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畢業(yè)設(shè)計(jì)（論文）
外文參考文獻(xiàn)譯文及原文
學(xué) 院 環(huán)境科學(xué)與工程學(xué)院
專 業(yè) 環(huán) 境 工 程
年級班別
學(xué) 號
學(xué)生姓名
指導(dǎo)教師
20xx年6月2日
對西班牙南方一個(gè)城市垃圾填埋場產(chǎn)生的沼氣能源的研究
Montserrat Zamora Jorge Ignacio Pe′ rez Pe′ rezb,
Ignacio Aguilar Pave′ sc, A′ ngel Ramos Ridaoa
西班牙格拉納達(dá)大學(xué)土建工程環(huán)境技術(shù)部,18071
西班牙格拉納達(dá)大學(xué)土建工程規(guī)劃建設(shè)部
2005年5月接收,2005年8月確認(rèn)
摘要
雖然垃圾填埋場不可避免產(chǎn)生廢棄的管理問題,但是它仍是最通常的解決城市生活垃圾的方法之一。垃圾填埋場是人為生產(chǎn)甲烷的重要來源。在這種情況下，歐盟已經(jīng)為可再生能源通過了歐盟政策結(jié)構(gòu)里面的沼氣的有效管理的規(guī)則。這是一項(xiàng)研究密封的垃圾填埋場能源恢復(fù)的例子, 但這種能源恢復(fù)是指垃圾填埋場氣體用來生產(chǎn)電能。這一研究的結(jié)果具有很強(qiáng)的經(jīng)濟(jì)生存能力, 這實(shí)現(xiàn)了早先的對安裝的工程. 以經(jīng)驗(yàn)和理論上模型的使用為基礎(chǔ)得出結(jié)果表示沼氣中有 250 到 550 N m3/h的甲烷和一個(gè)以全部流量的45% 比例。 目前它用來生產(chǎn)電力共計(jì)大約 4,500,000 千瓦 h/年。根據(jù)安裝的經(jīng)濟(jì)分析和內(nèi)在的恢復(fù)率 (IRR)估計(jì)開發(fā)時(shí)期為7年。
關(guān)鍵字: 垃圾填埋場氣體,能源恢復(fù),可再生能源,經(jīng)濟(jì)分析
目錄
1. 介紹 1
1.1垃圾填埋場氣體對環(huán)境的影響 1
1.2垃圾填埋場氣體是一個(gè)可重新開發(fā)能源來源 2
1.3. 法律問題 3
1.3.1. 關(guān)于方向性96/61/CE污染的聯(lián)合預(yù)防和控制 3
1.3.2. 垃圾填埋場99/31/CE的指導(dǎo) 3
1.3.3. 歐共體對97/C76/01廢物管理戰(zhàn)略的決議 3
1.3.4.一個(gè)關(guān)于甲烷放射減少的戰(zhàn)略交流 4
2. 格拉那達(dá)城市的垃圾填埋場 (西班牙) 5
2.1. 垃圾填埋場的結(jié)構(gòu) 5
2.2 垃圾的生產(chǎn)和特性 6
2.3 沼氣理論上的生產(chǎn)/生產(chǎn)量的定量化 7
3. 安裝設(shè)計(jì) 10
3.1. 收集和抽出系統(tǒng) 10
3.2. 能源可再生系統(tǒng) 11
4. 經(jīng)濟(jì)上的可行性 12
5. 結(jié)論 12
1. 介紹
1.1垃圾填埋場氣體對環(huán)境的影響
垃圾填埋場的垃圾處理能產(chǎn)生不少的環(huán)境問題,如水污染,臭氣,爆炸和燃燒，窒息,植物破壞,和溫室氣體排放[1-3].現(xiàn)在正用不同的方法來評估這些影響以便能找出解決方案[4-7].
垃圾填埋場氣體(LFG)是在衛(wèi)生垃圾填埋場中自然地發(fā)生有機(jī)廢物分解的副產(chǎn)物,是在生產(chǎn)那期間被微生物地斡旋降解廢物的有機(jī)部分.一個(gè)能生產(chǎn)大約 0.350 Nm3/公斤的沼氣的城市垃圾衛(wèi)生填埋場基本上能夠把生物能轉(zhuǎn)變成可使用的能源.[8,9].
垃圾填埋場氣體產(chǎn)生于有氧和無氧兩種情況。有氧的情況在垃圾處理之后立刻產(chǎn)生并混合到大氣空氣。 開始的有氧階段是非常短的,而且產(chǎn)生出的是由二氧化碳組成的一種氣體。由于氧氣被快速地被消耗, 長期的降解繼續(xù)在沒有氧氣中進(jìn)行,這種典型例子是 55% 的重要的能源價(jià)值產(chǎn)生一種瓦斯和一些揮發(fā)性的有機(jī)化合物 (VOC)甲烷和 45%的二氧化碳 [10-12].在20年內(nèi)大部份的CH4和CO2在垃圾填埋場里產(chǎn)生,但也可能持續(xù)50年或更久。
有兩種解決LFG污染問題的方法,它們是抽出和燃燒LFG,一個(gè)方法是過去用的減少壓力使其重新轉(zhuǎn)變成能源。能源發(fā)展部門稱為安達(dá)盧西亞計(jì)劃。由于LFG 和它的氣味問題,另一個(gè)解決方法是為了其他的目的而重復(fù)使用 LFG 。因?yàn)樗目傆?jì)化學(xué)能可以充分維持燃?xì)廨啓C(jī)的運(yùn)作,因此表明它是有價(jià)值的能源資源。 事實(shí)上,它能用來增加電力的生產(chǎn)的補(bǔ)足或者作為主要的燃料,如作為瓦斯和車輛燃料,或者作為熱量輸送給居民和工業(yè)使用. [1,13].
因?yàn)樗軠p少石燃料的使用而且能減少溫室效應(yīng)，所以作為一個(gè)燃料來源的沼氣使用是能和環(huán)境相適應(yīng)的。在個(gè)別研究中,二個(gè)溫室氣體之一CH4的產(chǎn)生幾乎是二氧化氮的21倍,對溫室效應(yīng)影響比超過二氧化碳更危險(xiǎn).[8,14].垃圾填埋場的CH4主要是人為產(chǎn)生的,而且估計(jì)占全部人為產(chǎn)生CH4的3-19% [15].因?yàn)樗黔h(huán)境的污染和能源不足的有創(chuàng)造力的解決，如能源資源的使用垃圾填埋場瓦斯的恢復(fù)是現(xiàn)在一個(gè)重要興趣的區(qū)域[16,17].
這篇文章是對位于南部西班牙(格拉那達(dá))在2003年秋天安裝的內(nèi)在燃燒引擎的衛(wèi)生垃圾填埋場能源潛能的一項(xiàng)研究.
1.2垃圾填埋場氣體是一個(gè)可重新開發(fā)能源來源
當(dāng)2001年的京都協(xié)議書和馬拉喀什協(xié)議開始生效后,發(fā)展中國家可能需在未來十年內(nèi)減少溫室氣體排放。以此相適應(yīng)，他們也將必須尋求一個(gè)方案將這個(gè)政策對社會影響減到最少。增加使用可重新開發(fā)能源技術(shù)的晉級似乎能解決這個(gè)問題[8,13,18].
在西班牙,這樣的能源技術(shù)被策略計(jì)劃和法律配置,關(guān)于使用可重新開發(fā)的能源來源的安裝的電力生產(chǎn), 產(chǎn)品浪費(fèi).
安達(dá)盧西亞當(dāng)?shù)胤秸呀?jīng)把它在這一個(gè)區(qū)域中的計(jì)劃,組織,和行動(dòng)的協(xié)調(diào)發(fā)展一系列的策略計(jì)劃當(dāng)作環(huán)境政策的一部份.在2000年第二計(jì)劃 當(dāng)作積極的國防工業(yè)(2003-2006)[21] 被實(shí)現(xiàn)。 這關(guān)于能源率先的所有指令及帶來的計(jì)劃在預(yù)定的時(shí)間內(nèi)將會在安達(dá)盧西亞實(shí)行,這一計(jì)劃保證環(huán)保而且達(dá)到了要在區(qū)域中使用豐富可重新開始發(fā)的能源資源的來源多元化。
在安達(dá)盧西亞的2000能源消費(fèi)方面共計(jì)11,569ktep和在相同的時(shí)間里可重新開發(fā)的能源占了649ktep。在能源消費(fèi)結(jié)構(gòu)中的生物能源占90%而水力能源占5.3%.[21].
在西班牙已經(jīng)有各種各樣的主動(dòng)描述來自城市的廢棄垃圾填埋場沼氣的產(chǎn)生如下列的例子[22].(阿斯圖里亞斯)以408,234 Tm/year廢儲蓄和六個(gè)引擎在750千瓦,一個(gè)引擎在300千瓦和二個(gè)引擎在250千瓦;(ii)Artigas(畢爾巴鄂)以243,361 Tm/year廢儲蓄和二個(gè)引擎在450千瓦;(iii)圣·馬科斯(桑河圣塞巴斯蒂昂)以146,172 Tm/year廢儲蓄和二個(gè)引擎在650千瓦; );(iv)Gungora(潘普洛納)以118,016 Tm/year廢儲蓄和一個(gè)引擎在750千瓦. 這些信息有力地證明生物能源是可再造能源的一個(gè)重大來源。生物能轉(zhuǎn)換能用的能量的例子在埋垃圾填埋場可以看到。
1.3. 法律問題
雖然在西班牙沒有在都市廢物受控儲蓄具體地調(diào)控沼氣高效率的管理的立法，歐共體出臺推薦并且被制定的政策已經(jīng)開始極大影響西班牙的方針。
1.3.1. 關(guān)于方向性96/61/CE污染的聯(lián)合預(yù)防和控制
合并到西班牙立法里作為由工業(yè)活動(dòng)生產(chǎn)的錫鉛軸承合金16/2002,方向性96/61/CE通過防止,并且減少大氣、水和土壤的污穢，并且包城市廢物的處理和排除。這個(gè)方針的顯著方面是以下列各項(xiàng) [23]:(i)歐共體的會員國必須采取必要的措施提供主管當(dāng)局保證設(shè)施通過最好的可利用技術(shù)的應(yīng)用特別是管理方面，在這種情況下所有恰當(dāng)?shù)念A(yù)防措施采取防止污染;(ii)必須高效率地使用能量和采取必要的措施防止嚴(yán)重的事故和減少可能的負(fù)面影響;(iii)當(dāng)工業(yè)設(shè)施關(guān)閉并且停止運(yùn)行時(shí)，必須采取必要的措施在活動(dòng)明確停止后避免所有污染風(fēng)險(xiǎn)和退回操作站到一個(gè)令人滿意的狀態(tài)(崗位關(guān)閉責(zé)任)。
1.3.2. 垃圾填埋場99/31/CE的指導(dǎo)
各種各樣的提案、共同基礎(chǔ)的草稿和討論以后在環(huán)境保護(hù)，方向性99/31/CE (真正的修改的1481/2001在西班牙法典)被立法并且通過了。它包含關(guān)于氣體管理的以下措施[24]:(i)采取適當(dāng)?shù)拇胧┛刂评盥駳怏w的儲積和散發(fā);(ii)在所有垃圾填埋，放置的生物可分解的廢物，氣體將恢復(fù)，被處理并回收。 (iii)垃圾填埋氣體只要可能對環(huán)境和公共衛(wèi)生產(chǎn)生負(fù)面影響都將被執(zhí)行就象避免的存貯、處理和再用;(iv)應(yīng)該監(jiān)測垃圾填埋每個(gè)部分的氣體。在氣體不可能被重復(fù)利用創(chuàng)造能量的那些垃圾填埋，它將被監(jiān)測站焚燒和處理。
1.3.3. 歐共體對97/C76/01廢物管理戰(zhàn)略的決議
決議97/C76/01在1997年2月24日通過了。在第35章中它具體地要求歐共體的成員應(yīng)該采取必要的環(huán)保措施保證垃圾填埋站點(diǎn)和其他的污染的地點(diǎn)恢復(fù)到對一個(gè)令人滿意的狀態(tài)[25]。
1.3.4.一個(gè)關(guān)于甲烷放射減少的戰(zhàn)略交流
為了考慮到甲烷放射對氣候的潛在作用，這些信息指出需要分析這樣的放射產(chǎn)生的問題并且需要確認(rèn)來源和排水設(shè)備站點(diǎn)。它也強(qiáng)調(diào)了建立一個(gè)共同的戰(zhàn)略必要。這將基本上包括對此減少放射的方法并且將被合并到會員國的一套立法指南里。
措施的實(shí)施是一個(gè)在特定時(shí)期將達(dá)到放射物的減少的目的。 建立的政治措施將根據(jù)他們的成本效益,潛在的經(jīng)濟(jì)效益和社會后果進(jìn)行評估.
根據(jù)一項(xiàng)較早的研究，主要焦點(diǎn)應(yīng)該是在甲烷放射，在1990年農(nóng)業(yè)、廢物和能量的最大的貢獻(xiàn)占?xì)W共體甲烷放射量的45,32和23%，分別在那些顯著的區(qū)段.
甲烷的主要來源是垃圾填埋放置的有機(jī)物的無氧發(fā)酵。通信COM (96) 557包括以下內(nèi)容[26]:(i)應(yīng)該將現(xiàn)有的垃圾填埋和新的垃圾填埋進(jìn)行區(qū)分對待;(ii)在現(xiàn)有的垃圾填埋情況下，當(dāng)局應(yīng)該為甲烷放射的管理合并基礎(chǔ)設(shè)施改進(jìn)他們的技術(shù)容量和環(huán)境水平;(iii)在新的垃圾填埋情況下，應(yīng)該嚴(yán)密監(jiān)測被授予許可證的受控絕氧儲蓄。無論如何，核實(shí)是否有限制甲烷放射的其他方式和為它召開會議和能量評估而合并有效率的系統(tǒng)是有必要的;(iv)當(dāng)這樣評估不可行時(shí)，基礎(chǔ)設(shè)施需為它的總?cè)紵〉糜行У淖饔?(v)最后，會員國應(yīng)該開發(fā)對甲烷氣開發(fā)的經(jīng)濟(jì)刺激傾向，這將有利于垃圾填埋技術(shù)的利用和有機(jī)物數(shù)量的減少。
在1999年4月26日決議99/296/CE，和修改過的關(guān)于二氧化碳監(jiān)視和其他溫室氣體的決議93/389/CEE出臺了,例如甲烷。這個(gè)決議肯定會員國應(yīng)該做存貨排氣和由他們的排水設(shè)備站點(diǎn)排除的來源，并且講述減少這樣放射所采取的政策和全國章程因而促進(jìn)他們的總排除。
很明顯，這些章程是為沼氣的高效率管理而采取模棱兩可的措施。然而確切的是需要減少和未處理的沼氣放射有在環(huán)境的負(fù)面地影響減到最小。
2. 格拉那達(dá)城市的垃圾填埋場 (西班牙)
2.1. 垃圾填埋場的結(jié)構(gòu)
這篇文章是對拉納達(dá)格東北部2公里的一個(gè)有300,000人口的南西班牙城市垃圾填埋的研究。這個(gè)表面積為46.54的垃圾填埋場從1984年開始運(yùn)行到1999年結(jié)束。在這個(gè)期間，垃圾沿山坡的河床放置的平均高度是870和500 m (參見圖 1).
垃圾填埋場是有一定密度的, 當(dāng)數(shù)年以后發(fā)現(xiàn)前面地布滿來自相同的區(qū)域的數(shù)層土壤和類似垃圾填埋場的物質(zhì)。 使填滿垃圾的垃圾填埋場的密度變緊密,垃圾變緊密的速度是0.7-0.9 Tm/m3.將它過濾并在垃圾填埋場流通的水池中被收集。氣體由一系列設(shè)施抽出所在30-35 m 的距離被分開。
1999年出于對緩解環(huán)境消極影響的考慮，垃圾填埋被封閉了。 隨后，計(jì)劃被草擬修建設(shè)施提取沼氣和重復(fù)利用它創(chuàng)造電能。 同年由INAGRA項(xiàng)目被執(zhí)行了(屬于CESPA3的公司)。
這個(gè)區(qū)域平均每年的秋天和冬天季節(jié)降雨降雪從66到400毫米變動(dòng).在格拉納達(dá)的平均每年的溫度主要依靠氣象臺測量得到。以Cartuja氣象臺為標(biāo)準(zhǔn)城市的平均溫度是15.3 1C，而在城市之外10公里的機(jī)場氣象臺它是14.81C.
格拉納達(dá)的溫度受內(nèi)華達(dá)山脈影響。最高溫度在夏天的數(shù)個(gè)月而最低溫度是在十二月和一月。平均每年溫度的熱量變化是很大的，共計(jì)差不多201C。 這是存在白天和夜間溫度之間的變化。
區(qū)域的潛在蒸發(fā)量，由Thornthwaite方法計(jì)算，在夏天數(shù)個(gè)月期間通常有一個(gè)氣流的時(shí)期可達(dá)范圍從700到900毫米。
垃圾填埋是在阿爾漢布拉宮一個(gè)大黏土狀水池底土下形成，上層結(jié)構(gòu)是由沙子制成，在下層中減少水傳輸容量。在垃圾掩埋場沒有表面的帶水層或地下水。
當(dāng)垃圾填埋場被密封之后，來自格拉那達(dá)城市的垃圾,連同其他的附近城市和城鎮(zhèn)的垃圾在格拉納達(dá)外面20公里處進(jìn)行植物堆肥，垃圾處理和最近在Alhendin鎮(zhèn)開始安裝堆肥設(shè)施.對植物產(chǎn)生主要作用的是： 金屬、紙和紙板、塑料和容器混雜，有機(jī)材料為天然肥料，其他為簡單廢物。
2.2 垃圾的生產(chǎn)和特性
在垃圾填埋場的最大處理量期間，總共有1,420,000Tm的垃圾進(jìn)入垃圾填埋場。垃圾生產(chǎn)的增量可以在圖2中看出。表明從1984年到1999年期間有相當(dāng)數(shù)量的垃圾進(jìn)入了垃圾填埋場。這是最近幾十年來垃圾數(shù)量的傾向特點(diǎn)和在和平社會的垃圾平均比率[18,27的]。
為了分析垃圾的宏觀構(gòu)成。表1得出了現(xiàn)場研究的結(jié)果。
垃圾的宏觀構(gòu)成
重量 (%)
濕度
(%)
垃圾干重
(%)
干燥垃圾的可降解性 (%)
容易
難
總計(jì)
有機(jī)成分
30.50
75.00
7.63
75.00
7.00
82.00
濕紙
24.00
20.00
19.20
30.00
20.00
50.00
硬紙板
1.50
35.00
0.98
10.00
20.00
30.00
紡織品
1.00
20.00
0.80
0.00
10.00
10.00
塑料
21.00
1.00
20.79
0.00
0.00
0.00
金屬
5.00
1.00
4.95
0.00
0.00
0.00
玻璃
12.00
1.00
11.88
0.00
0.00
0.00
其他或惰性物質(zhì)
5.00
1.00
4.95
5.00
16.00
21.00
合計(jì)
Total
100.00
28.83
71.17
11.82
5.44
17.26
表1垃圾填埋場的宏觀構(gòu)成
2.3 沼氣理論上的生產(chǎn)/生產(chǎn)量的定量化
一些方法已經(jīng)用于估計(jì)在垃圾處置站點(diǎn)CH4放射。 這些方法有很大的變化，不僅僅在于他們的假定，而且在于他們的復(fù)雜和需要的相當(dāng)多的資料。一些根據(jù)理論氣體出產(chǎn)量來估算，而另外一些使用優(yōu)先處理的動(dòng)能學(xué)式子[28-32]。
2.3.1. 沼氣的經(jīng)驗(yàn)預(yù)估
沼氣產(chǎn)生的估算是通過經(jīng)驗(yàn)計(jì)算，換句話說，計(jì)算是使用實(shí)驗(yàn)和理論的數(shù)據(jù)?；诶暮暧^性和先前區(qū)段的下降數(shù)據(jù)，以及對從垃圾填埋場散發(fā)的氣體樣品的分析，由此假設(shè)出可能的垃圾的化學(xué)式(參見表2)。
表2
可能的垃圾的化學(xué)式
C44 H70O29N
干燥成分 可降解成分 化學(xué)式
71.17% 17.26%
表3
沼氣產(chǎn)量和甲烷濃度的估算
甲烷產(chǎn)量 (m3/Tm) 沼氣產(chǎn)量 (m3/Tm) 甲烷濃度 (% v/v)
82.43 160.21 51.39
每噸垃圾生產(chǎn)的沼氣量已經(jīng)由分解等式定義出了。40年的分解結(jié)果在表3總結(jié)出來了。
2.3.2.沼氣理論上和真實(shí)的生產(chǎn)量
前面部分提出每噸垃圾產(chǎn)生的沼氣量已經(jīng)被假定計(jì)算出來。它是根據(jù)化學(xué)計(jì)量學(xué)演算出的假定數(shù)據(jù)，但在實(shí)際垃圾填埋場的情況卻復(fù)雜的多。其中一個(gè)重要的原因是潛在的垃圾填埋氣體生產(chǎn)的評估是分解動(dòng)能學(xué)。有些研究員使用根據(jù)預(yù)測出的知識構(gòu)成的等式或算法的模型來估算[23]; 其它使用以實(shí)驗(yàn)為基礎(chǔ)的模型受到外環(huán)境的約束[33]; 而且他們是基于領(lǐng)域測量上的研究 [29].
在這種情況下，決心發(fā)展一個(gè)理論-實(shí)際混合的方法即Tabasaran(1976) 運(yùn)動(dòng)模型[和后來的修正的韋伯(1996)模型30][31]. 這個(gè)方法在二個(gè)不同情況下允許每噸廢物的生產(chǎn)力曲線上下正常變化：(i)為快速地分解23%的無機(jī)垃圾(SDW)和34%有機(jī)垃圾(RDW)以及沼氣的生產(chǎn)和抽出而選取一個(gè)最佳的條件;(ii)一個(gè)比較糟糕的情況是有些地方的情況是不一樣的,如有些是有機(jī)材料的百分比為RDW 31%和無機(jī)材料的百分比為SDW 21%。
如果用不同的參數(shù)設(shè)置來評估對比這二種情況。這樣生產(chǎn)水平將獲得一個(gè)從115.92m3/Tm從172.43m3/Tm之間的有利變化。根據(jù)假設(shè)垃圾填埋氣體理論產(chǎn)生量160.21m3/Tm落在這范圍之內(nèi)。
但是，在垃圾填埋場里會發(fā)生更加復(fù)雜的反應(yīng)，并且產(chǎn)生其他化合物例如硫化氫、硫醇、CO、水蒸氣、N2和O2。而且，根據(jù)垃圾填埋場的開發(fā)系統(tǒng)和能量補(bǔ)救系統(tǒng)[34]，應(yīng)該使用甲烷修正系數(shù)(MCF)來使甲烷的最后的比例在45%左右，這在其他研究方面都可以獲得.[8,18,35]。
圖3顯示了甲烷氣含量為50和45%時(shí)的最好和最壞情況的生產(chǎn)曲線.
沼氣產(chǎn)量
(甲烷 45%)
沼氣產(chǎn)量
(甲烷50%)
圖 3. 最佳與最壞的沼氣產(chǎn)量分析.
讓我們感興趣的實(shí)際上是可利用的并且最可能的集中的生產(chǎn)，這里估計(jì)有45%甲烷含量的生產(chǎn)符合要求。沼氣在垃圾填埋場里作為可燃燒的氣體是以大約4000kcal/Nm3的低卡值(LCV)集中(根據(jù)它的甲烷內(nèi)容)，研究表明是在3861kcal/N m3LCV之下。這意味著沼氣有很高能量可以轉(zhuǎn)變成電能[14]。
沼氣單位(Nm3/h)
能量單位 (KW)
圖 4. 2002–2010.年中沼氣最大的開發(fā)潛能
圖4是一個(gè)開發(fā)時(shí)期中可用的沼氣最大的開發(fā)潛能。項(xiàng)目實(shí)用性取決于引擎或渦輪的使用，一般是7.5年(操作8000h/year)或8年(操作7500h/year)。設(shè)備將持續(xù)燃燒沼氣以達(dá)到高溫狀態(tài)。因?yàn)橐婊驕u輪的替換或大規(guī)模修理都是大投資.如果在低于期望的沼氣量,在經(jīng)濟(jì)上是不可行的。
在格拉納達(dá)的密封垃圾填埋場被認(rèn)為是產(chǎn)沼氣量相對比較高的垃圾填埋場，估計(jì)在250-550 N m3/h。 這將平均生產(chǎn)出4,500,000千瓦h(yuǎn)/year的電能。為此，一個(gè)活躍氣體匯集系統(tǒng)和排除系統(tǒng)發(fā)電的受控燃燒問題是必要的。為了獲得最佳的沼氣能量，把垃圾填埋氣體集中在一個(gè)地方是最佳的選擇。以下內(nèi)容是描述使用基礎(chǔ)設(shè)施反氣化垃圾填埋氣體并且概述能量補(bǔ)救系統(tǒng)。
3. 安裝設(shè)計(jì)
為沼氣提取和再用提議的技術(shù)可以認(rèn)為是標(biāo)準(zhǔn)技術(shù)。它是最新技術(shù)與歐共體和西班牙立法的完全相符。氣體提取和運(yùn)用系統(tǒng)設(shè)計(jì)是用于這些設(shè)施一般類型。根據(jù)這個(gè)設(shè)計(jì)計(jì)算總成本。以下簡要地描述設(shè)施的組成。
3.1. 收集和抽出系統(tǒng)
氣體匯集系統(tǒng)包括50口垂直的氣體提取井網(wǎng)絡(luò)，如圖5所見，脫水單位，高密度聚乙烯氣體運(yùn)輸管道和閃光。通過監(jiān)控儀器包括周期性調(diào)整油井控制這個(gè)系統(tǒng)活動(dòng)。氣體提取設(shè)備以吹風(fēng)機(jī)，在系統(tǒng)的吸壓力機(jī)為LFG的提取。氣體提取系統(tǒng)的撤除和重建是為了維護(hù)氣體高出產(chǎn)量。
3.2. 能源可再生系統(tǒng)
為了保證總環(huán)境補(bǔ)救垃圾填埋站點(diǎn)，必要的氣體處理設(shè)備，例如閃光，管道和吹風(fēng)機(jī)，是根據(jù)最佳的氣體生產(chǎn)曲線計(jì)量。然而，對于電力生產(chǎn)，學(xué)習(xí)安裝一個(gè)最佳類型的發(fā)電器是必要的(即根據(jù)最佳和最壞的情景)?？紤]到植物在7.5年(60,000 h)中操作量是8000 h/year，所以沼氣的流程容量低于50%不應(yīng)該是引擎的最大設(shè)計(jì)流程。
例如，研究表示836千瓦引擎在最佳條件下是可實(shí)行的。然而，發(fā)現(xiàn)624千瓦的電子引擎能為60,000h操作，而且無需在沼氣最佳或最壞情況下的50%設(shè)計(jì)流程，這就是選擇的引擎種類。
4. 經(jīng)濟(jì)上的可行性
垃圾填埋氣體(LFG)運(yùn)用的經(jīng)濟(jì)可行性取決于一定的因素，包括LFG質(zhì)量，地方設(shè)備能量價(jià)值(電、蒸汽、氣體或者其他獲得的產(chǎn)品)和選擇。標(biāo)準(zhǔn)經(jīng)濟(jì)下的LFG電力生產(chǎn)技術(shù)費(fèi)用效益分析。費(fèi)用劃分為基礎(chǔ)建設(shè)成本、每年運(yùn)行和維護(hù)(O&M)費(fèi)用，以及煤炭稅和能源稅，還有個(gè)重要費(fèi)用成本是環(huán)境保護(hù)。效益是電力能源的賣出[14]。
在進(jìn)行項(xiàng)目的收益計(jì)算時(shí)，應(yīng)該考慮到最好和最壞的情況，而且要包括分期償還款和開發(fā)費(fèi)用。垃圾填埋的經(jīng)濟(jì)可行性取決于資金流動(dòng)的經(jīng)濟(jì)分析，在3年期間和7年的另一個(gè)期間使用內(nèi)部退稅率(IRR)作為有利參量。
就這些經(jīng)濟(jì)上有利假設(shè)的最好和最壞的情況(參見圖6)，在IRR上沒有很大區(qū)別。這意味著垃圾填埋在7年里從經(jīng)濟(jì)和環(huán)境上可以令人滿意和有效益。
圖 6. 3—7年開發(fā)期中的內(nèi)部資源回收率.
5. 結(jié)論
經(jīng)驗(yàn)和理論設(shè)計(jì)模型是用3861kcal/Nm3LCV產(chǎn)生的沼氣的容量估算45%甲烷含量。
在垃圾填埋場對沼氣的產(chǎn)生分析表示，整體流速從250到550Nm3/h范圍變化，這說明潛在的平均電力生產(chǎn)力是4,500,000千瓦h(yuǎn)/year。根據(jù)這些數(shù)據(jù)，在7年的開發(fā)期間設(shè)備的經(jīng)濟(jì)能力為沼氣補(bǔ)救估計(jì)有IRR 20%。
得到的結(jié)果表示，格拉納達(dá)密封的垃圾填埋場沼氣利用在城市廢物管理中是一個(gè)非常好的選擇。此外，由于它可增加再造能源來源的用途并且減少甲烷和二氧化碳產(chǎn)生的溫室效應(yīng),對于用沼氣作為燃料來源滿足環(huán)境要求。
第一年的安裝和操作結(jié)果已經(jīng)出來了。我們將會在這篇文章上闡述這些結(jié)果，并且將來能出版這篇文章。
13
任務(wù)書
題目名稱
200噸/天城市生活垃圾衛(wèi)生填埋場設(shè)計(jì)
學(xué)生學(xué)院
環(huán)境科學(xué)與工程學(xué)院
專業(yè)班級
姓 名
學(xué) 號
一、畢業(yè)設(shè)計(jì)（論文）的內(nèi)容
（1）文獻(xiàn)檢索、資料收集和翻譯；
（2）制定設(shè)計(jì)方案和設(shè)計(jì)計(jì)算內(nèi)容；
（3）編寫設(shè)計(jì)說明書和繪制工程圖紙；
（4）工程概算和經(jīng)濟(jì)分析。
二、畢業(yè)設(shè)計(jì)（論文）的要求與數(shù)據(jù)
（1）基本設(shè)計(jì)參數(shù)。垃圾衛(wèi)生填埋量200噸/天，核算相應(yīng)的垃圾滲濾液產(chǎn)生量、填埋氣的產(chǎn)生量及處理措施。
（2）技術(shù)要求。垃圾衛(wèi)生填埋場設(shè)計(jì)滿足相應(yīng)的國家標(biāo)準(zhǔn)，工業(yè)企業(yè)設(shè)計(jì)衛(wèi)生標(biāo)準(zhǔn)、大氣污染控制技術(shù)標(biāo)準(zhǔn)、國家相關(guān)技術(shù)政策、凈化效率和操作適應(yīng)負(fù)荷范圍等。
（3）可靠性要求。包括預(yù)定使用壽命，設(shè)計(jì)可靠性分析以及設(shè)計(jì)結(jié)果的敏感性分析等。
（4）經(jīng)濟(jì)性要求。包括工程概算、成本分析和技術(shù)經(jīng)濟(jì)分析。
（5）其它要求：包括制造工藝要求、節(jié)能要求、安全要求、質(zhì)量檢測要求以及應(yīng)遵循的國家法令、政策、規(guī)范和標(biāo)準(zhǔn)等。
三、畢業(yè)設(shè)計(jì)（論文）應(yīng)完成的工作
（1）紙質(zhì)設(shè)計(jì)說明書及其電子版本；
（2）譯文及原文影印件。
（3）設(shè)計(jì)圖紙（平面布置圖、工藝流程圖、主要構(gòu)筑物圖、管道布置圖等）。
四、畢業(yè)設(shè)計(jì)（論文）進(jìn)程安排
序號
設(shè)計(jì)（論文）各階段名稱
地點(diǎn)
起止日期
1
文獻(xiàn)檢索及資料收集
圖書館
2007.4.2-2007.4.12
2
外文資料熟悉及翻譯
圖書館
2007.4.13-2007.4.20
3
工藝設(shè)計(jì)及說明書編寫
設(shè)計(jì)室
2007.4.21-2007.5.25
4
工程繪圖
設(shè)計(jì)室
2007.5.26-2007.6.10
5
答辯階段
課 室
2007.6.11-2007.6.15
五、應(yīng)收集的資料及主要參考文獻(xiàn)
[1] 趙毅等.有害氣體控制工程.北京：化學(xué)工業(yè)出版社，2001
[2] 熊振湖.費(fèi)學(xué)寧.池勇等編.大氣污染防治技術(shù)及工程應(yīng)用.北京：機(jī)械工業(yè)出版社，2003
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Study of the energy potential of the biogas produced by an urban waste landfill in Southern Spain
Montserrat Zamora Jorge Ignacio Pe′ rez Pe′ rezb,
Ignacio Aguilar Pave′ sc, A′ ngel Ramos Ridaoa
Section of Environmental Technology, Department of Civil Engineering, University of Granada, 18071 Granada, Spain
Section of Construction Engineering, Department of Civil Engineering, University of Granada, Granada, Spain
Received 8 April 2005; accepted 5 May 2005
Abstract
Sanitary landfills have been and continue to be one of the most common ways to dispose of urban waste although such landfills inevitably generate waste management problems. Landfills are an important source of anthropogenic CH4 emissions. In this sense the European Union has passed regulations regarding the effective management of biogas within the framework of an EU policy for renewable energies. The sealed landfill analyzed in this study is an example of energy recovery, but in this case the biogas generated by the landfill is being re-used to produce electrical energy. This article presents the results of the economic viability study, which was carried out previous to the construction of the installation. The results based on the use of empirical and theoretical models show the biogas to have a 45% proportion of methane and an overall flowrate ranging from 250 to 550 N m3/h. It is presently being used to produce electricity amounting to approximately 4,500, 000 kW h/year. The economic viability of the installation was estimated by means of the Internal Recovery Rate (IRR) for an exploitation period of 7 years.
Keywords: Landfill gas; Energy recovery; Renewable energy; Economic analysis
Contents
1. Introduction 1
1.1. Environmental impacts of landfill gas 1
1.2. Landfill gas as a renewable energy source 2
1.3. Legal questions 2
1.3.1. Directive 96/61/CE regarding the integrated prevention and control of pollution 3
1.3.2. Directive 99/31/CE on landfilling of waste 3
1.3.3. Resolution 97/C76/01 on an EU waste management strategy 3
1.3.4. Communication regarding a strategy for the reduction of methane emissions 4
2. An urban waste landfill in Granada (Spain) 5
2.1. Profile of the landfill 5
2.2. Production and characterization of wastes 6
2.3. Quantification of the theoretical production/yield of biogas 6
2.3.1. Empirical estimate of biogas 7
2.3.2. Theoretical and actual production of biogas 8
3. Installation design 10
3.1. Collection and extraction system 10
3.2. Energy recovery system 11
4. Economic viability 11
5. Conclusions 12
6. References 12
1. Introduction
1.1. Environmental impacts of landfill gas
Waste disposal in landfills can generate environmental problems such as water pollution, unpleasant odors, explosion and combustion, asphyxiation, vegetation damage, and greenhouse gas emissions [1–3]. Different methods are presently being used to evaluate these problems in order to find solutions for them [4–7].
Landfill gas (LFG) is a naturally occurring by-product of the decomposition of organic waste in sanitary landfills, and is produced during the microbially mediated degradation of the organic portion of waste. An example of the conversion of a biomass into usable energy can be seen in sanitary landfills that produce an amount of biogas of about 0.350 N m3/kg of solid urban waste [8,9].
Landfill gas is generated under both aerobic and anaerobic conditions. Aerobic conditions occur immediately after waste disposal due to entrapped atmospheric air. The initial aerobic phase is short-lived and produces a gas mostly composed of carbon dioxide.
Since oxygen is rapidly depleted, a long-term degradation continues under anaerobic conditions, thus producing a gas with a significant energy value that is typically 55% methane and 45% carbon dioxide with traces of a number of volatile organic compounds (VOC) [10–12]. Most of the CH4 and CO2 is generated within 20 years of landfill completion, whereas emissions may continue for 50 years or more.
There are two possible solutions for the problem of LFG emissions. One solution is the extraction and flaring of the LFG, a method often used in the past to reduce the pressure of the LFG as well as its odor. The other solution is to reuse LFG for other purposes. Since its total chemical energy is sufficient to sustain the operation of a gas turbine, it is evidently a valuable energy resource. In fact, it can be used as a supplementary or primary fuel to increase the production of electric power, as a pipeline quality gas and vehicle fuel, or even as a supply of heat and carbon dioxide for greenhouses and various industrial processes [1,13].
The use of biogas as a fuel source is environmentally sound because it contributes to a reduction of fossil fuel use and mitigates the greenhouse effect. In particular, the emissions of CH4, one of the two greenhouse gases emitted, are almost 21 times more dangerous than carbon dioxide for the greenhouse effect [8,14]. Landfills comprise the principal source of anthropogenic CH4 emissions, and are estimated to account for 3–19% of anthropogenic CH4 emissions globally [15]. The recovery of landfill gas for use as an energy resource is now an area of vital interest since it is a creative solution for both environmental pollution and energy shortage [16,17].
This article presents the results of a study of the energy potential of a sanitary landfill located in southern Spain (Granada) previous to the installation of internal combustion engines in the autumn of 2003.
1.2. Landfill gas as a renewable energy source
When the Kyoto Protocol and the Marrakech Agreement of 2001 go into effect, developing countries may have to significantly reduce greenhouse gas emissions in the coming decade. In a parallel way, they will also have to seek a way to minimize the socioeconomic impact of such a policy. The increased use and promotion of renewable energy technologies seem to be a viable solution [8,13,18].
In Spain the deployment of such energy technologies is regulated by strategic plans and laws such as the Plan de Fomento de Energ?′as Renovables1 (PLAFER) [19] and the Real Decreto 2818/98 [20] regarding electricity production by installations using renewable energy sources, waste products, and co-generation.
The Andalusian regional government, as part of its environmental policy, has developed a series of strategic plans regarding the planning, organization, and coordination of action in this area. In 2000 the second Plan Energe′tico de Andaluc?′a2 (2003–2006) [21] was implemented. This plan seeks to bring together all of the directives regarding energy initiatives that will be carried out in Andalusia during the stated time period. This plan is committed to environmental protection and targets the diversification of energy sources with a view to making use of the abundant renewable energy resources available in the region.
In 2000 energy consumption in Andalusia amounted to 11,569 ktep and within this same time period renewable energies accounted for 649 ktep. The contribution of biomass to the structure of energy consumption was 90% followed by hydraulic energy with 5.3% [21].
In Spain there have been various initiatives aimed at the recovery of biogas from urban waste landfills as shown in the following examples [22]: (i) Ser?′ n (Asturias) with waste deposits of 408,234 Tm/year and a nominal power of six engines at 750 kW, one engine at 300 kW, and two engines at 250 kW; (ii) Artigas (Bilbao) with waste deposits of 243,361 Tm/year and a nominal power of two engines at 450 kW; (iii) San Marcos (San Sebastian) with waste deposits of 146,172 Tm/year and a nominal power of two engines at 650 kW; (iv) Gungora (Pamplona) with waste deposits of 118,016 Tm/year of waste and a nominal power of one engine at 750 kW. This information is eloquent proof that biomass is a significant source of renewable energy. An example of the conversion of a biomass into usable energy can be seen in sanitary landfills.
1.3. Legal questions
Although in Spain there is no legislation that specifically regulates the efficient management of biogas in controlled deposits of urban waste, the European Union has published recommendations and enacted directives that have already begun to significantly affect Spain.
1.3.1. Directive 96/61/CE regarding the integrated prevention and control of pollution
Incorporated into Spanish legislation as Ley 16/2002, Directive 96/61/CE was passed to prevent and reduce the contamination of the atmosphere, water, and soil produced by industrial activity, and includes the treatment and elimination of urban waste. Salient aspects of this directive are the following [23]: (i) Member States of the European Union must take the necessary measures to provide that the competent authorities ensure that installations are operated in such a way that all the appropriate preventive measures are taken against pollution, in particular through application of the best available techniques; (ii) Energy must be used efficiently, and necessary measures taken to prevent serious accidents and limit possible negative impacts; (iii) When an industrial installation is closed down and ceases operation, necessary measures must be taken upon definitive cessation of activities to avoid any pollution risk and return the site of operation to a satisfactory state (post-closure responsibility).
1.3.2. Directive 99/31/CE on landfilling of waste
After various proposals, drafts, and discussions to find common ground on environmental protection, Directive 99/31/CE (Real Decreto 1481/2001 in the Spanish legal code) was enacted and passed. It contains the following regulations regarding the management of gases [24]: (i) Appropriate measures will be taken to control the accumulation and emission of landfill gas; (ii) At all landfills where biodegradable wastes are deposited, gas will be recovered, treated and recycled. If the gas obtained cannot be used to produce energy, it should be burnt; (iii) The storage, treatment, and reuse of landfill gas will be carried out in such a way as to avoid, insofar as possible, negative impacts on the environment and public health; (iv) Gas should be monitored at each section of the landfill. In those landfills in which gas cannot be reused to create energy, it will be monitored at the site where such gas is emitted or burnt.
1.3.3. Resolution 97/C76/01 on an EU waste management strategy
Resolution 97/C76/01 was passed on February 24, 1997. In Article 35 it specifically affirms that members of the European Union should take the necessary cleanup measures to guarantee the restoration of former landfill sites and other contaminated locations to a satisfactory state [25].
1.3.4. Communication regarding a strategy for the reduction of methane emissions
In order to take into account the potential effect of methane emissions on the climate, this communication points out the need to analyze the problems derived from such emissions as well as the need to identify sources and drainage sites. It also underlines the necessity of establishing a common strategy. This would basically consist of methods of reducing emissions as well as a set of guidelines in this regard that would be incorporated into the legislation of Member States.
Among the measures to be implemented would be the establishment of an objective for the reduction of emissions to be achieved in a given time period. The political measures established would be evaluated according to their cost–benefit in terms of potential economic and social consequences.
According to a previous study, the main focus should be on those sectors that make the largest contributions to methane emissions, notably agriculture, waste and energy which in 1990 accounted for 45, 32 and 23% of EU methane emissions, respectively.
The main source of the methane emissions derived from waste management is the anaerobic fermentation of the organic material deposited in landfills. Communication COM(96)557 includes the following recommendations [26]: (i) A distinction should be made between existing landfills and new landfills; (ii) In the case of existing landfills, authorities should improve their technological capacity and environmental level by incorporating the infrastructure necessary for the management of methane emissions; (iii) In the case of new landfills, the permits granted to controlled anaerobic deposits should be strictly monitored. In any case, it is always necessary to verify whether there are other ways of limiting methane emission, and at the same time incorporate highly efficient systems for its reception and energy evaluation; (iv) When such evaluation is not feasible, the infrastructure necessary for its total combustion should be available and operative; (v) Finally, Member States should develop economic incentives to favor the recovery of methane gas, the use of technologies, and the reduction of the amount of organic matter deposited in landfills.
Decision 99/296/CE published on April 26, 1999, modified Decision 93/389/CEE regarding the monitoring of CO2 and other greenhouse gases such as methane. This decision affirms that Member States should make an inventory of the sources of gas emissions and their elimination by drainage sites, as well as describe the policies and national regulations adopted to reduce such emissions, and thus facilitate their total elimination.
As can be observed, these regulations are somewhat ambiguous in reference to the measures to be taken for the efficient management of biogas. Nevertheless, what is clear is the message regarding the need to reduce and minimize the negative impact that uncontrolled biogas emission has on the environment.
2. An urban waste landfill in Granada (Spain)
2.1. Profile of the landfill
The landfill studied in this article is located 2 km northeast of Granada, a city in southern Spain with a population of 300,000 inhabitants. The landfill, with a surface area of 46.54 Has, was in active operation from 1984 to 1999. During this period, the waste was deposited on a hillside running along the river Beiro with an average altitude of 870 and 500 m (see Fig. 1).
The landfill is of medium density, and over the years was progressively covered with layers of soil from the same area and similar to that found in the bed of the landfill. The waste compacting process was carried out by means of compacting equipment, with a waste compacting degree of 0.7–0.9 Tm/m3. The leachate was collected in pools where it was pumped out again to be recirculated in the landfill. The extraction of the gas was carried out by a series of gas extraction wells separated by distances of 30–35 m.
In 1999 with a view to mitigating the negative environmental impact, the landfill was sealed. Subsequently, plans were drawn up to construct installations to extract biogas and reuse it to create electrical energy. The project was carried out that same year by INAGRA (company belonging to CESPA3).
The average annual precipitation in this region fluctuates from 66 to 400 mm during the seasons of autumn and winter. The average annual temperature in Granada largely depends on the weather station where the measurements are obtained. The average temperature is 15.3 1C as measured at the Cartuja weather station in the city, whereas it is 14.81 at the airport weather station, 10 km outside the city.
The temperature in Granada is influenced by the proximity of the Sierra Nevada mountain range. The highest temperatures occur during the summer months, while the lowest ones occur in December and January. The thermal variation in the average annual temperatures is significant, and amounts to almost 20 1C. This is the same variation that exists between daytime and nighttime temperatures.
The potential evapotranspiration of the area, as calculated by the Thornthwaite Method, reaches values ranging from 700 to 900 mm. There is generally a period of draught in the summer months.
The landfill is located on the Alhambra formation, made up of conglomerates and sands, immersed in a large clayey basin, reducing the capacity of water transmission in the subsoil. There are no aquifers or signs of surface or groundwater at the landfill site.
After the landfill was sealed, urban waste from Granada, as well as that from other neighboring cities and towns, was treated at the Planta de Recuperacio′n y Compostaje, a waste recovery and composting installation that had recently opened in the town of Alhendin, 20 km outside of Granada. The main products treated at this plant are: metals, paper and cardboard, plastics and containers of mixed composition, organic material for the elaboration of compost, other wastes.
2.2. Production and characterization of wastes
During its period of maximum activity, a total of 1,420,000 Tm of waste were deposited at the landfill. A clear increase of waste production can be observed in Fig. 2, which shows the amount of waste deposited at the landfill from 1984 to 1999. This is typical of tendencies in recent decades and in consonance with the average rate of waste generation [18,27].
The waste was analyzed in order to obtain its macroscopic composition. The results of the field study is appear in Table 1.
2.3. Quantification of the theoretical production/yield of biogas
A number of methods have been used to estimate CH4 emissions at waste disposal sites. These methods vary greatly, not only in their assumptions, but also in their complexity and in the amount of data required. Some are based on the theoretical gas yield, whereas others use a first-order kinetics equation [28–32].
2.3.1. Empirical estimate of biogas
Table 1
Macroscopic composition of the landfill waste
The estimate of biogas production has been carried out by means of empirical calculation, in other words, a calculation using both experimental and theoretical data. Based on the macroscopic characteristics of the waste and the degradability data given in the previous section, as well as the analysis of the sample of gas spontaneously emitted from the landfill, it was possible to postulate the chemical formula of the waste (see Table 2).
Macroscopic
composition of
waste
Weight (%)
Humidity
(%)
Weight of
dry waste
(%)
Degradability of dry waste (%)
Fast
Slow
Total
Organic waste
30.50
75.00
7.63
75.00
7.00
82.00
Wet Paper/
24.00
20.00
19.20
30.00
20.00
50.00
Cardboard
1.50
35.00
0.98
10.00
20.00
30.00
trimmings
Textiles
1.00
20.00
0.80
0.00
10.00
10.00
Plastic
21.00
1.00
20.79
0.00
0.00
0.00
Metals
5.00
1.00
4.95
0.00
0.00
0.00
Glass
12.00
1.00
11.88
0.00
0.00
0.00
Others and inert
5.00
1.00
4.95
5.00
16.00
21.00
matter
Total
100.00
28.83
71.17
11.82
5.44
17.26
Table 2
Estimated chemical formula of waste
Dry fraction Degradables Chemical formula
71.17% 17.26% C44 H70O29N
Table 3
Estimated biogas production and methane concentration
Methane production (m3/Tm) Biogas production (m3/Tm) Methane concentration (% v/v)
82.43 160.21 51.39
The amount of biogas produced per ton of waste has been defined by the decomposition equation. The results obtained for a 40-year decomposition period are summarized in Table 3.
2.3.2. Theoretical and actual production of biogas
The previous section presents the possible generation of biogas per ton of waste, the composition of which was calculated hypothetically. It is a stoichiometric calculation on the basis of hypothetical data, but reality inside an actual landfill is much more complex. Another element of great importance in the evaluation of potential landfill gas production is the kinetics of decomposition. Some researchers use models or algorithms based on equations that presuppose the exact knowled