Clean Coal Technology: A Novel Process for the Combustion of Coal Using an Oxygen Carrier

洁净煤技术：利用氧载体燃烧煤炭的新工艺

• 批准号: EP/D055725/1
• 负责人: John Dennis
• 金额: $ 33.23万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FD055725%2F1
• 关键词: Clean; Coal; Technology; Novel; Process

The global supply of electricity accounts for ~38% of total anthropogenic carbon emissions to the atmosphere or ~2,400 Mte/y (carbon basis), a figure projected to exceed 4,000 Mte/y by 2020. Globally, coal generates the largest share of world electricity production (39% of total delivered energy) followed by renewables (principally hydroelectricity) (20%), nuclear (17%), gas (15%) and oil (10%). Electricity production will increase by ~80% over the period 2000 to 2020, with the fraction generated from coal remaining at ~39%, due to increased exploitation of coal in India and China and steady growth in the USA. In the U.K., the most recent White Paper only envisages a future for coal provided ways can be found materially to reduce its carbon emissions , which therfore requires the sequestration of the CO2 arising from the combustion of the coal, or fuels derived from it, in the earth. The cost of sequestration is small (~ $4-8/ te C) compared to the costs of separation of CO2 from typical flue gases (~ $100 - 200/te C)so that such disposal only approaches viability if the CO2 is available in almost pure form, largely free of nitrogen and other inert gases.We wish to use chemical looping for the in situ gasification and combustion of coal in a process to produce CO2 and steam as pure products, without significant contamination by N2. In our proposed scheme, there would be one reactor, containing a bubbling fluidised bed of oxygen carrier, most likely a Cu-based oxide on a titania or alumina support, the durability of which has been demonstrated by other workers. The reactor would be operated in a cycle of three consecutive periods, t1, t2 and t3. During t1, the bed would be fluidised by steam, (or steam and CO2) and coal would be fed steadily to the bed, the temperature of which would be ~ 800 - 1000 C. Two events would occur:(1) the coal would undergo gasification (endothermic) by the steam to yield a synthesis gas containing CO and H2 (plus smaller amounts of CH4 and higher hydrocarbons): C(s) + H2O(g) = CO(g) + H2(g) (enthalpy of reaction: +131 kJ/mol),(2) the syngas would react with the surrounding CuO particles to give CO2 and steam by: CuO(s) + H2(g) = Cu(s) + H2O(g) and CuO(s) + CO(g) = CO2(g) + Cu(s) (enthalpies of reaction -86 kJ/mol and -127 kJ/mol, respectively).Copper has the only oxides which give exothermic reactions in (2); the heat produced exceeds that needed for the endothermic gasification reaction in (1). In effect, the metal oxide has been used in place of air, or cryogenically-produced O2, so that the products of combustion do not contain N2. Of course, this system can only function down to a certain degree of reduction of the metal oxide. Thus, after time t1, the feed of coal ceases and the remaining inventory of bed carbon is allowed to gasify and combust for a further period of time, t2, until the inventory is sufficiently small. At the end of t2, the bed is fluidised by air instead of steam for a period of time, t3, during which the reduced metal oxide carrier is regenerated in Cu + 0.5O2 = CuO (enthalpy of reaction -156 kJ/mol Cu). During t3 some carbon will be burnt off, originating either from coked metal oxide or from residual carbon inventory remaining after t2, so that there would be a small release of CO2 with the regenerating air, but this would be very much less than that emitted by direct combustion of the coal in air. Once the metal oxide has been regenerated, the cycle starts again at t1. Thus, the concept enables coal to be burnt cleanly with a rather smaller reduction in thermal efficiency than is obtained with other schemes for isolating the CO2, using e.g. cryogenically-separated oxygen from air.

全球电力供应占大气中人为碳排放总量的~38%，即~2,400 Mte/年（碳基），预计到 2020 年将超过 4,000 Mte/年。从全球来看，煤炭发电占世界电力生产的最大份额（占总输送能源的 39%），其次是可再生能源（主要是水力发电）（20%）、核能（17%）、天然气（15%） 和油（10%）。 2000 年至 2020 年期间，电力产量将增加约 80%，其中煤炭发电的比例将保持在约 39%，这是由于印度和中国煤炭开采量的增加以及美国的稳定增长。在英国，最新的白皮书只设想了煤炭的未来，前提是可以找到实质性减少碳排放的方法，因此需要将煤炭或源自煤炭的燃料燃烧所产生的二氧化碳封存在地球上。与从典型烟道气中分离 CO2 的成本（约 100 - 200 美元/te C）相比，封存成本很小（约 4-8 美元/te C），因此，只有当 CO2 几乎以纯净形式存在且基本上不含氮气和其他惰性气体时，这种处置才具有可行性。我们希望在生产 CO2 和蒸汽作为纯产品的过程中使用化学循环进行煤的原位气化和燃烧，而无需 N2 的严重污染。在我们提出的方案中，将有一个反应器，其中包含氧载体的鼓泡流化床，最有可能是二氧化钛或氧化铝载体上的铜基氧化物，其耐用性已被其他工作人员证明。反应堆将在三个连续周期t1、t2和t3的循环中运行。在 t1 期间，床层将被蒸汽（或蒸汽和 CO2）流化，煤将稳定地送入床层，床层温度约为 800 - 1000 C。会发生两个事件：（1）煤将被蒸汽气化（吸热），产生含有 CO 和 H2（加上少量 CH4 和高级烃）的合成气：C(s) + H2O(g) = CO(g) + H2(g)（反应热：+131 kJ/mol）,(2) 合成气将与周围的 CuO 颗粒发生反应，产生 CO2 和蒸汽： CuO(s) + H2(g) = Cu(s) + H2O(g) 和 CuO(s) + CO(g) = CO2(g) + Cu(s) （反应热 -86 kJ/mol 和 -127 kJ/mol，分别）。铜是唯一能在（2）中产生放热反应的氧化物；产生的热量超过(1)中吸热气化反应所需的热量。实际上，金属氧化物已用来代替空气或低温产生的 O2，因此燃烧产物不含 N2。当然，该系统只能在金属氧化物还原到一定程度时发挥作用。因此，在时间t1之后，停止煤的供给，并且允许床碳的剩余存量气化并燃烧另一时间段t2，直到存量足够小。在 t2 结束时，床层由空气代替蒸汽流化一段时间 t3，在此期间，还原的金属氧化物载体以 Cu + 0.5O2 = CuO 的形式再生（反应热 -156 kJ/mol Cu）。在t3期间，一些碳将被烧掉，这些碳要么来自焦化的金属氧化物，要么来自t2之后剩余的残余碳库存，因此再生空气中会释放少量的CO2，但这比煤在空气中直接燃烧所排放的要少得多。一旦金属氧化物再生，循环在 t1 处再次开始。因此，与其他隔离二氧化碳的方案（例如使用二氧化碳）相比，该概念使煤能够清洁燃烧，热效率的降低要小得多。从空气中低温分离氧气。

项目成果

Kinetics of the chemical looping oxidation of H2 by a co-precipitated mixture of CuO and Al2O3

• DOI: 10.1016/j.cherd.2010.08.003
• 发表时间: 2011-09
• 期刊: Chemical Engineering Research & Design
• 影响因子: 3.9
• 作者: S. Chuang;J. S. Dennis;A. Hayhurst;S. Scott