外文翻譯---煤礦通風系統(tǒng)中瓦斯散發(fā)的控制

1、<p><b>　　英文原文</b></p><p>　　Mitigation of Methane Emissions from Coal Mine Ventilation Air</p><p>　　Peter Carothers and Milind D.Deo</p><p><b>　　ABSTRACT</b

2、></p><p>　　U．S．EPA’s coalbed methane outreach program ,(CMOP)has prepared a technical assessment of techniques that combust trace amounts of coal mine methane contained in ventilation air. Control of meth

3、ane emissions from mine ventilation systems has been an elusive goal because of the magnitude of a typical airflow and the very low methane concentrations. One established and cost-effective use feeds the air into a prim

4、e mover in lieu of ambient combustion air. This method usually consumes just a fraction</p><p>　　KEYWORDS: Coal, Methane, Mining, Ventilation, Combustion, Regenerative, and Greenhouse Gas.</p><p&g

5、t;　　INTRODUCTION</p><p>　　This paper presents a summary of a draft U.S. Environmental Protection Agency (U．S．EPA) report. It is a technical assessment of existing and emerging processes capable of removing t

6、race amounts of methane contained in ventilation air streams at gassy underground coal mines.</p><p>　　Coaled methane (CBM) is methane that is formed during the coalification process and that resides within

7、the coal seam and adjacent rock strata. Coal mining activity releases methane that has not been captured with drainage systems. The methane then passes into mine workings and on to the atmosphere. Gassy underground mines

8、 release significant quantities of such methane, which is referred to as coal mine methane (CMM). When allowed to accumulate in mine working, CMM presents a substantial danger </p><p>　　The most universally

9、used method of degasification is dilution by ventilation. Ventilation systems consist of inlet and exhaust shafts and powerful fans that move large volumes of air through the mine workings to maintain a safe working envi

10、ronment. Exhausted ventilation air contains a very diluted amount of methane; typical concentrations range between 0.2 to 0.8% methane, well below the explosion limits. To date (with very few exceptions) ventilation syst

11、ems release the air-methane mixture to </p><p>　　Some operators to employ a variety of proven methods, capture and use drained CMM but the majority of drained ventilation air. Methane emissions from ventilat

12、ion air comprise the largest portion of all CMM liberation worldwide, and they are the most difficult to control. This paper examines the current and future possibilities for destroying and potentially using ventilation

13、air methane.</p><p>　　Global Importance of Ventilation Air Emissions</p><p>　　Methane is a potent greenhouse gas, approximately 21 times more effective per unit of weight than carbon dioxide in

14、terms of causing global warming over a 100-year time frame. Coal mine methane emissions account for approximately 10% of anthropogenic methane emissions worldwide, and they are the fourth largest source of methane releas

15、e in the US. By far the largest portion of this methane leaves the mines through the ventilation system. Therefore, the most logical and direct way to reduce CMM em</p><p>　　Barriers to Current Recovery and

16、Use</p><p>　　Ventilation airflows are very large, and the contained methane is so diluted that conventional combustion processes cannot oxidize it without supplemental fuel. Ventilation air s characteristics

17、 make it extremely difficult to handle and process and constitute technical barriers to its recovery and use.</p><p>　　Costly Air Handling Systems</p><p>　　Typical ventilation airflows are so en

18、ormous that a processing system will have to be very large and expensive. Each processing system will have to include a fan to neutralize any pressure drop caused by the reactor and avoid having the mines face costly inc

19、reases in electric power.</p><p>　　Low methane concentrations.</p><p>　　A methane-in-air mixture is explosive in a concentration range between about 4.5 and 15% . below 4.5% methane will not ign

20、ite or sustain combustion unless it can remain in an environment where temperatures exceed 1,000. therefore, any conventional method proposed to use ventilation air as a fuel, or even to destroy it, would require an endo

21、thermic reaction.</p><p>　　Variable flows and changing locations</p><p>　　Mine operators will face the flow variations typically exhibited by a ventilation system. As mine operations progress un

22、derground the working face tends to move away from the original ventilation shaft. A processing system built to accept a given flow will experience short-term periodic fluctuations and a probable decline over time as oth

23、er, more distant exhaust shafts take over.</p><p>　　IDENTIFICATION OF APPLICABLE TECHNOLOGIES</p><p>　　The technologies available to mitigate ventilation air emissions divide into two basic cate

24、gories: ancillary uses and principal uses.</p><p>　　Ancillary uses</p><p>　　The focus of projects in this category is on a primary fuel that is not ventilation air; thus employment of ventilatio

25、n air is ancillary and restricted to amounts that are convenient for the project. For example, a power plant of other prime mover may use ventilation air(instead of ambient air) as combustion air. Projects of this type n

26、ormally use only a fraction of the ventilation air. The technique requires a modest air handling and transport system that serves to bring ventilation air from th</p><p>　　Combustion turbines, or gas turbine

27、s, may also use ventilation air as combustion air. Since it contains useable fuel, the operator can cut back on the quantity of primary fuel. Solar Turbines, a division of Caterpiller Inc., has investigated this strategy

28、 for use with small (e.g., 3to 8MW) turbines located near mine ventilation shafts. Although the company has no field experience with the applications, albeit within very strict methane concentration limits that they impo

29、se to guarantee the safe </p><p>　　Principal uses</p><p>　　Technologies in this category would use ventilation air as the primary fuel and attempt to consume up to 100% of the ,ethane emitting f

30、ro, a single exhaust shaft. As discussed below, these systems ,ay also employ more concentrated fuels such as gob gas to enhance the utility or profitability of a given project. The authors identified two processes: a th

31、ermal oxidation process called the VOCSIDIZER, and a catalytic oxidation process called the Catalytic Flow-Reversal Reactor (CFRR). A description</p><p><b>　　CFRR</b></p><p>　　In 199

32、5 researchers at ERDL/Natural Resources Canada in Varennes, Quebec (also known as CANMET and NRCan) conceived of and developed the Catalytic Flow-Reversal Reactor expressly for use on coal mine ventilation air. The resea

33、rch team was aware of and wished to improve upon the TFRR to process mine ventilation air at lower temperatures, CANMET selected catalysts that reduce the combustion temperature of methane by several hundred degrees Cels

34、ius.</p><p>　　They have demonstrated the CFRR technology over a range of simulated conditions at small scale. CANMET and several Canadian private and government entities have formed a consortium to finance,

35、design, build, and operate an industrial-scale demonstration plant (approximately 8 to 10 m3/s) at the Phalen Mine in Nova Scotia. CANMET is also studying energy recovery options that are appropriate for the CFRR, especi

36、ally the gas turbine option.</p><p>　　Principles of operation</p><p>　　Figure 1 shows a schematic of a reverse-flow-reactor. This is a simple apparatus that consists of a large bed of silica gra

37、vel or ceramic heat exchange medium with a set of electric heating elements in the center. Airflow equipment such as plenums, ducts, valves, and insulation elements are fitted around and within the bed. Controls and anci

38、llary equipment are mounted nearby. The TFRR and CFRR have the same general appearance except the CFRR has zones on either side of the heat exchanger that co</p><p>　　If the gas is not heated to the combusti

39、on temperature o methane, the reaction will not start because there is no heat source. This situation is called a non-starter. Even if the reaction does start, the final conversion must be complete enough to heat the med

40、ia, and in turn, the gas in the next cycle to the auto-combustion temperature. Otherwise, the reactor will cool down over a number of cycles. This situation is called a blow-out.</p><p>　　After the initial c

41、ycles of a sustained operation, hot products of combustion and unreacted air continue through the bed, losing heat to the far side of the bed in the process. When the far side of the bed is sufficiently hot and the near

42、side has cooled, the reactor automatically reverses the direction of ventilation airflow. New ventilation air enters the far side of the bed and becomes hotter by taking heat from the bed. Close to the reactor’s center t

43、he methane reaches combustion temperature</p><p>　　In an ideal situation the temperature profile in the bed would be as shown in Figure 2. When the ventilation air flows from bottom to top it picks up heat f

44、rom contact with the hot solid media and its temperature increases. The gas temperature lags the solid temperature by a few degrees (about 20 to 50℃ in existing units) both while gaining and losing heat according to MEGT

45、EC. As the flow continues in the initial half cycle, the high temperature zone, with respect to both the solid and the gas, </p><p>　　As is observed in Figure 2, even with very efficient heat transfer the ex

46、it air temperature is at least a few degrees higher than the incoming ventilation air. As a result, if no energy is being generated internally, the bed would eventually cool. Both vendors claim that if the methane concen

47、tration in the incoming air is consistently about 0.15%and if the unit has been optimized to meet that parameter, the operation would be auto-thermic (i.e. it would support itself without additional applied </p>&

48、lt;p><b>　　中文譯文</b></p><p>　　煤礦通風系統(tǒng)中瓦斯散發(fā)的控制</p><p><b>　　摘要</b></p><p>　　美國環(huán)境保護委員會的關于煤體瓦斯擴散的項目,(CMOP)為點燃礦井通風空氣中包含的瓦斯的技術提供了一個技術評價。由于煤礦特有的氣流是很大的，且瓦斯?jié)舛群苄。虼藢ΦV通

49、風系統(tǒng)中瓦斯散發(fā)的控制是一個難以達到的目的。一個既定的和卓有成效方法是將空氣在一個充滿燃燒空氣的場所壓入一個極好的移動物體。這種方法只消耗很少一點風流，每個通風風井都可以提供。作者從技術和經(jīng)濟兩個方面評價了兩種可能接受鄰近風井的幾乎全部風流，氧化其中包含的瓦斯并生產(chǎn)出一種很有市場價值的能源的新出現(xiàn)的系統(tǒng)的可行性。 兩種系統(tǒng)都使用可再生的, 風流反向的反應堆. 一種系統(tǒng)在1000℃操作，另一種則使用催化劑使燃燒溫度減少幾百度。只要瓦斯的濃

50、度在確定的最小瓦斯?jié)舛戎?，反應堆就能通過諸如壓縮空氣或加壓水等工作流體交換高質(zhì)量的熱。本文討論了兩個作為例證的，通過反應堆提供能源收入和對溫室氣體排放的保證的能源項目，并提出了一個對投資資本回收很有利的手段。</p><p>　　關鍵字：煤,瓦斯,采礦,通風,燃燒,可再生的和溫室氣體</p><p><b>　　引言</b></p><p>

51、　　本文是對美國環(huán)境保護協(xié)會報告的草稿的總結。它是對現(xiàn)有的和新出現(xiàn)的，能夠除去包含在高瓦斯地下煤礦通風空流中的瓦斯的痕跡的技術的評估。</p><p>　　煤體瓦斯(CBM) 是在成煤過程中形成的停留在煤層縫隙和鄰近的巖石地層中的瓦斯。采礦活動釋放了那些抽排系統(tǒng)捕獲不到的瓦斯。這些瓦斯然后經(jīng)過煤礦的井巷散發(fā)到大氣中。高瓦斯地下礦井會釋放相當可觀的這樣的被稱為煤礦瓦斯(CMM)的瓦斯氣體。當這些瓦斯在煤礦井巷中積聚

52、時，會造成實質(zhì)性的火災和爆炸的危險。為了保證礦工安全和連續(xù)生產(chǎn), 高瓦斯礦的工作人員必須對他們礦井的瓦斯進行稀釋。.</p><p>　　最多最普遍地使用的降低瓦斯的方法是通風稀釋。通風系統(tǒng)包括進風井和排風井和使大量新鮮空氣在井下流動以保持一個安全的工作環(huán)境的強力的風機。乏風流中只包含很淡的瓦斯量；正常的濃度量在0.2到0.8% 的瓦斯含量中間,低于瓦斯爆炸界限。直到目前為止的通風系統(tǒng)都把空氣-瓦斯混合的乏風排放

53、到大氣中，從而排除或釋放瓦斯卻很少有人努力的去捕獲和使用它(有很很少的除外)。 工作人員可能通過強行在采前或采后從煤層中抽排瓦斯的瓦斯抽放技術作為通風的輔助措施。</p><p>　　一些工作人員會采用多種已被證明了的方法, 捕獲和使用抽出的CMM，但是大的部分CMM人仍然隨著井下風流釋放到大氣中。從井下風流中散發(fā)出來的瓦斯占全世界范圍內(nèi)瓦斯釋放的大部分，而他們是最難控制的部分。本文考察了當前的和未來為了破壞和潛

54、在地用通風空氣中瓦斯的可能性。</p><p>　　通風空氣散放的全球重要性</p><p>　　瓦斯是典型的溫室氣體，每單位重量的瓦斯在全球變暖的過去的100年內(nèi)發(fā)揮了比二氧化碳多大約21倍或更多的效用。大約10% 的anthropogenic瓦斯散發(fā)是煤礦瓦斯散發(fā)，而且他們是美國瓦斯釋放的第四大的來源. 迄今這些瓦斯的大部分存在于煤礦通風系統(tǒng)中。 因此，減少CMM的散發(fā)的最合理而直接的

55、出路應該是找出捕獲，處理和利用存在于通風井巷中的瓦斯的方法。本文評價了有望處理從單獨的井筒出來的全部風流的技。在美國的高瓦斯礦井中，一個典型的風井的風量在100到250 m3/s，或大約212,000到530,000cfm間浮動。本文的例子假定個體的容量為100 m3/s ，是煤礦可以使用一次或多次的一個實際的模塊的大小。 包含0.5%瓦斯含量的100 m3/s通風風量中每天將散發(fā)43,200 m3瓦斯或約1.525mmcfd。<

56、/p><p>　　當前的恢復和使用障礙</p><p>　　通風氣流是很大的，風流中包含瓦斯被稀釋的非常淡以至于傳統(tǒng)的燃燒過程如果沒有補充的燃料就不能氧化它。通風氣流的特征使它的控制、處理非常困難并對它的恢復和使用形成技術的障礙。</p><p><b>　　昂貴的空氣處理系統(tǒng)</b></p><p>　　典型的通風氣流是如

57、此巨大的以至于處理系統(tǒng)必然很大且非常昂貴的。每個處理系統(tǒng)必須包括能夠抵消任何反應堆引起的壓力下降和避免礦井面對昂貴的增加的電力消耗的風機。</p><p><b>　　很低的瓦斯?jié)舛?lt;/b></p><p>　　如果瓦斯和空氣的混合物中瓦斯的濃度在4.5%和 15%之間時將會發(fā)生爆炸。如果瓦斯?jié)舛仍?.5% 以下，瓦斯將不會被點燃或即使點燃也不會持續(xù)燃燒，除非它能在溫

58、度超過1000℃（1832°F）的環(huán)境中存留。因此，任何的傳統(tǒng)希望利用通風氣流作為燃料或甚至破壞它的方法都將需要吸熱的反應。</p><p>　　不同的風流和變化的位置</p><p>　　煤礦工作人員將面對一個典型的通風系統(tǒng)表現(xiàn)出來的風流變化。隨著地下煤礦的生產(chǎn)手段的進步，煤礦工作的重點有從原來的通風井巷轉(zhuǎn)移的趨勢。被建立起來接受給定的風流的處理系統(tǒng)將會經(jīng)歷短期的周期性波動和時

59、間的可能下降，距離更加長的排風井將會占據(jù)主導地位。</p><p><b>　　應用技術的驗證</b></p><p>　　可用的減輕通風空氣散發(fā)的技術分成兩大基本類別: 輔助的技術和主要技術。</p><p><b>　　輔助技術</b></p><p>　　這一類工程技術的注重的焦點是一種不是通

60、風空氣的優(yōu)質(zhì)燃料；因而對工程應用方便的通風空氣是輔助的和受限制的。例如, 發(fā)電廠或其他的原動力可能使用通風空氣(代替周圍的空氣) 作為燃燒空氣。 這種類型的工程技術通常只利用很少量的井下通風空氣。這種技術要求一個用來把通風空氣從礦井出風口傳送到生產(chǎn)原動力的系統(tǒng)的空氣入口的空氣適度控制和傳輸系統(tǒng)。澳洲的BHP鐵礦礦工小組創(chuàng)建的Appin和Tower項目提供了一個典型的輔助用途的例子。兩個發(fā)電功率分別達到40和54兆瓦特的發(fā)電廠均用兩個相同

61、功率的Caterpillar系列的內(nèi)燃發(fā)電機發(fā)電。從兩個煤礦抽出來的瓦斯氣體是主要的燃料, 但是卻要由包含在用來取代周圍空氣做每個發(fā)電機的燃燒空氣的井下通風空氣中的瓦斯（平均濃度為0.7%）作為補充燃料。這種方法使這項的燃料增加了10%，也消耗了20%的井下通風氣流中的瓦斯散發(fā)量。由于這項工程項必須依賴自然瓦斯作為主要燃料的補充。在缺乏可用的瓦斯氣期間，利用井下風流中的瓦斯是一種非常良好的經(jīng)濟節(jié)約。但BHP仍然沒有確定工程中用來作為空氣

62、替代品的部分操作花費和需要分出的資本。一個Caterpillar發(fā)言人聲明這些花費</p><p>　　內(nèi)燃輪機,或蒸汽輪機也都可以使用井下通風空氣作為燃燒空氣。因為它包含可以利用的燃料?？刂破骺梢詼p低主要燃料的量。Caterpiller 公司的Solar Turbines 考查了這種將小功率的(3到8MW)輪機設置在煤礦風井旁以便利用的方法。盡管公司在這種技術上沒有實際的經(jīng)驗，且是在非常嚴格的瓦斯?jié)舛认拗葡虏拍?/p>

63、勉強保證設備的操作安全，他們依然鼓勵將他用于實際中。</p><p><b>　　主要技術</b></p><p>　　這一類技術將井下空氣作為主要燃料，試圖消耗全部的從某一個排風井出來的井下空氣中的瓦斯。就像下面討論的一樣，這些系統(tǒng)也會應用更多的諸如瓦斯氣體的高濃度燃料來提高一個既定工程的用途和效益。作者提出兩種處理過程：一種是稱為VOCSIDIZER的放熱的氧化過

64、程，另一種是稱為CFRR的催化氧化過程。分別介紹如下：</p><p><b>　　CFRR</b></p><p>　　1995，ERDL\加拿大Varennes, Quebec的自然的資源研究所 (也以CANMET和NRCan聞名)的研究者們設想并發(fā)展了主要用于煤礦井下空氣的可逆流程的催化反應堆。研究小組曉得并希望改善TFRR以便能在較低的溫度下來處理礦通風空氣。

65、CANMET已選擇了可以使瓦斯的燃燒溫度減少幾百度攝氏度的催化劑。</p><p>　　他們已經(jīng)在小范圍內(nèi)的模擬環(huán)境下演示CFRR的技術。CANMET和一些加拿大的私人的和政府機構已經(jīng)組成了聯(lián)合公司在Nova Scotia 的Phalen煤礦來籌備，設計，建立和運行一個企業(yè)規(guī)模的演示系統(tǒng)(大約8到10 m3/s)。 CANMET也在研究能源的再回收項目，這對CFRR, 特別是風機的選擇都很有幫助。</p&g

66、t;<p><b>　　運行原理</b></p><p>　　圖1顯示了一個 流程可逆的反應的運行過程。這是一個簡單的設備，它由一個由二氧化硅或陶瓷材料的熱交換器制成的底座和中間的一套電加熱設備組成，并在內(nèi)部和周圍裝備如充氣設備，管， 閥和隔離設備等通風設備。TFRR和CFRR有大致相同的外形，但CFRR盛催化劑藥丸的熱交換器兩邊有圓環(huán)(隱藏)。這個過程中應用了反應區(qū)內(nèi)氣體（井

67、下空氣）和固體（用來有效的存儲和傳輸熱量的用傳熱材料制成的底座）的可逆熱交換。啟動操作流程時，電熱元件首先預熱底座，使其達到能夠引起燃燒的最小要求溫度(在TFRR中約為1000℃-1100℃)。 在第一次循環(huán)的前半段，溫度和周圍空氣相同的井下通風空氣進入并從同一方向穿過反應堆。當混合氣體的溫度開始到超越1000℃.時，瓦斯的氧化將在底座中心處發(fā)生。因而, 如果.這樣的溫度能夠在底座維持的話，瓦斯就可以100%的被轉(zhuǎn)化為二氧化碳和水。這個

68、反應堆的全部的三部分都有很好的隔熱裝置，所以很少熱量可以散發(fā)到環(huán)境中。 </p><p>　　如果井下空氣沒有被加熱到瓦斯的燃燒溫度，反應將不會開始，因為沒有熱來源。這鐘情況稱為不開始。即使反應開始進行，最終的轉(zhuǎn)化也必須達到足夠的程度以便加熱媒介，接下來，在下一個循環(huán)中的井下空氣才能達到自發(fā)燃燒的溫度。否則，在多次循環(huán)后反應結束，這鐘情況被稱為吹滅。在持續(xù)運行的初試循環(huán)之后，燃燒產(chǎn)物和沒有反應的空氣這些氣體繼續(xù)通

69、過底座，在此過程中將熱量傳遞到底座的邊緣上，當?shù)鬃倪吘壸銐虻臒岫虚g已經(jīng)冷卻下來時，反應會自動逆轉(zhuǎn)風流，新的井下空氣進入底座的邊緣處，并因而從底座吸收熱量而升溫變熱。在靠近反應堆的中間，瓦斯達到燃燒溫度，被氧化并產(chǎn)生熱量，在散發(fā)到空氣中之前傳遞到底座的邊緣處。</p><p>　　在理想情況下底座上的溫度變化如圖2所示。當井下空氣從底部流動到頂部時，將會從與傳熱的固體媒介的聯(lián)系處吸熱而溫度增加。根據(jù)MEGTEC

70、系統(tǒng)，無論吸熱還是放熱，氣體溫度稍微落后于固體溫度 (目前的設備中約為20到50℃)。</p><p>　　當風流在初始循環(huán)的前半段時，固體和氣體的高溫帶將會向上移動(對于示例的從下到上的流程順序)。流程反向后捕捉到這個方向上的偏移并防止它從遠離中心。循環(huán)的下半段從上到下流動，產(chǎn)生一個新的溫度變化的框架 ， 也在圖 2中表現(xiàn)出來。在預先計算的時間段內(nèi)，通常為2到10分鐘，通過轉(zhuǎn)變流動方向，可以保證高溫帶在反應堆的

71、中間保持住。</p><p>　　如圖2所示，即使有非常有效的熱傳遞，出口的空氣溫度至少比進口的井下空氣溫度要高幾度。因此，如果沒有從內(nèi)部產(chǎn)生的能量，底座最終將冷卻下來。兩方的銷售者都聲明如果進入的瓦斯?jié)舛确€(wěn)定在0.15%，且設備能很好的滿足各項參數(shù)，反應過程將自發(fā)進行（不需要額外的燃料和熱量就能維持運行）。這就意味著氧化這一定質(zhì)量的瓦斯將產(chǎn)生足夠的熱量來補充到出口氣流中。使其溫度比進口處的氣流溫度高出40℃。技