雙出頭秸稈液壓成型機(jī)的設(shè)計(jì),出頭,秸稈,液壓,成型,設(shè)計(jì) Fahad Rafai E-mail: refaeefa@hotmail.com 生物質(zhì)作為替代燃料用來(lái)發(fā)電 前言 電能有許多不同的產(chǎn)生來(lái)源而且可用不同的方式來(lái)生產(chǎn)。然而，各國(guó)競(jìng)相尋找能源，并試圖尋找的無(wú)限能源來(lái)生產(chǎn)電能。此外，生產(chǎn)電能而使用的礦物燃料，如石油，煤炭等，都會(huì)產(chǎn)生一些從能源成本到環(huán)境的污染等重大問(wèn)題。在上世紀(jì)末，工程師們開(kāi)始尋找新的能源，這些能源既具有與化石燃料相同的優(yōu)點(diǎn)勢(shì)外，同時(shí)也避免了其弊端。事實(shí)上，有一些能源因來(lái)自自然而著稱，這就是所謂的可再生能源。之所以稱它是可再生能源，是因?yàn)樗荒芎谋M并且可以重復(fù)使用。這種能源有不同種類和不同的形式，例如風(fēng)能，太陽(yáng)能，水能，水電能源，生物質(zhì)能等。 “在美國(guó)，自1973年以來(lái)便開(kāi)始大量利用生物質(zhì)，特別是木屑在熱能及電力應(yīng)用的利用上”。本文將探討利用生物質(zhì)作為電力行業(yè)中使用的替代燃料。文章開(kāi)頭，將涉及生物質(zhì)的背景和它的歷史來(lái)源。其次，將對(duì)利用生物質(zhì)能發(fā)電的電廠進(jìn)行調(diào)查。再次隨后，陳述一些利用生物質(zhì)的優(yōu)點(diǎn)和缺點(diǎn)。最后，一個(gè)結(jié)論將總結(jié)全文。 生物質(zhì)能簡(jiǎn)介 生物質(zhì)是世界上最古老的可再生能源之一。雖然我們一直在使用它，但很少有人知道它的學(xué)名。生物質(zhì)學(xué)名為活著的物質(zhì)，或具體地講，它是在死亡的樹(shù)木，樹(shù)枝，木材，農(nóng)作物，甚至動(dòng)物能量存儲(chǔ)能源的轉(zhuǎn)換，從而讓我們可以使用它。例如，“在今天的美國(guó)，物質(zhì)燃料的使用范疇，包括木屑，花草殘葉，農(nóng)業(yè)殘留物和城市碎木”。因此，生物質(zhì)能源可在任何時(shí)間和地點(diǎn)找到。事實(shí)上，如果生物質(zhì)不轉(zhuǎn)換成其它形式的話它將一無(wú)是處。因此，如果任何公司想利用生物質(zhì)能作為石油或天然氣的替代能源，就必須收集生物質(zhì)（植物，木材等）并將它在某一地點(diǎn)燃燒，燃燒產(chǎn)生的熱量可用于推動(dòng)汽輪機(jī)發(fā)電。同樣，電廠可以使用生物量在的燃燒中的氣化過(guò)程。在這種情況下，將把生物量加熱到極高溫度而產(chǎn)生可燃?xì)怏w，可用于推動(dòng)渦輪旋轉(zhuǎn)從而產(chǎn)生電能。據(jù)加州能源委員會(huì)的網(wǎng)頁(yè)介紹，加州每年生產(chǎn)約60萬(wàn)噸的生物質(zhì)，這意味著2000兆瓦的電能。事實(shí)上，這些能量足以滿足市場(chǎng)需求和約2百萬(wàn)戶人家使用。雖然生物質(zhì)能源已被使用多年，一些國(guó)家一直以來(lái)仍把它作為燃料用作發(fā)電。與此相反，一些國(guó)家因?yàn)槠鋵?duì)環(huán)境的負(fù)面影響而停止使用。有人說(shuō)，生物質(zhì)導(dǎo)致了環(huán)境的污染。但是，該能源的益處鼓勵(lì)一些企業(yè)使用它，例如，“BEG（生物質(zhì)能源集團(tuán)）推算，在蘇格蘭，生物質(zhì)產(chǎn)業(yè)有望在提供2000人就業(yè)崗位和促進(jìn)其他部門(mén)經(jīng)濟(jì)增長(zhǎng)的同時(shí)供應(yīng)多達(dá)450兆瓦的電力”。美國(guó)電子協(xié)會(huì)對(duì)生物質(zhì)的估計(jì)表明，每年美國(guó)有生物質(zhì)資源約5.9億濕噸（相當(dāng)于4.13億干噸）可供利用。事實(shí)上，生物質(zhì)發(fā)電可使用不同的方法，而各種方法都有各自的效率和生產(chǎn)力。 廢棄物發(fā)電 用化石燃料發(fā)電是世界上最通用的方法。然而，利用生物質(zhì)能發(fā)電，并遵守一些規(guī)定和限制會(huì)更有效率。眼下主要有四種類型的生物發(fā)電系統(tǒng)：直燃，混燒，煤氣化，模塊化系統(tǒng)。大多數(shù)發(fā)電廠使用生物質(zhì)直燃系統(tǒng)，用化石燃料來(lái)發(fā)電。圖1顯示了如何使用生物質(zhì)燃料在工廠中發(fā)電。生物質(zhì)的燃燒鍋爐產(chǎn)生高壓蒸汽，蒸汽被引入汽輪機(jī)，帶動(dòng)一系列氣動(dòng)渦輪葉片，使渦輪旋轉(zhuǎn)，而渦輪連接到發(fā)電機(jī)，因此，流動(dòng)的蒸汽致使渦輪旋轉(zhuǎn)，發(fā)電機(jī)旋轉(zhuǎn)和電力的生產(chǎn)。生物質(zhì)能鍋爐產(chǎn)生的電一般在50兆瓦范圍左右，相比燃煤發(fā)電廠中的15兆瓦左右。因此，有人建議，在一些電廠，如在美國(guó)亞什蘭的海灣發(fā)電站，在高負(fù)荷期使用煤而在低負(fù)荷期使用生物質(zhì)發(fā)電，這將節(jié)儉煤的使用。然而，到目前為止，用直接燃燒的木材發(fā)電是最省事的方法。另外，除非它和像煤一樣的其它能源組合使用，否則就可能沒(méi)有競(jìng)爭(zhēng)力。 圖1 用生物質(zhì)在電廠發(fā)電 生物質(zhì)能的優(yōu)點(diǎn)： 使用生物質(zhì)作為替代能源來(lái)發(fā)電具有一定的經(jīng)濟(jì)效益。再者，它也是一種有效的社區(qū)或工業(yè)區(qū)的資源來(lái)源。相比而言，即使發(fā)達(dá)國(guó)家能夠利用這一資源，以彌補(bǔ)其它像石油，天然氣或煤資源的不足。其中最重要的優(yōu)勢(shì)是它的價(jià)格低廉;而且是一種現(xiàn)成的能源。此外，它是一種可持續(xù)、可長(zhǎng)期使用的資源，它可以在任何時(shí)候任何地方很容易地發(fā)現(xiàn)使用。生物質(zhì)發(fā)電廠更大的優(yōu)勢(shì)是能幫助許多國(guó)家減少失業(yè)。施安那 貝爾德，中型項(xiàng)目的蘇格蘭綠黨的能源發(fā)言人說(shuō)： “就新的發(fā)電站的建立和它創(chuàng)造的相當(dāng)數(shù)量的就業(yè)機(jī)會(huì)而言，這是個(gè)好消息” 。如在蘇格蘭鄧弗里斯郡的洛克比建立的生物質(zhì)能源發(fā)電廠，將支持英國(guó)經(jīng)濟(jì)也將幫助政府降低失業(yè)率。 生物質(zhì)能的缺點(diǎn)： 如同任何可再生能源一樣，利用生物質(zhì)發(fā)電存在一定的缺陷。生物質(zhì)確實(shí)影響環(huán)境嗎？這個(gè)問(wèn)題已經(jīng)被問(wèn)了很多次。事實(shí)上，因?yàn)樗谌紵龝r(shí)會(huì)產(chǎn)生碳?xì)怏w，因此許多人擔(dān)心的是它在全球氣候變暖中的作用。然而，如果你了解生物質(zhì)周期的話，可能知道從這個(gè)角度看是錯(cuò)誤的。雖然生物質(zhì)可在世界任何地方看到，有些地方如在中東的沙漠地區(qū)，如沙特阿拉伯，找到足夠的可用作生物質(zhì)的植被是一件很困難的事。因此，把植被運(yùn)送到該地區(qū)，將是昂貴的和毫無(wú)用處的。 圖2 碳循環(huán) 結(jié)論： 總之，這篇文章已經(jīng)表明，使用生物質(zhì)的行業(yè)，特別是像發(fā)電廠這樣的工業(yè)，將有助于人們找到工作，并有助于各國(guó)政府減少失業(yè)率。此外，每年許多國(guó)家花費(fèi)數(shù)十億美元購(gòu)買石油或天然氣用來(lái)發(fā)電，為此，如果用生物質(zhì)作為替代能源來(lái)發(fā)電將是更加經(jīng)濟(jì)和有效。在電力市場(chǎng)，可以說(shuō)：能源就是金錢(qián)。就生物質(zhì)能源而言，這一說(shuō)法更為確切。此外，生物質(zhì)可用于不同的地方，這意味著更多的靈活性。雖然使用生物質(zhì)的電廠將產(chǎn)生功耗低于它使用化石燃料時(shí)而產(chǎn)生的電能，但在村莊和小城鎮(zhèn)，使用生物質(zhì)將比使用常用的化石燃料更為經(jīng)濟(jì)。 Biomass as an Alternative Fuel for Generating Electricity Written by : Eng. Fahad A. Rafai refaeefa@hotmail.com September Introduction Electrical energy has many different sources and can be produced in different ways. However, countries are competing to produce energy and trying to have unlimited sources for producing it. Moreover, producing electrical energy using normal fossil fuels, such as, oil, coal and so on has some major problems, from the cost of fuel to the pollution. At the end of the last century, engineers have started looking for new sources which have the same advantages as the fossil fuels while avoiding their disadvantages. In fact, there some sources were already known from the natural, one of them is called renewable energy. It called renewable because it will not run out and can be reproduced. This kind of energy has different types and can be found in different forms, for instance, wind energy, solar energy, hydroelectric energy, biomass energy and so on. "In the United States, since 1973 there has been a dramatic increase in biomass use, especially in thermal and electrical applications of wood residues". This essay will examine the using of biomass energy as an alternative fuel in the electricity industry. Initially, it will cover a brief background on biomass and include its sources and history. Secondly, the using of biomass for generating electricity in power plants will be investigated. Then, some of the advantages and disadvantages of using biomass will addressed . A conclusion will complete the essay. Biomass in Brief Biomass is one of the oldest sources of energy in the world. Although we have been using it all the time, it may have been never heard about its scientific name. Biomass known as living material or specifically, it is the conversion of the stored energy in the dead trees, tree branches, wood, crops and even animals into energy so that we can use it. For example, "The major categories of biomass fuels used in the United States today include, wood processing residues, in-forest residues, agricultural residues and urban wood residues". As a result, biomass energy can be found easily in any place and any time. In fact, biomass will not be useful for producing electrical power energy unless converted into another form. Consequently , if any company wants to use biomass as a source of energy instead of oil or gas, it will need to collect the biomass ( plants, wood and so on ) and burn it in special places, then the heat of this burning can be used in a steam turbine to generate electricity. In the same way, power plants can use biomass in a different process which called Gasification. In this case, biomass is going to be heated at very high temperature degrees to produce flammable gases which can be used to rotate the turbine and produce electricity. According to the California Energy Commission web site, California produces about 60 million tons of biomass every year, which means around 2000 megawatt of electrical power. In fact, this power is enough to market and could supply about two million homes. Although biomass energy has been used many years ago, some countries still use it as a fuel in electrical power generation until now. In contrast, some countries stopped using it because of its environmental impacts. It has been said that biomass has been contributing to the environmental pollution. However, the benefits of this energy encouraged some societies to use it, for instance, "BEG (The Biomass Energy Group) has concluded that a biomass industry in Scotland has the potential to supply as much as 450 MW of electricity from the wood fuel resource while employing over 2000 people and stimulating other sectors of the Scottish economy". In addition ，EIA (The Energy Information Administration) estimation of biomass resources shows that there are 590 million wet tons (equivalent to 413 million dry tons) of biomass available in the United States on an annual basis.In fact, biomass can be used in power plants using different methods and each method has its own efficiency and productivity. Electrical Power Generation from waste Generating electricity in power plants using fossil fuel is the most popular method in the world. However, using biomass to generate electricity can be efficient with some regulations and limitation. There are four main types of biomass power systems: direct-fired, co-fired, gasification, and modular systems. Most of the power plants which use biomass are direct-fired systems which use the same technique of fossil-fuel fired power plants. Figure 1 shows how to use biomass as fuel in power plants. The biomass is burned in a boiler to produce high-pressure steam. This steam is introduced into a steam turbine, where it flows over a series of aerodynamic turbine blades, causing the turbine to rotate. The turbine is connected to an electric generator, thus, as the steam flow causes the turbine to rotate, the electric generator turns and electricity is produced. Biomass power boilers are typically in the 50 MW range, compared to coal-fired plants in the 150MW range. Therefore, it was suggested that in some power plants, such as, the Bay Front Station in Ashland in the United States it would beneficial to operate the units ( turbines) using coal in the peak periods and using biomass in the low load periods . However, direct combustion of wood to generate electrical power is the most advanced method at present. Also, it might be not competitive unless used in combination with other sources, such as coal and gas. Figure 1: Using Biomass to produce electricity in power plants. Advantages of using Biomass: Using biomass as an alternative energy to generate electrical power has some economical benefits. Moreover, it can be a useful source for energy in the small societies or small industrial areas. In contrast, even developed countries can use this source to compensate for the lack of the other sources, such as, oil, gas or coal. One of the most important advantages of biomass is its cheap prices; also it is a readily available source of energy. In addition, it is a continuous and long term source, it can be found easily, any time and almost anywhere. One more advantage for biomass power plants is helping to reduce the unemployment in various countries, Shiona Baird, MSP, the Scottish Green Party's energy spokeswoman, said to The Scotsman: "The new power station, and the considerable number of jobs that it will create, is good news". This contribution by establishing a biomass power plant at Lockerbie, Dumfriesshire in Scotland it will support the economy in the UK and will help the government in its fight against unemployment. Disadvantages of using Biomass Like any renewable source, biomass has some disadvantages for using it to generate electrical power. Does biomass affect the environment? This question has been asked many times. In fact, many people are concerned about the contribution of biomass in the global warming because the combustion of biomass will produce carbon into the air. However, this point of view could be wrong if you understand the biomass cycle. Although biomass can be found anywhere in the world, some places like desert areas in the middle east such as Saudi Arabia, possibly will face difficulties to get enough plant and trees to be used as a biomass source. As a result, the transportation of the plant and tress to theses areas will be costly and using biomass in this case will be worthless. Figure 2: Carbon cycle. Conclusions: To sum up, this essay has shown that using biomass in industry and specifically in power plants to produce electrical power, would help many people to find jobs and could help the governments to diminish the unemployment rates. Moreover, every year, countries spend billions of dollars to sell oil or gas for generating electricity, for this reason, it will be more economical and useful if biomass has been used. In the electricity markets it can be said: energy is money. And by using biomass this saying can be verified. Moreover, biomass can be used in different methods which mean more flexibility. Although the power plants which use biomass will produce less power than that power plant which uses fossil fuel, still using small biomass units in the villages and small towns would be more economical than using normal fossil units. References : 1. Black, Wood-fuelled power station to be UK's first, The Scotsman, http://thescotsman.scotsman.com (_ August ____) 2. Haq, Z, The Energy Information Administration, Biomass for Electricity Generationhttp://www.eia.doe.gov/oiaf/analysispaper/biomass 3. Morris, G. The Value of the Benefits of U.S. Biomass Power, National Renewable Energy Laboratory, Berkeley, California, USA. 4. Overend, R.P. Production of Electricity from Biomass Crops – US Perspective. National Renewable Energy Laboratory, Golden, Colorado, USA 5. Slesser, M & Lewis, Biomass as a Nonfossil Fuel Source, A Halsted Press Book. 6. Promoting and Accelerating the Market Penetration of Biomass Technology in Scotland, Scottish Executive www.scotland.gov.uk/Resource/Doc/.pdf 7. Biomass, Energy matters http://library.thinkquest.org/types/biomass 8. Biomass Energy, Energy Quest http://www.energyquest.ca.gov/story/chapter.html 9.Figure1:BBCwebsite http://news.bbc.co.uk/hi/sci/tech/.stm. 10.Figure2:http://www.ucsusa.org/cleanenergy/renewable_energy_basics/offmenhow-biomass-energy-works.html 9