : 0,045 L fuel heating Biogas extraction : 4,9 MJe Energy recovery electricity fuel Deposing and compaction Transport Waste delivery injection in natural gas network 1,3 L fuel leachate Landfill : energy consumptionfor 1t waste
landfill emissions intensity leachate biogas landfill acceptable concentrations methane stage year 10 100 1000 controlling stage Landfill : problem of time limits
Composting biological treatment with oxygen • This process doesn’t product any energy but uses it. • It allows material recovery by transforming organic waste in compost which can be used in farming. • Not yet studied because of lack of data.
Wt heat machine S (T) Wg = -Ex Q (by agreement) Carnot engine Wc Qa = Q * Ta / T Ambient environment (Ta) Definition Exergy is the maximum part of energy in a system which can be changed in mecanic energy. mecanic and electric energy = pure exergy heat energy = exergy + loss
Exergetic assessment Rough estimates • Carnot factor : qc = 1 - Ta / T • exergetic output : hex = he + qchs Paris heating network : 0,432 (T = 240°C and Ta = 20°C) Incineration : 33 to 38% towards waste LHV 38 to 45% towards boiler steam Methanisation : 39,8% towards waste LHV 53,5% towards methane
Conclusion • delicate comparison because of : • different value for burnt and methanised waste • different value for steam and electricity • exergy = solution ? • similar quality measure for waste ?