CO_2捕获发展现状与障碍分析

CO2捕获后进行封存是目前被认为减少对大气碳排放和减缓气候变化的一项重要手段,而捕获技术是碳减排的关键技术之一。CO2的捕获主要通过燃烧后、燃烧前、富氧燃烧和工业分离技术来实现。虽然捕获CO2在技术上相对比较成熟,但投资、能耗、捕获成本等方面仍存在障碍,有待进一步研究。降低捕获成本和开发新技术是CO2捕获技术大规模应用和商业运作的基础。     

储存控制条件对尿液氮磷的影响

尿液源分离技术是现阶段国际研究热点,但其收集贮存过程中的尿素水解与磷沉淀问题影响该技术的推广应用。为了考察新鲜尿液的储存变化,对稀释、酸化和稀释酸化等储存控制条件对尿液尿素水解过程中pH、氨氮和磷酸盐的影响进行了研究。结果表明:稀释储存时,尿素会发生水解,pH值升高至9.19~9.25,氨氮量会升高,磷酸盐会减少20%~36%,而稀释因子1增加到6,沉淀减少了450~650 mg。初始酸化储存时,在初始pH小于4.00条件下,尿素水解会受到控制,磷沉淀损失会减少。稀释酸化储存时,在pH小于3.00及稀释因子2或3的条件下,尿素水解会受抑制且不发生磷沉淀。     

CO2捕集回收技术研究

主要介绍了常用的胺化合物吸收法、钙基吸收剂法、金属氧化物法等CO2捕集回收技术的最新研究进展及存在的问题,综合对比了各种方法的优缺点:胺化合物吸收法吸收速率快,但再生能耗较高,因此开发"高效低耗"的复合吸收剂成为研究的重点;钙基吸收剂法在高温环境下对CO2的吸收有较好的效果,但吸收剂的碳酸化转化率及热稳定性是有待解决的关键问题;金属氧化物法具有高的CO2吸收效率,但成本较高.在此基础上,探索了CO2捕集回收技术改进工艺,提出改善吸收剂性能、开发高效低耗的CO2选择性吸收剂将成为今后CO2捕集回收技术的研究方向.     

乙醇汽油对减少机动车污染排放的机理研究与分析

以93#国Ⅲ乙醇汽油(E10)、93#国Ⅲ普通汽油和93#国Ⅳ普通汽油为实验对象,对GB18352.3-2005中要求限定的CO、HC和NOx,以及颗粒物(PM)和CO2等主要污染物的排放进行了测量和对比研究,并对CO、HC、PM、NOx、CO2和苯系物等污染物的形成原因和减排机理进行了分析.和93#国Ⅲ普通汽油相比,93 #国Ⅲ乙醇汽油(E10)排放的尾气中:CO降低了19.7％,HC降低了16.4％;和93#国Ⅳ普通汽油相比,93#国Ⅲ乙醇汽油(E10)排放的尾气中:CO降低了1.8％,HC降低了12.9％,CO2降低了2.4％.研究表明,乙醇汽油在减少CO、HC、NOx、颗粒物和苯系物等有毒物质排放方面具有显著功效,使用乙醇汽油可以减少环境污染物的排放,显著改善空气质量.     

美国将100万吨CO2封存于地下

据《连载科学》报道，美国依利诺斯州开始了大型碳地下封存实验项目。该项目花费将达8400万美金，预计2012年，将往地下1981．2m深处封存100万吨CO2，用以测试地质封存的安全性和经济性。如果实验获得成功，美国几个州未来几年将向地下封存CO2高达1000亿吨。     

N-甲基二乙醇胺/哌嗪/羟乙基乙二胺三元复合溶液捕集烟气中CO2中试研究

化学吸收法是目前烟气回收CO2技术的研究热点,其中一类重要的吸收剂就是醇胺复合溶液.醇胺复合溶液具有对CO2吸收速率快、吸收容量大及再生简单的特点,成为烟气CO2吸收剂的首选.采用中试连续实验装置,以N-甲基二乙醇胺(MDEA)/哌嗪(PZ)/羟乙基乙二胺(AEEA)(摩尔比为0.70:0.15:0.15)三元复合溶液为吸收剂对烟气中CO2进行吸收处理.研究结果表明,吸收剂最佳摩尔浓度为3.0 mol/L,最佳吸收温度为40℃,最佳液气比为10 L/m3;再沸器的热负荷随着吸收温度、吸收剂浓度以及液气比的增加而增大,脱碳率随着入口烟气中CO2浓度的增加而降低.     

低温等离子体催化氧化甲烷的实验研究

采用电容耦合等离子体和催化剂协同作用对干空气中的甲烷进行了氧化实验,并和没有放置催化剂时进行了对比,结果表明,放置催化剂后甲烷的分解效率明显提高,反应产物中CO2的选择性增加,副产物NO和NO2的浓度减少,反应所需的能耗降低.甲烷的最终氧化产物为CO、CO2和H2O.     

地下停车库空气污染物排放实测研究

通过对上海市某商业地下停车库库内及排风管道的连续监测,获得了CO、NO、非甲烷总烃(NMHC)、PM10等空气污染物浓度数据。结果表明:(1)地下停车库的休息日车流量明显大于工作日,且工作日小时车流与车位比为20%~50%、休息日小时车流与车位比为20%~80%。(2)总体上,地下停车库内CO、NO、NMHC浓度呈明显变化规律,营业时间现峰值,非营业时间现谷值;地下停车库内CO、NO、NMHC变化规律和车库排风中具有较好的一致性。(3)车库排风中污染物浓度水平均低于地下停车库内。(4)营业时间的CO、NO、NMHC小时浓度平均值明显增大,约为非营业时间的2.42~3.67倍。(5)单车次CO、NOX、NMHC排放量最大值分别为0.855、0.070、0.214g/(辆·次)。(6)营业时间,除地下停车库内CO外,NO、PM10的8h时间加权平均值符合《工作场所有害因素职业接触限值化学有害因素》(GBZ 2.1—2007,其中未规定NMHC)中时间加权平均容许浓度(PC-TWA);地下停车库内CO出现33.3%的超标频率,最大占标率104%。     

碱性催化剂对农业废物液化产生生物油和气体的影响

采用热化学处理法对农业废物玉米秸秆和苹果渣进行处理,3种碱性物质Na2CO3、K2CO3和KOH作为催化剂,都能不同程度提高液化生物油收率、减少固体残渣收率.但碱性催化剂会降低气体收率,因而不适合作为以获得气体产物为目的的生物质气化试验的催化剂.就增加液化生物油收率方面而言,Na2CO3的催化效果最好,KOH催化效果次之,K2CO3的催化效果最差.     

微藻在生物减排CO2中的应用

微藻是一类单细胞或简单多细胞的微生物,其生长快速,并能够高效地固定各种来源的CO2,包括大气和工厂排放废气中所含的CO2及溶解性的碳酸盐.CO2的固定、生物能源的制备及污水的处理相结合为目前CO2的减排提供了一种前景非常好的技术选择.论述了热化学转化法(湿式碳化、热解及直接液化)等微藻生物质制备生物能源方法的研究状况,并分析了利用微藻生物减排CO2与污水处理相结合的可能性及目前的研究进展.     

The carbon-sequestration potential of municipal wastewater treatment

The lack of proper wastewater treatment results in production of CO(2) and CH(4) without the opportunity for carbon sequestration and energy recovery, with deleterious effects for global warming. Without extending wastewater treatment to all urban areas worldwide, CO(2) and CH(4) emissions associated with wastewater discharges could reach the equivalent of 1.91 x 10(5) t(CO2)d(-1) in 2025, with even more dramatic impact in the short-term. The carbon sequestration benefits of wastewater treatment have enormous potential, which adds an energy conservation incentive to upgrading existing facilities to complete wastewater treatment. The potential greenhouse gases discharges which can be converted to a net equivalent CO(2) credit can be as large as 1.91 x 10(5) t(CO2)d(-1) in 2025 by 2025. Biomass sequestration and biogas conversion energy recovery are the two main strategies for carbon sequestration and emission offset, respectively. The greatest potential for improvement is outside Europe and North America, which have largely completed treatment plant construction. Europe and North America can partially offset their CO(2) emissions and receive benefits through the carbon emission trading system, as established by the Kyoto protocol, by extending existing technologies or subsidizing wastewater treatment plant construction in urban areas lacking treatment. This strategy can help mitigate global warming, in addition to providing a sustainable solution for extending the health, environmental, and humanitarian benefits of proper sanitation.     

Separation and capture of CO2 from large stationary sources and sequestration in geological formations--coalbeds and deep saline aquifers

The topic of global warming as a result of increased atmospheric CO2 concentration is arguably the most important environmental issue that the world faces today. It is a global problem that will need to be solved on a global level. The link between anthropogenic emissions of CO2 with increased atmospheric CO2 levels and, in turn, with increased global temperatures has been well established and accepted by the world. International organizations such as the United Nations Framework Convention on Climate Change (UNFCCC) and the Intergovernmental Panel on Climate Change (IPCC) have been formed to address this issue. Three options are being explored to stabilize atmospheric levels of greenhouse gases (GHGs) and global temperatures without severely and negatively impacting standard of living: (1) increasing energy efficiency, (2) switching to less carbon-intensive sources of energy, and (3) carbon sequestration. To be successful, all three options must be used in concert. The third option is the subject of this review. Specifically, this review will cover the capture and geologic sequestration of CO2 generated from large point sources, namely fossil-fuel-fired power gasification plants. Sequestration of CO2 in geological formations is necessary to meet the President's Global Climate Change Initiative target of an 18% reduction in GHG intensity by 2012. Further, the best strategy to stabilize the atmospheric concentration of CO2 results from a multifaceted approach where sequestration of CO2 into geological formations is combined with increased efficiency in electric power generation and utilization, increased conservation, increased use of lower carbon-intensity fuels, and increased use of nuclear energy and renewables. This review covers the separation and capture of CO2 from both flue gas and fuel gas using wet scrubbing technologies, dry regenerable sorbents, membranes, cryogenics, pressure and temperature swing adsorption, and other advanced concepts. Existing commercial CO2 capture facilities at electric power-generating stations based on the use of monoethanolamine are described, as is the Rectisol process used by Dakota Gasification to separate and capture CO2 from a coal gasifier. Two technologies for storage of the captured CO2 are reviewed--sequestration in deep unmineable coalbeds with concomitant recovery of CH4 and sequestration in deep saline aquifers. Key issues for both of these techniques include estimating the potential storage capacity, the storage integrity, and the physical and chemical processes that are initiated by injecting CO2 underground. Recent studies using computer modeling as well as laboratory and field experimentation are presented here. In addition, several projects have been initiated in which CO2 is injected into a deep coal seam or saline aquifer. The current status of several such projects is discussed. Included is a commercial-scale project in which a million tons of CO2 are injected annually into an aquifer under the North Sea in Norway. The review makes the case that this can all be accomplished safely with off-the-shelf technologies. However, substantial research and development must be performed to reduce the cost, decrease the risks, and increase the safety of sequestration technologies. This review also includes discussion of possible problems related to deep injection of CO2. There are safety concerns that need to be addressed because of the possibilities of leakage to the surface and induced seismic activity. These issues are presented along with a case study of a similar incident in the past. It is clear that monitoring and verification of storage will be a crucial part of all geological sequestration practices so that such problems may be avoided. Available techniques include direct measurement of CO2 and CH4 surface soil fluxes, the use of chemical tracers, and underground 4-D seismic monitoring. Ten new hypotheses were formulated to describe what happens when CO2 is pumped into a coal seam. These hypotheses provide significant insight into the fundamental chemical, physical, and thermodynamic phenomena that occur during coal seam sequestration of CO2.     

Agricultural opportunities to mitigate greenhouse gas emissions

Agriculture is a source for three primary greenhouse gases (GHGs): CO(2), CH(4), and N(2)O. It can also be a sink for CO(2) through C sequestration into biomass products and soil organic matter. We summarized the literature on GHG emissions and C sequestration, providing a perspective on how agriculture can reduce its GHG burden and how it can help to mitigate GHG emissions through conservation measures. Impacts of agricultural practices and systems on GHG emission are reviewed and potential trade-offs among potential mitigation options are discussed. Conservation practices that help prevent soil erosion, may also sequester soil C and enhance CH(4) consumption. Managing N to match crop needs can reduce N(2)O emission and avoid adverse impacts on water quality. Manipulating animal diet and manure management can reduce CH(4) and N(2)O emission from animal agriculture. All segments of agriculture have management options that can reduce agriculture's environmental footprint.     

State of energy consumption and CO2 emission in Bangladesh

Carbon dioxide (CO2) is one of the most important gases in the atmosphere, and is necessary for sustaining life on Earth. It is also considered to be a major greenhouse gas contributing to global warming and climate change. In this article, energy consumption in Bangladesh is analyzed and estimates are made of CO2 emission from combustion of fossil fuel (coal, gas, petroleum products) for the period 1977 to 1995. International Panel for Climate Change guidelines for national greenhouse gas inventories were used in estimating CO2 emission. An analysis of energy data shows that the consumption of fossil fuels in Bangladesh is growing by more than 5% per year. The proportion of natural gas in total energy consumption is increasing, while that of petroleum products and coal is decreasing. The estimated total CO2 release from all primary fossil fuels used in Bangladesh amounted to 5072 Gigagram (Gg) in 1977, and 14 423 Gg in 1995. The total amounts of CO2 released from petroleum products, natural gas, and coal in the period 1977-1995 were 83 026 Gg (50% of CO2 emission), 72 541 Gg (44% of CO2 emission), and 9545 Gg (6% CO2 emission), respectively. A trend in CO2 emission with projections to 2070 is generated. In 2070, total estimated CO2 emission will be 293 260 Gg with a current growth rate of 6.34% y . CO2 emission from fossil fuels is increasing. Petroleum products contribute the majority of CO2 emission load, and although the use of natural gas is increasing rapidly, its contribution to CO2 emission is less than that of petroleum products. The use of coal as well as CO2 emission from coal is expected to gradually decrease.     

Fossil fuels in the 21st century

An overview of the importance of fossil fuels in supplying the energy requirements of the 21st century, their future supply, and the impact of their use on global climate is presented. Current and potential alternative energy sources are considered. It is concluded that even with substantial increases in energy derived from other sources, fossil fuels will remain a major energy source for much of the 21st century and the sequestration of CO2 will be an increasingly important requirement.     

Planning,Designing, Operating,and Regulating a Geologic Sequestration Repository as an Underground Landfill—A Review

ABSTRACT

Geologic sequestration appears to be a technically feasible method of storing carbon dioxide in underground aquifers in order to lower greenhouse gas emissions into the atmosphere. The overall feasibility of geologic sequestration is still in question and as such, has been the focus of intense research over the past decade. Researchers have looked to the oil/gas industry and water well industry for lessons learned and technical knowledge, however, a better industry to emulate may well be the waste industry. Viewing geologic sequestration repositories as underground landfills has a great many benefits. First, there is a plethora of existing research and investigations that are directly analogous to geologic sequestration projects. Second, the regulatory framework is rather mature and can be easily adapted to serve geologic sequestration. This paper conducts an extensive literature search of the environmental, waste, and geologic sequestration literature to ascertain planning, design, and operational methodologies, lessons learned, and concepts that are directly useful for geologic sequestration to improve the technical and regulatory framework. Lastly, the paper uses a hypothetical underground landfill geologic sequestration site (ULGSS) in Florida, USA to discuss some of the findings and implications from the literature. It is concluded that there are a number of literature findings from the waste and environmental arena that should be adapted for geologic sequestration.

IMPLICATIONS Geologic sequestration is a promising solution for greenhouse gas control. This work supports that notion but suggests further improvements to the technical and regulatory framework based upon an extensive review of the waste management and environmental literature. The improvements include suggestions in the areas of permitting, site selection, operations, cost accounting, and special waste handling. Some of these improvements are discussed using a hypothetical project site in Florida, USA.     

Planning, designing, operating, and regulating a geologic sequestration repository as an underground landfill--a review

Geologic sequestration appears to be a technically feasible method of storing carbon dioxide in underground aquifers in order to lower greenhouse gas emissions into the atmosphere. The overall feasibility of geologic sequestration is still in question and as such, has been the focus of intense research over the past decade. Researchers have looked to the oil/gas industry and water well industry for lessons learned and technical knowledge, however, a better industry to emulate may well be the waste industry. Viewing geologic sequestration repositories as underground landfills has a great many benefits. First, there is a plethora of existing research and investigations that are directly analogous to geologic sequestration projects. Second, the regulatory framework is rather mature and can be easily adapted to serve geologic sequestration. This paper conducts an extensive literature search of the environmental, waste, and geologic sequestration literature to ascertain planning, design, and operational methodologies, lessons learned, and concepts that are directly useful for geologic sequestration to improve the technical and regulatory framework. Lastly, the paper uses a hypothetical underground landfill geologic sequestration site (ULGSS) in Florida, USA to discuss some of the findings and implications from the literature. It is concluded that there are a number of literature findings from the waste and environmental arena that should be adapted for geologic sequestration.     

Effects of changes in climate on landscape and regional processes, and feedbacks to the climate system

Biological and physical processes in the Arctic system operate at various temporal and spatial scales to impact large-scale feedbacks and interactions with the earth system. There are four main potential feedback mechanisms between the impacts of climate change on the Arctic and the global climate system: albedo, greenhouse gas emissions or uptake by ecosystems, greenhouse gas emissions from methane hydrates, and increased freshwater fluxes that could affect the thermohaline circulation. All these feedbacks are controlled to some extent by changes in ecosystem distribution and character and particularly by large-scale movement of vegetation zones. Indications from a few, full annual measurements of CO2 fluxes are that currently the source areas exceed sink areas in geographical distribution. The little available information on CH4 sources indicates that emissions at the landscape level are of great importance for the total greenhouse balance of the circumpolar North. Energy and water balances of Arctic landscapes are also important feedback mechanisms in a changing climate. Increasing density and spatial expansion of vegetation will cause a lowering of the albedo and more energy to be absorbed on the ground. This effect is likely to exceed the negative feedback of increased C sequestration in greater primary productivity resulting from the displacements of areas of polar desert by tundra, and areas of tundra by forest. The degradation of permafrost has complex consequences for trace gas dynamics. In areas of discontinuous permafrost, warming, will lead to a complete loss of the permafrost. Depending on local hydrological conditions this may in turn lead to a wetting or drying of the environment with subsequent implications for greenhouse gas fluxes. Overall, the complex interactions between processes contributing to feedbacks, variability over time and space in these processes, and insufficient data have generated considerable uncertainties in estimating the net effects of climate change on terrestrial feedbacks to the climate system. This uncertainty applies to magnitude, and even direction of some of the feedbacks.     

Net carbon flux from agricultural ecosystems: methodology for full carbon cycle analyses

Agricultural ecosystems have the potential to sequester carbon in soils by altering agricultural management practices (i.e. tillage practice, cover crops, and crop rotation) and using agricultural inputs (i.e. fertilizers and irrigation) more efficiently. Changes in agricultural practices can also cause changes in CO2 emissions associated with these practices. In order to account for changes in net CO2 emissions, and thereby estimate the overall impact of carbon sequestration initiatives on the atmospheric CO2 pool, we use a methodology for full carbon cycle analysis of agricultural ecosystems. The analysis accounts for changes in carbon sequestration and emission rates with time, and results in values representing a change in net carbon flux. Comparison among values of net carbon flux for two or more systems, using the initial system as a baseline value, results in a value for relative net carbon flux. Some results from using the full carbon cycle methodology, along with US national average values for agricultural inputs, indicate that the net carbon flux averaged over all crops following conversion from conventional tillage to no-till is -189 kg C ha(-1) year(-1) (a negative value indicates net transfer of carbon from the atmosphere). The relative net carbon flux, using conventional tillage as the baseline, is -371 kg C ha(-1) year(-1), which represents the total atmospheric CO2 reduction caused by changing tillage practices. The methodology used here illustrates the importance of (1) delineating system boundaries, (2) including CO2 emissions associated with sequestration initiatives in the accounting process, and (3) comparing the new management practices associated with sequestration initiatives with the original management practices to obtain the true impact of sequestration projects on the atmospheric CO2 pool.     

Emissions tradeoffs among alternative marine fuels: total fuel cycle analysis of residual oil, marine gas oil, and marine diesel oil

Worldwide concerns about sulfur oxide (SOx) emissions from ships are motivating the replacement of marine residual oil (RO) with cleaner, lower-sulfur fuels, such as marine gas oil (MGO) and marine diesel oil (MDO). Vessel operators can use MGO and MDO directly or blended with RO to achieve environmental and economic objectives. Although expected to be much cleaner in terms of criteria pollutants, these fuels require additional energy in the upstream stages of the fuel cycle (i.e., fuel processing and refining), and thus raise questions about the net impacts on greenhouse gas emissions (primarily carbon dioxide [CO2]) because of production and use. This paper applies the Total Energy and Environmental Analysis for Marine Systems (TEAMS) model to conduct a total fuel cycle analysis of RO, MGO, MDO, and associated blends for a typical container ship. MGO and MDO blends achieve significant (70-85%) SOx emissions reductions compared with RO across a range of fuel quality and refining efficiency assumptions. We estimate CO2 increases of less than 1% using best estimates of fuel quality and refinery efficiency parameters and demonstrate how these results vary based on parameter assumptions. Our analysis suggests that product refining efficiency influences the CO2 tradeoff more than differences in the physical and energy parameters of the alternative fuels, suggesting that modest increases in CO2 could be offset by efficiency improvements at some refineries. Our results help resolve conflicting estimates of greenhouse gas tradeoffs associated with fuel switching and other emissions control policies.