Waste to Energy System in Shanghai City

Transcription

1 Waste to Energy System n Shangha Cty Group of Envronmental Systems, Department of Envronmental Studes M Ya-Y Zhang 1. Introducton In the past ffteen years, the economcs of Chna has mantaned contnuously fast growng, as shown n Fgure 1. At the mean tme, Chna has quckly urbanzaton, reflectng from the contnuous ncrement of urban populaton. As one of results, the producton of muncpal sold waste (MSW) n Chna has also been quck rsng. Accordng to Chna Statstcal Yearbooks, the produced MSW n 2004 was mllon tons, whch s more that twce as that n 1990 (Fgure 1). Furthermore, only about 52% of MSW n 2004 has been dsposed, n whch, 44% was santary landflled, 5% was composted, and 3% was ncnerated. The remaned 48% MSW was ust smply dumped on the open land or was not subected any treatment, whch has caused several envronmental and healthy hazards, such as odors, groundwater polluton, and spread of dseases by fles, rats, anmals or human scavengers. Fg. 1. The yearly growth of urban populaton, GDP, and MSW n Chna from 1990 to On the other hand, the producton and consumpton of energy has become a deep problem n Chna recently. As predcted by Komyama and coworkers 2, the total energy demand wll reach 2133 Mtoe n 2030, whch s more than twce as that n 2002 (1026 Mtoe). Actually, accordng to Chna Statstcal Yearbook, Chna has become the top second country n world for energy producton and consumpton n The total producton of energy n 2004 was bllon ton of standard coal, only covered over 90% of total consumpton. The remaned 10% energy need was dependent on the oversea markets. In 2004, the net crude ol mport n Chna was 117 mllon tons, accountng for 6.31% of the worldwde trade. Furthermore, the producton of energy n Chna s manly dependent on coal, whch has brought a deep polluton n Chna. MSW s composed of lots of organc carbon, whch contans plenty of potental energy. In fact, the ncneraton of MSW produces lots of heat, whch can be used for power generaton. Alternatvely, MSW upon landfll, can decompose to generate landfll gas (LFG), n whch 40-60% volume s methane. In the developed countres, such as Japan, U.S.A., and Europe, utlzaton of MSW for generaton of electrc power or heat recyclng has been recognzed as an mportant MSW dsposal methodology due to ts several benefts: () reducng the depleton of the earth s lmted natural resources; () reducng polluton produced by dschargng untreated waste; () drectly and ndrectly savng energy. Although Chnese government and other socal organzatons have already devoted more and more attenton on MSW reutlzaton, the level of MSW dsposal s stll very low. Most MSW energy potental has been wasted n the past. Therefore, there s an urgency to nvestgate and establsh an effcent system to recover the potental energy of MSW n Chna. Snce t s dffcult to carry out the nvestgaton on the whole country of Chna, here we choose Shangha cty as the nvestgaton obect (Fgure 2). Shangha cty s one of the top leadng metropolses n Chna. The above mentoned problem s much more serous n Shangha. Fg. 2. The locaton of Shangha cty 2. Investgaton methodology 1. Current stuaton study, ncludng the collecton of the basc data of Shangha cty. 2. Predcton of MSW amount and composton untl Evaluaton of energy recovery by current MSW dsposal system. 4. Optmzaton through model smulaton of the MSW management system n 2030, amng at the maxmzaton of energy recovery from waste. 5. Based on the case study, proposal of an effcent MSW manpulaton system for Shangha 1

2 n Lfe Cycle Assessment (LCA) s used as tool to analyss the recovery energy. The LCA boundary s explaned n Fgure 3. Energy Auxlary Materal Waste Transportaton of Waste to treatment facltes Incneraton Electrcty Generaton Energy Landfll Fg. 3. LCA boundary Emsson 0-1 programmng problem has been appled n the model smulaton to solve the faclty locaton problem n the future MSW management sytem. 3. Results and dscusson (1) Predcton of MSW generaton the future The predcton of MSW s based on the GDP value of Shangha cty. GDP data can partally reflect the real populaton n Shangha because the number of employees from out of Shangha would ncrease f the economy of Shangha s more actve. GDP s also related to the level of people daly lfe. Actually, the data of MSW amount are well ftted wth GDP from 1995 to 2005 by usng the followng equaton: MSW = log GDP (log GDP) 2 Where R2 = 0.99, the unt of MSW s kt, and the unt of GDP s 10 8 RMB. Komyama, et al. 2 (2) The composton of MSW n Shangha The composton of MSW s mportant factor. The change of composton of MSW n Shangha s dsplayed n Fgure 7. The data show that the content of food n MSW decreased gradually, whle that of plastcs and paper exhbted an ncreasng trend. Fg. 5. The change of MSW composton n Shangha from 1990 to (3) The MSW treatment n 2005 n Shangha Meshang Jadng Fg. 6. Management of MSW n 2005 Jangqao GDP (10 8 RMB) MSW (10 3 t) Laogang Year Fg.4. Predcton of MSW n Shangha Thus, The MSW was predcted by adoptng GDP growth rate as shown the followng two cases: Case 1: The economy of Shangha s proposed to mantan a constant growng fashon wth a constant rate of 8%. 3 Case 2: The growng rate for GDP s 8% n the perod of , then decrease 1% every 5 years. The average GDP growng rate over s 6%, consstent wth that reported by Fg. 7. Locaton of MSW management facltes and mass flow n Yuqao Fg. 8. Energy recovery n

3 (4) The MSW treatment n 2030 by model smulaton a) Prncple: 18 dstrcts as MSW generaton source. Only 9 suburbs can buld new facltes, ether ncneraton, or landfll. Total possble facltes s 18. Current faclty: 3 MSW Source S 1 S 2 S S 18 W d E-trans Fg. 10 Locaton of new plants and mass flow under Scenaro 1 Faclty F 1 F 2 F F 21 Y 1 Y 2 Y Y 21 E-const 1 E-proc 1 E-gen 1 E-const 2 E-proc 2 E-gen 2 E-const E-proc E-gen E-const 21 E-proc 21 E-gen 21 b) Scenaro study: Scenaro 1: Capacty of ncneraton plant 3,000 t/d; Capacty of landfll plant 5,000 t/d. Fg. 9. Smulaton Scheme Maxmzaton of Energy Recovered]: TotalEnergy = E-gen { E-trans + E-proc + E-const } [Condtons]: S = ( = 1, 2,, 18; = 1, 2,, 21) x x 0 ( = 1, 2,, 18; = 1, 2,, 21), x Q ( = 1, 2,, 18; = 1, 2,, 21) 0 Faclty should not be bult. Y = ( = 1-18) 1 Faclty should be bult. Y =1 ( = 19, 20, and 21) Y = p ( = 1, 2,, 21) where: S : total MSW mass at source (t/d) x : the mass of MSW transported from source to faclty (t/d) d : the transportaton dstance from source to faclty (km) p: the number of bult facltes Q: The handng capacty of faclty (t/d) E-gen: Energy generated at faclty per day (Mcal/d) E-trans: Energy consumpton for transportaton from source to faclty (Mcal/d) E-proc: Energy consumpton for treatment at faclty, (Mcal/d) E-const: Energy consumpton for constructon of faclty (Mcal/d) Fg. 11. Total Energy for each dsposal process n Scenaro 1 Scenaro 2: Capacty of ncneraton plant 5,000 t/d; Capacty of landfll plant 5,000 t/d. Fg. 12. Locaton of new plants and mass flow under Scenaro 2 Fg.13. Total Energy for each dsposal process n Scenaro 2 3

4 Scenaro 3: Capacty of ncneraton plant 8,000 t/d, Capacty of landfll plant 5,000 t/d. Fg. 14. Locaton of new plants and mass flow under Scenaro 3 Fg. 17. Total Energy for each dsposal process n Scenaro 4. c) Comparson: Transportaton Constructon Processng Generaton Balance Scenaro 3-95, ,593-6,826,007 13,457,830 6,338,444 Fg. 15. Total Energy for each dsposal process n Scenaro 3 Scenaro 4: Plastcs s separated and should be ncnerated; Capacty of ncneraton plant 8,000 t/d; Capacty of landfll plant 5,000 t/d. Fg. 18. Comparson among scenaros A larger capacty of ncneraton reduces wth both the transportaton energy and constructon energy. Separaton of plastcs greatly benefts the extracton energy from waste: mprove the energy generaton, reduce the energy consumpton for constructon and processng. 4. Future drecton (1) Includng cost and envronmental ndex (2) Includng compostng. Fg. 16. Optmzed mass flow n Scenaro 4 Reference 1. Chna Statstcal Yearbooks, R. Komyama, P. Zhang, Z. Lu, Z. L, and K. Ito, Chna s long-term energy outlook for 2030 by 31 provnces based on complng provncal statstcs and developng an economc model, the 22nd Conference on Energy System, Economcs, and Envronment, L. Kus, T. Wang, Chna s pattern of growth: movng to sustanablty and reducng nequalty, World bank Chna offce research workng paper No.2, pp.10. 4

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