中英文翻译-能源与环境工程

Power from coal with responsibility The technology to capture and store carbon pollution safely and effectively is developing fast. But without effective preparations now, vital opportunities will be lost, says Jon Gibbins.

The world faces an enormous challenge to produce the energy we need without damaging the lives of our children and grandchildren. Capturing the carbon dioxide produced from combustion of fossil fuels such as coal, oil and gas before it gets into the atmosphere and placing it instead in secure storage deep underground is a key to meeting our responsibilities. Welcome to the world of Carbon Capture and Storage, or CCS.

Carbon dioxide can be captured from all types of modern power plants, conventional steam boilers and integrated gasifier combined cycle plants that are planned for future construction. 'Post-combustion' systems wash carbon dioxide out of waste combustion gases before they go to the plant's chimney with a continuously-recycled solvent. State-of-the-art designs are a significant improvement over the small capture units that have been used for half a century to produce carbon dioxide for carbonated drinks, dry ice, fire extinguishers and other industrial uses.

In gasification-based power plants with 'pre-combustion' capture the coal gas is reacted with steam to make hydrogen, which can be burnt in a gas turbine to raise electricity without producing carbon dioxide. New power plants of either type are expected to have similar costs and performance with capture. In the longer term other types of capture system may be tried out to see if they can give better performance. Perhaps the best know of these is oxyfuel combustion; pure oxygen is produced and used to burn the coal, giving nearly pure CO 2 with little additional processing. But there are also a lot of ways in which the current post-combustion and pre-combustion systems can be improved. So, as with all other new technologies, there are plenty of opportunities for industries to compete to produce better products and for users to take advantage of a competitive market with multiple suppliers.

There is a catch: capturing carbon dioxide costs money. With current designs

about 25% extra fuel has to be burnt and additional equipment must be purchased. This adds between 30 and 40% to the cost of electricity. This may seem like a lot, but dividing the extra cost by the amount of carbon dioxide that is not emitted to atmosphere has been estimated to give 'abatement costs' of 25-30 € per tonne of CO2 (250-300 yuan or US$30-38), a price already reached last winter in the EU Emissions Trading Scheme (ETS). Although carbon prices are now lower, in the ETS and the international Clean Development Mechanism (CDM), it does show that financing CCS in China could be quite an effective way to offset emissions elsewhere in the world, especially as technology improves and capture costs go down. The key is reaching international agreement to pursue sustained and significant emission reductions.

Another way to finance CCS, at least at first, is through 'enhanced oil recovery' (EOR). Carbon dioxide, compressed to a liquid, can be placed underground in old oil and gas wells. In oil wells, the carbon dioxide can help to wash out oil that is stuck in the pores of the rock and cannot be released by other means. Current prices in the USA for carbon dioxide for EOR are around $20/tonne CO 2. Petrochina and CNOOC are currently examining similar EOR schemes in China. But, while old oil and gas reservoirs offer proven leak-tight storage and EOR can give an extra source of revenue, most of the potential storage capacity for carbon dioxide in China (and globally) is in deep layers of porous rock a kilometre or more underground that contain only salty water, known as saline aquifers. One of these, under the North Sea, has already been used successfully to store a million tonnes of CO 2 a year from the Norwegian Sleipner gas platform, and requires only a single injection pipe.

While we are waiting for the necessary political progress on climate change mitigation to make CCS a marketable service, Western governments have offered to work with China to find out how much carbon dioxide can be stored underground in China and where the best storage sites might be and also to build the first CO 2 capture plants in China. Preliminary results from an Australian storage capacity project are shown in Figure 1; this work will be continuing with a team of Chinese and international geologists. While it held the EU Presidency in 2005 the UK set up

the UK-EU-China Near-Zero Emissions Coal (NZEC) project, which is planned to lead to a jointly-designed and constructed power plant with carbon capture and storage starting operation by 2014. There are also other CCS-related research and capacity-building projects with the EU and, under bilateral agreements, with individual countries and the number of these is set to increase significantly.

Figure 1: Large sources of carbon dioxide in China and regions for prospective deep geological storage in China

China can also follow Western developments by seeing that new power plants are built to be 'capture-ready'. This means that a few simple and inexpensive changes (principally space in the right places and access to carbon dioxide storage sites) are included at the design stage so that capture equipment can be added without prohibitive costs in the future. Utility companies building power plants in Europe and the USA are already doing this in their domestic markets to make sure they can use CCS to avoid large cost penalties for CO 2 emissions in the future.

Another energy-related development that prepares for CCS is introducing new ways to use 'decarbonised' energy, electricity and hydrogen. Even when the carbon dioxide produced in the production process is captured, making synthetic gasoline or diesel fuel from coal still results in half of the coal carbon being emitted to atmosphere. In contrast, using electricity made from coal with CCS in an electric vehicle or a new plug-in hybrid vehicle or using hydrogen made from coal, releases

only about 10% of the carbon in the coal. Greater use of decarbonised energy reduces demand for expensive oil and natural gas in the short term and it can be produced from a wide range of non-fossil energy sources (nuclear, renewables, geothermal) as well as from fossil fuels with CCS. This allows the same motor vehicle technology to be sold into a wide range of markets and to be used unchanged while new energy technologies, like CCS, are introduced to tackle climate change.

In some respects the challenge of capturing billions of tonnes of carbon dioxide and pumping it deep underground sounds impossibly large. But this is because the world’s energy sector is itself so big. At the level of the power plant all that is required are some additional items of equipment: large but much less complex and costly than the existing steam or gas turbine generation machinery. Carbon dioxide capture and storage can similarly become a standard part of fossil fuel utilization – provided we act with urgency to use the irreplaceable opportunity that we have now to build up experience on CCS and to make all new power plants capture-ready, before growing awareness of climate change mandates widespread deployment.

负责任的燃煤发电：二氧化碳捕集和埋存世界正面临着一个巨大的挑战：如何生产我们需要的能源而不会对子孙后代的生活环境造成破坏。二氧化碳捕集和埋存（下称“碳捕集和埋存”）是实现我们责任的关键，因为这种技术的运用，能够捕集来自煤，石油，天然气等化石燃料燃烧产生的二氧化碳，并实现在地层深部埋存，防止二氧化碳排放到大气中。欢迎大家进入“碳捕集和埋存”的世界。

二氧化碳捕集能够在所有现代的发电厂进行，包括传统的蒸汽锅炉，和未来将要建设的煤气化联合循环机组。蒸汽锅炉使用“燃烧后捕集”系统，该系统使用不断循环的溶剂，在排放物到达烟囱前清洗出二氧化碳。目前，燃烧后捕集的先进技术是通过改进成熟小型的捕集机组发展起来的，在过去半个世纪里，小型捕集机组为饮料，干冰，灭火器等其他工业生产二氧化碳。

“燃烧前捕集”系统应用于气化炉为基础（如联合循环技术）的发电厂，通过气轮机燃烧煤气与水蒸汽反应产生的氢气，实现发电并防止二氧化碳排放。目前，用两种系统的新建发电厂有类似的预期性能和成本。从长远考虑，其他类型的碳捕集系统可能会被试验，看看是否能够实现比两种成熟系统更佳的性能。当中，氧燃料燃烧捕集系统（Oxyfuel）可能是最有名的，这种技术需要分离出用于燃煤的纯氧（纯氧与循环二氧化碳混合达到近空气的比例再进入燃烧室），产生接近纯净的二氧化碳，无需要太多额外的捕集过程。另一方面，有很多方式能够改良现在的燃烧后捕集和燃烧前捕集系统。因此，伴随着所有新的捕集技术，工业界有大量的机会去生产更好的产品来取得碳捕集的市场，用户也将受惠于有许多供应商选择的竞争环境。

总有人认为“捕集需要耗钱”是碳捕集埋存技术的毛病。如果使用现在的技术，捕集需要大约25%的额外燃料和购置额外的设备。这将增加30%到40%的发电成本。额外的成本看起来似乎很多，但平均下来，每吨二氧化碳的减排成本需要25至30欧元（相当于250至300人民币），在去年冬天欧盟排放权交易市场就曾经达到这个价格水平。尽管现在的欧洲排放交易的碳价格稍微低一些，但为中国的碳捕集项目提供资金，确实是一个弥补和减缓全球其它区域排放的有效方法，特别是当技术通过项目得到改良和实现捕集成本的下降。长远的关键是通过国际的共识和协定来进行可持续和有效的减排。

另一种为碳捕集和埋存融资的方式，至少是在最初阶段，可以通过提高石油采收率实现。当二氧化碳被加压为液态，能够放入地下石油或天然气田当中。在油田中，二氧化碳能够帮助把滞留在岩石孔中的石油冲洗出来，而其它方式是无法实现的。在美国，用于提高石油采收率的二氧化碳价格现在大约是20美元(160人民币) 每吨。中国石油和中国海洋石油现在正在为类似的二氧化碳提高石油采收率在中国的潜力进行考察。当旧的石油和天然气盆地能被证实二氧化碳的密封存储能力，提高石油采收率能够带来额外的收入来源。而中国乃至全球的大部分潜在的二氧化碳储存能力是在地下一千米或更深的含盐水层。其中的一个在北海，已经实现每年成功地储存一百万吨来自挪威Sleipner天然气田的二氧化碳，而且只需要一根注射管道。

正当我们期待着气候变化的必要政治过程使碳捕集和埋存成为一项有潜力的市场化服务，西方的政府已经着手与中国合作来寻找在中国的合适的场地配合最佳储存地点建设第一家二氧化碳捕集工厂。数据一是来自澳大利亚的初步结果；这项工作将会与中国和国际的地质学家团队继续完成。而在英国在2005年轮任欧盟主席国期间，建立里“英国-欧盟-中国燃煤近零排放项目”，该项目计划建立一个联合设计和建设的发电厂，并于2014年之前开始二氧化碳捕集的运作。另外，与欧洲以及在一些多边的协议和框架下，还有很多与碳捕集和埋存有关的科学研究和能力建设项目，而且数量在显著地上升。

数据一、中国的二氧化碳集中源和潜在的深层地质储存区域

中国能够沿着西方的发展方向通过对新建的发电厂进行“捕集预留”。这意味着在设计阶段包含一些简单和不昂贵的改良（原则上选择合适而且容易运输到地质埋存区域的场地），使得捕集设备将来能够被改装而不需要付出很高的代价。在欧美的电力企业已经开始在其国内对新建的发电厂进行捕集预留，来保证他们将来能够使用碳捕集和埋存技术来防止昂贵的二氧化碳排巨额罚款。

另一个适合碳捕集的能源相关发展是引入新的方法来使用低碳能源，电力和氢气。尽管二氧化碳在生产的过程中被捕集，从煤制造合成的汽油和柴油仍旧导致煤的一半碳以二氧化碳形式排放到大气。相比之下，如果使用来自燃煤的电力车辆，或者嵌入式的混合燃料车辆，或者使用来源于煤的氢气，并在燃煤过程进行碳捕集和埋存，煤当中仅仅10%的碳会被排放到大气中。低碳排放能源的广泛使用，短期内减少了对昂贵的石油和天然气的需求。这些低碳排放能源既能够来源于一系列的非化石能源如核能，再生能源，地热，也可以来自实施了碳捕集的化石燃料工厂。这就允许了同样的汽车技术能够在广阔的市场销售，而且引入碳捕集来解决气候变化不会产生影响。

某种意义上，捕集数以十亿吨的二氧化碳然后注入地底具有挑战性，看起来像不可能。这是因为全球的能源系统非常庞大。对于发电厂来讲，碳捕集的需要的是一些额外的设备：体积大但比现有蒸汽和燃气轮机要简单和便宜。气候变化的关注与共识正在增长，倘若我们在被强迫进行全面减排前行动起来，抓住一去不返的机遇，现在就积累碳捕集和埋存的经验，以及使所有的新电厂“捕集预留”，二氧化碳捕集和埋存将能够成为化石燃料厂的一个标准部分。