coal gasification the clean energy of the future

1、coal gasification: the clean energy of the future?by richard anderson business reporter, bbc news13 april 2014 last updated at 23:10 turning coal into gas is not as environmentally friendly as it sounds dirty it may be, but coal is cheap. for this simple reason, it remains the worlds main source of

2、power, providing a quarter of our primary energy and more than 40% of our electricity. and it will continue to do so for many years to come.the challenge, then, is how to harness coals energy more cleanly. while global attempts to develop carbon capture and storage (ccs) have stalled, a number of co

3、untries are looking at different ways to exploit their abundant coal reserves.not all are motivated by environmental concerns, but are driven instead by economics and a desire for energy independence.old and new the main technology being used is coal gasification - instead of burning the fossil fuel

4、, it is chemically transformed into synthetic natural gas (sng).the process is decades old, but recent rises in the price of gas mean it is now more economically viable. the us has dabbled in the technique, but china is going all out in a bid to satisfy its soaring demand for power and reduce its de

5、pendency on imported liquefied natural gas (lng). the countrys national energy administration has laid out plans to produce 50 billion cubic metres of gas from coal by 2020, enough to satisfy more than 10% of chinas total gas demand.not only does it make economic sense, but it allows china to exploi

6、t stranded coal deposits sitting thousands of kilometres from the countrys main industrial centres. transporting gas is, after all, a lot cheaper than transporting coal.coal gasification can also help address local pollution problems that have in recent months brought parts of the country to a virtu

7、al standstill.but there are two big problems. first, coal gasification actually produces more co2 than a traditional coal plant; so not only will china be using more coal, it will be doing so at a greater cost to the environment.as laszlo varro, head of gas, coal and power markets at the internation

8、al energy agency (iea), says: coal gasification is attractive from an economic and energy security perspective. it can be a nice solution to local pollution, but its overall carbon intensity is worse than coal mining, so it is not attractive at all from a climate change point of view.the us has expe

9、rimented with coal gasification in recent years indeed a study by duke university in the us suggests synthetic natural gas emits seven times more greenhouse gases than natural gas, and almost twice as much carbon as a coal plant.the second problem is water use. coal gasification is one of the more w

10、ater-intensive forms of energy production, and large areas of china, particularly in the western parts of the country that would host new gasification plants, already suffer from water shortages.mr varro says a recent iea report concluded that coal and coal gasification plants would use quite a subs

11、tantial portion of the available water in china.abundant reserves other countries are looking at different ways to get gas from coal. one method, particularly popular in australia, is coal-bed methane, a process allowing access to coal deposits that are too deep to mine. water is sucked out of the s

12、eam and the methane attached to the surface of the coal is freed and then collected. china, indonesia and mozambique are looking at coal-bed methane, while the us and canada also have abundant reserves.very little co2 is emitted, but the process is not without controversy. opponents highlight concer

13、ns about water contamination, land subsidence and disposing of waste water safely, while the water intensive process sometimes involves fracking.and yet coal-bed methane has fundamentally changed the dynamics of the gas industry in australia, according to phil hirschhorn, partner at the boston consu

14、lting groups energy practice in sydney.he says there are 200 trillion cubic feet of coal-bed methane resources in the country, with projects under construction to liquify and export 25 million tonnes of gas every year - equivalent to 10% of the entire global lng market.clean access a very different

15、way to produce gas from coal is known as underground coal gasification (ucg), a process that has been around since the 19th century but which has yet to become commercially viable on a grand scale - there is currently one working facility in uzbekistan and pilot projects in australia and south afric

16、a.heavy pollution has forced china to rethink how it exploits its coal reserves according to julie lauder, chief executive of the ucg association, the process is a new way of harnessing the energy of coal without the usual environmental impacts.technological developments and the rising price of gas

17、mean ucg is now a feasible way of accessing the vast resources of coal that are too deep to mine, she says. indeed, estimates suggest that as much as 85% of the worlds coal resources cannot be accessed through traditional mining techniques.opening them up to exploitation has potentially disastrous i

18、mplications for co2 emissions and climate change, but the industry says these resources can be accessed cleanly.the process involves pumping oxygen and steam through a small borehole into the coal seam to produce a small and controlled combustion. unlike coal-bed methane, therefore, the actual coal

19、is converted from a solid state into gas. the hydrogen, methane, carbon monoxide and co2 is then siphoned off through a second borehole.according to dr harry bradbury, founder and chief executive of uk clean energy company five quarters, this process results in 20% of the co2 produced from tradition

20、al coal mining.but his company is developing a process that requires no burning of coal, and which combines what dr bradbury calls solid state chemical engineering with releasing gases that are trapped not just in the coal, but in the surrounding rocks as well. and all of this takes place offshore,

21、relieving concerns about water contamination and subsidence, he argues.but the real advantage lies in the ability to capture the co2. we need to get more radical - we need to get to zero carbon, dr bradbury says. full carbon capture and storage is absolutely crucial.this can take place through re-in

22、jecting the co2 back into the coal seams, or by converting the carbon into products such as plastics and graphene, he says.the uk government has established a working party to investigate the merits of ucg, undoubtedly excited by the vast resources of coal sitting under the north sea. other governme

23、nts are equally keen to exploit new technologies to access their hidden coal seams.the problem, of course, is that the process depends entirely on wider efforts to develop ccs, efforts that have, so far, singularly failed to find a solution.until one is found, any attempts to gasify coal underground

24、 will either remain theoretical or will exacerbate the already grave problem of co2 emissions. and if recent efforts are anything to go by, we could be waiting a long time.燃煤气化：未来的清洁能源？译者：freakymind原文作者：richard anderson煤炭很脏，但是却很便宜。正因如此，燃煤目前仍然是世界主要的能量来源，它为我们提供了四分之一的主要能源需求以及超过40%的电力。在接下来的许多年里仍将如此。因此，我

25、们面临的挑战将是如何以更清洁的方式利用燃煤。尽管全球性的碳采集与储存(ccs)的尝试目前停滞不前，仍有一些国家正在探索新的方法来利用他们丰富的燃煤储量。并非所有这些国家都是出于环境利益的考量，而可能只是出于经济利益的考虑与能源独立的需要。老技术与新方法目前主流的燃煤处理方式是燃煤气化并非将它烧掉，而是通过化学方法将其转化为人造天然气（sng）。这项处理方法已经沿用了数十年，但是最近燃气价格的上涨让它在经济上更加可行了。美国已经开始涉足这项技术，但是中国正倾尽全力以满足其迅猛增长的能量需求并减少对进口液化石油气（lng）的依赖。中国国家能源局已经制定出一个要在2020年前利用燃煤生产500亿立方

26、米燃气的计划，足以满足中国对燃气总需求量的10%。这不仅在经济上是可行的，它也让中国可以将分布在离工业中心数千公里远的地方的煤矿利用起来。毕竟运输燃气的成本要比运送燃煤便宜得多。燃煤气化还有助于解决近几个月已让中国部分地区陷入实质上的停滞状态的空气污染问题但是当前这项技术还有两大问题。第一个问题是，燃煤气化比传统煤炭工厂产生的二氧化碳更多。因此，中国不仅要使用更多的燃煤，还要付出更高的环境代价。如国际能源署(iea)天然气、煤炭以及电力部门主管laszlo varro所说：“燃煤气化从经济及能源安全的角度都看是很吸引力的。“它可以成为一个很好的解决本地污染的解决方案，但是它总体的碳浓度(比煤炭

27、开采)更大，因此从气候变化的角度来看则一点也没有吸引力”。实际上，美国杜克大学的一项研究表明人造天然气的温室气体排放比天然气多七倍，而碳排放量则是煤炭工厂的两倍。第二个问题则是水的使用。燃煤气化是耗水较多的能源生产方式中的一种，但中国的大片区域，尤其是将要建设气化工厂的西部地区，已经饱受缺水问题的困扰。varro先生说到一份最近的iea报告得出了一项结论，煤炭与燃煤气化工厂会用掉“中国可用水资源的相当大一部分”。丰富的储量其他国家则在寻找不同的方法来从煤炭中得到燃气。在澳大利亚比较常见的一种方法是煤层气法，可以让人们得以利用埋藏太深而难以开采的煤层。这种方法将水从煤层中抽走，以使附着在煤炭表面的甲烷被释放出来，再将这些甲烷收集起来。中国，印度尼西亚及莫桑比克都在考虑煤层气，而美国与加拿大也有丰富的储量。尽管这种处理流程的二氧化碳排放量很低，但是它的采用也并非没有异议。反对者们强调了对水污染，地面沉降和废水排放方面的担心，而耗水流程有时又要用到液压破裂法。而据波士顿咨询集团在悉尼的能源业务合伙人菲尔赫塞豪恩所言煤层气已经“根本地改变了澳大利亚燃气行业的动态”。他提到，澳大利亚有200万亿立方英尺的煤层气资源，每年可以从中生产2,500万吨液化燃气相当于全球液化天然气市场产量的1